Investigation into the biogenesis of γ-nonalactone from fatty acid precursors during alcoholic fermentation by Saccharomyces cerevisiae

γ-Nonalactone is a ubiquitous wine aroma compound, associated with coconut and stone fruit descriptors. Despite its importance, biosynthetic pathways leading to γ-nonalactone formation during winemaking remain unclear, with only 4-oxononanoic acid confirmed as a precursor. Previous research in a model system demonstrated precursor activity from products generated through the lipoxygenation pathway of linoleic acid, via yeast-mediated biochemical reactions. In this work, investigation into putative precursors of this pathway, in addition to chemically similar compounds, was carried out in a wine-relevant matrix, via the supplementation of these compounds prior to alcoholic fermentation (AF) in synthetic grape medium. γ-Nonalactone concentrations in resulting wines were quantitated using stable isotope dilution assay-solid phase extraction-gas chromatography-mass spectrometry (SIDA-SPE-GC-MS). 4-Oxononanoic acid, linoleic acid, and its hydroperoxyl derivative 13-hydroperoxyoctadecadienoic acid (13-HPODE) were confirmed as precursors to γ-nonalactone, demonstrating the role of 13-HPODE in γ-nonalactone formation in winemaking for the first time. The bioconversion of 13-HPODE to γ-nonalactone using different Saccharomyces cerevisiae strains highlighted the role of yeast γ-nonalactone biogenesis during AF. Additionally, significant differences in γ-nonalactone concentrations were observed for different wine and laboratory S. cerevisiae strains, suggesting underlying differences in yeast metabolism is an important determinant of the aroma of this lactone in wine. • 4-Oxononanoic acid and linoleic acid confirmed as γ-nonalactone precursors in wine • New evidence in winemaking for role of 13-hydroperoxyoctadecadienoic acid (13-HPODE) • Yeast strain variation evident in their bioconversion of 13-HPODE to γ-nonalactone • Yeast fatty acid metabolism is a key determinant of wine γ-nonalactone concentrations