Hydrocolloids Structure and Properties

Hydrocolloids Structure and Properties
The building blocks for structure
Timothy J. Foster
18 month Meeting, Unilever Vlaardingen, March 29‐31, 2010
Manufactured Materials
Foams
Emulsions
Natural Materials
This shows a layer of onion (Allium) cells.
Targeting Hydrocolloids For Specific Applications:
Approach
Material
Properties
Ingredient
Microstructure
Process
Oral
Response
Packaging
Distribution
Storage
Process
(mouth/gut)
Process
Controlling Structure
(taste, flavour, texture)
DECONSTRUCTION
CONSTRUCTION
Ingredient
Controlled oral response
Designed texture/
appearance/
behaviour
Interaction with body mucins
(associative and new phase separation)
Microstructure changes as a
function of enzyme action
Ingredient
(enzymes)
In body functionality
Reconstruction
Impact on / of starting
materials / structures
Re-assembly of structures as a function of
digestion breakdown products and body secretions
(micelle formation, delivery vehicles)
Single Biopolymer systems
Hydrocolloid Structure/ Function
Need:
-
define biopolymer primary structure
-
understand the nature of the interaction / rates
-
understand the solvent effects
-
measure material properties
-
test influence of primary structure variation and
changes in environmental conditions on
mechanical properties.
Hydrocolloid Materials & Function
Gelling
Pectin
Alginate
Starch
Agar
Carrageenan
Gellan
Gelatin
Milk proteins
Egg proteins
Thickening
Pectin
Alginate
Starch
LBG
Guar gum
Xanthan
Emulsification
•
•
•
•
•
•
Gelatin
Milk proteins
Egg proteins
Soya proteins
Pea proteins
Gum Arabic
Hydrocolloid Materials & Function
Emulsification
Thickening
Gelling
• Gum Arabic
• Pectin
• Pectin
• Propylene glycol Alginate
• Alginate
• Alginate
• Sugarbeet pectin
• Starch
• Starch
• OSA starch
• Agar
• LBG
• Carrageenan • Guar Gum
• Xanthan
• Gellan
• lamda Carrageenan
• Curdlan
• Celluosics
• Cellulosics
• Succinoglycan • Beta Glucan
• Scleroglucan
• Mixtures
Protein structure
A protein is a polymer of amino acids
• Primary structure
– amino acid sequence
• Secondary structure
– spatial structure through interactions between amino acids that are near along the amino acid chain (e.g. α‐helix, β‐sheet)
• Tertiary structure
– spatial structure through interactions between amino acids that are far away along the amino acid chain
• Quaternary structure
– association of different amino acid sequences (e.g. haemoglobin)
Protein
Protein Structure:
Backbone
random coils
beta sheet
alpha helix
Charge
Determines Properties:
Interfacial properties
foams
emulsions
Gel forming
Structure of globular proteins
β‐lactoglobulin (β‐lg)
dimeric form at neutral pH
α‐lactalbumin (α‐la)
bovine serum albumin
(BSA)
Color caption:
α-Helix
β-Sheets
Cysteines
Turbid Gels
Carbohydrates…what do they look like?
• How do they differ?
H
CH2OH
6CH
2OH
O
5
H
H
OH
4
OH
H
Glucose
OH
1
OH
3
H
H
2
OH
H
OH
CH2OH
H
OH
H
H
Galactose
O
OH
OH
H
CH2OH
H
O
OH
CH2OH
O
OH
OH H
H
Mannose
OH
H
H
O
OH
OH
H
H
OH
H
OH
H
H
OH
H
H
OH
OH
Gulose
H
Sugar Interactions
• Glycosidic linkage
H
H
CH2OH
OH
OH
O
OH
OH
H
H
OH
OH
OH
O
OH
H
H
CH2OH
H
H
H
H
CH2OH
OH
OH
O
OH
H
H
+H20
OH
OH
O
O
OH
H
CH2OH
H
H
H
Polysaccharide
Structure /
Functionality
Sources of hydrocolloids
Botanical
starch, cellulose, galactomannans, pectin, gum arabic, karaya, tragacanth, beta glucan
Seaweeds
agar, carrageenan, alginate
Animal
gelatin, chitosan, hyaluronan
Bacterial
xanthan, gellan, dextran
Structural Features • Linear
– (homo- and hetero-)
• Linear – branched
– (homo- and hetero-)
• Branched
– (homo- and hetero-)
• Ordered helices
– (single, double, triple)
Polysaccharide thickeners
• The most efficient thickeners are;
• Linear,
• High molecular mass
• Charged
Alternative Hydrocolloids
Cashew Gum
Gum Karaya
Okra Gum
Caramania Gum (almond)
Cassava Starch
Chia Gum
Cocoyam Flour
Cowpea protein /starch
Detarium microcarpum polysaccharide
Flaxseed Gum
Hsian-tsao Leaf gum (Taiwan/China)
Lichenin
Lupin Protein
Moussul Gum (Plum)
Portulaca Oleracea
Psyllium gum
Rice Flour
Sassa Gum
Soy Bean Polysaccharide
Tara Gum
Tropical Starches
Yellow Mustard Gum
Aloe Gum
Gum Ghatti
Oat gum
Gum Tragacanth
Cassia Gum
Cherry Gum
Chickpea Flour
Combretum Gum
Cyclodextrins
Fenugreek gum
Gleditsia macracantha
Lesquerella Gum
Lucaena galactomannan
Manna Gum
Opuntia Ficus
Prickly Pear
Quince seed gum
Rye bran (beta d glucan / arabinoxylan)
Sorghum flour
Tamarind gum
Tremella Aurantia Poysaccharide
Yam
Typical Solution Properties
Hydrocolloid Structure/ Function
Need:
-
define biopolymer primary structure
-
understand the nature of the interaction / rates
-
understand the solvent effects
-
measure material properties
-
test influence of primary structure variation and
changes in environmental conditions on
mechanical properties.
Galactomannans
• Galactomannans include guar gum, locust bean gum (carob), fenugreek, cassia and tara gum.
• They have a high molecular mass (~ in excess of 500kDa) and consist of β 1,4 linked mannose residues with galactose units linked α 1,6.
• The M:G ratio is ~2:1 for guar, 3:1 for tara and 4:1 for locust bean gum.
• The galactose units are not evenly distributed along the chain.
LBG Structure / Functionality
• LBG can be fractionated wrt temperature of solubility.
• Cold soluble LBG (30C) has a higher G/ M than that soluble at high temperature (80C).
• LBG soluble at 80C has a galactose content of 16.6%, and gels at ambient temperature.
• Cold soluble LBG does NOT gel even when frozen & thawed.
• Not necessary for ice to be present, a non‐ionic interaction, dependent on solvent quality.
- The distribution of galactose sidechains is all important in dictating functionality.
Gelation Rate
1.0
1.3
[LBG]
Gelation Rate
2.0
20
50
65
Sucrose (%)
Gelation Rate
-8
10
Temperature
- Self association is kinetically controlled as a function of the number of available
junction zones
Properties of Hydrocolloids
Load (KN).
0.06
Typical polymer gel
properties
0.05
0.04
3%Gelatin
0.03
Dependent on Solvent quality,
Polymer fine structure, Junction
zone type / quantity
3%Agar
0.02
0.01
0
0
10
20
30
40
Strain (%).
50
60
70
Effect of Shear during Gelation: Fluid gel Particle formation
• Composite properties are dependent upon the number and size of particles produced.
• This in turn is dependent upon the polymer used, the polymer
concentration and the shear field.
Storage Modulus of Agar Gels Formed
Quiescently and Under Shear
G'(Pa)
1,000,000
Quiescent
Measurement Temperature = 10C
Sheared
100,000
10,000
1,000
SPREADABLE
SPOONABLE
100
POURABLE
10
0
1
2
3
[Agar]
4
5
• Due to the colloidal nature of their properties they provide
better dilution characteristics than their molecular
counterparts.
Viscosity (Pas)
1
Xanthan
0.1
0.01
0.1
Fluid gel
Level of Dilution
1
Mixed Biopolymers
Aqueous-based two-phase systems
Microstructure
o/w emulsion
water-in-water emulsion
25 μm
Phase Separation phenomena is used in the creation of food
products.
1.2
1.0
75% LBG / 25% PR
50% LBG / 50% PR
25% LBG / 75% PR
LBG (WT%)
0.8
0.6
*
0.4
*
0.2
*
0.0
0
2
4
6
8
10
12
14
MICELLAR CASEIN (WT%)
Phase diagram measured at 5C
16
18
20
Top phase: Gelatin
Aqueous-based two-phase systems
Example: Aqueous mixture of gelatin and maltodextrin
For charged polymers (polyelectrolytes) salt (type and
concentration) as well as pH are important parameters.
Bottom phase: Maltodextrin
Influence of varying polymer characteristics
Phase separation driven by molecular ordering of one
of the biopolymers.
12
Isothermal Binodal Evolution Owing to Ordering
10
[LH1] / % w/w
o
20 C
8
LH1 / SA2 No Salt
δ [SA2] / δt = 0.4 % / min
6
4
2
0
0
2
4
6
8
10
12
14
[SA2] / % w/w
• Schematic phase diagram showing the binodal as a function
of ordering at 20 °C
1.5
16
20oC
14
12
1.0
τ / cm
8
% Helix
% Helix
6
0.5
Turbidity
Turbidity
4
2
0
-1
% Helix
10
2
4
6
8
10
0.0
t / min
Process effects
Structure induced phase separation.
• Measure of gelatin helices required
to induce phase separation in a 4%
LH1e:4% SA2 mixture , in water,
when quenched to 20oC (top) and
25oC (bottom).
• Morphology when quenched to 20oC.
1.5
16
14
25oC
29min
1.0
% Helix
10
τ / cm-1
% Helix
12
Turbidity
8
6
0.5
4
2
0
10
20
30
t / min
40
0.0
50
4min
1min
Process effects on mixed
biopolymer systems.
Effect of shear during cooling
/ gelation of the gelatin
Gelling
biopolymer
forms
the dispersed
phase.
Structures based on aqueous-based two-phase systems
Scheme developed by Tolstoguzov*
*V
Tolstoguzov Journal of Texture Studies 11, 3 (1980) 199-215
Gel particle suspensions
Modification of (shear) rheology: Effect of fibre alignment
10
relative viscosity
50 μm
Dispersed phase
volume: 20%
1
0.01
0.1
1
shear stress [Pa]
10
100
Gel particle suspensions
Deposition: Non-food example
κ-carragenan fibres deposited on a hair. Spherical particles
of the same composition wash off during rinse.
SEM micrograph by M Kirkland
WO2003061607 A1
Ice Cream
Milk Protein
LBG
Air
Ice
0.0016
Comparative Properties
0.0014
Load (kN)
0.0012
0.001
0.0008
0.0006
0.0004
0.0002
0
-0.0002 0
20
Conventional
Formulation
Short texture
ie. snaps
40
60
Displacement (mm)
80
100
Maras
Formulation
GB 9930531
US 20010031304
Extensible texture
ie. stretches
Hydrocolloid functionality in Maras Ice Cream
% mean strain to failure
160%
140%
120%
100%
80%
60%
40%
20%
0%
Carrageenan
Gelatin
LBG
CMC
Xanthan
Guar
Sahlep
Prior Art formulations
All products here compared at 30% Overrun
Conclusion
• The fine structure of hydrocolloids plays a role in their properties (viscosity and gelation)
• Influence of process can alter the functionality (single and mixed systems)
• Hydrocolloid:Hydrocolloid interactions determine the gross properties of composites
Point of
dilution
STRUCTURE RETENTION
4000
3500
STRUCTURE CREATION
Viscosity / cP
3000
2500
2000
1500
150 um
1000
150 um
500
0
0
300
600
900
1200
1500
1800
2100
2400
2700
Time / s
Acknowledge ALL past and present colleagues for support and stimulation