Expanding process is a feed processing technology, extrusion feed cavity is virtually instantaneous expanding a high temperature process: mixture at a high temperature (110 -200 ℃), high pressure (25-lOOkg / cm2), and a high shear In a high-moisture (10% -20% or even 30%) environment, a bulky and porous feed is formed by continuous mixing, tempering, warming, aging, extrusion, and sudden depressurization.
1, the advantages of puffed feed
1.1 Increase the utilization rate of feed
The heat, humidity, pressure and various mechanical actions during the expansion process break the 1,4-glycosidic bond in the starch molecule to form low molecular weight products such as glucose, maltose, maltotriose and maltodextrin. The expansion process can make the starch paste. The degree of chemical conversion is increased, and the cell wall portion of the fibrous structure is destroyed and softened, and the digestible substance which is partially surrounded and combined is released, and the fat penetrates from the inside of the particle to the surface, so that the feed has a special aroma, and the palatability is improved, and thus the feeding rate is improved. improve. In addition, the protein in the vegetable protein feed can be passivated by some heat treatment to inactivate certain protease inhibitors such as antitrypsin, urease, etc., and the hydrogen bond and other secondary bonds in the protein are destroyed, resulting in the original polypeptide chain. The spatial conformation changes, causing the protein to denature, the denatured protein molecules are fibrillar, the peptide chain is loosely stretched, the molecular surface area is increased, the flow block is increased, and the contact with the enzyme in the animal is increased, thereby facilitating digestion and absorption of the aquatic animal. Improve nutrient digestibility by 10% -35%.
1.2 Reducing environmental pollution
Expanded floating fish feed has good stability in water. The feed pellets processed by extrusion and puffing rely on starch gelatinization and protein organization inside the feed to make the product have certain bonding or bonding strength. The stability is generally more than 12h, and the longest can reach 36h. Reduce the dissolution and precipitation loss of feed nutrients in water. According to the data, the use of puffed floating fish feed can save 5%-10% compared with powder or pellet feed, and can avoid the residue of feed in water and reduce water pollution.
1.3 Reducing the occurrence of diseases
Feed ingredients often contain harmful microorganisms, such as aerobic organisms, neutrophils, Escherichia coli, mold, Salmonella, etc., and the content of animal feed ingredients is relatively high. The high temperature, high humidity and high pressure of puffing can kill most harmful microorganisms. According to statistics, there are 10 000 E. coli per gram of raw materials, and less than 10 are left after puffing. Salmonella can be killed after being puffed at a temperature above 85 °C, which helps to maintain water quality and reduce Unfavorable environmental factors in aquaculture, while reducing the mortality of aquatic animals.
1.4 Improve the breeding density
Under artificial farming conditions, an increase in the density of farming means that the rate of return that farmers receive is higher. When the breeding density of the unit water body is increased, the space of the fish in the aquaculture water body is reduced, and the water quality requirements are also much higher than the natural environment. Since the use of puffed compound feed can reduce the feed coefficient and greatly reduce the residual bait and excrement discharged into the water body, it is possible to greatly increase the breeding density.
1.5 Extend the feed storage period
Extrusion processing improves the stability of the raw material by reducing the bacterial content and oxidation. When the extruded product is dried and cooled, the feed water activity (AW) has been reduced to 0.6 or even 0.4, which is equivalent to a moisture content of 8% to 10%, which better improves the storage stability of the feed.
1.6 Feeding management is convenient for
The aquatic product puffed feed can be suspended in the water surface (water) for a long time. It is not necessary to set up a feeding platform when feeding, and only need to feed at a fixed point. When the fish is ingested, it needs to float 10 water surface. It can directly observe the eating condition of the fish, adjust the feeding amount in time, and timely understand the growth and health of the fish. Therefore, the use of aquatic extruded feed helps to carry out scientific feeding management, which saves a lot of time and can be raised; high labor productivity.
1.7 Animals that can meet different feeding habits need
Expanded feed can be divided into three types: floating, slow sedimentation and rapid sedimentation according to different processing techniques. At present, about 80% of fish feed is sedimentation feed. For example, shrimp, salmon, scorpion, and yellow-tailed tuna all prefer to settle feed, while juveniles of squid, tilapia, carp, and most fish prefer floating feed. , catfish, tilapia feed equal preference for settling and floating feed. In addition, extruded feed can meet special requirements, such as low moisture feed, high-fiber diet and the like.
2, the disadvantage of extruded feed
2.1 Loss of Vitamins
Temperature, pressure, friction and moisture can cause loss of vitamins. American researchers reported that the extruded feed, VA, VD ,, loss of folate 1L% thiamine mononitrate and thiamine hydrochloride pigment loss rate of 11% and 17%, VC and VK loss rate of 50%, The same loss in hard pellet feed is halved. Cold Wing-chi, etc. at no natural foodstuffs, feeding carp with the extruded material, there are a small number of individual fish gills appear bloodshed, and destruction of heat-sensitive vitamins estimate of feed processing related.
2 .2 Loss of enzyme preparations
The optimum temperature for the enzyme is 35 - 40 °C and the maximum temperature is 50 °C. However, the temperature during the expansion granulation reaches 120-150 °C, accompanied by high humidity (causing high water activity in the feed) and high pressure (changing the spatial multidimensional structure of the enzyme protein and denaturation), under such conditions, The activity of most enzyme preparations will be lost. According to Coman, the survival rate of untreated glucanase in feed after granulation at 70 °C is only 10%; the treated glucanase is tempered for 30 s at a temperature of 75 °C, and its survival rate It is 64%, and the survival rate is only 19% after granulation at 90 °C. The phytase is also more than 50% after granulation at 70-90 °C.
2 .3 Loss of microbial preparations
At present, the microbial preparations used in feeds mainly include Lactobacillus, Streptococcus, Yeast, Bacillus, etc. These microbial preparations are particularly sensitive to temperature, and their activity will be completely lost when the puffing granulation temperature exceeds 85 °C.
2.4 Loss of Protein and Amino Acids
The high temperature during the expansion process causes a part of the reducing sugar in the raw material to react with the free amino acid, which reduces the utilization of some proteins. Further, the protein under basic conditions at high temperatures may be formed depends amino alanine, excessive heating, especially at higher pH values, can generate the partial amino acid racemization D- form amino acids, which are protein in The digestibility is greatly reduced. The most susceptible to loss of heat is lysine, followed by arginine and histidine. Using in vitro research methods, Wang Lin et al. determined that the grass carp and Luo Li measured the enzymatic kinetics of the seven different feed ingredients before and after the intestine of the gibel carp, which proved that the puffing had an effect on the protein hydrolysis rate of the feed ingredients. The enzymatic hydrolysis rate of fishmeal and meat bone powder decreased after puffing; the enzymatic hydrolysis rate of rapeseed meal, sub-powder and corn was increased, especially corn; the rate of enzymatic hydrolysis before and after puffing was not significant. Zhou Xinghua et al. studied the ex vivo digestibility of crude protein in puffed and non-expanded feed raw materials by similar research methods. It was found that puffing played a positive role in feed ingredients with low protein content and high starch content, while protein The high content has an adverse effect (except feather powder). Therefore, in the compound feed of fish, it is not advisable to use the soybean meal, fish meal and meat bone powder after puffing. 2.5 The production cost of the higher-expanded feed is more complicated than the general pellet feed, the equipment investment is high, the power consumption is high, and the output is low, so the cost is higher, generally about 20% higher than the cost of the pellet feed.
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