| As the important precursors of grape varietal aroma compounds,aroma terpene glycosides can be hydrolyzed and release free varietal aroma compounds during grape ripening and wine making process.Aroma glycosides are usually analyzed by gas chromatography-mass spectrometer(GC-MS)after hydrolyzed.In this study,GC-MS was used to study the aromatic terpene glycosides composition of different grape varieties with different maturity and wine made by them.And high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry(UPLC-QTOF/MS)was applied to analyse the aroma glycosides in molecular level.The results are as follows:(1)The GC-MS analysis result of aroma glycosides composition in different varieties of grapes.There were 8 species bond terpene aglycones in Muscat Hamburg and Mei Li,4species in Ecolly and 1 specie in Cabernet Sauvignon.Rose oxide,isopulegol,nerol oxide,and terpinolene were only found in Muscat Hamburg grape;hotrienol and menthol were only detected in Meili(maturity coefficient M=24.65).(2)The aroma terpene glycosides composition of Meili in different maturities was carried out with GC-MS and showed that the amount of glycosidic aglycones in Meili grapes increased generally during grape ripening: 3 in Meili(maturity coefficient M=10.17),8 in Meili(maturity coefficient M=24.65),6 in Meili(maturity coefficient M=28.84),9 in Meili(maturity coefficient M=29.55),and 6 in Meili(maturity coefficient M=42.92),and the variation pattern between them was undefined.The trend of the total content of bound aglycones released from hydrolysis was fluctuated as alphabet “N”.(3)The study analyzed the free and bound aroma substances in three different wines made from grapes in different maturity with GC-MS.The results showed that with the increase of raw material maturity,the content and variety of free terpene aglycones in wine made from grape in middle maturity had the highest value.Isogeraniol and terpilenol were detected merely in wine made from middle maturity,and linalool was the only terpene with suprathreshold OAV value.As for bound terpene aglycones whose concentration and kind increased slightly with the maturity increasing,8 of 12 terpene aglycones released fromenzymatic hydrolysis were detected in three wine samples,and wine sample made from high maturity grape had the highest content of nerol oxide,linalool,hotrienol,trans-geraniol and cedrol.Terpinene and linalool oxide,while the concentrations of geranylacetone were highest in wine sample made from low maturity grape and sample made from middle maturity grape,respectively.(4)The UPLC-Q-TOF / MS was established and applied to detect aromatic terpene glycosides of Muscat Hamburg,Cabernet Sauvignon,Ecolly,and Moscato Bianco and 15 terpene glycosides were detected: 13 in Muscat Hamburg,9 in Cabernet Sauvignon and Moscato Bianco,7 in Ecolly.Quantitative analysis results showed that there were 5 kinds of glycosides detected in every sample,and nerol-l-O-α-D-apiofuranosyl-(1→6)-1-β-D-glucopyranoside and 1,2-dihydroxy-linalool-l-O-[1-β-D-glucopyranoside] had the highest content in Muscat Hamburg,while the concentrations of furanosyllinalooloxide-7-O-[α-D-arabinofuranosyl-(1→6)-1-β-D-glucopyranoside),8-hydroxylinalool-8-O-[1-β-D-glucopyranoside] in Ecolly were higher than other samples.Comparing the results of GC/MS and UPLC-Q-TOF/MS of Muscat Hamburg wines,there was no one-to-one correspondence of terpene glycosides and their enzymatic aglycones in the specie and content levels,which mightly resulted from different sample pre-treatment of two instrumental analysis methods. |
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