Ultrasound assisted and supercritical carbon dioxide extraction of antioxidants from roasted wheat germ

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2008

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Gelmez, Nilüfer

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This study covers the extraction of antioxidants from wheat germ; which is the byproduct of the flour-milling industry and a rich source of antioxidants; with Ultrasound Assisted (UAE) and Supercritical Carbon Dioxide (SC-CO2) extractions. Extraction conditions were ultrasonication time (111 min), temperature (2060°C) and ethanol level (595%) for UAE, and pressure (148602 bar), temperature (4060°C) and time (1060 min) for SC-CO2 extraction. The extraction conditions were optimized based on yield (%), total phenolic contents (TPC, mg GAE/g extract) and antioxidant activities (AA, mg scavenged DPPH˙/g extract) of the extracts, using Central Composite Rotatable Design. Total tocopherol contents (TTC) of the extracts were determined, as well. UAE (at 60°C) with low ethanol level (~5-30%) and short times (1-3 min) provided protein rich extracts with high yield, medium TPC and AA. On the other hand, with high ethanol level (~90%) and long times (6-11 min), waxy structured extracts with low yield but high TPC and AA were obtained. SC-CO2 extraction at 442 bar, 40ºC and 48 min. enabled almost 100% recovery of wheat germ oil (9% yield) but TPC and AA of the extracts were low. On the contrary, the extracts obtained at lower pressures (~150bar) and shorter times (~10 min) at 50-60ºC had high TPC and AA since the oil yield was low. However, TPC and AA of these extracts were only half of those extracted by UAE. Maximum tocopherol (7.142 mg tocopherol/g extract) extraction was achieved at 240 bar, 56ºC for 20 min. Both of the methods extracted high amounts of tocopherols from roasted wheat germ (SC-CO2 extraction; 0.31 mg tocopherol/g germ, UAE; 0.33 mg tocopherol/g germ) but TTC of the extracts obtained by SC-CO2 extraction was superior compared to 1.170 mg tocopherol/g extract obtained by UAE at 9 min, 58ºC and 95% ethanol level. All these extracts with different characteristics have potential uses in cosmetic and food industry depending on the targeted specific application.

Subject Keywords

Chemical engineering., Wheat germ.

URI

http://etd.lib.metu.edu.tr/upload/12609364/index.pdf
https://hdl.handle.net/11511/17570

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

N. Gelmez, “Ultrasound assisted and supercritical carbon dioxide extraction of antioxidants from roasted wheat germ,” M.S. - Master of Science, Middle East Technical University, 2008.