A polyamide resin based method for adsorption of anthocyanins from blackberries

Abstract

The present study deals with the downstream processing of anthocyanins from blackberries in order to obtain anthocyanins in a purified form. Adsorption was carried out employing four different mesh sizes of polyamide resin and among these, the 60–100 mesh polyamide resin showed the highest adsorption capacity (4.41 mg mL⁻¹ of the adsorbent) and desorption capacity (3.29 mg mL⁻¹ of the adsorbent). Adsorption results were found to correlate best using the Freundlich equation at all the temperatures studied. The second order kinetics model was found to be more appropriate to describe the adsorption of anthocyanins. Under all conditions, the polyamide resin showed optimal adsorption and desorption capacity towards anthocyanins at an initial concentration of 0.75 mg mL⁻¹, an adsorption liquid pH of 1, an eluent pH of 3 and an ethanol concentration of 80%. The dynamic adsorption process parameters for the purification of anthocyanins using the 60–100 mesh polyamide resin were as follows: processing volume, 5 BV; the flow rate of adsorption, 5 BV per h; the temperature of adsorption, 15 °C; eluent volume, 3.5 BV and the flow rate of desorption, 5 BV per h. Polyamide resin adsorption resulted in a gram of concentrated blackberry extract that contained 432 mg of anthocyanins, which was superior to cation exchange resin adsorption (160 mg g⁻¹) and macroporous adsorbent resin adsorption (176 mg g⁻¹). This method provides an efficient and low-cost approach for anthocyanin purification for industrial applications.