Identification of wine aroma precursors in Moscato Giallo grape juice: A nuclear magnetic resonance and liquid chromatography–mass spectrometry tandem study

In this work, several aroma precursors present in Moscato Giallo grape juice were identified and characterized using LC-MS and NMR techniques. A preliminary separation of various fractions was obtained using adsorption on Amberlite (R) XAD resin and HPLC chromatography on a reverse phase column. Subsequently, U-HPLC with mass spectrometry allowed the identification of some compounds corresponding to mono-and disaccharides linked to terpenes. The MS-MS fragmentation step indicated which kind of glycosides, the moiety sequence and sometimes which kind of terpene were present. NMR enabled the correct identification of glycosides and terpene when the fraction analyzed was sufficiently concentrated and with few components. Twelve glycosidically bound terpenes were characterized: (E) and (Z)-furanosyl-linalooloxide-7-O-[alpha-D-apiofuranosyl-(1 <-> 6)-1-beta-D-glucopyranosidel (E)-furanosyl-linalooloxide-7-O-[1-beta-D-glucopyranoside], (Z)-8-hydroxylinalool-8-O-[1-beta-D-glucopyranoside], 1,2-dihydroxylinalool-1-O-[1-beta-D-glucopyranoside], linalool-3-O-[alpha-L-arabinofuranosyl-(1 -> 6)-1-beta-D-glucopyranosidel, linalool-3-O-[alpha-L-apiofuranosyl-(1 -> 6)-1-beta-D-glucopyranoside], linalool-3-O-[alpha-r-rhamnopyranosyl-(1 -> c-glucopyranoside], nerol-1-O-alpha-D-apiofuranosyl-(1 -> 6)-1-beta-D-glucopyranoside, geranio1-1-O-[alpha-L-arabinofuranosyl-(1 6)-1-beta-D-glucopyranoside], geranio-1-O-[alpha-L-rhamnopyranosyl-(1 6)-1-beta-D-glucopyranoside], and a geranic acid disaccharide derivative. It is the first time that this kind of compounds are directly detected and identified in a mixture with these two techniques.