Edible processing method of sheepskin

Abstract

The invention discloses a sheepskin edible processing method, and belongs to the technical field of food processing. The method mainly solves the problems that in the prior art, sheepskin degreasing is not thorough, the risk of chemical degreasing agent residue is high, and a solvent and a stabilizer are difficult to efficiently recycle. According to the technical scheme, the method is characterized by comprising the steps that firstly, unhaired wet sheepskin is placed in a hot water treatment tank, meanwhile, mechanical rolling and kneading are conducted, medium-frequency ultrasonic treatment is assisted, and primarily degreased sheepskin is obtained; then the sheepskin is transferred to an O / W type Pickering emulsion tank to be subjected to deep degreasing treatment, and the degreasing end point is accurately controlled by monitoring the change rate of the emulsion conductivity in real time; and then centrifuging to remove the emulsion on the surface to obtain the edible sheepskin with low fat content. And finally, distilling the separated emulsion, recovering the n-heptane solvent, and meanwhile, recovering the ferroferric oxide core-shell magnetic particles through magnetic separation and recycling the ferroferric oxide core-shell magnetic particles. The method is mainly used for processing the sheepskin into the edible collagen raw material with high efficiency, low residue and low cost.

Description

Technical Field

[0001] The present invention relates to the technical field of food processing, and more particularly to a method for processing sheepskin into an edible form. Background Art

[0002] Sheepskin, a byproduct of meat processing, is rich in collagen and has the potential to be developed into edible collagen products. However, effectively converting it into a safe, low-fat, edible raw material faces significant technical challenges, primarily in fat removal, collagen preservation, process controllability, and resource recycling.

[0003] First, sheepskin fat is mainly found in fat cells and is wrapped in tough cell membranes. Traditional physical or chemical degreasing methods are difficult to efficiently and thoroughly destroy these cell membrane structures, resulting in incomplete fat removal and high residual fat content (usually far above 1wt%). Residual fat not only affects the flavor and taste of the product, but is also more susceptible to oxidation and rancidity during storage, reducing product quality and safety. Existing physical methods (such as mechanical extrusion and hot water treatment) have limited destructive power on cell membranes, and long-term high-temperature treatment can easily lead to excessive denaturation and hardening of collagen, resulting in loss of the texture required for consumption; while chemical methods (such as the use of strong alkali and organic solvents) have improved degreasing effects, there is a risk of chemical reagent residues, making it difficult to meet food-grade safety requirements, and subsequent cleaning brings environmental pressure.

[0004] Secondly, in the pursuit of deep degreasing, how to avoid damage to collagen is a key difficulty. High temperature is an effective means to promote fat release and emulsification, but it can also easily cause thermal denaturation of collagen, resulting in structural shrinkage and increased toughness. The final product has a tough and rough taste and loses its edible value. Traditional methods find it difficult to strike a balance between the high temperature conditions required for effective degreasing and the mild conditions required to protect collagen. In particular, when using high-efficiency degreasing technologies such as subcritical water or supercritical fluid, the high temperature and high pressure environment required places stringent requirements on equipment, resulting in high investment and operating costs, making it difficult to widely use in industrialization.

[0005] Third, there is a lack of effective, controllable, and low-cost methods for deep degreasing, especially when dealing with stubborn residual fat. While existing high-efficiency degreasing technologies (such as high-frequency pulsed electric field-assisted degreasing and subcritical water treatment) are highly effective, they rely on specialized equipment and have high energy consumption and maintenance costs. Conventional methods like solvent emulsification degreasing make it difficult to monitor and precisely control the degreasing process in real time. Operators often rely on experience or fixed time intervals to determine the degreasing endpoint, which can easily lead to insufficient degreasing (excessive residual fat) or over-processing (wasting energy, potentially damaging collagen structure, or increasing solvent residue). This lack of process control directly impacts the fat content compliance rate and batch stability of the final product.

[0006] Fourth, the inefficient recycling and reuse of organic solvents and specialized additives (such as emulsion stabilizers) used in the process is a key constraint on cost control. Insufficient solvent purity (such as water or acid content) in the recovered solvents compromises their effectiveness and safety in the subsequent degreasing process. Furthermore, specialized additives (such as solid particle stabilizers) can aggregate, deactivate, or be lost at high temperatures or in complex systems, resulting in low recovery rates and difficult regeneration. This increases production costs and wastes resources. Few mature solutions exist that can simultaneously achieve efficient degreasing, cost-effective reagent recycling, and avoid secondary residues.

[0007] Finally, achieving green sustainability for the entire process faces difficulties. Deep degreasing and recycling of solvents and additives are key to reducing costs and environmental impacts, but existing technologies have bottlenecks in combining these aspects. The contradiction between efficient degreasing and collagen protection, the lack of process controllability, and the difficulty in high-quality and efficient recycling of solvents / additives are intertwined, restricting the large-scale, economical and environmentally friendly application of sheepskin edible processing technology. Therefore, it is of great practical significance to develop a sheepskin edible processing method that can not only ensure the degreasing effect and product edible quality, but also significantly reduce equipment investment and operating costs, and achieve efficient circulation of processing media. Summary of the Invention

[0008] One object of the present invention is to provide a method for processing sheepskin into edible collagen raw materials with high efficiency, low residue and low cost.

[0009] In order to achieve these purposes and other advantages of the present invention, according to one aspect of the present invention, the present invention provides a method for making sheepskin edible, comprising the following steps: Step 1: placing the wet sheepskin that has been dehaired and surface cleaned in a hot water treatment tank, treating it at a temperature of 95-100° C. and normal pressure for 30-60 minutes, and simultaneously mechanically tumbling and supplemented with medium-frequency ultrasonic treatment at a frequency of 20-40 kHz, with an ultrasonic power density of 30-50 W / L, so that the sheepskin fat cell membrane is destroyed by mechanical shearing and cavitation effects, and the released fat is emulsified by hot water to form an oil-water mixture, thereby obtaining a sheepskin that has been preliminarily degreased; Step 2: Immediately transfer the sheepskin treated in Step 1 to an O / W Pickering emulsion tank for treatment for a total time of 30-120 minutes, and terminate the treatment early when the conductivity change rate |Δσ / Δt| is less than 0.5 μS / cm·min under real-time monitoring; wherein the Pickering emulsion is composed of an n-heptane oil phase with a boiling point of 60-100° C. and an aqueous phase stabilizer of ferroferric oxide core-shell magnetic particles with a particle size of 10-100 nm, wherein the volume ratio of the oil phase to the aqueous phase is 1:1.5-1:2.5; Step 3: remove the sheepskin from the emulsion tank and separate and remove the surface emulsion by centrifuge at a speed of 1000-3000 rpm to obtain an edible sheepskin with a fat content of ≤0.5 wt% and a magnetic particle residue of ≤50 ppm; Step 4: transport the separated emulsion to a distillation tower, distill and recover n-heptane at a tower bottom temperature of 80-90°C, and simultaneously recover ferroferric oxide core-shell magnetic particles from the tower bottom liquid by magnetic separation, and recycle them for the Pickering emulsion preparation in step 2.

[0010] Preferably, a collagen protective agent is added to the aqueous medium in the hot water treatment tank in step 1, which is selected from at least one of polyols, reducing disaccharides, polyhydroxy compounds or edible inorganic salts, and the concentration of the collagen protective agent added to the aqueous medium is 5-25% w / v.

[0011] Preferably, the mechanical tumbling in step 1 is achieved by a scraper-type agitator provided in the tank, which operates at a rotation speed of 15-25 rpm, so that the sheepskins are continuously turned and rubbed against each other.

[0012] Preferably, the preparation method of the ferroferric oxide core-shell magnetic particles in step 2 is: 0.5-1.0 mol / L FeCl2 and FeCl3 solution were mixed according to Fe 2+ :Fe 3+ The mixture is mixed at a molar ratio of 1:1.8-2.2, 0.3-0.6 mol / L sodium citrate is added under nitrogen protection, 0.5-1.0 mol / L ammonia water is added dropwise at a constant rate at 50-60°C to a pH of 9.5-10.5, and after aging for 2-3 hours, magnetic separation is performed in a magnetic field with an intensity of 0.8-1.2 T, and the supernatant is discarded. The resulting magnetic precipitate is washed three times with hot deionized water at 60-70°C and then washed twice with anhydrous ethanol to obtain Fe3O4 nanoparticles with a particle size of 15-25 nm; The obtained Fe3O4 particles are dispersed in a mixed solvent of ethanol and water in a volume ratio of 3:1, and 0.1-0.3 wt% of hexadecyltrimethylammonium bromide accounting for the total mass of the mixed solvent is added. After ultrasonic treatment for 10-15 min, ethyl orthosilicate is added dropwise, and the dropping speed is controlled to be 0.5-1.0 mL / min and the mass ratio of ethyl orthosilicate to Fe3O4 is 1:2-1:3. The mixture is reacted at 40-45°C for 4-6 h to form a 5-8 nm silicon shell. After the reaction, magnetic separation is performed by a magnetic field with an intensity of 0.8-1.2 T, and the supernatant is discarded. The obtained particles are washed with ethanol and acetone three times each, and then dried in a vacuum drying oven at 60-80°C for 6-8 h to obtain Fe3O4 particles coated with a mesoporous silicon layer; The obtained Fe3O4 particles coated with the mesoporous silica layer were dispersed in toluene, and octyltrimethoxysilane was added at a molar ratio of 3:1-5:1 to Fe3O4. The mixture was refluxed at 110-120°C for 8-10 hours. After the reflux, the mixture was cooled to room temperature and magnetically separated in a magnetic field with an intensity of 1.0-1.5T. The supernatant was discarded, and the obtained particles were washed twice with toluene and then three times with n-heptane. The washed particles are placed in a tube furnace, heated to 350-450°C at a rate of 3-5°C / min under nitrogen protection, and calcined for 1-2 hours to completely remove any organic residues. The calcined particles are redispersed in n-heptane and magnetically separated using a magnetic field with an intensity of 1.0-1.5T. The supernatant is discarded to obtain pure Fe3O4 core-shell magnetic particles with a CTAB residue of less than 1ppm and a TEOS residue of less than 5ppm. Preferably, the sheepskin treatment process in the Pickering emulsion tank in step 2 includes: In the pre-infiltration stage, the sheepskin is immersed in the emulsion and then intermittent variable frequency stirring is started, running at a high speed of 200-300 rpm from 0 to 10 minutes, and then reducing the speed to 100-150 rpm from 10 to 30 minutes; In the deep degreasing stage, an ultrasonic field with a frequency of 28±2kHz and a power density of 50-80W / L is applied, and the magnetic field is turned on simultaneously, with a horizontal magnetic field strength of 0.3-0.5T and a vertical magnetic field strength of 0.1-0.2T; The rate of change of the emulsion conductivity was monitored in real time. When |Δσ / Δt| was less than 0.5 μS / cm·min, the magnetic field was suspended for 30 s and then re-measured for confirmation.

[0013] Preferably, the n-heptane recovered by distillation in step 4 is passed through a silanized 3Å molecular sieve column with a pore size of 0.33±0.02nm, and dehydrated and deacidified at 50-60°C to obtain a high-purity solvent with a water content of ≤30ppm and an acid value of ≤0.05mgKOH / g.

[0014] Preferably, the recovery process of the ferroferric oxide core-shell magnetic particles in step 4 is as follows: applying an axial gradient magnetic field in a distillation tower with an intensity of 0.8-1.0T in the bottom region, 0.3-0.5T in the middle region, and <0.1T in the top region, controlling the bottom temperature to 85±2°C to inhibit agglomeration of the magnetic particles; recovering the particles from the bottom liquid of the tower by subjecting it to a 1.0-1.5T magnetic field, dispersing it in 80°C hot n-heptane containing 0.8-1.2% oleic acid and oscillating it for 20 minutes to repair the hydrophobic surface of the particles.

[0015] Preferably, the recovered high-purity solvent and the particles after repairing the hydrophobic surface are mixed and transported back to the Pickering emulsion tank. The specific configuration process is as follows: The particles with repaired hydrophobic surfaces were dispersed in deionized water at a concentration of 0.7-1.1% w / v and ultrasonically treated at a frequency of 40 kHz and a power of 50 W / L for 10 min to obtain a homogeneous aqueous dispersion. Use high-purity solvent as the oil phase and inject it into the water phase at a constant speed according to the volume ratio of oil phase to water phase of 1:1.5-1:2.5, and the injection rate is 5-10L / min; The mixture was first homogenized in a high-speed homogenizer at 8000-10000 rpm for 3 min to form a coarse emulsion, and then homogenized at 12000-15000 rpm for 2 min to reduce the emulsion droplet size to 1.5 ± 0.3 μm; After 24-48 hours of static aging, the emulsion is transferred back to the Pickering emulsion tank for use in step 2, sheepskin treatment.

[0016] The present invention has at least the following beneficial effects: First, the present invention provides a method for processing sheepskin into an edible form. By adopting the combined effects of normal pressure hot water treatment, mechanical tumbling and medium-frequency ultrasound, the sheepskin fat cell structure is effectively destroyed and fat emulsification is promoted under mild conditions. It gets rid of the dependence on expensive high-pressure, high-temperature equipment (such as subcritical water reactors) and complex electric field systems, greatly reduces the initial equipment investment and subsequent energy consumption and maintenance costs, lays a good foundation for subsequent deep degreasing, and is more suitable for industrial promotion.

[0017] Second, adding collagen protective agents during the hot water treatment stage and controlling the treatment temperature and time can significantly reduce the damage to the sheepskin collagen structure caused by the treatment process, help maintain the natural conformation of the protein molecules, and the final product can maintain good texture and palatability, solving the contradiction between efficient degreasing and collagen protection.

[0018] Third, deep treatment with a Pickering emulsion of a specific composition, combined with real-time conductivity monitoring, can sensitively and objectively determine the dynamic changes in fat dissolution during the degreasing process, thereby achieving precise control of the degreasing endpoint, effectively avoiding under- or over-treatment, and ensuring that the fat content of the final product (≤0.5wt%) remains stable and meets the standard.

[0019] Fourth, one of the core advantages of this invention lies in the closed-loop recovery and regeneration system for the solvent and magnetic particles. By combining distillation and magnetic separation techniques, the n-heptane solvent is efficiently recovered; a unique surface repair process restores the emulsion stability of the magnetic particles. A specific configuration of these two allows them to re-form a highly efficient Pickering emulsion, enabling high-frequency, low-cost recycling of the core medium, significantly reducing material consumption and waste disposal costs.

[0020] Fifth, the entire process avoids the use of chemical degreasing agents such as strong alkalis and surfactants, fundamentally eliminating the risk of harmful chemical residues, ensuring a pure and safe final product. Combining atmospheric pretreatment with media circulation technology, the entire solution not only reduces production energy and material consumption but also minimizes the discharge of three wastes, demonstrating excellent economic and environmental performance, providing a reliable path for the high-value, green processing and utilization of sheepskin byproducts.

[0021] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below in conjunction with specific embodiments so that those skilled in the art can implement the invention with reference to the description.

[0023] It should be understood that terms such as “having”, “including” and “comprising” used herein do not preclude the existence or addition of one or more other elements or combinations thereof.

[0024] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial channels unless otherwise specified.

[0025] The present invention provides a method for processing sheepskin into an edible form, comprising the following steps: Step 1: placing the wet sheepskin that has been dehaired and surface cleaned in a hot water treatment tank, treating it at a temperature of 95-100° C. and normal pressure for 30-60 minutes, and simultaneously mechanically tumbling and supplemented with medium-frequency ultrasonic treatment at a frequency of 20-40 kHz, with an ultrasonic power density of 30-50 W / L, so that the sheepskin fat cell membrane is destroyed by mechanical shearing and cavitation effects, and the released fat is emulsified by hot water to form an oil-water mixture, thereby obtaining a sheepskin that has been preliminarily degreased; Step 2: Immediately transfer the sheepskin treated in Step 1 to an O / W Pickering emulsion tank for treatment for a total time of 30-120 minutes, and terminate the treatment early when the conductivity change rate |Δσ / Δt| is less than 0.5 μS / cm·min under real-time monitoring; wherein the Pickering emulsion is composed of an n-heptane oil phase with a boiling point of 60-100° C. and an aqueous phase stabilizer of ferroferric oxide core-shell magnetic particles with a particle size of 10-100 nm, wherein the volume ratio of the oil phase to the aqueous phase is 1:1.5-1:2.5; Step 3: remove the sheepskin from the emulsion tank and separate and remove the surface emulsion by centrifuge at a speed of 1000-3000 rpm to obtain an edible sheepskin with a fat content of ≤0.5 wt% and a magnetic particle residue of ≤50 ppm; Step 4: transport the separated emulsion to a distillation tower, distill and recover n-heptane at a tower bottom temperature of 80-90°C, and simultaneously recover ferroferric oxide core-shell magnetic particles from the tower bottom liquid by magnetic separation, and recycle them for the Pickering emulsion preparation in step 2.

[0026] In the above technical solution, in step 1, a normal-pressure, double-layered hot water tank can be used as the main body of the hot water treatment tank, equipped with a steam heating coil and a temperature control system. Mechanical tumbling can be achieved using a scraper-type agitator installed within the tank, while medium-frequency ultrasonic treatment is achieved using piezoelectric ceramic transducer arrays installed on the bottom and side walls of the tank. Deionized water can be used as the aqueous medium, and the wet sheepskin raw material can be sourced from fresh hides that have been mechanically dehaired and cleaned with a high-pressure water jet at a slaughterhouse.

[0027] In step 2, the Pickering emulsion tank used for deep degreasing can be equipped with a variable frequency agitator, an ultrasonic transducer array, and a permanent magnet assembly. The ferroferric oxide core-shell magnetic particles can be commercially available oleic acid-modified Fe₃O₄@SiO₂ nanoparticles (particle size 50±10 nm). The n-heptane solvent can be of industrial-grade purity (≥98%). The centrifuge in step 3 can be a horizontal spiral settling machine. The distillation column in step 4 can be equipped with a magnetic recovery device, and electromagnetic coils can be installed within the column to generate a gradient magnetic field.

[0028] During operation, wet sheepskin is placed in a hot water treatment tank, set to 98°C, and treated at atmospheric pressure for 40 minutes. A scraper-type agitator operates at 20 rpm, continuously turning and agitating the sheepskin. Simultaneously, ultrasonic waves with a frequency of 30 kHz and a power density of 40 W / L are activated to synergistically. Under these conditions, the sheepskin's fat cell membranes are destroyed by mechanical shear and cavitation, and the released fat is emulsified by the hot water, forming an oil-water mixture, resulting in a preliminarily degreased sheepskin.

[0029] The treated sheepskin was then immediately transferred to an O / W Pickering emulsion tank for deep degreasing. After immersion in the emulsion, the sheepskin was stirred at 250 rpm for the first 10 minutes. The stirring speed was then reduced to 120 rpm. An ultrasonic field with a frequency of 28 kHz and a power density of 60 W / L was applied, along with a horizontal magnetic field of 0.4 T and a vertical magnetic field of 0.15 T. During this process, an online sensor monitored the conductivity of the emulsion in real time. Treatment was terminated when the rate of change, |Δσ / Δt|, was detected to be less than 0.5 μS / cm·min for three consecutive times.

[0030] After the sheepskin is removed from the emulsion tank, it is immediately sent to a centrifuge and centrifuged at 2000 rpm for 5 minutes to remove the emulsion attached to its surface, thereby obtaining an edible sheepskin product with a fat content not higher than 0.5wt% and a magnetic particle residue that meets the standard.

[0031] The separated emulsion was transferred to a distillation tower for separation and recovery. n-heptane was distilled and recovered at a bottom temperature of 85°C. An axial gradient magnetic field was applied within the tower, with magnetic field strengths of 0.9T in the bottom region, 0.4T in the middle region, and less than 0.1T at the top. The recovered n-heptane vapor was condensed and passed through a silanized 3Å molecular sieve column with a pore size of 0.33nm. Dehydration and deacidification were performed at 55°C to obtain a high-purity solvent. The bottom liquid was subjected to a 1.2T magnetic field to recover Fe3O4 core-shell magnetic particles. The recovered particles were dispersed in an 80°C hot n-heptane solution containing 1% oleic acid and shaken for 20 minutes to restore the particles' hydrophobic surface properties.

[0032] This method uses hot water, mechanical tumbling, and medium-frequency ultrasonic pretreatment to effectively destroy the fat cell structure of sheepskin and promote fat emulsification under normal pressure and low temperature conditions, laying a good foundation for subsequent deep degreasing and significantly reducing equipment investment and energy consumption costs. The use of a Pickering emulsion with a specific composition for deep treatment, combined with real-time conductivity monitoring, can accurately control the degreasing process to ensure that residual fat in the sheepskin is fully removed. Centrifugal operation can effectively separate the emulsion system remaining on the sheepskin surface. The combined application of distillation and magnetic separation technology realizes the recycling and reuse of solvents and magnetic particles, forming a closed-loop circulation system for processing media, which greatly reduces material consumption costs and environmental burdens. The entire processing process links cooperate with each other, while ensuring the degreasing effect and product safety, and reflecting good economic and environmental characteristics.

[0033] In another technical solution, a collagen protective agent is added to the aqueous medium in the hot water treatment tank in step one, which is selected from at least one of polyols, reducing disaccharides, polyhydroxy compounds or edible inorganic salts, and the concentration of the collagen protective agent added to the aqueous medium is 5-25% w / v.

[0034] In the above technical solution, the hot water treatment tank described in step 1 can be equipped with a chemical addition system, which can include a liquid preparation tank with a stirring function and a metering pump. The liquid preparation tank can be installed next to the treatment tank and connected to the tank body via a pipeline. The metering pump can be installed on the liquid preparation tank outlet pipeline. The collagen protective agent can be selected from one or a combination of food-grade glycerin, sorbitol, trehalose, or disodium hydrogen phosphate. These raw materials can be obtained from food additive suppliers and their purity meets national food additive standards.

[0035] To implement this, first add the prescribed amount of deionized water to the mixing tank, start the agitator, and slowly add the collagen protective agent. A suitable concentration is 15% weight-to-volume (w / v), meaning 15 grams of the agent is dissolved per 100 milliliters of water. Once dissolved, the agent is pumped into the hot water treatment tank via a metering pump, where it mixes with the existing aqueous medium. This mixing process continues until the protective agent concentration is evenly distributed. The pre-treated wet sheepskin is then placed in the treatment tank for subsequent processing according to established procedures.

[0036] Adding collagen protective agents during the hot water treatment process can effectively reduce the damage to the collagen structure of sheepskin caused by heat treatment. This type of protective agent interacts with water molecules and collagen peptide chains through multiple hydroxyl groups or specific ionic groups in its molecules, helping to maintain the natural conformation and moisture content of the protein molecules, thereby slowing down the process of thermal denaturation. After this treatment, the integrity of the collagen fiber network of sheepskin is better maintained, and the microstructure is more dense and orderly. This is reflected in the final product, which is manifested as a more flexible texture, improved toughness when chewing, and a more palatable taste. In addition, the treated sheepskin also exhibits better functional properties in subsequent processing links, making it possible to obtain higher quality edible sheepskin products. This measure is an effective way to ensure degreasing efficiency while taking into account the edible quality of the product.

[0037] In another technical solution, the mechanical tumbling in step one is achieved by a scraper-type agitator provided in the tank, which operates at a rotation speed of 15-25 rpm, causing the sheepskins to continuously turn over and rub against each other.

[0038] In another technical solution, the mechanical tumbling in step 1 is achieved by a scraper-type agitator installed in the tank. This agitator consists of a motor, a speed reducer, and a scraper assembly. The scraper edge shape is adapted to the inner wall of the treatment tank. It operates at a speed of 15-25 rpm, causing the sheepskin to be continuously lifted, thrown, and rubbed against each other in the tank, achieving uniform mechanical action on the sheepskin tissue.

[0039] In practice, pre-treated wet sheepskin is first placed in a hot water treatment tank, where a hot water medium containing a collagen protective agent is injected. The scraper agitator is activated and set to 20 rpm. During operation, the scraper not only slowly propels the sheepskin within the tank but also causes it to flip up and down, ensuring that all parts of the sheepskin are adequately kneaded and squeezed. This mechanical action directly affects the sheepskin's fat cells, disrupting their membrane structure through continuous shear and friction, promoting the release of internal fat. Simultaneously, the friction between the sheepskins enhances the removal of surface impurities.

[0040] Mechanical tumbling, achieved through the use of a scraper-type agitator, produces a comprehensive and gentle mechanical action on the sheepskin during the normal pressure hot water treatment process. This mechanical action covers all areas of the sheepskin, including surface wrinkles and internal tissue. The slow speed setting ensures sufficient mechanical force while avoiding structural damage or entanglement that may occur with high-speed agitation. The special design of the scraper ensures that the sheepskin is fully turned over, reducing processing dead spots and improving treatment uniformity. This mechanical tumbling method directly destroys the fat cell structure through physical action, laying an excellent foundation for the subsequent deep degreasing process. It also provides good adaptability for processing sheepskin raw materials with different morphological characteristics.

[0041] In another technical solution, the preparation method of the ferroferric oxide core-shell magnetic particles in step 2 is: 0.5-1.0 mol / L FeCl2 and FeCl3 solution were mixed according to Fe 2+ :Fe 3+ The mixture is mixed at a molar ratio of 1:1.8-2.2, 0.3-0.6 mol / L sodium citrate is added under nitrogen protection, 0.5-1.0 mol / L ammonia water is added dropwise at a constant rate at 50-60°C to a pH of 9.5-10.5, and after aging for 2-3 hours, magnetic separation is performed in a magnetic field with an intensity of 0.8-1.2 T, and the supernatant is discarded. The resulting magnetic precipitate is washed three times with hot deionized water at 60-70°C and then washed twice with anhydrous ethanol to obtain Fe3O4 nanoparticles with a particle size of 15-25 nm; The obtained Fe3O4 particles are dispersed in a mixed solvent of ethanol and water in a volume ratio of 3:1, and 0.1-0.3 wt% of hexadecyltrimethylammonium bromide accounting for the total mass of the mixed solvent is added. After ultrasonic treatment for 10-15 min, ethyl orthosilicate is added dropwise, and the dropping speed is controlled to be 0.5-1.0 mL / min and the mass ratio of ethyl orthosilicate to Fe3O4 is 1:2-1:3. The mixture is reacted at 40-45°C for 4-6 h to form a 5-8 nm silicon shell. After the reaction, magnetic separation is performed by a magnetic field with an intensity of 0.8-1.2 T, and the supernatant is discarded. The obtained particles are washed with ethanol and acetone three times each, and then dried in a vacuum drying oven at 60-80°C for 6-8 h to obtain Fe3O4 particles coated with a mesoporous silicon layer; The obtained Fe3O4 particles coated with the mesoporous silica layer were dispersed in toluene, and octyltrimethoxysilane was added at a molar ratio of 3:1-5:1 to Fe3O4. The mixture was refluxed at 110-120°C for 8-10 hours. After the reflux, the mixture was cooled to room temperature and magnetically separated in a magnetic field with an intensity of 1.0-1.5T. The supernatant was discarded, and the obtained particles were washed twice with toluene and then three times with n-heptane. The washed particles are placed in a tube furnace, heated to 350-450°C at a rate of 3-5°C / min under nitrogen protection, and calcined for 1-2 hours to completely remove any organic residues. The calcined particles are redispersed in n-heptane and magnetically separated using a magnetic field with an intensity of 1.0-1.5T. The supernatant is discarded to obtain pure Fe3O4 core-shell magnetic particles with a CTAB residue of less than 1ppm and a TEOS residue of less than 5ppm. In the above technical solution, the preparation of the ferroferric oxide core-shell magnetic particles described in step 2 can be performed using a conventional chemical reaction apparatus. A double-layered glass reactor with stirring and temperature control can be used as the primary reaction vessel, equipped with a constant pressure dropping funnel and an online pH monitoring system. Magnetic separation can be performed using a permanent magnet separator (such as a neodymium iron boron magnet) or an electromagnetic separation device. A standard glass reflux condenser can be used for the reflux reaction. Chemically pure FeCl2·4H2O and FeCl3·6H2O raw materials can be used, and analytically pure reagents such as sodium citrate, ammonia, hexadecyltrimethylammonium bromide, ethyl orthosilicate, and octyltrimethoxysilane can be used. These chemical reagents can be obtained from conventional chemical reagent suppliers.

[0042] In a specific implementation, 0.8 mol / L FeCl2 solution and 0.8 mol / L FeCl3 solution were first mixed in a molar ratio of 1:2 for iron ions, transferred to a reactor, and purged with nitrogen. 0.5 mol / L sodium citrate solution was added, the temperature was maintained at 55°C, and 0.8 mol / L ammonia solution was added dropwise at a rate of 1 ml per minute until the pH reached 10.0. After aging for 2.5 hours, magnetic separation was performed using a 1.0 T magnetic field. The supernatant was discarded, and the resulting magnetic precipitate was washed three times with hot deionized water at 65°C, and then washed twice with anhydrous ethanol to obtain Fe3O4 nanoparticles.

[0043] The resulting particles were dispersed in a mixture of ethanol and water (3:1 by volume). Hexadecyltrimethylammonium bromide (0.2% by weight of the total solvent) was added and ultrasonicated for 12 minutes. Subsequently, ethyl orthosilicate (with a mass ratio of 1:2.5 to Fe₃O₄) was added dropwise at a rate of 0.8 ml / min. The mixture was reacted at 42°C for 5 hours to form a silica shell. After the reaction, magnetic separation was performed using a 1.0 T magnetic field, and the supernatant was discarded. The resulting particles were washed three times with ethanol and three times with acetone, followed by drying in a vacuum oven at 70°C for 7 hours to obtain Fe₃O₄ particles coated with a mesoporous silica layer.

[0044] The resulting mesoporous silica-coated Fe₃O₄ particles were dispersed in toluene, and octyltrimethoxysilane (molar ratio of 4:1 to Fe₃O₄) was added. The mixture was refluxed at 115°C for 9 hours. After reflux, the mixture was cooled to room temperature and magnetically separated using a 1.2T magnetic field. The supernatant was discarded, and the resulting particles were washed twice with toluene and then three times with n-heptane to completely remove unreacted silane coupling agent and byproducts.

[0045] To completely remove trace amounts of organic reagents (particularly CTAB) that may have remained during the preparation process, the washed particles were placed in a tube furnace and heated to 400°C at a rate of 5°C / min under nitrogen, where they were held for 1.5 hours. The calcined particles were then redispersed in n-heptane and subjected to final magnetic separation and washing in a 1.2T magnetic field, yielding high-purity Fe3O4 core-shell magnetic particles. HPLC and ICP-OES analysis revealed residual CTAB levels of less than 1 ppm and TEOS levels of less than 5 ppm.

[0046] The ferroferric oxide core-shell magnetic particles prepared by this method have a regular core-shell structure and good hydrophobic properties. The presence of the silicon shell improves the chemical stability of the particles and reduces the dissolution of the iron core. More importantly, through the above-mentioned rigorous multi-stage purification and high-temperature calcination process, it is ensured that any toxic reagent residues are removed to below the safety limit, fully meeting the safety requirements of food processing additives. The surface octyl modification gives the particles appropriate hydrophobicity, enabling them to effectively stabilize Pickering emulsions. The magnetic core ensures that the particles can be recycled and reused by magnetic separation. This type of particle exhibits good emulsion stability and reusability during the sheepskin degreasing process, providing a suitable solid-phase stabilizer material for the edible processing of sheepskin.

[0047] In another technical solution, the sheepskin treatment process in the Pickering emulsion tank in step 2 includes: In the pre-infiltration stage, the sheepskin is immersed in the emulsion and then intermittent variable frequency stirring is started, running at a high speed of 200-300 rpm from 0 to 10 minutes, and then reducing the speed to 100-150 rpm from 10 to 30 minutes; In the deep degreasing stage, an ultrasonic field with a frequency of 28±2kHz and a power density of 50-80W / L is applied, and the magnetic field is turned on simultaneously, with a horizontal magnetic field strength of 0.3-0.5T and a vertical magnetic field strength of 0.1-0.2T; The rate of change of the emulsion conductivity was monitored in real time. When |Δσ / Δt| was less than 0.5 μS / cm·min, the magnetic field was suspended for 30 s and then re-measured for confirmation.

[0048] In the above technical solution, the Pickering emulsion processing system described in step 2 can be equipped with an intelligent control device. The emulsion tank can be a stainless steel container with a jacket, equipped with a variable frequency stirring motor and a stepless speed regulation device. The ultrasonic field can be generated by a piezoelectric ceramic transducer array, which is evenly arranged on the bottom and side walls of the tank. The magnetic field can be generated by a permanent magnet group or an electromagnetic coil. The horizontal magnetic field assembly can be installed on both sides of the tank, and the vertical magnetic field assembly can be installed on the bottom of the tank. Conductivity monitoring can use an online conductivity sensor, which is installed at the liquid outlet of the tank and connected to the data acquisition system.

[0049] To accurately and real-time monitor the progress of deep degreasing of sheepskin, this invention employs an online conductivity monitoring system to dynamically track the conductivity trend of the Pickering emulsion and use the rate of change (Δσ / Δt) as an objective indicator for determining the degreasing endpoint. The system utilizes an industrial-grade four-electrode conductivity sensor with platinum electrodes and polytetrafluoroethylene or Hastelloy alloy as the sensor body and seals, ensuring excellent corrosion resistance and resistance to n-heptane solvents. The sensor is equipped with an intelligent conductivity transmitter that provides signal amplification, automatic temperature compensation, data output, and relay control. The sensor is mounted on a Pickering emulsion tank via a self-cleaning bypass circulation system. Specifically, an outlet is provided at the bottom of the tank's sidewall. A centrifugal pump continuously pumps the emulsion into a transparent, flow-controllable bypass measuring cell. The conductivity sensor is mounted vertically within the measuring cell, ensuring that the electrodes are fully immersed and facing the flow direction. The measured emulsion returns to the main processing tank via a pipe located above the measuring cell. This bypass installation method ensures that the measured emulsion can represent the overall composition of the tank, avoids the direct impact of mechanical collision and ultrasonic cavitation that may be suffered by the sensor when it is directly installed in the tank, and facilitates maintenance and cleaning without stopping the machine.

[0050] The conductivity transmitter transmits real-time, temperature-compensated conductivity signals to a central control system (such as a PLC or DCS). The control system has a built-in program that calculates the rate of change of conductivity, |Δσ / Δt| (unit: μS / cm·min), every minute. The control logic is as follows: When the average |Δσ / Δt| value for three consecutive sampling periods (i.e., three minutes) is below 0.5 μS / cm·min, the system determines that the degreasing rate has dropped to a critically low level. At this point, the system automatically turns off the magnetic field for 30 seconds to eliminate potential interference with the measurement. After 30 seconds, data is collected again for reconfirmation. If the reconfirmed results still meet the termination criteria, the system automatically terminates the process. This monitoring principle is based on the following: In the early stages of degreasing, a large amount of non-polar oil is extracted into the emulsion, causing a significant decrease in conductivity and a large negative Δσ / Δt value. As the amount of releasable fat decreases, the extraction rate slows, and the conductivity change trend slows. When Δσ / Δt approaches zero, the emulsion composition has stabilized and the degreasing reaction is essentially complete. Therefore, this threshold is a sensitive and reliable criterion for degreasing equilibrium. The conductivity change rate threshold (|Δσ / Δt| < 0.5μS / cm·min) is not an arbitrary theoretical value, but an empirical critical value determined based on extensive previous experiments that reliably indicates that the degreasing reaction is approaching equilibrium.

[0051] During specific implementation, the treatment program is started immediately after the sheepskin is immersed in the emulsion. A stirring speed of 250 rpm is used for the first 10 minutes to promote the penetration of the emulsion into the sheepskin tissue. After 10 minutes, the stirring speed is reduced to 120 rpm, and the 28 kHz ultrasonic field is turned on at the same time, and the power density is set to 60 W / L. The magnetic field system is started synchronously, and the horizontal magnetic field strength is adjusted to 0.4 T, and the vertical magnetic field strength is adjusted to 0.15 T. The conductivity change of the emulsion is continuously monitored during the treatment process. When the conductivity change rate is detected to be less than 0.5 μS / cm·min, the magnetic field effect is automatically suspended for 30 seconds and then re-tested for confirmation. If the re-test result still meets the termination condition, the entire treatment process is automatically stopped.

[0052] This phased treatment method allows for effective emulsion penetration and deep degreasing of sheepskin tissue. High-speed stirring in the early stages helps the emulsion quickly penetrate the pore structure of the sheepskin. Later, reduced stirring speeds, combined with ultrasonic and magnetic fields, promote the emulsification and removal of stubborn fat. Real-time conductivity monitoring provides objective insight into the degreasing process and helps accurately control the treatment endpoint. This method ensures the production of low-fat, edible sheepskin products.

[0053] In another technical solution, the n-heptane recovered by distillation in step 4 is passed into a silanized 3Å molecular sieve column with a pore size of 0.33±0.02nm, and dehydrated and deacidified at 50-60°C to obtain a high-purity solvent with a water content of ≤30ppm and an acid value of ≤0.05mgKOH / g.

[0054] In the above technical solution, the n-heptane purification system described in step 4 can be equipped with a molecular sieve adsorption device. A stainless steel fixed-bed adsorption column can be used as the molecular sieve column body, and the column can be equipped with a circulating heat medium jacket and a temperature control system. The silanized 3Å molecular sieve can be spherical particles with a packing density of 0.6-0.7g / mL. The heating system can be an electrically heated oil bath with a temperature control accuracy of ±1°C. For pressure monitoring, a digital pressure sensor can be installed in the inlet and outlet pipes of the molecular sieve column.

[0055] In practice, the recovered n-heptane is pre-cooled to 40°C before being passed through the molecular sieve column at a flow rate of 0.5 column volumes per hour. The column temperature is maintained at 55°C, and the operating pressure is controlled at 0.3 MPa. The molecular sieve column is regenerated regularly at 200°C while being purged with nitrogen. The treated n-heptane sample is then tested for moisture content using the Karl Fischer method, and for acid value using an acid-base titration method. When the molecular sieve reaches saturation, it must be replaced with a new one.

[0056] This treatment method effectively removes water and acidic substances from the recovered n-heptane. The regular pore structure of the molecular sieve enables selective adsorption, and the 0.33nm pore size effectively intercepts water molecules and organic acid molecules. Silanization treatment enhances the hydrophobicity of the molecular sieve and improves its adaptability to organic solvents. Temperature control helps maintain the stability of the adsorption process, and an appropriate flow rate ensures sufficient contact time. This method provides an effective means for quality control of the recovered solvent and facilitates solvent recycling.

[0057] In another technical solution, the recovery process of the ferroferric oxide core-shell magnetic particles in step 4 is as follows: applying an axial gradient magnetic field in a distillation tower with an intensity of 0.8-1.0T in the bottom region, 0.3-0.5T in the middle region, and <0.1T in the top region, controlling the bottom temperature at 85±2°C to inhibit agglomeration of the magnetic particles; recovering the particles from the bottom liquid of the tower through a 1.0-1.5T magnetic field, dispersing them in 80°C hot n-heptane containing 0.8-1.2% oleic acid, and oscillating them for 20 minutes to repair the hydrophobic surface of the particles.

[0058] In the above technical solution, the magnetic particle recovery system described in step 4 can integrate a magnetic field generator within the distillation tower. An electromagnetic coil assembly or permanent magnet array can be used to generate an axial gradient magnetic field. High-field-strength neodymium iron boron permanent magnets can be placed in the tower bottom area, medium-field-strength ferrite permanent magnets can be placed in the tower mid-section, and low-field-strength alnico permanent magnets can be placed in the tower top area. Temperature control can utilize a PT100 temperature sensor in conjunction with a PID temperature control system. A high-gradient magnetic separator can be used for particle recovery, and a temperature-controlled oscillating reactor can be used for surface remediation.

[0059] During operation, the distillation tower maintains a magnetic field strength of 0.9 T in the bottom region, 0.4 T in the middle region, and 0.05 T at the top. The bottom temperature is controlled at 85°C, with a temperature fluctuation range of ±2°C. The bottom liquid is initially recovered by a magnetic separator with a magnetic field strength of 1.2 T. The collected magnetic particles are then transferred to an n-heptane solution containing 1.0% oleic acid and oscillated at 80°C at a frequency of 120 vibrations per minute for 20 minutes. The treated particles are then magnetically separated and washed twice with fresh n-heptane for later use.

[0060] This gradient magnetic field design effectively suppresses magnetic particle aggregation during the distillation process. Different magnetic field intensities in different tower sections ensure effective particle retention while preventing particle aggregation caused by excessively strong magnetic fields. Proper temperature control helps maintain system stability, and oleic acid treatment repairs the hydrophobic surface of the particles, which may be damaged during the distillation process, restoring their emulsifying properties. This method provides a viable solution for the recovery and regeneration of magnetic particles, facilitating their multiple recycling.

[0061] In another technical solution, the recovered high-purity solvent and the particles with repaired hydrophobic surfaces are mixed and then transported back to the Pickering emulsion tank. The specific configuration process is as follows: The particles with repaired hydrophobic surfaces were dispersed in deionized water at a concentration of 0.7-1.1% w / v and ultrasonically treated at a frequency of 40 kHz and a power of 50 W / L for 10 min to obtain a homogeneous aqueous dispersion. Use high-purity solvent as the oil phase and inject it into the water phase at a constant speed according to the volume ratio of oil phase to water phase of 1:1.5-1:2.5, and the injection rate is 5-10L / min; The mixture was first homogenized in a high-speed homogenizer at 8000-10000 rpm for 3 min to form a coarse emulsion, and then homogenized at 12000-15000 rpm for 2 min to reduce the emulsion droplet size to 1.5 ± 0.3 μm; After 24-48 hours of static aging, the emulsion is transferred back to the Pickering emulsion tank for use in step 2, sheepskin treatment.

[0062] In the above technical solution, the emulsion regeneration system described in step 5 can be equipped with specialized configuration devices. A jacketed stirred tank can be used as the aqueous phase dispersion vessel, equipped with an ultrasonic generator and temperature control system. A metering pump and distributor can be used for oil phase injection, a shear homogenizer can be used for high-speed homogenization, and an insulated storage tank can be used for emulsion aging. Deionized water can be ultrapure water with a resistivity greater than 18 MΩ·cm. The oleic acid-modified Fe3O4 core-shell magnetic particles can be obtained from the aforementioned recovery process, and high-purity n-heptane can be obtained from the molecular sieve purification process.

[0063] In the specific implementation, the repaired magnetic particles are first dispersed in deionized water at a weight volume concentration of 0.9%, and ultrasonic treatment is performed at a frequency of 40kHz and a power of 50 watts per liter for 10 minutes to obtain a uniform aqueous dispersion. High-purity n-heptane is used as the oil phase, and is uniformly added to the aqueous phase at an injection rate of 8 liters per minute in a ratio of 1:2 by volume of the oil phase to the aqueous phase. The mixed solution is then transferred to a high-speed homogenizer, first processed at a speed of 9000 rpm for 3 minutes to form a coarse emulsion, and then increased to 13000 rpm for 2 minutes for refinement. The prepared emulsion is transferred to an insulated storage tank, and after aging at 25°C for 36 hours, it is returned to the Pickering emulsion tank by a transfer pump for standby use.

[0064] This configuration allows the recovered solvent and magnetic particles to reform into a stable Pickering emulsion. Ultrasonic treatment facilitates uniform dispersion of the magnetic particles in the aqueous phase, while appropriate oil phase injection rate and stirring conditions promote the formation of uniformly sized emulsion droplets. The static aging process stabilizes the emulsion system, facilitating penetration and degreasing during subsequent sheepskin processing. This method provides technical support for material recycling and helps reduce production costs.

[0065] Example 1 A method for processing sheepskin into an edible form comprises the following steps: Step 1: Place the wet sheepskin that has been dehaired and surface cleaned in a hot water treatment tank equipped with a scraper agitator. Add a collagen protective agent with a concentration of 15% weight-to-volume to the aqueous medium. The protective agent is composed of sorbitol and trehalose mixed in a mass ratio of 1:1. Set the treatment temperature to 98°C and treat for 40 minutes under normal pressure. At the same time, start the scraper agitator at a speed of 20rpm, and turn on the medium-frequency ultrasonic treatment system with a frequency of 30kHz and a power density of 40W / L. Under these conditions, the sheepskin fat cell membrane is destroyed by mechanical shear and cavitation effect, and the released fat is emulsified by hot water to form an oil-water mixture, and the sheepskin with preliminary degreasing is obtained.

[0066] Step 2: After treatment in Step 1, the sheepskin was immediately transferred to an O / W Pickering emulsion tank for treatment. The emulsion consisted of n-heptane with a boiling range of 80-90°C as the oil phase and an aqueous phase containing ferroferric oxide core-shell magnetic particles as a stabilizer. The volume ratio of the oil phase to the aqueous phase was controlled at 1:2. The sheepskin treatment in the emulsion tank was divided into two stages: a pre-infiltration stage in which the sheepskin was immersed in the emulsion and stirred at 280 rpm for 0-10 minutes, followed by a reduction in the stirring speed to 130 rpm for 10-30 minutes. The deep degreasing stage involved applying an ultrasonic field at a frequency of 28 kHz and a power density of 60 W / L, while simultaneously applying a horizontal magnetic field of 0.4 T and a vertical magnetic field of 0.15 T. During this process, the conductivity change rate of the emulsion was monitored in real time. If the change rate was less than 0.5 μS / cm·min, the magnetic field was suspended for 30 seconds and then retested for confirmation. The total treatment time was 60 minutes.

[0067] Step 3: Remove the sheepskin treated in Step 2 from the emulsion tank and immediately centrifuge it at 2000 rpm for 5 minutes to remove the emulsion from its surface. This step results in an edible sheepskin product with a fat content of no more than 0.5 wt% and a residual magnetic particle content of no more than 35 ppm.

[0068] Step 4: The emulsion separated in Step 3 is transferred to a distillation tower for separation and recovery. n-heptane is distilled and recovered at a bottom temperature of 85°C. An axial gradient magnetic field is applied within the tower, with magnetic field strengths of 0.9T in the bottom region, 0.4T in the middle region, and less than 0.1T at the top. The recovered n-heptane vapor is condensed and passed through a silanized 3Å molecular sieve column with a pore size of 0.33nm. Dehydration and deacidification treatment is performed at 55°C to obtain a high-purity solvent with a moisture content of less than 30ppm and an acid value of less than 0.05mgKOH / g.

[0069] The bottom liquid of the tower was subjected to a 1.2T magnetic field to recover the ferroferric oxide core-shell magnetic particles. The recovered particles were dispersed in an 80°C hot n-heptane solution containing 1% oleic acid and oscillated at a frequency of 120 times / min for 20 minutes to repair the hydrophobic surface properties of the particles.

[0070] The recovered high-purity n-heptane solvent and the surface-repaired magnetic particles were then subjected to an emulsion regeneration process: the repaired particles were first dispersed in deionized water at a concentration of 0.9% w / v and ultrasonically treated at a frequency of 40 kHz and a power of 50 W / L for 10 minutes to obtain a homogeneous aqueous dispersion. High-purity n-heptane was then injected into the aqueous dispersion at a constant rate of 8 L / min, with a volume ratio of 1:2 between the oil phase and the aqueous phase. The mixture was then transferred to a high-speed homogenizer and processed at 9,000 rpm for 3 minutes to form a coarse emulsion. The speed was then increased to 13,000 rpm for 2 minutes to refine the emulsion droplets to a particle size of approximately 1.5 μm. The prepared emulsion was then aged at 25°C for 36 hours. After completion, it was returned to the Pickering emulsion tank for use in the sheepskin treatment step 2, achieving material recycling.

[0071] The complete process described above ultimately yielded an edible sheepskin product with a fat content of 0.4wt% and a residual magnetic particle content of 35ppm. The n-heptane solvent recovery rate exceeded 92%, and the magnetic particles, after surface repair, exhibited excellent recyclability, capable of over 10 reuses.

[0072] Comparative Example 1 Compared to Example 1, mechanical tumbling and medium-frequency ultrasonic treatment were omitted. The wet sheepskin was placed in a normal-pressure hot water tank and immersed in 95°C water for 40 minutes, with low-speed stirring (50 rpm). A sorbitol-trehalose composite protective agent (15% w / v) was also added to the aqueous medium. The remaining steps were the same as in Example 1.

[0073] Comparative Example 2 Compared to Example 1, the magnetic particle-based Pickering emulsion treatment was omitted. After the hot water treatment in step 1, the sheepskin was transferred to a degreasing tank containing a 5% (by volume) aqueous solution of sodium dodecyl sulfate (SDS) surfactant and immersed at 60°C for 90 minutes with mechanical agitation only. The degreasing endpoint was determined empirically, and the fixation treatment was terminated after 90 minutes. The remaining steps were identical to those in Example 1.

[0074] Comparative Example 3 Compared to Example 1, the solvent and particle recycling system was eliminated. The emulsion treated in Step 2 was no longer subjected to distillation and magnetic separation, but was instead centrally treated as waste liquid. In each step, fresh n-heptane solvent and new ferrosoferric oxide core-shell magnetic particles were used to prepare the Pickering emulsion. The remaining steps were consistent with those in Example 1.

[0075] Comparative test of sheepskin product quality indicators The edible sheepskin products obtained in Example 1 and Comparative Examples 1-3 were taken as samples and tested respectively. The test results are shown in Table 1.

[0076] Table 1 As can be seen from Table 1, the overall effect of the sheepskin edible processing method provided by the present invention in Example 1 is significantly superior to the traditional process used for comparison. The edible sheepskin ultimately produced by this method has a low fat content and no chemical degreasing agent residue, resulting in a high product purity and food safety. In contrast, relying solely on hot water treatment (Comparative Example 1) cannot effectively achieve deep degreasing; the use of chemical degreasing agents (Comparative Example 2) introduces the risk of surfactant residues; and although eliminating the circulation system (Comparative Example 3) can also achieve a lower fat content, the cost is a significant increase in material consumption. Therefore, the method of the present invention successfully achieves efficient circulation of the processing medium while ensuring high product quality, demonstrating comprehensive technical advantages.

[0077] Material consumption comparison test The total amount of n-heptane solvent and the total amount of new ferrosoferric oxide core-shell magnetic particles consumed in treating one ton of fresh wet sheepskin in the examples and comparative examples are shown in Table 2.

[0078] Table 2 As shown in Table 2, the method of the present invention employed in Example 1 demonstrates significant advantages in controlling material consumption. Through its built-in recycling system, the unit consumption of solvents and functional materials during the production process is significantly reduced. Compared with the traditional single-use solution (Comparative Example 3), this method effectively avoids the continuous and large-scale input of materials, minimizing the production process's reliance on fresh raw materials. This efficient resource utilization model not only directly reduces raw material procurement costs but also eliminates the environmental burden of waste liquid treatment and material disposal at the source. It demonstrates outstanding economic and environmental performance, providing a reliable path for achieving green and sustainable industrial production.

[0079] Safety testing Safety testing was performed on the ferroferric oxide core-shell magnetic particles and the edible sheepskin product described in this application. All testing followed nationally standardized methods and was performed by an internal quality control laboratory. The test results are shown in Tables 3 and 4.

[0080] Table 3 Detection results of organic residues in ferroferric oxide core-shell magnetic particles Table 4 Safety test results of edible sheepskin finished products As shown in Tables 3 and 4, the data above fully demonstrate that the process of this invention can consistently produce magnetic particles with extremely low organic residues (CTAB <0.5 ppm, silicon residue <5.0 ppm). The residual particles in the final sheepskin product are well below the safety limit (≤50 ppm). Authoritative toxicology testing has verified that the particles are non-toxic, non-cytotoxic, and non-genotoxic, fully meeting the safety requirements for food processing applications.

[0081] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and examples shown and described herein.

Claims

1. A method for making sheepskin edible, characterized in that: The following steps are involved: Step 1: placing the wet sheepskin that has been dehaired and surface cleaned in a hot water treatment tank, treating it at a temperature of 95-100° C. and normal pressure for 30-60 minutes, and simultaneously mechanically tumbling and supplemented with medium-frequency ultrasonic treatment at a frequency of 20-40 kHz, with an ultrasonic power density of 30-50 W / L, so that the sheepskin fat cell membrane is destroyed by mechanical shearing and cavitation effects, and the released fat is emulsified by hot water to form an oil-water mixture, thereby obtaining a sheepskin that has been preliminarily degreased; Step 2: Immediately transfer the sheepskin treated in Step 1 to an O / W Pickering emulsion tank for treatment for a total time of 30-120 minutes, and terminate the treatment early when the conductivity change rate |Δσ / Δt| is less than 0.5 μS / cm·min under real-time monitoring; wherein the Pickering emulsion is composed of an n-heptane oil phase with a boiling point of 60-100° C. and an aqueous phase stabilizer of ferroferric oxide core-shell magnetic particles with a particle size of 10-100 nm, wherein the volume ratio of the oil phase to the aqueous phase is 1:1.5-1:2.5; Step 3: remove the sheepskin from the emulsion tank and separate and remove the surface emulsion by centrifuge at a speed of 1000-3000 rpm to obtain an edible sheepskin with a fat content of ≤0.5 wt% and a magnetic particle residue of ≤50 ppm; Step 4: transport the separated emulsion to a distillation tower, distill and recover n-heptane at a tower bottom temperature of 80-90°C, and simultaneously recover ferroferric oxide core-shell magnetic particles from the tower bottom liquid by magnetic separation, and recycle them for the Pickering emulsion preparation in step 2.

2. The method for making sheepskin edible according to claim 1, wherein: In step 1, a collagen protective agent is added to the aqueous medium in the hot water treatment tank, which is selected from at least one of polyols, reducing disaccharides, polyhydroxy compounds or edible inorganic salts. The concentration of the collagen protective agent added to the aqueous medium is 5-25% w / v.

3. The method for making sheepskin edible according to claim 1, wherein: The mechanical tumbling in step 1 is achieved by a scraper-type agitator provided in the tank, which operates at a speed of 15-25 rpm, causing the sheepskins to continuously turn over and rub against each other.

4. The method for making sheepskin edible according to claim 1, wherein: The preparation method of the ferroferric oxide core-shell magnetic particles in step 2 is: 0.5-1.0 mol / L FeCl2 and FeCl3 solution were mixed according to Fe 2+ :Fe 3+ The mixture is mixed at a molar ratio of 1:1.8-2.2, 0.3-0.6 mol / L sodium citrate is added under nitrogen protection, 0.5-1.0 mol / L ammonia water is added dropwise at a constant rate at 50-60°C to a pH of 9.5-10.5, and after aging for 2-3 hours, magnetic separation is performed in a magnetic field with an intensity of 0.8-1.2 T, and the supernatant is discarded. The resulting magnetic precipitate is washed three times with hot deionized water at 60-70°C and then washed twice with anhydrous ethanol to obtain Fe3O4 nanoparticles with a particle size of 15-25 nm; The obtained Fe3O4 particles are dispersed in a mixed solvent of ethanol and water in a volume ratio of 3:1, and 0.1-0.3 wt% of hexadecyltrimethylammonium bromide accounting for the total mass of the mixed solvent is added. After ultrasonic treatment for 10-15 min, ethyl orthosilicate is added dropwise, and the dropping speed is controlled to be 0.5-1.0 mL / min and the mass ratio of ethyl orthosilicate to Fe3O4 is 1:2-1:

3. The mixture is reacted at 40-45°C for 4-6 h to form a 5-8 nm silicon shell. After the reaction, magnetic separation is performed by a magnetic field with an intensity of 0.8-1.2 T, and the supernatant is discarded. The obtained particles are washed with ethanol and acetone three times each, and then dried in a vacuum drying oven at 60-80°C for 6-8 h to obtain Fe3O4 particles coated with a mesoporous silicon layer; The obtained Fe3O4 particles coated with the mesoporous silica layer were dispersed in toluene, and octyltrimethoxysilane was added at a molar ratio of 3:1-5:1 to Fe3O4. The mixture was refluxed at 110-120°C for 8-10 hours. After the reflux, the mixture was cooled to room temperature and magnetically separated in a magnetic field with an intensity of 1.0-1.5T. The supernatant was discarded, and the obtained particles were washed twice with toluene and then three times with n-heptane. The washed particles are placed in a tube furnace, heated to 350-450°C at a rate of 3-5°C / min under nitrogen protection, and calcined for 1-2 hours to completely remove any organic residues. The calcined particles are redispersed in n-heptane and magnetically separated using a magnetic field with an intensity of 1.0-1.5T. The supernatant is discarded to obtain pure Fe3O4 core-shell magnetic particles with a CTAB residue of less than 1ppm and a TEOS residue of less than 5ppm.

5. The method for making sheepskin edible according to claim 1, wherein: The sheepskin treatment process in the Pickering emulsion tank in step 2 includes: In the pre-infiltration stage, the sheepskin is immersed in the emulsion and then intermittent variable frequency stirring is started, running at a high speed of 200-300 rpm from 0 to 10 minutes, and then reducing the speed to 100-150 rpm from 10 to 30 minutes; In the deep degreasing stage, an ultrasonic field with a frequency of 28±2kHz and a power density of 50-80W / L is applied, and the magnetic field is turned on simultaneously, with a horizontal magnetic field strength of 0.3-0.5T and a vertical magnetic field strength of 0.1-0.2T; The rate of change of the emulsion conductivity was monitored in real time. When |Δσ / Δt| was less than 0.5 μS / cm·min, the magnetic field was suspended for 30 s and then re-measured for confirmation.

6. The method for making sheepskin edible according to claim 1, wherein: The n-heptane recovered by distillation in step 4 is passed through a silanized 3Å molecular sieve column with a pore size of 0.33±0.02nm and dehydrated and deacidified at 50-60°C to obtain a high-purity solvent with a water content of ≤30ppm and an acid value of ≤0.05mgKOH / g.

7. The method for making sheepskin edible according to claim 6, wherein: The recovery process of the ferroferric oxide core-shell magnetic particles in step 4 is as follows: applying an axial gradient magnetic field in the distillation tower, with an intensity of 0.8-1.0T in the bottom region, 0.3-0.5T in the middle region, and <0.1T in the top region, and controlling the bottom temperature to 85±2°C to inhibit agglomeration of the magnetic particles; recovering the particles from the bottom liquid of the tower by subjecting it to a 1.0-1.5T magnetic field, dispersing them in 80°C hot n-heptane containing 0.8-1.2% oleic acid and oscillating them for 20 minutes to repair the hydrophobic surface of the particles.

8. The method for making sheepskin edible according to claim 7, wherein: The recovered high-purity solvent and the particles with repaired hydrophobic surfaces are mixed and transported back to the Pickering emulsion tank. The specific configuration process is as follows: The particles with repaired hydrophobic surfaces were dispersed in deionized water at a concentration of 0.7-1.1% w / v and ultrasonically treated at a frequency of 40 kHz and a power of 50 W / L for 10 min to obtain a homogeneous aqueous dispersion. Use high-purity solvent as the oil phase and inject it into the water phase at a constant speed according to the volume ratio of oil phase to water phase of 1:1.5-1:2.5, and the injection rate is 5-10L / min; The mixture was first homogenized in a high-speed homogenizer at 8000-10000 rpm for 3 min to form a coarse emulsion, and then homogenized at 12000-15000 rpm for 2 min to reduce the emulsion droplet size to 1.5 ± 0.3 μm; After 24-48 hours of static aging, the emulsion is transferred back to the Pickering emulsion tank for use in step 2, sheepskin treatment.

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