LPT 311: Milk and Milk Products Technology (1+1)

PREPARATION OF DAHI

• In India curd is also called Dahi. As per PFA rules, dahi is a product obtained from pasteurised or boiled milk by souring using previously cultured milk or otherwise by using selective lactic cultures.

Apparatus required

• Stainless steel wares, glass wares, water bath, incubator, refrigerator, etc.

Starter required

• Good quality milk, starter culture which includes Streptococcus diacetylactis , Streptococcus cremoris, ith an aroma producing bacteria mainly Leuconostoc citrovorum or Leuconostoc dextranicum .

Procedure

• Pasteurise milk at 85^ºC for 10 min and cool the milk immediately (20-25^ºC) by keeping the container in running water, by simultaneous agitation. Add 0.5% of starter culture at this temperature and mix thoroughly.
• Distribute this cultured milk into a small sterile steel or glass container taking aseptic precautions, and fix a sterile aluminium cap.
• Permit the cultured milk to remain undisturbed for 16-18 hours at 22-25^ºC, or to reach the acidity of 0.8-0.98.

Requirements for dahi

Characteristics	Requirement for sweet dahi	Requirement for sour dahi
Acidity, lactic (percentage weight)	0.70	1.0
Yeast and mould count/gm	100	100
Coliform count/gm	10	10
Phosphatase test	Negative	Negative