Question

A child wonders as to why her mother touches the warm milk with her finger before adding a little curd to it for setting curd. Explain.

Answer 1

As the pH drops and becomes more acidic, the protein (casein) molecules attract one another and become "curdles" floating in a solution of translucent whey. This clumping reaction happens more swiftly at warmer temperatures than it does at cold temperatures. So mother checks the temperature of milk before adding a little curd to it for setting curd. Because curd and temperature both are responsible to increase the acidity of milk and curdling of milk.