Edexcel IGCSE Biology 5.7 Fermenter microorganism growth

Edexcel IGCSE Biology syllabusBiology 4BI1First assessment 2019

Practise yoghurt production by linking Lactobacillus, lactose, temperature control, anaerobic respiration and pH changes to lactic acid.

How this is tested

explain why milk is heated, then cooled to 40-46°C before bacteria are added
link Lactobacillus using lactose anaerobically to lactic acid and falling pH
interpret acidity or oxygen-level data as evidence for the rate of yoghurt production

[Maximum number: 5]

Yeast is a fungus used in the production of bread.

(a)

Yoghurt is another food that is produced using microorganisms.

[ 5 ]

(i)

Explain the importance of controlling the temperature in the different stages of yoghurt production.

[ 3 ]

(ii)

Explain the importance of changes in pH during yoghurt production.

[ 2 ]