Non-conventional Inactivated Dry Yeast: evaluation of their impact on the chemical, physical and sensory characteristics of white wines

The investigations carried out during this PhD project provided evidence of the significant biodiversity among thermally inactivated yeasts, revealing variations in protein, polysaccharide, and lipid content and composition. Notably, the observed biodiversity in oxygen consumption among TIYs, particularly those derived from non-Saccharomyces yeasts, presents exciting new opportunities for their application in winemaking. Furthermore, the evaluation of non-Saccharomyces TIYs in a real white wine context demonstrates positive effects on protein stabilization and browning prevention. Interestingly, the protein-stabilizing effect of TIY polysaccharides appears independent of the quantity released, suggesting alternative mechanisms may be involved. The adsorption of phenolic compounds by TIYs likely contributes to browning prevention, enhancing the visual appeal of white wines. Pilot-scale propagation trials for SL#64 biomass have demonstrated promising results, suggesting scalability for industrial production. The use of innovative, non-thermal inactivation techniques like high-pressure processing and Microfluidics offers a sustainable approach to yeast derivative production. These techniques have yielded derivatives with comparable impacts on fermentation kinetics and wine physicochemical properties to traditional methods. Furthermore, fermentation trials using SL#64-YDs exhibited improved kinetics compared to controls, underscoring the importance of organic substances contributed by these derivatives. Moreover, the increased polysaccharide content observed in wines treated with SL#64-YDs presents an intriguing avenue for further exploration, considering the multifaceted positive effects of polysaccharides on wine quality. For this purpose, were investigated the effects of SL#64-YDs on protein and tartaric stability, as well as sensory characteristics, in Garnacha Blanca and Tempranillo Blanco wines. Results indicate that certain derivatives, particularly those produced via PP, enhance protein stability, especially with extended contact times. However, the interaction of released polysaccharides with haze-forming proteins can partially offset this effect. No direct correlation was observed between added polysaccharides and tartaric stability. Sensory analysis revealed distinct groupings of wines based on treatment, but no clear relationship emerged between polysaccharide levels and sensory attributes. The aroma profile of the grape variety appears to influence treatment impact, with the less aromatic Garnacha Blanca exhibiting more pronounced sensory differences. Furthermore, contact time did not significantly affect sensory perception. Further research is needed to fully understand the long-term effects of yeast derivative polysaccharides on wine colloidal stability and sensory characteristics.