Gita Mallya, Ben Montpetit,* James Nelson, Kimberlee Marinelli, Ron Runnebaum, and Andre Knoesen
*UC Davis, 1 Shields Avenue, Davis, CA 95616 (benmontpetit@ucdavis.edu)

Each year in the wine industry, economic loss occurs due to stuck or sluggish fermentations and the corresponding off-flavors produced. While monitoring by using standard methods such as total soluble solids (density) may reveal a problem, often this occurs after wine quality has already been impacted and remediation techniques are less effective, more intrusive, and costly. The use of redox potential, or oxidation reduction potential (ORP), as a process parameter is being explored to predict fermentation outcomes early in fermentation, even before measurable changes in total soluble solids occur. ORP describes the tendency for molecules or ions to gain or lose electrons in relation to the chemical makeup of a solution being measured. Consequently, ORP values are sensitive to the fermentative activity of the yeast as metabolic products are released and alter the chemical conditions of the solution. This makes ORP a sensitive tool for understanding the state of the fermenting yeast in a must, even before sugar consumption can be measured. This study aimed to monitor ORP under varying nutrient conditions and with different yeast strains to better understand the relationship between ORP and fermentation outcomes. Several wine strains of Saccharomyces cerevisiae (EC1118, Elixir, CY3079, Montrachet, and RC212) were observed, as well as varying pH and nutrient conditions. Preliminary ORP data for stuck fermentations show indications of failure sooner than would a slowing sugar consumption rate.

Funding Support: Wine Spectator, ASEV, Jastro Shields Research Award