Antioxidant effects of citrus pomace extracts processed by super-heated steam

This study was performed to investigate the enhanced antioxidant effects of citrus pomace (CP) extracts processed by super-heated steam (SHS). CP extracts were obtained using a closed SHS system at three different temperatures (100, 200, and 300 °C) with an extraction time of 10 or 20 min. These extracts were evaluated for their antioxidant activities by measuring their DPPH, alkyl, and hydroxyl radical scavenging activity using Electron Spin Resonance (ESR) spectroscopy and for their protective effects against H2O2-induced oxidative stress in Vero cells. All extracts exhibited strong radical scavenging activities and protective effects against H2O2-induced Vero cell damage. Especially, the SHS-CP extracts obtained at 300 °C with extraction times of both 10 min and 20 min exhibited antioxidant activities that were significantly higher than those of ethanol extracts and SHS-CP extracts obtained at other temperatures. The total phenolic and flavonoid contents of SHS-CP extracts and their antioxidant activities were found to be increased with elevated processing temperatures. Moreover, gas chromatography/mass spectrometry (GC/MS) in the presence of a methylating reagent revealed that some characteristic polyphenols and polyhydroxycyclohexanes were present in the SHS-CP extracts. Thus, this study demonstrated that SHS extraction is an efficient and environmentally friendly method for extracting antioxidants from CP.