Aqueous extraction of oleic sunflower oil from whole plant by twin-screw extruder: feasibility study, influence of screw configuration and operating conditions
Aqueous extraction process using water alone as medium is an alternative to the solvent oil extraction process from oilseeds. It enables simultaneous recovery of oil and protein. The implementation of a co-rotating twin-screw extruder allows the aqueous extraction of oleic sunflower oil from whole plant.
Screw configuration, screw rotation speed and whole plant input flow rate affect directly the efficiency of liquid/solid separation. Wringing out the mixing is possible because of the natural abundance of fibers in stalk. However, the compression of the vegetable matter is imperfect to allow an expedient separation of the two phases. Lixiviation of oilseeds is also incomplete. The highest oil extraction yield obtained is 64.9% and residual oil content of fibrous cake meal is always higher than 13.1%. Hydrophobic phase produced is an oil-in-water emulsion. Its stability is ensured by the presence at interface of natural surface-active agents also extracted during the process, phospholipids and proteins. Hydrophilic extract contains soluble proteins but also hemicelluloses and pectins. Originated respectively from stalk, pith and head, these two molecular families also have some interesting surface-active properties. So the aqueous extraction produces a second hydrophobic phase when it is realised from whole plant. This water-in-oil-in-water emulsion is denser than aqueous phase. Its stability is ensured by the presence at interface of phospholipids, proteins, hemicelluloses and pectins. Fibrous cake meal is richer in fibers (up to 45.6% of cellulose and lignins against 33.1% in the whole plant) and other insoluble components. It is possible to upgrade it by thermopressing in such a way as to manufacture sound insulation panels
