Extraction of phenolic compounds from apple pomace, process modeling and antioxidant potential evaluation of extracts

Apple pomace, a byproduct of juice and cider production, is rich in phenolic compounds with antioxidant activity. This work studies the kinetics of solid-liquid extraction of phenolic compounds from apple pomace. Extraction kinetics were determined using a 50% water-ethanol solution and fitted to a phenomenological model. Equilibrium isotherms were also modeled. Effective diffusion coefficient values between 1.85x10(-11) and 7.37x10(-11) m(2)/s were found. External mass transfer resistance showed negligible results. The best yields (43.94%) were obtained at 60 degrees C with a solid-liquid ratio of 1:10 g/mL. Those conditions resulted in a total phenolic content of 9.95 mg gallic acid equivalents (GAE)/g apple pomace d.b., antioxidant FRAP activity of 5.07 mmol ascorbic acid equivalents (AAE)/100 g apple pomace d.b. and 3.74 mmol trolox equivalents (TRE)/100 g apple pomace d.b. based on a DPPH assay. Apple pomace extract efficiently stabilized sunflower oil and may represent a natural alternative to synthetic antioxidants.