Question

We need warm milk to set curd. Why do you think very cold or very hot milk cannot be converted to curd?

Answer 1

The optimum temperature for Lactobacillus acidophilus bacteria which converts milk into curd  is 40 degree celsius. Below this temperature the bacteria does not work properly.  

Answer 2

As we know that curd is made by the bacteria called lactobacillus. This bacteria grows and reproduces to make curd in warm milk. If the milk is too hot or cold, the bacteria will not be able to work properly and the curd will not formed.

Hope it helps.
Plz mark it as brainliest..