Christiane De Savigny

Composition and Wine Sensory Attributes of Chardonnay Musqué from Different Viticultural Treatments: Implications for a Winegrape Quality Model

ABSTRACT ‘Chardonnay Musqué’ vines in Beamsville, Ontario, were subjected in one trial to three treatments: (1) control (hedged only); (2) basal leaf removal (BLR) and cluster thinning and; (3) cluster thinning during five stages of berry development. Berries and musts from each treatment were analyzed for soluble solids (Brix), pH, titratable acidity (TA), as well as free and potential monoterpenes (FVT and PVT). Wines produced from each treatment were evaluated by descriptive analysis for aroma and flavor intensities. FVT and PVT of berries were higher in thinned vines compared to non-thinned vines. Cluster thinning at veraison yielded fruit with the highest FVT and PVT concentrations. Leaf-pulled vines produced fruit with increased pH, reduced TA and highest FVT and PVT. Wines from BLR and thinning treatments generally had higher muscat and floral/perfumy aromas, and could be separated based on overall quality. The chemical and sensory data were incorporated into a multiple regression model used to construct a grape quality model for aromatic white Vitis vinifera grape cultivars in the Niagara Peninsula. The model developed was able to predict overall quality based on Brix, pH, and berry FVT and PVT concentration. The model was partially validated by correlations between berry FVT and PVT vs. floral and muscat aromas in wines from three previous vintages. This model has potential for use to create a more equitable payment schedule for growers contracted to wineries for the purchase of high-quality grapes.

Use of Electrical Conductivity to Assess Irrigation Impacts on Grapevine Winter Hardiness

A simple method involving measurement of electrical conductivity of grapevine cane tissue was evaluated. ‘Sovereign Coronation’ vines on two sites were subjected to five irrigation treatments based upon reference evapotranspiration (ET0) and various crop coefficients (Kc): non-irrigated control; 100% ET0 × Kc = 0.75; 150% ET0 × Kc = 0.75 (ET0 × 1.12); 100% ET0 × Kc = 0.2 to 0.8; 150% ET0 × Kc = 0.2 to 0.8. ‘Chardonnay’ vines were likewise subjected to several irrigation treatments: non-irrigated control, early season deficit (irrigation until berry set), midseason deficit (irrigation until lag phase of berry growth), late season deficit (irrigation until veraison), and full season irrigation (irrigation until harvest). Cane samples were collected from December to March inclusive, and cane segments were subjected to multiple temperature treatments (−24, −26, −28, −30, −32°C) in addition to a non-treated control. Treated cane segments were thinly sliced and incubated in distilled water (t1) at room temperature and at 100°C (t2), after which the electrical conductivity (EC) was read. Two indices calculated from both EC values (ItA, ItB) were responsive to irrigation. However, there was little relationship between either ItA and ItB versus irrigation in ‘Sovereign Coronation’, likely because it is a very winter-hardy cultivar. Nonetheless, there was a relationship between both ItA and ItB versus irrigation in ‘Chardonnay’, whereby treatments to which high irrigation volumes were applied also had high ItA and ItB values, suggesting higher potential winter damage. In summary, the technique described herein is relatively inexpensive and not time-consuming and, therefore, may constitute a rapid method for assessment of grapevine winter injury.