Question

Which of the following is/are true when milk changes into curd?
i. Its state is changed from liquid to semi liquid.
ii. It changes colour.
iii. It changes taste.
iv. The change cannot be reversed.
Choose the correct statement.
A. i, ii
B. ii, iii
C. i, iii, iv
D. i, iv

Answer 1

Curd is made from milk by following a few easy steps. It can easily be prepared at home. The entire process in which milk is converted into curd is known as fermentation. A small amount of curd is added into milk as precursor curd. This provides the milk with the necessary lactobacillus bacteria.

Complete Answer:
The process of making curd from milk is a simple one. First the milk is boiled for a few minutes. In this process some of the extra water gets evaporated making the milk thicker. Then milk is allowed to cool back down to room temperature. One spoon of curd is added to the milk. This curd acts as a precursor. After adding this curd, the milk is mixed thoroughly. The milk gets converted to curd when it is kept overnight. This process is known as fermentation. During this process a few things happen:
Its state changes from liquid to semi liquid.
It does not change its colour.
Its taste changes.
This is a chemical process and it cannot be reversed.

Hence, the correct options are i, iii, and iv. So, the correct answer is option C.

Note:
The milk has two major types of proteins. They are whey protein and casein protein. When cheese is made, the whey protein is present in the water part and the casein protein is present in the cheese part. During fermentation lactic acid and casein react to form fibrous protein, which thickens the milk to give the texture of curd.