Characterization of Glycosidically Bound Aroma Compounds of País cv. grapes of different Chilean zones

Abstract

País grape has been estimated to arrive to Chile almost 500 years ago, being the first strain grown in this country. Traditionally, this grape has been used to mix with other varieties, to produce poor quality wines, but today is beginning to be used in the production of high quality wines. However, very little is known about the chemical characteristics of this variety. The aroma is one of the most important quality attributes of wine. Volatile compounds of this beverage may come from the grape (varietal aromas), from the fermentation process, from the ageing. The aromatic compounds are found in the grape in two forms: as free volatile compounds and as non-volatile compounds. The last ones, are aroma precursors present mainly as glycoconjugates formed by a sugar and an aglycone. They are potential natural sources of aroma because the hydrolysis of the bonds between the sugar and the aglycone, for example during the ripening of the fruit or the fermentation by the yeast, turns this molecule into an aromatic compound. These non-volatile compounds have been extensively studied in grapes due to their importance in the wine aroma. The aims of this work were to study glycosidic aroma precursors of País grapes from three Chilean zones from the Maule Region and determine where these compounds are mainly located in the grape (pulp or skin). For this purpose, grapes from three zones, Hualañé, Cauquenes and Itata were harvested post veraison and analyzed. The glycosides were extracted by passing the samples through the solid-phase extraction medium, and the aglycone was released by acid hydrolysis as described by Loscos et al. (2009). The extract was analyzed by gas chromatography mass spectrometry. The results showed that the principal groups of aroma precursors in País grapes were alcohols, aldehydes and terpenes. Among them, the most abundant was 2-ethyl-1-hexanol followed by benzaldehyde. In reference with the location of the aromatic precursors, the biggest amounts were found in the skins of all the samples. Among all the chemical groups, terpenes accounted the biggest amount differences between the skin and the pulp.

Loscos, N.; Hernández-Orte, P.; Cacho, J.; Ferreira, V. Comparison of the suitability of different hydrolytic strategies to predict aroma potential of different grape varieties. J. Agric. Food Chem. 2009, 57, 2468-80.

Acknowledgements: This study was supported by FONDECYT N°11140275.