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Food production

Food production

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Question 1

An industrial food scientist designed a process for the large-scale production of yogurt using a continuous-flow bioreactor. The protocol is summarised below:

  • Heat whole milk to 90 ∘C90\text{ }^\circ\text{C}90 ∘C and maintain this temperature for 15 minutes.
  • Cool the milk rapidly to 43 ∘C43\text{ }^\circ\text{C}43 ∘C.
  • Inoculate the milk with a starter culture of active bacteria.
  • Incubate the mixture inside the bioreactor at 43 ∘C43\text{ }^\circ\text{C}43 ∘C for 6 hours.
  • Cool the final product to 4 ∘C4\text{ }^\circ\text{C}4 ∘C to halt fermentation before packaging.
a.

Name a genus of bacterium typically present in the starter culture used for yogurt production.

[1]
b.

Explain why the milk is heated to 90 ∘C90\text{ }^\circ\text{C}90 ∘C for 15 minutes at the start of the process.

[2]
c.

Explain why the milk must be cooled to 43 ∘C43\text{ }^\circ\text{C}43 ∘C before inoculating it with the starter culture.

[2]
d.

Explain why the mixture is incubated at 43 ∘C43\text{ }^\circ\text{C}43 ∘C for 6 hours.

[2]
e.

During the 6-hour incubation, the pH of the mixture drops from approximately 6.5 to below 4.5. Describe and explain how this drop in pH helps to preserve the yogurt.

[3]
Markscheme

Food production Questions

  1. IGCSE
  2. /Biology
  3. /Food production

74 exam-style questions on Edexcel IGCSE Biology Food production. Each one has a worked solution and a mark scheme showing where the marks go.

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