B3

Topic 1 – Biotechnology

Microorganisms and Food

For years the food industry has been using microorganisms to produce cheese, yoghurt, chocolate, soy sauce, alcohol etc. And more recently we have started to use mycoproteins. Fermentation is when microorganisms break sugars down to release energy usually by anaerobic respiration. Yoghurt is basically fermented milk.  It is made by: The equipment is sterilised to kill off any unwanted microorganisms. The milk is pasteurised, heated up to 72 degrees Celsius for 15 seconds, again to kill any harmful microorganisms. Then the milk is cooled. A starter culture of bacteria is added, and the mixture is incubated, heated to about 40 degrees Celsius, in a vessel called a fermenter. 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 at this stage to make sure it’s the right consistency. Finally, flavours and colours are sometimes added and the yoghurt is packaged. Soy sauce is made by fermentation as well. There are different kinds of soy sauce, and they are generally quite complicated to make. This is the process behind one particular kind of soy sauce and it involves three kinds of microbes. Cooked soy beans and roasted wheat are mixed together. The mixture is fermented by the Aspergillus fungus. The mixture is fermented again by yeasts. The mixture is fermented again by Lactobacillus bacterium. The liquid is filtered to remove any gungy bits. Then it is pasteurised to kill off the microorganisms, and finally put into sterile bottles. A functional food is one that has some kind of health benefit beyond basic nutrition. For example, it might prevent some kind of disease, or it might promote your wellbeing. Plant Stanol Esters. Plant Stanol esters are chemicals that can lower blood cholesterol and reduce the risk of heart disease. Some food manufacturers add them to spreads and some dairy products. People who are worried about their blood cholesterol levels may choose these spreads over normal spreads.  Stanols occur naturally in plants, but in very small quantities. Stanols are produced commercially by using bacteria to convert sterols, types of fats found in plants like the soya bean into stanols. Prebiotics. Some people take substances called prebiotics to promote growths of good bacteria in the gut. Prebiotics are carbohydrates such as oligosaccharides. They are a food supply for good bacteria. Bad bacteria and humans can’t digest the prebiotics as they don’t have the right enzymes. Prebiotics occur naturally in foods like leeks, onions and oats, but you can’t get enough of them in a normal diet to cause a significant effect. This is why some people take supplements.

Microorganisms and food

Microorganisms are used when making lots of foods. Sometimes the microbial product is eaten but sometimes it is just used to help make a food. In the first two examples, the microbial product is used to produce a food. Enzymes. Enzymes such as invertase are used…