A milkman adds a very small amount of baking soda to fresh milk.

(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?

(b) Why does this milk take a long time to set as curd?

a) The milkman shifts the pH of the fresh milk from 6 to a slight alkalinity because, in an alkaline condition, the milk will not become sour or curdle due to the formation of lactic acid.

b) The milk takes time to set as curd because the addition of baking soda has made the milk basic, and the acids produced will take a longer time to neutralize the base.