4BI1

Food Production

Use of Biological Resources · 3 question types

Practise

Exam Frequency Analysis

Past paper frequency (2018 to 2024)

This topic accounts for approximately 7% of your exam marks.

stable
Low
Stable7%

Microorganisms in food production (yeast, yoghurt, fermenter conditions) and glasshouse/fertiliser yield questions recur across most series.

Yoghurt is made from milk using the bacterium .

  • Milk is first heated (pasteurised) to kill unwanted microorganisms, then cooled to about 40 °C, and a culture of Lactobacillus is added.
  • The bacteria respire the milk sugar lactose anaerobically, producing .
  • The lactic acid lowers the pH of the milk. The acidity makes the milk proteins clot (coagulate), thickening the milk into yoghurt and giving it its sharp, tangy taste.
  • The acidic conditions also help preserve the yoghurt by stopping the growth of many spoilage and harmful microorganisms.