Study and characterization of polyphenol oxidase from eggplant (Solanum melongena L.)

In this study the catecholase and cresolase activities of eggplant polyphenol oxidase (PPO) were investigated. Enzyme activity was determined by measuring the increase in absorbance using catechol as substrate and 3-methyl-2-benzothiazolinone hydrazone (MBTH) as coupled reagent. The effects of substrate specificity, heat inactivation, temperature, pH, and inhibitors were investigated to understand the enzymatic alteration of ready-to-eat preparations. Browning of vegetables was determined through a colorimeter. Decrease of lightness (L*) and increase of color difference values (ΔE*) were correlated with tissue browning. Antibrowning agents were tested on PPO under the same conditions. The enzyme activity was strongly inhibited by 0.4 M citric acid. Under natural pH conditions, the enzyme was also inhibited by tartaric acid and acetic acid. All of the results were used to understand the best conditions for food transformation (ready-to-eat and grilled eggplant slices).