No, not all the fruits. Enzymic browning can be observed in fruits such as apricots, pears, bananas, grapes, and avocados and vegetables such as aubergines, potatoes, lettuce. The enzyme polyphenol oxidase or tyrosinase that when in contact with oxygen catalyzes a biochemical reaction of plants phenolic compounds to brown pigments known as melanin, which results in the fruit or vegetable turning brown.