Biotechnology Processes

Question 1

What are the stages in baking?

Three stages

Answer 1

1) An active yeast mixtures added to flour and other ingredients, mixed and left to rise.
2) Dough is knocked back (excess air is removed), kneaded, shaped, and left to rise again.
3) Cooked in a hot oven - carbon dioxide bubbles expand so the bread rises more. The yeast cells are killed during cooking.

Question 2

What organism is used in baking?

Answer 2

Yeast

Question 3

What type of respiration occurs in baking?

Answer 3

Aerobic respiration.

Question 4

What organism is used in brewing?

Answer 4

Yeast

Question 5

What type of respiration occurs in brewing?

Answer 5

Anaerobic respiration

Question 6

What is produced from the yeast in brewing?

Answer 6

Ethanol

Question 7

Why are GM yeast cheaper than traditional yeast in brewing?

Answer 7

Ferment at lower temperatures

Question 8

What are the stages in brewing?

Five stages

Answer 8

1) Malting - barley germinates producing enzymes that break starch molecules down to sugars which yeast can use
- Seeds are then killed by slow heating but enzyme activity is retained to produce malt

2) Mashing - the malt is mixed with hot water (55-65ºC) and enzymes break down starches to produce wort.
- Hops are added for flavour & antiseptic qualities
- The wort is sterilised & cooled

3) Fermentation - wort is inoculated with yeast
- Temperature maintained for optimum anaerobic respiration (fermentation).
- Eventually, yeast is inhibited by falling pH, build up of ethanol and lack of oxygen.

4) Maturation - the beer is conditioned for 4-29 days at temperatures of 2-6ºC in tanks
5) Finishing - the beer is filtered, pasteurised and then bottled or canned with the addition of carbon dioxide

Question 9

What organism is used in cheese making?

Answer 9

Bacteria - feed on lactose in milk

Question 10

What are the stages in cheese making?

Five stages

Answer 10

1) The milk is pasteurised to kill off most natural bacteria & homogenised (fat droplets are evenly distributed around the milk)
2) It is mixed with bacterial cultures and sometimes chymosin enzyme & kept until the milk separates into solid curds and liquid whey
3) For cottage cheese, the curds are separated from the whey, packaged and sold.

4) For most cheese, the curds are cut and cooked in the whey then strained through draining moulds or cheesecloth.
- The whey is used for animal feeds.

5) The curds are put into steel or wooden drums & may be pressed.
- Left to dry, mature and ripen before eating as the bacteria continue to act.

Question 11

What organism is used in yogurt making?

Answer 11

Bacteria - Streptococcus thermophilus which produces lactic acid

And

Lactobacillus bulgaricus

Question 12

What are the stages in yoghurt making?

Four stages

Answer 12

1) Skimmed milk powder is added to milk and the mixture is pasteurised, homogenised, and cooled to about 47ºC
2) The milk is mixed with a 1:1 ratio of Streptococcus thermophilus and lactobacillus bulgaricus, which is incubated at 45ºC for 4-5 hours.
3) At the end of the fermentation, the yoghurt is put into cartons or mixed with previously sterilised fruit.
4) Thick set yoghurts are mixed & ferment in the pot