Colloids in red wines: new insights from recent research

Despite their significant impact on wine quality and stability, colloids in red wine remain relatively under-researched. a series of studies, developed in the context of the d-wines project, aimed to provide a comprehensive understanding of the structure, composition, and formation mechanisms of red wine colloids by studying monovarietal wines from 10 of the most significant italian red grape varieties.starting from the idea that proteins, polysaccharides, and tannins should be involved in colloid formation, 110 monovarietal red wines were analysed for these components, revealing high inter- and intra-varietal diversity [1]. despite this diversity, sds-page analysis of the proteins shows the presence of high molecular weight aggregates in all wines, whereas no free protein bands could be detected. this suggests that all proteins exist in an aggregated form, this aggregation being probably mediated by tannins. however, the studied varieties can be divided in two groups based on the mobility (dimension) of the aggregates, a distinction significantly related to the quantity of protein (bsa)-reactive tannins. this indicates that these compounds, whose quantity appears to be variety-related, determine the extent of aggregation.in a second step, an analytical method based on asymmetrical flow-field flow fractionation (af4) with online multidetection was developed to isolate and characterize red wine colloids in their native state [2]. af4 facilitated the quantification and size-separation of wine colloids. analysis of the separated colloidal fractions revealed varying proportions of proteins, polysaccharides, and phenolics, indicating that these compounds participate in colloid formation and likely determine their dimension and shape. the validity of the af4 method was confirmed by characterizing the colloidal composition of 24 italian wines selected from the previously analysed 110 red wines [3]. results confirmed the diversity in colloidal populations, which varied in size and compactness. relationships between compositional data of red wines [4] and their colloidal content and structures can be observed. in particular, red wine colloids also include polymeric pigments associated with proteins, and this can be an important aspect for the stability of red wines colour. in conclusion, the findings highlight the fundamental role of proteins in affecting the colloidal status of wine and allow to propose an updated model for colloidal aggregation in red wines. references marangon, m. et al. the macromolecular diversity of italian monovarietal red wines. oeno one 2022, 56, 81–90. marassi, v. et al. characterization of red wine native colloids by asymmetrical flow field-flow fractionation with online multidetection. food hydrocoll. 2021, 110, 106204–106204. marangon, m. et al. comprehensive analysis of colloid formation, distribution, and properties of monovarietal red wines using asymmetrical flow field-flow fractionation with online multidetection. food res. int. 2024, 187, 114414. giacosa, s. et al. diversity of italian red wines: a study by enological parameters, color, and phenolic indices. food res. int. 2021, 143, 110277–110277.