Abstract
Wine production by inoculated fermentation with commercial Saccharomyces cerevisiae strains is an ordinary practice in modern winemaking in order to assure the final quality of wine, although this procedure results in the production of highly homogeneous wines. The use of indigenous selected starters represents a useful tool to control alcoholic grape must fermentation, safeguarding the typical sensory characteristics of wine produced from specific regions. In this study, we selected three indigenous S. cerevisiae strains among 16 indigenous strains previously isolated from the spontaneous fermentation of Primitivo grapes, which were collected from the vineyards of three different cellars. The three selected starters (one for each cellar) were tested during fermentations at pilot scale by performing in each cellar two trials: one with an indigenous starter (specific for the winery), and one with the commercial starter AWRI796 (common to all the cellars). Starter dominance ability and influence on aromatic quality of the wine were used as criteria to test the suitability of these indigenous starters to be used at the cellar scale. The results obtained in this study showed that the indigenous strains were characterized by very high dominance ability, and the aromatic quality of wine was strongly influenced both by the inoculated strain and the interaction strain/grape must.
Highlights
In the traditional transformation of grape must into wine, the process is carried out by the metabolic activity of various yeast species and genera present on grape skin, in musts, and in winery equipment developing simultaneously or sequentially
In the first phase of the work, 16 S. cerevisiae strains previously isolated from the spontaneous fermentation of grapes were studied for some technological characteristics, such as resistance to antimicrobial compounds and hydrogen sulfide production (Table 1)
All the indigenous starters tested during pilot-scale vinification showed a dominance level higher than the commercial strain in all the cellars, confirming that indigenous yeast strains are better acclimated to the environmental conditions present in grape must to be fermented, being that these indigenous starters are highly competitive against yeast microflora that are naturally present in the grape must
Summary
In the traditional transformation of grape must into wine, the process is carried out by the metabolic activity of various yeast species and genera present on grape skin, in musts, and in winery equipment developing simultaneously or sequentially. The oenological practice of inoculated fermentation has determined a certain reduction and flattening of sensory characteristics of the final product, as a consequence of the decrease of diversity in microbial populations involved in fermentation [4,5]. Another problem is that the same commercial starter cultures were used for producing different wines, determining a uniformity in the wine characteristics, but the real number of commercial yeast strains is lower than we think, as manufacturers of different brands often designate the same strain with different codes or names [6,7].
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