Kinetic models for conventional and ultrasound assistant extraction of polyphenols from defatted fresh and distilled grape marc and its main components skins and seeds

Kinetic modeling is essential for industrial applications. The applicability of six mathematical models (parabolic diffusion, power law, Weibull's equation, Elovich's equation, second order rate, two- site kinetic models) to describe the kinetics of the conventional (CSLE) and ultrasound assistant extraction (UAE) of polyphenols (TPC) from fresh and distilled grape marc and its components, seeds and skins, after removal of non-polar compounds was studied. The best extraction yield of TPC for all the samples was obtained using UAE with ethanol-water mixture (57:43 v/v) as solvent, 200 W and 26 kHz after 30 min. The two-site kinetic model showed (R2 0.9965–1.000, NRMSD (%) 0.21–2.29) the best agreement with the experimental results. Important proanthocyanidins concentrations and significant antioxidant activity were observed both for fresh and distilled grape marc and its components. Fresh grape skins resulted particularly rich of oligomeric proanthocyanidins and the distilled ones of polymeric proanthocyanidins. These extracts could be used for different healthy purposes.