Question

why do we add some drops of butter milk to lukewarm milk to make curd

Answer 1

Milk is converted into curd by using the process of fermentation.

The liquid consists of globular proteins known as casein.

Butter milk comprises lactic acid bacteria and it reacts with the protein.

 During the process of fermentation, bacteria deploy enzymes to produce energy from lactose.

The acid helps to destroy the tertiary and the quaternary structure of proteins.

Answer 2

Answer:

Butter milk is the source of Lactic acid bacteria (Lactobacillus) for curdling the Lukewarm milk.

Those few drops of butter milk contains thousands of bacteria which acts as inoculum. iii) That is why we add few drops of butter milk to lukewarm milk.