CN115644456A - Water-soluble heme-polypeptide composite nutrient iron fortifier and preparation method thereof - Google Patents

Abstract

The invention discloses a water-soluble heme-polypeptide compound nutritional iron fortifier and a preparation method thereof, belonging to the field of food processing. In the present invention, porcine hemoglobin is subjected to acid hydrolysis, pH adjustment, washing, drying and precipitation to obtain porcine hemoglobin powder, and the porcine hemoglobin powder is dissolved in sodium carbonate solution and mixed with whey protein solution, and the pH of the mixed solution is adjusted to neutral , centrifuged or filtered to remove a small amount of insoluble part, freeze-dried or spray-dried to make a powder to obtain a water-soluble heme-polypeptide complex nutritional iron fortifier. The fortifier can not only supplement the iron needed by the human body well, but also whey protein has physiological functions such as regulating immunity and regulating lactose absorption, and the water-soluble heme-polypeptide complex nutrient iron obtained by combining heme iron with whey protein Fortifiers have high nutritional value and unique functional properties.

Description

A water-soluble heme-polypeptide compound nutritional iron fortifier and its preparation method

technical field

The invention belongs to the field of food processing, and in particular relates to a water-soluble heme-polypeptide composite nutritional iron fortifier and a preparation method thereof.

Background technique

my country is rich in livestock and poultry blood resources. Taking pigs as an example, the annual slaughtering volume in the country is about 640 million heads, and about 3 million tons of pig blood are produced. The dry matter of livestock and poultry blood is mainly protein, which accounts for 18.9% of the total blood mass. It is an ideal protein resource. At present, it is mainly processed into blood meal, protein powder, etc., which are used as animal feed, and a considerable part of blood is used as Direct discharge of waste not only wastes resources but also pollutes the environment.

Blood is composed of two parts: plasma (65%) and blood cells (35%). Blood cells include red blood cells, white blood cells and platelets, with red blood cells as the main. Porcine hemoglobin is the main component of porcine red blood cells, accounting for about 95% of the total protein of red blood cells and 67% of the total protein of whole blood. Porcine hemoglobin is a tetramer with a certain spatial conformation composed of four subunits, including two α subunits and two β subunits, each subunit is composed of a peptide chain and a heme molecule, and the peptide chain Coiled with each other and folded into a spherical shape, the heme molecules are wrapped inside. Porcine hemoglobin is not only high-quality protein, but also an important source of iron nutrition.

Iron is an essential trace element for the human body, and iron deficiency is a worldwide problem. Dietary iron is divided into heme iron and non-heme iron. Heme iron has high bioavailability and is easier to absorb than non-organic iron in plants or iron salts commonly used in food fortification. Traditional iron supplements such as ferrous sulfate, ferrous gluconate, ferrous fumarate, etc. are all inorganic iron or plant iron. 5% to 8%), large side effects (like symptoms such as nausea, flatulence, digestive organ disorders, diarrhea, and constipation), and have a special metal rusty taste, making it difficult to eat for a long time. Heme iron is a kind of biological iron. The content of iron in 100g pig blood is as high as 40mg or more. Heme iron is absorbed through the heme transporter, which is mainly expressed in the brush-shaped cells of duodenal enterocytes and liver cells. in the boundary membrane. In contrast, non-heme iron is transported into the body through nonselective iron channels that are easily affected by other metal ions. Therefore, the absorption of heme iron by humans is more complete than that of non-heme iron, and the bioavailability is high (absorption rate reaches 15% to 25%).

The average effective absorption rate of heme iron is 25%, and it can reach 40% when iron is deficient. In addition, the absorption of heme iron is also affected by food factors. Heme iron has been widely used as an iron fortifier in Japan, the United States and other countries. The most common heme iron-fortified foods in the Japanese market are low-calorie candies and low-calorie biscuits. There are mainly three types of heme iron fortifiers on the Chinese market: iron supplement tablets, iron supplement gummy, and iron supplement capsules. Heme iron tablets, biscuits, etc. are more convenient to carry, but the human body absorption rate of heme iron in a water-insoluble form is relatively low, while the absorption rate of heme iron in a dissolved state can be increased by 5 times. Since free heme iron is insoluble in water, most of the heme iron nutritional fortifiers on the market appear in solid form. At present, domestic and foreign researchers have explored ways and methods of increasing iron content in plant foods from many aspects, and have made great progress and efficacy, but there are few studies on ways and methods of increasing iron content in animal foods.

The water-soluble heme-polypeptide composite nutritional iron fortifier of the present invention can be added to any type of food as required, directly ingested as a solution state food or dissolved in the digestive juice after ingesting a solid food into the digestive tract, and the bioavailability Significantly higher than insoluble heme iron. In addition, in addition to supplementing iron, it can also supplement the eight essential amino acids needed by the human body. In addition, whey protein can also supplement protein, which is an ideal nutritional enhancer.

Contents of the invention

In the present invention, porcine hemoglobin or fresh porcine red blood cells undergo acid hydrolysis, so that heme, hydrophobic amino acids and small peptides enter the precipitate, then adjust the pH value to neutral, wash the precipitate with water, and clean acid, alkali and various water soluble substances. Sexual components, to obtain a mixture of heme, oligopeptides, and amino acids, this mixture is insoluble in water but soluble in sodium bicarbonate solution. The mixture is dried and dissolved in sodium carbonate solution, or directly added with sodium bicarbonate until dissolved, then mixed with whey protein aqueous solution, adjusted to neutral pH, and dried to obtain a water-soluble heme iron-polypeptide complex fortifier.

The object of the present invention is to provide a water-soluble heme-polypeptide complex nutrient iron fortifier and a preparation method thereof. The method of the present invention can obtain the heme iron nutritional enhancer that can be directly dissolved in water, which can make iron supplementation more convenient and efficient for iron-deficient people, and can also supplement polypeptides and proteins at the same time.

The object of the present invention is achieved through the following technical solutions:

A preparation method of a water-soluble heme-polypeptide composite nutrient iron fortifier, comprising the following steps: porcine hemoglobin is hydrolyzed with acid to obtain porcine heme, the porcine heme solution and whey protein solution are mixed, and the pH of the mixed solution is adjusted to Neutral, centrifuge or filter to remove the insoluble part, freeze-dry or spray-dry to make a powder to obtain a water-soluble heme-polypeptide complex nutrient iron fortifier powder.

The porcine heme solution is preferably obtained by dissolving porcine heme powder with sodium carbonate solution. The concentration of the sodium carbonate solution is preferably 0.01-0.1%. The method for preparing porcine heme by acid hydrolysis comprises the following steps: dissolving porcine hemoglobin in water, adjusting its pH to 1.5-2.5, high-temperature hydrolysis at 80-90°C for 6-12 hours, then adjusting the pH to 6.0-7.5, centrifuging, The precipitate was washed and then freeze-dried to obtain porcine heme powder.

The concentration of the porcine heme solution is preferably 0.15-0.75% (w/v).

The concentration of the whey protein solution is preferably 1.5-6.0% (w/v).

In the mixed solution, the concentration of whey protein is preferably 0.5-2.0% (w/v), and the concentration of porcine hemoglobin is preferably 0.1-0.5% (w/v).

The above pH adjustment is preferably adjusted using HCl solution and NaOH solution.

In the preparation method of the water-soluble heme-polypeptide composite nutritional iron fortifier, whey protein is added to form a nanocomposite with heme, and the heme can exist stably after being adjusted to neutral. It can be dissolved in water after being sprayed or freeze-dried, so as to prepare a water-soluble heme-polypeptide complex nutrient iron fortifier.

A water-soluble heme-polypeptide compound nutritional iron fortifier is obtained through the above preparation method. The fortifier can not only well supplement the iron elements needed by the human body, but also whey protein has physiological functions such as regulating immunity and regulating lactose absorption. Whey protein is known as the active protein in milk, which plays an important role in the metabolism, nutrition and health of the human body. Heme iron combined with whey protein has high nutritional value and unique functional properties.

The present invention has the following advantages:

(1) The bioavailability of heme iron is high, which can solve the problem of iron deficiency in the body;

(2) It can be added to any form of food as a high-efficiency iron supplement food;

(3) Easily soluble in water, easy to apply, and high in bioavailability;

(4) It can be used as an iron fortifier, and can also be used as a peptide/amino acid fortifier;

(5) Porcine hemoglobin, an important raw material for production, is cheap and easy to get, with abundant sources;

(6) The product has good stability and low hygroscopicity in high humidity environment;

(7) The production is simple and easy, and the implementability is strong.

Description of drawings

Figure 1 is the degree of hydrolysis of porcine hemoglobin at different times.

Fig. 2 is the SDS-PAGE picture of the hydrolyzed supernatant of porcine hemoglobin.

Figure 3 is the UV-Vis spectrum of the hydrolyzed precipitate of porcine hemoglobin.

Figure 4 is a chromatogram of heme. Among them (A) heme standard; (B) hydrolyzed 6h precipitated heme; (C) hydrolyzed 12h precipitated heme.

Figure 5 is a standard curve for hemoglobin quantification.

Figure 6 is the average particle size of whey protein-porcine heme complexes with different heme concentrations. In the figure, the concentration of whey protein is 1%, and the concentration of porcine heme powder is 0%, 0.1%, 0.3%, and 0.5% in sequence.

Figure 7 is the appearance characteristics of whey protein-heme nanocomposites with different porcine heme powder concentrations, (A) aqueous solution, (B) spray-dried. In the figure, the concentration of whey protein is 1%, and the concentration of porcine heme powder is 0%, 0.1%, and 0.3% in sequence.

Figure 8 is a microscopic view of whey protein-heme nanocomposites with different porcine heme powder concentrations. In the figure, the concentration of whey protein is 1%, and the concentration of porcine heme powder is 0% (A), 0.1% (B), 0.3% (C), and 0.5% (D).

Figure 9 shows the resolubility of whey protein-heme nanocomposites with different porcine heme powder concentrations. Figure A is the appearance, and Figure B is the measurement of solubility. Wherein the whey protein concentration is 1%, and the porcine heme powder concentration is 0.1%, 0.3%, 0.5%.

Figure 10 is the hygroscopicity of whey protein/heme complexes with different porcine heme powder concentrations. Wherein the concentration of whey protein (WP) is 1%, and the concentration of porcine heme powder (Heme) is 0.1%, 0.3%, 0.5%, and the moisture absorption rate of the compound is measured under the conditions of temperature 25°C and humidity 75%, respectively.

Detailed ways

The invention provides a preparation method of a water-soluble heme-polypeptide composite nutrient iron fortifier, which is a heme iron fortifier that can be directly dissolved in water.

1. Using fresh pig blood and whey protein powder as raw materials to prepare a water-soluble heme-polypeptide compound nutritional iron fortifier, specifically including the following steps:

(1) Take 2.5 L of fresh pig blood, add 250 mL of 3.0% (w/v) trisodium citrate (anticoagulant) to the solution, centrifuge at 3000 rpm for 10 min, collect the precipitate, and discard the supernatant.

(2) The collected porcine red blood cells were washed three times with 0.9% (w/v) physiological saline, and centrifuged at 3000 rpm for 10 min each time.

(3) Add 2 times the volume of pure water to the collected porcine red blood cells after washing, and gently stir for 20 minutes. Then the crushed solution was centrifuged at 10000rpm for 20min. Collect the supernatant and discard the precipitate. The supernatant collected at this time is called porcine hemoglobin stock solution, which is freeze-dried to obtain porcine hemoglobin powder.

(4) Porcine hemoglobin powder was dissolved in deionized water to make a porcine hemoglobin solution with a concentration of 2% (w/v), stirred at room temperature until completely dissolved, and then centrifuged at 8000 rpm for 10 minutes, discarding the precipitate and leaving the supernatant.

(5) Adjust the pH value of 2% porcine hemoglobin solution to 2.0 with 6mol/L HCl solution. Heat and hydrolyze in a water bath at 80°C for 12h, adjust the pH to 7.0 with 2mol/L NaOH solution, and then centrifuge at 8000rpm for 20min Discard the supernatant and save the precipitate. After the precipitate was washed with deionized water, it was centrifuged at 8000 rpm for 10 min, and repeated 3 times. The precipitate was freeze-dried for 24 hours and then ground into powder to obtain porcine heme powder.

(6) Porcine heme powder is dissolved in 0.1% sodium carbonate solution to make a heme solution with a concentration of 0.15-0.75% (w/v). Stir at room temperature in the dark until completely dissolved and then centrifuge at 8000rpm for 10 minutes. Discard the precipitate and keep it clear. The whey protein powder was dissolved in deionized water to make a 3% (w/v) whey protein solution, stirred at room temperature until completely dissolved, and then centrifuged at 8000 rpm for 10 min. Discard the pellet and keep the supernatant.

(7) Mix porcine heme solution and whey protein solution at a volume ratio of 1:2, stir until completely dissolved, adjust the pH to 7.0 with 2mol/L HCl solution, centrifuge at 8000rpm for 10min, discard the precipitate and keep the supernatant. Wherein the final concentration of whey protein is 1%, and the final concentration of porcine heme powder is 0.1-0.5%.

(8) The whey protein-heme compound solution is freeze-dried or spray-dried to make a water-soluble heme-polypeptide compound nutritional iron fortifier.

2. Prepare a water-soluble heme-polypeptide compound nutritional iron fortifier with commercially available hemoglobin powder, specifically including the following steps:

(1) The porcine hemoglobin powder was dissolved in deionized water to make a porcine hemoglobin solution with a concentration of 2%, stirred at room temperature until completely dissolved, and then centrifuged at 8000 rpm for 10 min, discarding the precipitate and leaving the supernatant.

(2) Adjust the pH value of 2% porcine hemoglobin solution to 2.0 with 6mol/L HCl solution. Heat and hydrolyze in a water bath at 80°C for 12h, adjust the pH to 7.0 with 2mol/L NaOH solution, and then centrifuge at 8000rpm for 20min Discard the supernatant and save the precipitate. After the precipitate was washed with deionized water, it was centrifuged at 8000 rpm for 10 min, and repeated 3 times. The precipitate was freeze-dried for 24 hours and then ground into powder to obtain heme powder.

(3) Porcine heme powder was dissolved in 0.1% sodium carbonate solution to make a heme solution with a concentration of 0.15-0.75%, stirred at room temperature in the dark until completely dissolved, and then centrifuged at 8000 rpm for 10 minutes, discarding the precipitate and keeping the supernatant. The whey protein powder was dissolved in deionized water to make a 3% whey protein solution, stirred at room temperature until completely dissolved, and then centrifuged at 8000 rpm for 10 min. Discard the pellet and keep the supernatant.

(4) Mix porcine heme solution and whey protein solution at a volume ratio of 1:2, stir until completely dissolved, adjust the pH to 7.0 with 2mol/L HCl solution, centrifuge at 8000rpm for 10min, discard the precipitate and keep the supernatant. Wherein the final concentration of whey protein is 1%, and the final concentration of porcine heme powder is 0.1-0.5%.

(5) The whey protein-heme compound solution is freeze-dried or spray-dried to prepare a water-soluble heme-polypeptide compound nutritional iron fortifier.

The advantages and effects of the present invention will be further described below in conjunction with specific examples.

Example 1

(1) Fully dissolve the commercially available porcine hemoglobin powder at a concentration of 2%, centrifuge at 8000rpm for 10min, remove the insoluble part, discard the precipitate and keep the supernatant.

(2) Adjust the pH of the 2% porcine hemoglobin solution to 2.0 with 6 mol/L HCl solution.

(3) Heat the porcine hemoglobin solution with a pH of 2.0 at 80°C for 12 hours, and take samples every 2 hours.

(4) After cooling the taken out porcine hemoglobin solution, adjust the pH to 7.0 with 2 mol/L/NaOH, and centrifuge at 8000 rpm for 20 min. The supernatant was collected to measure the degree of hydrolysis, the precipitate was washed with water and then centrifuged at 8000 rpm for 20 min, and repeated three times, the supernatant was discarded to retain the precipitate.

(5) Use ultraviolet spectrophotometer, SDS-PAGE electrophoresis, amino acid analyzer, high-performance liquid chromatography to determine the degree of hydrolysis, amino acid species, and heme content. As shown in Figure 1, the degree of hydrolysis reaches the maximum value after 12 hours of hydrolysis; as shown in Figure 2, the protein is hydrolyzed into amino acids after 12 hours of hydrolysis, and the band disappears; as shown in Table 1, the 16 kinds of amino acids after hydrolysis of porcine hemoglobin for 12 hours are measured As shown in Figure 3, the ultraviolet absorption intensity of heme iron porphyrin at 383nm place is stronger after hydrolysis 12h; The peak time of heme liquid phase after hydrolysis 12h as shown in Figure 4 is consistent with heme standard product. As shown in Table 2, according to the standard curve of heme standard ( FIG. 5 ), the hemoglobin content was higher after 12 hours of hydrolysis.

Table 1 Hydrolyzed amino acid content in porcine hemoglobin hydrolyzed precipitate

Table 2 Hydrolyzed amino acid content in porcine hemoglobin hydrolyzed precipitate

(6) Freeze-drying the washed precipitate in (4) to obtain porcine heme powder.

Example 2

(1) Fully dissolve the porcine heme powder at a concentration of 0.15%, 0.45%, and 0.75% with 0.1% sodium carbonate solution, centrifuge at 8000 rpm for 10 minutes, remove the insoluble part, keep the supernatant and discard the precipitate, and prepare a porcine heme solution.

(2) Fully dissolve the whey protein powder at a concentration of 3% with deionized water, centrifuge at 8000 rpm for 10 min, remove the insoluble part, keep the supernatant and discard the precipitate, and prepare a whey protein solution.

(3) Mix porcine heme solution and whey protein solution at a volume ratio of 2:1, adjust the pH to 7.0 with 2mol/L HCl, centrifuge at 8000rpm for 10min, remove the insoluble part, keep the supernatant and discard the precipitate.

(6) Utilize particle size analyzer to measure the particle size of three kinds of whey protein-heme composite solutions, as shown in Figure 6, particle size increases along with the increase of heme concentration in the composite solution, when pig heme powder concentration reaches 0.5% (w/v), the particle size reaches the maximum.

Example 3

(1) Fully dissolve the porcine heme powder at a concentration of 0.15%, 0.45%, and 0.75% with 0.1% sodium carbonate solution, centrifuge at 8000 rpm for 10 minutes, remove the insoluble part, keep the supernatant and discard the precipitate, and prepare a porcine heme solution.

(2) Fully dissolve the whey protein powder at a concentration of 3% with deionized water, centrifuge at 8000 rpm for 10 min, remove the insoluble part, keep the supernatant and discard the precipitate, and prepare a whey protein solution.

(3) Mix porcine heme solution and whey protein solution at a volume ratio of 2:1, adjust the pH to 7.0 with 2mol/L HCl, centrifuge at 8000rpm for 10min, remove the insoluble part, keep the supernatant and discard the precipitate. Take out and observe the appearance diagram (Fig. 7A), it can be seen that the color of the solution becomes darker with the increase of the hemoglobin concentration.

(4) Inhale the solution in step (3) into a spray dryer for drying. The spray dryer is set with an air inlet temperature of 140° C., a peristaltic pump speed of 15 rpm, a fan frequency of 60 Hz and an air outlet temperature of 70° C. to collect powder. Take out and observe the appearance picture (Fig. 7B), it is found that the color of the powder will continue to become darker with the increase of the hemoglobin concentration.

Example 4

(1) Fully dissolve the porcine heme powder at a concentration of 0.15%, 0.45%, and 0.75% with 0.1% sodium carbonate solution, centrifuge at 8000 rpm for 10 minutes, remove the insoluble part, keep the supernatant and discard the precipitate, and prepare a porcine heme solution.

(2) Fully dissolve the whey protein powder at a concentration of 3% with deionized water, centrifuge at 8000 rpm for 10 min, remove the insoluble part, keep the supernatant and discard the precipitate, and prepare a whey protein solution.

(3) Mix porcine heme solution and whey protein solution at a volume ratio of 2:1, adjust the pH to 7.0 with 2mol/L HCl, centrifuge at 8000rpm for 10min, remove the insoluble part, keep the supernatant and discard the precipitate.

(4) The supernatant in (3) was quick-frozen with liquid nitrogen and dried in a freeze dryer for 24 hours to form a powder, and its microstructure was observed.

(5) As shown in Figure 8, whey protein is a spherical nanoparticle, which becomes an irregularly shaped nanoparticle after adding heme, and the particle is the largest when the hemoglobin concentration is maximum.

Example 5

(1) Fully dissolve the porcine heme powder at a concentration of 0.15%, 0.45%, and 0.75% with 0.1% sodium carbonate solution, centrifuge at 8000 rpm for 10 minutes, remove the insoluble part, keep the supernatant and discard the precipitate, and prepare a porcine heme solution.

(2) Fully dissolve the whey protein powder at a concentration of 3% with deionized water, centrifuge at 8000 rpm for 10 min, remove the insoluble part, keep the supernatant and discard the precipitate, and prepare a whey protein solution.

(3) Mix porcine heme solution and whey protein solution at a volume ratio of 2:1, adjust the pH to 7.0 with 2mol/L HCl, centrifuge at 8000rpm for 10min, remove the insoluble part, keep the supernatant and discard the precipitate.

(4) Inhale the solution in step (3) into a spray dryer for drying. The spray dryer is set with an air inlet temperature of 140° C., a peristaltic pump speed of 15 rpm, a fan frequency of 60 Hz and an air outlet temperature of 70° C. to collect powder.

(5) Three different concentrations of whey protein-heme powder were dissolved in deionized water and centrifuged at 8000rpm for 10 minutes, no precipitation was found, and the solubility reached 98%. The results are shown in FIG. 9 .

Example 6

(1) Fully dissolve the porcine heme powder at a concentration of 0.15%, 0.45%, and 0.75% with 0.1% sodium carbonate solution, centrifuge at 8000 rpm for 10 minutes, remove the insoluble part, keep the supernatant and discard the precipitate, and prepare a porcine heme solution.

(2) Fully dissolve the whey protein powder at a concentration of 3% with deionized water, centrifuge at 8000 rpm for 10 min, remove the insoluble part, keep the supernatant and discard the precipitate, and prepare a whey protein solution.

(3) Mix porcine heme solution and whey protein solution at a volume ratio of 2:1, adjust the pH to 7.0 with 2mol/L HCl, centrifuge at 8000rpm for 10min, remove the insoluble part, keep the supernatant and discard the precipitate.

(4) Inhale the solution in step (3) into a spray dryer for drying. The spray dryer is set with an air inlet temperature of 140° C., a peristaltic pump speed of 15 rpm, a fan frequency of 60 Hz and an air outlet temperature of 70° C. to collect powder.

(5) Place different samples in a desiccator saturated with NaCl solution at a temperature of 25° C. and a humidity of 75%. Measure its mass at different time points (2, 4, 6, 8, 10, 12, 24, 48, 60, 72, 84, 96, 108, 120h...216h), and calculate the moisture absorption rate. As shown in Fig. 10, the results show that the moisture absorption rate is the lowest when the heme concentration is 0.5%.

It should be understood that the embodiments of the present invention are not limited by the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods , are all included within the protection scope of the present invention.

Claims (10)

1. A preparation method of a water-soluble heme-polypeptide composite nutrient iron fortifier is characterized by comprising the following steps: the method comprises the following steps: hydrolyzing porcine hemoglobin with acid to obtain porcine hemoglobin, mixing the porcine hemoglobin solution and whey protein solution, adjusting pH of the mixed solution to neutral or near neutral, centrifuging or filtering to remove insoluble part, and lyophilizing or spray drying to obtain powder of water soluble heme-polypeptide composite iron supplement.

2. The method for preparing a water-soluble heme-polypeptide complex nutrient iron fortifier according to claim 1, wherein the water-soluble heme-polypeptide complex nutrient iron fortifier comprises the following steps: the pig heme solution is obtained by dissolving pig heme in a sodium carbonate solution.

3. The method for preparing a water-soluble heme-polypeptide complex nutrient iron fortifier according to claim 2, wherein the water-soluble heme-polypeptide complex nutrient iron fortifier comprises the following steps: the concentration of the sodium carbonate solution is 0.01-0.1%.

4. The method for preparing a water-soluble heme-polypeptide complex nutrient iron fortifier according to claim 2, wherein: the method for preparing the porcine heme acid hydrolysis comprises the following steps: dissolving pig hemoglobin with water, adjusting the pH value to 1.5-2.5, hydrolyzing at 80-90 ℃ for 6-12 h, adjusting the pH value to 6.0-7.5, centrifuging, washing precipitates, and freeze-drying to obtain the pig hemoglobin powder.

5. The method for preparing a water-soluble heme-polypeptide complex nutrient iron fortifier according to claim 1, wherein the water-soluble heme-polypeptide complex nutrient iron fortifier comprises the following steps: the pH was adjusted using HCl solution and NaOH solution.

6. The method for preparing a water-soluble heme-polypeptide complex nutrient iron fortifier according to claim 1, wherein the water-soluble heme-polypeptide complex nutrient iron fortifier comprises the following steps: the concentration of the pig heme solution is 0.15 to 0.75 percent.

7. The method for preparing a water-soluble heme-polypeptide complex nutrient iron fortifier according to claim 1, wherein the water-soluble heme-polypeptide complex nutrient iron fortifier comprises the following steps: the concentration of the whey protein solution is 1.5-6.0%.

8. The method for preparing a water-soluble heme-polypeptide complex nutrient iron fortifier according to claim 1, wherein the water-soluble heme-polypeptide complex nutrient iron fortifier comprises the following steps: in the mixed solution, the concentration of whey protein is 0.5-2.0%, and the concentration of the pig heme is 0.1-0.5%.

9. The method for preparing a water-soluble heme-polypeptide complex nutrient iron fortifier according to claim 1, wherein: the pH was adjusted using HCl solution.

10. A water-soluble heme-polypeptide composite nutrient iron fortifier is characterized in that: obtained by the production method according to any one of claims 1 to 9.

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