Preparation method and application of digestion-resistant corn starch complex gel polymer

Abstract

The invention belongs to the field of starch processing, and relates to a preparation method and application of an anti-digestion corn starch complex gel polymer. The preparation method comprises the processes of plant protein pretreatment, protein cross-linking, corn starch gelatinization cross-linking and the like, the anti-digestion corn starch complex gel polymer is obtained, the dosage of cross-linking 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 the 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-digestion corn starch complex gel polymer obtained by the method provided by the invention has low expansibility, excellent freeze-thaw stability and higher thermal stability, has slow digestion and resistant starch content of 40% or more, can be used as a drug sustained-release auxiliary material and a low-glycemic-index food ingredient, and has a wide application prospect. The composition has excellent physiological functions, such as improvement of intestinal health, prevention of diabetes, weight control and the like, and is widely applied.

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 people's diet and is widely present in many staple foods and various other foods. It is not only an important source of basic energy for the human body, but also significantly affects health status and disease risk. Therefore, it is of scientific significance and practical value to slow down the digestion rate of starch in the human diet through various methods and create personalized nutritional starch-based products.

[0003] In recent years, various studies have shown that the digestion rate of starchy foods can be slowed down by adding other food ingredients. As an important component of starchy foods, protein not only affects starch digestibility and postprandial blood sugar response, but also improves the nutritional value and processing characteristics of starchy foods through interaction with starch. Exogenous protein has a similar effect on starch digestion as endogenous protein, and can also improve the physicochemical properties of food, such as gel formation ability, water retention and texture. Therefore, more and more research is focused on adding exogenous high-quality protein to starch to improve the nutritional and functional properties of starchy foods. For example, covalent cross-linking within / between exogenous protein molecules is achieved through cross-linking enzymes to form a network structure to wrap corn starch particles, thereby enhancing its digestibility. However, exogenous proteins have little effect on important attributes of cooking quality, such as thermal stability, freeze-thaw stability and swelling. Taking α-lactalbumin and β-lactoglobulin as examples, their effects on the thermal properties of corn starch are not significant. In addition, the protein network structure of current digestion-resistant starch substances is difficult to adapt to the swelling of starch, resulting in a decrease in cooking quality, and the digestibility needs to be further improved. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a digestion-resistant corn starch composite polymer and its preparation method and application. The present invention utilizes polyphenols and cross-linking enzymes to synergistically covalently cross-link plant proteins to form a protein network, and the cross-linked proteins wrap corn starch inside through physical entanglement and hydrogen bonding to form a digestion-resistant corn starch composite polymer. The composite polymer not only has good physical and chemical properties but also has good digestion resistance, and can be used to prepare special foods and release-controlled 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 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 the 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, wherein the mass ratio of corn starch to the plant protein is 2-8:1, stirring to fully disperse the corn starch to obtain a mixed suspension; then heating the mixed suspension to gelatinization, and cooling to obtain a digestion-resistant corn starch complex polymer.

[0010] The invention provides a method for improving the digestion resistance and physical and chemical 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 property of plant proteins. After the polyphenols and plant proteins are fully combined, a cross-linking enzyme is added. The polyphenols and the cross-linking enzyme cooperate to form a more orderly and compact protein network of the plant proteins, increase the contact area between the protein network and corn starch, and improve the hydrogen bonding force between the two. The close combination of the two can enhance the physical barrier effect of the protein network, more effectively resist the enzymatic hydrolysis of amylase, increase the ratio of slowly digestible starch and resistant starch, significantly change the starch composition in the digestion-resistant corn starch composite polymer, and overall enhance the digestibility of the digestion-resistant corn starch composite polymer.

[0012] At the same time, the interaction between the protein network and corn starch is enhanced, which improves the structural stability of the entire composite system, reduces its swelling, and makes it difficult for water to precipitate from the system, thereby improving the freeze-thaw stability of the digestion-resistant corn starch composite. In addition, the ordered and compact protein network can expose more hydrophobic amino acid residues, enhance the overall hydrophobicity of the complex, and improve its thermal stability.

[0013] The present invention does not require the order of dissolution of polyphenols and plant proteins in S1, and the two can be fully dissolved in the aqueous solution. Exemplarily, the present invention provides a method for preparing the plant protein solution: dissolving the plant protein in deionized water until it is fully hydrated, adjusting the pH value to 6.0-8.0, adding polyphenols, and stirring sufficiently 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] Illustratively, 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; 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 polyphenols are proanthocyanidins.

[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 may 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 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 gel polymer prepared by any one of the preparation methods described above.

[0030] The digestion-resistant corn starch composite polymer prepared by 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 vegetable 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 gel 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 complex 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 food, which can help prevent diabetes and its complications by slowing down the digestion rate of starch in food and reducing the risk of rapid increase in blood sugar, and is suitable for consumption by 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 people 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, low-calorie snacks, etc. By increasing the intake of resistant starch, the satiety time is prolonged, which helps to reduce food intake, thereby assisting 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 gel, sports drinks, nutrition bars, etc. Its slow digestion characteristics can provide a lasting energy supply, which 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, functional dietary fiber supplements, etc., 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 digestion-resistant corn starch composite polymer in the preparation of a carrier material for controlled release of functional active substances.

[0041] The digestion-resistant corn starch composite polymer provided by the present invention can be used to prepare a sustained-release drug carrier and applied to the production of pharmaceutical preparations. Through its slow digestion and absorption characteristics, the drug release time is prolonged, the frequency of medication is reduced, and a more stable drug effect is provided. For example, it can be used to prepare a gastric sustained-release preparation, a small intestinal sustained-release preparation, an oral colon-targeted drug controlled-release carrier, or to prepare a pharmaceutical functional hard candy or soft candy. 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 It is the freeze-thaw stability analysis result of each group of samples in Experimental Example 2 of the present invention;

[0044] Figure 3 This is the analysis result of starch components in various samples in Experimental Example 4 of the present invention. DETAILED DESCRIPTION

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

[0046] If no specific conditions are specified in the examples and experimental examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0047] Example 1

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

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

[0050] (1) Take 1 g of mung bean protein isolate, dilute to 100 mL with deionized water, place in a 4°C chromatography cabinet for full hydration for 12 h, and rapidly stir at 25°C to obtain a uniform protein stock solution. While maintaining a low-speed stirring of 160-180 rpm, adjust the pH value 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 at 40°C with continuous stirring 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) Weigh 8 g corn starch and add it to the solution containing the cross-linked protein, stir for 20 minutes to fully disperse the corn starch, and obtain a mixed suspension. Then, heat the mixed suspension in a boiling water bath for 30 minutes, and then cool 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, glutamine aminotransferase, 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 for full hydration for 12 h, and rapidly stir at 25°C to obtain a uniform protein stock solution. While maintaining a low-speed stirring of 160-180 rpm, adjust the pH value 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 corn starch and add it to the solution containing the cross-linked protein, stir for 20 minutes to fully disperse the corn starch, and obtain a mixed suspension. Then, heat the mixed suspension in a boiling water bath for 30 minutes, and then cool to 37° C. to prepare a digestion-resistant corn starch composite polymer.

[0059] Example 3

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

[0061] The specific preparation method is the same as that in 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] Embodiment 4-6

[0063] Examples 4-6 provide three digestion-resistant corn starch composite polymers, whose raw materials and preparation methods are basically the same as those of Example 3, except that the concentrations of proanthocyanidins are 0.001, 0.0015 and 0.002 g / mL, respectively, corresponding to the amounts of proanthocyanidins 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 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 laccase and the polyphenol used is chlorogenic acid to obtain the digestion-resistant corn starch composite polymer MBPI@Lac / CA 0.05 -CS.

[0066] Examples 8-10

[0067] Examples 8-10 provide three digestion-resistant corn starch composite polymers, whose raw materials and preparation methods are basically the same as those of Example 7, except that the concentrations of chlorogenic acid are 0.001, 0.0015 and 0.002 g / mL, respectively, and the corresponding amounts of chlorogenic acid are 0.1, 0.15 and 0.2 g, respectively, to obtain digestion-resistant corn starch composite polymers MBPI@Lac / CA0.1 -CS, MBPI@Lac / CA 0.15 -CS, MBPI@Lac / CA 0.2 -CS.

[0068] Embodiment 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 0.05 -CS.

[0070] Examples 12-14

[0071] Examples 12-14 provide three digestion-resistant corn starch composite polymers, whose 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, whose raw materials and preparation methods are basically the same as those of 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 the amounts of proanthocyanidins 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, whose raw materials and preparation methods are basically the same as those of 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, and the corresponding amounts of hydroxytyrosol are 0.05, 0.1, 0.15 and 0.2 g, respectively, 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, whose raw materials and preparation method 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 by 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 by 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 by soy protein isolate.

[0086] Comparative Example 7

[0087] This comparative example provides a gelatinized corn starch CS, the raw materials and preparation method of which are basically the same as those of Example 3, except that no proanthocyanidins and cross-linking enzymes are added, and the 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 gel polymer samples provided in Examples 3-26 and Comparative Examples 1-3 and the gelatinized corn starch sample provided in Comparative Example 7 were taken for 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 after sufficient vortex mixing, the sample is then treated in an 85°C water bath for 30min. After the water bath, the sample is immediately placed in an ice bath and quickly cooled to room temperature, then centrifuged at 4000g for 20min to separate the supernatant and precipitate, and the supernatant is placed at 105°C and dried until the weight no longer changes. Then measure the weight of the precipitate and the dried supernatant (soluble starch) to calculate the swelling force. For details, see 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 1As can be seen from b, 1d, and 1f, the swelling power 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 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 gel polymer samples provided in Examples 3-26 and Comparative Examples 1-3 and the gelatinized corn starch sample provided in Comparative Example 7 were taken for freeze-thaw stability analysis. The specific verification method is as follows:

[0096] The samples were stored at -20℃ for 24h, which was the first freeze-thaw cycle. At the same time, the same samples were stored at -20℃ for 24h, then taken out and thawed, and then stored at -20℃ for 24h 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 20min. 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 precipitate (g).

[0099] like Figure 2 As shown in the figure, with the addition of cross-linking enzyme and mung bean protein isolate, the dehydration rate of corn starch was significantly reduced from 64.37% to 54.64%, which indicates 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 dehydration rate of the composite polymer with mung bean protein isolate or soy protein isolate as substrate was further reduced, and proanthocyanidins and chlorogenic acid had a more significant effect on reducing the dehydration rate, among which MBPI@TG / PC 0.2 -CS has the lowest water separation rate of 43.18%. With the increase of freeze-thaw cycles, under the same experimental environment, the water separation 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, so mung bean protein isolate is preferred.

[0100] Experimental Example 3 Thermodynamic Property Analysis

[0101] The digestion-resistant corn starch composite gel polymer samples provided in Examples 3-26 and Comparative Examples 1-6 and the gelatinized corn starch sample provided in Comparative Example 7 were taken for 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, cover 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. Tables 1 and 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 starting 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 plant protein. From the data in the table, it can be seen that the starting temperature, peak temperature, and end temperature of the digestion-resistant corn starch composite polymer added with cross-linking enzymes increased compared to corn starch, and the gelatinization enthalpy change decreased; after adding polyphenols, the starting temperature, peak temperature, and end temperature of the digestion-resistant corn starch composite polymer were further increased, and the gelatinization enthalpy change was reduced, and the trend was obvious with the increase of polyphenol content.

[0110] Table 2 lists the effects of different types and amounts of cross-linking enzymes and polyphenols on the starting temperature (To), peak temperature (Tp), end temperature (Tc) and gelatinization enthalpy change of corn starch before and after catalysis using soy protein isolate as plant protein. The data changes in the table are the same as those in Table 1, showing the effect of polyphenols on increasing the starting temperature, peak temperature, and end temperature of digestion-resistant corn starch composite gel polymers and reducing the gelatinization enthalpy change. This shows that the method provided by the present invention can increase the gelatinization temperature of digestion-resistant corn starch composite gel polymers and reduce the gelatinization enthalpy change, 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 complex polymer in the soybean 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 complex polymer.

[0112] Example 4 Digestion Resistance Analysis

[0113] The digestibility resistance of the digestion-resistant corn starch composite gel 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] Take 5g of the above sample and put it into a test tube, place the test tube in a water bath oscillator at 37°C, shake at 150g for 10min, add 3mL of pepsin solution (5mg / mL, 250U / mg, 0.5M HCl-KCl solution, pH=1.5), and incubate at 37°C for 60min. After the incubation, enter the pancreatic digestion stage, that is, the reaction 0min, add 2mL of pancreatic amylase solution (10mg / mL, 8×USP, 0.5M sodium acetate buffer, pH=5.2) and 0.065mL of amyloglucosidase (260U / mL) to simulate the pancreatic digestion stage. And at the time points of 0min, 20min and 120min, after fully mixing the contents of the test tube, accurately take out 200μL of solution, and immediately add 1.8mL of anhydrous ethanol to terminate enzymolysis, use 8500g speed centrifugation for 5min, collect the supernatant to measure the glucose content. 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 content 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 phenomenon of reduced rapidly digestible starch and increased slowly digestible starch and resistant starch content, indicating that the digestion resistance of the digestion-resistant corn starch composite polymers can be enhanced after polyphenols, cross-linking enzymes and plant proteins are added to starch. In addition, by comparison, it can be seen that the digestion resistance of the composite polymers prepared using mung bean protein isolate is better than that of the composite polymers prepared using soy protein isolate, and it shows a dependence on the amount of polyphenols added, with the proportion of RS and SDS exceeding 40%, among which MBPI@TG / PC 0.2 -CS contains RS and SDS in a proportion of 50%, and although the digestion resistance of the composite gel 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 method for preparing the digestion-resistant corn starch composite gel polymer provided by the present invention can significantly improve the cooking-related physicochemical properties and digestion resistance characteristics of the digestion-resistant corn starch composite gel polymer.

[0121] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope 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 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; 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 the 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; S3: adding corn starch to the cross-linked protein solution, wherein the mass ratio of corn starch to the plant protein is 2-8:1, stirring to fully disperse the corn starch to obtain a mixed suspension; then heating the mixed suspension to gelatinization, and cooling to obtain a digestion-resistant corn starch complex polymer.

2. The method for preparing the digestion-resistant corn starch composite polymer according to claim 1, characterized in that: The plant protein is mung bean protein isolate or soy protein isolate; the concentration of the mung bean protein isolate or soy protein isolate is controlled to be 0.025-0.05 g / mL.

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

4. The method for preparing the digestion-resistant corn starch composite polymer according to claim 1, characterized in that: The polyphenols are food-derived polyphenols; and the concentration of the polyphenols is controlled to be between 0.0005 and 0.002 g / mL.

5. The method for preparing the digestion-resistant corn starch composite polymer according to claim 4, characterized in that: The polyphenol is proanthocyanidin, chlorogenic acid or hydroxytyrosol; preferably, the polyphenol is proanthocyanidin.

6. The method for preparing the digestion-resistant corn starch composite polymer according to claim 1, characterized in that: The cross-linking enzyme is transglutaminase, laccase or tyrosinase; the dosage of the cross-linking enzyme is 10 U / g plant protein; preferably, the cross-linking enzyme is transglutaminase.

7. The method for preparing the digestion-resistant corn starch composite polymer according to claim 1, characterized in that: 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 complex 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, low glycemic index food or functional food.

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

Images