Oil by-product in bovine hide pretreatment waste liquid, extraction method and application thereof

Abstract

The application belongs to the technical field of saponification grease refining extraction, and discloses a kind of oil and fat by-products in cowhide pretreatment waste liquid and extraction method and application.The application uses the combined waste liquid generated in the process of collagen peptide production as raw material, adopts non-isoelectric point salt-free gentle flocculation demulsification process, accurately controls the system pH to 4.6~5.0, can completely remove macromolecular impurities such as impure protein, dander gum, etc., while controllably retaining trace amounts of small molecule denatured collagen polypeptide, then through hydration degumming, alkali refining deacidification, water washing and drying, decolorization and deodorization processes to obtain finished oil and fat.The core physicochemical indexes of the oil and fat obtained by the application meet the standard of soap grease, and the saponification reaction efficiency, soap texture flexibility and foam performance are significantly better than those of traditional completely deproteinized refined beef tallow, realizing high-purity refining and performance synergistic effect of waste liquid oil and fat, high added value of by-products, and process adaptation to industrial large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of saponification and oil refining extraction technology, specifically relating to an oil by-product from bovine hide pretreatment waste liquid, its extraction method, and its application in the preparation of soap products. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] The applicant's research (patent CN114805550B) provides a method for producing collagen tripeptides from bovine hide. This method involves soaking fresh bovine hide in a 0.1 mol / L NaOH solution for degreasing. The degreased hide is then boiled in water. The resulting NaOH solution or aqueous solution contains a large amount of oily byproducts. These byproducts are subcutaneous free fats, and no sulfurizing agents or heavy metal reagents were used during the extraction process. They are high-quality fats that can be refined into high-value products.

[0004] However, existing research shows that pure butter soap is hard and brittle, prone to cracking, produces little lather, and has poor stability, making it difficult to meet the quality requirements of high-end personal care soaps. It typically requires the addition of chemical emulsifiers and moisturizing agents for modification. The inventors believe that the oil byproducts recovered in this application inevitably carry small-molecule proteins and collagen peptides dissolved from cowhide, which may improve saponification performance. Summary of the Invention

[0005] To address the problems existing in the background technology, this invention designs the waste liquid from the degreasing pretreatment stage of cowhide (denoted as pretreatment waste liquid) as the processing object, and refines the oil by-products therein, ultimately providing an oil by-product with good saponification performance.

[0006] To achieve the above-mentioned technical effects, the present invention provides the following technical content: In a first aspect, a method for extracting oily by-products from cowhide is provided, wherein the extraction method uses pretreatment waste liquid generated during the cowhide pretreatment stage as the treatment object to extract the oily by-products therein. The extraction method includes the following steps: S1. Demulsification and flocculation: Citric acid is added to the pretreated waste liquid to adjust the pH to 4.6-5.0, and the mixture is stirred slowly at room temperature for 20-30 minutes to obtain a demulsified solution; S2. Three-phase settling and separation: After the reaction is completed, the above demulsifier is transferred to a sealed container and settling until the three phases separate. The upper crude oil is collected, and the solid suspended particles are filtered out to obtain crude tallow. S3. Hydration and degumming treatment: After heating the obtained crude oil, add soft water and phosphoric acid, stir slowly to mix thoroughly, and let stand to remove phospholipids and water-soluble gum impurities; then test the acid value of the crude oil, add alkali solution to neutralize the deacidification reaction, let stand, separate and remove the bottom soap feet to obtain the deacidified oil; S4. Water washing for desalting and soap removal: The deacidified grease is washed with soft water for desalting, and then dried under vacuum. S5. Vacuum deodorization: After drying, the oil is added to a decolorizing agent for deep decolorization, and then deodorized to obtain the final product.

[0007] In the art, protein components in oils are generally considered harmful impurities. Conventional demulsification and flocculation methods typically employ a combination of complete isoelectric point determination of proteins and salting-out to enhance sedimentation, thereby removing all protein impurities. This application considers that the proteins dissolved in the aforementioned pretreated wastewater are non-putrefactive proteins that have undergone high-temperature boiling and are no longer biologically active. Furthermore, small-molecule collagen peptides possess both hydrophilic and lipophilic properties, making them suitable as natural, non-toxic emulsifiers to enhance the saponification properties of oils and compensate for the shortcomings of bovine oils, such as their coarseness and difficulty in complete saponification.

[0008] Based on this concept, this invention adds mild citric acid during the demulsification and flocculation stage, without adding any salting-out agents throughout the process. This process can thoroughly flocculate and remove large molecular proteins, skin flakes, and suspended impurities from the waste liquid, while stably retaining nano-sized collagen peptides that have undergone alkali hydrolysis and high-temperature denaturation. The simultaneous hydrophilic and lipophilic properties of these peptides are used to construct a natural emulsification system. Testing has shown that the oil byproducts obtained by this invention have excellent saponification properties, meeting the requirements for preparing high-end saponified products such as personal care soaps or handmade soaps.

[0009] In a preferred embodiment, the source of the pretreatment waste liquid is as follows: pretreatment waste liquid from the extraction of collagen peptides or small molecule collagen peptides from fresh cowhide, wherein no reagents other than sodium chloride or sodium hydroxide should be introduced during the pretreatment stage; in some embodiments verified by the present invention, the source of the pretreatment waste liquid includes at least one or a combination of the following: Part 1: Waste liquid from soaking cowhide in sodium chloride, wherein the mass fraction of sodium chloride is 3-7%; Part Two: A sodium hydroxide soaking solution for cowhide, wherein the concentration of sodium hydroxide is preferably 0.05~0.15 mol / L; Part Three: This is the waste liquid from boiling cowhide with water, with a boiling time not exceeding 30 minutes.

[0010] In a more effective embodiment, the pretreated waste liquid includes at least part three; in one embodiment verified by the present invention, the pretreated waste liquid is a mixture of parts one to parts three in a volume ratio of 1:1.5~2:5~6, and more preferably a volume ratio of 1:2:6.

[0011] In the preferred embodiment, during the three-phase settling and stratification step described above, the demulsifier is separated into three layers: the upper layer is crude oil, which can be collected by skimming under negative pressure; the middle layer is saline water, which can be reused in the pretreatment process of cowhide; and the lower layer is protein colloid flocculent residue, which can be separated and then subjected to harmless treatment such as composting.

[0012] In the more effective solution, the settling temperature is 50~70℃ and the settling time is 2~4h.

[0013] Preferably, the above-mentioned hydration degumming treatment step also includes the following preferred embodiments: The resulting crude oil is heated to 55-65°C. The amount of soft water added is 2-3 wt.% of the crude oil, and the amount of phosphoric acid added is 0.1-0.2 wt.% of the crude oil. After the addition is complete, the mixture is stirred slowly for 25-35 minutes and then allowed to stand for more than 60 minutes.

[0014] The alkaline solution is a sodium hydroxide solution with a concentration of 10-14% ( ). w / v The deacidification reaction is carried out at a temperature of 60-70℃ for 25-35 minutes. After the deacidification reaction, the mixture is allowed to stand for at least 50 minutes to remove the bottom soap residue.

[0015] Preferably, the water washing desalting and soap removal step also has the following preferred embodiments: The temperature of the soft water is 60~70℃, the washing time is 12~17min, and the water is allowed to stand for 25~35min before being drained in layers; the temperature of the vacuum drying is 95~105℃, the vacuum degree is -0.1~-0.09MPa, and the vacuum drying time is 40~60min.

[0016] Preferably, the above-mentioned vacuum deodorization step also includes the following preferred embodiments: The decolorizing agent is selected from one or a combination of several of the following: kaolin, activated carbon, diatomaceous earth, molecular sieve, or attapulgite. In one embodiment verified by the present invention, a combination of kaolin and activated carbon is used, wherein the amount of kaolin added is 2.0~3.0 wt.% of the oil, and the amount of activated carbon added is 0.2~0.5 wt.%. After adding kaolin and activated carbon to the dried oil, the temperature is raised to 100~120℃ and stirred under negative pressure for 25~36 minutes for decolorization, and then the decolorizing agent residue is removed by filtration.

[0017] The deodorization process employs vacuum deodorization at a temperature of 220-240℃ and a vacuum degree of ≤500Pa, with saturated steam introduced in a countercurrent manner for a deodorization time of 100-150 minutes.

[0018] Secondly, the method described in the first aspect provides an oily byproduct prepared by the extraction method described in the first aspect.

[0019] Thirdly, the application of the oil by-products described in the second aspect in the preparation of soap products is provided.

[0020] The soap products mentioned in the third aspect broadly refer to cleaning products with fatty acid metal salts as the core ingredients, including but not limited to saponified products used on the human body, clothing, in kitchens and bathrooms, or in industrial settings.

[0021] Furthermore, the aforementioned saponified products for human use include, but are not limited to, cleaning products for the face, body, hands, and infants, such as facial cleansers, shower gels, hand soaps, and makeup removers.

[0022] The aforementioned saponified products for clothing include, but are not limited to, laundry detergent, laundry soap, laundry liquid, antibacterial agents, etc.

[0023] The saponified products used in kitchens and bathrooms mentioned above include, but are not limited to, dishwashing liquid and stain remover.

[0024] The aforementioned saponified products used in industrial settings include industrial detergents, leather care agents, and textile detergents.

[0025] Compared with the prior art, the beneficial effects of the present invention are: 1. The raw material of this invention is waste liquid from cowhide pretreatment, including sodium chloride waste liquid, waste alkali liquid, and boiling waste liquid. In previous production processes, these three types of waste liquid were often treated and discharged after reuse. The process of this invention realizes high-value utilization of waste, significantly reducing environmental protection and production costs. The butter components contained therein are recovered and refined into qualified soap-making oils, transforming the waste liquid that originally needed to be treated and discharged into high-value-added oil products. This not only reduces the organic load and operating costs of the wastewater treatment system, but also extends the revenue space of by-products in the industrial chain, improving the overall economic efficiency and environmental friendliness of the collagen production process.

[0026] 2. This invention also cleverly utilizes the small amount of collagen peptides contained in the pretreated waste liquid, converting the inactive collagen peptides after boiling treatment into natural amphiphilic interfacial activity. This enhances the oil-water two-phase contact mass transfer during saponification, significantly accelerating the saponification reaction rate without the need for additional chemical emulsifiers. Compared with traditional pure tallow, the saponification homogenization time is shortened by more than 30%, the saponification conversion rate is increased by more than 6% under the same reaction time, and the reaction uniformity is better. The finished soap has lower free alkali and free fatty acid content, which can effectively reduce the production energy consumption and time costs of downstream soap manufacturers and reduce the product defect rate. Detailed Implementation

[0027] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0028] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0029] In the context of this specification, the word "comprising" is considered to mean "especially including". It should not be interpreted as "consisting of only".

[0030] As described in the background section, existing processes for processing collagen peptides from fresh cowhide often require pre-degreasing, which generates a significant amount of fatty components that can be refined into high-value products such as soaps and premium leather auxiliaries. To obtain a method for refining high-quality butter byproducts, this invention designs the following solution: I. Extracting Objects The waste liquid obtained during the pretreatment stage of cowhide pretreatment is derived from the waste liquid after filtering out solids during the pretreatment and denaturation stages in patent scheme CN114805550B. The waste liquid is obtained by combining the two.

[0031] II. Oil Extraction and Refining Scheme The extraction process route for oily byproducts from pretreated wastewater is as follows: 1. Demulsification and flocculation Option 1: Add dilute phosphoric acid to the pretreated waste liquid to adjust the pH of the system to 4.0~4.5. At the same time, add 2% sodium chloride by mass of the system as a salting-out agent. Stir at 60~80 r / min and keep at a constant temperature for 30 min to promote the flocculation and aggregation of all large molecular proteins and nano-sized small molecular collagen peptides in the waste liquid, and completely precipitate them out, so as to achieve complete removal of protein components.

[0032] Option 2: Add dilute phosphoric acid to the pretreated waste liquid, adjust the pH of the system to 4.6~5.0, stir at 60~80 r / min, and stir at a constant temperature for 30 min.

[0033] Option 3: Add food-grade citric acid to the pretreated waste liquid, adjust the pH of the system to 4.8~5.2, stir at 40~60 r / min, and stir at a constant temperature for 25 min.

[0034] 2. Three-phase static stratification After demulsification and flocculation, the liquid was transferred to a 60°C constant-temperature sealed settling tank and allowed to stand for 3 hours to complete the three-phase separation. The upper crude oil was recovered, and solid suspended particles were filtered out to obtain crude tallow.

[0035] 3. Hydration and degumming treatment The obtained crude tallow was heated and then 2.5% (by weight of the tallow) of 60°C constant-temperature soft water and 0.15% (based on pure H3PO4) of phosphoric acid were added. The mixture was stirred slowly for 30 minutes and allowed to stand for 90 minutes. The tallow system was allowed to separate into three layers from top to bottom: the upper layer was degummed crude tallow, the middle layer was a clear aqueous phase, and the bottom layer was a viscous gel. The middle and bottom layers were removed, leaving the upper degummed crude tallow. The acid value of the crude oleic acid was then measured, and a 12% sodium hydroxide solution was added. w / v Neutralize the acid value, stir at 65℃ for 30 minutes to complete the deacidification reaction, let stand for 60 minutes to separate and remove the soap residue at the bottom, and obtain the deacidified oil.

[0036] 4. Washing with water to remove salt and soap The deacidified grease is thoroughly washed with 65℃ constant-temperature soft water to completely remove residual salts, free alkali, and saponified substances. After washing, it is transferred to a vacuum drying tank and dried under 105℃ and -0.09MPa vacuum conditions for 40~60 minutes with stirring to completely remove moisture.

[0037] 5. Vacuum deodorization After drying, the oil is added to bleaching clay and activated carbon, and stirred under negative pressure at 110℃ for 30 minutes for decolorization. The adsorption residue is removed by plate and frame filter press. Finally, it is sent to a vacuum deodorization tank for 120 minutes for deodorization. After cooling and filtration, the final oil by-product is obtained.

[0038] III. Evaluation Indicators (a) Basic performance 1. Acid value (mgKOH / g) Referring to GB / T 5530-2005, weigh 3.00 g of the melted and well-mixed oil sample into an Erlenmeyer flask, add 50 mL of neutral ethanol, reflux in a water bath and gently boil for 5 min to dissolve the sample, add 3 drops of phenolphthalein indicator, and titrate with the standard solution while hot until a faint pink color persists for 30 s. Perform a blank test simultaneously and calculate using the following formula: Acid value (mgKOH / g) = (V V0)×c×56.1 / m V is the volume of standard solution consumed in the sample titration (mL); V0 is the volume of standard solution consumed in the blank titration (mL); c is the concentration of potassium hydroxide standard solution (mol / L); m is the sample mass (g); 56.1 is the molar mass of potassium hydroxide.

[0039] 2. Saponification value (mgKOH / g) Referring to GB / T 5534-2008, weigh 2.00 g of the molten and well-mixed oil sample into an Erlenmeyer flask, accurately add 25 mL of 0.5 mol / L potassium hydroxide ethanol solution, connect a reflux condenser, and reflux in a water bath at a gentle boil for 30 min to ensure complete saponification. After cooling, add 3 drops of phenolphthalein indicator and titrate with 0.5 mol / L hydrochloric acid standard solution until the red color disappears. Perform a blank test simultaneously and calculate using the following formula: Saponification value (mgKOH / g) = (V0) V)×c×56.1 / m V is the volume of standard hydrochloric acid solution consumed in the sample titration (mL); V0 is the volume of standard hydrochloric acid solution consumed in the blank titration (mL); c is the concentration of standard hydrochloric acid solution (mol / L); m is the sample mass (g); 56.1 is the molar mass of potassium hydroxide.

[0040] 3. Moisture and volatile matter Referring to GB / T 5528-2008, weigh 5.00 g of the well-mixed oil sample into a pre-weighed weighing bottle, place it in a 105℃ constant temperature drying oven and dry at normal pressure for 2 hours. Remove it and cool it to room temperature in a desiccator, then weigh it. Repeat the drying process until constant weight is achieved, and calculate the weight using the following formula: Moisture and volatile matter (%) = (m1) m2) / m×100 m1 is the total mass of the sample and weighing bottle before drying (g); m2 is the total mass of the sample and weighing bottle after drying (g); m is the sample mass (g).

[0041] 4. Insoluble impurities Referring to GB / T 5529-2021, weigh 5.00 g of the melted and mixed oil sample, add 50 mL of petroleum ether and stir thoroughly to dissolve. Filter the solution using a pre-weighed glass frit crucible. Wash the filter residue with hot petroleum ether until no oil residue remains. Dry the filter residue along with the crucible at 105℃ to constant weight. Calculate the weight using the following formula: Insoluble impurities (%) = (m2) m1) / m×100 m1 is the mass of the blank crucible (g); m2 is the total mass of the crucible after adding impurities and drying (g); m is the mass of the sample (g).

[0042] 5. Peroxide value Referring to GB / T 5538-2005, weigh 2.00 g of the well-mixed oil sample and place it in an iodine flask. Add 30 mL of chloroform-glacial acetic acid mixture to dissolve the sample, add 1.00 mL of saturated potassium iodide solution, stopper tightly, shake well, and place in the dark for 3 min. Remove the flask, add 100 mL of water, shake well, and titrate with 0.01 mol / L sodium thiosulfate standard solution until pale yellow. Add starch indicator and continue titrating until the blue color disappears. Perform a blank test simultaneously and calculate using the following formula: Peroxide value (meq / kg) = (V V0)×c×1000 / m V is the volume of sodium thiosulfate standard solution consumed in the sample titration (mL); V0 is the volume of sodium thiosulfate standard solution consumed in the blank titration (mL); c is the concentration of sodium thiosulfate standard solution (mol / L); m is the sample mass (g).

[0043] (II) Saponification Application Performance 1. Saponification conversion rate Weigh 20.00g of the melt-mixed oil sample, add the theoretical amount of sodium hydroxide solution precisely according to the measured saponification value, and saponify at a constant temperature of 70℃ with stirring for 60min; after the reaction, extract the unreacted free oil with petroleum ether, recover the solvent by rotary evaporation, weigh, and perform parallel experiments simultaneously, calculating according to the following formula: Saponification conversion rate (%) = (m1) m2) / m1×100 m1 is the initial total mass of oil (g); m2 is the mass of unreacted free oil obtained from extraction (g).

[0044] 2. Saponification reaction rate The homogeneous chronometry method was used to determine the conversion rate. The oil mass, alkali concentration and saponification temperature were fixed. Timing was started from the moment the alkali and oil were mixed, and the time it took for the system to transform from an oil-water two-phase system to a homogeneous transparent soap base was recorded. Alternatively, samples could be taken at 20 min, 40 min and 60 min to measure the instantaneous conversion rate and plot the reaction rate curve.

[0045] 3. Free alkali and free fatty acids in soap (%) Referring to the QB / T 2623 soap test method, take a finished soap sample that has been cured for 7 days, dissolve it in neutral ethanol, and titrate the free alkali with a standard hydrochloric acid solution; take another sample, extract the free fatty acids with neutral ether, and titrate with a standard potassium hydroxide solution. Calculate the mass ratio of the two samples to determine the degree of completeness of the saponification reaction.

[0046] 4. Soap body molding stability Take a standard soap sample that has been cured at room temperature for 7 days, and measure the hardness of the soap body using a needle penetration tester at 25°C. At the same time, visually observe whether there are cracks, delamination, oil return, or blooming. After being left at room temperature for 30 days, re-inspect the appearance and hardness changes to evaluate the long-term stability of the saponified product.

[0047] 5. Foam performance Referring to GB / T 7462, the initial foaming height and 5-minute foam retention height of soap solution were measured using a Roche foam meter to characterize foaming power and foam stability, reflecting the washing performance of the saponified product.

[0048] IV. Results of the Investigation Table 1 Comparison of the physicochemical properties of oil by-products obtained from schemes 1-3 The refined butter prepared by the three processes all had acid value, saponification value, moisture and volatile matter, and insoluble impurities within the qualified range for soap-making oils. There were no significant differences in the core physicochemical indicators, indicating that the controllable retention of small molecule collagen peptides does not reduce the basic purity and quality of the oil.

[0049] In Scheme 1 (complete deproteinization), no peptide residue was detected; in Scheme 2 (phosphate), the peptide residue was 0.052%, which is within the optimal synergistic range of 0.03% to 0.08%; and in Scheme 3 (citric acid), the peptide residue was 0.091%, indicating a higher retention level.

[0050] Regarding the peroxide value, both Scheme 2 and Scheme 3 showed lower values ​​than Scheme 1. Scheme 3, due to the metal ion chelation effect of citric acid, exhibited superior oxidative stability of the oil, further validating the positive effect of the mild flocculation process on oil quality.

[0051] Table 2 Comparison of Saponification Performance of Oil By-products Obtained from Schemes 1-3 Compared to the traditional complete deproteinization process of Scheme 1, the controlled peptide retention processes of Schemes 2 and 3 show significant improvements in saponification reaction efficiency and finished soap quality, as detailed below: The saponification reaction efficiency was significantly improved: the saponification conversion rates of Schemes 2 and 3 reached 95.7% and 96.8% after 60 minutes, respectively, which were 6.5% and 7.6% higher than those of Scheme 1 (89.2%). The time for the system to reach homogeneous soap base was shortened to 28 minutes and 24 minutes, respectively, which were 33.3% and 42.9% shorter than those of Scheme 1 (42 minutes). These results directly verify that the retained small molecule collagen peptides can act as natural surfactants to enhance the contact between the oil and water phases, significantly accelerate the saponification reaction rate, and improve the reaction completeness, which is consistent with the invention mechanism.

[0052] More uniform and thorough saponification reaction: The content of free alkali and free fatty acids in the finished soap prepared by schemes 2 and 3 is lower than that of scheme 1, eliminating the risk of residual oil and oil return caused by incomplete saponification, and the saponification uniformity is better.

[0053] The soap's molding and stability were significantly improved: soaps from schemes 2 and 3 showed higher penetration and a more flexible texture, exhibiting no cracking, oil reversion, or blooming after 30 days at room temperature; while the pure butter soap from scheme 1 was harder and more brittle, with slight cracking at the edges. This indicates that trace amounts of peptides can fill the gaps between soap molecules, improving the inherent defects of pure butter soap—its hardness, brittleness, and susceptibility to cracking—and enhancing the long-term stability of the finished product.

[0054] Foam performance is significantly improved: the initial foaming height of Scheme 2 and 3 is increased by 25.4% and 30.3% respectively, and the stable foaming height at 5 minutes is increased by 57.0% and 72.1% respectively. The foam is denser and more stable, and the washing experience is significantly better than that of traditional pure butter soap.

[0055] The above research results fully verify the technical effectiveness of the non-isoelectric point salt-free flocculation process of this invention: without sacrificing the basic physicochemical purity and storage stability of the oils, the saponification reaction efficiency and the overall quality of the finished soap can be significantly improved by controllably retaining trace amounts of small-molecule denatured collagen peptides, achieving a synergistic effect of "high purity and stability + saponification enhancement." This effect cannot be achieved by traditional complete deproteinization refining processes, demonstrating outstanding technological progress and patent inventiveness. Among them, Scheme 2 comprehensively balances quality and enhancement effects, making it the optimal process scheme; Scheme 3 offers more significant enhancement and is suitable for high-end soap raw material scenarios.

[0056] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0057] Example 1 This embodiment provides a method for extracting oily by-products from cowhide. The extraction method uses pretreatment waste liquid generated during the cowhide pretreatment stage as the extraction raw material. The source of the pretreatment waste liquid is as follows: 1) Take fresh cowhide, clean it, remove the hair, cut it into small pieces no larger than 4×4mm, add it to a sodium chloride solution with a mass fraction of 3-7%, soak it at room temperature for 1 hour, drain the water, and obtain sodium chloride waste liquid. 2) After soaking in brine, the cowhide is added to a 0.1 mol / L NaOH solution, stirred evenly at 3-5℃, soaked for 2-4 days, and washed with water 3-5 times to obtain waste alkaline solution; 3) Mix the pretreated cowhide and water at a mass ratio of 1:5, boil at 100℃ for 20-30 minutes under 0.8-1.0MPa conditions, cool to 50-60℃, and filter out solids such as cowhide through double-layer gauze to obtain the boiled waste liquid.

[0058] The above-mentioned sodium chloride waste liquid, waste alkali liquid and boiling waste liquid are combined and poured into a sealed insulated storage tank, and mixed and stirred for 15 minutes to achieve homogenization, which is the above-mentioned pretreated waste liquid.

[0059] The process for extracting oil by-products using the pretreated waste liquid as the processing target is as follows: 1. Demulsification and flocculation The homogenized waste liquid was fed into a heat-insulated reactor, and food-grade citric acid was slowly added dropwise under low-speed stirring to adjust the pH of the system to 4.6-5.0. No salting-out agent was added during the entire process. The reaction was carried out under constant temperature and stirring for 30 minutes to obtain the demulsifier.

[0060] 2. Three-phase static stratification After the reaction, the demulsified liquid was transferred to a 60°C constant-temperature sealed settling tank and allowed to stand for 3 hours to complete the three-phase separation. The upper layer after separation is the crude tallow layer, the middle layer is a salt-containing water phase that can be reused in the pretreatment washing process of cowhide, and the lower layer of protein colloid flocculent residue is centrally treated for harmlessness. The upper crude oil is collected by negative pressure skimming and filtered through an 80-mesh filter to remove solid suspended particles, thus obtaining crude tallow.

[0061] 3. Hydration and degumming treatment The obtained crude tallow was heated to 60°C, and 2.5% (by weight of the tallow) of constant-temperature soft water at 60°C and 0.15% (based on pure H3PO4) were added. The mixture was stirred slowly for 30 minutes and allowed to stand for 90 minutes. During this time, the water-absorbing and swollen phospholipid micelles and water-soluble colloidal impurities gradually coagulated and precipitated, becoming concentrated in the lower layer of the system along with the added phosphoric acid auxiliaries, forming a heavy colloidal aqueous phase. The upper layer was clear degummed crude tallow, which was discharged from the bottom of the apparatus for the next removal of phospholipids and water-soluble colloidal impurities. Subsequently, the crude oleic acid value was measured, and a 12% ( w / v Sodium hydroxide solution was added to the alkaline solution at a rate 0.05% higher than the theoretical neutralization amount. The reaction was carried out by stirring at a constant temperature of 65°C for 30 minutes to complete the deacidification reaction. After standing for 60 minutes, the soap residue at the bottom was separated and removed to obtain the deacidified oil.

[0062] 4. Washing with water to remove salt and soap Add 65°C constant-temperature soft water to the above-mentioned deacidified oil for a three-stage countercurrent wash, stirring for 15 minutes and letting it stand for 30 minutes in each stage before draining the water in layers. Repeat the washing process until the wastewater is neutral, foam-free, and turbid, thoroughly removing residual salts, free alkali, and saponified substances. After washing, transfer the oil to a vacuum drying tank and stir and dry it for 40-60 minutes at 105°C and -0.09MPa vacuum to completely remove moisture and trace volatiles.

[0063] 5. Vacuum deodorization After drying, the oil was mixed with 2.5 wt.% bleaching clay and 0.3 wt.% activated carbon, and stirred at 110°C under negative pressure for 30 min for decolorization. The adsorption residue was removed by plate and frame filter press. Finally, the oil was sent to a vacuum deodorization tank and deodorized by passing low-pressure saturated steam countercurrently for 120 min under vacuum conditions of 220~240°C and ≤500Pa. After cooling and filtration, the final oil by-product was obtained.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for extracting oily by-products from cowhide, characterized in that, The extraction method uses the pretreatment waste liquid generated during the cowhide pretreatment stage as the treatment object to extract the oily by-products therein. The extraction method includes the following steps: S1. Demulsification and flocculation: Citric acid is added to the pretreated waste liquid to adjust the pH to 4.6-5.0, and the mixture is stirred slowly at room temperature for 20-30 minutes to obtain a demulsified solution; S2. Three-phase settling and separation: After the reaction is completed, the above demulsifier is transferred to a sealed container and settling until the three phases separate. The upper crude oil is collected, and the solid suspended particles are filtered out to obtain crude tallow. S3. Hydration and degumming treatment: After heating the obtained crude oil, add soft water and phosphoric acid, stir slowly to mix thoroughly, and let stand to remove phospholipids and water-soluble gum impurities; then test the acid value of the crude oil, add alkali solution to neutralize the deacidification reaction, let stand, separate and remove the bottom soap feet to obtain the deacidified oil; S4. Water washing for desalting and soap removal: The deacidified grease is washed with soft water for desalting, and then dried under vacuum. S5. Vacuum deodorization: After drying, the oil is added to a decolorizing agent for deep decolorization, and then deodorized to obtain the final product.

2. The method for extracting oily by-products from cowhide as described in claim 1, characterized in that, The source of the pretreated waste liquid includes at least one or a combination of the following: Part 1: Waste liquid from soaking cowhide in sodium chloride, wherein the mass fraction of sodium chloride is 3-7%; Part Two: A sodium hydroxide soaking solution for cowhide, wherein the concentration of sodium hydroxide is preferably 0.05~0.15 mol / L; Part Three: This is the waste liquid from boiling cowhide with water, with a boiling time not exceeding 30 minutes.

3. The method for extracting oily by-products from cowhide as described in claim 2, characterized in that, The pretreated waste liquid includes at least three components; Furthermore, the pretreated waste liquid is a mixture of parts one to three in a volume ratio of 1:1.5~2:5~6, and more preferably a volume ratio of 1:2:

6.

4. The method for extracting oily by-products from cowhide as described in claim 1, characterized in that, In the three-phase settling and stratification step, the demulsifier is divided into three layers, with the upper layer being crude oil, which is collected by skimming under negative pressure. The settling temperature is 50~70℃ and the settling time is 2~4h.

5. The method for extracting oily by-products from cowhide as described in claim 1, characterized in that, In the hydration degumming process, the resulting crude oil is heated to 55-65°C. The amount of soft water added is 2-3 wt.% of the crude oil, and the amount of phosphoric acid added is 0.1-0.2 wt.% of the crude oil. After the addition is complete, the mixture is stirred slowly for 25-35 minutes and then allowed to stand for at least 60 minutes.

6. The method for extracting oily by-products from cowhide as described in claim 1, characterized in that, The alkaline solution is a sodium hydroxide solution with a concentration of 10-14% ( ). w / v The deacidification reaction is carried out at a temperature of 60-70℃ for 25-35 minutes. After the deacidification reaction, the mixture is allowed to stand for at least 50 minutes to remove the bottom soap residue.

7. The method for extracting oily by-products from cowhide as described in claim 1, characterized in that, In the water washing desalting and soap removal step, the temperature of the soft water is 60~70℃, the washing time is 12~17min, and the water is allowed to stand for 25~35min before being drained in layers; the temperature of the vacuum drying is 95~105℃, the vacuum degree is -0.1~-0.09MPa, and the vacuum drying time is 40~60min.

8. The method for extracting oily by-products from cowhide as described in claim 1, characterized in that, In the vacuum deodorization step, the decolorizing agent is selected from one or a combination of several of the following: white clay, activated carbon, diatomaceous earth, molecular sieve, or attapulgite. Furthermore, a combination of bleaching clay and activated carbon is used, wherein the amount of bleaching clay added is 2.0~3.0 wt.% of the oil, and the amount of activated carbon added is 0.2~0.5 wt.%. After adding bleaching clay and activated carbon to the dried oil, the temperature is raised to 100~120℃ and stirred under negative pressure for 25~36 minutes for decolorization, and then the decolorizing agent residue is removed by filtration. The deodorization process employs vacuum deodorization at a temperature of 220-240℃ and a vacuum degree of ≤500Pa, with saturated steam introduced in a countercurrent manner for a deodorization time of 100-150 minutes.

9. Oil by-products prepared by the extraction method according to any one of claims 1-8.

10. The application of the oil by-product of claim 9 in the preparation of soap products, characterized in that, The soap products include, but are not limited to, saponified products used on the human body, clothing, in kitchens and bathrooms, or in industrial settings. Furthermore, the saponified products for human use include, but are not limited to, cleaning products for the face, body, hands, and infants, and are further selected from facial cleansers, shower gels, hand soaps, or makeup removers. Furthermore, the saponified products used for clothing include, but are not limited to, laundry powder, laundry soap, laundry liquid, or antibacterial agents; Furthermore, the saponified products used in kitchens and bathrooms include, but are not limited to, dishwashing liquid and detergents; Furthermore, the saponified products used in industrial settings include, but are not limited to, industrial detergents, leather care agents, or textile detergents.

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