Influence of Cluster Exposure and Winemaking Processes on Monoterpenes and Wine Olfactory Evaluation of Golden Muscat

Abstract

Effects of cluster exposure and winemaking treatments on free- and potential-volatile terpenes (FVT, PVT), total soluble solids (TSS), titratable acidity (TA), phenols, pH, color, and potassium were studied. Canopies of Golden Muscat grape vines were manipulated by shoot positioning and basal leaf removal at fruit set to create shaded and exposed cluster conditions. Winemaking treatments included: control, four-hour skin contact prior to press, freeze concentration of must, and addition of β-glucosidase after fermentation. At harvest, exposed fruit had higher PVT levels in the pulp and skin fractions, and shaded grapes had lower FVT levels in the skin and pulp fractions. Accumulation of FVT and PVT differed between exposed and shaded fruit and between skin and pulp fractions. Exposed fruit contained more phenols and TSS and less TA than shaded fruit, and these differences remained in the wines. Wines made from exposed fruit contained greater FVT and PVT than wines from shaded fruit. Addition of β-glucosidase increased FVT. Other winemaking treatments had inconsistent effects on PVT and FVT levels.