Evaluation of protein-polysaccharide interactions through ζ-potential and particle size measurements to assess their functionality in wine.

Protein-polysaccharide-tannin interactions are important in every aspect of red wine production from physical stability to color, astringency, and body. For this model study, bovine serum albumin (BSA) was selected as the protein, while carboxymethyl cellulose (CMC), mannoproteins, and pectin were the model polysaccharides. Each protein-polysaccharide combination was analyzed for zeta (ζ) potential and particle size at neutral pH and within the wine-like solution. Mixtures were assessed regarding their protective, affinitive, and aggregative behaviors. Based on their individual ζ-potentials, pectin and mannoprotein were most stable at lower concentrations. At higher concentrations, they reduced the suspension's stability and increased the aggregate sizes. CMC consistently increased the stability of any solution under neutral pH conditions. However, with increasing concentrations, these large aggregates are expected to precipitate. Fruit pectin (FP) and BSA interactions seemed to be the main factors in the formation of visible precipitates at neutral pH. FP and the mannoprotein decreased stability enough to cause precipitation without haze formation. The mannoprotein decreased particle sizes, in both the suspension and precipitation, which may indicate greater selectivity toward proteins. FP also decreased the suspended particle sizes under wine conditions. These findings demonstrate the use of ζ-potential and particle size values to characterize macromolecular interactions in model systems and can also be used to indicate effective fining agents. PRACTICAL APPLICATION: This work demonstrates the capabilities of ζ-potential analysis paired with size particle measurements to predict and characterize the interactions between macromolecules in complex systems. The interactions between model wine macromolecules can be evaluated with this technology at a level that cannot be reached with any other analytical technique.
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