Method for preparing sodium alginate m / g sub-polysaccharide coproduction and application thereof

Abstract

This invention discloses a method for the co-production and application of sodium alginate M / G segment hypopolysaccharides, belonging to the field of marine biological polysaccharide processing technology. This invention employs dry selective radiation degradation technology to precisely break the GM / MG block linkage sites of sodium alginate while completely preserving the homopolymeric block structures of MM and GG, enabling the controllable preparation of hypopolysaccharide mixtures ranging from 5 to 20 kDa. Utilizing the solubility differences between the M and G segments in specific acidic and weakly alkaline systems, combined with acid-soluble fractionation, plate-and-frame filtration, alkali-soluble resolution, and gradient alcohol precipitation processes, the co-production of the two block hypopolysaccharides is achieved, with product purity reaching 80%-90%. This invention solves the technical problems of disordered acid hydrolysis degradation, low raw material utilization, and poor product purity associated with traditional methods. The process is green, controllable, and suitable for industrial production. Simultaneously, the high-purity G segment hypopolysaccharide is used to prepare thermally reversible gel-type fat substitutes, exhibiting excellent taste and processing performance, thus broadening the application scenarios of functional sodium alginate hypopolysaccharides.

Description

Technical Field

[0001] This invention belongs to the field of marine biological polysaccharide processing, and particularly relates to a method for the co-production and application of sodium alginate M-segment / G-segment subpolysaccharides. Background Technology

[0002] Sodium alginate is a linear natural polysaccharide extracted from brown algae, composed of β-D-mannuronic acid (M) and its C5 epimer α-L-guluronic acid (G) linked by β-1,4 glycosidic bonds. The sodium alginate molecular chain consists of three block structures: continuous M segments, continuous G segments, and alternating M and G segments (MG segments). The M and G segments exhibit different functional properties in different applications: the G segment, due to its specific binding with Ca²⁺ to form a classic "eggbox" structure, is the functional segment for alginate gelation; the M segment, due to its carboxyl and hydroxyl functional groups, possesses unique advantages in bioactivity and drug delivery carrier development.

[0003] In existing technologies, "hypopolysaccharides" specifically refer to low molecular weight polysaccharides with molecular weights between 5 kDa and 20 kDa. Polysaccharides in this molecular weight range possess unique physicochemical properties: their molecular weight is higher than that of conventional oligosaccharides (oligosaccharides typically consist of 2-20 monosaccharide units, with a molecular weight of approximately 300-3,000 Da), thus retaining some of the functional characteristics of polysaccharides; at the same time, their molecular weight is significantly lower than that of natural high molecular weight polysaccharides (sodium alginate typically has a natural molecular weight of 32-250 kDa or higher), thereby solving the technical bottlenecks of high molecular weight polysaccharides such as high viscosity and difficulty in dissolving at high concentrations during processing. More importantly, when sodium alginate is selectively degraded to the hypopolysaccharide range, high-purity polymannuronic acid (MM) and polyguluronic acid (GG) hypopolysaccharides can be obtained through subsequent separation and purification. These two hypopolysaccharides are composed of continuous mannuronic acid units and continuous guluronic acid units, respectively, and belong to a typical homopolymeric block structure. Due to the highly consistent configuration of the monosaccharide units in the molecular chain, the molecular chain structure itself has a high degree of regularity, and intermolecular and intramolecular hydrogen bonds are easily formed and arranged in an orderly manner, thus producing crystalline regions. This regular crystalline structure contrasts sharply with the amorphous state of natural sodium alginate (a heteropolysaccharide), giving the M-segment and G-segment hypopolysaccharides significantly different physicochemical properties.

[0004] In existing technologies, the separation of M and G segments from alginic acid is mostly carried out by acid hydrolysis combined with pH fractionation precipitation. Specifically, alginic acid is hydrolyzed for 3-5 hours to obtain a mixture of G, M and MG segments, and then fractionation is carried out by pH adjustment. The G segment remains insoluble under pH 2.8-4.0 conditions, while the M segment dissolves in the solution phase. This method has the following technical defects: (1) Acid hydrolysis is a non-selective degradation, the reaction is violent and uncontrollable, and it is easy to over-cleave polysaccharide chains, destroy the internal structure of M and G segments, resulting in uneven molecular weight distribution of the product and affecting its functional properties; (2) This process is a selective recovery of a single block, one of which is often discarded, and M and G segments cannot be co-produced and recovered, resulting in low raw material utilization and unsuitability for industrial-scale production; (3) The purity of the product is limited, and the purity of G segment is usually less than 70%, which is difficult to meet the needs of high value-added applications. Summary of the Invention

[0005] This invention addresses the technical problem in existing technologies where acid hydrolysis combined with pH fractionation precipitation separates the M and G segments, resulting in uneven molecular weight distribution of the products and the inability to achieve co-production and recovery. It proposes a method for the co-production of sodium alginate M / G segment hypopolysaccharides, simultaneously obtaining M-segment and G-segment hypopolysaccharides with molecular weights of 5-20 kDa and purity of 80%-90%.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for co-producing sodium alginate M-fraction / G-fraction subpolysaccharides includes the following steps: (1) Radiation degradation of dry product: Sodium alginate powder is degraded by ultraviolet light or γ-ray to obtain a mixture of low molecular weight sodium alginate polysaccharides with a weight average molecular weight of 5-20 kDa. (2) Acid-soluble fractionation: The radiation degradation products obtained in step (1) are dispersed in an aqueous solution with a pH of 3.0-3.5 and stirred until the M segment dissolves and the G segment remains insoluble, to obtain a mixed slurry of the M segment solution and the G segment precipitate; (3) Plate and frame filter M section: The slurry obtained in step (2) is filtered through a plate and frame filter press to separate the filtrate containing M section hypopolysaccharide and the filter cake containing G section hypopolysaccharide; (4) M-segment alcohol precipitation purification: The filtrate obtained in step (3) was purified by controlling the molecular weight of alcohol precipitation with different volume fractions of aqueous ethanol solution, the alcohol precipitate was collected, and dried to obtain high-purity M-segment polysaccharide. (5) Alkali dissolution and redissolution of G segment: After crushing the filter cake obtained in step (3), disperse it in an aqueous solution with a pH of 7.0-8.0, stir to redissolve G segment, and obtain G segment solution; (6) Plate and frame filtration to remove residue: The G-section solution obtained in step (5) is filtered through a plate and frame filter press to remove residual insoluble matter and obtain pure G-section filtrate. (7) G-segment alcohol precipitation purification: The filtrate obtained in step (6) was purified by controlling the molecular weight of alcohol precipitation with different volume fractions of aqueous ethanol solution, the alcohol precipitate was collected, and after drying, high-purity G-segment hypopolysaccharide was obtained.

[0007] Preferably, the wavelength of ultraviolet radiation is 200-400nm, the radiation power is 50-500W, and the radiation time is 1-24 hours; the absorbed dose of gamma radiation is 5-60kGy.

[0008] Preferably, the ultraviolet radiation wavelength is 254 nm or 365 nm; the absorbed dose of the gamma radiation is 10-40 kGy.

[0009] Preferably, the moisture content of the sodium alginate powder in step (1) before radiation degradation is controlled at 5%-15%.

[0010] Preferably, the pH value of the acidic aqueous solution in step (2) is adjusted by adding one or more of hydrochloric acid, sulfuric acid, acetic acid or citric acid, the temperature of the acidic aqueous solution is 4℃-25℃, and the stirring time is 30-120 minutes.

[0011] Preferably, the fractional alcohol precipitation in steps (4) and (7) includes the following sub-steps: first, a first alcohol precipitation is performed using an aqueous ethanol solution with a volume fraction of 30%-40%, and the precipitate is collected to obtain a high molecular weight fraction; then, a second alcohol precipitation is performed on the supernatant using an aqueous ethanol solution with a volume fraction of 50%-70%, and the precipitate is collected to obtain a medium molecular weight fraction; finally, a third alcohol precipitation is performed using an aqueous ethanol solution with a volume fraction of 80%-95%, and the precipitate is collected to obtain a low molecular weight fraction.

[0012] Preferably, the purity of the M-segment hypopolysaccharide obtained in step (4) is 80%-90% and the molecular weight is 5,000-20,000 Da; the purity of the G-segment hypopolysaccharide obtained in step (7) is 80%-90% and the molecular weight is 5,000-20,000 Da.

[0013] This invention also proposes the application of G-segment hypopolysaccharide prepared by the above method in the preparation of fat substitutes, comprising the following steps: (a) G-segment dissolution: The G-segment hypopolysaccharide prepared by any one of claims 1-7 is mixed with a weakly basic substance and dissolved in cold water to obtain a high-concentration G-segment hypopolysaccharide solution, wherein the mass percentage concentration of the G-segment hypopolysaccharide in the solution is 2%-15%, and the weakly basic substance is selected from one or more of sodium bicarbonate, potassium bicarbonate, and sodium hydroxide, and the amount added is 1%-10% of the mass of the polyuronic acid segment; (b) Emulsification and compounding: The high-concentration G-segment polysaccharide solution is mixed and emulsified with vegetable oil to form an emulsion, wherein the mass ratio of the vegetable oil to the G-segment solution is 1:4 to 4:1; (c) Low-temperature gelation: The emulsion obtained in step (b) is cooled at 0℃-10℃ to form a fat-like gel. (d) Shaping: The gel obtained in step (c) is shaped to obtain a fat substitute.

[0014] Preferably, the weakly alkaline substance in step (a) is sodium bicarbonate, and the amount added is 2%-5% of the mass of the polyuronic acid segment.

[0015] Preferably, an emulsifier is added in step (b), the emulsifier being selected from one or more of glyceryl monostearate, soybean lecithin, and sucrose fatty acid esters, and the amount added is 0.5%-5% of the oil mass.

[0016] Compared with the prior art, the advantages and positive effects of the present invention are as follows: (1) This invention utilizes the solubility difference between M-segment and G-segment in acidic and neutral / weakly alkaline media, combined with a process of radiation degradation of dry products, acid-soluble fractionation, and alkali-soluble resolution, to achieve efficient co-production of M-segment and G-segment hypopolysaccharides, significantly improving the comprehensive utilization rate of raw materials. Compared with traditional methods that can only selectively recover one segment of G-segment or M-segment while the other component is discarded, this invention can reduce production costs and reduce waste emissions.

[0017] (2) This invention utilizes the differences in sensitivity to radiation degradation of different block linkage sites to precisely control the dry system, radiation wavelength, power, irradiation dose and time, and sets the radiation conditions to a selective degradation window that is higher than the GM / MG glycosidic bond dissociation energy and lower than the MM / GG glycosidic bond dissociation energy. Due to the bond angle strain and steric hindrance caused by the configuration of the GM and MG linkage sites, the glycosidic bond dissociation energy is lower and it breaks preferentially under radiation. Meanwhile, the glycosidic bonds inside the MM and GG homopolymer segments are completely preserved. After degradation, a mixture of poly-M segment and poly-G segment subpolysaccharides is obtained with complete block sequences, which provides a basis for subsequent high-purity separation.

[0018] The dry system can significantly reduce the degradation rate, obtain a wider process control window, and facilitate selective cleavage; in the dry state, γ-rays easily generate hydroxyl radicals through hydrolysis to perform indiscriminate chain breakage, making it difficult to achieve site selectivity; this invention achieves site-selective cleavage of sodium alginate GM / MG by combining radiation type with the dry system, filling the technical gap of lacking GM specific cleavage enzymes, and opening up a new route for the preparation of high-purity homopolymer block polysaccharides.

[0019] (3) Segment M is soluble in an extended conformation under acidic conditions, while segment G is insoluble in a coiled-helical conformation. This invention performs acid-soluble fractionation at pH 3.0-3.5. Segment M enters the liquid phase, while segment G precipitates out. The two components are then recovered through plate and frame filtration and alkali dissolution / redissolution. Separation can be achieved solely through pH adjustment. Compared to existing methods such as calcium ion complexation and high-temperature separation, this method eliminates the need for metal complexing ions and a high-temperature reaction environment. The process conditions are milder, the operation is simpler, and the equipment requirements are reduced.

[0020] (4) The purity of the M-segment and G-segment hypopolysaccharides prepared by this invention can reach 80%-90%, which is better than the purity level of less than 70% in traditional pH fractionation. The obtained products are homopolymeric block structures with regular molecular chain configurations, which easily form intramolecular and intermolecular hydrogen bonds and crystalline regions, and have physicochemical properties that are different from natural heteropolymer sodium alginate. The M-segment hypopolysaccharide has good water solubility, and the G-segment hypopolysaccharide has pH-responsive dissolution characteristics and thermally reversible gelation ability, making it suitable as a base material for fat mimics.

[0021] (5) The G-segment polysaccharide prepared in this invention can be used to prepare fat substitutes to form a thermally reversible gel that simulates the processing and taste properties of animal fat. Detailed Implementation

[0022] To better understand the present invention, specific details are provided below with reference to embodiments. Example 1

[0023] One kilogram of dried sodium alginate powder (molecular weight 150 kDa, moisture content approximately 10%, source: Qingdao Haizhilin Biotechnology Development Co., Ltd.) was evenly spread in an ultraviolet (UV) photoreactor. Radiation degradation was performed using 254 nm UV light at a power of 200 W, a distance of 10 cm, and a duration of 4 hours, with the powder being constantly agitated during irradiation. After irradiation, the degradation product was passed through a 200-mesh sieve to obtain a powdered mixture of low-molecular-weight sodium alginate polysaccharides. Gel permeation chromatography (GPC) determined the weight-average molecular weight (Mw) of the radiation degradation product to be approximately 12,500 Da.

[0024] Weigh 500g of the above radiation degradation product and disperse it in 5L of hydrochloric acid aqueous solution with a pH of 3.2 (pH adjusted by 1M hydrochloric acid). Stir at 15°C for 60 minutes to fully dissolve segment M and keep segment G in a precipitated state. Filter the resulting slurry through a plate and frame filter press, collecting the filtrate and filter cake separately. The filtrate is an acidic solution containing segment M hypopolysaccharides, and the filter cake is a precipitate enriched with segment G hypopolysaccharides.

[0025] The filtrate was subjected to fractional alcohol precipitation: First, ethanol was slowly added to the filtrate until the ethanol volume fraction reached 35%, and the mixture was allowed to stand at 4°C for 6 hours. The precipitate was collected by centrifugation and dried to obtain the high molecular weight M-fraction subpolysaccharide fraction. Then, ethanol was added to the supernatant until the volume fraction reached 60%, and the mixture was allowed to stand at 4°C for 6 hours. The precipitate was collected by centrifugation and dried to obtain the medium molecular weight M-fraction subpolysaccharide fraction. Finally, ethanol was added to the supernatant until the volume fraction reached 85%, and the mixture was allowed to stand at 4°C for 6 hours. The precipitate was collected by centrifugation and dried to obtain the low molecular weight M-fraction subpolysaccharide fraction. The three fractions were combined to obtain approximately 215 g of M-fraction subpolysaccharide.

[0026] The filter cake was pulverized and dispersed in 3L of deionized water with a pH of 7.5 (pH adjusted with 0.1M sodium hydroxide). The mixture was stirred for 60 minutes to redissolve fraction G. The resulting fraction G solution was filtered through a plate and frame filter press to remove residual insoluble matter. The filtrate was subjected to fractional alcohol precipitation (ethanol volume fractions of 35%, 60%, and 85%, respectively) under the same conditions as above. The precipitates were collected and combined to obtain approximately 228g of fraction G hypopolysaccharide.

[0027] HPAEC-PAD analysis showed that the purity of the M-fraction subpolysaccharide was 85.1% and that of the G-fraction subpolysaccharide was 86.3%. GPC analysis showed that the Mw of the M-fraction subpolysaccharide was 12,800 Da and that of the G-fraction subpolysaccharide was 11,500 Da. Example 2

[0028] Take 1 kg of sodium alginate powder (molecular weight 200,000 Da, moisture content approximately 12%) and place it in... 60 Radiation degradation was carried out in a Co-γ irradiation field. The absorbed dose rate was 80 Gy / min, and the total absorbed dose was 25 kGy. After irradiation, the degradation products were passed through a 200-mesh sieve. GPC analysis showed that the weight-average molecular weight of the radiation degradation products was approximately 11,200 Da.

[0029] Weigh 500g of the above radiation degradation product and disperse it in 5L of hydrochloric acid aqueous solution with a pH of 3.5. Stir for 45 minutes at 20°C. Subsequent separation and purification steps are the same as in Example 1.

[0030] The purity of the M-segment subpolysaccharide was determined to be 84.2%, and the purity of the G-segment subpolysaccharide was 85.9%; the Mw of the M-segment subpolysaccharide was 10,500 Da, and the Mw of the G-segment subpolysaccharide was 9,800 Da. Example 3

[0031] One kilogram of dried sodium alginate powder (molecular weight 100,000 Da, moisture content approximately 8%) was subjected to ultraviolet (UV) radiation degradation treatment at a wavelength of 254 nm, with a UV power of 300 W and an irradiation time of 6 hours. GPC analysis showed that the weight-average molecular weight of the radiation degradation products was approximately 8,500 Da.

[0032] Weigh 500g of the above radiation degradation product and disperse it in 5L of citric acid aqueous solution with a pH of 3.0. Stir for 90 minutes at 10°C. Subsequent separation and purification steps are the same as in Example 1.

[0033] The purity of the M-segment subpolysaccharide was determined to be 86.7%, and the purity of the G-segment subpolysaccharide was 84.4%; the Mw of the M-segment subpolysaccharide was 8,200 Da, and the Mw of the G-segment subpolysaccharide was 7,600 Da.

[0034] Comparison of molecular weight fractionation effects: GPC analysis was performed on each fraction precipitated with ethanol from Example 1. The results showed that the molecular weight (Mw) of the fraction precipitated with 35% ethanol was approximately 18,500-22,000 Da, the Mw of the fraction precipitated with 60% ethanol was approximately 12,000-16,000 Da, and the Mw of the fraction precipitated with 85% ethanol was approximately 5,500-8,500 Da. This indicates that by adjusting the ethanol concentration during precipitation, the present invention can achieve precise molecular weight fractionation of the M and G segments of the hypopolysaccharide, meeting the differentiated molecular weight requirements of different application scenarios. Example 4

[0035] Take 50g of high-purity G-segment sodium alginate (purity 86.3%) prepared in Example 1, add 2g of sodium bicarbonate (4% of the mass of G-segment), and dissolve in 1L of deionized water under stirring at 10℃ to prepare a G-segment solution with a mass percentage concentration of approximately 5%, with a dissolution time of 1.5 hours. Take 200mL of soybean oil and mix it with the G-segment solution at a volume ratio of approximately 1:1.5, add 2g of glyceryl monostearate as an emulsifier, and emulsify under high shear emulsification conditions of 10000rpm for 5 minutes to form an oil-in-water emulsion. Transfer the emulsion to a mold and cool and gel at 4℃ for 4 hours to form a solidified fat-like gel. Shape the gel to obtain a fat substitute.

[0036] Performance testing: This fat substitute retains its shape when refrigerated at 4°C and completely melts when heated in an 80°C frying pan for 2 minutes, without any oil-water separation. Texture evaluation shows that its taste is close to natural beef fat, with no obvious gelling sensation.

[0037] Take 500g of plant protein tissue protein, add 200g of the aforementioned fat substitute, mix well, fill the mold, and let it stand in a cold storage at 4℃ for 12 hours to set. After slicing, the resulting marbled beef product has a uniform marbled fat texture, and its texture is close to that of real beef. Place the slices in a frying pan and fry over medium heat for 3-5 minutes. The fat simulated substance melts, releasing oil and obtaining a good aroma and taste.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for co-producing sodium alginate M-fraction / G-fraction secondary polysaccharides, characterized in that, Includes the following steps: (1) Radiation degradation of dry product: Sodium alginate dry product powder is degraded by ultraviolet light or γ-ray to obtain a mixture of low molecular weight sodium alginate polysaccharides with a weight average molecular weight of 5-20 kDa. (2) Acid-soluble fractionation: The radiation degradation products obtained in step (1) are dispersed in an aqueous solution with a pH of 3.0-3.5 and stirred until the M segment dissolves and the G segment remains insoluble, to obtain a mixed slurry of the M segment solution and the G segment precipitate; (3) Plate and frame filter M section: The slurry obtained in step (2) is filtered through a plate and frame filter press to separate the filtrate containing M section hypopolysaccharide and the filter cake containing G section hypopolysaccharide; (4) M-segment alcohol precipitation purification: The filtrate obtained in step (3) was purified by controlling the molecular weight of alcohol precipitation with different volume fractions of aqueous ethanol solution, the alcohol precipitate was collected, and dried to obtain high-purity M-segment polysaccharide. (5) Alkali dissolution and redissolution of G segment: After crushing the filter cake obtained in step (3), disperse it in an aqueous solution with a pH of 7.0-8.0, stir to redissolve G segment, and obtain G segment solution; (6) Plate and frame filtration to remove residue: The G-section solution obtained in step (5) is filtered through a plate and frame filter press to remove residual insoluble matter and obtain pure G-section filtrate. (7) G-segment alcohol precipitation purification: The filtrate obtained in step (6) was purified by controlling the molecular weight of alcohol precipitation with different volume fractions of aqueous ethanol solution, the alcohol precipitate was collected, and after drying, high-purity G-segment hypopolysaccharide was obtained.

2. The method for co-producing sodium alginate M-segment / G-segment secondary polysaccharides according to claim 1, characterized in that: In step (1), the wavelength of ultraviolet radiation is 200-400nm, the radiation power is 50-500W, and the radiation time is 1-24 hours; the absorbed dose of gamma radiation is 5-60kGy.

3. The method for co-producing sodium alginate M-segment / G-segment secondary polysaccharides according to claim 2, characterized in that: The ultraviolet radiation wavelength is 254 nm or 365 nm; the absorbed dose of the gamma ray radiation is 10-40 kGy.

4. The method for co-producing sodium alginate M-segment / G-segment secondary polysaccharides according to claim 1, characterized in that: The moisture content of the sodium alginate powder in step (1) before radiation degradation is controlled at 5%-15%.

5. The method for co-producing sodium alginate M-segment / G-segment secondary polysaccharides according to claim 1, characterized in that: The pH value of the acidic aqueous solution in step (2) is adjusted by adding one or more of hydrochloric acid, sulfuric acid, acetic acid or citric acid. The temperature of the acidic aqueous solution is 4℃-25℃ and the stirring time is 30-120 minutes.

6. The method for co-producing sodium alginate M-segment / G-segment hypopolysaccharides according to claim 1, characterized in that: The fractional alcohol precipitation described in steps (4) and (7) includes the following sub-steps: first, a first alcohol precipitation is performed using an aqueous ethanol solution with a volume fraction of 30%-40%, and the precipitate is collected to obtain a high molecular weight fraction; then, a second alcohol precipitation is performed on the supernatant using an aqueous ethanol solution with a volume fraction of 50%-70%, and the precipitate is collected to obtain a medium molecular weight fraction; finally, a third alcohol precipitation is performed using an aqueous ethanol solution with a volume fraction of 80%-95%, and the precipitate is collected to obtain a low molecular weight fraction.

7. The method for co-producing sodium alginate M-segment / G-segment secondary polysaccharides according to claim 1, characterized in that: The purity of the M-segment hypopolysaccharide obtained in step (4) is 80%-90%, and the molecular weight is 5,000-20,000 Da; the purity of the G-segment hypopolysaccharide obtained in step (7) is 80%-90%, and the molecular weight is 5,000-20,000 Da.

8. The application of a G-segment hypopolysaccharide prepared by the method according to any one of claims 1-7 in the preparation of fat substitutes, characterized in that, Includes the following steps: (a) G-segment dissolution: The G-segment hypopolysaccharide prepared by any one of claims 1-7 is mixed with a weakly basic substance and dissolved in cold water to obtain a high-concentration G-segment hypopolysaccharide solution, wherein the mass percentage concentration of G-segment hypopolysaccharide in the solution is 2%-15%, and the weakly basic substance is selected from one or more of sodium bicarbonate, potassium bicarbonate, and sodium hydroxide, and the amount added is 1%-10% of the mass of G-segment hypopolysaccharide; (b) Emulsification and compounding: The high-concentration G-segment polysaccharide solution is mixed and emulsified with vegetable oil to form an emulsion, wherein the mass ratio of the vegetable oil to the G-segment solution is 1:4 to 4:1; (c) Low-temperature gelation: The emulsion obtained in step (b) is cooled at 0℃-10℃ to form a fat-like gel. (d) Shaping: The gel obtained in step (c) is shaped to obtain a fat substitute.

9. The application according to claim 8, characterized in that: The weakly alkaline substance mentioned in step (a) is sodium bicarbonate, and the amount added is 2%-5% of the mass of the polyurethane segment.

10. The application according to claim 8, characterized in that: In step (b), an emulsifier is also added. The emulsifier is selected from one or more of glyceryl monostearate, soybean lecithin, and sucrose fatty acid esters, and the amount added is 0.5%-5% of the oil mass.

11. The application according to claim 8, characterized in that, The fat substitute melts completely into a liquid state within 1-5 minutes when cooked at a temperature ≥60℃.