YEAST DERIVATIVES FOR PRECISION OENOLOGY: EMERGING AND SUSTAINABLE APPLICATION FOR WINE PRODUCTION (WINNY)

Yeast derivative products (YDPs) have become widely employed in modern oenology, being used as tools to enhance fermentation kinetics, improve wine stability, and modulate sensory properties. Despite their increasing application, the mechanisms underlying their action remain only partially understood, and their use in winemaking is often based on empirical knowledge rather than on a comprehensive understanding of their chemical and functional characteristics. This PhD research represents the first systematic study in which an in-depth chemical characterization was performed on such a large number of YDPs, providing an unprecedented overview of their composition. Furthermore, it constitutes the first work in which these derivatives were tested across such a broad spectrum of enological trials. In particular, the attention was focused on (I) alcoholic and malolactic fermentations, (II) tartaric, protein and color stabilization, (III) and impact on aging of sparkling wine. The innovative approach of this thesis lied in the combination of a detailed analytical characterization with an extensive experimental evaluation, which together allow for the establishment of correlations between the chemical composition of YDPs and their oenological effects. Innovative techniques such as atomic force microscopy (AFM) and nuclear magnetic resonance (NMR) were also applied for the first time on YDPs. The results highlighted the strong variability among different commercial products, not only in terms of composition (i.e., proteins, polysaccharides, amino acids, glutathione, cysteine) but also regarding their capacity to influence fermentation kinetics, colloidal stability, antioxidant properties, protein haze formation, tartaric stabilization, and color preservation. This variability underscores the importance of considering the specific characteristics of each product, whose behavior depend not only on its intrinsic characteristics, but also on the wine matrix in which the product is employed. The findings provided new insights into how YDPs interact with the wine matrix, clarifying some aspects of their behavior while also revealing the complexity and multifactorial nature of their effects. By analyzing and comparing their performance in different winemaking contexts, this research implements the knowledge on YDPs and on the correlation between their characteristics and the oenological functions they can better exploit thus helping industries and oenologists in selecting the most suitable derivative according to the desired technological or sensory objective. In addition, the results contribute to a better understanding of the potential of YDPs as alternatives to traditional fining and stabilization agents, with particular relevance in the context of sustainable and precision oenology. Overall, this thesis demonstrated that the functionality of YDPs could not be dissociated from their chemical composition. It also showed that their potential in winemaking extends beyond their current applications, opening new perspectives for their rational use. The comprehensive dataset generated in this study lays the groundwork for further investigations into the mechanisms of action of YDPs, which remain incompletely understood but hold considerable promise for future innovation in the wine industry.