Abstract:

The heat inactivation kinetics of taro polyphenol oxidase (PPO) and peroxidase (POD) in the temperature range of 50°-80°C followed the first-order kinetic model. Both enzymes possessed two isoenzymes with varying heat stabilities. In the range of 60°-70°C, heat stable isoenzymes accounted for 33-34% of POD and 67-72% of PPO. E a and z values of heat stable isoenzymes were, respectively, 19.4 kcal.mol -1 and 25.9°C for POD, and 21 kcal.mol -1 and 25.5°C for PPO. The pH optimum was 5.9 for POD and 6.5 for PPO. POD was densely located on the surface of taro tubers whereas PPO was located more to the center. Taro PPO possessed both catechol oxidase and phlorOĞLUcinol oxidase activities but no laccase activity. Inhibition of PPO by EDTA, SO 2 , NaCl and ascorbic acid was also determined.

Keywords: