Nicola, FRANCESCA1,Michele, MATRAXIA1, Rosario, PRESTIANNI1,Valentina, CRAPARO1, Vincenzo, NASELLI1, Giancarlo, MOSCHETTI1, Luca, SETTANNI1, Raimondo, GAGLIO1, Antonella, MAGGIO2, Antonio, ALFONZO1
1 Department of Agricultural, Food and Forestry Science, University of Palermo, Viale delle Scienze 4, 90128 Palermo, Italy
2 Department of Biological, Chemical and Pharmaceutical Sciences and Technologies (STEBICEF), University of Palermo, Viale delle Scienze, Parco d’Orleans II, Palermo, building 17, Italy
Email contact: nicola.francesca[@]unipa.it
AIM: Recent studies on yeast ecology of non-oenological niches have highlighted the ability of some Saccharomyces cerevisiae yeasts to ferment grape must . Considering that the market for sparkling wines is highly competitive in terms of aromatic complexity, a technological selection of S. cerevisiae strains isolated from high-sugar matrices (honey and honey by-products) was carried out. Strains with high oenological performance were used as starter cultures on an industrial scale for the production of base wines for sparkling wine production.
METHODS: All S. cerevisiae isolates were subjected to genotypic identification (RFLP and sequencing of the D1/D2 region of the 26S rRNA gene)  and strain typing by interdelta analysis . Characterized strains were subjected to in vitro technology screening (H2S production, resistance to different concentrations of ethanol and potassium metabisulfite, capacity to grow at 10° and 15° and at pH 2.5, 2.8 and 3) . In order to determine the fermentation power and fermentation vigor, the strains with the optimal in vitro performance were subjected to micro-fermentation tests in grape must. The selected yeasts were used to ferment a must for the production of base wine and the products was subjected to sensory analysis.
RESULTS: Genotypic analysis conducted on 552 isolates identified the yeasts as S. cerevisiae. Strain typing allowed the characterize of 98 strains. In relation to technology screening results, 4 strains (SPF21, SPF42, SPF52 and SPF159) have been successfully used as starter cultures for the production of base wines at industrial level. Sensorial analysis done on different wines showed the absence of unpleasant odors and/or flavours and it was observed a significant increase of aromatic complexity and intensity.
CONCLUSIONS: Saccharomyces cerevisiae strains have shown a high fermentative capacity and represent a valid alternative for the improvement of the sensory characteristics of the final product. The microbial ecology of honey and its by-products is rich in Saccharomyces spp. with high fermentative capacity and potentially applicable in alcoholic fermentation. The use of unconventional yeasts, could be a valid alternative to characterize the base wine and improve the typicality of the sparkling wines in order to satisfy the demand of the consumers.