Yeast in Food Production (Edexcel IGCSE Biology)

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Yeast in Food Production

  • Microorganisms can be used by humans to produce foods and other useful substances
  • One example of this is the production of bread using yeast
  • Yeast is a single-celled fungus that can carry out both aerobic and anaerobic respiration

A typical fungal cell

Yeast is a single-celled fungus, similar to the one shown in the diagram above

Making bread

  • During bread making yeast is added to bread dough
  • The yeast produces enzymes that break down the starch in flour, releasing sugars that can be used by the yeast in respiration
    • The yeast begin to respire aerobically but will switch to anaerobic respiration when oxygen runs out
  • When yeast carries out anaerobic respiration it produces alcohol (ethanol) and carbon dioxide
  • The carbon dioxide produced by the yeast is trapped in small air-pockets in the dough, causing the dough to rise (increase in volume)
  • The dough is then baked in a hot oven to form bread
    • During baking any ethanol produced by the yeast is evaporated in the heat, so bread doesn't contain any alcohol
  • The yeast is killed by the high temperatures used during baking
    • This ensures there is no further respiration by the yeast

Glucose -> ethanol + carbon dioxide

The carbon dioxide produced by the anaerobic respiration of glucose is what makes bread dough rise

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Lára

Author: Lára

Expertise: Biology Lead

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.