Reaserch On Processing-technology And Quality Of Yellow Tea In Shandong

Yellow tea is one of the six kinds of traditional tea in our country,but the dynamics for research and development is little.Rencently,because of the advantages of high aroma and thick flavor,yellow tea is more and more popular.In order to caters to the demand of consumers , enrich the kinds of Shangdong tea, and increase the economic benefit of tea especially the summer tea, based on understanding the climatic characteristics , cultivation features of tea, suited-processing of leaves in Shandong, this paper discussed the best processing-technology of yellow tea ,and the best analysis condition and composition characteristics of aroma components in yellow tea was obtained,also the influence of quality in yellow tea was researched if microzyme was inoculated in the heaping for yellowing,thedifferences of sensory quality and biochemistry between yellow tea and green tea and the quality change of processing in yellow tea of every seasons were kown.The main results were as follows:1. The best processing technology of yellow tea were fresh leaves→placing of green leaves→evaporating green→slightly twising→heaping for yellowing lasting 48hours→heat energy dehydration (or bake-fry-bake dehydration).The aroma of made tea was fresh and sweet or scorch persistent,the liquor color was yellow bright, the flavor was fresh and mellow, infused of tea leaves were tender yellow. Among these processes, moderately placeing of green leaves, evaporating green, moderately twising have important value for reference to solve the technical problems of summer roasting green tea in Shandong, such as color dull and serious astringency. And the evaporating green was firstly applied to the yellow tea- processing.2.The most optimized conditions were using DVB/CAR/PDMS fiber to absorb aroma at 80℃for 1 hour and then aroma compounds were desorbed from the fiber in the injection of GC/MS at 230℃for one minute. 108 species of volatile components of yellow tea were detected by GC/MS, they consist of 32 hydrocarbons, 20 esters, 17 alcohols and aldehydes separately, 8 ketones, 4 oxygenates and nitrogen compounds separately, 3 acids, 2 sulfur compounds and one phenol. The content of aliphatic hydrocarbons and aldehydes were high and that of terpenes and aromatic compounds were low. Besides, some of characteristic aroma components of yellow tea, i.e .ethanedithiol, phenylethyl alcohol, butyl acrylate ect. were detected.3. Main effects of microzyme heaping for yellowing on yellow tea quality: the aroma style of yellow tea converted from scorch aroma to fresh and sweet, the liquor color became more green and brighter and the flavor more mellow and thick; the content of amino acid, soluble sugar, water extracts and flavonoid increased slightly, but tea polyphenol, caffeine, anthocyanin decreased slightly;there were 43 kinds of same components compared with common heaping for yellowing in the components of aroma. And there were 63 kinds of special components were found, accounting for 40.29% in total aroma components. The higher content of the special components were that diethyl-acetic acid(7.09%),(Z)-3-Hexadecene(2.59%),(Z)-2-Heptenal(2.28%),etc.4. The bitter material of tea polyphenol, anthocyanin etc were degraded in the processing of yellow tea in every season, the material content of the flavor of fresh and sweet, mellow and thick of amino acid, water extracts, soluble sugar increased, and the quantitative change in the heaping for yellowing was the most.5. The tea leaves were better in spring and autumn, the yellow tea and green tea had higher quality in this two seasons. But as the material concent of tea polyphenol, caffeine, anthocyanin were high, and amino acid low in summer, produced green tea tasted bitter and astringent but produced yellow tea in better quality.Compared with green tea, the decreased amplitude of tea polyphenol concent of yellow tea were respectively 11.51%,11.21%,13.92%,the ratio of TP &AA were respectively 13.87%,18.15%,15.97%; the increased amplitude of amino acid concent were respectively 2.74%,8.48%, 2.45%, the increased amplitude of water extracts concent were respectively 3.63%,2.80%,3.66%,and the concent of soluble sugar was higher, anthocyanin and caffeine were lower in spring , summer and autumn. So the flavor of yellow tea was more fresh and sweet, mellow and thick than green tea.