| Hubei province has a long history in congou black tea production and its flavor characteristics is advantageous,but tea quality is affected greatly by many factors,such as processing conditions,workers and their experience,the congou black quality were not stable,the quality assessment of tea depends on experienced staff,There is no standards for the process technologies and products classification,the progress of new products research and development were lagged.In recent years,new varieties of black tea,famous and excellent black tea and new products have developed rapidly,such as Yinghong 9cultivar,jinjunmei black tea and the oolong-black tea,which favored by consumers by virtue of its excellent flavor characteristics,Domestic congou black tea production scale is also rapidly expanding,In the past five years（2014-2018）,the output of black tea in China grew by 45.39%annually,The total production capacity in 2018 was 262 thousand tons,which become an important part of China’s tea industry.Hubei province as a major tea production,the black tea industry has also made considerable progress,However,the qualities and the flavor of Hubei congou black tea influenced by cultivation conditions and traditional techniques,which need to be explored,and the product quality and processing technologies also need to be improved.In order to improve the sensory and physicochemical quality of hubei congou black tea,the sensory evaluation,color difference determination,liquid chromatography（HPLC）,microsolid phase extraction（HS-SPME-GC-MS）and metabolome no-target detection the study was adopted in the study,The research on quality evaluation technology of the Hubei congou black tea was carried out and the processing parameters were systematically optimized.At the same time,the new products of xiachou congou black tea,famous and excellent needle black tea,jasmine black tea and oolong black tea were developed,which provide theoretical guidances and technical support for promoting the healthy and steady development of Hubei congou black tea industry,The main research content is reported as follows:1.Analysis of flavor characteristics and quality of Hubei congou black teaThe domestic congou black tea samples were collected,and 84 typical samples selected by the sensory evaluation methods,and the color difference meter,stoichiometry and headspace solid phase microextraction techniques and GC-MS,the color of dried tea,tea infusion s and infused leaves,the content of chemical and aroma components were determined,the relationship between the black tea and tea color,physical,chemical and aroma components and sensory quality also uncertain,the study in order to ascertain for the product quality standards of judgement and provide technology support.The color research rusluts shows that the color of dried tea,tea infusion and infused leaves of Hubei congou black tea was detected,which closely related to dry tea color,tea soup color and infused leaves color,the regression equations of dried tea,tea infusion and infused leaves color quality scores were established respectively by using binary polynomial stepwise regression method,After the follow-up sample fitting verification test,the error value is basically within 0.6,which show that it is feasible to predict the color quality of congou black tea by using the method,and the color quality of congou black tea can be evaluated quickly and accuratelyThe aroma research rusluts shows that the Hubei congou black tea is sweet andsugar content on the whole,However,the aroma of black tea in different regions is somewhat different in sensory sense.For example,the black tea in Yichang and Enshi regions were characterized by a strong and lasting sweetness and sugar fragrance,some samples have honey fragrances and flower and fruit fragrances,black tea samples in Xiangyang region has high fire fragrances,and black tea in Huangkang region has caramel fragrance,By using HS-SPME-GC-MS method,93 volatile components were detected,including alcohols,aldehydes,esters,ketones,aromatic hydrocarbons,alkenes,and hetero compounds,which alcohols and aldehydes were the main compounds,aroma volume in between 100.61～383.98μg·L-1,the 7 principal components extracted from 19 common ingredients,the cumulative contribution rate of 86.48%,the analysis found linalool,geraniol and methyl salicylate,1-octene-3-alcohol,beta-Malaysian ketene,beta-ionone,transgeranyl acetone,benzene acetaldehyde,decanal,hexanal,ransnerolidol,2-ethyl furan and limonene characteristics such as aroma components together to form the flavor characteristics of the sweetness of Hubei black tea and sugar is sweet.2.Research on key processing technology optimization and quality chemistry of Hubei congou black teaThe key processing technology of Hubei congou black tea was studied,According to the technological process of withering,rolling,fermentation and drying,processing parameters were optimized and to support and reduce the production the cost,in order to enrich the processing technology theory of congou black tea and provide scientific and technological support for the processing of Hubei congou black tea.The research results of process optimization show that the continuous and standardized processing process of black tea is proposed by optimizing the process parameter system and equipment selection of withering,rolling,unblocking,fermentation,drying processes.The production efficiency is 4-5 times that of the traditional process,and the quality of the manufactured products is improved by 1-2grades on average,Based on the key technologies obtained from the above research,which guided many enterprises such as Hubei Caihua tea co.,LTD and Hubei Jinguo Tea co.,LTD to produce congou black tea,and the service covers the main black tea producing areas in Hubei province.The congou black tea dried by different technologies（including hot air and heated roller methods）made with the same class of fresh tea leaves obtained from the Fudingdabai variety were compared and analyzed for their quality characteristics in terms of the sensory quality,tea brew color,main chemical components and antioxidant activity.Results indicated that the sensory score of hot air treatment was more than the heated roller treatment,the hue of tea brew color（a and b）,the content of theaflavins and thearubigins were much higher than hot roller treatment,while the content of water extract,free amino acids,tea polyphenol and the ratio of polyphenol to amino acids in hot air treatment were significantly higher;The main aroma substances like hyacinthin,decanal,linalool,trans–2–octen–1–ol,1–heptanol and methyl salicylate etc in hot air treatment showing sweet flavor,the antioxidant activity of hot air drying black tea were better than hot roller treatment.It is would be an effective means to enhance the quality of congou black tea.3.New product development and process optimization of Hubei congou black tea seriesBased on the characteristics of tea producing areas in Hubei province,new products of summer congou black tea,oolong black tea,jasmine black tea and needle black tea series are innovated and put forward according to the industrial development and technologies,and the optimized process is briefly introduced as follows:In order to improve the congou black tea quality in summer,different polyphenol oxidase from Jinshui NO1,Fengshui,Huanghua and E,li NO2 Pyrus Pyrifolia Nakai have been utilized to ameliorate the fermentation,and the sensory quality,chemical components and aroma of congou black tea in summer have been compared in present paper.Results indicated that notable differences in oxidation kinetics curves of polyphenol oxidase from different Pyrus Pyrifolia Nakai,The Jinshui NO1 and Fengshui has high enzyme activities,the maximum reaction rate approached the highest at 3 minutes and 5 minutes respectively,it could complement the low enzyme activities of tea at the initial stage of fermentation and promote the congou black tea permention in Summer.Meanwhile,the PPO in Jinshui NO1 could obviously improve the sensory quality,compared with the control,the brightness of tea and the tea brew hue increased significantly（P<0.01）,the content of theaflavins,the thearubigins and soluble sugar in black tea increased respectively（P<0.01）,while the content of aroma components also increased,such as phenylacetaldehyde,（E,E）-2,4-heptadienal,safranal,nerol,cis-linalool oxide,β-Ionone,trans-geranylacetone,α-Copaene etc.The all results indicated that,the application of polyphenol oxidase in Jinshui NO1provides an useful way on quality improvement of yihon black tea in summer.The oolong black tea new product development:with one bud and three leaves or one bud and four leaves from oolong tea varieties,the application of sun-withring and rocking process in oolong black tea processing to develop new products,which nerolidol,jasmone acid methyl ester,α-ionone,jasmine lactone,alpha olefin,indole with aroma component is much higher than traditional black tea,the new product qualities were improved and superior to the traditional tea products.at the same time sensory evaluation increased by 1 to 2 levels with heavy fragrances flavour quality characteristics.which guided many enterprises such as Hubei Enshi Xinyuan co.,LTD to produce oolong congou black tea 500 kg per day since 2015.In order to improve the tea appearance quality,the influencing factors on the quality of tea were evaluated based on the on single factor tests of semi-finished tea container,pressing manner,time duration for shaping,leaf feeding and temperature,the semi-finished tea container,time,leaf feeding and temperature were selected as the main effect factors with.The mathematical model of shaping technologies in processing famous and high quality needle black tea tea was established with single factor and orthogonal experiment.The opimal technique of shaping processing were:semi-finished tea container was 32%,temperature was 110℃,leaf feeding was 3 kg,and time duration for shaping was 30 min each time.With the above treatments,Therefore,the shaping technologies is reliable.which guided many enterprises such as Hubei Enshi Jinguo co.,LTD to produce needle shape congou black tea 200 kg per day since 2015. |
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