An innovative method for the purification of anthocyanins from grape skin extracts by using liquid and sub-critical carbon dioxide

Abstract This work describes a new and innovative method for the purification of anthocyanins from grape skin extracts as liquid matrix (LM), by using carbon dioxide (CO 2 ). The LM was obtained by extraction of anthocyanins from grape skins using a water/ethyl alcohol solution acidified with 0.2% trifluoroacetic acid (TFA). The CO 2 purification process produced a desired fraction (F1) containing pure anthocyanins, and a second fraction (F2) containing ethyl alcohol and other components of the grape skins. An yield of anthocyanin of about 85%, with respect to the starting overall anthocyanin content, was obtained under the following optimized process conditions: pressure 100–130 bar; temperature 30–40 °C; pH of LM 2–4; percentage of ethyl alcohol in the LM 25–30%; CO 2 flow rate 25–50 ml/min; LM flow/CO 2 flow ratio 3–10%. We have also demonstrated that the purification process allowed to eliminate ethyl alcohol from the anthocyanin extract without any thermal or chemical degradation, obtaining a high added value product which maintains its anthocyanin content and antioxidant activity unchanged.