C. Michael Sonza, Emily Kaneshiro, Tess Snyder, Bjarne Bartlett, James Osborne, and Christopher Curtin*
*Department of Food Science and Technology, Oregon State University, 3051 SW Campus Way, Corvallis, OR, 97331 (christopher.curtin@oregonstate.edu)

Oregon wine producers can face economic losses from wine spoilage from Brettanomyces bruxellensis infections. Despite precautions to mitigate infections by B. bruxellensis, such infections still occur. Variation in mitigation efficacy may be due to the emergence of sulfite-tolerant strains of B. bruxellensis in the wine production facility, as well as differences in quantity and strain of B. bruxellensis on the grapes entering the winery. Limited knowledge exists regarding whether known or novel sulfite-tolerant strains are present in OR wine facilities. Furthermore, the extent to which B. bruxellensis exists in vineyards is not well characterized due to the difficulty of isolating this yeast when more-abundant background yeast are present. This study seeks to address the limited understanding of the spoilage potential of B. bruxellensis strains found in OR cellars and vineyards.

We collected 100 Pinot noir cluster samples during the 2023 harvest from five different OR vineyards and will use an additional 105 cluster samples cryopreserved from the 2022 harvest. Collected vineyard samples will be grown in a selective enrichment medium that is currently being optimized to preferentially grow B. bruxellensis and limit background yeast growth. We also collected 52 wine samples and 79 environmental swabs representing seven OR cellars. Any identified B. bruxellensis isolates from the vineyard and cellar will be whole-genome sequenced and evaluated with sequence alignment to determine how related OR strains are to known strains outside of OR, particularly sulfite-tolerant strains. A preliminary enrichment formulation trial using cellobiose as the sole carbon source shows promising inhibition of background yeast, while not impeding growth of most B. bruxellensis isolates. The outcomes of this study will clarify the spoilage capacity of B. bruxellensis in OR wineries and vineyards, supporting wine producers to make informed decisions on how to best protect their wine from infections.

Funding Support: Oregon Wine Board