Question

give reason why a milkman add baking soda in the milk

Answer 1

Baking soda is a base. It is added to fresh milk to prevent the curdling of milk because it neutralise the lactic acid produced in the milk by the action of bacteria. ... This is why the milkman might add a trace of baking soda.

Answer 2

because baking soda reacts with lactobacillus present in the milk and forms foams

Also baking soda looks like milky so it also increases the concentration of milk