Modeling of polyphenol oxidase and peroxidase inactivation in coconut water during thermal treatment

Abstract

The effect of hot water bath temperature (80, 85, 90, 95 oC) and treatment time (2.5, 5, 7.5, 10 min) on enzymes (viz. Polyphenol oxidase and Peroxidase) and nutritional properties (viz. Ascorbic acid, Antioxidant activity and Total phenolic content) of tender coconut water (Cocos nucifera) was studied using 2 factor and 4 level factorial design. The treatment temperature and treatment time both had significant effect on ascorbic acid, total phenols, antioxidant activity, PPO and POD. The complete inactivation of POD achieved after thermal processing at 95 oC for 5 min but the complete inactivation of PPO obtained after 10 min, so PPO is more heat resistant than POD. Increase in process temperature and time had negative effect on PPO, POD, total phenols, antioxidant activity and ascorbic acid. The relation between independent variables and individual dependent variable was explained by a quadratic model. The regression coefficients and statistical results of the model were obtained from regression analysis. For all the dependent variables the R2 value of the quadratic model is higher than 0.9.