title: Aptitude of Saccharomyces yeasts to ferment unripe grapes harvested during cluster thinning for reducing alcohol content of wine.
abstract: Among the viticultural techniques developed to obtain wine with reduced alcohol content, the use of unripe grapes with low sugar and high malic acid concentration, harvested at cluster thinning, was recently explored. So far, no studies have evaluated the fermentation performances of Saccharomyces in unripe grape musts, in terms of fermentation ability and reducing malic acid contents, to improve the quality of this low-alcohol beverage. In this work, we evaluated 24 S. cerevisiae strains isolated from Italian and Croatian vineyards with different fermentation aptitudes. Moreover, four S. paradoxus were considered, as previous works demonstrated that strains belonging to this species were able to degrade high malic acid amounts in standard musts. The industrial strain S. cerevisiae 71B was added as reference. Sugar and malic acid contents were modified in synthetic musts in order to understand the effect of their concentrations on alcoholic fermentation and malic acid degradation. S. cerevisiae fermentation performances improved when glucose concentration decreased and malic acid level increased. The conditions that simulate unripe grape must, i.e. low glucose and high malic acid content were found to enhance S. cerevisiae ability to degrade malic acid. On the contrary, S. paradoxus strains were able to degrade high amounts of malic acid only in conditions that resemble ripe grape must, i.e. high glucose and low malic acid concentration. In fermentation trials when low glucose concentrations were used, at high malic acid levels S. cerevisiae strains produced higher glycerol than at low malic acid condition. Malic acid degradation ability, tested on the best performing S. cerevisiae strains, was enhanced in fermentation trials when unripe grape must was used.
authors.affiliation: Department of Agronomy Food Natural resources Animals and Environment (DAFNAE), University of Padova, Legnaro, PD, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Bovo
authors.affiliation: Department of Agronomy Food Natural resources Animals and Environment (DAFNAE), University of Padova, Legnaro, PD, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Nadai
authors.affiliation: Department of Agronomy Food Natural resources Animals and Environment (DAFNAE), University of Padova, Legnaro, PD, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Vendramini
authors.affiliation: Department of Agronomy Food Natural resources Animals and Environment (DAFNAE), University of Padova, Legnaro, PD, Italy.
authors.forename: Wilson Josè
authors.initials: WJ
authors.lastname: Fernandes Lemos Junior
authors.affiliation: Department of Agronomy Food Natural resources Animals and Environment (DAFNAE), University of Padova, Legnaro, PD, Italy; Interdepartmental Centre for Research in Viticulture and Enology (CIRVE), University of Padova, Conegliano, TV, Italy.
authors.forename: Milena
authors.initials: M
authors.lastname: Carlot
authors.affiliation: Department of Microbiology, Faculty of Agriculture, University of Zagreb, Zagreb, Croatia.
authors.forename: Andrea
authors.initials: A
authors.lastname: Skelin
authors.affiliation: Department of Agronomy Food Natural resources Animals and Environment (DAFNAE), University of Padova, Legnaro, PD, Italy; Interdepartmental Centre for Research in Viticulture and Enology (CIRVE), University of Padova, Conegliano, TV, Italy. Electronic address: alessio.giacomini@unipd.it.
authors.forename: Alessio
authors.initials: A
authors.lastname: Giacomini
authors.affiliation: Department of Agronomy Food Natural resources Animals and Environment (DAFNAE), University of Padova, Legnaro, PD, Italy; Interdepartmental Centre for Research in Viticulture and Enology (CIRVE), University of Padova, Conegliano, TV, Italy.
authors.forename: Viviana
authors.initials: V
authors.lastname: Corich
mesh_terms: D000431:Ethanol / Q000737:chemistry*; D005285:Fermentation; D005516:Food Microbiology; D005524:Food Technology; D006801:Humans; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D027843:Vitis / Q000378:metabolism*; D014920:Wine / Q000032:analysis / Q000382:microbiology*
chemical_list: D000431:Ethanol
keywords: Glycerol; Malic acid; Saccharomyces cerevisiae; Saccharomyces paradoxus; Unripe grape must