Method for preparing rice peptide with low cadmium content and high oligopeptide content

Abstract

The invention discloses a method for preparing low-cadmium high-oligopeptide-content rice peptide, which comprises the following steps of: dispersing rice flour or rice protein powder containing rice protein serving as a raw material in water to obtain a raw material solution; protease is added into the raw material liquid for enzymolysis to obtain enzymatic hydrolysate, and after enzyme deactivation, mixed liquid is obtained; filtering the mixed solution through a membrane, collecting penetrating fluid, drying and grinding to obtain rice peptide; wherein a membrane used for membrane filtration is an oxysilane modified cadmium ion imprinted ceramic membrane. According to the method, cadmium ions with potential safety hazards can be synchronously removed while the rice peptide with high oligopeptide content can be efficiently prepared.

Description

Technical Field

[0001] The invention relates to a method for preparing rice peptide with low cadmium content and high oligopeptide content, belonging to the technical field of protein deep processing. Background Art

[0002] Rice protein has the characteristics of high nutrition and low allergy. As a high-quality protein, it can be compared with shrimp, beef and other animal proteins. In addition, studies have shown that rice peptides not only inherit the advantages of rice protein in terms of low allergy, but also have multiple biological activities of bioactive peptides, such as lowering blood pressure, lowering cholesterol, anti-oxidation, promoting fat metabolism, etc. Therefore, after deep processing of rice protein, it has broad application value and prospects in the food, medicine, cosmetics and other industries.

[0003] Oligopeptides, whose molecular weight is usually less than 1200Da, are more easily absorbed by the human body and have stronger biological activity value than macromolecular peptides. At present, the industrial preparation of rice peptides is mainly based on intermittent enzymatic hydrolysis, which has the disadvantages of low efficiency, poor product uniformity, and low oligopeptide content in the product.

[0004] Application number is CN118064532A (a method for preparing rice polypeptide based on enzyme membrane reactor technology) Chinese patent, adopts membrane separation and enzymolysis process coupling method to prepare rice peptide, this method is based on enzyme membrane reactor technology, successfully prepares rice polypeptide with high biological activity and uniform molecular weight distribution. However, due to the existence of "enrichment effect" of rice protein to heavy metal element cadmium, the cadmium content in rice protein product can reach 7 times of rice, there is serious potential safety hazard. This method does not remove cadmium ions in the final product, there is potential safety hazard, and limits the application of rice peptide.

[0005] The Chinese patent application number CN106982981A (a method for preparing low-cadmium rice protein peptides by using composite membranes and electrochemistry) first prepares cadmium-containing rice peptides based on membrane separation technology, and then removes cadmium ions therein by electrochemical method to prepare low-cadmium rice peptides. This method has the disadvantages of uncontrollable enzymatic hydrolysis process and cumbersome process.

[0006] Therefore, how to achieve controllable enzymatic hydrolysis of rice protein, prepare rice peptides with high oligopeptide content and quickly and simultaneously remove cadmium ions that pose a safety hazard remains a technical challenge. Summary of the invention

[0007] The object of the present invention is to provide a method for preparing rice peptides with low cadmium content and high oligopeptide content, which can realize efficient preparation of rice peptides with high oligopeptide content and simultaneously remove cadmium ions which have potential safety hazards.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A method for preparing rice peptide with low cadmium content and high oligopeptide content comprises the following steps:

[0010] S1, take rice flour or rice protein powder containing rice protein as raw material, disperse in water to obtain stock liquid; Add protease to the stock liquid to obtain enzymolysis solution, and obtain mixed solution after enzyme inactivation;

[0011] S2, the mixed solution is filtered through a membrane, the permeate is collected, dried and then ground to obtain rice peptide;

[0012] The membrane used for membrane filtration is an oxysilane-modified cadmium ion imprinted ceramic membrane.

[0013] Preferably, in step S1, the solid-liquid ratio (w / v) of rice flour or rice protein powder containing rice protein to water is 1:(10-100);

[0014] During dispersion, the stirring speed is 300-1000 rpm and the stirring time is 1-6 hours. During the stirring process, alkali solution is added to adjust the pH to 6-11.

[0015] Preferably, in step S1, the protease is at least one of alkaline protease, neutral protease, trypsin and flavor protease;

[0016] The added amount of protease is 0.01-4% of the mass of the raw material, the enzymolysis pH is 6-11, and the enzymolysis temperature is 35-55°C.

[0017] When the raw material is rice flour containing rice protein, a filtration step is further performed after the enzyme inactivation in step S1, and the filtration method is suction filtration or plate and frame filtration.

[0018] When the raw material is rice flour containing rice protein, before the membrane filtration in step S2, a step of adding a protease to the mixed solution is also performed; wherein the protease is at least one of alkaline protease, neutral protease, trypsin and flavor protease, and the added concentration is 0.01-2% of the protein concentration in the mixed solution.

[0019] In step S2, the conditions of membrane filtration are: membrane surface flow rate 0.5-5 m / s, pressure 0.05-1 MPa, temperature 35-55°C.

[0020] In step S2, the average pore size of the membrane used for membrane filtration is 2-50 nm, the membrane structure is an asymmetric structure, and the number of channels is 1-30.

[0021] During the membrane filtration process, after the permeate volume reached 30-60% of the mixed liquid volume, a liquid replenishment operation was performed.

[0022] Preferably, the preparation method of the membrane used for membrane filtration is: using a ceramic membrane with an asymmetric structure as a modified original membrane, placing it in a modification liquid with oxysilane as a functional monomer, an epoxy compound as a cross-linking agent, and cadmium nitrate as a template, and performing pore modification by suction filtration or reverse suction filtration.

[0023] Preferably, the oxysilane used for modification is one of γ-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, and γ-(2,3-epoxypropyloxy)propyltrimethoxysilane; the crosslinking agent used for modification is one of epichlorohydrin, styrene oxide, and epoxidized fatty acid ester.

[0024] Preferably, in the modified solution, the concentration of the functional monomer is 2-10‰ (V / V), the concentration of the cross-linking agent is 3-7‰ (V / V), and the concentration of the template agent is 2-5‰ (W / V).

[0025] The beneficial effects of the present invention are:

[0026] The present invention is based on the separation and adsorption synergy of ion-imprinted ceramic membranes, and gives the ceramic membrane the ability to selectively adsorb cadmium ions without changing the separation performance of the ceramic membrane. The ion-imprinted ceramic membrane can effectively intercept macromolecular proteins / peptides and proteases, while ensuring the permeation of small molecule peptides and simultaneously removing cadmium ions. The method can prepare rice peptides with low cadmium and high oligopeptide content, which has higher preparation efficiency and better product biological activity value than traditional intermittent enzymolysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic diagram of a preparation device;

[0028] Figure 2 This is the microscopic morphology of the ceramic membrane before and after modification;

[0029] Figure 3 is the molecular weight distribution of the product of Example 1;

[0030] Figure 4 is the molecular weight distribution of the product of Example 2;

[0031] Figure 5 is the molecular weight distribution of the product of Example 3;

[0032] Figure 6 is the molecular weight distribution of the product of Example 4;

[0033] Figure 7 This is the molecular weight distribution of the product of Comparative Example 1. DETAILED DESCRIPTION

[0034] Figure 1 This is a diagram of a ceramic membrane modification device. Figure 2It is a microscopic morphology diagram of the ceramic membrane before and after modification. The modification method is: a ceramic membrane with an asymmetric structure is used as the modified original membrane, placed in a modification liquid (with oxysilane as a functional monomer, epoxy compound as a cross-linking agent, cadmium nitrate as a template, and ethanol as a solvent), and the pores are modified by suction filtration or reverse suction filtration.

[0035] Molecular weight distribution detection: Gel permeation chromatography (GPC, 1515, Waters, USA) was used to analyze the molecular weight distribution. The system was equipped with a gel permeation chromatography column (Superdex 30Increase 10 / 300GL, 300mm×10mm, Cytiva) and a UV detector (Waters 2487) with a detection wavelength of 214nm. The relative percentage of peptides in each molecular weight range was calculated by peak area normalization.

[0036] Cadmium ion content detection: Use plasma emission spectrometer to determine the cadmium ion content in the product.

[0037] Example 1

[0038] This embodiment provides a method for preparing rice peptide with low cadmium content and high oligopeptide content, specifically:

[0039] The rice was crushed and passed through a 60-mesh sieve. 40 g of rice flour was dispersed in water at a solid-liquid ratio of 1:20 (w / v). The pH of the system was adjusted to 10-10.5 with 1 M NaOH. 1% alkaline protease (based on the mass of rice flour) was added and enzymatic hydrolysis was carried out at 50° C. for 3 h. After coarse filtration with filter cloth, the enzyme was inactivated in a boiling water bath and filtered through a plate and frame to obtain liquid A.

[0040] An asymmetric ceramic membrane with an average pore size of 12 nm was prepared by using an asymmetric ceramic membrane as the modified original membrane, 8‰ (V / V) of γ-aminopropyltriethoxysilane as the functional monomer, 5‰ (V / V) of styrene oxide as the cross-linking agent, and 3‰ (W / V) of cadmium nitrate as the template. The modified cadmium ion imprinted ceramic membrane with an average pore size of 12 nm was prepared by filtration (sealing both ends of the modified original membrane, immersing it in the modification liquid, and vacuum filtration).

[0041] Feed liquid A was added to the membrane separation device, the pH of the feed liquid was adjusted to 7, 0.05% neutral protease (based on the protein concentration in the feed liquid) was added, the membrane separation device was started, and the solution was filtered through a modified cadmium ion imprinted ceramic membrane with an average pore size of 12 nm. The filtering conditions were a membrane surface flow rate of 2 m / s and an operating pressure of 0.2 MPa.

[0042] After filtering out half the volume of the initial feed solution, start the rehydration pump, and the rehydration solution is a rice protein mixture with a concentration of 1 / 4 of the initial feed solution. After continuing to filter for 5 hours, stop the reaction, collect the permeate, freeze-dry and grind it to obtain the rice peptide product.

[0043] Implementation effect: The molecular weight of the final product (molecular weight distribution such as Figure 3 As shown in the figure, the content of oligopeptides located at 200-1200Da can reach 61.34%, the cadmium ion removal rate of the final product is ≥90%, and the cadmium ion content is <0.1mg / kg, which is better than the national standard (0.2mg / kg).

[0044] Example 2

[0045] This embodiment provides a method for preparing rice peptide with low cadmium content and high oligopeptide content, specifically:

[0046] Rice protein powder was used as a raw material, and the rice protein powder was dispersed in water at a material-liquid ratio of 1:40 (w / v), and the pH of the system was adjusted to 8.5-9 with 1M NaOH to obtain material solution A.

[0047] An asymmetric ceramic membrane with an average pore size of 8 nm was prepared by using an asymmetric ceramic membrane with an average pore size of 8 nm as the modified original membrane, 5‰ (V / V) of γ-aminopropyltriethoxysilane as the functional monomer, 4.5‰ (V / V) of epichlorohydrin as the cross-linking agent, and 3‰ (W / V) of cadmium nitrate as the template. The modified cadmium ion imprinted ceramic membrane with an average pore size of 8 nm was prepared by filtration (sealing both ends of the modified original membrane, immersing it in the modification liquid, and vacuum filtration).

[0048] Feed liquid A was added to the membrane separation device, 0.05% alkaline protease (based on the mass of rice protein powder) was added, the membrane separation device was started, and the solution was filtered through a modified cadmium ion imprinted ceramic membrane with an average pore size of 8 nm. 1M NaOH was added during the filtration process to maintain the pH of the solution at 8.5-9. The filtration conditions were a membrane surface flow rate of 2 m / s and an operating pressure of 0.2 MPa.

[0049] After filtering out half the volume of the initial feed solution, start the rehydration pump, and the supplementary liquid is a rice protein mixture with a concentration of 1 / 8 of the initial feed solution. After continuing to filter for 5 hours, stop the reaction, collect the permeate, freeze-dry and grind it to obtain the rice peptide product.

[0050] Implementation effect: The molecular weight of the final product (molecular weight distribution such as Figure 4 As shown in the figure, the oligopeptide content at 200-1200Da can reach 63.19%, the cadmium ion removal rate of the final product is ≥95%, and the cadmium ion content is <0.05mg / kg, which is better than the national standard (0.2mg / kg).

[0051] Example 3

[0052] This embodiment provides a method for preparing rice peptide with low cadmium content and high oligopeptide content, specifically:

[0053] Rice protein powder was used as a raw material, and the rice protein powder was dispersed in water at a material-liquid ratio of 1:40 (w / v), and the pH of the system was adjusted to 8.5-9 with 1M NaOH to obtain material solution A.

[0054] An asymmetric ceramic membrane with an average pore size of 3.5 nm was prepared by reverse filtration (operating pressure 0.4 MPa, membrane surface flow rate 0.5 m / s) using an asymmetric ceramic membrane with an average pore size of 3.5 nm as the modified original membrane, 5‰ (V / V) 3-mercaptopropyltrimethoxysilane as the functional monomer, 4.5‰ (V / V) styrene oxide as the cross-linking agent, and 3‰ (W / V) cadmium nitrate as the template.

[0055] Feed liquid A was added to the membrane separation device, 0.05% alkaline protease (based on the mass of rice protein powder) was added, the membrane separation device was started, and the solution was filtered through a modified cadmium ion imprinted ceramic membrane with an average pore size of 3.5 nm. During the filtration process, 1 M NaOH was added to maintain the pH value of the feed liquid at 8.5-9. The filtration conditions were a membrane surface flow rate of 3 m / s and an operating pressure of 0.3 MPa.

[0056] After filtering out half the volume of the initial feed solution, start the rehydration pump, and the supplementary liquid is a rice protein mixture with a concentration of 1 / 8 of the initial feed solution. After continuing to filter for 7 hours, stop the reaction, collect the permeate, freeze-dry and grind it to obtain the rice peptide product.

[0057] Implementation effect: The molecular weight of the final product (molecular weight distribution such as Figure 5 As shown in the figure, the oligopeptide content at 200-1200Da can reach 67.05%, the cadmium ion removal rate of the final product is ≥95%, and the cadmium ion content is <0.04mg / kg, which is better than the national standard (0.2mg / kg).

[0058] Example 4

[0059] This embodiment provides a method for preparing rice peptide with low cadmium content and high oligopeptide content, specifically:

[0060] Rice protein powder was used as a raw material, and the rice protein powder was dispersed in water at a material-liquid ratio of 1:40 (w / v), and the pH of the system was adjusted to 8.5-9 with 1M NaOH to obtain material solution A.

[0061] An asymmetric ceramic membrane with an average pore size of 2 nm was prepared by reverse filtration (operating pressure 0.4 MPa, membrane surface flow rate 0.5 m / s) using an asymmetric ceramic membrane with an average pore size of 2 nm as the modified original membrane, 6‰ (V / V) γ-(2,3-epoxypropoxy)propyltrimethoxysilane as the functional monomer, 4.5‰ (V / V) epoxidized fatty acid ester as the cross-linking agent, and 3‰ (W / V) cadmium nitrate as the template.

[0062] Feed liquid A was added to the membrane separation device, 0.05% alkaline protease (based on the mass of rice protein powder) was added, the membrane separation device was started, and the solution was filtered through a modified cadmium ion imprinted ceramic membrane with an average pore size of 2 nm. 1M NaOH was added during the filtration process to maintain the pH of the solution at 8.5-9. The filtration conditions were a membrane surface flow rate of 3 m / s and an operating pressure of 0.3 MPa.

[0063] After filtering out half the volume of the initial feed solution, start the rehydration pump, and the supplementary liquid is a rice protein mixture with a concentration of 1 / 8 of the initial feed solution. After continuing to filter for 7 hours, stop the reaction, collect the permeate, freeze-dry and grind it to obtain the rice peptide product.

[0064] Implementation effect: The molecular weight of the final product (molecular weight distribution such as Figure 6 As shown in the figure, the content of oligopeptides located at 200-1200Da can reach 64.19%, the cadmium ion removal rate of the final product is ≥95%, and the cadmium ion content in the product is <0.04mg / kg, which is better than the national standard (0.2mg / kg).

[0065] Comparative Example 1

[0066] The difference from Example 3 is that an unmodified ceramic membrane is used to prepare rice peptides.

[0067] Rice protein powder was used as a raw material, and the rice protein powder was dispersed in water at a material-liquid ratio of 1:40 (w / v), and the pH of the system was adjusted to 8.5-9 with 1M NaOH to obtain material solution A.

[0068] Feed liquid A was added to the membrane separation device, 0.05% alkaline protease (based on the mass of rice protein powder) was added, the membrane separation device was started, and the solution was filtered through an unmodified ceramic membrane with an average pore size of 3.5 nm. During the filtration process, 1M NaOH was added to maintain the pH of the solution at 8.5-9. The filtration conditions were a membrane surface flow rate of 3 m / s and an operating pressure of 0.3 MPa.

[0069] After filtering out half the volume of the initial feed solution, start the rehydration pump, and the supplementary liquid is a rice protein mixture with a concentration of 1 / 8 of the initial feed solution. After continuing to filter for 7 hours, stop the reaction, collect the permeate, freeze-dry and grind it to obtain the rice peptide product.

[0070] Implementation effect: The molecular weight of the final product (molecular weight distribution such as Figure 7 As shown in the figure, the content of oligopeptides located at 200-1200Da can reach 67.73%, and the cadmium ion content in the final product is greater than 1.00mg / kg, which does not meet the national standard (0.2mg / kg) and poses a safety hazard.

Claims

1. A method for preparing low-cadmium high-oligopeptide content rice peptide, characterized in that: The steps include: S1, take rice flour or rice protein powder containing rice protein as raw material, disperse in water to obtain stock liquid; Add protease to the stock liquid to obtain enzymolysis solution, and obtain mixed solution after enzyme inactivation; S2, the mixed solution is filtered through a membrane, the permeate is collected, dried and then ground to obtain rice peptide; The membrane used for membrane filtration is an oxysilane-modified cadmium ion imprinted ceramic membrane.

2. The method for preparing low-cadmium high-oligopeptide content rice peptide according to claim 1, characterized in that, In step S1, the solid-liquid ratio (w / v) of rice flour or rice protein powder containing rice protein to water is 1:(10-100); During dispersion, the stirring speed is 300-1000 rpm and the stirring time is 1-6 hours. During the stirring process, alkali solution is added to adjust the pH to 6-11.

3. The method for preparing low-cadmium high-oligopeptide content rice peptide according to claim 1, characterized in that, In step S1, the protease is at least one of alkaline protease, neutral protease, trypsin and flavor protease; The added amount of protease is 0.01-4% of the mass of the raw material, the enzymolysis pH is 6-11, and the enzymolysis temperature is 35-55°C.

4. The method for preparing low-cadmium high-oligopeptide content rice peptide according to claim 1, characterized in that, When the raw material is rice flour containing rice protein, a filtering step is performed after the enzyme inactivation in step S1.

5. The method for preparing low-cadmium high-oligopeptide content rice peptide according to claim 1, characterized in that, When the raw material is rice flour containing rice protein, before the membrane filtration in step S2, a step of adding a protease to the mixed solution is also performed; wherein the protease is at least one of alkaline protease, neutral protease, trypsin and flavor protease, and the added concentration is 0.01-2% of the protein concentration in the mixed solution.

6. The method for preparing low-cadmium high-oligopeptide content rice peptide according to claim 1, characterized in that, In step S2, the conditions of membrane filtration are: membrane surface flow rate 0.5-5 m / s, pressure 0.05-1 MPa, temperature 35-55°C.

7. The method for preparing low-cadmium high-oligopeptide content rice peptide according to claim 1, characterized in that, In step S2, the average pore size of the membrane used for membrane filtration is 2-50 nm, and the number of channels is 1-30.

8. The method for preparing low-cadmium high-oligopeptide content rice peptide according to claim 1, characterized in that, The preparation method of the membrane used for membrane filtration is as follows: a ceramic membrane with an asymmetric structure is used as a modified original membrane, placed in a modification liquid with oxysilane as a functional monomer, an epoxy compound as a crosslinking agent, and cadmium nitrate as a template, and the pores are modified by suction filtration or reverse suction filtration.

9. The method for preparing low-cadmium high-oligopeptide content rice peptide according to claim 8, characterized in that, The oxysilane used for modification is one of γ-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane and γ-(2,3-epoxypropyloxy)propyltrimethoxysilane; the crosslinking agent used for modification is one of epichlorohydrin, styrene oxide and epoxidized fatty acid ester.

10. The method for preparing low-cadmium high-oligopeptide content rice peptide according to claim 8, characterized in that, In the modified solution, the concentration of the functional monomer is 2-10‰ (V / V), the concentration of the cross-linking agent is 3-7‰ (V / V), and the concentration of the template agent is 2-5‰ (W / V).

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