Abstract
Winemaking in cool climate viticultural areas can pose challenges due to difficulties in achieving optimal ripeness from climatic conditions that tend to vary vintage-to-vintage. To stabilize quality, the use of partially dehydrated grapes has been indicated as beneficial to the production of high-quality wine (“appassimento” style) despite climatic variation. Postharvest wine grape dehydration is a complex process that involves the concentration or formation of sugars, aromas, and flavours. One of the quality challenges facing appassimento style winemaking is elevated levels of undesirable oxidation compounds. The aim of this study was to characterize wines made from a local yeast isolate, Saccharomyces uvarum CN1, which demonstrates limited osmotolerance and may have application to this wine style, as it is a known lower producer of such compounds. Wines made with CN1 were compared to wines made with the accepted commercial standard, S. cerevisiae, EC1118. Fermentations (n = 24) were established at three target starting sugar concentrations from dehydrated Cabernet franc grapes (24.5, 26.0, and 27.5°Brix) and a control (21.5°Brix) and were assessed for volatile organic compound (VOC) composition via gas chromatography-mass spectrometry (GC-MS). Wines also underwent quantitative descriptive analysis to identify and quantify sensory attributes by a trained panel (n = 11). Results show that the wines fermented with the yeast isolate contain significant differences in the concentrations of VOCs in the wines. Sensorially, the wines differed in intensity for a number of attributes, including red fruit aroma, black fruit flavour, and length of finish both within Brix treatments and amongst yeast strains. The most important differentiating factor amongst these wines was the combination of yeast strain at the highest starting sugar concentration (27.5°Brix). These findings may assist winemakers by informing the yeast strain choice for optimizing appassimento style wine quality in cool climates.
Highlights
Wine aroma and flavour are important factors that influence quality
Grape sugars increased with drying time to achieve the target parameters. e ethanol concentration in the final wines was not significantly different between yeast strains, except at 24.5°Brix, where the EC1118 fermented wines yielded approximately 0.6% v/v more
Our results show higher concentrations of ethyl isobutyrate in CN1 wines when compared to EC1118 wines. is compound has been identified as the most abundant ethyl ester of branched esters in red wines [46] and contributes to a higher overall concentration of ethyl esters in wine fermented with our S. uvarum yeast
Summary
Wine aroma and flavour are important factors that influence quality. Wine is a complex matrix, with many suprathreshold odorants and nonimpact compounds simultaneously contributing to its aroma [1].e aromatic volatile compounds of both grapes and wine associated with a wine’s sensory quality are critical components of consumer response and acceptance [2,3,4].Volatile compounds in wine originate in the grape berry, which can depend on cultivar, viticultural, and vinification techniques. ey can come from yeast and bacterial metabolism, as well as postfermentative treatments such as oak wood extraction. Wine aroma and flavour are important factors that influence quality. Wine is a complex matrix, with many suprathreshold odorants and nonimpact compounds simultaneously contributing to its aroma [1]. E compounds that form along the vine to glass continuum result in a diverse range of aroma and flavour profiles and contribute to the complexity of wine [5,6,7]. Postharvest practices such as grape dehydration have a concentration effect on sugar and volatile compounds and impact the final wine aroma and flavour [8, 9].
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