Study On Technology Of Increase The Color Of Summer-autumn Green Tea

Rich in nutritious and efficacious ingredients to human health, tea is one of the world's three non-alcoholic beverageswhich is also China's national drink and the traditional export commodities. With the rapid development of society and people's living standards, the phenomenon of "high-grade tea is best seller, low-grade tea is dead stock" appeared. At present traditional famous green tea is often made in the spring, but the production season is short, raw material is difficult to meet market demand. Improving the quality of summer-autumn tea can increase resource utilization and tea prices, which create real economic benefits. To a certain degree, color of dry tea, soup and infused leaf reflect the quality of green tea. With the development of quality of summer-autumn tea, tea sales will become very easy.In this study, the vacuum freeze-drying technology was applied to tea processing. After summer-autumn tea rehydrate, in order to enhance the color of tea, compared vacuum freeze-drying, microwave drying, drying and far infrared drying technology, combined with sensory evaluation, color determination and chemical composition analysis, and investigated vacuum freeze-drying mechanism. The best parameters in green tea processing by vacuum freeze-drying technology were determined by orthogonal experiment. Longjing 43 is fresh tea leaves as raw material, which was used to do the test about tea and broken tea by the application of freeze-drying and the best way of follow-up drying. The conclusions are as follows:1.After tea samples rehydrate, compared vacuum freeze-drying, microwave drying, drying and infrared drying method found that:the-a/b value of dry tea and infused leaf are higher than the other samples by the vacuum freeze-drying. In the sensory evaluation, the color of tea samples by vacuum freeze-drying is better than other and is significantly better than CK, but water extractum and phenol ammonia ratio is lower than CK; The total flavonoids and flavonoid glycosides are higher than CK, and chlorophyll a, chlorophyll b, total chlorophyll content are lower than CK. Vacuum freeze-drying is propitious to color, total flavonoids and flavonoid glycosides enhancement.2.In the lyophilization experiment, the moisture content of tea is most important factors. Drying time have a greater impact on the brightness of dry tea and soup, freeze dryer pre-freezing temperature and water temperature have a greater impact on tea leaves color. The results showed that the optimal conditions is moisture content 45%, drying time 3 h. Freeze dryer pre-freezing temperature and rehydration temperature of tea has little effect on the experimental results.3.The broken tea was made by Longjing 43, which shape and soup color, the-a/b values of infused leaf are better than the other by microwave deactivation of enzymes, rolled and vacuum freeze-drying. The total points have no significant difference by sensory evaluation. Microwave deactivation of enzymes, cut and vacuum freeze-drying are in favor of the color of tea, especially the color of dry tea and soup.4.The shape and color of tea samples that is longjing43 is better than nonrehydration samples by microwave deactivation of enzymes, re-rolled and then vacuum freeze-drying, the -a and -a/b value of dry tea was significantly higher than the other, its sensory evaluation scores have no significant increase. Contains material are slightly different, in which caffeine increases. The color of dry tea can maintain by microwave deactivation of enzymes, re-rolled and then vacuum freeze-drying and then rehydration.