Evolution of Flavanol Glycosides during Red Grape Fermentation

Area of Science:

• Food Chemistry
• Enology
• Plant Biochemistry

Background:

• Flavanol glycosides are key compounds influencing wine sensory properties.
• Their presence and evolution during winemaking are not fully understood.
• Accurate quantification methods are crucial for understanding their role.

Purpose of the Study:

• To quantify monomeric and dimeric flavanol glycosides in Syrah (SYR) and Grenache (GRE) grapes and wines.
• To investigate the origin and evolution of these compounds during winemaking.
• To identify potential yeast biosynthesis and grape glycosidase activity.

Main Methods:

• Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry (UHPLC-MRM) was employed.
• Quantification was performed on grape tissues (seeds, skins) and wine samples.
• Analysis covered 22 distinct monomeric and dimeric flavanol mono- and diglycosides.

Main Results:

• Flavanol glycoside concentrations varied significantly across grape tissues and fermentation stages.
• Concentrations ranged from 0.7 ng to 0.700 µg/g in grapes and 0 to 60 µg/L in wines.
• Evidence suggests most glycosides originate in grapes, with differential extraction kinetics during winemaking.
• Yeast may biosynthesize one flavanol monoglycoside isomer; grape glycosidases likely convert others.

Conclusions:

• Flavanol glycoside profiles in grapes and wines are complex and tissue-dependent.
• Winemaking processes significantly impact flavanol glycoside concentrations.
• Both grape and yeast factors contribute to the final glycoside composition in wine.