Question

predict the reason.if a milk man does not add a very small amount of baking soda to fresh milk

Answer 1

before distributing milk if milk man does not add bakking soda to it then we canot keep it stock for much time
(*) By adding small amount of baking soda, the milkman shifts the pH of the fresh milk from 6 to slightly alkaline so that he can keep it for longer time as the milk in alkaline condition, does not set curd easily

Answer 2

Baking soda is a base. When this is added to milk, it acts as neutralizer with the lactic acid in the milk and thus it helps in neutralizing it without letting it form curd.

Specially when the temperatures are high there's a high possibility of milk, to turn into curd. Thus a little amount of adding baking soda helps the bacteria to be neutralized and doesn't start curdling.