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Magnitude of Viticultural and Enological Effects. II. Relative Impacts of Cluster Thinning and Yeast Strain on Composition and Sensory Attributes of Chardonnay Musqué

¹ Professor of viticulture, ² graduate student, ³ undergraduate thesis student, and ⁴ technician, Cool Climate Oenology and Viticulture Institute, Brock University, St. Catharines, ON, L2S 3A1 Canada.

^* Corresponding author (fax: 905 688-3104; email: areynold{at}brocku.ca)

Chardonnay Musqué vines were subjected to six crop levels (nonthinned control and cluster thinned at late bloom/early set, early stage I of berry growth, late stage I, lag phase, veraison) over four years (1999 to 2002). Wines were made from these treatments using yeast strain VL1 (Saccharomyces cerevisiae). Additional fruit from nonthinned vines was subjected to several enological treatments: EC1118 strain (S. bayanus) ± pectinase preparation Cinn-Free and VL3 strain (1999) and EC1118 ± Cinn-Free and AR2000 enzymes, and CY3079, D47, and VL3 strains (2000 and 2001). Enological treatments were compared chemically and sensorially and to the viticultural treatments. Thinning decreased yields and clusters per vine regardless of timing. Both berry and cluster weights decreased as time of thinning was delayed, suggesting yield compensation. Thinning at/after early stage I led to higher Brix, pH, and potentially volatile terpenes (PVT) relative to the control; titratable acidity (TA) decreased with later thinning; and free volatile terpenes (FVT) increased in some thinning treatments. There were substantial differences in wine pH, TA, and PVT among the different yeast strains and enzyme treatments. Use of prepress Cinn-Free led to increased TA and FVT, resulting from extraction of organic acids and terpenes from berry skins. VL1 increased wine TA and pH. VL1 and VL3 reduced wine PVT, perhaps because of enhanced ß-glucosidase activity and/or biosynthesis/biotransformation of terpenes. Despite chemical composition differences among viticultural treatments, wines differed little sensorially. However, sensory differences did occur among yeast treatments, with VL1 wines being distinctive. Several sensory attributes that distinguished between yeast treatment wines were correlated with PVT.

Key words: cluster thinning, enzymes, leaf removal, monoterpenes, wine quality, yeast