Preparation method of high-protein wheat germ nutritional compound granules

Abstract

The invention relates to the technical field of food, in particular to a preparation method of high-protein wheat germ nutritional compound granules. The method comprises the following steps: firstly, spraying chitosan on the surface of dry wheat germ powder, and then reducing the moisture content and inhibiting the enzyme activity through microwave treatment; the preparation method comprises the following steps: preparing wheat germ powder, then spraying sodium alginate to obtain stabilized wheat germ powder, finally, compounding the stabilized wheat germ powder with other nutritional ingredients, and carrying out high-pressure homogenization and spray drying to prepare the electuary. Through chitosan coating and microwave treatment, the nutrient retention rate and the storage stability of the wheat germs are remarkably improved, meanwhile, nutrient component loss and hidden danger of chemical additives in a traditional method are avoided, and an efficient and safe solution is provided for industrial application of the wheat germ nutrient compound granules.

Description

Technical Field

[0001] The invention relates to the technical field of food, and in particular to a method for preparing a high-protein wheat germ nutritional compound granule. Background Art

[0002] Wheat germ nutritional compound granules are functional granules made from wheat germ as the main raw material and combined with a variety of natural nutrients. It not only retains the natural nutrients of wheat germ such as high protein, high vitamin E and minerals, but also further enhances its nutritional value and health benefits by scientifically compounding other functional ingredients. As a by-product of wheat processing, wheat germ is rich in protein, fat, vitamins, minerals and other nutrients, and has extremely high nutritional value and health functions. However, the lipase and lipoxygenase activities in wheat germ are relatively high, and fat oxidation is prone to occur during storage, resulting in increased oleic acid value and peroxide value, thereby affecting the quality and shelf life of the product. In addition, the high moisture content of wheat germ also makes it easy to deteriorate in high temperature and high humidity environments, limiting its wide application in the food industry.

[0003] At present, traditional wheat germ stabilization treatment methods mainly include heat treatment, drying and chemical additives, but these methods often have problems such as high energy consumption, large loss of nutrients, and insufficient stability. For example, although simple heat treatment can reduce the moisture content, it may cause protein denaturation or increased fat oxidation; and the use of chemical additives may introduce food safety risks. Therefore, the development of a stabilization treatment method that can effectively inhibit the activity of lipase and lipoxygenase while retaining the nutrients of wheat germ has become the focus of current research. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a method for preparing a high-protein wheat germ nutritional compound granule to solve the problems of high lipase and lipoxygenase activity of wheat germ in the wheat germ nutritional compound granule, large loss of nutrients and insufficient stability.

[0005] Based on the above purpose, the present invention provides a method for preparing a high-protein wheat germ nutritional compound granule, comprising the following steps: (1) Add chitosan to edible acetic acid solution, stir for 20-40 minutes, then add glycerol, continue stirring for 10-30 minutes, let stand for 1.5-2.5 hours to remove bubbles in the solution, and obtain a chitosan solution; (2) Add sodium alginate to deionized water, stir for 20-40 minutes, and then let stand for 1.5-2.5 hours to remove bubbles in the solution to obtain a sodium alginate solution; (3) drying the wheat germ at 55-65° C. until the moisture content is less than 10%, and then grinding through a 80-120 mesh sieve to obtain wheat germ flour; (4) spraying the chitosan solution on the surface of the wheat germ powder and drying it to obtain the chitosan coated wheat germ powder; (5) placing the chitosan coated wheat germ powder in a microwave-specific dish and spreading it evenly to a thickness of 0.8-1.2 cm, and subjecting it to microwave treatment to obtain microwave-treated wheat germ powder; (6) spraying the sodium alginate solution on the surface of the microwave-treated wheat germ powder and drying it to obtain stabilized wheat germ powder; (7) adding stabilized wheat germ powder, soy protein isolate, maltodextrin and sucrose ester into deionized water, stirring for 20-40 minutes, then adding monoglyceride and natural vegetable oil, and shearing for 5-15 minutes to obtain a mixture A; (8) homogenizing the mixture A under high pressure to obtain a mixture B; (9) The mixture B is spray-dried to obtain a high-protein wheat germ nutritional compound granule.

[0006] Preferably, the concentration of the edible acetic acid solution in step (1) is 0.8 wt%-1.2 wt%.

[0007] Preferably, in step (1), the weight ratio of chitosan, edible acetic acid solution and glycerol is 5-15:400-600:15-25.

[0008] Preferably, in step (2), the weight ratio of sodium alginate to deionized water is 4-6:80-120.

[0009] Preferably, in step (4), the weight ratio of the chitosan solution to the wheat germ powder is 400-600:20-30.

[0010] Preferably, in step (5), the microwave treatment power is 350-450 W, and the treatment time is 150-200 s.

[0011] Preferably, in step (6), the weight ratio of the sodium alginate solution to the microwave-treated wheat germ powder is 80-120:15-25.

[0012] Preferably, in step (7), the weight ratio of the stabilized wheat germ powder, soy protein isolate, maltodextrin, sucrose ester, deionized water, monoglyceride and natural vegetable oil is 15-25:1-3:6-10:0.05-0.2:30-70:0.1-0.3:5-15.

[0013] Preferably, in step (7), the shearing temperature is 70-80°C and the shearing speed is 800-1200 rpm.

[0014] Preferably, the temperature of the high-pressure homogenization in step (8) is 75-85° C. and the pressure is 35-45 MPa.

[0015] Preferably, in step (9), the inlet air temperature of the spray drying is 170-190°C, the outlet air temperature is 70-90°C, and the time is 8-12s.

[0016] Beneficial effects of the present invention: The present invention provides a method for preparing a high-protein wheat germ nutritional compound granule. First, the moisture content of the wheat germ is significantly reduced by microwave treatment, while the retention rate of protein and fatty acids is increased, thereby ensuring the high nutritional value of the product. Secondly, chitosan coating technology is used in combination with microwave treatment to effectively inhibit the activity of lipase and lipoxygenase, significantly reduce the oleic acid value and peroxide value, thereby greatly improving the storage stability of the product.

[0017] The chitosan and sodium alginate treatment adopted by the present invention can form a cross-linked film on the surface of wheat germ, further blocking the penetration of oxygen and water, and enhancing the antioxidant capacity and long-term stability of the product. By optimizing the processing sequence, the barrier of the protective film to the release of water is avoided, and the uniformity and stability of the wheat germ in the preparation process are ensured. On the whole, the present invention not only improves the nutritional value of wheat germ, but also significantly prolongs its shelf life, providing a reliable guarantee for the industrial production of wheat germ nutritional compound granules. DETAILED DESCRIPTION

[0018] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0019] The wheat germ in the specific implementation manner of the present invention was purchased from Hebei Dark Horse Flour Co., Ltd.

[0020] Example 1: (1) 5 g of chitosan was added to 400 g of 0.8 wt% edible acetic acid solution, stirred for 20 min, and then 15 g of glycerol was added, and the stirring was continued for 10 min. The solution was allowed to stand for 1.5 h to remove bubbles in the solution, thereby obtaining a chitosan solution; (2) Add 4 g of sodium alginate to 80 g of deionized water, stir for 20 min, and then let stand for 1.5 h to remove bubbles in the solution to obtain a sodium alginate solution; (3) drying the wheat germ at 55° C. until the moisture content is 9.8%, and then grinding through an 80-mesh sieve to obtain wheat germ flour; (4) Spraying 400 g of chitosan solution on the surface of 20 g of wheat germ powder and drying at 55° C. for 20 h to obtain chitosan-coated wheat germ powder; (5) placing the chitosan coated wheat germ powder in a microwave-specific dish and spreading it flat to a thickness of 0.8 cm, and subjecting it to microwave treatment at a microwave treatment power of 350 W and a treatment time of 150 s to obtain microwave-treated wheat germ powder; (6) Spraying 80 g of sodium alginate solution on the surface of 15 g of microwave-treated wheat germ powder, and drying at 55 °C for 20 h to obtain stabilized wheat germ powder; (7) 15 g of stabilized wheat germ powder, 1 g of soy protein isolate, 6 g of maltodextrin and 0.05 g of sucrose ester were added to 30 g of deionized water and stirred for 20 min. Then, 0.1 g of monoglyceride and 5 g of natural vegetable oil were added and high-speed shearing was performed for 5 min at a shearing temperature of 70 °C and a speed of 800 rpm to obtain a mixture A. (8) subjecting mixture A to high pressure homogenization at a temperature of 75°C and a pressure of 35 MPa to obtain mixture B; (9) The mixture B is spray-dried at an inlet air temperature of 170°C and an outlet air temperature of 70°C for 8 seconds to obtain a high-protein wheat germ nutritional compound granule.

[0021] Example 2: (1) 10 g of chitosan was added to 500 g of 1 wt% edible acetic acid solution, stirred for 30 min, then 20 g of glycerol was added, stirred for 20 min, and allowed to stand for 2 h to remove bubbles in the solution, thereby obtaining a chitosan solution; (2) Add 5 g of sodium alginate into 100 g of deionized water, stir for 30 min, and then let stand for 2 h to remove bubbles in the solution to obtain a sodium alginate solution; (3) drying the wheat germ at 60° C. until the moisture content is 9.2%, and then grinding through a 100-mesh sieve to obtain wheat germ flour; (4) Spraying 500 g of chitosan solution on the surface of 25 g of wheat germ powder and drying at 60° C. for 24 h to obtain chitosan-coated wheat germ powder; (5) placing the chitosan coated wheat germ powder in a microwave-specific dish and spreading it flat to a thickness of 1 cm, and subjecting it to microwave treatment at a microwave treatment power of 400 W and a treatment time of 180 s to obtain microwave-treated wheat germ powder; (6) Spraying 100 g of sodium alginate solution on the surface of 20 g of microwave-treated wheat germ powder, and drying at 60 °C for 24 h to obtain stabilized wheat germ powder; (7) 20 g of stabilized wheat germ powder, 2 g of soy protein isolate, 8 g of maltodextrin and 0.1 g of sucrose ester were added to 50 g of deionized water and stirred for 30 min. Then, 0.2 g of monoglyceride and 10 g of natural vegetable oil were added and high-speed shearing was performed for 10 min at a shearing temperature of 75 °C and a speed of 1000 rpm to obtain a mixture A. (8) subjecting mixture A to high pressure homogenization at a temperature of 80° C. and a pressure of 40 MPa to obtain mixture B; (9) The mixture B is spray-dried at an inlet air temperature of 180°C and an outlet air temperature of 80°C for 10 seconds to obtain a high-protein wheat germ nutritional compound granule.

[0022] Example 3: (1) 15 g of chitosan was added to 600 g of 1.2 wt% edible acetic acid solution, stirred for 40 min, then 25 g of glycerol was added, stirred for 30 min, and allowed to stand for 2.5 h to remove bubbles in the solution, thereby obtaining a chitosan solution; (2) Add 6 g of sodium alginate to 120 g of deionized water, stir for 40 min, and then let stand for 2.5 h to remove bubbles in the solution to obtain a sodium alginate solution; (3) drying the wheat germ at 65° C. until the moisture content is 9.1%, and then grinding through a 120-mesh sieve to obtain wheat germ flour; (4) spraying 600 g of chitosan solution on the surface of 30 g of wheat germ powder, and drying at 60° C. for 24 h to obtain chitosan-coated wheat germ powder; (5) placing the chitosan coated wheat germ powder in a microwave-specific dish and spreading it flat to a thickness of 1.2 cm, and subjecting it to microwave treatment at a microwave treatment power of 450 W and a treatment time of 200 s to obtain microwave-treated wheat germ powder; (6) Spraying 120 g of sodium alginate solution on the surface of 25 g of microwave-treated wheat germ powder, and drying at 65 °C for 28 h to obtain stabilized wheat germ powder; (7) 25 g of stabilized wheat germ powder, 3 g of soy protein isolate, 10 g of maltodextrin and 0.2 g of sucrose ester were added to 70 g of deionized water and stirred for 40 min. Then, 0.3 g of monoglyceride and 15 g of natural vegetable oil were added and high-speed shearing was performed for 15 min at a shear temperature of 80 °C and a speed of 1200 rpm to obtain a mixture A. (8) subjecting the mixture A to high pressure homogenization at a temperature of 85° C. and a pressure of 45 MPa to obtain a mixture B; (9) The mixture B is spray-dried at an inlet air temperature of 190°C and an outlet air temperature of 90°C for 12 seconds to obtain a high-protein wheat germ nutritional compound granule.

[0023] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that no chitosan treatment is performed; the specific steps are as follows: (1) Add 5 g of sodium alginate into 100 g of deionized water, stir for 30 min, and then let stand for 2 h to remove bubbles in the solution to obtain a sodium alginate solution; (2) drying the wheat germ at 60° C. until the moisture content is 9.2%, and then grinding through a 100-mesh sieve to obtain wheat germ flour; (3) placing the wheat germ powder in a microwave-specific dish and spreading it flat to a thickness of 1 cm, and subjecting it to microwave treatment at a microwave treatment power of 400 W and a treatment time of 180 s to obtain microwave-treated wheat germ powder; (4) Spraying 100 g of sodium alginate solution on the surface of 20 g of microwave-treated wheat germ powder, and drying at 60 °C for 24 h to obtain stabilized wheat germ powder; (5) 20 g of stabilized wheat germ powder, 2 g of soy protein isolate, 8 g of maltodextrin and 0.1 g of sucrose ester were added to 50 g of deionized water and stirred for 30 min. Then, 0.2 g of monoglyceride and 10 g of natural vegetable oil were added and high-speed shearing was performed for 10 min at a shearing temperature of 75 °C and a speed of 1000 rpm to obtain a mixture A. (6) subjecting mixture A to high pressure homogenization at a temperature of 80° C. and a pressure of 40 MPa to obtain mixture B; (7) The mixture B is spray-dried at an inlet air temperature of 180°C and an outlet air temperature of 80°C for 10 seconds to obtain a high-protein wheat germ nutritional compound granule.

[0024] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that it is not treated with sodium alginate. The specific steps are as follows: (1) Add 10 g of chitosan to 500 g of 1 wt% edible acetic acid solution, stir for 30 min, then add 20 g of glycerol, continue stirring for 20 min, let stand for 2 h to remove bubbles in the solution, and obtain a chitosan solution; (2) drying the wheat germ at 60° C. until the moisture content is 9.2%, and then grinding through a 100-mesh sieve to obtain wheat germ flour; (3) Spraying 500 g of chitosan solution on the surface of 25 g of wheat germ powder and drying at 60° C. for 24 h to obtain chitosan-coated wheat germ powder; (4) placing the chitosan coated wheat germ powder in a microwave-specific dish and spreading it flat to a thickness of 1 cm, and subjecting it to microwave treatment at a microwave treatment power of 400 W and a treatment time of 180 s to obtain stabilized wheat germ powder; (5) 20 g of stabilized wheat germ powder, 2 g of soy protein isolate, 8 g of maltodextrin and 0.1 g of sucrose ester were added to 50 g of deionized water and stirred for 30 min. Then, 0.2 g of monoglyceride and 10 g of natural vegetable oil were added and high-speed shearing was performed for 10 min at a shearing temperature of 75 °C and a speed of 1000 rpm to obtain a mixture A. (6) subjecting mixture A to high pressure homogenization at a temperature of 80° C. and a pressure of 40 MPa to obtain mixture B; (7) The mixture B is spray-dried at an inlet air temperature of 180°C and an outlet air temperature of 80°C for 10 seconds to obtain a high-protein wheat germ nutritional compound granule.

[0025] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that no microwave treatment is performed; the specific steps are as follows: (1) Add 10 g of chitosan to 500 g of 1 wt% edible acetic acid solution, stir for 30 min, then add 20 g of glycerol, continue stirring for 20 min, let stand for 2 h to remove bubbles in the solution, and obtain a chitosan solution; (2) Add 5 g of sodium alginate into 100 g of deionized water, stir for 30 min, and then let stand for 2 h to remove bubbles in the solution to obtain a sodium alginate solution; (3) drying the wheat germ at 60° C. until the moisture content is 9.2%, and then grinding through a 100-mesh sieve to obtain wheat germ flour; (4) Spraying 500 g of chitosan solution on the surface of 25 g of wheat germ powder and drying at 60° C. for 24 h to obtain chitosan-coated wheat germ powder; (5) spraying 100 g of sodium alginate solution on the surface of 20 g of chitosan-coated wheat germ powder, and drying at 60° C. for 24 h to obtain stabilized wheat germ powder; (6) 20 g of stabilized wheat germ powder, 2 g of soy protein isolate, 8 g of maltodextrin and 0.1 g of sucrose ester were added to 50 g of deionized water and stirred for 30 min. Then, 0.2 g of monoglyceride and 10 g of natural vegetable oil were added and high-speed shearing was performed for 10 min at a shearing temperature of 75 °C and a speed of 1000 rpm to obtain a mixture A. (7) subjecting mixture A to high pressure homogenization at a temperature of 80° C. and a pressure of 40 MPa to obtain mixture B; (8) The mixture B is spray-dried at an inlet air temperature of 180°C and an outlet air temperature of 80°C for 10 seconds to obtain a high-protein wheat germ nutritional compound granule.

[0026] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that the chitosan coated wheat germ powder is first treated with sodium alginate and then subjected to microwave treatment; the specific steps are as follows: (1) Add 10 g of chitosan to 500 g of 1 wt% edible acetic acid solution, stir for 30 min, then add 20 g of glycerol, continue stirring for 20 min, let stand for 2 h to remove bubbles in the solution, and obtain a chitosan solution; (2) Add 5 g of sodium alginate into 100 g of deionized water, stir for 30 min, and then let stand for 2 h to remove bubbles in the solution to obtain a sodium alginate solution; (3) drying the wheat germ at 60° C. until the moisture content is 9.2%, and then grinding through a 100-mesh sieve to obtain wheat germ flour; (4) Spraying 500 g of chitosan solution on the surface of 25 g of wheat germ powder and drying at 60° C. for 24 h to obtain chitosan-coated wheat germ powder; (5) spraying 100 g of sodium alginate solution on the surface of 20 g of chitosan-coated wheat germ powder, and drying at 60° C. for 24 h to obtain sodium alginate-chitosan modified wheat germ powder; (6) placing the sodium alginate-chitosan modified wheat germ powder in a microwave-specific dish and spreading it flat to a thickness of 1 cm, and subjecting it to microwave treatment at a microwave power of 400 W and a treatment time of 180 s to obtain stabilized wheat germ powder; (7) 20 g of stabilized wheat germ powder, 2 g of soy protein isolate, 8 g of maltodextrin and 0.1 g of sucrose ester were added to 50 g of deionized water and stirred for 30 min. Then, 0.2 g of monoglyceride and 10 g of natural vegetable oil were added and high-speed shearing was performed for 10 min at a shearing temperature of 75 °C and a speed of 1000 rpm to obtain a mixture A. (8) subjecting mixture A to high pressure homogenization at a temperature of 80° C. and a pressure of 40 MPa to obtain mixture B; (9) The mixture B is spray-dried at an inlet air temperature of 180°C and an outlet air temperature of 80°C for 10 seconds to obtain a high-protein wheat germ nutritional compound granule.

[0027] Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that the wheat germ powder is not treated with chitosan and sodium alginate, but directly treated with microwaves; the specific steps are as follows: (1) Drying wheat germ at 60°C until the moisture content is 9.2%, and then grinding through a 100-mesh sieve to obtain wheat germ flour; (2) placing the wheat germ powder in a microwave-specific dish and spreading it flat to a thickness of 1 cm, and subjecting it to microwave treatment at a microwave treatment power of 400 W and a treatment time of 180 s to obtain stabilized wheat germ powder; (3) 20 g of stabilized wheat germ powder, 2 g of soy protein isolate, 8 g of maltodextrin and 0.1 g of sucrose ester were added to 50 g of deionized water and stirred for 30 min. Then, 0.2 g of monoglyceride and 10 g of natural vegetable oil were added and high-speed shearing was performed for 10 min at a shearing temperature of 75 °C and a speed of 1000 rpm to obtain a mixture A. (4) subjecting mixture A to high pressure homogenization at a temperature of 80°C and a pressure of 40 MPa to obtain mixture B; (5) The mixture B is spray-dried at an inlet air temperature of 180°C and an outlet air temperature of 80°C for 10 seconds to obtain a high-protein wheat germ nutritional compound granule.

[0028] Performance Test: Moisture content: Determined by constant weight method at 105℃ in GB / T 5497-1985; Protein determination: Determined according to GB / T 5511-2008; Fat determination: Determined according to GB / T5512-2008; Oleic acid value determination: according to GB / T5530-2005; Peroxide value determination: Determined according to GB / T5009.37-2003; Storage stability: The stabilized wheat germ powders in the examples and comparative examples were placed in an environment with a temperature of 55°C and a humidity of 80% for 0, 30 and 60 days, respectively, and the corresponding oleic acid value and peroxide value were tested. The results are shown in Table 1.

[0029] Table 1 Performance test results

[0030] Data Analysis: As can be seen from Table 1, the stabilized wheat germ powder prepared by the present invention has lower moisture, higher protein and fat content, the most important thing is that the wheat germ powder after the present invention is processed has lower oleic acid value and peroxide value, and, after placing 60d under the environment of high temperature and high humidity, still has lower oleic acid value and peroxide value, this result fully illustrates that the stabilization method adopted by the present invention can effectively suppress the activity of lipase and lipoxygenase in wheat germ. In addition, the method can also effectively suppress the infiltration of moisture and oxygen under the environment of high temperature and high humidity, thereby ensuring the long-term stability of wheat germ powder. This technology provides guarantee for the preparation process of wheat germ nutritional composite granules, effectively preventing wheat germ from going bad in the preparation process of nutritional composite granules.

[0031] It can be seen from the data of Example 2 and Comparative Example 1 in Table 1 that chitosan coating can effectively reduce the oleic acid value and peroxide value of wheat germ, and has a significant effect on improving storage stability. This is mainly because chitosan combined with microwave treatment can further reduce the water content of wheat germ, and the amino group has reducing properties, which can eliminate free radicals and inhibit oxidation. Moreover, after microwave treatment, chitosan can cross-link with sodium alginate to form a denser protective film, which effectively blocks oxygen and moisture, thereby further improving stability.

[0032] It can be seen from the data of Example 2 and Comparative Example 2 in Table 1 that sodium alginate treatment can effectively improve the storage stability of wheat germ, which is mainly due to the cross-linked film formed by chitosan and sodium alginate protecting the wheat germ.

[0033] It can be seen from the data of Example 2 and Comparative Example 3 in Table 1 that microwave treatment can significantly reduce the moisture content in wheat germ and increase the protein and fatty acid content. This phenomenon is mainly attributed to the energy effect generated during microwave treatment. The moisture evaporates due to heat, resulting in a significant decrease in the moisture content of wheat germ. At the same time, microwave treatment can also promote the retention and even increase of protein and fatty acids. This is because the energy of microwaves can quickly penetrate the material and heat it evenly. This uniform heating method helps to protect the structural stability of the protein. In addition, microwave treatment may also release more protein and fatty acids by changing the cell structure of wheat germ, thereby increasing their content.

[0034] It can be seen from the data of Example 2 and Comparative Example 4 in Table 1 that the order of chitosan treatment, microwave treatment and sodium alginate treatment is crucial. Microwave treatment after chitosan treatment and sodium alginate treatment will lead to a higher moisture content in the wheat germ and significantly deteriorate the storage stability. This is mainly because a protective film is formed after the chitosan treatment and sodium alginate treatment, thereby preventing the release of moisture inside the wheat germ.

[0035] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

Claims

1. A method for preparing a high-protein wheat germ nutritional compound granule, characterized in that: The following steps are involved: (1) Add chitosan to edible acetic acid solution, stir for 20-40 minutes, then add glycerol, continue stirring for 10-30 minutes, let stand for 1.5-2.5 hours to remove bubbles in the solution, and obtain a chitosan solution; (2) Add sodium alginate to deionized water, stir for 20-40 minutes, and then let stand for 1.5-2.5 hours to remove bubbles in the solution to obtain a sodium alginate solution; (3) drying the wheat germ at 55-65° C. until the moisture content is less than 10%, and then grinding through a 80-120 mesh sieve to obtain wheat germ flour; (4) spraying the chitosan solution on the surface of the wheat germ powder and drying it to obtain the chitosan coated wheat germ powder; (5) placing the chitosan coated wheat germ powder in a microwave-specific dish and spreading it evenly to a thickness of 0.8-1.2 cm, and subjecting it to microwave treatment to obtain microwave-treated wheat germ powder; (6) spraying the sodium alginate solution on the surface of the microwave-treated wheat germ powder and drying it to obtain stabilized wheat germ powder; (7) adding stabilized wheat germ powder, soy protein isolate, maltodextrin and sucrose ester into deionized water, stirring for 20-40 minutes, then adding monoglyceride and natural vegetable oil, and shearing for 5-15 minutes to obtain a mixture A; (8) homogenizing the mixture A under high pressure to obtain a mixture B; (9) spray drying the mixture B to obtain a high-protein wheat germ nutritional compound granule; In the step (1), the weight ratio of chitosan, edible acetic acid solution and glycerol is 5-15:400-600:15-25; In the step (2), the weight ratio of sodium alginate to deionized water is 4-6:80-120; In the step (4), the weight ratio of the chitosan solution to the wheat germ powder is 400-600:20-30; In the step (6), the weight ratio of the sodium alginate solution to the microwave-treated wheat germ powder is 80-120:15-25.

2. The method for preparing the high-protein wheat germ nutritional composite granules according to claim 1, characterized in that: The concentration of the edible acetic acid solution in step (1) is 0.8 wt%-1.2 wt%.

3. The preparation method of the high-protein wheat germ nutritional composite granules according to claim 1, characterized in that: In the step (5), the microwave treatment power is 350-450 W, and the treatment time is 150-200 s.

4. The method for preparing the high-protein wheat germ nutritional composite granules according to claim 1, characterized in that: In the step (7), the weight ratio of the stabilized wheat germ powder, soy protein isolate, maltodextrin, sucrose ester, deionized water, monoglyceride and natural vegetable oil is 15-25:1-3:6-10:0.05-0.2:30-70:0.1-0.3:5-15.

5. The method for preparing the high-protein wheat germ nutritional composite granules according to claim 1, characterized in that: In the step (7), the shearing temperature is 70-80°C and the shearing speed is 800-1200 rpm.

6. The method for preparing the high-protein wheat germ nutritional composite granules according to claim 1, characterized in that: In the step (8), the temperature of the high pressure homogenization is 75-85°C and the pressure is 35-45Mpa.

7. The method for preparing the high-protein wheat germ nutritional composite granules according to claim 1, characterized in that: In step (9), the inlet air temperature of the spray drying is 170-190°C, the outlet air temperature is 70-90°C, and the time is 8-12s.

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