Identification of free disaccharides and other glycosides in wine

Abstract

Free soluble carbohydrates of different wine samples were analyzed by GC–MS as their trimethylsilyloximes using a methylsilicone column. Besides α,α-trehalose, several β-glucosylglucoses such as cellobiose, sophorose, laminaribiose and gentiobiose were the main disaccharides identified. With the exception of gentiobiose, these disaccharides are now reported for the first time in wine. Lactose (4-O-β- d-galactopyranosyl- d-glucose), previously described in this product, was also tentatively identified. Several free glycosides: β-ethyl-glucoside and seven glyceryl-glycosides (including glucosides and galactosides) were also identified for the first time in wine. On the contrary, disaccharides in grape juice were mainly constituted of fructose derivatives, including sucrose, and no glycosides were detected. Although the total amount of disaccharides was different in white wines (<50 mg/L) from those in rosé and red wines (80–130 mg/L), the chromatographic profile was noticeably similar in all wine samples. The method here reported allows the identification of several carbohydrates which have not been previously detected in wines and could contribute to increase the understanding of enzymatic activity during winemaking.