In its 2018-19 fiscal year, the Oregon Wine Board of Directors granted $437,500 to researchers for nine projects with the potential to advance quality grape growing and winemaking in Oregon. The update below is part of a series to let you know about the status of these projects.
Dr. Chris Curtin is an assistant professor in the Department of Food Science and Technology at Oregon State University. His laboratory’s focus is on the role of microbes in fermentation. He has prepared the update below.
Dr. James Osborne, associate professor and enology extension specialist at OSU, is a co-investigator on this initiative.
Elucidating Brettanomyces paths of entry into the cellar
Brettanomyces yeasts are found in wine regions across the world, typically in red wine that is undergoing barrel maturation. How do they get there in the first place?
Anecdotal evidence points towards the vineyard, which would be consistent with the mounting genetic evidence showing that commercial wine strains of Saccharomyces cerevisiae are very closely related to their brethren in vineyards. The reason we know this is because many researchers have used enrichment methods to purify and isolate Saccharomyces yeasts from vineyards and other sources where they may be present in very low numbers relative to other microbes, and have analyzed their genetic code to determine how they are related to one another. This project is aimed at generating similar knowledge for Brettanomyces through the following specific objectives:
- Optimize enrichment protocols to reliably obtain Brettanomyces isolates from environmental samples;
- Comprehensively sample winery-related and surrounding environments from at least two collaborating wineries and enrich for Brettanomyces yeasts;
- Perform comparative genomics and evaluate spoilage potential of Brettanomyces environmental isolates relative to known wine spoilage strains.
Importance to the Oregon wine community:
Oregon is known for its high-quality Pinot noir, which is exemplified by “fresh” and “fruity” characteristics. As a lighter style of wine, it is particularly susceptible to Brettanomyces impact, with modest rates of infection leading to significant changes in sensory profile. Knowing where Brettanomyces resides outside the cellar is the first step towards a more holistic control strategy that incorporates efforts to minimize its entry into the cellar.
Progress so far:
We improved a published enrichment protocol to be more selective against other non-Saccharomyces yeasts and used it to attempt isolation of Brettanomyces from nearly 300 grape clusters sampled across four vineyards in the Willamette Valley. This preliminary trial yielded 15 samples from which we isolated presumptive Brettanomyces—all from one vineyard, interestingly. We are now in the process of whole-genome sequencing positively identified isolates.
Many of the samples we enriched did not yield Brettanomyces, though our efforts were hampered by other microbes that were able to grow under our conditions (non-Saccharomyces yeasts, molds, bacteria). We are in the process of further improving our Brettanomyces enrichment protocol to ensure we are able to reliably detect and isolate Brettanomyces when present in an environmental sample. With a revised protocol, this summer/fall we aim to extensively sample from participating vineyards and cellars, and also sample from surrounding non-cellar/non-vineyard environments.