Use of Microorganisms in Food B3

• Yeast is a single-celled organism which respires aerobically to produce carbon dioxide and water.
• It is used to make bread rise and produce wine.
• When yeast ANEROBICALLY respires, it produces ethanol and carbon dioxide, which is known as fermentation.
• Yeast can use natural sugars as an energy source, like grapes in wine.

1) Pasterise the milk to 72 degrees (this kills unwanted microorganisms).

2) Cool the milk.

3) The bacteria culture is added. This ferments lactose sugar into lactic acid.

4) The lactic acid clots and solidifies the milk, making yoghurt.

Extra Information: The bacteria is called lactobacillium bacteria.

1) A culture is added to warm milk.

2) Lactic fermentation occurs.

3) The result is solid curds and whey.

 4) Other bacteria or moulds may be added to enhance flavour.

5) Left to mature.

Wine:

1) Grapes are crushed to juices.

2) Yeast and water is added.

3) The yeast anerobically respires, using the natural sugars avalible, to produce ethanol.

4) The yeast is filtered out and the product is left to mature.

Beer:

1) Barley grains are first soaked in water, known as malting.

2) Enzymes are used to convert starch into natural sugars, known as germination.

3) Yeast and more water are added.

4) The yeast anerobically respires, using the natural sugars avalible, to produce ethanol.

5) The yeast is filtered out and the product is left to mature.