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The science of nutrition and healthy eating
The science of nutrition and healthy eating

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2.7 Digestion inside and outside the body

Biological washing powder contains enzymes that, although extracted from microbes such as bacteria, are very similar to those produced in our digestive system.

Proteases work in much the same way inside and outside the body, by breaking down proteins. These proteins could be inside the digestive system – a poached egg eaten for breakfast – or egg spilt down a child’s T-shirt digested inside the washing machine by a biological washing powder (Figure 8).

An image of stain remover being sprayed onto a piece of clothing.
Figure 8 Difficult stains on clothes may need special preparation before washing to start the process of ‘digestion’

Lipases break down fat, whether they are inside or outside the body. They act on the butter eaten with the poached egg, or in the washing machine, getting rid of the mark where the buttery knife fell into the child’s lap. Once the protein and/or fat in the stain have been digested by the enzymes in the washing powder, they no longer cling to the fabric and can be rinsed away.

Enzymes are a type of protein and proteins coagulate at high temperatures. So, if boiling water is used with a biological washing powder, the enzymes are denatured and do not work. Because silk is a protein, biological washing powder containing protease can start to digest and weaken the threads, which could seriously damage clothes made of silk.