Exploring different strategies of separation of antioxidant compounds from winery by-products via surfactant-assisted processes for process intensification and integration

The impact of Tween20 surfactant, applied in native form or as colloidal gas aphrons (CGAs), on the extractability/purification enhancement of antioxidant compounds from grape skins (GS), compared to conventional solid–liquid extraction (SLE), was evaluated. Three strategies were developed (S1: partial ethanol replacement during SLE with aqueous Tween20 solutions; S2: CGAs application to GS-extract suspension from SLE; S3: Tween20 addition to extracts before spray-drying). The effect of surfactant/solvent concentration (S1), extract/CGAs volumetric ratio (S2), and surfactant addition (S3) on total phenolic compounds (TPC), total anthocyanin compounds (TAC), and antioxidant power of recovered phases, was investigated. In S1, using surfactants could not significantly reduce ethanol percentage in solvent to achieve a given TPC yield, but similar TAC yields than those from SLE were obtained when partially replacing ethanol with Tween20. In S2, CGAs allowed an averaged 40% recovery of TPC, and TAC contained in crude extract, with only a slight detected additional TAC recovery from exhausted GS. Adding surfactants within spray-drying processes (S3) enhanced the water solubility of powdered extracts, despite reducing the powder/phenolics yield due to increased sample stickiness. Results demonstrated the potential of employing food-grade surfactants at different stages of grape pomace valorization process for the recovery of antioxidant extracts.