Abstract

Spontaneous grape must fermentations are consistently characterized by a sequential colonization of the substrate according to which apiculate yeasts (Hanseniaspora/Kloeckera), that predominate at the beginning of the process, are quickly replaced by Saccharomyces yeasts. In addition, other yeasts such as those belonging to the genera Candida, Torulaspora, Kluyveromyces, Zygosaccharomyces and Metschnikowia, may be present during must fermentation (Fleet, 2003). These “wild” yeasts have been considered for a long time responsible for wine defects. Thus, to inhibit their development and ensure the production of wines with repeatable characteristics, grape must is commonly treated with SO2 and inoculated with selected cultures of Saccharomyces cerevisiae. However, quantitative studies on the composition of the microflora of fermenting musts indicate that wild non-Saccharomyces yeasts may persist during inoculated fermentations (Mora et al., 1990) and produce high amounts of different metabolites and enzymes able to carry out the transformation of the aroma precursors present in grapes (Fernandez et al., 2000). Thus, non-Saccharomyces yeasts may influence the perceivable characteristics of the final product (Romano et al., 2003).
In this context, the possibility “to mimic” natural fermentations, maintaining the control of the fermentative process, represents an interesting approach to the improvement of the final quality of wine. In this study 105 isolates of non-Saccharomyces yeasts, belonging to different genera, naturally involved in spontaneous fermentations and coming from grape-musts of different origins, were identified and evaluated for their principal oenological characters. Fifteen strains showing interesting oenological characteristic are currently evaluated in fermentation processes carried out by mixed culture with S. cerevisiae.

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