Pasta products are traditionally made by extruding hydrated semolina at low temperature in a screw press. A previous experimental study on a fully-instrumented press has determined the influence of various process variables (hydration, control temperature and screw speed) on flow parameters, such as energy, pressure and temperature, and on pasta quality. In the present study, the hydrated durum wheat semolina was characterized by the determination of friction coefficients and compressibility curves, and by capillary theological measurements. Flow in the screw press and in the die was modelled by adapting the classical theory of single-screw extrusion for synthetic polymers. To account for the specific screw geometry (deep and curved channel), an approximate analytical model was developed and validated by experiment.