SECTION F: Microorganisms and Genetic Engineering

1. Milk is pasteurised at 85-95ºC for 15-30 minutes - to kill unwanted bacteria.

2. Milk is homogenised - to disperse the fat molecules.

3. Milk is colled to 40-45ºC and inoculated with a starter culture of lactic acid bacteria - so enzymes can survive.

4. Mixture is incubated at this temperature for several hours, while bacteria digest milk proteins and ferment lactose to lactic acid - to create optimum conditions for bacteria.

5. Thickend yogurt is stirred and colled to 5ºC.

6. Flavourings, colorants and fruits may be added before packaging. 

* LACTOBACILLUS + STREPTOCOCCUS bacteria comonly used.

1. Barley seeds are germinated. This requires heat, oxygen and water. They make amylase to digest starch into maltose to be used by the yeast for respiration.

2. Seeds are killed and dried to make malt. Enzymes aren't destroyed.

3. Malt is ground up and mixed with water in a mash tun. Amylase breaks down starch into maltose.

4. Malt is boiled and filtered.

5. Hops are added for taste and yeast is addedto ferment sugar making alcohol.

6. Beer is centrifuged, filtered and sometimes pasterised. Heated bacteria.

7. Beer is put into casks or barrels.

A fermenter is any vessel that is used to grow microorganisms used for fermentation.

They enable the environmental conditions such as temp, O2 and CO2 concentrations, pH and nutrient supply to be carefully controlled so that the microorganisms will yield their product most efficiently.