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 slightly alkaline because, in alkaline conditions, milk will not become sour or curdle easily, due to the formation of lactic acid.

The pH of a solution is a measure of the molar concentration of hydrogen ions in the solution and as such is a measure of the acidity or basicity of the solution. The pH scale ranges from 0 to 14. A pH less than 7 is acidic in nature. A pH of 7 is neutral. A pH greater than 7 is basic in nature.

(b) The milk takes a long time to set as curd because on adding baking soda, the milk becomes basic. The acids produced which set the milk to form a curd, are thus neutralized by the base.