2. Objectives:
At the end of this chapter, you will be able to:
Identify and determine the taste panel area.
Determine and understand the basic
requirements during sensory lab.
Determine the factors to choose and train
panelist.
Determine the factors influencing sensory
measurements.
3. Sensory laboratory
Pleasing natural shades and
maintenance of comfortable
temperature and humidity
conditions of the laboratory
set up are desirable.
Test room should be separated
by suitable distance from
congested are because &
noise and the opportunity this
would provide for unwanted
socializing.
Briefing room
Panel room
Preparation room
4. Sensory Laboratory Set Up and
Equipment
The physical setting must be designed so as to
minimize the subject's biases, maximize their
sensitizing, and eliminate variable which do not
came from the product themselves.
The test area should be centrally located, easy to
reach and free of crowding and confusion, as
well as comfortable, quite, temperature
controlled and free from odour & noise.
6. 1. The testing booths are located should be separated from sample
preparation room and wash room and store by a complete partition.
2. A temperature of about 20°C and RH of 62% in the testing room in
considered to be ideal.
3. The booths may be fairly simple or very elaborate, depending on the
funds available.
4. Many laboratories have a sink and tap built into each booth for
expectoration and to provide water for rinsing.
5. For descriptive analvsis and panel training sessions a round table that
permits discussion is required.
6. The color of the booths should not influence the appearance of the
product being judged. An off-white or light gray color is usually
recommended.
7. LIGHTING
Lighting should be uniform and should not
influence the appearance of the product to be
tested. The type of light used should be carefully
chosen if color and appearance are important
factors to be judged, since many fluorescent
lights distort color.
A common feature of many panel booths is a choice of
red, green, and / or blue lighting at low intensity obtained
through the use of colored bulbs or special filters. The
lights are used to mask visual differences between
samples in differences tests calling for the subject to
determine by taste ( or by feel, if appropriate) which
samples are identical.
8. TESTING SCHEDULE
The time of day that tests are run influences
results. Although this cannot be controlled if the
number of tests is large, late morning and mid
afternoon are generally the best times for testing.
9. The type of preparation equipment located in the
sample preparation area depends on the products
being tested.A well-equipped kitchen is a good
start, with specialized equipment being added
according to need.
The preparation area should have a good
ventilation system for removal of cooking odors.
Sufficient counter space for serving and
assembling samples for presentation is an
important requirement (Fig. 3).
PREPARATION ROOM &
SAMPLES PREPARATION
10. • A laboratory bench flush with the hatches so that samples
trays will side through. The hatch on the service counter
should preferably be constructed in such a manner that
there shall be no recognition of individual or either side
of partition.
• Benches, kitchen range, ovens, etc. for preparation.
• Refrigerator and freezer for storage of samples.
• Storage for glassware, dishes, glasses, trays, etc.
• Dishwashers, disposers, trash compactors, wastebaskets,
sinks, etc.
• Frozen storage for panel member treats, if used
• Large garbage containers for quick disposal of used
product, etc.
11.
12. Preliminary testing
Preliminary testing is usually necessary to
determine the method of preparation of the
product.
All the various factors, such as time and
temperature of thawing and cooking, amount
of water and size of pot for boiling, and time
and speed of blendjng, should be
predetermined and kept constant throughout
tests on the product.
The_preparation method should not impart
any foreign tastes or odors to the product.
13. Panelists are influenced by irrelevant
characteristics of the samples. Because of this,
every effort should be made to make the samples
from different treatments identical in all
characteristics except the one being judged. It is
sometimes necessary to grind dice, chop, or
puree the samples to obtain uniformity.
However, Kefford and Christie (1960) found that
judges prefer foods in their normal state. When
conducting acceptance or preference tests, it may
be better to present one sample at a time rather
than grind or puree the product to mask the
differences.
14. DILUTION AND CARRIERS
Most foods are served in the way in which
they are normally consumed.
The use of a carrier, such as crackers for
jam and frankfurters for catsup, adds to the
cost and effort, and it is often difficult to
select an appropriate carrier. Carriers are
also a source of experimental error because
the proportion of product to carrier may
not be constant, or the carrier may not be
of consistent quality.
15. SERVING TEMPERATURE
The temperature at which samples are served sometimes
presents problems. For acceptance/preference tests, the
samples should be served at the temperature at which
they are normal eaten.
Hot foods are usually served at 60oC-66oC. Ice cream
should be served at -10 to 20C and other foods at 40-
100C. To compare results, the same temperature should
be used during all tests with the product.
– Warming ovens with controlled temperature and
humidity are available.
– electrically heated beakers to keep samples hot.
– a water bath is fitted to hold beakers, and each
panelists is served from the beakers as he arrives.
– Blocks of styrofoam can be cut out to hold containers
and help maintain the temperature.
16. UTENSILS
Serving utensils should not impart anv taste or
odor to the product.
Identical containers should be used for each
sample so that no bias will be introduced from
this source.
It is wise to use colorlessor white containers.
Disposable dishes made from plastic, paper or
styrofoam are convenient when large numbers
are to be served, as in consumer tests, but it must
be determined beforehand that no taste is
transferres to the product.
17. QUANTITY OF SAMPLE
The Sensory EvaIuation Committee ofASTM
(1968) recommends that in discrimination tests,
each panel should receive at least 16ml (0.5 oz)
of a liquid and 28g (1oz) of a solid, and the
amount should be doubled for preference test.
The amount of sample presented should be
constant throughout the testing.
Panelists should receive enough sample to taste
back and forth until they can make a decision.
18. NUMBER OF SAMPLES
The number of samples that can be effectively
evaluated in one session should be determined
during preliminary testing.
The type of product being tested and the
experience of the judges must be consjdered
when deciding on the number of_sarnples to test
in one sessjon.
Motivation is an important factor in this regard.
Panelist often lose their desire to discriminate
before they lose their capability.
19. CODING AND ORDER OF PRESENTATION
the order of presentation of the samples to each
panelist is randomized or balanced. In larger
experiments, the order can be obtained from
tables of random numbers.
The code assigned to the samples should not give
the panelists any hint of the identity of the
treatments and the code itself should not
introduce any bias. Three-digit random numbers
obtained from tables of random numbers are
recommended for coding the samples.
20. RINSING
The panelists are provided with an agent for oral
rinsing between samples. Taste-neutral water at
room temperature is preferred by many
investigators.
21. INFORMATION ABOUT SAMPLES
As little information as possible about the test should be
given to the panelists, because this information may
influence results.
When a panel was told that tomato juice was made from
high quality raw ingredients, the ratings were much
higher than when the same samples were presented with
the information that low quality raw products had been
used (Pettit 1958).
This preconceived impression is called expectation error.
Panelists usually find what they expect to find. Because
of this expectation error, persons who are directly
involved with the experiment should not be included on
the panel.
22. CHOOSING AND TRAINING PANELISTS
Who are the panelists?
Panelists are usually office, plant, or research
staff. It should be considered a part of work
routine for personnel to serve as panelists. Full
cooperation of the supervisors of persons who
serve as panelists is necessary. No person should
be required to evaluate the foods to which he
objects
23. Number of panelist
The greater the number of persons on a semi
trained panel, the more likely it is that individual
variations will balance out.
However, a small highly trained panel will give
more reliable results than a large untrained panel.
A laboratory panel is usually composed of 10 to
20 persons with three or four replications by each
judge by each judge for each treatment.
24. Panelist condition
Persons who serve as panelists should be in
good health and should absent themselves when
suffering from conditions that might interfere
with normal functions of taste and smell.
Emotional factors, interest and motivation appear
to be more important than the age or sex of a
panelists.
It is generally recommended that panelists refrain
from smoking,chewing gum, eating or drinking
for at least 30 min before testing.
25. The motivation of the panelist affects his
response. An interested panelist is always more
efficient. The panelists should be made to feel
that panels are an important activity and that their
contribution is important.
Health, interest, availability, punctual, good verbal
and communication skills.
27. 1) Expectation error
Anv information the panelists receive about the test will
influence the results.
Panelists usually find what they expect to find.
Therefore,panelists should not be given detailed information
about the test.
Trick
provide only enough information for panelist to be
able to do the test
Try not to include people already involved in the
experiment (single blind)
Avoid codes that create inherent bias (1,A etc)
Since people generally associate “1” or “A” with “best”, it is
recommended that three digit random numbers be used.
28. 2) Leniency error –rate products based upon
feelings about researcher
3) Suggestion effect –response of other
panelists to product (need to isolate
panelists and keep them quiet)
29. 4) Stimulus Error
• Influence of irrelevant questions (e.g piece
size, color, uniformity)
• Try to mask unwanted difference (e.g. colored
lights)
5) Logical error –associated with stimulus error
tendency to rate characteristics that appear to be
logically associated (yellow and rancidity).
Control by masking differences
30. 6) Halo effect
caused by evaluating too many factors at one
time. Panelists already have an impression
about the product when asked about second
trait –will form a logical association (e.g. dry-
> tough)
Best to structure testing so that only one
factor is tested at a time (difficult to do)
31. 7) Positional effect –tendency to rate second
product higher or lower
2 products very different –panelists will
exaggerate differences and rate
‘weaker’sample lower than would
otherwise
Use random order. Use all possible
presentation orders
32. DESIGNING EXPERIMENTS AND CHOOSING
METHODS OF ANALYZING DATA
Because of the variability in results of sensory
tests, interpretation cannot be made by direct
examination. The results must be tested by
statistical methods. Results are usually expressed
in degrees of significance which is the probability
that the results are caused by chance
33. 1 2 3 4
State the basic taste on the different parts of the
tongue
