1, Extruding process for the application of the basic principle of extruding processing.
The main equipment for the screw extruder". The material is fed into the extruder, and the screw is pushed to drive the material to form an axial flow. At the same time, because of the spiral and the material, the material and the machine barrel and the material inside the mechanical friction, the material is strongly extrusion, mixing, shearing, the results of the material is further refined, homogenization. With increasing pressure, temperature rises, under high temperature, high pressure and high shear conditions, material properties change, by powder into a paste, starch gelatinization, denatured protein, fiber quality degradation, refinement, causing bacteria are killed, and improve health indicators, inactivation of toxic ingredients. When the paste material from the die orifice discharge moment, in the strong pressure difference, the material is puffing, drying, cooling, extrusion product structure is loose, porous, friable and good taste and flavor.
2, Expansion process and the characteristics of extruded products
2.1 high temperature and high pressure water heat treatment process material in the extrusion process, due to the heat generated by mechanical friction, or due to the fact that the extrusion chamber direct steam feed, or sent to extrusion chamber jacket in the indirect steam heating temperature and pressure gradually increased. Materials in the environment of high temperature and high pressure water swelling, soften texture, under the action of mechanical force collapsibility, refinement and homogenization, cell wall rupture, molecular structure were scattered and gelatinized starch and protein denaturation. Physical property changes. Therefore, the spiral extrusion machine has a "continuous steam cooking device," said.
2.2 biochemical reaction process water heat treatment process with the material of the biochemical change process. Some of the material, such as oil seed and meal, which contains a variety of anti nutritional and anti feeding component, under certain moisture and temperature conditions, these active substances gradually lose activity, weaken the destruction of endogenous digestive enzymes in digestive system of animals on farms, improve the efficiency of digestion and absorption and reduced excretion. This not only improves the feed potency, but also reduces waste and environmental pollution. From the biochemical process, the extrusion machine is a "biochemical reactor".
2.3 high temperature short-time sterilization process of the extrusion process of the maximum temperature of up to (130 ~ 160) C, while the material at high temperature for a short time, about 10 - 5 seconds. High temperature not only can kill pathogens, improve health indicators, but also can make a variety of harmful factors and enzyme inactivation, improve the quality of the feed. Therefore, the extrusion process is a process of high temperature and short time treatment of sterilization and detoxification.
2.4 to improve the chemical stability of the material, shelf life extension of high temperature the various microbial, eggs are killed, various enzymes (such as enzyme, lipase, deactivation, excluding the material deterioration of a variety of factors contributed to and prolong the shelf life.
2.5 the most effective way to improve the quality of materials extrusion processing, high temperature sterilization, improve the health indicators; water heat treatment, so that a variety of anti nutrition factors and anti feeding factor inactivation. High temperature and high pressure to make the material property changes, the quality of feed, feed to improve the quality of. Extrusion process make raw materials into clinker, which is feed industry epoch-making change. The feed industry has entered a new era of vigorous development, with the application of feed expanding technology, ideal protein system, biological system, and information network technology and molecular biology.
2.6 wide range of technological adaptability of the feed industry, the extrusion process can be described as flexible, wide range of applications. Extrusion technology can not only improve feeding quality of various conventional feeding raw materials, but also many unconventional material processing quality of feeding raw materials. Including wild plants, agricultural by-products, livestock and poultry slaughter waste, farm livestock manure, etc.. Can produce a variety of different specifications, different quality of livestock and poultry, aquatic products, pets (including rare animals). Industrial residue after dehydration by means of extrusion can be directly used for feeding raw materials bad; as auxiliary material for producing fermented feed or organic fertilizer. It is the most effective means to remove toxin, keep fresh and processed food, and to process food.
2.7 high grade product characteristics extrusion products rich variety of high grade characteristics: uniform, dense. By mixing the raw materials, into the extrusion section, full in the is squeezed, mixing, shearing, melting components, fully mixed, thaw for uniform material flow extrusion, extrusion, cutting, shaping and cooling, product texture uniform, dense, better than that of ring moulded particle products. Loose porous, density controllable. Expansion of this characteristic, the most able to adapt to the requirements of the aquatic product, the control of its density, can be made of heavy material or floating material, the duration of the material can be adjusted. Many factors of forming are satisfied. The porous structure of the loose porous structure can absorb large amount of liquid additives, and is convenient for the supplement and the flavor adjustment of the nutrient component. Taste and flavor. Extrusion puffing by cooling after texture crisp loose, produce various components of compound, and due to the high temperature generated by the Maillard reaction, all these factors constitute the palatability of puffed products is better than that of the original mixed materials and special flavor. These characteristics induce feeding animals to feed, feed intake and feed efficiency. This is completely different from the mixture added phagostimulants attractant often brings negative effect.
2. 8 can produce special-shaped material according to the requirements of users, change mold design, production of different shapes large particles, large shape or strip material, such as prawn feed, dogs, pet feed, rare animals such as. This is the pellet incapable of action.
After 3 extrusion puffing process physical change of feeding raw materials through extrusion process, the physical and chemical properties and some components of the biological activity occurred significant changes. These changes, some make the feed value can be improved, and some are caused by the loss of nutrients. The changes of physical properties of corn and vegetable protein raw materials are described as follows:
forage maize is the main raw material of starch. Corn starch content (71 ~ 72)%, of which amylose accounted for 27%. The main changes of starch during extrusion are "pasting" ". The original starch is a granular mass composed of starch particles. Tight structure, poor water absorption. Starch by the quenching and tempering to puffing machine, through hydrothermal process, starch particles in the wet, heat, mechanical extrusion, shear, the structure is damaged, molecular link is opened, particles are further collapse, forming colloidal gel pasting, alpha. Starch molecules were broken into short chain, which was degraded to soluble reducing sugar. Solubility, digestibility and flavor were improved. The pasting temperature of starch is related to the different degree of the temperature (i.e., the degree of paste). Development of digestive system of imperfect lactation of suckling pig, the weaning feed starch, gelatinization degree higher than 90%; aquaculture of raw starch absorption capacity of poor, feed the gelatinization degree should also be high.
Therefore, by extrusion puffing machine production of aquatic feed, should better than that of the ring die pelletizing machine production material, because the ring die pelletizing due to limited by temperature, which starch gelatinization degree is not high, generally not more than 50%. Gelatinization not only improves the rate of digestion and absorption, but also improve the granulation and forming effect is very good because of dextrin binder. The pasting of starch molecules cross linked, forming a network of space structure, in the moment after the loss of part of the expansion of water, cooling after the expansion of products to become the skeleton, so that products to maintain a certain shape. If the raw material formula contains little starch, or no starch, it is difficult to form a loose and porous structure. A certain formula of raw materials, such as high starch content, it is easy to be expanded, the product density is small. But with starch, if the content of branched chain starch is high, then the product is large, the density is small. Aquatic products must have the characteristics of the water or sink or float, the use of this expansion characteristics of starch is relatively easy to achieve this requirement. High content of modified starch products, slow water absorption, water holding time is long, this is also an important characteristic of aquatic feed should have.
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