Harnessing Biology

Question 1

What is the role of yeast in the production of food including bread?

Answer 1

-Yeast mixed into dough prior to baking
-While baking, Yeast rapidly uses up all Oxygen present in the dough via aerobic respiration
-As a result, anaerobic respiration will occur to produce Carbon Dioxide, which forms bubbles that make the dough rise, and Ethanol, which evaporates into the atmosphere

Question 2

Explain the process of yoghurt production

Answer 2

• Equipment sterilized to prevent bacterial and chemical contamination
• Milk heat treated at 85-95°C to kill bacteria (removes O2, kills harmful bacteria, and changes milk proteins)
• Cooled to 40-45°C, Lactobacillus bacteria added
• Incubated for hours at this temperature for digestion of milk proteins & lactose fermentation
• Lactobacillus converts lactose to lactic acid, thickening milk into yogurt
• Yogurt stirred and cooled to 4.5°C to slow down further bacterial fermentation

Question 3

What is the role of bacteria (Lactobacillus) in the production of yoghurt?

Answer 3

-Ferment milk sugar (lactose) into lactic acid
-Give yoghurt its acid taste