Dry and Wet pet food making machines: How to Choose the Right Feed Pelletizer for Your Raw Materials?

Dry extruders are better suited for "low-moisture, high-starch" raw materials. These include grains such as corn flour, rice flour, and wheat bran, as well as dehydrated fish meal and meat and bone meal (moisture content 10%-12%). Under the high temperature and pressure of a dry extruder, the starch in grains can be fully gelatinized, forming a stable extruded structure, and the low moisture content prevents the raw materials from sticking and clogging in the extrusion chamber. For example, when producing chicken feed with corn flour (12% moisture content), a dry extruder can quickly increase the starch gelatinization rate to over 85%, resulting in hard, crisp pellets suitable for chickens. However, dry extruders are less adaptable to high-fiber, high-protein raw materials—if alfalfa meal accounts for more than 30% of the raw material, the high coefficient of friction can cause a sudden increase in equipment load, even leading to screw jamming; if meat meal accounts for more than 40%, insufficient extrusion is likely, resulting in loose, brittle pellets.

Wet extruders, on the other hand, excel at processing "high-moisture, high-protein, multi-component mixed" raw materials. Fresh meat paste (60%-70% moisture content), fresh bone paste, and tofu residue, when directly fed into a dry extruder, can cause equipment blockage. A wet extruder, however, can control the moisture content of the raw materials within a reasonable range by adjusting the steam and drying processes. For example, in the production of high-end dog food, fresh chicken breast paste (65% moisture content) is mixed with corn flour. The wet extruder first injects steam to adjust the overall moisture content to 22%, and after processing, the drying system reduces the finished product's moisture content to 10%, preserving the fresh nutrients of the chicken while avoiding the problem of raw materials sticking together. For high-fiber raw materials, the steam softening effect of the wet extruder reduces fiber hardness and decreases screw wear; even with alfalfa meal accounting for 40%, stable production is possible.

The physical state of the raw materials also affects the selection of the extruder. Both types of equipment are suitable for powdery raw materials, but lumpy or granular raw materials need to be pulverized first. Dry extruders require higher pulverization precision (80 mesh or higher), otherwise large particles will accelerate equipment wear. Wet extruders, due to the softening effect of steam, can relax the pulverization precision requirement to 60 mesh, reducing raw material pretreatment costs. Furthermore, raw materials containing viscous components (such as syrup and oil) are more suitable for wet extruders—viscous raw materials tend to adhere to the screw surface in dry processing, leading to uneven material delivery; the moisture in wet processing dilutes the viscous components, reducing adhesion.

When selecting equipment, the "raw material-driven" principle should be followed: for basic feeds mainly composed of grains, dry extruders are preferred; for high-end feeds mainly composed of fresh meat, high protein, and high fiber, wet extruders are the inevitable choice. If the raw material composition is complex (such as a mixture of grains, meat meal, and vegetable meal), small-batch trial production is necessary—first mix the raw materials according to the formula, process them separately using both types of extruders, observe the puffing effect of the finished product and the operating status of the equipment, and then determine the final selection to avoid losses due to raw material compatibility issues.

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