Preparation method of selenium-rich rice vermicelli

Abstract

The application provides a preparation method of selenium-rich rice vermicelli and belongs to the technical field of food processing. The preparation method comprises the steps of rice pretreatment, selenium-rich rice bran pretreatment, raw material mixing, grinding, steamed powder extrusion, cooling and shaping, drying and packaging, and parameters of each step are optimized to ensure that process stability and product quality are improved simultaneously. Through the composite pretreatment process, the synergistic effect is realized, the selenium content of the finished product is greater than or equal to 0.5 mg / kg, the GI value is less than or equal to 55, the selenium bioavailability is greater than or equal to 65%, the breakage rate is 0%, the cooking loss is less than or equal to 6.7%, the rehydration rate is about 125%, the color is white and uniform, and no visible impurities are observed; the total drying time is shorter than that of the prior art, the method is suitable for industrial grinding production system, and the nutritional health, food quality and production efficiency are considered.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, and in particular relates to a method for preparing selenium-enriched rice noodles. Background Technology

[0002] Traditional rice noodle production revolves around a core system of soaking, grinding, steaming, and extruding rice. This process ensures a smooth texture and good formability, making it popular with consumers. However, in the context of the food industry's transformation towards nutritional value and high-value products, traditional rice noodles suffer from several drawbacks: a single ingredient leads to an unbalanced nutritional structure, with low levels of dietary fiber and minerals, and a high glycemic index (GI), making them unsuitable for modern consumers' nutritional health and blood sugar control needs.

[0003] In recent years, the degree of intensive processing of rice processing by-products has been low. Among them, rice bran, as a by-product with a large output in the rice processing process, is rich in dietary fiber, protein, and can accumulate trace elements. However, at present, most rice bran is used as feed or directly discarded, resulting in low added value and causing serious resource waste and environmental pressure.

[0004] To achieve the resource utilization of rice bran and simultaneously improve the nutritional quality of rice noodles, the industry has attempted to directly prepare rice noodles from brown rice or to add selenium-enriched rice bran to rice raw materials to prepare composite rice noodles. However, all of these attempts face key technical bottlenecks: due to the special fiber structure of brown rice bran or selenium-enriched rice bran, their compatibility with rice raw materials is extremely poor. If untreated brown rice or selenium-enriched rice bran is directly mixed with rice for grinding and extrusion, problems such as uneven dispersion of rice slurry and equipment blockage during the extrusion process are very likely to occur. More importantly, the sensory quality of the finished rice noodles is severely degraded, specifically manifested in visible impurities on the surface, uneven color, high breakage rate and high rate of slurry exudation during cooking, rough texture and weak anti-aging ability, making it difficult to meet consumers' basic sensory experience requirements for rice noodles.

[0005] While some pretreatment methods for rice bran have been explored in existing technologies, such as enzymatic hydrolysis, high-temperature / high-pressure treatment, microwave treatment, and combined treatments, these technologies mostly focus on solving single problems and have not formed a pretreatment scheme suitable for the traditional rice flour grinding-steaming-extrusion system to prepare high-quality rice noodles. They cannot effectively solve the problem of blending brown rice / rice bran with rice, improve the sensory quality of the finished product, or simultaneously meet core needs such as improving the bioavailability of selenium (ensuring efficient absorption of nutrients by the human body) and optimizing the product's GI value. At the same time, existing related preparation technologies generally suffer from long drying processes, resulting in low production efficiency and high energy costs, which further restricts the industrial promotion of selenium-enriched high-fiber rice noodles and the high-value transformation of rice processing by-products.

[0006] Therefore, developing a selenium-enriched rice bran (or brown rice) pretreatment process adapted to the traditional rice noodle production system can not only solve the problem of sensory quality deterioration caused by poor raw material integration, but also simultaneously achieve high-value utilization of rice bran by-products, improve the nutritional and health attributes of rice noodles (strengthening dietary fiber, improving selenium bioavailability, and reducing GI value), while taking into account production efficiency and energy consumption control. This has become the key to solving the pain points of selenium-enriched high-fiber rice noodle production, promoting the upgrading of the rice noodle industry and the efficient utilization of rice processing resources, and has important industrial value and research significance. Summary of the Invention

[0007] The method for preparing selenium-enriched rice noodles proposed in this invention focuses on the pretreatment process of selenium-enriched rice bran raw material powder, which is compatible with the traditional rice noodle production system produced by grinding, extrusion and other processes. While effectively improving the dietary fiber and selenium content of rice noodles, it also improves the sensory and nutritional quality of rice noodles, and successfully prepares a selenium-enriched rice noodle product with good sensory quality, low GI and high selenium bioavailability.

[0008] This invention proposes a method for preparing selenium-enriched rice noodles, comprising the following steps:

[0009] S1. Rice pretreatment: Soak selenium-enriched early rice in water, then drain. The moisture content of the rice after soaking should be controlled at 30%-35%. S2. Selenium-enriched rice bran pretreatment: After microwave treatment of selenium-enriched rice bran, water is added and then subjected to high temperature and high pressure treatment, drying, crushing, and sieving. The sieved material is the selenium-enriched high-fiber rice bran powder obtained from the pretreatment. Among them, the power of microwave treatment is 500-700W; the temperature of high temperature and high pressure treatment is 110℃-130℃, the time is 100-140min, and the pressure is 0.1MPa; S3. Raw material mixing: Mix the pretreated rice obtained in S1 and the pretreated selenium-enriched high-fiber rice bran powder obtained in S2 to obtain rice bran-rice mixed raw material; S4. Grinding: Add water to the above rice bran-rice mixture, grind it into a paste, and then sieve it to obtain rice paste; wherein, the mass ratio of rice bran-rice mixture to water is 1:1.2-1:1.5. S5. Steaming and extruding rice flour: The rice flour paste is steamed and then extruded into strips to obtain wet rice flour strips. S6. Cooling and shaping: Cool the above wet rice noodles to a surface temperature of 25-30℃; S7. Drying: First, dry at 38-42℃ for 1-1.5 hours, then raise the temperature to 43-47℃ and dry for 2-2.5 hours, controlling the moisture content of the finished product to 11±1%; S8. Packaging: Vacuum pack the dried rice noodles to obtain the finished selenium-enriched rice noodles.

[0010] Furthermore, S1 satisfies at least one of the following conditions: (1) The water temperature for soaking should be 25-30℃; (2) Soaking time in water is 8-10 hours; (3) The selenium content of selenium-enriched early rice is ≥0.3mg / kg.

[0011] Furthermore, S2 satisfies at least one of the following conditions: (1) The power of microwave processing is 500-700W; (2) The microwave treatment is specifically intermittent microwave treatment; preferably, the intermittent microwave treatment is a 10-second interval after every 20 seconds of radiation, with a total microwave working time of 2 minutes. (3) The water is added at a material-to-liquid ratio of 1:10-20 (g / mL); (4) The temperature for high temperature and high pressure treatment is 110℃-130℃.

[0012] Furthermore, S2 satisfies at least one of the following conditions: (1) The drying temperature is 40-65℃; the air velocity in the drying oven is controlled at 1.0-1.4m / s; (2) During crushing, the material temperature should be ≤40℃; (3) Crushing specifically involves crushing the rice bran to 200±10 mesh; (4) The grinding time is 3-5 minutes.

[0013] Furthermore, in S3, the mass ratio of the pretreated rice obtained in S1 to the pretreated selenium-enriched high-fiber rice bran powder obtained in S2 is (95-100):(2-5).

[0014] Furthermore, S4 satisfies at least one of the following conditions: During grinding, the mass ratio of rice bran-rice mixture to water is 1:1.2-1:1.5; After grinding, the sieve mesh size is 70-90 mesh.

[0015] Furthermore, S5 satisfies at least one of the following conditions: (1) The steaming temperature is 98-100℃; (2) The steaming time for rice paste is 3-5 minutes.

[0016] Furthermore, in S6, the cooling specifically refers to 15-20°C cold air cooling for 5-8 minutes.

[0017] Furthermore, in S7, the drying wind speed can be 1.2-1.8 m / s.

[0018] This invention has the following advantages: The present invention proposes a method for preparing selenium-enriched rice noodles, including rice pretreatment, selenium-enriched rice bran pretreatment, raw material mixing, grinding, steaming and extrusion, cooling and shaping, drying, and packaging. The parameters for each step have been systematically optimized, including the rice pretreatment, selenium-enriched rice bran pretreatment and their mixing ratio, grinding conditions, steaming conditions, and segmented drying conditions, to ensure that the resulting rice noodles have a high selenium content, low glycemic index (GI), high dietary fiber content, and excellent sensory quality. The rice bran pretreatment process employs a microwave + high-temperature and high-pressure composite process, which improves the selenium dissolution rate and dietary fiber retention rate, avoiding the performance limitations of single methods. Simultaneously, it disrupts the biomolecular structure of the rice bran, releasing bound selenium and significantly improving selenium bioavailability. The increased proportion of soluble dietary fiber in the pretreated rice bran slows down the digestion and absorption of starch in the rice noodles, giving the product a low GI characteristic. Pre-treated selenium-enriched rice bran is processed using various techniques, such as grinding and extrusion, to effectively increase the dietary fiber and selenium content of the rice noodles while improving their sensory and nutritional quality. The resulting rice noodles have a selenium content ≥0.5mg / kg, a breakage rate of 0%, a cooking loss of only 6.69%, balanced texture and color, and a sensory score ≥8.6. They remain translucent even after 12 hours of cooking and have a shelf life of ≥6 months at room temperature with a sealed container. Furthermore, their glycemic index (GI) is as low as 44, meeting the dietary needs of a wider range of people and addressing the issue of high GI values ​​in traditional selenium-enriched rice noodles. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A comparison of photos of the product obtained in Example 1 before and after cooking; Figure 2 A comparison of photos of the product obtained in Comparative Example 1 before and after cooking; Figure 3 Comparative Example 2: Photo comparison of the product before and after cooking; Figure 4 Comparative Example 3: Photo comparison of the product before and after cooking; Figure 5 Comparative Example 4: Photo comparison of the product before and after cooking; Figure 6 Comparative Example 5: Photo comparison of the product before and after cooking; Figure 7 Comparative Example 6: Photo comparison of the product before and after cooking; Figure 8 Comparative Example 7: Photo comparison of the product before and after cooking; Figure 9 Comparative Example 8: Photos showing the product before and after cooking; Figure 10 Comparative Example 9: Photo comparison of the product before and after cooking; Figure 11 A comparison of photos of the product obtained in Comparative Example 10 before and after cooking; Figure 12 A comparison of photos of the product obtained in Comparative Example 11 before and after cooking; Figure 13 Comparative Example 12: Photo comparison of the product before and after cooking; Figure 14 A comparison of photos of the product obtained in Comparative Example 13 before and after cooking; Figure 15 The bar chart shows the comparison of the gastrointestinal bioavailability of selenium in rice flour between the examples and comparative examples. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0022] The present invention will now be described in detail with reference to the embodiments.

[0023] To overcome the shortcomings of existing technologies, such as the limited performance of rice bran pretreatment products, nutrient loss in rice noodles due to unreasonable processing methods, long drying time, low selenium bioavailability, high GI value, and poor sensory experience, this invention provides a method for preparing selenium-enriched high-fiber rice noodles. Through comparative screening of multiple processing methods, the dual optimization of selenium-enriched high-fiber characteristics and processing quality is achieved.

[0024] This invention provides a method for preparing selenium-enriched rice noodles, comprising the following steps: S1. Rice pretreatment: Soak selenium-enriched early rice in water, then drain. The moisture content of the rice after soaking should be controlled at 30%-35%. S2. Selenium-enriched rice bran pretreatment: After microwave treatment of selenium-enriched rice bran, water is added and then subjected to high temperature and high pressure treatment, drying, crushing, and sieving. The sieved material is the selenium-enriched high-fiber rice bran powder obtained from the pretreatment. Among them, the power of microwave treatment is 500-700W; the temperature of high temperature and high pressure treatment is 110℃-130℃, the time is 100-140min, and the pressure is 0.1MPa; S3. Raw material mixing: Mix the pretreated rice obtained in S1 and the pretreated selenium-enriched high-fiber rice bran powder obtained in S2 to obtain rice bran-rice mixed raw material; S4. Grinding: Add water to the above rice bran-rice mixture, grind it into a paste, and then sieve it to obtain rice paste; wherein, the mass ratio of rice bran-rice mixture to water is 1:1.2-1:1.5. S5. Steaming and extruding rice flour: The rice flour paste is steamed and then extruded into strips to obtain wet rice flour strips. S6. Cooling and shaping: Cool the above wet rice noodles to a surface temperature of 25-30℃; S7. Drying: First, dry at 38-42℃ for 1-1.5 hours, then raise the temperature to 43-47℃ and dry for 2-2.5 hours, controlling the moisture content of the finished product to 11±2%; S8. Packaging: Vacuum pack the dried rice noodles to obtain the finished selenium-enriched rice noodles.

[0025] The method for preparing selenium-enriched rice noodles proposed in this invention includes steps such as rice pretreatment, selenium-enriched rice bran pretreatment, raw material mixing, grinding, steaming and extrusion, cooling and shaping, drying, and packaging. The parameters for each step have been systematically optimized, including the rice pretreatment, selenium-enriched rice bran pretreatment and their mixing ratio, grinding conditions, steaming conditions, and segmented drying conditions, to ensure that the resulting rice noodles have a high selenium content, low glycemic index (GI), high dietary fiber content, and excellent sensory quality. The rice bran pretreatment process employs a microwave + high-temperature and high-pressure composite process, which improves the selenium dissolution rate and dietary fiber retention rate, avoiding the performance limitations of single methods. Simultaneously, it disrupts the biomolecular structure of the rice bran, releasing bound selenium and significantly improving selenium bioavailability. The increased proportion of soluble dietary fiber in the pretreated rice bran can delay the digestion and absorption of starch in the rice noodles, giving the product a low GI characteristic. Pre-treated selenium-enriched rice bran is processed using various techniques, such as grinding and extrusion, to effectively increase the dietary fiber and selenium content of the rice noodles while improving their sensory and nutritional quality. The resulting rice noodles have a selenium content ≥0.5mg / kg, a breakage rate of 0%, a cooking loss of only 6.69%, balanced texture and color, and a sensory score ≥8.6. They remain translucent even after 12 hours of cooking and have a shelf life of ≥6 months at room temperature with a sealed container. Furthermore, their glycemic index (GI) is as low as 44, meeting the dietary needs of a wider range of people and addressing the issue of high GI values ​​in traditional selenium-enriched rice noodles.

[0026] In one embodiment of the present invention, in S1, the water temperature for soaking is 25-30°C.

[0027] In one embodiment of the present invention, in step S1, the soaking time with water is 8-10 hours. Specifically, it can be 8 hours, 9 hours, or 10 hours. After soaking for 1 hour, the rice begins to absorb water rapidly. After 8 hours, the moisture content tends to stabilize at 30%-35%, at which point the rice has suitable hardness, facilitating subsequent grinding. If the soaking time is insufficient, the rice has a low moisture content, which easily produces coarse residue during grinding, affecting the fineness of the rice paste. If the soaking time is too long, the rice structure is damaged, starch easily dissolves, leading to abnormal viscosity of the rice paste. Therefore, 8-10 hours is chosen.

[0028] In one embodiment of the present invention, in S1, the moisture content of the soaked rice needs to be controlled at 30%-35%, with the standard being that there is no hard core when squeezed by hand. This moisture content can ensure that the rice slurry has good fluidity during grinding, and that the starch and the subsequently added rice bran fiber can be fully combined.

[0029] In one embodiment of the present invention, in step S1, the selenium content of the selenium-enriched early rice is ≥0.3 mg / kg. The selenium-enriched early rice is rice processed from selenium-enriched early paddy rice.

[0030] In the S2 selenium-enriched rice bran pretreatment process of this invention, the "microwave + high temperature and high pressure" composite process has the best comprehensive performance, high selenium content and good sensory characteristics of the final product. Other existing methods (single enzymatic hydrolysis, single microwave, single high temperature and high pressure, single low temperature plasma or other combinations) all have single performance shortcomings and cannot meet multiple technical requirements.

[0031] In one embodiment of the present invention, in step S2, the power of the microwave treatment is 500-700W, preferably 600W. In this embodiment, if the power is too low, the rice bran fiber structure is not sufficiently damaged, resulting in a low selenium leaching rate. If the power is too high, the rice bran undergoes localized overheating and carbonization, leading to an excessively high selenium loss rate.

[0032] In one embodiment of the present invention, in S2, the microwave treatment is specifically intermittent microwave treatment. The intermittent microwave treatment specifically involves a 20-second radiation followed by a 10-second pause, with a cumulative microwave working time of 2 minutes. In this embodiment of the present invention, this heating method can avoid excessively high local temperatures and ensure uniform processing of the rice bran.

[0033] In one embodiment of the present invention, in step S2, the water is added at a material-to-liquid ratio of 1:10-20 (g / mL). Preferably, it is 1:15 (g / mL), that is, a material-to-liquid ratio of 1g / 15mL. In this embodiment of the present invention, when the material-to-liquid ratio is lower than 1:10, the rice bran cannot be fully soaked during high-temperature and high-pressure treatment, and the lipase is not completely deactivated. When the material-to-liquid ratio is higher than 1:20, the energy consumption for subsequent drying increases, and the nutrients in the rice bran are easily dissolved and lost.

[0034] In one embodiment of the present invention, in step S2, the high-temperature and high-pressure treatment is carried out at a temperature of 110℃-130℃ for a time of 100-140 minutes. Preferably, in step S2, the high-temperature and high-pressure treatment is carried out at 121℃ and 0.1MPa for 2 hours. In this embodiment of the present invention, if the temperature is too low or the time is too short, the product has a low rate of insoluble dietary fiber breakage; if the temperature is too high or the time is too long, the selenium content loss is high.

[0035] In one embodiment of the present invention, in step S2, the drying temperature is 40-65°C, preferably 60°C. More preferably, the drying specifically involves placing the rice bran in a 60°C oven and drying it until the moisture content is 13±0.5%. In this embodiment of the present invention, if the moisture content is too high, the rice bran is prone to clumping, making subsequent pulverization difficult; if the moisture content is too low, the fibers become brittle, resulting in uneven particle size of the rice bran after pulverization.

[0036] In one embodiment of the present invention, in S2, the air velocity of the drying oven is controlled to be 1.0-1.4 m / s.

[0037] In one embodiment of the present invention, in S2, pulverizing specifically involves pulverizing rice bran to 200±10 mesh.

[0038] In one embodiment of the present invention, in step S2, the pulverizing time is 3-5 minutes. The pulverizing speed is 13500 r / min.

[0039] In one embodiment of the present invention, in step S2, the material temperature is ≤40℃ during pulverization, preferably 35℃. A pulverizer is used for pulverization. Due to the temperature rise during pulverization, the selenium content in the rice bran is reduced.

[0040] In one embodiment of the present invention, in step S2, a 200-mesh sieve is used for sieving.

[0041] In one embodiment of the present invention, in step S3, the mass ratio of the pretreated rice obtained in step S1 to the pretreated selenium-enriched high-fiber rice bran powder obtained in step S2 is (95-100):(2-5). In this embodiment of the present invention, if the proportion of rice bran powder is too low, the dietary fiber content of the product will be low; if the proportion is too high, excessive rice bran fiber will cause poor subsequent rice slurry formation and easy breakage.

[0042] In one embodiment of the present invention, during step S4, the mass ratio of the rice bran-rice mixture to water is 1:1.2-1:1.5. In this embodiment, if the mass ratio is too low, the rice slurry concentration is too high, resulting in poor fluidity and difficulty in grinding; if the mass ratio is too high, the rice slurry concentration is too low, requiring extended steaming time and increasing energy consumption.

[0043] In one embodiment of the present invention, in step S4, an electric stone mill is used for grinding.

[0044] In one embodiment of the present invention, in step S4, the sieve after grinding is 70-90 mesh. Passing the slurry through a 70-90 mesh sieve after grinding removes residue; removing coarse residue ensures uniform fineness of the rice slurry and prevents clogging of the mold during subsequent extrusion.

[0045] In one embodiment of the present invention, in step S5, the rice paste is steamed in a rice steamer. The steaming temperature is 98-100℃.

[0046] In one embodiment of the present invention, in step S5, the steaming time of the rice paste is 3-5 minutes.

[0047] In one embodiment of the present invention, in S6, the cooling is specifically 15-20°C cold air cooling for 5-8 minutes.

[0048] In one embodiment of the present invention, in step S7, a segmented drying method is adopted: first, drying at 38-42℃ for 1-1.5 hours, and then raising the temperature to 43-47℃ for 2-2.5 hours. In this embodiment of the present invention, segmented drying can prevent the surface of the rice noodles from drying too quickly, resulting in residual internal moisture and affecting the shelf life; the moisture content of the finished product after drying needs to be controlled at 11±2%. If the moisture content is too low, the rice noodles will be too hard and easy to break; if the moisture content is too high, they will easily mold and deteriorate when stored at room temperature.

[0049] In one embodiment of the present invention, in S7, the drying wind speed can be 1.2-1.8 m / s, specifically 1.5 m / s.

[0050] In one embodiment of the present invention, in step S8, the dried rice noodles are cut into sections and then packaged.

[0051] The rice noodles obtained by this invention have a selenium content ≥0.5mg / kg (there are very few rice noodles with a selenium content exceeding 0.5mg / kg in the prior art), a significant dietary fiber content, and low GI characteristics, making them suitable for a wider range of people to consume; the selenium bioavailability is high, showing a significant improvement compared to rice noodles prepared from untreated rice bran.

[0052] The present invention will now be described in detail with reference to the embodiments.

[0053] Example 1 A method for preparing selenium-enriched rice noodles, comprising: (1) Rice pretreatment: Take 100 kg of selenium-enriched early rice and soak it in drinking water at 28℃ for 9 hours. After soaking, the water content of the rice is 32%. Drain the rice. (2) Pretreatment of selenium-enriched rice bran: Take 3.1 kg of selenium-enriched rice bran (selenium content 8 mg / kg, dietary fiber 32%), put it into a sieve bottle, and microwave intermittently at 600W (20s radiation, 10s interval, cumulative 2 min); add drinking water at a material-to-liquid ratio of 1:15 (g / mL), and treat at 121℃ and 0.1MPa for 2 h; dry in a 60℃ oven (wind speed 1.1 m / s) until the moisture content is 13.2%; grind at 13500 r / min for 4 min (material temperature 35℃), and sieve through a 200 mesh vibrating screen (35 Hz) (passing rate 85%) to obtain 2.8 kg of pretreated rice bran powder; (3) Raw material mixing: 100kg of pretreated rice and 2.8kg of rice bran powder are mixed evenly; (4) Grinding: Add 123.36 kg of drinking water (1:1.2), grind with an electric stone mill (0.08 mm gap), remove residue with an 80 mesh sieve, and obtain 198 kg of rice slurry; (5) Steaming and extrusion: Steam at 98℃ for 4 minutes using a continuous steamer (1.0m / min) and then extrude into strips; (6) Cooling and shaping: Cool with 18℃ cold air for 7 minutes until the surface temperature reaches 28℃; (7) Drying: Dry at 40℃ for 1.2h, then at 45℃ for 2.3h, the moisture content of the finished product is 11.2%; (8) Packaging: Cut into 20cm sections and vacuum pack to obtain finished rice noodles.

[0054] See product details Figure 1 .

[0055] It needs to be explained that, Figures 1-14 The image shows the rice strips before cooking on the left and after cooking on the right.

[0056] Example 2 Similar to Example 1, except that in step (2), 500W microwave intermittent processing is used.

[0057] Example 3 Similar to Example 1, except that in step (7), the product is dried at 38°C for 1 hour and at 44°C for 2 hours, and the moisture content of the finished product is 12.1%.

[0058] Test case Performance testing was performed on the selenium-enriched rice noodles obtained in Example 1. Nutritional indicators were assessed using atomic fluorescence spectrometry (AFS) to determine selenium content; bioavailability was assessed using a gastrointestinal simulated digestion method (results are shown in [link to results]). Figure 15The GI value was determined using an in vitro simulated digestion method, all of which are routine detection methods in this field. The results showed that the nutritional indicators were: selenium content 0.64 mg / kg, good selenium bioavailability, and a GI value of 44.

[0059] Quality indicators were determined using the physicochemical testing method for grain products, including breakage rate, cooking loss, and rehydration rate. Elasticity, hardness, chewiness, and resilience were tested using a texture analyzer. Colorimetry was measured using a colorimeter. The results are shown in Tables 1 and 2. Quality indicators: breakage rate 0%, cooking loss 6.69%, rehydration rate 125.38%, texture (hardness 1359.53g±147.71g, elasticity 0.908±0.034), colorimetry (L*=59.23, a*=-0.76, b*=2.47). Process adaptability: The pulping process is unobstructed, the extrusion is uniform, the drying process is free of cracks, and the shelf life at room temperature is 6 months.

[0060] Comparative Example 1 A single enzymatic hydrolysis pretreatment process was adopted. Same as Example 1, except for step (2), which is as follows: Take 3.1 kg of selenium-enriched rice bran of the same specifications as in Example 1, add 0.8% cellulase solution (pH adjusted to 4.5), and enzymatically hydrolyze in a constant temperature water bath at 50℃ for 2 hours. After enzymatic hydrolysis, the rice bran powder is obtained by inactivating the enzyme, drying, crushing and sieving. Rice noodles are then prepared according to the steps in Example 1.

[0061] During the process, it was found that when the enzymatically hydrolyzed rice bran powder was mixed with rice and ground into a slurry, a small amount of flocculent precipitate was present, and the grinding efficiency was slightly lower than that in Example 1. The finished product test results (using the same method as the test example) showed a selenium content of 0.44 mg / kg, a GI value of 63, a breakage rate of 5.88% after boiling in water, and a rehydration rate of 89.30%. The texture was rough after rehydration, mainly because the single enzymatic hydrolysis did not completely destroy the rice bran fiber structure, resulting in poor solubility of dietary fiber and insufficient release of selenium. This failed to balance nutrition, low GI characteristics, and sensory quality.

[0062] See product details Figure 2 .

[0063] Comparative Example 2 Employing a single high-temperature and high-pressure pretreatment process Same as Example 1, except for step (2), which is as follows: Take 3.1 kg of selenium-enriched rice bran of the same specifications as in Example 1, add drinking water at a material-to-liquid ratio of 1:15, and directly transfer it into a high-temperature and high-pressure reactor for treatment at 121°C for 2 hours without microwave pretreatment step, and obtain pretreated rice bran powder.

[0064] During the process, it was found that the rice bran slurry was prone to stratification during pretreatment, requiring an additional stirring step.

[0065] The finished product test results (using the same method as the test example) showed a selenium content of 0.48 mg / kg, a GI value of 66, a breakage rate of 5.88%, and a rehydration rate of 151.74%. After rehydration, the rice noodles became soft and mushy with poor elasticity. This was because the lack of microwave pretreatment to pre-destroy the rice bran fibers and the uneven degradation of the rice bran fibers after high-temperature and high-pressure treatment resulted in insufficient structural stability of the rice noodles, significantly reducing their low-GI characteristics and taste.

[0066] See product details Figure 3 .

[0067] Comparative Example 3 Using a single microwave pretreatment process Same as Example 1, except for step (2), which is as follows: Take 3.1 kg of selenium-enriched rice bran of the same specifications as in Example 1, treat it with the same microwave parameters as in Example 1 (600W, intermittent treatment for a total of 2 min), and then directly dry, crush, and sieve it. There is no high temperature and high pressure treatment step. The subsequent preparation process is the same as in Example 1.

[0068] During the process, it was found that the rice slurry had slightly poor fluidity during grinding, and some of the die holes were slightly blocked during extrusion.

[0069] The finished product test results (using the same method as the test example) showed a selenium content of 0.45 mg / kg, a GI value of 68, a breakage rate of 10.0%, and a rehydration rate of 126.17%. After rehydration, there were a few broken pieces, and the texture was rather hard. This was mainly because microwave treatment alone could not completely destroy the dense structure of rice bran fibers and could not effectively deactivate harmful enzymes such as lipases in rice bran. As a result, the product's nutrient retention rate, low GI characteristics, and molding quality were all inferior to those of the combined process.

[0070] See product details Figure 4 .

[0071] Comparative Example 4 Enzymatic hydrolysis + microwave + high temperature and high pressure pretreatment process is adopted. Same as Example 1, except for step (2), which is as follows: Take 3.1 kg of selenium-enriched rice bran of the same specifications as in Example 1, add 0.8% cellulase solution (pH adjusted to 4.5), and enzymatically hydrolyze in a 50℃ constant temperature water bath for 2 h. After enzymatic hydrolysis, treat with the same microwave parameters as in Example 1 (800W, intermittent treatment for a cumulative 2 min), add drinking water at a material-to-liquid ratio of 1:15, transfer to a high temperature and high pressure reactor, treat at 121℃ and 0.1MPa for 2 h, dry, pulverize, and sieve to obtain pretreated rice bran powder. The subsequent preparation process is the same as in Example 1.

[0072] During the process, it was found that the rice slurry was too fluid after enzymatic hydrolysis, which easily resulted in uneven thickness of rice noodles when extruding them. After high temperature and high pressure treatment, some rice bran powder showed slight clumping and needed to be crushed and sieved a second time.

[0073] The finished product test results (using the same method as the test example) showed a selenium content of 0.48 mg / kg, a GI value of 58, a breakage rate of 2.35%, a cooking loss of 7.56%, and a rehydration rate of 118.62%. After rehydration, the texture was slightly glutinous but lacked elasticity. This was mainly due to excessive compounding, which led to excessive gelatinization of the rice bran starch. Although this process could completely destroy the dense fiber structure and deactivate harmful enzymes, the excessive gelatinization of starch reduced the elasticity of the rice flour. At the same time, the enzymatic hydrolysis process caused a small amount of selenium to be lost. Overall, the quality was slightly inferior to the optimized combination process in Example 1.

[0074] See product details Figure 5 .

[0075] Comparative Example 5 Enzymatic hydrolysis + high temperature and high pressure pretreatment process is adopted Same as Example 1, except for step (2), which is as follows: Take 3.1 kg of selenium-enriched rice bran of the same specifications as in Example 1, add 0.8% cellulase solution (pH adjusted to 4.5), and enzymatically hydrolyze in a 50℃ constant temperature water bath for 2 hours. After enzymatic hydrolysis, no microwave treatment is required. Add drinking water directly at a material-to-liquid ratio of 1:15, transfer to a high temperature and high pressure reactor, treat at 121℃ and 0.1 MPa for 2 hours, dry, pulverize, and sieve to obtain pretreated rice bran powder. The subsequent preparation process is the same as in Example 1.

[0076] During the process, it was found that there were a small number of coarse particles in the rice paste during grinding. The rice noodles were easy to extrude but tended to stick together after being formed. After drying, some of the rice noodles cracked.

[0077] The finished product test results (using the same method as the test example) showed a selenium content of 0.42 mg / kg, a GI value of 62, a breakage rate of 4.72%, a cooking loss of 8.35%, and a rehydration rate of 132.45%. After rehydration, some rice noodles were soft and easily broken, mainly due to the lack of microwave pretreatment, uneven damage to rice bran fibers, and excessively rapid starch retrogradation after high-temperature and high-pressure treatment, resulting in poor rice noodle formability and water retention. At the same time, the inactivation of harmful enzymes was not thorough enough, and the GI value was slightly higher. The nutritional and taste quality were not as good as in Example 1.

[0078] See product details Figure 6 .

[0079] Comparative Example 6 Low-temperature plasma pretreatment process Same as Example 1, except for step (2), which is as follows: Take 3.1 kg of selenium-enriched rice bran of the same specifications as in Example 1. Without enzymatic hydrolysis, microwave and high temperature and high pressure reactor treatment, directly spread the selenium-enriched rice bran in a low temperature plasma treatment instrument, adjust the treatment power to 300W, the treatment time to 15min, and the discharge gap to 5mm, use air as the discharge gas, and perform plasma pretreatment at room temperature and pressure. After pretreatment, dry, crush and sieve to obtain pretreated rice bran powder. The subsequent preparation process is the same as in Example 1.

[0080] See product details Figure 7 .

[0081] During the process, it was found that the rice paste had poor fluidity during grinding, and the mold holes were significantly clogged during extrusion, requiring frequent mold cleaning. This made it difficult to form rice noodles, which were also prone to breakage.

[0082] The finished product test results (using the same method as the test example) showed a selenium content of 0.37 mg / kg, a GI value of 75, a breakage rate of 8.95%, a cooking loss of 7.88%, and a rehydration rate of 105.73%. After rehydration, the rice noodles were relatively hard and not fully rehydrated, with a noticeable hard core. This was mainly because the low-temperature plasma process alone could not completely destroy the dense structure of the rice bran fiber, thus failing to effectively release bound selenium and deactivate harmful enzymes in the rice bran. This resulted in a low selenium retention rate, a high GI value, and poor forming quality and rehydration, which was far inferior to the combined process in Example 1.

[0083] The test results obtained in Example 1 and Comparative Examples 1-6 are listed in Tables 1 and 2.

[0084] Table 1. Comparison of textures among treatment groups (TA-XT2i texture analyzer) Processing group Hardness (g) elasticity Chewable (g) responsive Example 1 (Microwave + High Temperature and High Pressure) 1359.531±147.708 0.908±0.034 1012.012±116.594 0.886±0.047 Comparative Example 1 (Single Enzyme Digestion) 1344.149±30.783 1.008±0.033 1283.531±79.621 0.857±0.017 Comparative Example 2 (Single High Temperature and High Pressure) 3199.385±412.821 0.909±0.036 2535.120±120.283 0.878±0.070 Comparative Example 3 (Single Microwave) 2914.848±252.421 0.869±0.010 2186.637±175.917 0.871±0.010 Comparative Example 4 (Enzymatic hydrolysis + Microwave + High Temperature and High Pressure) 1528.642±126.357 0.885±0.029 1186.325±98.472 0.862±0.035 Comparative Example 5 (Enzymatic hydrolysis + High temperature and high pressure) 2654.371±308.624 0.876±0.032 1987.542±132.685 0.859±0.041 Comparative Example 6 (Low-Temperature Plasma) 2896.453±287.519 0.858±0.02 2054.871±156.328 0.847±0.038 Table 2 Comparison of cooking quality among different treatment groups (GB / T 23587-2009) Processing group Broken strip rate (%) Cooking loss (%) Rehydration rate (%) GI value Example 1 (Microwave + High Temperature and High Pressure) 0 6.69 125.38 44 Comparative Example 1 (Single Enzyme Digestion) 5.88 8.88 89.30 63 Comparative Example 2 (Single High Temperature and High Pressure) 5.88 9.14 151.74 66 Comparative Example 3 (Single Microwave) 10 7.12 126.17 68 Comparative Example 4 (Enzymatic hydrolysis + Microwave + High Temperature and High Pressure) 2.35 7.56 118.62 58 Comparative Example 5 (Enzymatic hydrolysis + High temperature and high pressure) 4.72 8.35 132.45 62 Comparative Example 6 (Low-Temperature Plasma) 8.95 7.88 105.73 75 Comparative Example 7 Same as Example 1, except that in step (2), the microwave pretreatment power of rice bran is adjusted to 400W.

[0085] The finished product has a selenium content of 0.49 mg / kg, a GI value of 59, a breakage rate of 2.8%, and a rehydration rate of 121.5%. Although it meets the basic usage requirements, the selenium dissolution rate and dietary fiber solubility are lower than those of Example 1. The low GI characteristics and molding stability are slightly worse, indicating that parameters below the optimal value within the range cannot achieve optimal performance.

[0086] See product details Figure 8 .

[0087] Comparative Example 8 Same as Example 1, except that in step (2), the microwave pretreatment power of rice bran is adjusted to 900W.

[0088] After microwave treatment, the rice bran showed obvious scorch marks and a slight carbonized odor.

[0089] The finished product tested showed a selenium content of 0.43 mg / kg, a GI value of 64, a breakage rate of 4.2%, and a rehydration rate of 118.3%. The scorch marks caused the finished product to turn yellow, and the loss of selenium due to local high temperature increased. The low GI characteristics and sensory quality were significantly deteriorated, proving that exceeding the upper limit of the parameter range would lead to process failure.

[0090] See product details Figure 9 .

[0091] Comparative Example 9 Same as Example 1, except that in step (2), the high temperature and high pressure treatment temperature is adjusted to 140℃, the pressure is 0.260MPa, and the treatment time is 2h.

[0092] The processed rice bran slurry was slightly yellow in color. The finished product had a selenium content of 0.49 mg / kg, a GI value of 60, a breakage rate of 10.5%, and a rehydration rate of 122.8%. A small amount of selenium was lost due to decomposition at high temperature. Excessive modification of dietary fiber resulted in a slight decrease in the elasticity of the rice noodles. The low GI characteristics and taste were not as good as the optimal temperature parameters in Example 1.

[0093] See product details Figure 10 .

[0094] Comparative Example 10 Same as Example 1, except that in step (2), the high temperature and high pressure treatment temperature is adjusted to 95°C.

[0095] The pretreatment of rice bran did not sufficiently destroy the fiber structure. The finished product was tested and found to have a selenium content of 0.44 mg / kg, a GI value of 65, a breakage rate of 5.3%, and a rehydration rate of 119.6%. The low GI characteristics were lost, proving that parameters below the lower limit of the range would lead to a double deterioration in nutrition and quality.

[0096] See product details Figure 11 .

[0097] Comparative Example 11 Single-temperature drying process Same as Example 1, except that in step (7), the drying is carried out continuously at 50°C for 4.0 h.

[0098] During the drying process, the surface of the rice noodles dries out first, and the internal moisture is difficult to dissipate, resulting in a "dry outside and wet inside" phenomenon. The finished product was tested and found to have a selenium content of 0.57 mg / kg, a GI value of 62, a breakage rate of 4.8%, and a rehydration rate of 120.3%. After rehydration, the inside has a hard core, resulting in a poor taste. At the same time, the increased starch retrogradation rate leads to an increase in the GI value.

[0099] See product details Figure 12 .

[0100] Comparative Example 12 Segmented drying process Similar to Example 1, except that in step (7), the drying temperature in the first stage is adjusted to 34°C and the drying time is 2.2h; the drying temperature in the second stage is adjusted to 38°C and the drying time is 3.3h, with a total drying time of 5.5h. The rest of the process is the same as in Example 1.

[0101] The drying efficiency was relatively low. The finished product had a selenium content of 0.56 mg / kg, a GI value of 61, a breakage rate of 5.2%, and a rehydration rate of 119.7%.

[0102] See product details Figure 13 .

[0103] Comparative Example 13 Segmented drying process Similar to Example 1, the difference is that in step (7), the drying temperature in the first stage is adjusted to 46°C and the drying time is 0.8h; the drying temperature in the second stage is adjusted to 53°C and the drying time is 2.0h, with a total drying time of 2.8h.

[0104] The rice noodles were dried too quickly, resulting in obvious cracking and deformation. The finished product had a selenium content of 0.54 mg / kg, a GI value of 63, a breakage rate of 3.8%, and a rehydration rate of 118.5%. After rehydration, the cracked parts were prone to breakage, resulting in poor sensory quality. Furthermore, the high temperature caused abnormal starch gelatinization.

[0105] See product details Figure 14 .

[0106] As can be seen from Comparative Examples 11-13, the main difference between them and Example 1 lies in the different drying methods. Although the selenium content of the obtained products is not low, due to the different drying conditions, the water migration rate of the rice noodles and the interaction between starch and protein during the migration process and the structure of the composite product are changed to varying degrees (unable to form a uniform and dense network structure), resulting in poor rehydration effect and increased GI value.

[0107] The above are merely 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 within the protection scope of the present invention.

Claims

1. A method for preparing selenium-enriched rice noodles, characterized in that, Includes the following steps: S1. Rice pretreatment: Soak selenium-enriched early rice in water, then drain. The moisture content of the rice after soaking should be controlled at 30%-35%. S2. Selenium-enriched rice bran pretreatment: After microwave treatment of selenium-enriched rice bran, water is added and then subjected to high temperature and high pressure treatment, drying, crushing, and sieving. The sieved material is the selenium-enriched high-fiber rice bran powder obtained from the pretreatment. Among them, the power of microwave treatment is 500-700W; the temperature of high temperature and high pressure treatment is 110℃-130℃, the time is 100-140min, and the pressure is 0.1MPa; S3. Raw material mixing: Mix the pretreated rice obtained in S1 and the pretreated selenium-enriched high-fiber rice bran powder obtained in S2 to obtain rice bran-rice mixed raw material; S4. Grinding: Add water to the above rice bran-rice mixture, grind it into a paste, and then sieve it to obtain rice paste; wherein, the mass ratio of rice bran-rice mixture to water is 1:1.2-1:1.

5. S5. Steaming and extruding rice flour: The rice flour paste is steamed and then extruded into strips to obtain wet rice flour strips. S6. Cooling and shaping: Cool the above wet rice noodles to a surface temperature of 25-30℃; S7. Drying: First, dry at 38-42℃ for 1-1.5 hours, then raise the temperature to 43-47℃ and dry for 2-2.5 hours, controlling the moisture content of the finished product to 11±1%; S8. Packaging: Vacuum pack the dried rice noodles to obtain the finished selenium-enriched rice noodles.

2. The preparation method according to claim 1, characterized in that, S1 satisfies at least one of the following conditions: (1) The water temperature for soaking should be 25-30℃; (2) Soaking time in water is 8-10 hours; (3) The selenium content of selenium-enriched early rice is ≥0.3mg / kg.

3. The preparation method according to claim 1, characterized in that, S2 satisfies at least one of the following conditions: (1) The power of microwave processing is 500-700W; (2) The microwave treatment is specifically intermittent microwave treatment; preferably, the intermittent microwave treatment is a 10-second interval after every 20 seconds of radiation, with a total microwave working time of 2 minutes. (3) The water is added according to the material-to-liquid ratio of 1g:10-20mL; (4) The temperature for high temperature and high pressure treatment is 110℃-130℃.

4. The preparation method according to claim 1, characterized in that, S2 satisfies at least one of the following conditions: (1) The drying temperature is 40-65℃; the air velocity in the drying oven is controlled at 1.0-1.4m / s; (2) During crushing, the material temperature should be ≤40℃; (3) Crushing specifically involves crushing the rice bran to 200±10 mesh; (4) The grinding time is 3-5 minutes.

5. The preparation method according to claim 1, characterized in that, In S3, the mass ratio of the pretreated rice obtained from S1 to the pretreated selenium-enriched high-fiber rice bran powder obtained from S2 is (95-100):(2-5).

6. The preparation method according to claim 1, characterized in that, S4 satisfies at least one of the following conditions: During grinding, the mass ratio of rice bran-rice mixture to water is 1:1.2-1:1.5; After grinding, the sieve mesh size is 70-90 mesh.

7. The preparation method according to claim 1, characterized in that, S5 satisfies at least one of the following conditions: (1) The steaming temperature is 98-100℃; (2) The steaming time for rice paste is 3-5 minutes.

8. The preparation method according to claim 1, characterized in that, In S6, the cooling process specifically involves 15-20°C cold air cooling for 5-8 minutes.

9. The preparation method according to claim 1, characterized in that, In S7, the drying wind speed can be 1.2-1.8 m / s.

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