Expanded feed technology
Twin screw extruder
Puffing technology：
Puffing technology refers to that the material containing certain moisture is sent into the extruder. Driven by the screw rod and screw, the material moves forward to form an axial movement. The mechanical friction between the material and the screw, the material and the barrel and the interior of the material. The material is strongly extruded, stirred and sheared, so that the material is further refined and homogenized. Then, the pressure and temperature inside the cavity continue to increase and rise, and the material is under high temperature, high pressure Under the action of high shear force, the material components have complex physical and chemical changes. Finally, the paste material is ejected from the die hole, resulting in an instant pressure difference, and the material is expanded to form an expanded product with loose structure, porous and crisp.
Advantages of expansion technology: after expansion treatment, feed raw materials have unique flavor and fluffy feeling, good palatability, high gelatinization degree and good food attraction effect. At the same time, the long-chain structure of some organic substances such as protein and fat becomes short-chain structure, which makes it easier for animals to digest and absorb.
Material change
=Expansion extrusion=
Material state under high temperature, high pressure and high shear
Starch gelatinization and degradation:
After extrusion, starch mainly changed in two aspects. One is starch gelatinization. During the expansion process, the dense crystal structure of starch molecules is disassembled. The crystal structure absorbs water and disintegrates, the hydrogen bond breaks, and the expanded starch particles break into a viscous melt. At the outlet of the extruder, due to the sudden drop of pressure and the instantaneous loss of steam, a large number of expanded starch particles disintegrate and starch gelatinize to form many expanded feeds with micropores. On the other hand, starch is degraded, and the average molecular weight of starch is significantly reduced. Oligosaccharides with small molecular structure such as maltodextrin can be produced by cracking. Gelatinized starch has strong water absorption and much stronger bonding function than ordinary starch, which can reduce the use of starch in production and provide more choices for other raw materials. At the same time, the gelatinized starch can closely combine the protein with the starch matrix to form the rumen non degradable protein body of ruminants, that is, rumen protein, which improves the utilization of protein by ruminants.
Protein denaturation:
The material containing protein is subjected to the combined action of high temperature, high pressure and high shear force in the extruder. The tertiary and quaternary structures of protein are destroyed, the molecular structure of protein is extended and recombined, the surface tends to homogenize, and some intermolecular hydrogen bonds and disulfide bonds are broken, resulting in the final denaturation of protein. The degree of protein denaturation is closely related to the parameters in the extrusion process. During the expansion process, many anti nutritional factors are also inactivated, such as urease, antitrypsin and hemagglutinin in soybean, sinatase in rapeseed meal and polyphenols such as sinapiside produced by its decomposition of glucosinolates, gossypol in cottonseed, etc.
As a high-quality protein feed raw material, feather has a protein content of about 75% ~ 90%, which has become a favored material in feed raw materials. However, the protein of feather powder is mostly a cord like structure formed by several polypeptide chains arranged in parallel helix along the fiber. There are a large number of cross-linking bonds, disulfide bonds and hydrogen bonds between the chains, which makes it have a strong stable structure and strong hydrophobic force, so it is not easy to be digested and utilized by animals. The feeding value of untreated feather powder is very low, and the digestibility is only about 7%. After puffing, the keratin in feathers denaturates and cleaves the spatial structure of keratin, making it digestible and absorbable, and the digestibility can be increased to more than 70%.
Fatty
=Animal and vegetable oils=
Material state under high temperature, high pressure and high shear
Denaturation of fat:
Extrusion processing destroys the cell wall structure of oilseeds and releases the oil. This processing method can improve the utilization rate of oil. Puffing can also form complex products (lipoprotein) or (lipopolysaccharide) with fat and starch or protein, reduce the content of free fatty acids, passivate esterase, inhibit the degradation of oil, reduce the rancidity of oil components in the process of product storage and transportation, and is conducive to the long-term preservation of feed.
Increase palatability and digestibility:
The expanded feed has small particle size, crispness, coke flavor and improved palatability. The expanded feed has a loose and disordered structure, which provides a larger contact area for the enzyme, is conducive to the contact between starch chain, peptide chain and digestive enzyme, is conducive to the digestion and absorption of feed, and thus improves the digestibility of feed.
Fiber
=Plant raw material fiber=
Improve fiber solubility:
Extrusion can greatly reduce the content of crude fiber in feed. Through extrusion technology, during extrusion, due to the instantaneous expansion from high temperature and high pressure to the outlet, the lignin of each layer in the cell stroma and cell wall melts, part of the hydrogen bond breaks, and the high molecular material is decomposed into low molecular material. The original compact structure becomes fluffy, and some digestible substances are released, so as to improve the utilization rate of feed.
Conducive to feed storage and prolong feed shelf life:
Under the action of high temperature, high pressure and expansion, the material kills the content of mold, bacteria and fungi in the raw materials, so as to improve the hygienic quality of feed and effectively reduce the occurrence of animal diarrhea, gastroenteritis, dysentery and other diseases.
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