Preparation method and application of anti-digestive corn starch complex coacervates

Abstract

The application belongs to the field of starch processing and relates to a preparation method and application of anti-digestive corn starch complex coacervate. The preparation method comprises the processes of plant protein pretreatment, protein crosslinking and corn starch gelatinization crosslinking, and the anti-digestive corn starch complex coacervate is obtained, wherein the amount of crosslinking enzyme is 1-50 U / g of plant protein, the mass ratio of corn starch to plant protein is 2-8:1, the concentration of plant protein is controlled to be 0.01-0.05 g / mL, and the concentration of polyphenol is controlled to be 0.0005-0.002 g / mL. The anti-digestive corn starch complex coacervate obtained by the method has low swelling power, excellent freeze-thaw stability, higher thermal stability, and the content of slow-digestive and resistant starch is more than 40%, and can be used as a drug sustained-release auxiliary material and a low-glycemic-index food ingredient, and has excellent physiological functions such as improvement of intestinal health, prevention of diabetes, control of body weight and the like, and has wide application.

Description

Technical Field

[0001] The invention belongs to the technical field of resistant starch, and in particular relates to a preparation method and application of a digestion-resistant corn starch composite polymer. Background Art

[0002] Starch plays a vital role in the human diet, being present in many staple foods and a variety of other foods. It is not only a crucial source of essential energy for the human body but also significantly impacts health and disease risk. Therefore, various approaches to slowing the digestion of starch in the human diet and creating personalized, nutritious starch-based products have both scientific and practical value.

[0003] In recent years, various studies have demonstrated that the digestion of starchy foods can be slowed by adding other food ingredients. Protein, as a crucial component of starchy foods, not only influences starch digestibility and postprandial glycemic response but also, through interactions with starch, enhances the nutritional value and processing properties of starchy foods. Exogenous proteins have similar effects on starch digestion as endogenous proteins and can also improve food physicochemical properties, such as gel-forming ability, water retention, and texture. Consequently, increasing research is focusing on adding high-quality exogenous proteins to starch to enhance the nutritional and functional properties of starchy foods. For example, cross-linking enzymes can be used to achieve intramolecular and intermolecular covalent cross-linking of exogenous proteins, forming a network structure that wraps around corn starch granules and enhances their digestibility. However, exogenous proteins have little effect on key cooking properties, such as thermal stability, freeze-thaw stability, and swelling. For example, α-lactalbumin and β-lactoglobulin have little effect on the thermal properties of corn starch. Furthermore, the protein network structure of current starch-resistant materials is poorly adapted to starch swelling, resulting in reduced cooking quality and requiring further improvement in digestibility. Summary of the Invention

[0004] To address the above technical issues, the present invention provides a digestion-resistant corn starch composite polymer, its preparation method, and application. This invention utilizes polyphenols and a cross-linking enzyme to covalently cross-link plant proteins to form a protein network. The cross-linked proteins physically encapsulate the corn starch through entanglement and hydrogen bonding to form the digestion-resistant corn starch composite polymer. This composite polymer exhibits excellent physical and chemical properties and excellent digestion resistance, making it suitable for use in the preparation of specialty foods and controlled-release carriers.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a digestion-resistant corn starch composite polymer, comprising the following steps:

[0007] S1: fully dissolving the plant protein and polyphenols in deionized water, and adjusting the pH value of the solution to 6.0-8.0 to obtain a plant protein solution; controlling the concentration of the plant protein to be 0.01-0.05 g / mL, and the concentration of the polyphenols to be 0.0005-0.002 g / mL;

[0008] S2: adding a cross-linking enzyme to the plant protein solution described in S1, with the amount of the cross-linking enzyme being 1-50 U / g plant protein, and incubating the mixture with continuous stirring until cross-linking is completely gelled to obtain a mixed solution; inactivating the cross-linking enzyme in the mixed solution to obtain a cross-linked protein solution;

[0009] S3: adding corn starch to the cross-linked protein solution, with the mass ratio of corn starch to the plant protein being 2-8:1, stirring to fully disperse the corn starch to obtain a mixed suspension; then heating the mixed suspension until gelatinization, and cooling to obtain a digestion-resistant corn starch composite polymer.

[0010] The invention provides a method for improving the digestion resistance and physicochemical properties of digestion-resistant corn starch composite polymers, wherein the digestion-resistant corn starch composite polymers are formed by wrapping corn starch with a protein network structure formed by plant protein, cross-linking enzyme and polyphenols.

[0011] The present invention utilizes the strong affinity between polyphenols and proteins to enhance the gelling properties of plant proteins. After the polyphenols and plant proteins are fully combined, a cross-linking enzyme is added. The polyphenols and cross-linking enzyme work together to form a more ordered and compact protein network in the plant proteins, increasing the contact area between the protein network and corn starch and improving the hydrogen bonding force between the two. This close combination of the two enhances the physical barrier function of the protein network, more effectively resists amylase hydrolysis, increases the ratio of slowly digestible starch to resistant starch, significantly changes the starch composition in the digestion-resistant corn starch composite, and overall enhances the digestibility of the digestion-resistant corn starch composite.

[0012] At the same time, the interaction between the protein network and corn starch is enhanced, improving the structural stability of the entire composite system, reducing its swelling and making it difficult for water to precipitate out of the system, thereby improving the freeze-thaw stability of the digestion-resistant corn starch composite. Furthermore, the ordered, compact protein network exposes more hydrophobic amino acid residues, enhancing the overall hydrophobicity of the composite and improving its thermal stability.

[0013] The present invention does not require the order in which the polyphenols and plant proteins in S1 are dissolved, as long as they are fully dissolved in the aqueous solution. For example, the present invention provides a method for preparing the plant protein solution: dissolving the plant protein in deionized water until fully hydrated, adjusting the pH value to 6.0-8.0, adding polyphenols, and stirring thoroughly to obtain a plant protein solution. Furthermore, the hydration method is to dissolve the plant protein in deionized water, let it stand at 4°C for 12 hours, and then stir evenly.

[0014] For example, the present invention provides another method for preparing the plant protein solution: dissolving polyphenols in distilled water, stirring and dissolving to obtain a polyphenol solution; dissolving plant protein in the polyphenol solution, stirring until there is no dry powder, and adjusting the pH value to 6.0-8.0 to obtain a plant protein solution.

[0015] The method for inactivating the cross-linking enzyme in S2 can be a heating inactivation method. Specifically, the mixed solution is heated at 90-100° C. for 10-15 minutes.

[0016] The plant protein in S1 can be selected from any one or a combination of protein types derived from plants such as beans and grains.

[0017] Preferably, the plant protein is mung bean protein isolate or soy protein isolate; and the concentration of the mung bean protein isolate or soy protein isolate is controlled to be 0.025-0.05 g / mL.

[0018] More preferably, the plant protein is mung bean protein isolate; and the concentration of the mung bean protein isolate is controlled at 0.025 g / mL.

[0019] Preferably, the polyphenols are food-derived polyphenols; and the concentration of the polyphenols is controlled to be 0.0015-0.002 g / mL.

[0020] As the content of polyphenols increases, the interaction between the protein network and corn starch will be further enhanced, thereby improving the digestibility and physicochemical properties of the resulting digestion-resistant corn starch composite polymer.

[0021] More preferably, the polyphenol is proanthocyanidin, chlorogenic acid or hydroxytyrosol.

[0022] More preferably, the polyphenol is proanthocyanidin.

[0023] Preferably, the cross-linking enzyme is transglutaminase, laccase or tyrosinase; and the content of the cross-linking enzyme is 10 U / g plant protein.

[0024] More preferably, the cross-linking enzyme is transglutaminase.

[0025] The buffer used to adjust the pH value in S1 can be a phosphate buffer solution.

[0026] Preferably, the buffer used to adjust the pH value in S1 is a sodium phosphate buffer containing EDTA.

[0027] Preferably, the incubation temperature in S2 is 40° C. and the incubation time is 2 h.

[0028] Preferably, the gelatinization temperature in S3 is 80-100° C. and the time is 10-30 min.

[0029] In a second aspect, the present invention provides a digestion-resistant corn starch composite polymer prepared by any one of the preparation methods described above.

[0030] The digestion-resistant corn starch composite polymer prepared according to the preparation method provided by the present invention has good digestion resistance, wherein the content of digestion-resistant starch and slowly digestible starch is not less than 40%, and also has low swelling power, excellent freeze-thaw stability, and good thermal stability.

[0031] Preferably, the plant protein used in the digestion-resistant corn starch composite polymer is mung bean protein isolate.

[0032] More preferably, the polyphenol used in the digestion-resistant corn starch composite polymer is proanthocyanidin; and the cross-linking enzyme used is transglutaminase.

[0033] In a third aspect, the present invention provides the use of the above-mentioned digestion-resistant corn starch composite polymer in the preparation of digestion-resistant food, low glycemic index food or functional food.

[0034] The digestion-resistant corn starch composite polymer provided by the present invention can be prepared into a variety of digestion-resistant foods through further processing technology to meet different food application scenarios. For example, digestion-resistant starch can be prepared after drying and crushing.

[0035] The digestion-resistant corn starch composite polymer provided by the present invention can also be used to prepare low-glycemic index foods. By slowing down the digestion rate of starch in food, the risk of rapid blood sugar increase is reduced, which helps prevent diabetes and its complications. It is suitable for diabetic patients and people who want to control blood sugar.

[0036] The digestion-resistant corn starch composite polymer provided by the present invention can also be used to prepare special medical foods to meet the nutritional needs of diabetic patients or those on a low-carbohydrate diet, help reduce the risk of diabetes, control blood sugar, and reduce the occurrence of obesity-related diseases.

[0037] The digestion-resistant corn starch composite polymer provided by the present invention can be made into low-calorie, high-satiety weight management foods, such as meal replacement powders and low-calorie snacks. By increasing the intake of resistant starch, the feeling of fullness is prolonged, which helps reduce food intake, thereby assisting in weight control and weight loss.

[0038] The digestion-resistant corn starch composite polymer provided by the present invention can be used to prepare sports nutrition supplements, such as energy gels, sports drinks, nutrition bars, etc. Its slow digestion property can provide a long-lasting energy supply and is suitable for endurance athletes or people who exercise for a long time.

[0039] The digestion-resistant corn starch composite polymer provided by the present invention is rich in dietary fiber and can be used as a prebiotic ingredient to prepare intestinal health foods, such as prebiotic powder and functional dietary fiber supplements, to promote the growth of beneficial bacteria, regulate intestinal flora, improve intestinal function, and prevent intestinal diseases.

[0040] In a fourth aspect, the present invention provides the use of the above-mentioned digestion-resistant corn starch composite polymer in the preparation of a carrier material for the controlled release of functional active substances.

[0041] The digestion-resistant corn starch composite polymer provided by the present invention can be used to prepare sustained-release drug carriers and applied in the production of pharmaceutical preparations. Its slow digestion and absorption properties prolong drug release time, reduce medication frequency, and provide more stable drug efficacy. For example, it can be used to prepare intragastric sustained-release preparations, intra-small intestinal sustained-release preparations, oral colon-targeted drug controlled-release carriers, or functional pharmaceutical hard or soft candies. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is the expansion force analysis result of each group of samples in Experimental Example 1 of the present invention;

[0043] Figure 2 The freeze-thaw stability analysis results of each group of samples in Experimental Example 2 of the present invention are as follows;

[0044] Figure 3 These are the analysis results of starch components in various samples in Experimental Example 4 of the present invention. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0046] In the examples and experimental examples, if no specific conditions are specified, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if no manufacturer is specified, are commercially available conventional products.

[0047] Example 1

[0048] This embodiment provides a digestion-resistant corn starch composite polymer, which includes mung bean protein isolate, proanthocyanidins, transglutaminase, corn starch and water.

[0049] The specific preparation method consists of the following steps:

[0050] (1) Take 1 g of mung bean protein isolate and dilute to 100 mL with deionized water. Place in a 4°C chromatography cabinet to fully hydrate for 12 h, then rapidly stir at 25°C to obtain a uniform protein stock solution. While maintaining low-speed stirring at 160-180 rpm, adjust the pH of the protein stock solution to 6.0 with 0.1 mol / L sodium phosphate buffer containing 20 mM EDTA to obtain a mung bean protein isolate solution.

[0051] (2) Weigh 0.05 g of proanthocyanidins and add them to the mung bean protein isolate solution. After stirring for 5 minutes, add 1 U / g of mung bean protein isolate glutamine transaminase to the mixed solution and incubate with continuous stirring at 40 ° C for 2 hours until complete gelation. Then, heat the mixed solution at 90 ° C for 10 minutes to inactivate the enzyme and cool it to room temperature to obtain a cross-linked protein solution.

[0052] (3) 8 g of corn starch was weighed and added to the solution containing the cross-linked protein. The mixture was stirred for 20 min to fully disperse the corn starch to obtain a mixed suspension. The mixed suspension was then heated in a boiling water bath for 30 min and then cooled to 37°C to prepare a digestion-resistant corn starch composite polymer.

[0053] Example 2

[0054] This embodiment provides a digestion-resistant corn starch composite polymer, which includes mung bean protein isolate, proanthocyanidins, transglutaminase, corn starch and water.

[0055] The specific preparation method consists of the following steps:

[0056] (1) Take 5 g of mung bean protein isolate, dilute to 100 mL with deionized water, place in a 4°C chromatography cabinet to fully hydrate for 12 h, and then rapidly stir at 25°C to obtain a uniform protein stock solution. While maintaining low-speed stirring at 160-180 rpm, adjust the pH of the protein stock solution to 8.0 with 0.1 mol / L sodium phosphate buffer containing 20 mM EDTA to obtain a mung bean protein isolate solution.

[0057] (2) Weigh 0.2 g of proanthocyanidins and add them to the mung bean protein isolate solution. After stirring for 5 min, add 50 U / g of mung bean protein isolate glutamine transaminase to the mixed solution and incubate at 40 °C for 2 h with continuous stirring until complete gelation. Then, heat the mixed solution at 100 °C for 15 min to inactivate the enzyme and cool it to room temperature to obtain a cross-linked protein solution.

[0058] (3) Weigh 10 g of corn starch and add it to the solution containing the cross-linked protein. Stir for 20 minutes to fully disperse the corn starch to obtain a mixed suspension. The mixed suspension is then heated in a boiling water bath for 30 minutes and then cooled to 37°C to prepare a digestion-resistant corn starch composite polymer.

[0059] Example 3

[0060] This embodiment provides a digestion-resistant corn starch composite polymer comprising mung bean protein isolate, proanthocyanidins, transglutaminase, corn starch, and water. The concentration of the mung bean protein isolate is 0.025 g / mL, the concentration of the proanthocyanidins is 0.0005 g / mL, and the transglutaminase content is 10 U / g of mung bean protein isolate. The mass ratio of corn starch to mung bean protein isolate is 4:1.

[0061] The specific preparation method is the same as that of Example 1, except that 2.5 g of mung bean protein isolate and 0.05 g of proanthocyanidins are used to obtain digestion-resistant corn starch composite polymer MBPI@TG / PC0.05-CS.

[0062] Examples 4-6

[0063] Examples 4-6 provide three digestion-resistant corn starch composite polymers. The raw materials and preparation methods are basically the same as those in Example 3, except that the concentrations of proanthocyanidins are 0.001, 0.0015, and 0.002 g / mL, respectively, corresponding to proanthocyanidin dosages of 0.1, 0.15, and 0.2 g, to obtain digestion-resistant corn starch composite polymers MBPI@TG / PC. 0.1 -CS、MBPI@TG / PC 0.15 -CS and MBPI@TG / PC 0.2 -CS.

[0064] Example 7

[0065] This example provides a digestion-resistant corn starch composite polymer. The raw materials and preparation method are basically the same as those in Example 3, except that the cross-linking enzyme used is laccase and the polyphenol used is chlorogenic acid. The digestion-resistant corn starch composite polymer MBPI@Lac / CA is obtained. 0.05 -CS.

[0066] Examples 8-10

[0067] Examples 8-10 provide three digestion-resistant corn starch composite polymers. The raw materials and preparation methods are basically the same as those in Example 7, except that the concentrations of chlorogenic acid are 0.001, 0.0015, and 0.002 g / mL, respectively, corresponding to chlorogenic acid dosages of 0.1, 0.15, and 0.2 g, to obtain digestion-resistant corn starch composite polymers MBPI@Lac / CA.0.1 -CS, MBPI@Lac / CA 0.15 -CS, MBPI@Lac / CA 0.2 -CS.

[0068] Example 11

[0069] This embodiment provides a digestion-resistant corn starch composite polymer. The raw materials and preparation method are basically the same as those in Example 3, except that the cross-linking enzyme used is tyrosinase and the polyphenol used is hydroxytyrosol. The digestion-resistant corn starch composite polymer MBPI@Tyr / HT is obtained. 0.05 -CS.

[0070] Examples 12-14

[0071] Examples 12-14 provide three digestion-resistant corn starch composite polymers. The raw materials and preparation methods are basically the same as those of Example 11, except that the concentrations of hydroxytyrosol are 0.001, 0.0015, and 0.002 g / mL, respectively, and the corresponding amounts of hydroxytyrosol are 0.1, 0.15, and 0.2 g, respectively, to obtain digestion-resistant corn starch composite polymers MBPI@Tyr / HT 0.1 -CS, MBPI@Tyr / HT 0.15 -CS, MBPI@Tyr / HT 0.2 -CS.

[0072] Examples 15-18

[0073] Examples 15-18 provide four digestion-resistant corn starch composite polymers. The raw materials and preparation methods are basically the same as those in Example 3, except that mung bean protein isolate is replaced with soy protein isolate, and the concentrations of proanthocyanidins are 0.0005, 0.001, 0.0015, and 0.002 g / mL, respectively, corresponding to proanthocyanidin dosages of 0.05, 0.1, 0.15, and 0.2 g, to obtain digestion-resistant corn starch composite polymers SPI@TG / PC. 0.05 -CS、SPI@TG / PC 0.1 -CS、SPI@TG / PC 0.15 -CS、SPI@TG / PC 0.2 -CS.

[0074] Examples 19-22

[0075] Examples 19-22 provide four digestion-resistant corn starch composite polymers. The raw materials and preparation methods are basically the same as those in Example 7, except that mung bean protein isolate is replaced with soy protein isolate, and the concentrations of chlorogenic acid are 0.05%, 0.1%, 0.15%, and 0.2%, respectively, to obtain digestion-resistant corn starch composite polymers SPI@Lac / CA. 0.05-CS, SPI@Lac / CA 0.1 -CS, SPI@Lac / CA 0.15 -CS, SPI@Lac / CA 0.2 -CS.

[0076] Examples 23-26

[0077] Examples 23-26 provide four digestion-resistant corn starch composite polymers. The raw materials and preparation methods are basically the same as those in Example 11, except that mung bean protein isolate is replaced with soy protein isolate, and the concentrations of hydroxytyrosol are 0.0005, 0.001, 0.0015, and 0.002 g / mL, respectively, corresponding to hydroxytyrosol dosages of 0.05, 0.1, 0.15, and 0.2 g, to obtain digestion-resistant corn starch composite polymers SPI@Tyr / HT 0.05 -CS、SPI@Tyr / HT 0.1 -CS、SPI@Tyr / HT 0.15 -CS、SPI@Tyr / HT 0.2 -CS.

[0078] Comparative Examples 1-3

[0079] Comparative Example 1 provides a digestion-resistant corn starch composite polymer MBPI@TG-CS, the raw materials and preparation method of which are basically the same as those of Example 3, except that no proanthocyanidins are added.

[0080] Comparative Example 2 provides a digestion-resistant corn starch composite polymer MBPI@Lac-CS, the raw materials and preparation method of which are basically the same as those of Example 7, except that chlorogenic acid is not added.

[0081] Comparative Example 3 provides a digestion-resistant corn starch composite polymer MBPI@Tyr-CS, the raw materials and preparation method of which are basically the same as those of Example 11, except that hydroxytyrosol is not added.

[0082] Comparative Examples 4-6

[0083] Comparative Example 4 provides a digestion-resistant corn starch composite polymer SPI@TG-CS, the raw materials and preparation method of which are basically the same as those of Comparative Example 1, except that the mung bean protein isolate is replaced with soy protein isolate.

[0084] Comparative Example 5 provides a digestion-resistant corn starch composite polymer SPI@Lac-CS, the raw materials and preparation method of which are basically the same as those of Comparative Example 2, except that the mung bean protein isolate is replaced with soy protein isolate.

[0085] Comparative Example 6 provides a digestion-resistant corn starch composite polymer SPI@Tyr-CS, the raw materials and preparation method of which are basically the same as those of Comparative Example 3, except that the mung bean protein isolate is replaced with soy protein isolate.

[0086] Comparative Example 7

[0087] This comparative example provides a gelatinized corn starch CS. The raw materials and preparation method are basically the same as those in Example 3, except that no proanthocyanidins and cross-linking enzyme are added, and mung bean protein isolate is replaced by an equal amount of deionized water.

[0088] Experimental Example 1: Expansion Force Analysis

[0089] The digestion-resistant corn starch composite polymer samples provided in Examples 3-26 and Comparative Examples 1-3 and the gelatinized corn starch sample provided in Comparative Example 7 were subjected to swelling force analysis. The specific experiment is as follows:

[0090] Add 0.5g of digestion-resistant corn starch composite polymer sample to each 50mL centrifuge tube and record the weight of the mixed sample and the corresponding empty centrifuge tube. Then add 25mL of deionized water and vortex mix thoroughly. The sample is then treated in an 85℃ water bath for 30min. After the water bath, the sample is immediately placed in an ice bath and quickly cooled to room temperature. It is then centrifuged at 4000g for 20min to separate the supernatant and precipitate. The supernatant is dried at 105℃ until the weight no longer changes. The weight of the precipitate and the dried supernatant (soluble starch) is then measured to calculate the swelling force. The results are detailed in [1]. Figure 1 The expansion force formula is as follows:

[0091] SP(%)=M P / (M0-M S )×100;

[0092] Among them, M0, M S and M P Represent the weight of sample (g), soluble starch (g) and precipitate (g), respectively.

[0093] like Figure 1 As shown in the figure, compared with gelatinized corn starch CS and digestion-resistant corn starch composite polymer samples without added polyphenols, it can be observed that the swelling force of the composite polymer treated with cross-linking enzyme and polyphenols has decreased significantly, and the swelling coefficient gradually decreases with the increase of polyphenol content, indicating that polyphenols can enhance the interaction between cross-linked proteins and corn starch. Figure 1 a, 1c, 1c and Figure 1From Figures 1b, 1d, and 1f, it can be seen that the swelling force of the digestion-resistant corn starch composite polymer prepared using mung bean protein isolate as the exogenous protein is lower than that using soy protein isolate, and it has better swelling performance, so mung bean protein isolate is preferred.

[0094] Experimental Example 2 Freeze-thaw stability analysis

[0095] The digestion-resistant corn starch composite polymer samples provided in Examples 3-26 and Comparative Examples 1-3 and the gelatinized corn starch sample provided in Comparative Example 7 were subjected to freeze-thaw stability analysis. The specific verification method is as follows:

[0096] The samples were stored at -20℃ for 24 hours, which was the first freeze-thaw cycle. At the same time, the same sample was stored at -20℃ for 24 hours, then taken out and thawed, and then stored at -20℃ for 24 hours under the same conditions for thawing, which was the second freeze-thaw cycle. The two samples with different treatment methods were centrifuged at 3000g for 20 minutes. After solid-liquid separation, the weight of the precipitate was measured and the water separation rate was calculated. The results are as follows: Figure 2 The water separation rate formula is as follows:

[0097] SR(%)=(W P -W S ) / W P ×100;

[0098] Where: W P is the mass of the sample (g); W S is the mass of the sediment (g).

[0099] like Figure 2 As shown in the figure, with the addition of cross-linking enzyme and mung bean protein isolate, the water extraction rate of corn starch was significantly reduced from 64.37% to 54.64%, which shows that exogenous protein can effectively enhance the freeze-thaw stability of corn starch. When polyphenols were introduced into the digestion-resistant corn starch composite polymer, the water extraction rate of the composite polymer was further reduced, whether it was based on mung bean protein isolate or soy protein isolate. Proanthocyanidins and chlorogenic acid had a more significant effect on reducing the water extraction rate, among which MBPI@TG / PC 0.2 -CS has the lowest water extraction rate of 43.18%. With the increase of freeze-thaw cycles, under the same experimental environment, the water extraction rate of corn starch does not change much compared with the first time, but its change trend remains the same. Figure 2 The results show that compared with the digestion-resistant corn starch composite polymers provided by Examples 3-14 and Examples 15-26, the composite polymers prepared using mung bean protein isolate in Examples 3-14 have more stable freeze-thaw stability. Therefore, mung bean protein isolate is preferred.

[0100] Experimental Example 3 Thermodynamic Property Analysis

[0101] The digestion-resistant corn starch composite polymer samples provided in Examples 3-26 and Comparative Examples 1-6 and the gelatinized corn starch sample provided in Comparative Example 7 were subjected to thermodynamic property analysis. The specific verification method is as follows:

[0102] Take 2 mg of each of the above samples, add 6 mg of deionized water, mix and place in an aluminum crucible, seal and let stand at room temperature for 24 hours to reach equilibrium. The thermodynamic properties of the samples were measured using a differential scanning calorimeter (DSC), and the test was repeated three times. The test parameters were set as follows: the temperature was heated from 20°C to 100°C at a rate of 10°C / min, and an empty crucible was used as a reference standard. Table 1 and Table 2 list the starting temperatures (T o ), peak temperature (T p ), end temperature (T c ) and gelatinization enthalpy change (ΔH).

[0103] Table 1 Thermodynamic properties of digestion-resistant corn starch composite polymers in Examples 3-14

[0104] sample <![CDATA[T o (℃)]]> <![CDATA[T p (℃)]]> <![CDATA[T c (℃)]]> ΔH(J / g) CS 63.3±0.1 66.1±0.2 71.5±0.5 12.9±0.2 MBPI@TG-CS 65.5±0.1 67.5±0.2 73.5±0.3 10.8±0.2 <![CDATA[MBPI@TG / PC 0.05 -CS]]> 66.3±0.5 68.0±0.3 73.8±0.3 10.5±0.4 <![CDATA[MBPI@TG / PC 0.1 -CS]]> 66.6±0.2 68.6±0.4 74.3±0.6 10.3±0.2 <![CDATA[MBPI@TG / PC 0.15 -CS]]> 67.1±0.4 69.3±0.3 74.5±0.2 9.9±0.3 <![CDATA[MBPI@TG / PC 0.2 -CS]]> 67.7±0.3 69.1±0.3 74.4±0.1 9.4±0.4 MBPI@Lac-CS 65.7±0.2 67.6±0.5 73.7±0.1 11.3±0.4 <![CDATA[MBPI@Lac / CA 0.05 -CS]]> 66.2±0.3 67.9±0.4 73.9±0.3 10.8±0.2 <![CDATA[MBPI@Lac / CA 0.1 -CS]]> 65.8±0.3 67.5±0.3 74.4±0.2 10.6±0.4 <![CDATA[MBPI@Lac / CA 0.15 -CS]]> 66.4±0.4 68.2±0.4 74.3±0.1 9.9±0.1 <![CDATA[MBPI@Lac / CA 0.2 -CS]]> 66.7±0.3 68.5±0.1 74.6±0.4 9.7±0.1 MBPI@Tyr-CS 66.1±0.1 67.8±0.3 74.0±0.2 11.0±0.2 <![CDATA[MBPI@Tyr / HT 0.05 -CS]]> 65.9±0.2 67.5±0.1 74.3±0.1 10.7±0.1 <![CDATA[MBPI@Tyr / HT 0.1 -CS]]> 66.3±0.1 67.6±0.2 74.5±0.6 10.6±0.1 <![CDATA[MBPI@Tyr / HT 0.15 -CS]]> 66.7±0.6 67.9±0.3 74.6±0.1 10.3±0.2 <![CDATA[MBPI@Tyr / HT 0.2 -CS]]> 67.1±0.2 68.1±0.3 74.9±0.1 10.1±0.2

[0105] Table 2 Thermodynamic properties of digestion-resistant corn starch composite polymers in Examples 15-26

[0106]

[0107]

[0108] Note: Data are expressed as mean ± standard deviation of repeated measurements.

[0109] Table 1 lists the effects of different types and amounts of cross-linking enzymes and polyphenols on the onset temperature (To), peak temperature (Tp), end temperature (Tc), and gelatinization enthalpy change of corn starch before and after catalysis using mung bean protein isolate as the plant protein. The data in the table show that the onset temperature, peak temperature, and end temperature of the digestion-resistant corn starch composite polymer with the addition of cross-linking enzymes increased, while the gelatinization enthalpy change decreased compared to corn starch. The addition of polyphenols further increased the onset temperature, peak temperature, and end temperature of the digestion-resistant corn starch composite polymer and reduced the gelatinization enthalpy change, with the trend becoming more pronounced as the amount of polyphenols increased.

[0110] Table 2 lists the effects of different types and amounts of cross-linking enzymes and polyphenols on the onset temperature (To), peak temperature (Tp), end temperature (Tc), and gelatinization enthalpy change of corn starch before and after catalysis using soy protein isolate as the plant protein. The data in this table are similar to those in Table 1, demonstrating the effect of polyphenols in increasing the onset temperature, peak temperature, and end temperature of digestion-resistant corn starch composites and reducing their gelatinization enthalpy change. This demonstrates that the method provided by the present invention can increase the gelatinization temperature and decrease the gelatinization enthalpy change of digestion-resistant corn starch composites, thereby improving their thermal stability.

[0111] At the same time, compared with the data in Table 1 and Table 2, the four thermodynamic indicators of the digestion-resistant corn starch composite polymer in the soy protein isolate group were worse than those in the mung bean protein isolate group, which indicates that using mung bean protein isolate as a protein substrate can better enhance the thermal stability of the digestion-resistant corn starch composite polymer.

[0112] Example 4: Digestion Resistance Analysis

[0113] The digestion resistance of the digestion-resistant corn starch composite polymer samples provided in Examples 3-26 and Comparative Examples 1-3 and the gelatinized corn starch sample provided in Comparative Example 7 were analyzed. The specific verification method is as follows:

[0114] 5g of the above sample was taken separately and placed in a test tube. The test tube was placed in a 37°C water bath shaker and shaken at 150g for 10min. Then, 3mL of pepsin solution (5mg / mL, 250U / mg, 0.5M HCl-KCl solution, pH=1.5) was added and incubated at 37°C for 60min. After the incubation, the pancreatic digestion stage was entered, i.e., reaction 0min. 2mL of pancreatic amylase solution (10mg / mL, 8×USP, 0.5M sodium acetate buffer, pH=5.2) and 0.065mL of amyloglucosidase (260U / mL) were added to the test tube to simulate the pancreatic digestion stage. At 0min, 20min, and 120min, 200μL of the solution was accurately taken out after fully mixing the test tube contents and immediately adding 1.8mL of anhydrous ethanol to terminate the enzymatic hydrolysis. After centrifugation at 8500g for 5min, the supernatant was collected and the glucose content was measured. Glucose content was measured using a glucose oxidase kit, and the contents of rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) were calculated using the following formulas. Figure 3 .

[0115] RDS(%)=(G 20 -G0)×0.9 / TS×100;

[0116] SDS (%) = (G 120 -G 20 )×0.9 / TS×100;

[0117] RS(%)=[1-(RDS+SDS)]×100;

[0118] G0 represents the glucose content produced at 0 min of reaction; G 20 and G 120 are the glucose contents in the supernatant after 20 min and 120 min of enzymatic hydrolysis, respectively; TS represents the total starch content in the sample.

[0119] like Figure 3 As shown, the digestion-resistant corn starch composite polymers provided in Examples 3-26 all showed a decrease in rapidly digestible starch and an increase in the content of slowly digestible starch and resistant starch, indicating that the addition of polyphenols, cross-linking enzymes, and plant proteins to starch can enhance the digestion resistance of digestion-resistant corn starch composite polymers. In addition, by comparison, it can be seen that the digestion resistance of composite polymers prepared using mung bean protein isolate is better than that of composite polymers prepared using soy protein isolate, and it shows a dependence on the amount of polyphenols added. The proportion of RS and SDS in both polymers exceeds 40%, and MBPI@TG / PC 0.2 -CS contains RS and SDS in a proportion of 50%, and although the digestion resistance of the composite polymer obtained by using soybean protein isolate as the exogenous protein is improved, it is basically unrelated to the amount of polyphenols added. Therefore, mung bean protein isolate is preferred.

[0120] In summary, the preparation method of the digestion-resistant corn starch composite polymer provided by the present invention can significantly improve the cooking-related physical and chemical properties and digestion resistance of the digestion-resistant corn starch composite polymer.

[0121] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a digestion-resistant corn starch composite polymer, characterized in that: The following steps are involved: S1: fully dissolving the plant protein and polyphenols in deionized water and adjusting the pH of the solution to 6.0-8.0 to obtain a plant protein solution; the plant protein is mung bean protein isolate; the polyphenols are proanthocyanidins, chlorogenic acid, or hydroxytyrosol; controlling the concentration of the plant protein to be 0.01-0.05 g / mL, and the concentration of the polyphenols to be 0.0005-0.002 g / mL; S2: adding a cross-linking enzyme to the plant protein solution in S1, wherein the amount of the cross-linking enzyme is 1-50 U / g plant protein, and incubating the mixture with continuous stirring until cross-linking is completely gelled to obtain a mixed solution; inactivating the cross-linking enzyme in the mixed solution to obtain a cross-linked protein solution; wherein the cross-linking enzyme is transglutaminase, laccase, or tyrosinase; S3: adding corn starch to the cross-linked protein solution, with the mass ratio of corn starch to the plant protein being 2-8:1, stirring to fully disperse the corn starch to obtain a mixed suspension; then heating the mixed suspension until gelatinization, and cooling to obtain a digestion-resistant corn starch composite polymer.

2. The method for preparing the digestion-resistant corn starch composite polymer according to claim 1, wherein: The concentration of the mung bean protein isolate is controlled at 0.025-0.05 g / mL.

3. The method for preparing the digestion-resistant corn starch composite polymer according to claim 2, wherein: The concentration of the mung bean protein isolate was controlled at 0.025 g / mL.

4. The method for preparing the digestion-resistant corn starch composite polymer according to claim 1, wherein: The polyphenols are proanthocyanidins.

5. The method for preparing the digestion-resistant corn starch composite polymer according to claim 1, wherein: The dosage of the cross-linking enzyme is 10 U / g plant protein.

6. The method for preparing the digestion-resistant corn starch composite polymer according to claim 1, wherein: The cross-linking enzyme is transglutaminase.

7. The method for preparing the digestion-resistant corn starch composite polymer according to claim 1, wherein: The buffer used for adjusting the pH value in S1 is a sodium phosphate buffer containing EDTA; and / or The incubation temperature in S2 is 40°C and the incubation time is 2 h; and / or The gelatinization temperature in S3 is 80-100° C. and the time is 10-30 min.

8. Digestion-resistant corn starch composite polymer prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the digestion-resistant corn starch composite polymer according to claim 8 in the preparation of digestion-resistant food or low glycemic index food.

10. Use of the digestion-resistant corn starch composite polymer according to claim 8 in preparing a carrier material for controlled release of functional active substances.

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