Evaluation of the Phenol-Free Glycosyl-Glucose Determination

Abstract

Grape glycosides are, in part, an important source of varietal wine aroma and flavor. Aglycones may be aliphatic residues, monoterpenes, sesquiterpenes, norisoprenoids, or phenolic compounds. Studies were undertaken to evaluate and compare methods of isolating non-phenolic or phenol-free glycosides. Phenol-free glycoside fractions were obtained by three isolation methods: the addition of polyvinylpolypyrrolidone (PVPP), isolation at pH 10.0 using C18 solid phase extraction cartridges, or isolation at pH 13.0 using Oasis^TM hydrophilic-lipophilic balance (HLB) extraction cartridges. Glycoside separation using the Oasis cartridges reduced the phenol content of the phenol-free glycoside fractions in Chardonnay juice and wines by an average of 49.7% compared to 33.6 % using C18. The differences in the phenol concentration in the phenol-free glycoside fractions with these two methods were greater with red juices and wines. For the Cabernet Sauvignon juice and wines the phenol concentration was reduced by an average 103% and 73% using the Oasis and C18 cartridges, respectively.