Apparatus and methods for food production including a food preconditioner (228) operable to heat and partially pre-cook food ingredients, and a twin screw extruder (20) operable to further cook the preconditioned ingredients to create final food products. The extruder (20) includes a pair of hollow core extrusion screws (50, 52, 124, 126, 190) having elongated hollow core shafts (54, 128, 130, 192) equipped with helical fighting (56, 132, 134, 194) along the lengths thereof. The fighting (132, 134, 194) is also of hollow construction which communicates with the hollow core shafts (54, 128, 130, 192). The fighting (56, 132, 134, 194) also includes forward, reverse pitch sections (64, 162, 216). The extrusion screws (50, 52, 124, 126, 190) are designed to impart high levels of thermal energy into materials being processed in the extruders (20), without adding additional moisture.

A biaxial continuous kneading extrusion device (10) includes a biaxial kneading feeder (16) including two passage sections (11, 12) arranged in parallel in a state of communication with each other, and first and second kneading feed shafts (14, 15) rotatably arranged in the two passage sections, respectively, to knead a supplied material and a uniaxial screw section including a single passage section that receives the material fed out from the biaxial kneading feeder, and a separate screw shaft rotatably disposed in the single passage section to extrude the material. In each of the first and second kneading feed shafts, a mixing rotor is formed in at least one section in an axial direction, a maximum outer diameter section is formed in a section of an outer periphery of the mixing rotor, and a chip clearance is formed between the maximum outer diameter section and inner walls of the passage sections.