Influence of specific fermentation conditions on natural microflora of pomace in "Grappa" production

As reported in the European Community regulation, grappa is a spirit beverage made in Italy from marc that has been steam distilled or distilled after the addition of water. Grape marc from red grapes has already undergone alcoholic fermentation with the must and can be distilled immediately. Grape marc from white grapes does not contain ethanol but contains sugars that are fermented by spontaneous anaerobic fermentation during a storage period. The characteristic aroma of grappa consists of a large number of volatile compounds, which arise from various sources, the most important of which is yeast. Very few studies have been undertaken to characterize the natural populations of yeast during the fermentation of grape marc. The goal of this study was to understand how different pHs, temperatures and yeast starter cultures affect the growth and dynamics of yeast species involved in pomace fermentation, which could be the basis for improving the final quality of grappa production. We found that a temperature of 15°C has the greatest effect on improving the quality of the product. Unfortunately, due to the solid state of the grape marc and the impossibility of its mixing, it appears that acidification and the addition of yeast starter cultures during the silage period are not effective.