Basic principle of extrusion technology

The core equipment of continuous extrusion cooking process is extruder. The extruder has the functions of compression, mixing, mixing, melting, expansion and molding. The cavity of the extruder can be divided into 3-5 zones, and each zone can be heated by steam, electric heating or extrusion friction to achieve the purpose of cooking materials. Under the action of high temperature and high pressure in the cavity, the material gelatinized and protein denatured. When the material passes through the cavity of the extruder, soluble flavor substances and pigments can be injected into the material through the cavity under the action of high pressure. At the end of the extrusion cavity, the molten material is extruded through the die hole of the template under the action of high pressure. Due to the sudden drop of pressure, the water vapor quickly expands and dissipates, making the product form a porous structure, and then cutting the expanded material into a certain size product with a rotary knife. Single-screw extruder and twin-screw extruder are commonly used in breakfast cereal production. Twin-screw extruder has more advantages than single-screw extruder, because single-screw extruder has strict requirements on particle size, moisture and composition of materials, and it is prone to problems such as material backflow and screw wear.