Commercial red wines under the lens: A snapshot of colloidal diversity

Abstract

Red wine is a complex product whose sensory properties depend on the balance and interactions of its chemical components. Among these, colloids, organized assemblies of proteins, polyphenols, and polysaccharides, play a central role in shaping key qualitative attributes such as color, clarity, texture, stability, and overall quality (1). Although research has shown that these structures are organized rather than random aggregates, their formation, evolution, and variability in commercial red wines remain insufficiently characterized, limiting a comprehensive understanding of their contribution to wine diversity and stability. This study investigates the hypothesis that chemical composition and winemaking practices drive colloidal variability in red wine. To test this, twenty-three commercial monovarietal wines, comprising fifteen varieties from ten countries, were subjected to comprehensive physicochemical profiling. The analytical framework included assessment of pH, organic acids, sugars, alcohols, and chromatic attributes, together with colloidal characteristics and stability-related parameters. Specifically, Nanoparticle Tracking Analysis (NTA) was used to determine particle size and concentration, while phenolic and polysaccharide quantification, combined with SDS-PAGE, elucidated the role of proteins and protein-tannin aggregates. The results reveal substantial compositional variability, with an average colloidal particle size of ~220 nm and limited differences among samples, suggesting a potential upper stability limit for red wine colloids. Particle concentration varied widely and was positively correlated with wine turbidity (p = 0.49), while a significant negative correlation was observed between lactic acid and particle size (p = -0.45). This relationship likely reflects the effect of malolactic fermentation on pH, a parameter that should govern interaction among colloid-forming macromolecules. SDS-PAGE profiling identified bands of 20-40 kDa, corresponding to free heat-unstable proteins in specific samples, whereas wines with higher phenolic content exhibited larger protein-tannin aggregates. By clarifying these macromolecular relationships, this work identifies drivers of colloidal organization in red wine and establishes a framework for future research to elucidate the influence of variables such as pH and environmental factors on long-term colloidal evolution and stability.

References

1. Vernhet, A. (2019). Red wine clarification and stabilization. In: Red wine technology. Academic Press. 237-251.