Fluorescence correlation spectroscopy to unravel the interactions between macromolecules in wine

•FCS is an innovative method to study interactions between macromolecules in wine.•RGII causes protein aggregation, while the addition of MP has a protective effect.•Proteins interact strongly with tannins, precipitating protein-tannin complexes.•Presence of polysaccharides prevents precipitation of protein-tannin complexes. In this work, the interaction of wine macromolecules with a bovine serum albumin (BSA) was investigated using fluorescence correlation spectroscopy (FCS). FCS offers the opportunity to study molecular and macromolecular aggregation without disturbing the wine by introducing only very small amounts of fluorescently labelled molecules to the system. It was observed that the diffusion coefficient of fluorescently labelled BSA varies with the addition of wine macromolecules, indicating changes in the protein conformation and the formation of complexes and aggregates. The addition of a wine polysaccharide rhamnogalacturonan II-enriched fraction led to aggregation, while addition of a mannoprotein-enriched fraction exhibited a protective effect on protein aggregation. Proteins strongly interacted with tannins, leading to the precipitation of protein-tannin complexes, while the presence of polysaccharides prevented this precipitation. Finally, the application of FCS was demonstrated in real wines, to investigate the problem of protein haze formation through live monitoring of heat-induced aggregation in wine.