Valentina Olivera, Maria Jose Valera, Valentina Martin, Gabriel Perez, Eduardo Boido, Remi Schneider, Eduardo Dellacassa, and Francisco Carrau*
*Universidad de la Republica, Av. Gral. Flores 2124, 11800, Uruguay (fcarrau@fq.edu.uy)

Yeasts produce a diversity of secondary metabolites during fermentation that impact the flavor and aroma of wine. Among apiculate yeasts of the genus Hanseniaspora, the species Hanseniaspora vineae has been used at the winery scale with successful results, producing aroma compounds that expand the diversity of wine color and flavor. However, this species tolerates only moderate levels of ethanol (~10% v/v). The implementation of a mixed culture with Saccharomyces cerevisiae under controlled experimental conditions could be a useful strategy to obtain complete fermentations of mature grapes with increased flavor complexity. Co-inoculation with H. vineae strain 205 avoids the risks of undesirable yeasts that might have appeared under spontaneous fermentations but increases strain diversity during fermentation. However, some mixed culture fermentations are not successful due to nutrient competition and may require supplementation with assimilable nitrogen or vitamins. This work focuses on selecting commercial S. cerevisiae strains that can grow and ferment together with Hv 205 to obtain a complete fermentation and on how nutrient addition effects improve mixed-culture performance. Of 23 commercial yeasts evaluated, we present results of the best six S. cerevisiae partners to ferment with Hv 205 under sequential inoculation at 72 hrs. At the end of the fermentation, sensory evaluation and chemical analysis of aromas by gas chromatography-mass spectrometry were per- formed. Fermentation and sensory analysis in mixed cultures with S. cerevisiae strains 3C and E73 proved the best combinations for wine quality. More intense fruity and floral aromas were found than in conventional, single-strain fermentations. Nutrient additions such as diammonium phosphate, amino acids, yeast extract, the commercial additive Natuferm, and thiamine were evaluated when Saccharomyces was inoculated to improve completion of fermentations.

Funding Support: Agencia Nacional de Investigacion e Innovacion ANII ALI 2_2019_1_155314