Impact of yeast strain on the production of acetic acid, glycerol, and the sensory attributes of icewine

High concentrations of volatile acids, consisting mainly of acetic acid, are often found in icewine. Wine yeasts produce acetic acid as a by-product of the hyperosmotic stress response caused by high sugar concentrations (>35 Brix) in grape must. Volatile acid levels in icewine often exceed legal limits. We compared seven commercially available wine yeast strains (ST, N96, Vin13, Vin7, EC1118, 71B, V1116) for icewine production. Yeast strains were evaluated for acetic acid and glycerol formation, fermentation rates, and sensory characteristics. Fermentations were conducted using both synthetic grape must and Riesling icewine grape must obtained from a commercial winery. Fermentations were conducted until approximately 11% (v/v) ethanol was produced. The yeast strains fermented Riesling icewine must at different rates and fermentations were completed in 17 to 49 days. Acetic acid and glycerol formation were significantly different (p < 0.05) and linked to the yeast strain. Sensory analysis of the icewines produced with the different yeast strains showed significant differences for overall quality, perceived sulfur-like aroma, and color (p < 0.05). ST, N96, and EC1118 were identified as the most suitable yeast strains for the production of icewine.