Question

during summer season a milkman usually adds a very small amount of baking soda to fresh milk

Answer 1

During summer months the temperature remains high owing to which lactobacillus increases in milk resulting formation of lactic acid, minimizing the basic pH of milk.

This is the reason why a milkman adds baking soda to increase the overall pH of the milk, since baking soda is a base and helps to neutralize the milk in summers.

Answer 2

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. In hot weather, milk can go 'off' very quickly due to rapid bacterial growth.. ... This is why the milkman might add a trace of baking soda.