Effects of yeast inoculation on volatile compound production by grape marcs

Grape marcs are a by-product of winemaking that can be used for production of Grappa, a traditional Italian spirit. This plant material needs to undergo a fermentation process before distillation to allow production of ethanol from residual sugar and volatile aromatic compounds. To study the possible effect of selected yeast inocula on the fermentation process and subsequent quality of the distillate, a laboratory-scale fermentation of grape marcs was performed. The inoculated yeasts proved to be good colonizers of grape pomace and contributed markedly to rapid sugar consumption, which was completed within 5 days. Fermentation products were analysed by gas-chromatography. A time course analysis performed to determine the impact of the inoculated strains on the main aromatic compounds that are concentrated in the product after distillation provided evidence of a positive effect of yeast inoculation.