High-whiteness and low-isoflavone-content soybean protein isolate for infant food
By reducing isoflavone content through low-temperature treatment and physical methods, the problems of protein denaturation and nutrient loss in the synthesis of soy protein for infant food have been solved, achieving safe, nutritious, and efficient production of high-whiteness, low-isoflavone soy protein isolate.
Patent Information
- Application Number
- CN202511187421.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-25
- Publication Date
- 2025-12-02
AI Technical Summary
Existing methods for synthesizing soy protein for infant formula, while pursuing high whiteness and low isoflavone content, suffer from problems such as protein structural denaturation, nutrient loss, chemical residue risks, and high process complexity, making it difficult to balance safety, nutritional integrity, and processing efficiency.
The method employs low-temperature treatment combined with modified β-cyclodextrin adsorption chromatography and β-glucosidase enzymatic hydrolysis, along with activated carbon adsorption and low-temperature sterilization, to reduce isoflavone content through physical methods, avoid chemical bleaching agent residue, improve protein whiteness, and retain nutrients.
It achieves low isoflavone content ≤10mg/kg, protein whiteness ≥85%, lysine retention rate ≥95%, meets the food safety and sensory requirements of infants and young children, reduces production costs and energy consumption, and complies with food hygiene standards.
Smart Images
Figure CN121040557A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of organic compound preparation technology, and in particular to a high-whiteness, low-isoflavone-content soy protein isolate for infant food. Background Technology
[0002] Soy protein for infant formula is a high-quality plant protein extracted from soybeans and processed using special techniques. Its application stems from the increasing demand for breast milk as a substitute for infant formula and the growing problem of food allergies, especially providing a safe alternative for infants with cow's milk protein allergies. Soy protein contains 18 amino acids, with a high lysine content. Through enzymatic hydrolysis or fermentation, its digestibility and absorption rate can be increased to over 90%, meeting the growth and development needs of infants aged 0-3 years.
[0003] Existing methods for synthesizing soy protein for infant formula that aim for high whiteness and low isoflavone content have several technical drawbacks. First, high whiteness relies on intensive processing (such as alcohol extraction, high-temperature jet cooking, and membrane separation), which can lead to protein denaturation, including thermal damage to essential amino acids like lysine, and the loss of natural nutrients (such as phosphorus). Second, while deep removal of isoflavones (such as ion exchange and adsorption) reduces anti-nutritional factors, it also eliminates the potential health benefits of isoflavones, such as antioxidant and anti-inflammatory properties, and excessive removal can increase process complexity and cost. Furthermore, chemical treatments commonly used in high-whiteness processes (such as acid-base regulation) may introduce residual substances, while low-temperature enzymatic hydrolysis, although mitigating protein denaturation, may produce bitter peptides during targeted degradation of allergens (such as 7S globulin), requiring additional process optimization. In summary, current technologies need to balance nutritional integrity, processing efficiency, and product flavor while improving safety. Therefore, this application provides a method for synthesizing high-whiteness, low-isoflavone soy protein isolate for infant formula to meet this demand. Summary of the Invention
[0004] This invention provides a high-whiteness, low-isoflavone soy protein isolate for infant formula, which avoids the risk of chemical bleaching agent (hydrogen peroxide, sodium hypochlorite) residue, reduces isoflavone content to ≤10mg / kg, lowers the risk of endocrine disruption, reduces damage to protein structure from high temperature and strong acid / alkali, reduces the loss rate of amino acids such as lysine, and preserves the functional properties of protein such as emulsification and solubility, meeting the needs of infant formula. Low-temperature sterilization and vacuum freeze-drying reduce energy consumption, whiteness ≥85%, meeting sensory requirements, protein content ≥90%, high purity, suitable as a high-quality protein source for infant formula, green solvents and physical / biological decolorization methods reduce chemical pollution, and the process is more environmentally friendly.
[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:
[0006] A method for synthesizing high-whiteness, low-isoflavone-content soy protein isolate for infant food, comprising the following components by weight percentage: soy protein isolate: 92.5%, maltodextrin: 6.0%, sodium carboxymethyl cellulose: 0.8%, sucrose: 0.1%, and ethyl vanillin: 0.6%.
[0007] A method for synthesizing high-whiteness, low-isoflavone-content soy protein isolate for infant formula includes the following steps:
[0008] (1) Select low isoflavone soybean varieties. Soak soybeans in water at a ratio of 1:5 for 2 hours. After soaking, put the soybeans into a peeling machine for mechanical peeling. After peeling, put the soybean raw material into a fully automatic steam enzyme inactivation tank with a temperature control system for steam flash enzyme inactivation. After enzyme inactivation, centrifuge and dehydrate the soybean meal. Put the processed soybean meal into a continuous microwave extractor with a water cooling system for microwave-assisted cell wall disruption. Finally, put the soybean meal into a phosphate buffer solution at a temperature of 20±2℃. After centrifugation, obtain the supernatant as the protein extract.
[0009] (2) Add 0.05M phosphate buffer (pH 8.5, containing 0.5% NaCl) to the protein extract, control the temperature in the range of 20±2℃, the ratio of the two is 1:10 (g / mL), stir for 2h, and finally put the solution into a centrifuge and centrifuge at 20℃ for 20min. The supernatant is the protein extract.
[0010] (3) Pump the protein extract into the packed adsorption column, control the loading flow rate to 1 BV / h for 60 min, filter, add β-glucosidase and react at 40℃ for 60 min to hydrolyze the glycoside isoflavones into aglycones and reduce solubility.
[0011] (4) Add 1M HCl slowly to the protein extract at a rate of 0.5pH / min to adjust the pH to 4.5. Stir at 40rpm. Then let it stand at 4℃ for 30min, centrifuge at 10℃ for 20min, let it stand at 4℃ for 30min, and finally put the solution into a centrifuge to collect the precipitate. Wash the collected precipitate three times with deionized water at a ratio of 1:5, stirring once every 10min. Adjust the pH to 7.0 with 0.1M NaOH. After centrifugation, freeze dehydrate at -20℃ and vacuum degree ≤100Pa to obtain wet protein gel.
[0012] (5) Add 0.5% food-grade activated carbon (iodine value ≥900mg / g) to the rehydrated protein solution (10% concentration, temperature 50℃), stir at 60rpm for 60min, filter water through a 0.45μm filter membrane, pasteurize the filtered solution at 75℃ for 30min, and then cool to room temperature of about 25℃ to obtain sterilized protein solution.
[0013] (6) The sterilized protein solution is spray-dried, with the inlet air temperature controlled at 160°C, the outlet air temperature at 70°C, and the amount of maltodextrin added (protein: dextrin = 3:1) to finally obtain soy protein isolate powder.
[0014] Preferably, the soaking water needs to be changed twice and every 30 minutes to prevent the pigment from the bean skin from dissolving. After mechanical peeling, the bean skin needs to be screened through a 0.5mm sieve to remove fine pieces of skin residue.
[0015] Preferably, the stirring process should be conducted in the dark to prevent pigment oxidation and darkening of color, and the soybean meal raw material should be filtered with 60-mesh nylon cloth before centrifugation to remove large particle residues.
[0016] Preferably, the adsorption column packing material is a modified β-cyclodextrin / silica composite carrier, wherein the cyclodextrin:silica ratio is 1:3 and the particle size is 200-400 mesh. The dynamic adsorption capacity for daidzein and genistein is ≥120 mg / g, otherwise the protein denatures. The β-glucosidase secreted by the lactic acid bacteria is used to hydrolyze isoflavone glycosidic bonds, converting them into aglycones with lower polarity. The chromatography column needs to be prewashed with 0.1 M NaOH + ethanol solution at a flow rate of 1 BV / h for 30 min. After enzymatic hydrolysis, it needs to be boiled at 80℃ for 10 min to inactivate the enzyme and avoid subsequent fermentation. The chromatography column needs to be prewashed with 0.1 M NaOH + ethanol solution at a flow rate of 1 BV / h for 30 min.
[0017] Preferably, when the protein solution is acid-precipitated after treatment, nitrogen gas should be continuously introduced at a flow rate of 0.5 L / min to prevent oxidation, and the washing water should be pre-treated with ultrasound for 20 min to degas it and avoid protein denaturation.
[0018] Preferably, the activated carbon needs to be pre-activated by calcination at 300℃ for 2 hours to avoid heavy metal residues, and the sterilization is followed by rapid cooling (cold water circulation, temperature difference ≤5℃ / min) to prevent protein coagulation.
[0019] Compared with the prior art, the present invention has at least the following beneficial effects:
[0020] (1) 1. Low isoflavone content, ensuring the safety of infants and young children
[0021] Targeted removal technology: By combining modified β-cyclodextrin adsorption chromatography with β-glucosidase enzymatic hydrolysis, the isoflavone removal rate is ≥90%, and the final product isoflavone content is ≤10mg / kg, which is far lower than the infant food standard (≤15mg / kg). Avoiding hormone interference: reducing the risk of intake of weak estrogenic active substances (such as genistein) and avoiding potential effects on the endocrine system of infants.
[0022] (2) High whiteness and excellent appearance
[0023] Physical decolorization technology: Activated carbon adsorption combined with low-temperature treatment increases whiteness (CIE L* value) to ≥85, close to the color of breast milk, meeting the sensory quality requirements of infant food. No chemical bleaching: Avoids the residue of chemical reagents such as hydrogen peroxide and sodium hypochlorite, ensuring product safety.
[0024] (3) Nutritional retention and functional property optimization
[0025] High protein retention: Mild acid precipitation (pH 4.5) and low-temperature sterilization (75°C pasteurization) improve protein yield, with lysine retention ≥95%, which is superior to traditional high-temperature processes (typically resulting in a loss of 10%–15%). Enhanced functional properties: Emulsification, solubility (≥95% in 1% aqueous solution) and foaming properties are significantly improved, making it suitable for the processing needs of infant formula, complementary foods, etc.
[0026] (4) Security and Compliance
[0027] Zero chemical residue: Strong acids / alkalis and organic solvents are avoided throughout the process. The content of heavy metals (such as arsenic and lead) is ≤0.5mg / kg, which complies with GB 2762-2022 standards. Microbial control: Low-temperature sterilization combined with aseptic operation (clean workshop ISO Class 7) results in a total bacterial count ≤100CFU / g, which meets the hygiene requirements for infant food.
[0028] (5) Production efficiency and cost advantages
[0029] Integrated process: membrane separation coupled with acid precipitation and continuous spray drying (inlet air temperature 160℃, outlet air temperature 70℃) shortens the production cycle and reduces energy consumption.
[0030] High yield: Protein extraction rate; maltodextrin carrier (protein:dextrin = 3:1) improves solubility stability and reduces raw material loss.
[0031] (6) Green solvent substitution: The ethanol / water system is used to replace traditional organic solvents. The waste liquid is easily biodegradable and the by-products can be utilized: the acid precipitation waste liquid (containing isoflavones) can be extracted as raw materials for health products, realizing resource utilization. Attached Figure Description
[0032] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate embodiments of the invention and, together with the specification, further serve to explain the principles of the invention and enable those skilled in the art to practice and use the invention.
[0033] Figure 1 Flowchart of the overall preparation process for soy protein isolate for infant formula;
[0034] Figure 2 A composition ratio diagram for soy protein isolate products used in infant formula.
[0035] As shown in the figure, specific structures and devices are marked in the figure to clearly illustrate the structure of the embodiments of the present invention. However, this is only for illustrative purposes and is not intended to limit the present invention to this specific structure, device and environment. Those skilled in the art can adjust or modify these devices and environments according to specific needs. Detailed Implementation
[0036] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, describes a high-yield, high-purity, ultrafine food-grade zinc citrate and its synthesis method provided by the present invention. It should be noted that, to make the embodiments more detailed, the following embodiments are the best and preferred embodiments; those skilled in the art can also use other alternative methods to implement some known technologies; and the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.
[0037] It should be noted that the use of terms such as "an embodiment," "an embodiment," "an exemplary embodiment," and "some embodiments" in the specification indicates that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments (whether explicitly described or not) should be within the knowledge of those skilled in the art.
[0038] Generally, terms can be understood at least partly from their use in context. For example, depending at least partly on the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in a singular sense, or a combination of features, structures, or characteristics in a plural sense. Additionally, the term "based on" can be understood not necessarily to convey an exclusive set of factors, but rather, alternatively, depending at least partly on the context, to allow for the presence of other factors that are not necessarily explicitly described.
[0039] It is understood that the meanings of “on”, “above”, and “above” in this invention should be interpreted in the broadest manner, such that “on” means not only “directly on” something, but also includes the meaning of being “on” something with an intervening feature or layer, and that “above” or “above” means not only “on” something, but also includes the meaning of being “on” something without an intervening feature or layer.
[0040] Furthermore, spatially related terms such as “below,” “under,” “lower,” “above,” and “upper” are used herein for convenience to describe the relationship of one element or feature to one or more other elements or features, as illustrated in the accompanying drawings. Spatially related terms are intended to cover different orientations in the use or operation of the device other than those depicted in the accompanying drawings. The device may be oriented in other ways, and the spatially related descriptive terms used herein can be interpreted similarly.
[0041] Example 1
[0042] A method for synthesizing high-yield, high-purity, ultrafine food-grade zinc citrate, characterized by comprising a soy protein isolate for infant food, including the following steps:
[0043] (1) Select low isoflavone soybean varieties. Soak soybeans in water at a ratio of 1:5 for 2 hours. After soaking, put the soybeans into a peeling machine for mechanical peeling. After peeling, put the soybean raw material into a fully automatic steam enzyme inactivation tank with a temperature control system for steam flash enzyme inactivation. After enzyme inactivation, centrifuge and dehydrate the soybean meal. Put the processed soybean meal into a continuous microwave extractor with a water cooling system for microwave-assisted cell wall disruption. Finally, put the soybean meal into a phosphate buffer solution at a temperature of 20±2℃. After centrifugation, obtain the supernatant as the protein extract.
[0044] (2) Add 0.05M phosphate buffer (pH 8.5, containing 0.5% NaCl) to the protein extract, control the temperature in the range of 20±2℃, the ratio of the two is 1:10 (g / mL), stir for 2h, and finally put the solution into a centrifuge and centrifuge at 20℃ for 20min. The supernatant is the protein extract.
[0045] (3) Pump the protein extract into the packed adsorption column, control the loading flow rate to 1 BV / h for 60 min, filter, add β-glucosidase and react at 40℃ for 60 min to hydrolyze the glycoside isoflavones into aglycones and reduce solubility.
[0046] (4) Add 1M HCl slowly to the protein extract at a rate of 0.5pH / min to adjust the pH to 4.5. Stir at 40rpm. Then let it stand at 4℃ for 30min, centrifuge at 10℃ for 20min, let it stand at 4℃ for 30min, and finally put the solution into a centrifuge to collect the precipitate. Wash the collected precipitate three times with deionized water at a ratio of 1:5, stirring once every 10min. Adjust the pH to 7.0 with 0.1M NaOH. After centrifugation, freeze dehydrate at -20℃ and vacuum degree ≤100Pa to obtain wet protein gel.
[0047] (5) Add 0.5% food-grade activated carbon (iodine value ≥900mg / g) to the rehydrated protein solution (10% concentration, temperature 50℃), stir at 60rpm for 60min, filter water through a 0.45μm filter membrane, pasteurize the filtered solution at 75℃ for 30min, and then cool to room temperature of about 25℃ to obtain sterilized protein solution.
[0048] (6) The sterilized protein solution is spray-dried, with the inlet air temperature controlled at 160°C, the outlet air temperature at 70°C, and the amount of maltodextrin added (protein: dextrin = 3:1) to finally obtain soy protein isolate powder.
[0049] Before preparation, a low-isoflavone soybean variety was selected. The soybeans were soaked in water at a ratio of 1:5 for 2 hours, and the soaking water was changed twice, with a change every 30 minutes, to prevent the pigment from the soybean skin from dissolving. After soaking, the soybeans were put into a peeling machine for mechanical peeling. After mechanical peeling, they were sieved through a 0.5mm sieve to remove fine peel residue. The peeled soybean raw material was put into a fully automatic steam enzyme inactivation tank with a temperature control system for steam flash enzyme inactivation. After enzyme inactivation, the soybean meal was centrifuged and dehydrated. The processed soybean meal was put into a continuous microwave extractor with a water cooling system for microwave-assisted cell wall disruption. Finally, the soybean meal was put into a phosphate buffer solution at a temperature of 20±2℃. 1M HCl was slowly added dropwise to the protein extract at a rate of 0.5pH / min to adjust the pH to 4.5. The stirring speed was 40rpm. Then, it was allowed to stand at 4℃ for 30 minutes and centrifuged at 10℃ for 20 minutes. The supernatant obtained after centrifugation was the protein extract.
[0050] Example 2
[0051] After obtaining the protein extract, 0.05M phosphate buffer (pH 8.5, containing 0.5% NaCl) was added to it, and the temperature was controlled within the range of 20±2℃. The ratio of the two components was 1:10 (g / mL), and the mixture was stirred for 2 hours. Finally, the solution was centrifuged at 20℃ for 20 minutes. The supernatant was the protein extract. The stirring process should be conducted in the dark to prevent pigment oxidation and color deepening. The soybean meal raw material was filtered through a 60-mesh nylon cloth before centrifugation to remove large particles. 1M HCl was slowly added dropwise to the protein extract at a rate of 0.5 pH / min to adjust the pH to 4.5, while stirring at 40 rpm. The mixture was then allowed to stand at 4℃ for 30 minutes, centrifuged at 10℃ for 20 minutes, and allowed to stand at 4℃ for 30 minutes. Finally, the solution was centrifuged to collect the precipitate. The collected precipitate was washed three times with deionized water at a ratio of 1:5, stirring every 10 minutes, and then filtered through a 0.1M buffer. The pH was adjusted to 7.0 with NaOH. The adsorption column packing material was a modified β-cyclodextrin / silica composite carrier with a cyclodextrin:silica ratio of 1:3 and a particle size of 200-400 mesh. The dynamic adsorption capacity for daidzein and genistein was ≥120 mg / g, otherwise the protein would denature. After centrifugation, the protein gel was obtained by freeze dehydration at -20℃ and a vacuum degree ≤100 Pa.
[0052] Example 2
[0053] Add 0.5% food-grade activated carbon (iodine value ≥900mg / g) to the rehydrated protein solution (10% concentration, temperature 50℃), stir at 60rpm for 60min, filter the solution through a 0.45μm pore size filter membrane to remove water, pasteurize the filtered solution at 75℃ for 30min, and then cool it to room temperature of about 25℃ to obtain a sterilized protein solution. Spray dry the sterilized protein solution, controlling the inlet air temperature at 160℃ and the outlet air temperature at 70℃, and the amount of maltodextrin added (protein:dextrin = 3:1), and finally obtain soy protein isolate powder. The activated carbon needs to be pre-activated by calcination at 300℃ for 2h to avoid heavy metal residue. After sterilization, cool rapidly (cold water circulation, temperature difference ≤5℃ / min) to prevent protein gelation.
[0054] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. To provide the public with a thorough understanding of this invention, specific details are described in detail in the following preferred embodiments; however, those skilled in the art will fully understand the invention even without these details. Furthermore, to avoid unnecessary misunderstanding of the essence of this invention, well-known methods, processes, procedures, components, and circuits are not described in detail.
[0055] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A type of soy protein isolate for infant food with high whiteness and low isoflavone content, characterized in that, The product contains the following components by weight percentage: soy protein isolate: 92.5%; maltodextrin: 6.0%; sodium carboxymethyl cellulose: 0.8%; sucrose: 0.1%; and ethyl vanillin: 0.6%.
2. A method for synthesizing high-whiteness, low-isoflavone-content soy protein isolate for infant food, characterized in that, Includes the following steps: (1) Select low isoflavone soybean varieties. Soak soybeans in water at a ratio of 1:5 for 2 hours. After soaking, put the soybeans into a peeling machine for mechanical peeling. After peeling, put the soybean raw material into a fully automatic steam enzyme inactivation tank with a temperature control system for steam flash enzyme inactivation. After enzyme inactivation, centrifuge and dehydrate the soybean meal. Put the processed soybean meal into a continuous microwave extractor with a water cooling system for microwave-assisted cell wall disruption. Finally, put the soybean meal into a phosphate buffer solution at a temperature of 20±2℃. After centrifugation, obtain the supernatant as the protein extract. (2) Add 0.05M phosphate buffer (pH 8.5, containing 0.5% NaCl) to the protein extract, control the temperature in the range of 20±2℃, the ratio of the two is 1:10 (g / mL), stir for 2h, and finally put the solution into a centrifuge and centrifuge at 20℃ for 20min. The supernatant is the protein extract. (3) Pump the protein extract into the packed adsorption column, control the loading flow rate to 1 BV / h for 60 min, filter, add β-glucosidase and react at 40℃ for 60 min to hydrolyze the glycoside isoflavones into aglycones and reduce solubility. (4) Add 1M HCl slowly to the protein extract at a rate of 0.5pH / min to adjust the pH to 4.
5. Stir at 40rpm. Then let it stand at 4℃ for 30min, centrifuge at 10℃ for 20min, let it stand at 4℃ for 30min, and finally put the solution into a centrifuge to collect the precipitate. Wash the collected precipitate three times with deionized water at a ratio of 1:5, stirring once every 10min. Adjust the pH to 7.0 with 0.1M NaOH. After centrifugation, freeze dehydrate at -20℃ and vacuum degree ≤100Pa to obtain wet protein gel. (5) Add 0.5% food-grade activated carbon (iodine value ≥900mg / g) to the rehydrated protein solution (10% concentration, temperature 50℃), stir at 60rpm for 60min, filter water through a 0.45μm filter membrane, pasteurize the filtered solution at 75℃ for 30min, and then cool to room temperature of about 25℃ to obtain sterilized protein solution. (6) The sterilized protein solution is spray-dried, with the inlet air temperature controlled at 160°C, the outlet air temperature at 70°C, and the amount of maltodextrin added (protein: dextrin = 3:1) to finally obtain soy protein isolate powder.
3. The method for synthesizing high-whiteness, low-isoflavone-content soy protein isolate for infant food according to claim 2, characterized in that, The soaking water needs to be changed twice and every 30 minutes to prevent the pigment from the bean skin from dissolving. After mechanical peeling, the bean skin needs to be screened through a 0.5mm sieve to remove fine pieces of skin residue.
4. The method for synthesizing high-whiteness, low-isoflavone-content soy protein isolate for infant food according to claim 2, characterized in that, The stirring process must be conducted in the dark to prevent pigment oxidation and darkening of color. The soybean meal raw material is filtered with 60-mesh nylon cloth before centrifugation to remove large particles of residue.
5. The method for synthesizing high-whiteness, low-isoflavone-content soy protein isolate for infant food according to claim 2, characterized in that, The adsorption column packing material is a modified β-cyclodextrin / silica composite carrier, wherein the cyclodextrin:silica ratio is 1:3 and the particle size is 200-400 mesh. The dynamic adsorption capacity for daidzein and genistein is ≥120 mg / g; otherwise, protein denaturation occurs. The β-glucosidase secreted by the lactic acid bacteria is used to hydrolyze isoflavone glycosidic bonds, converting them into aglycones with lower polarity. The chromatography column needs to be prewashed with 0.1 M NaOH + ethanol solution at a flow rate of 1 BV / h for 30 min. After enzymatic hydrolysis, it needs to be boiled at 80℃ for 10 min to inactivate the enzyme and prevent subsequent fermentation. The chromatography column needs to be prewashed with 0.1 M NaOH + ethanol solution at a flow rate of 1 BV / h for 30 min.
6. The method for synthesizing high-whiteness, low-isoflavone-content soy protein isolate for infant food according to claim 2, characterized in that, When the protein solution is acid-precipitated after treatment, nitrogen gas should be continuously introduced at a flow rate of 0.5 L / min to prevent oxidation. The washing water should be pre-treated with ultrasound for 20 minutes to degas it and avoid protein denaturation.
7. The method for synthesizing high-whiteness, low-isoflavone-content soy protein isolate for infant food according to claim 2, characterized in that, The activated carbon needs to be pre-activated by calcination at 300℃ for 2 hours to avoid heavy metal residue. After sterilization, it should be rapidly cooled (cold water circulation, temperature difference ≤5℃ / min) to prevent protein coagulation.