Optimization of supercritical carbon dioxide extraction of antioxidants from roasted wheat germ based on yield, total phenolic and tocopherol contents, and antioxidant activities of the extracts

Effects of pressure (148–602 bar), temperature (40–60 °C) and time (10–60 min) on antioxidant (phenolics and tocopherols) contents and antioxidant activities of supercritical carbon dioxide (SC-CO2) extracts of roasted wheat germ were determined, using central composite rotatable design. The dependent variables were yield (%), total phenolic contents (TPC, mg gallic acid equivalent (GAE)/g extract), total tocopherol contents (TTC, mg tocopherol/g extract) and antioxidant activities (AA, mg scavenged 1, 1-diphenyl-2-picrylhydrazyl radical (DPPH)/g extract) of the extracts. The antioxidant purity of the extracts (TPC, TTC and AA) were high at extraction conditions where the extraction yield was low (148–165 bar, 40–60 °C and 10 min). The optimum extraction conditions found by maximizing all the dependent variables were 336 bar, 58 °C and 10 min, where 5.3% yield, 6 mg GAE phenolics/g extract, 6.7 mg tocopherol/g extract and 57.3 mg scavenged DPPH/g extract was predicted. The tocopherol yield under these conditions corresponded to almost complete recovery.