Study On The Technological Processing Of Shandong Yellow Tea

As the clone tea trees successfully introduced and the pruning technology enhanced in Shandong province,the mechanical picking will gradually replace manual picking,and the production cost will be also reduced. However,the leaves picked by machine are mature,and not suitable to make high-quality green tea and black tea.Because of the process of stuffy,yellow tea tastes mellow and sweet,and it has low requirements of raw material.In addition, Shandong people have the habit of drinking "old dry-roasted tea" for a long time, and the "old dry-roasted tea " is a kind of yellow tea which is made in Huoshan county,Anhui province.Therefore, researching and producing yellow tea in Shandong province can not only save the cost of production, enrich tea varieties, but also can meet the needs of people in Shandong yellow tea.This paper had setted different processes of withering, fixations, stack-cover and baking types made by tea leaves with3leaves in Shangdong province, and we had analyzed the differences of tea made in different months. The best processing-technology of yellow tea had been discussed. The main results were as follows:1. The quality of yellow tea would be better if using the method of "withering" during processing.The made tea had long and strong corn flavour, yellow and bright liquor and it tasted sweet and mellow.2.Fixations had significant effects on both chemical composition and sensory quality, besides, steaming was the best method to process Shandong yellow tea. The content of chlorophyll (0.31%), flavonoid glycosides (2.65%) and phenol ammonia ratio (4.27) in steamed leaves and the content of chlorophyll (0.29%), tea polyphonies (6.90%) and phenol ammonia ratio (3.58) in steamed yellow tea were the least, respectively. On the other hand, the content of soluble protein (4.39%) and flavonoid glycosides (2.04%) were the most. By the sensory method, it indicated that steamed yellow tea had long and strong rice crust aroma, and it tasted mellow and thick, and brewed tea leaves were yellow and bright. In conclusion, steaming is the best method of fixation to process Shandong yellow tea.3.Stack-cover methods and time had significant effects on both chemical composition and sensory quality of Shandong yellow tea.By wet stack-cover methods, time was short and small changed, but by dry stack-cover methods, time was long and change was big.3days was suitable for stuffing in dry environment, and the made tea had long and strong special aroma of yellow tea. Tea water was yellow bright, and it taste mellow with flowery flavour, sweet after taste, and brewed tea leaves were yellow and bright.3hours was suitable for stuffing in wet environment, and the made tea had long and strong flowery flavour. Tea water was orange bright, and it taste mellow and thick, and brewed tea leaves were yellow and bright. With the stuffing time increased, The biochemical component contents of7samples which were made by dry stack-cover methods displayed some changes.The contents of chlorophyll and soluble protein decreased first and then increased. Phenol ammonia ratio and the contents of free amino acids and soluble sugar increased first and then decreased, but he contents of flavone increased first and then tended towards stability. The biochemical component contents of7samples which were made by wet stack-cover methods also displayed some changes, but less than dry ones. The contents of chlorophyll and soluble sugar increased first and then decreased.4.208species of volatile components of yellow tea were detected by GC/MS, they consist of89hydrocarbons,34alcohols,28aldehydes,19esters,18ketones,16heterocycles,2ethers,1acid and amides separately. The5tea samples had32common aroma components, and the ratios of the total were41.67%(T1),53.59%(T2),49.98%(T3),35.09%(T4) and39.87%(T5) separately.With the baking temperature increased, the aroma types, content and ratio of aroma compounds of yellow tea changed: The contents of low-boiling aroma decreased or disappeared;The kinds and the contents of aroma with flowery, fruity and toasted aroma increased; Some aroma substances changed into isomers; The characterising ingredients among the5samples had significant differences. Besides, In the aspect of kinds, they had high contents of hydrocarbons, alcohols, aldehydes and heterocyclic, but low at others.The baking temperature not only affected the type and the concentration of aroma, but also affected liquor color and taste. Drying Shangdong yellow tea,and then baked at120℃or130℃can help us to get perfect tea.5. Make tea in Shangdong province, adopted the methods we studied, and then compared them which were made in June, July, August and September, by the chemical and sensory method.It indicated that Shandong tea leaves can be made to yellow tea from June to September.