B3 Biology Edexcel

Biotechnology has been used for many year to produce foods such as cheese, yoghurt, chocolate, soy sauce, alcohol, etc. More recently we have started using mycroproteins to make things like Quorn.

Bacteria Ferement Milk to make... Yoghurt.

1) The equipment is sterilised to kill off any unwanted microorganisms.

2) The milk is pasteurised (heated to 72C for 15 seconds). This is done to kill any harmful microorganisms. The milk is then cooled.

3) A starter culture of bacteria is added, and the mixture is incubated (heated up to 40C) in a vessel called a fermenter.

4) The bacteria ferment the lactose sugar in the milk to form lactic acid. Lactic acid causes the milk to clot, and solidify into yoghurt (a sample is taken to check it is the right consistency).

5) Finally, flavours and colours are added and the yoghurt is packaged.

Soy Sauce is also made by Ferementation.

1) Cooked soy beans and roasted wheat are mixed together.

2) The mixture is fermented by the Aspergillus fungus.

3) The mixture is fermented again by yeasts.

4) The mixture is then fermented again by Lactobactillus bacterium.

5) The liquid is filtered to remove any gungy bits.

6) It is then pasteurised to kill off the microorganisms, and finally put into sterile bottles.

Functional Foods.

They are foods which are known to have some kind of health benefit beyond basic nutrition.

Plant Stanol Esters.

1) Plant stanol esters are chemicals which can lower blood cholesterol and reduce the risk of heart disease.

2) Some food manufacturers add them to spreads and some dairy products, which leads people to want to by them for the health benefits.

3) Stanols occur naturally in plants, yet due to the minimal amount, they are produced commercially by using bacteria to converts sterols (types of fat found in plants like the soya bean) into stanols.

Prebiotics.

Some people take substances called prebiotics which promote growth of 'good bacteria' in the gut.

1) Prebiotics are carbohydrates such as oligosaccharides. They're a food supply for 'good' bacteria. 'Bad' bacteria and humans can't digest the prebiotic- they don't have the right enzymes.

2) Prebiotics occur naturally in foods like leeks, onions and oats, but within a normal diet it is impossible for the minimal amount in them to have a significant effect. This leads to people taking supplements.

Lots of Microbial Products are used in food.

Enzymes.

1) Enzymes such as invertase are used in the manufacture of sweets and other foods.

2) Invertase converts sucrose (a sugar) into glucose and fructose (different types of sugar) which taste sweeter, This means less sugar is needed for the same amount of sweetness. This means manufacturers can save money and produce lower-calorie sweet foods.

3) Invertase is naturally produced by a yeast called Saccharomyces cerevisiae.