Corn nutrient powder that can be mixed with cold water and preparation method thereof

Abstract

The present invention belongs to the technical field of agricultural and sideline product processing, and specifically relates to a corn nutritional powder that can be brewed in cold water and a preparation method thereof. The present invention obtains corn nutritional powder by mixing two different corn flours, and mixing with oat flour, konjac powder and inulin, and then extruding with a twin screw. The obtained high-fiber fresh corn nutritional powder has a good cold water brewing effect, and the agglomeration rate is only 0.01%, and the gelatinization degree and total dietary fiber are higher than the common corn nutritional powder on the market. In the present invention, the soluble dietary content of the high-fiber fresh corn nutritional powder is increased by the high temperature, high pressure and high shearing action of the twin screw extrusion equipment, and the total dietary fiber content is higher than that of commercially available products by compounding with other raw materials.

Description

Technical Field

[0001] The invention belongs to the technical field of agricultural and sideline product processing, and particularly relates to corn nutrient powder that can be diluted with cold water and a preparation method thereof. Background Art

[0002] Fresh corn is rich in dietary fiber, vitamins, glutamate, magnesium, selenium and other nutrients. The rich dietary fiber can promote gastrointestinal motility, and the low fat content can give you a strong sense of fullness. Studies have shown that consuming fresh corn can help reduce the incidence of high blood pressure, coronary heart disease, and diabetes. Fresh corn is known as the king of coarse grains.

[0003] The current fresh corn market is mainly based on fresh corn sales, and there is a problem of single product category, which makes it difficult to meet consumers' expectations and requirements for fresh corn food. Therefore, it is crucial to develop fresh corn products, enrich product categories, and provide consumers with more choices when choosing fresh corn products.

[0004] Instant powder refers to a kind of instant food made from various grains and can be eaten after being brewed with water. However, the instant powder currently sold on the market generally needs hot water or boiling water above 80℃ to be brewed, which is not convenient to eat. In addition, the corn instant powder on the market has the problems of low solubility index and serious caking when it is brewed with cold water at 15℃ to 25℃. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a corn nutritional powder that can be mixed with cold water and a preparation method thereof.

[0006] To achieve the above objectives, the specific technical solutions of the present invention are as follows.

[0007] The first aspect of the present invention provides a method for preparing corn nutritional powder that can be mixed with cold water, comprising the following steps:

[0008] Mixing fresh corn flour and common corn flour in a mass ratio of 2-5:4-8 to obtain mixed flour;

[0009] Mixing the mixed powder, oatmeal powder, konjac powder and inulin to obtain mixed nutritional powder;

[0010] The mixed nutritional powder is subjected to twin-screw extrusion to obtain an extrudate, and the extrudate is dried and crushed to obtain corn nutritional powder that can be mixed with cold water;

[0011] The conditions of the twin-screw extrusion are as follows:

[0012] The temperature of zone 1 is 40℃~100℃, the temperature of zone 2 is 50℃~100℃, the temperature of zone 3 is 70℃~100℃, the temperature of zone 4 is 60℃~120℃, the temperature of zone 5 is 70℃~130℃, the temperature of zone 6 is 80℃~140℃, the temperature of zone 7 is 90℃~150℃, and the temperature of zone 8 is 100℃~180℃; the screw speed is 80r / min~190r / min, and the feeding speed is 20r / min~60r / min.

[0013] The present invention can effectively reduce the caking rate of cold water brewing by controlling the mass ratio of fresh corn flour and common corn flour, and the starch content in fresh corn is higher, while the starch content in common corn is lower. Since the gelatinization characteristics and intermolecular interactions of starch directly affect the solubility and dispersibility of corn flour, it is necessary to control the mass ratio of fresh corn flour and common corn flour during the configuration process. Through twin-screw extrusion, eight extrusion temperature zones are set, and different temperatures are set for the eight extrusion temperature zones, and the precise temperature can be set for the shearing section, so that the obtained corn nutritious powder has a lower caking rate when brewed with water of different temperatures, and oatmeal powder, konjac powder, and inulin are added to further improve the dietary fiber content of the corn nutritious powder.

[0014] In another preferred embodiment, the particle size of the fresh corn flour and the common corn flour is 80-120 mesh, and the corn nutritional powder prepared at this mesh size has the lowest caking rate after brewing; the temperature of the cold water brewing is 15°C-25°C, and the caking rate of the corn nutritional powder in the present invention is only 0.1% under the condition of cold water brewing at 15°C-25°C.

[0015] In another preferred embodiment, the mass percentage of the oat flour in the corn nutritional powder is 20% to 45%; the mass percentage of the konjac flour in the corn nutritional powder is 5% to 25%; the mass percentage of the inulin in the corn nutritional powder is 5% to 20%, and the rest is mixed flour, totaling 100%.

[0016] In another preferred embodiment, the extrudate is dried at a temperature of 35°C to 45°C for a time of 30 min to 90 min.

[0017] In another preferred embodiment, the specific preparation process of the fresh corn flour is as follows:

[0018] The frozen fresh corn kernels are vacuum dried, crushed and sieved to obtain fresh corn flour.

[0019] In another preferred embodiment, the freezing temperature is -80°C to -50°C, and the time is 4h to 6h; the vacuum drying temperature is -60°C to -40°C, and the time is 36h to 52h, and the vacuum degree is 60Pa to 80Pa.

[0020] In another preferred embodiment, the specific preparation process of the common corn flour is as follows:

[0021] The corn kernels are dried and crushed to produce ordinary corn flour.

[0022] In another preferred embodiment, the corn kernels are dried at a temperature of 40° C. to 60° C. for 2 h to 4 h.

[0023] The second aspect of the present invention provides a corn nutritional powder that can be mixed with cold water. The corn nutritional powder that can be mixed with cold water is prepared by the preparation method provided by the first aspect of the present invention.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention can effectively reduce the agglomeration rate of cold water brewing by controlling the mass ratio of fresh corn flour and ordinary corn flour. The starch content in fresh corn is high, while the starch content in ordinary corn is relatively low. Through twin-screw extrusion, eight extrusion temperature zones are set, and different temperatures are set for the eight extrusion temperature zones. The temperature can be accurately set for the shearing section, effectively reducing the agglomeration rate of corn nutritional powder, solving the problem of poor solubility and easy agglomeration of traditional instant powder, and providing convenience for consumers.

[0026] The corn nutritional powder of the present invention can be prepared with cold water at 15°C to 25°C, breaking the limitation that hot water is required for preparation on the market. The gelatinization degree of the obtained high dietary fiber fresh corn nutritional powder is improved by a twin-screw extruder to 91.13%, which can not only improve the solubility and reduce the agglomeration rate, but also make it easier to be digested and absorbed by the human body.

[0027] (2) Through the high temperature, high pressure and high shearing effect of twin-screw extrusion equipment, the total dietary fiber content of corn nutritional powder increases to 19%. When compounded with other raw materials, the total dietary fiber content is higher than that of commercially available products. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The present invention is a process flow chart of the preparation process.

[0029] Figure 2 This is a flow chart of the preparation process of Example 1 of the present invention.

[0030] Figure 3 This is a picture of commercially available corn nutritional powder after being brewed with cold water.

[0031] Figure 4 This is a picture of the corn nutritional powder in Example 3 of the present invention after being brewed with cold water. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] Unless otherwise specified, the experimental methods described in the following examples are all conventional methods; the reagents and materials described are all commercially available unless otherwise specified.

[0034] The instant powder currently on the market needs to be brewed with hot water or boiling water above 80°C for consumption. However, when using cold water, i.e., 15°C to 25°C, for brewing, there are serious problems of difficulty in brewing and serious caking rate.

[0035] The embodiment of the present invention provides a corn nutrient powder that can be mixed with cold water and a preparation method thereof. The preparation process is as follows: Figure 1 As shown, fresh corn flour and ordinary corn flour are mixed in a mass ratio of 2-5:4-8 to obtain mixed flour; mixed flour, oat flour, konjac flour and inulin are mixed to obtain mixed nutritional powder; mixed nutritional powder is subjected to twin-screw extrusion to obtain extrudate, the extrudate is dried and crushed to obtain corn nutritional powder that can be mixed with cold water. The conditions of twin-screw extrusion are as follows: the temperature of zone 1 is 40℃~100℃, the temperature of zone 2 is 50℃~100℃, the temperature of zone 3 is 70℃~100℃, the temperature of zone 4 is 60℃~120℃, the temperature of zone 5 is 70℃~130℃, the temperature of zone 6 is 80℃~140℃, the temperature of zone 7 is 90℃~150℃, and the temperature of zone 8 is 100℃~180℃; the screw speed is 80r / min~190r / min, and the feeding speed is 20r / min~80r / min.

[0036] The present invention controls the mass ratio of fresh corn flour and common corn flour, reduces the agglomeration rate of cold water brewing, and sets eight different twin-screw extrusion temperature zones to set a more precise temperature for the shearing section, so that the agglomeration rate of the obtained corn nutritious powder can be controlled within 0.01% when brewed with cold water at 15°C to 25°C.

[0037] The commercially available corn nutritional powder in the following examples was purchased from Xuzhou Shidi Food Co., Ltd.

[0038] The model of the high-speed universal pulverizer is FW100, which was purchased from Tianjin Test Instrument Co., Ltd.

[0039] The micro twin-screw extruder was Process 11 Extruder Thermo Scientific.

[0040] Example 1

[0041] A method for preparing corn nutrient powder that can be mixed with cold water, such as Figure 2 As shown, the following steps are included:

[0042] S1. Prefreeze the fresh corn kernels in a -50°C refrigerator for 6 hours, and freeze-dry them in a vacuum freeze drying oven for 48 hours to obtain vacuum freeze-dried fresh corn kernels; wherein the temperature of the vacuum freeze drying oven is -50°C and the vacuum degree is 60 Pa.

[0043] S2. The vacuum freeze-dried fresh corn kernels in S1 are crushed by a high-speed universal crusher, and then passed through a 100-mesh sieve to obtain fresh corn flour.

[0044] S3. Put the common corn kernels into a hot air drying oven, dry them at 60° C. for 2 hours to obtain hot air dried common corn kernels, put the hot air dried common corn kernels into a high-speed universal grinder, grind them, and pass them through a 100-mesh sieve to obtain common corn flour.

[0045] S4. Mix fresh corn flour and common corn flour in a mass ratio of 5:8 to obtain mixed flour.

[0046] S5. Mix the mixed powder, oatmeal powder, konjac powder and inulin to obtain a mixed nutritional powder; wherein, by mass percentage, the proportions of the raw materials in the mixed nutritional powder are as follows:

[0047] A mixture of 45% oatmeal flour, 20% konjac flour, 13% inulin, and the rest is mixed flour, totaling 100%.

[0048] S6. Send the mixed nutrient powder into a micro twin-screw extruder. The temperature of the micro twin-screw extruder temperature zone is set as follows:

[0049] The temperature of zone 1 is 50°C, the temperature of zone 2 is 60°C, the temperature of zone 3 is 80°C, the temperature of zone 4 is 100°C, the temperature of zone 5 is 120°C, the temperature of zone 6 is 130°C, the temperature of zone 7 is 140°C, the temperature of zone 8 is 140°C, the screw speed is 190r / min, the feeding speed is 80r / min, and the extrudate is obtained.

[0050] S7. The extrudate is placed in a hot air drying oven for hot air drying at a temperature of 35° C. for 30 min. After drying, it is crushed again by a high-speed universal crusher and passed through a 100-mesh sieve to obtain corn nutritional powder.

[0051] Example 2

[0052] A method for preparing corn nutritional powder that can be mixed with cold water comprises the following steps:

[0053] S1. Prefreeze the fresh corn kernels in a -80°C refrigerator for 4 hours, and freeze-dry them in a vacuum freeze drying oven for 36 hours to obtain vacuum freeze-dried fresh corn kernels; wherein the temperature of the vacuum freeze drying oven is -50°C and the vacuum degree is 80 Pa.

[0054] S2. The vacuum freeze-dried fresh corn kernels in S1 are crushed by a high-speed universal crusher, and then passed through a 100-mesh sieve to obtain fresh corn flour.

[0055] S3. Place the common corn kernels in a hot air drying oven at 60° C. and dry them for 2 h to obtain hot air dried common corn kernels. Place the hot air dried common corn kernels in a high-speed universal grinder and grind them. Pass them through a 100-mesh sieve to obtain common corn flour.

[0056] S4. Mix fresh corn flour and common corn flour in a mass ratio of 2:4 to obtain mixed flour.

[0057] S5. Mix the mixed powder, oatmeal powder, konjac powder and inulin to obtain a mixed nutritional powder; wherein, by mass percentage, the proportions of the raw materials in the mixed nutritional powder are as follows:

[0058] A mixture of 30% oatmeal flour, 25% konjac flour, 11% inulin, and the rest is mixed flour, totaling 100%.

[0059] S6, feeding the mixed nutrient powder into a micro twin-screw extruder, and setting the temperature of the micro twin-screw extruder temperature zone to:

[0060] The temperature of zone 1 is 40°C, the temperature of zone 2 is 60°C, the temperature of zone 3 is 70°C, the temperature of zone 4 is 80°C, the temperature of zone 5 is 100°C, the temperature of zone 6 is 120°C, the temperature of zone 7 is 140°C, and the temperature of zone 8 is 180°C; the screw speed is 170r / min, and the feeding speed is 75r / min to obtain the extrudate.

[0061] S7. The extrudate is placed in a hot air drying oven for hot air drying at a temperature of 35° C. for 30 min. After drying, it is crushed again by a high-speed universal crusher and passed through a 100-mesh sieve to obtain corn nutritional powder.

[0062] Example 3

[0063] A method for preparing corn nutritional powder that can be mixed with cold water comprises the following steps:

[0064] S1. Prefreeze the fresh corn kernels in a -60°C refrigerator for 4 hours, and freeze-dry them in a vacuum freeze drying oven for 48 hours to obtain vacuum freeze-dried fresh corn kernels; the temperature of the vacuum freeze drying oven is -50°C, and the vacuum degree is 70 Pa.

[0065] S2. The vacuum freeze-dried fresh corn kernels in S1 are crushed by a high-speed universal crusher, and then passed through a 100-mesh sieve to obtain fresh corn flour.

[0066] S3. Put the common corn kernels into a hot air drying oven, dry them at 50° C. for 3 h to obtain hot air dried common corn kernels, put the hot air dried common corn kernels into a high-speed universal grinder, grind them, and pass them through a 100-mesh sieve to obtain common corn flour.

[0067] S4. Mix fresh corn flour and common corn flour in a mass ratio of 4:6 to obtain mixed flour.

[0068] S5. Mix the mixed powder, oatmeal powder, konjac powder and inulin to obtain a mixed nutritional powder; wherein, by mass percentage, the proportions of the raw materials in the mixed nutritional powder are as follows:

[0069] 35% oatmeal flour, 17% konjac flour, 11% inulin are mixed, and the rest is mixed flour, totaling 100%.

[0070] S6, feeding the mixed nutrient powder into a micro twin-screw extruder, and setting the temperature of the micro twin-screw extruder temperature zone to:

[0071] The temperature of zone 1 is 40°C, the temperature of zone 2 is 60°C, the temperature of zone 3 is 80°C, the temperature of zone 4 is 120°C, the temperature of zone 5 is 130°C, the temperature of zone 6 is 140°C, the temperature of zone 7 is 150°C, the temperature of zone 8 is 180°C, the screw speed is 190r / min, and the feeding speed is 80r / min to obtain an extrudate.

[0072] S7. The extrudate is placed in a hot air drying oven for hot air drying at a temperature of 45° C. for 90 min. After drying, it is crushed again by a high-speed universal crusher and passed through a 100-mesh sieve to obtain corn nutritional powder.

[0073] Comparative Example 1

[0074] A method for preparing corn nutritious powder that can be mixed with cold water, except that the number of temperature zones set for a twin-screw extruder is different from that in Example 3, the remaining steps are the same as those in Example 3, and specifically include the following steps:

[0075] S1. Prefreeze the fresh corn kernels in a -60°C refrigerator for 4 hours, and freeze-dry them in a vacuum freeze drying oven for 48 hours to obtain vacuum freeze-dried fresh corn kernels; the temperature is -50°C and the vacuum degree is 70 Pa.

[0076] S2. The vacuum freeze-dried fresh corn kernels in S1 are crushed by a high-speed universal crusher, and then passed through a 100-mesh sieve to obtain fresh corn flour.

[0077] S3. Put the common corn kernels into a hot air drying oven, dry them at 50° C. for 3 h to obtain hot air dried common corn kernels, put the hot air dried common corn kernels into a high-speed universal grinder, grind them, and pass them through a 100-mesh sieve to obtain common corn flour.

[0078] S4. Mix fresh corn flour and common corn flour in a mass ratio of 4:6 to obtain mixed flour.

[0079] S5. Mix the mixed powder, oatmeal powder, konjac powder and inulin to obtain a mixed nutritional powder; wherein, by mass percentage, the proportions of the raw materials in the mixed nutritional powder are as follows:

[0080] 35% oatmeal flour, 17% konjac flour, 11% inulin are mixed, and the rest is mixed flour, totaling 100%.

[0081] S6, feeding the mixed nutrient powder into the twin-screw extruder, and setting the temperature of the temperature zone of the micro twin-screw extruder to:

[0082] The temperature of zone 1 is 40°C, the temperature of zone 2 is 60°C, the temperature of zone 3 is 80°C, the temperature of zone 4 is 120°C, the temperature of zone 5 is 130°C, the temperature of zone 6 is 140°C, the screw speed is 190r / min, the feeding speed is 80r / min, and the extrudate is obtained.

[0083] S7. The extrudate is placed in a hot air drying oven for hot air drying at a temperature of 45° C. for 90 min. After drying, it is crushed again by a high-speed universal crusher and passed through a 100-mesh sieve to obtain corn nutritional powder.

[0084] Comparative Example 2

[0085] A method for preparing high-fiber fresh corn nutritional powder that can be prepared with cold water, except that the number of temperature zones set for a twin-screw extruder is different from that in Example 3, the remaining steps are the same as those in Example 3, and specifically include the following steps:

[0086] S1. Prefreeze the fresh corn kernels in a -60°C refrigerator for 4 hours, and freeze-dry them in a vacuum freeze drying oven for 48 hours to obtain vacuum freeze-dried fresh corn kernels; the temperature is -50°C and the vacuum degree is 70 Pa.

[0087] S2. The vacuum freeze-dried fresh corn kernels in S1 are crushed by a high-speed universal crusher, and then passed through a 100-mesh sieve to obtain fresh corn flour.

[0088] S3. Put the common corn kernels into a hot air drying oven, dry them at 50° C. for 3 h to obtain hot air dried common corn kernels, put the hot air dried common corn kernels into a high-speed universal grinder, grind them, and pass them through a 100-mesh sieve to obtain common corn flour.

[0089] S4. Mix fresh corn flour and common corn flour in a mass ratio of 4:6 to obtain mixed flour.

[0090] S5. Mix the mixed powder, oatmeal powder, konjac powder and inulin to obtain a mixed nutritional powder; wherein, by mass percentage, the proportions of the raw materials in the mixed nutritional powder are as follows:

[0091] 35% oatmeal flour, 17% konjac flour, 11% inulin are mixed, and the rest is mixed flour, totaling 100%.

[0092] S6, feeding the mixed nutrient powder into a micro twin-screw extruder, and setting the temperature of the micro twin-screw extruder temperature zone to:

[0093] The temperature of zone 1 was 40°C, the temperature of zone 2 was 60°C, the temperature of zone 3 was 80°C, the temperature of zone 4 was 120°C, the screw speed was 190 r / min, and the feeding speed was 80 r / min to obtain an extrudate.

[0094] S7. The extrudate is placed in a hot air drying oven for hot air drying at a temperature of 45° C. for 90 min. After drying, it is crushed again by a high-speed universal crusher and passed through a 100-mesh sieve to obtain corn nutritional powder.

[0095] The corn nutrient powder prepared in Examples 1 to 3 and the corn nutrient powder purchased on the market were brewed with cold water at 15°C, and the agglomeration rate was calculated. The results are shown in Table 1. Figure 3 As shown, the corn nutritional powder prepared in Example 3 is brewed as shown in FIG. Figure 4 shown.

[0096] Table 1 Agglomeration rate of different corn nutrient powders

[0097]

[0098] From the results in Table 1, it can be seen that the agglomeration rate of the corn nutritional powder prepared in Examples 1 to 3 of the present invention when brewed with cold water at 15° C. is better than that of the commercially available corn nutritional powder. And the agglomeration rate of Example 3 is the lowest.

[0099] The corn nutritional powders prepared in Example 3 and Comparative Examples 1 and 2 were brewed with cold water at 15° C., and the agglomeration rates were calculated. The results are shown in Table 2.

[0100] Table 2 Agglomeration rate of different corn nutrient powders

[0101]

[0102] From the results in Table 2, it can be seen that by reducing the number of temperature zones of the twin-screw extruder, the agglomeration rate of the obtained corn nutrient powder will increase when it is brewed with cold water at 15°C, which means that the present invention can set a more precise temperature for the shearing section by setting 8 temperature zones with different temperatures for extrusion, so that the agglomeration rate of the obtained corn nutrient powder is only 0.0103% under the condition of brewing with cold water at 15°C.

[0103] The gelatinization degree of the corn nutrient powder prepared in Examples 1 to 3 and the gelatinization degree of the corn nutrient powder purchased on the market were measured respectively. The results are shown in Table 3.

[0104] Table 3 Gelatinization degree of different corn nutrient powders

[0105]

[0106] From the results in Table 3, it can be seen that the gelatinization degree of the corn nutrient powder prepared in Examples 1 to 3 of the present invention is higher than that of the commercially available corn nutrient powder, and the gelatinization degree of the corn nutrient powder in Example 3 is the highest, reaching 91.13%, and is easier to be digested and absorbed by the human body.

[0107] The total dietary fiber content of the high-fiber fresh corn nutritional powder prepared with cold water in Examples 1 to 3 and the dietary fiber content of the corn nutritional powder purchased on the market were measured respectively. The results are shown in Table 4.

[0108] Table 4 Total dietary fiber content of different corn nutritional powders

[0109]

[0110] From the results in Table 4, it can be seen that the total dietary fiber content of the corn nutritional powder in Examples 1 to 3 of the present invention is significantly higher than that of commercially available corn nutritional powder. This is mainly because the present invention further increases the total dietary fiber content of the corn nutritional powder by adding oatmeal flour, konjac flour and inulin, thereby improving its nutritional value.

[0111] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing corn nutritional powder that can be mixed with cold water, characterized in that: The following steps are involved: Mixing fresh corn flour and common corn flour in a mass ratio of 4:6 to obtain mixed flour; Mixing the mixed powder, oatmeal powder, konjac powder and inulin to obtain mixed nutritional powder; The mixed nutritional powder is subjected to twin-screw extrusion to obtain an extrudate, and the extrudate is dried and crushed to obtain corn nutritional powder that can be mixed with cold water; The conditions of the twin-screw extrusion are as follows: The temperature of zone 1 is 40℃~50℃, the temperature of zone 2 is 60℃, the temperature of zone 3 is 70℃~80℃, the temperature of zone 4 is 80℃~120℃, the temperature of zone 5 is 100℃~130℃, the temperature of zone 6 is 120℃~140℃, the temperature of zone 7 is 140℃~150℃, and the temperature of zone 8 is 140℃~180℃; The screw speed is 80r / min~190r / min, and the feeding speed is 20r / min~80r / min; The temperature of the cold water is 15°C; The particle sizes of the fresh corn flour and the common corn flour are both 80 meshes to 120 meshes.

2. The method for preparing the corn nutritional powder that can be mixed with cold water according to claim 1, characterized in that: The mass percentage of the oat flour in the corn nutritious powder is 20% to 45%; the mass percentage of the konjac flour in the corn nutritious powder is 5% to 25%; the mass percentage of the inulin in the corn nutritious powder is 5% to 20%, and the rest is mixed flour, which totals 100%.

3. The method for preparing the corn nutritional powder that can be mixed with cold water according to claim 1, characterized in that: The extrudate is dried at a temperature of 35° C. to 45° C. for a time of 30 min to 90 min.

4. The method for preparing the corn nutritional powder that can be mixed with cold water according to claim 2, characterized in that: The specific preparation process of the fresh corn flour is as follows: The frozen fresh corn kernels are vacuum dried, crushed and sieved to obtain fresh corn flour.

5. The method for preparing the corn nutritional powder that can be mixed with cold water according to claim 4, characterized in that: The freezing temperature is -80°C to -50°C, and the freezing time is 4h to 6h; The vacuum drying is carried out at a temperature of -60°C to -40°C, for a time of 36h to 52h, and at a vacuum degree of 60Pa to 80Pa.

6. The method for preparing the corn nutritional powder that can be mixed with cold water according to claim 2, characterized in that: The specific preparation process of the common corn flour is as follows: The corn kernels are dried, crushed, and sieved to obtain ordinary corn flour.

7. The method for preparing the corn nutritional powder that can be mixed with cold water according to claim 6, characterized in that: The corn kernels are dried at a temperature of 40° C. to 60° C. for 2 h to 4 h.

8. The method for preparing the corn nutritional powder that can be mixed with cold water according to claim 1, characterized in that: The mesh number of the corn nutritional powder is 80-100 meshes.

9. A corn nutritional powder that can be mixed with cold water and is prepared by the preparation method according to any one of claims 1 to 8.

Images