Study On Optimization Of Processing Technology And Quality Formation Of The Particle Type Green Tea

The green tea is one of the largest outputs in China. As a type of green tea, the particle type green tea include pearl tea of Shaoxing, yongxi huoqing of Anhui and emerald of Guizhou, etc. Because of its suitablity for machine harvest, and availablity in late spring, summer and autumn fresh leaves as raw material, the particle type green tea has attracted more and more attention to improve the economic value of summer and autumn tea. This study proposed a processing technology which can products the high grade particle type green tea, based on the analysis the appearance quality of 11 particle type green tea, dynamic variation of appearance quality during the processing of particle type green tea, and the analysis the variation of volatile aroma compounds and non-volatile components during the processing of the particle type green tea.1. The key processing technology parameters of the particle type green tea was optimized through the studies of the influence of the picking standard of fresh leaves, the temperature of de-enzying, the time of first-step roasting and the temperature of shaping on the quality of the particle type green tea. The appropriate processing parameters is following:the harvested standard of fresh leaves, one bud and two or three leaves; the temperature of de-enzying,200-210℃; the time of the first-step roasting,15 min; the temperature of shaping and setting, 160-170℃. The quality of the particle type green tea reached a high grade with beautiful appearance, high aroma and fresh taste.2. The studies showed that the color changed from green to sepia to dark to depth fade gradually during the particle type green tea manufacturing, and the fresh leaves shape changed from more and more small to round and compact particles from fresh leaves to made tea. Based on the sensory evaluation results, the multiple linear regression (MLR) evaluation models of the shape and color were established. The correlation coefficient between predicted and measured values of tea color was 0.952 and 0.938; the correlation coefficient between predicted and measured values of tea shape was 0.965 and 0.936. These two models can evaluate the color and shape of the particle type green tea.3. Fifty aroma compounds were identified during the particle type green tea manufacturing from fresh leaves to dry tea. The aroma compounds, included hydrocarbons (33.40%), alcohols (31.77%), esters (11.64%), aldehydes (11.16%), ketones (7.54%), and acids (2.10%). The main aroma compounds of the particle type green tea were styrene, isopropyl acetate, benzaldehyde, benzene acetaldehyde,2,6,10-trimethyl-dodecane. acetophenone, linalool and its oxides, geranyl isovalerate, nerol, heptadecane, ethyl benzoate,2,6-di-tert-butyl-4-methylphenol and a-farnesene. The total amount of aroma substances showed a change of highâ†'lowâ†'high during the processing of the particle type green tea, and the aroma changed obviously in the stage of de-enzyming and shaping.4. The water content in the particle type green tea decreased during the manufacturing process. The loss of the water by first-step roasting and shaping reached 19.05% and 19.13% respectively. During the process, water extract decreased at first and then increased, tea polyphenols and total catechins decreased, some esters-catechins and simple-catechins decreased, and total amino acids increased. But different free amino acid showed different changing trends. Caffeine decreased in the stage of shaping, while flavonoids have no significant change. The change of free amino acids mainly depended on threonine, serine, asparagine, theanine, citrulline, y amino butyric acid and etc.