POLYPHENOL OXIDASE INHIBITORY AND ANTIOXIDANT ACTIVITY OF EXTRACT OF CANNA EDULIS KER STEM

Polyphenol oxidase (PPO) extracted from Canna edulis Ker rhizome was investigated. The substrate specificity was established as catechol > caffeic acid > chlorogenic acid > gallic acid > catechin. The optimum temperature and pH of the PPO activity were 20C and 6.8, respectively. The PPO was sensitive to many general inhibitors including C. edulis stem extract. Through response surface design, optimized inhibitor combination, containing 200 mg/L of citric acid, 284 mg/L of ascorbic acid, 67 mg/L of ethylenediaminetetraacetic acid and 8,000 mg/L of C. edulis stem extract, was obtained. With 96.73% of inhibition rate, the inhibitor combination could be developed as a natural additive used in the process of food preservation in the sight of safety of C. edulis aboveground part confirmed by animal experiment. In addition, the optimized inhibitor combination increased total phenol content and antioxidant activity of C. edulis rhizome. PRACTICAL APPLICATION In the sight of fresh food preservation influenced by polyphenol oxidase, additives are necessary to prevent the oxidation of polyphenol which is usually being in all fresh fruit and vegetable. The chemical synthesized additives always have various side effects and it has become a hot topic to research, and develop natural food additive with antioxidant activity. However, natural additives commonly have poor antioxidant activity. Therefore, it is a good choice to study interaction between natural extract and different chemical compounds and to develop inhibitor combination containing natural extract as main component. In this study, the optimized inhibitor combination (including 93.56% Canna edulis stem extract) was obtained through response surface design with an inhibition effect as high as 96.73%. The inhibitor combination could be developed as a natural additive used in the process of food preservation.