1. The impact of raw material expansion process on particle hardness
The puffing treatment of the raw materials can remove toxins in the raw materials, kill bacteria, eliminate harmful substances, denature the protein in the raw materials, and fully gelatinize the starch. At present, extruded raw materials are mainly used in the production of high-grade suckling pig feed and special aquatic feed. For special aquatic materials, after the raw materials are expanded, the starch gelatinization degree and the hardness of the formed particles increase, which is beneficial to improve the stability of the particles in water. For suckling pig feed, the pellets are required to be crisp and not too hard, which is conducive to the feeding of suckling pigs. However, the puffed suckling pig pellets have a high degree of gelatinization of starch, so the hardness of the feed pellets is also greater.
2. The impact of crushing process on particle hardness
The decisive factor in the crushing process for the hardness of the particles is the crushing particle size of the raw materials: Generally speaking, the finer the crushed particle size of the raw materials, the easier the starch will gelatinize during the conditioning process, and the stronger the binding effect in the pellets. The less easy to break, the greater the hardness. In actual production, according to the production performance of different animals and the size of the ring die aperture, the crushing particle size requirements should be adjusted appropriately.
3. The influence of steam quenching and tempering process on particle hardness
Steam conditioning is a key process in pellet feed processing, and the conditioning effect directly affects the internal structure and appearance of pellets. Steam quality and conditioning time are two important factors that affect the conditioning effect. High-quality dry saturated steam can provide more heat to increase the temperature of the material and gelatinize the starch. The longer the conditioning time, the longer the starch gelatinization degree. The higher the value, the denser the formed particle structure, the better the stability, and the greater the hardness. For fish feed, double-layer or multi-layer jacket tempering is generally used to increase tempering temperature and extend tempering time. It is more conducive to improving the stability of the fish pellets in water, and the hardness of the pellets is also increased accordingly.
4. The influence of raw material mixing, water addition and oil injection process on particle hardness
The mixing of raw materials can improve the uniformity of various particle size components, which is beneficial to keep the hardness of the particles basically the same and improve the product quality. In the production of hard pellets, adding 1% to 2% of water in the mixer is beneficial to improve the stability and hardness of the pellets. However, due to the increase of moisture, it brings negative effects to the drying and cooling of the particles. It is also unfavorable for product storage. In the production of wet pellet feed, up to 20%-30% of water can be added to the powder, and it is easier to add about 10% of water in the mixing process than in the conditioning process. The formed particles of high-moisture materials have low hardness, softness, and good palatability. This kind of wet pellet feed can be used in large-scale breeding enterprises. Wet pellets are generally not easy to store and generally require that they be produced and fed. Adding grease in the mixing process is currently a grease addition process commonly used in feed production workshops. Adding 1%-2% of grease to reduce the hardness of the particles is not significant, adding 3%-4% of grease can significantly reduce the hardness of the particles.