subjective evaluation in experimental foods

1. Subjective Evaluation

2. Introduction:
Subjective evaluation of a food is very important because it answers the important
question of how a food looks, smells, feels and tastes.
The individual consumer choice, combined with decisions of countless other
consumers dictates the quality of food being produced.
Sensory Evaluation:
Sensory evaluation (also referred to as effective testing) is done by panelist to access
color, taste, aroma, and texture (the aspects of food that involve the senses).
The Institute of Food Technologists (IFT) defines sensory evaluation as:
A scientific discipline used to evoke, measure, analyze and interpret reactions to
those characteristics of foods and materials as they are perceived by the senses of
sight, smell, taste, touch and hearing.

3. Subjective evaluation:

4. SUBJECTIVE VS OBJECTIVE EVALUATION
 Subjective Evaluation  Objective Evaluation
• A scientific discipline in which
characteristics of food are measure,
analyze and interpret their chemical
reaction by using instruments or standard
procedure and are not dependent on
observation of individual is known as
objective evaluation”
 Methods:
• Chemical method.
• Physicochemical method.
• Microscopic examination.
• Physical property evaluation.
• A scientific discipline in which
characteristics of food are measure,
analyze and interpret their chemical
reaction through different senses is called
subjective or sensory evaluation.”
 Methods:
• Sense of sight.
• Sense of smell.
• Sense of hearing.
• Sense of taste.
• Sense of touch.

6. SUBJECTIVE VS OBJECTIVE EVALUATION
Subjective Evaluation Objective Evaluation

7. Sensory organs and characteristics

8. Sensory organs:
Sensation is a physical process during which sensory systems respond
to stimuli and provide data for perception. A sense is any of the systems involved in
sensation. During sensation, sense organs engage in stimulus collection and
transduction. There are five sensory organs in human which help them to check food’s
quality, taste and appearance.
1. Sense of sight- EYE
2. Sense of Taste- TOUNGE
3. Sense of Sound- EAR
4. Sense of Touch- SKIN
5. Sense of Smell- NOSE
 Sensory organs and characteristics

9.  Sensory characteristic of Food:
 Appearance:
• It includes all visible attributes and derives from the interactions between a
substance or object and its environment as perceived by the human observer.
Surface characteristic of food products also contribute to their appearance.
• It includes sample size, shape, color, structure, transparency or turbidity, dullness
and gloss.

10. Aroma:
The food ordinarily is served hot or warm. The aromas vary greatly from
one food to another some of the descriptive words applicable to various
foods include spicy, floral, sulfur and woody.
Aroma can penetrate from a distance when comparatively volatile
compounds are abundant.
Aroma is influenced so much by temperature of the food.
Aroma can be evaluated by sniffing the food.
It triggers the attention of testers.

11.  Sensory characteristic of Food:
 Flavor:
• Flavor represents the composite
assessment of taste blended with odor
and sometimes sensations astringency,
burning or cooling in the mouth.
• This is a very important attribute of a
food and yet is difficult to
communicate.
• The temperature at which a food is
served may have an important
influence on the ability to detect taste
and to evaluate flavor.
• The best temperature range for flavor
evaluation is 20-30 degree C.

12.  Texture:
Texture is an expansive term requiring careful definition for persons serving
on a sensory panel as well as thoughtful inclusion in the scorecard.
The textural qualities of a food have a relationship to the appearance of a
product and to its evaluation in the mouth which relies on the mouthfeel of the
food.
Aspects of mouthfeel include sandy, slickness, sickness, hardness, crispness,
toughness, smoothness. Not all of these are appropriate for any single food.
But they suggest characteristic to be considered when evaluating texture.

13. Presentation of samples
Temperature for sample:
o It is important that all samples should be served at same temperature.
o Some foods may be served at ambient temperature (apple pie,
biscuits)
o Food shouldn’t be served at very hot or cold temperature
Serving Utensils:
o For all samples serving utensils should be same in size, color and
shape.
o White or clear containers are preferred. Plastic and disposable
containers, and knives, forks and spoons should be selected carefully
to ensure that they do not add flavor to the food.

14. .
 Coding samples:
 Samples are best identified by codes
rather than descriptive names, codes such
as A,B,C or 1,2,3 are given to samples.
 Color codes may be used particularly for
consumer testing.
 Sample size:
 Sufficient food should be provided to
each judge to enable him or her to
make decision.
 Enough sample of at least of two bites
or sip is required for judgments.
 For affective testing larger samples are
necessary. Normal sized samples are
not necessary.

15. Presentation of samples:
 Order of presentation:
In some experiments, judges tend to score the first samples presented higher
then others.
Contrast effect → higher then lower → increases the score → Balancing
the order of presentation → lower then higher → decreases the score
When large number of samples are taken in an experiment then randomizing
the order of presentation will help to minimize the psychological effects.
 Number of samples:
The number of samples that can be judged efficiently in one session is limited.
 More samples can be scored in color evaluation than in texture or flavor
evaluations which involve consumption of the product.
Score cards → fewer samples, simple evaluation system → more
samples.
If more samples are given to a single judge it makes evaluation difficult.
There is some disagreement as to the number of samples that a panelist can
effectively test in a session.

16.  Time for testing:
The best time for testing is midmorning(10a.m-12noon)or midafternoon(3-5p.m),
when the judges are neither too much fed nor too hungry.
Rinsing:
1.It is recommended that each panelist be provided with a glass of neutral, room
temperature water for rinsing between water.
2. Unsalted crackers, apple wedges, or very dilute lemon juice may be used to
remove flavors and food remainders from the mouth.
3. Cold water is avoided because it may dull the sense of taste.
4.Good quality water should be used.
Presentation of samples

17. Environment for Testing
Or
Selecting and training of panelists:

18. • Individuals should not be distracted.
• Judgment should be made independently and separately.
• Separate individual booths with light colors, well ventilated, temperature controlled and free of
foreign doors.
• Sliding doors used in large food research laboratories.
• Room other than preparation should be used for testing area.
• According to The American society for testing and materials stated, positive air pressure,
filtered air, controlled temperature and lightening as key factors for sensory evaluation.
• Far away from the preparation area to avoid aroma in testing area.
Selecting and training of panelists:
A. Selection of panel:
• In Analytic testing, if there are fewer persons , accept anyone to serve.
• They should be in good health.
• For descriptive and discrimination testing, panelists are selected on the basis of their thresholds
for basic tastes but does not been useful.
• Present actual samples to judges, replicated the samples presented to each judge and those who
are able to differentiated, are retained for panel.
•For flavor profile analysis, they are asked to identify four basic tastes in water solutions, rank
solutions of basic tastes in other of increasing intensity and identify at least 11 of 20 odorants.
 Environment for testing

19. B. Size of panel:
• Availability of qualified panelists, differences of panelists and inherent variability in
the product, influence the panel.
• It should be as large as possible to avoid any errors in testing.
• 5 panels are suggested for descriptive and discriminantion whereas 50 to 100 should
be used for affecting testing.
• The minutes before testing and for smoking, snacking and chewing gums for 20
minutes before test sessions.
• Use of reference standards to define terms and understand range of scale.
• If standard would not be constant then it would be misleading. Sensory Evaluation
Division of the IFT suggests that 24 consumer panelists are adequate for "rough product
screening".
C. Training the panelists:
• Panelists should be refrain from eating for at least 60 minutes before testing and for
smoking, snacking and chewing gums for 20 minutes before test sessions.
• Use of reference standards to define terms and understand range of scale.
• If standard would not be constant then it would be misleading.

20.  Methods of sensory evaluation

21.  Discrimination test
Divided into two groups: difference and sensitivity.
Different tests are used to determine if there is a difference
between or among samples on the basis of food quality. Like color,
texture and aroma of the sample.
It is carried out by small groups of trained judges.
The methods of discrimination testing commonly used are the
pair, comparison, triangle, duo-trio, and ranking tests

22. Discrimination/Difference Test

23. Paired comparison test:
 For a paired comparison test, two
samples are presented together and
the judge is asked whether there is a
difference in the samples with
respect to a specific characteristic.

24. Triangle Test
 Is used to improve
existing food products
 To determine consumer
acceptability of new food products..

25. Duo trio test
 The duo-trio test also involves
three samples, but the judge is
informed that the first sample
presented is a control.
 The panelist is asked to indicate
which of the other two samples
differs from the control.

26. Rating test

27.  Ranking test

30. Multiple Sample Difference Test

33.  Sensitivity test
•Sensitivity tests asses the ability of individuals to identify and detects different
aspects of food quality such as taste, aroma and astringency .
•Sensitivity tests help in training panelists for evaluating specific food products.
Sensitivity Threshold Test
•Sensitivity threshold to measure the ability of an individual to smell, taste or feel
specific characteristics in food or beverages or pure substances are used frequently
in selecting for evaluations in product research and development
•The panelists are presented with food beverages and pure substances such as water
for a specific characteristics such as sugar in increasing concentration.

34. Dilution Test
•This test is used to detect the presence of an
unknown substance added in small amount to a
natural food product. The quality and
acepatibility of test material is represented by
dilution number which denotes the percentage of
test material in the mixture of food products
.Bigger the dilution number better is the quality
of test material
E.g ;synthetic orange ingredient with natural
flavor
Dried whole milk in fresh milk
Margarine in butter

35.  Descriptive Tests
Test in this category include attribute rating, texture or
flavor profiling, and quantitative descriptive analysis as
well as some modifications of these methods.
•Descriptive tests usually are carried out by a small
group of highly trained
panelists. There are specialized difference tests, where
the panelists are not simply
asked whether they can determine differences between
the two products, but
are asked to rate particular aspects of the flavor of a
particular product on a scale.
•The use of understandable adjectives may make
judging relatively easy and precise.
For example, juiciness, a textural attribute of meat,
might be evaluated on a scale
consisting of the terms extremely juicy, moderately
juicy, slightly juicy, slightly
dry, moderately dry, and extremely dry.

36.  MAGNITUDE ESTIMATION:
Another scaling technique that has been adapted for use in food evaluation is
magnitude estimation. In this technique, which is a type of ratio scaling, panelists
are asked to develop the numerical scale that they will use in their own evaluations.
Example, if asked to evaluate the sweetness of orange juice, a
judge may assign a score of 50 to the first sample. If the judge feels that the
second sample is twice as sweet, a score of 100 is assigned; if it is half as sweet, a
score of 25 is assigned

37.  FLAVOUR PROFILE METHOD
•This method is used to define and analyze flavor (Caul, 1957).
Flavor
factors that are perceived are called character notes. A list of
those notes is made by each panel member during preliminary
work on the food being investigated.
The lists then are compared, and agreement is reached on which
notes are to be used in further work. The intensity of each
character note and the amplitude of the overall aroma and taste
are rated. For example, the character notes listed for one sample
of catsup were as follows:
sweet, salt, molasses, sour, cooked tomato, and spice complex.
• The textural characteristics of food may be evaluated with a
similar technique. A texture profile panel evaluates the
mechanical, geometrical, fat, and moisture properties of food.
Mechanical properties evaluated may include hardness,
fracturability, springiness, cohesiveness, chewiness, gumminess,
adhesiveness, and viscosity.

38.  Affective test:
• Affective test is used to determine if panelist like a product, if they prefer one product to
another or if they intend to use a product (acceptance). For example the acceptability of a
new chocolate being launched can be tested by a group of children selected from a school.
Since the number of panelists is large consumer testing require more time.
• The panelists are not trained and are asked to indicate their liking or disliking for the
product. Affective test are also known as preference tests, acceptance tests or consumer
tests and are used to ascertain a particular group of consumer prefer or like a food product.
• However it is possible for a judge to show a strong preference for a sample, but not use it
or accept it for reasons other than its likeability.
• Large panels (50-100) are used in this type of sensory evaluation and are often called
consumer panels because these tests employ a large group of untrained judges numbering
75-100 selected from general public.
• Several types of tests may be used to answer the questions posed in this type of testing.
The most commonly used evaluation technique for measuring acceptability is the hedonic
scale. The word hedonic is defined as consisting in, pleasure. Hedonic scales may have
five to
nine points.
• Hedonic (pleasure) scales in affective testing range from one extreme to the other, e.g like
very much to dislike very much. This type of testing is appropriate for consumer panels,
and is particularly appropriate when children are the judges because they pick the simple
face sketch that shows how they feel about the sample words are not used.

39. Smiley questionnaire:

40.  Interpretation of results in subjective evaluation:
The results of many of the descriptive and affective sensory methods described
can be studied by tabulating the data, including the score of each judge for each
sample, the means, the ranges, and the deviations from the mean.
Sources of error in the judging include variability in the performance of one
judge on duplicate samples as well as variability among several judges on the same
sample.
If an analysis is to be made, the original experiment should have been planned
with statistical analysis in mind, because it is difficult, and sometimes impossible,
to apply statistics to a completed experiment not appropriately planned.
References have been given to tables based on statistical analysis for several
discrimination and descriptive tests.
Correlations, or an indication of the relationship between two variables, can be
calculated between descriptive sensory data and objective data.
Computer analysis is essential for large, comprehensive sensory projects such as
the ones on fish texture and flavor.

41.  Presentation of results:
The influence of two sample presentation and instruction delivery protocols on
the results of consumer-based sensory evaluations was studied.
All samples were evaluated using hedonic scales and CATA (check-all-that-
apply) questions. Overall liking scores were found not to depend on the sample
presentation protocol.
Hedonic scale

42. CATA:

43. Thank you!