Enzymatic browning of lotus roots and its control during storage

Effects of temperature, pH value, substrate concentration and enzyme inhibitors on polyphenol oxidase (PPO) activity in lotus roots were investigated to control enzymatic browning of lotus roots. The results showed that the optimum pH value of PPO activity of lotus roots was 7.5, and the optimum temperature of PPO activity was 35℃. The kinetics of oxidation of pyrocatechol catalyzed by the complexes were studied. The Michaelis constant of o-dihydroxybenzene catalyzed by PPO was as follows: Km=0.0273 mol/L. Treatments of sodium sulfite or VC restrained the PPO activity significantly. Treatments of acetic acid, citric acid, phytic acid, papain or cysteine also restrained the PPO activity. The optimum treatment for controlling enzymatic browning was 0.2% VC +2% acetic acid + 0.03% sodium sulfite. Dipping in sodium sulfite and VC, adjusting pH values and storage at low temperature, etc. can be used for inhibiting PPO activity and control enzymatic browning of lotus roots.