ABSTRACT
Winemakers have access to a diverse range of commercially available Inactivated Dry Yeast Based products (IDYB) from various companies and brand names. Among these, thermally inactivated dried yeasts (TIYs) are utilized as yeast nutrients during alcoholic fermentation, aiding in the rehydration of active dry yeasts and reducing ochratoxin A levels during wine maturation and clarification. While IDYB products are generally derived from Saccharomyces spp., this study investigates into the biodiversity of those deriving from non-Saccharomyces for potential applications in winemaking. For that S. cerevisiae and non-Saccharomyces TIYs were produced, characterized for nitrogen and lipid content using FT-NIR spectroscopy, and applied in a wine-like solution (WLS) for analyzing and quantifying released soluble compounds. The impact of TIYs on oxygen consumption was also assessed. Non-Saccharomyces TIYs exhibited significant diversity in terms of cell lipid composition, and amount, composition, and molecular weight of polysaccharides. Compared to that of S. cerevisiae, non-Saccharomyces TIYs released notably higher protein amounts and nHPLC-MS/MS-based shotgun proteomics highlighted the release of cytosolic proteins, as expected due to cell disruption during inactivation, along with the presence of high molecular weight cell wall mannoproteins. Evaluation of antioxidant activity and oxygen consumption demonstrated significant differences among TIYs, as well as variations in GSH and thiol contents. The Principal Component Analysis (PCA) results suggest that oxygen consumption is more closely linked to the lipid fraction rather than the glutathione (GSH) content in the TIYs. Overall, these findings imply that the observed biodiversity of TIYs could have a significant impact on achieving specific oenological objectives.
ABSTRACT
The effect of industrial drying processes on phenols and polysaccharides of olive pomace (pâté) and pomegranate peel was studied, with the aim to re-use pomegranate and olive oil by-products. Pomegranate peel (Wonderful and G1 varieties) was oven-dried at different temperatures, taking into account peel thickness and size. Pâté was freeze-dried and oven dried at 50-110 °C, at lab scale; then, an industrial drying system (150 °C) was compared to freeze-drying. All dried samples were analyzed in terms of phenolic and polysaccharides compounds. Drying at room temperature of small pieces of pomegranate peel guaranteed the highest humidity removal and recovery of phenols. Sugar analysis, DLS and 1H NMR confirmed that polysaccharide fractions were not significantly affected by the highest drying temperatures (42 °C for pomegranate, 150 °C for pâté). The two drying procedures at large scale were suitable for avoiding degradation of phenols, maintaining the same profiles of the corresponding freeze-dried samples.
