A heat stable acidic emulsion stabilized by a legumin and a method for preparing the same

Abstract

This invention belongs to the field of soy globulin processing technology, specifically relating to a soy globulin-stabilized acidic emulsion and its preparation method. The emulsion comprises the following components by weight percentage: 1-5 wt% soy globulin; 5-20 wt% vegetable oil; and 75-94 wt% water. The soy globulin in this emulsion is a low-denaturation protein with a protein content of over 90%, obtained through a mild, non-acid precipitation (pH ≥ 5.5) and non-hydrolysis process. The soy globulin-stabilized acidic emulsion of this invention has a pH range of 3.0-5.0 and possesses advantages such as uniform appearance, high fluidity, high protein content, high thermal stability, and storage stability. Furthermore, the preparation process is simple and mild, suitable for large-scale production applications. The emulsion of this invention can be further dried to obtain powdered food or beverage products.

Description

Technical Field

[0001] This invention belongs to the field of soybean globulin processing technology, specifically relating to a soybean globulin-stabilized acidic emulsion and its preparation method. Background Technology

[0002] Acidic soy globulin milk beverages, with their advantages of being natural, healthy, nutritious, and having a unique taste, perfectly align with the upgrading trends in contemporary consumer concepts and are considered a healthier choice. The pH value of acidic soy globulin milk beverages is generally around 3.0-5.0. Compared to animal protein beverages (mainly casein and whey protein) that have long been prevalent in the market, their market share is relatively small. This is because acidic soy globulin emulsions are very sensitive to environmental stresses such as pH, ionic strength, and temperature. When the pH value in the emulsion approaches the isoelectric point of the protein, the reduced electrostatic repulsion causes instability phenomena such as aggregation, flocculation, and emulsification, making it impossible to obtain the soy globulin emulsion with superior stability under acidic conditions. Furthermore, if the protein purity is insufficient, a large amount of fiber, starch, and other impurities will be present in the system, directly affecting the protein's solubility and emulsifying properties. Therefore, the application of soy globulin in acidic protein beverages is greatly limited. How to control its stable dispersion under acidic conditions is the main bottleneck problem in the development of acidic soy globulin milk beverages.

[0003] Currently, the following methods are commonly used to prepare acidic emulsions of soybean globulin:

[0004] (1) Soybean globulin is obtained using the traditional alkali dissolution and acid precipitation process, and then the protein is used to prepare an emulsion. This method inevitably leads to problems such as complex process, large salt introduction, and energy consumption. In particular, isoelectric point acid precipitation can cause irreversible denaturation and aggregation of the protein, which greatly reduces the solubility and emulsifying properties of the protein, making it difficult to ensure the nutritional integrity and natural characteristics of the protein. If the protein is further used as a raw material to prepare an acidic emulsion, the protein is prone to flocculation and precipitation during heat treatment processes such as sterilization, making it difficult to carry out large-scale industrial production.

[0005] (2) Improve the emulsifying and acid-soluble properties of soy globulin by chemical modification or enzymatic modification. Hydrolysis or modification of protein can lead to problems such as impaired protein function, off-flavors, and weak emulsion stability. Furthermore, the active peptides produced by enzymatic hydrolysis can cause health problems such as disease and allergies.

[0006] (3) By adding natural macromolecular polysaccharides (such as carrageenan, gum arabic, etc.) to form complexes with proteins through electrostatic interactions, and then using these complexes to prepare emulsions, stability can be improved. The interaction between proteins and polysaccharides can only occur within a narrow range of polymer ratios, concentrations, and pH levels, making regulation difficult. Furthermore, the solubility of the polysaccharides and their stability in the emulsion system must be considered, potentially introducing uncertainties in practical product applications. In addition, the interaction requires adjusting the protein solution to acidity so that the protein molecules are positively charged and can combine with the negatively charged polysaccharides. Under these pH conditions, proteins are prone to denaturation; as time progresses, the degree of denaturation and hydrophobicity increase, easily leading to solid-liquid phase separation when the protein complexes with the polysaccharides, making it difficult to form a stable protein structure.

[0007] Based on current and previous scientific research, there is an urgent need to find a relatively mild and sustainable process to prepare lentinan while better preserving its original structure and functional properties, so as to improve the emulsification and stability of lentinan under acidic conditions.

[0008] Fennel protein is naturally derived, highly safe, and environmentally friendly, aligning with the modern food industry's natural and sustainable development direction. Compared to animal protein, genistein's biggest advantages are its low fat, cholesterol-free, and lactose-free nature, making it more suitable for individuals sensitive to dairy products or nuts, undoubtedly giving it a promising future in the protein beverage industry. However, due to the aforementioned issues of insufficient emulsification stability of genistein, there are currently no commercially available acidic emulsion products that use genistein as the sole protein source, without the addition of polysaccharides and emulsifiers, and can be rapidly produced and withstand intense heating. This invention utilizes only genistein as a raw material, obtaining high-purity genistein through a relatively mild process, and then adding vegetable oil to further prepare a high-protein acidic emulsion, which can be used as a functional yogurt beverage product or further dried to obtain a powdered food or beverage product. This invention solves the problem of insufficient emulsification and emulsification stability of genistein under acidic conditions, providing a solution for the high-value utilization of genistein and offering technical support for subsequent development and research. Summary of the Invention

[0009] To overcome the shortcomings and deficiencies of the prior art, this invention provides a stable acidic emulsion of soybean globulin and its preparation method. Soybean globulin is extracted through a mild process that is non-acid precipitation (pH≥5.5) and non-hydrolysis, which effectively solves the problems of poor solubility and insufficient emulsification of soybean globulin under acidic conditions. Based on this, an acidic emulsion of soybean globulin with high protein content, strong fluidity, uniform appearance, high thermal stability and storage stability is prepared.

[0010] The purpose of this invention is to provide a lentinan-stabilized acidic emulsion and its preparation method.

[0011] The present invention adopts the following technical solution:

[0012] A soy globulin-stabilized acidic emulsion, the components of which include: 1-5 wt% soy globulin; 5-20 wt% vegetable oil; and 75-94 wt% water.

[0013] The soy protein is a low-denaturation protein with a protein content of over 90%, obtained through a mild process that is non-acid precipitation and non-hydrolysis.

[0014] Preferably, the lentinan type is one or more of pea protein, soybean protein, mung bean protein, broad bean protein, and chickpea protein.

[0015] Preferably, the vegetable oil is at least one of the following edible oils: sunflower seed oil, rapeseed oil, corn oil, olive oil, flaxseed oil, etc.

[0016] The method for preparing the above-mentioned soy globulin-stabilized acidic emulsion includes the following steps:

[0017] Soy flour is dissolved in water, centrifuged, and the supernatant is collected. The pH is adjusted to 5.5-6.5, and the mixture is centrifuged again. The precipitate is collected, reconstituted, desalted, and dried to obtain soy globulin. Soy globulin is dispersed in water to obtain an aqueous phase. The pH is adjusted to 3.0-5.0. The aqueous phase is mixed with vegetable oil (oil phase), emulsified, and sterilized to obtain a stable acidic emulsion of soy globulin.

[0018] Preferably, the method for preparing the soy globulin-stabilized acidic emulsion does not require the addition of polysaccharides.

[0019] Preferably, the soybean flour is obtained by crushing at least one of defatted pea meal, defatted soybean meal, defatted mung bean meal, defatted broad bean meal, and defatted chickpea meal and then passing it through an 80-mesh sieve or by dry grading.

[0020] The soybean globulin described herein has not undergone isoelectric point precipitation, hydrolysis, thermal denaturation, or micronization. Specifically, isoelectric point precipitation involves adjusting the pH to acidic (pH < 5) to obtain protein precipitation; hydrolysis involves adding protease for enzymatic hydrolysis; thermal denaturation involves treatment in a thermal environment (≥ 70°C) for more than 10 minutes; and micronization involves shearing (≥ 3000 rpm, ≥ 5 minutes) after thermal denaturation treatment (or in a thermal environment (≥ 70°C)).

[0021] Preferably, the soybean powder is dissolved in water at a mass ratio of 1:7 to 1:20; and stirred at 200-500 rpm for 1.5-3 hours at 25°C to dissolve it.

[0022] Preferably, the centrifugation is carried out at a temperature of 4-25°C, with a centrifuge speed of 8000-10000 rpm and a centrifugation time of 10-20 min.

[0023] Preferably, the supernatant also contains at least one of sodium bisulfite, sodium bicarbonate, and sodium chloride, and the amount of sodium bisulfite used is such that the final concentration of salt ions in the mixed system is 0-150 mM.

[0024] Preferably, the pH adjusting solution used for adjusting the pH is one or more of edible organic or inorganic acids and their salts, including malic acid and its sodium and potassium salts, citric acid and its sodium and potassium salts, phosphoric acid and its sodium and potassium salts, gluconic acid and its sodium and potassium salts, acetic acid and its sodium and potassium salts, lactic acid and its sodium and potassium salts, carbonic acid and its sodium and potassium salts, sodium hydroxide, potassium hydroxide, and hydrochloric acid.

[0025] Preferably, the resolution condition is to adjust the pH of the solution to 6.5-7.5.

[0026] Preferably, the desalination is one or more of dialysis and ultrafiltration.

[0027] Preferably, the drying process is at least one of vacuum freeze drying, forced air drying, spray drying, and fluidized bed drying.

[0028] Preferably, the soybean globulin is dispersed in water to a mass fraction of 1-5 wt%; and then stirred at 200-400 rpm at 25°C for 1.5-3 hours to dissolve it.

[0029] Preferably, the water phase is mixed with the vegetable oil (oil phase) in a mass ratio of 95:5 to 80:20.

[0030] Preferably, the emulsification is performed by one or more of the following methods: high-pressure homogenization, ultrasonic homogenization, high-pressure microfluidic homogenization, and ball milling homogenization.

[0031] More preferably, the emulsification involves first performing pre-homogenization shearing at a speed of 3000-10000 rpm for 1-5 minutes, followed by high-pressure microjet homogenization 2-4 times under conditions of 30-100 MPa.

[0032] Preferably, the sterilization method is sterilization at a temperature of 95-121°C for 5-30 minutes.

[0033] The emulsion prepared by the above method has the following characteristics:

[0034] (1) The emulsion can still maintain good fluidity, uniform appearance and no obvious foreign matter after sterilization;

[0035] (2) The pH range of the emulsion is 3.0-5.0;

[0036] (3) The particle size range of the emulsion is 0.3-1.3 μm;

[0037] (4) The absolute value of the potential of the emulsion is 10-30mV;

[0038] (5) After being stored at room temperature for one week, the appearance of the emulsion and its various physicochemical indicators did not show any obvious abnormal changes.

[0039] A stable acidic emulsion of lentinan can be further dried to obtain a food or beverage product in powder form. The drying conditions are spray drying, with process parameters of inlet air temperature 100-150℃ and outlet air temperature 40-60℃.

[0040] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0041] (1) The globulin provided by this invention is a low-denatured protein that has not undergone acid precipitation (pH<5) and hydrolysis, with a protein content of over 90%. This invention cleverly utilizes conditions of specific ionic strength and slightly acidic pH to induce the spontaneous formation of regular spherical droplets from globulin, generating a single-phase biomolecular fluid composed of a high-concentration protein phase. This allows for the efficient extraction of globulin with good solubility and emulsifying properties under acidic conditions (pH range 3.0-5.0). Compared to the most commonly used alkali-soluble acid precipitation method, this invention avoids the intensive processing required for high purity and the damage to the tertiary structure of proteins caused by isoelectric point precipitation, better protecting the natural properties of globulin and providing a technical solution for the application of globulin in acidic emulsions. This invention does not require the participation of polysaccharides, making it simpler and easier to control, and reducing raw material costs.

[0042] (2) This invention provides a method for preparing a soy globulin-stabilized acidic emulsion, which fully utilizes the excellent emulsifying properties of low-denatured soy globulin and overcomes the problems of protein flocculation and insufficient emulsion stability often encountered in traditional acid precipitation methods. This emulsion contains 1-5 wt% high-quality soy globulin and requires no additional anionic polysaccharides, thickeners, or emulsifiers. It exhibits good sterilization and storage stability under acidic conditions. The emulsion has small particle size and high fluidity, achieving high protein content and high thermal stability, meeting the needs of users for direct consumption or tube feeding.

[0043] (3) The preparation process of the stable acidic emulsion of stigmoglobin of the present invention is simple, the processing conditions are mild, the processing does not involve any organic solvents, it is low-carbon and highly sustainable, and it is suitable for large-scale production applications. The present invention is of great significance for improving the commercial value of stigmoglobin and broadening its application fields. Attached Figure Description

[0044] Figure 1The solubility curves of pea protein extracted from different protein raw materials in Example 1 are shown in the pH range of 3.0-5.0.

[0045] Figure 2 The image shows the appearance of the pea protein acidic emulsion after sterilization at different pH values ​​(3.0, 3.5, 4.0, 4.5, 5.0) in Example 2.

[0046] Figure 3 The images show the appearance of the soy protein acidic emulsions with different formulations in Example 3 after sterilization.

[0047] Figure 4 The images show the appearance of pea protein acidic emulsions after sterilization at different protein concentrations in Example 4.

[0048] Figure 5 The image shows the appearance of the pea protein acidic emulsion after sterilization at different oil concentrations in Example 5.

[0049] Figure 6 This is a diagram showing the appearance of the soy globulin acidic emulsion in Example 6 after being stored at room temperature for one week. Detailed Implementation

[0050] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0051] In the following embodiments, the methods for determining the physicochemical properties of the emulsion are as follows:

[0052] Protein content determination: Kjeldahl method was used for determination.

[0053] Solubility determination method: Dissolve 1g of soybean protein in 100mL of water and stir thoroughly for 2 hours. Take a certain amount of protein solution for the determination of total protein content (Kjeldahl method). After centrifugation, take the supernatant and determine the protein content in the supernatant by Kjeldahl method. Protein solubility = protein content in supernatant / total protein content.

[0054] Emulsion particle size determination: Measured using a Mastersizer 3000 micrometer particle size analyzer. Parameter settings: Dispersed phase (oil phase) refractive index 1.5, absorbance 0.001; continuous phase refractive index 1.333; test temperature 25℃.

[0055] Emulsion potential determination: The zeta potential was determined using a Nano ZS nanoparticle size analyzer and a zeta potential analyzer. The emulsion was appropriately diluted, and the zeta potential was measured. Parameter settings: Dispersed phase (oil phase) refractive index 1.5, absorbance 0.001; continuous phase refractive index 1.333; test temperature 25℃.

[0056] Comparative Example 1:

[0057] 62.5g of pea flour (crushed and sieved) was evenly dispersed in 500g of water, the pH was adjusted to 8.0, and the mixture was stirred at 300rpm for 2 hours at 25℃ to dissolve. The insoluble precipitate was removed by centrifugation (8000rpm, 20min, 25℃). The pH of the supernatant was adjusted to 4.8, and the mixture was allowed to stand at room temperature for 1 hour. It was then centrifuged again (8000rpm, 20min, 25℃). The precipitate was collected, reconstituted, dialyzed, and freeze-dried to obtain alkali-soluble acid-precipitated pea protein.

[0058] The protein content, protein extraction rate, and zeta potential of the alkali-soluble and acid-precipitated pea protein prepared in Comparative Example 1 were determined, and the results are shown in Table 1 below (the percentages in parentheses in Table 1 refer to the protein content of the raw soybean flour):

[0059] Table 1. Protein content, extraction rate, and isoelectric point of pea protein extracted by alkali dissolution and acid precipitation method.

[0060] protein Alkali-soluble and acid-precipitated pea protein (25%) Protein content 85.5％ Protein extraction rate 28.4％ isoelectric point 4.8

[0061] Note: Protein extraction rate (%) = (Peanut protein content obtained from dried collection / Pea protein content in the protein raw material) × 100%

[0062] As shown in Table 1, the protein content of pea protein prepared by the alkali dissolution and acid precipitation method was 85.5% and the isoelectric point was 4.8, as determined by the Kjeldahl nitrogen determination method and Zeta-potential.

[0063] Comparative Example 2:

[0064] The alkali-soluble and acid-precipitated pea protein obtained in Comparative Example 1 was uniformly dispersed in three aqueous phases, with the mass fractions of alkali-soluble and acid-precipitated pea protein in the mixture being 1 wt%, 3 wt%, and 5 wt%, respectively. The mixture was stirred at 250 rpm for 2 hours at 25°C until completely dissolved, with the pH of the solution maintained at 7.0 throughout the process. After standing overnight at 4°C, the pH was adjusted to 4.0, and flaxseed oil was added to make the oil mass fraction in the mixture 10 wt%. The mixture was then sheared (5000 rpm, 2 min), homogenized under high pressure microfluidic jet (50 MPa, 3 times), and then packaged and sterilized (121°C, 15 min). The stability of the emulsion was then investigated. The states of the acidic alkali-soluble and acid-precipitated pea protein emulsion in Comparative Example 2 before and after sterilization are shown in Table 2 below.

[0065] Table 2. State of alkali-soluble and acid-precipitated pea protein acidic emulsion before and after sterilization.

[0066]

[0067] Note: Flocculation: The emulsion cannot maintain a uniform appearance after homogenization / heat sterilization, and has lumps, sediment, foreign matter visible to normal vision.

[0068] Table 2 shows that when the mass fraction of alkali-soluble and acid-precipitated pea protein was 1 wt% (sample 1), the emulsion exhibited obvious instability phenomena such as layering and flocculation before sterilization, and the instability was more severe after sterilization. When the mass fraction of protein was 3 wt% and 5 wt% (samples 2 and 3), the emulsion was in a gel-like solid state after sterilization and could not flow; the gelling property was stronger with increasing protein content. These results indicate that alkali-soluble and acid-precipitated pea protein cannot be used to prepare acidic emulsions with good sterilization stability.

[0069] Example 1:

[0070] 62.5g of pea flour (crushed and sieved) and 26.5g of dry-graded pea flour were evenly dispersed in two aqueous phases (500g each). The mixtures were stirred at 300rpm for 3 hours at 25℃ to dissolve the pea flour. Insoluble precipitates were removed by centrifugation (10000rpm, 15min, 25℃) (no centrifugation was required for dry-graded pea flour). Sodium chloride was added to the supernatant to make the final concentration of sodium chloride in the mixture 100mM. The pH was adjusted to 5.5, and the mixture was centrifuged again (8000rpm, 20min, 25℃). The precipitates were collected, reconstituted, dialyzed, and freeze-dried to obtain pea protein and dry-graded pea protein.

[0071] The protein content, protein extraction rate, and zeta potential of the pea protein (sample 1) and dry-fractionated pea protein (sample 2) prepared in Example 1 were determined and compared with those of the protein sample in Comparative Example 1. The results are shown in Table 3 below (the percentages in parentheses in Table 3 refer to the protein content of the raw soybean flour):

[0072] Table 3. Protein content, extraction rate, and isoelectric point of pea protein extracted from different protein sources.

[0073] sample 1 2 protein Pea protein (25%) Dry-graded pea protein (55%) Protein content 92.1％ 95.4％ Protein extraction rate 17.4％ 23.5％ isoelectric point 5.3 5.3

[0074] As shown in Table 3, the pea protein extracted in this embodiment (Sample 1) and the dry-graded pea protein (Sample 2) both have a protein content of over 90%. Furthermore, as the protein content of the raw materials increases, the introduced impurities (fiber, starch, etc.) decrease, further improving the protein content and extraction rate. In contrast, the pea protein prepared by the alkali-soluble acid precipitation method (Comparative Example 1) has a protein content of only 85.5%. This demonstrates that high-quality pea protein can also be obtained through a non-acid precipitation (pH ≥ 5.5) low-denaturation extraction process.

[0075] Figure 1This is the solubility curve of pea protein extracted from different protein raw materials in Example 1 within a pH range of 3.0-5.0. Figure 1 It can be seen that Sample 1 (pea protein) and Sample 2 (dry fractionation pea protein) have high solubility in the pH range of 3.0-5.0, which is significantly higher than that of the alkali-soluble and acid-precipitated pea protein in Comparative Example 1. Solubility plays a crucial role in the emulsifying properties of proteins.

[0076] By measuring the zeta potential of the three proteins, it was found that the isoelectric point of samples 1 and 2 was 5.3. When the pH of the system is far from the isoelectric point, the intermolecular repulsion of the protein molecules increases, and the molecules prevent aggregation through hydrophobic interactions, thus giving them a relatively small molecular size and flexibility.

[0077] Example 2:

[0078] (1) Disperse 62.5g of pea flour (pulverized and sieved) evenly in 500g of water, stir at 400rpm for 2h at 25℃ to dissolve, remove insoluble precipitate by centrifugation (8000rpm, 15min, 4℃), add sodium bisulfite to the supernatant to make the final concentration of sodium bisulfite in the mixture 50mM, adjust the pH to 5.75, centrifuge again (10000rpm, 10min, 4℃), collect the precipitate and reconstitute, ultrafilter, and dry by forced air to obtain pea protein.

[0079] (2) The pea protein obtained above was uniformly dispersed in three aqueous phases, so that the mass fraction of pea protein in the mixture was 2wt%. The mixture was stirred at 250 rpm for 2 h at 25℃ until completely dissolved, and the pH of the solution was kept constant at 7.0 during the process. After standing overnight at 4℃, the pH was adjusted to 3.0, 3.5, 4.0, 4.5 and 5.0. Rapeseed oil was added so that the mass fraction of oil in the mixture was 10wt%. Then the mixture was sheared (5000 rpm, 2 min) and homogenized by high pressure microjet (50 MPa, 3 times). The emulsion was then bottled and sterilized (121℃, 15 min) to examine its stability.

[0080] Figure 2 The images show the appearance of the sterilized pea protein acidic emulsions at different pH values ​​(3.0, 3.5, 4.0, 4.5, 5.0) in Example 2. Figure 2 It can be seen that under acidic conditions (pH range of 3.0-5.0), the pea protein emulsion prepared by the above method is milky white, uniform in appearance, and has no visible flocculation, precipitation or other instability phenomena, and has good fluidity and high thermal stability.

[0081] Example 3:

[0082] (1) Disperse 62.5g of bean flour (pea flour, soybean flour, mung bean flour, broad bean flour, chickpea flour, pulverized and sieved) evenly in 500g of water, stir at 400rpm for 2h at 25℃, remove insoluble precipitates by centrifugation (8000rpm, 20min, 15℃), add sodium chloride to the supernatant to make the final concentration of sodium chloride in the mixture 75mM, adjust the pH to 6.0, centrifuge again (8000rpm, 20min, 4℃), collect the precipitate, reconstitute, dialyze, freeze dry to obtain bean globulin (pea protein, soybean protein, mung bean protein, broad bean protein, chickpea protein).

[0083] (2) Disperse the soy globulin evenly in water to make the mass fraction of soy globulin in the mixture 4wt%. Stir at 300rpm for 3h at 25℃ until completely dissolved, and keep the pH of the solution constant at 7.0 during the process. After standing overnight at 4℃, adjust the pH to 4.8. Add olive oil to make the mass fraction of oil in the mixture 10wt%. Then shear (5000rpm, 2min) and homogenize by high pressure microjet (50MPa, 3 times). After the emulsion is bottled, sterilize (121℃, 15min) to obtain the sterilized soy globulin acidic emulsion.

[0084] The protein formulation and sterilization status of the samples in Example 3 are shown in Table 4 below:

[0085] Table 4. Protein formulation and sterilization status of the samples.

[0086]

[0087]

[0088] Figure 3 These are images showing the appearance of the different formulations of soy globulin acidic emulsions after sterilization (samples 1-5) in Example 3. Figure 3 As shown in Table 4, all five types of ginsenoglobulins examined in this system can be used to prepare acidic emulsions with small, stable, and uniform particle sizes, and the combination of different ginsenoglobulins also yields good results. Therefore, there is a wide variety of ginsenoglobulin types to choose from in acidic emulsion products.

[0089] Example 4:

[0090] (1) Disperse 62.5g of pea flour (pulverized and sieved) evenly in 500g of water, stir at 500rpm at 25℃ for 1.5h to dissolve, remove insoluble precipitate by centrifugation (9000rpm, 15min, 15℃), add sodium bicarbonate to the supernatant to make the final concentration of sodium bicarbonate in the mixture 150mM, adjust the pH to 6.25, centrifuge again (8000rpm, 20min, 25℃), collect the precipitate and reconstitute, dialyze, and fluidized bed dry to obtain pea protein.

[0091] (2) The pea protein obtained above was uniformly dispersed in five parts of aqueous phase, so that the mass fraction of pea protein in the mixture was 1wt%, 2wt%, 3wt%, 4wt%, and 5wt%, respectively. The mixture was stirred at 400 rpm for 1.5 h at 20°C until completely dissolved, and the pH of the solution was kept constant at 7.0 during the process. After standing overnight at 4°C, the pH was adjusted to 3.5, and corn oil was added so that the mass fraction of oil in the mixture was 10wt%. Then the mixture was sheared (5000 rpm, 2 min), homogenized by high pressure microjet (50 MPa, 3 times), and the emulsion was bottled and sterilized (121°C, 15 min) to obtain the sterilized pea protein acidic emulsion.

[0092] The protein formulation and sterilization status of the samples in Example 4 are shown in Table 5 below:

[0093] Table 5. Protein formulation and sterilization status of the samples.

[0094]

[0095]

[0096] Figure 4 The images show the appearance of the pea protein acidic emulsions after sterilization at different protein concentrations in Example 4. (See Table 5 and...) Figure 4 It can be seen that when the protein mass fraction in the emulsion is 1-5 wt% (samples 1-5), the emulsion still maintains good fluidity, uniform appearance, and no obvious foreign matter after sterilization. This shows that high-intensity sterilization treatment does not affect the stability and fluidity of the emulsion, and even a protein content as high as 5 wt% can meet the sterilization requirements of liquid emulsions. As the protein content increases, the emulsion particle size decreases, and the absolute value of the Zeta-potential increases. Generally speaking, the smaller the emulsion particle size, the higher the emulsion stability, while a larger absolute value of the potential indicates stronger electrostatic repulsion, which is also beneficial to emulsion stability. Therefore, under the condition of system stability, the addition range of pea protein in the emulsion is relatively large, which can adapt to and meet various processing requirements and product needs.

[0097] Example 5:

[0098] (1) Disperse 62.5g of pea flour (pulverized and sieved) evenly in 500g of water, stir at 300rpm at 20℃ for 2.5h to dissolve, remove insoluble precipitate by centrifugation (9000rpm, 10min, 4℃), adjust pH to 6.5, centrifuge again (10000rpm, 10min, 4℃), collect the precipitate and then reconstitute, ultrafilter and spray dry to obtain pea protein.

[0099] (2) The pea protein obtained above was uniformly dispersed in three aqueous phases, so that the mass fraction of pea protein in the mixture was 3wt%. The mixture was stirred at 250 rpm for 2.5 h at 25℃ until completely dissolved, and the pH of the solution was kept constant at 7.0 during the process. After standing overnight at 4℃, the pH was adjusted to 4.5. Sunflower seed oil was added so that the mass fraction of oil in the mixture was 5wt%, 10wt%, 15wt%, and 20wt%. Then, the mixture was sheared (5000 rpm, 2 min) and homogenized by high pressure microjet (50 MPa, 3 times). The emulsion was then bottled and sterilized (121℃, 15 min) to obtain the sterilized pea protein acidic emulsion.

[0100] The vegetable oil formulation and sterilized state of the samples in Example 5 are shown in Table 6 below:

[0101] Table 6. Vegetable oil formulations and sterilization status of the samples.

[0102]

[0103]

[0104] Figure 5 The images show the appearance of the pea protein acidic emulsions after sterilization at different oil concentrations in Example 5. (See Table 6 and...) Figure 5 It can be seen that when the mass fraction of vegetable oil in the emulsion is 5-20 wt%, the emulsion can still maintain a fluid state after sterilization, with a uniform appearance and no obvious instability phenomena such as flocculation, precipitation, or emulsification, and has good sterilization stability.

[0105] Example 6:

[0106] Pea protein was obtained according to the method in Example 2(1). The pea protein was uniformly dispersed in water to make the mass fraction of pea protein in the mixture 5 wt%. The mixture was stirred at 350 rpm for 2 h at 25 °C until completely dissolved. After standing overnight at 4 °C, the pH was adjusted to 3.8. Flaxseed oil was added to make the mass fraction of oil in the mixture 10 wt%. Then, the mixture was sheared (5000 rpm, 2 min) and homogenized by high pressure microfluidic jet (50 MPa, 3 times). The emulsion was then bottled and sterilized (121 °C, 15 min) to obtain the sterilized pea protein acidic emulsion. The emulsion was then stored at room temperature for one week to examine its stability.

[0107] Figure 6 This is a diagram showing the appearance of the soybean globulin acidic emulsion from Example 6 after one week of storage at room temperature. Figure 6 It can be seen that the pea protein acidic emulsion prepared by this invention, after being stored at room temperature for one week, exhibits a uniform appearance and shows no obvious instability phenomena such as flocculation, precipitation, or emulsification. Further determination of its various physicochemical data shows that the average particle size of the pea protein acidic emulsion is 2.18 μm, and the absolute value of the Zeta-potential is 28.7 mV, indicating that the emulsion has strong storage stability.

[0108] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A process for the preparation of heat stable acidic emulsions of legumin characterized in that, Includes the following steps: Soybean flour is dissolved in water, centrifuged, and the supernatant is collected. The pH is adjusted to 5.5-6.5, and the mixture is centrifuged again. The precipitate is collected, reconstituted, desalted, and dried to obtain soy globulin. The soy globulin is dispersed in water to obtain an aqueous phase. The pH is adjusted to 3.0-5.

0. The aqueous phase is mixed with vegetable oil, emulsified, and sterilized to obtain a heat-stable acidic emulsion of soy globulin. The components of the heat-stable acidic emulsion of soy globulin are 1-5 wt% soy globulin, 5-20 wt% vegetable oil, and 75-94 wt% water. The lentinan is a low-denaturation protein with a protein content of over 90%. The supernatant also contains at least one of sodium bisulfite, sodium bicarbonate, and sodium chloride, and the amount used is such that the final concentration of salt ions in the mixed system is 0-150 mM; the sterilization temperature is 95-121 ℃ and the time is 5-30 min.

2. The method for preparing a heat-stable acidic emulsion of lentinan according to claim 1, characterized in that, The lentinan is one or more of pea protein, soybean protein, mung bean protein, broad bean protein, and chickpea protein.

3. The method for preparing a heat-stable acidic emulsion of lentinan according to claim 1, characterized in that, The vegetable oil is at least one of sunflower seed oil, rapeseed oil, corn oil, olive oil, and flaxseed oil.

4. The method for preparing a heat-stable acidic emulsion of lentinan according to claim 1, characterized in that, The soybean flour is obtained by crushing at least one of defatted pea meal, defatted soybean meal, defatted mung bean meal, defatted broad bean meal, and defatted chickpea meal and then passing it through an 80-mesh sieve or by dry grading.

5. The method for preparing a heat-stable acidic emulsion of lentinan according to claim 1, characterized in that, The emulsification is achieved by one or more of the following methods: high-pressure homogenization, ultrasonic homogenization, high-pressure microfluidic homogenization, and ball milling homogenization.

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