Copigmentation of Simple and Acylated Anthocyanins with Colorless Phenolic Compounds

Abstract

The influence of pH and structure and concentration of copigment and pigment on the copigmentation reaction of anthocyanin-colorless phenolic compounds has been investigated. It has been found that the copigmentation effect displayed by chlorogenic acid, caffeic acid, and rutin was greater for the acylated pelargonidin, monardaein, than for the corresponding pelargonidin 3-glucoside, and malvin solutions exhibited the greatest copigmentation effects. The pH of maximum copigmentation effect was 3.2–3.7 for chlorogenic acid and 3.5–4.7 for caffeic acid and rutin. The equilibrium and stoichiometric constants for eight pigment-copigment combinations were determined and used to quantitate the association between pigments and copigments. The magnitude of the copigmentation effect is interpreted in terms of the acidity constant of the copigment and the hydration constant of the pigment. © 1993, American Chemical Society. All rights reserved.