A method for preparing an animal protein acid hydrolysis product

Abstract

The present application relates to animal protein resource utilization technical field, especially to a kind of preparation method of animal protein acid hydrolysis product, comprising: animal raw material is broken;Spray acid solution and mix after pumping into preparation tank, sterilization and acid hydrolysis are completed simultaneously, obtain first acid hydrolysate;Pressure unloading to washing and disinfecting drying tank truck, interface is equipped with disinfection device, tank truck does not enter factory, after disinfection, pump to storage tank;Pump into preparation tank for secondary sterilization;Oil and fat, second acid hydrolysate and bone residue are separated by three-phase centrifugation;Oil and fat is stored, second acid hydrolysate is concentrated, bone residue is ground, after mixing concentrated acid hydrolysate and bone powder, dry, package, obtain composite protein powder.The present application uses weak acid instead of strong acid, combined with two-stage temperature-pressure sterilization acidolysis and whole-process closed sterile transport, realizes the efficient hydrolysis of protein and the controllable regulation of molecular weight distribution.

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 animal protein acid hydrolysis. Background Technology

[0002] Currently, methods for the harmless disposal of diseased and dead livestock and poultry include incineration, rendering, deep burial, and sulfuric acid decomposition. Among these, sulfuric acid 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. The processed products, such as amino acids, can be used in agricultural production, and the oils are used for industrial purposes and are not used as raw materials for food production.

[0003] However, existing technologies for the harmless treatment of diseased and dead livestock and poultry still have many shortcomings: I. In conventional acidolysis processes, concentrated sulfuric acid is used as an acidifying agent. It is a strong acid that is highly corrosive to equipment and difficult to remove from materials. Second, in the existing sulfuric acid decomposition process, proteins are usually hydrolyzed into free amino acids, making it difficult to effectively control the content distribution of small peptides (molecular weight below 3000 Da); Third, in existing technologies, the high-temperature sterilization and protein acid hydrolysis of dead animals are often carried out in separate steps, which involves large investment, high energy consumption, and long production cycles.

[0004] Chinese invention patent CN103804032A, published on May 21, 2014, discloses a liquid amino acid complex produced from the protein of diseased and dead pigs and its application. The method uses lean meat from diseased and dead pigs as raw material, which is crushed and then acid-hydrolyzed with sulfuric acid. After acid hydrolysis, the liquid amino acid complex is obtained through further processing and can be diluted for foliar spraying as a liquid agricultural amino acid fertilizer. However, this technology still has the following shortcomings: First, the use of sulfuric acid as an acid hydrolysis catalyst is corrosive to the equipment, resulting in high equipment investment and maintenance costs; second, the acid hydrolysis products are mainly free amino acids with relatively low small peptide content, making it difficult to precisely control the molecular weight distribution; third, only the liquid amino acid component is recovered after acid hydrolysis, failing to fully utilize the protein and mineral resources in solid components such as bone residue; and fourth, the lack of fully enclosed and sterile protection measures during acid hydrolysis and transportation exposes the material to the environment, making it susceptible to contamination by other microorganisms. Summary of the Invention

[0005] Therefore, this invention provides a method for preparing products from the acid hydrolysis of animal proteins, overcoming the problems of strong acid corrosion of equipment, low content of small peptides, waste of bone residue resources, and insufficient aseptic protection during transportation in the prior art, comprising the following steps: Step S1: Crush the animal raw materials in a closed crusher; Step S2: The acid solution is evenly sprayed onto the surface of the minced meat using a pumping spraying process. After being evenly mixed by a dual-shaft roller shearing process, it is pumped into a melting tank. Sterilization and acid hydrolysis are completed simultaneously in the melting tank to obtain the first acid hydrolysate. Step S3: The first acid 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 acid 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 acid hydrolysate and bone residue; In step S6, the oil is pumped to an oil storage tank for storage, the second acid hydrolysate is concentrated by a low-temperature waste heat concentration device to obtain a concentrated acid hydrolysate, the bone residue is ground to obtain bone powder, the concentrated acid hydrolysate and the bone powder are mixed, dried and packaged for storage to obtain a composite protein powder.

[0006] Further, in step S1, the crushing process includes: The process is carried out in a negative pressure closed environment, crushing the particles to a size of 20mm to 50mm. The odorous gases generated during the crushing process are collected through a gas collection pipeline and then disposed of.

[0007] Further, in step S2, the acid solution is at least one of acetic acid, formic acid, and citric acid.

[0008] Further, in step S2, the acid solution is added at a rate of 0.14 mg / ton of crushed material. 3 Add in the appropriate proportion.

[0009] Further, in step S2, the sterilization and acid 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.

[0010] Furthermore, in step S3, the transfer is carried out using a sealed tanker truck. The tanker truck is cleaned, disinfected, and dried before the transfer. The first acid hydrolysate is unloaded under pressure into the tanker truck and then pumped to the storage tank.

[0011] Furthermore, disinfection devices are installed at the feed pipe head and pressurized unloading pipe head of the tanker truck.

[0012] 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.

[0013] Furthermore, in step S5, a three-phase horizontal screw discharge sedimentation centrifuge is used for solid-liquid separation.

[0014] Furthermore, in step S6, the solid content of the concentrated acid hydrolysate is 45% to 65%.

[0015] Compared with the prior art, the beneficial effects of the present invention are that, through the technical means of medium-strong acid catalysis, two-stage temperature and pressure progression, fully enclosed aseptic transport, solid-liquid mixing and grinding, and ultraviolet disinfection and storage, it solves the technical problems of existing strong acid corrosion equipment, uncontrollable small peptide content, easy contamination during transport, waste of bone residue resources, and single product form.

[0016] Furthermore, by using acetic acid with a mass percentage concentration of 30% instead of the traditional 98% concentrated sulfuric acid as the acidolysis catalyst, the technical problems of severe equipment corrosion caused by strong acids, high equipment investment and maintenance costs, and strong acids damaging specific amino acid chain segments such as tryptophan were solved, achieving the effect of significantly reducing the equipment corrosion rate and protecting the nutritional integrity of the product.

[0017] Furthermore, by employing a two-stage temperature-pressure progressive hydrothermal technology, which involves simultaneous sterilization and acid 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 acid hydrolysis processes have been solved, thus achieving controllable regulation of the molecular weight distribution of protein hydrolysis.

[0018] 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 acid 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 and phosphorus resources in bone residue are not fully utilized, have been solved. This has achieved the effect of increasing product yield and product protein content, and realized the full-value utilization of animal protein resources. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the steps of the preparation method of the animal protein acid hydrolysis product in this embodiment.

[0020] Figure 2 This is a bar chart comparing the content of small peptides in the product under different acid addition amounts and hydrolysis times in this embodiment.

[0021] Figure 3 The bar chart shows the molecular weight distribution of the products from Examples 4-4 (acid addition amount 2A, hydrolysis time 4h).

[0022] Figure 4 This is a schematic diagram of the equipment connection for the preparation method of animal protein acid hydrolysis products in this embodiment. Detailed Implementation

[0023] 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.

[0024] Please see Figure 1 As shown, it is a flowchart of the steps of the method for preparing animal protein acid hydrolysis products in this embodiment.

[0025] The present invention provides a method for preparing acid hydrolysates of animal proteins, comprising: Step S1: Crush the animal raw materials into 2cm-5cm pieces in a closed crusher; the animal raw materials are animals and their products infected with diseases as stipulated by the state, carcasses of animals that died of disease or with unknown causes, animals confirmed to be diseased before slaughter, animal products confirmed to be inedible during the slaughter process by quarantine or meat quality inspection, and other animals and animal products that should be harmlessly treated. It shall not include animals, products and tissues infected with anthrax or other spore-forming diseases, as well as bovine spongiform encephalopathy and scrapie.

[0026] Specifically, in step S1, the crushing process includes: The process is carried out in a negative pressure closed environment, crushing the particles to a size of 20mm to 50mm. The odorous gases generated during the crushing process are collected through a gas collection pipeline and then disposed of.

[0027] In this embodiment, the crusher adopts a fully enclosed structural design with an automatically opening and closing hydraulic top cover. An internal fan maintains a slight negative pressure of -50Pa to -100Pa, effectively preventing the escape of ammonia- and sulfur-containing odorous gases generated during the crushing process. The crusher's dual-shaft shearing rollers cut animal raw materials into meat scraps with a particle size of 20mm to 50mm, reducing the whole animal carcass to pumpable meat scraps. This facilitates material transport in pipelines and feeding into subsequent processes. This particle size range ensures the flowability of the material in subsequent pumping processes while avoiding excessive blood separation and increased energy consumption caused by overly fine grinding. The malodorous gas generated by crushing is drawn in by negative pressure through the gas collection pipe at the top of the crusher and sent to the waste gas treatment system of acid spray + alkali spray + photo-oxidation deodorization for purification. The spray liquid reacts with the malodor molecules in an acid-alkali neutralization reaction, converting pollutants such as NH3 and H2S into salts and water. The photo-oxidation unit breaks the chemical bonds of the malodor molecules with high-energy UV beams and uses ozone to oxidize them into CO2 and H2O, achieving emission standards.

[0028] Understandably, the particle size of the crushed material directly determines the subsequent pumping efficiency and the uniformity of the acid 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 acid hydrolysis solution penetrating into the fragments increases, preventing the proteins in the central part from fully contacting the acetic acid, 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 that the slurry has good fluidity for pumping through closed pipelines, while also ensuring that the fragments have sufficient specific surface area to fully contact the acid solution, allowing the protein hydrolysis reaction to proceed uniformly and avoiding the problems of wall sticking and energy consumption caused by excessive crushing.

[0029] To verify the beneficial effect of crushing particles in the range of 20mm to 50mm in step S1, animal carcasses from the same batch with similar weights were selected as experimental materials and randomly divided into 5 groups, each weighing 50kg. A biaxial shear crusher was used for crushing. By adjusting the aperture of the crusher's discharge screen, materials of the target particle size were obtained. After crushing, the material morphology, bulk density, angle of repose, and pumping power were measured. The appearance of each group of materials was visually observed and recorded after crushing. The materials were naturally filled into a 1L graduated cylinder, the surface was leveled, and the weight of the materials was measured to calculate the bulk density (kg / L). The injection method was used to measure the material. The material was allowed to fall freely from a funnel onto a horizontal platform to form a cone. The angle (°) between the inclined plane of the cone and the horizontal plane was measured; a smaller angle of repose indicates better flowability. A variable frequency screw pump was used to pump the material 10m (DN80 diameter) through a closed pipeline at the same speed, and the pumping unit energy consumption (kWh / t) was recorded. The results are shown in Table 1, which is a comparison table of material morphology and flowability parameters under different crushing particle sizes.

[0030] Table 1: Comparison of material morphology and flowability parameters under different crushed particle sizes

[0031] When the crushed particle size is 10mm, the material is excessively fined, resulting in a large amount of blood separation, a viscous paste-like consistency, a bulk density as high as 0.78kg / L, an angle of repose of 58°, and a pumping energy consumption as high as 8.2kWh / t, making pipeline transportation difficult. When the crushed particle size is 60mm, the material is mainly in block form with a low bulk density (0.52kg / L). Although the flowability is still acceptable, the fragments are too large, which is not conducive to the uniform adhesion and mixing of the acid solution in the subsequent spraying process.

[0032] This invention controls the crushed particle size within the range of 20mm to 50mm, the material is in the form of loose granules, the bulk density is 0.55 to 0.62 kg / L, the angle of repose is 35 to 42°, and the pumping energy consumption is only 4.0 to 4.8 kWh / t.

[0033] When the crushed particle size is 10mm, the material is too fine, resulting in a viscous paste-like consistency and making pumping difficult; when the particle size is 60mm, the fragments are too large, which is not conducive to subsequent mixing processes. This invention controls the crushed particle size to be between 20mm and 50mm, which ensures that the material has good flowability as loose granules, as well as suitable bulk density and low pumping energy consumption, providing a material basis for the uniform spraying and mixing of acid solution in the subsequent process.

[0034] In step S2, a solution of at least one of acetic acid, formic acid, and citric acid with a mass percentage concentration of 30% is uniformly sprayed onto the surface of the minced meat using a pump spraying process. After being uniformly mixed by biaxial roller shearing, the solution is pumped into a rendering tank. Through shearing and extrusion, the acid solution fully penetrates the internal tissue of the minced meat, ensuring uniform contact between the acid and protein at the molecular level, laying the foundation for the subsequent hydrolysis reaction in the rendering tank. The rendering tank is then sealed and heated to a core temperature ≥160℃ and a pressure ≥0.5MPa, and held at this temperature for ≥0.5h. Sterilization and acid hydrolysis are simultaneously completed in the rendering tank. After acid hydrolysis, the content of 3000Da small peptides in the solution can reach up to 91.4%, yielding the first acid hydrolysate. Specifically, in step S2, the acid solution is at least one of acetic acid, formic acid, and citric acid.

[0035] Understandably, traditional acid hydrolysis processes use 98% concentrated sulfuric acid as a catalyst, which severely corrodes equipment and the strong acid environment easily damages specific amino acid segments in proteins, affecting the nutritional integrity of the product. This invention uses organic acids such as acetic acid, formic acid, or citric acid instead of concentrated sulfuric acid. While maintaining the catalytic hydrolysis effect, it significantly reduces the risk of equipment corrosion. Furthermore, the organic acids can evaporate with the moisture during the subsequent drying process, leaving no strong acid residue in the final product and ensuring the safety of the product's application.

[0036] To verify the beneficial effects of using acetic acid, formic acid, or citric acid as an acidolysis catalyst in step S2, the following experiment was conducted; each group added 0.14 mg / ton of crushed material. 3 An acid solution (acetic acid / formic acid / citric acid / concentrated sulfuric acid) was used. The temperature and pressure conditions were: core temperature 160℃, pressure 0.5MPa, and holding time 0.5h. Meat pieces of the same batch, crushed to 20mm-50mm, were collected in groups of 50kg. The 3000Da small peptide content was determined by gel permeation chromatography (GPC). The corrosion rate of the equipment (material: 316L stainless steel, temperature 160℃, time 72h) was determined by the plate loss method. The results are shown in Table 2, which compares the hydrolysis effect and equipment corrosion under different acidifying agents.

[0037] Table 2. Comparison of hydrolysis effects and equipment corrosion under different acidifying agents.

[0038] Table 2 shows that the small peptide content in Example 2-1 was 91.4%, the highest among the four groups; in Example 2-2 it was 86.3%, slightly lower than the 88.2% in Comparative Example 2-1; and in Example 2-3 it was 83.1%, the lowest among the four groups. All three organic acids could hydrolyze proteins into small peptide fragments, with acetic acid showing the best hydrolytic effect, superior to concentrated sulfuric acid; formic acid and citric acid, although slightly less effective than concentrated sulfuric acid, still possessed good hydrolytic capabilities.

[0039] The corrosion rates of Examples 2-1 to 2-3 were only 0.10 to 0.22 mm / a, while the corrosion rate of Comparative Example 2-1 was as high as 1.20 mm / a, which is 5 to 12 times that of organic acids. This indicates that organic acids are almost non-corrosive to equipment, while concentrated sulfuric acid is severely corrosive to 316L stainless steel under the same conditions, requiring frequent equipment replacements for long-term use, significantly increasing equipment investment and maintenance costs. Concentrated sulfuric acid is far more corrosive to metallic materials than organic acids under high temperature and pressure conditions. At high temperatures, it reacts with metals to form sulfates and release corrosive gases, while organic acids have extremely weak corrosiveness to stainless steel. None of the three organic acids left a pungent odor after drying. Formic acid, although having a slight acidic smell during drying, completely evaporated after drying, while concentrated sulfuric acid remained in the final product, potentially affecting product quality.

[0040] Therefore, when acetic acid, formic acid, or citric acid is used as the acidolysis catalyst, effective protein hydrolysis can be achieved while maintaining an extremely low equipment corrosion rate, significantly superior to concentrated sulfuric acid. Acetic acid performs best in balancing small peptide content and low corrosion rate, while formic acid and citric acid also demonstrate industrial feasibility. This indicates that the present invention, by using organic acids instead of concentrated sulfuric acid as the acidolysis catalyst, effectively solves the technical problem of strong acid corrosion of equipment in existing technologies, significantly reducing equipment maintenance costs while maintaining excellent hydrolysis performance, and has promising prospects for industrial application.

[0041] Specifically, in step S2, the acid solution is added at a rate of 0.14 mg / ton of crushed material. 3 Add in the appropriate proportion.

[0042] In this embodiment, taking a 30% acetic acid solution as an example, 0.14 mg is added per ton of crushed material. 3 The acid solution is evenly sprayed onto the surface of the minced meat through atomizing nozzles at the top of the chemical treatment tank using a pumping and spraying process. It is then uniformly mixed by a dual-shaft roller shearing system, ensuring thorough contact and even distribution between the acid solution and the material. This ratio of acid solution ensures the acidic environment required for the hydrolysis reaction while avoiding the adverse effects of excessive acid on subsequent processes.

[0043] Understandably, if the amount of acid solution added is too small, the hydrogen ion concentration will be insufficient to effectively catalyze the breaking of protein peptide bonds, leading to incomplete hydrolysis and a decrease in the yield of small peptides. Conversely, if the amount of acid solution added is too large, it will not only increase acid consumption costs but may also lead to excessive hydrolysis, causing some small peptides to further degrade into free amino acids, while simultaneously increasing the acid volatilization burden during subsequent drying. This invention controls the amount of acid solution added to 0.14 mg per ton of crushed material. 3 This method ensures efficient protein hydrolysis while avoiding resource waste and over-hydrolysis, and achieves precise control over the amount of acid used.

[0044] Specifically, in step S2, the sterilization and acid 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.

[0045] In this embodiment, the sterilization and acid hydrolysis processes are carried out in a closed treatment tank. A jacketed steam heating method is used, and the treatment tank is heated to a core temperature ≥160℃ and a pressure ≥0.5MPa via a PLC control system, and held at this temperature for ≥0.5 hours. Under these temperature and pressure conditions, the high-temperature saturated steam causes irreversible denaturation of the proteins and nucleic acids of pathogenic microorganisms in the material, achieving complete inactivation; simultaneously, acetic acid releases hydrogen ions under high-temperature hydrothermal conditions. This process catalyzes the breaking of peptide bonds in proteins, causing large protein molecules to gradually degrade into smaller peptides and amino acids. The chemical reaction tank is equipped with a stirring device (30-50 rpm) to ensure uniform heating of the material, avoid localized overheating or coking, and ensure the consistency of the hydrolysis reaction.

[0046] Understandably, traditional chemical treatment methods only complete sterilization before discharging the material, while protein hydrolysis requires a separate acid hydrolysis tank, resulting in a lengthy and energy-intensive process. This invention utilizes the chemical treatment tank's temperature of 160℃ / 0.5MPa, which provides sufficient thermal energy to drive the acetic acid-catalyzed hydrolysis reaction, allowing sterilization and acid hydrolysis to be completed simultaneously within the same container. This simplifies the process in terms of both equipment investment and production cycle.

[0047] To verify the beneficial effects of step S2, which involves sealing the chemical treatment tank, heating it to a core temperature ≥160℃, a pressure ≥0.5MPa, and holding it at that temperature for ≥0.5h, different acid hydrolysis and sterilization conditions were set up. 50kg of the same batch of minced meat, crushed to 20mm–50mm, was pumped into the chemical treatment tanks. Each group received 0.14m³ of acid hydrolysis solution per ton of crushed material. 3The proportion of acetic acid solution with a mass percentage concentration of 30% was uniformly sprayed onto the surface of the minced meat using a pump spraying process, and then mixed evenly by biaxial roller shearing. Each group underwent processing in a rendering tank according to the temperature, pressure, and holding time specified in the table. After processing, samples were collected from the outlet of the rendering tank, and the total bacterial count (CFU / g) in the material was determined using the plate count method. After acid hydrolysis, the material samples were taken, allowed to stand for 30 minutes, and then the upper layer of oil was separated. The weight of the oil was weighed, and the oil extraction rate (%) was calculated as (weight of extracted oil / total lipid content of the material) × 100%. The results are shown in Table 3, which compares the sterilization and oil extraction rates under different rendering temperature and pressure conditions.

[0048] Table 3: Comparison of sterilization and oil extraction rates under different processing temperature and pressure conditions.

[0049] Comparative Example 3-1: Due to excessively low temperature and insufficient pressure, a large number of live bacteria remained in the material. Meanwhile, the low temperature and pressure conditions could not provide sufficient activation energy for the catalytic hydrolysis of acetic acid, and the oil precipitation rate was only 62.4%, with a large amount of oil remaining in the material, which was not conducive to subsequent three-phase centrifugal separation.

[0050] In contrast, Example 3-1 achieved complete sterilization with an oil extraction rate of 89.7%. This indicates that under these temperature and pressure conditions, high-temperature saturated steam achieved complete sterilization, and the animal fat was completely melted and extracted, laying the foundation for subsequent three-phase centrifugal separation.

[0051] The sterilization effect and oil extraction rate of Examples 3-2 were further improved, indicating that the temperature and pressure conditions of 180℃ / 0.6MPa are superior to 160℃ / 0.5MPa in terms of sterilization and oil extraction. Considering the energy consumption and cost of industrial production, 160℃ / 0.5MPa / 0.5h can achieve excellent sterilization and acid hydrolysis effects, and there is no need to excessively increase the temperature and pressure. When the temperature is only 130℃, the pressure is only 0.3MPa, and the holding time is only 0.5h, the sterilization effect is not up to standard (10 5 The oil extraction rate was only 62.4% (CFU / g), leaving a large amount of oil residue in the material, which was detrimental to subsequent three-phase centrifugal separation. This invention controls the temperature of the chemical treatment tank at ≥160℃, the pressure at ≥0.5MPa, and the holding time at ≥0.5h, ensuring complete sterilization and achieving an oil extraction rate of up to 89.7%, thus realizing efficient synergy between sterilization and acid hydrolysis.

[0052] To verify the necessity of acid in protein hydrolysis and the regulatory effects of acid dosage and hydrolysis time on the degree of hydrolysis, a comparative experiment was conducted under immobilized tank temperature and pressure conditions (160℃ / 0.5MPa) with different acid dosages (A being the baseline dosage, and 2A being twice the baseline dosage) and different hydrolysis times (2h and 4h). A sample without added acid served as the control group. Here, A is the baseline dosage, which is 0.14 mg / ton of crushed material. 3 A 30% acetic acid solution; 2A is 0.28m³ per ton of crushed material. 3 A 30% acetic acid solution was added. In each group, the appropriate amount of acetic acid solution was uniformly sprayed onto the surface of the minced meat using a pump-spraying process. After being uniformly mixed by biaxial roller shearing, the mixture was placed in a sealed reaction vessel and heated to a core temperature of 160℃ and a pressure of 0.5MPa, respectively, and kept at this temperature for 2 hours or 4 hours for acid hydrolysis. In the control group, no acetic acid solution was added; the minced meat was simply uniformly mixed by biaxial roller shearing and placed in a sealed reaction vessel, and treated under the same temperature and pressure conditions as the experimental group (core temperature 160℃, pressure 0.5MPa), respectively, and kept at this temperature for 2 hours or 4 hours.

[0053] The crude protein content of the samples was determined using the Kjeldahl method. The content of small peptides was determined using the trichloroacetic acid (TCA) precipitation method. For the acid-hydrolyzed sample, an equal volume of 15% trichloroacetic acid solution was added, mixed, and allowed to stand for 30 min. The mixture was then centrifuged at 4000 rpm for 15 min, and the supernatant was collected. The Kjeldahl method was used to determine the acid-soluble protein content in the supernatant. Small peptide content (%) = (acid-soluble protein content / crude protein content) × 100%. The molecular weight distribution was determined using gel permeation chromatography (GPC). The acid-hydrolyzed sample was filtered through a 0.45 μm filter membrane. Using phosphate buffer (pH 6.8) as the mobile phase, a TSKgel G2000SWXL column was used at a flow rate of 0.5 mL / min and a column temperature of 30℃. Detection was performed at a wavelength of 220 nm. A standard curve was established using standards (cytochrome C, aprotinin, bacitracin, oxidized glutathione, etc.), and the relative content of peptides in each molecular weight range was calculated using the peak area normalization method.

[0054] The results are shown in Table 4, which is a comparison of the content and molecular weight distribution of small peptides in the products under different acid addition amounts and hydrolysis times.

[0055] Table 4: Comparison of peptide content and molecular weight distribution under different acid addition amounts and hydrolysis times.

[0056] Table 4 shows that the content of small peptides obtained by the TCA method in Comparative Examples 4-1 to 4-4 without added acid was only 12.47% to 16.99%, and the proportion of proteins below 3000 Da in the GPC method was only about 9% to 10%, while the proportion of large molecular proteins above 10000 Da was as high as 26% to 34%. This indicates that even after high temperature and high pressure treatment, the degree of protein hydrolysis is extremely limited without the addition of acid, and acid is the key factor in triggering efficient protein hydrolysis. After adding acid, the content of small peptides obtained by the TCA method in Examples 4-1 to 4-4 increased significantly, reaching 62.83% to 98.87%, while the proportion of proteins below 3000 Da in the GPC method also showed a trend of enrichment towards small molecular peptides. Among them, the content of small peptides obtained by the TCA method in Example 4-4 reached 98.87%, the proportion of proteins below 3000 Da in the GPC method reached 85.53%, and the proportion of large molecular proteins above 10000 Da was only 0.08%, indicating that the protein was fully hydrolyzed into small molecular peptides under these conditions.

[0057] like Figure 2 As shown, the bar chart compares the content of TCA-processed small peptides under different acid addition amounts and hydrolysis times. The TCA-processed small peptide contents in Examples 4-1 to 4-4 ranged from 62.83% to 98.87%, while those in Comparative Examples 4-1 to 4-4 (acid-free control) ranged from only 12.47% to 16.99%, a significant difference indicating that acid is a key factor triggering protein hydrolysis. Furthermore, from Examples 4-1 to 4-4, by increasing the acid addition amount or extending the hydrolysis time, the TCA-processed small peptide content gradually increased from 62.83% to 98.87%, demonstrating that the present invention can achieve precise control of the degree of hydrolysis over a wide range by adjusting the acid addition amount and hydrolysis time, further verifying the stability and controllability of the technical solution of the present invention.

[0058] like Figure 3 The figure shows a bar chart of the molecular weight distribution of the product from Example 4-4 (acid addition 2A, hydrolysis time 4h). Under these conditions, 85.53% of the molecular weight was below 3000 Da, with the highest proportion (37.15%) in the 500–1000 Da range, followed by the 1000–2000 Da range at 32.08%, while large proteins above 10000 Da accounted for only 0.08%. This molecular weight distribution characteristic, along with the TCA-based small peptide content data (98.87%) in Table 4 under these conditions, indicates that the protein was fully hydrolyzed into small peptide fragments under these conditions.

[0059] Step S3: The first acid hydrolysate is unloaded under pressure from the harmless treatment center into a tanker truck that has been cleaned, disinfected, and dried. Disinfection devices are installed at the pressurized unloading pipe head and the tanker truck inlet pipe head. The tanker truck will transfer the first acid hydrolysate to the post-treatment area in a sealed manner. The tanker truck will not enter the area after that. After the tanker truck is disinfected in the disinfection area, the first acid hydrolysate will be directly pumped to the storage tank through the disinfected pipeline. The tanker truck outlet is connected to the fixed pipeline with a quick-connect clamp. In this embodiment, the harmless treatment center is the area where crushing and primary sterilization acid hydrolysis are completed; the post-treatment area is the area where secondary sterilization, three-phase separation, and subsequent drying and packaging are completed; and the disinfection area is a dedicated area for disinfecting the outer surface of the tanker trucks during transport. These three areas are isolated from each other to avoid cross-contamination during transport. After loading the first acid hydrolysate into the harmless treatment center, the tanker truck undergoes disinfection in the disinfection area before entering the post-treatment area for unloading. The tanker truck does not directly enter the interior of the post-treatment area.

[0060] Specifically, the transfer is carried out using a sealed tanker truck. The tanker truck is cleaned, disinfected, and dried before the transfer. The first acid hydrolysate is unloaded under pressure into the tanker truck and then pumped to the storage tank.

[0061] In this embodiment, the tanker truck sequentially enters the cleaning station, disinfection station, and drying station. Cleaning uses high-pressure hot water (temperature ≥80℃) to rinse the inner wall of the tank and the inlet and outlet pipes to remove visible residues. Disinfection uses peracetic acid or chlorine-containing disinfectant to spray the inner wall of the tank for ≥15 minutes. Drying uses hot air circulation at a temperature ≥60℃ until there are no visible water droplets on the inner wall of the tank.

[0062] It is understandable that if mobile tank trucks are not thoroughly cleaned and disinfected before transportation, residual material on the inner wall of the tank may breed bacteria, and the outer surface may carry pathogens, causing cross-contamination after loading the first acid hydrolysate. Existing technologies typically only involve simple rinsing of tank trucks before transfer, lacking a standardized pretreatment process of washing, disinfection, and drying. This invention cleans, disinfects, and dries the tank trucks before loading, ensuring that the tank trucks are in a clean and sterile state before loading the first acid hydrolysate. This eliminates the source of contamination from the very beginning of the transfer process. Together with subsequent interface disinfection and measures prohibiting tank trucks from entering the plant, this constitutes a complete microbial barrier system for the transfer process.

[0063] Specifically, the tanker truck is equipped with a disinfection device at its feed pipe and pressurized unloading pipe.

[0064] In this embodiment, the disinfection devices are installed at the end of the discharge pipe of the chemical tank (discharge pipe head) and the beginning of the inlet pipe of the tank truck (inlet pipe head). During unloading, the discharge pipe head is first connected to the inlet pipe head of the tank truck via a quick connector, and then the disinfection devices are activated to use ultraviolet sterilization (wavelength 254nm, irradiation intensity ≥3000μW / cm²). 2Sterilization time ≥ 30 seconds or online sterilization is performed by introducing 0.2 MPa saturated steam for 15–30 seconds. After aseptic treatment of the docking interface is completed, the valve is opened for pressurized unloading. The interface remains sealed throughout the material flow process.

[0065] It is understandable that the pipe joint is the most susceptible to contamination during material transfer. Existing technologies typically involve direct connection followed by unloading, leaving the joint exposed to air and posing a risk of pathogen invasion. This invention incorporates sterilization devices at both the unloading and inlet pipe heads, performing closed-loop online sterilization of the joints. This ensures that the material remains in a sterile environment throughout the entire transfer process, completely blocking the entry of pathogens through the joint.

[0066] Step S4: Pump the first acid hydrolysate in the storage tank to the chemical treatment tank, heat it to the center temperature of the processed material ≥180℃ and the pressure ≥0.6MPa, and keep it at the temperature for ≥0.5h for secondary sterilization to obtain sterilized material; 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.

[0067] In this embodiment, the secondary sterilization is carried out in a treatment tank. The first acid hydrolysate in the storage tank is pumped back to the treatment tank, and heated to a center temperature ≥180℃ and a pressure ≥0.6MPa by jacketed steam heating, and held at this temperature for ≥0.5h. The treatment tank is equipped with a stirring device (30rpm~50rpm) to ensure uniform temperature distribution of the material. After the secondary sterilization is completed, sterilized material is obtained. This step serves as a second sterilization guarantee to thoroughly kill any small amount of microorganisms or pathogens that may have been contaminated in the first acid hydrolysate during storage and transportation, while preventing microbial reactivation due to temperature drop after transportation.

[0068] It is understandable that after the first acid hydrolysate is transported and stored, despite the implementation of airtight and aseptic measures, there is still a risk of residual heat-resistant microorganisms or spores. Furthermore, the material temperature decreases during transport, potentially allowing microorganisms to reactivate. Existing technologies rely solely on a single sterilization process, lacking secondary protection after transport. This invention utilizes a secondary sterilization process, raising the processing temperature to 180℃ / 0.6MPa. This higher temperature and pressure conditions thoroughly inactivate any microorganisms that may be introduced during transport. Simultaneously, further hydrothermal hydrolysis of the protein at this temperature ensures more complete hydrolysis, guaranteeing absolute sterility of the material and stability of the product quality.

[0069] Step S5: The sterilized material is transported through a closed pipeline to a three-phase horizontal screw discharge sedimentation centrifuge to separate the grease, second acid hydrolysate and bone residue in one step. The three-phase horizontal screw discharge sedimentation centrifuge described in this embodiment is a continuous solid-liquid separation device. Sterilized material is fed into the centrifuge drum through a closed pipeline. The drum and screw conveyor rotate at a high speed of 3000 rpm to 4000 rpm under the drive of a differential gear, with a differential speed of 10 to 30 rpm. Due to density differences, the material forms three phases in the centrifugal force field. The light phase, oil, accumulates in the innermost layer of the drum and is continuously discharged by a centrifugal pump; the heavy phase, the second acid hydrolysate, is located in the middle layer and overflows from the drain port; the solid phase, bone residue, settles on the inner wall of the drum, is scraped off by the screw conveyor, and pushed to the slag outlet for discharge, achieving continuous three-phase separation in one operation.

[0070] Understandably, the material after secondary sterilization contains three components with significantly different densities: oil, acid hydrolysate, and bone residue. Existing technologies typically employ a two-step separation method involving filtration and settling for oil separation, which involves multiple pieces of equipment and lengthy processes. This invention utilizes a three-phase centrifuge to complete the three-phase separation in one step, simplifying the separation process. Furthermore, the entire process is carried out continuously in a closed pipeline, avoiding the impact of material exposure and the environment on the separation effect.

[0071] In step S6, the oil is pumped to a storage tank for storage. The second acid hydrolysate is concentrated to a solid content of 45%–65% using a low-temperature waste heat concentration device to obtain a concentrated acid hydrolysate. The bone residue is ground in a colloid mill to produce fine bone powder with a D90 ≤ 100 μm, which is continuously discharged from the outlet to obtain bone powder. Preferably, the bone powder particle size is controlled at D90 ≤ 75 μm (equivalent to 200 mesh or larger; within this range, the mixing uniformity of bone powder and concentrated acid hydrolysate is optimal, and the dispersibility and taste of the final product are also most ideal). The concentrated acid hydrolysate is mixed with the bone powder, dried, packaged, and stored to obtain a composite protein powder. Acetic acid evaporates with the moisture during the drying process, resulting in a low acetic acid residue in the composite protein powder after drying.

[0072] Specifically, in step S6, the solid content of the concentrated acid hydrolysate is 45% to 65%.

[0073] In this embodiment, the second acid hydrolysate is fed into a low-temperature waste heat concentration device, utilizing boiler exhaust gas or process waste heat (temperature 60℃~80℃) as a heat source to remove some of the water from the second acid hydrolysate through negative pressure evaporation. During the concentration process, a vacuum of -0.06MPa~-0.08MPa is maintained inside the device to allow the water to boil and evaporate at a lower temperature, avoiding the damage of heat-sensitive peptides and amino acids caused by high temperatures. Evaporation is stopped when the solid content of the concentrate reaches 45%~65%, yielding a concentrated acid hydrolysate, which is then sent to a drying device for final drying.

[0074] Understandably, if the solid content after concentration is below 45%, the concentrated acid hydrolysate will have excessively high water content, significantly increasing subsequent drying energy consumption. Furthermore, the liquid product will have high transportation costs and large packaging volume, making it unsuitable for long-term storage and transportation. If the solid content is above 65%, the concentrated solution will have excessively high viscosity, affecting pumping and discharge, and easily causing scaling on the inner wall of the concentration equipment, reducing heat transfer efficiency. Additionally, the high-viscosity material will be difficult to mix evenly with the subsequently added bone meal. This invention controls the solid content of the concentrated acid hydrolysate between 45% and 65%, significantly reducing the heat load for subsequent drying while ensuring the concentrated solution has suitable viscosity, guaranteeing uniform mixing with bone meal and smooth operation of the drying process.

[0075] To verify the beneficial effect of a solid content of 45%–65% in the concentrated acid hydrolysate in step S6, different concentrated solid contents were set. Second acid hydrolysate and bone residue from the same batch after three-phase centrifugation were divided into five groups according to the specified ratio. The second acid hydrolysate group was concentrated to the target solid content using a low-temperature waste heat concentration device. The bone residue group was ground in a colloid mill and then mixed with the concentrated acid hydrolysate before subsequent drying. Each group consisted of 10 kg. Each group was concentrated using a low-temperature waste heat concentration device at 70℃ and -0.07 MPa. The solid content was monitored in real time using an online refractometer. Evaporation was stopped after the target solid content was reached. After concentration, samples were taken to measure the dynamic viscosity of each group. Subsequently, the concentrated solutions of each group were spray-dried under the same conditions, and the drying time, drying energy consumption, and product state were recorded. The concentration energy consumption refers to the amount of steam consumed per unit of material during the concentration process (kg steam / kg material). In this embodiment, it is calculated based on the equivalent heat of 1000kJ for 1kg steam. The residue on the inner wall of the concentration equipment is determined by observing whether there is scale or char on the inner wall after concentration, and the weight of the residue (g) is quantified by weighing. The dynamic viscosity (mPa·s) of each group of concentrates is measured using a rotational viscometer under a constant temperature of 60℃ to evaluate the ease of pumping and mixing. The drying time is the time (h) required from the start of feeding to the outlet temperature stabilizing at the set value (80℃) during spray drying. The drying energy consumption is the heat energy consumed per unit of material during the drying process (kJ / kg). The product state is determined by visually observing the color, uniformity, and presence of agglomeration of the dried composite protein powder. The results are shown in Table 5, which is a comparison of the concentration and drying process effects under different concentrated solid contents.

[0076] Table 5: Comparison of Concentration and Drying Process Effects at Different Concentrated Solid Contents

[0077] In comparison, Examples 5-1 to 5-3 exhibit balanced performance across all parameters: no or only minimal residue on the inner wall of the concentration equipment; dynamic viscosity of 450–3500 mPa·s, within the pumpable range; moderate concentration time and energy consumption; and significantly lower drying time and energy consumption compared to Comparative Example 5-1. The products are all uniform in color and well-dried. Example 5-2 (55% solids content) achieves a good balance between concentration steam consumption (3.0 kg steam / kg) and drying energy consumption (2000 kJ / kg), resulting in the optimal overall process performance.

[0078] When the concentrated solids content is below 45%, the high moisture content of the product leads to increased energy consumption in subsequent drying and the product is prone to excessive moisture. When the concentrated solids content is above 65%, the excessive viscosity of the material leads to difficulties in pumping, severe scaling in the concentration equipment, and product agglomeration. This invention controls the solids content of the concentrated acid hydrolysate between 45% and 65%. Within this range, the product quality is uniform and stable, and the overall process effect of concentration and drying is optimized.

[0079] Please see Figure 4 The diagram shown is a schematic diagram of the equipment connection for the preparation method of the animal protein acid hydrolysis product in this embodiment.

[0080] Inside the harmless treatment center, the discharge port of the crusher is connected to the inlet of the chemical treatment tank via a sealed pipeline. The discharge port of the chemical treatment tank is connected to the inlet of the tank truck via a sealed pipeline. Disinfection devices are installed at the pressurized unloading pipe and the inlet of the tank truck. The tank truck passes through the disinfection area and is connected to the storage tank in the post-treatment area via a disinfected pipeline. The discharge port of the storage tank is connected to the chemical treatment tank (for secondary sterilization) via a sealed pipeline. The discharge port of the chemical treatment tank is connected to a three-phase horizontal screw discharge sedimentation centrifuge via a sealed pipeline. The three outlets of the three-phase centrifuge are connected to the oil storage tank, the colloid mill, and the bone residue collection device, respectively. The discharge port of the colloid mill is connected to the low-temperature waste heat concentration equipment. The discharge port of the concentration equipment is connected to the drying equipment. The discharge port of the drying equipment is connected to the finished product storage workshop equipped with an ultraviolet disinfection device.

[0081] To verify the beneficial effects of the key technical features in the overall technical solution of the present invention, dead pigs of the same batch and similar weight (about 80kg / head) were selected as experimental materials and randomly divided into an example group and multiple comparative groups, with a total weight of 100kg for each group.

[0082] Example group:

[0083] Step S1: The animal raw materials are crushed into meat pieces with a particle size of 35mm using a twin-shaft shear crusher. Step S2: Using a pump spraying process, a 30% acetic acid solution is evenly sprayed onto the surface of the minced meat. After being uniformly mixed by a dual-shaft roller shearing process, the mixture is pumped into a melting tank. The melting tank is sealed and heated to a core temperature of 160°C and a pressure of 0.5 MPa, and kept at this temperature for 0.5 hours. Sterilization and acid hydrolysis are completed simultaneously to obtain the first acid hydrolysate. Step S3: The first acid hydrolysate is unloaded under pressure into a tanker truck that has been cleaned, disinfected and dried. Disinfection devices are installed at the unloading pipe head and the inlet pipe head of the tanker truck. The tanker truck will transfer the first acid hydrolysate to the post-processing area in a sealed manner. After the tanker truck is disinfected, the first acid hydrolysate is directly pumped to the storage tank through the disinfected pipeline. Step S4: The first acid hydrolysate in the storage tank is pumped to the chemical treatment tank, heated to the center temperature of the material to be processed (180°C) and pressure (0.6 MPa), and kept at this temperature for 0.5 hours for secondary sterilization to obtain sterilized material. Step S5: The sterilized material is transported through a closed pipeline to a three-phase horizontal screw discharge sedimentation centrifuge to separate the grease, second acid hydrolysate and bone residue. In step S6, the oil is pumped to the storage tank for storage. The second acid hydrolysate is concentrated to a solid content of 55% by a low-temperature waste heat concentration device to obtain concentrated acid hydrolysate. The bone residue is ground by a colloid mill to obtain bone powder. The concentrated acid hydrolysate and bone powder are mixed, dried, packaged and stored in a workshop equipped with an ultraviolet sterilization device to obtain composite protein powder.

[0084] Comparative Example 1 (S1: Oversized crushed particles): Animal raw materials were crushed into 60mm pieces using a twin-shaft shear crusher with a 60mm aperture screen. The remaining steps and parameters were the same as in the example.

[0085] Comparative Example 2 (S2 adopts typical conditions of existing sulfuric acid decomposition method): The chemical preparation tank is heated to a core temperature of 100-120°C and a pressure of 0.15-0.2 MPa, and kept at this temperature for 5-6 hours for acid hydrolysis. The remaining steps and parameters are consistent with those of the example.

[0086] Comparative Example Group 3 (S2 acidifying agent is concentrated sulfuric acid): 98% concentrated sulfuric acid was used to replace 30% acetic acid as the acidolysis catalyst, and the remaining steps and parameters were consistent with those in the example.

[0087] Comparative Example Group 4 (S3 transfer process without aseptic guarantee): The tanker truck drove directly into the post-processing area for unloading, and no disinfection device was installed at the unloading pipe head and the tanker truck inlet pipe head. The remaining steps and parameters were consistent with the example.

[0088] Comparative Example Group 5 (S4 Secondary Sterilization Cancelled): The secondary sterilization operation in step S4 is omitted. The first acid hydrolysate is directly fed into the three-phase centrifugal separation tank. The remaining steps and parameters are consistent with those in the example.

[0089] Comparative Example Group 6 (S5 uses traditional separation method): Plate and frame filtration and static oil separation are used instead of three-phase horizontal screw discharge sedimentation centrifuge for solid-liquid separation and oil-water separation. The remaining steps and parameters are consistent with those in the example.

[0090] Comparative Example 7 (S6 Concentrated Solid Content Too Low): The second acid hydrolysate was concentrated to a solid content of 25% using a low-temperature waste heat concentration device. The remaining steps and parameters were consistent with those in the example.

[0091] Comparative Example Group 8 (S6 Concentration Solid Content Too High): The second acid hydrolysate was concentrated to a solid content of 85% using a low-temperature waste heat concentration device, and the remaining steps and parameters were consistent with those in the Example.

[0092] Except for the corresponding parameter changes, all other steps and process parameters in the above groups are consistent with those in the example to ensure the single-factor variable principle of the comparative experiment.

[0093] The following indicators were measured after the process was completed: Pumping energy consumption (kWh / t): Records the unit energy consumption of pumping material from the crusher outlet to the chemical tank through a closed pipeline after the S1 crushing is completed.

[0094] Residue on the wall of the chemical treatment tank (g): After acid hydrolysis in step S2 is completed, open the chemical treatment tank and use a stainless steel scraper to scrape off all the residue on the tank wall and bottom and collect it. Weigh the wet weight of the residue.

[0095] 3000Da peptide content (%): After acid hydrolysis in step S2, the sample was filtered, and the proportion of peptides with a molecular weight ≤3000Da in the filtrate was determined by gel permeation chromatography (GPC) to the total peptides.

[0096] Sterilization effect (log CFU / g): The total number of bacteria in the material after step S4 is detected by plate counting method. Those skilled in the art can perform the test according to existing technology.

[0097] Product yield (%): The percentage of the weight of the final obtained compound protein powder relative to the total solid weight of the raw materials.

[0098] Oil recovery rate (%): The percentage of the weight of the separated oil relative to the total lipid content in the raw material.

[0099] Product protein content (%): The crude protein content of the final product was determined by the Kjeldahl method.

[0100] Equipment corrosion rate (mm / a): The corrosion rate of the equipment was determined by the weight loss method of the inner wall of the chemical reaction tank.

[0101] Total bacterial count (CFU / g) after 6 months of storage: The total bacterial count was determined by plate counting after the product was stored at room temperature for 6 months.

[0102] Product appearance and smell: Visually observe the product's color and uniformity, and smell the product's odor.

[0103] The results are shown in Table 6, which is a summary data table comparing the core process indicators and product quality of the examples and each comparative example group.

[0104] Table 6: Summary of core process indicators and product quality comparison between the Example Group and each Comparative Example Group

[0105] The 3000Da peptide content in the Example Group reached 91.4%. The peptide content in Comparative Example Group 1 (particle size 60mm) was 72.4%, a decrease of 20.8% compared to the Example Group. This was because the larger fragments increased the mass transfer resistance of the acid hydrolysate penetrating into the fragments, preventing the central protein from fully contacting the acetic acid and resulting in uneven hydrolysis. The peptide content in Comparative Example Group 2 (100–120℃ / 0.15–0.2MPa / 5–6h) was only 52.3%, a decrease of 42.8% compared to the Example Group, indicating low protein hydrolysis and poor peptide enrichment. The peptide content in Comparative Example Group 3 (concentrated sulfuric acid) was 88.2%, slightly lower than the Example Group, indicating that the strong acidity of concentrated sulfuric acid caused some peptides to undergo further over-hydrolysis into free amino acids. The peptide content in the remaining Comparative Example Groups was the same as in the Example Group (91.4%), indicating that particle size, temperature and pressure conditions, and type of acidifier are key factors affecting peptide content, while subsequent processes have no impact on this indicator.

[0106] After secondary sterilization, the total bacterial count in the Example Group was <10 CFU / g, indicating that the sterilization effect was fully met. Comparative Example Group 5 (without secondary sterilization) did not meet the sterilization standard (<10 CFU / g). 3 The CFU / g count indicates that a small number of heat-resistant microorganisms or spores remain after a single sterilization; after 6 months of storage at room temperature, the total bacterial count has increased to 10. 5 The CFU / g result further demonstrates that residual bacteria can multiply in the product, severely impacting long-term storage stability. The other comparative groups all met sterilization standards, indicating that secondary sterilization is a crucial guarantee for ensuring complete sterilization compliance.

[0107] The product yield of the Example Group was 78.6%. The product yield of Comparative Example Group 6 (plate and frame filtration + static oil separation) was 72.3%, lower than the 8.0% of the Example Group. This is because the traditional separation method could not fully separate the three phases, resulting in the loss of some protein and oil with the bone residue. The product yield of Comparative Example Group 8 (85% solids content) was 75.2%, slightly lower than the Example Group. This is because the high solids content led to increased material viscosity and transport losses. The product yields of Comparative Examples 1, 2, 3, 4, 5, and 7 were all the same as the Example Group (78.6%), indicating that the separation method and the concentrated solids content are the main factors affecting the product yield.

[0108] The corrosion rate of the equipment in the example group was only 0.15 mm / a. The corrosion rate of Comparative Example Group 3 (98% concentrated sulfuric acid) was as high as 1.20 mm / a, an increase of 700% compared to the example group. This indicates that concentrated sulfuric acid is far more corrosive to equipment than acetic acid, requiring frequent equipment replacement with long-term use, significantly increasing maintenance costs and safety risks. The corrosion rates of the remaining comparative example groups were all similar to those of the example group (0.15 mm / a), indicating that the corrosion rate mainly depends on the type of acidifying agent, and other process parameters have no significant impact.

[0109] In the example, the total bacterial count was <10 CFU / g after 6 months of storage, and the product quality remained stable. In contrast, in Comparative Example 4 (tanker trucks directly entered the post-processing area without interface sterilization), the total bacterial count reached 10 CFU / g after 6 months of storage. 4 The CFU / g level in Comparative Example Group 5 was significantly higher than that in the Example Group, indicating that the lack of interface sterilization and aseptic protection during the transfer process could lead to the introduction and residue of pathogens or other microorganisms into the product, which could then multiply during storage and affect long-term stability. The total bacterial count in Comparative Example Group 5 reached 10 after 6 months of storage. 5 The CFU / g result further confirms the severe impact of incomplete sterilization on storage stability. The total bacterial count in the remaining comparative groups was <10 CFU / g after 6 months of storage, indicating that, provided sterilization standards are met, other process parameters have no significant impact on long-term storage stability. In summary, this invention, through its technical solutions of controlled particle size, medium-strong acid catalysis, a temperature and pressure progression design for first-stage sterilization and acid hydrolysis followed by second-stage sterilization, fully enclosed aseptic transport with tank trucks not entering the plant and interface disinfection devices, three-phase centrifugation + acid hydrolysis solution, low-temperature residual heat concentration to 45%–65%, and ultraviolet disinfection storage, achieves a 3000Da peptide content of 91.4%, complete sterilization, a product yield of 78.6%, an equipment corrosion rate of only 0.15 mm / a, and a total bacterial count <10 CFU / g after 6 months of storage.

[0110] The comparative example experiments demonstrated that each key technical feature played a role in different performance dimensions. In Table 6, each comparative example group only showed deterioration in the index corresponding to the changed step; other indexes remained the same as the example group. This further confirms the independent contribution of different features to different indexes. Specifically, excessively coarse particle size led to a 20.8% decrease in small peptide content; although the existing sulfuric acid decomposition method achieved sterilization, the small peptide content was only 52.3%, a 42.8% decrease compared to the example group; the elimination of secondary sterilization resulted in substandard sterilization; the replacement of acetic acid with concentrated sulfuric acid increased the corrosion rate by 700%; the traditional separation method led to an 8.0% decrease in product yield; and the direct entry of tank trucks into the post-processing area without interface disinfection caused the total bacterial count to increase from <10 CFU / g to 10 CFU / g after 6 months of storage. 4CFU / g. In addition, although Comparative Example 7 (concentrated solid content 25%) was the same as the Example Group in terms of product quality indicators in Table 6, its concentration of water content increased significantly after deviating from the solid content range of 45% to 65%, which led to increased energy consumption for subsequent drying, a more humid product, and was not conducive to long-term storage and transportation (see Comparative Example 5-1 in Table 5). This shows that the beneficial effects of this feature are mainly reflected in the dimensions of process smoothness and economy.

[0111] The above results fully demonstrate the independent contribution and combined effect of the key technical features of this invention in different performance dimensions. After the comprehensive implementation of each step, the final product achieves optimal levels in various indicators such as peptide content, sterilization effect, product yield, equipment corrosion resistance, and storage stability, achieving significant technical results.

[0112] 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 the acid hydrolysis of animal proteins, characterized in that, Includes the following steps: Step S1: Crush the animal raw materials in a closed crusher; Step S2: The acid solution is evenly sprayed onto the surface of the minced meat using a pumping spraying process. After being evenly mixed by a dual-shaft roller shearing process, it is pumped into a melting tank. Sterilization and acid hydrolysis are completed simultaneously in the melting tank to obtain the first acid hydrolysate. Step S3: The first acid 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 acid 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 acid hydrolysate and bone residue; In step S6, the oil is pumped to an oil storage tank for storage, and the second acid hydrolysate is concentrated by a low-temperature waste heat concentration device to obtain a concentrated acid hydrolysate. The bone residue is ground to obtain bone meal; The concentrated acid hydrolysate is mixed with the bone meal, dried, packaged, and stored to obtain a composite protein powder.

2. The method for preparing the product of animal protein acid hydrolysis 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, crushing the particles to a size of 20mm to 50mm. The odorous gases generated during the crushing process are collected through a gas collection pipeline and then disposed of.

3. The method for preparing the product of animal protein acid hydrolysis according to claim 2, characterized in that, In step S2, the acid solution is at least one of acetic acid, formic acid, and citric acid.

4. The method for preparing the product of animal protein acid hydrolysis according to claim 3, characterized in that, In step S2, the acid solution is added at a rate of 0.14 mg / ton of crushed material. 3 Add in the appropriate proportion.

5. The method for preparing the product of animal protein acid hydrolysis according to claim 4, characterized in that, In step S2, the sterilization and acid 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.

6. The method for preparing the product of animal protein acid hydrolysis according to claim 5, characterized in that, In step S3, the transfer is carried out using a sealed tanker truck. The tanker truck is cleaned, disinfected, and dried before the transfer. The first acid hydrolysate is unloaded under pressure into the tanker truck and then pumped to the storage tank.

7. The method for preparing the product of animal protein acid hydrolysis according to claim 6, characterized in that, The tanker truck is equipped with a disinfection device at its feed pipe and pressurized unloading pipe.

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

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