Extraction of anthocyanins from red cabbage and purification using adsorption

There is an increasing interest in anthocyanins, as natural food colorants, in food products and also in pharmaceutical products due to their antioxidative potential. The present study deals with extraction and purification of anthocyanins from red cabbage. Conventional extraction methods of anthocyanin from plant material are nonselective and yield pigment solutions with large amounts of byproducts such as sugars, organic acids and proteins. Some of these impurities may accelerate anthocyanin degradation. Different extracting media were used and the mixture of 50% (v/v) ethanol and acidified water resulted in maximum anthocyanin content (390.6 mg/L). In order to obtain anthocyanins in a purified form, adsorption was carried out with six different adsorbents. Among these, nonionic acrylic ester adsorbent, namely Amberlite XAD-7HP, showed the highest adsorption capacity (0.84 mg/mL of resin) and desorption ratio (92.85%). Adsorption results were found to be correlated best using the Langmuir isotherm equation especially at low temperature. The resulting anthocyanin solution after purification was free from sugars, which are the major cause for degradation of anthocyanin. No browning was observed and chroma increased by 27% compared to crude anthocyanin. (C) 2012 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.