Biopreservation of 'Birgah' Eggplant from Polyphenol Oxidase Activity Assayed In Vitro with Onion (Allium Cepa L.) by-products.

Eggplants are vegetables largely consumed in many recipes as fresh and whole product or, morerecently, as minimally processed vegetable (MPV). The main issue in diced eggplant consists in theoxidation due to polyphenol oxidase (PPO, EC 1.14.18.1), an enzyme producing pigments responsiblefor the undesirable dark color which spoiled the product. The aim of this work was to study fresh orheat-treated (100 °C for 15 min) onion by-products (paste, juice and bagasse) in order to evaluate invitro the PPO enzyme inhibition capacity in minimally processed eggplant cv. 'Birgah'. The heatedonion juice was the most suitable anti-browning extract among all by-products tested, followed bypasteurised paste and fresh juice (54.2, 41.2 and 37.3 % reduction in PPO activity, respectively). Datasuggested that the thermal treatment enhances the effects of the extracts probably due to a synergicaction between some endogenous active compounds present in onion and Maillard reaction productsobtained during heating