Preparation method of wheat alpha-glucosidase inhibitory peptide microcapsule

Abstract

The invention relates to the technical field related to microcapsules, in particular to a preparation method of a wheat alpha-glucosidase inhibitory peptide microcapsule, which comprises the following steps: by taking wheat vital gluten as a raw material, carrying out enzymolysis by alkaline protease to obtain alpha-glucosidase inhibitory peptide, and then carrying out enzymolysis by adopting a sodium alginate-chitosan composite wall material system to obtain the wheat alpha-glucosidase inhibitory peptide microcapsule. By optimizing key parameters such as the core-wall ratio of 1: 2.632, the calcium chloride concentration of 2.48% and the curing time of 31.83 min, the double-layer microcapsule with the pH response characteristic is prepared by an ionic gel method. The embedding rate of the prepared microcapsule reaches 78.26%, the 2-hour release rate in simulated gastric juice (pH 2.0) is smaller than or equal to 21.38%, the 4-hour accumulative release rate in simulated intestinal juice is larger than or equal to 84.98%, and stomach protection and intestinal targeted release of the active peptide are achieved; meanwhile, the peptide loss rate of the product under the storage condition of 4 DEG C is less than or equal to 11.13%, the loss rate in the environment with the pH value of 2.0 is only 12.72%, and the stability of the active peptide is remarkably improved. The obtained product can effectively protect the activity of the alpha-glucosidase inhibitory peptide and improve the bioavailability of the alpha-glucosidase inhibitory peptide, and a new scheme is provided for developing functional hypoglycemic food.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of microcapsules, and particularly relates to a preparation method of wheat alpha-glucosidase inhibitory peptide microcapsules. BACKGROUND

[0002] In recent years, with the global incidence of metabolic diseases such as diabetes continuing to rise, the development of safe and effective alpha-glucosidase inhibitors has become a hot spot in the research of functional foods. Alpha-glucosidase is a key enzyme in carbohydrate digestion, and inhibiting its activity can delay glucose absorption, thereby helping to regulate postprandial blood glucose levels. At present, although the commonly used alpha-glucosidase inhibitors (such as acarbose) in clinical practice have certain efficacy, they may cause side effects such as gastrointestinal discomfort. Therefore, extracting bioactive peptides from natural food proteins as alternative inhibitors has the advantages of high safety and small side effects.

[0003] Wheat gluten is a by-product of wheat starch processing, and is rich in glutelin. After enzymatic hydrolysis, peptide segments with alpha-glucosidase inhibitory activity can be released. However, these active peptides are easily inactivated by factors such as temperature, pH and enzymolysis during processing, storage and digestion, and may be degraded by gastric acid and proteases after oral administration, resulting in reduced bioavailability. Therefore, how to improve the stability of wheat alpha-glucosidase inhibitory peptides and achieve their controlled release in the intestinal tract is a difficult point in current research.

[0004] Microcapsule technology is an effective means of protecting bioactive ingredients. The sodium alginate-chitosan system is widely studied due to its good biocompatibility, degradability and pH responsiveness. Sodium alginate can form gel microspheres by cross-linking, and chitosan as an outer coating can further enhance the mechanical strength of the microcapsules and improve their stability in gastric acid environment. However, in the prior art, there are few studies on the microencapsulation of wheat alpha-glucosidase inhibitory peptides, and there are generally problems such as low embedding rate and insufficient sustained-release performance. In addition, traditional microcapsule preparation methods (such as spray drying) may cause loss of peptide activity due to high temperature, and pure sodium alginate microspheres are easily disintegrated prematurely in a simulated gastrointestinal environment, affecting the targeted delivery of active peptides. 2+

[0005] Therefore, it is of important scientific significance and application value to develop a microcapsule preparation method that is simple in process, low in cost, and can effectively protect the activity of wheat alpha-glucosidase inhibitory peptides and improve their oral bioavailability. SUMMARY

[0006] The present application aims to provide a preparation method of wheat alpha-glucosidase inhibitory peptide microcapsules, so as to solve the problems of poor stability and low delivery efficiency of active peptides in the prior art.

[0007] ​To achieve the above object, the present application provides the following technical scheme: a preparation method of wheat alpha-glucosidase inhibitory peptide microcapsules, comprising the following steps:

[0008] S1: taking gluten as raw material, preparing wheat alpha-glucosidase inhibitory peptide by enzymatic hydrolysis method;

[0009] S2: dissolving sodium alginate in water to form a solution, adding wheat alpha-glucosidase inhibitory peptide and surfactant Tween 80, and mixing uniformly to obtain a peptide mixture;

[0010] S3: taking chitosan-acetic acid solution containing calcium chloride as wall material, dropping into the peptide mixture, preparing microcapsules by ion gel method, and obtaining wheat alpha-glucosidase inhibitory peptide microcapsule product after solidification and drying treatment.

[0011] Preferably, step S1 specifically comprises:

[0012] Disperse the gluten in pure water, the solid-liquid ratio is 1:20 (g / mL), after uniform stirring, heat in boiling water bath, cool, then add alkaline protease for enzymatic hydrolysis, obtain the enzymatic hydrolysis solution, sequentially perform enzyme inactivation, centrifugation, take the supernatant, concentrate, vacuum freeze-drying to obtain wheat alpha-glucosidase inhibitory peptide, and perform inhibition rate determination, wherein the addition amount of alkaline protease is 6000 U / g.

[0013] Preferably, in step S2,

[0014] The core-wall mass ratio is 1:2.632;

[0015] The concentration of sodium alginate solution is 1.5%;

[0016] The mass fraction of calcium chloride is 2.48%;

[0017] The dosage of Tween 80 is 0.4 g;

[0018] The solidification time is 31.83 min.

[0019] Preferably, in step S3,

[0020] The chitosan solution is prepared by dissolving chitosan in 1% acetic acid solution;

[0021] The mass fraction of the calcium chloride solution is 2.48%;

[0022] The solidification time is 31.83 min, and the solidification temperature is 45°C.

[0023] Preferably, the specific operation of ion gel method in step S3 is:

[0024] The peptide mixture is slowly added dropwise into the chitosan-acetic acid solution containing calcium chloride under continuous stirring, the pH is adjusted to 5.0, and the microcapsule product is obtained after filtration, washing, and freeze-drying.

[0025] A preparation method of wheat alpha-glucosidase inhibitor peptide microcapsules,

[0026] The microcapsule has a sodium alginate-chitosan double-layer structure and an embedding rate of greater than or equal to 78.26%.

[0027] The release rate in simulated gastric juice (pH 2.0) for 2 hours is less than or equal to 21.38%, and the cumulative release rate in simulated intestinal juice (pH 6.5) for 4 hours is greater than or equal to 84.98%.

[0028] More preferably, the peptide loss rate is less than or equal to 11.13% under storage conditions of 4°C, and the peptide loss rate is less than or equal to 12.72% in a pH 2.0 environment.

[0029] A method for improving the stability of wheat alpha-glucosidase inhibitor peptides, which microencapsulates active peptides by using the above-mentioned preparation method of wheat alpha-glucosidase inhibitor peptide microcapsules, so that the product realizes slow release in a simulated gastrointestinal environment.

[0030] Preferably, the preparation process parameters of the microcapsule are determined by response surface method optimization, and the optimization model is: embedding rate

[0031] = 77.1 - 0.41A - 0.45B + 1.54C - 4.05AB + 1.21AC - 0.063BC - 9.75A 2 - 4.17B 2 - 4.2C 2 wherein A is the core-wall ratio, B is the mass fraction of calcium chloride (%), and C is the solidification time (min).

[0032] A functional hypoglycemic food additive comprising the above-mentioned wheat alpha-glucosidase inhibitor peptide microcapsule.

[0033] Compared with the prior art, the present application has the following beneficial effects:

[0034] 1. The wheat alpha-glucosidase inhibitor peptide microcapsule with a double-layer structure is prepared by taking wheat alpha-glucosidase inhibitor peptide as the core material and sodium alginate and chitosan as the wall material, which greatly improves the stability and slow-release performance of the wheat alpha-glucosidase inhibitor peptide, and the preparation process of the method is simple and has good embedding effect.

[0035] 2. By optimizing the sodium alginate-chitosan composite wall material system (core-wall ratio 1:2.632, calcium chloride concentration 2.48%) and the solidification process (31.83 min), an embedding rate of greater than or equal to 78.26% is achieved.

[0036] 3. Adopting mild ionic gel method (low temperature operation of 45℃) to avoid high temperature damage of traditional spray drying, accurately controlling key parameters (core wall ratio, solidification time, etc.) through response surface model, good process repeatability. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 Figure for the influence of single factor experiment on the preparation method of the wheat alpha-glucosidase inhibitory peptide microcapsule on the microcapsule embedding rate;

[0038] Figure 2 Interaction three-dimensional diagram of the response surface method optimization process for the preparation method of the wheat alpha-glucosidase inhibitory peptide microcapsule;

[0039] Figure 3 Figure for the influence of environmental factors on the preparation method of the wheat alpha-glucosidase inhibitory peptide microcapsule on the stability of the microcapsule;

[0040] Figure 4 Cumulative release curve diagram of the microcapsule in simulated gastrointestinal fluid for the preparation method of the wheat alpha-glucosidase inhibitory peptide microcapsule. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0042] Please refer to Figures 1-4 The present application provides a technical solution: a preparation method of wheat alpha-glucosidase inhibitory peptide microcapsule, comprising the following steps:

[0043] S1: Taking gluten as raw material, preparing wheat alpha-glucosidase inhibitory peptide through enzymatic hydrolysis method;

[0044] S2: Dissolve sodium alginate in water to form a solution, add wheat alpha-glucosidase inhibitory peptide and surfactant Tween 80, and mix uniformly to obtain a peptide mixture;

[0045] S3: The chitosan-acetic acid solution containing calcium chloride is used as wall material, and is added dropwise into the peptide mixture to prepare microcapsules by ionic gel method, and the wheat alpha-glucosidase inhibitory peptide microcapsule product is obtained after solidification and drying treatment.

[0046] Further, step S1 is specifically: the vital gluten is dispersed in pure water, the ratio of material to liquid is 1:20 (g / mL), after stirring uniformly, boiling water bath heating, cooling, then adding alkaline protease for enzymolysis, obtaining the enzymolysis liquid, the enzymolysis liquid is sequentially subjected to enzyme inactivation, centrifugation, taking the supernatant, concentrating, vacuum freeze-drying to obtain the wheat alpha-glucosidase inhibitor peptide, and the inhibition rate is determined.

[0047] Further, the addition amount of alkaline protease is 6000 U / g.

[0048] Further, in step S2, the core-wall mass ratio is 1:2.632.

[0049] Further, in step S2, the concentration of sodium alginate solution is 1.5%.

[0050] Further, in step S2, the mass fraction of calcium chloride is 2.48%.

[0051] Further, in step S2, the amount of Tween 80 is 0.4 g.

[0052] Further, in step S2, the solidification time is 31.83 min.

[0053] Further, in step S3, the chitosan solution is chitosan dissolved in 1% acetic acid solution.

[0054] Further, a kind of microcapsule for improving the stability and digestion characteristics of wheat alpha-glucosidase inhibitor peptide is prepared by the method described above.

[0055] The following describes the embodiments of the present application, the following described embodiments are exemplary, only for explaining the present application, and cannot be understood as the limitation of the present application, the specific technology or condition not noted in the embodiments is carried out according to the technology or condition described in the literature in the art or according to the product instruction, the reagent or instrument not noted by the manufacturer is all the conventional product that can be obtained from the market.

[0056] The materials and reagents used in the following examples are as follows:

[0057] Vital gluten; alkaline protease; pepsin; trypsin; sodium alginate; chitosan (food grade); anhydrous calcium chloride; glacial acetic acid; Tween 80; Bradford protein concentration determination concentration kit; other reagents are domestic analytical pure reagents.

[0058] The instruments and equipment used in the following examples are as follows:

[0059] Electronic balance; refrigerated centrifuge; microplate reader; constant temperature magnetic stirrer; shaking incubator; constant temperature incubator.

[0060] The evaluation index used in the following examples:

[0061] (1) Determination of the inhibition rate of wheat α-glucosidase inhibitory peptide

[0062] 50 μL of PBS (0.1 M, pH 6.8), 20 μL of sample solution and 10 μL of α-glucosidase (1 U / mL) were taken respectively, and reacted at 37°C for 10 min, then 20 μL of pNRG (5 mM) was added, and reacted at 37°C for 20 min, 50 μL of Na2CO3 solution (1 M) was added dropwise to terminate the reaction, and the absorbance value was determined at 405 nm wavelength using an enzyme marker. A parallel control system was set in this experiment, wherein the blank group was replaced with an equal volume of phosphate buffer instead of the sample solution in the reaction system, and the rest of the reaction conditions were consistent with the experimental group. The inhibition rate of wheat polypeptide on α-glucosidase was calculated according to formula (I).

[0063]

[0064] In the formula, R is the inhibition rate of α-glucosidase; As is the absorbance value of the sample group; Asb is the absorbance value of the sample blank; Ac is the absorbance value of the control group; and Acb is the absorbance value of the control blank.

[0065] (2) Determination of the content of wheat α-glucosidase inhibitory peptide

[0066] Determination of the standard curve: The protein sample was diluted with PBS to prepare protein standards with concentrations of 0, 0.125, 0.25, 0.5, 0.75, 1, and 1.5 mg / mL. 5 μL of different concentrations of protein standards and samples were taken respectively and added to the protein standard wells of the 96-well plate, and 250 μL of G250 staining solution was added to each well. After standing at room temperature for 5 min, the absorbance values of each group were determined at a wavelength of 595 nm. The standard curve was drawn with the standard protein sample concentration as the abscissa and the absorbance as the ordinate: y = 0.4922x + 0.5986, R 2 = 0.9929.

[0067] The absorbance value of the sample solution to be tested was determined by the above method, and the content of the peptide in the sample solution was calculated by substituting the standard curve.

[0068] (3) Determination of the embedding rate of wheat α-glucosidase inhibitory peptide microcapsules

[0069] The CaCl2 cross-linking solution and the washing solution obtained by filtering and washing the microcapsules were combined, 1 mL of the mixed solution was taken, and the content of free wheat peptide in the mixed solution was determined by the Coomassie brilliant blue method, and the embedding rate of the wheat α-glucosidase inhibitory peptide microcapsules was further calculated according to the following formula (II).

[0070] B = (1 - m0 / m) x 100% (II)

[0071] In the formula: B is the embedding rate of polypeptide; m is the total amount of added peptide, unit g; m0 is the content of wheat α-glucosidase inhibitor peptide in the solution, unit g.

[0072] (4) Stability test of wheat α-glucosidase inhibitor peptide microcapsule

[0073] Effect of pH on microcapsule: Prepare buffer solutions with pH values of 2.0, 4.0 and 6.5, and place 0.5 g of microcapsule in a centrifuge tube. Add 10 mL of each pH value buffer solution, respectively, and let it stand at room temperature for 6 h in the dark. After centrifugation, measure the content of inhibitory peptide in the supernatant.

[0074] Effect of temperature on microcapsule: Set the microcapsule storage temperature to 4, 37 and 50°C, respectively. Then place 0.5 g of microcapsule in a centrifuge tube, and add 10 mL of pH 6.5 buffer solution, respectively. Let it stand in the dark for 6 h, and then measure the content of inhibitory peptide in the supernatant after centrifugation.

[0075] Effect of calcium ion concentration on microcapsule: Prepare calcium chloride solutions with concentrations of 0.1, 0.5 and 1.0 mol / L, respectively. Then place 0.5 g of microcapsule in a centrifuge tube, and add 10 mL of each concentration of calcium chloride solution, respectively. Let it stand at room temperature in the dark for 6 h, and then measure the content of inhibitory peptide in the supernatant after centrifugation.

[0076] (5) In vitro digestion characteristics of wheat α-glucosidase inhibitor peptide microcapsule

[0077] Weigh 0.5 g of microcapsule and disperse it in 30 mL of simulated gastric juice. Place it in a 37°C shaking incubator at 200 r / min and digest it in the dark for 2 h. After the simulated gastric digestion is completed, add an equal volume of simulated intestinal juice to it, and continue to digest it in the dark at 37°C and 200 r / min for 4 h. During the digestion process, collect 1 mL of sample every hour and supplement it with an equal volume of fresh digestion solution and solid solution. Measure the content of polypeptide in the solution, and calculate the cumulative release rate of wheat α-glucosidase inhibitor peptide in the microcapsule during the simulated gastric and intestinal juice digestion process according to formula (III):

[0078]

[0079] In the formula: Y is the cumulative release rate; m1 is the total amount of peptide in the microcapsule, unit g; m2 is the total amount of peptide released from the microcapsule in the simulated gastric and intestinal juice.

[0080] Example 1 Preparation of wheat α-glucosidase inhibitor peptide microcapsule

[0081] (1) Preparation of wheat α-glucosidase inhibitor peptide

[0082] The gluten powder was dispersed in pure water with a solid-liquid ratio of 1:20 (g / mL), stirred uniformly, and then boiled in a water bath for 10 min. After cooling to room temperature, alkaline protease was used for enzymolysis, with the enzyme addition amount controlled at 6000 U / g. The enzymolysis solution was heated in a boiling water bath for 10 min for enzyme inactivation, and then centrifuged at 10000 r / min for 10 min to obtain the supernatant for freeze-drying, thereby obtaining wheat polypeptide for subsequent use.

[0083] (2) Preparation of wheat α-glucosidase inhibitor peptide microcapsules

[0084] Sodium alginate was dissolved in deionized water to prepare a sodium alginate solution, and chitosan was dissolved in 1% acetic acid to prepare a chitosan-1% acetic acid solution. The solution was allowed to swell for 2 h, and a calcium chloride solution was prepared for standby use. 0.5 g of wheat peptide sample was weighed, and 50 mL of sodium alginate solution was used to completely dissolve the sample. Then, 0.4 g of Tween 80 solution was immediately added, and the mixture was thoroughly mixed. Subsequently, 50 mL of calcium chloride solution was thoroughly mixed with 50 mL of chitosan-1% acetic acid solution, and the mixed peptide sodium alginate solution was slowly added dropwise under the condition of 45°C, with constant stirring and adjustment of the pH of the solution to 5.0. After the mixed sample solution was solidified for 30 min, the microcapsule sample was filtered and washed multiple times, and then dried in a freeze dryer to obtain the wheat α-glucosidase inhibitor peptide microcapsule sample.

[0085] Example 2 Single-factor experiment design

[0086] The initial process conditions (core-to-wall ratio 1:3, calcium chloride mass fraction 2.0%, and solidification time 20 min) were fixed, and five groups of different core-to-wall ratios (1:1, 1:2, 1:3, 1:4, and 1:5), solidification times (10, 20, 30, 40, and 50 min), and calcium chloride mass fractions (1.0%, 1.5%, 2.0%, 2.5%, and 3.0%) were set to explore their effects on the microcapsule embedding rate. Through the above single-factor variable control, the independent effects of each factor on the microcapsule embedding rate were determined.

[0087] (1) Box-Behnken response surface test

[0088] According to the results of the single-factor experiment, the core-to-wall ratio (A), the calcium chloride mass fraction (B, %), and the solidification time (C, min) were selected as independent variables, and the embedding rate was selected as the response value. The response surface optimization experiment was performed by DesignExpert V8.0.6 software. The three-factor three-level coding is shown in Table 1.

[0089] Table 1 Factors and levels of response surface test

[0090]

[0091] Results and Analysis of Example 3

[0092] Single-factor experimental results

[0093] See results Figure 1 As shown in Figure A, the encapsulation effect is optimal when the core-to-wall material ratio is 1:3, achieving an encapsulation rate of 78.65%. A lower core-to-wall material ratio results in a lower encapsulation rate, possibly due to insufficient core material content leading to inadequate encapsulation within the microcapsules. Conversely, as the ratio increases, the microcapsule walls become thinner, resulting in some core material not being completely encapsulated, thus reducing the encapsulation rate. Therefore, a core-to-wall material ratio of 1:3 yields the highest encapsulation rate.

[0094] Figure 1 As shown in Figure B, the mass fraction of calcium chloride has a significant impact on the encapsulation efficiency. The encapsulation efficiency of the microcapsules initially increases and then decreases with increasing calcium chloride mass fraction. The highest encapsulation efficiency (77.56%) is achieved at a calcium chloride mass fraction of 2.5%, while the encapsulation efficiency is only 54.31% at 1%. Lower calcium chloride mass fractions result in lower encapsulation efficiency, possibly due to insufficient cross-linking between calcium ions and sodium alginate, leading to core material leakage. Conversely, excessively high calcium ion concentrations hinder the binding of chitosan to sodium alginate due to the strong electrostatic interaction between sodium alginate and calcium ions, thus reducing the encapsulation efficiency. Therefore, an encapsulation efficiency of 2.5% calcium chloride mass fraction yields the best results.

[0095] Figure 1 As shown in Figure C, the microcapsule encapsulation rate initially increased and then decreased with increasing curing time. When the curing time was 30 min, the microcapsule encapsulation rate was 80.26%, significantly higher than the other four groups. Among the five groups, the encapsulation rates were lower at fixed curing times of 10 min and 50 min, indicating that the reaction between calcium ions and the wall material requires a certain amount of time. Shorter curing times prevent calcium ions from fully diffusing into the sodium alginate, resulting in incomplete cross-linking and a lower encapsulation rate. Conversely, excessively long curing times and continuous stirring can damage the wall material, further reducing the encapsulation rate. Therefore, the optimal curing time is 30 min.

[0096] Response surface methodology results

[0097] The results are shown in Table 2. Analysis of variance and regression analysis were performed on the data in Table 2 to fit the experimental results. Using core-to-wall ratio (A), calcium chloride mass fraction (B), and curing time (C) as independent variables, the regression equation was obtained: [Embedding ratio]

[0098] =77.1-0.41A-0.45B+1.54C-4.05AB+1.21AC-0.063BC-9.75A 2 -4.17B 2 -4.2C 2 Table 2 Response Surface Experimental Design and Results

[0099]

[0100]

[0101] Table 3 shows that the regression model is highly significant (P<0.0001), and the lack-of-fit term is not significant (P=0.0672>0.05), indicating that the equation fits well. The coefficient of determination R2=0.9834 and the correction coefficient R2Adj=0.9622 indicate that the actual value and the predicted value are highly correlated. Furthermore, C has a significant impact on the embedding rate (P<0.05), and AB has a significant interaction effect (P<0.05).

[0102] Table 3. Analysis of variance of the regression equations

[0103]

[0104] Note: **, P<0.01, extremely significant effect; *, P<0.05, significant effect.

[0105] A 3D response surface plot reflects the pairwise influence of factors on the response value; the steeper the 3D surface plot, the more significant the interaction between the two factors. Figure 2 A significant interaction between A and B is observed (P<0.05), consistent with the results of the analysis of variance. The optimal microencapsulation process conditions, determined using response surface methodology, were: a core-to-wall mass ratio of 1:2.632, a calcium chloride mass fraction of 2.48%, and a curing reaction time of 31.83 min. Under these conditions, the encapsulation efficiency reached 78.26%. Based on practical operation, the parameters were adjusted to a core-to-wall ratio of 1:2.7 (mass ratio), a calcium chloride mass fraction of 2.5%, and a curing time of 32 min. Three parallel experiments were conducted, yielding an average encapsulation efficiency of 79.86%. The predicted values ​​are close to the experimental values, indicating high reliability of the model.

[0106] (1) Stability study of wheat α-glucosidase inhibitory peptide microcapsules

[0107] Effect of pH on microcapsule stability

[0108] like Figure 3 As shown in Figure A, the loss rate of wheat α-glucosidase inhibitory peptides exhibited a significant upward trend with increasing pH. When the pH reached 6.5, the peptide loss rate was as high as 33.98%; while at pH values ​​of 2 and 4, the peptide loss rates were relatively low, at 12.72% and 14.31%, respectively. The pH of the human small intestine environment is close to that of pH 6.5, indicating that the microencapsulated wheat peptides can be rapidly released in the small intestine, thereby contributing to improved bioavailability.

[0109] Effect of temperature on microcapsule stability

[0110] Depend on Figure 3 As shown in Figure B, the peptide loss rates of wheat peptides in the microcapsules at 4℃, 37℃, and 60℃ were 11.13%, 13.45%, and 29.36%, respectively. The peptide loss rate gradually increased with increasing temperature; the highest loss rate was observed at 60℃, likely because high temperatures damage the microcapsule shell, causing wheat peptides to leak out and thus increasing the loss rate. In contrast, the wheat peptide loss rates were relatively low at 4℃ and 37℃, indicating that the wheat α-glucosidase inhibitory peptide microcapsules are more resistant to storage within this temperature range.

[0111] Effect of calcium ion concentration on microcapsule stability

[0112] Depend on Figure 3 As shown in C, the loss rate of peptides in the microcapsules increased continuously with the increase of calcium ion concentration, reaching 13.54%, 15.34%, and 25.09% respectively. This indicates that the ion concentration significantly affects the stability of the microcapsules, and excessively high concentrations will have an adverse effect on the storage of wheat α-glucosidase inhibitory peptide microcapsules.

[0113] (2) Release properties of wheat α-glucosidase inhibitory peptide microcapsules

[0114] The release characteristics of wheat peptides during simulated gastrointestinal digestion, such as Figure 4 As shown, in the first hour of gastric digestion, only 12.41% of the wheat peptides were released from the microcapsules, demonstrating the protective effect of the microcapsules on the core material. As gastric digestion continued for 2 hours, the cumulative release rate of wheat peptides from the microcapsules reached 21.38%. During intestinal digestion, the alkaline environment of the intestine led to the gradual degradation of the microcapsule shell, prompting a further significant release of wheat peptides. The cumulative release rate reached 40.57% in the first hour and increased to 76.91% in the second hour, subsequently stabilizing. Finally, after 6 hours of simulated gastrointestinal digestion, the cumulative release rate reached 84.98%. These results indicate that the wheat α-glucosidase inhibitory peptide microcapsules exhibit good controlled-release and sustained-release effects under simulated gastrointestinal digestion conditions.

[0115] In conclusion, the wheat α-glucosidase inhibitory peptide was used as the core material, sodium alginate-chitosan was used as the complex wall material, and the freeze-drying method was used to prepare the microcapsules. The preparation process of the microcapsules was optimized by single factor test and response surface test. The optimal preparation process of the microcapsules was as follows: the core / wall ratio was 1:2.632, the mass fraction of calcium chloride was 2.48%, and the solidification time was 31.83 min. Under the optimal conditions, the embedding rate of the microcapsules was 78.26%. The loss rate of the peptides in the microcapsules was determined by adjusting different pH, temperature and calcium ion levels, and the stability of the microcapsules was evaluated. Finally, the in vitro gastrointestinal simulation digestion test showed that the cumulative release rate of the wheat peptides in the microcapsules was only 21.38% in the first 2 h before digestion, and the wheat peptides were released in large amounts after entering the intestine, indicating that the microencapsulation of the wheat peptides could effectively resist the stomach environment and realize the release in the intestine. The above results showed that the microencapsulation of the wheat peptides could effectively improve the stability of the product, prolong the storage period, and also provide a certain theoretical basis for the development of blood glucose-lowering products.

[0116] While embodiments of the present application have been shown and described, it is to be understood that the embodiments described are merely divergences, modifications, replacements and variations of the embodiments, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing wheat α-glucosidase inhibitory peptide microcapsules, characterized in that, Includes the following steps: S1: Wheat α-glucosidase inhibitory peptide was prepared by enzymatic hydrolysis using wheat gluten as raw material; S2: Dissolve sodium alginate in water to form a solution, add wheat α-glucosidase inhibitory peptide and surfactant Tween 80, mix well to obtain peptide mixture; S3: A chitosan-acetic acid solution containing calcium chloride was used as the wall material and added dropwise to the peptide mixture. Microcapsules were prepared by ion gelation and then cured and dried to obtain wheat α-glucosidase inhibitory peptide microcapsule products.

2. The method for preparing wheat α-glucosidase inhibitory peptide microcapsules according to claim 1, characterized in that, Step S1 specifically includes: Gluten powder was dispersed in pure water at a ratio of 1:20 (g / mL), stirred evenly, heated in a boiling water bath, cooled, and then alkaline protease was added for enzymatic hydrolysis to obtain the hydrolysate. The hydrolysate was then subjected to enzyme inactivation, centrifugation, and the supernatant was collected, concentrated, and then freeze-dried under vacuum to obtain wheat α-glucosidase inhibitory peptide. The inhibition rate was then determined, with the amount of alkaline protease added being 6000 U / g.

3. The method for preparing wheat α-glucosidase inhibitory peptide microcapsules according to claim 1, characterized in that, In step S2, Core-to-wall mass ratio: 1:2.632; The concentration of the sodium alginate solution is 1.5%; The mass fraction of calcium chloride is 2.48%. The dosage of Tween 80 is 0.4g; The curing time was 31.83 min.

4. The method for preparing wheat α-glucosidase inhibitory peptide microcapsules according to claim 1, characterized in that, In step S3, The chitosan solution is prepared by dissolving chitosan in a 1% acetic acid solution; The calcium chloride solution has a mass fraction of 2.48%.

5. The method for preparing wheat α-glucosidase inhibitory peptide microcapsules according to claim 1, characterized in that, The specific operation of the ionogel method in step S3 is as follows: The peptide mixture was slowly added dropwise to a chitosan-acetic acid solution containing calcium chloride under continuous stirring. The pH was adjusted to 5.0, and after solidification, the mixture was filtered, washed, and freeze-dried to obtain the microcapsule product.

6. The wheat α-glucosidase inhibitory peptide microcapsules prepared by the method according to any one of claims 1-5 are characterized in that, The microcapsules have a sodium alginate-chitosan bilayer structure with an encapsulation efficiency of ≥78.26%. The release rate was ≤21.38% in simulated gastric fluid (pH 2.0) after 2 hours and ≥84.98% in simulated intestinal fluid (pH 6.5) after 4 hours.

7. The wheat α-glucosidase inhibitory peptide microcapsules according to claim 6, characterized in that, The peptide loss rate is ≤11.13% under storage conditions at 4℃ and ≤12.72% under pH 2.0 conditions.

8. A method for improving the stability of wheat α-glucosidase inhibitory peptides, characterized in that, The active peptides are microencapsulated using any of the methods described in claims 1-5, enabling sustained release of the product in a simulated gastrointestinal environment.

9. The method for preparing wheat α-glucosidase inhibitory peptide microcapsules according to claim 1, characterized in that, The preparation process parameters of the microcapsules were determined by response surface methodology, and the optimization model is as follows: Encapsulation rate = 77.1 - 0.41A - 0.45B + 1.54C - 4.05AB + 1.21AC - 0.063BC - 9.75A 2 -4.17B 2 -4.2C 2 Where A is the core-to-wall ratio, B is the mass fraction of calcium chloride (%), and C is the curing time (min).

10. A functional hypoglycemic food additive, characterized in that, Microcapsules containing wheat α-glucosidase inhibitory peptides as described in any one of claims 6-7.

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