Tess Snyder, Bjarne Bartlett, Jacob Martin, James Osborne, and Chris Curtin*
*Oregon State University – Department of Food Science and Technology, 3051 SW Campus Way, Corvallis, OR, 97331 (christopher.curtin@oregonstate.edu)

The apiculate yeast genus Hanseniaspora has been observed in association with grapes, grape must, and the early stages of wine fermentation for more than 100 years. Most enological research in that time has focused on the species Hanseniaspora uvarum due to its notable capacity to cause spoilage, especially in wines made using the cold-soak process, but detection of apiculate yeast does not always denote spoilage. In recent years, there has been research into the potential benefits of species such as Hanseniaspora vineae in producing more complex wines. Furthermore, large-scale DNA sequencing-based (metabarcoding) vineyard ecology studies have suggested there could be regionally variable populations of Hanseniaspora species. Does this mean that fruit from different vineyards could yield spoiled or complex wines depending on which Hanseniaspora species are present? As a first step toward addressing this question, in this study we are determining which of the 22 recognized Hanseniaspora species are present on Pinot noir grapes in the Willamette Valley AVA and which species persist during cold-soak and fermentation. In addition, our sampling design evaluates geographic differences in species make-up within vineyards, between vineyards, and between sub-AVAs. During the 2022 harvest, 108 commercially ripe multi-cluster samples were taken across 12 vineyards, six each in two geographically distinct sub-AVAs. Subsamples were taken at crush, after six days of cold-soak and after 10% completion of initial must sugar content (TT_10). Preliminary analysis shows the expected significant positive correlation between initial total soluble solids and TT_10 along with a significant negative correlation between must CFU and TT_10. Importantly, there was no significant difference between sub-AVAs for these parameters, suggesting our ability to detect geographic differences in yeast populations will not be skewed due to initial conditions. Currently we are evaluating the presence of Hanseniaspora species in each sample using metabarcoding analysis.

Funding Support: OWRI, OSU