Separation of anthocyanins extracted from red cabbage by adsorption onto chitosan films

Anthocyanin pigments are suitable as natural dyes for food, cosmetics and dietary supplements, due to the demand for healthier products and their antioxidant properties. This work aimed to extract the anthocyanin pigments from red cabbage and its separation of the solution by adsorption operation onto chitosan films. The anthocyanin was extracted from red cabbage in water hot at 90 °C by 15 min. Chitosan was obtained from shrimp waste, and its films were produced by casting technique (tensile strength of 25.1 ± 1.9 MPa, elongation of 10.5 ± 3.5% and thicknesses of 103.1 ± 1.3 μm). The anthocyanin adsorption assays were performed in batch, and the highest adsorption capacity was around 140 mg g^-1. The equilibrium experimental data were adjusted by Henry, Langmuir and Freundlich models, and all models showed a good fitting (R² ≥ 0.96 and ARE ≤ 6.5%). The thermodynamic parameters represented endothermic and physical adsorption. The kinetic behavior was evaluated by empirical models, being the pseudo-first order model that showed the best fitting (R² ≥ 0.97 and ARE ≤ 8.5%). This work presented suitable information about the anthocyanin molecules immobilization onto chitosan films and, these results could be important to the use these pigments with chitosan in different areas.