Low-nitrogen-emission high-absorption type aquatic fish compound feed and processing technology thereof

Abstract

The application relates to the technical field of aquatic feed processing, and discloses a low-nitrogen-emission high-absorption type aquatic fish compound feed and a processing technology thereof, which comprises enzyme-decomposed fish pulp, enzyme-decomposed black soldier fly worm powder and a compound active water solution and the like raw materials. The processing technology is as follows: solid-phase base materials are mixed in a double-shaft paddle mixer; a compound water solution containing sodium hexametaphosphate and sodium pyrosulfite is prepared; the base materials are fed into a double-shaft differential modifier, steam is passed and the water solution is injected for conditioning; the materials are sent into a co-rotating double-screw extruder for puffing and forming; the materials are dried by a belt dryer and cooled by a counterflow cooler to obtain finished products. Through the deep cooperation of the preferred multi-source enzyme-decomposed protein raw materials and the specific temperature and pressure conditioning and puffing process, the application improves the digestion and absorption rate of nutrient substances in the aquatic intestinal tract, reduces the nitrogen source emission in excrement, guarantees the efficient weight gain of fish and reduces the eutrophication pollution of the breeding water body.

Description

Technical Field

[0001] This invention relates to the field of aquatic feed processing technology, specifically to a low-nitrogen-emission, high-absorption compound feed for aquatic fish and its processing technology. Background Technology

[0002] The processing of compound feed for aquatic fish relies on extrusion puffing technology. Powdered raw materials are mixed in a mixer to obtain a solid matrix. The solid matrix is ​​then fed into a conditioner for hydrothermal treatment. The hydrothermally treated material enters a twin-screw extruder. The twin-screw extruder utilizes the mechanical shear force generated by the internal screws and the heat energy provided by the barrel to gelatinize the material. The gelatinized material is extruded through a die, then dehydrated in a dryer, and further cooled in a counter-current cooler to finally obtain the finished pelleted feed.

[0003] The existing processing technology has defects. Relying solely on steam heating in the conditioner prevents the proper denaturation of nutrients within the material, resulting in low digestibility and absorption rates for aquatic fish. Undigested nitrogen is excreted into the aquaculture water with their feces, causing water pollution. When the material enters the twin-screw extruder, the single-set barrel temperature causes the feeding area to heat up too quickly, leading to material agglomeration and disrupting the continuous extrusion and puffing process. The lack of controlled pre-pressure during extrusion at the die prevents the formation of a porous structure in the finished product. This lack of porous structure causes the feed to sink rapidly after being introduced into the aquaculture water, preventing timely ingestion by aquatic fish. The feed that sinks to the bottom decomposes, resulting in resource waste.

[0004] To address the issues of low digestibility and absorption rates, material clumping and breakage during extrusion, and waste due to finished product sinking in water caused by existing processing techniques, a novel processing technology for compound feed for aquatic fish is needed. This technology can be developed by changing the liquid addition method during conditioning, adjusting the segmented temperature control parameters of the extruder, and modifying the die-holding pressure steps. This will improve material digestibility, maintain stable extrusion processing, and impart porous suspension properties to the finished product.

[0005] Therefore, this invention proposes a low-nitrogen-emission, high-absorption compound feed for aquatic fish and its processing technology to address the shortcomings of existing technologies. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a low-nitrogen-emission, high-absorption compound feed for aquatic fish and its processing technology. This solves the problems of low digestibility and absorption rate of compound feed by aquatic fish leading to nitrogen pollution of aquaculture water, rapid heating of materials in the feeding area of ​​a twin-screw extruder causing agglomeration and clumping, and the lack of porous structure in the finished product leading to sinking and waste.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] The first aspect of this invention provides a low-nitrogen-emission, high-absorption formulated feed for aquatic fish, comprising the following raw materials in parts by weight:

[0009] 5.0-12.0 parts enzymatically hydrolyzed fish paste powder, 6.0-15.0 parts enzymatically hydrolyzed black soldier fly powder, 25.0-30.3 parts enzymatically hydrolyzed soybean meal, 18.0-25.0 parts high-gluten flour, 3.5-6.5 parts puffed soybeans, 2.0-5.0 parts yeast hydrolysate, 4.8-5.65 parts feed additives, 1.0-2.0 parts aquatic premix, 1.5-2.5 parts calcium dihydrogen phosphate, 0.8-1.2 parts fumaric acid, and 1.5-2.0 parts clinoptilolite powder.

[0010] The second aspect of this invention provides a processing technology for a low-nitrogen-emission, high-absorption compound feed for aquatic fish.

[0011] The processing technology for low-nitrogen-emission, high-absorption formulated feed for aquatic fish includes the following steps:

[0012] The following ingredients by weight are added to a twin-shaft paddle mixer: enzymatically hydrolyzed fish paste powder, enzymatically hydrolyzed black soldier fly powder, enzymatically hydrolyzed soybean meal, high-gluten flour, puffed soybeans, yeast hydrolysate, feed additives, aquatic premix, calcium dihydrogen phosphate, fumaric acid, and clinoptilolite powder. The ambient temperature of the twin-shaft paddle mixer is controlled at 15-30℃. The twin-shaft paddle mixer is turned on and mixed for 120-180 seconds to obtain a solid phase base material.

[0013] Add 6.2-11.9 parts of production water to a stainless steel mixing tank, heat the production water to a constant temperature of 35-40℃, add 0.2-0.3 parts of sodium hexametaphosphate and 0.015-0.03 parts of sodium metabisulfite to the production water, turn on the mechanical agitator of the stainless steel mixing tank, control the speed of the mechanical agitator to 150-200 rpm, and control the mechanical agitation time to 15-20 minutes to obtain a composite active aqueous solution;

[0014] Solid-phase material is continuously and quantitatively fed into a biaxial differential speed conditioner. Saturated steam at a pressure of 0.3-0.4 MPa is introduced into the biaxial differential speed conditioner. Using a high-pressure liquid addition pump, the injection pressure of the high-pressure liquid addition pump is controlled at 0.6-0.8 MPa. A composite active aqueous solution is injected into the biaxial differential speed conditioner, so that the solid-phase material is heated to 80-85℃ in the biaxial differential speed conditioner. The residence time of the solid-phase material in the biaxial differential speed conditioner is controlled at 40-60s to obtain a wet-heat material.

[0015] The wet, hot material is forcibly fed into a co-rotating twin-screw extruder equipped with a feeding section, a melting section, and a homogenizing section. The barrel temperature of the feeding section is set to 60-70℃, the barrel temperature of the melting section is set to 95-105℃, the barrel temperature of the homogenizing section is set to 110-115℃, and the screw speed is set to 300-350 rpm. The material is extruded through a die with orifices to complete the puffing and forming process. The front pressure of the die is adjusted to maintain at 2.8-3.2 MPa to obtain wet pellet feed.

[0016] The wet pelleted feed is pneumatically conveyed to a multi-layer belt dryer for hot air drying. The temperature of the hot air in the multi-layer belt dryer is controlled at 85-90℃. The feed is then cooled to room temperature in a counter-current cooler before packaging to obtain a low-nitrogen emission, high-absorption compound feed for aquatic fish.

[0017] Sodium hexametaphosphate and sodium metabisulfite are mixed in heated and constant-temperature production water to obtain a composite active aqueous solution. Using a high-pressure liquid addition pump, the composite active aqueous solution is injected into a twin-shaft differential speed conditioner with saturated steam at 0.3-0.4 MPa, controlled by an injection pressure of 0.6-0.8 MPa. The saturated steam heats the solid-phase material to 80-85℃, and the residence time is controlled at 40-60 seconds to obtain a wet-heat material. The co-rotating twin-screw extruder has a feeding section, a melting section, and a homogenizing section. The barrel temperature of the feeding section is set to 60-70℃, the barrel temperature of the melting section to 95-105℃, and the barrel temperature of the homogenizing section to 110-115℃.

[0018] Hot, moist material is forcibly fed into a co-rotating twin-screw extruder. Combined with a screw speed of 300-350 rpm, the material is extruded through a die with perforations to complete the puffing process. The pre-pressure of the die is adjusted to maintain 2.8-3.2 MPa. A composite active aqueous solution is injected using a dual-shaft differential conditioner and a high-pressure liquid additive pump. This, combined with the segmented barrel temperature settings of the co-rotating twin-screw extruder, completes the puffing process, resulting in a low-nitrogen-emission, high-absorption formulated feed for aquatic fish.

[0019] This invention provides a low-nitrogen-emission, high-absorption formulated feed for aquatic fish and its processing technology, which has the following beneficial effects:

[0020] 1. This invention involves adding sodium hexametaphosphate and sodium metabisulfite to production water and mixing them at a constant temperature to obtain a composite active aqueous solution. A high-pressure liquid addition pump, controlling the injection pressure at 0.6-0.8 MPa, injects the composite active aqueous solution into a biaxial differential speed conditioner that is supplied with saturated steam at 0.3-0.4 MPa. This causes the solid-phase material to be heated to 80-85°C within the conditioner and held for 40-60 seconds to obtain a wet-heat material. The composite active aqueous solution, combined with saturated steam, performs hydrothermal treatment on the solid-phase material, improving the digestibility and absorption rate of formulated feed by aquatic fish and reducing nitrogen emissions from fish excrement.

[0021] 2. This invention features a co-rotating twin-screw extruder with a feeding section, a melting section, and a homogenizing section. The barrel temperature of the feeding section is set at 60-70℃, the melting section at 95-105℃, and the homogenizing section at 110-115℃. The co-rotating twin-screw extruder is configured with stepped heating conditions along the conveying direction of the humid material, combined with a screw speed of 300-350 rpm. This prevents the humid material from agglomerating due to excessive heating, ensuring a uniform melting state within the extruder and maintaining continuous extrusion and expansion stability.

[0022] 3. This invention maintains the front pressure of the die head at 2.8-3.2 MPa, allowing the molten, hot, wet material to be extruded through the die head with perforations to achieve puffing and forming of wet pellet feed. The front pressure of the die head, combined with the flash expansion action, creates a porous structure inside the wet pellet feed. This porous structure increases the suspension time of the feed in the aquaculture water, facilitating feeding by aquatic fish and preventing the feed from sinking and rotting. A multi-layer belt dryer controls the temperature at 85-90℃ for hot air drying, combined with a counter-current cooler to cool to room temperature, ensuring the finished product is dehydrated and set. Attached Figure Description

[0023] Figure 1 This is a Fourier transform infrared spectrum of the compound feed of the present invention.

[0024] Figure 2 This is a graph showing the thermomechanical properties of the compound feed of the present invention.

[0025] Figure 3 This is a gel permeation chromatogram of the compound feed of the present invention.

[0026] Figure 4 This is a diagram showing the change in the main extruder current during the compound feed processing of this invention.

[0027] Figure 5 This is a graph showing the cumulative ammonia nitrogen in the water during the aquaculture process using the formulated feed of this invention. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1:

[0030] This embodiment provides a processing technology for low-nitrogen-emission, high-absorption compound feed for aquatic fish, including the following steps:

[0031] 8.0 parts by weight of enzymatically hydrolyzed fish paste powder, 12.0 parts by weight of enzymatically hydrolyzed black soldier fly powder, 28.0 parts by weight of enzymatically hydrolyzed soybean meal, 22.0 parts by weight of high-gluten flour, 5.0 parts by weight of puffed soybean, 3.5 parts by weight of yeast hydrolysate, 5.0 parts by weight of feed additive, 1.5 parts by weight of aquatic premix, 2.0 parts by weight of calcium dihydrogen phosphate, 1.0 part by weight of fumaric acid and 1.75 parts by weight of clinoptilolite powder were added into a twin-shaft paddle mixer. The ambient temperature of the twin-shaft paddle mixer was controlled at 22°C. The twin-shaft paddle mixer was turned on and mixed for 150 seconds to obtain a solid phase base material.

[0032] Add 8.425 parts of production water to a stainless steel mixing tank, heat the production water to a constant temperature of 38°C, add 0.25 parts of sodium hexametaphosphate and 0.02 parts of sodium metabisulfite to the production water, turn on the mechanical agitator of the stainless steel mixing tank, control the speed of the mechanical agitator to 175 rpm, and control the mechanical agitation time to 18 minutes to obtain a composite active aqueous solution.

[0033] Solid-phase material is continuously and quantitatively fed into a biaxial differential speed conditioner. Saturated steam at a pressure of 0.35 MPa is introduced into the biaxial differential speed conditioner. Using a high-pressure liquid addition pump, the injection pressure of the high-pressure liquid addition pump is controlled at 0.7 MPa. The composite active aqueous solution is injected into the biaxial differential speed conditioner, so that the solid-phase material is heated to 82°C in the biaxial differential speed conditioner. The residence time of the solid-phase material in the biaxial differential speed conditioner is controlled at 50 s to obtain a wet hot material.

[0034] The wet, hot material is forcibly fed into a co-rotating twin-screw extruder equipped with a feeding section, a melting section, and a homogenizing section. The barrel temperature of the feeding section of the co-rotating twin-screw extruder is set to 65°C, the barrel temperature of the melting section is set to 100°C, the barrel temperature of the homogenizing section is set to 112°C, and the screw speed is set to 325 rpm. The material is extruded through a die head with die holes to complete the puffing and forming process. The front pressure of the die head is adjusted to maintain at 3.0 MPa to obtain wet pellet feed.

[0035] The wet pelleted feed is pneumatically conveyed to a multi-layer belt dryer for hot air drying. The temperature of the hot air in the multi-layer belt dryer is controlled at 88°C. The feed is then cooled to room temperature in a counter-current cooler before packaging to obtain a low-nitrogen emission, high-absorption compound feed for aquatic fish.

[0036] Example 2:

[0037] This embodiment provides a processing technology for low-nitrogen-emission, high-absorption compound feed for aquatic fish, including the following steps:

[0038] 12.0 parts by weight of enzymatically hydrolyzed fish paste powder, 15.0 parts by weight of enzymatically hydrolyzed black soldier fly powder, 30.3 parts by weight of enzymatically hydrolyzed soybean meal, 25.0 parts by weight of high-gluten flour, 6.5 parts by weight of puffed soybeans, 5.0 parts by weight of yeast hydrolysate, 5.65 parts by weight of feed additives, 2.0 parts by weight of aquatic premix, 2.5 parts by weight of calcium dihydrogen phosphate, 1.2 parts by weight of fumaric acid and 2.0 parts by weight of clinoptilolite powder were added into a twin-shaft paddle mixer. The ambient temperature of the twin-shaft paddle mixer was controlled at 30°C. The twin-shaft paddle mixer was turned on and mixed for 180 seconds to obtain a solid-phase base material.

[0039] 11.9 parts of production water were added to a stainless steel mixing tank. The temperature of the production water was heated and kept constant at 40°C. 0.3 parts of sodium hexametaphosphate and 0.03 parts of sodium metabisulfite were added to the production water. The mechanical stirring of the stainless steel mixing tank was turned on and the stirring speed was controlled at 200 rpm for 20 minutes to obtain a composite active aqueous solution.

[0040] Solid-phase material is continuously and quantitatively fed into a biaxial differential speed conditioner. Saturated steam at a pressure of 0.4 MPa is introduced into the biaxial differential speed conditioner. Using a high-pressure liquid addition pump, the injection pressure of the high-pressure liquid addition pump is controlled at 0.8 MPa. The composite active aqueous solution is injected into the biaxial differential speed conditioner, so that the solid-phase material is heated to 85°C in the biaxial differential speed conditioner. The residence time of the solid-phase material in the biaxial differential speed conditioner is controlled at 60 s to obtain a wet-heat material.

[0041] The wet, hot material is forcibly fed into a co-rotating twin-screw extruder equipped with a feeding section, a melting section, and a homogenizing section. The barrel temperature of the feeding section of the co-rotating twin-screw extruder is set to 70℃, the barrel temperature of the melting section is set to 105℃, the barrel temperature of the homogenizing section is set to 115℃, and the screw speed is set to 350 rpm. The material is extruded through a die head with die holes to complete the puffing and forming process. The front pressure of the die head is adjusted to maintain at 3.2 MPa to obtain wet pellet feed.

[0042] The wet pelleted feed is pneumatically conveyed to a multi-layer belt dryer for hot air drying. The temperature of the hot air in the multi-layer belt dryer is controlled at 90°C. The feed is then cooled to room temperature in a counter-current cooler before packaging to obtain a low-nitrogen emission, high-absorption compound feed for aquatic fish.

[0043] Example 3:

[0044] This embodiment provides a processing technology for low-nitrogen-emission, high-absorption compound feed for aquatic fish, including the following steps:

[0045] 5.0 parts by weight of enzymatically hydrolyzed fish paste powder, 6.0 parts by weight of enzymatically hydrolyzed black soldier fly powder, 25.0 parts by weight of enzymatically hydrolyzed soybean meal, 18.0 parts by weight of high-gluten flour, 3.5 parts by weight of puffed soybeans, 2.0 parts by weight of yeast hydrolysate, 4.8 parts by weight of feed additives, 1.0 part by weight of aquatic premix, 1.5 parts by weight of calcium dihydrogen phosphate, 0.8 parts by weight of fumaric acid and 1.5 parts by weight of clinoptilolite powder were added into a twin-shaft paddle mixer. The ambient temperature of the twin-shaft paddle mixer was controlled at 15°C. The twin-shaft paddle mixer was turned on and mixed for 120 seconds to obtain a solid phase base material.

[0046] Add 6.2 parts of production water to a stainless steel mixing tank, heat the production water to a constant temperature of 35°C, add 0.2 parts of sodium hexametaphosphate and 0.015 parts of sodium metabisulfite to the production water, turn on the mechanical agitator of the stainless steel mixing tank, control the speed of the mechanical agitator to 150 rpm, and control the mechanical agitation time to 15 minutes to obtain a composite active aqueous solution.

[0047] Solid-phase material is continuously and quantitatively fed into a biaxial differential speed conditioner. Saturated steam at a pressure of 0.3 MPa is introduced into the biaxial differential speed conditioner. Using a high-pressure liquid addition pump, the injection pressure of the high-pressure liquid addition pump is controlled at 0.6 MPa. The composite active aqueous solution is injected into the biaxial differential speed conditioner, so that the solid-phase material is heated to 80°C in the biaxial differential speed conditioner. The residence time of the solid-phase material in the biaxial differential speed conditioner is controlled at 40 s to obtain a wet hot material.

[0048] The wet and hot material is forcibly fed into a co-rotating twin-screw extruder equipped with a feeding section, a melting section, and a homogenizing section. The barrel temperature of the feeding section of the co-rotating twin-screw extruder is set to 60℃, the barrel temperature of the melting section is set to 95℃, the barrel temperature of the homogenizing section is set to 110℃, and the screw speed is set to 300rpm. The material is extruded through a die head with a die hole to complete the puffing and forming process. The front pressure of the die head is adjusted to maintain at 2.8MPa to obtain wet pellet feed.

[0049] The wet pelleted feed is pneumatically conveyed to a multi-layer belt dryer for hot air drying. The temperature of the hot air in the multi-layer belt dryer is controlled at 85°C. The feed is then cooled to room temperature in a counter-current cooler before packaging to obtain a low-nitrogen emission, high-absorption compound feed for aquatic fish.

[0050] Comparative Example 1:

[0051] Compared with Example 1, the difference lies in the location of the addition of the composite active aqueous solution in the processing technology. Instead of using a high-pressure liquid addition pump to inject the composite active aqueous solution into the biaxial differential conditioner, the high-pressure liquid addition pump is used to inject the composite active aqueous solution into the co-rotating twin-screw extruder. All other aspects are the same.

[0052] Comparative Example 2:

[0053] Compared with Example 1, the difference is that sodium metabisulfite is not added to the raw materials of the formula, but all other ingredients are the same.

[0054] Comparative Example 3:

[0055] Compared with Example 1, the difference is that sodium hexametaphosphate is not added to the raw materials of the formulation, but all other ingredients are the same.

[0056] Comparative Example 4:

[0057] Compared with Example 1, the difference is that the high-gluten flour in the formula is replaced with an equal amount of tapioca starch, while the rest are the same.

[0058] Comparative Example 5:

[0059] Compared with Example 1, the difference is that the enzymatically hydrolyzed fish paste powder in the formula is replaced with an equal amount of conventional fish meal, the enzymatically hydrolyzed black soldier fly powder is replaced with an equal amount of conventional black soldier fly powder, and the enzymatically hydrolyzed soybean meal is replaced with an equal amount of conventional soybean meal; all other aspects are the same.

[0060] Test Example 1:

[0061] The low-nitrogen emission, high-absorption compound feeds for aquatic fish prepared in Example 1, Comparative Example 2, and Comparative Example 3 were collected as test samples.

[0062] Each test sample was placed in an experimental pulverizer for grinding and pulverization, and the powder material that passed through a standard test sieve with a aperture of 0.15 mm was collected.

[0063] The sieved powder is spread evenly in a drying dish and transferred to a vacuum freeze dryer. The drying temperature is set to -50°C and the pressure inside the drying chamber is maintained at 10 Pa. The drying process is carried out for 24 hours to remove moisture.

[0064] In a dry room temperature environment with controlled humidity of 40%, 2.1 mg of dried test sample powder was weighed and mixed with 198.5 mg of spectrally pure potassium bromide powder. The mixture was then placed in an agate mortar and ground clockwise for 3 minutes until the powder was evenly distributed.

[0065] The mixed powder is transferred to a special stainless steel tablet mold and pressed for 2 minutes under a hydrostatic pressure of 15 MPa using a hydraulic press to produce a transparent test tablet with uniform thickness.

[0066] Turn on the Fourier transform infrared spectrometer and preheat for 30 minutes. Perform a blank scan with pure potassium bromide pellets as the background. Fix the test pellet in the sample chamber and set the wavenumber range of the infrared scan to between 4000 cm⁻¹. -1 Up to 400cm -1 Between these points, the instrument's spectral resolution was set to 4 cm⁻¹. -1 The number of scans per measurement is set to 32.

[0067] Export the raw infrared spectral data obtained from the scan, perform baseline leveling using software, and extract wavenumbers of 2550 cm⁻¹. -1 1650cm -1 And 1045cm -1 The spectral absorbance values ​​of specific absorption peaks in the vicinity are summarized and recorded.

[0068] Table 1. Absorbance data of characteristic peaks in Fourier transform infrared spectra of different compound feed samples

[0069] Example 1 0.0463 0.4312 0.2458 Comparative Example 2 0.0075 0.4187 0.2372 Comparative Example 3 0.0451 0.4206 0.0384

[0070] The test results are as follows:

[0071] Figure 1 In the figure, the horizontal axis represents the wave number, with the unit being cm. -1 The vertical axis represents transmittance, in percentages (%). Figure 1 The solid line represents Example 1, the dashed line represents Comparative Example 2, and the dotted-dash line represents Comparative Example 3.

[0072] Based on the data in Table 1 and Figure 1 The results show that different formulation components participated in the structural rearrangement and chemical bond transformation of the raw material macromolecules during the extrusion process. (Observation wavenumber: 2550 cm⁻¹) -1 Regarding the absorption of the SH stretching vibration peaks nearby, the absorbance value of Example 1 is higher than that of Comparative Example 2. The removal of sodium metabisulfite from the formulation of Comparative Example 2 indicates that sodium metabisulfite, under the thermomechanical processing conditions of steam introduced into a biaxial differential conditioner and a co-rotating twin-screw extruder, promotes the reduction and breakage of disulfide bonds in the gluten protein network, generating free thiol structures.

[0073] This transformation of disulfide bonds into thiol groups reduces the cross-linking constraints between protein molecules, which is beneficial for enhancing the rheological extensibility of the material during the melting stage inside the barrel.

[0074] Observation wavenumber 1045cm -1 Near the characteristic absorption peak of POC, the absorbance of Example 1 and Comparative Example 2 is higher, while the absorbance of Comparative Example 3 is lower. The formulation of Comparative Example 3 removes sodium hexametaphosphate, indicating that sodium hexametaphosphate, as a polyanionic substance, under the temperature and pressure conditions of the extruder homogenization section, forms a strong polyelectrolyte complex and hydrogen bond synergistic effect with free amino groups and polyvalent cations (such as calcium ions) in the compound feed, promoting the construction of a three-dimensional physical cross-linked network. (Binding wavenumber 1650 cm⁻¹) -1 The changes in absorbance of the amide I band in the vicinity, as observed in Example 1 with the addition of sodium metabisulfite and sodium hexametaphosphate, resulted in alterations in the secondary structure ratio of the protein after processing at specific temperature steps. Initially, sodium metabisulfite broke disulfide bonds to soften the material, followed by cross-linking and reconstruction of the internal network framework by sodium hexametaphosphate. The combination of these two processes altered the water-swelling resistance of the formulated feed, providing structural support for morphological stability after the feed was placed in water.

[0075] Test Example 2: Rheological and Thermomechanical Property Curve Testing of Extruded Materials

[0076] The wet and hot materials obtained from the processing steps of the biaxial differential conditioner in Example 1, Comparative Example 2 and Comparative Example 4 were collected as test samples and sealed and kept in a constant temperature chamber at 82°C for later use.

[0077] Turn on the torque rheometer and calibrate the instrument. Set the initial test temperature of the rheometer test mixing chamber to 100℃, which corresponds to the barrel temperature of the melting section of the co-rotating twin-screw extruder.

[0078] Accurately weigh 62.5 grams of the test sample under heat preservation conditions, quickly put it into the test mixing chamber of the torque rheometer, and close the pressing slider.

[0079] Set the rotor speed of the torque rheometer to 60 rpm, start the data acquisition program, and record the torque change of the material under shearing action in the mixing chamber.

[0080] When the program reaches the 5th minute, the rheometer heating system is controlled to steadily increase the temperature at a rate of 2°C per minute until the mixing chamber temperature reaches 112°C, which corresponds to the barrel temperature of the homogenization section of the co-rotating twin-screw extruder, and then the temperature is maintained at a constant level.

[0081] Shear tests were continuously conducted, with a total test duration of 20 minutes. Raw data on the thermomechanical properties of torque as a function of test time were exported using the accompanying software.

[0082] The peak torque value in the early stage of the test and the equilibrium torque value when the material is in a stable gelatinized state at the 18th minute were extracted from the exported data. The corresponding apparent viscosity was calculated and recorded in combination with the instrument parameters.

[0083] Table 2. Torque rheological and thermomechanical properties of different compound feed samples

[0084] Example 1 18.24 11.47 1026.5 Comparative Example 2 26.83 16.92 1489.1 Comparative Example 4 16.51 9.08 741.3

[0085] The test results are as follows:

[0086] Figure 2 In the figure, the horizontal axis represents the test time in minutes, and the vertical axis represents the torque in N·m. Figure 2 The solid line represents Example 1, the dashed line represents Comparative Example 2, and the dotted line represents Comparative Example 4.

[0087] Based on the data in Table 2 and Figure 2 The results show that different formulation components altered the thermomechanical processing resistance of the wet, hot materials in the torque rheometer. The peak torque and equilibrium torque values ​​of Comparative Example 2 were higher than those of Example 1. Based on the component ratios, Comparative Example 2, by removing sodium metabisulfite, resulted in the disulfide bonds in the gluten protein being in a fully cross-linked state, leading to higher shear resistance and melt strength in the 100°C to 112°C temperature range. This higher torque, in actual operation of the co-rotating twin-screw extruder, would translate into excessive mechanical frictional heat, causing excessive temperature rise inside the barrel and increasing the likelihood of Maillard reactions in the enzymatically hydrolyzed fish paste powder and soybean meal. Example 1, containing sodium metabisulfite, weakened the dough, reduced the apparent viscosity and processing torque of the material, and improved the smoothness of the processing.

[0088] Observing the test data and curve trend of Comparative Example 4, its equilibrium stable torque value was low, and the curve fluctuated in the later part of the test. Comparative Example 4 used tapioca starch to replace high-gluten flour in an equal amount, removing the protein network framework support provided by gluten protein. Tapioca starch faces the problems of over-gelatinization and degradation and depolymerization under heating and continuous shearing conditions, and cannot form a continuous phase rheological morphology with viscoelastic properties. Example 1 combined high-gluten flour and sodium metabisulfite to adjust the rheological properties of the materials, so that the torque curve smoothly transitioned to the equilibrium state, ensuring the extrusion stability during co-rotating twin-screw extrusion molding.

[0089] Test Example 3:

[0090] The solid base material that had been mixed but not yet conditioned in Example 1, the finished compound feed obtained after drying and cooling in Example 1, and the finished compound feed obtained after drying and cooling in Comparative Example 2 were collected as test samples.

[0091] Accurately weigh 5.0 g of each test sample powder and place them in 50 mL centrifuge tubes. Add 25 mL of chromatographic grade n-hexane and place them in a reciprocating shaker at 200 rpm for 40 minutes to degrease. Discard the supernatant and place the bottom precipitate in a fume hood to allow the residual solvent to evaporate naturally.

[0092] Weigh 1.2 g of the defatted and dried powder sample and place it in a glass stoppered test tube. Add 15 mL of 0.1 mol / L hydrochloric acid solution and place the tube in an ultrasonic water bath generator. Extract the sample ultrasonically for 30 minutes at a frequency of 40 kHz, maintaining the water bath temperature at 25 ℃ during the extraction process.

[0093] The extracted suspension was transferred to a high-speed refrigerated centrifuge and centrifuged at 8000 rpm for 15 minutes at 4°C.

[0094] The supernatant after centrifugation was aspirated and filtered through a polyethersulfone microporous membrane with a pore size of 0.22 μm. The filtrate was collected as the test solution for gel permeation chromatography.

[0095] Turn on the high performance liquid chromatograph and connect the gel permeation chromatography column. Set the mobile phase to a mixed solution prepared by deionized water, acetonitrile and trifluoroacetic acid in a volume ratio of 80:20:0.1.

[0096] The elution flow rate of the liquid chromatography pump was controlled at 0.5 mL / min, the column oven temperature was maintained at 30℃, and the detection wavelength of the ultraviolet detector was set to 220 nm.

[0097] A 20 μL sample solution was injected into the chromatographic analysis system using an autosampler, and the chromatographic elution curve data was recorded over 30 minutes. The relative peak area percentage for different molecular weight ranges was calculated based on the logarithmic equation of retention time and standard molecular weight.

[0098] Table 3. Molecular weight distribution of proteins and peptides in samples from different processing stages and formulations.

[0099] Example 1 Solid-phase base material 17.62 29.84 52.54 Example 1 Finished Feed 22.18 31.05 46.77 Comparative Example 2: Finished Feed 34.51 30.12 35.37

[0100] The test results are as follows:

[0101] Figure 3 In the figure, the horizontal axis represents retention time in minutes, and the vertical axis represents response intensity in mV; the solid line represents the solid substrate of Example 1, the dashed line represents the finished feed of Example 1, and the dotted line represents the finished feed of Comparative Example 2.

[0102] Based on the data in Table 3 and Figure 3The content shows that the processing of wet and hot materials in a twin-shaft differential conditioner and a co-rotating twin-screw extruder affects the distribution of peptides and free amino acids in the raw materials. Comparing the test data of the solid-phase base material of Example 1 and the finished feed of Example 1, after conditioning and extrusion molding, the proportion of components with a molecular weight less than 500 Da decreased from 52.54% to 46.77%, while the proportion of macromolecular components increased, indicating that the thermomechanical processing triggered the reaction and consumption of some small molecules.

[0103] Observing the data of the finished feed of Comparative Example 2, the proportion of free amino acids and dipeptides with a molecular weight less than 500 Da decreased to 35.37%, while the proportion of components with a molecular weight greater than 3000 Da increased to 34.51%. Figure 3 The elution curve shows a relatively wide absorption peak in the short retention time region.

[0104] Based on the aforementioned rheological test results of the extruded materials, it can be seen that the removal of sodium metabisulfite from the formulation of Comparative Example 2 caused an increase in the shear resistance of the material in the homogenization section of the extruder.

[0105] The mechanical friction exerted by the rotor on the high-viscosity material caused the internal temperature of the barrel to deviate from the set 112℃, forming localized high-temperature hotspots. Under this high-temperature environment accompanied by high shear, the free amino acids provided by the enzymatically hydrolyzed fish paste powder and enzymatically hydrolyzed soybean meal underwent Maillard reactions with the reducing sugars produced by the degradation of high-gluten flour and puffed soybeans.

[0106] Free amino acids are converted into large-molecule browning products through thermal degradation and cross-linking polymerization, resulting in the thermal loss of nutritional small-molecule peptides. The sodium metabisulfite in the formulation of Example 1 exerts a synergistic effect of both physical cooling and chemical inhibition. Physically, it weakens the dough, reducing the mechanical frictional heating effect; chemically, the sulfite ions released from sodium metabisulfite in a humid and hot environment can directly react with the carbonyl groups of reducing sugars produced by the degradation of extruded soybeans, competitively blocking the Maillard cross-linking polymerization of free amino acids at the chemical source. This dual approach ensures the retention rate of free nutrients in the finished compound feed.

[0107] Test Example 4: Comparison of Industrial Extrusion Energy Consumption and Processing Stability

[0108] Prepare the solid-phase base material and composite active aqueous solution required for processing in Example 1, Comparative Example 1 and Comparative Example 2.

[0109] Start the co-rotating twin-screw extruder and its associated feeding device, twin-shaft differential conditioner and high-pressure liquid addition pump, and wait for each section of the barrel of the co-rotating twin-screw extruder to heat up to the set temperature and maintain constant temperature operation for 15 minutes.

[0110] According to the feeding positions and process parameters set in each embodiment and comparative example, the solid base material and the composite active aqueous solution were continuously and quantitatively fed into the corresponding processing equipment for trial operation.

[0111] After the co-rotating twin-screw extruder continuously extrudes wet pellet feed and the production status is initially stable, turn on the data acquisition module of the equipment's central control panel.

[0112] The extruder main unit current and die head pressure data were continuously collected for 60 minutes, with the data sampling frequency set to 6 times per minute.

[0113] After the test cycle ends, feeding is stopped and the equipment is cleaned. The original operation records in the data acquisition module are exported, and the specific mechanical energy consumption and the fluctuation range of various parameters within the 60-minute processing cycle are calculated.

[0114] Table 4. Operating energy consumption and stability parameters of co-rotating twin-screw extruders under different processing technologies

[0115] Example 1 142.3 4.1 3.05 0.12 98.6 Comparative Example 1 148.7 18.5 2.94 0.68 105.2 Comparative Example 2 165.2 7.8 3.42 0.25 118.4

[0116] The test results are as follows:

[0117] Figure 4 In the figure, the horizontal axis represents processing time in minutes, and the vertical axis represents the host current in amperes (A). The solid line represents Example 1, the dashed line represents Comparative Example 1, and the dotted line represents Comparative Example 2.

[0118] Based on the data in Table 4 and Figure 4 The content shows that changes in processing parameters and formulation components directly affect the continuous operation energy consumption and dynamic stability of the co-rotating twin-screw extruder. Observing the operating parameters of Comparative Example 1, the fluctuation range of its main current and die pressure is higher than that of Example 1, and in... Figure 4 The current curve exhibits high-frequency oscillations and irregular abrupt changes. In Comparative Example 1, the injection point of the composite active aqueous solution was changed from a biaxial differential conditioner to a co-rotating twin-screw extruder, resulting in a shortened contact and mixing time between the solid matrix and the composite active aqueous solution. The material failed to complete thermal expansion before entering the extruder, causing uneven local moisture distribution within the barrel, leading to frequent fluctuations in screw torque and reducing the stability of continuous production. Example 1 used a conditioner to pre-inject the aqueous solution and maintain a 50-second residence time, ensuring a uniform moisture distribution in the material.

[0119] Comparing the data from Example 1 and Comparative Example 2, Comparative Example 2 shows higher average host current and specific mechanical energy consumption. Figure 4The baseline current shifted upwards overall. In Comparative Example 2, sodium metabisulfite was removed from the formulation, and the disulfide bonds in the gluten protein of the high-gluten flour failed to undergo reduction and breakage. The material maintained a high shear viscosity in the melting and homogenizing sections of the extruder, increasing the work load required for the main motor of the extruder to overcome the frictional resistance of the material, resulting in an increase in overall energy consumption. Example 1 utilized a process of separately adding solid-phase base material and composite active aqueous solution and then combining them in the conditioning stage, which promoted the transformation of disulfide bonds to thiol groups, reducing material viscosity and extrusion mechanical energy consumption.

[0120] Test Example 5:

[0121] The finished compound feeds obtained after drying and cooling treatment in Example 1, Comparative Example 3 and Comparative Example 4 were collected as test samples.

[0122] Select a standard stainless steel test basket with an aperture of 2.0 mm, place each test sample in a drying oven and dry it at 60°C for 2 hours to unify the initial moisture content. After cooling, accurately weigh 10.0 g of each group of test samples and place them in the corresponding test basket.

[0123] Turn on the constant temperature oscillating water bath, inject deionized water and set the water bath temperature to 25℃, and adjust the reciprocating oscillation frequency to 40 times per minute.

[0124] The test basket containing the sample is suspended on the oscillation frame of the water bath, ensuring that the test sample is completely submerged below the water surface. Timing is then started and continuous immersion and oscillation are performed.

[0125] The test basket was removed from the water and left to drain for 5 minutes after soaking for 30, 60, 90 and 120 minutes respectively.

[0126] After draining, the test basket, along with the remaining sample residue, was transferred to a forced-air drying oven at 105°C and baked for 4 hours until constant weight was achieved.

[0127] After drying, the residue was transferred to a desiccator and cooled to room temperature. The weight of the residue was measured, and the mass loss rate at different soaking time points was calculated based on the difference between the initial dry weight of the sample before soaking and the dry weight of the residue.

[0128] Table 5. Data on the change of solubility rate of different compound feed samples in water with soaking time.

[0129] Example 1 2.31 4.18 6.02 7.94 Comparative Example 3 4.67 8.92 14.15 19.38 Comparative Example 4 10.25 22.41 35.83 47.62

[0130] The test results are as follows:

[0131] According to the data in Table 5, the selection of binders and crosslinking agents in the formulation plays a decisive role in the water resistance of the compound feed after molding. Observing the test data of Example 1, its solubility loss rate remained at a low level of 7.94% during the 120-minute soaking period.

[0132] Based on mechanistic analysis, in Example 1, the gluten protein in the high-gluten flour, after bond breaking due to sodium metabisulfite reduction, unfolds under the high temperature and high pressure environment of a co-rotating twin-screw extruder. Subsequently, sodium hexametaphosphate, acting as a polyanionic cross-linking agent, promotes polyelectrolyte complexation and cross-linking between protein, starch molecules, and the material matrix, forming a dense three-dimensional network framework. This network framework hinders the rapid penetration of water molecules into the feed pellets and reduces the dissolution rate of enzymatically hydrolyzed fish paste powder and small molecule peptides under water flow.

[0133] Comparing the data of Example 1 and Comparative Example 3, the solubility loss rate of Comparative Example 3 showed an increasing trend at all time points. The formulation of Comparative Example 3 removed sodium hexametaphosphate, resulting in a lack of polyphosphate-mediated ion complexation reactions in the extrusion homogenization stage. The resulting feed pellets lacked an anti-hydration protective layer, making the internal nutrients prone to dissolution and stripping after moisture intrusion.

[0134] Observing the test curve of Comparative Example 4, its solubility loss rate increased with time, reaching 47.62% at 120 minutes, indicating that the feed was in a state of disintegration. Comparative Example 4 used cassava starch to replace high-gluten flour in an equal amount, thus removing the gluten protein skeleton. A simple starch matrix, after extrusion and gelatinization, will undergo excessive water absorption, swelling, degradation, and depolymerization once soaked in water, failing to maintain the integrity of the feed and resulting in a significant loss of nutrients. The specific cross-linking formula used in Example 1 ensured the morphological stability and water quality protection function of the low-nitrogen-emission, high-absorption aquatic feed during the feeding process.

[0135] Test Example 6:

[0136] The compound feeds prepared in Example 1 and Comparative Example 5 during the processing stage were collected. In the previous solid-phase base mixing step, 0.5% by mass of yttrium oxide was added to both formulations as an inert exogenous indicator to participate in the subsequent conditioning and extrusion molding processes.

[0137] Largemouth bass with an initial average weight of 50.5 grams were selected as experimental fish and randomly assigned to multiple fiberglass culture tanks equipped with independent circulating filters and bottom sewage collection devices. 30 fish were stocked in each tank, the water temperature was controlled at 26℃, and the dissolved oxygen concentration was maintained at 6.5 mg / L.

[0138] A 14-day basic acclimatization period was conducted, during which the animals were fed basic feed at regular intervals each day to help them adapt to the environment. After the acclimatization period, a formal testing period of 28 days began.

[0139] During the test period, the formulated feeds of Example 1 and Comparative Example 5 were fed twice a day, morning and evening, at a feeding rate of 2.5% of the total fish body weight. One hour after feeding, the uneaten feed was removed by siphoning and dried, and the dry weight of the uneaten feed was recorded.

[0140] Two hours after feeding, the feces collection device at the bottom of the breeding tank was turned on to continuously collect the excreted feces. The collected feces were placed in a freezer at -20°C for freezing and storage. After the test period, they were collected and freeze-dried in a vacuum.

[0141] The crude protein content in the compound feeds of Example 1 and Comparative Example 5, as well as the corresponding freeze-dried feces, was determined using a Kjeldahl nitrogen analyzer. The mass fraction of yttrium oxide in the feeds and feces was determined using inductively coupled plasma atomic emission spectrometry. The apparent digestibility of crude protein was calculated using the exogenous indicator method.

[0142] During the 28-day test period, water samples were taken from each aquaculture tank at fixed time points every 4 days. The total ammonia nitrogen concentration in the aquaculture water was determined by Nessler's reagent spectrophotometry, and the cumulative increase of ammonia nitrogen in the water with aquaculture time was recorded under different feed feeding conditions.

[0143] Table 6. Data on apparent digestibility of crude protein and total nitrogen in excrement of different compound feeds

[0144] Example 1 89.34 2.15 1.06 Comparative Example 5 78.47 4.31 2.45

[0145] The test results are as follows:

[0146] Figure 5 In the figure, the horizontal axis represents the aquaculture time in days, and the vertical axis represents the ammonia nitrogen concentration in the water in mg / L. Figure 5 The solid line represents Example 1, and the dashed line represents Comparative Example 5.

[0147] Based on the data in Table 6 and Figure 5 The results show that the pretreatment state of the raw materials and the control of extrusion processing parameters in the formula are directly related to the intestinal absorption efficiency of aquatic animals and the environmental load of the aquaculture environment. Observing the test results of Comparative Example 5, its apparent digestibility of crude protein was 78.47%, and the total nitrogen content excreted in feces reached 4.31%. Combined with the differences in the formula, it can be seen that Comparative Example 5 used conventional fishmeal and conventional soybean meal that had not undergone enzymatic hydrolysis as the main protein sources. These conventional raw materials contain large molecular weight proteins and anti-nutritional factors.

[0148] Large protein molecules require a relatively long time to undergo proteolytic reactions in the short intestines of fish. Undigested protein components are converted into nitrogenous excrement and discharged into the water. Figure 5 The results show that the ammonia nitrogen concentration in the aquaculture tank of Comparative Example 5 increased rapidly over time.

[0149] Example 1 uses low-molecular-weight enzymatically hydrolyzed fish paste powder and enzymatically hydrolyzed soybean meal in its formulation, directly providing free amino acids and small-molecule peptides that can be absorbed by intestinal epithelial cells. Example 1 is accompanied by a processing technology that includes sodium metabisulfite for viscosity reduction and temperature step control, avoiding local hot spots caused by excessive shear torque in the extruder barrel, reducing Maillard cross-linking polymerization reactions induced by excessive thermomechanical heat generation of free amino acids, and maintaining the biological value of small-molecule nutrients.

[0150] This combination of raw material selection and process control resulted in an apparent crude protein digestibility of 89.34% in Example 1, with a corresponding decrease in total fecal nitrogen content to 2.15%. Most of the ingested nitrogen was converted into fish protein deposits, reducing nitrogen waste emissions into the environment. Figure 5 The gradual accumulation of ammonia nitrogen in the water body in Example 1 confirms the technical mechanism of reducing nitrogen pollution in water bodies and improving nutrient utilization.

Claims

1. A low-nitrogen-emission, high-absorption formulated feed for aquatic fish, characterized in that, Made from the following raw materials in parts by weight: Enzymatically hydrolyzed fish paste powder: 5.0-12.0 parts; Enzymatically hydrolyzed black soldier fly powder: 6.0-15.0 parts; Enzymatically hydrolyzed soybean meal: 25.0-30.3 parts; High-gluten flour: 18.0-25.0 portions; Puffed soybeans: 3.5-6.5 parts; Yeast hydrolysate: 2.0-5.0 parts; Feed additives: 4.8-5.65 parts; Aquatic premix: 1.0-2.0 parts; Calcium dihydrogen phosphate: 1.5-2.5 parts; Fumaric acid: 0.8-1.2 parts; Clinoptilolite powder: 1.5-2.0 parts; Production water: 6.2-11.9 parts; Sodium hexametaphosphate: 0.2-0.3 parts; Sodium metabisulfite: 0.015-0.03 parts.

2. The low-nitrogen emission, high-absorption formulated feed for aquatic fish according to claim 1, characterized in that, Made from the following raw materials in parts by weight: 8.0 parts of enzymatically hydrolyzed fish paste powder, 12.0 parts of enzymatically hydrolyzed black soldier fly powder, 28.0 parts of enzymatically hydrolyzed soybean meal, and 22.0 parts of high-gluten flour; 5.0 parts puffed soybeans, 3.5 parts yeast hydrolysate, 5.0 parts feed additives, and 1.5 parts aquatic premix; 2.0 parts of calcium dihydrogen phosphate, 1.0 part of fumaric acid, 1.75 parts of clinoptilolite powder, 8.425 parts of production water, 0.25 parts of sodium hexametaphosphate, and 0.02 parts of sodium metabisulfite.

3. The low-nitrogen-emission, high-absorption formulated feed for aquatic fish according to claim 1, characterized in that, Made from the following raw materials in parts by weight: 12.0 parts of enzymatically hydrolyzed fish paste powder, 15.0 parts of enzymatically hydrolyzed black soldier fly powder, 30.3 parts of enzymatically hydrolyzed soybean meal, and 25.0 parts of high-gluten flour; 6.5 parts puffed soybeans, 5.0 parts yeast hydrolysate, 5.65 parts feed additives, and 2.0 parts aquatic premix; 2.5 parts calcium dihydrogen phosphate, 1.2 parts fumaric acid, 2.0 parts clinoptilolite powder, 11.9 parts production water, 0.3 parts sodium hexametaphosphate, and 0.03 parts sodium metabisulfite.

4. A processing technology for a low-nitrogen-emission, high-absorption compound feed for aquatic fish, characterized in that, The preparation of a low-nitrogen-emission, high-absorption formulated feed for aquatic fish according to any one of claims 1-3 includes the following steps: Enzymatically hydrolyzed fish paste powder, enzymatically hydrolyzed black soldier fly powder, enzymatically hydrolyzed soybean meal, high-gluten flour, puffed soybeans, yeast hydrolysate, feed additives, aquatic premix, calcium dihydrogen phosphate, fumaric acid and clinoptilolite powder are put into a twin-shaft paddle mixer and mixed to obtain a solid phase base material. Production water, sodium hexametaphosphate, and sodium metabisulfite were added to a stainless steel mixing tank and stirred to obtain a composite active aqueous solution. The solid-phase material is fed into a biaxial differential speed conditioner, saturated steam is introduced, and the composite active aqueous solution is injected to obtain a wet-heat material. The wet, hot material is fed into a co-rotating twin-screw extruder for puffing and molding to obtain wet pellet feed. The wet pelleted feed is sent to a multi-layer belt dryer for hot air drying and then cooled in a counter-current cooler to obtain a low-nitrogen emission, high-absorption compound feed for aquatic fish.

5. The processing technology for a low-nitrogen-emission, high-absorption compound feed for aquatic fish according to claim 4, characterized in that, The ambient temperature of the twin-shaft paddle mixer is controlled to be 15-30℃; The mixing time of the dual-shaft paddle mixer is controlled to be 120-180 seconds.

6. The processing technology for a low-nitrogen-emission, high-absorption compound feed for aquatic fish according to claim 4, characterized in that, The temperature of the production water is heated and kept constant at 35-40°C; The stirring speed of the stainless steel mixing tank is controlled at 150-200 rpm; The stirring time should be controlled to be 15-20 minutes.

7. The processing technology for a low-nitrogen-emission, high-absorption compound feed for aquatic fish according to claim 4, characterized in that, The solid-phase base material is continuously and quantitatively fed into the biaxial differential conditioner. Saturated steam at a pressure of 0.3-0.4 MPa is introduced into the dual-shaft differential conditioner; The composite active aqueous solution is injected into the biaxial differential conditioner using a high-pressure liquid addition pump, and the injection pressure of the high-pressure liquid addition pump is controlled to be 0.6-0.8 MPa.

8. The processing technology for a low-nitrogen emission, high-absorption compound feed for aquatic fish according to claim 7, characterized in that, The solid-phase material is heated to 80-85°C in the biaxial differential conditioner; The residence time of the solid phase material in the biaxial differential conditioner is controlled to be 40-60 s.

9. The processing technology for a low-nitrogen emission, high-absorption compound feed for aquatic fish according to claim 4, characterized in that, The co-rotating twin-screw extruder is provided with a feeding section, a melting section and a homogenization section; The barrel temperature of the feeding section is set to 60-70℃, the barrel temperature of the melting section is set to 95-105℃, and the barrel temperature of the homogenization section is set to 110-115℃. The screw speed of the co-rotating twin-screw extruder is set to 300-350 rpm.

10. The processing technology for a low-nitrogen-emission, high-absorption compound feed for aquatic fish according to claim 4, characterized in that, The co-rotating twin-screw extruder completes the puffing and forming process through a die head with die holes, and the front pressure of the die head is adjusted to maintain at 2.8-3.2 MPa; The temperature of the hot air in the multi-layer belt dryer is controlled at 85-90°C, and the air enters the counter-current cooler to be cooled to room temperature before packaging.

Images