Colloids in red wines: new insights from recent reserach.

Despite their significant impact on wine quality and stability, colloids in red wine are under-researched. Recent studies from the D-wines (Diversity of the Italian Wines) project aimed to elucidate the structure, composition, and formation mechanisms of red wine colloids by analysing monovarietal wines from 10 Italian red grape varieties. Colloid-forming molecules, specifically proteins, polysaccharides, and tannins, were examined in over 100 wines, revealing significant diversity. Electrophoretic analysis demonstrated that all proteins in the wines exist as high molecular weight aggregates, likely mediated by tannins. Moreover, these wines could be categorized into two groups based on their protein aggregate mobility and protein-reactive tannin quantity. An analytical method using Asymmetrical Flow-Field Flow Fractionation (AF4) with online multidetection, developed to isolate and characterize red wine colloids in their native state, revealed the diversity in colloidal populations, attributed to varying proportions of proteins, polysaccharides, and phenolics. A correlation analysis on red wines' compositional data and colloidal content and structures showed that polymeric pigments associated with proteins are crucial for red wine colour stability. Overall, the findings underscore the role of proteins in wine colloids, leading to the proposal of an updated model for colloidal aggregation in red wines. 1 Introduction