Identification And Quantitative Analysis Of Glycoside Aroma Precursors In Instant Oolong Tea

Glycoside aroma precursors are one of the important ways to release aroma from tea.The composition of glycoside aroma precursors is an important reference index for the selection of high aroma tea varieties and the accurate control of tea processing.Due to the low content of glycoside aroma precursors and the difficulty in preparing standard substances,the identification and quantitative analysis of glycoside precursors in tea tissues and products are limited.This study oolong tea and instant oolong tea powder as the research object,based on liquid chromatography mass spectrometry(LC-MS)and enzyme explanation release aroma coupling gas chromatography mass spectrometry(GC-MS)technology to analyze measurement study glycosidic aroma precursors,establish glycosidic aroma precursors in tea and its processed products analysis method,the results are as follows:(1)Instant oolong tea through Amberlite XAD-2 macroporous resin separation for coarse glycosidic precursors,the β-D-glycosidase digestion combined with GC-MS analysis,13 species of glycosidic aroma precursors were identified,including cis-3-hexen-l-ol,hexanol,2-heptanol,1-heptanol,1-octen-3-ol,6-methyl-5-heptene-2-ol,octanol,linalool,dehydrolinalool,nonanol,geraniol,benzaldehyde and methyl salicylate;By HPLC-MS analysis,only four kinds ofβ-D-glucoside precursors were detected,namely nonanol β-D-glucoside,cis-3-hexen-1-ofβ-D-glucoside,benzaldehyde β-D-glucoside and hexanol β-D-glucoside,respectively.The glycoside precursor was further purified by semi-preparative HPLC,and the glycoside precursor components were collected for 20-30 min.Four glycoside precursors,mainly cis-3-hexen-l-ol,2-heptanol,linalool and methyl salicylate,were identified by the enzymatic hydrolysis ofβ-D-glycosidase and GC-MS analysis.However,only one glycoside precursor was detected by HPLC-MS analysis,which was benzaldehyde β-D-glucoside.The results indicated that HPLC-MS analysis could lead to the omission of some glycoside precursors,and the combination of enzyme interpretation and GC-MS analysis could detect more glycoside aroma precursors.(2)A quantitative method for the determination of glycoside aroma precursors in instant oolong tea was studied by enzymatic interpretation and GC-MS analysis.The time of releasing aroma components by enzyme interpretation was optimized to 1.5 h,and the standard curve for quantitative analysis of 13 glycoside precursor compounds was established.And using hexanolβ-D-glucoside,octanol β-D-glucoside and phenethyl alcohol β-D-glucoside as the object,to evaluate the effectiveness of the method for detecting glycoside precursors of instant oolong tea by enzymatic interpretation releasing aroma and GC-MS analysis,the detection limits were 6.33μg/L,7.24 μg/L and 10.56 μg/L,the quantitative limits were 21.11 μg/L,24.14 μg/L and 35.20μg/L,the standard addition recovery range were 82.06%-93.39%,90.14%-101.09%and 70.25%-88.63%,the intraday precision was 1.44%,3.08%and 7.39%,and the daytime precision was 2.81%,4.64%and 8.57%,respectively.The results indicated that under the optimal conditions of enzyme-interpreted aroma release,the combination of enzyme-interpreted aroma release and GC-MS analysis could effectively and accurately determine the glycoside precursors in the instant oolong tea.(3)Using enzyme release aromas combined with GC-MS analysis of a kind of oolong tea glycosidic precursors for testing,the results showed that the oolong tea in β-D-glucoside class aroma precursors concentration for:cis-3-hexen-l-ol β-D-glucoside was 1726.97 μg/L,methyl salicylate β-D-glucoside was 264.98 μg/L,phenyl ethanol β-D-glucoside was 100.26 μg/L and benzyl alcohol β-D-glucoside was 90.16 μg/L;β-primerveroside class aroma precursors concentration for:cis-3-hexen-1-ol β-primerveroside was 751.34 μg/L,3-methyl-butanolβ-primerveroside was 171.14 μg/L and benzaldehyde β-primerveroside was 53.85 μg/L;vicianoside class aroma precursors concentration for:cis-3-hexen-l-ol vicianoside was 461.12μg/L and 3-methyl-butanol vicianoside was 155.59 μg/L;rutinoside class aroma precursors concentration for:cis-3-hexen-1-ol rutinoside was 503.60 μg/L and 3-methyl-butanol rutinoside was 133.52 μg/L.(4)Using enzyme release aromas combined with GC-MS analysis of a kind of instant oolong tea glycosidic precursors for testing,the results showed that the instant oolong tea inβ-D-glucoside class aroma precursors concentration for:geraniol β-D-glucoside was 23965.33μg/L,cis-3-hexen-1-ol β-D-glucoside was 8243.92 μg/L and hexanol β-D-glucoside was 1140.90μg/L;β-primerveroside class aroma precursors concentration for:geraniol β-primerveroside was 2442.15 μg/L,cis-3-hexen-l-of β-primerveroside was 1317.43 μg/L,linalool β-primerveroside was 768.53 μg/L and hexanol β-primerveroside was 209.26 μg/L;vicianoside class aroma precursors concentration for:cis-3-hexen-1-ol vicianoside 1738.63 μg/L was and 3-methyl-butanol vicianoside was 227.82 μg/L;rutinoside class aroma precursors concentration for:cis-3-hexen-1-ol rutinoside was 2486.51 μg/L and 3-methyl-butanol rutinoside was 394.91μg/L.This paper results show that the enzyme interpretation release aromas combined with GCMS analysis and compared with HPLC-MS analysis can be more comprehensive testing class glycosidic aroma precursors in the tea products,is the quantitative detection of class glycosidic precursors in tea and its processed products,effective method for oolong tea and instant oolong tea contains β-D-glucoside,β-primerveroside,vicianoside and rutinoside and a variety of glycosidic aroma precursors,among which rutinoside were first discovered in tea and its processed products.In this paper,an improved method for the analysis of glycoside aroma precursors in tea and its processed products was established,and novel glycoside precursors in tea and its processed products were found,which provided a methodology and a reference for new components for the selection of high flavor tea varieties and the precise control of tea processing.