Materials to be expanded enter the feeding bin and are fed into the conditioner by the feeder, and after conditioned by steam in the conditioner, materials enter the extruding chamber. Materials with certain moisture enter the extruder machinery and flow axially through being pushed by the screw. Due to the mechanical friction between the screw and materials, the machine cylinder and materials as well as the friction between material particles, the materials are intensively extruded, stirred and cut, so that they are further pulverized and homogenized.
Since the temperature rises along with the increasing pressure, the properties of materials change under conditions of high temperature, high pressure and high shear force, that is, powdery materials become a pasty mass, starch is gelatinized, protein is modified, fiber is partially degraded and fined, pathogenic bacteria are killed, hygienic indexes are improved and toxic substances are inactivated.
Under the action of great pressure difference, the pasty materials are expanded, dehydrated and cooled as soon as they sprayed out of the die holes. The porous of the cooking extruder expanded product is crisp with loose structure, fine in palatability and flavor.
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