Effect of organic acids on the alteration of black rice anthocyanins by Enterobacter aerogenes NBRC 13534

In a previous study, it was reported that Enterobacter aerogenes and four organic acids are involved in the alteration of black rice anthocyanins. To investigate the factors involved in altering the coloration of black rice anthocyanins, organic acids (caffeic acid, ferulic acid, malonic acid, and p-hydroxybenzoic acid) were individually added to potato dextrose agar medium containing black rice anthocyanins and cultured with E. aerogenes NBRC 13534 at 37°C for five days. As a result, the color change of black rice anthocyanins was found in the medium supplemented with caffeic acid or ferulic acid among the four organic acids. HPLC analysis of anthocyanins in each medium revealed three new peaks not found in the original black rice anthocyanins in the sample supplemented with caffeic acid. Also, two new peaks were observed in the medium supplemented with ferulic acid.   Key words: Anthocyanin, anthocyanin modification, black rice, Enterobacter aerogenes, microorganism, color, pigment.