Oxidative stability of walnut oils extracted with supercritical carbon dioxide

Supercritical carbon dioxide (SC-CO2) was used to partially defat walnuts, and the oxidative stability of the extracted walnut oils was assessed. The SC-CO2-extracted oils were less stable during accelerated storage in the dark than was pressed walnut oil, as determined by PV, headspace analysis by solid-phase microextraction, and sensory methods. The SC-CO2-extracted oils, however, exhibited greater photo-oxidative stability than did pressed walnut oil by all of these methods, possibly because of the presence of chlorophyll in the pressed oil. Oxidative stability indices and tocopherol contents were significantly lower in the SC-CO2-extracted oils than in pressed oil.