Impact of a pectic polysaccharide on oenin copigmentation mechanism

•Anthocyanin-polysaccharide interaction is fundamental for anthocyanins stabilization.•Color stability of oenin was enhanced in the presence of catechin.•Pectic polysaccharide acted as a oenin copigment strengthening its color.•KCP for oenin-catechin interaction decreased in the presence pectic polysaccharide. Copigmentation plays an important role in the colors provided by anthocyanins. However, little attention has been paid to the interaction between anthocyanins and cell wall compounds (e.g. polysaccharides) and the impact of this interaction on anthocyanins color, a fundamental issue to be considered in industrial applications of these pigments as food colorants. The copigmentation binding constants (KCP) for the interaction between malvidin-3-O-glucoside and (+)-catechin in the presence of low methoxylated pectic polysaccharide were determined. The values obtained showed that in the presence of pectic polysaccharide the copigmentation binding constants decreased. These results probably suggest the occurrence of competition equilibrium in which the presence of pectin limited the association between catechin and oenin. 1H NMR studies revealed that the dissociation constant determined for these complexes was very similar in absence and presence of 1.5g/L pectin with this polysaccharide apparently not affecting the strength of anthocyanin-catechin binding.