Question

why do milkman add sodium bicarbonate to milk and why do milk take longer time to be curden

Answer 1

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.
(b) Due to the addition of baking soda this milk becomes slightly basic because of which acids produced in this milk due to bacterial actions are neutralized. Hence, this milk takes longer time to set as curd.
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Hope this helps..

Answer 2

milkman add sodium bicarbonate and water in milk to increase the amount of milk. because sodium bicarbonate is white and they add it with water so people can't understand it's real milk or sodium bicarbonate. milk take a longer time to convert into curd because when lactobacillus bacteria don't get much heat then they can't convert milk to curd fastly .