Fruit Maturation of 'Okanagan Riesling' Grapes: Effect of Site, Year, and Basal Leaf Removal

Abstract

'Okanagan Riesling' ( Vitisspp.) berries were sampled for 2 years from two vineyards to document relationships between standard harvest indices (°Brix, titratable acidity, pH) and monoterpene and volatile ester flavor components. Experiment 1 (1987) compared a high heat unit site (Inkameep) and a low heat unit site (Summerland), and showed that pH and total volatile esters (TVE) were higher at Inkameep when sites were compared using data corrected for 10°C base accumulated heat units (growing degree days; GDD). Experiment 2 (1988) also tested the impact of basal leaf removal on fruit composition at the two sites. Influence of site was less in 1988, and only titratable acidity (TA) and pH were affected by site. Basal leaf removal increased concentrations of flavor compounds and reduced TA in the berries, and increased TVE in the juices. Tasters distinguished between sites on the basis of wine aroma and flavor, and between control and basal leaf removal wines from the Inkameep site on the basis of flavor Site effects on fruit composition were partly contingent upon GDD but season, crop load, and canopy density may have also played a role.