Understanding the Evolution of Fresh Mushroom Off-Flavor in Wine over the Course of Fermentation

Fresh mushroom off-flavor (FMOff) is a defect in wines characterized by a mushroom aroma. To date, it has been mainly linked to compounds such as 1-octen-3-one, 1-octen-3-ol, 1-hydroxyoctan-3-one, and octane-1,3-diol. In practice, winemakers have observed changes in FMOff perception during alcoholic (AF) and malolactic fermentations (MLF), suggesting that yeasts and bacteria play a role in aroma modification. To investigate the FMOff metabolism, synthetic must was supplemented with analytical standard molecules (octane-1,3-diol, 1-hydroxyoctan-3-one, and 1-octen-3-one). Their evolution was monitored during AF and after MLF. The effect of the yeast strain was also investigated and validated in natural grape must. The results showed that yeasts and bacteria metabolize 1-octen-3-one into 3-octanone and finally into 3-octanol during fermentation. The production of octane-1,3-diol in must supplemented with 1-hydroxyoctan-3-one confirms a biochemical link between these compounds, which was also verified in natural matrices. Approximately 30% of the 1-hydroxyoctan-3-one was metabolized into octane-1,3-diol, and 70% remained unidentified, opening an avenue for future work.