Characterization of Saccharomyces uvarum CN1 for Its Use in Aromatic White Wine Production and Mitigation of Negative Aromas from Rot-Affected Fruit

Abstract

Sour rot and Botrytis cinerea infections pose significant challenges to grape growers and wineries by negatively impacting wine quality. Infected fruit is associated with elevated concentrations of compounds, primarily acetic acid, that compromise sensory properties. To ensure quality, wineries commonly set acetic acid thresholds (0.20–0.24 g/L), rejecting fruit that exceeds these limits and causing economic losses and production delays. A locally isolated yeast, Saccharomyces uvarum CN1, shows potential for acetic acid reduction. Previous work demonstrated CN1’s ability to metabolize acetic acid and enhance volatile aroma compounds (VOCs) in red wines; however, its impact on aromatic white wines remains unexplored. This study investigated Riesling fermentations at three rot levels (0%, 20%, and 40% w/w) inoculated with CN1 or commercial S. cerevisiae EC1118. CN1-fermented wines exhibited substantial reductions in acetic acid compared to juice values (13-fold at 0% rot, 6-fold at 20%, and 5-fold at 40% ) yielding final concentrations of 0.05–0.02 g/L. GC–MS analysis showed CN1 wines contained significantly higher levels of VOCs such as ethyl isobutyrate, 2-phenylethanol, and hexanol, and significantly lower concentrations of acetate esters and medium-chain fatty acids than EC1118 wines. Sensory analysis revealed that EC1118 wines were associated with higher tropical aroma and flavour at 0% and 40% rot, while CN1 wines were rated higher in musty aroma (40% rot) and rubber flavour (20% rot). Although some differences in sensory profile may require further optimization, with targeted use, CN1 has potential as part of a strategy for recovering fruit that might otherwise be rejected.