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