Research Of Processing Technology And Quality Of Hanzhong Congou Black Tea

Black tea accounts for more than 70%of the world's total production and it is dominant in the market of international tea export trade as well.Therefore,its market is greatly potential.Congou black tea is one of the unique teas in China,which is processed with bud and fresh leaves of tea plants and subjected to withering,rolling,fermenting,drying and other procedures.During the processing,nutrient substances and hygienically components were formed,such as tea polyphenols,amino acids and tea pigments,which play an important role in the formations of color,aroma and have benefits on anti-cancer,anti-oxidation,promoting digestion and improving appetite.This project investigated the following studies in order to make full use of Hanzhong raw teas from the summer and autumn to produce high quality congou black tea,to better meet the divertive demand of market,to improve the economic efficiency and to promote the development of Hanzhong tea industry.The technological parameters of Hanzhong congou black tea were optimized.The black tea were analysised byusing traditional chemical analysis,UV-spectrophotometry,high performance liquid chromatography?HPLC?;inductively coupled plasma optical emission spectroscopy?ICP-OES?,automatic amino acid analyzer;principal components analysis?PCA?method.?1?Research on processing technology of Hanzhong congou black tea:Leave sort with wind?1 bud 1 leaf and 1 bud 2 leaves were separated as raw materials wind sorter?,Compound withering?room temperature:23?-25?,leaves thickness:2-3cm;After 12h natural withering,samples were moved to outdoor with temperature of 27?-32?and leaves thickness of 1-2cm;Sun withering of 3h was following and leaves were turned over 1 time or2 times during this processing until the leaves were shriveled up and softened by the sun?,staged rolling?ambient temperature is 27-30?;leaves weights are 30kg;the speed of twisting machine is 55-60r/min;Lightly knead for 30 min-heavy knead for 60 min-Lightly knead for 30 min were processed until the leaves strip rope was tight,juice full spillover was on the leaves'surface and the color turned red?,Natural fermentation?rolled leaves were put the into the clean and wet fermentation baskets and covered with clean and wet but not dripping cotton.Samples were then move to the fermentation room with room temperature of34-40?,relative humidity of 70%-80%,leaves temperature of 38?-42?and fermentation time of 4.5-5h?,Drying and moisture regain?the leaves were put into the rotary baking machine after fermentation as the temperature of 120?to dry for about 4 h and spread at normal temperature for cooling and moisture regain for 3-4 days?,perfumed in low temperature?the black tea leaveswere spread in bamboo plates of perfuming machine after moisture regain with the temperature at 80?for1.5 h,then samples were repacked and put in warehousing after spread for cooling for about 2h.?.The sensory evaluation showed that Hanzhong congou black tea produced by this processing had the feature of tight and thinshape,golden color,high-lasting aroma,strong glycol,sweet after-taste and hypertrophy and soft leaves.?2?The analysis of biochemical components of Hanzhong congou black tea:results of the conventional chemical components of the tea?moisture 4.66%;water extract 57.56%;total ash content 5.60%,in which the insoluble ash accounted for 1.80%,water soluble ash accounted for 98.20%,acid-insoluble ash accounted for 0.20%?showed that there were small differences between the data?except acid-insoluble ash in different months?after LSD_0.05analysis;results of the functional substances of the tea?tea polysaccharide 3.22%,free amino acids 3.22%,theanine 1.49%,tea polyphenol 9.80%,catechin 3.02%,caffeine 3.94%,theaflavins 0.28%,thearubigins 6.00%,theabrownine 8.08%?showed that there were large differences after LSD_0.05 analysis except for the tea polyphenols in different months.This result showedthat the functional substanceswere susceptible to the factors of environment,climate,processing condition and so on.Hanzhong congou black tea has high water extraction,tea polysaccharide,free amino acids and tea pigments.However,the tea polyphenol content is low.So it owns the quality of red color,strong,fresh and slightly astringenttaste.?3?The analysis of metal elements contents in Hanzhong congou black:The types of metal elements in the tea are abundant and contentsare suitably medium?Li 1.625 mg/kg,Mn17.703 mg/kg,Ni 74.752 mg/kg,Sr 0.361 mg/kg,Zn 12.749 mg/kg,Ba 0.771 mg/kg,Mg90.013 mg/kg,Fe 6.323 mg/kg,Ga 117.145 mg/kg,Cu 0.776 mg/kg,Al 13.871 mg/kg?.There are no harmful heavy metal elements detected such asCr,Pb and Cd.The results indicated that soil and environment of Hanzhong tea plantations are unpolluted and the congou black tea has good quality.There were large differences of metal elements in different months after LSD_0.05 analysis,showing that the contents of metal elements have a relationship with the climate and environment.?4?Analysis of the types and contents of amino acids in Hanzhong congou black tea:there were 32 kinds of amino acids detected.The average content is 32.399 mg/g and the content of theanine was more than 50%.Types of essential amino acids were complete?tryptophan could not be checked out because of hydrolysis?.The contents were high levels and the average content was 2.595 mg/g.The first limiting amino acids were mainly cystine+methionine.Taste amino acids were all checked out and the content were high with the average at 24.931 mg/g.The contents of amino acids of congou black tea are diversity in different seasons:summer>spring>autumn.The contents of total amino acids,essential amino acids and taste amino acids of summer are the highest,so summer black tea's quality and nutritional value are the best.This may be related to the high temperature,longer sunshine and rich rainfall in summer,which promotes the process of nitrogen metabolism of the tea plants.The results showed that the amino acids of Hanzhong congou black tea are diversity and high levels which may result inthe fresh and sweet taste.?5?Model construction of the liquor color and taste evaluations of Hanzhong congou black tea:the model of Hanzhong congou black tea liquor color and taste evaluations is constructed by using principal component analysis?F=0.4197F₁+0.2602F₂+0.1363F₃+0.0849F₄?.Contribution rate is up to 90.10%.The calculation results of the model compared withthe sensory evaluation showed that the two kinds of evaluation methods had high consistency.So the model is feasibility.This method reduces the error of subjective judgment caused by the sensory evaluation,and data analysis results are more objective.It opens up a new way for the liquor color and taste evaluations of Hanzhong congou black tea.