Fermentation of Sauvignon blanc grape marc extract yields important wine aroma 3-sulfanylhexan-1-ol (3SH)

Abstract

Grape marc, comprised of grape stems, seeds and skins, is an underutilised and potentially problematic waste material produced by the wine industry in often overwhelming quantities. This work aims to showcase this abundant waste material, for the first time, as a potentially valuable technological tool for improving wine quality through the production of the aroma compound 3-sulfanylhexan-1-ol (3SH) during fermentation.A scaled-up eco-friendly solid-liquid extraction method, using 100% water, to extract thiol precursor compounds 3-S-cysteinylhexan-1-ol (Cys-3SH) and 3-S-glutathionylhexan-1-ol (GSH-3SH) from Sauvignon blanc grape marc was undertaken. Quantitation of the vacuum-dried crude extract dissolved in model wine, using liquid chromatography tandem mass spectrometry (LC-MS/MS), showed that the extract contained 1.9 μg Cys-3SH and 11.46 μg GSH-3SH per gram of grape marc extract. Addition of low (14.6 g L−1) and high (58.3 g L−1) quantities of grape marc extract to synthetic grape medium inoculated with a commercial wine yeast strain, yielded appreciable concentrations of 3SH in finished wines (average of 216 ng L−1 for the low addition and 1244 ng L−1 for the high addition). Interestingly, the grape marc extract was found to accelerate the fermentation rate of the yeast, rather than cause inhibition or toxicity.