Metabolomics Study Of Non-volatile Components In The Processing Of Fu Brick Tea

Fu brick tea is a kind of dark tea,which is accepted by consumers because of its unique quality flavor.The change of non-volatile components in the processing of brick tea plays a crucial role in the formation of its taste quality.At present,the research on the non-volatile components of fu brick Tea is mainly concentrated on a certain kind of substances,and the change law of the whole non-volatile components in the processing of fu brick tea is still unclear,which hinders the in-depth study on the formation mechanism of the taste quality fu brick Tea.In this study,FTIR and UPLC-MSMS were combined with multivariate statistical analysis methods to study the composition and changes of non-volatile components in the processing of fu brick tea.The main research results are as follows:?1?The FTIR analysis was used to study the changes of non-volatile functional groups during the processing of fu brick tea.The results showed that the processing process of fu brick tea was divided into three stages.the first stage included the samples of Maocha period,the pile-fermentation and the first of fungus growing,and the second stage consisted of the samples on the third day of fungus growing and the6th day of fungus growing.The three stages included flowering from the 9th day to the 22nd day of fungus growing.The difference in absorption bands between the different stages is 983-1929 cm^-1,2010-2390 cm^-1,2848-225 cm^-1 and 3415-3963cm^-1,which mainly represent the hydroxyl and amino groups of carbohydrates,proteins,and amide II.Absorption of the peaks of glucomannan,arabinan and tea polyphenols.Curved fitting analysis of differential absorption bands showed that the absorption bands of carbohydrate,protein hydroxyl and amino groups,glucomannan,tea polyphenolic peak and arabinose decreased first and then increased during processing,while amide the absorption intensity of the II band and tea polyphenolic peaks first increased and then decreased.The change of the absorption intensity of these functional groups represented a certain trend of the non-volatile components with the same functional groups.?2?The differences in the extraction efficiency of non-volatile components of fu brick tea were compared between boiling water,70%methanol and methanol.The results showed that the extraction ability of the compounds in the bricks of three different solvents was methanol>70%methanol>boiling water.A total of 87non-volatile components were identified from three different solvent extracts,56 of which were differential metabolites.Boiling water has a good extraction effect on amino acids,nucleosides and organic acid compounds,but it is inferior to dimeric catechins,flavan-3-ols,flavonoids/flavonoid glycosides;methanol has a good extraction effect on flavan-3-ols,but have poorer extraction effects on amino acids,flavonoids,nucleosides,organic acids and phenolic acids;but 70%methanol for dimeric catechins,Flavan-3-ol,flavonoids/flavonoid glycosides,organic acids and phenolic acids have good extraction effects.?3?UPLC-MSMS was used to study the composition and dynamic changes of non-volatile components in the processing of fu brick tea.The results showed that 108compounds were identified during the processing of fu brick Tea,including 3 kinds of alkaloids,6 kinds of amino acids,1 aroma precursor,4 kinds of carbohydrates,11kinds of dimeric catechins,,16 flavan-3-ols,37 flavonoids/flavonoid glycosides,4nucleosides,6 organic acids,one peptidoglycan,14 phenolics and 5 other classified compounds.The total amount of non-volatile components in the processing of sapphire tea showed a downward trend.Amino acids,phenolic acids and organic acids were the main non-volatile components before and after processing,reduced separately by 65.89%,53.07%and 16.7%.The alkaloids and peptidoglycans in the processing of fu brick tea showed no significant trend,and the carbohydrates,aroma precursors,nucleosides,phenolic acids,amino acids,flavan-3-ols and flavonoids/flavonoids decreased.Organic acid compounds are on the rise in the processing of brick tea.?4?Multivariate statistical analysis was used to study the differential non-volatile components in the processing of fu brick tea.The results showed that the processing process of fu brick tea was divided into four stages,the first stage is the Maocha sample,and the second stage is the pile-fermentation and the first of fungus growing,The sample and the 3rd day of fungus growing,the third stage is the 6th day day of fungus growing and the 9th day of fungus growing,and the fourth stage is the12th day of fungus growing.The 15th day of fungus growing,the 18th day of fungus growing and the 22nd day of fungus growing.Among them,there are 31 different metabolites in the first and second stages,mainly flavan-3-ol and flavonoid/flavonoid glycosides;20 different metabolites in the second and third stages,with flavan-3-Alcohols,organic acids and phenolic acids are the main components;26 differential metabolites in the third and fourth stages,mainly amino acids,flavan-3-ols and phenolic acids.In addition,it was found that 29 characteristic ions may be closely related to the metabolism of eurotium cristatum,and their contents were significantly increased in the logarithmic growth stage of Coronaria sphaeroides,and existed in a large amount in the finished tea of fu brick tea.