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6.7 Lactobacillus and yoghurt
Exam question
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Describe how yoghurt is made.
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Total for this question: 4 marks
6.7 Lactobacillus and yoghurt
Exam question
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Explain why milk is heated before adding Lactobacillus.
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Total for this question: 2 marks
6.7 Lactobacillus and yoghurt
Exam question
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Explain why the milk is cooled before adding the bacteria.
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Total for this question: 2 marks
6.7 Lactobacillus and yoghurt
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What substance makes yoghurt sour?
(1)Total for this question: 1 mark
6.7 Lactobacillus and yoghurt
Exam question
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Explain why lactic acid causes milk to thicken.
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Total for this question: 2 marks
6.7 Lactobacillus and yoghurt
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Explain why the yoghurt is kept at about 40 °C.
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Total for this question: 2 marks
6.7 Lactobacillus and yoghurt
Exam question
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Explain why the acidity of yoghurt helps preserve it.
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Total for this question: 2 marks
6.7 Lactobacillus and yoghurt
Exam question
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Illustrative data.
| Time / h | pH |
|---|---|
| 0 | 6.6 |
| 2 | 6.0 |
| 4 | 5.1 |
| 6 | 4.6 |
| 8 | 4.4 |
Plot pH against time. Join your points with straight lines using a ruler.
(5)Graph skills: SLAPUK and choosing a scale
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Total for this question: 5 marks
6.7 Lactobacillus and yoghurt
Exam question
Mark points shown after marking
| Time / h | pH |
|---|---|
| 0 | 6.6 |
| 2 | 6.0 |
| 4 | 5.1 |
| 6 | 4.6 |
| 8 | 4.4 |
Explain the change in pH.
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Total for this question: 2 marks
6.7 Lactobacillus and yoghurt
Exam question
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| Time / h | pH |
|---|---|
| 0 | 6.6 |
| 2 | 6.0 |
| 4 | 5.1 |
| 6 | 4.6 |
| 8 | 4.4 |
Calculate the mean rate of pH change in the first 4 hours.
(2)Total for this question: 2 marks
6.7 Lactobacillus and yoghurt
Exam question
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State the sugar in milk that Lactobacillus uses.
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Total for this question: 1 mark
6.7 Lactobacillus and yoghurt
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Suggest why all equipment is sterilised.
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Total for this question: 2 marks
6.7 Lactobacillus and yoghurt
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Explain why yoghurt is refrigerated after it is made.
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Total for this question: 2 marks
6.7 Lactobacillus and yoghurt
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Identify the type of respiration carried out by Lactobacillus in yoghurt-making.
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Total for this question: 1 mark
6.7 Lactobacillus and yoghurt
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Compare fermentation by yeast and by Lactobacillus.
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Total for this question: 2 marks
