Extrusion technology to feed industry at the beginning of the 20th century during the 5O of the United States, during extrusion technology to 8O abroad has become the fastest growing new feed processing technology. Extrusion is a combination of water, pressure, temperature and mechanical shear factors and the role of the completed, the process of extrusion machine bore temperature up to 90 200, extension of time to squeeze 2-30 s, a materials occur Series of physical, chemical changes, such as the promotion of pasting starch, protein degeneration as well as mildew and harmful micro-organisms and toxic components of inactivation, increase the digestibility of nutrients to improve the palatability of feed, feed particles to promote the stability and storability, and so on. As a result, expanded use of technology to feed raw materials for pre-treatment, sterilization can achieve disinfectant to curb anti-nutritional factors and improve protein utilization. For some low-cost feed materials, puffing after treatment alternative to the use of high-value raw materials without affecting the quality of feed, lower feed costs for the development of new feed resources has played an important role.
1. Extrusion technology and major equipment
1.1 extruder
Extruder from the main power transmission devices, feeding devices, pre-quality, extrusion parts and components such as the cutting device. Extrusion is a core component parts by the screw, outside the tube and die by the general composition of the outer tube of the screw extruder will be divided into the number of single-screw extruder and twin-screw extruder. As the twin-screw extruder investment, in addition to the production of special feed some less things to use. At present, in the feed industry is the most widely used single screw extruder, with less investment, simple operation based on the merits of expanded in the process of whether or not to the materials in the water, the extruder can be divided into dry and wet Expander Extruder. Dry Extruder rely on mechanical friction and pressure on the material for heating pressure to deal with this method is suitable for water-bearing grease and more processing of raw materials, such as full-fat extruded soybeans. For other less fat and water content of the materials in the extrusion process is an accession to the need of steam or water, often using wet Expander. Extruder bore into the general assembly is easy to configure the necessary replacement parts and maintenance. Machine-bore segments are straight and spiral groove-type groove. There are straight-cut trench, stirring, generally located in the middle bore extruder; spiral-groove contribute to the advancement of materials, usually located in the mouth feed site, close to the template of the segments are designed to spiral groove, so that the pressure and a template Expected to maintain a uniform. Single screw from a material feed-to-end, Lo root gradually bold, the fixed Lo pitch film gradually shallow, so that the material inside the machine gradually reduce capacity. At the same time, screw in the middle of the installation of a number of diameter ranging from the lock cut in order to reduce the flow of materials and enhance the ripening. Twin-screw extruder of parallel twin-screw each other, there are 4 kinds of forms: non-engagement with the rotating, non-relative rotating mesh, mesh and mesh with the rotation relative to the rotation. Among non-engagement twin-screw extruder can be used as the separation of the two tied for the use of screw, different and full of material. Twin-screw extruders in the processing and quality control on flexibility has its advantages, processing of viscous, oil or very wet, as well as raw materials in a single-screw extruder will spin the raw materials.
1.2 Expander
Expansion is another form of pressure, the use of heat, water and friction so that the ripening of raw materials, mainly due to the expansion of the local chamber, the spiral, cone-shaped die components. Played a major screw conveyor, squeeze, cut and so on, screw length and diameter ratio of 7-16:1, its structure and the mix of different products on the expansion of the quality of the impact. It plays a sleeve of friction materials, extrusion. Export-mode conical shape and size of the ring gap, not only affect the expansion pressure and product quality, but also related to the expansion process can proceed smoothly. Extruder with the main difference between the parameters of screw and die structure of the material. Extruder compression ratio is 2:1 to 4:1, and the expander compression ratio to 2.6:1 to 1.05:1. As a result of this structural differences in the expansion of the material inside the pressure to weak, ordinary Palestinians in the 5O below normal temperatures lower than 135, and the extruder pressure and temperature to exceed this range. After the expansion of the material about 3% of water loss, the expansion of the materials can be used directly, and granulation can be used as the first procedure. Expanded particles by the palatability of feed, feed conversion rate, well received by the market.
2 extrusion machine applications
2.1 extrusion machine in the soybean processing
Extrusion technology soybeans in the broader application. Under certain conditions, extrusion, not only of soybean anti-nutritional factors, such as anti-trypsin, pulse-inactivating enzymes, and the high-temperature, high pressure, high shear is conducive to the instantaneous effect of protein variability, so that the starch paste, soybean oil cell rupture So that the three are to improve digestibility. Many studies have shown that pressure can significantly increase the nutritional value of soybeans. Squeeze for the full-fat soybean feed, and the traditional increase in the oil feed, not only on the nutritional value of an advantage, but also in animal feed processing of oils and fats do not need to add equipment to increase and squeeze through the elimination of the soybean contains anti - Nutritional factors, especially the early post-weaning feed the anti-nutritional factors, so as to avoid the early post-weaning digestive function disorders, intestinal inflammation and diarrhea in piglets. Extrusion technology is to make more and more above-mentioned advantages in the processing of applications.
2.2 extrusion machine in the fish feed processing
Extruders of the unique features is to change the bulk feed, which can be made of floating, sinking or slow the fall of fish feed. Floating fish processing and feed into the needs of steam and water, the materials contain at least 20% of the starch, starch and energy to play a binder material. The different levels of fish intake, can produce different density of fish feed, so that the feed floating in the water at different locations. Floating feed not only improve feed efficiency, more cultured person is allowed to see the fish feed, to avoid over-feeding, improving water quality in fish ponds to prevent the occurrence of fish diseases and reduce feed waste.
2.3 extrusion machine in the pet food processing
Squeeze the production of pet food originated in the 1950s. Feed pets can be divided into categories: dry products, dry products, soft products. Production of dry pet food extrusion of water is in 28 percent of a 225. Squeeze dry production process and products produced products similar to the stem, but before squeezing meat or meat by-product size and dry mixing materials, the typical water pressure 3O% in a range of 35%, without lowering the former storage Water. Soft products also contain meat or meat by-products, high-fat, 27% of its water content of a 32% can be more easily change its shape. More than 3 kinds of pet food containing high water must be added, such as propylene glycol, or preservatives sorbic acid methyl ester, and DH in order to preserve value to 4-5.5.
3 trends
Extrusion technology is increasingly widely used in feed industry. Comprehensive development of foreign and domestic trends in the development of the status quo, extrusion technology should be in the following areas of development.
3.1 Development and the development of multi-function, high-power squeezing of the equipment
At present, the domestic extrusion equipment is characterized by simple functions, the narrow scope of application, the power less than 110 kW, not very productive. In the largest foreign power is up to 360 kW ". As a result of dry and wet extrusion machine operation and control is very unstable, and their use is restricted, a great number of units are dedicated to research in this area. Shepherd the recent century-long MY 165 extrusion machine to make new progress in applied research. Its application to control the density of the feed system, not only to control the density of its products 100% of the sinking, and improved productivity, resulting in improved performance, further enhanced the scope of its application . This machine extruded full-fat soybean production to the mode) 4 IWlfll hole, for example, squeezing out the color of the product Huang Liang, yield more than 6 t / h.
3.2 importance extrusion technology
Foreign extrusion technology has been widely used in food, feed pets, floating and sinking fish feed, chicken feed, pig, and so on, the technology is more mature. In the United States, in 1990 the extrusion processing production in 1983 is 5 times, only to a pet food sales in 1990 amounted to 8o million. China's food processing industry in the wider application, and the feed used in the narrower, generally used only for the full-fat soybean extrusion. Extrusion of soybean production in general 500-800 kg / h (dry), is the higher the cost. Other raw materials processing, such as rice bran squeeze, squeeze a large number of virus-free meal to promote the application of yet, so its great potential for development. With the feed industry development and improvement of people's lives, to feed extrusion of the demand will grow increasingly extrusion technology will become more important, the prospect will get better and better. |