Food production- Microorganisms

Question 1

yeast and respirtation

Answer 1

yeast is a very useful microorganism. when yeast respires aerobically, it turns sugar into c02, but when there isn’t enough oxygen, yeast respires anaerobically, turning sugar into C02 and alcohol

Question 2

what do we use to make beer

Answer 2

anerobically respiring yeast

Question 3

Fermentation

Answer 3

it is the production of ethanol. It occurs when yeast breaks down sugars in the absence of oxygen. Fermentation is used to make alcoholic drinks, such as beer and wine.

Question 4

stages of making yeast

Answer 4

• sugar is extracted from plants
• yeast is added, mixture is kept warm
• air and other microorganims are kept out of the fermentation container using an air lock
• fermentation is allowed to continue (the carbon dioxide helps to keep the air out)
• the mixture is clarified by settling anf filtration
• the drink is pasteurised then stored in casks or bottles

Question 5

why are claryiying agents sometimes added

Answer 5

to remove particles and make it clearer

Question 6

why is the beer pasteurised (heated)

Answer 6

to kill any remaining yeast left in the beer and to compleley stop fementation

Question 7

The respiration rate of yeast depends on its coniditons

Answer 7

you can do experiments to investihate how the rate of co2 production by yeast changes under different conditions.. You can do the same experiment to measure how each of the following factors effect the rate:

temp
conc of sugar

Question 8

how could you alter the expeiment ot make it more accu rat

Answer 8

by replacing the second tube with a gas syringe- and measure the volume of gas produced insead

Question 9

experiment to show the effect of changing temp on co2 production

Answer 9

1) mix together some sugar, yeast and distilled water, then add the mixture to a test tube.
2) attach a bung with a tube leading to the second test tube of water
3) place the tube containing the yeast mixture in a water bath at a certain temp
4) leave the tube to warm up a bit and then count how many bubbles are produced in a given time period (e.g. one min) use this to calculate the rate of co2 production (which gives an indication of respiration rate
5) repeat with water bath at different temps
6) respiration is controlled by enzymes- so as temp increases, so should the rate of repistation up until the optium point