Question

Sid saw his grandmother adding little amount of curd to a bowl full of warm milk. When he asked his grandmother why she did this, grandmother replied, she is preparing curd for the next day. Why do you think Sid's grandmother added curd to the milk?

• A. The lactic acid present in the curd that was added will turn all the milk in the bowl into curd
• B. The curd added as inoculum contains alkaline substances that can cause precipitation of milk proteins to form curd
• C. The curd that was added contained microbes that will multiply and ferment the milk to form curd
• D. The curd that was added will absorb all the water from the milk causing it to curdle

Answer 1

The correct option is C The curd that was added contained microbes that will multiply and ferment the milk to form curd

Curd is obtained by the fermentation activity of lactic acid bacteria (LAB) such as Lactobacillus on milk. For the preparation of curd, milk at around 40°C is inoculated with a small amount of curd containing the LAB (lactic acid bacteria). These bacteria anaerobically breakdown or ferment the lactose sugar present in milk into lactic acid. With the increase in lactic acid concentration, the pH of milk reduces considerably, causing the milk proteins to undergo coagulation and partial digestion. These coagulated proteins form the curd.

So, the correct answer is 'The curd that was added contained microbes that will multiply and ferment the milk to form curd'.