Supercritical fluid extraction of oil from millet bran

Prose millet bran [Panicum miliaceum (L)], variety Dakota White, was extrac ted with supercritical carbon dioxide (SC-CO2) to yield crude oil. The effe cts of operating parameters (pressure, temperature, and-specific solvent fl ow) and of features of the raw material (moisture content and particle size ) on oil extraction were investigated. Complete de-oiling of ground millet bran pellets was achieved under 300 bar at 40 degrees C with a specific sol vent flow of 2-10 h(-1) within 200 to 500 min. Solvent requirements were 20 -30 kg CO2/kg raw material. Composition of crude SC-CO2 oil extracted under optimal conditions, i.e., fatty acid profile, amount of unsaponifiables, t ocopherols, free fatty acids, sterols, sterol esters, waxes, hydrocarbons, and phospholipids, was compared to that of crude oil obtained by petroleum ether extraction. These two oils were similar in terms of fatty acid profil e and amount of free fatty acids, unsaponifiables, peroxides, and tocophero ls. They differed in respect to phospholipids (present in petroleum ether-e xtracted oil and absent in SC-CO2 extracted oil), metals, and waxes (lower revels in SC-CO2 extracted oil). The effects of extraction procedures on ox idative stability of crude SC-CO2 oil were studied. Ensuring that all piece s of the extractor in contact with the oil were in stainless steel; cleanin g the separator, i.e., washing with KOH, rinsing, purging with N-2 and CO2, and heating; performing a couple of extractions before the main extraction ; and achieving the extraction without interruption all positively influenc ed the oxidative stability of the oil. Conversely, increasing CO2 purity ab ove 99.5% had no effect. Oxidative stability of the SC-CO2 oil extracted un der these conditions was only slightly lower than that of the oil extracted with petroleum ether.