Method for reducing interaction between starch and protein in corn kernels and application of method

Abstract

The invention discloses a method for reducing interaction between starch and protein in corn kernels and application thereof. The invention belongs to the technical field of corn processing. The invention aims to solve the technical problems of long treatment time, large usage amount of chemical reagents and poor separation effect of the existing starch and protein separation method. The method comprises the following steps: (1) storing newly harvested corn cobs in a constant-temperature and constant-humidity box to complete after-ripening of corn; (2) threshing, crushing and soaking the after-ripening corn cobs, and stripping seed coats and germs; and (3) soaking in a certain concentration of SDS solution for the second time, then continuously soaking in a stirring state, centrifuging, discarding supernate, and washing, drying, crushing and sieving precipitates. According to the method, corn after-ripening and a chemical reagent method are combined for weakening interaction of starch and protein in corn kernels, and theoretical basis and technical support can be provided for accurate separation and efficient preparation of corn components.

Description

Technical Field

[0001] The invention belongs to the technical field of corn processing, and particularly relates to a method for reducing the interaction between starch and protein in corn kernels and an application thereof. Background Art

[0002] As an important food resource, corn plays a pivotal role in ensuring food security and meeting nutritional and health needs. The moisture content of newly harvested corn is high, above 30%, with high respiration intensity and high lipid content. It is easy to absorb moisture and become rancid, and is not resistant to storage. Studies have shown that the starch extraction rate of newly harvested corn is low, and the resistant starch content is high, which is not conducive to consumption and further processing. During the storage period, the physiological and biochemical properties, physicochemical properties, nutritional components and processing quality of newly harvested corn are continuously improved. Starch and protein in corn account for about 80% of the total mass of corn, and are mainly found in the corn endosperm. Starch and protein are a whole. Oval or polygonal starch granules are combined with protein matrix. The protein matrix is ​​a network-like connective layer that wraps starch granules. At the same time, starch granules are also connected by flocculent protein. The two exist in the form of a composite structure in corn kernels, and it is difficult to completely separate the two.

[0003] The combination of starch and protein, two high molecular polymers, is not accomplished by a single action, but is the result of the combined effects of covalent bonds and various non-covalent interactions. These forces are distributed in the side chains, fragments or polymers of the complex structure composed of the two to maintain the complex structure of the combination. The combination between starch and protein is caused by a large number of interactions between different fragments and side chains in their molecules. Starch has a strong orientation when chemical reactions occur due to the stereo effect of its structure; protein molecules tend to form various advanced structures due to the influence of intramolecular forces and hydrophobic interactions, so that some active groups are embedded inside the structure.

[0004] Certain chemical reagents can destroy or affect the interaction between starch and protein, thus separating starch and protein into two phases. Therefore, the molecular interaction between the two can be analyzed by changing the structure and properties of the starch-protein complex after adding different chemical reagents, such as urea, sodium chloride and pH regulators. However, the above methods all have problems such as long processing time, large amount of chemical reagents used, and poor separation effect of starch and protein. Summary of the invention

[0005] The purpose of the present invention is to solve the technical problems of long processing time, large amount of chemical reagents used and poor separation effect in the existing separation method of starch and protein, and to provide a method for reducing the interaction between starch and protein in corn kernels and its application.

[0006] One of the objects of the present invention is to provide a method for reducing the interaction between starch and protein in corn kernels, the method being carried out according to the following steps:

[0007] (1) storing the newly harvested corn cobs in a constant temperature and humidity chamber to complete the ripening of the corn;

[0008] (2) threshing, crushing, and soaking the ripened corn cobs, and removing the seed coat and germ;

[0009] (3) Soaking the sample in a SDS solution of a certain concentration for a second time, then continuing to soak the sample under stirring, centrifuging and discarding the supernatant, and washing, drying, crushing and sieving the precipitate.

[0010] It is further defined that the storage conditions in step (1) are: relative humidity of 50-60%, temperature of 10-20° C., and storage time of 35-45 days.

[0011] It is further defined that in step (2), the powder is broken into 6-8 petals.

[0012] It is further defined that the soaking temperature in step (2) is room temperature and the soaking time is 6-10 hours.

[0013] It is further defined that the concentration of the SDS solution in step (3) is 1-3 wt %.

[0014] It is further defined that the second soaking temperature in step (3) is room temperature, the time is 0.5-1.5h, and the soaking is continued for 3-5h.

[0015] It is further defined that the material-liquid ratio of the secondary soaking in step (3) is 1:(2-4).

[0016] A second object of the present invention is to provide a product obtained by the above method.

[0017] The third object of the present invention is to provide an application of the product obtained by the above method in the food field.

[0018] A fourth object of the present invention is to provide an application of the above method as a pretreatment for extracting and separating starch from a starch-protein complex.

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

[0020] The present invention combines corn after-ripening and chemical reagent method to weaken the interaction between starch and protein in corn kernels, which can provide a theoretical basis and technical support for the precise separation and efficient preparation of corn components. The interaction between starch and protein is reduced by after-ripening, and on this basis, the starch-protein complex is treated by adding chemical reagents to further destroy the interaction between starch and protein, which is beneficial to the separation of starch and protein, resulting in an increase in the free starch content. The method has the characteristics of simple process, low cost, and low energy consumption, and can effectively improve the starch extraction rate, purity and processing utilization rate, laying a foundation for the screening of the best after-ripening conditions for corn, the precise separation of corn components, and the research and development of high-quality corn starch-based foods. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1A is the starch extraction rate of the composites after different treatments after extraction in the application example;

[0022] Figure 1B is the protein residue in the starch extracted by the application example after different treatments of the composite;

[0023] Figure 2 The molecular weight distribution of proteins in the composites after different treatments in Example 1 and Comparative Example 1 and Comparative Example 3; A-unripened, B-ripened at 15°C for 40 days;

[0024] Figure 3 The rheological curves of the composites after different treatments in Example 1 and Comparative Example 1 and Comparative Example 3; A-unripened, B-ripened at 15°C for 40 days;

[0025] Figure 4 X-ray diffraction spectra and relative crystallinity of the composites after different treatments in Example 1 and Comparative Example 1 and Comparative Example 3; A-unripened, B-ripened at 15°C for 40 days;

[0026] Figure 5 AB is the hydrogen bond docking interaction diagram between protein and starch molecule; A-gliadin, B-glutenin; Figure 5 CD is the hydrophobic interaction docking diagram between protein and starch molecule; C-gliadin, D-glutenin;

[0027] Fig. 6A This is the curve of protein RMSD changing with time during the protein and starch composite simulation process;

[0028] Figure 6B This is the curve of protein RMSF changing with time during the protein and starch composite simulation process;

[0029] Figure 6C This is the curve of protein Rg changing with time during the protein and starch composite simulation process;

[0030] Fig.6D This is the curve of SASA change over time during the protein and starch composite simulation process;

[0031] Fig. 6E This is the curve of the change of the number of hydrogen bonds of protein over time during the simulation of protein-starch composite;

[0032] In Figure 6, Corn glutelin-0: a complex of corn gluten and starch that has not been ripened; Corn glutelin-40: a complex of corn gluten and starch that has been ripened at 15°C for 40 days; Zein-0: a complex of zein and starch that has not been ripened; Zein-40: a complex of zein and starch that has been ripened at 15°C for 40 days. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0035] The terms "comprising," "including," "having," "containing," or any other variations thereof, as used in the following examples, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus comprising the listed elements is not necessarily limited to only those elements, but may include other elements not expressly listed or inherent to such composition, step, method, article, or apparatus.

[0036] The "one embodiment" or "embodiment" of the present invention refers to a specific feature, structure or characteristic that can be included in at least one implementation of the present invention. The "in one embodiment" that appears in different places in this specification does not refer to the same embodiment, nor is it a separate or selective embodiment that is mutually exclusive with other embodiments.

[0037] The endpoints and any values ​​of the ranges disclosed in the invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this article.

[0038] Example 1: The method of reducing the interaction between starch and protein in corn kernels in this example is carried out according to the following steps:

[0039] (1) placing the newly harvested corn cobs in a constant temperature and humidity chamber at a relative humidity of 55% and a temperature of 15° C. for 40 days to complete the ripening of the corn;

[0040] (2) threshing the ripened corn cobs, breaking them into 6-8 petals, soaking them in 25° C. distilled water for 8 h, and removing the seed coat and embryo;

[0041] (3) Place in a 2 wt% SDS solution with a solid-liquid ratio of 1:3, soak for a second time at 25°C for 1 h, then continue soaking for 4 h under stirring, centrifuge at 4000 r / min for 10 min, discard the supernatant, rinse the precipitate with distilled water and centrifuge, repeat three times to remove residual reagents, dry the precipitate at 40°C, crush and pass through an 80-mesh sieve.

[0042] Comparative Example 1:

[0043] The difference between this comparative example and Example 1 is that the post-ripening of step (1) is not performed, and the newly harvested corn cobs are directly subjected to the operation of step (2). The other steps and parameters are the same as those of Example 1.

[0044] Comparative Example 2:

[0045] The difference between this comparative example and Example 1 is that the post-ripening conditions in step (1) are: storage for 30 days at a relative humidity of 55% and a temperature of 25° C. The other steps and parameters are the same as those in Example 1.

[0046] Comparative Example 3:

[0047] The difference between this comparative example and Example 1, Comparative Example 1 and Comparative Example 2 is that: in step (3), the samples are placed in different solutions for secondary immersion, and the solutions are distilled water, HCl solution with a pH of 5.0, NaOH solution with a pH of 9.0, NaCl solution with a concentration of 3wt% and urea solution with a concentration of 3wt%. The other steps and parameters are the same as those of Example 1, Comparative Example 1 and Comparative Example 2.

[0048] Application examples:

[0049] The methods of Example 1 and Comparative Examples 1-3 are used as pretreatment methods to extract starch from the treated product. The extraction process is as follows: the treated product is wet-milled in a colloid mill, and the obtained starch slurry is filtered on a 100-mesh nylon filter cloth. The filtrate is allowed to stand at room temperature for 4 hours, and the starch precipitate is centrifuged at 4000 r / min for 10 minutes. The starch precipitate is washed with distilled water, and the upper yellow protein is scraped off. The process is repeated 3 times to obtain a lower white precipitate, which is then placed in a 40° C. forced air drying oven and dried for 24 hours to obtain corn starch.

[0050] Detection test (I)

[0051] Determination of starch and protein content: The total starch assay kit (K-TSTA) was used to determine the starch extraction rate of the application example, and the Kjeldahl method was used to determine the residual protein in the starch obtained in the application example.

[0052] The results are shown in Figure 1. Figure 1 shows the extraction rate of starch and the amount of protein residue in starch after treatment with different reagents. Figure 1A It can be seen that the starch extraction rate of the samples treated with distilled water (control group Ctrl) after ripening at 15℃ for 40 days (89.07%) and 25℃ for 30 days (88.24%) increased by 3.81% (15℃ for 40 days) and 2.84% (25℃ for 30 days) respectively compared with the non-ripened samples (85.80%), indicating that corn ripening increases the starch extraction rate. Regardless of whether the corn is ripened or not, the starch extraction rate of all treatments is higher than that of the control group, indicating that the non-covalent interactions between various molecules jointly maintain the structure of starch. Compared with the control group, the starch extraction rate of all samples increased the most after being treated with sodium dodecyl sulfate (SDS), and the samples without ripening, ripening at 15℃ for 40 days, and ripening at 25℃ for 30 days increased from 85.82%, 89.07% and 88.24% to 91.26%, 95.56% and 93.45%, respectively. This is because the long hydrophobic chains in SDS will react with the non-polar groups in the protein molecules, resulting in the exposure of the hydrophobic side chains in the molecules and the change of the molecular conformation of the protein, thereby weakening the binding ability of starch and protein through hydrophobic interactions, thereby increasing the extraction rate of free starch.

[0053] Depend on Figure 1BIt can be seen that the residual protein content in starch of the control group sample (0.58%) ripened at 15°C for 40 days was reduced by 14.71% compared with the non-ripened sample (0.68%), and the sample (0.65%) ripened at 25°C for 30 days was reduced by 4.41%, indicating that the ripening of corn improves the starch purity. Regardless of whether the corn was ripened or not, the protein residue in the starch of the SDS-treated group was the most different from that of the control group. The samples of the unripened, 15℃ ripened for 40 days and 25℃ ripened for 30 days decreased from 0.68%, 0.58% and 0.65% to 0.32%, 0.24% and 0.28%, respectively, which was reduced by 52.94% (unripened), 58.62% (15℃ ripened for 40 days) and 56.92% (25℃ ripened for 30 days). This is because the non-polar ends in the SDS molecules enable them to interact with the hydrophobic regions of the protein molecules, weakening the hydrophobic interaction between starch and protein, resulting in a sharp decrease in the protein residue in the starch, indicating that the addition of SDS promotes the separation of starch and protein and improves the purity of starch. Therefore, the ripening of corn leads to the weakening of the interaction between starch and protein, and SDS greatly destroys the hydrophobic interaction between starch and protein, which is conducive to the extraction of high-purity corn starch.

[0054] Detection test (II)

[0055] Polyacrylamide gel electrophoresis (SDS-PAGE) analysis: 30 mg of starch-protein complexes after different treatments were added to 1 mL of loading buffer (5× loading buffer diluted 5 times), mixed and heated in a 95°C water bath for 5 min, cooled, centrifuged in a centrifuge at 10,000 r / min for 15 s, and 10 μL of supernatant was loaded, and electrophoresis was performed under a steady flow of 20 mA. After completion, the gel was stained with 0.25% R-250 Coomassie brilliant blue solution and decolorized with acetic acid / methanol decolorization solution.

[0056] Effects of different treatments on the molecular weight distribution of proteins in the complex before and after ripening Figure 2As shown. The electrophoresis of corn protein treated by different methods mainly showed three obvious bands at 14.4kDa, 22kDa and 50-70kDa, which were the subunits of glutenin, the a-subunit of alcohol-soluble protein and the aggregates of alcohol-soluble protein. Compared with the corn that was not ripened, the a-subunit of the corn alcohol-soluble protein after ripening (ripened at 15℃ for 40 days) showed two obvious separated bands at 22kDa, indicating that the ripening process may lead to the dissociation of alcohol-soluble protein, which may be related to the decrease in the molecular weight of corn alcohol-soluble protein and the weakening of hydrogen bonding during the ripening period. The 50-70kDa band is mainly caused by the alcohol-soluble protein subunit with a molecular weight of 22kDa forming a larger molecular weight aggregate through intramolecular and intermolecular disulfide bonds, and the treatment with different reagents has little effect on this band. In addition, the electrophoretic band of the a-subunit of alcohol-soluble protein in the sample treated with SDS basically disappeared. This is because SDS destroyed the hydrophobic interaction of proteins, completely disintegrated the protein aggregates, made the proteins more dispersed, and hydrolyzed the large molecular weight polypeptides into small molecular weight and released them into the solution, which is consistent with the rapid decrease in protein content after SDS treatment.

[0057] Detection test (III)

[0058] Rheological property determination: accurately weigh 3g starch-protein complex sample into an aluminum box, add 25mL of distilled water, stir well and heat at 50℃ for 1min, then raise the temperature to 95℃ within 3.75min at 12℃ / min, keep at 95℃ for 2.5min, and then drop to 50℃ within 3.75min to complete the gelatinization of the sample. The gelatinized products (starch-protein complex) obtained in Example 1 and Comparative Examples 1-3 were cooled at room temperature and placed on a rheometer using a plate-plate measurement system with a plate diameter of 4.0cm, a gap of 1.0mm, and a temperature of 25℃. The dynamic viscoelastic properties were measured at an angular frequency of 0.1-100rad / s and a strain of 1%, and the changes in the storage modulus (G′) and the loss modulus (G″) with the angular frequency were recorded.

[0059] Figure 3The effects of different treatments on the rheological curves of the composite samples before and after ripening are shown in Figure 2. Different chemical reagent treatments reduce the G′ of the composite samples by destroying the corresponding interaction forces. The G' of all samples was much higher than G", indicating that the rheological behavior of the samples was closer to solid and had higher elasticity. The samples treated with SDS, pH 9 and urea were the most different from the control group in the unripened samples, indicating that hydrophobic interactions dominated in the unripened corn, and hydrogen bonds and electrostatic interactions also participated in the connection between starch and protein. The G' of the composite sample treated with SDS in the sample ripened for 40 days at 15℃ was significantly lower than that of the control group, while pH 9 and urea treatment led to a significant increase in G', which may be due to the weak electrostatic interaction and hydrogen bonding between starch and protein in the ripened corn. The pH value changes the charge distribution of the amino acid side chains, thereby changing the electrostatic interaction between proteins, reducing the repulsive force and free space between molecules, and then polymerization promotes the formation of the network. Urea destroys the intramolecular and intermolecular hydrogen bonds, making the protein structure unstable, increasing the free starch content, and enhancing the viscoelasticity of starch in the composite sample. Therefore, in the corn ripened for 40 days at 15℃, the hydrophobic interaction between starch and protein is still dominant, but all interactions are weakened, and the effect of SDS is the most obvious.

[0060] Detection test (IV)

[0061] Crystal structure characterization: The product samples obtained in Example 1 and Comparative Examples 1-3 were analyzed by X-ray diffractometer to reveal their crystal structures. The X-ray source used was Cu-Ka, and the sample was scanned at a speed of 5° / min, a power of 40 kV, a current flow of 40 mA, and a step width of 0.02° (2θ). The relative crystallinity of the X-ray diffraction pattern in the range of 5-40° was calculated using MDI-Jade 6.0 software.

[0062] Effects of different treatments on the X-ray diffraction patterns of composite samples before and after ripening Figure 4 As shown. The 2θ values ​​showed obvious diffraction peaks at 15° and 23°, respectively, and double peaks at 17° and 18°, indicating that the treatment with different chemical reagents had no effect on the crystal structure of the complex. The relative crystallinity of the samples treated with SDS and pH 5 in the unripened samples increased by 11.71% and 7.57% respectively compared with the control. SDS treatment resulted in the removal of the protein layer and reduced the interaction between proteins, which provided more contact opportunities for the starch molecules in the sample, thereby increasing the crystallinity of the treated samples. The relative crystallinity of the samples in the NaCl treatment group was 5.26% lower than that in the control group. The H + ions dissociate, causing Na +The ions are freed to the surface of starch molecules and are bound or wrapped by starch molecules, and Na + The radius of the ion is larger than that of H + ions, thereby inhibiting the formation of hydrogen bonds and starch retrogradation. Compared with the control group, the relative crystallinity of the SDS-treated samples after 40 days of ripening at 15°C increased by 10.68%, and the relative crystallinity of the NaCl-treated group decreased by 4.57% compared with the control group. Therefore, regardless of whether the corn is ripened or not, the interaction between starch and protein is mainly hydrophobic and electrostatic interaction. Hydrogen bonds also play a certain role in the unripened corn samples, and the interaction between starch and protein in the ripened corn tends to weaken. The separation effect of starch and protein in the SDS-treated corn is the best.

[0063] Testing and testing (V)

[0064] Molecular docking and molecular dynamics simulation of starch and protein

[0065] Molecular docking and visualization: Molecular docking was completed in AutoDock4 by inserting starch molecules into the macromolecular protein construct and docking, as well as configuring the operation method and docking parameters. The minimum binding energy was calculated using the PDBQT format. The PDBQT format of the composite system can be converted to the PDB format using the OpenBabel GUI software. Finally, the resulting PDB format file was visualized using Maestro 11.5.

[0066] Molecular dynamics (MD) simulations were performed using GROMACS 2020.3 software. The size of the simulation box was optimized so that the distance between each atom of the protein and the simulation box was greater than 1.0 nm. Water molecules were then filled with densities of 0.3 and 0.14 in the unripened and ripened samples, respectively. In order to make the simulated system electrically neutral, Cl - and Na + ions replaced water molecules. According to the steepest descent method, 5.0×10 4The energy optimization of the whole system was carried out in order to minimize the energy consumption of the whole system and finally reduce the unreasonable contact or atomic overlap in the whole system. After the energy minimization, the first stage equilibrium was carried out with the NVT combination for 100ps at 288.15 / 298.15K to stabilize the temperature of the system. The second stage equilibrium was simulated with the NPT combination under the conditions of 1bar and 100ps. The main purpose of the simulation is to optimize the interaction between the target protein and the solvent and ions to make the simulation system fully pre-equilibrated. All MD simulations were carried out in an isostatic environment with a temperature of 288.15 / 298.15K and a pressure of 1 atm for 50ns. The temperature and pressure were controlled by V-rescale and Parrinello-Rahman methods, respectively, and the temperature and pressure coupling constants were 0.1 and 0.5ps, respectively. The van der Waals forces were calculated using the Lennard-Jones function, and the non-bonded cutoff distance was set to 1.4nm. The bond lengths of all atoms were constrained by the LINCS algorithm. The long-range electrostatic interactions were calculated by the Particle Mesh-Ewald method with a Fourier spacing of 0.16 nm.

[0067] Results (1): Molecular docking of starch and protein: Molecular docking revealed that the docking scores of alcohol-soluble protein, glutenin and starch were -5.0 and -5.6, respectively, indicating that glutenin has a stronger binding effect with starch. Among them, starch has hydrogen bonding with Ala87, Gln91, Ser99, Tyr109 and Ala116 of alcohol-soluble protein and Thr139, Gln182 and Gln200 of glutenin ( Figure 5 In addition, starch also has hydrophobic interactions with 12 amino acids around prolamin, including Gln113, Ala121, Leu95, Leu98, Ala102, Asn128, Thr88, His80, Ile83, Asn124, Leu120, and Val125, and 17 amino acids around glutenin, including Arg2, Leu10, Ser178, Ile179, Ile197, Leu13, Ala203, Met204, Pro138, Ala140, Cys148, Cys136, Pro142, Leu132, Val3, Val6, and Leu193 ( Figure 5 CD).

[0068] Results (2): Root mean square deviation of starch and protein complexes: RMSD is a measure of the coordinate deviation of a specific atom relative to a reference structure and is often used to assess whether a simulation system has reached stability. A stable RMSD value indicates that a stable equilibrium has been reached between two different conformations. Fig. 6AAs shown, Corn glutelin-0, Corn glutelin-40, Zein-0, and Zein-40 reach equilibrium after 10 ns, 10 ns, 30 ns, and 10 ns, respectively, and can be used to study the interaction behavior.

[0069] Results (3): Root mean square fluctuation of starch and protein complex: RMSF is the fluctuation of each atom relative to its average position, which characterizes the structural changes in the average time and gives a characterization of the flexibility of each region of the protein. Figure 6B We can see that in the gluten-starch composite system, the RMSF values ​​of amino acids in the 32-55 and 75-100 regions of the Corn glutelin-0 group were significantly higher than those of the Corn glutelin-40 group, indicating that the ripening process significantly affected the mobility of amino acids at this stage. In the alcohol-soluble protein-starch composite system, the RMSF value of Zein-0 was also generally higher than that of Zein-40, indicating that in the alcohol-soluble protein-starch composite system, the molecular conformation of the ripened sample was more loose.

[0070] Results (4): Gyratory radius of starch and protein complex: Rg is used to demonstrate the compactness of the protein structure during the simulation process. It is the distance between the center of mass of all atoms and their ends within a specific time interval. Figure 6C It shows that in the gluten-starch composite system, the Rg values ​​of Corn glutelin-0 and Corn glutelin-40 show a downward trend and are significantly lower than the corresponding alcohol-soluble proteins. In addition, in the alcohol-soluble protein-starch composite system, it also shows a fluctuating downward trend, and the Rg of the two proteins in the composite before ripening is lower than that after ripening, indicating that for the two proteins, the gluten structure is tighter, and the protein structure in the composite system of the two proteins and starch after ripening becomes looser.

[0071] Results (5): Solvent accessible surface area of ​​starch and protein complexes: Solvent accessible surface area is the area of ​​solutes calculated by the interaction between van der Waals forces and solvent molecules. The solvent accessible surface area of ​​proteins decreases with the increase of protein compactness, so changes in SASA can predict changes in protein structure. Fig.6D As shown in the figure, as the simulation process progresses, the SASA value of the protein-starch complex shows a downward trend, indicating that the tightness of starch to protein increases. Within the simulated 50ns time, the SASA of the cooked gluten-starch complex is lower than that of the uncooked sample, indicating that the conformation of the uncooked complex is more open.

[0072] Result (6): Number of hydrogen bonds between starch and protein: Fig. 6EAs shown in the data, the average numbers of hydrogen bonds between Corn glutelin-0, Cornglutelin-40, Zein-0 and Zein-40 proteins and starch were 6.67, 3.93, 5.69 and 5.14, respectively, indicating that there is a strong hydrogen bond interaction between protein and starch, and the number of hydrogen bonds in the post-ripening protein-starch system is significantly reduced.

[0073] In summary, the interactions between starch and protein in corn are mainly hydrophobic interaction, electrostatic interaction and hydrogen bond, and compared with alcohol-soluble protein, glutenin is more tightly bound to starch. The binding effect between starch and protein in corn after 40 days of ripening at 15°C is most significantly reduced. The use of SDS to treat the complex can weaken the interaction between starch and protein to a greater extent, release starch from the protein wrapping, thereby exerting its processing characteristics and improving the extraction rate, purity and processing utilization rate of corn starch.

[0074] The above are only preferred specific embodiments of the present invention, which are all different implementations based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for reducing the interaction between starch and protein in corn kernels, characterized in that: The method: (1) storing the newly harvested corn cobs in a constant temperature and humidity chamber to complete the ripening of the corn; (2) threshing, crushing, and soaking the ripened corn cobs, and removing the seed coat and germ; (3) Soaking the sample in a SDS solution of a certain concentration for a second time, then continuing to soak the sample under stirring, centrifuging and discarding the supernatant, and washing, drying, crushing and sieving the precipitate.

2. The method according to claim 1, characterized in that: The storage conditions in step (1) are: relative humidity of 50-60%, temperature of 10-20° C., and storage time of 35-45 days.

3. The method according to claim 1, characterized in that In step (2), the fruit is broken into 6-8 petals.

4. The method according to claim 1, characterized in that In step (2), the soaking temperature is room temperature and the soaking time is 6-10 hours.

5. The method according to claim 1, characterized in that: The concentration of the SDS solution in step (3) is 1-3 wt %.

6. The method according to claim 1, characterized in that In step (3), the second soaking temperature is room temperature, the time is 0.5-1.5h, and the soaking is continued for 3-5h.

7. The method according to claim 1, characterized in that In step (3), the secondary soaking material-liquid ratio is 1:(2-4).

8. The product obtained by the method according to any one of claims 1 to 7.

9. Use of the product according to claim 8 in the food field.

10. Use of the method according to any one of claims 1 to 7 as a pre-treatment for extracting and separating starch from starch-protein complexes.

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