Why does a cut surface of brinjal turns Brown?

When a brinjal is cut, its flesh is exposed to oxygen in the air. This oxygen reacts with the polyphenol oxidase enzyme in the brinjal, which in turn oxidizes the phenolic compounds in the brinjal. This oxidation reaction produces brown pigments called melanin, which are responsible for the browning of the cut surface.

The browning reaction in brinjals can be slowed down by several methods. One way is to store brinjals in a cool, dark place. Another way is to add an antioxidant, such as lemon juice or ascorbic acid, to the cut surface of the brinjal. Antioxidants help to inhibit the oxidation reaction that causes browning.