Throughout the whole process of pellet feed processing, in addition to feed formula, the processes that affect the pellet hardness of pellet feed include: crushing process of raw materials; puffing process of raw materials; mixing, adding water and fuel injection of raw materials; Selection of molds in the granulation process; post-curing and post-spraying processes; drying and cooling processes, etc.
1. The effect of crushing process on particle hardness
The decisive factor for the particle hardness in the pulverization process is the pulverization particle size of the raw material: generally speaking, the finer the pulverized particle size of the raw material, the easier the starch is to gelatinize during the conditioning process, and the stronger the bonding effect in the granule, the better the particle size. The harder it is to break, the greater the hardness. In actual production, according to the production performance of different animals and the size of the aperture of the ring die, the crushing particle size needs to be adjusted appropriately.
2. The influence of the puffing process of the raw material on the hardness of the particles
The puffing treatment of the raw materials can remove toxins in the raw materials, kill bacteria, eliminate harmful substances, denature the proteins in the raw materials, and fully gelatinize the starch. At present, the puffed raw materials are mainly used for the production of high-grade suckling pig feed and special aquatic product feed. For special aquatic products, after the raw materials are expanded, the starch gelatinization degree increases, and the hardness of the formed particles also increases, which is beneficial to improve the stability of the particles in water. For suckling pig feed, the particles are required to be crispy and not too hard, which is conducive to the feeding of suckling pigs. However, the puffed suckling pig pellets have a high degree of starch gelatinization and a higher hardness of the feed pellets.
3. The influence of mixing of raw materials, water addition and oil injection on particle hardness
The mixing of raw materials can improve the uniformity of various particle size components, which is beneficial to keep the particle hardness basically the same and improve the product quality. In the production of hard pelleted feed, 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 in moisture, there is a negative effect on the drying and cooling of the particles. It is also detrimental to the storage of the product. In the production of wet pellet feed, up to 20% to 30% moisture can be added to the powder, and about 10% moisture can be added during the mixing process, which is easier than adding during the conditioning process. The granules formed by high-moisture materials have low hardness, soft and soft, 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 are generally required to be fed after production. Adding oil and fat during the mixing process is a common oil-adding process in feed production workshops. Adding 1% to 2% of oil and fat has no significant effect on reducing the hardness of particles, but adding 3% to 4% of oil can significantly reduce the hardness of particles.
4. The effect 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 quality of pellets. Steam quality and conditioning time are two important factors affecting the conditioning effect. High-quality dry and saturated steam can provide more heat to increase the temperature of the material and make starch gelatinized. The longer the conditioning time, the starch gelatinization degree. The higher the value, the denser the particle structure after forming, the better the stability and the greater the hardness. For fish feed, double or multi-layer jackets are generally used for conditioning to increase conditioning temperature and prolong conditioning time. It is more beneficial to improve the stability of fish meal particles in water, and the hardness of the particles increases accordingly.
5. Influence of pelletizing die on pellet hardness
Technical parameters such as the aperture and compression ratio of the ring die of the feed pellet machine affect the hardness of the pellets. The hardness of the pellets formed by the ring die with the same aperture but different compression ratios increases significantly with the increase of the compression ratio. Selecting a suitable compression ratio ring die can produce particles with suitable hardness. The length of the particles has a significant effect on the bearing capacity of the particles. For the particles of the same diameter, the longer the particle length is, the greater the measured hardness will be if the particles have no defects. Adjust the position of the cutter to maintain the proper particle length, so that the hardness of the particles can be kept basically the same. The particle diameter and cross-sectional shape also have a certain influence on the particle hardness. In addition, the material of the ring die also has a certain influence on the appearance quality and hardness of the pellets. There are obvious differences between the pellet feed produced by the ordinary steel ring die and the stainless steel ring die.
6. Influence of post-curing and post-spraying process on particle hardness
Post-curing and post-spraying processes are rarely used in livestock and poultry feed production processes, but are widely used in fish feed and special aquatic feed production processes. Post-curing can fully gelatinize the starch inside the granules, make the internal structure of the granules more compact, prevent the infiltration of water, and help improve the stability of aquatic feed granules in water, and also improve the hardness of the granules.
7. Influence of drying and cooling process on particle hardness
In order to prolong the storage time of feed products and ensure the product quality within a certain period of time, it is necessary to dry and cool the feed pellets. In the test of particle hardness measurement, by measuring the hardness of the same product multiple times with different cooling times, it is found that the particles with low hardness are not significantly affected by the cooling time, while the particles with higher hardness are cooled with the cooling time. As time increases, particle hardness decreases. This may be because the brittleness of the particles increases as the water inside the particles is lost, affecting the particle hardness. At the same time, after the particles are rapidly cooled with a large air volume and slowly cooled with a small air volume, it is found that the hardness of the former is lower than that of the latter, and the surface cracks of the particles are increased. It is also worth mentioning that the large hard particles are crushed to make the large particles into small ones, which can significantly reduce the hardness of the particles.
In the process of pellet feed processing, there are still many factors that affect pellet hardness. With the in-depth research of more and more scientific and technological workers who are keen on feed processing technology, more and more methods of regulating pellet hardness have been adopted. It is believed that in the near future, we will be able to process pellet feeds that all kinds of animals like.