Topic 9 - Bacteria and Making Yogurt

Question 1

what is fermentation?

Answer 1

when microorganisms break sugars down to release energy

Question 2

how is yoghurt made?

Answer 2

1. equipment is sterilised to kill unwanted microorganisms
2. milk is pasteurised to kill unwanted microorganisms
3. lactobacillus bacteria are added and the mixture is incubated in a fermenter
4. the bacteria ferment the lactose sugar in the milk to form lactic acid
5. lactic acid causes milk to clot and solidify into yoghurt
6. flavours and colours are added

Question 3

what are microorganisms grown in (in industry)?

Answer 3

fermenter

Question 4

what do fermenters contain which help microorganisms reproduce?

Answer 4

liquid culture medium

Question 5

how are nutrients needed for fermentation provided in fermentors?

Answer 5

nutrients needed by the microorganisms for growth are provided in the liquid culture medium

Question 6

how is rate of respiration kept high in fermentors?

Answer 6

pH is monitored and kept at the optimum level for the microorganism’s enzymes
temperature is kept at the optimum level by a water-cooled jacket.
if oxygen is needed, its added by pumping in sterile air

Question 7

why are fermentors sterilised?

Answer 7

sterilisation kills unwanted microbes, so microorganisms aren’t competing with each other and the product isn’t contaminated

Question 8

why do fermentors have paddles?

Answer 8

so microorganisms can be kept in contact with fresh medium, so they can always access the nutrients needed.