Abstract: Apparatus for the expansion of oil bearing seeds and of the kind comprising at least one screw (11) rotatable in a barrel (10) for conveying seed through the barrel from one end to the other, there being a die plate (14) having orifices (15) therein at the output end of the barrel and through which the seed material is extruded by the action of the screw or screws, there being a plurality of throttle needles (17) having portions (19) of tapering cross-section and movable linearly with respect to said orifices thus to vary the effective cross-sectional area thereof in response to conditions within the barrel such as temperature as detected by a temperature sensor (22), the cylindrical wall of the barrel being either wholly plain or in part comprised by a plurality of circumferentially spaced axially extending bars forming a press cage, the position of the throttle needles ensuring control of the state of the seed material prior to extrusion through the die plate.