Question

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

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

Answer 1

• The pH value of milk is $6$ i.e. it is mildly acidic in nature.
• Due to the action of bacteria, the milk is converted into curd as a result, lactic acid is formed which is more acidic in nature.
• Thus, the pH value of the milk is reduced as it turns to curd.
• Hence, to stop that, Baking soda or Sodium bicarbonate $\left({\mathrm{NaHCO}}_3\right)$ is added, which makes the solution slightly alkaline.
• So in this process, the pH of the milk increases and this prevents the milk from turning into curd sooner.

Hence, a milkman shifts the pH of the fresh milk from 6 to slightly alkaline to prevent the milk from turning into curd.