18. Textbook questions VII

1. Fresh milk has a pH of \(6\). How do you think the pH will change as it turns into curd? Explain your answer.

 

The pH of fresh milk is given as \(6\), so when it turns into curd with the help of yeast, the pH decreasesincreases. This is because curd contains acetic acidlactic acidmalic acid, which is acidic in nature.

We also know the pH range of acids is from \(0 to 7\). Therefore the pH of curd will be \(<6\) than that of the fresh milk.

 

2. A milkman adds a very small amount of baking soda to fresh milk.
a. Why does he shift the pH of the fresh milk from \(6\) to slightly alkaline?
b. Why does this milk take a long time to set as curd?