Preparation method of black corn anthocyanin-protein compound

Abstract

A preparation method of a black corn anthocyanin-protein compound relates to the field of preparation of anthocyanin-protein composites.The method comprises the steps that black corn flour is degreased through petroleum ether, then an ethanol water solution is added into the degreased black corn flour, stirring and suction filtration are conducted, supernate is taken, a NaCl solution is added, centrifugation is conducted, and precipitates are dialyzed and freeze-dried to obtain the black corn anthocyanin-protein compound. And the black corn anthocyanin-protein compound is prepared. According to the preparation method disclosed by the invention, the anthocyanin-protein compound is directly obtained from a raw material (black corn), a green technology is combined with the use of a green solvent, a novel effective method is provided for preparing the anthocyanin-protein compound, and moreover, the anthocyanin-protein compound has a good application prospect. According to the method, anthocyanin decomposition caused when anthocyanin is independently extracted or anthocyanin and protein are compounded to prepare the anthocyanin-protein compound is avoided, the prepared anthocyanin-protein compound is stable, the conformation of protein can be influenced by the compound, and the quality and the nutritional value of the protein are further influenced.

Description

Technical Field

[0001] The invention relates to the field of preparation of anthocyanin-protein complexes, in particular to a method for preparing a black corn anthocyanin-protein complex. Background Art

[0002] Black corn, also known as black glutinous corn, is a general term for corn with black and purple kernels. It is also called purple corn and is a plant of the genus Zea of ​​the Poaceae family. It is rich in anthocyanins, polysaccharides, amino acids and various minerals, and has extremely high nutritional value. The content of protein, fat and selenium in black corn kernels is 1.23 times, 1.3 times and 3-8.5 times that of ordinary corn, respectively, and the content of anthocyanins is 4.3 times that of blueberries. Compared with ordinary corn, it has higher nutritional value and better health benefits, and has multiple functions such as antioxidant, anti-cancer, and memory regulation. At present, there are related products such as black corn vinegar, black corn wine, and black corn noodles on the market, but the small number of product types limits the further upgrading of the black corn industry, and it is urgent to develop new black corn products.

[0003] Anthocyanin is a natural colored flavonoid phenolic compound formed by the combination of anthocyanidin and various monosaccharides in plants to form glycosides. It is a general term for natural pigments in plants. It can make the roots, stems, flowers and fruits of many plants appear in different colors such as orange, pink, red, purple and blue. Structurally, anthocyanin is derived from anthocyanidin and is composed of aromatic rings, oxygen-containing heteroaromatic rings and aromatic rings. Anthocyanin, as a soluble phenolic compound, is most abundant in the cell vacuoles of the epidermis and subcutaneous tissue of plants. Affected by plant development conditions and environmental conditions, anthocyanin is prone to degradation to varying degrees. Studies have shown that anthocyanin also has a variety of unique physiological activities, such as preventing heart disease, lowering blood sugar, anti-aging, anti-cancer and anti-inflammatory effects. The safety and non-toxicity of anthocyanin make it widely used in the food industry to give or improve the color of processed products. Due to its excellent characteristics such as natural source, non-toxic safety and biological function, anthocyanin has attracted widespread attention from researchers and is often used in the fields of medicine, food, cosmetics, etc.

[0004] As one of the three essential nutrients for the human body, protein has good biocompatibility and biodegradability and is often used in food processing, but its functional properties need to be improved.

[0005] Studies have shown that proteins have good surface properties, self-assembly properties and gelation characteristics. They can form a combination through non-covalent and covalent interactions without changing the structure of anthocyanins. Anthocyanins are fixed in the protein structure cavity, which can reduce the loss of pyranose cations and thus have a positive effect on the stability of anthocyanins. After anthocyanins are complexed with proteins, the functional properties of proteins will be improved, such as surface hydrophobicity, emulsification, and foaming properties. The interaction between the two can affect each other's morphology, antioxidant capacity, thermal stability, emulsification properties, and bioavailability in the food system.

[0006] In recent years, scientific and technological workers at home and abroad have conducted research and development on the interaction between anthocyanins and proteins, mainly studying the effects of proteins on the stability protection and bioavailability of anthocyanins, the effects of anthocyanins on the functional properties of proteins, and the industrial applications of the combination of the two.

[0007] However, the methods for preparing anthocyanin-protein complexes in the prior art basically prepare anthocyanin and protein in advance, then mix the anthocyanin and protein, and treat them under different process conditions (such as magnetic field treatment, ultra-high pressure treatment, etc.) to obtain anthocyanin-protein complexes. Currently, there is no method for directly preparing anthocyanin-protein complexes using black corn as raw material. Summary of the invention

[0008] The present invention aims to provide a method for preparing a black corn anthocyanin-protein complex, so as to prepare the anthocyanin-protein complex by a technical idea different from the prior art, enrich the preparation path of the anthocyanin-protein complex, and broaden the types of new products prepared by deep processing of black corn.

[0009] In order to achieve the above-mentioned purpose, the specific scheme adopted by the present invention is: a method for preparing a black corn anthocyanin-protein complex, which comprises defatting black corn flour with petroleum ether, adding an ethanol aqueous solution to the defatted black corn flour, stirring, filtering, taking the supernatant and adding a NaCl solution, centrifuging, dialyzing the precipitate, and freeze-drying to obtain the black corn anthocyanin-protein complex.

[0010] As a further optimization of the above technical solution: the concentration of the ethanol aqueous solution is 20-95%, and the concentration of the NaCl solution is 0.8-1.2%.

[0011] As a further optimization of the above technical solution: after adding ethanol aqueous solution to defatted black corn flour, magnetic stirring is carried out at 25-75° C. for 1-24 hours, and then suction filtration is performed.

[0012] As a further optimization of the above technical solution: after taking the supernatant and adding NaCl solution, place it at 4°C for 1-24h and then centrifuge it.

[0013] As a further optimization of the above technical solution: the volume ratio of the supernatant and the NaCl solution is 1:1.

[0014] As a further optimization of the above technical solution: the dialysis method is specifically as follows: collecting the precipitate obtained by centrifugation, transferring the precipitate into a dialysis bag, and then placing it in ice water for magnetic stirring.

[0015] As a further optimization of the above technical solution: the molecular weight of the dialysis bag is 3000Da.

[0016] As a further optimization of the above technical solution: the defatting method of black corn flour is specifically as follows: petroleum ether is added to the black corn flour, magnetically stirred at room temperature for 1-24 hours, and air-dried to remove the petroleum ether to obtain defatted black corn flour.

[0017] As a further optimization of the above technical solution: the ratio of the added amount of black corn flour and petroleum ether is 1g:2-50mL.

[0018] As a further optimization of the above technical solution: the black corn kernels are crushed and then passed through a 40-200 mesh sieve to obtain the black corn flour.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention uses black corn flour as a raw material, adds petroleum ether for defatting treatment, adds ethanol aqueous solution to the filter residue for extraction, centrifuges to separate the extract, and finally mixes the extract with a NaCl solution, freeze-dries to obtain a finished black corn anthocyanin-protein complex product. The green technology is combined with the use of green solvents, which is environmentally friendly. The reaction can be carried out at room temperature without producing toxic products or decomposing antioxidants, and provides a new and effective method for preparing anthocyanin-protein complexes. At the same time, the present invention uses more common and cheaper black corn flour as a raw material, broadens the types of new products obtained by deep processing of black corn, and the technology adopts an alcohol-soluble extraction method, which effectively shortens the extraction time. At the same time, the process is simple and the preparation cost is low. Alcohol solvents are not only easy to recover, but also can dissolve some organic compounds that are not easily soluble in water. The alcohol extraction process does not cause losses such as protein decomposition, and the activity of the extract is relatively high.

[0021] 2. The present invention obtains anthocyanin-protein complex directly from a raw material (black corn), avoiding the decomposition of anthocyanin caused by extracting anthocyanin alone or preparing anthocyanin-protein complex by compounding anthocyanin and protein. The prepared anthocyanin-protein complex is stable, and the non-free anthocyanin can delay the oxidation process of anthocyanin after interacting with protein macromolecules, thereby improving the stability of anthocyanin and inhibiting the decomposition of anthocyanin, effectively stabilizing the black corn anthocyanin-protein complex, and the complex will affect the conformation of the protein and further affect its quality and nutritional value. At the same time, the method is simple in process and suitable for differentiated applications in different products. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The SDS-PAGE profile of black corn anthocyanin-protein complex;

[0023] Figure 2 The UV spectra of black corn protein and black corn anthocyanin-protein complex;

[0024] Figure 3 This is the infrared spectrum of black corn protein and black corn anthocyanin-protein complex;

[0025] Figure 4 This is a physical picture of the supernatant of ethanol extraction of defatted black corn flour;

[0026] Figure 5 These are the actual pictures of the precipitates obtained by ethanol-NaCl extraction and ethanol-ice water extraction. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further elaborated in detail below in conjunction with specific embodiments. The parts of the present invention that are not described and disclosed in detail in the following embodiments should be understood as the prior art known or should be known to those skilled in the art.

[0028] The invention discloses a method for preparing a black corn anthocyanin-protein complex. The method comprises the following steps: defatting black corn flour with petroleum ether, adding an ethanol aqueous solution to the defatted black corn flour, stirring, filtering, taking a supernatant, adding a NaCl solution, centrifuging, dialyzing a precipitate, and freeze-drying the precipitate to prepare the black corn anthocyanin-protein complex.

[0029] Specifically, the method comprises the following steps:

[0030] S1: Select mature, fresh and dried black corn kernels, use a universal grinder to grind the black corn kernels into powder, and then pass the black corn powder through a 40-200 mesh sieve for later use.

[0031] S2: Mix black corn flour and petroleum ether in an amount of 1 g:2-50 mL, stir magnetically at room temperature for 1-24 h, filter to obtain a filter residue, place the filter residue in a cool and ventilated place to dry, remove the petroleum ether, and obtain defatted black corn flour.

[0032] S3: Add 20-95% ethanol solution to defatted black corn flour, and extract with magnetic stirring at 25-75°C for 1-24h.

[0033] S4: Filtration: Filter the sample extracted in S3, take the supernatant, and remove the residue precipitate.

[0034] S5: Precipitation: Add NaCl solution to the supernatant obtained in the above S4 at a volume ratio of 1:1, and place at 4° C. for 1-24 hours, wherein the concentration of the NaCl solution is 0.8-1.2%.

[0035] S6: Centrifugation: Set the centrifuge speed to 6000 r / min, the centrifugation time to 15 min, and the temperature to 4° C. to centrifuge the sample solution after being placed in step S5 for 1-24 hours.

[0036] S7: Dialysis: Collect the precipitate from the centrifuged sample, transfer it into a dialysis bag, and place it in ice water for magnetic stirring.

[0037] S8: freeze drying: freeze drying the dialyzed sample (i.e. the precipitate in the dialysis bag) to obtain the black corn anthocyanin-protein complex.

[0038] It should be noted that the dialysis in step S7 of the present invention is to purify the anthocyanin-protein complex. The dialysis method can separate the anthocyanin-protein complex from other small molecules such as inorganic salts, monosaccharides, disaccharides and other impurities by using a semipermeable membrane, and can also separate proteins of different molecular sizes. The anthocyanin-protein complex solution to be purified is placed in a dialysis bag made of a semipermeable membrane, and the dialysis bag is immersed in water or a buffer solution. The biomacromolecules with large molecular weight in the sample solution are trapped in the bag, while the salt and small molecules are continuously diffused and dialyzed to the outside of the bag until the concentrations inside and outside the bag reach equilibrium.

[0039] The selection of the molecular weight cutoff of the dialysis bag is based on the molecular weight of the macromolecules reserved in the membrane and the molecular weight of the small molecule pollutants to be removed. The anthocyanin-protein complex extracted in the present invention passes through a dialysis bag with a molecular weight of 3000Da.

[0040] Example 1

[0041] A method for preparing a black corn anthocyanin-protein complex comprises the following steps:

[0042] S1: Select mature, fresh and dried black corn kernels, use a universal grinder to grind the black corn kernels into powder, and then sieve the black corn powder through 80 mesh for later use.

[0043] S2: Add 100 mL of petroleum ether to 10 g of black corn flour, stir magnetically at room temperature for 8 h, filter to obtain a residue, place the residue on filter paper, and blow dry in a cool and ventilated place to remove the petroleum ether to obtain defatted black corn flour.

[0044] S3: Add 80% ethanol solution to defatted black corn flour and extract with magnetic stirring at 50°C for 4 h.

[0045] S4: Filtration: Filter the sample solution extracted in S3, take the supernatant, and remove the residue precipitate.

[0046] S5: Precipitation: Add an equal volume of NaCl solution to the supernatant obtained in S4 above, and place at 4°C for 12 hours, wherein the concentration of the NaCl solution is 1%.

[0047] S6: Centrifugation: Set the centrifuge speed to 6000 r / min, the centrifugation time to 15 min, and the temperature to 4° C. to centrifuge the sample solution after being placed in step S5 for 12 hours.

[0048] S7: Dialysis: Collect the precipitate from the centrifuged sample, transfer it into a dialysis bag with a molecular weight of 3000Da, and place it in ice water for magnetic stirring.

[0049] S8: freeze drying: freeze drying the dialyzed sample (i.e. the precipitate in the dialysis bag) to obtain the black corn anthocyanin-protein complex.

[0050] Example 2

[0051] A method for preparing a black corn anthocyanin-protein complex comprises the following steps:

[0052] S1: Select mature, fresh and dried black corn kernels, use a universal grinder to grind the black corn kernels into powder, and then sieve the black corn powder through a 40-mesh sieve for later use.

[0053] S2: Add 20 mL of petroleum ether to 10 g of black corn flour, stir magnetically at room temperature for 1 h, filter to obtain a residue, place the residue on filter paper, and blow dry in a cool and ventilated place to remove the petroleum ether to obtain defatted black corn flour.

[0054] S3: Add 20% ethanol solution to defatted black corn flour and extract with magnetic stirring at 25°C for 1 h.

[0055] S4: Filtration: Filter the sample solution extracted in S3, take the supernatant, and remove the residue precipitate.

[0056] S5: Precipitation: Add an equal volume of NaCl solution to the supernatant obtained in S4 above, and place at 4°C for 1 hour, wherein the concentration of NaCl solution is 0.8%.

[0057] S6: Centrifugation: Set the centrifuge speed to 6000 r / min, the centrifugation time to 15 min, and the temperature to 4° C. to centrifuge the sample solution after being placed for 1 hour in step S5.

[0058] S7: Dialysis: Collect the precipitate from the centrifuged sample, transfer it into a dialysis bag with a molecular weight of 3000Da, and place it in ice water for magnetic stirring.

[0059] S8: freeze drying: freeze drying the dialyzed sample (i.e. the precipitate in the dialysis bag) to obtain a complex, i.e. the black corn anthocyanin-protein complex.

[0060] Example 3

[0061] A method for preparing a black corn anthocyanin-protein complex comprises the following steps:

[0062] S1: Select mature, fresh and dried black corn kernels, use a universal grinder to grind the black corn kernels into powder, and then sieve the black corn powder through 200 mesh for later use.

[0063] S2: Add 500 mL of petroleum ether to 10 g of black corn flour, stir magnetically at room temperature for 24 h, filter to obtain a residue, place the residue on filter paper, and blow dry in a cool and ventilated place to remove the petroleum ether to obtain defatted black corn flour.

[0064] S3: Add 95% ethanol solution to defatted black corn flour and extract with magnetic stirring at 75°C for 24 hours.

[0065] S4: Filtration: Filter the sample solution extracted in S3, take the supernatant, and remove the residue precipitate.

[0066] S5: Precipitation: Add an equal volume of NaCl solution to the supernatant obtained in S4 above, and place at 4°C for 24 hours, wherein the concentration of the NaCl solution is 1.2%.

[0067] S6: Centrifugation: Set the centrifuge speed to 6000 r / min, the centrifugation time to 15 min, and the temperature to 4° C. to centrifuge the sample solution after being placed in step S5 for 24 hours.

[0068] S7: Dialysis: Collect the precipitate from the centrifuged sample, transfer it into a dialysis bag with a molecular weight of 3000Da, and place it in ice water for magnetic stirring.

[0069] S8: freeze drying: freeze drying the dialyzed sample (i.e. the precipitate in the dialysis bag) to obtain the black corn anthocyanin-protein complex.

[0070] Comparative Example 1

[0071] This comparative example is the same as steps S1-S4 of Example 1, except that:

[0072] S5: Add an equal volume of pre-cooled ice water to the supernatant obtained in step S4 and place at 4°C for 24 hours.

[0073] S6: Centrifugation: Set the centrifuge speed to 6000 r / min, the centrifugation time to 15 min, and the temperature to 4° C. to centrifuge the sample solution after being placed in step S5 for 24 hours.

[0074] S7: Dialysis: Collect the precipitate from the centrifuged sample, transfer it into a dialysis bag with a molecular weight of 3000Da, and place it in ice water for magnetic stirring.

[0075] S8: freeze drying: freeze-dry the sample after dialysis (ie, the precipitate in the dialysis bag) to obtain a composite.

[0076] Below, the experimental results of Example 1 of the present invention and Comparative Example 1 are analyzed. First, for the convenience of explanation, the method used in the example of the present invention is called ethanol-NaCl extraction, and the method used in the comparative example is called ethanol-ice water extraction.

[0077] <Anthocyanin content>

[0078] The anthocyanin content can directly reflect the difference in extraction effect between ethanol-NaCl extraction and ethanol-ice water extraction. The supernatant of ethanol extraction of defatted black corn flour is light pink ( Figure 4 ), there was no significant difference in appearance between the precipitates obtained by the two methods of ethanol-NaCl and ethanol-ice water ( Figure 5 ). The anthocyanin content in the complex extracted by ethanol-NaCl was 0.138±0.097mg / mg complex by pH differential method, while the anthocyanin content in the complex extracted by ethanol-ice water was 0.065±0.510mg / mg complex. This indicates that the complex extracted by ethanol-NaCl method can better retain the anthocyanin. It is speculated that this is because anthocyanin has an ortho-hydroxyl structure, which can react with Na + The formation of complexes increases its stability and makes it less likely to be degraded during extraction and separation. Table 1 Anthocyanin extraction content in black corn complex

[0079] <Protein content>

[0080] The BCA method for determining protein content has the characteristics of simple operation, high sensitivity, small coefficient of variation, accurate and reliable results, and little influence by interfering substances. The present invention determines the protein in the black corn anthocyanin-protein complex prepared in Example 1 by the BCA method. The protein content can intuitively reflect the ethanol-NaCl extraction effect. After testing, the protein content in the black corn anthocyanin-protein complex prepared in Example 1 is relatively high, which is 24.81±0.45 mg / g black corn. The specific experimental data are shown in Table 2: Table 2 Protein extraction content in black corn

[0081] Qualitative identification of proteins>

[0082] SDS-PAGE electrophoresis is used for qualitative identification, purity and impurity control, and quantitative determination of proteins. The molecular weight of anthocyanin-protein complex extracted by ethanol-NaCl can be detected by SDS-PAGE electrophoresis. Figure 3 As shown, the molecular weights of anthocyanin-protein complexes extracted by ethanol-NaCl were determined by SDS-PAGE electrophoresis to be 100 kDa, 40 kDa, 25 kDa and 20 kDa.

[0083] <Ultraviolet spectrum>

[0084] Ultraviolet-visible spectrophotometry (UV-Vis) is a method that uses the continuous spectrum of electromagnetic waves in the ultraviolet-visible region as a light source to illuminate the sample and study the relative intensity of light absorption by the molecules of a substance.

[0085] The black corn anthocyanin-protein complex prepared in Example 1 and commercially available black corn protein were taken, and their mass concentrations were adjusted to 0.1 mg / mL using 80% ethanol solution, and spectral scanning was performed at 190-1000 nm with a wavelength interval of 1 nm.

[0086] The experimental results are as follows Figure 2 As shown in the figure, the black corn protein can be detected by UV spectroscopy with two main characteristic absorption peaks, a peptide bond characteristic absorption peak at about 200nm, and an absorption peak of tryptophan residues and tyrosine residues in the protein at a wavelength of 280nm. In addition to these two absorption peaks, the black corn anthocyanin-protein complex also has an absorption peak of anthocyanin acylation structure at 300-330nm. The ultraviolet absorption of the black corn anthocyanin-protein complex is weakened, indicating that anthocyanin interacts with protein and the hydrophobicity of the aromatic amino acid microenvironment is enhanced.

[0087] <Infrared Spectrum>

[0088] Infrared spectroscopy is the ability of molecules to selectively absorb infrared rays of certain wavelengths, which causes transitions in the vibrational energy levels and rotational energy levels of the molecules. By detecting the absorption of infrared rays, the infrared absorption spectrum of the substance can be obtained, which is also called molecular vibration spectrum or vibration-rotation spectrum.

[0089] Figure 3 The infrared spectra of the black corn anthocyanin-protein complex prepared by the present invention and commercially available black corn protein are shown in FIG.

[0090] Amide A at 3400-3440 cm -1 There is an absorption peak at 3431 cm, which is related to NH stretching vibration. -1 The amide A of the black corn anthocyanin-protein complex appears at 3417 cm -1 Black corn protein appears near 1647cm -1 The absorption at 1619 cm-1 is the C=O stretching vibration of amide I, while the absorption peak intensity of amide I in the black corn anthocyanin-protein complex is significantly weakened and red-shifted to 1619 cm-1. -1 Black corn protein and black corn anthocyanin-protein complex at 1513 cm -1 、1562cm -1 The absorption at 1331 cm is the characteristic absorption peak of the amide II band, reflecting the CN stretching vibration and NH bending vibration of the protein. -1 、1338cm -1 The weak absorption peak at 1478 cm is caused by NH deformation vibration. -1 、1464cm -1 、1415cm -1 The CH bending vibration occurs at 3417 cm -1 It is speculated that the hydroxyl stretching vibration absorption peak is at 2975 cm -1 The nearby absorption peak is presumably the CH stretching vibration absorption peak of the methoxy group, 2890 cm -1 The peak at the center is speculated to be the methylene peak. There are characteristic groups such as hydroxyl, methoxy, and oxygen-containing heterocyclic rings in the complex, which are also characteristic groups of anthocyanins. Overall, the peak shape of the amide band in the black corn anthocyanin-protein complex has changed significantly, and it is speculated that anthocyanins bind to proteins, causing changes in the protein structure.

[0091] In summary, it can be seen from the ultraviolet spectrum that the black corn anthocyanin-protein complex and black corn protein have two characteristic absorption peaks, the strong absorption peak near the wavelength of 200nm is the absorption peak of the peptide bond, and the weak absorption peak appearing near the wavelength of 280nm is the absorption peak of the tyrosine and tryptophan residues in the protein. In addition to these two absorption peaks, the black corn anthocyanin-protein complex has a weak absorption peak at 300-330nm, which is the absorption peak of the anthocyanin acylation structure. Compared with black corn protein, the ultraviolet absorption of the black corn anthocyanin-protein complex is weakened, indicating that anthocyanins interact with proteins. It can be seen from the infrared spectrum that compared with black corn protein, the peak shape of the amide band in the black corn anthocyanin-protein complex changes significantly, which is speculated to be the combination of anthocyanin substances and proteins, resulting in changes in the protein structure. The results of the two parts of the ultraviolet spectrum and the infrared spectrum can show that the complex prepared in Example 1 is an anthocyanin-protein complex.

[0092] Anthocyanins have antioxidant, anti-cancer, anti-inflammatory, vision protection, and weight loss effects, but anthocyanins are very sensitive to the environment and are easily affected by external factors such as pH, light, temperature, enzymes, and sugars, which can lead to degradation. Proteins have good surface properties, self-assembly properties, and gelation properties. They can form a combination through non-covalent and covalent effects without changing the structure of anthocyanins. Anthocyanins are fixed in the protein structure cavity, which can reduce the loss of pyranose cations and thus have a positive effect on the stability of anthocyanins. The binding effect of proteins on anthocyanins can be divided into covalent binding and non-covalent binding. The interaction between the two can affect each other's morphology, antioxidant capacity, thermal stability, emulsification properties, and bioavailability in the food system (as reported in literature research). The present invention directly obtains anthocyanin-protein complexes from a raw material (black corn), thereby avoiding the decomposition of anthocyanin caused by extracting anthocyanin alone or preparing the anthocyanin-protein complex by compounding anthocyanin and protein. The prepared anthocyanin-protein complex is stable, and the non-free anthocyanin can delay the oxidation process of anthocyanin after interacting with protein macromolecules, thereby improving the stability of anthocyanin, inhibiting the decomposition of anthocyanin, and effectively maintaining the stability of the black corn anthocyanin-protein complex.

[0093] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a black corn anthocyanin-protein complex, characterized in that: The black corn flour is defatted by petroleum ether, and then an ethanol aqueous solution is added to the defatted black corn flour, stirred, filtered, the supernatant is taken and a NaCl solution is added, centrifuged, the precipitate is dialyzed, and freeze-dried to obtain the black corn anthocyanin-protein complex.

2. The method for preparing a black corn anthocyanin-protein complex according to claim 1, characterized in that: The concentration of the ethanol aqueous solution is 20-95%, and the concentration of the NaCl solution is 0.8-1.2%.

3. The method for preparing a black corn anthocyanin-protein complex according to claim 1, characterized in that: After adding ethanol aqueous solution to defatted black corn flour, magnetic stirring was carried out at 25-75° C. for 1-24 hours, and then suction filtration was performed.

4. The method for preparing a black corn anthocyanin-protein complex according to claim 1, characterized in that: The supernatant was taken and NaCl solution was added, and then placed at 4°C for 1-24 hours before centrifugation.

5. The method for preparing a black corn anthocyanin-protein complex according to claim 1, characterized in that: The volume ratio of the supernatant and the NaCl solution was 1:

1.

6. The method for preparing a black corn anthocyanin-protein complex according to claim 1, characterized in that: The specific dialysis method is: collecting the precipitate obtained by centrifugation, transferring the precipitate into a dialysis bag, and then placing it in ice water for magnetic stirring.

7. The method for preparing a black corn anthocyanin-protein complex according to claim 6, characterized in that: The molecular weight of the dialysis bag is 3000Da.

8. The method for preparing a black corn anthocyanin-protein complex according to claim 1, characterized in that: The defatting method of black corn flour is as follows: petroleum ether is added to the black corn flour, magnetically stirred at room temperature for 1-24 hours, and air-dried to remove the petroleum ether, thereby obtaining defatted black corn flour.

9. The method for preparing a black corn anthocyanin-protein complex according to claim 1, characterized in that: The ratio of the added amount of black corn flour and petroleum ether is 1g:2-50mL.

10. The method for preparing a black corn anthocyanin-protein complex according to claim 1, characterized in that: The black corn kernels are crushed and then passed through a 40-200 mesh sieve to obtain the black corn flour.

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