Caroline Merrell, Bojana Leonard, Samantha Young, Torey Arvik, and Thomas S Collins*
*Washington State University, 359 University Drive, Richland, WA 99354 (tom.collins@wsu.edu)

Microscale or bucket-scale fermentations have been used to evaluate the impact of vineyard smoke exposures prior to harvest. While chemical analysis or sensory evaluation of the resulting wines can be used to identify affected blocks, a key
limitation for their usefulness is the amount of time required to complete fermentation, along with lack of temperature control and the amount of space required. Using smaller-scale fermentations in glass canning jars, fermentation temperatures can be maintained in ad hoc water baths warmed by sous vide heaters. At 85°F, nanoscale fermentations can be completed in three to four days. Space requirements are also greatly reduced with canning jar fermentations. To evaluate whether the different fermentation scales produce comparable results, 12 lots of smoke-affected Cabernet Sauvignon grapes were fermented in triplicate using both systems. The microscale fermentations completed fermentation in eight days, while the nanoscale fermentations completed fermentation in four to five days. Guaiacol concentrations in the affected wines ranged from not detected to 3.2 µg/L in the microscale fermentations, compared to 1.6 to 5.2 µg/L in the nanoscale. Concentrations of the other smoke-exposure markers also correlated well between the two fermentation scales. Fifteen commercial vineyard lots were also evaluated using both nano- and microscale fermentations, both of which were compared with the results of the commercial fermentation of those vineyard lots. Concentrations of smoke-exposure markers were similar in both the – and nanoscale fermentations and concentrations of marker compounds
in both scales correlated well with concentrations in the production-scale wines. These results suggest that the use of nanoscale temperature-controlled fermentations can provide more timely results, with good predictive ability of concentration of smoke exposure compounds in production-scale wines.

Funding Support: Washington State Wine Commission Jackson Family Wines