The main equipment for extruded fish feed pellet production is fish feed extruder machine. The material is fed into the extruder, and the screw drives the material to form an axial flow. Due to the mechanical friction between the screw and the material, also material and the barrel, and the inside of the material, the material is squeezed, stirred, and sheared intensively. As a result, the material is further refined and homogenized. As the pressure increases gradually, the temperature rises . Under high temperature, high pressure, and high shear conditions, the physical properties of the material change from powder to paste, starch gelatinization, protein denaturation, and partial fiber degradation, Refinement, pathogenic bacteria are killed, sanitary indicators are improved, and toxic ingredients are inactivated. When the paste material is ejected from the die hole, under the action of the strong pressure difference, the material is puffed, which loses water, and the temperature is lowered. The puffed product has a loose, porous and crisp structure, and has good palatability and flavor.
Features of extruded feed pellet
1 Due to the heat generated by mechanical friction,high temperature and high pressure hydrothermal treatment process for the material in the extrusion process , or due to the direct steam sent into the expansion cavity. The material absorbs water and expands under high temperature and high pressure environment, the texture is softened and cell wall is broken, the molecular structure is broken, the starch is gelatinized, and the protein is denatured under the action of mechanical force. The physical properties have undergone a qualitative change. Therefore, the extruded fish feed pellet machine is also known as the "continuous digester".
2 The hydrothermal treatment process is accompanied by the biochemical change process of the material. Some certain materials, like oilseeds and their cakes, contain a variety of anti-nutritional and anti-feeding ingredients. Under certain moisture and certain temperature conditions, these active substances lose their activity gradually , which weakens the endogenous effects in the digestive system of feeding animals. The destruction of digestive enzymes improves the efficiency of digestion and absorption and reduces excretion. This not only improves feed potency, but also reduces waste and environmental pollution.
3 High temperature and short-time sterilization make the maximum temperature of the extrusion process can reach (130-160) ℃,the material in the high temperature section is about 5-10 seconds. High temperature can not only kill pathogenic bacteria, improve sanitation indicators, but also inactivate various harmful factors and enzymes, and improve the quality of feed. Therefore, the extrusion process is a high-temperature and short-term process for sterilization and detoxification.
4 Improve the chemical stability of materials and extend the shelf life. High temperature kills various microorganisms and eggs, and inactivates various enzymes (such as oxidase, lipase, etc.), which eliminates various factors that contribute to material deterioration and prolongs the shelf life.
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