Synergistic Bathochromic and Hyperchromic Shifts of Anthocyanin Spectra Observed Following Complexation with Iron Salts and Chondroitin Sulfate
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Grape anthocyanins are not traditionally used on complexation studies, as the main compounds lack a catechol group. In this study, concomitant metal complexation (Fe2+ and/or Fe3+) and co-pigmentation with chondroitin sulfate (CHS) were shown to synergistically affect the color spectra of grape anthocyanins at varying pHs. In general, the addition of iron salts resulted in small reductions in maximum absorbance at pH 3 and a bathochromic shift at pH 4 and 5. On the other hand, CHS resulted in hypochromic shifts at pH 3 and 4. When combined, these compounds broadened the peak at higher wavelengths associated with blue color, and resulted in significantly higher (p < 0.05) area under the curve at these wavelengths even at pH 3. Interestingly, this synergistic effect seemed to work only at low pH. All observed effects were achieved using low concentrations of metals and CHS. The results should interest those aiming to achieve anthocyanin color modulation through metal complexation at modest loadings.
KeywordsAnthocyanin Co-pigmentation Chondroitin sulfate Iron Spectra analysis
This work has been fully supported by resources within the Department of Food Science at Cornell University.
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