| Chuanhuang No.1 is a characteristic tea variety in Sichuan.It was selected by Sichuan Agricultural University and several units through continuous cutting propagation of a mutant single plant in Fuding Dabai Tea Garden in Pujiang County.The new shoots of this tea variety are tender yellow in spring,summer and autumn,with outstanding specificity,high yield,good quality and stable variety.It has great ornamental value and tea product processing and utilization value.At present,Chuanhuang No.1 is mainly used for the processing of spring green tea,while the green tea processed in summer and autumn is bitter and astringent,which leads to the serious waste of tea gardens in summer and autumn and the low utilization rate of tea resources.It is extremely important to increase the utilization of Chuanhuang No.1 tea variety resources.This study intends to develop and utilize the summer and autumn raw materials of Chuanhuang No.1,and develop a special floral yellow tea.By introducing the shaking process and optimizing the processing technology,the bitterness of the tea soup is reduced and its special flavor is increased.At the same time,the quality formation of the tea is systematically studied.The results are as follows:1.The single factor experiment was carried out using fresh leaves of Chuanhuang No.1 in summer and autumn.The results showed that the tea quality was the best when the second shaking time was 14 min,the yellowing temperature was 50°C,the yellowing time was 7 h and the drying temperature was 95°C.The results of sensory evaluation were as follows: the shape of tea was tender yellow with red;the aroma is sweet,the flower fragrance is rich,the soup color is yellow and bright,the taste is thick and mellow,and the leaf bottom is tender yellow and red.2.The results of process optimization of floral yellow tea based on response surface design showed that the optimum process parameters of floral yellow tea were as follows :fresh leaves(5 kg)→ spreading(room temperature,spreading 12 h)→ shaking(4 min)→standing(1 h)→ shaking(14 min)→ standing(1 h)→ fixing(300°C,1min)→ rolling(15 min,light pressure)→ stuffy yellow(50°C,7 h)→ initial drying(80°C,60 min)→drying(95°C,120 min).The processed dry tea has a tight shape,tender yellow with red,sweet floral fragrance with chestnut fragrance,yellow and bright soup color,mellow taste and sweet floral fragrance,and yellow and red leaf bottom.Compared with the green tea and yellow tea processed by the same batch of raw materials,the contents of water extract,amino acid,soluble sugar,caffeine,thearubigin and theabrownin in the flower-flavored yellow tea increased with the processing of the same batch of raw materials under the optimal process.Compared with the fresh leaves,the increases of the finished tea were4.86%,7.58%,4.21%,3.06%,35.29% and 22.30%,respectively,which were higher than those of the finished green tea and the finished yellow tea.The contents of tea polyphenols,catechins and total chlorophyll decreased with the processing.The decrease of tea polyphenols,catechins and total chlorophyll in processed tea was 10.39%,28.59% and52.38% respectively,which was lower than that of green tea and yellow tea.PCA and HCA analysis based on the color parameters of the processed products during the processing of floral yellow small tea showed that shaking and yellowing were the main processes that caused the color difference of floral yellow small tea.The PCA model R2 of the process sample tea sample and tea infusion during the processing was 0.816 and 0.858,respectively,and Q2 was 0.692 and 0.718,respectively.3.The microstructure of the leaves of each product during the processing of yellow tea showed that the leaf tissue structure of the fresh leaves was complete,and the epidermal tissue,palisade tissue and stomata were clear.The leaf cells of withered leaves shrank slightly,but the cell structure and morphology changed little compared with fresh leaves.The edge cells of the leaves of the leaves were broken obviously,and the cell shrinkage was aggravated.The leaf cell tissue structure of de-enzyming leaves was similar to that of shaking green leaves.The leaves of the rolled leaves are obviously broken and the color is deepened;the cell structure of stuffy yellow leaves did not change significantly compared with rolling,but there was no large number of chloroplasts.4.The volatile components of the key process samples and finished tea samples of floral yellow tea were analyzed by GC-MS,and the green tea and traditional yellow tea made from the same batch of raw materials were used as controls.The results showed that43 kinds of aroma substances were detected in the flower-flavor yellow tea,the relative content was 42.69%,and the types of aroma were the highest.However,24 kinds of substances were detected in fresh leaves,and the relative content was 24.48%,and the types of aroma substances were the lowest.During the processing of floral yellow tea,the types of aroma substances in the key processing steps are increasing.Compared with the three kinds of finished tea,the aroma types of floral yellow tea were the highest,followed by green tea,and the traditional yellow tea was the lowest.There were 13 kinds of different aroma substances in the key processing steps of flower-flavor yellow tea,which were linalool,phenylacetaldehyde,geraniol,pentamethylbenzene,diisobutyl phthalate,benzyl alcohol,benzaldehyde,(E)-oxidized linalool,trans-linalool oxide(furans),octanol,dibutyl phthalate,α-farnesene and 2-methyl valeric anhydride.These substances may be the key substances for the aroma formation of flower-flavor yellow tea.There were 7 kinds of different aroma substances in the three kinds of finished tea,which were linalool,phenylacetaldehyde,benzaldehyde,ionol,α-farnesene,benzyl alcohol and(E)-linalool oxide.They may be the key substances that cause the difference in aroma of floral yellow tea. |
