Study Of The Taste Quality In Different Types Of White Tea Based On Metabolomics Analysis

Taste is an important index to influence the quality of tea.Different types of white tea have different flavor characteristics because of the difference of raw material tenderness.In this study,we applied a variety of taste evaluation methods(traditional evaluation method,taste equivalentquantification method and electronic tongue)to investigate the taste quality characteristics of three types of white tea(Silver Needle,White Peony and Shou Mei).Furthermore,a metabolomics method based on ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry(UHPLC-Q-TOF/MS)was applied to investigate the chemical compositions.And then,the taste equivalent-quantification and dose-over-threshold(DoT)determination on the taste qualities were applied to comprehensively characterize the white tea types for the first time.The results were listed as follows:(1)Traditional sensory evaluation results: the taste score divided into Silver Needles > White Peony > Shou Mei,the taste characteristics of Silver Needles was sweet and refreshing.The taste characteristics of White Peony was similar to Silver Needles,but its freshness was slightly lower than Silver Needles.The taste characteristics of Shou Mei was mellow and pure,only a few samples of Shou Mei were refreshing.The taste equivalent-quantitative evaluation results: Silver Needle had a high umami value,a high bitterness value and a high astringency value,White Peony had a high umami value,a low bitterness value and a low astringency value,Shou Mei had a low umami value,a low bitterness value and a low astringency value.The result of the principal component analysis of the electronic tongue showed that the technology of electronic tongue can be used to distinguish the different types of white tea.(2)The non-volatile metabolite differences among Silver Needle,White Peony,and Shou Mei white teas were comprehensively characterized by the metabolomics investigation using UHPLC-Q-TOF/MS.These three types of white tea significantly differ in their contents of catechins,dimeric catechins,amino acids,phenolic acids,flavonol/flavone glycosides,and aroma precursors.The content of galloylated catechins,proanthocyanin,theasinensin A,theasinensin F,caffeine,phenolic acids(eg.chlorogenic acid,theogallin and strictinin),amino acids(eg.theanine,proline and asparagine),AMP and aroma primeverosides in Silver Needle were significantly higher than those of in Shou Mei.The content of non-galloylated catechins,theasinesin B,quinic acid,4-p-coumaroylquinic acid,amino acid(eg.phenylalanine,tyrosine and glutamic acid)and flavonol glycosides(kaempferol glycosides,quercetin glycosides,myricetin glycosides and apigenin glycosides)in Shou Mei were significantly higher than those of in Silver Needle.The non-volatile metabolite characteristics of White Peony show that the content of catechin,dimeric catechins,amino acids,alkaloids,nucleotides and aroma primeveroside were similar to Silver Needle,however,the content of quinic acid,4-p-coumaroylquinic acid,kaempferol glycosides,quercetin glycosides and myricetin glycosides were similar to Shou Mei.(3)Metabolite content comparison and partial least-squares(PLS)regression analysis suggest that theanine,aspartic acid,asparagine,and AMP were positively correlated with the umami taste in white tea,and flavan-3-ols,theasinensins,procyanidin B3,and theobromine had positive correlations with higher bitterness and astringency tastes.In addition,puckering astringent(-)-epigallocatechin gallate(EGCG),(-)-epicatechin gallate(ECG)and theogallin,bitter-tasting caffeine,and mouth-drying/velvety-like astringent ?-aminobutyric acid(GABA)were identified as key taste compounds of white tea infusion by absolute quantification and DoT factor calculations.