Abstract: Four different samples of tea polyphenols were used for studying isomerization of tea catechins undergoing various time processes and pH conditions during high temperature sterilization.The inhibitory function of vitamin C,gallic acid,citric acid on isomerization of tea catechins werealso studied.The results indicated that the optimal concentration of vitamin C inhibiting isomerization of catechins was 0.1 mg/mL,while citric acid significantly inhibited isomerization of catechins when the concentration was over 0.3 mg/mL,and gallic acid dose-dependently inhibited the isomerization of catechins and showed highest potential activity among three compounds.Besides,the stability of tea catechinswas also studied during an amibient temperature and high pressure condition or a low temperature(60 ℃) and negative pressure condition.The results indicated the pressure showed no effect on the stability of catechins while temperature was an important factor on that.

Key words: epicatechins, nonepicatechins, vitamin C, gallic acid, citric acid