Fruit Maturation of Four Vitis vinifera Cultivars in Response to Vineyard Location and Basal Leaf Removal

Abstract

Fruit maturation patterns of four Vitis vinifera cultivars (Bacchus, Pearl of Csaba, Schönburger, Siegerrebe) were examined over a two-year period to study relationships between standard harvest indices [soluble solids (°Brix), titratable acidity (TA), and pH] and monoterpene flavor compounds. Experiment 1 in 1987 compared relatively high heat unit (growing degree day; GDD) sites in Oliver, British Columbia (1568°C - 1642°C GDD; Region II) with low GDD sites in Kelowna (1163°C - 1312°C GDD; Region I) for each cultivar. Oliver sites produced fruit with higher berry weights, °Brix, and pH than Kelowna fruit, and TA was lower also for Oliver fruit for some cultivars on some sampling dates. Free volatile terpenes (FVT) and potentially volatile terpenes (PVT) were higher for Bacchus, Pearl of Csaba, and Schönburger fruit from Oliver during the early phases of fruit maturity, but these differences disappeared as fruit approached full ripeness. FVT and PVT in Siegerrebe were highest in Kelowna fruit. When data were regressed on GDD to account for site-based phenological differences (e.g., bloom date and veraison), pH, FVT, and PVT were highest in most cases at the Kelowna sites for any given GDD, and TA was usually lower. Experiment 2 in 1988 examined the effect of basal leaf removal at each of the sites. Site-based differences in fruit composition were similar in 1988 to 1987 regardless of whether data were compared directly or regressed on GDD. Basal leaf removal had a small, but significant, impact on berry composition, but lowered TA, pH, and potassium, and increased FVT and PVT in the juices of 2/4 and 4/4 cultivars, respectively. Tasters could discern between sites and between leaf removal and non-leaf removal treatments on an aroma and flavor basis for some cultivars and found, in most cases, that leaf removal wines had highest muscat and floral aromas and flavors.