Impact of Grape Maturity and Ethanol Concentration on Sensory Properties of Washington State Merlot Wines

Chaptalization and saignee-watering back were used to investigate the effects of modifying ethanol concentrations on sensory properties of Merlot wines made from fruit harvested at different maturities. Fruit was harvested on three dates with soluble solids concentrations of 20, 24, and 28 Brix. At each harvest, one- third of the must was fermented at the natural soluble solids concentration, and the other two- thirds were manipulated to match the other harvests' Brix, leading to wine ethanol concentrations of 11.6, 14.0, and 16.2% for each of the three soluble solids concentrations. Both fruit maturity and ethanol concentration had significant effects on the chemical and sensory profiles of the wines. Wine physical viscosity increased with increasing ethanol concentrations, and wine color was positively impacted, with higher ethanol concentrations favoring the formation of polymeric pigments leading to darker wines. Wines made from unripe fruit (20 Brix) were characterized by green flavors and sour taste in the sensory analysis, whereas wines made from overripe fruit (28 Brix) were described as fruity and sweet. Manipulations targeting the adjustment of ethanol had a greater effect on wine sensory properties than fruit maturity: wines made from ripe (24 Brix) or overripe fruit adjusted to low ethanol concentrations were described similarly to wines made from unripe fruit, and wines made from unripe or ripe fruit adjusted to high ethanol concentrations were described similarly to wines made from overripe fruit. The results of this study demonstrate that both ethanol concentration and manipulations to achieve desired ethanol concentrations have a large influence on wine chemistry and sensory properties, and suggest that wine ethanol concentration is more important for the sensory profiles of wines than is fruit maturity at harvest.