High-fiber sweet potato rice and preparation method thereof

Abstract

This invention belongs to the field of food processing technology, specifically relating to a high-fiber sweet potato processed rice and its preparation method. The high-fiber sweet potato processed rice provided by this invention is obtained through the following method: a mixture of rice flour, wheat flour, and oat flour (roasted using a roasting process), defatted soybean protein, and puffed high-fiber sweet potato flour are mixed and kneaded into a dough. The dough is then kept warm and cooked while being dehumidified. Next, it is granulated using a twin-screw extruder. During the extrusion process, excess moisture is removed from the granules through vacuuming. After extrusion molding, the granules are dried. This invention, through improvements to the processed rice process, produces high-fiber sweet potato processed rice that is smooth, rich in dietary fiber, and has a unique sweet potato aroma. Furthermore, the processed rice is rich in various dietary fibers, making it nutritious and palatable.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to a high-fiber sweet potato processed rice and its preparation method. Background Technology

[0002] Brown rice, whole wheat flour, and mixed grains have poor palatability and are not favored by consumers. However, excessive processing will cause a large loss of vitamins, minerals, and trace elements. Moreover, people have long suffered from oral ulcers, high blood pressure, diabetes, obesity, and other diseases due to excessive consumption of refined rice and flour. Therefore, there is an urgent need to develop nutritionally balanced functional staple foods.

[0003] Dietary fiber is a type of high-molecular-weight component, mainly composed of polysaccharides, that cannot be digested by human digestive enzymes. Among them, sweet potato dietary fiber has the widest range of applications. Studies have shown that sweet potato dietary fiber has a bulking effect, easily inducing a feeling of fullness. It can also increase the water content and quality of feces and the frequency of intestinal peristalsis. It has effects such as regulating blood sugar, increasing the viscosity of small intestinal contents, and reducing the absorption rate of glucose. In recent years, in order to improve people's refined diet, many nutritional rice products containing sweet potato dietary fiber have appeared on the market, such as the sweet potato and taro health rice prepared in patent CN104041752A, the sweet potato compound nutritional rice prepared in patent CN102860469A, and the fresh sweet potato regenerated rice in patent CN106562210A.

[0004] However, because sweet potatoes have a high content of dietary fiber and the fiber is coarse, they do not absorb water easily. If they are directly mixed with other grain flours to make processed rice, air bubbles and granules will easily enter due to their poor water absorption, thus affecting the appearance of the finished rice.

[0005] In addition, the dough needs to be matured during the preparation of regenerated rice. During the maturation process, the dough will produce some water, which will affect the texture of the dough and make it less malleable in the later stage. Furthermore, during the extrusion and granulation process of the dough, the water contained in the dough cannot be eliminated in a short time, which will create pores in the regenerated rice product and affect the sensory and color of the product. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a high-fiber sweet potato processed rice and its preparation method.

[0007] The high-fiber sweet potato processed rice provided by this invention comprises the following raw materials in parts by weight: 100-120 parts rice flour, 80-85 parts wheat flour, 50-55 parts oat flour, 30-40 parts high-fiber sweet potato flour, 5-10 parts defatted soybean protein, and 2-3 parts salt.

[0008] This invention also provides a method for preparing the above-mentioned high-fiber sweet potato processed rice. Specifically, a mixture of rice flour, wheat flour, oat flour (roasted using a roasting process), defatted soybean protein, and puffed high-fiber sweet potato flour is mixed and kneaded into a dough. The dough is then kept warm and cooked while being dehumidified. Finally, it is extruded and granulated using a twin-screw extruder. During the extrusion process, excess moisture in the granules is removed by vacuuming. After extrusion molding and drying, the rice-grain-shaped high-fiber sweet potato processed rice product is produced.

[0009] Furthermore, the above-mentioned method for preparing high-fiber sweet potato processed rice includes the following steps:

[0010] S1. Mix rice flour, wheat flour, and oat flour in an iron pot and stir-fry to obtain mixed grain flour.

[0011] S2, puffing high-fiber sweet potato flour to obtain puffed high-fiber sweet potato flour;

[0012] S3, put the defatted soybean protein, the mixed grain powder stir-fried in S1, and the puffed high-fiber sweet potato powder in S2 into the mixer, add water while mixing, add salt after mixing evenly, and continue mixing to form uniform dough particles.

[0013] S4. After the dough particles in S3 have matured, they are granulated using a twin-screw extruder. During the extrusion granulation process, excess moisture in the particles is removed by vacuuming to obtain smooth granular rice grains.

[0014] S5, the granular rice grains in S4 are dried to a moisture content of 17-19% and then subjected to ultraviolet disinfection treatment to obtain high-fiber sweet potato processed rice.

[0015] The required weight proportions of each raw material in the process of preparing the above-mentioned high-fiber sweet potato processed rice are as follows: 100-120 parts rice flour, 80-85 parts wheat flour, 50-55 parts oat flour, 30-40 parts high-fiber sweet potato flour, 5-10 parts defatted soybean protein, and 2-3 parts salt.

[0016] Preferably, in step S1, rice flour, wheat flour, and oat flour are mixed, poured into an iron pot, and stir-fried at 50-60℃ for 4-8 minutes.

[0017] In step S1 of this invention, rice flour, wheat flour, and oat flour are first stir-fried in an iron pot. The main purpose is to promote the Maillard reaction by stir-frying the raw material powders, so that more aroma intermediates are produced in the raw material powders, thereby improving the aroma of the raw material powders and making the aroma rich and mellow. However, during the stir-frying process, it is necessary to reasonably control the stir-frying temperature and the stir-frying time to adjust the content of amino compounds and carbonyl compounds, prevent the generation of acrylamide and advanced glycation end products (AGEs), and avoid excessive caramelization reaction.

[0018] Preferably, in step S2, microwave puffing is performed on the high-fiber sweet potato flour, with a microwave power of 450-500 W and a microwave treatment time of 1-4 min.

[0019] In fact, the intermolecular gaps of high-fiber sweet potato flour are too small, making it difficult for water to penetrate into its interior. Therefore, it easily absorbs water and coagulates into a paste on its outer surface, making it difficult for the sweet potato flour particles inside to dissolve well. This can easily lead to raw particles being wrapped up. In this invention, the high-fiber sweet potato flour is microwave-expanded, causing the cells inside the sweet potato flour raw material to rupture and the bound water to evaporate rapidly. This further makes the internal structure of the sweet potato flour raw material more complex, increases the specific surface area, and exposes more accessible edges while the cells are ruptured. This enhances the adhesion and adsorption of specific substances to the raw material, and the water holding capacity is also increased, thus helping to avoid the above-mentioned situation of raw particles being wrapped up or undercooked.

[0020] Preferably, in step S3, the amount of water added accounts for 20-30% of the total weight of the raw material powder, the water temperature is 50-60℃, and the amount of salt added accounts for 0.5-1.2% of the total weight of the raw material powder.

[0021] Preferably, in S3, after adding water, the dough becomes semi-fluid.

[0022] Preferably, in S4, the dough particles obtained in S3 are placed at 50-55℃ for 30-35 minutes to mature. During maturation, the dough is dehumidified. The matured material is granulated using a twin-screw extruder. During the extrusion granulation process, excess moisture in the particles is removed by vacuuming. The screw speed is 75-80 rpm, and the temperature at the end of the barrel is 105-110℃.

[0023] During the maturation process of dough particles, a large amount of water is released. If the dough particles are not treated in any way, the resulting matured dough will have a high water content, a soft texture, and poor shape retention in the later stages. Therefore, this invention adds a dehumidification operation while maturing the dough particles. This involves removing the excess water generated during the maturation process and using the dehumidifier pipes in the equipment to uniformly transfer hot air through the material conveying pipes, thus drying the material evenly and making it more conducive to the later extrusion and shaping of the dough.

[0024] Preferably, in step S5, the granular rice grains obtained in step S4 are placed in an environment of 45-50°C and dried for 25-35 minutes until the moisture content of the granular rice grains is 17-19%.

[0025] The beneficial effects of this invention are as follows:

[0026] (1) A processed rice rich in high-fiber sweet potato flour and various grain components is provided. In the preparation process of processed rice, the Maillard reaction is promoted by frying various grain flours in advance, so that the raw material flour has a strong aroma, thereby improving the taste of processed rice.

[0027] (2) By using microwave to puff the high-fiber sweet potato flour, the internal structure of the sweet potato flour particles becomes more complex, which improves the water holding capacity of the high-fiber sweet potato flour and avoids the phenomenon of raw particles being wrapped in the processed rice. The processed rice produced has a more uniform color and a more beautiful color.

[0028] (3) The present invention uses a specific device in the process of preparing reconstituted rice, namely, adding a component with dehumidification function and a component with vacuum drying function to the traditional extrusion granulation device;

[0029] The above improvements not only avoid the problem of dough softening due to excessive moisture content during dough maturation, but also prevent the pressure inside the extrusion channel from rising during dough extrusion granulation. If the moisture in the material does not turn into water vapor, the pressure will drop sharply to atmospheric pressure the moment the material is discharged from the extrusion granulation device. The moisture contained therein will quickly turn into superheated steam and cause the volume to expand rapidly, resulting in porous interior after the product cools down, thus affecting the morphology of the processed rice. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the apparatus used in the high-fiber sweet potato rice processing process provided in Embodiment 1 of the present invention;

[0031] Among them, 1-feeding port, 2-material conveying and stirring device, 201-pipeline, 202-stirring component, 3-dehumidifier, 301-control device, 302-ventilation duct, 4-power unit, 401-telescopic rod, 402-extrusion plate, 5-vacuum pump, 501-control valve, 502-pressure gauge, 503-pressure reducing equipment pipeline, 504-switch, 6-extrusion granulation device;

[0032] Figure 2 The images are scanning electron microscope images of high-fiber sweet potato starch particles before and after microwave puffing treatment in Example 2 of the present invention.

[0033] Figure 3 This is a schematic diagram showing the appearance of the high-fiber sweet potato processed rice prepared in Example 2 of the present invention;

[0034] Figure 4 This is a schematic diagram showing the appearance of the high-fiber sweet potato processed rice prepared in Comparative Example 3 of the present invention.

[0035] Figure 5The graph shows the water absorption and water solubility of the high-fiber sweet potato processed rice prepared in each experimental group in Experiment Example 2 of this invention. Detailed Implementation

[0036] To enable those skilled in the art to better understand the present invention, the present invention will now be further described in conjunction with specific embodiments.

[0037] Example 1

[0038] The equipment used in the processing of high-fiber sweet potato rice has the following structure:

[0039] It includes a feeding port 1 and a material conveying and stirring device 2 directly connected to the discharge port of the feeding port 1. The material conveying and stirring device 2 includes a material conveying pipe 201 and a stirring component 202 installed in the material conveying pipe 201.

[0040] The dehumidifier 3 is connected on one side to the pipe 201 of the material conveying and stirring device 2 via the ventilation pipe 302, and on the other side to the control device 301.

[0041] The extrusion channel has a power device 4 installed at the upper hollow end. The power device 4 includes a telescopic rod 401 and an extrusion plate 402 connected to the telescopic rod.

[0042] An extrusion granulation device 6 is provided at the bottom of the extrusion channel; a pressure reducing device pipeline 503 is provided on the extrusion channel, and a switch 504 is provided; the extrusion channel is connected to a vacuum pump 5 through a pipeline, and a control valve 501 and a pressure gauge 502 are provided on the connected pipeline.

[0043] In actual operation, the material is fed through the feeding port 1, then stirred and matured by the material conveying and stirring device 2, and then enters the extrusion channel through the lower port of the material conveying and stirring device 2. It is then extruded, granulated and discharged with the help of the power device 4 and the extrusion granulation device 6 set in the extrusion channel.

[0044] During the research process on the preparation of processed rice, the inventors discovered that the following problems generally exist when using existing equipment to prepare processed rice:

[0045] Firstly, during the process of rotating and mixing dough particles and maturing the dough, a large amount of water is generated. This water is difficult to drain from the device in a short time, resulting in a high water content in the matured dough, which is severely softened and makes subsequent extrusion and shaping operations more difficult.

[0046] Secondly, during the extrusion granulation process of dough particles, the pressure inside the cavity of the extrusion channel increases. If the moisture in the material has not turned into water vapor, the pressure will drop sharply to atmospheric pressure the instant the material is discharged from the extrusion granulation device. The moisture contained therein will quickly turn into superheated steam and cause the volume to expand rapidly, resulting in porous interior after the product cools down.

[0047] Therefore, in order to solve the above-mentioned problems that occur during the preparation of processed rice, the inventors have improved the original device by adding a component with dehumidification function and a component with vacuum drying function to the traditional extrusion granulation device. This is the most important improvement and innovation of the existing device in this invention.

[0048] The specific working principle of the device provided by this invention is as follows:

[0049] After the processed raw material powder is added to the granulation device through the feeding port 1, the raw material powder enters the pipe 201 of the material conveying and stirring device 2. Under the action of the stirring component 202, it is mixed evenly and matured. At the same time, the control device 301 of the dehumidifier 3 is turned on to remove the moisture that may be generated during the stirring and maturation process from the pipe 201, controlling the humidity to 25%-30%. It should be noted that since the humidity controller is a common structure used in this field, it will not be described in detail here, and the structure diagram of the humidity controller will not be drawn. After maturation, the dough particles enter the extrusion channel from the lower end of the material conveying and stirring device for extrusion granulation. When the power device 4 drives the extrusion plate 402 to move up and down in the extrusion channel through the extension and retraction of the telescopic rod 401, it extrudes the mixed material. The pressure will increase during extrusion. At this time, the valve 501 is opened to start the vacuum pump 5 to reduce pressure, and the pressure is controlled by the pressure gauge 502 to prevent excess moisture from turning into water vapor and affecting the shape and density of the rice grains. Finally, the extrusion granulation device 6 discharges the material.

[0050] Example 2

[0051] A method for preparing high-fiber sweet potato processed rice, using the apparatus described in Example 1, is as follows:

[0052] Stir-fry 108 parts rice flour, 81 parts wheat flour, and 51 parts oat flour in an iron pot at 55°C for 7 minutes. Microwave 35 parts high-fiber sweet potato flour in a microwave oven at 480 W for 3 minutes. Mix the processed raw materials with 6 parts defatted soybean protein and feed them into the feeding port 1. Add 2 parts salt and 22% water (35°C) of the total weight of the raw materials. Under the stirring action of the material conveying and stirring device 2, knead the mixture into uniform dough particles and cook it at 50°C for 34 minutes. At the same time, turn on the dehumidifier 3 to remove excess water. After cooking, extrude the product through the granulation device 6 using a twin-screw extruder with a screw speed of 75 rpm and a barrel end temperature of 109°C. Run a vacuum pump to reduce pressure during extrusion. After extrusion, bake the product at 46°C for 33 minutes to control the moisture content of the product to 18%, thus obtaining high-fiber sweet potato reprocessed rice.

[0053] In this embodiment, scanning electron microscope (SEM) images of the sweet potato flour particles before and after microwave puffing are attached. Figure 2 As shown, where Figure 2 a represents the particle structure of sweet potato starch without microwave puffing treatment. Figure 2 b shows the particle structure of sweet potato starch after microwave puffing.

[0054] As can be clearly seen from the figure, the sweet potato starch granules that have not undergone microwave puffing have a relatively intact structure and are not easily absorbing water; while the sweet potato starch granules that have undergone microwave puffing have a significantly damaged structure, forming a porous structure, which is conducive to improving the water absorption of the sweet potato starch.

[0055] Furthermore, the surface morphology of the high-fiber sweet potato processed rice prepared in this embodiment is shown in the attached figure. Figure 3 As shown in the figure, the processed rice grains are uniform in color and there are no grains that are coated.

[0056] Example 3

[0057] The preparation method of high-fiber sweet potato processed rice in this embodiment differs from that in Example 2 in that the rice flour, wheat flour, and oat flour are stir-fried in an iron pot for 5 minutes.

[0058] In addition, the high-fiber sweet potato flour was microwaved in a microwave oven at 480 W for 1 minute, and the rest of the operation and operating parameters were exactly the same as in Example 2, to obtain high-fiber sweet potato processed rice.

[0059] The results showed that the aroma of the high-fiber sweet potato processed rice prepared in this embodiment was weak, and some of the processed rice grains contained raw grains.

[0060] Example 4

[0061] The only difference between the preparation method of high-fiber sweet potato processed rice in this embodiment and that in Example 2 is that the amount of water added is 30% of the total weight of each mixed raw material, and the rest of the operation and operating parameters are exactly the same as in Example 2, so as to obtain high-fiber sweet potato processed rice.

[0062] Compared to the high-fiber sweet potato processed rice prepared in Example 2, the processed rice obtained in this example showed obvious adhesion of particles.

[0063] Comparative Example 1

[0064] Unlike Example 2, the raw material powder is not stir-fried in S1, but everything else is the same as in Example 2.

[0065] Comparative Example 2

[0066] Unlike Example 2, microwave puffing is not performed in S2, but everything else is the same as in Example 2.

[0067] Comparative Example 3

[0068] Unlike Example 2, the dough in S3 is not dehumidified after maturation; otherwise, it is the same as in Example 2.

[0069] The surface morphology of the high-fiber sweet potato processed rice prepared in this comparative example is shown in the attached figure. Figure 4 As shown in the figure, there is obvious raw grain encapsulation in the rice grains, and the color uniformity and appearance of the processed rice grains are poor, with obvious spots in the processed rice.

[0070] Comparative Example 4

[0071] Unlike Example 2, the apparatus in Example 1 was no longer used for preparation; instead, a conventional apparatus was used to prepare high-fiber sweet potato processed rice.

[0072] Experimental Example 1

[0073] The high-fiber sweet potato processed rice prepared in Examples 2-4 and Comparative Examples 1-4 was cooked, and the sensory evaluation of the cooked rice was carried out. The sensory evaluation criteria are shown in Table 1 below.

[0074] Table 1 Sensory Evaluation Criteria for Rice

[0075]

[0076] The sensory scores of the high-fiber sweet potato processed rice prepared in Examples 2-4 and Comparative Examples 1-4 are shown in Table 2 below.

[0077] Table 2 Sensory scores of high-fiber sweet potato processed rice prepared in different experimental groups

[0078] sample odor Appearance Palatability taste Cold rice texture Sensory scores Example 2 18.33±0.47 18.33±0.47 26.33±0.32 23.33±0.78 4.33±0.12 90.67±1.61a Example 3 16.01±0.81 16.33±0.52 23.67±0.47 20.33±0.47 3.67±0.14 80.00±1.73b Example 4 15.67±0.46 12.33±0.14 21.00±0.82 17.67±0.31 3.00±0.01 69.67±0.88cd Comparative Example 1 14.67±0.34 14.67±0.71 19.33±0.41 18.00±0.96 3.33±0.59 70.00±1.08cd Comparative Example 2 16.00±0.83 16.00±0.82 20.33±0.52 18.00±0.56 3.33±0.15 73.67±1.45bc Comparative Example 3 16.67±0.41 13.33±0.09 16.33±0.74 15.67±0.43 2.33±0.07 64.33±1.45d Comparative Example 4 16.67±0.53 14.00±0.82 19.00±0.23 17.00±0.16 3.00±0.01 69.67±1.68cd

[0079] The data above shows that the product obtained in Example 2 has the highest scores in terms of aroma and appearance. This is because the longer frying and microwave puffing times promote the Maillard reaction, giving the raw powder a rich aroma. The extended puffing time makes the internal structure of the sweet potato starch more complex, improves water retention, and avoids the phenomenon of raw particles being wrapped.

[0080] Experimental Example 2

[0081] The water solubility index (WSI) and water absorption index (WAI) of the high-fiber sweet potato processed rice prepared in Examples 2-4 and Comparative Examples 1-4 were determined, and the results are shown in Table 3 and Appendix. Figure 5 .

[0082] Table 3. Water solubility and water absorption of high-fiber sweet potato processed rice prepared in different experimental groups.

[0083] Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Water solubility index (%) 9.28 8.74 8.88 7.50 7.70 6.84 7.21 Water absorption index (%) 4.92 4.57 4.18 4.23 3.67 4.26 4.48

[0084] The results showed that the water absorption and water solubility of rice grains increased when microwave-expanded high-fiber sweet potato flour was added. In Example 2, the product exhibited the best water absorption and water solubility when microwave-expanded for 3 minutes.

Claims

1. A method for preparing high-fiber sweet potato processed rice, characterized in that, The steps include the following: S1. Mix rice flour, wheat flour, and oat flour and pour them into an iron pot. Stir-fry at 50-60℃ for 7-8 minutes to obtain mixed grain flour. S2, microwave puffing is used to puff high-fiber sweet potato flour to obtain puffed high-fiber sweet potato flour. The microwave power is 450-500 W and the microwave treatment time is 3-4 min. S3. Place the defatted soybean protein, the mixed grain powder stir-fried in S1, and the puffed high-fiber sweet potato powder in S2 into a mixer. Add water while mixing. The amount of water added should be 20-22% of the total weight of the raw material powder. The water temperature should be 50-60℃. After mixing evenly, add salt and continue mixing to form uniform dough particles. S4. The dough particles obtained in S3 are placed at 50-55℃ for 30-35 minutes to mature. During maturation, the dough is dehumidified and then granulated using a twin-screw extruder. During the extrusion granulation process, excess moisture in the particles is removed by vacuuming to obtain smooth granular rice grains. S5, the granular rice grains in S4 are dried to a moisture content of 17-19% and then subjected to ultraviolet disinfection treatment to obtain high-fiber sweet potato processed rice. The required weight proportions of each raw material in the process of preparing the above-mentioned high-fiber sweet potato processed rice are as follows: 100-120 parts rice flour, 80-85 parts wheat flour, 50-55 parts oat flour, 30-40 parts high-fiber sweet potato flour, 5-10 parts defatted soybean protein, and 2-3 parts salt.

2. The method for preparing high-fiber sweet potato processed rice as described in claim 1, characterized in that, In S3, the amount of salt added accounts for 0.5-1.2% of the total weight of the raw material powder.

3. The method for preparing high-fiber sweet potato processed rice as described in claim 1, characterized in that, In S4, the matured material is granulated using a twin-screw extruder. During the extrusion granulation process, excess moisture in the particles is removed by vacuuming. The screw speed is 75-80 rpm, and the temperature at the end of the barrel is 105-110℃.

4. The method for preparing high-fiber sweet potato processed rice as described in claim 1, characterized in that, In S5, the granular rice grains obtained in S4 are placed in an environment of 45-50℃ and dried for 25-35 minutes until the moisture content of the granular rice is 17-19%.

5. The method for preparing high-fiber sweet potato processed rice as described in claim 1, characterized in that, It is prepared using the following method: S1. Mix rice flour, wheat flour, and oat flour and pour them into an iron pot. Stir-fry at 50-60℃ for 7-8 minutes to obtain mixed grain flour. S2, microwave puffing is used to puff high-fiber sweet potato flour to obtain puffed high-fiber sweet potato flour. The microwave power is 450-500 W and the microwave treatment time is 3-4 min. S3. Place the defatted soybean protein, the mixed grain powder stir-fried in S1, and the puffed high-fiber sweet potato powder in S2 into a mixer. While mixing, add 20-22% of the total weight of the raw material powder and 50-60℃ warm water. After mixing evenly, add 0.5-1.2% of the total weight of the raw material powder and continue mixing to form uniform dough particles. S4. The dough particles obtained in S3 are placed at 50-55℃ for 30-35 minutes to mature. During maturation, the dough is dehumidified. The matured material is then granulated using a twin-screw extruder. During the extrusion granulation process, excess moisture in the particles is removed by vacuuming to obtain smooth granular rice particles. The screw speed is 75-80 rpm and the temperature at the end of the barrel is 105-110℃. S5. Place the granular rice grains from S4 into an environment of 45-50℃ and dry for 25-35 minutes until the moisture content of the rice grains is 17-19%. Then, perform ultraviolet disinfection treatment to obtain high-fiber sweet potato processed rice.

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