Maria Alessandri and Alan Bakalinsky*
*Oregon State University, 100 Wiegand Hall, 3051 SW Campus Way, Corvallis, OR 97331 (alan.bakalinsky@oregonstate.edu)

While USDA regulations for organic winemaking prohibit deliberate addition of sulfite to wines, they do not prohibit the presence of naturally-occurring sulfite. This contrasts with the regulations in the European Union that allow the use of sulfite as a mild antimicrobial agent and antioxidant, which disadvantages U.S. winemakers. Previous studies have found that sulfite production during fermentation by wine strains of Saccharomyces cerevisiae is variable and that certain strains appear to produce enough to potentially substitute for the additions prohibited by USDA regulations. Such strains could be useful to winemakers who are already making organic wine or who are interested in entering the organic market, particularly for white wines made without malolactic fermentation or barrel aging. We have found that nitrogen availability during fermentation is one source of variability and have analyzed the effect of variable levels and different forms of assimilable nitrogen on sulfite production. We have also found that establishing a genetic basis for the inheritance of “high sulfite production” among progeny of wine x laboratory strain hybrids was complicated by the observation that laboratory strains cannot ferment must under normal winemaking conditions. To avoid such artifacts related to genetic background, crosses between “high” and “low” sulfite-producing wine strain derivatives were initiated and sulfite production is being evaluated under uniform growth conditions. Genetic and genomic analyses of the progeny are on-going and are expected to reveal the genetic requirements for the “high sulfite production” phenotype.

Funding Support: USDA-ARS Pacific NW Center for Small Fruits Research