Sensory Evaluation of Dahi

5/13/2012

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Introduction

�FSSR (2011) Definition of Dahi:

� DAHI OR CURD means the product:

� Obtained from pasteurized or boiled milk by souring, natural or otherwise, by a harmless lactic acid or other bacterial culture.

� It may contain added cane sugar

� Dahi shall have the same minimum percentage of milk fat and milk solids-not- fat as the milk from which it is prepared

� Milk solids may also be used in preparation of this product.

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Desirable Characteristics of dahi

�Colour & Appearance

�Cow milk dahi: yellowish creamy-white

�Buffalo milk dahi: creamy-white

�Free from browning & visible foreign matter

�Smooth & glossy surface w/o any free whey on

sides or top

�Sometimes, a cream or malai layer on the top is

indication of wholesomeness & purity, hence

considered as a desirable attribute


�Flavour

� A pleasant, sweetish aroma & a clean acid taste aredesirable in dahi

� Derived from the overall blend of the delicatediacetyl aroma & clean acid taste of LA

� Skimmed milk dahi lacks the natural rich flavourand considered as flat

� Should not show any sign of bitterness, raw,yeasty, cheesy, sharp & unclean off-flavours

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�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


�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

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Score Card for Dahi

Score Card

Attribute Perfect Score

Container & closure 5

Flavour 45

Body & Texture 30

Acidity 10

Colour & appearance 10

Total 100

Technique for Sensory Evaluation of dahi

i. Dahi is tempered to 10-15°C for proper judging

ii. Condition of the container/package for fullness, cleanliness

& general appearance should be noted

iii. Remove the closure lid & immediately observe the aroma by

inhaling the product

iv. Examine the appearance of dahi for uniformity of colour &

presence of air holes & free whey

v. Place a spoonful of dahi in the mouth. Manipulate it is inside

mouth by tongue and note the tactual properties on the

tongue & between teeth for grittiness

vi.Note whether the acidity level is pleasant & typical to the

product

vii. Mark the score card

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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:

1. Higher set temperature

2. Slow/insufficient cooling after setting

3. 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:

1. Residual cleaning/sanitizing compound

2. Antibiotic in the milk supply

3. Result of bacteriophage attack

3. Lacks freshness: Fresh ingredients should be used in dahi making. Ingredients should be stored at low temperature.


� 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:

1. use of poor quality/old milk contaminated with psychrotrophicor spoilage bacteria

2. starter culture with proteolytic activity

3. finished product being stored too high a temperature

6. Cooked: a slight amount of cooked flavour is desirable. Gives an aroma like caramelized sugar, butterscotch, egg-like odour to dahi.

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� Texture related

1. Wheying off/Syneresis/Free whey: Translucent, greenish-yellow liquid on the surface & around the sides of the cup:Causes:1. Too low pH

2. Disruptionof the coagulum before setting

3. Heat shock of dahi

4. Rough transportation after setting

5. 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 themouth. Caused by:1. Insufficient heat treatment 2. Dahi SNF too low


� Texture related

4. Ropiness: placing the bottom of spoon on the top of the dahimass, lifting the spoon. Trail of rope >2 inch: ropiness. Causesof culture contamination or EPS producing strains.

5. Chalky/powdery texture: caused by too much SMP use in dahimaking.

Education

Sensory Evaluation of Dahi