The expander is also called EXPANDER. It is also known as the ring gap extruder in China. Its working principle is the same as that of the extruder. It uses mechanical energy to increase the heat added to the powder before granulation. The powder is forced to pass through the narrow gap between the screw and the die under pressure, resulting in compaction and shearing, intense friction with the screw and the cylinder, and a large amount of heat to achieve ripening, sterilization and Improve the purpose of granulation. The difference lies in the adjustable die gap of the expander. During the work, the die gap can be adjusted to control the extrusion, friction and shear strength of the powder in the tempering chamber, thereby controlling the heat diffused into the powder. Generally, the expander can generate a pressure of 40 Pa for the material and a temperature of 120 ° C - 130 ° C. The material stays under these conditions for 3 to 5 seconds, and physical changes occur very quickly, so that the starch gelatinization degree of the material and the protein are soluble. The degree is significantly improved, however, the heat-sensitive nutrients in the material are also greatly lost in this high temperature process.