Study On Continuous Green-making Technique Of Oolong Tea With Slow Speed

As the key procedure for the development of oolong tea specific quality,greenmaking could be affected by many factors,including the choice of processing machinery,the control of green-making intensity,the temperature and humidity in the narrow,blocking space,as well as the air circulation.In the past,through the observation and constant summary of tea harvesting,tea farmers have explored the most suitable climate for the production of oolong tea,namely "north wind " climate,and formed the concept of alteration between shaking and withering,in this way,the most adaptive local processing conditions was mastered.Various greenmaking tricks spring up,such as the unique hand-touching skill in Guangdong oolong tea producing area,and the stacking method after shaking,common in northern Fujian.Even with the limited condition,oolong tea the semi-fermented tea with fresh,mellow taste and rich flavor are still be created.With the progress and development of society,tea processing will certainly not stop at the manual or semi-mechanized stage,continuous and automated production is just around the corner.Thanks to the more comprehensive and in-depth theoretical research,the visualization and datamation of experience will become reality and eventually get rid of the dependence on experience.In this study,Baiye Dancong variety were used as raw materials,and traditional processing and continuous low-speed green-making methods were used.Five different sets of shading parameters were set for each processing method.At the end of the green-making step,the conventional oolong tea procedure were followed,including fixing,rolling and drying.The evaluation of green effect mainly includes the following aspects: sensory evaluation of tea;Determination and analysis of polyphenols,amino acids,alkaloids and other contents;detection and analysis of tea aroma;Real-time quantitative PCR analysis of polyphenol oxidase and ?-glycosidase genes related to quality formation.The research results are as follows.Under the different ways and frequency of green-making,the characters of oolong tea has a big difference in appearance,taste,the color of tea soup,aroma and tea leaf.The top 3 tea samples in the evaluation score are respectively the tea with four-times continuous greenmaking treatment,the tea with five-times continuous green-making treatment and the tea with three-times normal green-making treatment,which are tasted fresh,mellow and aromatic.The poor quality performance belongs to the tea sample with four-times normal green-making treatment and the tea sample with one-times normal green-making,which contain the mature stuffy taste and green taste.In terms of biochemical components,variance analysis showed that there was no significant difference in the biochemical components such as water extract,tea polyphenol content and total free amino acids between the two processes,that is,the new process of continuous low-speed rolling green tea could be equal to the ordinary one in terms of material transformation and quality formation of oolong tea.The higher the number of shaking,the lower the content of water extract,tea polyphenols and catechins.The content of amino acids increased with the increase of shaking times,and the content of theobromine and theobromine decreased slightly,which was relatively stable.In connection to aroma components and relative contents,the main aroma substances of oolong tea samples with ordinary and continuous green-making are hotrienol,methyl salicylate,?-linalool,trans-geraniol,2,6-dimethyl-1,3,5,7-octatetraene,benzaldehyde,terpinen-4-ol,p-Cymenene,limonene and ?-ionone,among which the relative content of such as ?-linol,terpinen-4-ol,cis-geraniol,and methyl salicylate,which are in ordinary green-making tea,is generally slightly higher than that of continuous green-making tea,and the more the number of shakes,the lower the relative content.The relative contents of aroma components such as hotrienol,2,6-dimethyl-1,3,5,7-octatetraene,olivetol,nerolidol,indoles,2-acetylpyrrole and cis-hexanioc acid-3-hexene ester increased with the number of shaking.With the progression of the process,the expression of polyphenol oxidase related genes in both the ordinary group and the continuous group showed an increasing trend.The expression of polyphenol oxidase in the ordinary group reached the maximum value after the 5th rocking,while that in the continuous group reached the maximum value after the 4th rocking,and the former was lower than the latter.The expression of ?-glucosidase related genes also showed an increasing trend with the increase of the number of green-making step,and the maximum value of the common green-making group and the continuous greenmaking group was reached after the fourth green-making,thus causing the change of the content and aroma components.