Biology Revision (Microorganism and Food) EDEXCEL

The mould fungus Aspergillus niger is used to produce Citric Acid. Citric Acid is added to fizzy drinks, sweets,jams and jellies to enhance (bring out) the flavour in these foods. Citric Acid also prevents the breakdown of Vitamin C in food.

Different species of the bacterium Acetobacter are used to produceVitamin C

To produce invertase we use the yeast fungus called Saccharomyces cerevisiae. The enzyme (invertase) converts the sugar sucrose into glucose and fructose which are different types of sugars, which make the taste sweeter. As well as saving money; this also means that lower-calorie sweet foods are produced. It is used in the manufacture of sweets.

The amino acid called Glutamic Acid is produced by Corynebacterium glutamicum.

When it is neutralised it makes a sodium salt called Monosodium glutamate (MSG).When added to food, this enhances the flavour of the food. It's popular in Chinese foods.

Cheese is made by the use of a substance called Rennet which is vital to the process of cheese making.

Rennet is traditionally obtained from the lining of a calf's stomach. It contains an enzyme called Chymosin which makes the milk curdle/clot.

However, this is a problem for vegetarians as they wouldn't want to eat cheese which uses rennet from animals. SO, vegetarian cheese can be made by using Gentically Modified (GM) Bacteria. This is much better because it is more acceptable to vegetarians, it contains fewer impurities and its activity is more predictable.

• Enzymes are used to cut the chymosin gene from the cow.
  
• A Vector is used to put the gene into the bacteria DNA
• The DNA then starts to produce Chymosin.
  

Gelling Agents are added to food to make it thicker and less runny. Ice creams, gellies etc contain gelling agents.

An example of a common gelling agent is Gelatine which comes from animal bones.

However foods which do contain Gelatine are unacceptable to vegetarians. There are alternatives to Gelatine such as Carrageen Extract which comes from the reddish purple seaweed called Carrageen