How does addition of a small amount of curd to fresh milk help formation of curd ? Mention a nutritional quality that gets added to the curd ?

How does addition of small amount of curd to fresh milk,help formation of curd ? Mention a nutritional quality that get added to the curd.

Formation of curd from milk is

Formation of curd from milk is___.

For setting curd, a small amount of curd is added to warm milk. The microbes present in the curd help in setting if the temperature of the mixtuire remains approximately between 35^(@)C" to "40^(@)C . At places, where room temperature remains mch below the range, setting of curd becomes difficult.Suggest a way to set curd in such a situation.