exam questions

Question 1

compare the way yeast is used in the process of baking and brewing (6)

Answer 1

baking
- yeast respires aerobically to produce CO2
- yeast is added to flour & other ingredients, process of knocking back/kneading
- yeast cells are killed upon cooking in a hot oven

brewing
- yeast respires anaerobically to produce ethanol
- malt is produced and mashed, then innoculated with yeast
- GM yeast ferments at lower temperatures, clumps together and sinks

Question 2

define homogenisation (1)

Answer 2

a process by which the fat droplets from milk are emulsified and the cream does not separate

Question 3

define pasteurisation

Answer 3

the partial sterilisation of a product, such as milk or wine, to make it safe for consumption and improve its keeping quality

Question 4

explain why homogenisation & pasteurisation are important processes in cheese/yoghurt making (2)

Answer 4

• improved texture/flavour
• longer shelf life
• better digestion
• prevents cross contamination

Question 5

give 2 differences between the production of cheese & yoghurt (2)

Answer 5

• yoghurt is cooled before being mixed with bacteria
• yoghurt is made by first adding skimmed milk powder to milk before pasteurising