Oxidation of foods

Food can also be affected by the oxygen in air. When some fresh fruit, such as an apple or pear, is cut or peeled, the outside surfaces darken and turn brown, making the food seem unattractive. The browning is caused by enzymes [enzymes: proteins which catalyse or speed up chemical reactions inside our bodies ] in the fruit reacting to the oxygen in the air. By adding an acid (eg lemon juice) or sugary solution (eg syrup), the enzymic browning or discolouring action is slowed down.

The diagram below shows three key ways to reduce the action of air content and reduce discolouration.