Question

if you add few drops curd to Lukewarm milk why it does not converting into curd​

Answer 1

Since there is no appropriate temperature for lactobacillus bacteria to grow, there is no growth of lactobacillus and chilled milk won't convert into curd but there will be slight changes in its taste due to the presence of small amount of lactobacillus bacteria.

Answer 2

Answer:

Curd contains bacteria like Lactobacillus acidophilus which is responsible for making milk into curd.

When the milk is too hot or too cold for bacteria to grow and multiply, they won't be able to use up the milk and form curd