Use of Lactase in Dairy Industry- Milk and whey (the clear fluid obtained during cheese making) contain about 4.7% (w/v) lactose. Adults having their origins in Northern Europe and Indian subcontinent are tolerant to lactose. But a great majority of the adults of remaining regions are intolerant to lactose, e.g., 97%, 90% and 70% of Thai, Chinese and black

American populations; respectively. In addition, some rare individuals are intolerant to lactose due to lactase deficiency or some other metabolic defects. Lactose intolerant individuals suffer from diarrhoea abdominal cramps, flatulence and, in severe cases, dehydration and even death, when they consume normal milk. Clearly, such persons need low­-lactose milk/milk preparations.

(ii) From Aspergillus niger or A. oryzae. They are added to milk or whey at ~2000 U/kg and incubated for 1 day at 5°C; about 50% of the lactose becomes hydrolysed making the milk/whey sweeter.

In addition, when the milk/whey is condensed or frozen, lactose does not form crystals. Lactase is used in production of ice creams, and sweetened, flavoured and condensed milks. Lactase-treated whey powder is used either in part or ful1, in place of the skimmed milk powder in ice cream recipes; this also improves the creaminess of ice creams.