ANTHOCYANINS AS FOOD COLORANTS —A REVIEW

A number of factors affecting anthocyanin stability and color are discussed in this review. The anthocyanins are probably the most spectacular of plant pigments since they are responsible for most of the red, purple and blue pigmentation of flowers, fruits and vegetables. However, because of their highly reactive nature, anthocyanins readily degrade, or react with other constituents in the media, to form colorless or brown colored compounds. The presence of an ox-onium ion adjacent to carbon 2 makes the anthocyanins particularly susceptible to nucleophilic attack by such compounds as sulfur dioxide, ascorbic acid, hydrogen peroxide and even water. Loss of anthocyanin pigmentation also occurs in the presence of oxygen and various enzymes, and as a result of high temperature processing. A certain degree of pigment stabilization may be conferred by acylation with various organic acids, copigmentation, self-association and/or metal chelation. In addition, pH has a marked effect on anthocyanin stability, and on the color of media containing these pigments. A number of anthocyanin-rich sources have been investigated for their potential as commercial pigment extracts. Although their application is primarily limited to acidic media, continued research on the chemistry of anthocyanins may lead to application and stabilization of these pigments in a wider variety of food products.