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 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 (Δ 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 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. CONCLUSION Green tea extract may be an effective anti‐browning agent for short‐time stored cloudy apple juices.