Puffing is a new feed processing technology. The feed puffing in the extrusion chamber is actually a high temperature instantaneous process:  The mixture is under high temperature (110-200 ℃), high pressure (25-l00kg/cm2), high shear force, and high moisture (10%-20% or even 30%). Through continuous mixing, quenching and tempering, temperature boosting, curing, extrusion die hole and sudden depressurization, a kind of bulky porous feed is formed.  
 
Advantages of extruded feed  
1.1 improve the utilization rate of feed expanding in the process of hot, wet, stress and all sorts of mechanical action, the starch molecules within 1, 4 - glycosidic bond rupture and generate glucose, wheat malt sugar, malt sugar and maltodextrin and other low molecular weight products, bulk chemical processing can make the starch gelatinization degree enhancement, the structure of the fiber cell wall part was damaged and softening,  Release part of the surrounded, combined digestible substances, while fat from the internal infiltration of particles to the surface, so that the feed has a special flavor, improve palatability, and thus improve the rate of intake.  In addition, the protein in plant sex protein feed, the over moderate heat treatment can be blunted some protease inhibitors such as pancreatic resistance protease, urease, and makes the hydrogen bonds in proteins and other key destroyed, cause change polypeptide chain original space conformation, the protein denaturation, denatured protein molecules into fiber shape, loose peptides extend,  Increased molecular surface area, flow retardation, increased contact with animal enzymes, which is conducive to the digestion and absorption of aquatic animals, can improve the nutrient digestion efficiency of 10%-35%.  

1.2 Reduce pollution to the environment Puffed floating fish feed has good stability in water.  To extrude puffs processing feed particles, is to rely on the starch gelatinization and protein tissue inside the feed so that the product has a certain bond or binding force, its stability is generally up to 12h, up to 36h, so can reduce the feed nutrients in the water dissolved and sedimentation loss.  Data show that the general use of puffed floating fish feed than powder or pellet feed can save 5 % -10 %, and can avoid feed residues in water, reduce water pollution.  

1.3 Reduce the occurrence of diseases Feed raw materials often contain harmful microorganisms, such as aerobic organisms, neutrophilic bacteria, escherichia coli, mold, salmonella, etc., while the content of dynamic feed raw materials is relatively high.  The effect of high temperature, high humidity and high pressure can kill most harmful microorganisms.  Data show that the number of escherichia coli per gram of raw materials up to 10 000, puking only less than 10, salmonella in the 85 ℃ above high temperature puking, the basic can be killed, which helps to maintain water quality and reduce adverse environmental factors aquaculture, at the same time reduce the mortality of aquatic animals.  
Hope you could see the fish feed extruder machine in LIMA Machinery.
Disadvantages of extruded feed  
2.1 Vitamin Loss Temperature, pressure, friction and moisture all contribute to vitamin loss.  American scholars reported that the loss of VA, VD, folic acid was 1L %, the loss rate of ammonium sulphate mononitrate and ammonium sulphate hydrochloride was 11 % and 17 %, the loss rate of VK and VC was 50 %, and the loss was halved in hard pellet feed.  Leng Yongzhi et al. fed carp with puffable food under the condition of no natural food, and a small number of fish had gill bleeding, which was estimated to be related to the destruction of heat-sensitive vitamins in the process of feed processing.  

2.2 Loss of enzyme Preparation The optimum temperature of enzyme is 35-40 ℃, and the maximum temperature is not more than 50 ℃.  However, the activity of most enzyme preparations will be lost at the temperature of 120-150 ℃ in the pelleting process, accompanied by high humidity (resulting in higher water activity in the feed) and high pressure (denaturation by changing the spatial multidimensional structure of enzyme proteins).  According to Coman, the survival rate of untreated glucanase in feed after pelletizing at 70 ℃ was only 10%;  The survival rate of the treated glucanase was 64% when the temperature was 75 ℃ for 30s, while the survival rate was only 19% when the temperature was 90 ℃, and the activity of phytase decreased by more than 50% when the temperature was 70-90 ℃.  

2.3 Loss of Microbial Preparations At present, the most widely used microbial preparations in feed mainly include Lactobacillus, streptococcus, yeast, bacillus, etc. These microbial preparations are particularly sensitive to temperature, and all their activities will be lost when the extrusion pelletizing temperature exceeds 85 ℃.