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 longer time to set as curd?

(a) Since fresh milk is slightly acidic in nature, the milkman adds little baking soda to make the milk slightly alkaline. This will prevent the milk from getting sour due to lactic acid formation.

(b) For setting into a curd, the lactic acid, formed during curdling, needs to first neutralize the alkali present in the milk. Hence, the slightly alkaline milk takes longer time to set as curd.