Non-Saccharomyces yeasts in controlled mixed culture fermentation in winemaking: the role of metabolic interactions

One of the most important technological advances in winemaking is the control of alcoholic fermentation through the inoculationof the grape juice with selected cultures of Saccharomyces cerevisiae. In the last decade several studies revaluated the involvement of non-Saccharomyces yeasts during alcoholic fermentation and their role in the metabolic impact and aroma complexity of the final product. Indeed, non-Saccharomyces yeasts may produce high amounts of different metabolites and enzymes able to release aroma compounds from precursors present in grape must (Fernandez et al., 2000). Thus, non-Saccharomyces yeasts may influence the perceivable characteristics of the final product (Romano et al., 2003). In view of the fact that natural fermentations remain uncontrolled processes, several studies have evaluated the possibility of using controlled multistarter cultures to increase the quality of wines. The use of non-Saccharomyces wine yeasts, together with Saccharomyces strains as part of multistarter fermentations, has been proposed as a tool to take advantages of natural fermentation and maintain the control of the fermentative process (Ciani et al., 2006, Anfang et al., 2009; Ciani et al., 2010). We evaluated the oenological aptitude of non-Saccharomyces wine yeasts belonging to nine different genera. Selected non-Saccharomyces strains with a commercial S. cerevisiae strain were used to set up mixed must microfermentations estimating biomass and fermentation evolution as well as analytical profile of wines. Results of screening allowed to select some non-Saccharomyces yeasts with suitable oenological properties. The comparison between mixed and pure fermentations showed variations in the analytical profiles. The presence and permanence of non-Saccharomyces yeasts during must mixed fermentations positively influence the final product. In particular, yeast interactions frequently allowed the reduction of some negative compounds produced by non-Saccharomyces yeasts such as acetic acid, and the enhancement of favourable aroma compounds (2-phenylethanol, phenylethyl acetate, isoamyl acetate). This work is financed by Consorzio Tuscania, Firenze.