| Due to the economic development, the problem of labor shortage is becoming more and more prominent in our labor intensive tea industry. Using machine to pluck and make good quality tea is becoming the inevitable trend for further development in tea industry. To make full advantages of machine-plucking tea fresh leaves, this study was carried out to test the next refining process and relationship between baking and aroma in Fujian Nanping Experimental Station, on the base of machine-plucking and manufacturing semifinished spring and summer Wuyi Rock tea.Online production mode was adopted in trials, based on preliminary experiments. By a comparative study of color selection parameters, the key process of refining, and measuring the hourly output of machine, proportions of three passage tea, chromaticity values and graded tea, tea stem and yellow leaf contents of samples, we can optimize the parameters of color selection. The results showed that, for the first color selection with Anke brand color sorter, optimum parameters of spring Wuyi Rock tea for the lesion size of upper sorting room was15, lower sorting room was11, and optimum parameters of summer Wuyi Rock tea for the lesion size of upper sorting room was2, lower sorting room was1. Comparatively, for the second color selection with DAEWON brand color sorter, optimum parameters of spring Wuyi Rock tea for light values of upper heterochromatic grain pattern and lesion pattern were68%, lower heterochromatic grain pattern was68%, lesion pattern was65%, and optimum parameters of summer Wuyi Rock tea for light values of upper heterochromatic grain pattern and lesion pattern were75%, lower heterochromatic grain pattern was75%, lesion pattern was70%.To study the effect of baking technology on improving aroma qualities of middle and low graded tea, different baking paremeters of temperature and time were set. Results showed that best baking parameters for Spring Wuyi Rock tea were baking at170℃for30min during first firing, and then lowering the temperature to140℃for30min during full firing. Comparatively. the best baking parameters for Summer Wuyi Rock tea were170℃for30min during first firing,170℃for35min during full firing.The final tea product was a mixture of30%spring Wuyi Rock tea and70%summer Wuyi Rock tea after baking respectively, on the base of actual production. According to sensory evaluation, two blending options were screened.27tea tasters from different regions joined to sensory evaluate the two blending samples. The results showed that the number proportions of tasters who prefer control,blending one and three were11%,33%and56%, and that the qualities of two blending samples are better than the control.The yield of main product of spring Wuyi Rock tea was56.7%, low-grade tea was13.3%, and that of summer Wuyi Rock tea was35.1%for main product,24.1%for low-grade tea. With preliminary calculation, the cost of semi-finished tea was36000RMB, while the total value of final tea product could reach to115458RMB. By online optimization, the drafts of refining technological process of machine-plucking Wuyi Rock tea was completed.The improved SDE method, combined with GC-MS analysis, was applied to find the best extraction conditions of Wuyi Rock tea aroma and the results suggested that the best extraction temperature was100℃, extraction time was3.0h and extraction quality was25.0g. With this method, this paper studied aroma qualities of different tea samples under different baking temperature and time. The results indicated that different baking temperature and time had no significant effects on the number of aroma components of Wuyi Rock tea, but with the increasing temperature, for the spring Wuyi Rock tea, the contents of alcohols, acids, hydrocarbons, nitrogen compounds decreased, esters increased and the total amount of aroma decreased. At the same time, the sum of floral and fruity aroma components showed a decreasing trend and baking fragrant aroma components showed an increasing trend. Similarly, for the summer Wuyi Rock tea, with the increasing temperature, the contents of alcohols, hydrocarbons, nitrogen compounds decreased, the contents of esters, aldehydes, acids, phenols, heterocyclic oxygen compound generally showed an increasing trend, and floral and fruity aroma substances and baking fragrant aroma components had similar variation with spring Wuyi Rock tea. And the burnt smell tea, whose content of floral and fruity substances was lowest and baking fragrant aroma components was highest, such as2,5-dimethyl-Pyrazine, furfural,1-(2-furanyl)-Ethanone,5-methyl-2-Fur ancarboxaldehyde,1-ethyl-1H-Pyrrole-2-carbo xaldehyde, lH-Pyrrole-2-carboxaldehyde and other substances generated a lot and their contents were significantly higher than other tea samples’, was with the highest temperature. Meanwhile, the study results showed that the ratio of floral and fruity aroma components and baking fragrant aroma components is between0.5to2.5, which increased with the decreasing temperature. After curvilinear regression analysis, the results indicated that there is a significant correlation between ratios (x) and scores (y) and their regression equation is y=10.130In x+76.232, correlation coefficient reaches0.939. |
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