Inactivation Kinetics and Thermodynamics Parameters of Polyphenol Oxidase and Peroxidase Activities in an Extract from of Violet Eggplant (Solanum melongena L.)

Abstract

Enzymatic browning is associated with the action of polyphenol oxidases (PPO) and peroxidases (POD). The products of these enzymes cause undesirable changes of color and flavor of processed eggplant products. The present study aimed to evaluate kinetic properties and thermodynamics parameters of PPO and POD activities for controlling this undesirable process in extract from of violet eggplant. The effect of heat treatment on polyphenol oxidase and peroxidase activities in violet eggplant were studied over a range of 30 to 80 °C. T1/2-values of enzymatic activities are between 6.15 ± 0.03 and 13,27 ± 0,04 min at 80 °C, they decreased with increasing temperature, indicating a difference thermostability of each enzyme. D- and k-values decreased and increased, respectively, with increasing temperature, indicating faster of these enzymes inactivation at higher temperatures. Results suggested that polyphenol oxydase and peroxidase were relatively thermostable enzymes with a Z-value which from 50.25 and from 88.33 °C and Ea of 41.21 and of 27.78 kJmol-1. Thermodynamic parameters were also calculated. The Gibbs free energy ΔG values range from 43.24 ± 0,03 to 91.45 ± 0,01 kJ/mol. These kinetic data can be used to predict prevention of browning in the violet eggplant (Solanum melongena L.) by thermal inactivation of enzymes.