Aqueous extraction of oil from sunflower seeds in batch reactor: reorganization of the mixing in three formulated fractions

Abstract

Aqueous extraction process is an alternative to the solvent oil extraction process from oilseeds. It enables simultaneous recovery of oil and protein. Water extraction of sunflower oil is carried out with a mixer (model Waring Blendor, USA) as batch reactor (seeds/water: 15/85). This only apparatus carries out two essential unit operations: conditioning and grinding of sunflower seeds and liquid/solid extraction. However, lixiviation of kernels is incomplete. After five minutes of extraction, the mixture reorganizes by centrifugation in three formulated fractions: the insoluble phase (31.1% of the mixture), the hydrophilic phase (61.4% of the mixture) and the hydrophobic phase (7.5% of the mixture). Oil extraction yield obtained is 46.6%. Residual oil content of raffinate is 39.2% instead of 49.7% in sunflower seeds. Aqueous extraction process also results in an impoverishment of oil cake into water-soluble substances contained initially in kernels: proteins and minerals. Raffinate is on the contrary richer in insoluble proteins and fibers (26.1% for cellulose and lignins instead of 17.1% in sunflower seeds). An additional stage of extraction would allow a better oil impoverishment of the insoluble phase before its possible use for animal feeding. It would be also possible to upgrade it by thermopressing. Panels obtained have mechanical characteristics comparable with those of other experimental materials. Hydrophilic phase is the dominating fraction. It contains proteins (31.8% of dry residue), minerals (8.2% of dry residue) and hemicelluloses. Its oil content means that centrifugation does not allow an expedient separation between hydrophilic phase and hydrophobic phase. After concentration of organic substances by ultrafiltration, it is possible to collect proteins by isoelectric precipitation. These water-soluble proteins can be used for their surface-active properties. Hydrophobic phase is an oil-in-water emulsion. It is lighter than hydrophilic phase (0.94 for its density). Lipids represent 83.8% of its dry residue. Its stability is ensured by the presence at interface of natural surface-active agents also extracted during the process, phospholipids and proteins. Demulsification is possible by alcoholic extraction. It enables the edible oil isolation. Oil consumption is possible for human feeding but also for non food uses like biolubricants market. Hydrophobic phase can also be used without any modification for the manufacture of paintings and cosmetics or for the treatment of surfaces with hydrophilic matter.