The stability and color of purified cyanidin-3-glucoside and raspberry juice extract in the presence of selected metal ions was investigated. Production of metal-anthocyanin complexes was suggested by changes in color of the samples as shown by L, a, and hue angle values. Complex formation was indicated by HPLC in raspberry juice samples treated with Sn++ but not in samples of purified cyanidin-3-glucoside. According to the colorimetric values, complex formation occurs with cyanidin-3-glucoside and A1+++ at pH 2.0 and 3.0 and with Sn++ at pH 4.0 and 3.0. Similar complex formation occurs with these metals and raspberry juice extract at the same respective pH values.
1Present address: Miles Laboratories Inc., Elkhart, Indiana.
2Present address: Dept. of Vet. Animal Science, Mass. Agricultural Experiment Station University of Massachusetts, Amherst, Massachusetts 01003.