Use In Vivo of Natural Anti-Browning Agents Against Polyphenol Oxidase Activity in Minimally Processed Eggplant

Plant polyhenol oxidase (PPO, EC 1.14.18.1) is responsible along with other oxidases for the enzymatic browning reaction occurring during handling, storage and processing of vegetables. This work aimed at assessing the efficacy in vivo of some natural anti-browning agents in minimally processed eggplants. They were collected, washed, diced, submitted to dipping with inhibitors (L-ascorbic, benzoic, citric, ferulic and L-glutamic acid) at three concentrations (0.2, 0.5 and 1 %) and packed in ordinary atmosphere bags (PET), covered by a double barrier film and refrigerated for 7 days (4.0 +/- 0.5 degrees C, 95 % RH). The enzymatic activity was inhibited by addition of all anti-browning agents tested. At t=7 the greatest reduction in PPO activity was observed at the highest concentrations (0.5 and 1 %) of the inhibitors in the following order: ferulic acid (-43 %), L-glutamic acid (-32 %), citric acid (-27 %), L-ascorbic acid (-21 %) and benzoic acid (-15 %). These positive effects were also translated in terms of browning index, demonstrating the efficacy of the anti-browning treatments studied to extend the shelf-life of minimally processed eggplants.