Microorganisms

Explain the role of yeast in bread production

Explain the role of yeast in bread production

1. as the dough rises (proves) trapped yeast cells give off carbon dioxide. Carbon dioxide is a waste product of anaerobic respiration.

2. sugars released from enzymatic breakdown of starch in bread flour allows the yeast to continue to respite anaerobically.

3. the carbon dioxide produced is trapped in bubbles in the dough.

4. when dough is baked, pockets of gas expand and bread rises.

5. as the yeast dies (caused by high temperatures) bread stops rising, but pockets of carbon dioxide are left, so bread maintains its shape.

Explain a practical to investigate the effects of temperature on the proving of dough

1. Put equal portions of dough into transparent cups. Incubation temperature written on the cup.

2. mark the height of the dough in each container.

3. put in fridge, lab bench, incubator and warm oven for 1 hour.

4. mark new height in each container and calculate the increase in height for each temperature.

Explain the role of bacteria (Lactobacillus) in the production of yogurt.

1. Lactobacillus bacteria can use a lactose (sugar found in milk) and convert it into lactic acid.

2. Fermentation process - bacterial starter (Lactobacillus) added to milk.

3. milk kept at 37-44 degrees Celsius for 4-6 hours.

4. as lactic acid is produces, pH of milk becomes more acidic.

5. acidity makes milk coagulate (go solid)

6. acidity also prevents growth of other microorganisms, so acts as a preservative.

Explain the use of an industrial fermenter

• microorganisms grow and reproduce in fermenters. Microorganisms needed for food production.

Why are suitable condition required in a fermenter?

• optimum conditions = more growth.

• maximum yield of products from the microorganisms.

why are aseptic precautions important?

• increases product yield because microorganisms aren’t competing with other organisms.

• products don’t get contaminated

nutrients

• nutrients provided in the liquid culture medium.

• paddles agitate/stir the contents to ensure even distribution of nutrients.

optimum temperature

• temperature monitored for optimum level. (fermenter gets hot because of microorganisms respiring)

• water-cooled jacket ensures fermenter doesn’t get too hot otherwise enzymes denature.

optimum pH

• pH kept at optimum level.

• enzymes work most efficiently = high rate of reaction

• product yield high

oxygenation

• oxygen provided if respiration of microorganism is aerobic.

aseptic precautions

• vessels sterilized with superheated-systems. kills unwanted microbes.

• sterile air supply ensures conditions aren’t contaminated.