Polyphenol oxidase determination in eggplant

In this study the catecholase and cresolase activities of different vegetables polyphenol oxidase (eggplant PPO and artichoke PPO) are described. Both enzymes showed catecholase activity. No activity was found toward monophenol. Enzyme activity was n determined by measuring the increase in absorbance when using catechol as substrates and 3-methyl-2-benzothiazolinone hydrazone (MBTH) as coupled reagent. The effect of substrate specificity, heat inactivation, temperature, pH and inhibitors were investigated to identify the most appropriate cultivar of different vegetables for ready-to-eat preparations. Browning of vegetables has been determined through digital imaging. Decrease of lightness (L*) and increase of colour difference values (dE*) were correlated with vegetables' browning. Antibrowning agents were tested on PPO under the same conditions. The enzyme activity was strongly inhibited by L-ascorbic acid 0,4 mM. Under a natural pH conditions, the enzyme was also inhibited by tartaric acid and citric acid at 100 mM.