Method for preparing thick corn slurry through enzyme addition and extrusion

Abstract

The invention relates to a method for preparing thick corn pulp through enzyme addition and extrusion. The method comprises the following steps: crushing corn to obtain corn flour; uniformly dispersing at least one of medium-temperature alpha-amylase, high-temperature alpha-amylase and saccharifying enzyme in purified water to prepare enzymatic hydrolysate; performing twin-screw extrusion on corn flour and the enzymatic hydrolysate to obtain corn coarse pulp; and grinding, centrifuging, homogenizing, sterilizing and filling the coarse corn pulp to obtain the thick corn pulp. According to the method, the extrusion technology and the enzymolysis technology are combined, the effect of the enzyme on the extrusion substrate is enhanced by utilizing the efficient activity of the extrusion induction enzyme, the method is efficient in short time and energy-saving, and the continuous production of the thick corn slurry can be realized. The stability, liquefaction degree, sweetness and sensory quality of the thick corn pulp are remarkably improved, no extra stabilizer or thickener needs to be added, the thick corn pulp is green and safe, the requirement of consumers for the taste of the thick corn pulp is met, and the consumer market of the thick corn pulp is expanded.

Description

Technical Field

[0001] The invention relates to the technical field of efficient biological conversion in food processing, and in particular to a method for preparing corn concentrate by enzyme-adding extrusion. Background Art

[0002] Corn is a grass plant. It has become one of the most widely consumed food crops due to its rich nutrients and unique flavor. Corn has a high carbohydrate content (accounting for 70% to 80% of dry matter), mainly in the form of starch, and is an important source of energy for the human body. Corn has a low glycemic index, which enables it to release energy slowly and helps stabilize blood sugar levels. Corn contains about 8% to 12% protein and is rich in dietary fiber, which helps promote intestinal health and prevent constipation. In addition, dietary fiber can delay the absorption of sugar and has a certain blood sugar regulating effect. The fat content in corn is moderate, especially the corn germ is rich in unsaturated fatty acids such as linoleic acid and oleic acid, which helps lower cholesterol levels and maintain cardiovascular health. Corn contains more B vitamins (especially B1 and B6) and vitamin E, which can promote energy metabolism and enhance immunity. It is also rich in minerals such as potassium, magnesium, iron, and zinc, which helps prevent hypertension, anemia, and bone diseases. The natural antioxidant ingredients contained in corn, such as zeaxanthin, lutein, and beta-carotene, are beneficial to eye health and skin protection. In addition, the flavonoids and anthocyanins in yellow and purple corn have antioxidant and anti-inflammatory properties.

[0003] Corn is a multifunctional economic crop with a wide range of uses in food, feed, medicine and other fields. Fresh corn can be directly boiled, roasted, and steamed, and it tastes sweet. Dried corn can be ground into corn flour to make traditional foods such as corn tortillas, corn porridge, and corn paste. With the advancement of modern agricultural technology and the increasing demand for healthy food, plant-based grain slurry drinks are constantly developing. Corn concentrate, as a high-nutrition grain concentrate, is made from corn as the main raw material. It has a strong corn flavor and unique taste. It is rich in dietary fiber and a large amount of bioactive substances. Long-term drinking can effectively prevent diseases. With the improvement of market demand and people's health awareness, corn concentrate is expected to be widely promoted and applied, becoming an important force in promoting the development of local economy and human health.

[0004] There are two mainstream methods for producing corn concentrate on the market. One is the refining method, which is to mix corn with other substances after refining it or to grind corn and other substances together to prepare corn concentrate. For example, patent CN104770815A discloses a corn concentrate cereal beverage containing suspended sweet corn kernels and a production method thereof, and specifically discloses that the corn after cooking is ground and then compounded with sweet corn kernels, condensed milk, non-dairy creamer, white sugar, suspension stabilizer, emulsifier, edible flavor and edible natural pigment to prepare the corn concentrate cereal beverage; patent CN103829303A discloses a sweet corn concentrate and a preparation process thereof, and specifically discloses that the cooked sweet corn is pulped and then compounded with white sugar, a composite stabilizer (xanthan gum, etc.), maltodextrin, sweet corn flavor, etc. to prepare the corn concentrate. Although the above method can obtain corn concentrate with a certain solid content, the components of the prepared corn concentrate contain more additives, which affect the taste and nutritional value of the corn concentrate on the one hand, and on the other hand, the addition of additives may also cause safety problems. Another method commonly used to produce corn concentrate is enzymatic hydrolysis, that is, using amylase and other enzymes to hydrolyze corn to obtain corn concentrate. For example, patent CN102283414A discloses a konjac cereal beverage and a preparation method thereof, that is, after mixing cereal powder with hot water and grinding, adding a composite enzyme thereto for enzymolysis, and obtaining cereal concentrate after enzyme inactivation. The main problem of preparing cereal concentrate by enzymatic hydrolysis is that the enzymatic hydrolysis conditions are strict, the enzymatic hydrolysis time is long, and the cereal concentrate prepared by enzymatic hydrolysis usually also needs to add some stabilizers and thickeners, and the addition of stabilizers and thickeners also affects the taste and safety of the concentrate. Summary of the invention

[0005] In view of the above problems, the object of the present invention is to provide a method for preparing corn concentrate by enzyme extrusion, using an extruder as an enzymatic hydrolysis reactor to induce the enzyme to exhibit high-efficiency activity. The method combines extrusion technology with enzymatic hydrolysis technology, can achieve short-term and high-efficiency enzymatic hydrolysis, and can be produced continuously. The solid content of the relevant enzymatic hydrolysis product is high and the product stability is good. With the changes in market demand, corn concentrate is expected to be widely promoted and applied.

[0006] In view of the above object, the present invention first provides a method for preparing corn concentrate by enzyme extrusion, comprising the following steps:

[0007] (1) crushing corn and sieving to obtain corn flour;

[0008] (2) uniformly dispersing the enzyme preparation in purified water to obtain an enzymatic hydrolyzate;

[0009] (3) placing the corn flour obtained in step (1) and the enzymatic hydrolyzate obtained in step (2) in a solid feeding bin and a liquid feeder of a twin-screw extruder respectively, and performing reaction extrusion by the twin-screw extruder to obtain enzymatically hydrolyzed corn slurry;

[0010] (4) grinding the extruded enzymatic hydrolysate obtained in step (3) using a colloid mill;

[0011] (5) separating the residue from the product obtained in step (4) by horizontal screw centrifugation;

[0012] (6) homogenizing the product obtained in step (5) using a homogenizer;

[0013] (7) sterilizing and filling the product obtained in step (6) to obtain the final product of enzymatic corn concentrate.

[0014] In one embodiment of the present invention, the sieving in step (1) refers to sieving through a 50-100 mesh sieve.

[0015] In one embodiment of the present invention, in step (2), the enzyme preparation in the enzymatic hydrolysis solution is at least one of medium-temperature α-amylase, high-temperature α-amylase and saccharifying enzyme.

[0016] In one embodiment of the present invention, in step (2), the activity of the medium-temperature α-amylase is 300-600 KUN / g, the activity of the high-temperature α-amylase is 50-200 KUN / mL, and the activity of the saccharifying enzyme is 100-500 AGU / g.

[0017] In one embodiment of the present invention, in step (2), the amount of enzyme preparation added to the enzymatic hydrolysis solution is 1‰ to 10‰ of the mass of corn flour.

[0018] In one embodiment of the present invention, in step (3), the six areas of the extrusion cavity are divided into: areas I to V are extrusion enzymatic hydrolysis areas, and area VI is an extrusion enzymatic hydrolysis and high-temperature enzyme inactivation area; area I is 50-80°C, area II is 60-85°C, area III is 65-90°C, area IV is 70-100°C, area V is 80-110°C, and area VI is 90-120°C.

[0019] In one embodiment of the present invention, in step (3), the extrusion temperature is 50°C to 120°C, the solid (corn flour) feeding rate is 3 to 30 kg / h, the liquid (enzyme hydrolysate) feeding rate is 5 to 50 L / h, and the screw speed is 50 to 500 r / min.

[0020] In one embodiment of the present invention, the grinding fineness of the colloid mill in step (4) is 250-350 mesh, and the grinding time is 0.5-2 min.

[0021] In one embodiment of the present invention, the centrifugal process in step (5) has a rotation speed of 2000-3000 r / min and a centrifugal time of 1-5 min.

[0022] In one embodiment of the present invention, the homogenization process pressure in step (6) is 30-60 MPa, the homogenization is performed 1-2 times, and each time is 5-60 seconds.

[0023] In one embodiment of the present invention, the sterilization conditions in step (7) are: sterilization temperature 105-135° C., sterilization time 10-60 s.

[0024] In one embodiment of the present invention, the solid content of the corn concentrate is between 30% and 50%.

[0025] The invention also discloses corn concentrate prepared according to the method.

[0026] Beneficial effects:

[0027] (1) The present invention combines enzymatic hydrolysis technology with extrusion technology, and uses an extruder as an enzyme-catalyzed bioreactor to induce the enzyme to exhibit high-efficiency activity, thereby improving the utilization rate of the enzyme, which is beneficial to reducing costs and significantly improving the stability, sweetness, liquefaction degree and taste of corn concentrate.

[0028] (2) Compared with the technical solutions of using medium-temperature α-amylase alone or using medium-temperature α-amylase in combination with other enzymes, using only high-temperature α-amylase to perform extrusion enzymatic hydrolysis on corn flour can significantly improve the stability and sensory properties of corn concentrate, significantly increase the reducing sugar content in the concentrate, and improve the sweetness of the concentrate.

[0029] (3) The solid content of the corn concentrate prepared by the present invention can reach up to 31.83%, the reducing sugar content can reach up to 248.72 mg / g, the DE value can reach up to 78.14%, and the sensory score can reach up to 95.9 points. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the reducing sugar standard curve;

[0031] Figure 2 The figure is a schematic diagram of the preparation process of corn concentrate of the present invention. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention will be described in a complete and clear manner below. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them.

[0033] Raw materials: The enzyme preparations used in the examples and comparative examples were purchased from Beijing Novozymes Co., Ltd. The medium-temperature α-amylase activity was 480 KUN / g, the high-temperature α-amylase activity was 120 KUN / mL, and the saccharifying enzyme activity was 300 AGU / g.

[0034] Example 1

[0035] A method for preparing corn concentrate by enzyme extrusion comprises the following steps:

[0036] (1) crushing corn so that 100% of it passes through an 80-mesh sieve to obtain corn flour;

[0037] (2) Dispersing the medium-temperature α-amylase in purified water to prepare an enzymatic hydrolyzate, wherein the amount of the medium-temperature α-amylase added to the enzymatic hydrolyzate is 5‰ of the mass of the corn flour.

[0038] (3) putting corn flour into a solid feeding bin, pouring the enzymatic hydrolyzate into a liquid feeder, and reacting and extruding in a twin-screw extruder, wherein the temperatures of zones I to VI of the extruder are 70° C., 75° C., 80° C., 85° C., 90° C., and 95° C., respectively, the feeding rate is 5 kg / h, the screw speed is 150 r / min, and the liquid feeding rate is 8 L / h, to obtain enzymatic hydrolyzed corn slurry;

[0039] (4) Grind the corn pulp colloid to a fineness of 300 mesh for 1 min, then centrifuge at 2500 r / min for 2 min, homogenize once with a homogenizer at a pressure of 40 MPa for 30 s each time, sterilize at 120° C. for 30 s, and perform aseptic cold filling to obtain a finished corn pulp concentrate.

[0040] Example 2

[0041] A method for preparing corn concentrate by enzyme extrusion comprises the following steps:

[0042] (1) crushing corn so that 100% of it passes through an 80-mesh sieve to obtain corn flour;

[0043] (2) Dispersing the medium-temperature α-amylase and the high-temperature α-amylase in purified water to prepare an enzymatic hydrolyzate, wherein the amount of the medium-temperature α-amylase added to the enzymatic hydrolyzate is 2‰ of the mass of corn flour, and the amount of the high-temperature α-amylase added to the enzymatic hydrolyzate is 3‰ of the mass of corn flour.

[0044] (3) putting corn flour into a solid feeding bin, putting enzymatic hydrolyzate into a liquid feeder, and reacting and extruding in a twin-screw extruder, wherein the temperatures of zones I to VI of the extruder are 75° C., 80° C., 85° C., 95° C., 105° C., and 115° C., respectively, the feeding rate is 5 kg / h, the screw speed is 150 r / min, and the liquid feeding rate is 8 L / h, to obtain enzymatic hydrolyzed corn slurry;

[0045] (4) Grind the corn pulp colloid to a fineness of 300 mesh for 1 min, then centrifuge at 2500 r / min for 2 min, homogenize once with a homogenizer at a pressure of 40 MPa for 30 s each time, sterilize at 120° C. for 30 s, and perform aseptic cold filling to obtain a finished corn pulp concentrate.

[0046] Example 3

[0047] A method for preparing corn concentrate by enzyme extrusion comprises the following steps:

[0048] (1) crushing corn so that 100% of it passes through an 80-mesh sieve to obtain corn flour;

[0049] (2) Dispersing medium-temperature α-amylase and saccharifying enzyme in purified water to prepare an enzymatic hydrolyzate, wherein the amount of medium-temperature α-amylase added to the enzymatic hydrolyzate is 3‰ of the mass of corn flour, and the amount of saccharifying enzyme added to the enzymatic hydrolyzate is 2‰ of the mass of corn flour.

[0050] (3) putting corn flour into a solid feeding bin, putting enzymatic hydrolyzate into a liquid feeder, and reacting and extruding in a twin-screw extruder, wherein the temperatures of zones I to VI of the extruder are 60° C., 65° C., 75° C., 80° C., 85° C., and 95° C., respectively, the feeding rate is 5 kg / h, the screw speed is 150 r / min, and the liquid feeding rate is 10 L / h, to obtain enzymatic hydrolyzed corn slurry;

[0051] (4) Grind the corn pulp colloid to a fineness of 300 mesh for 1 min, then centrifuge at 2500 r / min for 2 min, homogenize once with a homogenizer at a pressure of 40 MPa for 30 s each time, sterilize at 120° C. for 30 s, and perform aseptic cold filling to obtain a finished corn pulp concentrate.

[0052] Example 4

[0053] A method for preparing corn concentrate by enzyme extrusion comprises the following steps:

[0054] (1) crushing corn so that 100% of it passes through an 80-mesh sieve to obtain corn flour;

[0055] (2) High temperature α-amylase is dispersed in purified water to prepare an enzymatic hydrolyzate, wherein the amount of high temperature α-amylase added to the enzymatic hydrolyzate is 5‰ of the mass of corn flour.

[0056] (3) putting corn flour into a solid feeding bin, putting enzymatic hydrolyzate into a liquid feeder, and reacting and extruding in a twin-screw extruder, wherein the temperatures of zones I to VI of the extruder are 80° C., 85° C., 90° C., 95° C., 105° C., and 115° C., respectively, the feeding rate is 5 kg / h, the screw speed is 150 r / min, and the liquid feeding rate is 8 L / h, to obtain enzymatic hydrolyzed corn slurry;

[0057] (4) Grind the corn pulp colloid to a fineness of 300 mesh for 1 min, then centrifuge at 2500 r / min for 2 min, homogenize once with a homogenizer at a pressure of 40 MPa for 30 s each time, sterilize at 120° C. for 30 s, and perform aseptic cold filling to obtain a finished corn pulp concentrate.

[0058] Comparative Example 1

[0059] A method for preparing corn concentrate by enzyme extrusion comprises the following steps:

[0060] (1) crushing corn so that 100% of it passes through an 80-mesh sieve to obtain corn flour;

[0061] (2) Disperse the medium-temperature α-amylase in purified water and mix it with corn flour in advance. The water content of the mixture is 25%. The water content is balanced at room temperature of 25°C for 12 hours. The required amount of medium-temperature α-amylase added is 5‰ of the mass of corn flour.

[0062] (3) putting the premixed corn flour into a solid feeding bin and the purified water into a liquid feeder, and extruding the mixture in a twin-screw extruder, wherein the temperatures of zones I to VI of the extruder are 70° C., 75° C., 80° C., 85° C., 90° C., and 95° C., respectively, the feeding rate is 5 kg / h, the screw speed is 150 r / min, and the liquid feeding rate is 8 L / h, to obtain enzymatically hydrolyzed corn slurry;

[0063] (4) Grind the corn pulp colloid to a fineness of 300 mesh for 1 min, then centrifuge at 2500 r / min for 2 min, homogenize once with a homogenizer at a pressure of 40 MPa for 30 s each time, sterilize at 120° C. for 30 s, and perform aseptic cold filling to obtain a finished corn pulp concentrate.

[0064] Test Method

[0065] Solid content:

[0066] The moisture content of corn concentrate was determined by the first method direct drying method according to the national standard GB 5009.3-2016 to obtain its solid content.

[0067] Solid content (%) = 100% - sample moisture content (%)

[0068] Reducing sugar content:

[0069] First, prepare a glucose standard solution with a concentration of 1 mg / mL. Take 0, 0.2, 0.4, 0.6, 0.8, and 1.0 mL of the glucose standard solution in a centrifuge tube, add deionized water to 1.0 mL, accurately add 1.5 mL of DNS color developer, heat in a boiling water bath for 5 min, and then quickly cool to room temperature. Accurately add 1.5 mL of deionized water to dilute and mix, measure the absorbance at a wavelength of 540 nm, and draw a standard curve, such as Figure 1As shown. Secondly, take 1.0g sample, add 20mL deionized water, vortex for 1min, centrifuge at 8000g for 10min, separate the supernatant; take the precipitate, add 20mL deionized water, centrifuge at 8000g for 10min, combine the two supernatants, and make up to volume in a 100mL volumetric flask for later use. Take 200μL of the fixed-volume supernatant in a 2ml centrifuge tube, add 200μL deionized water and 300μL DNS colorimetric agent, boil in a water bath for 5min and quickly cool to room temperature, add 300μL deionized water again, mix well, and color at a wavelength of 540nm on an enzyme reader, and read the absorbance; finally, use the standard curve to calculate the reducing sugar content of the sample.

[0070] DE value:

[0071] The percentage of reducing sugar content (calculated as glucose) in the sample to dry matter is called DE value. The calculation formula of DE value is as follows:

[0072] DE value = (reducing sugar content%) / (dry matter content%) × 100%

[0073] Among them, dry matter refers to the mass of solid matter remaining after the sample is dried and all water is removed.

[0074] Sensory evaluation:

[0075] Invite 50 test volunteers to evaluate the appearance, flavor, taste, etc. of corn concentrate. The specific evaluation method is shown in Table 1. A total of 50 valid results were collected.

[0076] Table 1 Corn milk sensory evaluation scoring rules

[0077]

[0078]

[0079] Except for sensory evaluation, all experiments were repeated three times, and the results were expressed as mean ± standard deviation. SPSS25.0 software was used to analyze the data with one-way analysis of variance and Duncan test, and p < 0.05 was considered statistically significant.

[0080] Table 2 Solid content, reducing sugar content and DE value of corn concentrate

[0081]

[0082] Table 3 Sensory evaluation scores of corn concentrate

[0083]

[0084] Solid content refers to the percentage of the mass of the solid part remaining after removing water from corn concentrate to the total mass of corn concentrate. This indicator is usually used to measure the proportion of solid matter in liquid or semi-solid samples, and is an important parameter for evaluating food, beverages, etc. The solid content of the corn concentrate prepared in Examples 1 to 4 and Comparative Example 1 is about 30%, indicating that the extrusion synergistic enzymatic hydrolysis technology can significantly improve the product concentration. Traditional enzymatic hydrolysis technology can only obtain enzymatic products with a solid content of less than 20%. Not only does the enzymatic hydrolysis time take a long time, but a thickener needs to be added to increase the product concentration. Compared with traditional enzymatic hydrolysis, the present invention can prepare a high-solid content corn concentrate product without the addition of a thickener by one enzymatic hydrolysis, which provides food safety while also reducing enterprise costs.

[0085] The reducing sugar content is closely related to the degree of enzymatic hydrolysis and liquefaction of corn concentrate, the sweetness of the product, etc. Starch is broken down into smaller sugar molecules under the action of amylase. Amylase can cut the glycosidic bonds in starch molecules, gradually degrade and liquefy them into dextrin and maltose, and finally generate glucose. The higher the reducing sugar content, the higher the sweetness of the corn concentrate and the better the degree of enzymatic hydrolysis and liquefaction. DE value is an important indicator to measure the reducing sugar content in starch or starch hydrolysate. DE value reflects the degree of starch hydrolysis. The higher the value, the more thorough the starch hydrolysis and the more simple sugars are generated.

[0086] Compared with Examples 1 to 4, the corn concentrate prepared in Example 4 has the highest reducing sugar content, better stability, palatability and sweetness. This is attributed to the complete gelatinization of high-temperature extruded corn starch, and the high-temperature α-amylase cuts the α-1,4 glycosidic bonds in the starch molecules to produce short-chain dextrins or maltose, which are finally decomposed into glucose. High temperature accelerates the complete enzymatic hydrolysis and liquefaction of starch, thereby increasing the reducing sugar content and product sweetness. The corn concentrate obtained after extrusion enzymatic hydrolysis has a high DE value, indicating that the enzymatic hydrolysis sample of this scheme has high sweetness, low viscosity, and high starch liquefaction degree. At the same time, the cost of the high-temperature α-amylase selected in Example 4 is low, which can minimize the production cost of the enterprise and stabilize the product properties. In Comparative Example 1, the enzyme is mixed with corn flour in advance, but because the enzyme preparation is not in complete contact with the corn flour, the starch molecular chain cannot be effectively sheared, the small molecule sugar or dextrin obtained by liquefaction is less, the enzymatic hydrolysis effect is poor, and the resulting enzymatic corn concentrate has a low reducing sugar content.

[0087] The sensory evaluation scores of Examples 1 to 4 were compared. In terms of smell, Examples 1 and 3 had a fresh corn aroma, while Examples 2 and 4 had a stronger aroma. In terms of appearance, Examples 1 to 4 were all stable without water separation and stratification. The color was consistent with the color of the corn itself. In terms of taste, Examples 1, 2, and 4 had a suitable corn sweetness, while Example 3 had a slightly lighter sweetness. In terms of taste, Examples 1 to 2 and 4 had a moderate taste. In comprehensive comparison, Example 4 had a higher sensory score, followed by Examples 1 and 2, and Example 3 had the lowest score.

[0088] In short, the reducing sugar content, DE value, sensory score, etc. of Example 4 are better. The reason is that the twin-screw extrusion method of the present invention has multiple extrusion temperature zones, a long extrusion cavity, a large contact area, a long action time, and a large number of shearing times, which is conducive to the deep liquefaction of starch. The six temperature zones have stable extrusion enzymatic hydrolysis temperatures and concentrated action temperatures, which are conducive to the maximum enzymatic hydrolysis of high-temperature α-amylase, prolonging the action time of the enzyme, and improving the utilization efficiency, thereby achieving efficient production, significantly improving the stability of corn concentrate, palatability and sensory scores, and increasing the application value of corn concentrate.

[0089] The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing corn concentrate by enzyme extrusion, characterized in that: The following steps are involved: (1) Grinding corn through a 50-100 mesh sieve to obtain corn flour; (2) uniformly dispersing the enzyme preparation in purified water to obtain an enzymatic hydrolyzate; (3) placing the corn flour obtained in step (1) and the enzymatic hydrolyzate obtained in step (2) in a solid feeding bin and a liquid feeder of a twin-screw extruder respectively, and performing reaction extrusion by the twin-screw extruder to obtain enzymatically hydrolyzed corn slurry; (4) grinding the extruded enzymatic hydrolysate obtained in step (3) using a colloid mill; (5) separating the residue from the product obtained in step (4) by horizontal screw centrifugation; (6) homogenizing the product obtained in step (5) using a homogenizer; (7) sterilizing and filling the product obtained in step (6) to obtain the final product of enzymatic corn concentrate.

2. The method according to claim 1, characterized in that In step (2), the enzyme preparation in the enzymatic hydrolysis solution is at least one of a medium-temperature α-amylase, a high-temperature α-amylase and a saccharifying enzyme, wherein the medium-temperature α-amylase has an activity of 300 to 600 KUN / g, the high-temperature α-amylase has an activity of 50 to 200 KUN / mL, and the saccharifying enzyme has an activity of 100 to 500 AGU / g.

3. The method according to claim 1, characterized in that In step (2), the amount of enzyme preparation added to the enzymatic hydrolysis solution is 1‰ to 10‰ of the mass of corn flour.

4. The method according to claim 1, characterized in that: In step (3), the six areas of the extrusion cavity are divided into: areas I to V are extrusion enzymatic hydrolysis areas, and area VI is an extrusion enzymatic hydrolysis and high-temperature enzyme inactivation area; area I is 50-80°C, area II is 60-85°C, area III is 65-90°C, area IV is 70-100°C, area V is 80-110°C, and area VI is 90-120°C.

5. The method according to claim 1, characterized in that In step (3), the extrusion temperature is 50°C to 120°C, the solid feed rate is 3 to 30 kg / h, the liquid feed rate is 5 to 50 L / h, the screw speed is 50 to 500 r / min, and the solid content of the extruded slurry is 30% to 50%.

6. The method according to claim 1, characterized in that In step (4), the colloid mill has a grinding fineness of 250 to 350 meshes and a grinding time of 0.5 to 2 min.

7. The method according to claim 1, characterized in that In step (5), the centrifugal process speed is 2000-3000 r / min, and the centrifugal time is 1-5 min.

8. The method according to claim 1, characterized in that In step (6), the homogenization process pressure is 30-60 MPa, and the homogenization times are 1-2 times, each time for 5-60 seconds.

9. The method according to claim 1, characterized in that: The sterilization conditions in step (7) are: sterilization temperature 105-135°C, sterilization time 10-60s.

10. Corn concentrate prepared according to the method of any one of claims 1 to 9, wherein the solid content of the corn concentrate is 30% to 50%.

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