Matt Garcia and James Osborne*
*Oregon State University, 100 Wiegand Hall, Oregon State University, Corvallis, OR, 97331 (james.osborne@oregonstate.edu)

Malolactic fermentation (MLF) is an integral step in red wine production. Traditionally conducted after alcoholic fermentation, MLF can occur concurrently with alcoholic fermentation by inoculating with Oenococcus oeni soon after the initiation of alcoholic fermentation. Although a concurrent fermentation reduces the overall time required to ferment, there are concerns about excessive acetic acid production, color loss, and competition with Saccharomyces cerevisiae. If concurrent fermentations are to become more widely used, a better understanding of this winemaking technique is necessary. This study investigated the effect of MLF timing on Pinot noir wine properties, particularly color. The use of a non-Saccharomyces yeast during cold soaking was also studied due to potential interactions with O. oeni and production of acetaldehyde, a key compound involved in the formation of stable color. Six non-Saccharomyces yeast cultures were assessed for acetaldehyde production under cold-soak conditions in a model grape juice. T. delbrueckii Alpha produced the highest concentration of acetaldehyde (71.8 mg/L) and was selected for use in Pinot noir winemaking experiments. Pinot noir wines were produced with and without cold soaking, with and without T. delbrueckii Alpha, and with concurrent or sequential MLF. Only minor differences in the time to completion of alcoholic fermentation or MLF were observed between the treatments, suggesting that concurrent MLF did not impact the performance of the alcoholic fermentation. Acetaldehyde concentrations changed throughout wine production. At the end of cold soak, the treatments inoculated with T. delbrueckii Alpha contained significantly more acetaldehyde (21.5 mg/L) than their uninoculated counterparts (3.4 mg/L). Further, these treatments also had the highest acetaldehyde concentrations during alcoholic fermentation. Acetaldehyde rapidly decreased after O. oeni inoculation. The significance of these changes in acetaldehyde on color will be determined when wines are assessed for various color parameters, including anthocyanins and polymeric pigments.

Funding Support: Oregon Wine Board