Study On The Effects Of Different Shading Conditions On The Quality Components Of Tea Leave

Matcha has unique flavor,color and pharmacological health effects.It is widely used in the production and processing of food,chemical products and health care products.Tea milling is the raw material for making matcha tea.Shading cultivation has an important influence on the quality of tea milling.Therefore,it is of great significance to study the effects of different shading conditions on the changes of quality components of tea milling to improve the quality of matcha tea.In this study,four shading rates(plot,S50%,S65%,S80%,S95%)were analyzed,and the four shading treatments were further divided into three coverage heights(sub plot,C20 cm,C40 cm,C60 cm)and shading time(4,8,12,14,16,18 and 20 days).The effects of tea quality components of four tea varieties;at the same time,the content changes of quality components in different tissues of tea shoots under shading treatment were analyzed.Through integrated analysis,the shading conditions that help to improve the quality of ground tea were clarified.These results will provide a reliable theoretical basis for improving the quality of matcha.The main results are as follows:(1)Correlation analysis and OPLS-DA analysis were used to comprehensively analyze the correlation between shading treatment conditions and quality components of ground tea.Correlation analysis showed that there were different degrees of correlation between shading days,shading rate and coverage height and different quality components of ground tea.OPLS-DA analysis showed that the main quality components of ground tea changed significantly in the early stage of shading,and changed little after 12 days of shading.(2)The content of milled tea quality components is determined by the tenderness of tea shoots and shading level.With the extension of shading time,the quality components of ground tea showed a downward trend;the effects of different shading treatments on the content of tea milling quality components of four tea varieties were different.Compared with the control,the contents of chlorophyll,free amino acid and theanine of four tea varieties increased under four shading rates,and the content of tea polyphenols decreased.The caffeine content of Zhenong 113,Xiangshanzao 1 and Jinxuan decreased under the shading rate of 50%,and increased under the other three shading rates;The caffeine content of Japanese tea cultivar Yabukita increased under four shading treatments.When the coverage height was 60 cm,the grinding quality of the four tea varieties was better.(3)The effects of different shading treatments on the milling quality index and hundred-bud weight of four tea varieties were consistent.Compared with the control,the ratio of phenol to ammonia decreased under the four shading rates,and the catechin quality index increased.The bitterness index of catechin increased at 95%shading rate and decreased at the other three shading rates.Covering height and shading time had no significant effect on the quality index of ground tea.The effects of different shading treatments on the 100-bud weight of different tea varieties were consistent,and the 100-bud weight decreased significantly under the four shading rates.(4)By comparing and analyzing the changes of chlorophyll content,tencha quality component content and hundred bud weight of different tea varieties under shading days,shading rate and coverage height,we determined the shading conditions that helped to improve the quality of tencha and the quality of tencha reached grade 1 :shading rate was 80%,coverage height was 60 cm,and shading time was 12 days.(5)Shading treatment changed the distribution of quality components in different tissues of tea shoots.In the early stage of shading treatment,the distribution ratio of free amino acids and theanine in leaves increased.In the late stage of shading treatment,the distribution ratio of free amino acids and theanine in leaves decreased,and the distribution ratio in stems increased.The distribution ratio of tea polyphenols and caffeine in leaves increased,and the distribution ratio in stems decreased.The contents of free amino acids and theanine were the highest in stems,while the contents of tea polyphenols and caffeine were the opposite.The distribution ratio of total free amino acids and theanine in leaves was negatively correlated with caffeine and tea polyphenols.Long-term shading was not conducive to the formation of tea quality.