abstract
In Mediterranean countries the most diffuse practice to obtain the valorization of grape marc, the main
by-product from winemaking, is the production of spirits. During this process, marc storage for sugar
fermentation represents a crucial step, since side-fermentations leading to off-flavours production can
very easily occur. In this study we evaluated the effect of the addition of two yeast strains, inoculated
separately at the beginning of the storage period, into marcs from two Italian grape varieties with the
aim to control the development of autochthonous microbiota and to improve spirit quality. The presence
of the inoculated strains was monitored by means of PCR-based approaches. A commercial Saccharomyces
cerevisiae strain, chosen as this species is notably the best ethanol producer, showed excellent
ability to dominate the autochthonous microflora and to reduce off-flavours as demonstrated by
chemical analysis and sensory evaluation. A Saccharomycodes ludwigii strain, chosen for increasing
varietal compounds thus enhancing spirit aroma, showed a level of implantation not sufficient to assure
a clear beneficial effect on quality. The implantation level of this strain was affected by S. cerevisiae
competition since the highest level was found in grape marc with lower sugar content, where indigenous
S. cerevisiae were less persistent.
abstractIn Mediterranean countries the most diffuse practice to obtain the valorization of grape marc, the mainby-product from winemaking, is the production of spirits. During this process, marc storage for sugarfermentation represents a crucial step, since side-fermentations leading to off-flavours production canvery easily occur. In this study we evaluated the effect of the addition of two yeast strains, inoculatedseparately at the beginning of the storage period, into marcs from two Italian grape varieties with theaim to control the development of autochthonous microbiota and to improve spirit quality. The presenceof the inoculated strains was monitored by means of PCR-based approaches. A commercial Saccharomycescerevisiae strain, chosen as this species is notably the best ethanol producer, showed excellentability to dominate the autochthonous microflora and to reduce off-flavours as demonstrated bychemical analysis and sensory evaluation. A Saccharomycodes ludwigii strain, chosen for increasingvarietal compounds thus enhancing spirit aroma, showed a level of implantation not sufficient to assurea clear beneficial effect on quality. The implantation level of this strain was affected by S. cerevisiaecompetition since the highest level was found in grape marc with lower sugar content, where indigenousS. cerevisiae were less persistent.
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