Recovery of phenolic compounds from a grape marc extract with collidal gas aphrons

One of the main problems of solvent extraction of antioxidants from natural sources is the purity of the final extracts. Purities higher than 20% are reported for extractions from fruit seeds (one of the richest part of plants in these compounds) but values are generally lower, in particular when the starting material is an industrial waste, such as grape marc [1]. Further purification steps would be required in order to extract value added products which typically will be based on membrane separations and/or chromatography. The development of cost effective methods for the extraction of added-value products from agricultural and food waste streams remains a challenge. In our laboratory we have developed a flotation based separation for the recovery of value added food products. The separation is based on the generation of microbubbles, colloidal gas aphrons (CGA) which are a surfactant-stabilized microbubbles (10-100 m) generated by intense stirring of a surfactant solution at high speeds (>8000 rpm) [2]. In previous studies we have demonstrated that gallic acid (GA) in its anionic form can be recovered from aqueous solutions using colloidal gas aphrons (CGA) generated from the cationic surfactant cetyltrimethylammonium bromide (CTAB) [1]. Furthermore preliminary experiments with grape marc extracts confirmed the potential application of this separation for the recovery of polyphenols from complex feedstocks. [1]. The aim of the present study is to investigate the recovery of antioxidant compounds from a red grape marc extract by CGA flotation. The specific objectives are to: (i) concentrate and separate polyphenols in the surfactant phase (ii) get a better understanding of the CGA-polyphenols interactions and separation mechanism (iii) selectively separate different classes of phenolic compounds.