Process for the preparation of oligomaltose and its use

Abstract

The application discloses a preparation method of oligomaltose and application thereof, and the method comprises the following steps: taking high straight corn kernels as raw materials, and carrying out microwave cooking and pulse electric field synergistic treatment, so that the corn kernels are softened, the starch-protein compound structure is destroyed, the corn kernels have more excellent processing performance, and more oligomaltose can be prepared by compounding alpha-amylase, alpha-glucoside transglycosidase and maltotriose enzyme; and the prepared immobilized composite enzyme has high thermal stability, can guarantee the efficiency and effect of enzymolysis reaction, has high controllability of enzymolysis, can be repeatedly used, reduces production cost, has high overall yield and purity, can replace serum protein to feed young animals, promotes the development of an immune system, increases the immunity of an organism, improves the disease resistance and growth, and reduces the probability of diseases.

Description

Technical Field

[0001] This invention relates to the field of maltodextrin technology, and more specifically, to a method for preparing maltodextrin and its application. Background Technology

[0002] Maltodextrose is an oligosaccharide composed of 3 to 10 glucose units linked by α-1,4 glycosidic bonds. It is a novel sugar source that can prolong energy supply time, enhance physical endurance, combat fatigue, and is easily digested and absorbed. It features low sweetness, low osmotic pressure, high viscosity, good moisture retention, low hygroscopicity, and strong thickening properties, giving it excellent adaptability to food processing. Simultaneously, maltodextrose is also an important prebiotic, promoting the proliferation of beneficial bacteria such as Bifidobacteria in the gut and inhibiting the growth of harmful bacteria, thereby maintaining the balance of the intestinal microecology, improving intestinal function, enhancing the body's immune function, and providing resistance to disease. Therefore, the application of maltodextrose in the aquaculture industry has a very broad prospect. Many oligosaccharides are usually prepared by controlling the hydrolysis of starch. In the production of oligosaccharides, the glycosidic bonds of starch molecules are partially hydrolyzed to produce at least one oligosaccharide, and typically, a mixture of several oligosaccharides is produced. Such mixtures of oligosaccharides usually include at least one maltodextrose.

[0003] Existing technologies typically use corn starch as a raw material, preparing it through enzymatic action followed by liquefaction, concentration, and drying processes. However, the resulting maltodextrin production remains low, and it is prone to clumping, thus limiting its applications. Furthermore, existing technologies often employ free enzymes, resulting in low reusability and higher costs. Summary of the Invention

[0004] Therefore, to address the problems of low yield and easy agglomeration of oligomaltose prepared in existing technologies, which limit its application, and the low reusability and high cost resulting from the use of free enzymes in existing technologies, this invention provides a method for preparing oligomaltose and its application. The specific technical solution is as follows:

[0005] A method for preparing oligomaltose, the method comprising the following steps:

[0006] S1. High amylose corn kernels are pretreated, then water is added for microwave cooking, then ground at low speed, then subjected to pulsed electric field treatment, and dried to obtain mixture A.

[0007] S2. Add water to the mixture A, stir evenly, add immobilized complex enzyme, react for 1 h to 3 h, recover the immobilized complex enzyme, and obtain mixture B;

[0008] S3. After filtering the mixture B, activated carbon is added for decolorization, and after dialysis, dialyzed solution is obtained.

[0009] S4. The immobilized complex enzyme is added to the dialysis solution and treated for 15-20 hours. After centrifugation, the supernatant is collected, concentrated, and spray-dried to obtain oligomaltose.

[0010] Further, in step S1, the pretreatment is as follows: water is added to the high amylose corn kernels so that the water content accounts for 10% to 15% of the total mass, and the mixture is stirred at a speed of 500 r / min to 1000 r / min for 30 min to 40 min. Then, the mixture is placed in a peeling machine for several peeling processes so that the peeling rate reaches more than 90%. Finally, the mixture is crushed and passed through an 80-120 mesh sieve.

[0011] Furthermore, in step S1, the microwave cooking power is 250W to 300W, and the time is 15min to 20min.

[0012] Furthermore, in step S1, the rotation speed of the low-speed grinding is 150 r / min to 200 r / min.

[0013] Further, in step S1, the electric field strength of the pulsed electric field treatment is 20KV / cm to 25KV / cm, the pulse frequency is 200Hz to 250Hz, and the treatment time is 5min to 10min.

[0014] Further, in step S2, the ratio of the mixture A to water is (5g~10g) / 10mL.

[0015] Further, the preparation method of the immobilized complex enzyme is as follows: α-amylase, α-glucosidase and maltotriase are mixed to obtain a mixed enzyme, then glutaraldehyde is added, and crosslinking is carried out at 0-4℃ for 1-2 hours. Then sodium alginate solution is added, mixed evenly, and sodium acetate buffer is added. After hardening for 1-3 hours, the immobilized enzyme is obtained.

[0016] Furthermore, the mass ratio of the α-amylase, α-glucosidase and maltotriase is (1-5):(1-9):(1-7).

[0017] Furthermore, the amount of glutaraldehyde added accounts for 10% to 15% of the mass of the mixed enzyme.

[0018] In addition, the present invention also provides an application of maltodextrin, wherein the application is the use of maltodextrin in the feeding of young animals.

[0019] Compared with the prior art, this application has the following beneficial effects:

[0020] 1. This invention uses high-straight corn kernels as raw materials. After microwave cooking and pulsed electric field synergistic treatment, the nutritional components of the corn are preserved while the corn kernels are softened and the starch-protein complex structure is destroyed, giving them better processing performance.

[0021] 2. This invention combines α-amylase, α-glucosidase, and maltotriase to produce more oligomaltose; and the immobilized complex enzyme has high thermal stability, which not only ensures the efficiency and effect of the enzymatic hydrolysis reaction, but also ensures a high degree of controllability of the enzymatic hydrolysis. Furthermore, the immobilized complex enzyme can be reused, reducing production costs.

[0022] 3. The oligomaltose prepared by the process of the present invention contains fewer macromolecular sugars and impurities, and has higher purity and yield. It can replace serum protein in feeding young animals, promote the development of the immune system, increase the body's immunity, improve disease resistance and promote growth, and reduce the probability of disease. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of the invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0025] An embodiment of the present invention discloses a method for preparing oligomaltose, the method comprising the following steps:

[0026] S1. High amylose corn kernels are pretreated, then water is added for microwave cooking, then ground at low speed, then subjected to pulsed electric field treatment, and dried to obtain mixture A.

[0027] S2. Add water to the mixture A, stir evenly, add immobilized complex enzyme, react for 1 h to 3 h, recover the immobilized complex enzyme, and obtain mixture B;

[0028] S3. After filtering the mixture B, activated carbon is added for decolorization, and after dialysis, dialyzed solution is obtained.

[0029] S4. The immobilized complex enzyme is added to the dialysis solution and treated for 15-20 hours. After centrifugation, the supernatant is collected, concentrated, and spray-dried to obtain oligomaltose.

[0030] In one embodiment, in step S1, the pretreatment is as follows: water is added to high amylose corn kernels so that the water content accounts for 10% to 15% of the total mass, and the mixture is stirred at a speed of 500 r / min to 1000 r / min for 30 min to 40 min. Then, the mixture is placed in a peeling machine for several peeling processes so that the peeling rate reaches more than 90%. Finally, the mixture is crushed and passed through an 80-120 mesh sieve.

[0031] In one embodiment, in step S1, the microwave cooking power is 250W to 300W and the time is 15min to 20min.

[0032] In one embodiment, in step S1, the rotational speed of the low-speed grinding is 150 r / min to 200 r / min.

[0033] In one embodiment, in step S1, the electric field strength of the pulsed electric field treatment is 20KV / cm to 25KV / cm, the pulse frequency is 200Hz to 250Hz, and the treatment time is 5min to 10min.

[0034] In one embodiment, in step S2, the ratio of the mixture A to water is (5g~10g) / 10mL.

[0035] In one embodiment, the immobilized complex enzyme is prepared as follows: α-amylase, α-glucosidase and maltotriase are mixed to obtain a mixed enzyme, then glutaraldehyde is added, and the mixture is crosslinked at 0-4°C for 1-2 hours. Sodium alginate solution is then added, the mixture is mixed evenly, and sodium acetate buffer is added. After hardening for 1-3 hours, the immobilized enzyme is obtained.

[0036] In one embodiment, the mass ratio of the α-amylase, α-glucosidase and maltotriase is (1-5):(1-9):(1-7).

[0037] In one embodiment, the amount of glutaraldehyde added is 2% to 5% of the mass of the mixed enzyme.

[0038] In one embodiment, the sodium alginate solution has a mass percentage concentration of 20% to 45%.

[0039] In one embodiment, the volume ratio of the mixed enzyme to the sodium alginate solution is (1-7):(10-15).

[0040] In one embodiment, in step S2, the amount of the immobilized complex enzyme added accounts for 3% to 8% of the mass of the mixture A.

[0041] In one embodiment, in step S2, the reaction temperature is 60°C to 85°C.

[0042] In one embodiment, in step S3, the amount of activated carbon added accounts for 5% to 10% of the mass of mixture B.

[0043] In one embodiment, in step S3, the DE value of the dialysate is greater than 30.

[0044] In one embodiment, in step S4, the amount of immobilized complex enzyme added accounts for 4% to 7% of the mass of the dialysate.

[0045] In one embodiment, in step S4, the processing temperature is 60°C to 95°C.

[0046] In one embodiment, in step S4, the centrifugation speed is 5000 r / min to 8000 r / min, and the time is 3 min to 10 min.

[0047] In one embodiment, the spray drying process involves preheating the spray dryer for 5 minutes to achieve an inlet air temperature of 80°C–90°C and an outlet air temperature of 60°C–70°C. The concentrated liquid is then fed into the spray drying tower under a high-pressure homogenization pressure of 15MPa–25MPa, with spray drying performed at an inlet air temperature of 100°C–120°C, an outlet air temperature of 65°C–90°C, and a feed flow rate of 3.5L / h–7.0L / h. Using spray drying reduces the probability of oligomaltose clumping and allows for its application in animal feed.

[0048] In addition, the present invention also provides an application of maltodextrin, wherein the application is the use of maltodextrin in the feeding of young animals.

[0049] The above method produces high yields of oligomaltose, the immobilized complex enzyme can be reused, and the overall production cost is controllable.

[0050] The implementation schemes of the present invention will now be described in detail with reference to specific embodiments.

[0051] Example 1:

[0052] A method for preparing oligomaltose includes the following steps:

[0053] S1. Add water to high amylose corn kernels so that the water content accounts for 12% of the total mass, and stir at 800 r / min for 35 min. Then place them in a peeling machine for several peeling processes to achieve a peeling rate of over 90%. Then crush them and pass them through an 80-mesh sieve. Then add water and microwave cook them at 250W for 15 min. Then grind them at 150 r / min. Then treat them with a pulsed electric field with an electric field strength of 20 KV / cm and a pulse frequency of 200 Hz for 10 min. After drying, obtain mixture A.

[0054] S2. Mix α-amylase, α-glucosidase and maltotriase in a mass ratio of 5:7:3 to obtain a mixed enzyme. Then add 3% glutaraldehyde (by mass of the mixed enzyme) and crosslink at 0°C for 2 hours. Add 35% sodium alginate solution (by mass percentage), mix well, add sodium acetate buffer, and harden for 3 hours to obtain an immobilized enzyme.

[0055] Add water to mixture A at a ratio of 8g / 10mL, stir until homogeneous, then add 5% (by mass) of immobilized complex enzyme to mixture A, react at 85°C for 3 hours, and recover the immobilized complex enzyme to obtain mixture B.

[0056] S3. After filtering the mixture B, add 7% activated carbon (by mass of the mixture B) for decolorization, and then perform dialysis to obtain the dialysate.

[0057] S4. Continue to add 4% of the immobilized complex enzyme (by mass of the dialysate) to the dialysate, treat at 90°C for 15 hours, centrifuge at 6000 r / min for 5 minutes, take the supernatant, concentrate to obtain the concentrate.

[0058] S5. Preheat the spray dryer for 5 minutes to bring the inlet air temperature to 85°C and the outlet air temperature to 60°C. Then, send the concentrate into the spray drying tower under a high-pressure homogenization pressure of 15MPa. Spray dry the concentrate under the conditions of an inlet air temperature of 100°C, an outlet air temperature of 65°C, and a feed flow rate of 5.0L / h to obtain oligomaltose.

[0059] Example 2:

[0060] A method for preparing oligomaltose includes the following steps:

[0061] S1. Add water to high amylose corn kernels so that the water content accounts for 13% of the total mass, and stir at 800 r / min for 40 min. Then place them in a peeling machine for several peeling processes to achieve a peeling rate of over 90%. Then crush them and pass them through a 100-mesh sieve. Then add water and microwave cook them at 260W for 15 min. Then grind them at 180 r / min. Then treat them with a pulsed electric field with an electric field strength of 22 KV / cm and a pulse frequency of 220 Hz for 6 min. After drying, obtain mixture A.

[0062] S2. Mix α-amylase, α-glucosidase and maltotriase in a mass ratio of 4:7:4 to obtain a mixed enzyme. Then add 4% glutaraldehyde (by mass of the mixed enzyme) and crosslink at 0°C for 2 hours. Add 38% sodium alginate solution (by mass percentage), mix well, add sodium acetate buffer, and harden for 3 hours to obtain an immobilized enzyme.

[0063] Add water to mixture A at a ratio of 8g / 10mL, stir until homogeneous, then add 5% (by mass) of immobilized complex enzyme to mixture A, react at 80°C for 3 hours, and recover the immobilized complex enzyme to obtain mixture B.

[0064] S3. After filtering the mixture B, add 7% activated carbon (by mass of the mixture B) for decolorization, and then perform dialysis to obtain the dialysate.

[0065] S4. Continue to add the immobilized complex enzyme, accounting for 7% of the mass of the dialysate, to the dialysate, treat at 95°C for 16 hours, centrifuge at 8000 r / min for 8 minutes, take the supernatant, concentrate to obtain the concentrate.

[0066] S5. Preheat the spray dryer for 5 minutes to bring the inlet air temperature to 90°C and the outlet air temperature to 70°C. Then, send the concentrate into the spray drying tower under a high-pressure homogenization pressure of 25MPa. Spray dry the concentrate under the conditions of an inlet air temperature of 120°C, an outlet air temperature of 90°C, and a feed flow rate of 6.0L / h to obtain oligomaltose.

[0067] Example 3:

[0068] A method for preparing oligomaltose includes the following steps:

[0069] S1. Add water to high-amylose corn kernels so that the water content accounts for 15% of the total mass, and stir at 1000 r / min for 30 min. Then place them in a peeling machine for several peeling processes to achieve a peeling rate of over 90%. Then crush them and pass them through a 120-mesh sieve. Then add water and microwave cook them at 300W for 15 min. Then grind them at 150 r / min. Then treat them with a pulsed electric field with an electric field strength of 25 KV / cm and a pulse frequency of 250 Hz for 5 min. After drying, obtain mixture A.

[0070] S2. Mix α-amylase, α-glucosidase and maltotriase in a mass ratio of 5:8:2 to obtain a mixed enzyme. Then add 3% glutaraldehyde (by mass of the mixed enzyme) and crosslink at 0°C for 2 hours. Then add 40% sodium alginate solution (by mass percentage), mix well, add sodium acetate buffer, and harden for 3 hours to obtain an immobilized enzyme.

[0071] Add water to mixture A at a ratio of 8g / 10mL, stir until homogeneous, then add 5% (by mass) of immobilized complex enzyme to mixture A, react at 80°C for 2 hours, and recover the immobilized complex enzyme to obtain mixture B.

[0072] S3. After filtering the mixture B, add 8% activated carbon (by mass of the mixture B) for decolorization, and then perform dialysis to obtain the dialysate.

[0073] S4. Continue to add the immobilized complex enzyme, accounting for 7% of the mass of the dialysate, to the dialysate, treat at 95°C for 18 hours, centrifuge at 6000 r / min for 8 minutes, take the supernatant, concentrate to obtain the concentrate.

[0074] S5. Preheat the spray dryer for 5 minutes to bring the inlet air temperature to 90°C and the outlet air temperature to 65°C. Then, send the concentrate into the spray drying tower under a high-pressure homogenization pressure of 22MPa. Spray drying is carried out under the conditions of an inlet air temperature of 110°C, an outlet air temperature of 85°C, and a feed flow rate of 4.5L / h to obtain oligomaltose.

[0075] Comparative Example 1:

[0076] The difference between Comparative Example 1 and Example 3 is that Comparative Example 1 contains a single α-amylase, while the rest is the same as Example 3.

[0077] Comparative Example 2:

[0078] The difference between Comparative Example 2 and Example 3 is that Comparative Example 2 contains a single α-glucosidase, while the rest is the same as Example 3.

[0079] Comparative Example 3:

[0080] The difference between Comparative Example 3 and Example 3 is that Comparative Example 3 contains a single maltotriase, while the rest is the same as Example 3.

[0081] Comparative Example 4:

[0082] The difference between Comparative Example 4 and Example 3 is that the preparation method of the immobilized complex enzyme is different; otherwise, it is the same as Example 3. The preparation method of the immobilized complex enzyme in Comparative Example 4 is as follows:

[0083] A mixed enzyme was obtained by mixing α-amylase, α-glucosidase and maltotriase in a mass ratio of 5:8:2. Then, 10% of the mass of gelatin was added to the mixed enzyme, and the mixture was heated to 65°C and stirred for 20 minutes. After cooling, the immobilized enzyme was obtained.

[0084] Comparative Example 5:

[0085] The difference between Comparative Example 5 and Example 3 is that in Comparative Example 5, α-amylase, α-glucosidase and maltotriase in a mass ratio of 5:8:2 were mixed to obtain a mixed enzyme, which was then added directly for use, without immobilization treatment. Otherwise, it was the same as Example 3.

[0086] Comparative Example 6:

[0087] The difference between Comparative Example 6 and Example 3 is that Comparative Example 6 did not undergo microwave cooking, but otherwise it was the same as Example 3.

[0088] Comparative Example 7:

[0089] The difference between Comparative Example 7 and Example 3 is that Comparative Example 7 was not subjected to pulsed electric field treatment, but otherwise it was the same as Example 3.

[0090] Comparative Example 8:

[0091] The difference between Comparative Example 8 and Example 3 is that Comparative Example 8 uses a conventional drying process instead of spray drying. Specifically, the drying process of Comparative Example 8 is as follows: the concentrate is dried at a temperature of 110°C for 40 minutes, and the rest is the same as that of Example 3.

[0092] The immobilized complex enzymes prepared in Examples 1-3 and the immobilized complex enzymes prepared in Comparative Examples 1-4 were subjected to performance tests, and the results are shown in Table 1 below.

[0093] The method is as follows: Weigh several grams of immobilized enzyme, add an appropriate amount of acetate buffer (pH 5.0), and then add 1 mL of 2% (w / w) methyl α-glucosidase. Shake in a 40℃ water bath for 1 hour. After the reaction is complete, take 1 mL of the reaction solution, add 3 mL of enzyme complex reagent, incubate in a 36℃ water bath for 40 minutes, cool to room temperature, and then add 6 mL of distilled water to bring the volume to 10 mL. Measure the absorbance at 505 nm. Add 1 mL of diluted free enzyme to 8 mL of distilled water, heat to boiling for 10 minutes to inactivate the enzyme, and then add 1 mL of 2% methyl-α-glucosidase transglycoside solution. Under these conditions, the amount of enzyme that generates 1 pg of glucose by the free enzyme acting on methyl-α-glucosidase after 1 hour is defined as one activity unit.

[0094]

[0095]

[0096] Analysis of the data in Table 1 shows that this application obtains a mixed enzyme by mixing α-amylase, α-glucosidase, and maltotriase, then cross-linking it with specific glutaraldehyde, and finally encapsulating it with sodium alginate solution. This results in an immobilized composite enzyme with excellent physical strength and high activity recovery rate, allowing for reuse. However, in Comparative Examples 1-3, which immobilized single enzymes, the overall enzyme activity recovery rate was lower than that of Example 3. In Comparative Example 4, the use of gelatin encapsulation not only resulted in an immobilized composite enzyme with poor strength but also a low enzyme activity recovery rate, failing to meet the requirements for reuse.

[0097] In addition, the products prepared in Examples 1 to 3 and the products prepared in Comparative Examples 1 to 8 were analyzed to obtain the conversion rate of oligomaltose. The results are shown in Table 2 below.

[0098] Table 2:

[0099]

[0100]

[0101] Analysis of the data in Table 2 shows that this application, through optimizing the composition of the immobilized complex enzyme and the preparation process of oligomaltose, achieves a synergistic effect, effectively increasing the conversion rate of oligomaltose. Furthermore, the oligomaltose obtained after spray drying is less prone to clumping, whereas the oligomaltose obtained using the conventional drying process in Comparative Example 8 exhibited clumping, indicating that spray drying helps reduce the probability of oligomaltose clumping. Simultaneously, the treatment of the complex enzyme during preparation also affects the composition of the obtained oligomaltose, leading to agglomeration during later storage. Therefore, through the optimization of the process in this application, oligomaltose with more stable storage performance can be obtained.

[0102] Application example:

[0103] The oligomaltose prepared in Example 3 was applied to the feeding of young animals, specifically weaned piglets. A control group was set up, and the application groups were fed the same basal diet as the control group, except that the application group received an additional 0.6% (w / w) of the oligomaltose prepared in Example 3. Application Example 2 differed from Application Example 1 in that the amount of oligomaltose added was 0.8%, otherwise the same. Application Example 3 differed from Application Example 1 in that the amount of oligomaltose added was 1%, otherwise the same. Application Example 4 differed from Application Example 1 in that the amount of oligomaltose added was 1.2%, otherwise the same. Application Example 5 differed from Application Example 1 in that the amount of oligomaltose added was 1.5%, otherwise the same. The reduction rate of diarrhea compared to the control group is shown in Table 3.

[0104] Table 3:

[0105]

[0106] The data analysis in Table 3 shows that the oligomaltose prepared in this application can be used in the feeding of young animals, and can significantly improve the immune function of piglets and reduce the incidence of disease.

[0107] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0108] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing oligomaltose, characterized in that, The preparation method includes the following steps: S1. High amylose corn kernels are pretreated, then water is added for microwave cooking, then ground at low speed, then subjected to pulsed electric field treatment, and dried to obtain mixture A. S2. Add water to the mixture A, stir evenly, add immobilized complex enzyme, react for 1 h to 3 h, recover the immobilized complex enzyme, and obtain mixture B; The immobilized complex enzyme is prepared as follows: α-amylase, α-glucosidase and maltotriase are mixed to obtain a mixed enzyme, then glutaraldehyde is added, and crosslinking is carried out at 0-4℃ for 1-2 hours. Then sodium alginate solution is added, mixed evenly, and sodium acetate buffer is added. After hardening for 1-3 hours, the immobilized enzyme is obtained. S3. After filtering the mixture B, activated carbon is added for decolorization, and after dialysis, dialyzed solution is obtained. S4. The immobilized complex enzyme is added to the dialysis solution and treated for 15-20 hours. After centrifugation, the supernatant is collected, concentrated, and spray-dried to obtain oligomaltose.

2. The preparation method according to claim 1, characterized in that, In step S1, the pretreatment is as follows: water is added to the high amylose corn kernels so that the water content accounts for 10% to 15% of the total mass, and the mixture is stirred at a speed of 500 r / min to 1000 r / min for 30 min to 40 min. Then, the mixture is placed in a peeling machine for several peeling processes so that the peeling rate reaches more than 90%. Finally, the mixture is crushed and passed through an 80-120 mesh sieve.

3. The preparation method according to claim 1, characterized in that, In step S1, the microwave cooking power is 250W~300W and the time is 15min~20min.

4. The preparation method according to claim 1, characterized in that, In step S1, the rotation speed of the low-speed grinding is 150 r / min to 200 r / min.

5. The preparation method according to claim 1, characterized in that, In step S1, the electric field strength of the pulsed electric field treatment is 20KV / cm~25KV / cm, the pulse frequency is 200Hz~250Hz, and the treatment time is 5min~10min.

6. The preparation method according to claim 1, characterized in that, In step S2, the ratio of mixture A to water is (5g~10g) / 10mL.

7. The preparation method according to claim 1, characterized in that, The mass ratio of α-amylase, α-glucosidase and maltotriase is (1~5):(1~9):(1~7).

8. The preparation method according to claim 1, characterized in that, The amount of glutaraldehyde added is 10% to 15% of the mass of the mixed enzyme.

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