Melaney Schmidt, Scott Dwyer,* and Russell Moss
*Chemeketa Community College, 215 Doaks Ferry Rd. NW, Salem, OR 97304 (sdwyer4@chemeketa.edu)

Adding sulfur dioxide (SO2) at crush is common in wine production for its antimicrobial and antioxidant activity. SO2 additions also increase color extraction during maceration and fermentation. The aim of this study was to investigate the extraction of phenolic compounds and to observe alcoholic and malolactic fermentation kinetics with increasing rates of SO2 added to Pinot noir at crush. Pinot noir from a single vineyard block was sorted, destemmed, and divided into four equal 0.75-ton lots. All winemaking parameters between lots were identical except for increasing rates of SO2 additions made prior to fermentation. Additions were made as a 5% (w/v) potassium metabisulfite solution using rates of 50 (control), 100, 150, and 200 ppm. Following alcoholic fermentation and prior to pressing, 228 L of free run juice from each lot was racked to four identical and neutral French oak barrel and inoculated with 1g/hL malolactic bacteria. Lots had similar alcoholic fermentation kinetics, but different malolactic fermentation (MLF) kinetics. The control lot completed MLF (<0.1 g/L) 10 days post-racking, with a linear increase in completion time relative to SO2 concentration at crush thereafter up to 26 days. At 27 days postaddition, there was a 49% total increase in color intensity (420 + 520 + 620 nm) that was linear (R2 = 0.97) with increased SO2 addition. At 25 days postaddition, tannin concentration had increased by 28.5% between the control and the 200 ppm lot, as well as an increase of 30% in total anthocyanin content. Additionally, a 100% overall linear increase in the concentration of resveratrol (R2 = 0.95) was observed between treatments. These results suggest that increased concentrations of sulfur added at crush could be used to increase anthocyanin and tannin concentration without preventing or significantly delaying malolactic or alcoholic fermentation.

Funding Support: Chemeketa Community College Wine Studies Program