La technologie d'extrusion bi-vis, une solution originale et performante pour le bioraffinage du tournesol plante entière

The objective of this study is to evaluate the feasibility of an aqueous process for the biorefinery of sunflower whole plant using a co-rotating twin-screw extruder. Traditionally, aqueous extraction of oil is looked upon as an environmentally cleaner alternative technology to the solvent extraction (Rosenthal et al., 1996) and the twin-screw extruder carries out three essential unit operations continuously: conditioning and grinding of whole plant, liquid/solid extraction and liquid/solid separation. Wringing out the mixing is favoured thanks to the stalk fibers. However, drying of the cake meal is not optimal and lixiviation of cotyledon cells within the seed is incomplete. Extraction efficiency depends on the operating conditions: screw rotation speed, input flow rates of whole plant and water. In best conditions, oil yield is 57% and residual oil content in the cake meal is 14%. These conditions lead to the co-extraction of proteins, pectins and hemicelluloses. Protein yield is 44% and residual protein content in the cake meal is 7%. Oil is extracted in the form of two oil-in-water emulsions stabilized by phospholipids and proteins at interface. An aqueous extract containing part of the water-soluble constituents from whole plant, mainly proteins and pectins, is also generated. As a mixture of fibers and proteins, the cake meal can be moulded by thermo-pressing. Panels have promising mechanical properties in bending