UC Davis

Each year in the wine industry, economic loss occurs due to stuck or sluggish fermentations and the corresponding off-flavors produced. While monitoring using standard methods such as °Brix levels may reveal a problem, often the indication is after the quality of the wine has already been impacted and remediation techniques are less effective or intrusive and costly. The use of redox potential, also called Oxidation Reduction Potential (ORP), as a process parameter is being explored in order to predict fermentation outcomes early in fermentation, theoretically before measurable changes in °Brix levels occurs. ORP reports on 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 in 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 or with different yeast strains to better understand the relationship between ORP and fermentation outcomes. Wine strains of Saccharomyces cerevisiae – EC1118, Elixir, CY3079, Montrachet, and RC212 – were observed, as well as varying pH and nutrient conditions used. ORP values showed repeatable patterns based on fermentation conditions which could be used to assist winemakers in monitoring and decision-making.