Understanding the chemical stability of carrot anthocyanins provides insights into their potential applications as food colorants

Food colorants are among the most interesting additives used in the food industry, because the color is intrinsically-linked to the visual appeal and the quality perception of food products. Among them, synthetic dyes are generally considered to have high stability under a relatively broad range of food-storage conditions varying in temperature, pH, light intensity, and oxygen concentration. However, their consumption has been associated with various conditions negative for health, ranging from allergic reactions to potential carcinogenesis. As result, there is increasing interest in the development of chemically-stable food colorants from natural sources that may help replace synthetic dyes. Among such natural sources, anthocyanins, which are water-soluble flavonoid pigments that provide red, violet, and blue hues to plant tissues, may have potential as food dyes. However, the physicochemical and biological properties of these pigments depend on many factors including their molecular structure, pH, temperature, and presence of other macromolecules (e.g., polyphenols) that can influence their stability. In recent years, anthocyanins from purple carrots have been studied with regard to pigment composition, and their chemical stabilities evaluated under different temperature and pH conditions in comparisons, side-by-side, with other natural and synthetic food dyes. In addition, a number of anthocyanin stabilizing agents have been tested for increasing the stability of these pigments. In general, the studies conducted to date have revealed great potential for carrot anthocyanins as food colorants. However, a number of factors can strongly influence their chemical stability, including the carrot genotype, which conditions total pigment content and composition, particularly with regards to the proportion of acylated (AA) versus non-acylated anthocyanins (NAA) and, within AA, the type of aromatic acids attached to the cyanidin glycoside; the pH and temperature; other accompanying macromolecules; and the food matrix. This work discusses recent results, by our group and others, on the potential use of carrot anthocyanins as natural colorants for the food industry.