Wet and dry feed extrusion machinery

There are two types of extruded feed using twin-screw feed extrusion machinery: dry extrusion and wet extrusion. Below, we analyze and compare these two different extrusion methods in the dog food extrusion process. Dry extrusion requires adding water to the raw materials during production. The raw materials are not preconditioned before entering the extrusion chamber, and all the heat generated during the extrusion process is produced by the raw materials under mechanical compression through the screw, shear plate, and extrusion chamber.

The difference between wet expansion and dry expansion is that before expansion, the raw materials are pre-conditioned by adding steam or moisture to increase temperature and pre-cook them. The so-called conditioning refers to the thermal and moisture effect of steam on pet food raw materials, which pre-gelatinizes the starch, denatures the protein, and softens the raw materials, thereby improving the expansion and granulation effect and quality of dog food.

In the wet extrusion processing technology of dog food, the pre-conditioning technique holds very significant importance.

1. Improve the expansion and granulation capacity. By pre-treating the raw materials and preheating them with steam, the raw materials are softened, which is more conducive to shaping, while reducing wear on the screw.

2. By using preconditioning technology to increase particle density, reduce dust rate, minimize losses during dog food processing, and maintain a hygienic production environment; 3. Promote starch gelatinization and protein denaturation, improving pets' digestion and absorption of food. The results show that the starch gelatinization rate can reach 35% to 45%, while without steam pretreatment, the starch gelatinization rate is only about 15%.

4. More thoroughly kill harmful bacteria; high-temperature steam can kill most E. coli and Salmonella during the preconditioning process, greatly improving the safety and hygiene standards of pet food dog food; 5. Use conditioning technology to facilitate the addition of liquid nutrients, improving the nutrition of pet food.

Wet fish feed extrusion machine.jpg Dry feed extrusion machine.jpg

Wet extrusion also has the advantages of good puffing effect and stable expansion rate. In the dog food processing process, the use of wet extrusion and preconditioning technology plays a very important role and significance. However, compared with dry extrusion, it also has disadvantages such as expensive equipment, high equipment requirements, and cumbersome equipment control. According to the quality adjustment method, it is the aforementioned dry and wet extrusion methods. It can be divided into single-screw feed extrusion machinery and twin-screw feed extrusion machinery.

The extrusion process of single-screw feed extrusion machinery is relatively simple and widely used. It can be used for products with high moisture content and fat content greater than 17%, achieving a starch gelatinization degree of over 90%. Compared with single-screw feed extrusion machinery, twin-screw feed extrusion machinery is more complex in equipment and structure, but it offers advantages such as stable extrusion performance, high product yield, high production efficiency, and being essentially sterile after extrusion. In recent years, extrusion technology has been widely applied in pet food and dog food processing technology, especially after the 1980s, when it rapidly developed in pet food, semi-moist food, and other snack foods. Extrusion technology has greatly improved the palatability, nutrition, digestion and absorption, health and safety, transportation, and storage of pet food.