Studies On The Effect Of Different Tea Shoot Maturity On The Quality Of Green Tea Based On Metabolomics And The Processing Technology Of Green Tea Bag

Green tea is one of the main types of tea in China,which belongs to"non-fermented"type.Dried and steamed fresh leaves inactivate polyphenol oxidase,so they contain lower catechin oxidation level(<1%),and more catechins than black tea and Longjing tea(catechin oxidation level is 5-16%).In addition,green tea is rich in minerals,vitamins,caffeine,tea polyphenols and other components,and has health benefits such as anti-cancer,anti-fibrosis properties and neuroprotective ability.It has long been regarded as a natural drug in China,and is now one of the most popular beverages in the world.Wuyuan green tea is a product of China geographical indication and of world-famous,which produced in Wuyuan County,Jiangxi Province.William Ukers,an American scholar,wrote in his"All About Tea"published in 1935:"Wuyuan green tea is the best quality of Chinese green tea".In addition to the manufacturing method and geographical difference,the maturity of fresh tea shoot used as a raw material for processing is also a very important factor affecting the quality of green tea.Even if the tea shoot were grown in the same place and manufactured under the same condition,the tea product have different market prices based on the maturity of fresh tea shoot.In the case of Wuyuan green tea market,the tea product processed from buds are believed to be of highest quality thus the most famous and expensive type,followed by those made from one bud with one leaf,one bud with two leaves,and one bud with three leaves.In addition,green tea processed by each tea shoot maturity has its own unique quality,mainly in terms of aroma,flavor,and soup color,which affect consumers'preference.At present,the influence of different tea shoot maturity on the quality of green tea has not been studied,thus this paper discusses the influence of tea shoot maturity on green tea from the following six chapters:Chapter 1:The main bioactive components of green tea were introduced.The definition of metabonomic,the common chemometric techniques of metabonomic,including unsupervised and supervised learning models,and the research progress of metabonomic in the field of tea in recent years were discussedChapter 2:Quantitative determination of gallic acid,caffeine,catechins and amino acids in green tea processed from different tea shoot maturity was carried out by high performance liquid chromatography and amino acid analyzer.The results showed that the contents of gallic acid and caffeine decreased with tea shoot maturity.Catechins were mainly divided into two groups:with ascorbic acid group(EGCG and ECG)and without ascorbic acid group(C,EC and EGC).EGCG,ECG and total catechins contents decreased significantly during tea shoot maturation,while C,EC and EGC showed the opposite trend.Amino acids include theanine and 17 free amino acids,the content of which reached the highest in green tea made from one bud and two leaves.Chapter 3:The change trend of total phenolic content(TPC)and total flavonoid content(TFC)in green tea during tea shoot maturity was discussed,and antioxidant and?-glucosidase and pancreatic lipase inhibitory activity of green tea were studied from the perspective of antioxidant,hypoglycemic and hypolipidemic effects of green tea on human body.Correlation analysis was used to study the relationship between TPC,TFC and antioxidant and?-glucosidase and pancreatic lipase inhibitory activity.The results showed that TPC,TFC decreased with tea shoot maturity,the antioxidant activity was relatively high in the tender tea shoot,and the IC₅₀ values of?-glucosidase and pancreatic lipase inhibitory activity increased during the age of tea shoot,which meant that their inhibitory activity continue to decrease.Correlation studies showed that TPC and TFC were positively correlated with the three in-vitro activities.Chapter 4:Based on gas chromatography-mass spectrometry combined with metabonomic to explore the influence of different tea shoot maturity on the volatile components of green tea.Using Mass Hunter mass profile software to screen the original data step by step,and through strict standard qualitative conditions,32 different volatiles were identified.The results of principal component analysis and heatmap showed that four kinds of green tea made with different tea shoot maturity were obviously distinguished.According to the undesirable and pleasure aroma types,32different volatile compounds were divided into Groups I and II.The relative content of Group I increased with the tea shoot maturity while the relative content of Group II decreased.Chapter 5:Based on ultrahigh performance liquid chromatography-quadrupole time of flight mass spectrometry and non-targeted metabonomic,the effect of different tea shoot maturity on non-volatile compounds in green tea were explored.Peak extracted,normalized,aligned and filtered step by step of the original data in positive and negative ions were conducting by using Mass Hunter mass profile software,and778 and 1274 compounds were obtained respectively.Principal component analysis and cluster analysis results showed that there were significant differences among four kinds of green tea made by different tea shoot maturity.Through the search for characteristic metabolites and strict qualitative conditions,32 characteristic metabolites were identified,mainly amino acids,phenolic acids,flavanols and flavonols.Orthogonal partial least square analysis of 32 characteristic metabolites and three in-vitro activities revealed that most of the polyphenols and flavonoids have a significant correlation with the three in-vitro activities.Chapter 6:This chapter explained the processing process of green tea bags,so as to deepen the understanding of the production process of green tea bags,and provide theoretical basis and guidance for its production.