Green tea extract as an anti-browning agent for cloudy apple juice

BACKGROUND: 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 gL(-1), 2 gL(-1) and 3 gL(-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 (Delta E*), browning index (BI), yellowness index (YI), and the absorbance at 420 nm (A(420)). RESULTS: 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 gL(-1), 2 gL(-1) and 3 gL(-1) tea extract decreased by 53%, 74%, and96%, respectively. Browning of apple juice during storage decreased with increased concentration of green tea extract. After 48h, extract at 1 gL(-1), 2gL(-1) and 3 gL(-1) inhibited browning of juice expressed as BI by 48%, 60%, and 86%, respectively, comparing to pure apple juice. CONCLUSION: Green tea extract may be an effective anti-browning agent for short-time stored cloudy apple juices. (C) 2016 Society of Chemical Industry