42nd SASEV VIRTUAL CONFERENCE 3-5 November 2020

Galactomannoproteins of Schizosaccharomyces japonicus: a new tool towards wine protein stability Paola Domizio Dipartimento di Scienze e Tecnologie Agrarie, Alimentari, Ambientali e Forestali (DAGRI), Università degli Studi di Firenze, Via Donizetti 6, 50144 Firenze Corresponding Author E-mail: paola.domizio@unifi.it The utilization of commercial preparations of yeast polysaccharides (PSs), mainly mannoproteins, for wine colloidal and tartrate salt stabilization, is a common practice in the wine industry. In particular, PSs deriving from the cell wall of Saccharomyces cerevisiae are at present, the ones of choice. Unfortunately, this yeast releases limited amounts of mannoproteins in the growth medium, thus rendering economically unfeasible their direct isolation from the culture broth. On the contrary, the wine yeast Schizosaccharomyces japonicus releases significant amounts of PSs, in particular galactomannoproteins, during the alcoholic fermentation. Here, with the aim of evaluating whether these galactomannoproteins may find application in the wine industry, PSs released from Sch. japonicus were recovered by ultrafiltration, chemically characterized and their impact of on the colloidal stability wine was assessed. Interestingly, and contrary to that observed for S. cerevisiae, it was found that Sch. japonicus PSs can be easily recovered from the growth medium. Moreover, they reduced protein haze to around half of the initial values thus showing a positive effect on wine protein heat stability. In particular, the visible haziness of the heated proteins decreased as the concentration of added PSs increased, revealing an exponential relationship between concentration of additive and the extent of haze protection. The results obtained through SDS PAGE analysis of the haze and of the supernatant after the heat test of the wine were consistent with the turbidity measurements. Moreover, particles size distributions of the heat-treated wines, evaluated by Dynamic Light Scattering (DLS), showed a decrease in the average dimension of the protein aggregates as the concentration of added PSs increased. In conclusion, although further studies are needed to characterize the active components of the pool of macromolecules released into the media, to understand their role in the protein haze protection and evaluate their impact on wine features, these results are compatible with the hypothesis of a future exploitation of Sch. japonicus PSs for the stabilization of wine.