Preliminary Study On The Productions Of C6-C9 And Jasmonate-related Aroma Compounds In Processing Black Teas

Black tea is an important tea drink in the people's daily diet.The flavor components play an important role in the quality of black tea.The aroma of tea soup is an important indicator to judge the quality of tea.The aroma of tea comes from simple terpene compounds,lipid degradation and oxidative degradation of carotene during processing.Methyl jasmonate and C6-C9 compounds produced from the oxidation degradation of tea lipids are important aroma components produced in the processing of black tea,and play an important role in the taste and quality of black tea.Therefore,it is of great theoretical value and practical significance to study the mechanism of lipid oxidation degradation of tea during black tea processing.In this study,the production of methyl jasmonate and C6-C9 in black tea processing was preliminarily detected.Heads space solid-phase microextraction and Gas chromatography-Mass spectrometry were used.GC-MS and High performance liquid chromatography-coupled esi-mass spectrometry found that a large number of aroma components with different lipid oxidation degradation sources,such as C6-C9 compounds and MeJA,were generated in the processing of black tea.The molecular biological basis of the production of these aroma compounds was discussed according to the known synthesis pathways,catalytic enzymes and coding genes of these metabolites.Through bioinformatics and genomic analysis of tea tree,it was found that a set of metabolic genes related to C6-C9 and MeJA synthesis pathway,such as phosolipase A(PLA)and Lipoxygenase(LOX),also exist in tea tree.Moreover,there are multiple copies of candidate genes in the tea tree genome.We further found that key genes in MeJA metabolism pathway can be specifically inhibited by antisense oligonucleotide inhibition technology(asODN)to change aroma components,which proves that these metabolic genes play a decisive role in the production of aroma substances in tea processing.Hydroperoxide lyase(HPL)was further cloned and the protein was expressed by different strains of bacteria.Four main conclusions are drawn:1.Black tea processing produces a large amount of C6-C9 and MeJA aroma substances;2.It's synthetase gene encoding,such as LOX,HPL,Allene oxide synthase(Allene oxide synthase,AOS),Allene oxide cyclase(Allene oxide cyclase,AOC),12-oxygen generation-diene acid reductase(12-oxophytodienoic acid reductase,OPR),acx(Acidic xylanase,ACX and JA carboxyl methyltransferase(JMT)have different expression patterns in different tissues and during tea processing.3.Inhibition of LOX(TEA003727.1),AOS(TEA001041.1),and HPL(TEA008699.1)was found to alter the aroma composition of tea,such as Hexanal,2-hexenal,(E)-,1-hexanol,2-ethyl-,MeJA,etc.4.HPL1 and HPL2 proteins were successfully induced,and HPL2 enzyme activity was detected and analyzed.