MODIFIED ATMOSPHERE PACKAGING OF READY TO COOK IDLI

Transcription

MODIFIED ATMOSPHERE PACKAGING OF READY TO COOK IDLI
BATTER
THESIS
Submitted to the Pondicherry University
for the award of the degree
DOCTOR OF PHILOSOPHY
In
FOOD SCIENCE AND NUTRITION
By
M. DURGADEVI
DEPARTMENT OF FOOD SCIENCE AND TECHNOLOGY
PONDICHERRY UNIVERSITY
PUDUCHERRY-605 014
DECEMBER – 2011
Pondicherry University
Department of Food Science and Technology
Dr. H. PrathapKumar Shetty
Reader and Head (i/c)
CERTIFICATE
This is to certify that this thesis entitled “Modified atmosphere packaging of
ready to cook idli batter” is a record of research work done by the candidate, Miss.
M. Durgadevi, during the period of her study in the Department of Food Science and
Technology, Pondicherry University, Puducherry under my supervision. This
research work has not previously been formed the basis for award of any degree,
diploma, associateship or fellowship or any other similar title and that it represents
entirely an independent work of the candidate.
Signature of Guide
Signature of H.O.D
Signature of Dean
R.V. Nagar, Kalapet, Puducherry- 605 014, India
Ms. M. Durgadevi
Department of food Science and Technology
Pondicherry University
Puducherry-605 014
DECLARATION
I hereby declare that the thesis entitled “Modified atmosphere packaging of
ready to cook idli batter” submitted to Pondicherry University in partial fulfillment
of the requirement for the award of Doctor of Philosophy in Food Science and
Nutrition, is my original work and has not been previously formed the basis for
award of any degree, diploma, associateship, fellowship or any other similar title.
Puducherry
Date:
(M. Durgadevi)
ACKNOWLEDGEMENT
I express my humble gratitude to the Vice Chancellor, Pondicherry
University, Dr. J.A.K.Tareen for granting me permission to carry out my research
work in the Department of Food Science and Technology, Pondicherry University as
the first Scholar of the department.
I express my thanks to Dean of Life Sciences, Dr. P.P.Mathur for providing
all necessary facilities to the Department to carry out my research.
I express my profound gratitude to my supervisor Dr. H. PrathapKumar
Shetty, Reader and Head (i/c), Department of Food Science and Technology,
Pondicherry University who explored in me the art of doing research and helped me
advance in my independent thinking. I appreciate the freedom given to me
throughout the research period and the ceaseless and dynamic guidance. I also thank
him for the necessary facilities and arrangements provided to carry out my research
successfully.
I thank my Doctoral committee members Dr. Jeevarathinam (Head,
Department of Microbiology) and Dr. Shakthivel (Head, Department of
Biotechnology) for providing valuable suggestions and constructive criticism on my
work.
I would like to express my gratefulness to my Doctoral committee member
Dr. John Don Bosco, Reader Department of Food Science and Technology for his
guidance, granting permission to operate the equipments in his Product
Development Lab. I also thank him for his moral support and encouragement to
complete my work successfully.
I am happy to thank Dr. Narayanasamy Sangeetha, Assistant Professor,
Department of Food Science and Technology for her continuous support, and for
granting permission to carry out my experiments in Food and Nutrition lab.
I sincerely thank Dr. S.Hari priya, Assistant Professor, Department of Food
Science and Technology for her valuable suggestions and comments on my work
progress and for helping me throughout the study period.
I thank Dr. K.V.Sunooj, Assistant Professor, Department of Food Science
and Technology for motivating me throughout the study period and helping me in
operating texture analyzer.
I express my sincere gratitude to Dr. R.Ravi, Department of Sensory
Sciences, CFTRI, for guiding me in statistical analysis, for making himself available
to clarify all queries whenever required, for the patience shown towards my work
progress and for supporting me to complete the study successfully.
I express my gratitude to Dr. Vishnuvardhan, Assistant Professor,
Department of Statistics, Pondicherry University and Miss. Anusuya, guest lecturer,
Department of Food Science and technology for supporting my study with statistical
guidance.
I thank my non-teaching staffs Mrs. Gomathi, Mr. Chakravarthy, Mrs.
Kolanchiammal, Miss. Chandra, Mrs. Valliammal, and Mr. Angappin for helping
me with the needed amenities.
I thank Dr. Sundar for inspiration and guidance given to carry out my
research.
I thank all my colleagues S. Uma Maheswari, D. Sumitha, C.Saravanan,
Sanjay Prathap Singh, P. Vasanthakumari, M. Pushpadevi, M. Shakthi
Kandamoorthy, K.Devi, S.J.Cynthia, Soumya Bhol, Ravindra Kumar Agarwal,
Ch.Koteeswara Reddy, Shabir and P.Vandarkuzhali, for their help rendered during
my research period and for the moral support given.
I also thank research assistants Santhalakshmi and Venkadesaperumal for
their timely help.
I thank to Dr. Kumari who encouraged me to do my research work at
Pondicherry University. I thank Dr. Saraswathi, Dr. K.S. Pushpa, Dr. S.S.
Vijayanchali and Mrs. Kavitha Mythili, Mr. Devanarayanan, Dr. C. K. Venil for
their encouragement.
I express my sincere thanks to University Grants Commission for providing
me Junior Research Fellowship without which I must not have carried out my
research work. I express my thanks to Tamil Nadu Rice Research Institute, TNAU,
and Aduthurai for providing me ADT3 variety black gram dhal throughout my study
period. I also express my thanks to SID, IISc, Bangalore for helping me to carry out
LC-MS analysis for my samples.
I thank all the respondents of my study who patiently supported my survey.
I thank Dr.Victor Anand raj and family, Dr. Bhusan Sudhakar and family,
Dr. Vellari and family, Dr.Shiva Sankar and family, Dr. Tokozu and family,
Dr.Sherry and family, Dr.Hannah Rachael Vasanthi, Dr.Rejena, Anandh uncle, Rena
aunty, Ellan anna, Sujitha akka, Pastor Kima, Deepa aunty and family, Phelix uncle
and family and all PUCF friends for encouraging my research work through prayers
and for the care shown in my personal life.
My special thanks to my dear friends Sharen Elizabeth Thomas, Gita, Aliza
Princy, Ithayamalar, Venkataramaiah, Murali, Srikanth, Ravindra, Ramachitra and
family, Shanmuga Sundari, Indhumathi, Kayalvizhi, Suman, Rajinish, Vijaya
Bharathy, Vikram, Vinayagam, Mayilvaganan, Supriya, Maya and Vijayalakshmi
for their continuous support to carry out my work.
My humble thanks to my parents Mr.R.Manoharan and Mrs.M.Janaki , my
sister Mrs.M.Ahiladevi, brother-in-law Mr.J.Arokiaraj, my brother Mr. M. Prasanna
Venkateshwaran, my sister-in-law Mrs.Jothi , my niece Baby. A. Thilaka Catheriene
and Mr. K. Durga Prasad and family for all moral support, financial assistance, love,
care, and encouragement showered on me throughout my study period.
Above all, I owe my humble gratefulness and faithfulness to my Lord
Almighty for His continuous grace and blessings to finish my research work
successfully.
ABBREVATIONS
ADT3
- Aduthurai
ANOVA
- Analysis of Variance
BMI
- Body Mass Index
BV
- Biological Value
CA
- Controlled Atmosphere
CCRD
- Central Component Rotatable design
DC
- Digestibility Co-efficient
FAA
- Free Amino Acids
FAN
- Free α-amino Nitrogen
FER
- Feed Efficiency Ratio
FOS
- Fructo-oligosaccharide
HM
- High Molecule
HUDCO
- Housing and Urban Development Corporation
IR20
- International Rice 20
LCMS
- Liquid Chromatography Mass Spectrometry
LDPE
- Low Density Poly Ethylene
MAP
- Modified Atmosphere Packaging
MS
- Mild Steel
NDOs
- Non Digestible oligosaccharides
NPU
- Net Protein Utilization
NSP
- Non Starch polysaccharides
PCA
- Principal Component Analysis
PER
- Protein Efficiency Ratio
PP
- Poly Propylene
QDA
- Quantitative Descriptive Analysis
RA
- Relative abundance
RPER
- Relative Protein Efficiency Ratio
RSM
- Response Surface Methodology
SCFA
- Short Chain fatty Acid
TAG
- Triacylglycerol
TPA
- Texture Profile Analysis
VLDL
- Very Low density Lipoprotein
WHO
- World Health Organization
v/v
- volume/volume
w/w
- weight/weight
h
- Hour
Pa
- Pascal
mm
- Milli meter
mL
- Milli liter
g
- Gram
µL
-Micro liter
N
- Newton
Ns
- Newton second
CONTENTS
1
1.1
1.2
1.2.1
1.2.2
1.2.3
1.2.3.1
1.2.3.2
1.2.4
1.2.5
1.2.6
1.2.6.1
1.2.6.2
1.2.6.3
1.2.6.4
1.2.7
Introduction and review of literature
Introduction
Review of literature
Significance of fermented foods
Positive health outcomes of breakfast consumption
Idli and its properties
Nutritional composition of idli
Physico- chemical parameters of idli
Rice - a staple food grain in idli making
Black gram- a protein source in idli making
Oligosaccharides in foods
Conversion of polysaccharides into oligosaccharides
Physiological properties of oligosaccharides
Animal studies on oligosaccharides
Applications of FOS in food formulations
Modified atmosphere packaging
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1
2
2
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5
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6
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2.1
2.2
2.2.1
2.2.2
2.2.3
2.2.4
2.3
2.3.1
2.3.2
2.3.3
2.3.4
2.4
Transition in the preparation and consumption of idli among the
population of Puducherry
Introduction
Materials and Methods
Selection of area
Selection of tool for data collection
Selection of respondents
Data analysis
Results and discussion
Socio-economic profile of the selected respondents
Consumption pattern of breakfast among the selected respondents
Preparation of idli at household level
Preference for commercial idli batter against home-made batter
Conclusion
3
3.1
3.2
3.2.1
3.2.2
3.2.3
Texture optimization of idli
Introduction
Materials and methods
Materials
Preparation of idli
Experimental design
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3.2.3.1
3.2.3.2
3.2.3.3
3.2.3.4
3.2.4
3.3
3.3.1
3.3.2
3.3.3
3.3.4
3.3.5
3.3.6
3.3.7
3.4
Response surface methodology
Optimization of idli
Instrumental color measurement
Texture profile analysis (TPA)
Statistical analysis
Effect of rice varieties on rice batter volume
Effect of black gram on batter volume
Effect of ratios of rice to black gram dhal on batter volume
Response surfaces
Instrumental color measurement of idli
Texture parameters
Simultaneous optimization
Conclusion
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4
4.1
4.2
4.2.1
4.2.2
4.2.3
4.2.3.1
4.2.3.2
4.2.3.3
4.2.3.4
4.2.4
4.2.4.1
4.3
4.3.1
4.3.1.1
4.3.1.2
4.3.1.3
4.3.2
4.3.2.1
4.3.2.2
4.3.3
4.3.4
4.3.5
4.3.6
4.4
Process optimization of idli using sensory attributes
Introduction
Materials
Preparation of idli
Experimental design
Response surface methodology
Optimization of idli using RSM
Sensory analysis of idli
Quantitative descriptive analysis (QDA)
Statistical analysis of data
Principal component analysis (PCA)
Desirable parameters of idli
Color
Fluffiness and sponginess of idli
Fermented aroma
Negative drivers of liking
Stickiness of the idli
Sourness of idli
Overall quality of the idli
Simultaneous optimization
Principal component analysis (PCA)
Optimization of texture and sensory attributes
Conclusion
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5
5.1
5.2
5.2.1
5.2.2
5.2.3
5.3
5.3.1
5.3.2
5.4.3
5.4
Nutritional composition of optimized idli
Introduction
Nutritional composition of the idli
Determination of fatty acids and alcohols
Determination of oligosaccharides
Nutritional composition of idli
Fatty acids and alcohols in optimized idli
Disaccharides and oligosaccharides in optimized idli
Conclusion
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6
6.1
6.2
6.2.1
6.2.2
6.2.2.1
6.2.2.2
6.2.2.3
6.2.2.4
6.2.2.5
6.3
6.3.1
6.3.2
6.3.3
6.3.4
6.4
Improving the shelf-life of ready to cook idli batter
Introduction
Materials
Methods
Preparation of batter
Selection of packaging materials
Experiment I
Experiment II
Experiment III
Respiration dynamics
Experiment I
Experiment II
Experiment III
Conclusion
Executive summary and conclusion
Practical implications / recommendations
References
Annexures
List of publications
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LIST OF PLATES
2.1
3.1
3.2
3.3
3.4
6.1
6.2
City map of Puducherry showing selected areas for the study
Color flex
Cutting idli with the designed mould
One inch cubic mould and SMS/75mm compression probe
Texture analyzer
Modified atmosphere packaging machine
Respirometer connected to gas analyzer
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LIST OF TABLES
2.1
2.2
2.3
2.4
2.5
2.6
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4.1
4.2
4.3
4.4
4.5
4.6
4.7
5.1
5.2
5.3
6.1
6.2
6.3
6.4
6.5
6.6
Age and sex wise distribution of the selected respondents (N=300)
Educational and economic status of the selected respondents (N=300)
Details on breakfast consumption (N=300)
Idli preparation at household level (N=300)
Fermentation time and measures followed to control fermentation of idli
batter at households (N=300)
Details about purchase of commercial idli batter (N=300)
Central composite rotatable design: coded and actual values of independent
variables
Effect of rice varieties on the batter volume after fermentation
Effect of black gram (var. Adt 3) on the batter volume after fermentation
Idli batter volume characteristics as affected by parboiled rice and black
gram dhal (without husk)
Experimental design: CCRD with actual levels of independent variables for
color parameters
Experimental design: CCRD with coded and actual levels of independent
variables for TPA
Regression co-efficient for dependent TPA parameters
Analysis of variance (ANOVA) for dependent TPA parameters: f values
Simultaneous optimization of process parameters by desirability approach
Sensory attributes used for sensory analysis of idli
Experimental designs and mean scores of desirable sensory attributes
Experimental designs and mean scores of undesirable sensory attributes
Regression co-efficient for sensory parameters
Regression co-efficient for overall quality of idli
Combined analysis of texture and sensory attributes
Proximate composition of optimized idli
List of fatty acids and alcohols
List of disaccharides and oligosaccharides
Thickness of packaging materials map of idli batter
Gas treatment used in experiment II
Gas treatment used in experiment III
Change in gas mixture over storage period
Concentration of gases in LDPE (0.014mm) during the storage period
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103
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6.7
6.8
6.9
6.10
6.11
6.12
6.13
2
2.1
2.2
2.3
3.1
3.2a
3.2b
3.2c
3.3a
3.3b
3.3c
3.3d
3.4a
3.4b
3.5a
3.5b
3.5c
3.5d
3.5e
3.5f
Sensory scores of the product made from batter packaged in LDPE
(0.014mm)
Sensory scores of the product made from batter packed in LDPE (0.012mm)
(0.009mm)
Comparison of gas mixture on the first day and seventh day of storage
TPA parameters of idli made from map batter
Overall quality of idli
LIST OF FIGURES
Socio-economic profile of the selected respondents
Details on idli preparation at household level
Details on fermentation time and measures to fermentation
Flowchart showing work design for TPA of idli
A. Effect of rice varieties on batter volume after fermentation
B. Effect of type of black gram dhal on batter volume after fermentation
C. Effect of ratios of rice to black gram dhal on batter volume after
fermentation
Response surface graph showing relation between independent parameters
on L*
on a*
on b*
on chroma
Fig.3.3.a texture profile of idli made of ratio 3:1.25 at 12 h fermentation
time
Fig.3.3.b texture profile of idli made of ratio 3:2 at 12 h fermentation time
Fig.3.3.a response surface graph showing relation between independent
parameters on hardness
on adhesiveness
on springiness
on cohesiveness
on chewiness
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4.1a
4.1b
4.1c
4.1d
4.2a
4.2b
4.2c
4.2d
4.3
4.4
5.1
5.2
5.3
5.4
5.5
5.6
6.1
6.2a
6.2b
6.3a
6.3b
6.4a
6.4b
6.5a
6.5b
6.6a
6.6b
6.7a
6.7b
6.8a
on resilience
Response surface graph for color
Response surface graph for fluffiness
Response surface graph for sponginess
Response surface graph for fermented aroma
Response surface graph for compactness
Response surface graph for firmness
Response surface graph for stickiness
Response surface graph for sourness
Response surface graph showing the overall quality of the idli
Principal component analysis (PCA) biplot of experimental design points
over sensory attributes of idli
Typical chromatogram and mass spectra showing fatty acids in nonfermented batter
Typical chromatogram and mass spectra showing fatty acids and alcohols in
fermented batter
Typical chromatogram and mass spectra showing fatty acids in optimized
idli
Typical chromatogram and mass spectra showing disaccharides and
oligosaccharides in non-fermented batter
oligosaccharides in fermented batter
oligosaccharides in optimized idli
Change in gas concentration during its fermentation time
Treatment 1 (0% CO2) showing change in CO2 level (%) among different
packaging material
Treatment 1 (0% CO2) showing change in O2 level (%) among different
packaging material
packaging material
packaging material
packaging material
packaging material
Treatment 1 (0% CO2 and 15% O2) showing percentage of CO2 (%)
Treatment 1 (0% CO2 and 15% O2) showing percentage of O2 (%)
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6.8b
6.9a
6.9b
6.10a
6.10b
6.11a
6.11b
6.12a
6.12b
6.13a
6.13b
6.14a
6.14b
6.15
6.16
Treatment 4 (15% CO2 and 15% o2) showing percentage of O2 (%)
Treatment 5 (0% CO2 and 17.5% O2) showing percentage of CO2 (%)
Treatment 5 (0% CO2 and 17.5% O2) showing percentage of O2 (%)
Treatment 8 (15% CO2 and 17.5% O2) showing percentage of CO2 (%)
Treatment 8 (15% CO2 and 17.5% O2) showing percentage of O2 (%)
Comparison of sensory scores of idli made from treatment 1 (0% CO2 and
15% O2)
Comparison of sensory scores of idli made from treatment 6 (5% CO2 and
15% O2)
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INTRODUCTION AND
REVIEW OF LITERATURE
0
MODIFIED ATMOSPHERE PACKAGING OF READY TO COOK
IDLI BATTER
1.1 INTRODUCTION
Fermented cereals, pulses and meat are consumed throughout the world both as means of
preservation by identifying their texture, aroma and flavour in addition to their health
benefits. Idli, one of the most common traditional cereal-pulse based fermented breakfast
product is consumed mostly in the southern part of India and Sri Lanka. Idli is the most
preferred breakfast product due to its soft texture, mild pleasant flavour and aroma, easy
digestibility and known health and nutritional benefits. Even with rapid social transition,
idli still remains to be the choice of breakfast for the population either at home or homeaway. With rapid urbanization, idli is one of the most served products in the restaurants
and catering establishments.
Idli being a lactic acid bacteria fermented product, is
traditionally prepared by rice and dhal soaked, ground and fermented before steamed and
consumed. With rapid urbanization, Ready to cook, packaged fermented batter is made
available in the cities by household vendors, frequently with quality and safety problems.
In spite of heavy demand there has not been proper commercialization of the product due
to lack of set quality parameters as well as issues with the shelf life of the product. There
has also been an effort made to develop starter cultures aimed at preparing the final
product with consistent sensory parameters. However these starter cultures did not
become popular due to their inferior sensory characteristics. Efforts are being made by
various research groups to develop appropriate and acceptable starter cultures for idli.
In spite of heavy demands organized food industries have not taken up the
commercialization of ready to cook idli batter in view of short shelf life. Even the
commercial prospects of scientifically developed starter cultures will remain curtailed till
the shelf life of ready to cook batter is considerably extended.
In the pursuit of extension of shelf life of ready to cook idli batter, a microbiologically
dynamic fermentation medium with other several factors needs to be kept in mind. The
product should be close to the natural as any change in the dynamics of the fermentation
flora could lead to unacceptable product characteristics. Although only a few fermented
1
products or preserved with Modified Atmosphere Packaging (MAP), most of them are
packaged after the fermentation/maturation process.
In this work an effort has been made to scientifically optimize the process of preparation
of ready to cook idli batter and packaging the ground product in the initial stages of
fermentation with optimized gas combinations supporting slow but desirable
fermentation process extending the product shelf life without affecting texture and
sensory characteristics.
1.2 REVIEW OF LITERATURE
The review of literature of the current study is done under the following headings:
1.2.1. Significance of fermented foods
1.2.2. Positive health outcomes of breakfast consumption
1.2.3. Idli and its properties
1.2.4. Rice - A staple food grain in idli making
1.2.5. Black gram - A protein source in idli making
1.2.6. Oligosaccharides in foods
1.2.6. Shelf life of fermented foods
1.2.1. SIGNIFICANCE OF FERMENTED FOODS
Fermented foods are those foods which have been subjected to the action of
microorganisms or their enzymes to produce desirable biochemical changes and results in
significant modification to the food. Fermented foods provide variety to the diet
supplying nutrients predominantly proteins and amino acids. The process of fermentation
also aids in detoxification (Campbell-Platt, 1994). Fermentation plays diverse roles like
enhancing the diet with wide range of
flavours, aromas and textures, preserving
substantial amounts of food through lactic acid, alcoholic, acetic acid, alkaline
fermentations, enriching food substrates with nutrients and also reducing cooking times
2
and fuel requirements (Steinkraus, 1994). Lactic acid fermented foods are common in
tropical countries and these foods give improved organoleptic qualities (Cookey et al.,
1987).
Fermentation affords a natural way to reduce the volume of the material to be
transported, abolish undesirable components, enhance the nutritive value and improve
appearance of the food, decrease the energy required for cooking and make a safer
product (Simango, 1997). Fermented foods are produced worldwide by various
manufacturing techniques, raw materials and microorganisms. However, there are only
four main fermentation processes which include alcoholic, lactic acid, acetic acid and
alkali fermentation (Soni and Sandhu, 1989). Alcohol fermentation results in the
production of ethanol, and yeasts are the predominant organisms (e.g. wines and beer),
fermented milks and cereals are mainly conceded out by lactic acid bacteria. A second
group of bacteria significant in food fermentation is the acetic acid producers
(Acetobacter species). Acetobacter sp. converts alcohol to acetic acid in the presence of
excess oxygen (McKay and Baldwin, 1990). Likewise, fermentation significantly
improves the protein quality as well as the level of amino acid particularly lysine in
maize, millet, sorghum, and other cereals (Hamad and Fields, 1979). Fermentation also
leads to improvement in the shelf life, texture, taste and aroma of the final product.
During cereal fermentation a number of volatile compounds are formed, which contribute
to a composite blend of flavours in the products (Chavan and Kadam, 1989).
The presence of aromas representative of acetic acid and butyric acid make fermented
cereal based products more appetizing. Traditional fermented foods prepared from most
common types of cereals (such as rice, wheat, corn or sorghum) are well known in
various parts of the world. Some are utilized as colorants, spices, beverages and breakfast
or light meal foods, while a few of them are used as key foods in the diet. The
microbiology of many of these fermented products is quite complex and not known. In
most of these products, fermentation is natural and involves mixed cultures of yeasts,
bacteria and fungi. Some microorganisms may participate in parallel, while others act in a
sequential manner with exchanging dominant flora during the course of the fermentation.
The common bacteria involved in fermentation are species of Leuconostoc,
3
Lactobacillus, Streptococcus, Pediococcus, Micrococcus and Bacillus. The fungi genera
Aspergillus, Paecilomyces, Cladosporium, Fusarium and Saccharomyces (yeast) are most
often found in certain products (Blandino et al, 2003).
1.2.2. POSITIVE HEALTH OUTCOMES OF BREAKFAST CONSUMPTION
Studies done by Agostoni, et al., (2010) disclose that breakfast represents a healthy habit
and association with positive health outcomes proves breakfast should be consistent with
local and family dietary behaviours. Policies and interventions supportive of breakfast
consumption are therefore encouraged. According to neurobehavioral data, the good
example of parents and access to a variety of palatable and pleasant breakfast foods
should drive children to choose self select breakfast models with balanced composition,
while respecting recommended dietary allowances. A balanced macronutrient
composition, the proposition of a variety of models leading to a total energy density
preferably within lower ranges (< 1 to 1.5), as well as glycemic indices in the lower range
for the same food class, could emphasize the positive short and long term health
outcomes which is now attributable to breakfast.
Regular breakfast consumption can have a multitude of positive health benefits, yet
young people are more likely to skip breakfast than any other meal. Given the evidence
that dietary behaviours established in childhood and adolescence track into adulthood
along with evidence that breakfast skipping increases with age, identifying correlates of
children's and adolescent's breakfast behaviour is imperative. Few studies have examined
the same specific family correlates of breakfast consumption, limiting the possibilities of
drawing strong or consistent conclusions. Parental breakfast eating and living in twoparent families were the correlates supported by the greatest amount of evidence in
association with adolescent's breakfast consumption. The results suggest that parents
should be encouraged to be positive role models to their children by targeting their own
dietary behaviours and that family structure should be considered when designing
programmers to promote healthy breakfast behaviours (Pearson et al., 2009).
Eating breakfast is important for the health and development of children and adolescents.
Reports on the findings of an Australian survey of 699 thirteen year old concerning the
4
extent of skipping breakfasts, indicated approximately 12 percent of the sample skipped
breakfast. Gender was the only statistically significant socio demographic variable, with
females skipping at over three times the rate of males. Skippers were more likely to be
dissatisfied with their body shape and to have been on a diet to lose weight than were
those who ate breakfast (Shaw, 1998).
Wesnes et al., (2003) reported in their study that a typical breakfast of cereal rich in
complex carbohydrates can help maintain mental performance over the morning.
Frequency of breakfast and cereal consumption decreased with age. Days eating breakfast
were associated with higher calcium and fiber intake in all models, regardless of
adjustment variable. After adjusting for energy intake, cereal consumption was related to
increased intake of fiber, calcium, iron, folic acid, vitamin C, zinc, and decreased intake
of fat and cholesterol. Cereal consumption as part of an overall healthful lifestyle may
play a role in maintaining a healthful Body Mass Index (BMI) and adequate nutrient
intake among adolescent girls (Barton et al., 2005).
1.2.3. IDLI AND ITS PROPERTIES
1.2.3.1. Nutritional composition of idli
Idli, a very popular fermented breakfast food consumed in the Indian subcontinent,
consists mainly of rice and black gram. Idli fermentation was carried out in the
conventional way in a batter having rice to black gram in the ratios of 2:1, 3:1 and 4:1 at
room temperature. It makes an important contribution to the diet as a source of protein,
calories and vitamins, especially B-complex vitamins, compared to the raw unfermented
ingredients. It can be produced locally and used as a dietary supplement in developing
countries to treat people suffering from protein calorie malnutrition and kwashiorkor
(Nagaraju and Manohar, 2000).
Adding Saccharomyces cerevisiae, along with natural bacterial flora of the ingredients,
was the best method for standardizing idli fermentation in terms of improved
organoleptic characteristics, leavening and nutritional constituents. Traditional idli
fermentation involves several bacteria and yeasts, contributed by the ingredients rice
(Oryza sativa), black gram (Phaseolus mungo) and the environment, with overall
5
dominance of the former in bringing about various changes. Idli fermentation is
accompanied by an increase in total acids, batter volume, soluble solids, reducing sugars,
non protein nitrogen, free amino acids, amylases, proteinases and water soluble vitamins
B1, B2 and B12 contents, thus accounting for improved digestibility and nutritional value
of the staples. Novel idli batter prepared by replacing conventional black gram with other
legumes, revealed significant change but with difference in the levels of some
biochemical constituents (Soni and Sandhu, 1989).
Idli, Dhokla, Nan, Kulcha, Bread, Jalebi, Bhatura, Bhalla, Dosa, Gulgule and Wadian
were prepared in the laboratory using traditional fermentation techniques. The fermented
batter of idli and dosa contained higher amount of available lysine, cystine and
methionine. After processing, maximum retention of lysine, methionine and cystine was
observed in steamed idli (Riat and Sadana, 2009).
Growth and nitrogen balance feeding trials were conducted with rats to determine the
protein quality of idli, a fermented steamed cake prepared from beans (Phaseolus
vulgaris) and rice. Feed Efficiency Ratio (FER), Protein Efficiency Ratio (PER) and
Relative PER (RPER) of fermented idli diets were significantly lower (p<0.05) than the
FER, PER and PER of unfermented idli diets. The Digestibility Coefficient (DC) and Net
Protein Utilization (NPU) of fermented idli diets were significantly lower (p<0.05) than
the DC and NPU of unfermented idli diets. Biological Value (BV) of fermented and
unfermented idli diets was similar to the BV of a caesin control diet. Fermentation does
not improve the protein quality of idli prepared from beans and rice (Joseph and
Swanson, 1994).
1.2.3.2. Physico chemical parameters of idli
Balasubramanian and Viswanathan (2007a) has shown that idli batter was prepared from
soaking polished parboiled rice and decorticated black gram. The blend a ratio of 2:1, 3:1
and 4:1 (v/v) and the batter was allowed for fermentation (0, 6, 12, 18 and 24 h) adding
two percent of salt. Other legumes such as soybeans and Great Northern beans could be
substituted for black gram in preparation of idli (Reddy et al., 1981). Fermentation time
of the batter varies from 14 to 24 h with overnight fermentation being the most frequent
6
time interval. The ingredients for idli are carefully washed, soaked in water separately,
grounded, mixed, and finally allowed to ferment overnight. When the batter has been
raised sufficiently, it is cooked by steaming and served hot. The product has a very soft
and spongy texture and a desirably sour flavour and taste. The black gram was washed
several times, first with tap water and finally with distilled water to remove the surface
microorganisms. These were found to produce off flavour in the idli unless they were
washed out (Mukherjee et al., 1965).
Mukherjee et al., (1965), studied the fermentation of idli batter. The microorganisms
responsible for the characteristic changes in the batter were isolated and identified.
Although there is a sequential change in the bacterial flora, the predominant
microorganism responsible for souring, as well as for gas production, was found to be
Leuconostoc mesenteroides. In the later stages of fermentation, growth of Streptococcus
faecalis and, followed by Pediococcus cerevisiae became significant. The fermentation of
idli demonstrates a leavening action caused by the activity of the hetero fermentative
lactic acid bacterium, L. mesenteroides. As far as is known, this is the first record of a
leavening action produced exclusively by the activity of a lactic acid bacterium.
Idli is traditional fermented rice and black gram based breakfast food of South India. Idli
batter was prepared from soaking polished parboiled rice and decorticated black gram for
4 h at 30 ± 1oC in water. The soaked mass was ground to 0.5 to 0.7 mm particle size
batter using wet grinder with adequate amount of water. The idli batter parameters such
as bulk density, pH, total acidity, flow behaviour index and consistency coefficients were
studied for different fermentation times and blend ratios. The bulk density, pH and
percentage total acidity of batter during different fermentation times and blend ratios
ranged between 0.94 and 0.59 g/cm3, 5.9 and 4.1 and 0.443 and 0.910%, respectively.
The consistency coefficient at any fermentation time shows increasing trend as the rice to
black gram ratio increased. The flow behaviour index indicated strong non-Newtonian
fluid behaviour (pseudoplastic) of idli batter at different fermentation times and blend
ratios (Balasubramanian and Viswanathan 2007a).
The rheology of the idli batter was assessed using a Brookfield viscometer having disc
spindles. Power law model with yield stress adequately fitted the data. Yield stress values
7
were in the range of 13-43 Pa and reached a maximum value at 7 h of fermentation. Flow
behaviour indices were in the range of 0.287-0.605. Flow behaviour indices at 23 h were
significantly lower than those at 0 h. Consistency index values, at any fermentation time,
increased as the rice to black gram ratio increased. Mean particle size ranged from 500 to
600 micro meter and there was no definite trend noticed with respect to time of
fermentation and rice to black gram ratio. There was a steep change in volume increase
after 4-h fermentation (Nagaraju and Manohar, 2000).
The idli batter comprises lactic acid bacteria and yeasts and causes an improvement in the
nutritional, textural and flavour characteristics of the final product. The desirable flavour
compounds such as ketones, diols and acids were found to be present up to eight days of
storage, whereas undesirable flavours like sulphurous and oxazolidone compounds,
ethanone and thiazole appeared in the batter subsequent to six days of storage. The
sensory attributes of idli (final product) prepared from the stored batter related well to the
determined flavour profile (Agrawal et al., 2000).
The work done by Nisha et al., (2005) stabilized the idli batter at room temperature (2830°C) and refrigerated storage (4-8°C) by using various hydrocolloids and some surfaceactive agents. The batter was evaluated in terms of decrease in volume, and whey
separation. While hydrocolloids gave good stabilization, surface-active agents failed to
stabilize the batter and they reduced whey separation. Among the various hydrocolloids,
0.1percent guar gave best batter stabilization, and idli made after ten days of room
temperature and 30 days of refrigerated storage of batter were found to be of acceptable
quality.
Reduction in the fermentation time of the idli batter is of great commercial significance
for large-scale idli production and can be potentially achieved by addition of enzymes.
The study done by Iyer and Anathanarayan, (2008) was undertaken to explore the
possibility of expediting the idli batter fermentation process by adding an exogenous
source of α-amylase enzyme. 5, 15 and 25 U per 100 g batter of amylase added to the idli
batter was allowed to ferment. Different parameters were monitored and sensory
attributes were also studied and compared with that of the control set. The fermentation
8
time was reduced from a conventional 14 h to 8 h and the sensory attributes of the final
product were also successfully maintained.
Texture Profile Analysis (TPA) test was performed for idli, making cylinder samples
(13.5 mm diameter, 10 mm long) of idli. In Pearson correlation matrix, majority of the
parameters were positively correlated at p<0.01 and p<0.05. The firmness value
positively correlated with gumminess and chewiness, which depicts the soft nature of idli
(Balasubramanian and Viswanathan 2007b).
1.2.4. RICE - A STAPLE FOOD GRAIN IN IDLI MAKING
Cereal grains particularly rice, form a major source of dietary nutrients for all people,
particularly those in the developing countries. However, compared with animal foods,
nutritional quality of cereal grains is inferior due to lower protein content, deficiency of
certain essential amino acids, lower protein and starch availabilities, and the presence of
some antinutritional factors. Fermentation of cereals for a limited period of time
improves amino acid composition and vitamin content, increases protein and starch
availabilities, and lowers the levels of antinutrients. The traditional foods prepared by
fermentation of cereals in different parts of the world are briefly described and future
research needs to improve their nutritional contribution are addressed (Chavan et al.,
1989).
Cereals are deficient in lysine, but are rich in cysteine and methionine. Legumes, on the
other hand, are rich in lysine but deficient in sulphur containing amino acids. Thus, by
combining cereal with legumes, the overall protein quality is improved (Camphell-Platt,
1994). Fermented foods prepared from cereals and legumes are an important part of the
human diet in Southeast Asia and parts of East Africa. The popularity of legume based
fermented foods is due to desirable changes including texture and organoleptic
characteristics. Improvement in digestibility and enhancement of keeping quality, partial
or complete elimination of anti-nutritional factors or natural toxins, increased nutritive
value, and reduced cooking time (Joseph, 1994).
Cereal grains constitute a major source of dietary nutrients all over the world. Although
cereals are deficient in some basic components, fermentation may be the most simple and
9
economical way of improving their nutritional value, sensory properties, and functional
qualities. Products produced from different cereal substrates (sometimes mixed with
other pulses) fermented by lactic acid bacteria, yeast and/or fungi (Blandino et al., 2003).
Rice colour changes from white to amber during parboiling (soaking and steaming).
Colour parameters indicated that, during soaking, yellow bran pigments leaches out in the
water. The levels of the Maillard precursors (i.e., reducing sugars and free α-amino
nitrogen (FAN)) depends on soaking temperature and time: leaching of RS was
compensated by enzymatic formation for long soaking times (>60 min), while proteolytic
activity was too low to compensate for FAN leaching. Parboiled rice soaking under
nitrogen, oxygen, or ambient conditions and determination of polyphenol oxidase activity
allowed to conclude that the effect of enzymatic colour changes on the soaked rice colour
was rather small. Colour measurements of brown and milled mildly, intermediately, and
severely parboiled rice samples showed that both brown and milled rice samples were
darker and more red and yellow after parboiling and that the effect depended on the
severity of parboiling conditions. Furthermore, steaming affected the rice colour more
and in a way opposite to that observed in soaking (Lamberts et al., 2006).
Parboiled brown rice contained considerably more Reducing Sugars (RS) but less sucrose
and Free Amino Acids (FAA) than raw brown rice. On milling, there was considerable
loss of sucrose and FAA from raw rice, but very little from parboiled rice; reducing
sugars changed little in either. Processing conditions affected the contents of sugars and
FAA. Maximum increase in RS and decrease in sucrose content occurred after soaking at
60C. Controlled incubation of rice flour, intact grain, separated germ and deemed rice in
water showed that considerable changes in sugars and FAA occurred in all cases, the
magnitude depending on the circumstances, but a greater part of the sugars leached out
into the water during soaking (Ali and Bhattacharya, 1980).
Grinding characteristics of raw and parboiled rice were evaluated in various wet grinding
systems like, mixer grinder, stone grinder and colloid mill. The duration of grinding had
inverse effect on the particle size and direct impact on the starch damage as well as
energy consumption in batch grinders. Stone grinder was the least energy efficient and
specific energy consumption for grinding raw rice (160.6 kJ/kg) was nearly twice as that
10
of mixer grinder (74.9 kJ/kg). Parboiled rice required longer duration of grinding
compared to raw rice, consequently specific energy consumption was higher (∼220
kJ/kg) (Sharma et al., 2008). Wet grinding is a critical step in the preparation of batter
based traditional food products. It involves both physical and chemical changes while dry
grinding is a mere size reduction operation. In wet grinding of cereals, the protein matrix
holding the starch granules is destroyed, releasing the starch granules from the protein
network (Kent and Evers, 1994). A colloid mil was comparatively evaluated with
domestic wet grinding systems, namely, a mixer grinder and a stone grinder for grinding
of raw rice, parboiled rice and black gram. The wet ground samples were finer in particle
size compared with dry ground samples. The starch damage was the least in black gram
followed by raw rice and parboiled rice in dry grinding. In wet grinding, the starch
damage in black gram as well as raw rice remained more or less same whereas the
parboiled rice showed greater damage. Parboiled rice required 2.5 to 3 times more energy
(216-252 kJ/kg) as that of raw rice (72-108 kJ/kg) for grinding in the mixer grinder and
the stone grinder (Solanki et al., 2005)
The nutritional quality of wild rice tends to be comparable with other cereals
characterized by a high content of starch and protein and a low fat content. As a whole
grain, wild rice is also a good source of dietary fibre (Qiu et al., 2010).The presence of
Streptococcus faecalis in the fermented batter, the presence of pharmacological active
amines such as thiamine was expected but they were not detected (VanVeen, et al.,
2008).
Parboiled brown rice contained considerably more (RS) but less sucrose and FAA than
raw brown rice. On milling, there was considerably loss of sucrose and FAA from raw
rice, but very little from parboiled rice; reducing sugars and FAA. Maximum increase in
RS and decrease in sucrose content occurred after soaking at 600 C (Ali et al., 2007).
Larsen et al., (2000) opines that rice is an important crop, forming a staple food for many
of the world‘s population. A study showed there was an effect of severely pressure
parboiled rice reduced the glycaemic index.
Brown rice malt from Indica and Japonica type rice were prepared and their nutrient
composition as well as Non-Starch Polysaccharide (NSP) contents and also some of the
11
physicochemical characteristics were determined. The activity of α- and β-amylases in
the un-germinated (native) rice was negligible but increased considerably on germination.
Malting altered the chemical composition of both Indica and Japonica rice to a small
extent but caused noticeable changes in the pasting characteristics. Controlled
germination or malting causes considerable changes in the physicochemical and
biochemical properties of both Indica and Japonica rice (Mohan et al., 2010). Whole
grain rice is rich in phenolic compounds. The effect of γ-irradiation on the main phenolic
compounds in the rice grains of three genotypes (black, red, and white) was investigated.
Three phenolic acids (p-coumaric acid, ferulic acid, and sinapinic acid) were identified as
major phenolic compounds in all rice samples, while two anthocyanins (cyanidin-3glucoside and peonidin-3-glucoside) were identified in pigmented grain samples (Zhu et
al., 2010).
1.2.5. BLACK GRAM A PROTEIN SOURCE IN IDLI MAKING
Blackgram (Phaseolus mungo) is a pulse traditionally used in the preparation of
South Indian breakfast foods, such as idli, which is relished for its soft and spongy
texture (Susheelamma and Rao, 1979a). The components responsible for these
properties are the surface active proteins that generate a foam and as a result
impart
a
porous
structure
to
the
food,
and
the viscogenic
mucilaginous
polysaccharide (~6%) that stabilizes the porous structure against thermal disruption
during steaming. The overall carbohydrate composition (Bhat and Tharanathan,
1986) and the structure function characteristics of the total polysaccharides of black
gram have been reported. During fermentation of black gram, for the preparation of
leavened foods, it was found that the mucilaginous polysaccharide undergoes
compositional
and
rheological
changes
(Muralikrishna
et al.,1987). Here,
the
fermentation is due to the activities of endogenous microflora (endophytes) in black
gram, in particular Leuconostoc mesenteroides, yeasts, lactic acid bacteria and
coliforms. More than one oligosaccharide was observed as in green gram (stachyose,
maltohexaose), sorghum (stachyose, maltotriose), barley (stachyose, raffinose), wheat
(stachyose, raffinose) and black gram (stachyose, raffinose). In ragi, bajra and rice malt
oligosaccharides were absent. Germination of seeds for 48 h resulted in complete loss of
12
stachyose and raffinose in cereals and pulses. The maltotriose content in pulses
completely disappeared on germination but among cereals, 45.1 and 57.3 percent loss
was observed in sorghum and maize, respectively (Sampath et al., 2008). In black gram
after fermentation, apparent viscosity of cold paste increased. Some of the properties such
as intrinsic viscosity, swelling and solubility after fermentation were reported by them.
Fermentation and steaming approximately 40 per cent reduction in oligosaccharides
resulting in reduced flatulence in the body (Koh and Singh, 2009).
Nutritional benefits are produced in legume fermentations, when microorganisms break
down the flatulence causing indigestible oligosaccharides, such as stachyose and
verbascose are broken down into the absorbable monosaccharaides and disaccharides.
Biosynthesis of B vitamins in food fermentations has been recognized to be of major
nutritional significance, particularly in Africa where high-carbohydrate diets, particularly
maize diets can be deficient in essential B vitamins, the significance of B vitamin
synthesis during fermentation to maize and sorghum beers in southern Africa was
recognized by the use of the term ‗biological ennoblement‘ by Platt (1964).
1.2.6. OLIGOSACCHARIDES IN FOODS
Carbohydrates are classified into monosaccharide, disaccharides, oligosaccharides and
polysaccharides. Oligosaccharides are low molecular weight carbohydrates consisting 3
to 10 sugar monomers (Voragen, 1998). Oligosaccharides withstand salivary hydrolysis
and digestive enzymes of human animal intestine so these oligosaccharides are not
absorbed in the upper digestive tract and are able to reach the colon unaltered. In colon,
oligosaccharides interact with the microflora and affecting immunomodulation (Reiffova
and Nemcova, 2006). The non-digestible oligosaccharides promote the growth of
beneficial bacteria in the colon, chiefly the Bifidobacteria sp., and are thus recognized as
prebiotics (Mussatto and Mancilha, 2006). Most of the known prebiotics and prebiotic
candidates are nondigestible oligosaccharides, obtained by extraction from plants (e.g.,
chicory inulin), followed by enzymatic hydrolysis (e.g., oligofructose from inulin) and by
synthesis (by trans-glycosylation reactions) from mono and/or disaccharides such as
sucrose
(fructooligosaccharides)
and
lactose
(trans-galactosylated
oligosaccharides/galactooligosaccharides) (Crittenden and Playne, 1996). Among the
13
prebiotics, inulin and oligosaccharides are the most studied and have been recognized as
dietary fibre worldwide (Moshfegh et al., 1999).
1.2.6.1Conversion of polysaccharides into oligosaccharides
Polysaccharides are the major source of bioactive oligosaccharides and around twenty
different types of non-digestible oligosaccharides (NDOs) are described for prebiotic
activities. Fructooligosaccharides, galacto-oligosaccharides, xylo-oligosaccharides and
galacturono-oligosaccharides are predominant NDOs with prebiotic characteristics.
Oligosaccharides are recognized as non-cariogenic, non-digestible and low-calorie
molecules and can be used as natural food preservatives. Chitosan and oligochitosans,
inhibits growth of pathogens and extends shelf-life of food products (Barreteau et al.,
2006).
Glycosyl-hydrolases and polysaccharide lyases, are used to obtain oligosaccharide from
polysaccharides. Polysaccharide chains were broken down by polysaccharide lyases and
form a double bond at new reducing end (Michaud et al., 2003). Polysaccharide
hydrolase cleave glycosidic bond by transfer of a H2O molecule and act as
exohydrolases/endohydrolases (Boels et al., 2001; Bojarova and Kren, 2007). Enzyme
used for the purpose must be specific to the substrate should be more efficient. The
solution for having enzyme specificity is to use bacteria to produce particular enzyme.
From the bacteria the specific enzyme of the polysaccharide can be isolated, purified and
concentrated and used (Sutherland, 1999).
1.2.6.2. Physiological properties of oligosaccharides
Oligosaccharides possess important physicochemical properties. They are used as food
ingredients as their physiological properties were beneficial to human health. The NDOs
can be used as low caricinogenic sugar surrogates in products like confectionery,
chewing gums, yoghurts and drinks (Crittenden and Playne, 1996). Many NDOs are not
digested by humans because the human body doesn‘t have the enzymes necessary to
hydrolyze certain units of monosaccharides. Compounds include carbohydrates where
fructose, galactose, glucose and/or xylose are the monosaccharides units. This property of
NDOs makes the suitable for use in sweet, low-caloric diet foods, and for consumption
14
by individuals with diabetes (Crittenden and Playne, 1996; Rivero-Urgell and
Santamaria-Orleans, 2001).
Most oligosaccharides were quantitatively hydrolyzed in the upper part of the GIT. The
resulting monosaccharides are transported through the portal blood to the liver and
subsequently, to the circulatory system. These carbohydrates are important for health as
they serve as both substrates and regulators for major metabolic pathways. Nevertheless,
some oligosaccharides present specific physicochemical properties resist to the digestive
process, reaching the caeco colon. In the caeco-colon, most of the nondigestible
oligosaccharides were hydrolyzed to small oligomers and monomers and further
metabolized by most of the anaerobic bacteria. Such a metabolic process, known as
fermentation, not only serves the bacteria by providing energy for proliferation, but it
also produces gases (H2, CO2, CH4), which are metabolically useless to the host, and
small organic acids (Short-Chain Fatty Acids – SCFA) such as acetate, propionate,
butyrate and L-lactate. Even though they do not provide the body with monosaccharaides,
the non-digestible oligosaccharides are indirect energy substrates and metabolic
regulators (Delzenne and Roberfroid, 1994). The amounts and types of SCFA produced
in the colon depend on the type of NDO substrate as well as on the composition of the
intestinal flora (Sako et al., 1999).
Oligosaccharides serve as substrate for growth and proliferation of anaerobic bacteria,
mainly the Bifidobacteria, which inhibit the growth of putrefactive and pathogenic
bacteria present in the caeco-colon (Sangeetha et al., 2005).
NDOs leads to decrease of pH in the colon and consequently, in faeces, resulting from
the production of SCFA. Lower pH values inhibit the growth of certain pathogenic
bacteria species while stimulating the growth of the bifidobacteria and other lactic acid
species (Manning and Gibson, 2004). An increase in faecal dry weight excretion, which
is related to the increased number of bacteria resulting from the extensive fermentation of
NDOs (Bielecka et al., 2002)
The indigestible quality of NDOs means that they have effects similar to dietary fibre,
and thus prevent constipation. The end products of NDOs fermentation by colonic
15
bacteria, the SCFA, are efficiently absorbed and utilized by the human colonic epithelial
cells, stimulating their growth as well as the salt and water absorption, increasing thus the
humidity of the fecal bolus through osmotic pressure, and consequently improving the
intestinal motility (Rivero-Urgell and Santamaria-Orleans , 2001).
NDOs help in
inhibition of diarrhea, especially when it is associated with intestinal infections
(Roberfroid and Slavin, 2000).
An increase in absorption of different minerals, such as iron, calcium, and magnesium
take place due to the binding/sequestering capacity of the NDOs. The minerals that are
bound/sequestered and, consequently, are not absorbed in the small intestine reach the
colon, where they are released from the carbohydrate matrix and absorbed. The increase
on calcium absorption, in particular, reduces the risk of osteoporosis since this mineral
promotes an increase in the bone density and bone mass. The hypotheses most frequently
proposed to explain this enhancing effect of NDOs on mineral absorption are the osmotic
effect, acidification of the colonic content due to fermentation and production of SCFA,
formation of calcium and magnesium salts of these acids, hypertrophy of the colon wall
(Younes, 1996).
Beneficial effect on the carbohydrates and lipids metabolism is that oligosaccharides lead
to a decrease in the cholesterol, triglycerides and phospholipids concentration in the
blood, reducing thus the risk of diabetes and obesity. Changes in the concentration of
serum cholesterol have been related with changes in the intestinal microflora. Some
strains of Lactobacillus acidophilus assimilate the cholesterol present in the medium,
while others appear to inhibit the absorption of cholesterol through the intestinal wall. On
the other hand, the changes in lipid metabolism were suggested to be a consequence of a
metabolic adaptation of the liver that might be induced by SCFA (Daubiol et al., 2000).
NDOs aid in reduction of cancer risk, mainly the gut cancer. This anti-carcinogenic effect
appears to be related to an increase in cellular immunity, the components of the cell wall
and the extra-cellular components of bifidobacteria. Faecal physiological parameters such
as pH, ammonia, p-cresol, and indole are considered to be risk factors not only for colon
cancer development but also for systemic disorders. It has been demonstrated in a human
study that the intake of trans-galactosylated disaccharides reduces the faecal pH as well
16
as ammonia, p-cresol and indole concentrations with an increase in bifidobacteria and
lactobacilli and a decrease in bacteroid populations. These alterations may be considered
to be beneficial in reducing the risk of cancer development. A low colonic pH may also
aid in the excretion of carcinogens (Delzenne and Roberfroid ,1994)
1.2.6.3 Animal studies on Oligosaccharides
Feeding mice with diets supplemented with inulin and oligofructose increased activities
of natural killer cells and phagocytes and enhanced T-lymphocyte functions compared to
mice fed diets with cellulose or lacking fibre. These results are consistent with the
observations of heightened resistance to systemic infections with Listeria spp. and
Salmonella spp., the lower incidence and growth of tumours after exposure to
carcinogens and transplanted tumour cells and are in agreement with enhanced innate and
acquired immune functions provided by Lactobacillus and other LAB. Supplementing
diets with FOS should increase production of SCFA, and particularly butyrate, and can be
predicted to strengthen mucosal defences and enhance response to health challenges
(Buddington et al., 2002).
Colonic fermentation of FOS results in the synthesis of short chain fatty acids, which
influences the lipid metabolism in human beings. Feeding male Wistar rats on a
carbohydrate rich diet containing 10 percent FOS significantly lowers serum
triacylglycerol (TAG) and phospholipid concentration (Delzenne et al., 2002).
FOS reduces post-prandial triglyceridemia by 50% and avoids the increase in serum free
cholesterol level occurring in rats fed with a Western type high fat diet. FOS protects rats
against steatosis (liver TAG accumulation) induced by fructose, or occurring in obese
Zucker fa/fa rats. FOS given at the dose of 10 percent in the diet of male Wistar rats for
30 days reduces postprandial insulinemia by 26 percent (Daubiol et al., 2000).
Animal studies provide strong evidence that FOS inhibit secretion of TAG rich Very Low
Density Lipoprotein (VLDL) particles via inhibition of de novo fatty acid synthesis. High
levels of fat present inmost human diets mean that rates of hepatic de novo fatty acid
synthesis are extremely low, since exogenous dietary fatty acids provide all the required
substrate for hepatic triacylglycerol synthesis (Parks, 2002).
17
Dietary treatment with inulin/oligofructose (15 percent) incorporated in the basal diets for
experimental animals resulted in (a) reduction of the incidence of mammary tumours
induced in Sprague Dawley rats by methyl-nitrosourea (b) inhibited the growth of
transplantable malignant tumours in mice and (c) decreased the incidence of lung
metastases of a malignant tumour implanted intramuscularly in mice. It is reported that
the dietary treatment with FOS/inulin significantly potentiated the effects of subtherapeutic doses of six different cytotoxic drugs commonly utilized in human cancer
treatment (Taper and Roberfroid, 2002).
Roberfroid and Slavin, (2000) has reported that feeding rats with FOS (10 percent) for a
few weeks decreased uremia in both normal and nephrectomized rats. Dietary FOS
enhanced faecal nitrogen excretion and reduced renal excretion of nitrogen in rats. This
occurs because these fermentable carbohydrates serve as energy source for the intestinal
bacteria, which during growth also require a source of nitrogen for protein synthesis.
1.2.6.4 Applications of FOS in food formulations
Inulin and oligofructose are ingredients that deliver a number of important nutritional
benefits as well as contribute functional properties that enhance shelf life and taste profile
of various food products like nutrition bars (Izzo and Niness, 2001). FOS can be used as
the sole sweetening agent and gives 34 percent calorie reduction compared with sucrose
standard. Organoleptic characteristics of the products are claimed to be very similar, with
the test sample having a lower sweetness and a softer texture. FOS can be used with
inulin to replace all the sugar and reduce the fat content and give excellent mouth feel
characteristics. Since the freezing point depression is less with oligo-fructose than with
sugar, the texture can be harder. Hard candies, gums, and marshmallows can be made
while achieving significantly reduced energy values (Murphy, 2001).
1.2.7 MODIFIED ATMOSPHERE PACKAGING
The common perception that modified atmospheres are useful for improving storability
has significant historical precedent. The written history of the use of modified
atmospheres can actually be traced back at least 2000 years to the use of underground,
sealed silos (Owen, 1800) where atmosphere modification was detected as ―foul air‖ that
18
was dangerous to enter and was likely a result of O2 depletion and CO2 accumulation due
to the respiratory activity of the grain. The modified atmosphere was unintentional,
although probably beneficial. The foul air in the storages would presumably control
rodent and insect pests, thereby acting to preserve the quality and storage life of the grain.
The potential for a positive impact from alteration in the respiratory gases O2 and CO2
became increasingly known through the early research of Berard (1821), Mangin (1896),
Kidd and West (1914, 1927, 1945), and Blackman and Parija (1928).
Gas modification technologies can be segregated into two classes based on the manner in
which the atmospheres are generated and maintained. One class of technologies is
referred to as Controlled Atmosphere (CA) storage, in which the atmosphere is either
manually or mechanically controlled to achieve target headspace gas concentrations. In
CA storages, O2 and CO2 concentrations can be modulated independently from one
another. The second class of technologies is (MAP), in which a package possessing a film
or foil barrier passively limits gas exchange by the living produce enclosed in the
package, thereby altering the headspace atmosphere. In MAP, both oxygen and carbon
dioxide are modified simultaneously and their concentrations at steady state are a
function of one another. In MAP, the primary route of gas exchange may be through gaspermeable film, perforations in film, or both. In what is referred to as active or intelligent
packaging techniques, packages may be flushed with specific gas mixtures designed to
obtain a desired initial atmospheric composition, gases may be actively released or
scavenged in the package, a partial vacuum can be imposed, biologically active materials
can be incorporated in the package, sensors may be used to respond to the product or
package conditions, and so on. The aim of MAP (passive, active, or intelligent in design)
is to take advantage of physiological responses of the enclosed plant material or plant or
human pathogens to the respiratory gases O2 and CO2. Presumably, MAP use is intended
to maintain product quality, thereby ensuring appropriate value to the consumer and
adequate cash flow back through the marketing and handling chain such that the
production and marketing system is sustainable .Knowledge of the physiological
responses to atmosphere modification is beneficial in terms of anticipating improved
quality retention as a result of technology investment (Beaudry, 2008).
19
Atmosphere modification in a package requires a barrier through which gas exchange is
restricted. Enclosing an actively respiring product within a package composed all or in
part of a film that acts as a gas barrier reduces O2 and increases CO2, creating gradients
across the film barrier. These gradients provide the driving force for gas flux into or out
of the package. In passive MAP, a package always tends toward steady state, in which O2
and CO2 levels are constant and O2 uptake and CO2 production by the product are equal
to those permeating through the package, a situation that exists only when the respiratory
rate is constant or nearly so. The steady-state levels of O2 and CO2 within a package are
dependent on the interaction of respiration of the product and the permeability properties
of packaging film or micro- perforations (Beaudry et al., 1992; Cameron et al., 1989;
Jurin and Karel, 1963; Kader et al., 1989).
MAP should be carefully designed, as a system incorrectly designed may be ineffective
or even shorten the shelf life of the product. The design should take into consideration not
only steady-state conditions, but also the dynamic process, because if the product is
exposed for a long time to unsuitable gas composition before reaching the adequate
atmosphere, the package may have no benefit. The design of Modified atmosphere
package depends on a number of variables, the characteristics of the product, its mass, the
recommend atmosphere composition, the permeability of the packaging materials to
gases and its dependence on temperature and the respiration rate of the product as
affected by different gas composition and temperature. Since, respiration rate modelling
is vital to the design of MAP for fresh fruits and vegetables (Fonseca et al., 2002).
Temperature is exceptionally important in package design, continuous and perforated
films differ in their response to temperature changes. The O2 and CO2 permeability of
continuous films increases with temperature, while the diffusion of gases through
perforations is extremely insensitive to temperature changes. O2 permeation over LDPE
increases 200% in 0 to 15°C, an exchange of O2 over perforations increases only 11% at
the same temperature range.
Depends on the rate of respiration and transmission, the
atmosphere modification can be achieved quickly or relatively slow.
At lower
temperatures, atmosphere modification will take several days, that some package systems
cannot achieve steady-state environments prior to the end of their shelf-life. In many
20
cases, purging the package atmosphere with CO2, N2 or a combination of gases is often
desirable during filling and sealing to rapidly obtain the maximum benefits of MAP.
Product temperature affects storability more than any other factor. Pre-cooling and
temperature maintenance during handling and shipping were critical in preserving
quality. Temperature also significantly affects permeability of film and thereby the O2
and CO2 content of the package. The elevated rate of respiration at high temperature
could be used to rapidly establish the desired package atmosphere, but this would only be
useful in the few circumstances in which it would be more important to rapidly establish
the atmosphere than to slow physiological processes, eg., to reduce cut-surface browning.
Negative Responses in MAP show that respiration gets reduced as O2 becomes limiting,
but there is usually a limit to which O2 can be reduced. The lower O2 limit is frequently
considered to be the level of O2 that induces fermentation. This fermentation threshold is
not always the lower O2 limit in commercial practice, however, because lower O2 levels
may confer benefits that outweigh the loss in flavour or other quality parameters.
Ethanol, acetaldehyde, ethyl acetate and lactate are products of fermentation that can
contribute to the development of off-flavours as well as physical injury (Kays, 1997;
Mattheis and Fellman, 2000).
With regard to MAP study done by Fandos et.al (2000) on Cameros cheese, it was found
that packaging in 50%CO2/50%N2 and 40%CO2/60%N2 were the most effective
conditions for extending the shelf life of cheese with good sensory characteristics. MAP
studies have been done in iced fresh hake slices (Pastoriza et al, 1996), Fresh cut
mangoes (Aguliar et al, 2000), fresh-cut ice berg lettuce (Fan et al, 2003), refrigerated
sea bass slices (Masniyom et al, 2002), blueberry (Song et al, 2002), minimally
processed mango and pineapple fruits (Martínez-Ferrer et al, 2002), pomegranate (Artes
et al, 2000).
From the review of literature and state of the art it is clear that there are no studies on
optimization of idli with respect to components and fermentation time taking into
consideration, both instrument based texture analysis and 15mm rating scale and
combination of RSM and PCA to evolve the optimized parameters for idli. In addition
there are no studies which deal with improvement of shelf life of idli batter with modified
21
atmosphere packaging. In continuation with this, the present study has been planned with
an objective to improve the shelf life of ready to cook idli batter using modified
atmosphere packaging.
The set objective is achieved through following the three major sub-objectives:
1.
To understand the presently followed practices for the preparation of idli.
2.
To optimize the process of preparation of the product with respect to
ingredient ratios and fermentation time.
3.
To improve the shelf-life of ready to cook idli batter by optimized process.
22
TRANSITION IN THE PREPARATION AND CONSUMPTION OF IDLI
AMONG THE POPULATION OF PUDUCHERRY
2.1 INTRODUCTION
Idli occupies a special place in the diets of Indians and is one of the predominant choices
of food in the daily diet particularly as a breakfast food. Idli being a fermented food
possesses a great significance as it provides aroma and soft texture and also act as a
nutritious food. The current study was undertaken among the selected population to study
the preference of idli, consumption pattern of breakfast, preparation of idli at household
level and preference of commercial idli batter against homemade batter.
2.2 MATERIALS AND METHODS
2.2.1 Selection of area
The area selected for the study was Union Territory of Puducherry which has a
population of 12.44 lakhs (Puducherry population census, 2011) representing multilingual and multi-cultural population. Eight areas namely Kalapet, Muthaiyalpet,
Villiyanur, Gorimed, Thattanchavadi, Lawspet, Vandrampet and Uppalam were selected
for the study .Plate 2.1 shows selected areas in the city map of Puducherry.
Plate 2.1 City map of Puducherry showing selected areas for the study
23
2.2.2 Selection of tool for data collection
An oral interview schedule was formulated to collect information regarding the
consumption of idli and preference of commercial idli batter. Interview schedule
(Annexure - I) included questions regarding socio-economic status, preference for idli,
preparation of idli at house hold level, consumption pattern of idli and commercial idli
batter. This formulated tool was tested on a pilot population, based upon the suggestions
the corrections were implemented and the questionnaire was used to collect information
from the respondents.
2.2.3 Selection of respondents
In total 300 respondents were randomly surveyed for the study irrespective of the cultural
and linguistic background
2.2.4 Data Analysis
The collected data were statistically treated for distributional analysis using SPSS
Statistical software (18.0).
2.3 RESULTS AND DISCUSSION
The results and discussion of the present study is discussed under the following
2.3.1 Socio-economic profile of the selected respondents
2.3.2 Consumption pattern of breakfast among the selected respondents
2.3.3 Methods of preparation of idli at household level
2.3.4 Preference for commercial idli batter against home-made batter
2.3.1 Socio-economic profile of the selected respondents
The details on the age, sex, educational qualification, employment and economic status of
the respondents are discussed. Table 2.1 shows the age (Fig. 2.1.a) and sex-wise
distribution of the selected respondents. Table 2.1 showed that, 62 per cent of the selected
respondents were in the age group of 21 to 40and only 2.66 per cent were in the age
group of 61 to70 years. Among 300 respondents, four per cent people were male and 96
per cent people were female. From this data, it is clearly noted that the study is correlated
with female respondents who are the majority home makers. Women are the integral part
of family (Jan and Akhtar, 2008) and vital force in the decision making concerning child
24
growth, money management, health and nutrition, and socio-economic progress of the
family.
Table 2.1
Age and sex wise distribution of the selected respondents (N=300)
Particulars
Percentage (%)
Age (in years)
21-30
31.66
31-40
31.66
41-50
26.33
51-60
07.66
61-70
02.66
Male
03.66
Female
96.33
Sex
From Table 2.2 and Fig. 2.1.b it was noted that 82 per cent of the selected population
were literates and 18 per cent were illiterates. According to HUDCO (2004), the total
family income for low income group ranged from Rs. 2500 to Rs. 4500, for middle
income Rs. 4501 to Rs.7500 and for high income Rs. 7501 and above. In the present
study majority (50%) of the population fell under high income group, 22 per cent
belonged to middle income group and 18.3 per cent fell below low income group
(Fig.2.1.c). Hence the study covered the respondents from almost all income groups with
regard to occupational status. Of the population majority (71%) was housewives and 22
per cent were labourer earning daily wages and six per cent were only self-employed
(Fig.2.1.d)
25
a. Age wise (in years) distribution of the
respondents
c. Monthly income of the respondents
b. Educational qualification of the respondents
26
d. Occupational status of the
respondents
Fig. 2.1 Socio-economic profile of the selected respondents
Table 2.2
Educational and economic status of the selected respondents (N=300)
Particulars
Percentage (%)
Educational qualification
Illiterate
18.00
Primary school
12.00
Higher secondary
33.00
High school
16.33
Graduate
20.66
Monthly income (Rs.)
<2500
18.3
2501-4500
09.7
4501-7500
22.0
>7501
50.0
Occupational status
Housewife
71.33
Labourer
22.33
Self-employment
06.33
2.3.2 Consumption pattern of breakfast among the selected respondents
Details about breakfast items preferred and consumed by the selected population are
shown in Table 2.3. It was found that 85 per cent consumed breakfast regularly and
fifteen per cent of the selected population has shown to skip breakfast. In the study done
by Agostoni et al., (2010) it was reported that nearly 10-30 per cent of the breakfast
skippers are found throughout the world which is in par with the current study.
27
Table 2.3
Details on breakfast consumption (N=300)
Particulars
Percentage (%)
Breakfast intake
Eating breakfast
Skipping breakfast
84.66
15.33
Items preferred
Idli
69.30
Dosa
21.00
Oats
09.70
Items consumed
Idli
25.00
Dosa
20.00
Chapathi
18.00
Noodles
13.85
Poori
12.15
Oats porridge
05.40
Bread
05.60
Studies done by Reddy et.al (1981) and Balasubramanian and Viswanathan (2007a)
showed that idli is a breakfast food and the current study reassures the same with 69 and
21 per cent of the selected population preferring to take idli and dosa respectively as
breakfast item daily . Further it was noted that only 25 per cent consume idli daily and 20
per cent consume dosa daily. The interesting fact is that 99 per cent of the respondents
have a liking for idli as breakfast.
28
2.3.3 Preparation of idli at household level
In spite of 71 per cent being housewives among the selected population, Table 2.4
revealed that only seven per cent of the population grind idli batter at home daily whereas
majority (58.33%) grinds only once in a week (Fig.2.2.a). Most of the respondents reveal
it due to the reason that grinding idli batter is laborious. For idli making majority of the
population (68%) prefer parboiled rice (Fig.2.2.b).
Table 2.4
Idli preparation at household level (N=300)
Particulars
Percentage (%)
Frequency of grinding idli batter
Daily
07.00
Once in a week
58.33
Twice in a week
28.66
Once in a month
06.00
Variety of rice
Parboiled rice
68.03
Ration rice (provided at PDS)
19.30
Mixed rice
12.66
Type of black gram dhal
Husk removed (decorticated)
34
Husk removed after soaking
49
Both
17
Ratio of rice: black gram dhal
3:1
99.70
8:1
00.30
29
Only 34 per cent used decorticated black gram whereas 49 per cent used black gram with
husk after soaking (Fig.2.2.c). Ratio of the raw ingredients in idli making is an important
criterion for the texture of the idli. In the current study majority (99.7%) of the
respondents used 3:1 ratio of rice and black gram dhal respectively. The findings
regarding the preparation of idli at house hold level is supported by the study done by
Balasubramanian and Viswanathan (2007b) who reported that idli batter was prepared
from soaking polished parboiled rice and decorticated black gram for 4 hour at 30±1C in
water and the soaked ingredients were ground to 0.5-0.7-mm particle size batter using
wet grinder with adequate amount of water. The blend ratios of 2:1, 3:1, 4:1(v/v) batter
were allowed for fermentation adding two percent of salt. From the survey it was also
found that 100 per cent of the respondents added fenugreek as an additional ingredient in
idli making.
Generally after grinding idli batter, the batter is left for fermentation. Fermentation time
varied between 5 h to 12 h at the selected households (Table 2.5 and Fig.2.3.a). Majority
(71.3%) of them fermented the idli batter for 11 to 12 h. The texture of idli is influenced
by many variables like raw material, quantity, soaking time, grinding conditions,
fermentation time and temperature are adjuncts on quality of idli (Desikachar et al.,
(1960) and Radhakrishnamurthy et al., (1961). Fermentation of idli batter is an essential
step because as reported by Mukherjee et al., (1965), Rajalakshmi and Vanaja (1967) the
microorganisms present in black gram dhal helps in acidification and leavening of the
batter by which gas, acid and several volatile compounds are formed during fermentation
which contribute to a complex blend of flavours in the products (Chavan and Kadam,
1989). The household measures to control fermentation of idli batter to extend the shelflife are shown in Table 2.5 and Fig.2.2.b. Majority (73%) stored the idli batter in
refrigerated condition, 19 per cent store idli batter over water tub, and rest of the selected
population place betel leaves (4.33%), lady‘s finger (1.66%) and coconut slices (1%)
over the idli batter respectively. The scientific reasons for these measures expect for
refrigeration is still in dark.
30
a. Frequency of grinding idli batter at house hold level
b. Variety of rice used by respondents for making idli
c. Type of black gram dhal used for idli making
Fig. 2.2 Details on idli preparation at household level
31
a. Fermentation time of batter at household level
b. Measures to control fermentation at household level
Fig.2.3 Details on fermentation time and measures to fermentation
32
Table 2.5
Fermentation time and measures followed to control fermentation
of idli batter at households (N=300)
Particulars
Percentage (%)
Fermentation time (h)
05-06
04.30
07-08
00.70
09-10
23.70
11-12
71.30
Measures to control fermentation
Refrigerator
73.33
Placing over water
19.33
Betel leaves
04.33
Lady‘s finger
01.66
Coconut slices
01.00
Plantain leaves
00.33
2.3.4 Preference for commercial idli batter against home-made batter
From Table 2.4 it was discussed that only seven per cent of the selected population
ground idli batter daily, but Table 2.3 show that 45 per cent of the selected population
consume idli and dosa every day for breakfast. This is because 49 per cent of the
respondents have shown interest to purchase ready to cook idli batter every day (Table
2.6). The cost variation of the commercial idli batter may be due to the quality of
ingredients used and the type of packaging. Majority (31.3%) purchase batter which
range between Rs. 10 to Rs.12, 26 per cent purchase between Rs. 13 to Rs.16. Regarding
colour of the commercial idli batter majority (59%) of the selected population expressed
that the colour was pale and unappealing and 64 per cent criticized that the commercial
33
idli batter had thin consistency which gave poor quality of idli and so it was used for dosa
making.
Table 2.6
Details about purchase of commercial idli batter (N=300)
Particulars
Percentage (%)
Frequency of purchase
Daily
49.3
Weekly
21.0
Monthly
19.7
Cost in rupees
7-9
16.3
10-12
31.3
13-16
26.3
17-20
14.7
21-30
00.7
Nil
10.7
Colour
Bright
41.00
Pale
58.99
Consistency
Thick
35.33
Thin
64.00
Preference
Like
47.23
Dislike
52.77
34
Among the selected population 53 per cent disliked commercial idli batter especially for
its aroma, out of which 31 per cent expressed problems regarding quality and shelf-life of
the batter. The study revealed that all the respondents (100%) will purchase ready to cook
idli batter if the batter quality, fermented aroma and shelf-life are improved.
2.4 CONCLUSION
The results of the survey indicates the practices currently followed by the population, not
statistically representative is similar to the practices reported in literature such as variety
of rice, type of black gram, ratio of ingredients used for idli making, fermentation time
and shelf –life of the batter.
35
TEXTURE OPTIMIZATION OF IDLI
3.1 INTRODUCTION
Indigenous or native fermented foods have been prepared and consumed for thousands of
years, and are strongly linked to culture and tradition. The fermented foods are better in
terms of nutrition and easy for digestion than the normal cooked foods. The fermentation
process causes enrichment and improvement of food through flavour, aroma, and change
in texture, preservation by providing organic acids, nutritional enrichment, reduction of
exogenous toxins and reduction in the duration of cooking. During traditional
fermentation process, locally available ingredients, which may be of plant or animal
origin, are converted into edible products by the physiological activities of
microorganisms and have distinct odour (Steinkraus 1996, Reddy and Salunkhe 1980)
namely Lactobacillus sp. and Pediococcus sp. which produce organic acids such as lactic
acid and acetic acid, alcohol and carbon dioxide (Caplice and Fitzgerald 1999) and
reduce the pH, thereby inhibiting the growth of food spoiling microorganisms. These
fermented foods can be preserved for several days (Tamang, 1998) and also have
therapeutic properties (Sekar and Mariappan, 2007). There are different types of
fermented foods in which a range of different substrates are metabolized by a variety of
microorganisms to yield products with unique and appealing characteristics (Caplice and
Fitzgerald 1999). Among all traditional fermented foods in India, idli is a white,
fermented (acid leavened), steamed, soft and spongy texture product, widely popular and
consumed in the entire South India. Idli is the resultant product from the naturally
fermented batter made from washed and soaked rice (Oryza sativa L.) and dehusked
black gram dhal (Phaseolus mungo L.). Apart from its unique texture properties, idli
makes an important contribution to the diet as a source of protein, calories and vitamins,
especially B-complex vitamins, compared to the raw unfermented ingredients (Reddy et
al., 1982).
Traditionally, rice and black gram in various proportions are soaked and ground adding
water in mortar and pestle to yield a batter with the desired consistency. Parboiled rice is
preferred over raw rice for idli and dosa with rice: black gram usually fermented at 3:1
36
(Steinkraus et al, 1967, Jama and Varadaraj, 1999) weight ratio for making soft and
spongy textured idli (Nazni and Shalini 2010). Black gram, the leguminous component of
idli batter, serves not only as effective substrate but also provides the maximum number
of micro-organisms for fermentation (Balasubramanian and Viswanathan, 2007a). As a
result of fermentation, (Padhye and Salunkhe, 1978) observed a significant increase in
predicted biological value. Fermentation also improves the protein efficiency ratio (PER)
of idli over the unfermented mixture (Van Veen et al, 1967).
Idli preparation in the conventional manner takes at least 18 h. The available instant idli
pre-mixes do not provide the desired textural characteristic and also lack the typical
fermented aroma and on the other hand, idli prepared in different households do not have
consistent quality (Nisha et al, 2005). Fermented foods in general have immense scope
for commercialization as foods with improved nutritional value as well as functional
foods. Fermented foods with scientifically developed starter cultures can aid the
commercialization of these products. However scientific optimization of the process is
the basic necessity for commercialization of any product including the fermented foods.
Several researchers have used RSM successfully to optimize the conditions for making
products like boondi (Ravi and Susheelamma, 2005), tandoori roti, puri and parotta
(Saxsena and Haridasrao, 1996 and Vatsala 2001) .The current study is undertaken to set
an optimized condition for the preparation of idli which will help the manufacturers at
industrial level to produce idli with the desired textural property. This would also help to
make proprietary products using proper starter culture. The main objectives of this study
were to explore the effect of rice and black gram dhal and fermentation time on the
texture of idli, analyzing the instrumental texture profile (TPA) parameters as a function
of raw material composition and fermentation time and to find the optimum levels to
maximize the desirable textural properties of idli using RSM.
37
3.2.1 Materials
Different rice varieties namely IR 20 idli rice, raw rice, broken rice, ration rice and red
rice were procured from local market and black gram variety Aduthurai 3 (ADT3) which
has 24.16
per cent protein content was procured from Tamil Nadu Rice Research
Institute (TRRI), Aduthurai, Tamil Nadu, India. They were cleaned and stored at
refrigerated conditions until use.
3.2.2 Preparation of idli
Before framing the design using CCRD, preliminary trails were conducted to choose the
ratios of rice to black gram dhal. The trails were done using the rice to black gram dhal
ratios as 3:0.5, 3:1, 3:1.5, 3:2, 3:2.5 and 3:3 respectively where rice ratios were kept
constant and the dhal ratios varied. The fermentation time varied between 10 to 14h. In
the trial, idli made from the ratio 3:1 and 3:1.5 with a fermentation time between 11 to 12
h gave better results. Based on this, the maximum and minimum values for the
independent variables were chosen to frame the model. The rice and black gram dhal
were mixed at different ratios as per the CCRD (Table 2.1). The rice and dhal were
soaked for 4 h and ground separately to a coarse consistency and mixed together with
salt. The batter was left overnight (time based on the developed design) for fermentation.
The fermented batter was mixed thoroughly to expel the gas formed due to the release of
carbon-dioxide .The batter was poured in idli mould, and steamed in the idli steamer for
15 minutes. The idli were brought to room temperature and then used for instrumental
texture profile.
3.2.3 Experimental design
3.2.3.1 Response surface Methodology
RSM is a collection of statistical and mathematical techniques useful for developing,
improving, and optimizing processes in which a response of interest is influenced by
several variables and the objective is to optimize this response. RSM has important
38
application in the development and formulation of new products, as well as in the
improvement of existing product. It helps to study the effect of the independent variables,
alone or in combination, on the responses. In addition to analyzing the effects of the
independent variables, it provides a mathematical model, which describes the
relationships between the independent and dependent variables (Myers and Montgomery,
1995). RSM has been very popular for optimization studies in recent years. RSM reduces
the number of experiment trials needed to evaluate multiple parameters and their
interactions. The graphical perspective of the mathematical model has led to the term
Response Surface Methodology. Generally an optimization study involving RSM has
three stages. The first stage is the preliminary experimental trials, in which the
determination of the independent variables and their limits are carried out. The second
stage involves the selection of appropriate experimental design followed by prediction
and verification of the model equation. The last stage is the generation of response
surface plots as well as contour plots of the responses as a function of the independent
parameters and determination of optimum conditions.
The model used in RSM is
generally a full quadratic equation or the diminished form of the equation. The second
order model can be written as Eqn.1.
…………….Eqn. 1
where Y is the predicted response, β0, β j, β
jj
and β
ij
are regression coefficients for
intercept, linear, quadratic and interaction coefficients respectively, k is the number of
independent variables and Xi and Xj are coded independent variables.
Response surface methodology has been widely applied in the food industry optimizing
complex processes and products (Wong et al, 2003, Lee et al, 2006 and Sin 2006). In the
present study RSM was used to determine the optimum conditions of two independent
variables (rice to black gram dhal ratio and fermentation time) on the TPA and colour
attributes of idli. A CCRD was constructed using software package Statistica (1999) from
StatSoft, OK, USA. Five levels of each predictor variable were incorporated into the
developed design. Table 1 shows levels of predictor variables.
39
3.2.3.2 Optimization of idli
The procedure was based on the hypothesis that quality attributes of idli were
functionally related to rice to black gram dhal ratio and fermentation time, and attempts
were made to fit multiple regression equations describing the responses. Two coded
independent variables in the process were rice to black gram dhal ratio (X1) and
fermentation time (X2). Five levels of each of the independent variable were chosen for
the study (Table 3.1); thus, there were 13 combinations, including the replicates of the
center point that were performed in random order, based on an experimental CCRD for
two factors. The dependent variables were hardness, adhesiveness, springiness,
cohesiveness, chewiness and resilience and colour attributes.
Table 3.1
Central composite rotatable design: Coded and actual values of independent
variables
Experimental
design points
Rice : black gram Ratio
(w / w)
Actual
1
3 : 0.72
2
3 : 0.72
3
3 : 1.78
4
3 : 1.78
5
3 : 0.50
6
3 : 2.00
7
3 : 1.25
8
3 : 1.25
9
3 : 1.25
10*
3 : 1.25
*Centre point repeated 3 times
Fermentation time
(h)
Coded
Actual
Coded
-1.000
-1.000
1.000
1.000
-1.414
1.414
0.000
0.000
0.000
0.000
10.58
13.42
10.58
13.42
12.00
12.00
10.00
14.00
12.00
12.00
-1.000
1.000
-1.000
1.000
0.000
0.000
-1.414
1.414
0.000
0.000
3.2.3.3 Instrumental Colour Measurement
The colour parameters of idli were measured using a Hunter Lab colour flex model A601012-312 (Hunter Associates laboratory, Reston, VA). The equipment was standardized
each time with white and black standards. Samples were scanned to determine lightness
(L*), red-green (a*) and yellow-blue (b*) colour components (Olajide, 2010). As in the
40
work done by (Ronald and Daniel, 1998) the hue angles were derived as the arctangent of
b*/a* expressed as degrees and the chroma values were also calculated as the square root
of the sum of the squared values of both CIE a* and CIE b*.
The chroma and Hue angle were calculated by the formula Eqn.2 and Eqn. 3,
respectively.
…………….Eqn. 2
…………….Eqn. 3
Where a* indicated Red-Green colour components, while b* indicates yellow to blue
colour components (Ali, 2008).Plate 3.1 shows the picture of colour flex.
Plate 3.1 Color flex
3.2.3.4 Texture profile analysis (TPA)
The TPA test consists of compressing a bite-size piece of idli two times in a reciprocating
motion that imitates the action of the jaw. The idli was cooled to room temperature and
was cut into an inch cube (Plate 3.3) using an inch cubic mould (Plate 3.2.a). The texture
of each idli was analyzed using SMS/75mm (Plate 3.2.b) compression platen in Texture
41
Rice (IR20 idli rice) and Black
gram dhal (ADT3) (ratio based
on the experimental design)
Soak (4h) and grind
Ferment the ground batter (Based
on the experimental design)
Pour batter in idli mould and steam
for 15 minutes
Cool idli to room temperature and
cut the centre using one inch cubic
mould
TPA of cut idli using SMS/75mm
compression platen
Statistical Analysis
(RSM; Regression)
42
Fig.3.1 Flow chart showing work design for TPA of idli
Analyzer (Stable Micro Systems, Surrey,UK). The extra top and bottom layers were
sliced off to make the idli fit to the mould. The cut piece was placed on the heavy duty
platform and the test speed was set to 5mm/sec and the probe compressed 50% of the idli
to get the TPA of the idli. Based on the force deformation curves, several parameters like
adhesiveness, springiness, cohesiveness, chewiness and resilience can be calculated.
Plate 3.2 Cutting idli with the designed mould
43
a)
b)
Plate 3.3 One inch cubic mould and SMS/75mm compression probe
Plate 3.4 Texture analyzer
44
3.2.4 Statistical Analysis
The independent variables and dependent variables (responses) were fit to the secondorder polynomial function and examined for the goodness of fit. The R2 or coefficient of
determination is defined as the ratio of explained variation to the total variation and is a
measure of the degree of fit (Haber and Runyon, 1997). All experimental designs and
statistical data were analyzed and response surfaces, ANOVA, regression analysis were
reported using Statistica (StatSoft, OK, USA) statistical software.
The results of chapter 3 are discussed under the flowing heads:
3.3.1Effect of rice varieties on rice batter volume
3.3.2 Effect of black gram on batter volume
3.3.3 Effect of ratios of rice to black gram dhal on batter volume
3.3.4 Response surfaces
3.3.5 Instrumental Colour measurement of idli
3.3.6 Texture parameters
3.3.7 Simultaneous optimization
3.3.1 Effect of rice varieties on rice batter volume
In the present study five varieties of rice namely ration rice, raw rice; broken rice, red rice
and parboiled rice were used for idli making. The rise in CO2 production can be
correlated with the increase in batter volume (Sridevi et al., 2010).The percentage of
increase in batter volume was significant (p< 0.05) in the batter prepared with ration rice,
followed by parboiled rice, raw rice, broken rice, and red rice. Though there is high
increase in batter volume, after expulsion of gas the volume of batter gets significantly
decreased in ration rice, whereas the batter volume did not show significant (p< 0.05)
decrease in parboiled rice. Table 3.2 and Fig 3.2.a shows the effect of rice varieties on
batter volume. The sensory score of idli showed variation with the variety of rice used.
As the idli prepared from parboiled rice is very soft when compared with idli made with
other varieties. Parboiled rice may be best suited for idli making which is in par with the
45
result reported by Juliano and Sakurai (1985) that parboiled rice is better suited than raw
rice for producing idli , i.e., it is soft without becoming sticky. The idli prepared using
very light coloured parboiled rice are preferred by consumers traditionally accustomed
to eating raw rice. Sowbhagya et al., (1991) studied the effect of variety, parboiling and
ageing of rice on the quality of idli and reported that the normal parboiled rice is best
suited for making idli as shown by its higher scores for softness. In the present study the
idli made of parboiled rice is soft and it may also be due to fact proved by Sharma et al.,
(2008) that the greater starch damage in parboiled rice during wet grinding, attribute to its
greater susceptibility to undergo damage owing to its softness after soaking as well as to
the longer duration of grinding favouring parboiled rice to be suited for idli making. Roy
et al., (2010) noted that the hardness and adhesion of cooked rice were dependent not
only on the moisture content but also on the forms and variety of rice. Roy et al., (2004),
Roy et al., (2008), Islam et al., (2001) and Shimizu et al., (1997) reported that the
hardness of the cooked rice depend on the moisture content of cooked parboiled and
untreated rice. In case of idli, steaming increases the moisture content of idli and it is a
major factor that makes idli made with parboiled rice softer and for the same reason that
red rice has acquired more moisture which affected its texture losing firmness.
3.3.2 Effect of black gram on batter volume
The percentage of increase in batter volume was significant (p< 0.05) at five per cent
level (Table 3.3) for the batter made from parboiled rice and black gram used with husk,
and thou the idli made from the same batter were spongy, the colour was unappealing to
the panel members. The difference in batter volume was not significantly higher with the
batter made from the black gram with husk removed. On the other hand, though, the
percentage of increase in batter volume was low (38.9%) in the batter made from
parboiled rice and black gram dhal with husk removed after soaking,
46
Table 3.2
Effect of rice varieties on the batter volume after fermentation
Varieties of rice
Batter characteristics
Ration
rice
Raw
rice
Broken
rice
Red
rice
211.1±1.55 b
218.6±0.98 c
200.5±0.14 a
238.2±0.14 e
299.7±1.41 d
275.8±2.61 b
248.8±2.61 a
293.7±3.53 c
38.1±1.27 c
42.0±0.70 d
26.2±0.35 b
24.1±0.21 a
23.3±0.28 a
202.0±0.56 e
150.8±0.84 a
181.0±0.70 c
193.0±1.83 d
158.0±1.41 b
Batter volume decreased after
expulsion of expulsion of gas (%)
34.0±1.41 b
49.7±0.00 d
34.4±0.63 b
22.4±1.41 a
46.1±0.0 c
Sensory Rank
I
IV
II
III
V
Initial volume of the batter (cm3)
Final volume of the batter (cm3)
Batter volume increased after
fermentation (%)
Volume of the batter after
expulsion of gas (cm3)
Parboiled
rice
221.6 ±2.05 d
306.1± 3.74 e
mean values in a row with different letters differ significantly p<0.05 by LSD (n=3)
the texture was very spongy and the colour was also appealing making this variation a
better choice in terms of colour and texture on sensory basis. Fig 3.2.b shows the effect of
variation in black gram dhal on batter volume.
3.3.3 Effect of ratios of rice to black gram dhal on batter volume
The percentage of increase in batter volume was high for the ratio 3:3.5 (w/w) of rice to
black gram dhal respectively with 5% significance followed by other ratios such as 3:3,
3:2.5 and so on. When the texture of idli was compared on sensory basis, the idli made
of ratio 3:1 was very spongy compared to idli made of other ratios of rice and black gram
dhal showing that the proportions of compositions of the substrate also have an important
role in the outcome of the product. Table 3.4 and Fig 3.2.c shows the effect of ratios of
ingredients on batter volume. Hence for the further study parboiled rice namely IR 20,
black gram variety namely ADT 3 with husk removed after soaking was used to find the
effect of ingredients and descriptive sensory profile of idli.
47
Table 3.3
Effect of black gram (var. ADT 3) on the batter volume after fermentation
Black gram
BHR
Batter characteristics
Initial volume of the batter (cm3)
BHRAS
BWH
271.4 ±0.14 c
226.1 ±0.84 a
339.2±0.131 b 376.9 ±0.07 c
324.1 ±0.00a
28.6 ±0.00 a
38.9 ±0.07 b
043.3 ±0.07 c
248.7 ±0.35 b
256.3 ±0.42 c
211.1 ±0.07 a
26.7 ±0.00 a
32.0 ±0.00 b
34.9±0.14 c
263.8±0.14 b
Final volume of the batter (cm3)
Batter volume increased after
fermentation (%)
Volume of the batter after
expulsion (cm3)
Batter volume decreased after expulsion
of gas (%)
Sensory Rank
II
I
III
Mean values in a row with different letters differ significantly p<0.05 by LSD (n=3)
BHR-black gram husk removed; BHRAS-black gram husk removed after soaking; BWH -black gram with husk
Table 3.4
Idli batter volume characteristics as affected by parboiled rice
and black gram dhal (without husk)
Rice and black gram ratio (w/w)
Batter
characteristics
Initial volume of the
batter (cm3)
Final volume of the
batter (cm3)
Batter volume
increase after
fermentation (%)
Volume of the batter
after expulsion (cm3)
Batter volume
decrease after
expulsion of gas (%)
Sensory Rank
3:1
3 : 1.5
3:2
3 : 2.5
3:3
3 : 3.5
150.7 ±0.07a
241.2±0.28c
301.5±0.21d
324.1 ±0.14e
339.2 ±1.13f
414.6 ±0.07g
248.7±1.13a
316.6 ±0.84c
422.7 ±0.07d
452.3 ±0.07e
467.4 ±0.00f
603.1 ±0.07g
65.0 ±0.0a
31.3 ±0.07c
40.2 ±0.07d
39.6 ±0.28e
37.8 ±0.35f
45.5 ±3.0.07g
158.3 ±0.21a
173.4 ±0.0b
233.7 ±0.14d
248.7 ±0.28e
256.3 ±0.14f
301.5 ±0.0g
36.3 ±0.28b
45.2 ±0.28d
44.7 ±0.28c
45.0 ±1.41d
44.2 ± 1.13c
50.0±0.14e
I
III
II
IV
V
VI
Mean values in a row with different letters differ significantly p<0.05 by LSD (n=3)
48
Fig.3.2.a Effect of rice varieties on batter volume after fermentation
Fig.3.2.b Effect of type of dhal on batter volume after fermentation
Fig.3.2.c Effect of ratios of rice to black gram dhal on batter volume after
fermentation
49
3.3.4 Response surfaces
Several parameters namely raw material variety, quality, their proximate composition,
raw material composition, particle size, temperature etc., affect the texture of idli but still,
the texture of idli is very unique from the consumer point of view. Among all the
parameters mentioned, fermentation time is one of the key factors which can affect the
texture due to its air production and leavening action. The texture of the cooked idli is a
subject of interest, to judge and optimize the production process of good textured idli
with the selection of the ingredients and the process. The fermentation periods are
slightly different for idli making owing to the difference in raw materials, composition,
process and region (Balasubramanian and Viswanathan, 2007b).
3.3.5 Instrumental Colour measurement of idli
Colour of the idli is one of the most important parameter for the acceptability of the
product. The colour of the idli showed variation based on the ratio of rice and black gram
dhal used. The L*, a*, b* values and graph are shown in Table 3.5 and Fig.3.3.a, b, c
respectively. The L* value which correspond to lightness ranged from 73.40 to 75.99
indicating the difference in the proportion of black gram dhal used. The positive values of
b* indicates yellowness in the idli, which may be due to the use of black gram with husk
for soaking. The chroma (Fig.3.3.d) values are closer to the b* values. The hue angle
value corresponds to whether the object is red, orange, yellow, green, blue, or violet (Ali
et al, 2008). The negative values in the hue angle shows that the product deviates from
the colour adding positive factor to the current study because lightness in the colour of
the idli is an important factor in the view of customer perception. The intensity of chroma
is low for the idli made with the ratio of 3:0.5 and is higher for the idli made from the
ratio 3:2 showing that the ratio of rice and dhal used for idli making has an impact on the
intense of chroma of the idli.
50
Table 3.5
Experimental design: CCRD with actual levels of independent variables for colour
parameters
Instrumental colour parameters
Experimental
design points
L*
a*
b*
Chroma
1
74.03 + 0.07
-0.44+0.021
11.52+ 0.064
11.56
Hue angle
(°)
-87.72
2
74.13 + 0.07
-0.57+0.007
10.60+0.035
10.59
-86.92
3
75.76 + 0.11
-0.25+0.028
12.21+0.085
12.15
-88.92
4
73.99 + 0.06
-0.24+0.021
13.57+0.007
13.56
-89.03
5
75.57 + 0.07
-0.76+0.035
10.01+0.360
9.936
-85.79
6
75.78 + 0.03
-0.02+0.070
15.97+0.085
16.03
-89.89
7
73.40 + 0.11
-0.43+0.014
13.09+0.177
12.96
-88.14
8
74.32 + 0.51
-0.13+0.014
11.88+0.205
11.74
-89.14
9
74.35 + 0.11
-0.40+0.007
10.56+0.163
10.44
-87.81
10*
74.36 + 0.05
-0.43+0.028
10.61+0.361
10.35
-87.73
*Centre point replicated 3 times
51
Fig. 3.3.a. Response surface graph showing relation between independent parameters on L*
Fig. 3.3.b Response surface graph showing relation between independent parameters on a*
52
Fig.3.3.c Response surface graph showing relation between independent parameters on b*
Fig.3.3.d Response surface graph showing relation between independent parameters on Chroma
53
3.3.6 Texture parameters
The experimental values for the response variables of texture analysis are shown in Table
3.6. Figure 3.4.a and Figure 3.4.b shows the typical TPA graph. Hardness of idli is
indicated by the maximum force required to compress the idli and usually represented by
the first peak in the graph. The hardness of the idli (Fig.3.5.a) varies between a minimum
force of 20.58 N to a maximum force of 44.19 N i.e., the minimum force was required to
compress idli of ratio 3:0.72 at 13.42 h fermentation time and the maximum force for the
ratio 3:1.78 at 10.58 h of fermentation time. This variation in the force is due to the
variation in the ratio of the ingredients and fermentation time of the batter. Higher the
force shows that harder is the idli. ANOVA results indicated that the ratio of rice and
black gram dhal used for idli making (in the linear effect) is significant (P< 0.05) to the
hardness of the idli. The co-efficient of regression is given in Table 3.7. The goodness of
fit was high with R2 value =0.942.
Adhesiveness of idli can be defined as the negative force area for the first bite and
represents the work required to overcome the attractive forces between the surface of the
cut piece of idli and the surface of the probe with which the idli comes into contact, i.e.
the total force necessary to pull the compression plunger away from the food. The
negative area in the graph is taken as the adhesiveness. The adhesiveness of the idli varies
between -0.00051N s to -0.05127 N s. If the product is sticky, the adhesiveness will be
higher. Ghasemi et al, (2009) reported that the adhesiveness may be due to the
gelatinization and more fluidity of rice starch structure in the cooked samples. As idli is
adhesive in nature, to optimize the product minimum adhesiveness can be considered. In
the current study since the batter was coarse ground and cooking time was constant the
adhesiveness must be due to the ratio of rice and dhal and the quality of the ingredient.
The minimum adhesiveness is obtained for the idli made of ratio 3:0.5 at 12 h
fermentation time and the maximum adhesiveness is obtained for the ratio 3:0.72 at
10.58h fermentation time. Fig. 3.5.b shows the response surface graph for adhesiveness.
54
Force (N)
Time (sec)
Fig.3.4.a Texture profile of idli made of ratio 3:1.25 at 12 h fermentation time
Force (N)
Time (sec)
Fig.3.4.b Texture profile of idli made of ratio 3:2 at 12 h fermentation time
55
Table 3.6
Experimental design: CCRD with coded and actual levels of independent variables
for TPA
Experi
mental
design
point
1
Dependent variables
Hardness
(N)
Adhesiveness
(N s)
Springiness
Cohesiveness
Chewiness
Resilience
23.73±2.01
-0.0512±0.0045
0.926±0.33
0.876±0.12
1963.61± 16.26
0.595 ± 0.12
2
20.58±1.42
-0.0337±0.0038
0.960±0.28
0.819±0.04
1650.89±14.05
0.562 ± 0.52
3
44.19±2.02
-0.0284±0.0042
0.809±0.41
0.643±0.09
2344.08±21.01
0.340 ± 0.41
4
36.57±2.24
-0.0005±0.0037
0.847±0.20
0.674±0.07
2127.97±16.42
0.404 ± 0.24
5
20.66±3.52
-0.0051±0.0069
0.854±0.32
0.912±0.17
1845.66±18.01
0.654 ± 0.42
6
32.47±4.13
-0.0290±0.0053
0.965±0.48
0.825±0.02
2333.37±14.01
0.511 ± 0.54
7
35.36±1.41
-0.0085±0.0075
0.733±0.24
0.526±0.04
1389.17±13.32
0.285 ± 0.10
8
24.12±2.14
-0.0008±0.0061
0.916±0.42
0.755±0.04
1701.18±12.42
0.483 ± 0.27
9
30.85±0.05
-0.0062±0.0047
0.928±0.31
0.876±0.02
2557.13±11.14
0.579 ± 0.13
10*
30.72±1.28
-0.0057±0.0039
0.913±0.31
0.885±0.06
2532.79±15.05
0.574 ± 0.41
*Centre point replicated 3 times
Springiness is the height that the idli recovers during the time that elapses between the
end of the first bite and the start of the second bite, usually in TPA the first compression
and second compression. The difference between the first peak and the second peak in
the graph is taken as springiness. The springiness of idli depends on the quantity of the
dhal used because the soft spongy texture observed in the leavened steamed idli made
out of black gram is due to presence of two components, namely surface active
protein (globulin) and a polysaccharide (arabinogalactan) in black gram (Susheelamma
and Rao 1974, 1979a, 1979b, 1980). The specialty of black gram in idli preparation is due
to the mucilaginous property which helps in the retention of carbon-dioxide evolved
during fermentation (Nazni and Shalini, 2010). In the current study the springiness
varied from 0.733 to 0.965. The maximum springiness is obtained for the ratio 3:2 at 12 h
56
fermentation time. Hence the result reveals that the quantity of black gram dhal used has
a major role in the springiness of the idli. The response surface graph in 3D is depicted in
Fig.3.5.c showing the relation between rice to black gram dhal ratio and fermentation
time on springiness. From the ANOVA table it is clear that the independent variables in
the linear effect showed a significant influence on the springiness of the idli and the
model showed high goodness of fit (R2 = 0.909) .
Cohesiveness is defined as the ratio of the positive force area during the second compression to
that during the first compression. Cohesiveness may be measured as the rate at which the material
disintegrates under mechanical action. The cohesiveness is minimum (0.526) for the ratio
3:1.25 at 10 h fermentation time and maximum (0.912) for the ratio 3:0.5 at 12 h
fermentation time. Both the independent variables namely rice to black gram dhal ratio
in linear effect and fermentation time in quadratic effect is significant at 5 % level on the
cohesiveness of the idli. The graph in Fig.3.5.d shows an initial increase in the
cohesiveness as the fermentation time increases, but gradually decreases with further
increase in fermentation time.
57
Fig.3.5.a Response surface graph showing relation between independent parameters on hardness
Fig.3.5.b Response surface graph showing relation between independent parameters on adhesiveness
58
Fig.3.5.c Response surface graph showing relation between independent parameters on springiness
Fig.3.5.d Response surface graph showing relation between independent parameters on cohesiveness
59
Fig.3.5.e Response surface graph showing relation between independent parameters on Chewiness
60
Fig.3.5.f Response surface graph showing relation between independent parameters on resilience
61
Table 3.7
Regression co-efficient for dependent TPA parameters
Regression Co-efficient
Independent
variables
Mean/Interaction
1. Rice : Dhal ratio (L)
Rice : Dhal ratio (Q)
2. Fermentation time (L)
Fermentation time (Q)
1L by 2L
R2
Hardness
Springiness Cohesiveness Chewiness Resilience
34.390
-2.254
-5.873
00.00
-4.602
31.132
1.981
-3.517
0.147
-1.645
0.942
-0.182
-0.001
0.525*
-0.021
0.008
0.908
-0.529
-0.049
1.161*
-0.049*
0.042
0.886
661.94
-378.64
4241.93*
-178.51*
63.76
0.85
-0.603
-0.003
0.906*
-0.038*
0.036
0.931
L - Linear effect; Q - Quadratic effect; *=P < 0.05
Table 3.8
Analysis of Variance (ANOVA) for dependent TPA parameters: F values
Dependent parameters
Independent
variables
1L by 2L
Hardness
000.000
241.174*
000.000
063.752
1050.770*
Springiness Cohesiveness Chewiness Resilience
15.644*
0.001
15.404*
7.401
0.138
12.755*
0.228
5.074
11.447*
1.027
11.161*
1.134
0.487
12.628*
0.198
0.524*
96.244
3.823*
2.724*
31.967
L - Linear effect; Q - Quadratic effect; *=P < 0.05
Chewiness is defined as the product of hardness x cohesiveness x springiness and is
therefore influenced by the change of any one of these parameters. Lower the chewiness
softer is the idli. The chewiness of the idli varied between 1389.172 for the ratio 3:1.25
at10 h fermentation time to 2557.135 for the ratio 3:1.25 at 12 h fermentation time. It is
proved by the ANOVA table (Table 3.8) that the ratio of rice to black gram dhal in linear
effect and fermentation time in quadratic effect also have significant impact (P < 0.05)
62
on the chewiness of the idli. As hardness, springiness and cohesiveness show significant
influence because of the independent variable hence the chewiness of the idli will also be
affected by the both independent and dependent variables. The chewiness (Fig.3.5.e) of
the idli varied for the same ratio of idli with difference in fermentation time which relates
the decrease in cohesiveness with further increase in fermentation time.
Resilience is a measurement of how the sample recovers from deformation both in terms
of speed and forces derived. It is taken as the ratio of areas from the first probe reversal
point to the crossing of the x-axis and the area produced from the first compression cycle.
The resilience varies between 0.285 for the ratio 3:1.25 at 10 h fermentation time to 0.654
for the ratio3:0.50 at 12 h fermentation time. Lower resilience value shows that the
product can recover faster from deformation proving the firmness of the product. The
response surface graph in 3D is depicted in Fig.3.5.f showing the relation between rice to
black gram dhal ratio to fermentation time on resilience of the idli. From the ANOVA
table it is evident that the resilience of the idli is influenced significantly by rice to black
gram dhal ratio in linear effect and by fermentation time both linear and quadratic effect.
The closer the value of R2 approaches unity, the better the empirical model fit the actual
data (Nuraliaa et al., 2010). As the R2 value for resilience (0.932) was closer to unity and
the result of resilience fit to the actual data.
Simultaneous optimization was performed on the TPA parameters like hardness,
adhesiveness, springiness, cohesiveness, chewiness and resilience by imposing
desirability constraints. In case of springiness, the softer idli shows high springiness.
Hence the software take into account of the values of independent and dependent values
and finally gives a maximum desirable score and the condition at which the maximum
score can be obtained with some constraints by assigning maximal desirability score as
one and minimal desirability score as zero. Table 3.9 shows the constraints imposed for
good textured idli with the desirable value for both independent and dependant variables.
The maximum desirable score that can be achieved with the desirable value will be
0.8279. On the basis of these calculations good textured idli could be made when 3:1.575
63
(mass) ratio of rice to black gram dhal respectively is fermented for 14 h. The optimum
results were validated by performing the experiment at the optimized ratio and
fermentation time by comparing the observed and the predicted values. The predicted
values are shown in Table 3.9. The predicted values were insignificant with observed
values indicating the appropriateness of the model developed.
Table 3.9
Dependent variables
Independent parameters
Rice : dhal
Fermentation
ratio (w/w)
time (h)
3 : 1.575
14.00
TPA
Overall
Constraints
Predicted
Observed
imposed
values
values
Hardness
Minimum
19.340
019.92 ± 01.03
Adhesiveness
Minimum
-0.030
-0.032 ± 00.01
Springiness
Maximum
0.947
0.930 ± 00.14
Cohesiveness
Minimum
0.773
000.78 ± 00.02
Chewiness
Minimum
1299.7
1286.8 ± 32.20
Resilience
Maximum
0.555
0. 547 ± 00.030
L* (lightness)
Maximum
75.16
075.21 ± 00.58
parameters
and L* values
Desirability
score
0.8279
3.4 CONCLUSION
The optimization results indicated that the optimum ratio of rice to black gram dhal is
3:1.575 (w/w), with 14 h of fermentation time will provide the product with maximum
score for desirable textural parameters.
64
PROCESS OPTIMIZATION OF IDLI USING SENSORY
ATTRIBUTES
4.1 INTRODUCTION
Fermented foods are defined as foods that have been subjected to the action of selected
microorganisms by which a biochemically and organoleptically modified substrate is
produced, resulting in an acceptable product for human consumption (Tamang, 1998).
There are different types of fermented foods, in which a range of different substrates are
metabolized by a variety of microorganisms to yield products with unique and appealing
characteristics (Campbell-Platt, 1994). Fermented foods supply important nutrients,
particularly proteins and amino acids. People become familiar with particular fermented
foods produced in their part of the world, and many of these foods became an integral
part of the local diet (Caplice and Fitzgerald, 1999) and culture, and were regarded as
essential for human consumption and nutrition.
Idli is one such food, which is prepared from low cost staple crop, which helps to
improve health. Its composition includes rice and black gram. In the traditional idli batter,
fermentation takes place due to the microflora present in the raw materials and in the
environment leading to the several changes that has impact on digestibility and nutritional
value bringing about desirable changes (Soni and Sandhu, 1989). The example of idli
illustrates the opportunities of co- fermentation of cereals (rice) and leguminous seeds
(black gram) (Young and Pellet, 1994).
A large proportion of the world cereal production is processed by fermentation prior to
consumption. The enhancement of attractive flavour and texture and the improved shelflife and digestibility as a result of fermentation, are important reasons for fermenting
cereals before consumption (Nout, 2009). Characteristic variables such as water content,
i.e. before and after soaking or fermentation, duration and temperature affect the cereal
fermentation (Hammes and Ganzle, 1998). This sour and spongy type breakfast food
(idli) of India and Sri Lanka constitutes an important group of naturally fermented food
(Ramakrishnan, 1979).
65
Legume contains more of proteins than cereals (Geervani and Theophilus, 1981).
Changes in the nutritive value of proteins as a result of fermentation are particularly
important for cereals and legumes. These sources of protein often are of lower nutritional
quality than animal products, and they tend to be major dietary sources of protein for
people with marginal and sub-marginal protein intake. Therefore, fermentation processes
that consistently improve protein quality or availability of cereal or legumes could have a
positive impact on the diets of people (McFeeters, 1988).
Cereal and legume being the important component of idli, the present study is done to
find out the interrelationship between the substrates during fermentation at different
fermentation time and different ratios of the substrates on the sensory attributes of idli
including desirable and non-desirable parameters with the objectives to select the
ingredients for optimum desirable product characteristics and to identify the optimum
levels of ingredients and fermentation time with respect to sensory attributes using
Response Surface Methodology (RSM).
4.2.1 Materials
In the current study, the most commonly used local variety of rice namely IR 20idli rice
and a protein rich black gram variety Aduthurai 3 (ADT3) which were chosen from the
preliminary study were used.
4.2.2 Preparation of Idli
Before framing the design using CCRD, preliminary trails were conducted to choose the
best suited rice, variation of black gram and ratios of rice and black gram dhal. The
varieties of rice chosen were parboiled rice, raw rice, ration rice, broken rice and red rice.
The variations in black gram dhal were black gram with husk, husk removed and husk
removed after soaking. The different ratios of rice to black gram dhal used were 3:1,
3:1.5, 3:2, 3:2.5, 3:3 and 4:1 respectively.
The difference in batter volume after
fermentation and the texture of idli based on sensory was used to screen the ingredients
and ratios. The result of the preliminary study is discussed to show the reason for
choosing the maximum and minimum values for the independent variables chosen to
66
frame the model. The rice and black gram dhal were mixed at different ratios as per the
CCRD. To carry out the experiment framed using CCRD, the rice and black gram dhal
were soaked for 4 h and ground separately to a coarse consistency and mixed together.
The batter was left overnight (time based on the developed design) for fermentation with
addition of salt. The fermented batter was mixed thoroughly to expel the gas formed due
to the release of carbon-dioxide. The batter was poured in idli mould, and steamed in the
idli steamer for 15 minutes. The cooked idlis were subjected to sensory analysis.
4.2.3 Experimental design
4.2.3.1 Response Surface Methodology
A response surface methodology as explained by Box and Wilson (1951) was conducted
to determine the relative contributions of two predictor variables (ratio of rice to black
gram dhal and fermentation time) to the quality of the idli. RSM is an effective tool for
optimizing complex processes and has been widely applied in the food industry (Wong et
al, 2003; Lee et al, 2006; Sin et al, 2006). A CCRD was constructed using software
package Statistica (1999). Maximum and minimum predictor values were chosen after
carrying out preliminary cooking trails. Five levels of each predictor variable were
incorporated into the design. Table 4.1 shows levels of predictor variables. RSM reduces
the number of experiment trials needed to evaluate multiple parameters and their
interactions. For idli preparation different ratios of rice to black gram dhal and
fermentation time can be optimized using RSM keeping temperature constant (30o C).
4.2.3.2 Optimization of idli using RSM
The procedure was based on the hypothesis that quality attributes (desirable and
undesirable parameters) of idli were functionally related to ratios of rice to black gram
dhal and fermentation time, and attempts were made to fit multiple regression equations
describing the responses. Two coded independent variables in the process were rice to
black gram dhal ratio (X1) and fermentation time (X2). Five levels of each of the
independent variable were chosen for the study; thus, there were 15 combinations,
including the replicates of the centre point that were performed in random order, based on
an experimental CCRD for two factors as shown in Table 3.1 (Chapter 3).
67
4.2.3.3 Sensory analysis of idli
Idli samples were coded and served to ten panel members for analysis. The desirable
parameters included were colour, fluffiness, sponginess and fermented aroma. The
undesirable parameters included were compactness, firmness, stickiness and sourness.
The score card also had an option to give the score for overall quality of the sample. The
attributes selected were shown in Table 3. The panelists evaluated three sets of samples
at separate time. The first set included samples made with ratios 3:0.5 and 3:0.72 of rice
and black gram dhal respectively, the second set included samples made with ratio
3:1.25 and the third set included samples made with ratios of 3:1.78 and 3:2 with the
respective fermentation time as shown in Table 3.1. In each set 3 samples of idli were
placed for evaluation. The panel members were given a fifteen point rating scale to
evaluate the idli. The ranges of the quality of idli were given by panelist by marking a
line on the rating scale. The marking in the rating scale was counted as the score by using
a measurement scale.
4.2.3.4 Quantitative Descriptive Analysis (QDA)
The principle of QDA is based on the ability to train panelists to measure specific
attributes of a product in a reproducible manner to yield a comprehensive quantitative
product description amenable to statistical analysis (Ghosh and Chattopadhyay, 2011).
The panel members were selected and trained as how to evaluate the sample based on the
desirable and undesirable parameters for idli. PCA of the fermented food sample was
performed with the data collected from the panelists after scoring through 150 mm
unstructured scale. The descriptive sensory attributes are shown in Table 4.1.
4.2.4 Statistical analysis of data
The fitness of good was found through R2 or coefficient of determination (Haber and
Runyon 1977). All experimental designs and statistical data were analyzed and response
surface graphs, ANOVA, regression analysis were reported using Statistica (StatSoft,
OK, USA) software.
68
Table 4.1
Sensory attributes used for sensory analysis of Idli
Sensory attribute
Description
Range
The colour of the idli range from pale yellow Low to high
Color
to white
Appearance
Fluffiness
Compactness
Texture
Sponginess
Firmness
Stickiness
Aroma
Fermented
Taste
Sour
Overall quality
The extent of fluffy appearance after cooking
the batter
The lack of porous nature in the idli
The soft feeling obtained by the panelist while
touching the idli
The rigid nature of idli experienced by the
panelist by touch or bite
The adhesiveness of the idli experienced on
touch
Low to high
Low to high
Low to high
Low to high
Low to high
The characteristic aroma after the fermentation
of rice and dhal
Low to high
The range showing the extent of fermentation
on tasting
Low to high
The impact of the product based on other
sensory attributes expressed by the panelist
revealing the acceptability of the product
Low to high
4.2.4.1 Principal Component Analysis (PCA)
Principal component analysis (PCA) is a statistical technique that can be applied to QDA
data to reduce the set of dependent variables (i.e., attributes) to a smaller set of
underlying variables (called factors) based on patterns of correlation among the original
variables (Lawless and Heymann, 1998).
69
The results are discussed under the following heads:
4.3.1 Desirable parameters of idli
4.3.2 Negative drivers of liking
4.3.3 Overall quality of the idli
4.3.1 Desirable parameters of Idli
The desirable and undesirable parameters of idli were evaluated by sensory analysis
because the evaluation of different cooked varieties of idli revealed the wide acceptance
of the conventional product due to its attractive aroma, taste and consistency (Soni and
Sandhu, 1989). The sensory parameters as shown in Table 4.1 were studied for the idli
made from the parboiled rice and black gram dhal with husk removed after soaking with
the ratios framed using CCRD at varying fermentation time. The idli showed large
difference in the sensory parameters in relation to the ratios and timing of fermentation
which is supported by the study done by Ghosh and Chattopadhyay (2011) who reported
that the changes during fermentation affect the physical properties like appearance,
texture, aroma, flavour and overall acceptability and these parameters are vital to assess
the acceptability of the product in the consumer point of view. Table 4.2 shows the score
given by panel members for desirable parameters. Table 4.4 shows the regression coefficient values for the desirable parameters. The R2 values for colour, fluffiness,
sponginess were 0.953, 0.915 and 0.806 respectively which reaches unity favouring the
product.
4.3.1.1 Colour
The colour of the idli varied with the difference in ratios of the ingredients and change in
fermentation time. There was improvement in the colour of idli with increase in
fermentation time. As the ratio of black gram dhal increased there was gradual decrease
in brightness of idli colour due to the black gram dhal content. The R2 value (Table 4.4)
for colour was found to be 0.953. Fig.4.1.a to Fig 4.1.d shows the response surface graphs
for desirable parameters.
70
Table 4.2
Experimental designs and mean scores of desirable sensory attributes
Sensory attributes
Overall quality
Experimental Colour
Fluffiness
design points
1
8.7±0.22
08.2±0.26
2
9.2±0.14
07.4±0.38
3
6.9±0.21
10.1±0.38
4
7.3±0.29
10.7±0.41
5
8.6±0.19
08.0±0.39
6
5.2±0.42
11.4±0.67
7
8.6±0.23
09.6±0.51
8
8.3±0.49
10.2±0.54
9
9.1±0.46
09.7±0.43
10*
8.8±0.44
10.2±0.64
* Centre point repeated 3 times
Sponginess
09.7±0.47
10.6±0.43
11.0±0.83
11.2±0.62
07.6±0.35
12.3±0.51
10.4±0.46
11.3±0.32
11.5±0.58
11.4±0.51
Fermented
aroma
10.2±0.69
11.1±0.62
10.2±0.47
10.9±0.46
09.6±0.43
09.5±0.42
08.3±0.61
11.4±0.61
10.4±0.60
10.7±0.47
09.2±0.34
08.7±0.33
11.4±0.73
11.7±0.43
07.5±0.27
11.6±0.59
09.8±0.41
11.7±0.59
12.1±0.33
11.9±0.49
4.3.1.2 Fluffiness and sponginess of idli
Texture of idli is very critical from consumer point of view, it should be spongy, soft and
fluffy (Ramakrishnan 1979, Radhakrishnamurthy et al., 1961and Desikachar et al.,
1960). The texture of idli is influenced by many variables like raw material, quantity,
soaking time, grinding conditions, fermentation temperature and time and adjuncts on
quality of idli (Desikachar et al., (1960); Radhakrishnamurthy et al., (1961). The
fluffiness and sponginess increased with increase in the ratio of black gram dhal and
fermentation time. The maximum score for fluffiness
71
Fig.4.1.a Response surface graph for colour
Fig.4.1.b Response surface graph for fluffiness
72
Fig.4.1.c Response surface graph for sponginess
Fig.4.1.d Response surface graph for fermented aroma
73
is 11.4 for the idli made of ratio 3:2 at 12 h fermentation time. The R2 value for fluffiness
was 0.915.
The important factor affecting the texture (sponginess, firmness and stickiness) of the
idli is the starch content of the ingredients which is supported by the study done by
Tharanathan and Mahadevamma (2003), that apart from its energy contribution, starch
content is the major factor which governs the texture of idli and as a result, to the
organoleptic properties of food. It was reported that the spongy texture of idli is also due
to the presence of surface active proteins (globulin) that generate a foamy character
resulting in the porous structure to the idli and this porous structure is stabilized even
during steaming process by the presence of viscogenic mucilaginous polysaccharide
called arabinogalactan (Susheelamma and Rao, 1979) proving that this viscosity and
foam stabilizing properties of native polysaccharide is a special functional value of foods
prepared from black gram (Tharanathan et al.,1994). As the starch content of IR20 rice is
79.5 per cent and that of black gram is 52 percent and the protein content of rice and dhal
were 6.46 and 24.16 respectively the texture of the developed idli is found to be good.
4.3.1.3 Fermented aroma
In case of fermented foods the shelf-life, texture, taste and aroma of the final product is
improved because of fermentation. The changes in fermentation depend on the available
nutrients in the starting materials, the unique metabolic abilities of the fermenting
microorganisms and possible interactions among all of these elements (McFeeters, 1987).
The response surface graph reveals that fermented aroma increased with increase in
fermentation time. Mukherjee et al., (1965), Rajalakshmi and Vanaja (1967) have
reported that black gram naturally possess L. mesenteroides, and the gas, acid and
several volatile compounds are formed during fermentation which contribute to a
complex blend of flavours in the products (Chavan and Kadam, 1989).
4.3.2 Negative drivers of liking
The compactness was high for the idli made with ratio 3:1.25, followed by 3:0.5
and
low for the idli made of ratio 3:2 (Table 4.3). This shows that the proportion of the
74
ingredients have a direct impact on the quality of the product. Fig.4.2.a shows that
compactness decreased with increase in fermentation time and with high quantity of
black gram dhal. The firmness (Fig.4.2.b) of the idli was high for the ratio 3:0.5 and it
was noted that firmness decreased with increase in black gram dhal quantity. The
undesirable parameter does not insist that the attributes are not required for the product
but should have moderate effect on the product. The attributes such as compactness,
firmness and stickiness when high are generally disliked by the consumers. Table 4.4
shows the regression co-efficient values for the undesirable parameters
Table 4.3
Experimental designs and mean scores of undesirable sensory attributes
Experimental
Compactness
Firmness
Stickiness
Sourness
1
8.7±0.57
9.2±0.47
11.3±0.46
8.5±0.40
2
8.5±0.46
9.6±0.53
11.1±0.50
9.6±0.58
3
9.2±0.58
5.8±0.42
9.8±0.44
8.9±0.45
4
8.1±0.55
6.2±0.43
9.2±0.41
10.3±0.38
5
9.4±0.74
11.5±0.50
8.3±0.43
8.2±0.37
6
7.8±0.65
5.3±0.35
7.4±0.35
8.1±0.53
7
9.7±0.65
5.8±0.52
7.1±0.35
6.4±0.29
8
8.1±0.53
4.9±0.52
7.1±0.38
9.7±0.42
9
8.5±0.68
5.7±0.44
7.7±0.43
9.1±0.44
10*
8.7±0.51
5.4±0.53
7.4±0.35
9.3±0.49
design points
* centre point repeated 3 times
75
Fig.4.2.a Response surface graph for compactness
Fig.4.2.b Response surface graph for firmness
76
Fig.4.2.c Response surface graph for stickiness
Fig.4.2.d Response surface graph for sourness
77
4.3.2.1 Stickiness of the idli
The physicochemical properties such as moisture content, adhesion and hardness are all
induced by the processing conditions which affect the textural as well as eating quality of
rice. The parboiling treatment given to rice decreases the stickiness (Roy et al., (2004),
Kato et al., (1983), Biswas et al., (1988) and Islam et al., (2001). Rice with low amylose
content is generally soft when cooked, whereas rice with high amylose content has higher
grain hardness (Juliano, 1971). High-amylose rice has more long chains than lowamylose rice (Hizukuri et al., (1989) and Radhika et al., (1993). The more long chains,
the firmer the rice is when cooked and vice-versa (Bhattacharya, 2004). Rice with high
water binding capacity normally yields soft texture cooked rice (Mohapatra and Bal,
2006). In the present study the amylose content was low in the parboiled rice (32%) and
black gram dhal (17%) compared to the amylopectin content (Table 5.1) hence the
stickiness is due to the ratios of rice and black gram dhal and the fermentation time. An
optimum ratio and fermentation time can yield a product with low to minimum stickiness.
Fig 4.2.c shows the response graph for stickiness of idli.
4.3.2.2 Sourness of Idli
Fig.4.2.d show that sourness increased with increase in fermentation time. The sourness
was high (10.3) for the idli made of ratio 3:1.78 at 13.42 h fermentation time. Increase in
fermentation time increases the acidity of the batter due to microbial growth which leads
to increase in sourness of the batter. The R2 value for sourness was found to be 0.884.
78
Table 4.4
Regression co-efficient for sensory parameters
Fermented
aroma
Compactness
Firmness
Stickiness
Sourness
-6.367
-2.919
-18.396
-6.970
16.848
27.570
36.448
-17.399
6.722
-0.551
10.968
3.152
3.359
-18.180
-15.245
0.959
-3.332*
-1.068
-2.465
-0.974
-0.112
5.804
5.762
-0.77
2.019
1.899
3.4125
2.072
-1.357
-1.353
-2.905
3.677
-0.081
-0.101
-0.121
-0.061
0.059
0.055
0.125
-0.132
-0.033
0.465
-0.233
-0.066
-0.299
0.000
-0.132
0.099
0.953
0.915
0.806
0.646
0.941
0.948
0.853
0.884
Colour
Sponginess
Regression co-efficients
Fluffiness
Independent
variables
Mean/Interaction
1. Rice : Dhal ratio
(L)
Rice : Dhal
ratio (Q)
2. Fermentation
time (L)
Fermentation
time (Q)
1L by 2L
R2
L = linear effect; Q = quadratic effect; *= p < 0.005
Table 4.5
Regression co-efficient for overall quality of idli
Independent variables
Regression co-efficients
Mean/Interaction
1L by 2L
R2
L = linear effect; Q = quadratic effect; *= p < 0.005
79
-39.697
10.062
-4.263*
7.0723
-0.299
0.266
0.952
4.3.3 Overall quality of the idli
Table 4.4 shows that the overall quality of the idli in sensory attribute was high (12.1) for
the ratio 3:1.25 at 12 h fermentation time. Fig 4.3 illustrates the surface graph showing
the relation between ratios of rice and black gram dhal and fermentation time on the
overall quality of idli taking into consideration all sensory attributes of idli. From Table
4.5 it was known that the overall quality of the idli was at 5% level of significance with
the change in ratio of rice to dhal ratio in quadratic effect. The R2 value for overall
quality was 0.952.
Fig.4.3 Response surface graph showing the overall quality of the idli
Simultaneous optimization was performed for sensory attributes parameters like colour,
appearance, texture, taste, aroma and overall quality by imposing desirability constraints.
In case of sponginess, the softer idli shows high sponginess. Hence the software finally
gives a maximum desirable score and the condition at which the maximum score can be
80
obtained with some constraints by assigning maximal desirability score as 1 and minimal
desirability score as 0. Table 4.5 shows the constraints imposed for idli with better
sensory attributes with the desirable value for both independent and dependant variables.
The maximum desirable score that can be achieved with the desirable value will be
0.7439. On the basis of these calculations good idli could be made when the rice to black
gram dhal ratio is 3:1.475 (w/w), fermented for 10.2 h. The optimum results were
validated by performing the experiment at the optimized ratio and fermentation time by
comparing the observed and the predicted values. The predicted values are shown in
Table 4.5. The observed and predicted values were not significantly different (P >0.05)
which confirmed the optimization results.
Table 4.5
Independent
Dependent variables
parameters
Overall
Rice : dhal
Fermentation Sensory
Constraints
Predicted
Observed
ratio
time (h)
parameters
imposed
values
values
Colour
Maximum
08.00
08.20±0.64
Fluffiness
Maximum
09.81
09.60±0.72
Sponginess
Maximum
11.01
10.70±1.42
Fermented aroma
Optimum
09.35
08.70±0.30
Compactness
Optimum
09.35
08.80±0.39
Firmness
Minimum
05.26
05.60±0.42
Stickiness
Optimum
07.87
08.10±0.32
Sourness
Optimum
07.60
07.30±0.28
Overall Quality
Maximum
10.89
10.60±0.51
Desirability
score
(w/w)
3 : 1.475
10.2
0.7439
4.3.5 Principal Component Analysis (PCA)
Sensory scores were subjected to PCA analysis. The PCA analysis revealed that PC1 and
PC2 accounted for 78 percent of the total variance in the data matrix. It is clear from the
plot that sensory attributes like sponginess and fluffiness associated with each other
81
strongly on the positive side of the PC1 axis while firmness, compactness, stickiness
were clustered together on the negative side of the PC1 axis. The third cluster is formed
by fermented aroma and sourness on the positive side of PC2 axis. Sample from the
experimental design point 6 was closely associated with desirable sensory attributes like
sponginess and fluffiness followed by sourness and fermented aroma. On the other hand,
design points 5, 1 and 2 were closely correlated with undesirable sensory attributes like
firmness, compactness and stickiness (Fig.4.4). From the PCA biplot it is clear that PCA
Fig.4.4 Principal Component Analysis (PCA) biplot of experimental design points
over sensory attributes of idli (refer Table 3.1 for design points)
is a powerful technique which can discriminate the samples and attributes within the data
matrix, depending upon their inter relationships.
4.3.6 Optimization of texture and sensory attributes
The optimization results indicated that the optimum ratio of rice to black gram dhal is
3:1.575 (w/w), with 14 h of fermentation time will provide the product with maximum
82
score for desirable textural parameters. On sensory analysis followed by RSM analysis of
idli prepared from various combinations of ingredients fermented at different durations
up to 14 h, the rice and dhal combination of 3:1.475 fermented to 10.2 h was found to be
the best accepted product. The results of both texture and sensory were combined to get
an optimized result which gave idli with the best instrumental texture quality as well as
sensory attributes. The impact making attributes of the idli chosen were shown in table
4.6. From the table it was found that the observed values and the predicted values showed
no significant difference (p > 0.05) and the model fits the design.
Table 4.6
Combined analysis of texture and sensory attributes
Independent
parameters
Dependent variables
Sensory /
Texture
Constraints
Imposed
Predicted
Values
Colour
Maximum
10.11
10.60±0.36NS
Sponginess
Stickiness
Sourness
Overall quality
Hardness
Springiness
Maximum
Minimum
Minimum
Maximum
Minimum
Springiness
11.70
07.01
07.42
12.14
25.15
0.892
11.31±0.67 NS
07.40±0.41 NS
07.70±0.19 NS
11.85±0.86 NS
24.83±1.07 NS
00.91±0.06 NS
Resilience
Maximum
NS
= No Significant difference, (p> 0.05)
0.641
00.62±0.03 NS
Rice:dhal
(w/w)
3:1.18
Fermentation
time (h)
12.02
Observed
values
Overall
Desirability
score
3.4 CONCLUSION
On sensory analysis followed by RSM analysis of idli prepared from various
combinations of ingredients fermented at duration up to 14 h, rice and dhal combination
of 3:1.475 fermented to 10.2 h was found to be the best accepted product. On merging
TPA and sensory results (Chapter 3 and 4) an optimized ratio of 3:1.18 and fermentation
time of 12.02 h was evolved.
83
0.714
NUTRITIONAL COMPOSITION OF OPTIMIZED IDLI
5.1 INTRODUCTION
Adequate nutrition through food is necessary for human life. Essential micro and
macronutrients required for growth, metabolic regulations and physiological functions is
provided by foods. The World Health Organization (WHO) recognizes the importance of
breakfast in human diet. Nutritional value of idli has been reported in numerous
publications; however, there are few studies on optimized idli. In this study the
nutritional composition of optimized idli and its ingredients were studied without any
starter cultures. Total carbohydrates and fats were broken down by natural fermentation
process into oligosaccharides and fatty acids. Oligosaccharides have been known for its
prebiotic activity thereby it enhances the probiotic flora in the human gut.
5.2.1 Nutritional composition of the idli
Nutritional composition of the raw ingredients (idli rice - IR 20, black gram variety ADT
3) and optimized idli were determined. Nutrients like starch, amylose, total
carbohydrates, total sugars by Sadasivam and Manickam (2008), protein, fat and crude
fibre (Cunniff, 1995) were estimated.
5.2.2 Determination of fatty acids and alcohols
Fatty acids and alcohols were determined for the unfermented, fermented idli batter and
idli prepared after optimized fermentation time. One gram of the sample was weighed
and suspended into 10 ml of methylene chloride. The extraction of fatty acids and
alcohols was done using the method followed by Agrawal et al., (2000). The extracted
samples were analyzed for fatty acids and alcohols using Liquid Chromatography – Mass
Spectrophotometer (LC-MS) (Thermo Finnigan Surveyor and Thermo LCQ Deca XP
MAX). The experimental column used in LC-M was BDS HYPERSIL C18 and the
volume of sample injected was 10µL.
84
5.2.3 Determination of oligosaccharides
The determination of fatty acids and alcohols were done for the unfermented, fermented
idli batter and idli prepared after optimized fermentation time. The extraction of
oligosaccharides was performed as per Carlsson et al., (1992). The extracted samples
were analyzed using LC-MS (Thermo Finnigan Surveyor and Thermo LCQ Deca XP
MAX). The experimental column used in LC-MS was BDS HYPERSIL C18 and the
volume of sample injected was 10µL.
The results are discussed under the following heads:
5.4.1 Nutritional composition of idli
5.4.2 Fatty acids and alcohols in optimized idli
5.4.3 Disaccharides and oligosaccharides in optimized idli
5.3.1 Nutritional composition of idli
Proximate analysis of idli showed 81.60 g% total carbohydrates, in which starch was 75.0
g % (Amylose - 31.00, Amylopectin - 44.00). Protein content of rice and black gram were
6.46 g %, and 24.16, and optimized idli was found to be 10.21 g%. The fat and crude
fibre concentrations in optimized idli were 00.10 ± 0.01 and 00.28 ± 0.01 g% respectively
(Table 5.1). The carbohydrate level was comparatively high in optimized idli than
protein, fat and crude fibre.
Presence of amylose and amylopectin considerably influences rice starch digestion in the
gastrointestinal tract, influencing faecal excretion and constitution, postprandial blood
glucose response and total cholesterol. Amylose content is normally used to evaluate
some properties of product consumption such as cohesion and softness and also aid the
control of biologically relevant parameters such as blood glucose and triglyceride
concentration (Denardin et al, 2007). Amylose and amylopectin are fermented in the
gastro-intestinal tract by 72% of the human colonic bacteroid strains (Salyers et al,
1977a, b). This study shows that the amylose and amylopectin in idli will help in the
growth of gut microflora supporting the starch polysaccharide as a prebiotic. The good
85
amount of starch in idli is attributed by its raw ingredients. Starch were broken down to
form reducing sugars and oligosaccharides which led to reduction in starch content in idli
compared to the raw ingredients.
Parameters
(g % ± SD)
Table 5.1
Proximate composition of optimized idli
Rice
Black gram
(Variety IR 20)
(Variety ADT3)
Idli
(3:1.18)
Starch
79.50 ± 2.90
52.00 ± 1.21
75.00 ± 2.84
Amylose
32.00 ± 1.60
17.00 ± 0.74
31.00 ± 1.42
Amylopectin
47.50 ± 2.37
35.00 ± 1.62
44.00 ± 2.08
Total carbohydrates
84.00 ± 3.52
65.80 ± 3.02
81.60 ± 3.42
Protein
06.46 ± 0.32
24.16 ± 1.20
10.21 ± 0.50
Fat
00.27 ± 0.13
00.87 ± 0.02
00.10 ± 0.01
Crude fibre
00.20 ± 0.01
00.70 ± 0.03
00.28 ± 0.01
The protein content of idli prepared from combination of different starter culture namely
Pediococcus pentosacens, Enterococcus faecium MTCC 5153, Ent. faecium IB2 with
Candida versatilis were 3.3, 3.2 and 3.2 respectively (Sridevi et al, 2010). In a study
done by Nazni and Shalini (2010) the protein content of the developed idli prepared from
pearl millet was found to be 9.16g and the corresponding standard idli had 7.0 g whereas
the protein content of the optimized idli in the current study was high (10.21 g %) which
is found to be nutritionally rich even without addition of starter culture or millets. The
major contribution of protein to the idli was attributed by the variety of black gram used
when compared to rice.
Decrease in fat content of idli was noted when compared to raw ingredients which may
be due to the degradation of fats into fatty acids during fermentation process by
microorganisms.
86
5.3.2 Fatty acids and alcohols in optimized idli
Fatty acids and alcohols were analyzed in unfermented batter (Fig.5.1), Fermented batter
(Fig.5.2), and idli (Fig.5.3) using LC-MS. Pentacontanoic acid, Hexadecanoic acid,
Pentadecanoic acid, Nonadecanoic acid, Hexacosane, Nonacosane, Nonacosanol, 9Decanal, Decyl decanoate were present in unfermented batter, in which Relative
Abundance (RA) of Pentacontanoic acid was maximum (38 %). In fermented batter
Pentacontanoic
acid,
Decanoic
acid,
Octadecanoic
acid,
Hexadecanoic
acid,
Pentadecanoic acid, Nonadecanoic acid, Hexacosane, Nonacosane, Nonacosanol, 9Decanal, Decyl decanoate, Propanol and 2-Pentanone were present. Fatty acids and
alcohol profile of idli was similar to fermented batter but Pentadecanoic acid and
Nonacosanol were absent in final idli. The relative abundance (RA) of Fatty acids and
alcohols in unfermented batter, fermented batter and idli is given in Table 5.2.
Table 5.2
List of fatty acids and alcohols
Unfermented batter
Acids
RA
(%)
Pentacontanoic acid 38
Hexadecanoic acid 11
Pentadecanoic acid 21
Nonadecanoic acid 19
Hexacosane
11
Nonacosane
12
Nonacosanol
18
9-Decanal
6
Decyl decanoate
8
-
Fermented batter
Acids
RA
(%)
Pentacontanoic acid 23
Decanoic acid
12
Octadecanoic acid
10
Hexadecanoic acid 100
Pentadecanoic acid 8
Nonadecanoic acid 19
Hexacosane
11
Nonacosane
19
Nonacosanol
26
9-Decanal
8
Decyl decanoate
20
Propanol
10
2-Pentanone
10
87
Idli
Acids
Decanoic acid
Octadecanoic acid
Hexadecanoic acid
Pentadecanoic acid
Nonadecanoic acid
Hexacosane
Nonacosane
9-Decanal
Decyl decanoate
Propanol
2-Pentanone
RA
(%)
58
20
100
19
10
19
12
20
10
10
Fig. 5.1 Typical chromatogram and mass spectra showing fatty acids in
unfermented batter
88
Fig. 5.2 Typical chromatogram and mass spectra showing fatty acids and alcohols in
fermented batter
89
Fig. 5.3 Typical chromatogram and mass spectra showing fatty acids in optimized
idli
Mahadevappa and Raina (1978), reported that among the five varieties of legumes
namely cow pea, field gram, red gram, horse gram and black gram, the major saturated
fatty acid was palmitic acid which constitutes 15-25% in the neutral lipids, 20-40%
in the glycolipids, and 26-30% in the phospholipids. It was also found that in the
90
two black gram
(P. mungo T9 and Khargan 3) varieties, the fatty acid profile is
characterized by exceptionally high levels of linolenic acid in all lipid classes: 60%
in the neutral lipids, 50% in the glycolipids, and 33% in the phospholipids,
accompanied in all categories by about 10% of linoleic acid and 15-20% of oleic acid.
High levels of the two unsaturated essential fatty acids could have nutritional
implications. In the present study, Hexadecanoic acid which is known as palmitic acid
was found to be 100% in relative abundance in idli when compared to unfermented
batter. Octadecanoic acid which is called as stearic acid was absent in unfermented batter
but appear after fermentation in fermented batter and as well with a relative abundance of
10 – 20 %. Stearic acid is a long chain fatty acid consisting of 18 carbon atoms without
double bonds. Ahrens et al. (1957), Keys et al., (1965), Hegsted et al. (1965 and 1993),
and Yu et al (1995) found that saturated fatty acids with chain lengths more than 10
carbon atoms generally raised blood cholesterol levels whereas polyunsaturated fatty
acids – PUFA (primarily linoleic acid) lowered blood cholesterol levels; and
monounsaturated fatty acids had either a neutral or mildly hypo-cholesterolemic effect on
blood cholesterol levels. These investigators also found that the stearic acid, a saturated
fatty acid did not increase blood total or low density lipoprotein (LDL) cholesterol levels
(bad cholesterol). Study by Yu et al. (1995), reported that adults were fed controlled,
whole-food diets, to evaluate the effect of stearic acid on blood lipid levels revealed that
stearic acid, showed no effect on LDL, and high density lipoprotein (HDL). A metaanalysis done by Mensink (2003) consisting of 35 controlled trials showed that when
stearic acid replaced carbohydrate in the diet it had a neutral effect on blood lipid and
lipoprotein levels.
In foods like chocolate and lean red meats it was reported that their in-take does not
increase the risk of cardiovascular disease because of high levels of stearic acid part in
their saturated fatty acid. Similarly lean red meat (beef) and lean white meat (chicken,
fish) are equally effective in reducing total and LDL cholesterol in adults fed lipidlowering diets (Ding et al., 2006, Davidson et al., 1999, Hunninghake et al., 2000, Scott
et al., 1994 and Melanson et al., 2003) may be attributed in part to red meat‘s higher
content of stearic acid compared to that in chicken or fish. The flavour characteristic
known to be prevalent in idli batter appear from the combination of raw materials (rice
91
and black gram) and microbial starter cultures (natural inoculum) which helps in
fermentation. Buttery et al., (1988) reported that ketones composed of ethanone,
pentanone and butanones are found in rice. In the present study as the fermentation
begins, it leads to the formation of 2-pentanone which is found to appear in fermented
batter and not in unfermented batter. Polyunsaturated fatty acids play a primary role in
the development of ketones and this source has been attributed to black gram dhal
(Steinkraus et al. 1967). Microorganisms during fermentation lead to acidification of the
raw material producing organic acids, mainly lactic acid. Also, their production of acetic
acid, ethanol, aroma compounds, bacteriocin, exopolysaccharides and several enzymes
improve shelf life, microbial safety, texture, and play a role increasing the pleasant
sensory profile of the end product (Leroy and De Vuyst 2004). This finding supports the
current study that the fermentation of idli batter helped in the formation of acetic acid,
Dodecanol, Propanol and phenyl ethyl alcohol that improved the texture and sensory
profile of the optimized idli.
5.4.3 Disaccharides and oligosaccharides in optimized idli
Table 5.3 shows the list of disaccharides and oligosaccharides present in unfermented
batter, fermented batter and in idli. Trehalose, maltose, melezitose, maltotriose,
maltotetrose, maltopentose and maltohexose that were absent in unfermented batter
appeared in fermented batter and idli which is due to the breakdown of polysaccharides
into oligosaccharides and disaccharides during the process of fermentation. Typical
chromatograms and mass spectra showing disaccharides and oligosaccharides for
unfermented batter (Fig.5.4), fermented batter (Fig.5.5) and idli (Fig.5.6) are shown
below.
Crittenden & Playne, (1996) proved in their study that oligosaccharides in doses of <15
g/day increase bifidobacteria numbers in the colon. Authors suggest that a daily intake of
10 g of galacto-oligosaccharides is sufficient to cause a bifidogenic effect. Seeds of
legumes, lentils, and mustard are rich source of raffinose oligosaccharides (Johansen et
al., 1996; Sánchez-Mata et al., 1998). Hate et al (1983) reported that clinical data of
Japanese researchers suggest a regular addition of fructooligosaccharides to diet lowers
92
total cholesterol and triglyceride in blood which is proved by Losada and Olleros (2002)
that fructooligosaccharides increase production of volatile fatty acids by the action of gut
microflora on oligosaccharides have effect on cholesterol in the liver.
Table 5.3
List of Disaccharides and Oligosaccharides
Compound
Saccharose
Trehalose
Maltose
Melezitose
Raffinose
Maltotriose
Stachyose
Maltotetrose
Verbascose
Maltopentose
Maltohexose
Non-Fermented batter
+
+
+
+
-
Fermented batter
+
+
+
+
+
+
+
+
+
+
+
Idli
+
+
+
+
+
+
+
+
+
+
-
Cereal grains consist of at least two types of oligosaccharides such as galactosyl
derivatives and fructosyl derivatives. Galactosyl derivatives include sucrose, stachyose
and raffinose and fructosyl derivatives include sucrose and fructo-oligosaccharides
(Henry and Saini, 1989). Table 5.3 shows that the presence of raffinose in unfermented,
fermented batter and idli was attributed by the raw ingredient black gram dhal. This
finding was supported by the Voragen (1998) who indicated that raffinose and stachyose
in soya bean and other pulses and leguminous seeds are examples of naturally occurring
non-digestible oligosaccharides.
93
Fig. 5.4 Typical chromatogram and mass spectra showing Disaccharides and
oligosaccharides in unfermented batter
94
oligosaccharides in fermented batter
95
oligosaccharides in optimized idli
96
Results showed that there was reduction in the abundance of disaccharides and
oligosaccharides namely saccharose, trehalose, melezitose, maltotriose, maltopentose and
raffinose in idli compared to fermented batter. Onigbinde and Akinyele (1983) also had
proposed that decrease in the levels of raffinose, stachyose, and verbascose during
cooking might be attributed to heat hydrolysis to disaccharides and monosaccharides or
to the formation of other compounds. Basha (1992) showed that the rate of
oligosaccharide breakdown increased with increasing acid concentration. This rope with
the current study which shows that steaming of fermented batter to get idli may decrease
the level of abundance of oligosaccharides in idli when compared to fermented batter.
The acidic medium is caused by the action of microorganisms during fermentation
process (Sridevi et al, 2010).
The isomers of trehalose showed an increase in bifidobacteria population similar to
fructooligosaccharides giving high prebiotic index in the in-vitro fermentation (Sanz et
al, 2005). Carbohydrates can also act as prebiotics for selected bacterial group within the
gut reducing the pathogen population by increasing immunity (Gibson, 1998). Presence
of disaccharides and oligosaccharides in idli will possibly help to improve the health by
improving the gut microflora.
5.4 CONCLUSION
The fatty acids namely Decanoic acid, Octadecanoic acid and Hexadecanoic acid were of
high relative abundance in idli compared to unfermented batter. Regarding the
oligosaccharide profile, the sugars namely trehalose, maltose, melezitose, maltotriose,
maltotetrose and maltopentose were formed during fermentation. The process of
fermentation has led to the increase in nutrient content of the idli.
97
IMPROVING THE SHELF LIFE OF READY TO COOK IDLI
BATTER
6.1 INTRODUCTION
Ready to cook idli batter which was optimized to give desired quality parameters in the
earlier chapters (3 and 4) could only be successfully commercialized as a viable product
only its shelf-life is increased substantially from approximately one day to at least several
days.Idli, unlike other ready to cook food products rapidly gets over fermented as it is a
live actively growing bacterial medium, although common spoilage problems are less.
This is a challenge in terms of its preservation and shelf life. Ready to cook idli batter is
already available in the market as a packaged product. For several years prepared by local
vendors as a perishable product sold on daily basis or stored and sold under refrigerated
conditions. For the first time we have hypothesized that modification of gaseous
environment in the packaged form could regulate the fermentation flora in the medium
leading to longer shelf life. Second part of the hypothesis is that regulating the gaseous
exchange with the external environment could support the modified atmosphere in the
packaged product to work long.
MAP helps to preserve foods by reducing microbial spoilage thereby increasing
storability. MAP is done to maintain the freshness of the produce when purchased.
Success of MAP packaged foods depends on the quality of raw material and hygienic
practices followed during preparation and packaging, the gas mixture used for packaging
and the packaging material. The gases used in MAP are CO2, O2 and N2. Researchers
have successfully applied MAP to perishable foods like fruits, vegetables, flesh foods and
certain dairy products.
6.2.1 Materials
1. Modified Atmosphere Packaging machine (VAC Star-Swiss)
2. Head space analyzer (Dansensor, Italy)
3. Gas mixer (Dansensor, Italy)
4. Packaging materials- LDPE, PP, HM
98
6.2.2 Methods
6.2.2.1 Preparation of batter
The selected IR20 idli rice and ADT3 variety black gram dhal were taken in the
optimized ratio of 3:1.18. The quantity required varied for each set of experiment.
Ingredients were soaked and ground and were immediately packaged in the packaging
materials Fig.6.1 shows the research design of this chapter.
6.2.2.2 Selection of packaging materials
Three packaging materials namely low density poly ethylene (LDPE), Poly propylene
(PP), High Molecular (HM) were used for packing the idli batter. The thickness of the
packaging materials is given in Table 6.1. Dimension of the packaging material was 6×10
inches. 100g of the batter was filled in each pack.
Table 6.1
Thickness of packaging materials
Packaging materials
Thickness (mm)
LDPE
0.009
LDPE
0.012
LDPE
0.014
PP
0.003
PP
0.005
HM
0.002
HM
0.006
6.2.2.3 MAP of idli batter
MAP was done using Modified Atmosphere Packaging machine (VAC Star-Swiss). MAP
machine consists of three gas cylinders viz., oxygen, carbon dioxide and nitrogen, each of
which is connected to a gas mixer provided with a separate cylinder where the required
combination of gases can be set and stored temporarily in buffer tank. Gas analyzer is
another important component of the MAP machine which helps to check if the gas is
mixed in the expected combination and the same is used for determining gas in the head
99
space of the packaged sample as and when required. Plate 6.1 shows the MAP machine.
The batter in each packet was packaged with modified air of required combination.
Plate 6.1 Modified Atmosphere Packaging (MAP) machine
6.2.3
Respiration dynamics of the idli batter
Respiration dynamics was carried out to find the percentage of oxygen utilized and
percentage of carbon dioxide released during fermentation of batter. Respirometer as
designed by Bosco (1997) was used. Plate 6.2 shows the picture of respiration dynamics
done for the idli batter using respirometer connected to gas analyzer. The respirometer
consists of a glass jar without spout of capacity 250 mL resting on a flat MS plate and
covered with another MS plate. Both the plates had hole at each corner through which
bolt were inserted. By tightening the nuts of these bolts, the glass jar could be closed with
the cover plate. The joint between the glass jar and the cover plate was made air tight by
providing a neoprene rubber gasket. The cover plate had one hole at the centre where the
gas septum had been fixed for sampling the gas. Gas tightness of Respirometer was
verified by the respirometer ability to hold 50 mm vacuum for 15 minutes as done by
100
Brown (1922). For the experiment, 100g of fresh ground batter was taken in 250 ml
beaker. Atmospheric air was maintained inside the beaker. The Respirometer was
connected to the gas analyzer to monitor the change in gas environment every half an
hour. The experiment was conducted for 12.02h (optimized fermentation time).
Plate 6.2 Respirometer connected to gas analyzer
101
6.2.4 EXPERIMENT I
Experiment I was carried out to find suitable packaging material for idli batter. The study
was designed for 3 days (Sridevi et al., 2010), hence a total of 126 packets (7 packaging
materials × 6 gas treatments × 3 days) were required. Based on the optimized ratio, batter
was prepared. In each packaging material 100g of batter was packaged with gas treatment
of
0% CO2, 5% CO2, 10% CO2, 15% CO2 and vacuum packaging and sealed. The
package in which no treatment was done served as the control. The packaged batters were
stored in room temperature (30 C). Each day 42 packets representing 7 packaging
material and 5 gas treatments were analyzed for the gas mixture using gas analyzer.
6.2.5
EXPERIMENT II
In experiment II, the idli batter was packaged and sealed with 12 gas treatments and three
controls were used. Batter placed in vessel served as control I, batter packaged and sealed
with ordinary sealing machine served as control II, the batter packaged in packaging
material but not sealed served as control III. The gas treatments are shown in Table 6.2.
The study was done using selected 3 packaging material. Hence a total of 215 samples
were required. The MA packaged batter and control packs were stored in room
temperature (30 C). Each day 43 samples stored in three different packaging materials
with 12 gas treatments including 3 controls were analyzed for the gas concentrations (%)
followed by sensory analysis of the idli cooked from packaged batter. Overall quality
based on the colour, texture, fermented aroma of the idli was assessed.
102
Table 6.2
Gas treatment used in experiment II
Treatments
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
6.2.6
CO2 (%)
00
05
10
15
00
05
10
15
00
05
10
15
Control I
Control II
Control III
O2 (%)
N2 (%)
15.0
85.0
15.0
80.0
15.0
75.0
15.0
70.0
17.5
82.5
17.5
77.5
17.5
72.5
17.5
67.5
20.0
80.0
20.0
75.0
20.0
70.0
20.0
65.0
Batter in vessel
Batter in unsealed package
Batter packaged with ambient air
EXPERIMENT III
In experiment III, selected one packaging material and 8 gas treatments and control were
used. Gas treatments are shown in Table 6.3. In this experiment the batter packages were
left to check the extended shelf life of the batter.
Table 6.3
Gas treatment used in experiment III
Treatments
CO2 (%)
O2 (%)
N2 (%)
1
0
15.0
85.0
2
0
12.5
87.5
3
0
10.0
90.0
4
0
07.5
92.5
5
5
15.0
80.0
6
5
12.5
82.5
7
5
10.0
85.0
8
5
07.5
87.5
103
6.3
RESULTS AND DISCUSSION
6.3.1
Respiration dynamics
Respiration is usually the measure oxygen uptake or the production of CO2, producing
heat and water vapour. The results of respiration dynamics give an idea to flush the
package with required atmosphere so that steady state conditions are reached
immediately (Zagory and Kader, 1988). The O2 consumption and CO2 evolution differ
based on the composition such as fatty acids, sugars or organic acids of the respiring
sample (Dilley et al, 1990 and Platenius, 1942).
Fig.6.1 Change in gas concentration during its fermentation time
Fig.6.1 showed the O2% consumed and CO2 % evolved during the fermentation of idli
batter. As fermentation began, the O2% declined from 21% to 13.9%. The increase in
CO2% began after 2 h and gradually increased from 0% to 12.9%. The results showed
that 100g of idli batter consumed 7.1% O2 and produced 12.9% of carbon dioxide. Based
on the results of respiration dynamics MAP of ready to cook idli batter was done with
different gas treatments and the results are discussed below.
104
6.3.2
EXPERIMENT I
Table 6.4 shows the changes in atmosphere of the packaged idli batter. In treatment1
where the package was packed with lack of oxygen and carbon dioxide (0% O2 and 0%
CO2) showed a gradual increase in CO2 over three days of storage. This increase in CO2
is a result of fermentation of idli batter inside the package. The O2 (%) remained zero in
the LDPE packages but HM and PP showed increase in O2, which meant that the
packaging material permitted permeability of air. Fig.6.2 shows the changes in gas
mixture among different packaging material over three days of storage.
In treatment 2 where the package was flushed with 5% CO2, it was found that there was
increase in CO2 % from 5% to a maximum of 14.4 % CO2 in LDPE packaging material
during the second day of storage. In the packaging material PP (0.003mm) there was
decrease in CO2 to 0.8% on the third day. The O2 concentration in PP (0.003mm) and
HM (0.002 mm) were not maintained inside the package. Fig.6.3 shows the changes in
gas mixture among different packaging material over three days of storage.
In treatment 3 where the 10% CO2 was flushed in the package, LDPE of higher thickness
showed fermentation effect on the batter with increase in CO2, whereas in LDPE of lower
thickness, PP and HM the change in gas system was not gradual.
In treatment 4, the package was flushed with 15% CO2, increased in LDPE of medium
and lower thickness and the concentration of CO2 varied in other packaging materials
over the storage period. Fig.6.4 shows the changes in gas mixture among different
packaging materials.
Treatment 5 was vacuum packaging and over the storage period the gas concentrations
were not analyzed as the pressure was too low to detect the gas in the head space.
Treatment 6 was control with lack of gas treatments but package had ambient gas
composition. The atmospheric air in package favoured fermentation of batter which led to
decrease in O2 concentration.
From the results of experiment I it was inferred that gas permeability differed with
different packaging material. The O2 permeability was less than that of CO2 in LDPE of
varying thickness helped to maintain the atmosphere within the package compared to
other packaging materials. This result is supported by the study done by Bosco (1997),
105
who reported that, the O2 permeability of LDPE and PP was less than that of CO2 and the
variation in permeability of a film is due to the fact that the film were purchased from
the retail market at different places and might be from different batches of production
Table 6.4
Change in gas mixture over storage period
Packaging
material
LDPE (0.14 mm)
Treatment 1
Treatment 2
Treatment 3
Treatment 4
Treatment 5
Treatment 6
LDPE (0.12 mm)
Treatment 1
Treatment 2
Treatment 3
Treatment 4
Treatment 5
Treatment 6
LDPE (0.009 mm)
Treatment 1
Treatment 2
Treatment 3
Treatment 4
Treatment 5
Treatment 6
PP (Thin)
Treatment 1
Treatment 2
Treatment 3
Treatment 4
Treatment 5
Treatment 6
Day 1
CO2 (%) O2 (%)
Day 2
Day 3
CO2 (%) O2 (%) CO2 (%) O2 (%)
0.114
5.6
10.5
14.2
0
0
0.009
0.1
0.008
21
11
6.3
13.8
12.4
2.1
0
1.07
0
0
14.8
11.1
10.9
15.5
8.9
4.2
0.017
0.009
0
19.4
7.15
0.114
5.6
10.5
14.2
0
0
0.009
0.1
0.008
21
10.3
10.6
12.6
14.9
4.1
0
5.4
0
0.011
7.56
10
10.8
15.4
14.9
3.1
0.265
5.2
0.09
0
12.6
0.114
5.6
10.5
14.2
0
0
0.009
0.1
0.008
21
10.3
14.4
12.9
10.5
3.3
0
0.484
0
0.095
8.91
12.8
15
5.2
12.6
0.3
0
1.2
0.036
0.015
19.8
0.114
5.6
10.5
14.2
0
0
0.009
0.1
0.008
21
9.9
13.5
11.3
13.4
0
0.112
19.5
19.1
0.908
20.3
12.7
0.8
1.2
15.2
0.3
0.112
19.5
19.1
0.908
19.8
106
PP (Thick)
Treatment 1
Treatment 2
Treatment 3
Treatment 4
Treatment 5
Treatment 6
HM (Thin)
Treatment 1
Treatment 2
Treatment 3
Treatment 4
Treatment 5
Treatment 6
HM (Thick)
Treatment 1
Treatment 2
Treatment 3
Treatment 4
Treatment 5
Treatment 6
0.114
5.6
10.5
14.2
0
0
0.009
0.1
0.008
21
5.1
10.8
14.3
15.2
8.2
0.549
0.001
0.032
0.001
6.2
10.2
15
15
14.6
0
0.539
0.001
0
0.149
0.3
0.114
5.6
10.5
14.2
0
0
0.009
0.1
0.008
21
3.4
2.8
0
0.7
0.4
3.18
0.04
20.4
19.6
19.5
11.6
5.9
0.8
1
0
9.5
19.2
18.9
19.3
20.3
0.114
5.6
10.5
14.2
0
0
0.009
0.1
0.008
21
3.4
6
0.5
0.1
0.3
4
0.5
19.3
20.3
19.7
19.7
7.3
2.8
4.1
0.1
9.7
0.6
17.1
9.39
20.2
At low oxygen levels, anaerobic respiration can occur, resulting in production of
substances that contribute to off-flavours and odours (Lee et al, 1995 and Zagory 1995).
Hence the idli prepared from the batter were subjected to sensory analysis only for its
texture. Idli made from the batter packaged in different packaging material scored very
low rating which might be due to deterioration of the batter.
The experiment was
repeated with combination of both O2 and CO2 in LDPE of varying thickness.
107
Fig. 6.2.a Treatment 1 (0% CO2) showing change in CO2 level (%) among different
packaging material
Fig. 6.2.b Treatment 1 (0% CO2) showing change in O2 level (%) among different
packaging material
108
packaging material
packaging material
109
packaging material
packaging material
110
6.3.3
Experiment II
Table 6.5 to 6.8 shows the changes in gas concentrations in the packaging materials with
idli batter. The 12 treatments showed the rate of fermentation of batter in different MAP
system in different packaging material at room temperature (30 C). Treatment 1 to 12
showed increase in concentration of CO2% within 48h of packaging which is due to the
evolution of CO2 during fermentation of the batter.
Treatment 1 showed gradual increase in fermentation rate of the batter for five days of
storage period compared to other treatments. The percentage of O2 decreased gradually
from 15% to 1.75% (LDPE 0.12mm). Fig.6.5 showed the changes in concentration of
CO2 and O2 among LDPE of varying thickness. The batter in treatments 5 to 12 which
were flushed with 17.5% to 20% O2 led to complete consumption of O2 in LDPE of 0.014
and 0.012mm by the batter supporting fermentation and also whey separation. During
storage of batter whey separation persisted (Nisha et al, 2005). The reason stated by
Nisha et al was that idli batter is foam in which gas molecules are entrapped in a solidliquid phase. The batter collapse and whey separates when the high energy interface takes
place during air-water interface. Fig.6.5 to 6.14 shows the depletion of O2 curve. LDPE
of 0.009mm did not support the MAP system showing variations in gas concentration
over the period of batter storage.
The gas combination was not analyzed for control I and II as they were exposed to the
atmospheric air. The O2 (%) concentration in control III was zero per cent and that of
CO2 decreased from 11% (2nd day) to 5.7 % (5th day) during storage. It showed that the
oxygen was consumed for the fermentation process and the carbon dioxide evolved was
decreased due to its permeability through the packaging material.
111
Table 6.5
Treatments
1
2
3
4
5
6
7
8
9
10
11
12
Day 0
CO2 (%) O2 (%)
00
15.0
05
15.0
10
15.0
15
15.0
00
17.5
05
17.5
10
17.5
15
17.5
00
20.0
05
20.0
10
20.0
15
20.0
Gas combinations
Day 1
Day 2
Day 3
CO2 (%) O2 (%) CO2 (%) O2 (%) CO2 (%) O2 (%)
08.1
9.40
10.4
02.2
00
0.00
07.0
7.31
03.3
13.6
6.8
0.44
05.4
11.2
02.6
14.7
1.2
18.8
02.5
16.7
05.4
0.707
4.4
4.09
04.3
6.38
08.0
0.087
6.9
0.94
09.6
0.72
04.0
04.59
00
0.00
12.2
0.23
13.7
0.077
6.1
0.40
10.1
1.26
05.3
0.730
6.1
0.19
22.1
0.001
08.1
0.024
6.3
0.16
16.7
0.12
08.1
0.045
4.9
0.09
16.5
4.11
10.3
0.205
8.5
1.13
14.9
3.03
07.1
02.06
7.5
0.14
112
Day 4
CO2 (%) O2 (%)
6.2
1.500
5.9
0.453
8.3
2.740
4.7
0.424
4.3
2.660
5.9
0.085
6.6
0.000
4.6
0.172
5.4
0.076
4.9
0.134
2.8
9.460
6.0
0.361
Day 5
CO2 (%) O2 (%)
6.2
0.000
6.2
7.000
6.0
3.100
5.5
0.600
9.6
0.850
6.4
0.002
6.1
0.800
5.7
0.70
5.8
0.137
5.0
0.142
7.1
0.873
5.8
0.197
Table 6.6
Treatments
1
2
3
4
5
6
7
8
9
10
11
12
Day 0
CO2 (%) O2 (%)
00
15.0
05
15.0
10
15.0
15
15.0
00
17.5
05
17.5
10
17.5
15
17.5
00
20.0
05
20.0
10
20.0
15
20.0
Gas combinations
Day 1
Day 2
Day 3
CO2 (%) O2 (%) CO2 (%) O2 (%) CO2 (%) O2 (%)
07.2
07.05
09.3
3.524
10.1
2.650
07.6
04.72
03.0
9.780
05.4
0.601
11.0
07.85
09.6
0.759
08.2
0.534
05.7
12.40
05.5
0.486
04.8
0.291
12.4
00.54
08.3
0.206
00.4
20.10
15.4
02.10
08.7
1.450
08.1
0.622
06.9
03.79
06.2
0.246
08.8
8.470
16.2
0.268
08.8
0.071
07.2
0.453
19.3
0.161
05.7
0.164
05.8
0.017
05.3
14.50
15.7
0.000
07.0
0.000
05.0
13.60
08.0
5.150
04.3
0.238
15.2
03.14
06.6
8.910
09.3
0.152
113
Day 4
CO2 (%)
O2 (%)
11.7
1.95
05.7
0.71
08.2
3.16
03.9
0.26
08.4
0.113
07.2
0.044
05.4
0.197
04.9
0.194
05.4
0.367
05.1
0.161
07.5
0.252
04.9
0.185
Day 5
CO2 (%) O2 (%)
11.9
01.75
04.0
00.29
05.5
00.09
00.0
00.00
05.8
11.10
00.2
20.80
04.9
00.22
09.2
01.42
05.8
00.03
07.2
00.36
06.6
00.37
09.1
00.24
Table 6.7
Treatments
1
2
3
4
5
6
7
8
9
10
11
12
Day 0
CO2 (%) O2 (%)
00
15.0
05
15.0
10
15.0
15
15.0
00
17.5
05
17.5
10
17.5
15
17.5
00
20.0
05
20.0
10
20.0
15
20.0
Day 1
CO2 (%) O2 (%)
10.2
09.45
01.1
18.90
08.3
05.49
16.5
00.43
17.3
00.24
18.7
00.31
07.8
05.29
13.5
00.69
10.9
01.26
11.2
06.71
17.9
00.12
10.0
00.27
Gas combinations
Day 2
Day 3
CO2 (%) O2 (%) CO2 (%) O2 (%)
09.0
0.08
1.7
18.1
08.9
2.54
4.9
0.12
04.0
1.87
6.0
6.61
05.4
9.69
0.2
20.5
09.3
0.16
1.0
20.2
06.2
0.42
7.8
1.21
04.5
1.96
8.9
1.03
08.9
0.06
5.3
11.3
11.3
0.91
4.6
0.19
12.5
1.22
5.9
0.17
09.5
0.29
10.4
0.65
05.4
0.77
3.8
2.37
114
Day 4
CO2 (%)
O2 (%)
7.2
08.69
8.9
00.79
4.8
00.34
9.3
03.35
5.4
00.20
2.4
18.40
5.4
11.90
14
01.61
10.8
00.04
7.3
00.52
8.0
00.04
11.2
02.19
Day 5
CO2 (%) O2 (%)
05.6
00.16
09.3
00.12
07.7
00.09
04.6
014.3
06.6
00.29
08.5
01.79
06.1
06.20
10.0
00.39
05.7
00.09
10.5
01.65
04.4
13.20
07.7
00.09
Storage period
Fig 6.5.a Treatment 1 (0% CO2 and 15% O2) showing percentage of CO2 (%)
Storage period
Fig.6.5. b Treatment 1 (0% CO2 and 15% O2) showing percentage of O2 (%)
115
Storage period
Fig 6.6.a Treatment 2 (5% CO2 and 15% O2) showing percentage of CO2 (%)
Storage period
Fig 6.6.b Treatment 2 (5% CO2 and 15% O2) showing percentage of O2 (%)
116
Storage period
Fig. 6.7.a Treatment 3 (10% CO2 and 15% O2) showing percentage of CO2 (%)
Storage period
Fig. 6.7.b Treatment 3 (10% CO2 and 15% O2) showing percentage of O2 (%)
117
Storage period
Storage period
118
Storage period
Fig. 6.9.a Treatment 5 (0% CO2 and 17.5% O2) showing percentage of C O2 (%)
Storage period
Fig. 6.9.b Treatment 5 (0% CO2 and 17.5% O2) showing percentage of O2 (%)
119
Storage period
Fig. 6.10.a Treatment 8 (15% CO2 and 17.5% O2) showing percentage of CO2 (%)
Storage period
Fig. 6.10.b Treatment 8 (15% CO2 and 17.5% O2) showing percentage of O2 (%)
120
Storage period
Storage period
121
Storage period
Storage period
122
Storage period
Storage period
123
Storage period
Storage period
124
Table 6.8
(0.014mm)
Treatments
1
2
3
4
5
6
7
8
9
10
11
12
Control I
Control II
Control III
Day 1
Sensory scores
Day 2
Day 3
Day 4
Day 5
8.1
7.5
5.2
9.3
8.5
8.5
8.1
6.4
8.8
8.3
8.1
8.0
6.7
8.0
8.2
9.1
8.5
8.5
8.3
7.3
7.7
5.7
7.2
7.7
8.2
8.0
8.0
5.2
7.4
1
5.2
1
5.4
1
1
1
1
1
3.5
3.7
3.0
-
7.1
5.1
1
1
7.2
6.2
1
1
6.1
7.3
4.3
7.3
-
1
5.1
1
1
7.7
7.0
1
1
1
7.1
1
1
-
Table 6.9
(0.012mm)
Treatments
1
2
3
4
5
6
7
8
9
10
11
12
Control I
Control II
Control III
Day 1
Sensory scores
Day 2
Day 3
Day 4
Day 5
3.0
4.0
6.2
6.3
6.1
6.3
8.2
6.3
8.2
8.5
8.5
8.2
6.8
7.4
7.5
7.3
7.1
7.4
7.2
6.5
8.3
8.5
7.2
6.3
7.3
4.2
6.0
4.7
6.2
9.0
5.0
6.2
5.1
5.7
7.3
5.1
6.3
6.2
6.1
6.6
5.3
-
8.2
5.4
7.9
6.4
5.2
8.9
6.8
7.7
6.4
5.9
5.4
4.0
-
Table 6.10
125
8.3
5.6
6.9
6.8
6.8
8.5
6.4
5.9
5.2
6.0
6.7
5.2
-
Sensory scores of the product made from batter packaged in LDPE (0.009mm)
Treatments
1
2
3
4
5
6
7
8
9
10
11
12
Control I
Control II
Control III
Day 1
Sensory scores
Day 2
Day 3
Day 4
Day 5
7.5
8.1
5.4
8.2
8.0
8.3
8.5
8.2
5.3
7.8
5.2
5.0
6.8
7.3
7.1
6.4
5.3
5.9
4.5
6.1
6.2
6.3
8.1
8.3
7.4
8.1
6.3
5.0
6.8
3.8
3.7
2.7
4.3
2.7
1.6
2.7
1.8
3.2
2.9
3.2
1.6
-
1.5
1.5
1.7
1.3
1.4
4.0
6.2
1.7
6.5
5.7
5.3
5.2
-
1.6
1.8
1.9
1.4
1.7
1.6
1.5
1.8
5.2
4.3
2.5
2.0
-
Table 6.8 to 6.10 showed the sensory scores of idli made from batter treated with
different gas combinations in different packaging material. The sensory score represented
the overall quality of the idli. Sensory scores of idli prepared on the second day of storage
showed high acceptability which might be due to the reason that the batter had been
fermented and gave idli of high acceptability. The scores ranged from 4.2 to 9.1
(treatment 11 in LDPE -0.012 mm and treatment 1 in LDPE- 0.014 mm). The sensory
scores on the third, fourth and fifth day showed poor acceptability of the product except
for treatments in LDPE 0.012 which increased during the storage period. The highest
score obtained was 9 for treatment 1 (Fig.6.15) followed by 7.3 for treatment 6 (Fig.6.16)
on the fifth day of storage.
The batter in control I was discarded due to over fermentation after 24 h followed by
fungal contamination. The batter in control samples were evaluated for sensory for a
maximum two days whereas the batter in packages was used for idli preparation and
evaluated for sensory on all storage days in spite of its poor scores. Thou there was whey
separation which made idli harder, the packaged batter used for idli preparation when
compared to control.
126
The results of experiment II discussed from gas concentration in different treatments and
different packaging material showed that LDPE of medium thickness (0.012 mm) may
support to maintain the MAP system inside the packaged atmosphere when compared to
LDPE of other thickness . The gas treatment of 0% CO2 with 15% O2 and 5% CO2 with
15% O2 were found to extend the shelf-life of the batter compared to other gas treated
samples and control samples.
Fig. 6.15 Comparison of sensory scores of idli made from
treatment 1 (0% CO2 and 15% O2)
127
Fig. 6.16 Comparison of sensory scores of idli made from
treatment 6 (5% CO2 and 15% O2)
6.3.4
Experiment III
The observations of experiment III are shown in Table 6.11. It was found that the
percentage of carbon dioxide increased in all treatments except for 8 which showed very
low CO2% and low O2%. The consumption of O2 percentage was high showing complete
decrease of O2 percentage in the package. During fermentation of batter oxygen is
consumed and when the fall is below 1% may lead to anaerobic respiration (Lee et al,
1995 and Zagory 1995). In the table 6.11, on the seventh day of storage, all treatments
showed poor concentrations of O2% except treatment 1 which showed 1.4% O2. Initial
pH of the fresh batter 6.41 and change in pH of the batter in different treatments over
seven days of storage showed decrease in pH. The change in pH is associated with the
development of Streptococcus faecalis producing both lactic acid, which lowers the pH
and carbon dioxide which leavens the batter (Balasubramanian and Viswanathan, 2007a).
The control sample was discarded on the third day due to fungal contamination.
128
Table 6.11
Comparison of gas mixture on the first day and seventh day of storage
Treatments
Day 0
Day 7
CO2 (%)
O2 (%)
CO
(%)
O
2
2 (%)
pH
pH
1
0
15.0
6.41
11.3
1.4
4.32
2
0
12.5
6.41
12.6
0.4
4.10
3
0
10.0
6.41
10.3
0.7
4.31
4
0
07.5
6.41
12.4
0.9
4.31
5
5
15.0
6.41
12.9
0.0
4.28
6
5
12.5
6.41
14.6
0.5
4.00
7
5
10.0
6.41
13.1
0.6
4.10
8
5
07.5
6.41
3.4
0.0
4.22
Control
Ambient atmosphere
6.41
-
Table 6.12
TPA parameters of idli made from MAP batter
Treatments
Hardness (N)
1
17.020±4.68
2
Springiness
Cohesiveness
-07.257±5.58
0.874±0.07
0.671±0.02
1024.01±333.8
0.386±0.02
21.455±1.22
-09.924±5.52
0.814±0.05
0.622±0.04
1106.65±95.3
0.337±0.04
3
21.705±2.72
-09.907±3.39
0.829±0.02
0.645±0.00
1181.11±116.7
0.364±0.02
4
19.500±2.63
-15.461±13.27
0.852±0.11
0.663±0.09
1112.96±155.5S
0.369±0.06
5
27.315±2.55
-10.757±05.48
0.870±0.01
0.686±0.07
1045.67±35.7
0.383±0.03
6
28.955±0.45
-12.552±02.95
0.843±0.04
0.624±0.05
1229.40±131.8
0.356±0.05
7
28.571±0.21
-09.417±06.58
0.858±0.05
0.666±0.03
1339.51±34.7
0.377±0.03
8
27.152±0.52
-14.790±00.09
0.904±0.06
0.720±0.00
1761.41±9.2
0.336±0.01
Control
-
Adhesiveness (N s)
-
-
-
Chewiness
-
The texture of idli prepared from the treated batter was analyzed and Table 6.12 shows
the TPA values of the idli. The hardness of the idli ranged between a minimum of 17.02
N (treatment 1) to a maximum hardness of 28.95 N (treatment 6). The hardness of idli
was low for the treatments 1 to 4 when compared to other treatments which were due to
the whey separation seen in treatment 5 to 8. The maximum springiness was found for the
idli made from the treatment 8 followed by idli made from treatment 1 and 5.
129
Resilience
-
Cohesiveness was maximum for the idli made from the treatment 8 followed by 2 and 6.
Resilience was maximum for the idli made of treatment 1 (0.386) followed by treatment
7 (0.377). The texture profile values when compared with the optimized value show that
idli made from treatments 1 to 4 were soft compared to idli made from other treatments.
Treatments
Table 6.13
Overall quality of idli
CO2 (%)
O2 (%)
Overall quality
1
0
15
8.6 ± 0.84
2
0
12.5
7.0 ± 0.00
3
0
10
7.0 ± 1.34
4
0
7.5
7.4 ± 2.4
5
5
15
5.8 ± 0.49
6
5
12.5
6.4 ± 0.49
7
5
10
6.6 ± 0.70
8
Control
5
7.5
Batter packaged with
ambient air
4.0 ± 5.65
-
Table 6.13 shows the scores of overall quality of the idli made from MAP treated batter.
The maximum score was 8.6 (Treatment 1) followed by 7.4 (Treatment 4). The overall
comparison of the sensory scores show that treatments 1 (8.6), 2 (7.0) and 4 (7.4) had
high scores respectively when compared to treatments 5 to 8. Studies done by Day
(1996) and Zagory and Kader, (1988) showed that by modifying the atmospheric oxygen
level, particularly by lowering the oxygen concentration inside the package, the
respiration rate of the packaged produce is slowed down and the sensory shelf life can be
extended which cannot be applied to the current study. Idli batter being a live product
which produces 12.9% of CO2 during fermentation requires oxygen in order to maintain
aerobic condition and to sustain the aroma of the fermented batter and the final product
when the batter is steamed. Hence the study done by Song et al., (1998) Mattheis and
130
Fellman, (2000) supports the current study who reported that production of aromatic
compounds of many fruit, including apple, banana, pear, peaches, strawberries and
others, can be adversely affected by low O2 and elevated CO2 i.e., synthesis of aroma
compounds are generally suppressed. As mentioned in chapter 4, fermented aroma is one
the criteria of idli which will be considered for sensory analysis and hence the treatment
with high O2% may support the sensory quality of MAP packaged idli. The result of table
6.13 show that idli made from batter packaged with 0% to 5% CO2 and O2 ranging from
7.5% to 15% gave better results compared to all other treatments applied in the above
experiments.
6.4 CONCLUSION
From this study it can be concluded that ready to cook idli batter packaged in medium
thickness (0.012 mm) LDPE flushed with 0% CO2 and 7.5 to 15% O2 could increase the
shelf-life up to seven fold increase without compromising the sensory qualities at room
temperature.
131
EXECUTIVE SUMMARY AND CONCLUSION
Major objective of this work was to extend the shelf life of ready to cook idli batter using
modified atmosphere packaging and the sub-objectives were
1.
To understand the presently followed practices for the preparation of idli.
2.
To optimize the process of preparation of the product with respect to
ingredient ratios and fermentation time.
3.
To improve the shelf-life of ready to cook idli batter by optimized process.
First chapter was conceptualized with an objective to understand the presently followed
practices for the preparation of idli. A survey based study was conducted in eight regions
through an oral interview scheduled which covered a sample size of 300. The results of
the survey indicated that at house hold level 68% of the selected population preferred
parboiled rice. Only 34 per cent used decorticated black gram whereas 49 per cent used
black gram with husk removed after soaking. Majority (99.7%) of the respondents used
3:1 ratio of rice and black gram dhal for preparing idli. Fermentation time varied between
5 h to 12 h at the selected households. Majority (71.3%) of them fermented the idli batter
for 11 to 12 h and 73% stored the idli batter in refrigerated condition. The results were
similar to the practices reported in literature such as variety of rice, type of black gram,
ratio of ingredients used for idli making, fermentation time and shelf –life of the batter.
Chapter 3 was aimed to optimize the process of preparation of the product with respect to
ingredient ratios and fermentation time based on the instrumental texture profile of the
idli using response surface methodology. Before framing the design using Central
Composite Rotatable Design, preliminary trails were conducted to choose the best suited
rice, variation of black gram and ratios of rice and black gram dhal. Five differently
processed rice and ADT3 variety dhal were used for the preliminary study. Results of the
preliminary study showed that IR20 parboiled rice and ADT3 variety black gram dhal
with husk removed after soaking were best suited for idli making. The rice and black
gram dhal were mixed at different ratios as per the CCRD. The independent parameters
for this study were ratios of rice to black gram dhal and fermentation time. The dependent
132
parameters were the texture attributes namely hardness, adhesiveness, springiness,
cohesiveness, chewiness and resilience.
The results obtained were subjected to regression analysis and ANOVA. Based on the
results certain constraints were imposed on the dependent parameters to get idli with
better texture properties and the predicted values were obtained for the dependent
parameters.
From the study it was concluded that the optimum ratio of rice to black gram dhal is
3:1.575 with an optimum fermentation time of 14 h where a desirable value of 0.8279
will be obtained for the product. The results were validated by preparing idli at the
optimized conditions. The results prove the designed model to be valid.
Chapter 4 focused on the objective to identify the optimum ratios of ingredients and
fermentation time with respect to sensory attributes using Response Surface Methodology
(RSM). The desirable sensory attributes were colour, fluffiness, sponginess and
fermented aroma. The undesirable parameters were compactness, stickiness, firmness and
sourness. The idli were prepared according to the framed design. The semi-trained panel
members evaluated the idli using a 15mm rating scale. Data were analyzed using RSM
and constraints were imposed on the experimental results as in Chapter 3. On sensory
analysis followed by RSM analysis of idli prepared from various combinations of
ingredients fermented at different duration up to 14 h, rice and dhal combination of
3:1.475 fermented to 10.2 h was found to be the best accepted product.
Principal Component Analysis was done to find the interrelationship between the sensory
attributes of the idli. The PCA analysis revealed that PC1 and PC2 accounted for 78% of
the total variance in the data matrix. It was clear that sensory attributes like sponginess
and fluffiness associated with each other strongly on the positive side of the PC1 axis
while firmness, compactness, stickiness were clustered together on the negative side of
the PC1 axis. The third cluster is formed by fermented aroma and sourness on the
positive side of PC2 axis. Sample from the experimental design point 6 was closely
associated with desirable sensory attributes like sponginess and fluffiness followed by
sourness and fermented aroma. On the other hand, design points 5, 1 and 2 were closely
correlated with undesirable sensory attributes like firmness, compactness and stickiness.
133
The texture and sensory data were analyzed together by imposing constraints on the
principal parameters of idli resulting in an optimized ratio of 3:1.18 with a fermentation
time of 12.02 h.
Chapter 5 dealt with the chemical components of nutritional importance in the optimized
product. The final product was low in fat indicating the break down into fatty acids
during fermentation. Analysis of fatty acid profile and oligosaccharide profile was done
using LCMS. The fatty acids namely Decanoic acid, Octadecanoic acid and
Hexadecanoic acid were of high relative abundance in idli compared to unfermented
batter. Regarding the oligosaccharide profile, the sugars namely trehalose, maltose,
melezitose, maltotriose, maltotetrose and maltopentose were formed during fermentation.
Results showed that the process of fermentation has led to the increase in nutrient content
of the idli.
Chapter 6 aimed to improve the shelf-life of the batter using modified atmosphere
packaging. Respiration dynamics was studied out to find the percentage of oxygen
utilized and percentage of carbon dioxide released during fermentation of batter. Three
packaging materials namely low density poly ethylene (LDPE), Poly propylene (PP),
High Molecular (HM) of varying thickness were used for packing the idli batter. Twenty
three gas combinations were used for MAP. The MAP packaged batter was stored at
30C and analyzed for gas mixture followed by texture and sensory analysis of the
product during the storage period. The results of the respiration dynamics of the idli
batter showed that the batter consumed 7% of O2 and evolved 12.6- 13% CO2 at 12.02 h
fermentation time. From this study it can be concluded that RTC idli batter packaged in
medium thickness LDPE flushed with 0% CO2 and 7.5 to 15% O2 could increase the
shelf-life up to seven fold increase without compromising the sensory qualities at 30C.
134
Practical implications / Recommendations
Based on the results and interpretations of this work following recommendations can be
made to further improve the commercial prospects of ready to cook idli batter.
1. A detailed survey on the consumer perception and acceptance as well as problems
associated with the currently available packaged ready to cook idli batter should
be done to estimate the true potential of commercial ready to cook idli batter.
2. Detailed study on shelf-life of Modified atmosphere packaged batter under
refrigerated conditions should be done.
3. In-depth instrumental analysis of flavour and aroma compounds needs to be done.
135
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153
Annexure-I
ORAL INTERVIEW SCHEDULE
1. Name
:
2. Age
:
3. Sex
:
4. Address
:
a) Male
b) Female
5. Educational qualification:
7. Occupation:
8. Monthly income:
9. Marital status:
a) single
10. Type of family: a) nuclear
b) married
b) joint
11. Native place:
12. At what time do you take breakfast?
a) 7-8 am b) 8-9 am) 9-10 am
13. Do you skip breakfast?
a) Yes
b) No
14. If yes, reasons to skip breakfast?
15. What are the food items you prefer for breakfast?
a) Idly b) Dosai c) Poori d) Chapatti e) Oats
16. What are the breakfast items you usually prepare?
17. How often do you consume idly?
a) Weekly b) Daily c) Monthly
18. How long years are you consuming Idli?
19. Do you like Idli?
a)Yes b) No
154
20. Do you prepare Idli at home?
a) Yes b) No
21. If no, from where do you get Idli?
a)Hotel b) Idli stall
22. Do you buy as Idli batter?
a) Yes b) No
23. Which is convenient to buy?
a) Batter
b) Idli
24. How often do you buy Idli batter?
a) Daily b) Weekly c) Monthly
25. Where do you buy Idli batter?
a) Household b) Departmental store
26. What is the brand name?
27. Do you buy Idli batter in the same or different shop?
28. Do you store the purchased batter or buy only when necessary?
29. Do you enquire about the ingredients and quality of the Idli batter while buying?
a) Yes b) No
30. Do you like the quality of that Idli batter?
a) Yes b) No
31. Does the Idli prepared from such batter taste good?
a) Yes b) No
32. Do you prepare dosa from such batter?
a) Yes b) No
33. Do you check the manufacturing date while buying?
a) Yes b) No
155
34. Does the purchased Idli batter contain required amount of salt?
a)Yes b) No
35. What will be consistency of the purchased Idli batter?
a) Thick b) thin c) Normal
36. What will be the texture of the purchased Idli batter?
a) Smooth b) coarse
37. Why do you prefer to buy Idli batter rather than preparing at home?
a)Convenient b)Taste good c) Time saving d) Any other please specify
38. Do you buy Idli batter as cups measurement or in packet?
a) Cup
b) Packet
39. What is the cost of one cup of batter?
40. What is the cost of one packet of batter?
41. How many Idli can be made from one cup or one packet of batter?
42. Do you think it is hygienic to buy as batter?
a)Yes b) No
43. What will be the colour of Idli prepared from purchased batter?
44. Do you grind Idli batter at home?
a) Yes b) No
45. How often do you grind for Idli?
a) Once in a week
b) Twice a week
c) Daily
d) Once in a month
46. In what proportion you take rice and dhal?
a) 3:1 b) 3:1.5 c) 3:2
156
47. Which variety of rice and dhal you use?
48. Do you always use same variety of rice and dhal?
a) Yes b) No
49. Have you used with some other varieties of rice and dhal? Why?
a) Yes
b) No
50. How many times do you wash the rice and dhal before soaking?
51. What is the quantity of water you use to soak the rice and dhal?
52. For how many hours do you soak?
53. When do you usually grind the rice and dhal?
a) Morning b) Afternoon c) Evening d) Night
54. Do you mix any additional ingredient along with dhal?
a) Yes b) No
55. What are the additional ingredients you use?
a) Rice flakes b) fenugreek c) Any other please specify
56. If yes, what is the proportion of the additional ingredient?
57. What is the purpose of the additional ingredient?
58. Which ingredient do you grind first?
a) Rice b) Dhal
59. Which equipment you use to grind?
a) Grinder
b) Mixie
c) Hand pound
60. Which do you think is the best equipment for grinding Idli batter?
61. Does the dhal that you use increase in volume while grinding?
a) Yes
b) No
157
62. If it does not increase in volume what will be the impact on Idli?
63. How long will you grind rice and dhal?
64. Do you grind them together or separately?
65. Till what consistency do you grind rice and dhal?
a)Thick b)Thin c) Normal
66. What will be the texture of mixed batter?
a)Coarse b) smooth
67. What will be the consistency of Idli batter after mixing?
68. Do you add salt before or after fermentation?
69. How long do you leave the batter for fermentation?
70. Do you add curd or yeast to favor fermentation?
a) Yes
b) No
71. What kind of vessel do you prefer to ferment the batter?
a) Plastic b) Ever silver c) Mud pot d) Any other
72. Do you mix the batter with hand or ladle?
73. Whom do you prefer to mix batter and so why?
74. Does your batter get fermented overnight?
a) Yes b) No
75. Does the batter volume increase after fermentation?
a) Yes b) No
76. Do you get any respective flavour from fermented batter?
a) Yes b) No
77. Usually what will be the colour of your Idli?
a) White
c) Light yellow
158
78. If the batter does not ferment do you get better Idli?
a) Yes b) No
79. How do you control fermentation to increase the shelf life of the batter?
80. Do you prepare dosa from the same batter?
a) Yes b) No
81. If the acidity increases, do you use that batter to prepare Idli?
a) Yes b) No
82. Which utensil do you prefer to prepare Idli?
a) Idli cooker b) Idli vessel
83. How many minutes do you steam?
84. How will you check if the Idli is cooked or not?
85. Do you give Idli as lunch for school going children?
a) Yes b) No
86. How many times do you take Idli per day when the batter is available?
87. Do you prepare Idli regularly or only when some is sick at home?
a) Yes b) No
88. Do you give Idli for the sick people?
a) Yes b) No
89. Why do you prefer Idli during convalescent period?
90. Is your consumption of Idli increased when compared to the past years?
91. What do you think is the main reason?
92. Why don‘t go buy Idli as batter to prepare Idli?
93. If it is a hygienically prepared, healthy batter will you be ready to buy?
a) Yes b) No
159
Annexure-II
Sensory analysis score card for Idli
Name: ___________
Date: ___________
-Taste the given samples and indicate intensity of perceived attributes by marking on the line at
appropriate place.
-Cleanse your palate with water in between samples.
COLOUR
---- | ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ---- | ---Low
High
APPEARANCE
Fluffiness
---- | ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ---- | ---Low
High
Compactness
---- | ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ---- | ---Low
High
TEXTURE
Sponginess
---- | ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ---- | ---Low
High
Firmness
---- | ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ---- | ---Low
High
Stickiness
---- | ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ---- | ---Low
High
AROMA
Fermented
---- | ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ---- | ---Low
High
160
TASTE
Sour
---- | ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ---- | ---Low
High
OVERALL QUALITY
---- | ----- . ----- . ----- . ----- . ----- . ----- . --|-- . ----- . ----- . ----- . ----- . ----- . ---- | ---Very Poor
Fair
Very Good
Comments:
Signature:
161
List of Publications
1. Transition in the Preparation and Consumption of Idli among the People of
Puducherry, Durgadevi, M and Prathapkumar H. Shetty, Indian Journal of
Nutrition and Dietetics (In Press).
2. Effect of Ingredients on Texture Profile of Fermented Food- Idli, Durgadevi, M
and Prathapkumar H. Shetty APCBEES Procedia Journal (In Press).
3. Effect of Ingredients on Sensory Profile of Idli using Response Surface
Methodology, Durgadevi, M and Prathapkumar H. Shetty, Journal of Food
Science and Technology (Under revision).
List of Proceedings
1. Presented a poster entitled ―Perception and consumption pattern of idli among the
people of Puducherry‖ in the International conference on Traditional foods (Dec
1-3, 2010) conducted at Pondicherry University.
2. Presented a poster entitled ―Process optimization of the texture and sensory
attributes of idli using response surface methodology (RSM)‖ in the National
conference on Agro Food Processing Technologies (Nov 3-4, 2011) conducted at
Pondicherry University.
3. Presented a poster entitled ―Effect on ingredients on the texture and sensory
attributes of an Indian fermented food, Idli‖ in the Fifth International Conference
on Fermented foods, health status and social well being: Challenges and
Opportunities (Dec 15-16, 2011) at CFTRI, Mysore.
162

MODIFIED ATMOSPHERE PACKAGING OF READY TO COOK IDLI

Transcription

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