Question

The function of rennet used in cheese making is to

• A. produce lactic acid
• B. produce carbon dioxide
• C. coagulate the milk proteins
• D. produce ethanol

Answer 1

The correct option is C coagulate the milk proteins

Cheese is a fermented milk product. The first step of cheese production includes curdling of milk using lactic acid bacteria such as Lactobacillus sp.

These bacteria ferment the milk sugar lactose to form lactic acid. This lowers the pH of milk which causes the milk protein casein to denature (unfold). The denatured proteins aggregate/coagulate to precipitate as curd. Rennet is the commercial form of rennin. Rennet is an enzyme that is added to aid the curdling process. Rennet helps to hydrolyse casein to help it coagulate into a gel like structure.

Ethanol and carbon dioxide are not produced during cheese making.
So, the correct answer is 'coagulate the milk proteins'.