**4.5 Antibrowning and antioxidant properties**

Enzymatic browning in minimally-processed fruits and vegetables is linked to discoloration and discoloration of phenolic compounds catalysed by polyphenol oxidase (PPO) enzyme, which converts polyphenolic substrates to dark pigments in the presence of oxygen. Edible coating especially incorporated with antibrowning substances can control PPO activity, and in the other hand, can provide a strong barrier for oxygen. The antibrowning substances mostly used are ascorbic acid,

thiol-containing compounds (cysteine and glutathione), carboxylic acids (citric and oxalic acid), phenolic acids and resorcinols. These reduce o-quinones resulted from the action of PPO enzymes, back to their phenolic substrates [21].
