摘要：

Enzymatic browning of fruits and vegetables and their products is an important factor worsening their quality. The influence of five green tea extracts at the concentrations of 1 g L-1 , 2 g L-1 and 3 g L-1 on polyphenol oxidase (PPO) activity in fresh cloudy apple juice was investigated. Moreover, PPO inhibition by tea extract and colour stability of juice during short-time refrigerated storage was studied. The changes of juice colour during storage was expressed as the total colour differences (ΔE*), browning index (BI), yellowness index (YI), and the absorbance at 420 nm (A420 ). All extracts inhibited PPO activity in fresh apple juice in concentration-dependent manner. PPO activity in pure apple juice decreased by 7% after 48 h, whereas PPO activity in samples with 1 g L-1 , 2 g L-1 and 3 g L-1 tea extract decreased by 53%, 74%, and 96%, respectively. Browning of apple juice during storage decreased with increased concentration of green tea extract. After 48 h, extract at 1 g L-1 , 2 g L-1 and 3 g L-1 inhibited browning of juice expressed as BI by 48%, 60%, and 86%, respectively, comparing to pure apple juice. Green tea extract may be an effective anti-browning agent for short-time stored cloudy apple juices. © 2016 Society of Chemical Industry.

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