Nutritional pet food based on low-value seawater product and preparation method thereof

Abstract

The invention relates to the technical field of pet food processing, and discloses a nutritional pet food based on a low-value seawater product and a preparation method thereof, and the preparation method comprises the following steps: desalting raw materials, and mechanically separating into a meat soft component and a hard calcium component; adding antioxidant such as rosemary extract into the soft meat component for pulping, and performing constant-temperature enzymolysis with compound protease to obtain enzymolysis meat pulp; the hard calcium component is subjected to high-temperature and high-pressure steaming and softening and multi-stage crushing to obtain ultramicro bone paste with the particle size D90 smaller than 50 [mu] m; and taking 60-80 parts of slurry and 15-30 parts of bone paste, adding sodium alginate and other structural stabilizers and nutrient supplements, mixing, and carrying out high-pressure homogenization, vacuum freeze-drying and nitrogen-filled packaging to obtain the bone paste. The processing contradiction of hard bones and soft meat of low-value marine products is solved through split-flow modification and texture structure recombination; the bioavailability of calcium is greatly improved by the micron-sized bone paste; in-situ antioxidation is combined with a freeze-drying technology, so that lipid rancidity is effectively inhibited, and the product is endowed with a crisp porous structure and excellent rehydration and palatability.

Description

Technical Field

[0001] This invention relates to the field of pet food processing technology, specifically to a nutritional pet food based on low-value marine products and its preparation method. Background Technology

[0002] The fishing and processing of aquatic products typically generates large quantities of low-value byproducts such as small miscellaneous fish, fish heads, fish bones, fish skin, and scraps of shrimp and crab meat. While these biological resources are rich in protein, calcium, and trace elements, their high bone content, inconsistent sizes, and susceptibility to spoilage limit their current utilization; they are mostly processed into low-value fishmeal feed or disposed of as waste. This approach not only wastes valuable marine protein and mineral resources but also imposes a significant organic pollution load on the ecological environment.

[0003] Existing pet food mainly includes extruded dry food, wet food canned food, and freeze-dried food. Traditional extruded dry food often uses high-temperature, high-pressure extrusion, which can easily destroy heat-sensitive nutrients such as vitamins and unsaturated fatty acids in the raw materials. Furthermore, to meet the demands of the extrusion process, the formula often contains a high proportion of starch, making it difficult to fully meet the nutritional needs of pets as carnivores. While wet food canned food is more palatable, its high moisture content increases transportation and storage costs. Additionally, chemical preservatives are usually added to inhibit microbial growth, which can burden pets' health with long-term consumption. Although vacuum freeze-dried food has advantages in nutrient retention and rehydration, most freeze-dried products on the market currently use high-value whole meat from livestock and poultry or high-grade fish as raw materials. The high cost of raw materials leads to high prices for the final product, limiting its market penetration.

[0004] Developing freeze-dried pet food directly from these low-value marine products presents numerous challenges in practical application. First, the high proportion and hard texture of bones and shells in these products make them difficult to process into a digestible state suitable for pets using conventional grinding processes. Coarse bone fragments not only affect the product's palatability but also limit calcium bioavailability and may even damage the pet's digestive tract. Second, marine products are rich in polyunsaturated fatty acids, which are highly susceptible to oxidation during processing, crushing, and storage, leading to a rancid odor that severely impacts a pet's appetite. Furthermore, simple mixing processes cannot address the differences in physical texture between the meat components and the hard bone calcium components, resulting in a loose structure, easy powdering, or localized hardening after freeze-drying. Therefore, the industry urgently needs a technological solution that can systematically address the difficulties in processing, easy oxidation, and low utilization rates of low-value marine products, and produce highly nutritious, palatable, and additive-free pet food. Summary of the Invention

[0005] The technical problem solved by this invention is that existing low-value marine products have problems in pet food processing, such as low raw material utilization, difficulty in the absorption of bone calcium by organisms, easy oxidation and rancidity of lipids during processing and storage, and poor rehydration and palatability of freeze-dried products.

[0006] To address the above problems, the present invention provides the following technical solution: In a first aspect, the present invention provides a nutritional pet food based on low-value marine products, employing the following technical solution: It is made from the following raw materials in parts by weight: 60-80 parts of enzymatically hydrolyzed meat paste; 15-30 parts of ultrafine bone paste; 1-5 parts of structural stabilizer; and 0.5-2 parts of nutritional fortifier. The enzymatically hydrolyzed meat paste is obtained by enzymatic hydrolysis of the soft meat components of low-value marine products. The ultrafine bone paste is obtained by micronization of the hard calcium components of low-value marine products.

[0007] By adopting the above technical solution, this invention solves the problem of mismatch between the processing characteristics of soft and hard components by utilizing component splitting and texture recombination technology. Its specific mechanism of action is as follows: First, the low-value marine product raw materials are separated into a soft, fleshy component and a hard, calcium-rich component, and then modified according to their biochemical characteristics. After enzymatic hydrolysis, the large molecular weight myofibrillar protein of the soft, fleshy component is converted into short-chain peptides and amino acids, forming a viscoelastic continuous phase matrix; the hard, calcium-rich component is micronized to form fine particles as the dispersed phase.

[0008] Secondly, under the bridging effect of the structural stabilizer, the polypeptide segments generated by enzymatic hydrolysis undergo physical adsorption and entanglement with the surface of the ultrafine bone paste particles, constructing a protein gel-bone paste particle interpenetrating network structure. Microscopically, this system presents a stable suspension with a protein gel as the framework and bone paste particles uniformly filled. During the subsequent freeze-drying process, this network structure can resist the stress generated by ice crystal sublimation, preventing framework collapse and thus forming uniformly distributed porous channels within the finished product, resulting in both a crisp texture and excellent rehydration properties.

[0009] Preferably, the structural stabilizer is selected from at least one of sodium alginate, pregelatinized starch and egg yolk lecithin; the enzymatically hydrolyzed meat slurry contains 0.02%-0.05% by mass of a natural antioxidant, which is selected from rosemary extract or tea polyphenols.

[0010] By adopting the above technical solutions, the chemical and physical stability of the system can be improved: First, in response to the high levels of unsaturated fatty acids in marine products, this invention introduces rosemary extract or tea polyphenols at the initial stage of pulping. During the mechanical crushing process that causes cell rupture and lipid exposure to oxygen, the phenolic hydroxyl groups in the antioxidant act as hydrogen donors, rapidly binding with lipid free radicals and blocking the chain reaction of lipid peroxidation, thus inhibiting the formation of aldehydes and ketones—off-flavor substances—from the source.

[0011] Secondly, sodium alginate, pregelatinized starch, or egg yolk lecithin act as hydrophilic and lipophilic structural stabilizers, adsorbing at the interface between ultrafine bone paste particles and the aqueous phase, reducing the solid-liquid interfacial tension, and using the steric hindrance effect to hinder the sedimentation and agglomeration of high-density bone paste particles, ensuring that the compound slurry maintains an isotropic and uniform state during the homogenization and pre-freezing stages, and avoiding stratification or local hardening of the finished product.

[0012] Preferably, the particle size D90 of the ultrafine bone paste is less than 50 μm; and the moisture content of the nutritional pet food is less than or equal to 5%.

[0013] By adopting the above technical solutions, the bioavailability of minerals is effectively improved and the product shelf life is extended. On the one hand, controlling the particle size (D90) of bone meal to the micron level (below 50 μm) disrupts the dense hydroxyapatite crystal structure of bone tissue, causing its specific surface area to increase exponentially. When the product enters the pet's digestive tract, the micron-sized bone meal particles can fully contact gastric acid (hydrochloric acid), accelerating the acidolysis reaction and rapidly dissociating the insoluble calcium phosphate salt into free calcium ions (Ca). 2＋ It combines with phosphate ions, thereby significantly improving the absorption efficiency of calcium in the body.

[0014] On the other hand, controlling the moisture content of the final product to below 5% can reduce the water activity (Aw) of the system to below the critical point for microbial growth, preventing bacteria and mold from multiplying and inhibiting the activity of residual enzymes, thus ensuring the long-term stability of the product under preservative-free conditions at room temperature.

[0015] Secondly, the present invention provides a method for preparing nutritional pet food based on low-value marine products, using the following technical solution: Low-value marine product raw materials are desalinated and then mechanically separated to obtain soft meat components and hard calcium components, respectively. The meat tender components are pulped, and natural antioxidants and complex proteases are added for constant-temperature enzymatic hydrolysis. After the reaction is completed, the temperature is raised to inactivate the enzyme and sterilize, resulting in enzymatically hydrolyzed meat pulp. The hard calcium component was softened by steaming under high pressure, and then subjected to multi-stage pulverization to obtain ultrafine bone paste. The enzymatically hydrolyzed meat slurry, the ultrafine bone paste, the structural stabilizer and the nutrient fortifier are mixed and homogenized under high pressure to obtain a compound homogenized slurry. The compounded homogeneous slurry was pre-frozen, and then subjected to sublimation drying and desorption drying under vacuum conditions to obtain freeze-dried pet food semi-finished product; The freeze-dried pet food semi-finished product is sealed and packaged in a low-humidity environment to obtain the nutritional pet food.

[0016] By adopting the above technical solution, this invention employs a step-by-step processing and recombinant compounding strategy, which solves the problem of simultaneously preserving meat nutrients and softening bones under single processing conditions: First, appropriate processing energy levels are matched to the soft and hard components of low-value marine products, which have significantly different physical properties. The soft meat components are processed under mild enzymatic hydrolysis conditions, avoiding excessive protein denaturation and charring caused by prolonged high-temperature heating, thus preserving heat-sensitive nutrients to the greatest extent. The hard calcium components, on the other hand, are processed under high temperature and high pressure to overcome their dense physical structure.

[0017] Secondly, this method utilizes the differences in rheological properties between components to construct a composite system. The enzymatically hydrolyzed meat slurry serves as the continuous phase matrix, providing a viscoelastic network; the softened and pulverized bone paste acts as the dispersed phase filler, providing rigid support. After mixing, homogenization, and freeze-drying, a solid product with uniform texture and well-developed pore structure is formed, avoiding the problems of rough texture or bone residue caused by traditional cooking processes.

[0018] Preferably, the desalination process involves immersing the low-value marine product raw material in 3-5 times its volume of deionized water or softened water, and rinsing it with stirring at room temperature for 30-60 minutes.

[0019] By employing the above technical solution, efficient desalination is achieved through a concentration gradient-driven mass transfer process. Deionized or softened water, as a solvent with low ionic strength, creates an osmotic pressure difference with the raw material tissue fluid, promoting the diffusion of inorganic salt ions from the interstitial spaces into the aqueous phase. By limiting the liquid-to-solid ratio to 3-5 times and the rinsing time to 30-60 minutes, the diffusion and loss of water-soluble proteins and flavor nucleotides are effectively controlled while ensuring sufficient salt dissolution, preventing the raw material from becoming bland and losing nutrients due to over-soaking.

[0020] Preferably, the isothermal enzymatic hydrolysis conditions are as follows: adjust the pH of the slurry to 6.5-7.5, add 0.1%-0.3% of the total mass of the slurry of the complex protease, and react at 45-55℃ for 1.5-3 hours; the temperature-inactivation and sterilization conditions are as follows: raise the temperature to 85-95℃ and keep it at that temperature for 10-15 minutes.

[0021] By employing the above technical solution, enzyme engineering technology is used to perform targeted cleavage of proteins. Within a selected pH and temperature range, the complex protease is in an optimal catalytic activity state, capable of specifically cleaving peptide bonds in myofibrillar proteins, degrading them into small-molecule peptides and amino acids, thereby improving the product's digestibility and releasing meat flavor. The subsequent heating step inactivates the enzyme through thermal denaturation, terminating the hydrolysis reaction to prevent the formation of bitter peptides. Simultaneously, the heat effect kills pathogenic microorganisms in the slurry, ensuring the food's biosafety.

[0022] Preferably, the conditions for steaming and softening are: temperature 115-125℃, pressure 0.10-0.15MPa, and time 20-40 minutes; the multi-stage pulverization is carried out using a coarse pulverizer and a colloid mill.

[0023] By employing the above-mentioned technical solution, the organic-inorganic composite structure of bone is destroyed using the principle of hydrothermal degradation. At 115-125℃ and the corresponding saturated vapor pressure, water molecules penetrate into the bone tissue, causing collagen fibers to undergo thermal depolymerization and gelatinization. This leads to the loosening of the organic matrix network in the bone, weakening its binding force on hydroxyapatite crystals. The softened bone tissue is then easily pulverized to the micron level under the shearing force of a colloid mill, thus solving the technical problem of traditional mechanical pulverization being unable to handle hard fish bones and easily producing high-temperature charring.

[0024] Preferably, the pressure of the high-pressure homogenizer is 25-40 MPa.

[0025] By employing the above technical solution, the cavitation and shear effects generated by high-pressure fluid are utilized to refine the slurry components. Under pressure of 25-40 MPa, the compounded slurry is subjected to strong impact and shear when passing through the homogenizing valve, forcing the agglomerated protein particles and bone paste particles to disperse, significantly increasing the specific surface area of ​​the dispersed phase. This allows the structural stabilizer to be more fully adsorbed at the particle interface, thereby constructing a long-term stable suspension emulsion system and preventing precipitation and stratification during subsequent freezing.

[0026] Preferably, the pre-freezing conditions are: freezing at -35℃ to -45℃ for 2-4 hours; the sublimation drying and desorption drying conditions are: vacuum degree controlled at 10-20Pa, heating plate temperature linearly increased to 0-10℃ for sublimation drying, and then increased to 35-45℃ for desorption drying.

[0027] By adopting the above technical solution, the phase change process of water and the formation of micropore structure were precisely controlled.

[0028] First, the deep freezing at -35℃ to -45℃ allows the free water in the slurry to rapidly nucleate and grow into fine, uniform ice crystals, thus avoiding the formation of large ice crystals that could damage the gel network framework.

[0029] Secondly, during the sublimation drying stage, the vacuum environment of 10-20 Pa lowers the boiling point and sublimation point of water. Combined with programmed heating, the ice crystals directly sublimate into water vapor and escape, leaving interconnected microporous channels in situ, which gives the product good rehydration properties.

[0030] Third, appropriately increasing the temperature during the drying stage provides the activation energy needed to break the hydrogen bonds between the material and the bound water, removing residual moisture to a safe level while avoiding Maillard reaction browning caused by excessively high temperatures.

[0031] Preferably, the low-humidity environment is a relative humidity of 30%-40%; high-purity nitrogen is used to fill the sealed packaging; and the low-value marine product raw materials are selected from at least one of small miscellaneous fish, shrimp heads, anchovies, fish fillets, crab shells, tuna heads, scallop scraps, and fish bones.

[0032] By employing the above technical solution, the storage environment of the product is controlled through physical barriers. Given that freeze-dried products have a high specific surface area and porous structure, they are highly susceptible to moisture absorption and oxidation. Controlling the humidity of the packaging environment and replacing the air inside the packaging bag with inert nitrogen directly cuts off the oxygen source required for lipid oxidation and prevents the reabsorption of moisture from the air. This inhibits microbial growth and delays rancidity of fatty acids without the addition of chemical preservatives, ensuring the product's shelf-life stability.

[0033] This invention provides a nutritional pet food based on low-value marine products and its preparation method. It has the following beneficial effects: 1. This invention achieves high-value utilization of all components of low-value marine products, improving the bioavailability of nutrients. It employs a soft and hard component separation process. On one hand, enzymatic hydrolysis converts large-molecule proteins in the meat into easily digestible small-molecule active peptides and amino acids. On the other hand, high-temperature cooking combined with micronization processes transforms waste bones into ultrafine bone paste with a particle size of less than 50μm, disrupting the dense mineralized structure of the bones and increasing the surface area for calcium dissolution in the digestive tract. This treatment method not only solves the resource waste problem caused by low-value marine waste but also effectively overcomes the technical shortcomings of low protein digestibility and poor calcium absorption by pets in traditional coarsely processed products.

[0034] 2. This invention solves the problems of easy oxidation and rancidity and difficulty in preservation of high-fat seafood raw materials by combining in-situ anti-oxidation and freeze-drying. Natural antioxidants (rosemary extract or tea polyphenols) are introduced in the early stages of raw material crushing and pulping, blocking free radical chain reactions the moment lipids are exposed to air, thus inhibiting the formation of aldehydes and ketones and other off-odor substances at the source. Combined with vacuum freeze-drying technology, moisture is removed to below 5% under low temperature and low pressure, maximizing the preservation of heat-sensitive nutrients and bioactive substances. These technical features enable the product to maintain stable quality for a long time without the addition of chemical preservatives, avoiding the impact of rancid odor caused by oil oxidation on pet health.

[0035] 3. This invention improves the palatability and rehydration performance of the product through texture recombination and enzymatic flavor enhancement technology. The flavor nucleotides and amino acids released during the enzymatic hydrolysis process give the product a natural meat flavor, which can strongly attract pets without the need for additional artificial palatability enhancers. At the same time, the structural stabilizer and bone-meat compound system maintain the support of the micro-skeleton during the freeze-drying process, forming a uniformly distributed microporous structure. This structural feature gives the product a crispy texture and ensures that the product can quickly absorb water and soften when rehydrated. This solves the problems of rough texture caused by bone residue in traditional pet food and hard texture and difficulty in rehydration caused by high temperature drying. Detailed Implementation

[0036] Example 1: This embodiment provides a nutritional pet food based on low-value marine products and its preparation method, including the following steps: S1. Frozen small miscellaneous fish and shrimp heads were selected as low-value marine product raw materials. After thawing and cleaning, they were immersed in three times their volume of deionized water and rinsed at room temperature for 30 minutes to perform desalination. The desalinated low-value marine product raw materials were sent to a bone and meat separator, and mechanically separated to obtain a 65% yield of soft meat component and a 35% yield of hard calcium component.

[0037] S2. Add the soft meat components to a meat chopper, add 0.02% (w / w) of a natural antioxidant (rosemary extract) to form a paste, and adjust the pH of the paste to 6.5. Then add 0.1% (w / w) of a complex protease (a 2:1 mixture of neutral protease and flavor protease), and hydrolyze at 45°C for 1.5 hours. After the reaction is complete, immediately raise the temperature to 85°C and hold for 10 minutes to inactivate the enzyme and sterilize. After cooling, obtain the enzymatically hydrolyzed meat paste.

[0038] S3. Place the hard calcium component in a high-pressure cooking kettle and cook at 115℃ (0.10MPa) for 20 minutes to soften it. Then, pulverize the softened aggregate through a coarse pulverizer and a colloid mill in multiple stages, controlling the particle size D90 at the end of the grinding process to be less than 50μm to obtain ultrafine bone paste.

[0039] S4. In the mixing tank, take 60 parts by weight of enzymatically hydrolyzed meat paste and mix it with 15 parts by weight of ultrafine bone paste, and add 1 part by weight of structural stabilizer (sodium alginate) and 0.5 parts by weight of nutrient fortifier. After stirring evenly, pump it into a high-pressure homogenizer and perform secondary homogenization at a pressure of 25 MPa to obtain a homogeneous compound homogenized paste.

[0040] S5. Inject the compounded homogenized slurry into the mold and place it in a quick-freezing chamber at -35°C for 4 hours. Then transfer it into a vacuum freeze-drying chamber, control the vacuum degree at 20Pa, and linearly raise the temperature of the heating plate from -30°C to 0°C for sublimation drying according to the program, and then raise it to 35°C for desorption drying until the moisture content of the product drops to 5%, thus obtaining the freeze-dried pet food semi-finished product.

[0041] S6. In an environment with a relative humidity of 30%, take out the freeze-dried pet food semi-finished product, put it into a composite aluminum foil bag and fill it with high-purity nitrogen to seal it, and you will get nutritious pet food.

[0042] Example 2: This embodiment provides a nutritional pet food based on low-value marine products and its preparation method, including the following steps: S1. Frozen anchovies, fish fillets, and crab shells were selected as low-value marine product raw materials. After thawing and cleaning, they were immersed in four times their volume of softened water and rinsed at room temperature for 45 minutes to desalinate. The desalinated low-value marine product raw materials were then fed into a bone and meat separator, where they were mechanically separated to obtain a 60% yield of soft meat components and a 40% yield of hard calcium components.

[0043] S2. The soft meat components are fed into a meat chopper, and 0.035% (w / w) of a natural antioxidant (tea polyphenols) is added for pulping. The pH of the pulp is adjusted to 7.0. Then, 0.2% (w / w) of a complex protease is added, and the mixture is enzymatically hydrolyzed at 50°C for 2.25 hours. After the reaction is complete, the temperature is immediately raised to 90°C and held for 12 minutes to inactivate the enzyme and sterilize. After cooling, the enzymatically hydrolyzed meat pulp is obtained.

[0044] S3. Place the hard calcium component in a high-pressure autoclave and cook at 120℃ (0.12MPa) for 30 minutes to soften it. Then, pulverize the softened aggregate through a coarse pulverizer and a colloid mill in multiple stages, controlling the particle size D90 at the end of the grinding process to be less than 40μm to obtain ultrafine bone paste.

[0045] S4. In the mixing tank, take 70 parts by weight of enzymatically hydrolyzed meat paste and 22 parts by weight of ultrafine bone paste, and add 3 parts by weight of structural stabilizer (pregelatinized starch) and 1.2 parts by weight of nutritional fortifier. After stirring evenly, pump it into a high-pressure homogenizer and perform secondary homogenization at a pressure of 32 MPa to obtain a homogeneous compound homogenized paste.

[0046] S5. Inject the compounded homogenized slurry into the mold and place it in a quick-freezing chamber at -40℃ for 3 hours. Then transfer it into a vacuum freeze-drying chamber, control the vacuum degree at 15Pa, and linearly increase the temperature of the heating plate from -30℃ to 5℃ for sublimation drying according to the program, and then increase it to 40℃ for desorption drying until the product moisture content drops to 4.5%, to obtain the freeze-dried pet food semi-finished product.

[0047] S6. Under an environment with a relative humidity of 35%, take out the freeze-dried pet food semi-finished product, put it into a composite aluminum foil bag, fill it with high-purity nitrogen and seal it to obtain nutritious pet food.

[0048] Example 3: This embodiment provides a nutritional pet food based on low-value marine products and its preparation method, including the following steps: S1. Frozen tuna heads, scallop scraps, and fish bones were selected as low-value marine product raw materials. After thawing and cleaning, they were immersed in 5 times their volume of deionized water and rinsed at room temperature for 60 minutes to perform deep desalination. The desalinated low-value marine product raw materials were then fed into a bone and meat separator, where they were mechanically separated to obtain a 55% yield of soft meat components and a 45% yield of hard calcium components.

[0049] S2. Add the soft meat components to a meat chopper, add 0.05% (w / w) of a natural antioxidant (rosemary extract) to form a paste, and adjust the pH of the paste to 7.5. Then add 0.3% (w / w) of a complex protease and hydrolyze at 55°C for 3 hours. After the reaction is complete, immediately raise the temperature to 95°C and hold for 15 minutes to inactivate the enzyme and sterilize. After cooling, obtain the enzymatically hydrolyzed meat paste.

[0050] S3. Place the hard calcium component in a high-pressure autoclave and cook at 125℃ (0.15MPa) for 40 minutes to soften it. Then, pulverize the softened aggregate through a coarse pulverizer and a colloid mill in multiple stages, controlling the particle size D90 at the end of the grinding process to be less than 30μm to obtain ultrafine bone paste.

[0051] S4. In the mixing tank, take 80 parts by weight of enzymatically hydrolyzed meat paste and mix it with 30 parts by weight of ultrafine bone paste, and add 5 parts by weight of structural stabilizer (egg yolk lecithin) and 2 parts by weight of nutritional fortifier. After stirring evenly, pump it into a high-pressure homogenizer and perform secondary homogenization at a pressure of 40 MPa to obtain a homogeneous compound homogenized paste.

[0052] S5. Inject the compounded homogenized slurry into the mold and place it in a quick-freezing chamber at -45℃ for 2 hours. Then transfer it into a vacuum freeze-drying chamber, control the vacuum degree at 10Pa, and linearly increase the temperature of the heating plate from -30℃ to 10℃ for sublimation drying according to the program, and then increase it to 45℃ for desorption drying until the moisture content of the product drops to 4%, thus obtaining the freeze-dried pet food semi-finished product.

[0053] S6. In an environment with a relative humidity of 40%, take out the freeze-dried pet food semi-finished product, put it into a composite aluminum foil bag and fill it with high-purity nitrogen to seal it, and you will get nutritious pet food.

[0054] Comparative Examples 1-5: Comparative Example 1: Compared with Example 2, the difference is that in step S1, only the surface of the raw material is cleaned, and the desalination step of immersing in 4 times the volume of softened water and stirring and rinsing for 45 minutes is omitted. The rest are the same.

[0055] Comparative Example 2: The difference from Example 2 is that no natural antioxidant tea polyphenols were added during the pulping process in step S2; all other aspects are the same.

[0056] Comparative Example 3: Compared with Example 2, the difference is that after the enzymatic hydrolysis reaction in step S2, the enzyme inactivation step of heating to 90°C and holding for 12 minutes was omitted, and the subsequent compounding was carried out directly after cooling. All other aspects are the same.

[0057] Comparative Example 4: Compared with Example 2, the difference is that in step S3, only coarse pulverization is performed, and the colloid mill ultrafine pulverization step is omitted. The final bone paste particle size D90 is controlled to be about 300μm. All other aspects are the same.

[0058] Comparative Example 5: Compared with Example 2, the difference is that step S5 is replaced with a hot air drying process, that is, the material after injection molding is placed in a forced-air drying oven and dried at 60°C for 12 hours until the moisture content is below 4.5%, and the rest are the same.

[0059] Test Examples 1-5: Test Example 1: Basic Physicochemical Indicators and Nutritional Compliance Test This test verifies the control of nutritional components and salt content of the pet foods prepared in Examples 1 to 3 under different process parameters.

[0060] Experimental steps: Take 500g of each of the freeze-dried products prepared in Examples 1, 2 and 3, crush them using a pulverizer and pass them through a 40-mesh sieve, mix them evenly and place them in a desiccator for later use.

[0061] According to GB / T 6435-2014 "Determination of Moisture in Feed", weigh 2-5g of sample, dry it in an oven at 105℃ until constant weight, and calculate the mass loss.

[0062] According to GB / T 6432-2018 "Determination of Crude Protein in Feed - Kjeldahl Method", the sample was digested with sulfuric acid, distilled, and titrated with hydrochloric acid standard solution. The total nitrogen content was calculated and multiplied by a coefficient of 6.25.

[0063] According to GB / T 6433-2025 "Determination of Crude Fat in Feed", anhydrous diethyl ether was used for reflux extraction for more than 6 hours, and the residue was weighed after the solvent was evaporated.

[0064] According to GB / T 6439-2023 "Determination of water-soluble chloride in feed", after the sample is extracted with water, the sodium chloride content is calculated by titrating with silver nitrate standard solution using potassium chromate as an indicator.

[0065] According to GB / T 6436-2018 "Determination of Calcium in Feed" and GB / T 6437-2018 "Determination of Total Phosphorus in Feed - Spectrophotometric Method", the calcium and total phosphorus contents of the samples were determined after dry ashing and acid dissolution, and the calcium-to-phosphorus ratio was calculated.

[0066] Experimental data: Table 1. Test results of physicochemical properties of finished products from Examples 1-3 Note: "-" indicates that the standard does not set mandatory limits.

[0067] Experimental conclusion: According to the data in Table 1, the water-soluble chloride content in all three examples was controlled between 0.23% and 0.48%, meeting the requirements for low-salt food. Example 3 had the lowest chloride content, indicating that the desalination effect increased with prolonged rinsing time. Effective desalination treatment prevented a significant decrease in the eutectic point of the material due to excessively high salt concentration. The moisture content in all three examples was below 5%, indicating that the material maintained a good frozen state during freeze-drying, without melting collapse or pore blockage caused by an excessively low eutectic point. This ensured complete sublimation of moisture, and the desalination pretreatment effectively guaranteed the freeze-drying process.

[0068] The increased proportion of ultrafine bone paste in the formula raised the calcium content of the finished product from 1.85% to 2.91%, while the crude protein content, although slightly reduced, remained above 63%. The enzymatic hydrolysis and steaming softening processes preserved the protein and minerals in the raw materials, maintaining a calcium-to-phosphorus ratio between 1.2:1 and 1.42:1. This indicates that the system after combining ultrafine bone paste and enzymatically hydrolyzed meat paste is homogeneous, and the homogenization process did not cause component stratification.

[0069] All physicochemical properties of Examples 1 to 3 meet the nutritional standards of the American Feed Control Association. Within the set process parameters, namely an enzymatic hydrolysis temperature of 45-55°C and a rinsing time of 30-60 minutes, pet food with qualified physicochemical properties and stable structure can be prepared, demonstrating the feasibility of industrial production.

[0070] Test Example 2: In vitro simulated gastric juice calcium dissolution rate test This test compares the calcium dissolution behavior of the finished products prepared in Example 2 and Comparative Example 4 in simulated gastric juice to verify the effect of bone paste micronization on calcium bioavailability.

[0071] Experimental steps: Weigh 2.0g of sodium chloride and 3.2g of pepsin (activity 3000U / mg), dissolve them in an appropriate amount of distilled water, add 7.0mL of concentrated hydrochloric acid, dilute to 1000mL, and adjust the pH to 1.5 to prepare artificial gastric juice.

[0072] Accurately weigh 2.00 g of each of the pulverized samples from Example 2 and Comparative Example 4, place them in 250 mL Erlenmeyer flasks, and add 100 mL of artificial simulated gastric juice preheated to 37 °C.

[0073] The conical flask was placed in a constant temperature shaking incubator, with the temperature set at 37℃ and the rotation speed at 100r / min to simulate the digestive environment of gastric peristalsis.

[0074] At four time points—0.5 hours, 1.0 hours, 2.0 hours, and 4.0 hours—5 mL of digestion solution was collected and centrifuged at 4000 r / min for 5 minutes to remove undissolved residue.

[0075] The supernatant was collected, and the concentration of free calcium ions was determined by EDTA complexometric titration. The calcium dissolution rate at different time points was calculated based on the total calcium content of the sample.

[0076] Experimental data: Table 2. Comparison of calcium dissolution rates in simulated gastric juice between Example 2 and Comparative Example 4 Experimental conclusion: According to the data in Table 2, the calcium dissolution rate and final dissolution amount in simulated gastric juice of Example 2 were higher than those of Comparative Example 4. After digestion for 0.5 hours, the dissolution rate of Example 2 was 43.12%, while that of Comparative Example 4 was 11.05%; after digestion for 2.0 hours, the dissolution rate of Example 2 reached 85.29%, while that of Comparative Example 4 was 28.61%; after digestion for 4.0 hours, the dissolution rate of Comparative Example 4 was less than 35%.

[0077] The data differences reflect the impact of bone paste micronization on calcium release. Comparative Example 4, despite high-temperature cooking, still had a physical particle size of approximately 300 μm. The hydroxyapatite crystals in the bone were encapsulated by the collagen matrix, resulting in a small contact area with hydrogen ions, and the dissolution reaction was limited by the solid-liquid interface diffusion rate. Example 2, through ultrafine grinding with a colloid mill, reduced the particle size to below 40 μm, increasing the particle specific surface area. In an acidic environment, the micron-sized bone paste particles underwent a displacement reaction with hydrogen ions, converting insoluble bone calcium into free calcium ions.

[0078] Simply softening bones at high temperatures is insufficient for efficient calcium utilization; it requires ultrafine grinding to disrupt the bone's microstructure. The ultrafine bone paste prepared in this invention exhibits high solubility in acidic environments, improving the digestibility of low-value fish bones and enhancing calcium source utilization.

[0079] Test Example 3: Accelerated Oxidation Stability Test This test compares the degree of lipid oxidation of the finished products prepared in Example 2 and Comparative Example 2 under accelerated aging conditions to verify the impact of in-situ antioxidant process on product shelf-life stability.

[0080] Experimental steps: Take 200g of each of the freeze-dried products from Example 2 and Comparative Example 2, crush them, spread them evenly on a clean enamel plate, and place them in a constant temperature and humidity chamber at 40℃ and 60% relative humidity.

[0081] 30g samples were randomly taken on days 0, 15, and 30 of the experiment.

[0082] According to GB 5009.227-2023 "National Food Safety Standard - Determination of Peroxide Value in Food", fat was extracted from the sample, and the peroxide value (POV) was determined and calculated.

[0083] According to GB 5009.181-2016 "National Food Safety Standard - Determination of Malondialdehyde in Food", after extraction and colorimetric reaction, the absorbance of the sample was measured and the content of thiobarbituric acid reactants (TBARS) was calculated.

[0084] Experimental data: Table 3. Accelerated oxidation stability test results of Example 2 and Comparative Example 2 Note: POV represents peroxide value, reflecting the content of products in the early stage of oil oxidation; TBARS represents thiobarbituric acid reactant value, reflecting the content of aldehydes in the later stage of oil oxidation; MDA is malondialdehyde.

[0085] Experimental conclusion: According to the data in Table 3, the POV and TBARS values ​​of Example 2 were lower than those of Comparative Example 2 throughout the entire accelerated test cycle.

[0086] On day 0, the POV value of Comparative Example 2 was 4.65 meq / kg, higher than that of Example 2 (3.24 meq / kg), indicating that the raw materials had undergone oxidation during the preparation process. No antioxidants were added to Comparative Example 2, and the polyunsaturated fatty acids reacted upon exposure to oxygen after cell wall disruption.

[0087] After 30 days of storage, the POV value of Comparative Example 2 increased to 45.17 meq / kg, and the TBARS value reached 3.42 mg / kg, indicating a high degree of fat oxidation and the production of secondary oxidation products such as malondialdehyde. Example 2, on day 30, had a POV value of 7.92 meq / kg and a TBARS value of 0.61 mg / kg, indicating a lower degree of oxidation.

[0088] Introducing antioxidants during the pulping and crushing stage inhibits initial oxidation during processing and oxidative rancidity during finished product storage, reducing the generation of aldehyde and ketone odor substances.

[0089] Test Example 4: Rehydration Performance and Structural Collapse Test This test compares the volume shrinkage rate and rehydration rate of the finished products prepared in Example 2, Comparative Example 1, and Comparative Example 5 to verify the influence of desalination process and drying method on the structure of the finished product.

[0090] Experimental steps: Ten regularly shaped cubic samples were randomly selected from the injection molding and freezing stages of Examples 2, 1, and 5. The length, width, and height were measured using calipers, and the initial volume was calculated. .

[0091] After the sample has completed the drying process, measure its length, width, and height again, and calculate its volume after drying. Calculate the volume shrinkage rate ( ; Weigh the dried sample. Immerse it completely in distilled water at a constant temperature of 40°C.

[0092] After soaking for 30 seconds, remove the sample, drain the surface water, and weigh it. Calculate the 30-second rapid rehydration ratio .

[0093] Continue soaking for 5 minutes, then remove, drain, and weigh. Calculate the complete rehydration ratio in 5 minutes. .

[0094] Experimental data: Table 4. Test results of volume shrinkage rate and rehydration performance of each group of samples. Experimental conclusion: According to the data in Table 4, the volume shrinkage rate of Example 2 was 3.42%, compared to 41.56% for Comparative Example 1 and 58.21% for Comparative Example 5. Regarding rehydration performance, Example 2 absorbed 2.85 times its own weight in 30 seconds, which is higher than 1.12 times for Comparative Example 1 and 0.45 times for Comparative Example 5.

[0095] The data differences reflect the impact of desalination protection and drying methods on the microstructure. In Example 2, after desalination treatment, the material had a higher eutectic point. Under vacuum, water sublimated from ice crystals, leaving interconnected microporous channels and an intact skeletal structure. During rehydration, water molecules entered the interior through capillary action.

[0096] Comparative Example 1 was not desalted. The high concentration of salt in the intercellular spaces led to a decrease in the eutectic point. During the drying process, the material underwent localized melting, resulting in structural collapse and volume shrinkage. Pore blockage affected rehydration.

[0097] Comparative Example 5 used hot air drying, where the surface tension generated by the evaporation of liquid water caused volume shrinkage, resulting in a dense texture, and the outer hard shell prevented moisture from entering. Desalination pretreatment and vacuum freeze-drying are necessary conditions for forming a porous structure and rehydration properties.

[0098] Test Example 5: Evaluation of Pet Palatability and Sensory Flavor This test, conducted using the double-basin feeding method and sensory evaluation panel, compared the palatability differences between Example 2 and Comparative Examples 2, 3, and 5, verifying the effects of enzymatic debittering, antioxidant, and drying processes on product flavor.

[0099] Experimental steps: Twenty healthy adult cats, weighing 3.5-5.5 kg, were selected and given a 3-day acclimatization period before the test.

[0100] A two-bowl selection method was used. Each cat was simultaneously provided with two identical food bowls, each containing 50g of the sample from Example 2 and 50g of the comparative sample (Comparative Example 2, Comparative Example 3, or Comparative Example 5). The left and right food bowls were randomly swapped to eliminate positional preference.

[0101] The feeding time was set at 30 minutes. After the feeding time, the remaining feed was collected and weighed, and the feed intake of each sample was calculated. The intake ratio (IR) was calculated as: intake of the sample to be tested / (intake of Example 2 + intake of the sample to be tested).

[0102] A 10-person sensory evaluation team was formed to descriptively score the samples. Evaluation indicators included: umami intensity (enzymatic hydrolysis effect), bitterness intensity (residual hydrophobic peptides), rancidity intensity (fat oxidation), and texture crispness (dry structure). Scoring was based on a 0-10 scale, with higher scores indicating a stronger characteristic.

[0103] Experimental data: Table 5. Statistical analysis of sensory scores and food intake ratios for each group of samples. Note: - indicates that this item is used as a reference standard and has no relative comparison value.

[0104] Experimental conclusion: According to the data in Table 5, the sensory indicators and pet intake ratio of Example 2 are better than those of the other pairs.

[0105] Comparative Example 3 had a bitterness intensity score of 8.67 and a relative intake ratio of 0.09. This group omitted the enzyme inactivation step, allowing the protease to remain active during subsequent processing, continuously hydrolyzing the polypeptide chain and leading to the accumulation of hydrophobic amino acids such as leucine and phenylalanine, resulting in bitterness. Example 2 controlled the degree of hydrolysis through high-temperature enzyme inactivation, inhibiting the formation of bitter peptides while preserving umami substances, achieving an umami score of 8.75.

[0106] Comparative Example 2 had a rancidity score of 7.92 and an intake ratio of 0.18. No antioxidants were added during the pulping and cell-wall breaking stage, causing the unsaturated fatty acids in the seafood raw materials to oxidize upon exposure to air, producing aldehydes and ketones. Pets are sensitive to oxidized odors, leading to reduced feed intake.

[0107] Comparative Example 5 scored 2.45 for crispness and 3.55 for umami. Hot air drying caused the product surface to harden and the interior to become dense, failing to create a crisp texture, and continuous heating led to the decomposition of some heat-sensitive flavor compounds. Example 2, combining enzymatic hydrolysis control, in-situ antioxidant processes, and vacuum freeze-drying, ensured the product's umami, low bitterness, and crisp structure.

Claims

1. A nutritional pet food based on low-value marine products, characterized in that, Made from the following ingredients in parts by weight: 60-80 portions of enzymatically hydrolyzed meat paste; 15-30 parts of ultrafine bone paste; 1-5 parts of structural stabilizer; Nutritional fortifier 0.5-2 parts; The enzymatically hydrolyzed meat paste is obtained by enzymatic hydrolysis of the soft meat components of low-value marine products; the ultrafine bone paste is obtained by micronization of the hard calcium components of low-value marine products.

2. The nutritional pet food based on low-value marine products according to claim 1, characterized in that, The structural stabilizer is selected from at least one of sodium alginate, pregelatinized starch and egg yolk lecithin; the enzymatically hydrolyzed meat paste contains 0.02%-0.05% of a natural antioxidant by weight of the total enzymatically hydrolyzed meat paste, and the natural antioxidant is selected from rosemary extract or tea polyphenols.

3. A nutritional pet food based on low-value marine products according to claim 1, characterized in that, The particle size D90 of the ultrafine bone paste is less than 50 μm; the moisture content of the nutritional pet food is ≤5%.

4. A method for preparing nutritional pet food based on low-value marine products, characterized in that, The nutritional pet food based on low-value marine products according to any one of claims 1-3 includes the following steps: Low-value marine product raw materials are desalinated and then mechanically separated to obtain soft meat components and hard calcium components, respectively. The meat tender components are pulped, and natural antioxidants and complex proteases are added for constant-temperature enzymatic hydrolysis. After the reaction is completed, the temperature is raised to inactivate the enzyme and sterilize, resulting in enzymatically hydrolyzed meat pulp. The hard calcium component was softened by steaming under high pressure, and then subjected to multi-stage pulverization to obtain ultrafine bone paste. The enzymatically hydrolyzed meat slurry, the ultrafine bone paste, the structural stabilizer and the nutrient fortifier are mixed and homogenized under high pressure to obtain a compound homogenized slurry. The compounded homogeneous slurry was pre-frozen, and then subjected to sublimation drying and desorption drying under vacuum conditions to obtain freeze-dried pet food semi-finished product; The freeze-dried pet food semi-finished product is sealed and packaged in a low-humidity environment to obtain the nutritional pet food.

5. The method for preparing a nutritional pet food based on low-value marine products according to claim 4, characterized in that, The specific steps of the desalination process are as follows: immerse the low-value marine product raw material in 3-5 times its volume of deionized water or softened water, and stir and rinse at room temperature for 30-60 minutes.

6. The method for preparing a nutritional pet food based on low-value marine products according to claim 4, characterized in that, The conditions for isothermal enzymatic hydrolysis are as follows: adjust the pH of the slurry to 6.5-7.5, add 0.1%-0.3% of the total mass of the slurry of the complex protease, and react at 45-55℃ for 1.5-3 hours; The conditions for temperature-induced enzyme inactivation and sterilization are: heating to 85-95℃ and holding at that temperature for 10-15 minutes.

7. A method for preparing a nutritional pet food based on low-value marine products according to claim 4, characterized in that, The conditions for steaming and softening are: temperature 115-125℃, pressure 0.10-0.15MPa, and time 20-40 minutes; The multi-stage pulverization process employs a coarse pulverizer and a colloid mill.

8. A method for preparing a nutritional pet food based on low-value marine products according to claim 4, characterized in that, The pressure of the high-pressure homogenizer is 25-40 MPa.

9. A method for preparing a nutritional pet food based on low-value marine products according to claim 4, characterized in that, The pre-freezing conditions are: freezing at -35°C to -45°C for 2-4 hours; The conditions for sublimation drying and desorption drying are as follows: the vacuum degree is controlled at 10-20 Pa, the temperature of the heating plate is linearly increased to 0-10℃ according to the program for sublimation drying, and then increased to 35-45℃ for desorption drying.

10. A method for preparing a nutritional pet food based on low-value marine products according to claim 4, characterized in that, The relative humidity of the low-humidity environment is 30%-40%; The sealed packaging is filled with high-purity nitrogen. The low-value marine product raw materials are selected from at least one of the following: small miscellaneous fish, shrimp heads, anchovies, fish fillets, crab shells, tuna heads, scallop scraps, and fish bones.

Images