The optimisation of solid–liquid extraction of antioxidants from apple pomace by response surface methodology

Response surface methodology using two food grade solvents, acetone and ethanol, was used to optimise antioxidant extraction from industrially generated apple pomace. Efficiency of extraction was optimised by measuring antioxidant activity, phenol content and three individual polyphenol groups. Conditions for optimal antioxidant activity as measured by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay were 56% ethanol, 80 °C and 31 min. Using these conditions an antioxidant value of 444 mg Trolox/100 g DW was obtained. For acetone extraction the optimal conditions were 65% acetone, 25 °C and 60 min, resulting in an antioxidant value of 436 mg Trolox/100 g DW. Both ethanol and acetone would be suitable to replace methanol for a food grade and more environmental friendly solid–liquid extraction of antioxidants.