Fermented Milk Products: Curd, Yoghurt, Lassi, Chhana and Paneer
Fermented Milk Products tests cultures, incubation, coagulation and syneresis. Curd and yoghurt depend on lactic acid; chhana and paneer depend on acid or heat-acid coagulation.
Products and cultures
Curd (dahi) uses mesophilic lactic cultures and sets at about 30-37 C. Yoghurt uses Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus at about 40-45 C. Lassi is a diluted, sweetened or salted fermented milk drink. Chhana is acid-coagulated milk, typically from cow milk, with high moisture. Paneer is pressed chhana-type curd with lower moisture and a firm body.
Worked example
100 kg milk has 12.6% total solids. Paneer is about 55% total solids and 45% moisture. If 80% of milk solids is recovered in paneer, recovered solids = 12.6 × 0.80 = 10.08 kg. Paneer mass = 10.08 / 0.55 = 18.3 kg, or about 18% yield. Lower recovery or higher moisture lowers yield.
Traps
Do not use a yoghurt thermophilic culture for traditional dahi without considering incubation temperature. Excess acid or high coagulation temperature makes hard, rubbery chhana. Cutting and pressing too early causes high losses; too late causes excessive syneresis. Do not confuse chhana moisture with paneer moisture.