Wheat oligopeptide chelated calcium and preparation method thereof

Abstract

The invention relates to the technical field of deep processing of plant source active calcium, in particular to wheat oligopeptide chelated calcium and a preparation method thereof. The invention provides a preparation method of wheat oligopeptide chelated calcium, which comprises the following steps: taking wheat hydrolyzed protein as a raw material, performing enzymolysis on the wheat hydrolyzed protein by using alkaline protease and flavourzyme in sequence, and then performing chelation reaction with calcium chloride to obtain peptide calcium reaction liquid; performing impurity removal on the peptide calcium reaction liquid by using diatomite and perlite combined with plate frame filtration, performing filtration and sterilization by using a microfiltration membrane, and finally performing drying to obtain the wheat oligopeptide chelated calcium. Various detection indexes of the wheat oligopeptide chelated calcium prepared by the method meet related standard requirements, and marketization and industrialization application of the plant source peptide calcium chelate is promoted.

Description

Technical Field

[0001] This invention relates to the field of deep processing technology of plant-derived active calcium, and in particular to a wheat oligopeptide chelated calcium and its preparation method. Background Technology

[0002] Peptide-calcium chelates, as a novel calcium supplement, possess independent chelation and transport systems. They prevent phytate precipitation in the intestines, promoting absorption and thus serving as excellent carriers for calcium absorption and transport. Peptide-calcium chelates offer dual nutritional functions, acting as both a calcium supplement and a source of bioactive peptides. In recent years, research on calcium ion chelate peptides from plant sources, especially agricultural byproducts, has gained increasing attention. Wheat oligopeptides possess various physiological functions and are characterized by low cost, high water solubility, easy absorption, strong bioactivity, and good processability. Wheat oligopeptides typically consist of 2-6 amino acid molecules with a molecular weight below 3000 Da and a balanced amino acid composition. Reports on wheat oligopeptides often indicate their immune-enhancing, antioxidant, and immune system-regulating effects, making them a good source for preparing chelated calcium.

[0003] Current reports on wheat peptide calcium are mostly limited to small-scale experimental preparations. When applied to actual production, the parameters are too complex to control. Specifically: 1. Enzymatic hydrolysis often uses wheat gluten as the raw material. While the amount of precipitation can be controlled in small-scale trials due to the poor water solubility and emulsifying properties of this plant-derived protein, large-scale production results in significant precipitation and severe clumping, leading to incomplete enzymatic hydrolysis and precipitation, directly affecting the yield of subsequent oligopeptides (e.g., CN106244655A, A protein peptide and its calcium chelate and preparation method). 2. After the chelation reaction, anhydrous ethanol is often used to precipitate the chelated calcium (CN117099869, A method for preparing wheat protein peptide chelated calcium). This consumes a large amount of anhydrous ethanol, posing safety risks in actual production and making it impractical. Furthermore, the high raw material cost increases the overall production cost. 3. In the preparation process, wheat peptides are often dried after enzymatic hydrolysis to obtain powder, which is then chelated with calcium ions. This adds a reaction step, increases reaction time and cost, and is inconvenient for production operations. 4. The lack of a sterilization step results in a short product shelf life, making it difficult to distribute and sell. 5. After the enzymatic hydrolysis and chelation reactions, centrifugation is often used to remove impurities. This is commonly used in laboratories, but it is costly for large-scale production and unsuitable for rapid, large-scale impurity removal. Therefore, it is necessary to provide a production method for wheat peptide calcium chelates that can be applied to practical production. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing wheat peptide-calcium chelate. This method uses wheat hydrolyzed protein as raw material and prepares a wheat peptide-calcium chelate with high peptide-calcium content through nanofiltration, enzymatic hydrolysis, chelation, diatomaceous earth and perlite combined plate and frame filtration for impurity removal, filter membrane sterilization, and drying. This method can be applied to actual production.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing wheat oligopeptide chelated calcium, comprising the following steps: (1) The wheat hydrolysate was sequentially hydrolyzed using alkaline protease and flavor protease to obtain the hydrolysate; (2) Mix the enzymatic hydrolysate and calcium chloride and react for 2-4 hours to obtain the peptide calcium reaction solution; (3) After mixing the peptide calcium reaction solution with diatomaceous earth and perlite, the mixture is filtered through a plate and frame filter to obtain a coarse filtrate; the coarse filtrate is then subjected to nanofiltration and concentration to obtain a secondary filtrate. (4) The concentrated secondary filtrate was microfiltered sequentially using filter cartridges with a filtration precision of 0.45 μm and 0.22 μm to obtain a sterile reaction solution; (5) The sterile reaction solution was dried to obtain wheat oligopeptide chelated calcium.

[0006] Preferably, in step (1), the mass ratio of the wheat hydrolysate to the alkaline protease is 100:0.70~0.80; the enzyme activity of the alkaline protease is 56000~60000U / g; the temperature for enzymatic hydrolysis using the alkaline protease is 50~60℃, the hydrolysis time is 2~3h, and the pH for hydrolysis is 8~9.

[0007] Preferably, in step (1), the mass ratio of the wheat hydrolysate to the flavor protease is 100:2~3; the enzyme activity of the flavor protease is 3500~4500U / g; the temperature for enzymatic hydrolysis using the flavor protease is 45~55℃, the hydrolysis time is 1~2h, and the hydrolysis pH is 6~7.

[0008] Preferably, in step (2), before the enzyme hydrolysate and calcium chloride are mixed and reacted, the content of solids in the enzyme hydrolysate is determined; the mass ratio of solids to calcium chloride is 2:0.5~1.5. The mixing reaction is carried out at a temperature of 65-70°C and a pH of 8.0-8.5.

[0009] As a preferred option, in step (3), before mixing the peptide calcium reaction solution with diatomaceous earth and perlite, the content of solids in the peptide calcium reaction solution is determined. The amount of diatomaceous earth added is 3-7% of the solid mass; the amount of perlite added is 3-7% of the solid mass. The peptide calcium reaction solution is mixed with diatomaceous earth and perlite by stirring; the mixing time is 15~25 min.

[0010] Preferably, in step (3), the pore size of the plate and frame filter is 3~10μm; and the pressure of the plate and frame filter is 0.4~0.6MPa.

[0011] Preferably, in step (3), the molecular weight cutoff of the nanofiltration is 150~200 Da; the pressure of the nanofiltration is 0.8~2.0 MPa; and the temperature of the nanofiltration is 50~65℃. The concentration is performed by heating; the concentration temperature is 70~85℃.

[0012] Preferably, in step (4), the pressure of the microfiltration is 0.1~0.2MPa; and the flow rate of the microfiltration is 300~500kg / h.

[0013] Preferably, in step (5), the drying is spray drying; the inlet air temperature of the drying is 170~180℃, the outlet air temperature is 70~80℃, and the processing capacity is 100~500kg / h.

[0014] The present invention also provides the preparation method described above for preparing wheat oligopeptide chelated calcium.

[0015] The beneficial effects of this invention are: This invention provides a method for preparing wheat oligopeptide chelated calcium. In this method, (1) wheat hydrolyzed protein is used instead of gluten as the raw material for preparing wheat peptides. Wheat hydrolyzed protein mainly contains gliadin and glutenin, which are the same as the components of gluten. However, wheat hydrolyzed protein is wheat protein that has undergone preliminary hydrolysis. Its water solubility and emulsifying properties are better than those of gluten. Under the premise of ensuring the stability of wheat protein raw materials, its molecular weight is reduced, and its water solubility and emulsifying properties are improved, which is conducive to the full reaction; (2) nanofiltration is used to remove calcium ions that have not been fully chelated, replacing the anhydrous ethanol precipitation step, reducing costs and improving production operability; (3) an enzymatic hydrolysis-chelation one-step reaction is used, which reduces the molecular weight of the wheat protein and improves its water solubility and emulsifying properties. After adjusting the temperature and pH of the wheat hydrolysate, calcium chloride is directly added to carry out the chelation reaction, saving reaction time and omitting the first drying process; (4) The filter membrane sterilization process is added, the 0.45μm filter cartridge is pre-treated for filtration, and the 0.22μm filter cartridge is used for secondary filtration sterilization to meet the microbial limits specified in relevant standards; (5) Diatomaceous earth and perlite adsorb impurities, and combined with plate and frame filtration, the centrifugation process is replaced. By utilizing the microporous structure and strong adsorption performance of these two filter aids, the flow rate of the filtered liquid is increased while the fine suspended matter is effectively removed, significantly improving the filtration efficiency. Plate and frame filtration is simple to operate, has a wide range of applications, stable pressure, high filtration efficiency, and the squeeze filtration mode can quickly remove impurities. Attached Figure Description

[0016] Figure 1 Flowchart for the preparation of wheat oligopeptide chelated calcium; Figure 2 The results represent the relative percentage of peptides with relative molecular masses in the range of 189 to 10000. Figure 3 The results include the detection of moisture, lead content, total arsenic content, total bacterial count, coliform count, calcium content, zearalenone content, ochratoxin A content, deoxynivalenase content, and aflatoxin B1 content. Detailed Implementation

[0017] This invention provides a method for preparing wheat oligopeptide chelated calcium, comprising the following steps: (1) The wheat hydrolysate was sequentially hydrolyzed using alkaline protease and flavor protease to obtain the hydrolysate; (2) Mix the enzymatic hydrolysate and calcium chloride and react for 2-4 hours to obtain the peptide calcium reaction solution; (3) After mixing the peptide calcium reaction solution with diatomaceous earth and perlite, the mixture is filtered through a plate and frame filter to obtain a coarse filtrate; the coarse filtrate is then subjected to nanofiltration and concentration to obtain a secondary filtrate. (4) The concentrated secondary filtrate was microfiltered sequentially using filter cartridges with a filtration precision of 0.45 μm and 0.22 μm to obtain a sterile reaction solution; (5) The sterile reaction solution was dried to obtain wheat oligopeptide chelated calcium.

[0018] In this invention, in step (1), the wheat hydrolysate needs to be dissolved before enzymatic hydrolysis. The specific steps are: mix the wheat hydrolysate with water to obtain a mixture with a concentration of 15~20% (w / v) and stir for 30~60 min. The concentration is preferably 17-18% (w / v), more preferably 17.5% (w / v); The stirring time is preferably 40-50 min, and more preferably 45 min; The water is preferably deionized water.

[0019] In this invention, in step (1), the mass ratio of the wheat hydrolysate to the alkaline protease is 100:0.70~0.80, preferably 100:0.75; the enzyme activity of the alkaline protease is 56000~60000U / g, preferably 57000~59000U / g, more preferably 58000U / g; the temperature for enzymatic hydrolysis using the alkaline protease is 50~60℃, preferably 53~57℃, more preferably 55℃, the hydrolysis time is 2~3h, preferably 2.5h, and the pH for hydrolysis is 8~9, preferably 8.5. The alkaline protease needs to be inactivated at 90°C for 15 minutes after enzymatic hydrolysis.

[0020] In this invention, in step (1), the mass ratio of the hydrolyzed wheat protein to the flavor protease is 100:2~3, preferably 100:2.5; the enzyme activity of the flavor protease is 3500~4500U / g, preferably 3800~4200U / g, more preferably 4000U / g; the temperature for enzymatic hydrolysis using the flavor protease is 45~55℃, preferably 48~52℃, more preferably 50℃, the hydrolysis time is 1~2h, preferably 1.5h, and the hydrolysis pH is 6~7, preferably 6.5. The flavor protease needs to be inactivated at 95°C for 15 minutes after enzymatic hydrolysis.

[0021] In this invention, in step (2), before the enzymatic hydrolysate and calcium chloride are mixed and reacted, the content of solids in the enzymatic hydrolysate is determined; the mass ratio of solids to calcium chloride is 2:0.5~1.5, preferably 2:1; The enzymatic hydrolysate needs to be cooled to 65°C before the solids content is determined; Before the reaction is carried out, water needs to be added to bring the solid-liquid mass ratio to 1:5. The solution used to adjust the pH is a 3 mol / L sodium hydroxide solution; The temperature of the mixing reaction is 65~70℃, preferably 67~68℃, more preferably 67.5℃, and the pH is 8.0~8.5, preferably 8.2~8.3, more preferably 8.3; The mixing reaction time is preferably 2.5 to 3.5 hours, and more preferably 3 hours.

[0022] In this invention, in step (3), before mixing the peptide calcium reaction solution with diatomaceous earth and perlite, the content of solids in the peptide calcium reaction solution is determined. The amount of diatomaceous earth added is 3-7% of the solid weight, preferably 4-6%, and more preferably 5%; the amount of perlite added is 3-7% of the solid weight, preferably 4-6%, and more preferably 5%. The peptide calcium reaction solution is mixed with diatomaceous earth and perlite by stirring; the mixing time is 15-25 min, preferably 18-22 min, and more preferably 20 min.

[0023] In this invention, in step (3), the pore size of the plate and frame filter is 3~10μm, preferably 5~8μm, and more preferably 6.5μm; the pressure of the plate and frame filter is 0.4~0.6MPa, preferably 0.5MPa; The nanofiltration membrane has a molecular weight cutoff of 150-200 Da, preferably 170-180 Da, and more preferably 175 Da; the nanofiltration pressure is 0.8-2.0 MPa, preferably 1.2-1.6 MPa, and more preferably 1.4 MPa; the nanofiltration temperature is 50-65°C, preferably 55-60°C, and more preferably 57.5°C. The concentration is performed by heating; the concentration temperature is 70~85℃, preferably 75~80℃, and more preferably 77.5℃. The concentration is reduced to a solid content of 20-30%, preferably 23-27%, and more preferably 25%.

[0024] In this invention, in step (4), the pressure of the microfiltration is 0.1~0.2MPa, preferably 0.15MPa; the flow rate of the microfiltration is 300~500kg / h, preferably 350~450kg / h, and more preferably 400kg / h; Before microfiltration, the concentrated secondary filtrate needs to be cooled to below 80°C.

[0025] In this invention, in step (5), the drying is spray drying; the inlet air temperature of the drying is 170~180℃, preferably 173~177℃, more preferably 175℃, the outlet air temperature is 70~80℃, preferably 73~77℃, more preferably 75℃, and the processing capacity is 100~500kg / h, preferably 200~400kg / h, more preferably 300kg / h.

[0026] The present invention also provides the preparation method described above to prepare wheat oligopeptide chelated calcium; The pH of the wheat oligopeptide chelated calcium is 6.5-7.5, preferably 6.8-7.2, and more preferably 7.0; the moisture content of the wheat oligopeptide chelated calcium is 5-8%, preferably 6-7%, and more preferably 6.5%.

[0027] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0028] Example 1: A method for preparing wheat oligopeptide chelated calcium

[0029] (1) Mix wheat hydrolysate and deionized water to obtain a 20% (w / v) mixture and stir for 30 min to form a uniform suspension; First stage: heat to 55℃ in a water bath and adjust pH to 8.5, add 0.75% of alkaline protease with an enzyme activity of 58000 U / g according to the amount of wheat hydrolysate, hydrolyze for 2 h, and inactivate the enzyme at 90℃ for 15 min; Second stage: cool to 50℃ and adjust pH to 6.5, add 3% of flavor protease with an enzyme activity of 4000 U / g according to the amount of wheat hydrolysate, hydrolyze for 1 h, and inactivate the enzyme at 95℃ for 15 min; (2) Cool the enzymatic hydrolysate to 65°C, determine the solid content in the enzymatic hydrolysate, add food-grade calcium chloride at a solid-to-calcium chloride mass ratio of 2:1, add water to make the solid-liquid mass ratio 1:5, adjust the pH to 8.3 with 3mol / L sodium hydroxide solution, heat to 65°C, react for 3h to obtain the peptide calcium reaction solution; (3) Determine the solid content in the peptide calcium reaction solution; add 5% diatomaceous earth and 5% perlite according to the solid content, stir and mix for 20 min, and then filter by plate and frame filter with a pore size of 10 μm and a filtration pressure of 0.5 MPa to obtain coarse filtrate; adjust the temperature to 65℃, and use a 200 Da nanofiltration membrane to filter the coarse filtrate a second time with a filtration pressure of 0.9 MPa to remove free divalent calcium ions and obtain secondary filtrate; heat the secondary filtrate at 75℃ to concentrate it to a solid content of 25% to obtain concentrated secondary filtrate; (4) Cool the concentrated secondary filtrate to below 80°C and pass it through microfiltration cartridges with filtration precision of 0.45μm and 0.22μm in sequence, controlling the pressure at 0.2MPa and the flow rate at 400kg / h to obtain a sterile reaction solution; (5) The sterile reaction solution was subjected to an inlet air temperature of 175℃, an outlet air temperature of 75℃, and a processing capacity of 300kg / h to obtain wheat oligopeptide chelated calcium.

[0030] The preparation process of wheat oligopeptide chelated calcium is shown in the following flowchart. Figure 1 As shown in the figure, the peptide calcium powder is wheat oligopeptide chelated calcium.

[0031] Example 2: A method for preparing wheat oligopeptide chelated calcium

[0032] (1) Mix wheat hydrolysate and deionized water to obtain a 15% (w / v) mixture and stir for 40 min to form a uniform suspension; First stage: heat to 50℃ in a water bath and adjust pH to 8, add 0.70% of alkaline protease with an enzyme activity of 60000 U / g according to the amount of wheat hydrolysate, hydrolyze for 2.5 h, and inactivate the enzyme at 90℃ for 15 min; Second stage: cool to 45℃ and adjust pH to 6, add 2% of flavor protease with an enzyme activity of 4500 U / g according to the amount of wheat hydrolysate, hydrolyze for 2 h, and inactivate the enzyme at 95℃ for 15 min; (2) Cool the enzymatic hydrolysate to 65°C, determine the solid content in the enzymatic hydrolysate, add food-grade calcium chloride at a solid-to-calcium chloride mass ratio of 2:0.8, add water to make the solid-liquid mass ratio 1:5, adjust the pH to 8.0 with 3mol / L sodium hydroxide solution, raise the temperature to 70°C, and react for 2.5h to obtain the peptide calcium reaction solution; (3) Determine the solid content in the peptide calcium reaction solution; add 4% diatomaceous earth and 6% perlite according to the solid content, stir and mix for 25 min, and then filter by plate and frame filter with a pore size of 5 μm and a filtration pressure of 0.6 MPa to obtain coarse filtrate; adjust the temperature to 65℃, and use a 150 Da nanofiltration membrane to filter the coarse filtrate a second time with a filtration pressure of 2.0 MPa to remove free divalent calcium ions and obtain secondary filtrate; heat the secondary filtrate at 70℃ to concentrate it to a solid content of 30% to obtain concentrated secondary filtrate; (4) Cool the concentrated secondary filtrate to below 80°C and pass it through microfiltration cartridges with filtration precision of 0.45μm and 0.22μm in sequence, controlling the pressure at 0.1MPa and the flow rate at 300kg / h to obtain a sterile reaction solution; (5) The sterile reaction solution was subjected to an inlet air temperature of 170℃, an outlet air temperature of 70℃, and a processing capacity of 200kg / h to obtain wheat oligopeptide chelated calcium.

[0033] Example 3: A method for preparing wheat oligopeptide chelated calcium

[0034] (1) Mix wheat hydrolysate and deionized water to obtain a mixture with a concentration of 18% (w / v), and stir for 60 min to form a uniform suspension; First stage: heat to 60℃ in a water bath and adjust pH to 9, add 0.80% of alkaline protease with an enzyme activity of 56000 U / g according to the amount of wheat hydrolysate, hydrolyze for 3 h, and inactivate the enzyme at 90℃ for 15 min; Second stage: cool to 55℃ and adjust pH to 7, add 3% of flavor protease with an enzyme activity of 3500 U / g according to the amount of wheat hydrolysate, hydrolyze for 1.5 h, and inactivate the enzyme at 95℃ for 15 min; (2) Cool the enzymatic hydrolysate to 65°C, determine the solid content in the enzymatic hydrolysate, add food-grade calcium chloride at a solid-to-calcium chloride mass ratio of 2:1.5, add water to make the solid-liquid mass ratio 1:5, adjust the pH to 8.5 with 3mol / L sodium hydroxide solution, heat to 65°C, react for 4h to obtain the peptide calcium reaction solution; (3) Determine the solid content in the peptide calcium reaction solution; add 6% diatomaceous earth and 4% perlite according to the solid content, stir and mix for 15 min, and then filter by plate and frame filter with a pore size of 8 μm and a filtration pressure of 0.4 MPa to obtain coarse filtrate; adjust the temperature to 50℃, and use a 180 Da nanofiltration membrane to filter the coarse filtrate a second time with a filtration pressure of 0.8 MPa to remove free divalent calcium ions and obtain secondary filtrate; heat the secondary filtrate at 85℃ to concentrate it to a solid content of 20% to obtain concentrated secondary filtrate; (4) Cool the concentrated secondary filtrate to below 80°C and pass it through microfiltration cartridges with filtration precision of 0.45μm and 0.22μm in sequence, controlling the pressure at 0.15MPa and the flow rate at 500kg / h to obtain a sterile reaction solution; (5) The sterile reaction solution was subjected to an inlet air temperature of 180℃, an outlet air temperature of 80℃, and a processing capacity of 500kg / h to obtain wheat oligopeptide chelated calcium.

[0035] Experiment Example 1: Index Detection

[0036] Zhengzhou Guozhun Testing Technology Co., Ltd. was commissioned to test the wheat oligopeptide chelated calcium prepared in Example 1. The test indicators included: relative percentage of peptides with relative molecular mass between 189 and 10000, moisture content, lead content, total arsenic content, total bacterial count, coliform count, calcium content, zearalenone content, ochratoxin A content, deoxynivalenase content, and aflatoxin B1 content. The test methods and results are as follows: Figures 2-3 As shown; The results show that all the test indicators of the wheat oligopeptide chelated calcium prepared in Example 1 of this invention meet the relevant standard requirements and can be put into the market for sale, thus promoting the marketization and industrial application of plant-derived peptide calcium chelates.

[0037] Comparative Example 1: Preparation of wheat oligopeptide chelated calcium by alcohol precipitation

[0038] (1) Mix wheat hydrolysate and deionized water to obtain a 20% (w / v) mixture and stir for 30 min to form a uniform suspension; First stage: heat to 55℃ in a water bath and adjust pH to 8.5, add 0.75% of alkaline protease with an enzyme activity of 58000 U / g according to the amount of wheat hydrolysate, hydrolyze for 2 h, and inactivate the enzyme at 90℃ for 15 min; Second stage: cool to 50℃ and adjust pH to 6.5, add 3% of flavor protease with an enzyme activity of 4000 U / g according to the amount of wheat hydrolysate, hydrolyze for 1 h, and inactivate the enzyme at 95℃ for 15 min; (2) Cool the enzymatic hydrolysate to 65°C, determine the content of solids in the enzymatic hydrolysate, add food-grade calcium chloride at a solids to calcium chloride mass ratio of 2:1, add water to make the solid-liquid mass ratio 1:5, adjust the pH to 8.3 with 3mol / L sodium hydroxide solution, raise the temperature to 65°C, react for 3h to obtain the peptide calcium reaction solution; (3) After cooling the peptide calcium reaction solution to room temperature, centrifuge at 4000 r / min for 10 min, precipitate the supernatant with 6 times anhydrous ethanol, let it sit overnight, centrifuge at 6000 r / min for 10 min, dry the precipitate, and obtain wheat oligopeptide chelated calcium.

[0039] Experimental Example 2: Detection of Chelate Yield

[0040] The yields of wheat oligopeptide chelates prepared in Example 1 and Comparative Example 1 were calculated using the formula, and the results are shown in Table 1. The formula is: ; In the formula: W is the yield of the chelate, in %; m is the mass of wheat oligopeptide chelated calcium, in g; M is the total amount of peptide (content of solids in the enzymatic hydrolysate) and calcium chloride added during the reaction, in g; Table 1. Chelate yield

[0041] The results showed that the yield of wheat oligopeptide chelated calcium prepared in Example 1 of this application was significantly higher than that in Comparative Example 1. Therefore, the present invention uses nanofiltration membrane filtration instead of alcohol precipitation, which improves the yield of peptide calcium chelate by more than 20% while removing impurities and purifying the product.

[0042] Comparative Example 2: Preparation of wheat oligopeptide chelated calcium by autoclaving

[0043] (1) Mix wheat hydrolysate and deionized water to obtain a 20% (w / v) mixture and stir for 30 min to form a uniform suspension; First stage: heat to 55℃ in a water bath and adjust pH to 8.5, add 0.75% of alkaline protease with an enzyme activity of 58000 U / g according to the amount of wheat hydrolysate, hydrolyze for 2 h, and inactivate the enzyme at 90℃ for 15 min; Second stage: cool to 50℃ and adjust pH to 6.5, add 3% of flavor protease with an enzyme activity of 4000 U / g according to the amount of wheat hydrolysate, hydrolyze for 1 h, and inactivate the enzyme at 95℃ for 15 min; (2) Cool the enzymatic hydrolysate to 65°C, determine the solid content in the enzymatic hydrolysate, add food-grade calcium chloride at a solid-to-calcium chloride mass ratio of 2:1, add water to make the solid-liquid mass ratio 1:5, adjust the pH to 8.3 with 3mol / L sodium hydroxide solution, heat to 65°C, react for 3h to obtain the peptide calcium reaction solution; (3) Determine the solid content in the peptide calcium reaction solution; add 5% diatomaceous earth and 5% perlite according to the solid content, stir and mix for 20 min, and then filter by plate and frame filter with a pore size of 10 μm and a filtration pressure of 0.5 MPa to obtain coarse filtrate; adjust the temperature to 65℃, and use a 200 Da nanofiltration membrane to filter the coarse filtrate a second time with a filtration pressure of 0.9 MPa to remove free divalent calcium ions and obtain secondary filtrate; heat the secondary filtrate at 75℃ to concentrate it to a solid content of 25% to obtain concentrated secondary filtrate; (4) Place the concentrated secondary filtrate into the sterilizer, set it to 121℃ for 20 minutes, and start sterilization after exhausting the cold air. After cooling naturally until the pressure reaches zero, open the lid and take it out. After cooling, a sterile reaction solution is obtained. (5) The sterile reaction solution was subjected to an inlet air temperature of 175℃, an outlet air temperature of 75℃, and a processing capacity of 300kg / h to obtain wheat oligopeptide chelated calcium.

[0044] Experimental Example 3: Detection of Chelation Rate

[0045] The chelation rate of wheat oligopeptide chelated calcium prepared in Example 1 and Comparative Example 2 was calculated using the formula, and the results are shown in Table 2. The formula is:

[0046] In the formula, W is the chelation rate, in %; m1 is the calcium content in wheat oligopeptide chelated calcium (measurement method refers to GB5009.92—2016, Method I: Flame Atomic Absorption Spectrometry), in mg; and m2 is the calcium content in the calcium chloride added during the reaction, in mg. Table 2 Chelation rate

[0047] The results show that the chelation rate of wheat oligopeptide chelated calcium prepared in Example 1 of this application is significantly higher than that of wheat oligopeptide chelated calcium obtained in Comparative Example 1. Therefore, the sterilization method of this application using a double microporous membrane not only meets the sterility requirements, but also preserves the activity of small molecule peptides to the greatest extent through low-temperature sterilization.

[0048] As can be seen from the above embodiments, the present invention provides a wheat oligopeptide chelated calcium and its preparation method. The present invention prepares a wheat peptide calcium chelate with high peptide calcium content that can be applied in actual production through nanofiltration, enzymatic hydrolysis, chelation, diatomaceous earth and perlite combined plate and frame filtration for impurity removal, filter membrane sterilization, and drying.

[0049] 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 method for preparing a wheat oligopeptide chelated calcium, characterized in that, The preparation method comprises the following steps: (1) sequentially using alkaline protease and flavor protease to hydrolyze wheat hydrolyzed protein to obtain an enzyme hydrolysate; (2) mixing the enzyme hydrolysate and calcium chloride to react for 2-4 hours to obtain a peptide calcium reaction solution; (3) mixing the peptide calcium reaction solution, diatomite and perlite, and then performing plate and frame filtration to obtain a crude filtrate; performing nanofiltration and concentration on the crude filtrate to obtain a second filtrate after concentration; (4) sequentially using filter cartridges with filter precision of 0.45 μm and 0.22 μm to microfilter the second filtrate after concentration to obtain a sterile reaction solution; (5) drying the sterile reaction solution to obtain wheat oligopeptide chelated calcium.

2. The production method according to claim 1, characterized by, In step (1), the mass ratio of the wheat hydrolyzed protein and the alkaline protease is 100:0.70-0.80; the enzyme activity of the alkaline protease is 56000-60000 U / g; the temperature for enzyme hydrolysis using the alkaline protease is 50-60 ℃, the time for enzyme hydrolysis is 2-3 hours, and the pH for enzyme hydrolysis is 8-9.

3. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of the wheat hydrolyzed protein and the flavor protease is 100:2-3; the enzyme activity of the flavor protease is 3500-4500 U / g; the temperature for enzyme hydrolysis using the flavor protease is 45-55 ℃, the time for enzyme hydrolysis is 1-2 hours, and the pH for enzyme hydrolysis is 6-7.

4. The method of claim 1, wherein, In step (2), the content of solid in the enzyme hydrolysate is determined before mixing the enzyme hydrolysate and calcium chloride to react; the mass ratio of the solid and calcium chloride is 2:0.5-1.5; the temperature for the mixing reaction is 65-70 ℃, and the pH is 8.0-8.

5.

5. The method of claim 1, wherein, In step (3), the content of solid in the peptide calcium reaction solution is determined before mixing the peptide calcium reaction solution, diatomite and perlite; the addition amount of the diatomite is 3-7% of the mass of the solid; the addition amount of the perlite is 3-7% of the mass of the solid; the mixing of the peptide calcium reaction solution, diatomite and perlite is stirring mixing; and the mixing time is 15-25 minutes.

6. The method of claim 1, wherein, In step (3), the pore size of the plate and frame filtration is 3-10 μm; and the pressure of the plate and frame filtration is 0.4-0.6 MPa.

7. The preparation method according to claim 1, characterized in that, In step (3), the molecular weight cut-off of the nanofiltration is 150-200 Da; the pressure of the nanofiltration is 0.8-2.0 MPa; and the temperature of the nanofiltration is 50-65 ℃; the concentration is heating concentration; and the temperature of the concentration is 70-85 ℃.

8. The method of claim 1, wherein, In step (4), the pressure of the microfiltration is 0.1-0.2 MPa; and the flow rate of the microfiltration is 300-500 kg / h.

9. The method of claim 1, wherein, In step (5), the drying is spray drying; the inlet air temperature of the drying is 170-180 ℃, the outlet air temperature is 70-80 ℃, and the processing capacity is 100-500 kg / h.

10. The wheat oligopeptide chelated calcium prepared by the preparation method of any one of claims 1-9.

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