An extruder (100) for use in a dispenser (1) of a loose product (30) for the preparation of beverages, comprising: a housing (110), defining a product inlet (112), a product outlet (114), and a bore (116) that interconnects the product inlet and the product outlet; a screw feeder (120) including a screw blade (124) that is both rotatably and translatably received in the bore (116), such that it is axially movable along the longitudinal axis (/) between a first position and a second position; and a first sealing device (126b) that is configured to releasably fluidtightly seal a portion of the bore (116) interconnecting the product inlet (112) and the product outlet (114) in dependence of the axial position of the screw blade (124).