Study on preparation of low-caffeine tea by vacuum sublimation treatment

Base on the sublimation properties of caffeine, we took the method of vacuum subimation to remove caffeine from green tea and studies the impact of this process on the quality of green tea.The results showed that the caffeine from tea samples was in combination state, not easy to sublimate, so a direct vacuum sublimate process could remove 15% of caffeine at the most.Through the study of different pretreatment impact on the removal rate of caffeine, the results showed that water infiltration combined with ultrasonic-microwave collaborative extractor pretreatment was the most effective.The optimal process for the vacuum sublimation method was:infiltrates tea with two times its mass of water, deal the samples with co-extraction instrument of ultrasoundmicrowave and the parameters are microwave power of 300W, ultrasonic power of 50W, processing time 60s, vacuum sublimate at 90℃ for 4h, the tea caffeine removal rate reached to 62.24%, main active ingredients tea polyphenol loss rate of less than 10%, and the loss of non-ester type catechins larger than esterified catechins.