Effect of pH, temperature and iron on the stability of anthocyanins from black-skinned peanuts (Arachis hypogaea L.)

As public concerns about the safety of synthetic colorants increases, natural colors are assuming greater importance in the food and beverage industries. Anthocyanins are non poisonous abundant natural pigments. However, color deterioration during storage and processing limits their application as commercial colorants. The pigment extracts from black peanut skin are natural and safe colorants. The goal of this study was to study the effect of pH, temperature, metal ions, and ascorbic acid on the stability of pigments from the skins of black peanuts. The addition of Iron (Fe3+) rapidly generated black or dark brown precipitate, but other metal ions did not significantly affect the absorbance of anthocyanins. The ideal conditions for extraction of anthocyanins from black peanut skins were pH 2.0 and 60°C. Key words: Black peanut, pre-extraction coloring, anthocyanin, stability, extrusion.