A method for preparing an animal protein alkali hydrolysis product

Abstract

The present application belongs to the field of animal protein hydrolysis technology, and particularly relates to a preparation method of animal protein alkali hydrolysis product. In view of the problems in the existing alkali hydrolysis process, such as strong alkali corrosion of equipment, degradation of amino acids, uncontrollable molecular weight of product and easy pollution during transportation, a first alkali solution is added in a closed crusher to remove odor gas; a second alkali solution is added in a chemical preparation tank to simultaneously complete sterilization and alkali hydrolysis; the product is transported to a post-treatment area through a sterile tank truck; secondary sterilization is performed; oil, alkali hydrolysis liquid and bone residue are obtained through three-phase centrifugal separation; after low-temperature concentration, the alkali hydrolysis liquid is mixed with ground bone powder and dried to obtain a composite protein powder. By adjusting the alkali addition amount and the hydrolysis time, the content of small peptides below 3000 Da in the product reaches 70% to 90%, the nutritional integrity of amino acids is effectively protected, the whole process is closed and sterile, and the comprehensive utilization of each component of animal carcasses is realized.

Description

Technical Field

[0001] This invention relates to the field of animal protein resource utilization technology, and in particular to a method for preparing products of alkaline hydrolysis of animal protein. Background Technology

[0002] According to the "Technical Specifications for Harmless Treatment of Dead and Diseased Animals" (Agricultural Medical Document

[2017] No. 25), harmless treatment methods include incineration, rendering, deep burial, and sodium hydroxide decomposition. Among these, sodium hydroxide decomposition is explicitly listed in the technical specifications, and its scope of application includes infected animals and their products as stipulated by the state, carcasses of animals that died from disease or whose cause of death is unknown, and animals confirmed to be diseased before slaughter.

[0003] Alkaline hydrolysis is an animal tissue processing technology developed in recent years. It uses alkaline substances such as NaOH or KOH under high temperature and pressure to catalyze the hydrolysis of animal tissue into harmless solid residues and liquid products, achieving both sterilization and decomposition of the tissue. This method offers advantages such as complete inactivation of pathogenic microorganisms, no production of harmful gases, and simple operation. The processed amino acids and small peptides can be used in agricultural production, while the oils are used for industrial purposes and are not used as raw materials for food production. This technology is simple to operate, has high biosafety, and provides a new technical means for the harmless treatment of infected animals or animals that have died from unknown causes.

[0004] However, existing alkaline hydrolysis treatment technologies for the harmless disposal of diseased and dead livestock and poultry still have many shortcomings: I. In conventional alkaline hydrolysis processes, strong alkalis such as NaOH or KOH are used as hydrolyzing agents. Although they can effectively catalyze the hydrolysis of proteins, strong alkalis are highly corrosive to equipment under high temperature and high pressure conditions. Special materials with alkali corrosion resistance are required for equipment, resulting in high equipment investment and maintenance costs. Second, during alkaline hydrolysis, most amino acids are damaged to varying degrees and racemize. The resulting product is a mixture of D-amino acids and L-amino acids. Except for tryptophan, arginine, cystine, serine and lysine will undergo conformational changes, leading to the loss of essential amino acids, reduced protein nutritional integrity, and difficulty in effectively controlling the distribution of small peptides (molecular weight below 3000 Da) in the product. Third, in the existing technology, although the high-temperature sterilization of dead animals and the alkaline hydrolysis of proteins can be completed in the same container, alkaline hydrolysis usually needs to be carried out under high temperature (above 150°C) and high pressure conditions, the reaction time is long (usually 5 to 6 hours), the production cycle is long and the energy consumption is high. Fourth, after alkaline hydrolysis, solid-liquid separation is usually carried out directly, and the separated bone residue is only treated as waste residue, which fails to make full use of the protein, calcium, phosphorus and other mineral resources in the bone residue. Fifth, the lack of fully enclosed and sterile protection measures during the hydrolysis and transfer of materials exposes them to the factory environment, which can easily lead to secondary contamination by pathogens or other microorganisms.

[0005] Chinese invention patent CN117816719A, published on April 5, 2024, discloses a harmless alkaline hydrolysis treatment method for livestock and poultry organic waste. This method uses livestock and poultry organic waste (including carcasses of diseased or dead livestock and poultry) as raw material. After determining the single-processing mass using weighing equipment, the waste is crushed and transferred to an alkaline hydrolysis container. A potassium hydroxide aqueous solution is added at a mass ratio of 1:4 to 5 with the waste. The container is sealed, heated to a maximum of 150°C, and pressurized to 0.4 MPa to 0.6 MPa. The reaction is allowed to proceed for 6 to 18 hours. After the reaction, the reaction product is filtered and processed into a sterile aqueous solution and organic solids. However, this technology still has the following shortcomings: firstly, the use of a strong alkali causes strong corrosion to the equipment under high temperature and high pressure conditions; secondly, it is difficult to effectively control the distribution of small peptides in the product during alkaline hydrolysis; and thirdly, the hydrolysis process places high demands on the temperature and pressure resistance of the equipment. Summary of the Invention

[0006] Therefore, this invention provides a method for preparing products from the alkaline hydrolysis of animal proteins, overcoming the problems of severe equipment corrosion, difficulty in controlling small peptide content, and harsh hydrolysis conditions in existing technologies. The method includes the following steps: Step S1: The animal raw materials are crushed in a closed crusher, and a first alkaline solution is added to the crusher during the crushing process to remove the odor gas released during the crushing process. The first alkaline solution is a weak alkaline solution that can neutralize nitrogen-containing and sulfur-containing odor gases. In step S2, the second alkaline solution is evenly sprayed onto the surface of the minced meat using a pumping spraying process. After being sheared and mixed evenly by a dual-shaft roller, it is pumped into a rendering tank, where sterilization and alkaline hydrolysis are simultaneously completed to obtain the first alkaline hydrolysate. The second alkaline solution is a weakly alkaline solution that can catalyze the hydrolysis of proteins. Step S3: The first alkaline hydrolysate is transferred to a storage tank in the storage plant area through a closed pipeline and a transfer tanker truck. Step S4: The first alkaline hydrolysate in the storage tank is pumped to the chemical treatment tank for secondary sterilization to obtain sterilized material; Step S5: The sterilized material undergoes solid-liquid separation to separate oil, second alkaline hydrolysate, and bone residue. In step S6, the oil is pumped to an oil storage tank for storage, the second alkaline hydrolysate is concentrated by a low-temperature waste heat concentration device to obtain a concentrated alkaline hydrolysate, the bone residue is ground to obtain bone powder, the concentrated alkaline hydrolysate and the bone powder are mixed, dried and packaged for storage to obtain a composite protein powder.

[0007] Further, in step S1, the crushing process includes: The process is carried out in a negative pressure closed environment, and the particles are crushed to a size of 20mm to 50mm.

[0008] Further, in step S1, the first alkaline solution is a sodium bicarbonate solution with a mass percentage concentration of 5% to 15%.

[0009] Further, in step S2, the alkaline solution is at least one of sodium bicarbonate and disodium hydrogen phosphate solution.

[0010] Further, in step S2, the alkaline solution is added at a ratio of 5% to 20% of the weight of the crushed material.

[0011] Further, in step S2, the sterilization and alkaline hydrolysis process includes: The temperature is raised to a core temperature greater than or equal to 160℃, the pressure is greater than or equal to 0.5MPa, and the holding time is greater than or equal to 0.5h.

[0012] Further, in step S3, the transfer includes: The cleaned, disinfected and dried transfer tanker is connected to the sealed pipeline at the discharge port of the chemical preparation tank. The residual pressure inside the chemical preparation tank is used to discharge the first alkaline solution under pressure into the transfer tanker through the sealed pipeline. After unloading, the tanker truck is sealed, and the first alkaline hydrolysate is transported in a sealed manner to the post-processing area. After the tanker truck arrives at the post-processing area, it connects to a sealed pipeline via a receiving interface, and the first alkaline hydrolysate is pumped into the storage tank through the sealed pipeline.

[0013] Furthermore, in step S4, the secondary sterilization involves heating to a center temperature of ≥180°C, applying a pressure of ≥0.6MPa, and holding for ≥0.5h.

[0014] Furthermore, in step S5, a three-phase horizontal screw discharge sedimentation centrifuge is used for solid-liquid separation.

[0015] Furthermore, in step S6, the solid content of the concentrated alkaline hydrolysate is 45% to 65%.

[0016] Compared with the prior art, the beneficial effects of the present invention are that, through the technical means of medium-strong alkali catalysis, two-stage temperature and pressure progression, fully closed aseptic transportation, solid-liquid mixing and grinding, and ultraviolet disinfection and storage, it solves the technical problems of existing strong alkali corrosion equipment, uncontrollable small peptide content, easy contamination during transportation, waste of bone residue resources, and single product form.

[0017] Furthermore, by using at least one of sodium bicarbonate or disodium hydrogen phosphate to replace traditional sodium hydroxide or potassium hydroxide as an alkaline hydrolysis catalyst, the technical problems of severe stress corrosion of equipment under high temperature and high pressure conditions, high equipment investment and maintenance costs, and strong alkali causing racemic destruction of most amino acids and affecting the nutritional integrity of the product are solved. This achieves the effect of significantly reducing the corrosion rate of equipment and protecting the nutritional integrity of the amino acids in the product.

[0018] Furthermore, by employing a two-stage temperature-pressure progressive hydrothermal technology, which involves simultaneous sterilization and alkaline hydrolysis at 160℃, 0.5MPa, and 0.5h in one stage, followed by secondary sterilization at 180℃, 0.6MPa, and 0.5h in the other stage, the technical problems of difficulty in precisely controlling the degree of protein hydrolysis, wide molecular weight distribution, and low content of small peptides in traditional alkaline hydrolysis processes have been solved, thus achieving controllable regulation of the molecular weight distribution of protein hydrolysis.

[0019] Furthermore, by grinding the bone residue after three-phase centrifugation into micron-sized bone powder using a colloid mill, and then mixing it with concentrated alkaline hydrolysate and drying it, the technical problems of traditional processes where bone residue is only treated as waste or used for low-value purposes, and the rich protein and calcium-phosphorus resources in bone residue are not fully utilized, are solved. This achieves the effect of increasing product yield and product protein content, and realizes the comprehensive recycling and utilization of animal protein resources.

[0020] Furthermore, by installing a disinfection device at the junction of the discharge pipe of the chemical treatment tank and the inlet pipe of the tank truck, and in conjunction with a fully enclosed aseptic transfer system that allows the tank truck to be transported directly through the disinfected pipeline without entering the factory, the technical problem of lack of aseptic guarantee and susceptibility to secondary contamination by pathogens or miscellaneous bacteria during the transfer process in traditional processes has been solved. This achieves the effect of a total bacterial count of <10 CFU / g after long-term storage, ensuring the long-term storage stability and biosafety of the product. Attached Figure Description

[0021] Figure 1 This is a flowchart of the steps in the preparation method of the animal protein alkaline hydrolysis product in this embodiment; Figure 2 This is a flowchart illustrating the steps of crushing and adding sodium bicarbonate solution in this embodiment; Figure 3 This is a flowchart illustrating the steps of simultaneous alkaline hydrolysis and sterilization in this embodiment; Figure 4 This is a flowchart illustrating the pressurized unloading and closed transfer steps in this embodiment; Figure 5 This is a flowchart of the secondary sterilization steps in this embodiment; Figure 6 This is a flowchart of the solid-liquid separation steps in this embodiment; Figure 7This is a flowchart illustrating the steps for processing, packaging, and storing the solid-liquid separation product in this embodiment. Detailed Implementation

[0022] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0023] Please see Figure 1 The diagram shown is a flowchart of the steps for preparing the alkaline hydrolysis product of animal protein in this embodiment.

[0024] This invention provides a method for preparing products from alkaline hydrolysis of animal proteins, comprising: Step S1: Crush the animal raw materials into 20mm-50mm pieces in a closed crusher, and add 10% sodium bicarbonate solution into the crusher during the crushing process to neutralize or absorb the nitrogen-containing and sulfur-containing odorous gases released during the crushing process. Please see Figure 2 As shown, it is a flowchart of the steps of crushing and adding sodium bicarbonate solution in this embodiment.

[0025] In this embodiment, the specific process of step S1 includes: Step S11: Crush the animal raw materials into 20mm-50mm pieces in a closed crusher; Step S12: Add 10% sodium bicarbonate solution to the crusher during the crushing process to neutralize or absorb the nitrogen- and sulfur-containing odorous gases released during the crushing process.

[0026] Specifically, in step S1, the crushing process includes: The process is carried out in a negative pressure closed environment, and the particles are crushed to a size of 20mm to 50mm.

[0027] Understandably, the particle size of the crushed material directly determines the subsequent pumping efficiency and the uniformity of the alkaline hydrolysis reaction. If the particle size is less than 20 mm, the material is viscous and pasty, increasing pipeline transport resistance and pumping energy consumption. Furthermore, fine bone meal is prone to depositing and coking in the chemical processing tank, affecting heat transfer efficiency. If the particle size is greater than 50 mm, the mass transfer resistance of the alkaline hydrolysis solution penetrating into the fragments increases, preventing the proteins in the central part from fully contacting the alkaline solution, leading to uneven hydrolysis and a decrease in the yield of small peptides. This invention controls the material particle size to 20 mm–50 mm through biaxial shear crushing. This ensures both good slurry flowability for pumping through closed pipelines and sufficient specific surface area for the fragments to fully contact the alkaline solution, allowing the protein hydrolysis reaction to proceed uniformly and avoiding the problems of wall sticking and energy consumption caused by excessive crushing.

[0028] Specifically, in step S1, the first alkaline solution is a sodium bicarbonate solution with a mass percentage concentration of 5% to 15%.

[0029] In this embodiment, the first alkaline solution is a weakly alkaline solution capable of neutralizing nitrogen- and sulfur-containing odorous gases, with a pH value of 7.5 to 10.0 at 25°C.

[0030] It is understandable that the crushing of animal carcasses will produce a large amount of foul-smelling gases. Traditional processes usually use back-end collection and treatment, which has the problems of large equipment investment and high operating costs. However, this invention directly adds sodium bicarbonate solution to a closed crusher, and uses its weak alkalinity to neutralize acidic odor gases such as hydrogen sulfide and ammonia in situ, thereby achieving the effect of eliminating foul odors from the source and reducing the exhaust gas treatment load.

[0031] Please see Figure 3 This is a flowchart of the steps for simultaneous alkaline hydrolysis and sterilization in this embodiment; In this embodiment, the specific process of step S2 includes: Step S21: The second alkaline solution is uniformly sprayed onto the surface of 20mm-50mm minced meat using a pump spraying process, and then sheared and mixed evenly by a dual-shaft roller to obtain alkalized minced meat. The mass percentage concentration of the second alkaline solution is 5%-20%, and the amount of the second alkaline solution added is 5%-20% of the weight of the minced material. Step S22: The alkalized minced meat is pumped to the rendering tank through a closed pipeline, and the rendering tank is then sealed. Step S23: Heat the material to a center temperature ≥160℃ and a pressure ≥0.5MPa, and keep it warm for ≥0.5h. Simultaneously complete sterilization and alkaline hydrolysis in the chemical preparation tank to obtain the first alkaline hydrolysate. The content of small peptides below 3000Da in the first alkaline hydrolysate is 70%~90%.

[0032] Specifically, in step S2, the second alkaline solution is at least one of sodium bicarbonate and disodium hydrogen phosphate solution.

[0033] Understandably, in the field of alkaline hydrolysis for the harmless treatment of diseased and dead livestock and poultry, traditional processes typically use sodium hydroxide or potassium hydroxide as alkaline hydrolysis catalysts. While these can achieve effective protein hydrolysis, the severe corrosion of equipment by strong alkalis and the racemic destruction of amino acids at high temperatures remain technical bottlenecks restricting the industry's development. This invention replaces traditional soluble strong alkalis with sodium bicarbonate or disodium hydrogen phosphate (weak alkalis), utilizing their low free OH groups... - The high concentration or high temperature decomposition gas production characteristics significantly reduce the equipment corrosion rate while ensuring hydrolysis efficiency, and at the same time protect the nutritional integrity of amino acids, achieving efficient, mild and low-corrosion alkaline hydrolysis treatment.

[0034] Specifically, in step S2, the alkaline solution is added at a ratio of 5% to 20% of the weight of the crushed material.

[0035] In this embodiment, the mass percentage concentration of the second alkaline solution is 5%–20%, and 50–200 kg of alkaline solution is added per ton of crushed material, i.e., the amount of alkaline solution added is 5%–20% of the weight of the crushed material. It is uniformly sprayed onto the surface of the minced meat using a pumping and spraying process, and then pumped to the chemical treatment tank after being uniformly crushed and mixed by a biaxial roller shearing process. The concentration and amount of alkaline solution added are two key synergistic parameters affecting hydrolysis efficiency and product molecular weight distribution. The concentration of the alkaline solution determines the effective amount of alkali provided per unit volume of alkaline solution, while the amount added determines the total alkali supply in the material system. Together, they determine the total effective alkali in the system (i.e., alkali solute mass = solution mass × concentration). When the concentration is below 5%, even if the amount added reaches the upper limit (20%), the total amount of free hydroxide ions in the system is still insufficient to achieve efficient hydrolysis within 0.5 hours, and the content of small peptides below 3000 Da is difficult to reach more than 70%. When the concentration is above 20%, the viscosity of the alkaline solution increases, the uniformity of pumping and spraying decreases, and local over-alkali will exacerbate the racemic destruction of amino acids. When the amount added is less than 5%, the alkali solution cannot fully wet the surface of all materials, resulting in uneven hydrolysis and a large amount of residual large protein molecules. When the amount added is more than 20%, the excess alkali will over-catalyze the breaking of peptide bonds, causing small peptides to be further hydrolyzed into free amino acids. At the same time, it will increase the amount of acid required for subsequent neutralization and concentration energy consumption. Furthermore, the excess alkali will exacerbate the racemic destruction of amino acids at high temperatures.

[0036] This invention controls the concentration of the second alkaline solution by mass percentage at 5%–20% and the amount added at 5%–20% of the weight of the crushed material. Through synergistic optimization of these two aspects, it ensures sufficient effective alkali in the system for efficient protein hydrolysis while avoiding the negative effects of localized over-alkaliness or insufficient alkali. It maintains a small peptide content of 70%–90% below 3000 Da while maximizing the protection of the product's nutritional integrity. It is understood that in the alkaline hydrolysis process of animal protein, the amount of alkali added directly affects the molecular weight distribution and amino acid integrity of the hydrolysate. In existing technologies, the amount of sodium hydroxide added often lacks precise control, leading to a wide molecular weight distribution or severe amino acid damage. This invention, by precisely controlling the amount of alkali added at 5%–20% of the weight of the crushed material, achieves controllable molecular weight distribution and protection of amino acid nutritional integrity while ensuring efficient hydrolysis.

[0037] Specifically, in step S2, the sterilization and alkaline hydrolysis processes include: The temperature is raised to a core temperature greater than or equal to 160℃, the pressure is greater than or equal to 0.5MPa, and the holding time is greater than or equal to 0.5h.

[0038] Understandably, in the field of harmless treatment of diseased and dead animals, traditional processes typically involve separate steps of high-temperature sterilization and alkaline hydrolysis of proteins, resulting in large equipment investments, high energy consumption, and long production cycles. This invention, however, combines both processes in a single treatment tank, achieving sterilization and alkaline hydrolysis simultaneously under high temperature and high pressure. The high temperature denatures the proteins and degrades the nucleic acids of pathogens, achieving complete inactivation and sterilization. Simultaneously, the high-temperature hydrothermal environment enhances the nucleophilic attack of the alkaline solution on the peptide bonds of proteins. Hydroxide ions attack the carbonyl carbon in the peptide bonds, causing them to break, and the large protein molecules are gradually degraded into smaller peptides and free amino acids. The treatment can be completed within 0.5 hours, significantly shortening the process time and reducing energy consumption and equipment investment. Please see Figure 4 This is a flowchart of the pressurized unloading and closed transfer steps in this embodiment.

[0039] In this embodiment, the specific process of step S3 includes: Step S31: Connect the cleaned, disinfected and dried transfer tanker to the sealed pipeline at the outlet of the chemical preparation tank. Set a sterilization device at the joint between the tanker's inlet pipe and the sealed pipeline. Open the chemical preparation tank's outlet valve and use the residual pressure inside the tank to unload the first alkaline hydrolysate into the transfer tanker through the sealed pipeline. Sterilize the connection in real time during the unloading process. Step S32: After unloading, seal the tanker truck and transport the first alkaline hydrolysate to the post-processing area in a sealed manner. Step S33: After the tanker arrives at the post-processing area, it does not enter the area. Instead, it connects to a sealed pipeline through the receiving interface of the post-processing area. A sterilization device is installed at the connection point, and the first alkaline hydrolysate is pumped into a storage tank for temporary storage via the sterilization device.

[0040] Specifically, in step S3, the transfer includes: The cleaned, disinfected and dried transfer tanker is connected to the sealed pipeline at the discharge port of the chemical preparation tank. The residual pressure inside the chemical preparation tank is used to discharge the first alkaline solution under pressure into the transfer tanker through the sealed pipeline. After unloading, the tanker truck is sealed, and the first alkaline hydrolysate is transported in a sealed manner to the post-processing area. After the tanker truck arrives at the post-processing area, it connects to a sealed pipeline via a receiving interface, and the first alkaline hydrolysate is pumped into the storage tank through the sealed pipeline.

[0041] In this embodiment, the post-processing area is an independent region located at a different physical address from the harmless treatment center. Material transfer between this area and the harmless treatment center is carried out via tank trucks. The harmless treatment center and the post-processing area are independently set up. The harmless treatment center is used to complete crushing, alkaline hydrolysis, and primary sterilization operations, while the post-processing area is used to complete secondary sterilization, three-phase separation, and product post-processing operations.

[0042] Understandably, in the field of harmless treatment of dead animals, the sterilized materials in traditional processes are usually dried into solids and then transported to the post-processing area for resource utilization in an exposed manner via ordinary vehicles. During the transportation process, the materials are exposed to the plant environment, posing a risk of secondary contamination by pathogens. Furthermore, the materials need to be rehydrated in the post-processing area, resulting in energy waste. In contrast, this invention uses sterile tank trucks that have undergone washing, disinfection, and drying, combined with pressurized closed pipeline unloading and interface sterilization devices, to achieve fully closed and sterile transportation of alkaline hydrolysate in liquid form. This avoids the risk of contamination during transportation and saves the energy consumption of drying and rehydration.

[0043] Please see Figure 5 This is a flowchart of the secondary sterilization steps in this embodiment.

[0044] In this embodiment, the specific process of step S4 includes: Step S41: The first alkaline hydrolysate in the storage tank is pumped to the chemical preparation tank through a closed pipeline; Step S42: After sealing the chemical tank, heat the material to a center temperature ≥180℃ and a pressure ≥0.6MPa. Step S43, heat preservation time ≥ 0.5h, perform secondary sterilization to obtain sterilized material.

[0045] Specifically, in step S4, the secondary sterilization involves heating the material to a center temperature greater than or equal to 180°C, applying a pressure greater than or equal to 0.6 MPa, and holding the material for 0.5 hours.

[0046] Understandably, in the field of harmless treatment of dead animals, there is a potential risk of secondary contamination by pathogens during the transfer of materials from the harmless treatment center to the post-treatment area. Traditional processes often neglect aseptic protection during the transfer process or rely solely on end-product testing for indirect control. However, this invention performs secondary high-temperature and high-pressure sterilization on the transferred materials, using higher temperatures and pressures as a safety redundancy. This not only completely eliminates the risk of pathogen contamination that may be introduced during the transfer process, but also further promotes the deep hydrolysis of proteins and the disintegration of the material's tissue structure, providing dual protection for subsequent high-purity separation and the nutritional integrity of the product.

[0047] Please see Figure 6 This is a flowchart of the solid-liquid separation steps in this embodiment.

[0048] In this embodiment, the specific process of step S5 includes: Step S51: Pump the sterilized material into a three-phase horizontal centrifuge; Step S52: Start the three-phase horizontal centrifuge, control the rotation speed to 3000-4000 rpm, the separation factor to 2000-4000 g, and the separation temperature to 60-80℃ to carry out solid-liquid separation. Step S53: After separation, oil, second alkaline hydrolysate and bone residue are obtained respectively.

[0049] Specifically, in step S5, a three-phase horizontal screw discharge sedimentation centrifuge is used for solid-liquid separation.

[0050] Understandably, in the field of post-processing of animal protein alkaline hydrolysis products, the material after alkaline hydrolysis is a three-phase mixture of oil, water, and solid. Traditional processes usually only perform simple solid-liquid separation, and the separation of oil and alkaline hydrolysate is incomplete. A large amount of protein and oil remain in the bone residue, resulting in resource waste. However, this invention uses a three-phase horizontal centrifuge to complete the three-phase continuous separation in a centrifugal force field by utilizing density differences. This achieves high-purity classification and recovery of each component of oil, alkaline hydrolysate, and bone residue, providing a high-quality raw material guarantee for the industrial utilization of oil, the concentration of alkaline hydrolysate for fertilizer production, and the protein recovery of bone residue.

[0051] Please see Figure 7 This is a flowchart illustrating the steps for processing, packaging, and storing the solid-liquid separation products in this embodiment.

[0052] In this embodiment, the specific process of step S6 includes: Step S61: The separated grease is pumped into an oil storage tank for storage. The oil storage tank is equipped with a heating and heat preservation device to control the storage temperature at 50-70°C, so that the grease is kept in a liquid state for subsequent pumping and transfer. Step S62: The separated second alkaline hydrolysate is pumped to a low-temperature waste heat concentration device and concentrated at 45-65°C and a vacuum of -0.08 to -0.095 MPa until the solid content is 45%-65%, thus obtaining a concentrated alkaline hydrolysate. Step S63: The separated bone fragments are ground in a colloid mill until the fineness is ≤200μm to obtain bone powder; Step S64: The concentrated alkaline hydrolysate and the bone powder are mixed at a mass ratio of 1:0.2 to 0.5. The mixture is dried at low temperature until the moisture content is ≤10%. After packaging, it is stored in a storage workshop equipped with an ultraviolet sterilization device to obtain composite protein powder.

[0053] Specifically, in step S6, the solid content of the concentrated alkaline hydrolysate is 45% to 65%.

[0054] Understandably, in the field of alkaline hydrolysate concentration, traditional processes use high-temperature evaporation concentration, which can quickly dehydrate, but the high temperature will seriously damage the nutritional value of small peptides and heat-sensitive amino acids. However, this invention utilizes low-temperature residual heat to vacuum concentrate to 45%-65% solid content at 45-65℃, which not only protects the nutritional integrity of the product, but also reduces the storage and transportation volume and subsequent drying energy consumption, achieving the dual goals of saving energy and ensuring activity.

[0055] Example 1

[0056] This embodiment provides a method for preparing alkaline hydrolysate of animal protein, the specific steps of which are as follows: Step S1: The collected diseased and dead livestock raw materials are weighed and transported to the crusher. They are crushed into meat pieces of 2-5 cm in a closed environment under negative pressure. During the crushing process, a sodium bicarbonate solution with a mass percentage concentration of 10% is added to the crusher. The amount added is 5% of the weight of the crushed material to neutralize or absorb the nitrogen-containing and sulfur-containing odorous gases released during the crushing process.

[0057] In step S2, a 10% sodium bicarbonate solution (by weight) is uniformly sprayed onto the surface of the minced meat using a pump-spraying process. The amount added is 10% of the weight of the minced material. The mixture is then uniformly crushed and mixed using a dual-shaft roller shearing system. The mixed material is pumped to a processing tank via a closed pipeline. The processing tank is then sealed, and the stirring device is activated. A circulating heat source is introduced through the jacket to raise the material to a core temperature of not less than 160℃ and a pressure of not less than 0.5MPa. The temperature is maintained for 2 hours. Sterilization and alkaline hydrolysis are simultaneously completed in the processing tank, yielding the first alkaline hydrolysate. No meat shreds appear in the solution after alkaline hydrolysis.

[0058] Step S3: After sterilization, the first alkaline hydrolysate is unloaded under pressure through a closed pipeline into a transfer tanker. The tanker is cleaned, disinfected, and dried before transfer. A sterilization device is installed at the connection between the tanker's inlet pipe and the closed pipeline; the connection is sterilized in real-time during unloading. After being transported to the post-processing area in a sealed manner, the tanker does not enter the area. Instead, it connects to the closed pipeline via a receiving interface, and the first alkaline hydrolysate is pumped through the sterilization device into a storage tank for temporary storage.

[0059] Step S4: The first alkaline solution in the storage tank is pumped to the chemical treatment tank through a closed pipeline. After the chemical treatment tank is sealed, it is heated to a temperature of not less than 180°C and a pressure of not less than 0.6 MPa at the center of the material, and the temperature is maintained for 1 hour for secondary sterilization to obtain sterilized material.

[0060] Step S5: The sterilized material is pumped into a three-phase horizontal centrifuge for solid-liquid separation. The three-phase horizontal centrifuge has a rotation speed of 3000-4000 rpm, a separation factor of 2000-4000 g, and a separation temperature of 60-80℃. After separation, oil, second alkaline hydrolysate, and bone residue are obtained respectively.

[0061] Step S6: The oil is pumped into a storage tank equipped with a heating and insulation device to control the storage temperature at 50–70°C. The second alkaline hydrolysate is pumped into a low-temperature waste heat concentration device, where it is concentrated to a solid content of 55% using waste heat resources at 45–65°C and -0.08–-0.095 MPa, yielding a concentrated alkaline hydrolysate. The bone residue is ground in a colloid mill to a fineness ≤200 μm to obtain bone powder. The concentrated alkaline hydrolysate and bone powder are thoroughly mixed in a mixer at a mass ratio of 1:0.2–0.5. The mixture is then dried at low temperature to a moisture content ≤10%, packaged and stored in a workshop equipped with an ultraviolet sterilization device to obtain composite protein powder.

[0062] Example 2: The difference between this example and Example 1 is that the heat preservation time in step S2 is 4 hours, while the other steps and parameters are the same as in Example 1.

[0063] Example 3: The difference between this example and Example 1 is that the amount of sodium bicarbonate solution added in step S1 is 20% of the weight of the crushed material, which is twice the amount of sodium bicarbonate added in Example 1; the heat preservation time in step S2 is 2 hours, and the remaining steps and parameters are the same as in Example 1.

[0064] Example 4: The difference between this example and Example 1 is that the amount of sodium bicarbonate solution added in step S1 is 20% of the weight of the crushed material, which is twice the amount of sodium bicarbonate added in Example 1; the heat preservation time in step S2 is 4 hours, and the remaining steps and parameters are the same as in Example 1.

[0065] Comparative Example 1: The difference between this comparative example and Example 1 is that sodium bicarbonate solution is not added in step S1, while the remaining steps and parameters are the same as in Example 1.

[0066] Comparative Example 2: The difference between this comparative example and Example 2 is that sodium bicarbonate solution is not added in step S1, while the remaining steps and parameters are the same as in Example 2.

[0067] Comparative Example 3: The difference between this comparative example and Example 3 is that sodium bicarbonate solution is not added in step S1, while the remaining steps and parameters are the same as in Example 3.

[0068] Comparative Example 4: The difference between this comparative example and Example 4 is that sodium bicarbonate solution is not added in step S1, while the remaining steps and parameters are the same as in Example 4.

[0069] The alkaline hydrolysis products prepared in Examples 1-4 and Comparative Examples 1-4 were tested respectively. The test results are shown in Table 1, which is a data table of test results of alkaline hydrolysis products under different process conditions.

[0070] In this embodiment, the determination methods for each detection item are as follows: Crude protein content was determined using the Kjeldahl method. Small peptide content was determined using the trichloroacetic acid precipitation method: the alkaline hydrolysate sample was mixed with an equal volume of 15% trichloroacetic acid, allowed to stand for 10 minutes, centrifuged at 12000g for 15 minutes, and the supernatant was used to determine the soluble nitrogen content using the Kjeldahl method. Small peptide (as a percentage of crude protein) = soluble nitrogen content / total nitrogen content × 100%. Molecular weight distribution was determined using gel permeation chromatography (GPC), with peptide molecular weight standards as a reference, and the peak area percentages of components below 3000 Da and above 10000 Da were calculated respectively.

[0071] Table 1: Detection results of alkaline hydrolysis products under different process conditions

[0072] Note: 1) "Small peptides (percentage of crude protein)" is the percentage of soluble nitrogen in the total crude protein, determined by the trichloroacetic acid precipitation method, reflecting the content of small molecule peptides that can be directly absorbed by plants; "Percentage below 3000 Da (%)" and "Percentage above 10000 Da (%)" are the peak area percentages determined by gel permeation chromatography, reflecting the distribution ratio of peptides in specific molecular weight ranges in the total peptides. The different detection methods and metrological standards of the two methods are normal.

[0073] 2) Although no alkali was added in Comparative Examples 1 to 4, under hydrothermal conditions of high temperature and high pressure (160℃ / 0.5MPa / 2h or 4h), the endogenous protease in animal tissues and the synergistic effect of thermo-pressure could still promote the degradation of some proteins into small peptides. Therefore, the content of small peptides was about 10% to 14%, but this value was significantly lower than that of the examples with added alkali (54% to 90%), indicating that the present invention significantly promoted the deep hydrolysis of proteins through alkali catalysis.

[0074] Compared with Comparative Examples 1 to 4, which did not add alkaline solution, the content of small peptides in their products was only 10.91% to 14.55%, and the proportion of small peptides below 3000 Da was only 8.10% to 9.30%. Moreover, the residual amount of large molecular proteins above 10000 Da was as high as 25.93% to 33.94%, indicating that the degree of protein hydrolysis was extremely low when no alkali was added, and most of the protein still existed in the form of large molecules.

[0075] The peptide content in Example 1 was 54.61%, while in Example 2 it increased to 73.34%, a 34.3% increase compared to Example 1. The peptide content in Example 3 was 65.13%, and in Example 4 it increased to 90.96%, a 39.7% increase compared to Example 3. This indicates that, under the same alkali addition conditions, appropriately extending the incubation time can significantly increase the peptide content.

[0076] Under alkaline hydrolysis conditions of 2 hours, the peptide content in Example 1 was 54.61%, and the peptide content in Example 3 was 65.13%, representing an increase of 19.3% compared to Example 1. Under alkaline hydrolysis conditions of 4 hours, the peptide content in Example 2 was 73.34%, and the peptide content in Example 4 was 90.96%, representing an increase of 24.0% compared to Example 2. This indicates that under the same incubation time, appropriately increasing the amount of alkali can significantly promote protein hydrolysis.

[0077] The small peptide content of Examples 1-4 is 54.61%-90.96%, which is much higher than that of Comparative Examples 1-4 (10.91%-14.55%). This indicates that the present invention uses sodium bicarbonate as an alkaline hydrolysant, which effectively protects the nutritional integrity of the protein while achieving efficient hydrolysis. The product is rich in small peptides and free amino acids, and can be directly used as a high-quality organic nitrogen source for agricultural production.

[0078] In summary, this invention achieves highly efficient hydrolysis of diseased and dead livestock and poultry protein under mild hydrolysis conditions by using sodium bicarbonate instead of traditional strong alkali, combined with simultaneous sterilization alkaline hydrolysis, fully enclosed aseptic transport, and secondary sterilization. The product has a high content of small peptides, controllable molecular weight distribution, and good amino acid nutritional integrity. Moreover, the entire process is carried out in a closed and sterile environment, effectively solving the technical problems of strong alkali corrosion of equipment, racemic destruction of amino acids, uncontrollable product molecular weight, and easy contamination during transport in traditional alkaline hydrolysis processes.

[0079] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for preparing products from alkaline hydrolysis of animal protein, characterized in that, Includes the following steps: Step S1: The animal raw materials are crushed in a closed crusher, and a first alkaline solution is added to the crusher during the crushing process to neutralize the nitrogen-containing and sulfur-containing odor gases released during the crushing process. The first alkaline solution is a weak alkaline solution that can neutralize the nitrogen-containing and sulfur-containing odor gases. Step S2: The second alkaline solution is evenly sprayed onto the surface of the minced meat using a pumping spraying process to catalyze protein hydrolysis. After being uniformly mixed by a dual-axis roller shearing process, it is pumped to a rendering tank where sterilization and alkaline hydrolysis are completed simultaneously to obtain the first alkaline hydrolysate. The second alkaline solution is a weakly alkaline solution that can catalyze protein hydrolysis. Step S3: The first alkaline hydrolysate is transferred to a storage tank in the post-processing area through a closed pipeline and a transfer tanker truck. Step S4: The first alkaline hydrolysate in the storage tank is pumped to the chemical treatment tank for secondary sterilization to obtain sterilized material; Step S5: The sterilized material undergoes solid-liquid separation to separate oil, second alkaline hydrolysate, and bone residue. In step S6, the oil is pumped to an oil storage tank for storage, the second alkaline hydrolysate is concentrated by a low-temperature waste heat concentration device to obtain a concentrated alkaline hydrolysate, the bone residue is ground to obtain bone powder, the concentrated alkaline hydrolysate and the bone powder are mixed, dried and packaged for storage to obtain a composite protein powder.

2. The method for preparing the product of alkaline hydrolysis of animal protein according to claim 1, characterized in that, In step S1, the crushing process includes: The process is carried out in a negative pressure closed environment, and the particles are crushed to a size of 20mm to 50mm.

3. The method for preparing the product of alkaline hydrolysis of animal protein according to claim 2, characterized in that, In step S1, the first alkaline solution is a sodium bicarbonate solution with a mass percentage concentration of 5% to 15%.

4. The method for preparing the product of alkaline hydrolysis of animal protein according to claim 3, characterized in that, In step S2, the second alkaline solution is at least one of sodium bicarbonate and disodium hydrogen phosphate solution.

5. The method for preparing the product of alkaline hydrolysis of animal protein according to claim 4, characterized in that, In step S2, the second alkaline solution is added at a ratio of 5% to 20% of the weight of the crushed material.

6. The method for preparing the product of alkaline hydrolysis of animal protein according to claim 5, characterized in that, In step S2, the sterilization and alkaline hydrolysis processes include: The temperature is raised to a core temperature greater than or equal to 160℃, the pressure is greater than or equal to 0.5MPa, and the holding time is greater than or equal to 0.5h.

7. The method for preparing the product of alkaline hydrolysis of animal protein according to claim 6, characterized in that, In step S3, the transfer includes: The cleaned, disinfected and dried transfer tanker is connected to the sealed pipeline at the discharge port of the chemical preparation tank. The residual pressure inside the chemical preparation tank is used to discharge the first alkaline solution under pressure into the transfer tanker through the sealed pipeline. After unloading, the tanker truck is sealed, and the first alkaline hydrolysate is transported in a sealed manner to the post-processing area. After the tanker truck arrives at the post-processing area, it connects to a sealed pipeline via a receiving interface, and the first alkaline hydrolysate is pumped into the storage tank through the sealed pipeline.

8. The method for preparing the product of alkaline hydrolysis of animal protein according to claim 7, characterized in that, In step S4, the secondary sterilization involves heating the material to a center temperature greater than or equal to 180°C, applying a pressure greater than or equal to 0.6 MPa, and holding the material for 0.5 hours.

9. The method for preparing the product of alkaline hydrolysis of animal protein according to claim 8, characterized in that, In step S5, a three-phase horizontal screw discharge sedimentation centrifuge is used for solid-liquid separation.

10. The method for preparing the product of alkaline hydrolysis of animal protein according to claim 9, characterized in that, In step S6, the solid content of the concentrated alkaline hydrolysate is 45% to 65%.

Images