Human panels can be used for color, flavor,
juiciness, appearance, texture, rancidity --just about anything
– But the results must be used with caution
panels have great potential --- but can easily mislead as
well because of human variables
Options in sensory panel analyses
1. “trained” – relatively small (10 - 20 people) panel and trained
specifically for characteristics to be evaluated
2. consumer
– must be large (100+) because it is highly variable
– must be simple --- ask for preferences or differences
only --- not a scaled value
i.e. “3” on a 5 point scale for color
General guidelines for panels
1. sample selection – representative
2. sample handling
– cooking, serving temperature, appearance, sanitation,
safety
3. selection of panelists
– screen for color-blindness, sensitivity to specific
flavors, age, sex, dietary life styles, bias about the
product, reduce “test” mentality
General guidelines for panels
4. lighting - controlled as appropriate for test, mask color for
flavor evaluation
5. isolation
– booths without interaction with others
6. standards/clearing agents
– a reference sample can be useful
i.e. Oscar Mayer hot dog
– pictures for color comparison
– water, fruit juice, unsalted crackers should be provided
to return taste buds to a starting point
General guidelines for panels
7. sample codes
– use 3 digit random numbers
– bias for A,B,C, D sequence
8. limit samples to ~ 9 maximum at any one time
9. use an appropriate scale
– numbers in the middle of a numerical sequence are less
different than those on the ends
Scales –
Many types of scales or scoring systems
-may be structured word scales or graphics.
-structured scale of 7 to 10 points is recommended
because panelists will avoid using the end points on
the scale.
-fewer than 7 points scale may not allow the
panelists to show the degree of variation observed.
Hedonic scale
The word " hedonic" is of Greek origin and relates to
degree or magnitudes of like or dislike.
Rank preference
-rank samples in order of preference
-more than 4 or 5 samples in a ranking test creates
difficulty for the panelists to rank products
More re-testing is generally done in order to assure the
correct positioning of the rankings.
10. randomize order of samples evaluated
– a large difference between two samples will be given a
larger differential in score if one immediately follows
the other than if there are others between them
Method concepts used for sensory evaluations by
taste panels
a) Preference
-most often done with large, untrained consumer panels
b) Discrimination
-determines how products perceived and significance of
difference. it requires trained panel example
– uses triangle tests, paired comparison, ranking or
scale scoring
1. Triangle test
-panelists receive three coded samples, two of the samples
are the same and that one is different (chance = 33%)
-panelists identify the odd sample
- often used as a tool in quality assurance programs
to insure that samples from different production lots
are not different
- also used in product development studies to check
effect of ingredient substitutions or changes in
processes
2. Duo- Trio test
-three samples are presented : one sample is labeled
"R"(reference) and the other two are coded. One of the
coded samples is identical to "R" and the other coded
sample is different.
-panelists identify the sample that is same or different
from the reference (chance = 50%)
-both Triangle and Duo-Trio may be used to screen
panelists for their ability to repeatably select a specific
trait when tasting products for flavor, the Duo-Trio test
is often used instead of the Triangle test because the
Duo-Trio requires less tasting.
3. Paired comparison test
-a pair of coded samples is presented for comparison on
the basis of some specified characteristic (saltiness,
sweetness etc.)
-similar to the triangle tests but fewer samples are
required and there is less tasting. The statistical
value is not as strong with the paired comparison as it
is with triangle test (chance = 50%)
4. Ranking test
-an extension of paired- comparison tests.
-panelists receive three or more coded samples and are
asked to rank samples for intensity of some specific
characteristic.
-often used to screen one or two "best samples' from a
group of samples rather than to thoroughly test all
samples.
-no indication of the magnitude of difference between
samples is obtained because samples are only
evaluated in relationship to each other.
5. Scale scoring (descriptive, structured)
-Hedonic scale, usually 9 points
9-extremely desireable
8-very
7-moderately
6-slightly
5-neither nor
4-slightly undesireable
3-moderately
2-very
1-extremely
Line scales (unstructured)
Flavor:
extremely
extremely
desireable
undesireable
c) Descriptive methods
-discrimination of qualitative and quantitative traits of a
sample by use of a small ( 5- 10) member, very highly
trained panel
-highly sophisticated, analytical approach
-techniques such as flavor profile, textural profile and
QDA ( quantitative descriptive analysis) are used.
-requires at least three evaluative processes; 1.
discrimination of the trait ; 2. description of the trait;
and 3. quantifying the trait.
The steps of discrimination and description of traits are
qualitative.
-language used is developed through careful training
and practice with the panel.
-panelists develop a common vocabulary for various
sensory stimuli with descriptive language.
The third step in descriptive analysis is to quantify the traits
as to how strong they are, and sometimes the order of
detection, i.e. flavor profile (Arthur D. Little Co.)
-provides a total picture or profile of a food product
-may be used to suggest instrumental methods or more
commonly as a method of quality assurance or quality
control.
Review laboratory manual pp.82-87 for a
variety of forms that can be used in our lab.
A structured (numerical) scale (p.82 and p.
86) or a unstructured line scale (p. 87)
would probably work best for most 460/560
products.
-you select the characteristics to be
scored for your product. Prepare and
bring score sheet to lab. to use
Texture measurements
Options:
1. Human panels
-same considerations for panel selection,
sample preparation, sample evaluation,
etc. as for flavor and color
-latest development in textural analyses with
sensory panels is coordinating sound (crunch,
crackle, snap, etc.) with textural assessment
2. Texture instruments
a. Instron – used a great deal in many industries,
previously used for food but less common
now
b. Texture Analyser-TA XT2i (Meat Lab.)
c. instruments allow several texture measures
including texture profile analysis (TPA)
Texture Analyser
Texture measurements
1. Compression (tomatoes, strawberries, etc. force without rupture)
2. Penetration/puncture (sausage skin “snap”)
3. Shear (resistance to cutting, toughness)
4. Extrusion (resistance to flow or pumping)
5. Tension (stretch, i.e., rubber band or
stretch to break, i.e., restructured ham)
6. Breaking/bending (bone strength)
7. Texture profile analysis (TPA)
Compression test
Warner-Bratzler shear test
Tension measurement
Texture Profile Analysis (TPA)
1. TPA uses compression, release,
recompression and re-release, often called
the “two bite” test.
2. Provides several different textural
properties
3. Correlates very well with sensory panel
evaluations.
TPA results
Hardness or Firmness = maximum force of first
compression (height of first peak)
Cohesiveness = area under peak 2/area under peak 1
Gumminess = Hardness X Cohesiveness
Springiness = height of sample recovery in the second compression
Adhesiveness = maximum negative force after 1st compression