Non-Saccharomyces Yeast on Wine Quality – Part 2, Aroma and Flavor Development (year 1)

In Fall 2009, fermentations using high hydrostatic pressure (HHP) treated grapes were conducted using grapes from Woodhall vineyard (Alpine, OR). Grapes were harvested at 24.8 °Brix (TA 0.76 g/L and pH 3.58). After HHP treatment, grapes were transferred to sterile micro-fermentors and inoculated with different yeast. There were total 4 different blends of yeasts used in the fermentations, which were S. cerevisiae MERIT.ferm (MS), MERIT.ferm + Kluyveromyces thermotolerans (60:40 ratio) (MK), MERIT.ferm + Kluyveromyces thermotolerans + Torulaspora delbrueckii (60:20:20 ratio) (MKT), and a S. cerevisiae isolated from an active fermentation in a winery that does not inoculate with commercial starter cultures (AR). All fermentors were then placed in a temperature controlled room set at 27_. All of the fermentations completed alcoholic fermentation (sugar < 0.5 mg/L) in less than 144 hrs. After pressing, wines were allowed to settle for 48 hours at 4_, sterile filtered through a 0.45 um cartridge filter, bottled and stored at 13__ until analysis (GC-MS analysis occurred 10 months post-pressing). Each treatment has 3 replica, so total 12 wine samples were studied.. The result demonstrated that the volatile compounds were very similar in the four yeast treatments but the concentrations varied a lot. MKT treatment had the highest concentration of ethyl esters of acetate, butanoate, hexanoate, octanoate, and decanoate, as well as ethyl vanillate. However, both MK and MS treatments had higher concentration of branch-chained esters such as isoamyl acetate, ethyl 2-methylbutanoate and ethyl 3-methylbutanoate . In addition, fermentation yeasts showed an effect on terpene alcohol concentration. MKT treatment had the highest level of geraniol. The yeast treatment did not show impact on the concentration of linalool, citronellol and ?-damascenone. The newly isolated non-Saccharomyces yeasts from local wineries will be evaluated in 2011.