Quality Of Stored White Tea And The Optimization Of Processing Technology

In this study,Fujian white tea and Zhejiang white tea were used to analyze different raw material grades and different aging time.The different varieties of Zhejiang white tea were naturally stored and sampled at different degrees of aging,combined with the pile-up experiment and the blended test.All samples were teasted by sensory analysis,physical and chemical analysis and chemometric analysis.The chemical substance of aged white tea and process optimization of the white tea were discussed.The main research results are as follows:(1)The sensory quality and chemical composition of white tea vary significantly within different aging time.The changes in sensory quality are mainly reflected in three aspects of color,aroma and taste.The aging trend of color appears to be green decreases,yellow,red and brown increases.The overall aroma is clear and the aroma are weakened within the process of aging,but the flavor of jujube and sweetness are constantly increasing.The taste is characterized by a decrease in freshness and greenness,and an increase in sweetness and aging.Correlation analysis between the chemical components and the degree of aging time showed that there was a significant positive correlation between vitexin-2-O-rhamnoside and aged degree,and the correlation coefficient was larger than 0.6.Besides,theophylline,epigallocatechin,epigallocatechin gallate,glutamic acid,glutamine,asparagine,arginine,valine,phenylalanine and isoleucine have significant negative correlation,and the correlation coefficient is greater than 0.6.12 components with significant correlation with aging degree at 0.01 level and correlation coefficient greater than 0.6 were selected for principal component analysis.The cumulative variance contribution rate of the first three principal components is 76.13%,and three types of different stored time white tea in the score map were distinguished.The amino acid substances play an important role in distinguishing different storaged time white teas.(2)The withered tea leaves with water content of 18%-20%were tested for different pile-up time and different pile-up temperatures.The results showed that a certain period of pile-up after withered was conducive to the sweetness and sweetness of white tea.Pile-up temperature of 35°C can promote the production of sweet substances faster than the normal temperature environment,but the pile-up time is better not to exceed 15 days.Long time of pile-up would produce oil taste.The comparison test of different drying methods showed that the low temperature and long drying time can significantly improve the sweetness of the tea soup,and the light wave drying method has a significant effect on improving the white tea aroma quality.(3)Through sensory evaluation and taste evaluation of white tea of different varieties and different regions,through product style design,blending and learning from each taste factor,new products with good aroma and taste was been explored.