CN111393685A - Method for preparing antioxidant soybean protein cold gel by tannic acid crosslinking - Google Patents
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Abstract
The invention discloses a method for preparing antioxidant soybean protein cold gel by tannic acid crosslinking, and relates to a preparation method of modified soybean protein gel. The invention aims to solve the technical problem that the existing soybean protein cold gel has insufficient functional characteristics. The method comprises the following steps: preparing a soybean protein isolate water solution, adjusting the pH value to 9-11, adding a tannic acid water solution with the pH value equal to that of the soybean protein isolate water solution according to the proportion of 88-146 mu mol of tannic acid added into each gram of soybean protein isolate, stirring and reacting under the condition of keeping the mixed solution in contact with oxygen, then carrying out centrifugal treatment to remove gas to obtain a gel pre-solution, and storing the gel pre-solution in a refrigerator at the temperature of 0-4 ℃ to obtain the antioxidant soybean protein cold gel. The covalent binding rate of the protein and the tannic acid is as high as 65.47-95.06%, the cold gel has excellent performance, can carry heat-sensitive nutrients or functional active substances, and is used in the fields of food and medical treatment.
Description
Technical Field
The invention relates to a preparation method of modified soy protein gel.
Background
The soybean protein is a high-quality vegetable protein, has wide source, low price and high nutritive value, and simultaneously has excellent performances of degradability, biocompatibility, thermal stability, no pollution, environmental protection and the like. The soybean protein has good gel property, and is often used for improving the structure of related food. The denaturation of soybean protein is the basis of gel formation, and protein gels formed by heating or adding coagulants (mainly including acids, metal salts, coagulants and the like) have high elasticity, viscosity and plasticity, can be used as carriers of solvents, flavor substances, saccharides and other active ingredients, and are widely applied to the food industry.
Currently, the study of thermal gelation is the most extensive, for example, the fourth part of the study on the microstructure and characteristics of soy protein-based colloids in the university of south china university of china university of china "is to add soy protein isolate into water, fully hydrate, mix with tannic acid solution, adjust to acidity, heat to 85 ℃ in water bath with stirring and shearing in a high-speed dispersion machine, cool, and spray-dry to obtain protein-based gel particles. But their intense processing results in partially limited application of protein gels. The conventional preparation method of soybean protein cold gel is generally to heat soybean protein to denature the soybean protein to form aggregates, cool the aggregates and add salt (Ca)2+,Mg2+) Chinese patent with application number 201611031553.9 discloses a preparation method of soybean protein isolate cold gel, which comprises ball-milling soybean protein isolateAdding water, heating in a 90-100 ℃ water bath for 10-30 minutes, cooling to 10-30 ℃, adding glucolactone, stirring uniformly, then preserving heat at 20-30 ℃ for 0.5-2 hours to form gel, and finally preserving heat at 1-5 ℃ for 10-15 hours to fully after-ripen the gel, thereby completing the preparation of the cold gel. The method enhances the gelling property of the isolated soy protein by mixing and ball milling, so that the isolated soy protein can carry out gelling reaction under the condition of low temperature. Although the cold gel treatment makes up the application defects of the thermal gel on heat-sensitive substances and active substances to a certain extent, the cold gel only changes the food system in the sense form and does not endow the food with new activity.
Disclosure of Invention
The invention aims to solve the technical problem of insufficient functional characteristics of the existing soybean protein cold gel, and provides a method for preparing antioxidant soybean protein cold gel by tannic acid crosslinking.
The method for preparing the antioxidant soybean protein cold gel by tannic acid crosslinking comprises the following steps:
adding the isolated soy protein into water, stirring for at least 2 hours by using a magnetic stirrer, and storing in a refrigerator at the temperature of 0-4 ℃ to obtain an aqueous solution of the isolated soy protein;
adjusting the pH value of the soybean protein isolate water solution to 9-11 by using NaOH solution;
preparing a tannic acid aqueous solution according to the proportion of adding 88-146 mu mol of tannic acid to each gram of soybean protein isolate, adjusting the pH value of the tannic acid aqueous solution to be equal to the pH value of the soybean protein isolate aqueous solution, mixing the soybean protein isolate aqueous solution and the tannic acid aqueous solution, stirring and reacting for 9-10 h at the temperature of 22-26 ℃, and keeping the mixed solution in contact with oxygen during stirring and reacting; after the reaction is finished, carrying out centrifugal treatment to remove gas to obtain a gel pre-solution;
fourthly, placing the gel pre-solution in a refrigerator with the temperature of 0-4 ℃ for storage and solidification to obtain the antioxidant soybean protein cold gel.
Furthermore, in the step one, the mass percentage concentration of the soy protein isolate in the soy protein isolate water solution is 12-13%.
Furthermore, in the step one, the time for storing in the refrigerator is 8-12 h.
Furthermore, in the second step, the concentration of the NaOH solution is 1-1.2 mol/L.
Furthermore, the rotation speed during the centrifugal treatment in the third step is 4000-5000 rpm/min, and the centrifugal treatment time is 15-20 min.
Further, in the fourth step, the mixture is stored in a refrigerator for 8-12 hours to be solidified.
In the invention, the soybean protein, a high molecular material, contains a plurality of active side groups, such as amino, carboxyl, hydroxyl and sulfydryl, and can chemically react with a plurality of substances. Tannic acid is a natural water-soluble polyphenol compound, and is a secondary metabolite derived from plants. The protein can be crosslinked with tannic acid under alkaline conditions. After the covalent reaction under alkaline environment occurs, the structure of the protein is changed, and whether the protein structure is unfolded or not directly influences the gel ability of the protein. The gel with antioxidant activity can be prepared while changing the sensory properties of food by crosslinking tannic acid and soy protein isolate. The invention creatively utilizes the covalent reaction of polyphenol protein in an alkaline environment to prepare the protein cold gel, selects the proper concentration of tannic acid to ensure that the covalent bonding rate of the protein and the tannic acid is as high as 65.47-95.06 percent, has excellent cold gel performance, and obviously improves the oxidation resistance activity of soybean protein. The cold gel can carry heat-sensitive nutrients or functional active substances, and the application of the protein gel is widened.
The preparation method is simple in preparation process, is carried out at room temperature, is not added with organic reagents, is mild and safe in means, is green and environment-friendly, and can be applied to the fields of food, medical treatment and the like.
Drawings
FIG. 1 is a graph showing the results of the tryptophan content test on 15 kinds of soybean protein tannin complexes prepared in examples 1 to 3;
FIG. 2 is a graph showing the results of testing the covalent binding rate of 15 kinds of soybean protein tannin complexes prepared in examples 1 to 3;
FIG. 3 is a photograph showing the results of electrophoretic identification of the soybean protein tannin complex prepared in examples 1 to 3;
FIG. 4 is a Fourier infrared spectrum of 15 soy protein tannin complexes prepared in examples 1-3;
FIG. 5 is a Fourier infrared spectrum of 15 soy protein tannin complexes prepared in examples 1-3;
FIG. 6 is a graph showing the DPPH radical scavenging ability of 15 soybean protein tannin complexes prepared in examples 1 to 3;
FIG. 7 is a graph showing the ABTS radical scavenging ability of 15 soybean protein tannin complexes prepared in examples 1-3;
FIG. 8 is a graph showing the iron ion reduction ability of 15 kinds of soybean protein tannin complexes prepared in examples 1 to 3;
FIG. 9 is a comparison graph of water binding capacity of 15 antioxidant soy protein cryogels prepared in examples 1-3;
FIG. 10 is a graph showing hardness comparison of 15 antioxidant soy protein cryogels prepared in examples 1-3;
FIG. 11 is the SEM pictures of 5 antioxidant soy protein cryogels prepared at pH11 and different tannin concentrations in example 1.
Detailed Description
The following examples are used to demonstrate the beneficial effects of the present invention:
example 1: the method for preparing the antioxidant soybean protein cold gel by tannic acid crosslinking comprises the following steps:
adding the isolated soy protein into water according to the mass percentage concentration of the isolated soy protein of 12 percent, stirring for 2 hours by using a magnetic stirrer, and then storing for 8 hours in a refrigerator at the temperature of 4 ℃ to ensure complete dissolution to obtain an aqueous solution of the isolated soy protein;
adjusting the pH value of the soybean protein isolate aqueous solution to 11 by using NaOH solution to obtain a soybean protein isolate aqueous solution;
thirdly, taking 5 parts of soybean protein isolate aqueous solution, and preparing tannic acid aqueous solution according to the proportion that 29 mu mol, 58 mu mol, 88 mu mol, 117 mu mol and 146 mu mol of tannic acid are respectively added into each gram of soybean protein isolate in the soybean protein isolate aqueous solution to obtain 5 groups of soybean protein isolate aqueous solution and tannic acid aqueous solution corresponding to the soybean protein isolate aqueous solution; regulating the pH values of the five parts of tannic acid aqueous solution to 11, mixing the soybean protein isolate aqueous solution and the tannic acid aqueous solution in each group, stirring and reacting the mixed solution at the temperature of 25 ℃ for 9 hours, and keeping the mixed solution in contact with oxygen during the stirring and reacting; after the reaction is finished, carrying out centrifugal treatment for 15min at the rotating speed of 4000rpm/min to remove gas, and obtaining 5 gel pre-solutions; taking a part of each gel pre-solution, placing the gel pre-solution in deionized water for dialysis for 48 hours, and freeze-drying to obtain five soybean protein-tannin complexes for characterization of protein properties;
and fourthly, placing the gel pre-solutions in a refrigerator with the temperature of 4 ℃ for 8 hours for solidification to obtain five antioxidant soybean protein cold gels.
In the present example, the soybean protein cold gel prepared by adding tannic acid in an amount of 29. mu. mol and 58. mu. mol per gram of isolated soybean protein in step III was used for comparison.
Example 2: the method for preparing the antioxidant soybean protein cold gel by tannic acid crosslinking comprises the following steps:
adding the isolated soy protein into water according to the mass percentage concentration of the isolated soy protein of 12 percent, stirring for 2 hours by using a magnetic stirrer, and then storing for 8 hours in a refrigerator at the temperature of 4 ℃ to ensure complete dissolution to obtain an aqueous solution of the isolated soy protein;
adjusting the pH value of the soybean protein isolate aqueous solution to 10 by using NaOH solution to obtain a soybean protein isolate aqueous solution;
taking 5 parts of soybean protein isolate water solution, and then respectively adding 29 mu mol, 58 mu mol, 88 mu mol, 117 mu mol and 146 mu mol of tannic acid into each gram of soybean protein isolate to prepare five kinds of tannic acid water solution so as to obtain 5 groups of soybean protein isolate water solution and tannic acid water solution corresponding to the soybean protein isolate water solution; adjusting the pH values of the five parts of tannic acid aqueous solution to 10, mixing the soybean protein isolate aqueous solution and the tannic acid aqueous solution in each group, stirring and reacting the mixed solution at the temperature of 25 ℃ for 9 hours, and keeping the mixed solution in contact with oxygen during the stirring and reacting; after the reaction is finished, carrying out centrifugal treatment for 15min at the rotating speed of 4000rpm/min to remove gas, and obtaining 5 gel pre-solutions; taking a part of each gel pre-solution, placing the gel pre-solution in deionized water for dialysis for 48 hours, and freeze-drying to obtain five soybean protein-tannin complexes for characterization of protein properties;
and fourthly, placing the gel pre-solutions in a refrigerator with the temperature of 4 ℃ for storage for 8 hours to obtain five antioxidant soybean protein cold gels.
In the present example, the soybean protein cold gel prepared by adding tannic acid in an amount of 29. mu. mol and 58. mu. mol per gram of isolated soybean protein in step III was used for comparison.
Example 3: the method for preparing the antioxidant soybean protein cold gel by tannic acid crosslinking comprises the following steps:
adding the isolated soy protein into water according to the mass percentage concentration of the isolated soy protein of 12 percent, stirring for 2 hours by using a magnetic stirrer, and then storing for 8 hours in a refrigerator at the temperature of 4 ℃ to ensure complete dissolution to obtain an aqueous solution of the isolated soy protein;
adjusting the pH value of the soybean protein isolate aqueous solution to 9 by using NaOH solution to obtain the soybean protein isolate aqueous solution;
taking 5 parts of soybean protein isolate water solution, and then respectively adding 29 mu mol, 58 mu mol, 88 mu mol, 117 mu mol and 146 mu mol of tannic acid into each gram of soybean protein isolate to prepare five kinds of tannic acid water solution so as to obtain 5 groups of soybean protein isolate water solution and tannic acid water solution corresponding to the soybean protein isolate water solution; regulating the pH values of the five parts of tannic acid aqueous solution to 9, mixing the soybean protein isolate aqueous solution and the tannic acid aqueous solution in each group, stirring and reacting the mixed solution at the temperature of 25 ℃ for 9 hours, and keeping the mixed solution in contact with oxygen during the stirring and reacting; after the reaction is finished, carrying out centrifugal treatment for 15min at the rotating speed of 4000rpm/min to remove gas, and obtaining 5 gel pre-solutions; taking a part of each gel pre-solution, placing the gel pre-solution in deionized water for dialysis for 48 hours, and freeze-drying to obtain five soybean protein-tannin complexes for characterization of protein properties;
and fourthly, placing the gel pre-solutions in a refrigerator with the temperature of 4 ℃ for storage for 8 hours to obtain five antioxidant soybean protein cold gels.
In the present example, the soybean protein cold gel prepared by adding tannic acid in an amount of 29. mu. mol and 58. mu. mol per gram of isolated soybean protein in step III was used for comparison.
The tryptophan content and covalent binding rate of the total 15 soybean protein tannin complexes prepared in examples 1, 2 and 3 were determined as follows:
1. the method for measuring the content of tryptophan comprises the steps of uniformly mixing 1M L16M nitric acid and 0.9M L sample of soybean protein tannin complex, taking out immediately after being subjected to water bath at 50 ℃ for 15min, cooling in ice-water bath, adding 5 mol/L NaOH solution 4M L and equal volume of anhydrous ethanol, fully mixing, and measuring the content of a sample solution A in the sample solution by using an ultraviolet spectrophotometer360And A430The absorbance of the sample was calculated by using the following formula.
C＝0.5357×A430-0.35714×A360
Wherein C is the concentration of tryptophan residues, A430 is the absorbance at 430nm, and A360 is the absorbance at 360 nm.
2. The method for measuring covalent bonding rate comprises redissolving soybean protein tannin complex sample before and after dialysis in deionized water at concentration of 1mg/m L, adding 2.5m L Folin phenol reagent into sample solution 0.5m L, mixing, reacting at room temperature in dark place for 5min, adding 10% Na2CO3And after uniform mixing, reacting for 2 hours in a dark place at room temperature, measuring a light absorption value at 760nm by using an ultraviolet spectrophotometer, and taking the aqueous solution after the same treatment as a blank control.
Preparing tannin standard substance solutions with different concentrations, and drawing a light absorption value-tannin concentration standard curve by the same detection method. The covalent binding rate of tannic acid to SPI was calculated using the following formula.
3. Sodium dodecyl sulfate-polypropylene gel electrophoresis test: the concentrations of the concentrated gel and the separating gel are respectively 5% and 12%, and a Marker with the molecular weight distribution of 25-100 kDa is selected for carrying out SDS-PAGE electrophoresis test.
4. Determination of antioxidant Activity: the antioxidant activity of the compound is measured by taking DPPH free radical scavenging capacity, ABTS free radical scavenging capacity and FARP iron ion reducing capacity as indexes, and the standard substance is selected to be Trolox.
5. The specific determination method of the soybean protein cold gel hardness comprises the following steps: a probe model TA10 (diameter: 12.7mm) was used, and the test speed was 0.5mm/s 19. The gel pre-solution formed a gel in a glass container having a height of 50mm and an internal diameter of 35 mm. The sample was tested without removing it from the container. The maximum penetration force, defined as the force required to break the gel, was measured and expressed as gel stiffness.
The results of the tryptophan content test on the 15 soybean protein tannin complexes prepared in examples 1 to 3 are shown in FIG. 1, and the results of the covalent binding rate test are shown in FIG. 2.
As can be seen from FIG. 1, compared to the soy protein isolate control, the tryptophan content of the soy protein-tannin complex is significantly reduced, quinone formed by oxidation of the tannin side chains can react with tryptophan in the soy protein, resulting in a reduced tryptophan content, the tryptophan content gradually decreases as the tannin concentration increases, the tryptophan content is 7.5 to 15mg/m L when the tannin is added at a ratio of 88 to 146 μmol per gram of soy protein isolate, which is selected in the present invention, indicating that the tannin is covalently bound to the soy protein, and the tryptophan content increases when the tannin is added at a level of less than 88 μmol per gram of soy protein isolate.
As can be seen from FIG. 2, when the proportion of tannic acid added to each gram of soy protein isolate is 88-146 μmol selected by the invention, the covalent bonding rate is as high as 65.47% -95.06%. When 117 mu mol of tannic acid is added into each gram of soy protein isolate and the pH value is 11, the binding rate reaches the highest value of 95.06 percent; when the tannin addition ratio is lower than 88. mu. mol per gram of soy protein isolate, the binding rate is low.
The photograph of the soybean protein-tannin complexes prepared in examples 1 to 3 is shown in FIG. 3, wherein M is protein Marker, SPI is control soybean protein isolate, lanes 1, 2 and 3 are soybean protein-tannin complexes prepared at pH 9, 10 and 11 with a tannin concentration of 58. mu. mol/g SPI, and lanes 4, 5 and 6 are soybean protein-tannin complexes prepared at pH 9, 10 and 11 with a tannin concentration of 117. mu. mol/g SPI. As can be seen from FIG. 3, bands with molecular weight of more than 100kDa appear in lanes 1-6, and dark color accumulation appears at the comb-shaped wells, probably due to the polymerization of isolated soy protein with tannic acid to form macromolecular polymers, which accumulate at the comb-shaped wells because of too large molecular weight to pass through the gel network. A lighter band of subunits of the complex compared to subunits in the SPI control ( lanes 2 and 4, for example) indicates that the subunits are involved in the covalent reaction; at the same tannin concentration, the subunit bands in lanes 4, 5, and 6 become progressively lighter, indicating that the extent of covalent reaction increases with increasing pH.
Fourier infrared spectrum analysis is carried out on the 15 soybean protein tannin compounds prepared in the examples 1-3, and obtained Fourier infrared spectrum charts are shown in figures 4 and 5, wherein in figure 4, a is SPI, and b-d are infrared spectrums of the compounds prepared under the conditions that the pH value is 9, 10 and 11 and the tannin concentration is 117 mu mol/g SPI in sequence; FIG. 5, wherein a is tannic acid, b is SPI, and c-g are IR spectra of complexes prepared at tannic acid concentrations of 146, 117, 88, 58, 29 μmol/g SPI at pH11, respectively; as can be seen from FIGS. 4 and 5, the spectrum of Soybean Protein Isolate (SPI) mainly shows a main peak of 3272cm-1(amide A band, representing N-H stretch and hydrogen bond) 1635cm-1(amide I band, representing C-O stretch/hydrogen bond and COO-) and 1524cm-1(amide II band, representing C-N telescopic and N-H bending modes). The peak of the soy protein tannin complex absorption near the amide A band was shifted compared to the control SPI, indicating the-NH of the protein2Participates in the reaction; tannic acid is 3300cm-1The absorption peak (-OH stretching vibration) does not appear in the covalent complex, indicating that phenolic hydroxyl groups participate in the reaction of protein and polyphenol. 868cm of tannic acid-1The absorption peak is out-of-plane bending vibration of the aromatic ring, and the compound is red-shifted to 979cm-1, and belongs to in-plane bending vibration. Of complexes prepared at a tannin concentration of 58, 29. mu. mol/g SPIThe peak intensity is lower. The peak intensity of the compound prepared under the conditions that the concentration of the tannic acid is selected to be 146, 117 and 88 mu mol/g SPI is higher and the change is more obvious.
The antioxidant activity of the 15 soybean protein tannin complexes prepared in examples 1 to 3 was measured. The resultant DPPH radical scavenging ability is shown in FIG. 6, the ABTS radical scavenging ability is shown in FIG. 7, and the iron ion reducing ability is shown in FIG. 8. As can be seen from FIGS. 6, 7 and 8, the composite prepared at a tannic acid concentration of 146 μmol/g SPI exhibited the highest overall oxidation resistance.
For DPPH free radical scavenging, the complexes prepared at tannin concentrations of 29 and 58. mu. mol/g SPI were comparatively poor, whereas the complexes prepared at tannin concentrations of 88, 117 and 146. mu. mol/g SPI selected by the present invention had a DPPH free radical scavenging of between 60 and 150. mu. mol Trolox/m L sample.
As for ABTS free radical scavenging capacity, only the comparative compound prepared under the condition that the concentration of tannic acid is 29 mu mol/g SPI is poor, and the ABTS free radical scavenging capacity difference of the compounds prepared under other conditions is not obvious, and reaches 160-185 mu mol Trolox/m L sample.
As for the iron ion reducing capability, the iron ion reducing capability of the compound prepared under the conditions of tannic acid concentrations of 88 and 117 and 146 mu mol/g SPI selected by the invention is better, and the slightly worse of the compound prepared under the conditions of tannic acid concentrations of 29 and 58 mu mol/g SPI selected by the invention is 80-200 mu mol Fe2+and/L sample.
The phenolic substances of tannins can be oxidized into respective quinones in an alkaline solution or in the presence of polyphenol oxidase, and the quinones can react with free amino groups of proteins to make the compound have antioxidant activity.
The 15 antioxidant soybean protein cold gels prepared in examples 1 to 3 were subjected to water binding measurement. The obtained water binding capacity comparison chart is shown in fig. 9, and it can be seen from fig. 9 that the water binding capacities of the 15 antioxidant soybean protein cold gels are all more than 95%.
The 15 antioxidant soybean protein cold gels prepared in examples 1 to 3 were subjected to hardness measurement. The hardness comparison graph is shown in FIG. 10, and it can be seen from FIG. 10 that the antioxidant soy protein-cold gel prepared under the conditions of the tannic acid concentration of 117. mu. mol/g SPI and the pH value of 11 has the highest hardness. On the premise of consistent concentration of tannic acid, the hardness of the antioxidant soybean protein cold gel prepared under the condition of pH value of 11 is higher than that of the antioxidant soybean protein cold gel prepared under the condition of pH value of 9 or 10.
In example 1, scanning electron micrographs of 5 antioxidant soy protein cryogels prepared at pH11 and different tannin concentrations are shown in FIG. 11, where A-E are 50 μm images of antioxidant soy protein cryogels with tannin concentrations of 29, 58, 88, 117, 146 μmol/g SPI, and F is a 50 μm image of pH11 compared to SPI at the same concentration; a-F are 20 μm images corresponding to A-F. As can be seen from FIG. 11, the 3 antioxidant soybean protein cold gels prepared under the conditions of pH11 and tannin concentrations of 88, 117 and 146 μmol/g SPI have uniform and dense texture and ordered arrangement; after covalent crosslinking, the gel presents an oval or round network structure, and the pore wall of the gel is smooth. The porosity of 2 antioxidant soybean protein cold gels prepared under the conditions of pH value of 11 and tannin concentration of 29 and 58 mu mol/g SPI is slightly larger, but is also smaller than that of the soybean protein used as a control, which is consistent with the change trend of gel hardness. The change of the microstructure indicates that the protein polyphenol has changed chemical bonds due to covalent reaction, so that the microstructure is changed.
Claims (6)
1. A method for preparing antioxidant soybean protein cold gel by tannic acid crosslinking is characterized by comprising the following steps:
adding the isolated soy protein into water, stirring for at least 2 hours by using a magnetic stirrer, and storing in a refrigerator at the temperature of 0-4 ℃ to obtain an aqueous solution of the isolated soy protein;
adjusting the pH value of the soybean protein isolate water solution to 9-11 by using NaOH solution;
preparing a tannic acid aqueous solution according to the proportion of adding 88-146 mu mol of tannic acid to each gram of soybean protein isolate, adjusting the pH value of the tannic acid aqueous solution to be equal to the pH value of the soybean protein isolate aqueous solution, mixing the soybean protein isolate aqueous solution and the tannic acid aqueous solution, stirring and reacting for 9-10 h at the temperature of 22-26 ℃, and keeping the mixed solution in contact with oxygen during stirring and reacting; after the reaction is finished, carrying out centrifugal treatment to remove gas to obtain a gel pre-solution;
fourthly, placing the gel pre-solution in a refrigerator with the temperature of 0-4 ℃ for storage and solidification to obtain the antioxidant soybean protein cold gel.
2. The method for preparing antioxidant soybean protein cold gel by tannin crosslinking as claimed in claim 1, wherein in the first step, the concentration of the isolated soybean protein in the isolated soybean protein water solution is 12-13% by mass.
3. The method for preparing antioxidant soybean protein cold gel through tannic acid crosslinking as claimed in claim 1 or 2, wherein in the first step, the storage time in a refrigerator is 8-12 h.
4. The method for preparing antioxidant soybean protein cold gel through tannic acid crosslinking as claimed in claim 1 or 2, wherein in the second step, the concentration of NaOH solution is 1-1.2 mol/L.
5. The method for preparing antioxidant soybean protein cold gel through tannic acid crosslinking according to claim 1 or 2, wherein the rotation speed during the centrifugal treatment in the third step is 4000-5000 rpm/min, and the centrifugal treatment time is 15-20 min.
6. The method for preparing antioxidant soybean protein cold gel through tannic acid crosslinking according to claim 1 or 2, wherein the cold gel is stored in a refrigerator for 8-12 h to achieve solidification in the four steps.
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| CN115039830A (en) * | 2022-06-15 | 2022-09-13 | 浙江省农业科学院 | Preparation method of shellac co-folded soybean protein isolate cold gel |
| CN115669795A (en) * | 2022-11-14 | 2023-02-03 | 东北农业大学 | Method for preparing quercetin-containing emulsion gel by squeezing pretreated soybean protein |
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| CN115669795A (en) * | 2022-11-14 | 2023-02-03 | 东北农业大学 | Method for preparing quercetin-containing emulsion gel by squeezing pretreated soybean protein |
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