Abstract:

In order to reveal the oxidation-induced browning mechanism of the extracts from Jerusalem artichoke,the basic enzymatic properties of polyphenol oxidase（PPO） in Jerusalem artichoke were investigated by using a spectrophometer,with catechol as the substrate.In the investigation,the kinetics of enzymatic browning was investigated,and the effects of pH value,temperature,substrate concentration and enzyme concentration on the browning,as well as the effects of different substrates on the emzyme activity,were analyzed.The results show that（1） the optimal pH value and temperature for the enzymatic oxidation are respectively 4.8 and 35℃;（2） the PPO in Jerusalem artichoke is of poor thermal stability,with most of it deactivating after being heated at 85℃ for 5min;（3） the enzymatic browning accords with the Michaelis equation,and the kinetic parameters Km and Vmax are respectively 0.013mol/L and 7.5mmol/s;（4） the activity of PPO first greatly and then slightly increases with the enzyme concentration,with 0.8mL as the critical PPO dosage;and（5） the PPO in Jerusalem artichoke only affects o-polyphenol.

Key words: Jerusalem artichoke, polyphenol oxidase, enzymatic property, browning, oxidation