Cabernet Sauvignon accounts for over 50% of red wine grape acreage in Washington state. It typically is the last cultivar to be harvested in the late fall, which often occurs after freezing temperatures have been recorded. Several reports from wineries across the state have suggested that Cabernet Sauvignon wines made from fruit harvested after an early frost can present rose and floral aromas. These aromas are often described as atypical by Washington state winemakers. Anecdotal evidence suggests that the inclusion of freeze damaged leaf material into the fermentation is the taint source. We have investigated these claims by studying how the addition of leaf matter into the fermentation affects the sensory and chemical character of the Cabernet Sauvignon wine. Two fermentation experiments were conducted during the 2019 vintage, for which either chilled leaf material or freeze killed leaf material were added to the must. Chilled leaves were live harvested from Cabernet Sauvignon vines in the Roza Vineyard; then chilled in a commercial refrigerator at 0°C for 7-days. The freeze killed leaves were hand collected from Cabernet Sauvignon vines in the Horse Heaven Hills. The experimental fruit was harvested from the Cold Creek vineyard at 26.8 and 27.4 Brix for the chilled and freeze killed leaf experiments respectively. Preliminary chemical and bench sensory analysis showed no indication of rose taint in fermentations with additions of chilled leaf material, but fermentations with freeze killed leaf material showed clear evidence of rose aroma. The phenolic composition of wines fermented with the addition of freeze killed material showed significant reduced concentration of anthocyanins, tannins, and iron reactive phenolics. Descriptive analysis of the wines found significant reduction in varietal characters (dark fruit, vegetal characters) and a proportional increase in floral, (aroma & aftertaste) citrus, and stone fruit attributes with the leaf additions.  A significant reduction in astringency was found the highest dose rates. Using GC-SPME we have found 45 compounds that significantly increase proportionally with the dead leaf additions including terpenes and benzyl alcohols.

Investigation of atypical aromas in Cabernet Sauvignon wines caused by vine frost exposure

ACS Fall 2020 Virtual Meeting

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