Technological Study On Preparation Of Low Caffeine Instant Tea With Fresh Tea Leaves

Instant tea is very popular in consumers for its advantages of convenient, fast and hygienic. Caffeine is the main flavor substances of instant tea. Because of the modern researchs showing that the caffeine has some harmful effects to human body, people began to develop low caffeine instant tea. At the same time, in order to meet the psychological needs of the modern consumer pursuing of fashion, nature, return to one’s original nature, the people began to accelerate the use of fresh tea leaves for processing instant tea. This study developed the processing technic of processing low caffeine instant green tea and black tea with fresh tea leaves, which took the application status of tea processing technology as the background. The processing technic of processing low caffeine instant green tea was as below:taking the fresh old age tea leaves as raw materialâ†'-decaffeinated with hot waterâ†'using the high efficiency traditional hot water leaching fresh tea leavesâ†'deslagging by centrifugationâ†'membrane concentrationâ†'vacuum drying. The processing technic of processing low caffeine instant black tea was as below:taking the fresh old age tea leaves as raw materialâ†'decaffeinated with hot waterâ†'-taking the broken fresh leaves as the exogenous enzyme for the fermenting to get black tea embryoâ†'extracting with hot waterâ†'deslagging by centrifugationâ†'membrane concentrationâ†'vacuum drying. The experiment conclusions were as followed: (1) The degree of important influence the decaffeination from big to small was ordinal:temperature> time> pH> liquid-solid ratio. The degree of important influence the leaching of catechin of from big to small was ordinal:time> temperature> pH> liquid-solid ratio. The optimum conditions of decaffeination were the temperature of95℃, the time of5min, the liquid to solid ratio of1:12and the pH=5.5. Verified by pilot plant tests, the removal rate of caffeine was82.72%and the retention rate of catechin was95.75%under the optimum conditions.(2) The degree of important influence the extraction from big to small was ordinal: temperature> time> pH> liquid-solid ratio. The optimal extraction conditions of instant green tea powder were the extracting temperature of95℃, the extraction time of75min, the ratio of liquid to solid of1:18and the pH=5.5. Verified by pilot plant tests, the caffeine content of low caffeine instant tea processing with fresh tea leaves was only7.86mg/g under the optimum conditions, which was below the low caffeine instant tea with maximize10.0mg/g. Comparing with the general instant tea, the low caffeine instant tea processing with fresh tea leaves was more refreshing when tasting. However, the yield of the low caffeine instant tea processing with fresh tea leaves was only12.8%, which is much lower than the yield of the processing of instant tea processing with tea finished product. However, through the analysis of economic benefit and ecological benefit, low caffeine instant tea produced with fresh leaf was better than the instant tea produced with tea finished product. Through the sensory evaluation, we found that the quality of low caffeine instant tea produced with fresh leaf was also slightly better.(3) Through the comprehensive evaluation, when the addition of exogenous enzymes was7:3, the quality of decaffeinated black tea was best. Namely, per70g decaffeinated fresh leaf add30g chopped fresh leaf as enzyme source and followed by8:2. The degree of important influence the extraction of theaflavin from big to small was ordinal:pH>temperature>liquid-solid ratio>time. The degree of important influence the extraction of thearubigins from big to small was ordinal:liquid-solid ratio>time>pH>temperature. The optimal extraction conditions of instant black tea powder were the extracting temperature of95℃, the extraction time of30min, the ratio of liquid to solid of1:15and the pH=5.5. Through the sensory evaluation, we found that the quality of decaffeinated instant black tea produced with fresh leaf was better. Compared with the traditional processing methods, the yield of21.4%was not poor. Therefore the technology can be applied to industrial production of the low caffeine instant tea.