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Reza Tabaraki,Shahrbanoo Rastgoo 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.4
Agricultural industries produce substantial quantities of phenolic-rich by-products, which have gained muchattention due to their antioxidant properties. Ultrasonic technology was applied for extraction of antioxidants from thewalnut green husk using ethanol as a food grade solvent. Response surface methodology (RSM) was used to optimizeexperimental conditions. The responses were total phenolic content (TPC), ferric reducing antioxidant power (FRAP),scavenging activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and yield. TPC varied from 6.28 to 7.23mg GA g−1dry sample. FRAP and DPPH values varied from 0.33 to 0.46 mmol Fe2+ g−1 of dry sample and 33.98% to 56.31% inhibition,respectively. Extraction yields ranged from 33.04% to 38.72%. The optimal conditions were 60% ethanolwatermixture as solvent, temperature of 60 oC and extraction time of 30 min. Comparison of ultrasonic-assisted extraction(UAE) and conventional extraction was shown that TPC, FRAP, DPPH and yield obtained by UAE during30 min were significantly higher than by conventional extraction during 16 hours. The extract can be used as substituteof synthetic antioxidants for food products, color and oxidative stabilization.