Winery's own yeasts

The EU-funded project, in which several wineries in the Palatinate and one winery in the Netherlands are participating, aims to develop methods for producing winery-specific yeasts. At the same time, this gives rise to several areas of research focused on establishing molecular biology methods. First, samples of spontaneous fermentations at the winery are collected, and S. cerevisiae strains are isolated. Then, SSR or microsatellite markers are applied. These are short repetitive sequences in the genome that allow for the creation of a molecular “fingerprint” of each strain. This technique has been successfully established at the Rural Area Service Center (DLR) Rhenish Palatinate. In addition, it is possible to compare the pattern of a strain with that of a pure culture yeast. This makes it possible to determine whether the isolated yeasts are identical to a pure culture yeast. By using molecular biological markers, the diversity of S. cerevisiae strains can be determined. Fermentations are conducted on a pilot scale using these strains. This allows the fermentation behavior of each strain to be determined. A sensory evaluation using the napping method is conducted jointly with the winery on the wines from the experimental fermentations. Ultimately, the winery selects a strain to be used for fermentations the following fall. The partner wineries are very satisfied with the initial results from using the winery’s own yeast, and wines have already been produced on a large scale.

The use of molecular biological markers to distinguish between S. cerevisiae strains and the use of estate-specific yeasts offer opportunities for numerous research projects. For example, research is being conducted on the forms in which these yeasts are supplied, namely liquid yeast or freeze-dried yeast. In addition, the use of estate-specific yeasts is being investigated for wineries in new grape varieties, including those resistant to fungal diseases (PiWis). It has already become apparent that the use of estate-specific yeasts with the PiWi grape variety Calardis blanc could indeed be a viable alternative to commercial yeast products. In addition, estate-specific yeasts were tested for secondary fermentation in sparkling wine production and successfully implemented at a winery. In sparkling wine production, too, completely foregoing pure-culture yeasts would be an option. Furthermore, molecular biological markers serve as a tool for gaining insight into the diversity within the species S. cerevisiae. The number of strains in various fermentation vats was examined, allowing for general conclusions to be drawn as to whether the yeasts isolated from spontaneous fermentations are genetically identical to commercial yeast strains or not.