A method for reducing the digestibility of waxy corn flour by adding sodium fatty acid

Abstract

The application discloses a method for reducing the digestibility of waxy corn flour by adding sodium fatty acid, and belongs to the corn flour processing field.The method comprises the following steps: S1, waxy corn flour preparation;S2, waxy corn flour suspension preparation;S3, waxy corn flour gelatinization;S4, preparation of a compound solution;and S5, preparation of waxy corn flour with low digestibility.The waxy corn flour prepared by the method has the advantages that the digestibility of the waxy corn flour is significantly changed by adding sodium fatty acid with different carbon chain lengths, the preparation method is simple and easy to implement, and the application provides a brand-new technical method for the regulation of the digestibility of waxy corn flour products and the development of a new product base of slow-digestible waxy corn flour.

Description

Technical Field

[0001] This invention belongs to the field of corn flour processing, and specifically relates to a method for reducing the digestibility of glutinous corn flour by adding sodium fatty acid. Background Technology

[0002] Waxy corn, also known as sticky corn or glutinous corn, is a superior variety of corn, belonging to the category of high-protein, low-fat foods. Waxy corn contains essential amino acids, protein, fat, and various trace elements necessary for human growth and development. It contains 70-75% starch, 8-9% protein, 4-5% fat, and 2% various vitamins, with amylopectin accounting for over 95% of the total starch content. Compared to regular corn, waxy corn has higher levels of palmitic acid, oleic acid, lysine, crude protein, and crude fat. The germ also contains more alanine and glutamic acid, especially lysine, which is 16-74% higher than in regular corn. Furthermore, the protein content of waxy corn kernels is significantly higher than in regular corn, thus greatly enhancing its nutritional value and edible quality.

[0003] Currently, there are relatively few products made from glutinous corn flour on the market because it is easily digested and absorbed by the human body. This rapid digestion can easily cause a hyperglycemic reaction after ingestion, and some people with high blood sugar cannot consume it. This greatly limits the application of glutinous corn flour in staple foods, leading to a waste of glutinous corn resources. Therefore, reducing the digestibility of glutinous corn flour to increase its added value is one of the main research directions. At present, there are many studies on reducing starch digestibility by altering the original structure and properties of natural starch, mainly divided into physical methods, chemical methods, and enzymatic methods. Among them, physical and enzymatic methods are considered green methods because they do not involve the addition of chemical reagents. It is well known that chemical modification of corn flour can effectively change its starch structure, thereby reducing digestibility. Moreover, chemical modification is cheaper and more feasible than physical and enzymatic modification. However, chemical modification often has negative impacts on consumer safety and the environment. Therefore, there is a need to research a safe, environmentally friendly, and simple chemical modification method to reduce the digestibility of glutinous corn flour. Summary of the Invention

[0004] Technical issues

[0005] The rapid digestibility of glutinous corn flour limits its application in staple foods, necessitating the research of a safe, environmentally friendly, and simple chemical modification method to reduce its digestibility.

[0006] Technical content

[0007] The general term for sodium salts of fatty acids is sodium fatty acid. The physicochemical properties of sodium fatty acids vary depending on their carbon chain length, and they can be classified into short-chain, medium-chain, and long-chain types according to carbon chain length. In the food industry, sodium fatty acids are often used as emulsifiers due to their unique structure. Because of their antiplatelet, anticoagulant, and lipid-lowering effects, sodium fatty acids are also frequently added to functional foods.

[0008] Sodium fatty acids, as an additive, have attracted attention regarding their safety and usage limits. Recently, the EFSA Expert Group on Food Additives and Nutritional Sources (ANS) reassessed the safety of sodium fatty acid salts and other similar substances as food additives, concluding that sodium fatty acid salts and similar substances do not require an Allowable Daily Intake (ADI) and that there are no safety concerns regarding their addition to food.

[0009] Adding sodium fatty acids of different carbon chain lengths to reduce the digestibility of glutinous corn flour is a safe chemical technique. The method is simple and easy to implement, providing a new technical approach for regulating the digestibility of glutinous corn flour products and developing new slow-digesting glutinous corn flour base materials.

[0010] The purpose of this invention is to provide a method for reducing the digestibility of glutinous corn flour by adding sodium fatty acids with different carbon chain lengths. By adding sodium fatty acids with different carbon chain lengths, the interaction between amylopectin and amphiphilic molecules can occur, affecting the microstructure, short-range ordered structure, and crystallization characteristics of glutinous corn flour, thereby significantly changing the digestibility of glutinous corn flour. The preparation method is simple and easy to implement, providing a brand-new technical method for regulating the digestibility of glutinous corn flour products and developing new slow-digesting glutinous corn flour product base materials.

[0011] To achieve the above objectives, the present invention provides a method for reducing the digestibility of glutinous corn flour by adding sodium fatty acids of different carbon chain lengths, comprising the following steps:

[0012] S1. Preparation of glutinous corn flour: Grind glutinous corn kernels into powder, sieve them, and obtain sieved glutinous corn flour A;

[0013] S2. Preparation of glutinous corn flour suspension: Mix glutinous corn flour A with water to obtain glutinous corn flour suspension B;

[0014] S3. Gelatinization of glutinous corn flour: Heat and stir the glutinous corn flour suspension B described in step S2 to obtain gelatinized glutinous corn flour suspension C;

[0015] S4. Preparation of complex solution: Sodium fatty acid is added to the gelatinized glutinous corn flour suspension C described in step S3, and stirred to obtain complex solution D;

[0016] S5. Preparation of low-digestibility glutinous corn flour: The complex D described in step S4 is dried, pulverized and sieved to obtain low-digestibility glutinous corn flour.

[0017] Furthermore, the glutinous corn used in step S1 is Wannuo 2000, with an amylopectin content of 65-100%.

[0018] Furthermore, the mesh size of the sieve described in step S1 is 80 to 120 mesh.

[0019] Furthermore, the concentration of the glutinous corn flour suspension in step S2 is 5-10% (W / W, dry basis).

[0020] Furthermore, the heating in step S3 is performed by continuous stirring for 15 to 35 minutes under a water bath at 70 to 100°C.

[0021] Furthermore, the sodium fatty acid in step S4 is a sodium fatty acid with a carbon chain length of 6 to 18.

[0022] Preferably, the sodium fatty acid used in step S4 is sodium hexanoate, sodium myristate, sodium decanoate, or sodium oleate.

[0023] Specifically, the sodium fatty acid used in step S4 can be sodium oleate.

[0024] Furthermore, the amount of sodium fatty acid added in step S4 is 30-60% of the mass of the glutinous corn flour.

[0025] Furthermore, the stirring described in step S4 is performed by stirring in a hot water bath at 95°C for 30–60 minutes.

[0026] Furthermore, the mesh size of the sieve described in step S5 is 80 to 120 mesh.

[0027] The present invention provides a glutinous corn flour with low digestibility obtained by the above method.

[0028] The application of the low-digestibility glutinous corn flour provided by this invention in the food industry.

[0029] This invention provides a method for improving the short-range molecular order and crystallinity of glutinous corn starch, comprising the following steps:

[0030] 1. Preparation of glutinous corn flour: Grind glutinous corn kernels into powder, sieve them, and obtain sieved glutinous corn flour A;

[0031] 2. Preparation of glutinous corn flour suspension: Mix glutinous corn flour A with water to obtain glutinous corn flour suspension B;

[0032] 3. Gelatinization of glutinous corn flour: Heat and stir the glutinous corn flour suspension B described in step S2 to obtain the gelatinized glutinous corn flour suspension C;

[0033] 4. Preparation of complex solution: Sodium fatty acid is added to the gelatinized glutinous corn flour suspension C described in step S3, and stirred to obtain complex solution D;

[0034] 5. Preparation of glutinous corn flour with low digestibility: The complex D described in step S4 is dried, pulverized and sieved to obtain glutinous corn flour with low digestibility.

[0035] Furthermore, the glutinous corn used in step 1 is Wannuo 2000, with an amylopectin content of 65-100%.

[0036] Furthermore, the concentration of the glutinous corn flour suspension in step 2 is 5-10% (W / W, dry basis).

[0037] Furthermore, the heating in step 3 is carried out by continuous stirring for 15 to 35 minutes under a water bath at 70 to 100°C.

[0038] Furthermore, the sodium fatty acid in step 4 is a sodium fatty acid with a carbon chain length of 6 to 18.

[0039] Preferably, the sodium fatty acid used in step S4 is sodium hexanoate, sodium myristate, sodium decanoate, or sodium oleate.

[0040] Specifically, the sodium fatty acid used in step S4 can be sodium oleate.

[0041] Furthermore, the amount of sodium fatty acid added in step 4 is 30-60% of the mass of the glutinous corn flour.

[0042] Furthermore, the stirring described in step 4 is performed by stirring in a hot water bath at 95°C for 30–60 minutes.

[0043] Beneficial effects

[0044] This invention uses a safe chemical technique to prepare glutinous corn flour. By adding sodium fatty acids with different carbon chain lengths, the digestibility of glutinous corn flour is significantly reduced. The preparation method is simple and easy to implement, providing a brand-new technical method for regulating the digestibility of glutinous corn flour products and developing new slow-digesting glutinous corn flour product base materials. Attached Figure Description

[0045] Figure 1 This is a graph showing the in vitro enzymatic digestibility of glutinous corn flour modified with sodium fatty acids of different carbon chain lengths according to the present invention.

[0046] Figure 2 The microstructure of glutinous corn flour modified with sodium fatty acids of different carbon chain lengths according to the present invention is shown under a scanning electron microscope.

[0047] Figure 3The top image shows the infrared spectra of glutinous corn flour modified with sodium fatty acids of different carbon chain lengths according to the present invention. The bottom image shows the 1045 / 1022 cm⁻¹ values ​​in the corresponding FTIR spectra. -1 The absorbance ratios are shown in the data. Different lowercase letters in the data indicate significant differences in the short-range molecular order of glutinous corn flour modified with sodium fatty acid of different carbon chain lengths (P<0.05).

[0048] Figure 4 This is the X-ray diffraction pattern of glutinous corn flour modified with sodium fatty acids of different carbon chain lengths according to the present invention. Detailed Implementation

[0049] The invention will be further illustrated below through specific implementation examples.

[0050] Raw material source: Wan Nuo 2000 was purchased from Jinan Kairuide Seed Industry Co., Ltd., and stored in a cool and ventilated place.

[0051] Example 1:

[0052] S1. Preparation of glutinous corn flour: Put the raw material Wannuo 2000 (branched chain content of 98.72%) into a pulverizer for coarse grinding. The coarsely ground particles are passed through a 100-mesh sieve to obtain the target glutinous corn flour A.

[0053] S2. Preparation of glutinous corn flour suspension: A certain mass of glutinous corn flour A is mixed evenly with deionized water in a four-necked round-bottom flask to obtain a 6% (w / w, dry basis) glutinous corn flour suspension B.

[0054] S3. Gelatinization of glutinous corn flour: The target glutinous corn flour suspension B described in step S2 is continuously stirred for 30 minutes in a water bath at 95°C to obtain the target gelatinized glutinous corn flour suspension C.

[0055] S4. Preparation of the complex solution: Sodium hexanoate with an addition amount of 50% of the mass of glutinous corn flour and a carbon chain length of 6 was then added to the gelatinized glutinous corn flour suspension C described in step S3. The complex solution was then placed in a hot water bath at 95°C for 40 minutes to obtain the target complex solution D.

[0056] S5. Preparation of low-digestibility glutinous corn flour: After the reaction is completed, the complex D described in step S4 is freeze-dried, pulverized and passed through a 100-mesh sieve. The final sample is sealed and stored for later use to obtain the target low-digestibility glutinous corn flour final product.

[0057] Example 2:

[0058] The preparation was carried out according to the preparation process of Example 1, except that the sodium fatty acid added in step S4 was sodium myristate with a carbon chain length of 10, and the target complex solution C was obtained.

[0059] Example 3:

[0060] The preparation process was carried out according to Example 1, except that the sodium fatty acid added in step S4 was sodium decanoate with a carbon chain length of 14, resulting in the target complex solution C.

[0061] Example 4:

[0062] The preparation process was carried out according to Example 1, except that the sodium fatty acid added in step S4 was sodium oleate with a carbon chain length of 18, resulting in the target complex solution C.

[0063] Comparative Example 1:

[0064] The glutinous corn flour A prepared according to step S1 of Example 1 is not subjected to any subsequent processing.

[0065] Comparative Example 2:

[0066] S1, S2, and S3 were prepared according to the preparation process in Example 1.

[0067] S4. Preparation of gelatinized glutinous corn flour: After the reaction is completed, the gelatinized corn flour suspension described in step S3 is freeze-dried, pulverized and passed through a 100-mesh sieve. The final sample is sealed and stored for later use to obtain the target gelatinized glutinous corn flour final product.

[0068] Example 5:

[0069] The glutinous corn flour prepared in Examples 1-4 and Comparative Example 1 was subjected to digestibility tests.

[0070] The in vitro enzymatic digestibility of glutinous corn flour was determined using the DNS colorimetric method. Preparation of the digestive enzyme solution: Accurately weigh 0.2 g of porcine pancreatic α-amylase, add 5 mL of phosphate buffer (10 mmol / L pH = 7.0), vortex for 3 min, then centrifuge at 8000 rpm for 20 min in a centrifuge pre-cooled to 4℃. Transfer 0.2 mL of the supernatant and dilute to a 10 mL volumetric flask with phosphate buffer, shake well, and store at 4℃ for later use. Accurately weigh 80 mg of sample powder into a 50 mL reaction tube, add 12 mL of phosphate buffer (10 mmol / L pH = 7.0), and prepare a total reaction solution of 20 mL. Place the prepared sample in a 37℃ water bath and magnetically stir for 30 min to achieve equilibrium. Then add 1 mL of the prepared digestive enzyme solution to begin the reaction. At specific time points (0, 10, 20, 40, 60, 90, 120, 150, 180, 210, and 270 min), 1 mL of the reaction solution was taken, and 1.5 mL of DNS was added. The mixture was reacted in a boiling water bath for 5 min, then rapidly cooled with ice water, and finally brought to a final volume of 25 mL with ultrapure water. After thorough mixing, the OD value at 540 nm was measured using a microplate reader, and the reducing sugar content produced by starch hydrolysis was calculated based on the standard curve. Each experiment was performed in triplicate. Figure 1 As shown.

[0071] Example 6:

[0072] Other performance tests were conducted on the glutinous corn flour prepared in Examples 1-4 and Comparative Examples 1-2.

[0073] The microstructure of sodium fatty acid-glutinous corn flour was studied using a thermal field emission scanning electron microscope (JSM-7800F, equipped with an Oxford Instruments X-Max50 energy dispersive spectrometer and a backscattered electron diffractometer). Before observation, a gold-palladium coating was applied to the sample using a gold sputtering module in a high-vacuum evaporator under an argon atmosphere after placing the sample on a tray. Figure 2 As shown.

[0074] The short-range order of glutinous corn flour was determined using Fourier transform infrared spectroscopy (Spectrum Two). The sample was mixed with nitric bromide at a ratio of 1:100 (w / w), thoroughly ground, and an appropriate amount of the mixture was weighed and pressed into thin tablets using a tablet press. Test parameters: scanning wavelength range 4000–500 cm⁻¹. -1 The total number of scans was 32, and the resolution was 4cm. -1 Using air as a blank background. For 1200–800cm... -1 The infrared spectra within the wavelength range were subjected to Fourier deconvolution processing, resulting in a full width at half maximum (FWHM) of 19 cm. -1 The enhancement factor is 1.9, and the calculation is 1045cm. -1 / 1022cm -1 The peak intensity ratio reflects the short-range order of the sample. OMNIC 8.2.0 software was used to process and analyze the spectra. Figure 3 As shown.

[0075] The crystallinity of glutinous corn flour was determined using an X-ray diffractometer (Shimadzu XRD-7000S). Before testing, the sample was stored in a 100% desiccator for 12 hours to minimize moisture absorption. A small amount of sample was placed in the sample trough, flattened, and tested at room temperature. The measurement conditions were: target type: Cu; voltage: 40 kΩ; current: 40 mA; scanning range: 10°–40° (2θ); scanning speed: 49 μS / min. Based on the diffraction pattern, the crystallinity was obtained by dividing the area of ​​the crystals by the total area using Jade and Origin software.

[0076] The results show:

[0077] 1. Digestibility characteristics analysis: Figure 1 The graph shows the in vitro enzymatic digestibility of glutinous corn flour with sodium fatty acids of different carbon chain lengths. As can be seen from the graph, after 270 min, Comparative Example 1 achieved 83.66% digestibility by porcine pancreatic α-amylase. Compared to Comparative Example 1, the digestibility of Examples 1, 2, 3, and 4 showed a regular decreasing trend with increasing sodium fatty acid carbon chain length, with final digestibility of 78.08%, 75.17%, 69.63%, and 48.23%, respectively. This indicates that the digestibility of glutinous corn flour is negatively correlated with the carbon chain length of the sodium fatty acid, meaning that digestibility exhibits a sodium fatty acid carbon chain length-dependent effect.

[0078] 2. Observation using a scanning electron microscope: Figure 2 The microstructure of glutinous corn flour with sodium fatty acids of different carbon chain lengths under a scanning electron microscope is shown in the figure. As can be seen from the figure, in Comparative Example 1, starch granules are present, interspersed with fragments of protein germ and seed coat. The larger granules are typically polyhedral with rounded edges, while some smaller granules are elliptical, and the granule surface has fine pores. In Comparative Example 2, the smooth and relatively regular starch granule structure disappears. Due to complete gelatinization, the starch chains escape, and the surface of the crystalline granules is damaged, with larger pores and a honeycomb structure. Compared with Comparative Examples 1 and 2, the pore size and density of the structures in Examples 1, 2, 3, and 4 are different. As the carbon chain length of the sodium fatty acid increases, the sodium fatty acid binds more tightly to the starch granules, the pores become smaller, and the surface becomes smoother. This indicates that sodium fatty acids with longer carbon chains can better bind to glutinous corn flour to form a complex, reducing the binding sites with enzymes and thus increasing enzyme resistance.

[0079] 3. Short-range orderliness analysis: Figure 3The image shows the Fourier transform infrared (FTIR) spectra of glutinous corn flour with added sodium fatty acids of different carbon chain lengths. (The image is located at 3380.0 cm⁻¹.) -1 and 2922.0cm -1 The nearby absorption peaks are the stretching vibration peaks of the hydroxyl group and the methylene group in starch, respectively. Figure 3 As can be seen, compared with Comparative Examples 1 and 2, in Examples 1, 2, 3, and 4, with the increase of the carbon chain length of the added sodium fatty acid, the characteristic peak of the hydroxyl group in the complex shifts to a lower wavenumber, indicating that the interaction between the hydroxyl groups in amylopectin is enhanced, forming new hydrogen bonds. This may be because the long-chain sodium fatty acid reacts with amylopectin, reducing the steric hindrance of starch molecules, increasing the connection between starch chains, and enhancing the interaction. The characteristic peak of the methylene group in the complex generally shifts to a higher wavenumber, but the shift is small, indicating that sodium fatty acid has a small effect on the interaction between methylene group molecules in starch. This may be because sodium fatty acid and amylopectin are in a weakly bound state, weakening the hydrophobic interaction between them. (FTIR spectra at 1045 / 1022 cm⁻¹) -1 The change in the absorbance ratio is often used to characterize the short-range order of helical structures; in Example 4, the ratio is 1045 / 1022 cm⁻¹. -1 The higher infrared absorption ratio indicates that the short-range molecular order of Example 4 is higher than that of other comparative examples and examples. This, to some extent, reduces the accessibility of digestive enzymes to starch in the complex and enhances its resistance to enzymatic hydrolysis. These results are generally consistent with the digestibility results of the complex.

[0080] 4. Analysis of crystallization characteristics: Figure 4 X-ray diffraction patterns of glutinous corn flour with added sodium fatty acids of different carbon chain lengths under X-ray diffraction. Figure 4 It can be seen that Comparative Example 1 exhibits characteristic peaks at 15, 17, 18, and 23.5° (2θ), showing a typical A-type crystalline structure. Comparative Example 2 shows no obvious diffraction peaks due to gelatinization, possibly because the crystalline regions of starch were severely damaged during high-temperature gelatinization, and the molecular chains were disordered during aging, failing to form an ordered crystalline structure. After adding sodium fatty acid, Examples 1, 2, 3, and 4 showed crystalline peaks at 13.5°, 19.5°, 22°, 24°, and 25°, belonging to the B+V type crystalline structure. The changes in crystal type fully demonstrate that the internal crystalline structure of glutinous corn flour changed after modification with sodium fatty acid of different carbon chain lengths. Compared with Comparative Example 1, the relative crystallinity of Examples 1, 2, 3, and 4 increased significantly, gradually increasing from 12.28% to 22.40%. This indicates that with the increase of the sodium fatty acid carbon chain length, the resulting complex has a more highly ordered structure. Increased structural order leads to the formation of ordered, compact molecular arrangements, enhancing the starch's resistance to enzymatic hydrolysis.

[0081] In summary, the method of reducing the digestibility of glutinous corn flour by adding sodium fatty acids with different carbon chain lengths can regulate the in vitro enzymatic digestibility of glutinous corn flour by changing its micro-network structure and short-range order, thereby achieving the goal of reducing the digestibility of glutinous corn flour. This is a safe, effective, and feasible technical means, providing a brand-new technical approach for regulating the digestibility of glutinous corn flour products and developing new slow-digesting glutinous corn flour product base materials.

[0082] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for reducing the digestibility of glutinous corn flour by adding sodium fatty acid, comprising the following steps: S1. Preparation of glutinous corn flour: The glutinous corn kernels are crushed and sieved to obtain sieved glutinous corn flour A; the amylopectin content of the selected glutinous corn is 98.72%~100%; S2. Preparation of glutinous corn flour suspension: Mix glutinous corn flour A with water to obtain glutinous corn flour suspension B; S3. Gelatinization of glutinous corn flour: Heat and stir the glutinous corn flour suspension B described in step S2 to obtain gelatinized glutinous corn flour suspension C; S4. Preparation of the complex solution: Sodium fatty acid is added to the gelatinized glutinous corn flour suspension C described in step S3, and stirred to obtain complex solution D; the sodium fatty acid is sodium oleate; the amount of sodium fatty acid added is 50-60% of the mass of glutinous corn flour; S5. Preparation of low-digestibility glutinous corn flour: The complex D described in step S4 is dried, pulverized and sieved to obtain low-digestibility glutinous corn flour.

2. The method according to claim 1, characterized in that, The glutinous corn selected in step S1 is Wannuo 2000.

3. The method according to claim 1, characterized in that, The mesh size of the sieve described in step S1 is 80~120 mesh.

4. The method according to claim 1, characterized in that, The mass concentration of the glutinous corn flour suspension in step S2 is 5-10%.

5. The method according to claim 1, characterized in that, The heating in step S3 is performed by continuous stirring for 15 to 35 minutes in a water bath at 70 to 100°C.

6. The method according to claim 1, characterized in that, The stirring described in step S4 is performed by stirring in a hot water bath at 95°C for 30-60 minutes.

7. A glutinous corn flour with low digestibility, prepared by the method according to any one of claims 1 to 6.

8. The application of the low-digestibility glutinous corn flour according to claim 7 in the food industry.

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