Advantages of extruded feed

Extrusion technology is a commonly used technology in modern feed processing. After the feed is processed by extrusion technology, it can make starch gelatinization and degradation, protein denaturation, reduce anti-nutritional factors, increase palatability and many other advantages in the feed; however, there are also disadvantages such as generating indigestible substances, destroying vitamins, and increasing costs.1 Extrusion technology

Extrusion technology means that the material containing a certain amount of moisture is sent into the extrusion extruder. Under the push of the screw rod and the screw, the material moves forward in the axial direction, and the material and the screw, the material and the barrel, and the mechanical friction inside the material. , the material is strongly squeezed, stirred and sheared, which is further refinement and homogenization of the material, and the pressure and temperature inside the machine cavity continue to increase and rise. Under the action of high temperature, high pressure and high shear force, the material is Complicated physical and chemical changes have taken place in the composition of materials. Finally, the paste material is ejected from the die hole, and a pressure difference is instantly generated, and the material is puffed, thereby forming a puffed product with loose, porous and crisp structure.

2 Advantages of puffing technology

After the feed raw material is extruded, it has a unique fragrance and fluffy feeling, good palatability, high degree of gelatinization, and has a good feeding effect. At the same time, the long-chain structure of some organic substances such as proteins and fats changes into short-chain structures, making it easier for animals to digest and absorb.

2.1 Starch gelatinization and degradation

After extrusion and puffing, starch mainly changes in two aspects. The first is starch gelatinization. During the expansion process, the dense crystal structure of starch molecules is disintegrated, the crystal structure absorbs the hydrolyzate, the hydrogen bond is broken, and the expanded starch particles are broken and become a viscous melt. Due to the sudden pressure drop at the outlet of the extruder, a large amount of steam is instantly lost, and a large number of extruded starch granules are disintegrated, starch gelatinization, and many extruded feeds with micropores are formed. On the other hand, starch is degraded, the average molecular weight of starch is significantly reduced, and oligosaccharides with small molecular structures 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 amount of starch used 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 a non-degradable protein body in the rumen of ruminants, that is, rumen-passing protein, which improves the utilization of protein by ruminants.

2.2 Protein denaturation

The protein-containing material is subjected to the comprehensive action of high temperature, high pressure and high shear force in the extruder. The tertiary and quaternary structure of the protein is destroyed, the molecular structure of the protein is stretched and reorganized, the surface tends to be homogenized, and the intermolecular hydrogen bonds and disulfide bonds are partially broken, resulting in the final denaturation of the protein. The degree of protein denaturation is closely related to the parameters of the extrusion process. During the puffing process, many anti-nutritional factors are also passivated, such as urease, antitrypsin and hemagglutinin in soybean, myrosinase in rapeseed meal and polyphenolic compounds such as glucosinolates produced by decomposing glucosinolates. of gossypol etc.

Feather, as a high-quality protein feed material, has a protein content of about 75% to 90%, and has become a popular material in feed materials. However, the protein of feather meal is mostly a cord-like structure composed of several polypeptide chains arranged in parallel along the fiber. The strong hydrophobic force makes it difficult to be digested and utilized by animals. The untreated feather meal has a very low feed value, and the digestibility is only about 7%. After puffing, the keratin protein in the feather is denatured, and the spatial structure of the keratin protein is cracked, making it a digestible and absorbable state, and the digestibility can be increased to more than 70%.

2.3 Degeneration of fat

The extrusion process destroys the cell wall structure of the oilseed and releases the oil in it. This processing method can improve the utilization rate of oil. Expansion can also form a complex product (lipoprotein) or (lipopolysaccharide) with fat and starch or protein, which reduces the content of free fatty acids, at the same time inactivates esterase, inhibits the degradation of oil, and reduces the storage and transportation of products. The rancidity of oil components is beneficial to the long-term preservation of feed.

2.4 Increase palatability and digestibility

The extruded feed has small particle size, crispness, and emits a coke fragrance, which improves the palatability. The extruded feed becomes a loose and disordered structure. This change provides a larger contact area for enzymes, which is conducive to the contact of starch chains, peptide chains and digestive enzymes, and is conducive to the digestion and absorption of feed, thereby improving the digestion of feed. Rate.

2.5 Improve fiber solubility

Extrusion can greatly reduce the crude fiber content in the feed. Through the extrusion puffing technology, due to the instantaneous expansion of high temperature and high pressure until the outlet during extrusion, the intercellular substance and the layers of lignin in the cell wall are melted, some hydrogen bonds are broken, and the macromolecular substances are decomposed into low molecular substances. The original compact structure It becomes fluffy, and it also releases some digestible substances, thereby improving the utilization rate of the feed.

2.6 It is beneficial to feed storage and prolong the shelf life of feed

Under the action of high temperature and high pressure and puffing, the content of mold, bacteria and fungi in the raw material is killed, thereby improving the hygienic quality of the feed and effectively reducing the occurrence of animal diarrhea, gastroenteritis and diarrhea.