A method for preparing potassium phytate from corn soaking water

Abstract

The present invention discloses a method for preparing potassium phytate from corn soaking water, first corn soaking water is subjected to a first filtration through a nanofiltration membrane with a molecular weight cut-off of 1500 2000Da, and permeate is collected; the permeate is subjected to a second filtration through a nanofiltration membrane with a molecular weight cut-off of 500 1000Da, to obtain a potassium phytate solution. The present invention utilizes potassium ions and phytic acid radicals originally present in corn soaking water, and by using a specific nanofiltration membrane, a potassium phytate product is filtered and obtained. Compared to prior art, phytic acid radicals are adsorbed using ion exchange resins, and then potassium phytate is prepared by eluting with potassium chloride solution. The present invention does not use resin, and does not need to add potassium ions, and has the advantages of simple process, low production cost and environmental friendliness.

Description

Technical Field

[0001] The invention relates to the technical field of corn soaking water reuse, and in particular to a method for preparing potassium phytate from corn soaking water. Background Art

[0002] Phytic acid, also known as inositol hexaphosphate, is widely present in various plant tissues, such as corn, rice bran, and wheat bran. It is the primary storage form of phosphorus in plants. Phytates, produced by combining phytic acid with metal bases, have a wide range of applications in food, medicine, and cosmetics. For example, potassium phytate, when added to skin creams, can effectively prevent and treat acne, improve blood circulation in the skin, and promote hair and nail growth.

[0003] Corn starch production often utilizes wet milling, and corn steepwater is a major wastewater source. Typically, processing one ton of corn generates approximately 0.8 tons of corn steepwater. Corn steepwater contains a large number of valuable substances, including protein, phytic acid, lactic acid, and lipopolysaccharides, with the phytic acid content being approximately 1-2%. Therefore, recovering phytic acid from corn steepwater and producing a variety of phytates tailored to market needs can achieve high-value utilization of corn steepwater, generating significant economic and social benefits.

[0004] In the prior art, the method for preparing potassium phytate from corn soaking water is mostly carried out using anion exchange resin method, such as document CN115819450A, which records that corn soaking water is first subjected to anion resin adsorption, then the anion resin is eluted with dilute hydrochloric acid, and the eluent obtains phytic acid solution through decolouring, and the phytic acid solution is then adsorbed by anion resin, and after adsorption, potassium chloride solution is eluted to obtain potassium phytate solution (the effect of this step is to introduce potassium ions and phytic acid radicals to obtain potassium phytate); the potassium phytate solution is subjected to membrane filtration, and the obtained trapped liquid is a crude potassium phytate solution. The shortcomings of the above-mentioned prior art are: 1. multiple resin adsorption and analysis are adopted, and resin cost is higher, resulting in huge investment in the method, high operating cost, complex process, and a large amount of wastewater is produced; 2. it is necessary to externally introduce potassium ions (potassium chloride eluent) to prepare potassium phytate, resulting in additional input, and poor economy.

[0005] In view of the problems existing in the prior art, it is urgent to establish a process for preparing potassium phytate with low production cost, simple process and environmental friendliness. Summary of the Invention

[0006] In view of this, the object of the present invention is to provide a method for preparing potassium phytate from corn soaking water, which is used to overcome the problems of the prior art of using ion exchange resin to adsorb phytate and then eluting it with potassium chloride solution to prepare potassium phytate, such as huge investment, high operating costs, complex process, and generation of a large amount of wastewater.

[0007] In order to achieve the above object, the present invention provides a method for preparing potassium phytate from corn soaking water, comprising the following steps:

[0008] The corn soaking water is first filtered through a nanofiltration membrane with a molecular weight cut-off of 1500-2000 Da to obtain a retentate 1 and a permeate 1;

[0009] The permeate 1 is filtered through a nanofiltration membrane with a molecular weight cut-off of 500-1000 Da to obtain a potassium phytate solution and a permeate 2.

[0010] The present invention provides a method for preparing potassium phytate from corn soaking water. First, the corn soaking water is filtered through a nanofiltration membrane with a molecular weight cutoff of 1500-2000Da, and the permeate is collected; the permeate is filtered through a nanofiltration membrane with a molecular weight cutoff of 500-1000Da to obtain a potassium phytate solution. Corn soaking water itself contains about 2% phytic acid and about 1% potassium. The molecular weight of potassium phytate is 888Da. By setting a suitable nanofiltration membrane, potassium phytate can be directly separated from the corn soaking water. Compared with the prior art, which uses ion exchange resin to adsorb phytic acid and then elutes it with potassium chloride solution to prepare potassium phytate, the present invention does not use resin, does not require an elution process, and does not require the addition of potassium ions. The equipment investment is small, the intermediate product can be further processed to prepare protein products, does not generate wastewater, and has the advantages of simple process, low production cost and environmental friendliness.

[0011] In addition, the potassium phytate prepared by the present invention can also be used to prepare potassium dihydrogen phosphate. The phosphorus and potassium in the potassium dihydrogen phosphate prepared from the raw materials are both derived from the plant (corn) itself, and have good plant homology. The prepared potassium dihydrogen phosphate has the advantage of being easily absorbed by crops. DETAILED DESCRIPTION

[0012] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0013] The present invention provides a method for preparing potassium phytate from corn soaking water, comprising the following steps:

[0014] The corn soaking water is first filtered through a nanofiltration membrane with a molecular weight cut-off of 1500-2000 Da to obtain a retentate 1 and a permeate 1;

[0015] The permeate 1 is filtered through a nanofiltration membrane with a molecular weight cut-off of 500-1000 Da to obtain a potassium phytate solution and a permeate 2.

[0016] The present invention first performs a first filtration on corn soaked water through a nanofiltration membrane with a molecular weight cutoff of 1500-2000Da to obtain a retentate 1 and a permeate 1. In the present invention, the molecular weight cutoff of the nanofiltration membrane used in the first filtration is preferably 1500-2000Da, and the filtration pressure of the first filtration is preferably 3-4MPa; the present invention has no special requirements on the source and performance of the nanofiltration membrane, and a commercially available product can be used, for example, a nanofiltration membrane with a transmittance of less than 70% can be used. The present invention also includes controlling the progress of the first filtration, and when the refractive index of the retentate 1 reaches 24-26, the first filtration process can be stopped. Potassium phytate has a molecular weight of 888Da and can enter the permeate through the nanofiltration membrane in the first filtration, thereby achieving preliminary separation of potassium phytate.

[0017] After obtaining the permeate 1, the present invention performs a second filtration on the permeate 1 through a nanofiltration membrane with a molecular weight cutoff of 500-1000Da to obtain a potassium phytate solution and a permeate 2. In the present invention, the molecular weight cutoff of the nanofiltration membrane used for the second filtration is preferably 500-1000Da, and the filtration pressure of the second filtration is preferably 3-4MPa; the present invention has no special requirements on the source and performance of the nanofiltration membrane, and a commercially available product can be used, such as a nanofiltration membrane with a retention rate of ≥95%. The present invention also includes controlling the progress of the second filtration, and when the refractive index of the potassium phytate solution reaches 24-26, the second filtration process can be stopped; the concentration of the obtained potassium phytate solution is preferably 20-30wt%. The permeate of the first filtration contains potassium phytate and a portion of small molecule proteins. The small molecule proteins can be removed by the second filtration, and potassium phytate is retained in the retentate. Through the second filtration, further separation of potassium phytate is achieved to obtain a potassium phytate solution.

[0018] It should be understood that the two main components contained in corn steep water are phytic acid (potassium phytate) and crude protein (zein). Therefore, the main concept of the present invention is that the molecular weight of potassium phytate is 888Da. If a nanofiltration membrane is used to intercept the macromolecular protein and remove the small molecular protein, leaving the material with a molecular weight of around 888Da (potassium phytate and some protein) in the middle part, potassium phytate can be separated from other substances to obtain a higher content of potassium phytate. Table 1 below shows the molecular weight distribution of protein in corn steep water.

[0019] Table 1 Molecular weight distribution of protein in corn soaking water

[0020] Molecular weight / Da ＞10000 10000-5000 5000-3000 3000-2000 2000-1000 1000-500 500-180 ＜180 Dry basis content / % 2.20 5.72 7.05 5.47 9.97 11.96 38.44 19.19

[0021] The present invention further includes, before the first filtration of the corn-soaked water through a nanofiltration membrane with a molecular weight cutoff of 1500-2000Da, pre-filtering the corn-soaked water through a ceramic membrane with a molecular weight cutoff of 10,000-20,000Da to obtain a retentate 2 and the pre-filtered corn-soaked water. In the present invention, the molecular weight cutoff of the ceramic membrane is preferably 10,000-20,000Da; the filtration pressure of the pre-filtration is preferably 3-4MPa; the present invention does not specifically limit the source and performance of the ceramic membrane; commercially available products can be used. The purpose of using a ceramic membrane for pre-filtration in the present invention is to initially remove macromolecular substances in the corn-soaked water, improve the efficiency of subsequent nanofiltration membrane filtration, reduce filtration pressure, and increase the service life of the nanofiltration membrane.

[0022] Before pre-filtering the corn steep water through a ceramic membrane with a molecular weight cutoff of 10,000-20,000 Da, the present invention further includes pre-treating the corn steep water to remove suspended impurities. In the present invention, preferably, the pre-treatment involves separation by a hydrocyclone, membrane filtration, or static sedimentation to remove suspended impurities. When using a hydrocyclone, the ratio of the separator body diameter to the overflow pipe diameter is preferably (2-3):1, and the ratio of the underflow to the feed volume is preferably 1:(20-30). When using membrane filtration, microfiltration membranes are preferably used, and the membrane pore size is preferably 0.5-1 μm. The present invention does not specifically limit the operating pressure of membrane filtration; commonly used operating parameters in the art can be used. When using static sedimentation, the static time is preferably 1-2 hours. The purpose of the pre-treatment in the present invention is to remove suspended impurities, such as starch and corn husks, from the corn steep water. Removal of these impurities facilitates subsequent nanofiltration membrane filtration. The removed impurities can also be returned to the starch factory for further production of other valuable products. The present invention also includes further processing / utilization of by-products in the production process, preferably including: mixing the retained liquid 1 and the retained liquid 2 and concentrating them by evaporation to a concentrated liquid with a solid content of 30-50wt%, and spray-drying the concentrated liquid to produce a protein powder product; further including: evaporating and concentrating the permeate 2 to obtain a small peptide liquid fertilizer with a solid content of 30-50wt%; and / or; further including: spray-drying the small peptide liquid fertilizer to produce a small molecule protein powder product. In the present invention, the conditions for the evaporation and concentration are preferably: a temperature of 60-100°C and a pressure of -0.08MPa to -0.1MPa; the conditions for the spray drying are preferably: an inlet air temperature of 150-200°C and an outlet air temperature of 90-100°C.

[0023] After obtaining potassium phytate solution, the present invention also includes applying the potassium phytate to prepare potassium dihydrogen phosphate;Specifically including:Add solid potassium hydroxide to the potassium phytate solution, adjust pH to 4.5-5.5, hydrolyze 5-15h under 150-200 DEG C of conditions to obtain hydrolyzed solution;The hydrolyzed solution is filtered to remove hydrolysis residue (calcium magnesium phosphate) to obtain a filtrate;Phosphoric acid is added to the filtrate to adjust pH to 3.0-3.5, with a cooling rate of 2-10 DEG C / h, under stirring at 100-300rpm, drop the temperature and crystallize, stop crystallization when the temperature is reduced to 30-45 DEG C, and filter to obtain potassium dihydrogen phosphate crystals and crystallization mother liquor. The present invention is not particularly limited to filtering to remove hydrolysis residue and filtering to obtain the filtration process in potassium dihydrogen phosphate crystals, such as 3-10um filter paper can be used for filtration. The obtained crystallization mother liquor of the present invention is a mixture of potassium dihydrogen phosphate and inositol, and the two can be separated according to the difference in solubility of the two in water.

[0024] It should be noted that in the process of producing potassium phytate by the mode of anion resin adsorption in the prior art, since potassium belongs to cation, the resin only adsorbs phytate, not potassium ions; After adsorption is completed, it is necessary to use potassium salt (such as potassium chloride) to elute the resin, adsorb chloride ions onto the resin, replace phytate, so as to obtain potassium phytate, therefore, the potassium obtained in this method is actually derived from the added potassium chloride, rather than the plant homology potassium present in corn soaking water itself. And the potassium phytate obtained by nanofiltration membrane filtration (without adding any substance) in the present invention all comes from corn soaking water, belongs to the composition of plant homology, and the potassium dihydrogen phosphate prepared by potassium phytate also possesses plant homology, i.e., possesses good crop absorptivity.

[0025] In order to better illustrate the technical solution of the present invention, the present invention also provides the following specific examples. It should be understood that the raw materials used in the following examples are all commercially available raw materials unless otherwise specified. In particular, the main components of 3 batches of corn steep water are listed in Table 2 below, and the batch corn steep water is provided by Zhucheng Haotian Pharmaceutical Co., Ltd.

[0026] Table 2 Corn soaking water for batches 1-3

[0027] batch protein Phytic acid lactic acid carbohydrate starch residue Inorganic salts water 1 5％ 1.5％ 1.5％ 0.02％ 1％ 0.2％ 88％ 2 5.2％ 1.4％ 1.4％ 0.01％ 0.8％ 0.1％ 89％ 3 4.8％ 1.6％ 1.5％ 0.01％ 0.8％ 0.1％ 90％

[0028] Example 1

[0029] S1. Take 300L of corn soaked water from batch 1 and filter through a nanofiltration membrane with a molecular weight cutoff of 1800Da at a filtration pressure of 3MPa to obtain 140L of retentate 1 and 160L of permeate 1;

[0030] S2. The 160 L permeate 1 was filtered for a second time through a nanofiltration membrane with a molecular weight cutoff of 700 Da at a filtration pressure of 3 MPa. When the refractive index of the retentate reached 25, 9.6 L of potassium phytate solution and 150.4 L of permeate 2 were obtained.

[0031] Example 2

[0032] S1. Take 300L of corn soaked water from batch 2 and filter through a nanofiltration membrane with a molecular weight cutoff of 1500Da at a filtration pressure of 3.5MPa to obtain 150L of retentate 1 and 150L of permeate 1;

[0033] S2. The 150 L permeate 1 was filtered for a second time through a nanofiltration membrane with a molecular weight cutoff of 500 Da at a filtration pressure of 3.5 MPa. When the refractive index of the retentate reached 26, 9 L of potassium phytate solution and 141 L of permeate 2 were obtained.

[0034] Example 3

[0035] S1. Take 300L of corn soaked water from batch 3 and filter through a nanofiltration membrane with a molecular weight cutoff of 2000Da at a filtration pressure of 4MPa to obtain 130L of retentate 1 and 170L of permeate 1;

[0036] S2. The 170 L permeate 1 was filtered for a second time through a nanofiltration membrane with a molecular weight cutoff of 1000 Da at a filtration pressure of 4 MPa. When the refractive index of the retentate reached 24, 10.2 L of potassium phytate solution and 159.8 L of permeate 2 were obtained.

[0037] Example 4

[0038] S1. Take 300L of corn soaked water from batch 1 and pre-filter through a ceramic membrane with a molecular weight cutoff of 15,000Da at a filtration pressure of 3.5MPa to obtain 20L of retentate 2 and 280L of pre-filtered corn soaked water;

[0039] S2. The 280L pre-filtered corn soaked water was first filtered at a filtration pressure of 3MPa through a nanofiltration membrane with a molecular weight cutoff of 1800Da to obtain 140L of retentate 1 and 140L of permeate 1;

[0040] S3. The 140 L permeate 1 was filtered for a second time through a nanofiltration membrane with a molecular weight cutoff of 700 Da at a filtration pressure of 3 MPa. When the refractive index of the retentate reached 25, 8.4 L of potassium phytate solution and 131.6 L of permeate 2 were obtained.

[0041] Example 5

[0042] S1. Take 300L of corn soaked water from batch 2 and pre-filter through a ceramic membrane with a molecular weight cutoff of 10,000Da at a filtration pressure of 3MPa to obtain 22L of retentate 2 and 278L of pre-filtered corn soaked water;

[0043] S2. The 278L pre-filtered corn soaked water was first filtered at a filtration pressure of 3.5MPa through a nanofiltration membrane with a molecular weight cutoff of 1500Da to obtain 150L of retentate 1 and 128L of permeate 1;

[0044] S3. The 128 L permeate 1 was filtered for a second time through a nanofiltration membrane with a molecular weight cutoff of 500 Da at a filtration pressure of 4 MPa. When the refractive index of the retentate reached 26, 7.68 L of potassium phytate solution and 120.3 L of permeate 2 were obtained.

[0045] Example 6

[0046] S1. Take 300L of corn soaked water from batch 3 and pre-filter through a ceramic membrane with a molecular weight cutoff of 20,000Da at a filtration pressure of 4MPa to obtain 18L of the retentate 2 and 282L of pre-filtered corn soaked water;

[0047] S2. The 282L pre-filtered corn soaked water was first filtered at a filtration pressure of 4MPa through a nanofiltration membrane with a molecular weight cutoff of 2000Da to obtain 130L of retentate 1 and 152L of permeate 1;

[0048] S3. The 152 L permeate 1 was filtered for a second time through a nanofiltration membrane with a molecular weight cutoff of 1000 Da at a filtration pressure of 3.5 MPa. When the refractive index of the retentate reached 24, 9.1 L of potassium phytate solution and 142.9 L of permeate 2 were obtained.

[0049] Example 7

[0050] S1. Take 300L of corn soaked water from batch 1 and feed it to the hydrocyclone. The separator body diameter and the overflow pipe diameter ratio were 2.5:1, the bottom flow rate and the feed rate ratio was 1:25, and 290L of clear liquid and 10kg of precipitate were obtained.

[0051] S2. The 290L supernatant was pre-filtered at a filtration pressure of 3.5MPa through a ceramic membrane with a molecular weight cutoff of 15000Da to obtain 20L of the retentate 2 and 270L of pre-filtered corn soaked water;

[0052] S3. The 270L pre-filtered corn soaked water was first filtered at a filtration pressure of 4MPa through a nanofiltration membrane with a molecular weight cutoff of 1800Da to obtain 120L of retentate 1 and 150L of permeate 1;

[0053] S4. The 150 L permeate 1 was filtered for a second time through a nanofiltration membrane with a molecular weight cutoff of 700 Da at a filtration pressure of 3 MPa. When the refractive index of the retentate reached 25, 9 L of potassium phytate solution and 141 L of permeate 2 were obtained.

[0054] Example 8

[0055] S1. Take 300L of corn soaking water from batch 2 and filter through a 0.8um microfiltration membrane to obtain 290L of clear liquid and 10kg of precipitate;

[0056] S2. The 290L supernatant was pre-filtered at a filtration pressure of 4MPa through a ceramic membrane with a molecular weight cutoff of 10,000Da to obtain 18L of the retentate 2 and 268L of pre-filtered corn soaked water;

[0057] S3. The 268L pre-filtered corn soaked water was first filtered at a filtration pressure of 3.5MPa through a nanofiltration membrane with a molecular weight cutoff of 1500Da to obtain 120L of retentate 1 and 148L of permeate 1;

[0058] S4. The 148 L permeate 1 was filtered for a second time through a nanofiltration membrane with a molecular weight cutoff of 500 Da at a filtration pressure of 3 MPa. When the refractive index of the retentate reached 26, 8.88 L of potassium phytate solution and 139.1 L of permeate 2 were obtained.

[0059] Example 9

[0060] S1. Take 300L of corn soaking water from batch 3 and place it in a settling tank. After standing for 1h, 8kg of sediment was discharged from the bottom of the tank to obtain 292L of clear liquid;

[0061] S2. The 292L supernatant was pre-filtered at a filtration pressure of 3MPa through a ceramic membrane with a molecular weight cutoff of 20,000Da to obtain 17L of the retentate 2 and 269L of pre-filtered corn soaked water;

[0062] S3. The 269L pre-filtered corn soaked water was first filtered at a filtration pressure of 3.5MPa through a nanofiltration membrane with a molecular weight cutoff of 2000Da to obtain 118L of retentate 1 and 151L of permeate 1;

[0063] S4. The 151 L permeate 1 was filtered for a second time through a nanofiltration membrane with a molecular weight cutoff of 1000 Da at a filtration pressure of 4 MPa. When the refractive index of the retentate reached 24, 9.06 L of potassium phytate solution and 141.9 L of permeate 2 were obtained.

[0064] Example 10

[0065] 140L of retained solution 1 and 20L of retained solution 2 in Example 4 were mixed and concentrated by evaporation at 80°C under a pressure of -0.1 MPa to obtain 57.4L of a concentrated solution with a solid content of 40wt%. The concentrated solution was spray-dried (inlet air temperature of 150°C, outlet air temperature of 90°C) to prepare 25.0kg of a protein powder product.

[0066] Example 11

[0067] The 141L permeate 2 among Example 2 was concentrated by evaporation at 60 ℃ and pressure-0.1Mpa condition to obtain 34.2L of small peptide liquid fertilizer with a solid content of 50wt%; and then spray-dried (inlet air temperature 200 ℃, outlet air temperature 100 ℃) to make 17.4kg of small molecule protein powder product.

[0068] Example 12

[0069] Take 2000 ml of the potassium phytate solution in Example 1, add 25 g of solid potassium hydroxide, adjust the pH to 5, and hydrolyze at 160 ° C for 10 h to obtain 1980 ml of hydrolyzate; the hydrolyzate is filtered to remove 40 g of hydrolysis residue (calcium magnesium phosphate) to obtain 1900 ml of filtrate; phosphoric acid is added to the filtrate to adjust the pH to 3.5, and the mixture is cooled and crystallized at a cooling rate of 5 ° C / h under stirring at 200 rpm. Crystallization stops when the temperature drops to 40 ° C, and the mixture is filtered and dried to obtain 208 g of potassium dihydrogen phosphate crystals.

[0070] Example 13

[0071] Take 2000 ml of the potassium phytate solution in Example 1, add 23.2 g of solid potassium hydroxide, adjust the pH to 4.5, and hydrolyze at 150 ° C for 5 h to obtain 1990 ml of hydrolyzate; the hydrolyzate is filtered to remove 35 g of hydrolysis residue (calcium magnesium phosphate) to obtain 1915 ml of filtrate; phosphoric acid is added to the filtrate to adjust the pH to 3.0, and the mixture is cooled and crystallized at a cooling rate of 2 ° C / h under stirring at 100 rpm. The crystallization stops when the temperature drops to 30 ° C, and the mixture is filtered and dried to obtain 210 potassium dihydrogen phosphate crystals.

[0072] Example 14

[0073] Take 2000 ml of the potassium phytate solution in Example 1, add 26 g of solid potassium hydroxide, adjust the pH to 5.5, and hydrolyze at 200 ° C for 15 h to obtain 1900 ml of hydrolyzate; the hydrolyzate is filtered to remove 50 g of hydrolysis residue (calcium magnesium phosphate) to obtain 1820 ml of filtrate; phosphoric acid is added to the filtrate to adjust the pH to 3.2, and the mixture is cooled and crystallized at a cooling rate of 10 ° C / h under stirring at 300 rpm. Crystallization stops when the temperature drops to 45 ° C, and the mixture is filtered and dried to obtain 205 potassium dihydrogen phosphate crystals.

[0074] Comparative Example 1

[0075] The 1800Da nanofiltration membrane used in the first filtration in Example 1 was replaced with a 2800Da nanofiltration membrane, while other conditions remained unchanged, and finally 9.5L of potassium phytate solution was obtained.

[0076] Comparative Example 2

[0077] The 500Da nanofiltration membrane used in the second filtration in Example 2 was replaced with a 300Da nanofiltration membrane, and other conditions remained unchanged, ultimately obtaining 10.5 L of potassium phytate solution.

[0078] Table 3 below lists the concentrations and protein contents of the potassium phytate solutions obtained in some of the above examples and comparative examples.

[0079] Table 3 Concentration and protein content of potassium phytate solutions obtained in some examples and comparative examples

[0080]

[0081]

[0082] Test Case

[0083] A. Detection of Phytic Acid

[0084] Accurately measure 1 mL of sample (dilute or increase appropriately when the content is high or low), transfer it to a conical flask, add 30-50 mL of purified water, adjust the pH to 1.9-2.2 with 0.2 mol / L nitric acid solution, add 2-3 drops of xylenol orange indicator, shake well, and quickly titrate with 0.02 mol / L thorium nitrate standard solution. The end point is when the color changes from yellow to pink and does not fade for 30 seconds. Record the volume of thorium nitrate titrant consumed.

[0085] Calculation formula:

[0086]

[0087] Note: C1: concentration of thorium nitrate standard solution (mol / L);

[0088] V1: volume of thorium nitrate titrant consumed during titration (mL);

[0089] V2: added sample volume mL;

[0090] 0.33-Milligram molar ratio of phytic acid to thorium nitrate complex.

[0091] B. Protein Detection

[0092] The protein detection refers to the national standard GB / T6432-2018 Determination of crude protein in feed (Kjeldahl method).

[0093] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing potassium phytate from corn soaking water, characterized in that: The following steps are involved: The corn steep water was pre-filtered through a ceramic membrane with a molecular weight cut-off of 10,000-20,000 Da to obtain a retentate 2 and pre-filtered corn steep water; The pre-filtered corn soaking water is first filtered through a nanofiltration membrane with a molecular weight cutoff of 1500-2000Da, and the filtration pressure of the first filtration is 3-4Mpa to obtain a retentate 1 and a permeate 1; The permeate 1 is subjected to a second filtration through a nanofiltration membrane with a molecular weight cutoff of 500-1000 Da. The filtration pressure of the second filtration is 3-4 MPa. The second filtration is stopped when the refractive index of the potassium phytate solution reaches 24-26 to obtain a potassium phytate solution and a permeate 2.

2. The method according to claim 1, characterized in that The filtration pressure of the pre-filtration is 3-4 MPa.

3. The method according to claim 1 or 2, characterized in that Before pre-filtering the corn soaking water through a ceramic membrane with a molecular weight cutoff of 10,000-20,000 Da, the method further includes: pre-treating the corn soaking water to remove suspended impurities therein.

4. The method according to claim 1, wherein Also includes: The retentate 1 and the retentate 2 are mixed and concentrated by evaporation to a concentrate with a solid content of 30-50 wt %, and the concentrate is spray-dried to prepare a protein powder product.

5. The method according to claim 1, characterized in that Also includes: The permeate 2 is evaporated and concentrated to obtain a small peptide liquid fertilizer with a solid content of 30-50wt%; and / or, The method further comprises the following steps: spray-drying the small peptide liquid fertilizer to prepare a small molecule protein powder product.

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