During the first year of this project, wine fermentation and aging at various amounts of lees were conducted by Dr. James.P.Osborne as a part of a separate project “Formation of volatile sulfur compounds in Pinot noir post-fermentation. Part 1: Role of grape amino acid content and wine lees composition”. Two yeast strains, and three lee levels for used in the study. Initial samples were collected for amino acids and volatile sulfur analysis. Additional samples were taken after 2 and 4 weeks and 2 months of storage and assessed for the same parameters. The project is still at very early stage, and limited results showed:
- The concentrations of volatile sulfur compounds in the wines fermented with both two yeasts were low after fermentation and pressing. All of the major volatile sulfur compounds were analyzed including H2S, mercaptans, disulfides, thiol esters. Saccharomyces cerevisiae P1Y2 produced lower levels of methyl thioacetate and methionol than Saccharomyces cerevisiae RC212.
- Heavy lee loading resulted higher level of H2S initially, but the difference diminished after aging. No significant differences were observed for other volatile sulfur compounds at different levels of lees.
- After 2 months of aging, some sulfur compounds such as methionol decreased while some sulfur compounds like methyl thioacetate kept consistent.
- Some industrial samples were analyzed, and high levels of H2S were detected in some of the wine samples, and industrial partners responded with cupper treatment.