Characterization of Yeast-Derived Peptides Released during Model Wine Fermentation and Aging

Saccharomyces cerevisiae’s bioactive peptides produced during wine fermentation and Aging are of growing research interest due to their potential health benefits. Lees Aging is a common winemaking practice that triggers the release of yeast compounds, such as polysaccharides, proteins, and peptides, which contribute to wine stability as well as quality. While mannoproteins have been widely addressed, yeast-borne peptides are lesser-known in the wine characterization context. Such peptides are linked with antioxidant activity that may be of interest in view of a reduction in sulfite additions in wine, as well as with putative health-promoting activity. This work focuses on peptides released from yeast under model wine fermentation, during extended contact with model wine. The aim of this thesis is to purify, quantify, and characterize this fraction to assess its antioxidant potential. While the yeast contribution to fermentation is overshadowed by interactions with grape-borne compounds, fermentation was performed in a model system (synthetic must) with Saccharomyces cerevisiae EC1118 as the inoculum, collecting samples at 0, 7, 240 days, and 2 years from the inoculum. Following centrifugation and ultrafiltration (<3 kDa), peptides were recovered from the filtrate using Sep-Pak C18 cartridges for purification. So obtained samples were used for peptide quantification and antioxidant activity. Peptide quantitation was performed using a colorimetric assay, while antioxidant activity was determined using the DPPH radical scavenging assay, as well as evaluating the browning development in the presence of catechin. Polysaccharides, sugar content, as well and organic acids, were quantified using HPLC to monitor fermentation and autolysis. Results indicated increased peptide content at the early fermentation stages, where it remained stable thereafter, with peptides always exhibiting antioxidant activity, especially the ones released after 7 days. Such results provide evidence that bioactive peptides are released by yeast autolysis, where they contribute to the technological and functional attributes of wine under fermentation. More studies are suggested where the putative health benefits of such peptides can be evaluated as technological and functional food ingredients.