Practise yoghurt production by linking Lactobacillus, lactose, temperature control, anaerobic respiration and pH changes to lactic acid.
Yeast is a fungus used in the production of bread.
Yoghurt is another food that is produced using microorganisms.
Explain the importance of controlling the temperature in the different stages of yoghurt production.
An explanation that makes reference to three of the following:
- milk is heated at 70−95∘C/ pasteurised / eq
- to kill any microorganisms / bacteria / eq
- cooled / kept at 40−45∘C/eq(1)
- so Lactobacillus bacteria added can survive/ eq
- provide optimum temperature for enzymes / optimum temperature for respiration / optimum temperature for fermentation / eq
Explain the importance of changes in pH during yoghurt production.
An explanation that makes reference to two of the following:
- milk has a pH of 6.7 / 7 / about neutral / eq
- lactic acid produced / eq
- this makes the pH drop / become more acidic / eq
- stops other bacteria growing / preserves the yoghurt / clots milk / makes solid / eq