This document provides information about sensory evaluation of dairy products. It discusses the requirements for sensory evaluation including having a proper laboratory, selecting and training sensory panel members, and using a scorecard. It describes the ideal conditions for sensory evaluation booths. It outlines the desirable sensory characteristics for fermented dairy products, including appearance, flavor, body, texture, and acidity. It provides a sample scorecard and evaluation techniques for dairy products like dahi. It also lists undesirable sensory attributes to avoid. The goal is to train panel members to consistently evaluate dairy products based on relevant sensory factors.

1. Kaushik Khamrui
Dairy Technology Division
National Dairy Research
Institute, Karnal

2. Introduction
Sensory evaluation: measurement of a food
product’s quality based on information received
from the five senses i.e., sight, smell, taste, touch &
hearing.
Signals: transmitted via CNS to brain - integrated
with past experiences, expectations, and other
conceptual factors - response in summarized.
Four principal quality factors: appearance, flavour,
texture & nutrition
First three are ‘sensory acceptability factors’
determined via sensory evaluation (Bourne, 2002)
‘Sensory acceptability factors’ – deciding factor for
consumers’ acceptability

3. Requirements of Sensory Evaluation
1. Proper sensory evaluation
laboratory
2. Selection of sensory panel
members/evaluators, and
3. Score-card
4. Training of the panel members.

4. 1. Sensory Evaluation Laboratory
i. Meeting cum Briefing room
ii. Sample preparation room
iii. Testing booths
iv. Office

5. Sensory Evaluation Laboratory

6. Sensory Evaluation Booths

7. Sensory Evaluation Booths
Conditions
0.9m x 0.6m
20-22°C 60-62%
RH
Free from
odour
Adequate light
Counter with
opening

8. 2. Selection of Sensory Panel Members
The evaluator: availability, interest & motivation.
Qualities:
Attitude towards foods: should not have strong liking or
disliking towards a dairy product
Aptitude and knowledge: have ability to concentrate &
unbiased. Should have: basic knowledge on the sensorial
attributes .
Health: good health with normal organoleptic sensitivity,
free from anosmia and ageusia.
Age: 18-50 years.
Other requirements: smoking, chewing pan and taking
intoxicants - at least an hour before the test. Should not use
odoriferous substances.

9. 3. Score card, sample numbers and quantity
Sensory card: simple, brief, easy to follow and all important
sensorial attributes are included in it.
Clearly printed and the matter should be arranged in
logical sequence.
Terminologies used shall be clear and understandable.
Normally 3-5 samples with average intensity of flavour for
each sitting are optimum.
The amount of each sample 50-100 ml or gm which is
sufficient for one generous sip or bite.
The test should be carried out preferably one hour before
or after lunch.

10. 4. Training of the panel members
Evaluators: should like a calibrated instrument and
provide reproducible results.
Training: detect, recognize and describe sensory
stimuli
Acquainted with:
desirable and undesirable attributes
correct terminology
use of score card
scoring technique, &
sequence of observations.
Must start with a large group of people : finally a
trained panel comprising of 5-7 members should be
retained

11. Desirable Sensorial Characteristics of
Functional Fermented Dairy Products
Functional dairy products: as similar as possible to that
of the original product
Sensory Attributes of Functional Dahi
Colour & Appearance
Cow milk dahi: creamy-white with yellowish tinge
Buffalo milk dahi: creamy-white
Free from browning & visible foreign matter
Smooth & glossy surface w/o any free whey on sides or
top
A cream layer on the top is indication of wholesomeness
& purity, hence considered as a desirable attribute

12. Desirable Characteristics of dahi
Flavour
A pleasant, sweetish aroma & a clean acid taste
are desirable in dahi
Derived from the overall blend of the delicate
diacetyl aroma & clean acid taste of LA
Skimmed milk dahi lacks the natural rich flavour
and considered as flat
Should not show any sign of bitterness, raw,
yeasty, cheesy, sharp & unclean off-flavours

13. Desirable Characteristics of dahi
Body & Texture
Good quality dahi is a weak gel like junket when
made from whole milk
Body: firm, homogenous & free from gas holes/
air bubbles
On cutting it should appear clean/sharp
Graininess/lumpiness, ropy, shrunken, thin &
wheying off should be absent in dahi

14. Desirable Characteristics of dahi
Acidity
Range 0.75-0.85 % LA is appropriate for good
quality dahi
Excessive acidity imparts too much
sourness/sharp/astringent taste to the product
Low acidity is considered as raw/bland dahi

15. Score Card for Dahi
Score Card
Attribute Perfect Score
Container & closure 5
Flavour 45
Body & Texture 30
Acidity 10
Colour & appearance 10
Total 100

16. Technique for Sensory Evaluation of dahi
1. First look at outside of container - for any smudges,
manufacturing date & batch no. is easy to read and in the
proper place.
2. Open the container without disturbing the product, view the
top, notice for any possible yeast or mould growth,
discolouration, watery liquid exudates.
3. While opening notice the amount of force to peel-off the lid.
4. Look the sides for possible indications that the product may
have sunken.
5. Tip the cup upside down on a plate puncture the cup bottom
lift the cup & scrape out of the remainder of any dahi in the
cup bottom with the help of a spatula or spoon.
6. Dahi “mound” left on a plate. Notice is made of any unusual
aromas.

17. Technique for Sensory Evaluation of dahi
7. After the dahi has been placed on the plate, first notice how
the dahi appears on the plate. The dahi should resemble a
thick mass with little no running.
8. Notice the colour. Should resemble from the type of milk
from which it is prepared otherwise the product is criticized
as “atypical color”.
9. Place a spoonful of Dahi in the mouth & notice how the dahi
clings or sticks to the tongue and sides of the mouth.
10. While moving around the dahi inside the dissipate fast, it is
perceived to be ‘weak’.
11. If is sticks or sticks to the tongue and sides of the mouth
and requires some force to be applied to move around it is
perceived to be ‘thick’.

18. Technique for Sensory Evaluation of dahi
12. After noticing the texture the flavour sensations are
perceived and where in the mouth they are observed are
recognized.
13. One of the first sensations is acidity of dahi. The sensation
is on the sides of tongue. Sensing too high an amount of
acid can cause this flavour note to be over-powering.
14. Notice other strong off-flavours also e.g., oxidized, atypical
(foreign), old ingredient, unclean and yeasty.
15. Expectorate (split it out) the dahi. After the acid and sweet
sensations, the next flavours that are noticed are cooked,
too high or low flavouring.
16. Finally, after expectorating some off-flavours that are
noticed. These include rancid, bitter, old ingredient, lacks
freshness, unnatural flavors, and acetaldehyde.
17. Different penalties are prescribed for different attributes and
defects.

19. Scoring Guide for Functional Fermented Milk Products
Quality according Grade Defect & Intensity Approximate Score (% of the
to the Grade of Perfect Score)
Dairy Products
Excellent A No defect More than 90%
Good B Flavour: Flat, slight More then 80%
cooked/stale/acidic/rancid/insuffici But less then 90%
ent/ salty
Consistency/Texture: defects of
only slight intensity
Package: Smudgy print but
readable
Fair C Flavour: Definite cooked/ flat. More then 60%
Slight rancid/oxidized/metallic/ But less then 80%
fishy/ yeasty/mouldy/ acidic
Consistency/Texture: Any texture
defect of definite intensity
Package: Slightly smudgy print &
deformed container
Poor D Flavour: Any flavour defect of the Less then 59%. The products are
higher intensity as given above for generally unacceptable at this
grade C score
Consistency/Texture: Pronounced
defect
Package: Pronounced smudgy
print & deformed container

20. Undesirable Attributes of dahi
Flavour related
1. High acidic: Certain amount of acid needed to coagulate
the proteins & form coagulum typical to dahi. If acid level
too high taste become sharp, harsh & offensive. Caused by:
I. Higher set temperature
II. Slow/insufficient cooling after setting
III. Temperature abuse during distribution/storage
2. Low acid: Dahi should exhibit an acid taste. Consumers can
easily detect the ‘low-acid’ taste of dahi. Caused by low
culture activity:
I. Residual cleaning/sanitizing compound
II. Antibiotic in the milk supply
III. Result of bacteriophage attack
3. Lacks freshness: Fresh ingredients should be used in dahi
making. Ingredients should be stored at low temperature.

21. Undesirable Attributes of dahi
Flavour related
4. Insufficient flavour: Absence of typical dahi flavour.
Caused by low citrate level in milk and destruction of
diacetyl. Rapid cooling after setting helps to prevent this
defect.
5. Bitter: Offensive aftertaste sensed at the back sensed at
the of tasting sequence. Caused by:
i. use of poor quality/old milk contaminated with psychrotrophic
or spoilage bacteria
ii. starter culture with proteolytic activity
iii. finished product being stored too high a temperature
4. Cooked: a slight amount of cooked flavour is desirable.
Gives an aroma like caramelized sugar, butterscotch,
egg-like odour to dahi.

22. Undesirable Attributes of dahi
Texture related
1. Wheying off/Syneresis/Free whey: Translucent, greenish-
yellow liquid on the surface & around the sides of the cup:
Causes:
I. Too low pH
II. disruption of the coagulum before setting
III. Heat shock of dahi
IV. Rough transportation after setting
V. Freezing/thawing of dahi
2. Gel like/too firm: has the appearance of a formed gel in the cup,
and a very firm set. Using excessive Exo-polysaccharide (EPS)
producing cultures.
3. Weak: appears “runny” or liquid like or no residence time in
the mouth. Caused by:
1. Insufficient heat treatment 2. Dahi SNF too low

23. Undesirable Attributes of dahi
Texture related
4. Ropiness: placing the bottom of spoon on the top of the dahi
mass, lifting the spoon. Trail of rope >2 inch: ropiness.
Causes of culture contamination or EPS producing strains.
5. Chalky/powdery texture: caused by too much SMP use in
dahi making.