Colorant Properties and Stability of Amaranthus Betacyanin Pigments

Color, spectral characteristics, and stability of betacyanin pigments of 21 genotypes from 7 Amaranthus species were evaluated. Wide variation in color characteristics and significant differences in pigment stability were found as much within as between Amaranthus species. Amaranthus betacyanins, like red beet pigments, were susceptible to temperature and also affected by pH, light, air, and water activity, with better pigment stability at lower temperatures (≤14 °C) in the dark and in the absence of air. Storage stability at 25 °C of dried Amaranthus pigments (t_1/2 = 23.3 months) was longer than that of aqueous pigment extracts (t_1/2 = 1.04 months), indicating that the dried pigments were stable enough to be used as commercial colorants. The betacyanins from some better pigment genotypes (Cr015, Sheng07, Tr010, Cr072, Cr017, etc.) exhibited brighter red-violet color characteristics and were similar in stability to red radish anthocyanins under selected conditions. These characteristics of Amaranthus pigments give them considerable potential for development for use in the food industry, particularly for low-temperature uses.