Application of fodder expansion technology in animal production
Abstract: the technology of puffing is a widely used technology in modern feed processing. After puffing technology, feed can make starch gelatinized and degraded, protein denatured, reduce anti nutritional factors and increase palatability, but there are also some unfavorable factors such as producing non digestible substances, destroying vitamins and increasing cost. The paper summarizes the technology of fodder expansion and its advantages and disadvantages.
Key words: puffing; advantages; shortcomings; feed
1 expansion technology
Puffing technology refers to the water containing material is fed into the extruder, screw, screw in the role, the material forward into the axial movement, the material and the material barrel and screw, and the material mechanical friction effect, the material is strongly mixing, extrusion, shear, the material to further refinement, homogenization subsequently, the machine cavity internal pressure and temperature increasing and the increase of materials under high temperature and high pressure and high shear stress under the effect of the material composition of complex physicochemical changes take place. Finally, the paste material is ejected from the mold hole, resulting in pressure difference in a short time. The material is expanded to form a porous product with a porous structure and crisp expansion, so as to achieve the purpose of extrusion and expansion. In the process of expansion, materials have changed greatly in texture, structure and appearance. The effect of material expansion is closely related to the technical parameters such as extrusion temperature, feed speed, raw material moisture, screw speed, die size and so on.
2 advantages of expansion technology
Feed raw materials after extrusion, has a unique flavor and fluffy, good palatability, high gelatinization degree, has the attraction of good. At the same time, the long chain structure of some organic compounds, such as protein and fat, is changed into short chain structure, which makes the animals more easily digested and absorbed.
Gelatinization and degradation of 2.1 starch
After extruding, the starch is mainly changed in two aspects. The first is starch gelatinization. During expansion, the dense crystal structure of starch molecules is broken up. The crystal structure begins to absorb and disintegrate, and the hydrogen bonds begin to break, and the expanded starch granules break up and become a thick molten body. At the outlet of the extruder, due to sudden pressure drop, steam instantly dissipated, resulting in a large number of expansive starch granules disintegrating and starch pasting, forming a lot of microporous puffed corn. On the other hand, starch degradation, the average molecular weight of starch decreased obviously, and small molecular oligosaccharides such as maltodextrin could be produced by cracking. Gelatinized starch has strong water absorption and stronger adhesion than common starch. It can reduce the amount of starch used in production and provide more opportunities for other raw materials. Gelatinized starch combines protein tightly with starch substrate to form a rumen degradable protein, that is, rumen protein, which improves ruminant's utilization of protein.
2.2 protein denaturation
Protein containing material in the extruder under high temperature, the comprehensive effect of high pressure and high shear stress, protein 3 level and 4 level structure was destroyed, stretching, recombinant protein molecular structure, the surface is uniform, intermolecular disulfide bond, two part fracture, eventually leading to protein denaturation. The degree of protein denaturation is closely related to the parameters in the process of extrusion. Puffing process also passivated many anti nutritional factors, such as urea enzyme, trypsin inhibitor and haemagglutinin in soybean, glucosinase in rapeseed meal, glucosinolates produced by glucosinolates, gossypol in cottonseed and so on.
Feathers are the keratinized derivatives of poultry epidermal cells, accounting for 5% to 11% of the body weight. The feather bar and its lower foe are the by-products of poultry slaughtering or down products. The protein content is 75% to 90%. It is a kind of high quality feed protein raw material. But the protein of feather meal is mostly a cable structure formed by several polypeptide chains parallel to the fiber axis. There is a large number of cross links, two sulfur bonds, hydrogen bonds and hydrophobic interactions among the chains. Therefore, its structure is very stable, and it is not easy to be digested and utilized by animals. The value of untreated feathery feed is very low, and the pepsin digestibility in vitro is only about 7%. After puffing, the horny protein denatured in the feathers to break the space structure of the horny protein, making it a digestible and absorption state and increasing the digestibility. The results show that the digestibility of puffed feather powder in vitro can be over 70%, which is higher than that of hydrolyzed feather powder from 20% to 30%.
2.3 fat release
The extrusion process destroys the cell wall of the oil seed and releases the oil. This processing method can improve the utilization of oil. Under the ideal processing conditions, the digestibility of the processed fat is close to the digestibility of the oil extracted from the leach meal. Extrusion can also be fat and starch or protein to form a composite product of lipoprotein or lipopolysaccharide, reduce the content of free fatty acid, and the passivation lipase, inhibit oil degradation, reduce oil product storage and transportation in the process of rancidity.
2.4 increase palatability and digestibility
The puffed feed has small granularity, crisp and crisp flavor, and the palatability is improved. Puffed feed showed a loose and disordered structure. This change provided a larger contact area for the action of enzymes, decreased steric hindrance, and exposed starch chains and peptide chains, which accelerated the speed of enzyme action, was beneficial to digestibility and absorption of feed, and improved feed digestibility.