Color enhancing effect of carboxylic acids on anthocyanins

The color enhancing effect of aromatic and aliphatic carboxylic acids on anthocyanin-glucosides was investigated in this work. The color of black rice anthocyanin-rich fraction was successfully improved after the addition of aromatic acids (p-coumaric acid, ferulic acid, and sinapic acid), aliphatic acid (lipoic acid) and tannic acid (as a complex acid). The addition of carboxylic acids showed an enhancing and stabilizing effect on the color of black rice juice during storage, which was observed through changes in CIELAB and spectrophotometric parameters. Sinapic, ferulic, and p-coumaric acids enhanced the color of black rice juice the most, with the highest efficiency for the dimethoxylated cinnamic acid derivate (sinapic acid). New anthocyanin-derived pigments were first isolated through silica gel TLC and identified using Maldi-Mass spectrometry at m/z values of 613, 659, 673, and 639, respectively, for vinylpyranoanthocyanins formed after adding coumaric, ferulic, sinapic, and lipoic acids. Based on these experimental results, the addition of carboxylic acids in an anthocyanin-rich fraction can be used as an efficient tool for their color enhancement and stability.