Stabilizing effect of montmorillonite on acerola juice anthocyanins

This study was conducted to evaluate color and anthocyanin stability of clarified acerola juice (CAJ) as affected by montmorillonite (Mnt) at different concentrations (0-6 wt%, dry basis). While non-complexed CAJ suffered noticeable color degradation with time and pH variations, the presence of Mnt (especially at 4-6 wt%) not only changed the initial color of CAJ but also made it more stable with time and pH changes. CAJ/Mnt mixtures were ultracentrifuged in order to separate them into supernatants and anthocyanin-complexed Mnt precipitates. The supernatants presented decreasing anthocyanin contents with increasing Mnt concentrations, indicating pigment retention by the precipitates. X-ray diffraction of precipitates showed that Mnt interlayer spacing was increased by increasing anthocyanin/Mnt ratios, corroborating anthocyanin intercalation. FTIR revealed a band at 1530 cm^-1 ascribed to formation of anthocyanin-Mnt complexes. Moreover, chromatograms indicated the selective adsorption of two compounds by Mnt, which were identified by LC-MS as cyanidin-3-O-rhamnoside and pelargonidin-3-O-rhamnoside.