| The preparation conditions of green-tea beverages was studied. The results show that the optimal extraction conditions are: extraction time is 10 min.; the ratio of water and tea is100:1; extraction temperature is 90℃ ; extraction pH is about 5.5-6.0. The better clarify effect was achieved with using multiple clarificant (STPP: SHMP: β-CD=1: 1: 2; addition:0.4g/L) after comparison of mono-clarificant such as STTP, SHMP, β -CD. Ultrasonic and Microwave sterilization was used to substitute the traditional high-temperature method. The results of tea sterilization declared that ultrasonic and microwave could thorough kill bacillus and eumycetes and it has less influence on the tea quality than the high temperature way. Maximum Tea polyphenols could be reservered and least browning and precipitate were formed in the process. Therefore, ultrasonic and microwave sterilization is one of the best tea sterilization methods. The experiments show that the main reason that the Tea Cream were easily formed in the tea infusion is the reaction of Tea polyphenols, caffeine, protein and metallic ion. H-bonds were formed between phenol hydroxyl group in phenol chemicals, keto-amino group in caffeine and peptide linkage of protein. Co-acervation makes particle larger and tea turbidity. The main react is the interaction between main components Tea polyphenols and caffeines, but the reaction of protein and Tea polyphenols could not be ignored. An effective way to solve the problem of Tea polyphenols precipitate is using multi-clarificant in the tea clarify process.
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