Competitive benchmarking of several brands of

Competitive Benchmarking on Sensory Quality
Application to Modena Balsamic Vinegar
Application Note
Results obtained at Alpha MOS Laboratory (Toulouse, France) with balsamic vinegars graded
by the Modena Vinegar Consortium (CABM) ranking system and other products purchased
from a food retailer
Balsamic Vinegar is used as a seasoning to
enhance taste in food products. Two types of
Balsamic Vinegar can be distinguished. The
most common is industrial/commercial vinegar,
easily found in supermarket for salad dressing.
The second type consists of traditional vinegars
of higher sensory quality, made according to
traditional methods with long steps of maturation
in wood casks.
Modena (Italy) is a well-known area of Balsamic
Vinegar production, production which is strictly
regulated by the Consortium of Balsamic
Vinegar that controls the D.O.P. (Protected
Origin Designation) observance. The products
must comply with specific criteria to carry the
CABM (Consorzio Aceto Balsamico di Modena)
seal. Thereby a quality label has been
developed to certify the level of sensory quality
of Modena vinegars. This label is symbolized by
the attribution of grape leaves (from 1 to 4
leaves from lowest to highest quality) after
sensory evaluation.
AroChembase: Kovats Index library
for chemical pre-screening & sensory
characterization
The AroChembase (Alpha MOS, France) is an
add-on module that can be used within the
HERACLES E-Nose software, known as
AlphaSoft. It consists of a library of chemical
compounds with name, formula, CAS number,
molecular weight, Kovats retention Index,
sensory attributes and related bibliography.
It allows to pre-screen the chemical compounds
and give sensory features from the HERACLES
chromatograms.
Objective
Vinegar is difficult to assess due to an important
pungent sensation that limits the number of
analysis that can be conducted by a human
panel.
This application note describes the analysis of
the overall aroma & taste profile of various
Modena Balsamic Vinegars using electronic
nose and electronic tongue instruments.
Flash Gas Chromatography E-Nose
The HERACLES Electronic Nose (Alpha MOS,
France) is based on the technology of ultra fast
chromatography and includes two short columns
of different polarities (DB5 apolar and DB1701
slightly polar), coupled to 2 Flame Ionization
Detectors (FID). Therefore, 2 chromatograms
are obtained simultaneously, allowing a sharper
identification of the chemical compounds.
The embedded Tenax trap located before the
columns allows pre-concentration of the injected
fraction prior to rapid thermo desorption, in order
to improve analysis sensitivity.
With high heating rates (up to 20°C/second), this
reduces the time of analysis producing results in
seconds and analysis can be run every 4
minutes.
Fig. 1: Ultra Fast GC based HERACLES Electronic Nose
Electronic Tongue Analyzer
The ASTREE Electronic Tongue (Alpha MOS,
France)
analyzes
dissolved
compounds
responsible for taste in liquid solutions. It uses
ChemFET (Chemical modified Field Effect
Transistor) sensors.
For this study, the ASTREE was equipped with a
set of sensors designed for assessing the global
taste profile as well as for ranking products
based on taste attributes such as sourness,
sweetness or umami for instance. This sensor
set coupled with automated data processing
functionality allows to provide for each taste of
interest a relative intensity compared with other
samples on a 1-12 scale, from the least to the
most intense taste perception.
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Aroma Analysis
3
1
Characterization of Traditional Vinegars
Aroma
The nature of the main volatile compounds
detected in the headspace of vinegar samples
was investigated using their Kovats retention
indices (Table 3) thanks to AroChemBase
software module. Most of the chemicals are
esters and aldehydes, common to all vinegars
but presenting variations in their concentration:
for example compounds characterized by
873/944 (resp. Retention Index on DB5 /
Retention Index on DB1701 column) and
608/678 (identified as ethyl acetate) were found
with the highest concentration in the commercial
brand SD9 and in the 4-leaves grade vinegar.
Ethyl acetate is a volatile ester typical of vinegar
that gives strong and fruity odor to the product,
and results from the maturation process.
2
2
1
1
Fig. 2: ASTREE Electronic Tongue
1
2
3
16 or 48 position Autosampler (80 or 15 mL
beakers).
Array of 7 electrochemical sensors (crossselective & partially specific) + 1 reference
electrode potentiometric measurement.
Electronic unit for acquisition & autosampler
control.
Analytical Method
Retention time
Samples
Fourteen brands of Balsamic
Vinegar of different qualities
were analyzed:
1 supreme (4 grape leaves),
1 excellent (3 grape leaves),
1 good (2 grape leaves),
11 of “salad dressing” grade
(1 grape leaf).
DB5
3.3
3.6
www.alpha-mos.com
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4.5
Table 1: HERACLES e-nose parameters for vinegar aroma
analysis (headspace injection)
25 ml
120 s
180 s
Table 2: ASTREE e-tongue parameters for vinegar taste
analysis
2/4
Pungent, ether
558
Propanal
Ethereal, wine-like,
grape
4.8
447
580
5.7
7.0
608
678
Ethylacetate
7.1
10.5
654
775
Acetic acid
-
708
Sensory note
Ethanal
4.0
8.8
1g in a 20mL vial
20 min at 40°C
6s
170°C
40°C
5s
250°C
50 s
1500 ms
40°C (5s) to 270°C (3s) @ 5°C/ s
16 psi
280°C
50 s
5 min
405
416
Acetone /
ethanol
Pineapple
Sour
-
Ethylpropionate
Pineapple, sweet,
wine like, fruity
Oily-whiskey / onionwine
13.8
731
848
3-methylbutanol /
2-methylbutanol
11.5 13.2
768
839
Dimethylbutyrate
Apple
15.1 19.3
827
979
Furfural
Sweet / almond
9.8
Sample volume
Acquisition time
Time per analysis
4.2
salad dressing
Analytical Conditions
Quantity of sample
Sample incubation
Sampling time
Injection temperature
Trap temperature
Trap pre-purge time
Trap desorption temp.
Trap purge time
Injection time
Column temp. program
Column pressure program
FID temperature
Acquisition time
Time between 2 injections
DB1701
Kovats Index Possible
matching
DB5 DB1701 compounds
15.2 16.5
849
913
16.3 17.8
873
944
Ethylisopentanoate /
Ethyl-2
Apple, green, plum
-methylbutyrate
3-methylbutylacetate /
Banana / pear
Isoamylacetate
Table 3: Characterization of the main volatile compounds
identified in the headspace of balsamic vinegar by their
Kovats indexes
Focusing on traditional vinegars, a selection of
six specific compounds allows to obtain an odor
map (fig. 3) with a clear discrimination of the
quality grades. The 6 components selected to
build this map correspond to the following
Retention Indices:
- on DB5: 405 – 447 – 607 – 755 – 873
- on DB1701: 516 – 558 – 678
On this map (fig.3), the black axes show the link
between the selected retention time and the
discrimination impact on each quality.
SD9
Gold standard
SD6
SD8 SD10
SD1
SD11
SD5 SD3
Figure 3: Odor map (Principal Components Analysis) of the 3
traditional vinegars on Heracles e-nose with selected
compounds
SD4
Figure 5: Statistical Quality control (SQC) chart of balsamic
vinegars on Heracles e-nose system
Commercial brands are projected out of the
highest grade area (green area on fig. 5). Most
of them are borderline to grade 2 (red area) or 3
(orange area).
As on the PCA model (fig. 4), only SD9 vinegar
showed a specific profile that differs from all
grades.
Comparative aroma profiling of all vinegars
The odor map based on Principal Component
Analysis (PCA, fig. 4) showed a clear
discrimination of the vinegars grade based on
their volatile composition. The 4-leaves and 3leaves traditional balsamic were significantly
different from all commercial products. The
aroma profile of the 2-leaves vinegar is close to
some commercial brands (SD1, SD3, SD4, SD5,
SD6). Commercial brands SD2, SD7, SD8,
SD10, SD11 are quite different from traditional
vinegars, and SD9 is different from both groups.
www.alpha-mos.com
SD2
SD7
Taste Analysis
Comparative taste profiling of all vinegars
Based on ASTREE E-Tongue measurements, a
general taste map can be set up by using
Principal Components Analysis (fig. 6).
Four-leaves grade vinegar is significantly
different from all other products.
Figure 4: Modena balsamic vinegar: general odor map
(Principal Components Analysis) on Heracles e-nose
Quality Control Model
In order to guarantee that balsamic vinegars
from Modena area meet the MBV Consortium
quality requirements, a quality control model can
be built (fig. 5) with the 4-leaves vinegar as the
gold reference. This model will help authenticate
traditional balsamic vinegars.
Figure 6: Taste map (Principal Components Analysis) of
balsamic vinegars on Astree e-tongue
Ranking of vinegars based on sourness,
umami & saltiness attributes
Sourness intensity will prevail on the global taste
appreciation of vinegars, linked with fermentation
and maturation time.
Umami is another remarkable taste in fermented
products like vinegar. The composition of
dissolved compounds evolves in vinegars and
taste too will be modified over time, according to
grape variety and fruit ripe.
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The different vinegars were ranked based on
sourness and umami attributes, and results
plotted on a 2-dimension map (fig. 7).
ASTREE e-tongue gave complementary
information
on
samples
discrimination
especially for three tastes of interest: sourness,
umami and saltiness. In commercial brands,
saltiness variation was important whereas it
was not for leaves-graded vinegars.
2-leaves
3-leaves
Gold
standard
(4-leaves)
Figure 7: Taste map of Umami vs. Sourness perception on
Astree e-tongue for balsamic vinegars
Based on sourness and umami taste scales,
the characteristics of the three traditional
vinegars are varying: four-leaves grade has a
significantly lower sourness and umami taste
compared to three-leaves and two-leaves.
Two-leaves and three-leaves grades show
equivalent sourness and umami intensities.
SD1 and SD5 brands show the most extreme
differences for the two measured attributes.
www.alpha-mos.com
SD2, SD11 and SD6 have taste characteristics
close to two-leaves and three-leaves vinegars.
Figure 8: Classification of balsamic vinegars based on
saltiness intensity using Astree e-tongue
Leaves-labeled vinegars showed equivalent
saltiness (fig. 8) whereas higher differences
were perceptible within the group of
commercial products.
Conclusion
HERACLES
e-nose
showed
a
clear
discrimination between leaves-graded vinegars
with a good correlation of odor quality with leaf
grade. This makes this system useful for
checking the profiles of unknown or suspicious
samples and rapidly identifying some causes
of odor differences.
Alpha MOS France
20 avenue Didier Daurat
31400 Toulouse – France
Ph: +33 5 62 47 53 80
[email protected]
www.alpha-mos.com
Alpha MOS America
7502 Connelley Drive, Suite 110
Hanover, MD 21076-1705 – USA
Ph: (410) 553-9736
[email protected]
Alpha MOS China
Suite 705A, Xin Da Tower
#322 Xian Xia Road
Shanghai, P. R. China, 200336
Ph: 86 (0) 21 6208 1655
[email protected]
Alpha MOS Japan
Jowa Takanawa Bld. Minato-ku 8F
1-5-4 Takanawa
4/4
Tokyo 108-0074 - Japan
Ph: +81-3-5475-3291
[email protected]