copigments

Copigments are molecules that form non-covalent associations with pigment molecules, most often anthocyanins, to alter color properties in plant tissues and in foods such as wine. In plants, copigmentation can stabilize and deepen red, blue, or purple hues by creating discrete pigment–copigment complexes in the vacuole.

Mechanism: The interaction typically involves pi‑pi stacking between the aromatic rings of the flavylium cation in the anthocyanin and aromatic rings of the copigment, complemented by hydrogen bonding and electrostatic contacts. These complexes shift the light-absorption spectrum toward longer wavelengths (bathochromic shift) and increase color intensity (hyperchromia). The magnitude of the effect depends on pH, temperature, concentrations, and the ratio of pigment to copigment.

Common copigments include hydroxycinnamic acids (such as caffeic and chlorogenic acids), flavonols (quercetin, kaempferol), and tannins (catechin and proanthocyanidins).

Occurrences and relevance: Copigmentation influences flower and fruit color, contributing to hue stability during development and maturation. In wine, copigmentation between anthocyanins and phenolic copigments can markedly deepen the red color and help stabilize it at low pH; processes such as maceration and aging, temperature, and SO2 exposure modulate the effect.

Significance: Understanding copigmentation aids horticultural breeding for color traits and winemaking for color management and sensory perception.