Question 22 – Food production - Edexcel Biology Questions

A student researched the traditional method for making cheese and found the following guidelines:

Heat fresh milk in a pan to $∘C75\text{ }^\circ\text{C}$ and maintain this temperature for 15 seconds.
Cool the milk down to $∘C30\text{ }^\circ\text{C}$ .
Add the starter culture containing active lactic acid bacteria.
Incubate the mixture at $∘C30\text{ }^\circ\text{C}$ for 12 hours to allow fermentation.
Separate the solid curds from the liquid whey to obtain the cheese.

Name a genus of bacterium typically added in the starter culture to ferment milk.

Explain why the milk is heated to $∘C75\text{ }^\circ\text{C}$ at the start.

Explain why the milk must be cooled to $∘C30\text{ }^\circ\text{C}$ before adding the starter culture bacteria.

Explain why the mixture is kept at a warm temperature of $∘C30\text{ }^\circ\text{C}$ for 12 hours.

During fermentation, the pH of the mixture drops significantly. Describe and explain how this decrease in pH helps to preserve the cheese.

A student researched the traditional method for making cheese and found the following guidelines:

Heat fresh milk in a pan to $∘C75\text{ }^\circ\text{C}$ and maintain this temperature for 15 seconds.
Cool the milk down to $∘C30\text{ }^\circ\text{C}$ .
Add the starter culture containing active lactic acid bacteria.
Incubate the mixture at $∘C30\text{ }^\circ\text{C}$ for 12 hours to allow fermentation.
Separate the solid curds from the liquid whey to obtain the cheese.

Name a genus of bacterium typically added in the starter culture to ferment milk.

Explain why the milk is heated to $∘C75\text{ }^\circ\text{C}$ at the start.

Explain why the milk must be cooled to $∘C30\text{ }^\circ\text{C}$ before adding the starter culture bacteria.

Explain why the mixture is kept at a warm temperature of $∘C30\text{ }^\circ\text{C}$ for 12 hours.

During fermentation, the pH of the mixture drops significantly. Describe and explain how this decrease in pH helps to preserve the cheese.

Food production