This study examined the impact of interactions among nitrogen concentration, composition, and elemental sulfur (S⁰) on volatile sulfur compound (VSC) content of Pinot noir wine. Fermentations were conducted using Pinot noir grapes where yeast assimilable nitrogen (YAN) was adjusted from 110 mg N/L to 250 mg N/L with either diammonium phosphate (DAP) or an amino acid mixture matching a typical Pinot noir grape composition. Ten mg/g S⁰ was also added to some treatments. DAP additions increased production of H₂S by Saccharomyces cerevisiae UCD522 while amino acid additions decreased H₂S formation regardless of S⁰ addition. Fermentations with both DAP and S⁰ produced the most total H₂S, with 35 to 45% more H₂S than ferments where only S⁰ or DAP additions were made. YAN concentration and composition and S⁰ also impacted the concentration of other VSCs in the wine postfermentation. In particular, the addition of S⁰ increased the concentration of methyl thioacetate (MeSOAc) in the wines as did higher YAN concentrations. The type of nitrogen added (ammonium vs. amino) had less impact on MeSOAc concentration than the increase in YAN did. This suggests that while the presence of S⁰ is one factor impacting the concentration of VSCs postfermentation, high YAN concentrations may also play a role. Experiments were also conducted to reduce the amount of residual S⁰ on Pinot noir grapes prior to fermentation. Pinot noir grapes received an application of S⁰ (wettable or microthiol) one week prior to harvest. Prefermentation cold soaking the grapes followed by draining off the juice reduced the amount of S⁰ remaining on the grapes and resulted in significantly less H₂S production during fermentation. Cold settling the juice that was drained off decreased the concentration of S⁰ below detection and allowed the juice to be added back to the original grapes.

Funding Support: Oregon Wine Board