1 Basic principle of puffing processing Puffing process applied in feed production
Its main equipment is “ screw extruder †. The material is fed into the extruder, and the screw screw pushes the material to form an axial flow. At the same time, due to the mechanical friction between the spiral and the material, the material and the barrel, and the inside of the material, the material is strongly squeezed, stirred, and sheared, and the material is further refined and homogenized. As the pressure gradually increases, the temperature rises accordingly. Under the conditions of high temperature, high pressure and high shear, the physical properties of the material change, from powder to paste, starch gelatinization, protein denaturation, partial degradation of fiber, Refined, pathogenic bacteria are killed, health indicators are improved, and toxic components are inactivated. When the paste material is ejected from the die hole, under the strong pressure difference, the material is puffed, dehydrated and cooled. The puffed product structure is loose, porous, crisp, and has good palatability and flavor.
　　 2 characteristics of puffing process and puffed products
2 . 1 high temperature and high pressure hydrothermal treatment process material in the extrusion process, due to the heat generated by mechanical friction, or due to the direct steam sent to the expansion chamber, or the indirect steam into the expansion chamber jacket heating temperature and pressure gradually rise high. The material swells under high temperature and high pressure environment, softens texture, collapses, refines and homogenizes under the action of mechanical force, cell wall rupture, molecular structure is broken up, starch gelatinization, protein denaturation. Physical properties change qualitatively. Therefore, the spiral extrusion type extruder is also known as the " continuous digester " .
2 . 2 Biochemical reaction process The hydrothermal treatment process is accompanied by the biochemical process of materials. Certain materials, such as oilseeds and their cakes, contain a variety of anti-nutritional and anti-feeding ingredients. Under certain conditions of moisture and temperature, these active substances gradually lose their activity, weakening the endogenous source of the animal's digestive system. The destruction of digestive enzymes improves digestion and absorption efficiency and reduces excretion. This not only increases feed potency, but also reduces waste and environmental pollution. From the perspective of biochemical processes, the extrusion extruder is a " biochemical reactor " .
2 . 3 High temperature short-time sterilization and detoxification process The maximum temperature of the extrusion process can reach ( 130 ~ 160 ) °C , while the material in the high temperature section is very short, about 5 - 10 seconds. High temperature can not only kill pathogenic bacteria, improve health indicators, but also inactivate various harmful factors and enzymes, and improve the quality of feed. Therefore, the extrusion process is a high-temperature short-time process for sterilization and detoxification.
2 . 4 Improve the chemical stability of the material, prolong the shelf life, and kill various microorganisms and eggs, and inactivate various enzymes (such as oxidase, lipolytic enzyme, etc.), eliminate various factors that contribute to material deterioration, and extend the shelf life. .
2 . 5 The most effective improvement of material quality extrusion and expansion processing, high temperature sterilization, improve the health indicators; hydrothermal treatment, a variety of anti-nutritional factors and anti-feeding factors inactivated. High temperature and high pressure produce qualitative changes in material properties, feed quality is improved, and feed potency is increased. The extrusion process makes the raw material mature, which is an epoch-making change in the feed industry. The feed expansion technology, the ideal protein system, the biological system titer system, and the application of information network technology and molecular biology have made the feed industry enter a new era of vigorous development.
2 . 6 Extensive process adaptability As far as the feed industry is concerned, the extrusion process can be described as flexible and versatile. The extrusion process not only improves the quality of feeding of a variety of conventional feed materials, but also processes a large amount of unconventional materials into high-quality feed materials. These include wild plants, agricultural by-products, livestock and poultry slaughter waste, livestock and poultry manure from farms. It can produce a variety of different specifications, different quality of livestock and poultry materials, aquatic products, pets (including rare animals) materials. After the industrial waste residue is dehydrated, it can be directly used as a feed material by extrusion and expansion; as an auxiliary material, it can be used to produce fermented feed or organic fertilizer. Detoxification, fresh-keeping processing of oil cakes, deep processing of grain, and extrusion process are the most effective techniques.
2 . 7 High-grade product characteristics Extruded products are rich in high-grade properties: uniform and compact. The raw materials mixed by the ingredients enter the extrusion and expansion chemical section, and the whole process is in the environment of being squeezed, stirred, sheared and melted, and the components are fully mixed, and melted into a uniform stream extrusion, puffing, cutting, cooling and setting. The product texture is uniform and compact, which is superior to ring mold granulation products. Loose and porous, the density is controllable. This characteristic of the puffed product can best adapt to the requirements of the aquatic material, control its density, and can be made into a sinking material or a floating material, and the water holding time of the material can also be adjusted. Many factors of forming are satisfied. The loose porous structure has a large adsorption surface area and can adsorb a large amount of liquid additives, which facilitates the supplementation of nutrients and the adjustment of flavor. Palatability and flavor. The loosened texture of the extruded puff after cooling, the composite product produced by various components, and the Maillard reaction due to high temperature, all of which constitute the palatability of the puffed product over the original mixture and Special flavor. These characteristics induce feeding animals to feed and increase their feed intake and feeding efficiency. This is completely different from the addition of an attractant to the mixture, which often has a negative effect.
2. 8 can produce special materials according to user requirements , change the mold design , can produce large particles, large blocks or strips of different shapes, such as prawn material, police dog material, pet materials, rare animal materials. This is incompetent for ring mold granulation.