QUANTIFICATION OF GLYCOSIDES IN GRAPES, JUICES, AND WINES THROUGH A DETERMINATION OF GLYCOSYL GLUCOSE

An analytical assay for glycosylated secondary metabolites of grapes, juices and wines, through quantification of glycosyl glucose (G-G), ha s been optimized and validated. The glycosides are isolated on Cls rev ersed-phase silica gel and hydrolyzed with sulfuric acid at 100 degree s C; the released glucose is determined enzymatically. The accuracy an d precision of the assay, determined from the gradients and coefficien ts of determination of linear regression curves for the recovery of a standard glycoside from wine, juice or homogenized fruit extract range d, respectively, from 0.957 to 1.021 and from 0.991 to 0.997. Some exa mples of application of the assay are presented-the decrease of G-G in wines with aging, the range of G-G in Shiraz juices from different re gions, and the development of G-G in ripening fruit.