Flavonol Glycosides In Small/Middle-leaf Tea Varieties And Their Effects On Taste Quality Of Longjing Tea

Flavonol glycosides in tea play an important role in formation of tea taste quality.At present,researches on the composition characteristics of flavonol glycosides have mostly focused on their aglycone types,but less attention has been paid to different types of glycosylation level in flavonol glycosides.Based on an improved ultra-high performance liquid chromatography-mass spectrometry method,the composition characteristics of flavonol glycosides in tea were analyzed by using different types of aglycones and glycosylation level in this thesis.Through statistical methods such as principal component analysis and one-way analysis of variance,relationship between the composition characteristics of flavonol glycosides in tea trees and the processing suitability of tea tree varieties has been established,researches on composition characteristics and change rules of flavonol glycosides both in fresh leaves of different growth stages and Longjing tea processing was carried out,which provide theoretical basis and data support for the improvement of tea processing technology based on raw materials.Relying on traditional sensory evaluation methods and qualitative evaluation by attributes,the contribution of flavonol glycoside components to the taste quality and different taste attributes of Longjing tea was discussed,which is beneficial for study on the mechanism of Longjing tea taste quality.The main research results are as follows:(1)There existed a close relationship with the composition characteristics of flavonol glycosides in tea and the processing suitability of tea tree varieties.The level of Galactosylrhamnosyl-glucoside(Galrhaglu)and Galactoside(Gal)was higher in tea varieties which are suitable for green tea processing,the total amount of Galrhaglu glycosides in tea variety“Wuniuzao” was 6.92mg/g,and the total amount of Gal glycosides in “Longjing change” was 2.89mg/g.While Glucoside(Glu)level,especially the level of glucoside in Myricetin(RMG),was higher in black tea processing suitable tea varieties.RMG in variety “Zhenong 121” reached 4.0.The composition characteristics of flavonol glycosides in different tea varieties were closely related to their parent sources,among which the level of Galrhaglu,Glucosyl-rhamnoside(Glurha)and Glu had obvious differences.(2)Flavonol glycosides in different tenderness of spring shoots and in leaves on spring mature shoot with different leaf site showed a law of content that the related substances increased first and then decreased as the maturity of the new shoots and leaves increased.Shoots with one bud and two or three leaves and the second/third leaf on shoot had most abundant flavonol glycosides.In spring shoots with different tenderness,the changes of Glurhaglu level,Glu level as well as content of total flavonol glycoside(TFOG)played the leading role.Meanwhile,the changes of TFOG’s content,Glu level and the content of Kaempferol-3-O-galactosyl-rhamnoside(Kae-3-O-galrha)played the leading role in leaves of different positions.Tea trees grow by seasons,the content of flavonol glycosides in mature new shoots in summer was significantly higher than that in new shoots growing in spring,the total flavonol glycosides in maturity summer shoots of variety “ Jiukeng ” reached 21.2mg/g,in which the total content of myricetin and quercetin glycosides,and Glu level playing the leading role.(3)The content of flavonol glycosides decreased to varying degrees during some key processes such as withering,fixation and moisture regaining stage in Longjing tea processing,and Longjing tea made by different techniques have various taste styles.Taste quality of Longjing tea was closely related to flavonol glycosides.The taste score,thickness and umami attributes of the tea soup are significantly negatively correlated with the composition characteristics of flavonol glycosides,while the concentration and astringency attributes are significantly positively correlated with it.In particular,the correlation coefficient between Myricetin-3-O-galactosyl-rhamnosyl-glucoside and concentration attribute was 0.676,reaching a high correlation level.Generally,the total amount of myricetin glycosides and myricetin-3-O-glucoside as well as Glucoside level played a leading role in taste quality of Longjing tea.