Method for preparing short-outer-chain maltodextrin through multiple enzymolysis

Abstract

The invention relates to a method for preparing short-outer-chain maltodextrin through multiple times of enzymolysis, and belongs to the technical field of starch biology. The method comprises the following steps: adding high-temperature-resistant alpha-amylase into starch milk, heating to gelatinize the starch milk, cooling, adding beta-amylase, carrying out primary enzymolysis reaction, cooling and removing impurities to obtain primary reaction liquid; repeatedly adding beta-amylase into the primary reaction liquid for enzymolysis and cooling for impurity removal to obtain multi-stage enzymolysis reaction liquid; and drying the obtained multi-stage enzymolysis reaction liquid to obtain the short-outer-chain maltodextrin. The prepared maltodextrin with the short outer chain has the advantages of being low in molecular weight, high in branching degree and short in outer chain, and the structure is not prone to forming double helixes and can hinder combination of digestive enzymes and continuous attack of inner chains, so that the dissolution rate and the stability of a solution are improved, the proportion of fast digestible starch is reduced, and the functional characteristics of the maltodextrin are optimized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of starch biotechnology, and particularly relates to a method for preparing short outer chain maltodextrin through multiple enzymolysis. BACKGROUND

[0002] Maltodextrin is a mixture of polysaccharides and oligosaccharides obtained by partial hydrolysis of starch, and the dextrose equivalent (DE) is generally less than 20. The main components of maltodextrin include α-glucose chains with different degrees of polymerization, mainly connected by α-1, 4-glycosidic bonds, and a small amount of branched structures formed by α-1, 6-glycosidic bonds. According to the US Food and Drug Administration (FDA), maltodextrin is a recognized safe food additive, easy to digest and non-toxic, and is widely used in the food industry. The functional properties of maltodextrin mainly depend on the degree of hydrolysis. Maltodextrin with DE 15-20 has more small sugar components, obvious sweetness, can cause browning, has good color development effect, good solubility and weak viscosity. Maltodextrin with DE 10-15 has moderate small sugar ratio, low sweetness, good solubility and suitable viscosity. Maltodextrin with DE 5-10 has more high molecular sugar components and a small amount of low molecular small sugar components, so this maltodextrin has no obvious sweetness, is not easy to absorb moisture and has strong viscosity. Maltodextrin with DE < 5 has good adhesive and gel properties due to low degree of hydrolysis. However, the application of maltodextrin also has certain limitations. Ordinary high-DE maltodextrin has a large content of reducing sugar and is easy to cause browning during high-temperature treatment. Ordinary low-DE maltodextrin contains more linear dextrin in the molecule, and the molar mass distribution is uneven, which causes coagulation and sedimentation in the solution after standing for a period of time due to the association between molecules, and the transparency decreases. In addition, maltodextrin is easy to digest and can cause rapid rise of blood glucose in the human body after being ingested, which is not conducive to maintaining blood glucose homeostasis and achieving sustained energy supply, and does not meet the needs of contemporary consumers for healthy food. Therefore, it is of great significance to modify maltodextrin through certain means to improve the application performance of maltodextrin.

[0003] Currently, the main methods for improving the properties of maltodextrin include chemical modification and enzymatic modification. Although chemical modification (such as esterification, cross-linking and etherification) can improve the physicochemical properties of maltodextrin, it will produce a large amount of wastewater, causing environmental pollution and posing health risks. In contrast, enzymatic modification has more application prospects due to its green and environmentally friendly nature and the ability to produce "clean label" ingredients. Beta-amylase (EC 3.2.1.2) is an exo-enzyme that can hydrolyze alpha-1,4-glucosidic bonds from the non-reducing end of glycogen or starch, continuously releasing maltose. When beta-amylase acts on starch, maltose and beta-limit dextrin are generated. Preliminary studies have found that the beta-amylase hydrolysis rate of beta-limit dextrin obtained by traditional one-step hydrolysis is still 18.12%, indicating that the modification of the outer chain of starch in the existing technology is still not sufficient enough, limiting the improvement of its functional properties. Therefore, there is an urgent need to develop a strategic enzymatic method to further shorten the length of the outer chain of amylopectin and improve the functional properties of maltodextrin. SUMMARY

[0004] To solve the above problems, the present application provides a method for preparing short outer chain maltodextrin by multiple enzymatic hydrolysis. The maltodextrin prepared by the present application has the characteristics of low molecular weight, high branching degree and short outer chain. This structure is not easy to form a double helix and can hinder the binding of digestive enzymes and the continuous attack on the inner chain, thereby improving the dissolution rate and the stability of the solution, reducing the proportion of fast digestible starch, and optimizing the functional properties of maltodextrin.

[0005] The present application is achieved by the following technical solutions:

[0006] The first object of the present application is to provide a method for preparing short outer chain maltodextrin by multiple enzymatic hydrolysis, comprising the following steps:

[0007] (1) Adding a high-temperature-resistant alpha-amylase to the starch milk, heating to gelatinize the starch milk, and then adding beta-amylase to perform one-step enzymatic hydrolysis reaction after cooling, and removing impurities by cooling to obtain a one-step reaction liquid;

[0008] (2) Repeating the addition of beta-amylase for enzymatic hydrolysis and cooling to remove impurities to the one-step reaction liquid obtained in step (1) to obtain a multi-stage enzymatic hydrolysis reaction liquid;

[0009] (3) Drying the multi-stage enzymatic hydrolysis reaction liquid obtained in step (2) to obtain short outer chain maltodextrin.

[0010] In an embodiment of the present application, in step (1), the concentration of the starch milk is 5% to 30% (w / w);

[0011] And / or, the pH value of the starch milk is 5.0 to 6.0.

[0012] In an embodiment of the present application, in step (1), the starch milk is obtained by dispersing starch in water.

[0013] In one embodiment of the present application, in step (1), the starch in the starch milk is selected from one or more of tapioca starch, normal corn starch, waxy corn starch, potato starch, rice starch and wheat starch.

[0014] In one embodiment of the present application, in step (1), the high-temperature resistant alpha-amylase is added in an amount of 0 U / g to 5 U / g of dry substrate.

[0015] In one embodiment of the present application, in step (1), the temperature for gelatinization is 80°C to 95°C.

[0016] And / or, the time for gelatinization is 0.5 h to 2 h.

[0017] In one embodiment of the present application, in step (1), the beta-amylase is added in an amount of 1000 U / g to 3000 U / g of dry starch.

[0018] In one embodiment of the present application, in step (1), the temperature for enzymatic reaction is 50°C to 60°C; and the time is 12 h to 24 h.

[0019] In one embodiment of the present application, in step (1), the method for removing impurities is adding yeast for removing impurities; and the yeast is added in an amount of 0.5 wt% to 3 wt%.

[0020] In one embodiment of the present application, the yeast is selected from high-sugar-tolerant yeast.

[0021] In one embodiment of the present application, in step (1), the temperature for removing impurities is 30°C to 40°C.

[0022] In one embodiment of the present application, in step (2), the number of repetitions is ≥1.

[0023] In one embodiment of the present application, in step (2), the beta-amylase is added in an amount of 1000 U / g to 3000 U / g of dry starch.

[0024] In one embodiment of the present application, in step (2), the temperature for enzymatic reaction is 30°C to 40°C; and the time is 24 h to 48 h.

[0025] In one embodiment of the present application, in step (2), after cooling and removing impurities, there is further decolorization and desalination treatment.

[0026] In one embodiment of the present application, the decolorization is activated carbon decolorization; and the activated carbon is added in an amount of 1 wt% to 2 wt%.

[0027] And / or, the temperature for decolorization is 30°C to 40°C.

[0028] And / or, the time of decolorization is 0.5h-12h.

[0029] In one embodiment of the present application, the desalination is to remove salt ions in the reaction solution by using cation and anion exchange resin.

[0030] The second object of the present application is to provide short outer chain maltodextrin prepared by the method.

[0031] The third object of the present application is to provide the application of the short outer chain maltodextrin in special medical use formula food, probiotic product, health product, meal replacement product or pharmaceutical product.

[0032] The above technical solutions of the present application have the following advantages compared with the prior art:

[0033] 1. The present application provides a method for preparing short outer chain maltodextrin by multiple enzymatic hydrolysis. By controlling the number of enzymatic hydrolysis reactions and conditions, the length of the starch molecule outer chain is gradually shortened. Compared with single enzymatic hydrolysis process, the present method reduces the β-amylase hydrolysis rate of the product from 18.12% to below 4%, and the molecular weight distribution is more uniform.

[0034] 2. The present application reduces the fast digestible component ratio of the product from 93.25% (raw material cassava starch) to 64.91% by multiple enzymatic hydrolysis process, which is reduced by 24.17% compared with ordinary maltodextrin, and the resistant component content is increased to 29.50%. The process retains the α-1, 6 glycosidic bond inside the molecular chain, which increases the branching degree of the product by 13.05% compared with ordinary maltodextrin, and the change of molecular structure significantly delays the in vitro digestibility.

[0035] 3. The molecular weight of the product obtained by the present application is less than 10 4 Da, the dissolution speed is shortened by half compared with traditional maltodextrin, and the solution viscosity is lower than 11mPa·s. This characteristic makes it suitable for health food systems that require rapid dispersion, while ensuring slow digestion function, and solves the common processing problem of high solid content system.

[0036] 4. The product obtained by the present application has short outer chain structure and narrow molecular weight distribution characteristics, and the formed solution has a light transmittance of 97.2%, which remains highly transparent after 30 days of storage at 4℃, overcoming the defect of ordinary maltodextrin that is easy to separate out during cold storage, and has good transparency stability.

[0037] 5. The process condition involved in the present application is mild, the reaction specificity is strong, and industrial production can be realized without complex equipment, which has good industrial application prospect and is conducive to the research and development and popularization of short outer chain maltodextrin related products. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to make the content of the present application more easily understood, the present application is further described in detail below according to specific embodiments of the present application and in conjunction with the accompanying drawings, in which:

[0039] Figure 1 is the multiple enzymatic hydrolysis process flow of the present application;

[0040] Figure 2 is the storage stability of the ordinary malt dextrin and enzymatic hydrolysis product solution in Example 6 of the present application at 4℃, wherein (A) is the state stored for 0 days, and (B) is the state stored for 30 days. DETAILED DESCRIPTION

[0041] The present application is further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present application and implement it, but the embodiments are not limiting to the present application.

[0042] The experimental methods used in the following examples are conventional methods, and the materials, reagents, etc. used are commercially available, unless otherwise specified.

[0043] The detection methods used in the following examples are as follows:

[0044] (1) In vitro simulated digestion

[0045] Mix 50 mg pepsin with 10 mL HCl (0.05 mol / L) solution, vortex oscillation for 5 min to fully mix, and prepare pepsin solution, which is stored in ice bath and prepared for use. Mix 3 g porcine pancreatic enzyme with 20 mL deionized water, vortex oscillation for 5 min to fully mix, and centrifuge at 4℃, 3500 g for 10 min, take 15 mL supernatant, and mix with 0.8 mL amyloglucosidase to prepare mixed enzyme solution, which is stored in ice bath and prepared for use.

[0046] Accurately weigh 0.1 g of the sample (dry basis) into 2.5 mL of sodium acetate buffer (0.25 mol / L, pH 5.2), heat in a boiling water bath for 30 min to gelatinize the sample, then add 15 glass beads, and preheat in a 37℃ water bath shaker at 160 r / min for 10 min. Then, add 1.67 mL of pepsin solution, and shake for 30 min to simulate the gastric digestion process. After the gastric digestion, add 2.5 mL of sodium acetate buffer (pH 5.2), continue to shake for 30 min, and add 0.83 mL of mixed enzyme solution to simulate the intestinal digestion process. At 20 min and 120 min of the simulated intestinal digestion, respectively, 200 μL of the digestion solution is taken out into 5 mL of 66.6% ethanol to terminate the reaction, and the mixture is centrifuged at 3500 g at room temperature for 5 min, then 0.05 mL of the supernatant is accurately taken out, and the glucose content is determined by the glucose oxidase method, and the proportions of rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS) components are calculated. The specific calculation formula is as follows:

[0047] RDS (%) = G 20 × 0.9 × 100

[0048] SDS (%) = (G 120 -G 20 ) × 0.9 × 100

[0049] RS (%) = 100 - RDS - SDS

[0050] wherein G 20 represents the proportion of glucose produced by the sample digestion for 20 min, and G 120 represents the proportion of glucose produced by the sample digestion for 120 min.

[0051] (2) Viscosity

[0052] The product is prepared into a 30% (w / w) solution on the sample table of a rheometer, CP50 clamps are selected, the gap is 0.1 mm, the temperature is set to 25℃, the shear rate is 50 s -1 , and the viscosity is expressed by mPa·s.

[0053] (3) Dissolution rate

[0054] Accurately weigh 1 g sample for use, take 20 mL beaker, add 10 mL, water temperature 25℃ of distilled water, put the magnetic stirrer rotor into the beaker, adjust the speed to 1000 r / min, pour the weighed sample into the beaker within 10 s, start timing with a stopwatch when the sample is poured, and observe and record the time required for the sample to completely dissolve to transparent.

[0055] (4) Structure analysis

[0056] β-amylase hydrolysis rate: 10 mg of sample was weighed, and a sample solution of 5 mg / mL was prepared with 50 mmol / L, pH 5.5 phosphate buffer. The sample was fully gelatinized by heating in a boiling water bath for 30 min. After the sample solution was incubated in a 55℃ water bath for 15 min, 10 U / mg of β-amylase was added, and the reaction was maintained at 50℃ for 24 h. After the reaction was completed, the reaction was terminated by boiling in a water bath for 30 min. The solution was filtered through a 0.22 μm water filter membrane, and the maltose content in the solution was analyzed by high-performance anion exchange chromatography to calculate the β-amylase hydrolysis rate of the sample.

[0057] Molecular weight distribution: 10 mg of sample was weighed, and a sample solution of 5 mg / mL was prepared with deionized water. The sample was fully gelatinized by heating in a boiling water bath for 30 min, and then filtered through a 0.22 μm filter. The molecular weight distribution and weight average molecular weight of the sample were analyzed by high-performance size exclusion chromatography.

[0058] Glycosidic bond ratio: 50 mg of sample was weighed and dispersed in 1 mL of heavy water (D2O). The sample was gelatinized by boiling for 30 min. After cooling to room temperature, 0.5 mL of the sample solution was transferred to a nuclear magnetic tube. The sample was analyzed by nuclear magnetic resonance hydrogen spectrum analysis, and the α-1,6 glycosidic bond ratio of the sample was calculated based on the peak areas at 5.37 ppm and 4.95 ppm chemical shifts.

[0059] The materials used in the following examples are as follows:

[0060] Thermostable α-amylase was purchased from Jiangsu Bolide Biological Products Co., Ltd.

[0061] β-amylase (product number M-100H) was purchased from Shandong Yantai Mai Tel Biotechnology Co., Ltd.

[0062] High-sugar-resistant yeast was purchased from Angel Yeast Co., Ltd.

[0063] Example 1: Effect of three-step enzymatic hydrolysis on in vitro digestibility of products

[0064] This example provides a method for preparing short outer chain maltodextrin by three-step enzymatic hydrolysis, and the specific steps are as follows:

[0065] (1) cassava starch was dispersed in water to obtain a 10% (w / w, based on dry weight) starch milk, which was preheated at 60°C for 10 min with stirring and adjusted to pH 6.0, and then heated to 90°C for gelatinization for 1 h, and then cooled to 60°C;

[0066] (2) 3000 U / g of β-amylase was added to the starch paste obtained in step (1), and the reaction was carried out at constant temperature for 12 h;

[0067] (3) The product obtained in step (2) was cooled to 32°C, and 2 wt% of high-sugar-tolerant yeast was added for removal of impurities;

[0068] (4) The product obtained in step (3) was heated to 37°C, the pH of the solution was adjusted to 5.5, and the same mass of high-sugar-tolerant yeast and β-amylase as in the first modification was added, and the reaction was carried out at constant temperature for 36 h;

[0069] (5) Step (4) was repeated so that the β-amylase enzymolysis was carried out three times in this example;

[0070] (6) The product obtained in step (5) was added with 1 wt% of activated carbon for decolorization at 37°C for 30 min, and then centrifuged and filtered through a 0.22 μm filter to remove the yeast and activated carbon;

[0071] (7) The solution obtained in step (6) was desalted by ion exchange resin and concentrated;

[0072] (8) The solution obtained in step (7) was freeze-dried to obtain the final short outer chain maltodextrin.

[0073] Example 2:

[0074] This example provides a method for preparing short outer chain maltodextrin by secondary enzymolysis, and the specific implementation is similar to that of Example 1, except that step (5) is not included, and secondary β-amylase enzymolysis is used in this example.

[0075] Comparative Example 1:

[0076] This comparative example provides a method for preparing short outer chain maltodextrin by single enzymolysis, and the specific implementation is similar to that of Example 1, except that steps (4) and (5) are not included.

[0077] Comparative Example 2

[0078] This comparative example provides a method for preparing short outer chain maltodextrin by single enzymolysis using high-temperature-resistant α-amylase and β-amylase, which is similar to Example 1, except that step (1) is adjusted as follows: 1 U / g of high-temperature-resistant α-amylase is added to the starch milk, and the reaction is carried out at 90°C for 0.5 h; and steps (4) and (5) are not included.

[0079] The in vitro digestion performance of each group of products and ordinary malt dextrin was analyzed by in vitro simulated digestion method, and the results are shown in Table 1.

[0080] Table 1. Effect of enzyme hydrolysis times on in vitro digestion performance of products

[0081] Sample Fast digest starch (%) Slow digest starch (%) Resistant starch (%) Regular maltodextrin 89.08 9.14 1.77 Single enzymatic hydrolysis (Comparative Example 1) 83.70 5.28 11.02 Single enzymatic hydrolysis (Comparative Example 2) 80.76 5.49 13.76 Double enzymatic hydrolysis (Example 2) 77.35 4.62 18.03 Triple enzymatic hydrolysis (Example 1) 75.68 5.69 18.64

[0082] The results show that compared with ordinary malt dextrin, the digestion characteristics of the products subjected to β-amylase hydrolysis change significantly, and the digestion rate gradually slows down with the increase of the number of enzyme hydrolysis. Although the traditional single enzyme hydrolysis process can reduce the proportion of fast digestible starch in the product, a large amount of starch component is still rapidly converted into glucose within the first 20 minutes of simulated small intestine digestion. The second enzyme hydrolysis further optimizes the digestion performance of the product, reducing the proportion of fast digestible starch to 77.35%. The third enzyme hydrolysis product has the most significant effect on digestion delay, reducing the proportion of fast digestible starch to 75.68% and increasing the proportion of resistant starch to 18.64%. This result shows that multiple enzyme hydrolysis can delay the digestion of starch by changing the molecular structure of starch (such as increasing the branching degree).

[0083] Example 3: Effect of multiple enzyme hydrolysis on viscosity and dissolution time of products

[0084] The viscosity and dissolution time of ordinary malt dextrin and products prepared by different enzyme hydrolysis times at 25°C are shown in Table 2.

[0085] Table 2. Effect of enzyme hydrolysis times on viscosity and dissolution time of products

[0086] Sample Viscosity (mPa-s) Dissolution time (s) Regular maltodextrin 57.74 106.67 Single enzymatic hydrolysis (Comparative Example 1) 269.38 119.33 Double enzymatic hydrolysis (Example 2) 17.26 59.20 Triple enzymatic hydrolysis (Example 1) 10.98 54.50

[0087] The results show that the viscosity of 30% (w / w) ordinary malt dextrin aqueous solution is 57.74 mPa·s, while the viscosity of the single enzyme hydrolysis product increases significantly to 269.38 mPa·s. In contrast, after the second enzyme hydrolysis, the viscosity of the product drops sharply, even lower than that of ordinary malt dextrin, and the viscosity of the third enzyme hydrolysis product drops to 10.98 mPa·s.

[0088] In terms of dissolution performance, ordinary malt dextrin takes 106.67 s to completely dissolve, and the single enzyme hydrolysis product has a slightly longer dissolution time due to its higher molecular weight and greater solution viscosity. In contrast, the dissolution efficiency of the product after the second enzyme hydrolysis is significantly improved, and the third enzyme hydrolysis product only takes 54.50 s to dissolve at room temperature. This result shows that multiple enzyme hydrolysis can reduce the viscosity of malt dextrin aqueous solution and improve the dissolution rate, meeting the application requirements of fast-dissolving foods or pharmaceutical excipients.

[0089] Example 4: Effect of thermostable α-amylase on digestion performance of multiple enzyme hydrolysis products

[0090] The present embodiment provides a method for preparing short outer chain maltodextrin by multiple enzymatic hydrolysis, and the specific implementation is similar to that of embodiment 1, except that:

[0091] Step (1) is adjusted as follows: cassava starch is dispersed in water to obtain a 10% (w / w, based on dry basis) starch milk, preheated at 60°C for 10 min under stirring, and the pH is adjusted to 6.0. 0 U / g, 0.1 U / g, 1 U / g, and 5 U / g of high-temperature-resistant alpha-amylase are added to the starch milk, respectively, and the temperature is increased to 90°C for 0.5 h of gelatinization reaction.

[0092] It is found through experiments that when the addition amount of high-temperature-resistant alpha-amylase is higher than 5 U / g, the yield of the product is further reduced to less than 10%, resulting in low raw material utilization and high production cost, which is not suitable for large-scale industrial production. Therefore, the comparative experiment under the condition of higher addition amount of high-temperature-resistant alpha-amylase is not performed.

[0093] The in vitro digestion performance of each group of products is analyzed by an in vitro simulated digestion method, and the results are shown in Table 3.

[0094] Table 3. Effect of high-temperature-resistant alpha-amylase on in vitro digestion of multiple enzymatic hydrolysis products

[0095] Sample Fast digest starch (%) Slow digest starch (%) Resistant starch (%) 0 U / g 75.68 5.69 18.64 0.1 U / g 75.98 3.35 20.67 1 U / g 71.11 7.01 21.89 5 U / g 64.91 5.59 29.50

[0096] The results show that the addition of high-temperature-resistant alpha-amylase in the preparation of multiple enzymatic hydrolysis products can delay the digestion characteristics of the products. Compared with the multiple enzymatic hydrolysis products prepared without the addition of high-temperature-resistant alpha-amylase, the product prepared with a small amount (0.1 U / g) of high-temperature-resistant alpha-amylase has no significant change in in vitro digestion. It is possible that the limited hydrolysis ability of a small amount of high-temperature-resistant alpha-amylase on starch branches results in similar structural characteristics of the obtained products, thereby showing no significant difference in in vitro digestion. With the increase of the addition amount of high-temperature-resistant alpha-amylase, the proportion of rapidly digestible starch in the product gradually decreases, reaching a maximum of 10.77%, and the content of resistant starch (RS) increases by 10.86%. This indicates that alpha-amylase and beta-amylase act on cassava starch together, reducing the number of alpha-1, 4 glycosidic bonds, generating dextrin with short outer chains and high branches, and with the increase of the addition amount of high-temperature-resistant alpha-amylase, the branched starch is continuously degraded, exposing more reducing ends, the obtained product has a lower degree of polymerization and a higher degree of branching, which can hinder the combination of digestive enzymes and the continuous attack on the inner chain, so that the digestion of the product gradually decreases.

[0097] Example 5: Effect of high-temperature-resistant alpha-amylase on viscosity and dissolution time of multiple enzymatic hydrolysis products

[0098] The viscosity and dissolution time of the multiple products prepared with different addition amounts of high-temperature-resistant alpha-amylase at 25°C are shown in Table 4.

[0099] Table 4. Effect of thermostable alpha-amylase on viscosity and dissolution time of multiple enzymatic hydrolysis products

[0100] Sample Viscosity (mPa-s) Dissolution time (s) 0 U / g 10.98 54.50 0.1 U / g 9.97 42.33 1 U / g 5.75 26.50 5 U / g 4.51 12.50

[0101] The results show that the introduction of thermostable alpha-amylase in the multiple enzymatic hydrolysis process can further reduce the solution viscosity of the product and shorten the dissolution time. With the increase of the amount of thermostable alpha-amylase, the solution viscosity of the product gradually decreases, and the lowest can reach 4.51 mPa·s, which is reduced by 58.93% compared with the sample without thermostable alpha-amylase. At the same time, the dissolution time of the product is gradually shortened, and the fastest can reach 12.50 s to completely dissolve, and the dissolution efficiency is improved by 4.36 times. This phenomenon is attributed to the fact that the addition of thermostable alpha-amylase can randomly act on the alpha-1, 4 glycosidic bond of starch molecules, and the molecular chain is hydrolyzed more completely, and the product has lower molecular weight and degree of polymerization. As the space steric hindrance is reduced, it is not easy to form a tight network structure in the solution, and finally it shows lower viscosity and easier dispersion and dissolution.

[0102] Example 6: Storage stability of product solution

[0103] The storage stability of 30% (w / w) ordinary maltodextrin (commercially available) and the enzymatic hydrolysis product solution (30% (w / w)) of the present application within 30 days is shown in Table 6. Figure 2 The ordinary maltodextrin solution gradually changed from transparent to milky white when stored at 4°C for 2-4 days, while the once enzymatic hydrolysis product and the multiple enzymatic hydrolysis product solution stored at 4°C remained clear and transparent. These results show that ordinary maltodextrin has a high content of linear molecules and contains long outer chain structures, and during storage, macromolecular polymerization will show a tendency to retrogradation, making the solution turbid, while beta-amylase hydrolysis can inhibit maltodextrin retrogradation.

[0104] Example 7: Structural analysis of product

[0105] The beta-amylase hydrolysis rate, molecular weight and alpha-1, 6 glycosidic bond ratio of each group of samples were determined, and the results are shown in Table 5.

[0106] Table 5. Structure of maltodextrin prepared by different processes

[0107]

[0108] The results showed that the β-amylase hydrolysis rate of ordinary maltodextrin was as high as 54.69%, indicating that it contained a large amount of outer chain structure and was easy to be hydrolyzed by β-amylase. In contrast, the β-amylase hydrolysis rate of the product of traditional one-step enzymatic hydrolysis decreased to 18.12%, but part of the maltose was still released after the action of β-amylase; and the use of multi-step enzymatic hydrolysis process could further reduce the β-amylase hydrolysis rate of the product to 3.54%, and with the increase of the addition amount of thermostable α-amylase from 0 U / g to 5 U / g, the hydrolysis rate gradually decreased to the lowest of 2.20%, indicating that multi-step enzymatic hydrolysis could promote the shortening of starch outer chain and form maltodextrin with short outer chain structure.

[0109] The molecular weight of the starch one-step enzymatic hydrolysis product was much higher than that of ordinary maltodextrin, reaching 2.81 x 10 5 g / mol, indicating that under the initial action of β-amylase, cassava starch only had weak degradation, and the degree of polymerization of glucose units was still high. In contrast, after using the multi-step enzymatic hydrolysis process, the molecular weight of the product was greatly reduced to 7.59 x 10 3 g / mol, indicating that multi-step enzymatic hydrolysis effectively broke the long chain of starch. With the increase of the addition amount of thermostable α-amylase, the degree of starch liquefaction increased, smaller oligosaccharide fragments were generated, and the molecular weight of the product further decreased to the lowest of 1.61 x 10 3 g / mol.

[0110] The proportion of α-1,6 glycosidic bond of ordinary maltodextrin was 4.94%, which was consistent with its characteristic of mainly linear molecular structure. After one-step enzymatic hydrolysis of starch by β-amylase, due to the specific hydrolysis of α-1,4 glycosidic bond, the proportion of α-1,6 glycosidic bond increased to 9.81%, and the branched structure increased. After using the multi-step enzymatic hydrolysis process, the proportion of α-1,6 glycosidic bond of the product further increased to 14.07%, indicating that the synergistic effect of α-amylase and β-amylase could effectively enhance the degree of starch branching. With the increase of the addition amount of thermostable α-amylase, the proportion continued to gradually increase, reaching the highest of 17.99%, forming short outer chain maltodextrin with high branched structure.

[0111] Based on the above structural characteristics, the multiple enzymatic hydrolysis process can significantly shorten the outer chain of the final product, while achieving a significant reduction in molecular weight and a significant increase in branch density. To further optimize the product structure, a multiple enzymatic hydrolysis process using a high-temperature-resistant α-amylase and β-amylase was used. The α-amylase randomly cuts the α-1, 4 glycosidic bond to provide more action sites for the β-amylase, thereby forming a special structure with short outer chains and high branches. This structure gives the product significant functional advantages: (1) The dense branch structure can hinder the binding of digestive enzymes and the continuous attack on the inner chain, and the proportion of fast-digestible starch is reduced by at most 24.17% compared with ordinary malt dextrin, and the digestion rate is delayed; (2) The short chain structure with low degree of polymerization reduces the interaction between molecules, and the solution viscosity is reduced from 57.74 mPa·s to 4.51 mPa·s compared with ordinary malt dextrin, and the dissolution time is shortened from 106.67 s to 12.50 s; (3) The shortened outer chain length effectively inhibits the formation of double helix structure, and the product has no retrogradation phenomenon after storage at 4℃ for 30 days. Therefore, compared with ordinary malt dextrin, the product prepared by the process has low digestibility, low viscosity, high solubility and high stability, and has broad application prospects in special medical use formula food, health functional food, pharmaceutical excipients and cosmetics, etc. The process has the characteristics of mild reaction conditions, strong controllability, easy industrialization and other characteristics, which provides an important technical path for the development of new functional carbohydrate materials.

[0112] Obviously, the above examples are only examples for clarity and do not limit the embodiments. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, all the embodiments need not and cannot be exhausted. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for producing short outer chain maltodextrin by multiple enzymatic hydrolysis, characterized by, The method comprises the following steps: (1) adding thermostable alpha-amylase into starch milk, heating to gelatinize the starch milk, adding beta-amylase after cooling to perform a first enzymatic reaction, removing impurities after cooling, and obtaining a first reaction solution; (2) repeating the addition of beta-amylase and cooling to remove impurities to obtain a multi-stage enzymatic reaction solution; (3) drying the multi-stage enzymatic reaction solution to obtain short outer chain maltodextrin.

2. The method of claim 1, wherein, In step (1), the concentration of the starch milk is 5%-30%. And / or, the pH value of the starch milk is 5.0-6.

0.

3. The method of claim 1, wherein, In step (1), the starch in the starch milk is selected from one or more of tapioca starch, ordinary corn starch, waxy corn starch, potato starch, rice starch, and wheat starch.

4. The method of claim 1, wherein, In step (1), the addition amount of the thermostable alpha-amylase is 0 U / g-5 U / g dry substrate.

5. The method of claim 1, wherein, In step (1), the gelatinization temperature is 80°C-95°C. And / or, the gelatinization time is 0.5 h-2 h.

6. The method of claim 1, wherein, In step (1), the addition amount of the beta-amylase is 1000 U / g-3000 U / g dry starch.

7. The method of claim 1, wherein, In step (1), the enzymatic reaction temperature is 50°C-60°C; and the time is 12 h-24 h.

8. The method of claim 1, wherein, In step (1), the method for removing impurities is adding yeast; and the addition amount of the yeast is 0.5 wt%-3 wt%.

9. The method of claim 1, wherein, In step (1), the removal temperature is 30°C-40°C.

10. The method of claim 1, wherein, In step (2), the number of repetitions is ≥1.

11. The method of claim 1, wherein, In step (2), the addition amount of the beta-amylase is 1000 U / g-3000 U / g dry starch.

12. The method of claim 1, wherein, In step (2), the enzymatic reaction temperature is 30°C-40°C; and the time is 24 h-48 h.

13. The method of claim 1, wherein, In step (2), after cooling and removing impurities, decolorization and desalination treatment are further included.

14. The method of claim 13, wherein, The decolorization is activated carbon decolorization; and the addition amount of the activated carbon is 1 wt%-2 wt%; And / or, the decolorization temperature is 30°C-40°C; And / or, the decolorization time is 0.5 h-12 h.

15. The method of claim 13, wherein, The desalination is removing salt ions in the reaction solution by using cation and anion exchange resins.

16. Short outer chain maltodextrin prepared by the method in any one of claims 1-15.

17. Use of the short outer chain maltodextrin in claim 16 in special medical use formula food, probiotic product, health care product, meal replacement product, or medical product.

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