β-Glucosidase activity in wine yeasts: Application in enology

A method for quantifying β-glucosidase activity in wine yeasts is reported. After selecting the appropriate strain, conditions for enzyme synthesis were optimized: synthesis of extracellular enzyme was induced by the presence of cellobiose in the medium under aerobic conditions, with peak production at 42 h growth. The enzyme was partially purified and biochemically characterized. At the same time, aroma precursors were measured in various musts from grapes grown in Castilla la Mancha (Spain) in order to quantify potential aroma, using a laboratory-developed method based on glycoside retention in reversed-phase C18 columns, recovery by elution with appropriate solvents and acid hydrolysis. This provided information on the most suitable substrate for wine yeast β-glucosidase enzymes. Finally, wines were made at laboratory scale using a selection of white grape varieties ranging from highly aromatic to neutral (Muscat, Riesling and Airén), adding yeast enzyme to the wine and comparing the results to those obtained with a widely used commercial enzyme preparation of fungal origin. Release of glycoside terpenes was measured by the method indicated above and by gas chromatography/mass spectrometry. Results were satisfactory and displayed good correlation, showing that enzymes obtained from wine yeasts could be used in place of the commercial fungal enzyme preparations currently used in winemaking.