Kinetics and inactivation of peroxidase from carrot by alternative methods

In this study, carrot peroxidase was inactivated by heat treatment, microwave heating and high hydrostatic pressure. Activity of carrot peroxidase was determined by using pyrogallol, guaiacol and o-dianisidine as hydrogen donor. The kinetics of peroxidase catalyzed reaction followed Michaelis-Menten model and Km and V.max were determined by each hydrogen donor. Low Km was found by o-dianisidine and activity of enzyme for inactivation experiments was determined by using this hydrogen donor. Thermal inactivation of carrot peroxidase was studied in the range of 35 to 75°C. Complete inactivation of carrot peroxidase was seen after 10 min heating at 75°C. The kinetics of peroxidase inactivation showed biphasic first order behaviour indicating the presence of heat resistant and heat labile fractions of carrot peroxidase, while at 75 °C, peroxidase showed monophasic first order behaviour. Heat resistant fraction of carrot peroxidase was found to be 35 %. Activation energies of heat resistant and heat labile fractions of carrot peroxidase were found as 14.8xl04 j/mol and 8.96xl04 j/mol, respectively. Inactivation of carrot peroxidase by microwave heating was carried out at 2450 MHz and at different powers. Biphasic behaviour of enzyme inactivation was observed for the microwave treatment at 70 and 210 Watt, whereas at 350 and 700 WattABSTRACT KINETICS AND INACTIVATION OF PEROXIDASE FROM CARROT BY ALTERNATIVE METHODS SOYSAL, Çiğdem Ph. D. in Food Engineering Supervisor: Prof. Dr. Zerrin SÖYLEMEZ December 2003, 96 pages In this study, carrot peroxidase was inactivated by heat treatment, microwave heating and high hydrostatic pressure. Activity of carrot peroxidase was determined by using pyrogallol, guaiacol and o-dianisidine as hydrogen donor. The kinetics of peroxidase catalyzed reaction followed Michaelis-Menten model and Km and V.max were determined by each hydrogen donor. Low Km was found by o-dianisidine and activity of enzyme for inactivation experiments was determined by using this hydrogen donor. Thermal inactivation of carrot peroxidase was studied in the range of 35 to 75°C. Complete inactivation of carrot peroxidase was seen after 10 min heating at 75°C. The kinetics of peroxidase inactivation showed biphasic first order behaviour indicating the presence of heat resistant and heat labile fractions of carrot peroxidase, while at 75 °C, peroxidase showed monophasic first order behaviour. Heat resistant fraction of carrot peroxidase was found to be 35 %. Activation energies of heat resistant and heat labile fractions of carrot peroxidase were found as 14.8xl04 j/mol and 8.96xl04 j/mol, respectively. Inactivation of carrot peroxidase by microwave heating was carried out at 2450 MHz and at different powers. Biphasic behaviour of enzyme inactivation was observed for the microwave treatment at 70 and 210 Watt, whereas at 350 and 700 Watt