A method for producing high free type soybean isoflavone content soybean protein
By using high-temperature acid hydrolysis and multi-stage centrifugation, the content of free soy isoflavones in soy protein is increased, solving the problems of low protein solubility and poor functionality in existing technologies, and realizing the efficient production of high-purity, high-functionality soy protein.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- KEDONG YUWANG SOY PROTEIN FOOD CO LTD
- Filing Date
- 2023-01-09
- Publication Date
- 2026-08-04
AI Technical Summary
In existing soybean protein production processes, the use of sodium hydroxide to adjust pH results in low protein solubility in low-temperature soybean meal, incomplete precipitation at the isoelectric point, protein loss, increased difficulty in wastewater treatment, and poor product functionality.
By employing a low-cost hydrolysis method for soy isoflavones, combined with the principle of protein denaturation, and through high-temperature acid hydrolysis and multi-stage centrifugation, the content of free soy isoflavones is increased. Vacuum degassing is used to remove the beany odor and enhance the health benefits of the product.
The free isoflavone content in soy protein is increased to 100-600 times that of ordinary soy protein isolate, with low cost, simple process, stable product properties, improved purity and recovery rate, and improved flavor.
Abstract
Description
Technical Field
[0001] This invention relates to a method for producing soybean protein with high free soy isoflavone content, and particularly to a process for acid extraction and isoelectric point precipitation of soybean protein; this invention can be applied to the production of specific proteins. Background Technology
[0002] Soy isoflavones are secondary metabolites found in soybeans, existing in four forms: free aglycones, glucosides, malonyl glucosides, and acetylglucosides. There are a total of 12 different structures, including 9 bound glycosides and 3 free aglycones. Naturally occurring soy isoflavones are 97%–98% in the form of β-glucosides, with only about 1%–3% existing in the form of free aglycones, including genistein, daidzein, and genistein. Literature reports that aglycone-form soy isoflavones have higher bioactivity than glycoside-form soy isoflavones, with genistein and daidzein playing the major roles. Most commercially available soy isoflavone products are glycoside-type. Due to the high bioavailability of soy isoflavone aglycones, soy isoflavone aglycone products will occupy a very important position in the health supplement market.
[0003] Current soybean protein production process scheme: CN201310177654.7 A soybean protein rich in isoflavone aglycones and its preparation method. The invention discloses a soybean protein rich in isoflavone aglycones and its preparation method, including the following steps: (1) Prepare glucosidase enzyme solution, prepare pure natural soybean isoflavone HAC-NaAC dispersion, and then add the enzyme solution to the above dispersion to obtain soybean isoflavone aglycones by enzymatic hydrolysis; (2) Add deionized water to low-temperature defatted soybean meal powder, adjust the pH, stir thoroughly, centrifuge the evenly dispersed soybean meal liquid to remove residue, and dialyze the supernatant to obtain crude soybean meal slurry; (3) Mix isoflavone aglycones with crude soybean meal slurry, adjust the pH, and perform spray cooking. The resulting liquid is quickly cooled in an ice bath; (4) After cooling, the liquid is dialyzed and spray dried to obtain soybean protein rich in isoflavone aglycones.
[0004] The drawbacks of the existing technology described above are as follows: This method uses sodium hydroxide as a pH adjuster to adjust the pH so that the protein in the low-temperature soybean meal dissolves under alkaline conditions, followed by precipitation with hydrochloric acid at the isoelectric point. Sodium chloride is generated during this process. Under alkaline conditions, 15S soybean globulin has extremely low solubility, almost negligible. Low concentrations of sodium chloride can increase protein solubility, which is detrimental to isoelectric point precipitation. Furthermore, soybean protein contains various protein components with a wide isoelectric point range of 4.0-5.8. The commonly used isoelectric point control is between 4.5 and 4.8. Within this range, some proteins cannot precipitate, resulting in protein loss. This lost protein needs to be precipitated with polyaluminum chloride and then removed through a biochemical reaction, wasting protein resources and increasing the difficulty of wastewater treatment. This process uses relatively large amounts of acid and alkali, and the extracted protein is a mixture of most soybean proteins, resulting in poor functionality. Summary of the Invention
[0005] This invention provides a method for producing soy protein with high free soy isoflavone content. It utilizes a low-cost soy isoflavone hydrolysis method and the principle of protein denaturation to increase the free isoflavone content in soy protein, thereby improving the health benefits of the product and solving the problems mentioned in the background art.
[0006] To solve the above-mentioned technical problems, this invention discloses a method for producing soy protein with high free soy isoflavone content, comprising the following steps: a) Extraction: Mix raw soybean meal and water in a weight ratio of 1:6-15, heat to 90-95℃, add food-grade acid, adjust the pH value to 1.5-2.0, stir for 30-45 minutes, then crush using a pulverizing device and transfer to a storage tank to obtain the extract. Store it for 30 minutes to wait for separation. b) Centrifugation: The extract from step a) is centrifuged to obtain soybean residue and soybean milk. c) Secondary separation: Dilute the primary soybean residue from step b) at a ratio of one part soybean residue to four parts water, crush it using a crushing device, transport it to a storage tank, store it for 15-20 minutes, and then separate it to obtain secondary soybean residue and secondary soy milk. d) Mixing: Mix the primary soy milk and the secondary soy milk to obtain mixed soy milk; e) Cooling: Cool the mixed soy milk to 15-20℃ to obtain cooled soy milk; f) Isoelectric point precipitation: Adjust the pH of the cooled soy milk in step e) to 4.4-4.8, and allow it to settle to obtain a protein suspension; g) Centrifugation: The protein suspension from step f) is centrifuged to obtain an acidic solid protein slurry; h) Neutralization: Stir the acidic solid protein slurry with 3-5 times its weight of water, and add an alkaline processing aid to adjust the pH to 6.5-7.5; i) Sterilization: Sterilize the neutralized liquid obtained in step h) at 155-165℃ for 3-8 seconds, and then perform flash degassing after sterilization; j) Drying: The soybean protein liquid after flash evaporation and degassing is spray-dried.
[0007] Preferably, the soybean meal in step a) is low-temperature defatted soybean meal.
[0008] Preferably, the pulverizing equipment in steps a) and c) is a multi-stage homogenizing pump or other wet pulverizing equipment.
[0009] Preferably, the food-grade acid in step a) is hydrochloric acid or citric acid.
[0010] Preferably, in step e), the cooling process employs vacuum degassing or tubular heat exchange.
[0011] Preferably, the alkaline processing aid in step h) is an alkaline processing aid for the food industry.
[0012] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows: The total aglycone content of the soybean protein of this invention can reach 100 to 600 times that of ordinary soybean protein isolate, and the production cost is low, the process is simple, and the properties are stable. This invention improves the degree of hydrolysis of acid-hydrolyzed glycoside-type soy isoflavones by using high temperature, denatures and accumulates some 11S and 7S soy proteins by using high temperature, and at the same time increases the solubility of free soy isoflavones, promotes the carbonyl-amine reaction between soy protein and reducing sugar, and forms soy flavor substances. By utilizing the principle of protein denaturation, the content of free isoflavones in soy protein is increased, thereby improving the health function of the product. This invention separates denatured soybean protein and increases the relative content of free soybean isoflavones; This invention improves the recovery rate of free soy isoflavones through secondary separation; By cooling, the solubility of free soy isoflavones and soy protein is reduced, thereby increasing the recovery rate of free soy isoflavones and soy protein. Vacuum degassing removes some of the beany-smelling substances, enhancing the flavor of the protein. The protein suspension was centrifuged to obtain an acidic solid-phase protein slurry; soluble monosaccharides, oligosaccharides, ash and other components were removed to improve the purity of free soy isoflavones and soy protein. The soybean protein prepared by this invention has a soy isoflavone content as high as 36,545 ppm, of which free soy isoflavones account for as high as 82.5%. Detailed Implementation
[0013] The specific embodiments of the present invention will be described in further detail below with reference to the examples. These examples are for illustrative purposes only and are not intended to limit the scope of the invention.
[0014] Furthermore, in this invention, the use of terms such as "first" and "second" is for descriptive purposes only and does not specifically refer to any order or sequence, nor is it intended to limit the invention. They are merely used to distinguish components or operations described using the same technical terms and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions and features of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If a combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.
[0015] This invention provides a method for producing soy protein with high free soy isoflavone content, comprising the following steps: a) Extraction: Mix raw soybean meal and water in a weight ratio of 1:6-15, heat to 90-95℃, add food-grade acid, adjust the pH value to 1.5-2.0, stir for 30-45 minutes, then crush using a pulverizing device and transfer to a storage tank to obtain the extract. Store it for 30 minutes to wait for separation. b) Centrifugation: The extract from step a) is centrifuged to obtain soybean residue and soybean milk. c) Secondary separation: Dilute the primary soybean residue from step b) at a ratio of one part soybean residue to four parts water, crush it using a crushing device, transport it to a storage tank, store it for 15-20 minutes, and then separate it to obtain secondary soybean residue and secondary soy milk. d) Mixing: Mix the primary soy milk and the secondary soy milk to obtain mixed soy milk; e) Cooling: Cool the mixed soy milk to 15-20℃ to obtain cooled soy milk; f) Isoelectric point precipitation: Adjust the pH of the cooled soy milk in step e) to 4.4-4.8, and allow it to settle to obtain a protein suspension; g) Centrifugation: The protein suspension from step f) is centrifuged to obtain an acidic solid protein slurry; h) Neutralization: Stir the acidic solid protein slurry with 3-5 times its weight of water, and add an alkaline processing aid to adjust the pH to 6.5-7.5; i) Sterilization: Sterilize the neutralized liquid obtained in step h) at 155-165℃ for 3-8 seconds, and then perform flash degassing after sterilization; j) Drying: The soybean protein liquid after flash evaporation and degassing is spray-dried.
[0016] Preferably, the soybean meal in step a) is low-temperature defatted soybean meal.
[0017] Preferably, the pulverizing equipment in steps a) and c) is a multi-stage homogenizing pump or other wet pulverizing equipment.
[0018] Preferably, the food-grade acid in step a) is hydrochloric acid or citric acid.
[0019] Preferably, in step e), the cooling process employs vacuum degassing or tubular heat exchange.
[0020] Preferably, the alkaline processing aid in step h) is an alkaline processing aid for the food industry.
[0021] The present invention specifically includes the following embodiments. Example 1: A method for producing soy protein with high free soy isoflavone content includes the following steps: a) Extraction: Low-temperature defatted soybean meal and water are mixed in a weight ratio of 1:6, heated to 90°C, food-grade acid is added, pH is adjusted to 1.5, and stirred for 30 minutes. The mixture is then pulverized using a multi-stage homogenizer pump and transferred to a storage tank to obtain the extract. The extract is stored for 30 minutes to await separation. b) Centrifugation: The extract from step a) is centrifuged to obtain soybean residue and soybean milk. c) Secondary separation: The primary soybean residue from step b) is diluted with a ratio of one part soybean residue to four parts water, pulverized using a multi-stage homogenizing pump, and then transported to a storage tank. After storage for 15 minutes, it is separated to obtain secondary soybean residue and secondary soy milk. d) Mixing: Mix the primary soy milk and the secondary soy milk to obtain mixed soy milk; e) Cooling: Cool the mixed soy milk to 15°C to obtain cooled soy milk; f) Isoelectric point precipitation: Adjust the pH of the cooled soy milk in step e) to 4.4, and allow it to settle to obtain a protein suspension; g) Centrifugation: The protein suspension from step f) is centrifuged to obtain an acidic solid protein slurry; h) Neutralization: Stir the acidic solid protein slurry with 3 times its weight of water, and add an alkaline processing aid to adjust the pH to 6.5; i) Sterilization: Sterilize the neutralized liquid obtained in step h) at 155°C for 3 seconds, and then perform flash degassing; j) Drying: The soybean protein liquid after flash evaporation and degassing is spray-dried.
[0022] In this embodiment: the content of soy isoflavones in soy protein was detected to be 31,523 ppm, of which free soy isoflavones accounted for 79.5%.
[0023] Example 2: A method for producing soy protein with high free soy isoflavone content includes the following steps: a) Extraction: The raw material, low-temperature defatted soybean meal, is mixed with water at a weight ratio of 1:8, heated to 95°C, food-grade acid is added, the pH value is adjusted to 2.0, and after stirring for 45 minutes, it is pulverized using a multi-stage homogenizing pump and transported to a storage tank to obtain the extract. The extract is stored for 30 minutes to wait for separation. b) Centrifugation: The extract from step a) is centrifuged to obtain soybean residue and soybean milk. c) Secondary separation: The primary soybean residue from step b) is diluted with water at a ratio of one part soybean residue to four parts water, pulverized using a multi-stage homogenizing pump, and then transported to a storage tank. After storage for 20 minutes, it is separated to obtain secondary soybean residue and secondary soy milk. d) Mixing: Mix the primary soy milk and the secondary soy milk to obtain mixed soy milk; e) Cooling: Cool the mixed soy milk to 20°C to obtain cooled soy milk; f) Isoelectric point precipitation: Adjust the pH of the cooled soy milk in step e) to 4.8, and allow it to settle to obtain a protein suspension; g) Centrifugation: The protein suspension from step f) is centrifuged to obtain an acidic solid protein slurry; h) Neutralization: Stir the acidic solid protein slurry with 5 times its weight of water, and add an alkaline processing aid to adjust the pH to 7.5; i) Sterilization: Sterilize the neutralized liquid obtained in step h) at 165°C for 8 seconds, and then perform flash evaporation degassing; j) Drying: The soybean protein liquid after flash evaporation and degassing is spray-dried.
[0024] In this embodiment: the content of soy isoflavones in soy protein was detected to be 33,554 ppm, of which free soy isoflavones accounted for 80.1%.
[0025] Example 3: A method for producing soy protein with high free soy isoflavone content includes the following steps: a) Extraction: The raw material, low-temperature defatted soybean meal, is mixed with water at a weight ratio of 1:6.8, heated to 94°C, food-grade acid is added, the pH value is adjusted to 1.59, and after stirring for 35 minutes, it is pulverized using a multi-stage homogenizing pump and transported to a storage tank to obtain the extract. The extract is stored for 30 minutes to await separation. b) Centrifugation: The extract from step a) is centrifuged to obtain soybean residue and soybean milk. c) Secondary separation: The primary soybean residue from step b) is diluted with a ratio of one part soybean residue to four parts water, pulverized using a multi-stage homogenizing pump, and then transported to a storage tank. After storage for 18 minutes, it is separated to obtain secondary soybean residue and secondary soy milk. d) Mixing: Mix the primary soy milk and the secondary soy milk to obtain mixed soy milk; e) Cooling: Cool the mixed soy milk to 18°C to obtain cooled soy milk; f) Isoelectric point precipitation: Adjust the pH of the cooled soy milk in step e) to 4.5, and allow it to settle to obtain a protein suspension; g) Centrifugation: The protein suspension from step f) is centrifuged to obtain an acidic solid protein slurry; h) Neutralization: Stir the acidic solid protein slurry with 4 times its weight of water, and add an alkaline processing aid to adjust the pH to 6.8; i) Sterilization: Sterilize the neutralized liquid obtained in step h) at 159°C for 5 seconds, and then perform flash evaporation degassing; j) Drying: The soybean protein liquid after flash evaporation and degassing is spray-dried.
[0026] In this embodiment: the content of soy isoflavones in soy protein was detected to be 33,326 ppm, of which free soy isoflavones accounted for 81.3%.
[0027] Example 4: A method for producing soy protein with high free soy isoflavone content includes the following steps: a) Extraction: Low-temperature defatted soybean meal and water are mixed at a weight ratio of 1:7, heated to 93°C, food-grade acid is added, the pH value is adjusted to 1.7, and after stirring for 40 minutes, the mixture is pulverized using a multi-stage homogenizing pump and then transported to a storage tank to obtain the extract. The extract is stored for 30 minutes to await separation. b) Centrifugation: The extract from step a) is centrifuged to obtain soybean residue and soybean milk. c) Secondary separation: The primary soybean residue from step b) is diluted with water at a ratio of one part soybean residue to four parts water, pulverized using a multi-stage homogenizing pump, and then transported to a storage tank. After storage for 17 minutes, it is separated to obtain secondary soybean residue and secondary soy milk. d) Mixing: Mix the primary soy milk and the secondary soy milk to obtain mixed soy milk; e) Cooling: Cool the mixed soy milk to 16°C to obtain cooled soy milk; f) Isoelectric point precipitation: Adjust the pH of the cooled soy milk in step e) to 4.7, and allow it to settle to obtain a protein suspension; g) Centrifugation: The protein suspension from step f) is centrifuged to obtain an acidic solid protein slurry; h) Neutralization: Stir the acidic solid protein slurry with 3.5 times its weight of water, and add an alkaline processing aid to adjust the pH to 7.2; i) Sterilization: Sterilize the neutralized liquid obtained in step h) at 163°C for 6 seconds, and then perform flash evaporation for degassing; j) Drying: The soybean protein liquid after flash evaporation and degassing is spray-dried.
[0028] In this embodiment: the content of soy isoflavones in soy protein was detected to be 36,545 ppm, of which free soy isoflavones accounted for 82.5%.
[0029] Comparative Example 1: A method for producing soy protein with high free soy isoflavone content includes the following steps: a) Extraction: Mix the raw material, low-temperature defatted soybean meal, with water at a weight ratio of 1:10, at a water temperature of 50℃, stir for 45 minutes, and then wait for separation. b) Centrifugation: Centrifuge the extract from step a) to obtain primary soybean residue and primary soy milk. Wash the primary soybean residue with water to obtain secondary soybean residue and secondary soy milk. Mix the primary and secondary soy milk. c) Acid precipitation: Adjust the pH of the mixture of primary and secondary soy milk to 4.8 and allow it to settle; precipitate at the isoelectric point and recover the protein.
[0030] d) Centrifugation: The acid precipitate from step c) is centrifuged to obtain an acidic solid protein slurry; e) Neutralization: The acidic solid protein slurry is diluted with 2 times the amount of water and homogenized at a homogenization pressure of 50 MPa. The diluted acidic protein solution and diluted food-grade alkali are continuously neutralized through a static mixer to adjust the pH to 7.2; Brix content 12.5.
[0031] f) Sterilization: The protein slurry is subjected to high-temperature instantaneous sterilization at 149°C for 8 seconds; this sterilization process achieves the desired sterilization effect. g) Vacuum degassing: After sterilization, vacuum degassing is performed, with the vacuum level controlled to 70 kPa; vacuum degassing removes the beany odor. h) Spray drying: Protein powder is produced by spray drying; In the comparative example: the soy protein contained 3214 ppm of soy isoflavones, of which free soy isoflavones accounted for 15.3%.
[0032] As described above, this invention separates denatured soy protein, increasing the relative content of free soy isoflavones; utilizes secondary separation to improve the recovery rate of free soy isoflavones; reduces the solubility of free soy isoflavones and soy protein by cooling, further improving their recovery rate; removes some beany-smelling substances through vacuum degassing to enhance the protein's flavor; centrifuges the protein suspension to obtain an acidic solid-phase protein slurry; and removes soluble monosaccharides, oligosaccharides, ash, and other components to improve the purity of free soy isoflavones and soy protein. The soy protein prepared by this invention has a soy isoflavone content as high as 36545 ppm, with free soy isoflavones accounting for as high as 82.5%, far exceeding the comparative example.
[0033] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.
[0034] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A method for producing high-isoflavone content soy protein of high free type, characterized by, Includes the following steps: a) Extraction: Mix raw soybean meal with water at a weight ratio of 1:6-15, heat to 90-95℃, add food-grade acid, adjust the pH value to 1.5-2.0, stir for 30-45 minutes, then crush using a pulverizing device and transfer to a storage tank to obtain the extract, which is stored for 30 minutes to await separation; the soybean meal in step a) is low-temperature defatted soybean meal; b) Centrifugation: The extract from step a) is centrifuged to obtain soybean residue and soybean milk. c) Secondary separation: Dilute the primary soybean residue from step b) at a ratio of one part soybean residue to four parts water, crush it using a crushing device, transport it to a storage tank, store it for 15-20 minutes, and then separate it to obtain secondary soybean residue and secondary soy milk. d) Mixing: Mix the primary soy milk and the secondary soy milk to obtain mixed soy milk; e) Cooling: Cool the mixed soy milk to 15-20℃ to obtain cooled soy milk; f) Isoelectric point precipitation: Adjust the pH of the cooled soy milk in step e) to 4.4-4.8, and allow it to settle to obtain a protein suspension; g) Centrifugation: The protein suspension from step f) is centrifuged to obtain an acidic solid protein slurry; h) Neutralization: Stir the acidic solid protein slurry with 3-5 times its weight of water, and add an alkaline processing aid to adjust the pH to 6.5-7.5; i) Sterilization: Sterilize the neutralized liquid obtained in step h) at 155-165℃ for 3-8 seconds, and then perform flash evaporation degassing; j) Drying: The soybean protein liquid after flash evaporation and degassing is spray-dried.
2. The method for producing high-isoform soy protein with high soy isoflavone content according to claim 1, characterized by, The pulverizing equipment in steps a) and c) is a multi-stage homogenizing pump or other wet pulverizing equipment.
3. The method of producing high-isoform soy protein of claim 1, wherein the soy protein is a high-isoform soy protein having a content of 0.5% or more of the glyceollins. In step a), the food-grade acid is hydrochloric acid or citric acid.
4. The method of producing high-isoform soy protein of claim 1, wherein the soy protein is a soy protein isolate. In step e), cooling is achieved using vacuum degassing or tubular heat exchange.
5. The method of producing high-isoform soy protein of claim 1, wherein the soy protein is a soy protein isolate. The alkaline processing aid in step h) is an alkaline processing aid for the food industry.