Kinetic Characterization and Thermal Inactivation of Peroxidase in Aqueous Extracts from Sweet Corn and Waxy Corn

The objective of this study was to evaluate the activity, kinetic behavior, and thermal inactivation kinetics of peroxidase (POD) in aqueous extracts from two kinds of milk ripe stage corn, sweet corn and waxy corn. Optimum activities using guaiacol as the hydrogen donor were obtained for sweet corn at pH 4.8 and for waxy corn at pH 6.0. The kinetics of POD showed characteristics which were dependent upon the concentrations of guaiacol and H2O2. The guaiacol K (m) values for sweet corn POD and waxy corn POD were 11.01 and 23.01 mM, respectively, whereas the H2O2 K (m) values for sweet corn POD and waxy corn POD were 2.85 and 0.33 mM, respectively. Thermal treatment of enzymatic aqueous extracts was carried out at different time-temperature combinations in the range of 0-25 min and 60-85 A degrees C. Arrhenius plot determination and calculated thermodynamic parameters suggested that the inactivation of POD followed first-order reaction kinetics, and the activation energy (E (a)) for inactivation of sweet corn POD (114.36 kJ/mol) was slightly lower compared with waxy corn POD (119.72 kJ/mol). There were several notable similarities between the inactivation kinetics in the two corn cultivars.