Food production

A student makes yoghurt at home. The stages of the process they followed are described below:

Step A: Heat milk to $85∘C85^\circ\text{C}$ for 20 minutes to pasteurise it.
Step B: Sterilise the fermenting jars by exposing them to steam.
Step C: Cool the pasteurised milk down to $40∘C40^\circ\text{C}$ .
Step D: Stir a starter culture containing Lactobacillus bacteria into the cooled milk.
Step E: Pour the mixture into the sterilised jars and seal them.
Step F: Incubate the sealed jars in a water bath maintained at $37∘C37^\circ\text{C}$ to $44∘C44^\circ\text{C}$ for 6 hours.
Step G: Place the yoghurt in a refrigerator at $4∘C4^\circ\text{C}$ .

Identify the matching letters of the two steps that are designed to destroy unwanted microorganisms that would compete with the starter culture.

[2]

Explain why the milk must be cooled to $40∘C40^\circ\text{C}$ in Step C before the Lactobacillus is added in Step D.

[2]

Explain what would happen to the yoghurt production if the jars in Step E had not been sterilised in Step B.

[2]

Explain how the rate of yoghurt production would be affected if the water bath temperature in Step F dropped to $20∘C20^\circ\text{C}$ .

[2]

The student decides to consume yoghurt enriched with calcium. State one role of calcium in maintaining a healthy human body.

[1]

Food production Questions