Aqueous solutions of non-ionic surfactant mixtures as mediums for green extraction of polyphenols from red grape pomace

Grapevine production is predominantly oriented towards winemaking, consequently generating large amount of polyphenol-rich waste. Micellar solutions of surfactants are recognized for their ability to efficiently solubilize compounds from different plant material. This study examined potential of water solutions of mixtures of non-ionic surfactants Brij S20 (BS20) and poloxamer 407 (P407) for the extraction of polyphenols from red grape pomace. Critical micelle concentrations of extraction mediums (mixtures of BS20/P407 1:1, 1:9 and 9:1) were determined. Total phenolic content, individual phenolic profile and antioxidant capacity of extracts were examined. Measurement of hydrodynamic radii of micelles before and after extraction was performed. Water, water:ethanol (1:1) and pure BS20 and P407 extracts were used for comparison. Values of experimental critical micelle concentrations decreased with decreasing mole fraction of P407 and synergistic interactions between components of mixed micelles were observed. Total phenolic contents of BS20/P407 (9:1) and (1:1) extracts were 54.49 +/- 0.12 and 54.73 +/- 0.26 mg GAE/g DW, respectively, and these values are up to 19% higher than those obtained with pure surfactants. The most pronounced increase in solubilization efficiency in mixed micelles (BS20/P407 (1:1) and (9:1)) was observed for less polar compounds (e.g., quercetin, kaempferol and rutin) compared to a single-surfactant-micelles. All investigated systems showed an increase in micelle size after extraction. The present study has demonstrated green method for extraction of polyphenols from grape pomace with assistance of water solutions of non-ionic surfactant mixtures, which could be useful for further practical applications.