Modulation of the ‘flinty’ aroma compound phenylmethanethiol during fermentation: impacts of yeast starter culture and nitrogen supplementation

The sulfur compound phenylmethanethiol (PMT) has been associated with ’flinty’ and ’struck-match’ aromas in wine, and it is considered to be an important contributor to the flavour of certain white wine styles. Little is known about the factors driving the formation of this potent sulfur aroma compound during winemaking conditions, as well as the precursors/pathways that might be involved in its formation. In this study, we demonstrate that a range of practical winemaking strategies may have significant implications on the final concentration of PMT in wine. Specifically, the choice of yeast strain used to perform alcoholic fermentation was shown to modulate the formation of this ‘flinty’ compound under laboratory-scale conditions, and in the absence of oak. The nutritional level of the fermentation media was also found to significantly impact PMT formation by yeast, as nitrogen additions in the form of inorganic nitrogen promoted the formation of PMT. Finally, the potential role of both benzaldehyde and hydrogen sulfide as precursors to PMT formation was also explored, as well as the contribution of other alternative pathways.