Differentiating Polymeric Pigments from Polysaccharide–Polyphenol Adducts via a Modified Spectrophotometric Precipitation Assay

An accurate account of polymeric pigments (PP) and their reactions with other red wine constituents is critical for evaluating the color stability and any pigment-associated organoleptic properties. It is known that polysaccharides can react with pigments and influence their analytical appearance and method accuracy. This study evaluates the interactions that occur between polysaccharides and pigments in a model system and two red wines that are different in age. Implementing a further modified spectrophotometric assay, it is possible to discern the differences between the pigments that are based on polymeric polyphenols and those that are incorporating polysaccharides in their molecule structure. The assay provides effective differentiation of protein-precipitable and polyphenol-based precipitable PP. Distinction between the two becomes more noticeable with the addition of polysaccharides to the wines. Despite the apparent depiction of these polysaccharides, their impact varied between the two wines. Variations between wines establish the greater instability of the PP in older wines. The precipitability of PP in the older wine was initially greater and continued to increase more rapidly throughout the study than that of PP in the younger wine. The assay permits better characterization of polysaccharide–polyphenol adducts and their effects on wine and color stability.