Study On Quality Identification And Process Qptimization Of High Quality Zhangping Shuixian Tea

In order to satisfy the growing consumption demand of high-quality Zhangping Shuixian tea,and promote the high-quality transformation and development of the Zhangping Shuixian tea industry.In this study,quality identification and process optimization of high-quality Zhangping Shuixian tea were carried out in view of the two urgent problems in the development of Zhangping Shuixian tea industry,which only rely on sensory evaluation and lack more objective and accurate judgment basis,and the low excellent rate of production and processing of Zhangping Shuixian tea.Taking ordinary Zhangping Shuixian tea and high-quality Zhangping Shuixian tea represented by Zhangping Shuixianwangzi tea and Zhangping Shuixiangongzhu tea as samples.The key factors affecting different quality types of Zhangping Shuixian tea and different flavor types of high quality Zhangping Shuixian tea were explored by sensory evaluation,biochemical composition determination and multivariate analysis.Based on the research results of high-quality Zhangping Shuixian tea and the actual production demand of Zhangping Shuixian tea,experiments with different thickness of indoor withering tealeaves,different temperatures and times of moisture redistribution and different baking temperatures were carried out to provide reference for the process optimization of Zhangping Shuixian tea.The main results are as follows :(1)Compared with ordinary Zhangping Shuixian tea,high-quality Zhangping Shuixian tea had a strong and mellow taste and lower bitterness,with an obvious fragrance of osmanthus or orchid,which was fragrant and lasting.The contents of caffeine,tea polyphenols and water extract were the key to identify the taste quality of Zhangping Shuixian tea in different quality types.The difference in the contents of1-pentene-3-ol,hexanol,2-methylbutanal,α-pinene,cis-2-pentenol,α-farnene,indole,D-limonene,3,5,5-trimethylhexanal,3-carene,4-methylcyclohexanol and cis-jasmonone were the key to distinguish the aroma of Zhangping Shuixian tea in different quality types.The decrease of polyphenols and caffeine content in high quality Shuixian tea was an important factor for the reduction of bitter taste.The contents of n-hexanol,α-farnesene,indole,D-limonene and cis-jasmonone were significantly increased,which was an important factor promoting floral intensity.(2)Among high-quality Zhangping Shuixian tea,Shuixianwangzi tea and Shuixiangongzhu tea have different flavor and quality.Shuixianwangzi had strong and astringency in its taste and sweet osmanthus fragrance in its aroma.Shuixiangongzhu had mellow and sweet after taste flavor and faint scent with orchid fragrance.The difference in the contents of caffeine,tea polyphenols,and thearubigins are characteristic nonvolatile components to identify differences in their tastes.The difference in the contents of 3-carene,cis-3-Hexenyl Acetate,1-Hexanol,α-pinene,and D-limonene are characteristic volatile components to identify differences in their tastes.(3)The study on the effect of different thickness of indoor withering tealeaves on the flavor and quality of Zhangping Shuixian tea showed that the whole process of 2cm thinspreading thickness was better than that of 2-8 cm gradual thickening spreading thickness was better than that of 8cm thick spreading thickness.Compared with the other two kinds of spreading thickness,the whole 2 cm thin spreading thickness was beneficial to reduce the content of tea polyphenols,caffeine and increase theaflavins content,promote the improvement of flavor concentration and alcohol and return to sweet.It decreased the content of cil-2-pentenol,and increased the content of 1-pentene-3-ol,ocimene,3-carene,n-nonyl acetate,2-methyl butanal and 2-ethyl furan,which promoted the fading of the green gas of Zhangping Shuixian tea,and formed the fragrant and long orchid and sweet fragrance.(4)The study on the effects of different room temperatures and times of moisture redistribution on the flavor and quality of Zhangping Shuixian tea showed that compared with normal temperature,low temperature moisture recovery was more conducive to retaining water extract content,reduce the tea polyphenol and phenol ammonia ratio,increase the perilla alcohol,1-pentene-3-alcohol,linalool,4-methyl cyclohexanol,3,4-dimethyl benzyl alcohol,tetrahydrolavandulol,1-octyl alcohol and 2-methyl butyl aldehyde content of volatile,retain tea concentration and reduce bitterness,form a strong floral fragrance.The study on different times of moisture redistribution showed that the optimal moisture redistribution’s time at low temperature was 4h,which was beneficial to increase the content of free amino acids,reduce the contents of tea polyphenols,caffeine and flavonoids,promote the increase of the content of volatile compounds of 2-methylfuran,linalool,phenethyl alcohol and carvinol,which maintained the concentration and alcoholicity of tea soup,reduced the bitterness and increased the sweetness,and improved the orchid aroma and durability of tea.The optimal moisture redistribution’s time at room temperature was 2 h,which can better retain the content of water extract,increase the content of free amino acid to reduce the ratio of phenol to ammonia,and increase the content of 2-methyl-butanal to reduce the content of cis-2-pentenol,which was helpful to maintain the concentration of tea,reduce the bitterness and promote the appearance of orchid and sweet fragrance.(5)The study on the influence of different baking temperatures on the flavor and quality of Zhangping narcissus tea showed that,with the increase of baking temperature,the flavor concentration and sweetness of Zhangping Shuixian tea increased and then decreased.In addition,tea fragrance increased and then decreased,and changed from strong orchid fragrance to sweet and burnt fragrance.Under different baking temperatures,baking tea samples at the temperature of "90 ℃-80 ℃-70 ℃" had the best flavor quality,which was conducive to increasing the contents of water extract,soluble sugar and theaflavins,while decreasing the contents of caffeine and theabrownin increased the flavor concentration and sweetness,and decreased the content of cis-2-pentenol.Increased dehydrolinalool,linalool,β-caryophylene,1-pentene-3-ol,α-farnene,hexanol,2-methylbutyraldehyde,1-ethyl-1h-pyrrole and 2-methylfuran promote fragrant and persistent orchid and sweet fragrance.