Question

________ bacteria turn the milk sour.

Answer 1

Lactic acid bacteria:

1. Certain lactic acid bacteria turn the milk sour.
2. They convert lactose sugar of milk into lactic acid.
3. It coagulates the milk protein casein to form curd.
4. The semisolid component (curd) is separated from the fluid and is made into cheese.
5. Moulds are used for ripening of cheese to give it characteristic flavour and aroma.

Final answer : Lactic acid bacteria turn the milk sour.