(Wines&Vines) - Lucy Joseph, a researcher at the University of California, Davis, has been visiting parts of California’s wine country on the search for native yeasts.

Finding yeast isn’t really much of a challenge, especially in places like Napa County, but Joseph is seeking “autochthonous yeast,” or strains of Saccharomyces that are confirmed through sequence analysis to be indigenous to the West Coast.

Joseph is the yeast culture curator for the UC Davis Department of Viticulture & Enology and works in the lab of microbiologist and yeast specialist Dr. Linda Bisson. Joseph will discuss the heritage yeast project during the full-day session “Wine Flavor 101A: The Microbes of Wine Quality” at UC Davis on Jan. 13. The seminar features presentations about other research, panel discussions and technical tastings focused on wine microbiology.

So far Joseph and other members of the Bisson lab have visited five California regions including Lake County, Yuba and Nevada counties; Big Sur and San Luis Obispo in the Central Coast, Napa County and the Lodi AVA. The search so far has yielded 20 strains of Saccharomyces as well as several other types of yeasts. 

The yeast come from a variety of habitats, and Joseph and the other researchers are staying clear of wineries. “We have been trying to stay away from any areas that are near wineries when we are hunting wild Saccharomyces,” she told Wines & Vines. “We have been to vineyards that are in isolated areas and have oak trees around them. Hardwood trees are a natural habitat for Saccharomyces, especially at wound or disease sites where sap is present.”

Joseph said she attempts to keep at least 5 kilometers away from any working wineries when collecting samples. “We purposely avoid areas where there may be contamination from commercial yeast sources,” she said. “Staying away from wineries can be a challenge in some areas, like Napa County.”

UC Davis winemaking students used five of the “heritage” Saccharomyces strains identified through the research project during the 2015 harvest, and only one was able to complete fermentation. The others stalled at 11% to 12% alcohol. The students, however, preferred the aromas of wines fermented with the selected indigenous yeasts rather than the aromas of wines made with commercial strains or a spontaneous fermentation.

Joseph plans on making more trips to Mendocino and Sonoma counties, Paso Robles and Santa Barbara. The goal is to profile the diversity of native species as well as define “a genetic signature” for autochthonous Saccharomyces to identify truly indigenous strains. More and more winemakers these days are touting their “native” fermentations, and finding strains that truly are native to California and provide consistent and complete fermentations would likely have strong commercial appeal.