Effect of Pulsed Electric Field on the Activity of Apple Polyphenol Oxidase

Abstract:

The product quality of fresh apple and apple juice could be deteriorated by the enzymatic browning of polyphenol oxidase （PPO）. The possibility to deactivate of PPO through the pulsed electric field （PEF） was discussed. The condition to deactivate PPO enzymatic activity was optimized by the response surface analysis based on the results of single-factor experiments，such as voltage，residence time，frequency，and pulse width. The optimal condition was achieved with 25 kV of voltage，530 Hz of frequency，8 μs of pulse width，and 45 s of residence time，under which the inhibition rate of PPO activity reached to 51.86%. The color value and browning index of fresh prepared apple juice were directly related to the relative activity of PPO. PEF could inhibit the enzymatic browning of apple juice. For the apple juice prepared from the fruit treated under the optimal deactivation condition，the color value was significantly larger than that of the control group （P<0.01）. The content of total soluble solids and solution pH did not show significant change （P> 0.05），while the content of ascorbic acid decreased insignificantly （P>0.05）.