Why does an apple turn brown

We all know that an apple turns brown after being cut or beaten. The same phenomenon can be observed in mangoes, avocados, or potatoes, for example. An apple loses its quality when beaten and is less marketable for traders. But why does browning occur at all?

The apple is the fruit of the apple tree and it is a very popular fruit. It comes from Central Asia, probably from the territory of today's Kazakhstan.^[1] Kazakhstan's largest city, Almaty, even carries the Kazakh word for the apple Alma in its name. Worldwide production of apples is in third place after banana and watermelon.^[2] Half of apple production comes from China.^[3]

Browning of an apple is an undesirable phenomenon because it causes a change in taste and color, as a result of which the apple loses its economic value if it is still on the sale. This is the so-called enzymatic browning, because browning is caused by enzymes from the group of polyphenol oxidases, which are found in apples, contribute to the change in the color of the apple. However, browning requires the presence of oxygen. The so-called phenolic substances are converted to chirons in the presence of oxygen and by the action of an enzyme. This result of forming brown compounds. There is no reaction in the intact apple.^[4]

Browning can be significantly slowed down by boiling an apple in hot water or dripping with lemon juice. Vitamin C is an antioxidant that prevents browning. If a fruit or vegetable turns brown, it means that it contains relatively little vitamin C. Apples, pears, bananas, cherries, peaches or, for example, plums have very little vitamin C compared to oranges, strawberries, or raspberries.^[5]