- Meat contains fibres which are tough if you don’t beat it to break up the fibres. Pineapple juice, which contains enzymes that tenderise the meat, is sometimes added to meat in recipes to break down the protein fibres.
- The equipment is sterilised before production to kill any unwanted microorganisms.
- The milk is then pasteurised to kill the unwanted bacteria in the milk which could cause the milk to spoil when fermenting. The milk is heated to a certain temperature for a certain amount of time before immediately cooling after is removed from the heat.
- A mixture of Streptococcus and Lactobacillus are added in the starter culture. These bacteria respire anaerobically and thus produce lactic acid from the glucose in the milk in which they are added to.
- The bacteria ferment the lactose sugar in the milk to form lactic acid. The lactic acid makes the yoghurt become more acidic. The pH drop denatures the proteins in the milk and thus causes it to have a smooth consistency as it begins to clot and thicken.
- Flavours and colourings may be added to the yoghurt before being packaged and sold.
Enzymes for sweets
- The disaccharide sucrose is made up of glucose and fructose.
- One enzyme widely used in food manufacture is invertase. Invertase is produced by cultivating yeast called Sacchoromyces cerevisae in fermenters.
- The sugar that we get from sugarcane and sugarbeet is mostly sucrose. Invertase/sucrase converts sucrose to glucose and fructose.
- The mixture of glucose and fructose is sweeter than the original sucrose (fructose is very sweet) so less is needed to make sweet foods. It is also good for making soft-centered sweets.
- An example of how this works:
- A solid form of the centre of the chocolate is made using sucrose. A small amount of invertase is added before it is covered in chocolate.
- During storage, for a couple of weeks at 18⁰C, the enzyme partially liquefies the sucrose within the chocolate. This makes the soft centre.
Enzymes for washing powders
- Washing powders contain detergents that cannot remove some kinds of stains. Therefore many washing powders also contain enzymes, including proteases and lipases.
Proteases break down proteins, such as haemoglobin in blood stains. Lipids break down fats, such as grease.
- The products can easily be washed out with water whereas the stain cannot.
- Biological washing powers are more effective at working at low temperatures (e.g. 30⁰C) than non-biological washing powders.
- The enzymes work best a pH 7. Hard water can sometimes be alkaline, as they contain high levels of calcium, which can damage the enzymes.
- Special stain removers can be bought to remove wine, blood or oil stains. Some are solvents but some contain specific enzymes that will break down the stain.
Enzymes for cheese-making
- Chymosin is the enzyme used to make the curds and whey, the beginning of the cheese. Traditionally, the enzyme is from calves’ stomachs. Chymosin affects the protein in the milk, making it separate into curds, protein and fat, and whey.
- In order to make blue cheese such as stilton, fungi is also used in cheese production.
- Because using enzymes from animals make it impossible for vegetarians and vegans to eat it, scientists have a found a new way of producing chymosin. In the 1980s, it was discovered that bacteria could be genetically modified to produce the enzyme.
- They took the calf gene for chymosin and inserted in into the bacterial plasmid, which then was inserted into the bacteria to produce chymosin. Now, most chymosin is made from genetically modified yeast. This enables a much easier and cheaper way of producing large quantities of very pure chymosin rather than getting it from calves (in the form of rennet).
Genetically modified organisms
- Making a genetically modified organism use recombinant DNA technology. This means that different pieces of DNA are recombined in a new way.
- One of the first examples of this technology was the production of bacteria that contained the human gene for making insulin. This is how it is done:
- A plasmid is removed from a bacterium.
- The insulin gene is cut out of a human chromosome using a restriction enzyme. These enzymes recognise specific sequences of DNA and cut the DNA at these points. The cut leaves one of the DNA strands with unpaired bases – this is called a sticky end.
- The plasmid is cut open using the same restriction enzyme which leaves the same sticky ends.
- The plasmid and human insulin gene are mixed together.
- Ligase added to join the sticky ends together. This produces recombinant DNA.
- The recombinant DNA is inserted into the bacterium.
- The modified bacterium is grown in a fermenter. Soon enough, millions of bacteria would have grown which produce insulin.
- These bacteria are now transgenic as they contain a gene transferred from another species.
- Enzymes are significantly used in biotechnology. They are usually immobilised which means they are trapped on/ in an inert material. This means that they can be used time after time.
- For example, lactase can be immobilised into beads and then be put into milk. This is done to break down the lactose (into soluble glucose and galactose) found in milk to make lactose-free milk. This is useful for people who are lactose intolerant and also as a food for cats who do not make the lactase enzyme.
- Immobilised enzymes can be made by mixing an enzyme with sodium alginate solution. Drops of this to calcium chloride solution would create insoluble beads of calcium alginate containing the enzyme.
Enzymes and food production
- Enzymes are important in the production of many types of food and drink. They are used to produce things as varied as vegetarian cheeses, sweets, baby foods and many types of fruit juice.
- They speed up the production of these foods and make them much cheaper for us to buy.
- Enzymes such as cellulase and pectinase are used to produce fruit juice. Pectinase separates the plant cells from each other and cellulase breaks down the cellulose cell walls. As a result more juice can be extracted from the cells.
- Cellulase is produced by the microorganisms which are found in the digestive system of cows. This enzyme helps them break down the cell walls in grass.