Preparation method of rice product

Abstract

The invention relates to the field of food processing, in particular to a preparation method of a rice product, which comprises the following steps: pretreatment of rice bran: performing low-temperature degreasing, enzymolysis removal of antinutritional factors, microwave modification and superfine grinding to eliminate oxidation odor, break fiber structure and improve compatibility with starch; mixing and tempering the raw materials: uniformly mixing refined rice, the prepared pretreated rice bran, broken rice, modified starch, fructo-oligosaccharide and xanthan gum according to the weight percentage sum of 100%, adding deionized water to adjust the moisture content, stirring, standing and tempering; low-temperature pre-gelatinization: controlling the temperature and the humidity to preliminarily gelatinize the starch and enhance the binding force with rice bran fibers; performing microwave pre-puffing to form uniform initial micropores; performing vacuum low-temperature puffing: performing puffing at a low vacuum degree, retaining nutrition and expanding micropores; vacuum cooling: rapidly cooling to prevent oxidation; and post-treatment: spraying tea polyphenol, screening and then vacuum packaging. The rice product is rich in nutrition, long in shelf life and not easy to deteriorate.

Description

Technical Field

[0001] This invention relates to the field of food processing, and specifically to a method for preparing rice products. Background Technology

[0002] Rice puffed foods are popular with consumers due to their convenience and crispy texture, but existing preparation methods have several shortcomings that urgently need to be addressed. On the one hand, traditional processes often use refined rice as the sole main ingredient, resulting in a lack of dietary fiber and functional components in the products. On the other hand, the utilization rate of by-products such as rice bran (containing more than 30% dietary fiber and oryzanol) and broken rice generated during rice processing is less than 10%, which not only wastes resources but also increases environmental pressure. More importantly, rice bran itself presents a significant processing bottleneck—its high content of crude fat and lipoxidase can easily lead to oxidative off-flavors and shortened shelf life if added directly; furthermore, its dense fiber structure has poor compatibility with the starch matrix, easily causing problems such as mold blockage during puffing, hard cores, and insufficient crispness.

[0003] Furthermore, traditional methods lack targeted equipment selection and parameter control. For example, pregelatinization does not specify the material layer thickness, microwave puffing does not standardize the spreading thickness, and vacuum puffing does not stabilize vacuum fluctuations. These defects lead to high moisture absorption, rapid loss of crispness, and a noticeable softening of the texture after being left at room temperature for 3 months. At the same time, the high-temperature processing mode results in a generally high oil content (≥15%), which does not conform to contemporary healthy eating trends. Therefore, developing a method for preparing rice puffed products that can achieve high value-added processing of rice by-products, complex nutritional functions, and stable and controllable processes has significant industrial value. Summary of the Invention

[0004] To address the problems of the prior art, this invention provides a method for preparing rice products.

[0005] The objective of this invention can be achieved through the following technical solution: a method for preparing rice products, comprising the following steps: S1. Deep pretreatment of rice bran: The rice bran is subjected to low-temperature degreasing, enzymatic removal of anti-nutritional factors, microwave modification and ultra-fine grinding in sequence. The pretreated rice bran is used for later use to eliminate the oxidative odor of rice bran, break the dense fiber structure and improve compatibility with starch matrix. S2. Raw material mixing and conditioning: Refined rice, pretreated rice bran prepared in step S1, broken rice, modified starch, fructooligosaccharides, and xanthan gum are mixed evenly according to a total weight percentage of 100%. Deionized water is added to adjust the moisture content, and the mixture is stirred and allowed to stand for conditioning to ensure uniform dispersion of the raw material components and adjust the moisture content to a suitable processing state. The modified starch is at least one of acetylated starch and hydroxypropyl starch phosphate. S3. Low-temperature pregelatinization: The conditioned mixed raw materials are pregelatinized under set temperature and humidity conditions to initially gelatinize the starch, enhance the binding force with rice bran fiber, and avoid subsequent puffing and hard core. S4. Microwave pre-expansion: The pre-gelatinized raw material is fed into a tunnel microwave device for pre-expansion, forming uniform initial micropores inside the raw material, laying the foundation for subsequent vacuum expansion. S5. Vacuum low-temperature puffing: The microwave pre-expanded raw material is quickly transferred into a vacuum puffing tank and puffed under set vacuum and temperature conditions. The vacuum environment is used to reduce the puffing temperature, avoid nutrient loss, and at the same time allow the initial micropores to fully expand. S6. Vacuum Cooling: Transfer the expanded product into a vacuum cooling tank for rapid cooling to prevent oxidation and deterioration of the product at high temperatures. S7. Post-processing: Spray the cooled product with an antioxidant, screen it, and vacuum pack it to further inhibit oxidation, remove debris to ensure product shape, and extend shelf life.

[0006] Further improvements include the following steps in step S1: S11. Low-temperature degreasing: Feed the rice bran into a low-temperature screw press, control the pressing temperature at 60-65℃ and the pressing pressure at 0.8-1.2MPa, and press continuously for 20-30 minutes; S12. Enzymatic removal of anti-nutritional factors: Add deionized water to defatted rice bran and adjust the material-to-liquid ratio to 1:5-1:8 (g / mL). Then add 0.2-0.3% phytase by dry weight of rice bran and adjust the pH of the system to 5.0-5.5. Place the system in a constant temperature water bath and enzymatically hydrolyze at 55-60℃ for 30-40 minutes. After enzymatic hydrolysis, raise the temperature to 90℃ and keep it at that temperature for 10 minutes to inactivate the phytase. S13. Microwave modification: After enzymatic hydrolysis, rice bran is freeze-dried to a moisture content of ≤8%, pulverized to 100-120 mesh, and then fed into a microwave modification device. A fixed frequency microwave of 2450MHz is used, the power is controlled at 250-300W, and the process is carried out for 25-35 seconds, during which the bran is turned over once every 5 seconds. S14. Ultrafine grinding: The microwave-modified rice bran is fed into an air jet mill, and the grinding pressure is controlled at 0.6-0.8MPa and the feeding speed is 10-15kg / h, and the rice bran is ground to 200-250 mesh.

[0007] In a further improvement, in step S2, the raw materials, by weight percentage, are as follows: 50-65% refined rice, 18-25% pretreated rice bran, 10-15% broken rice, 3-6% modified starch, 1-3% fructooligosaccharides, and 0.1-0.5% xanthan gum.

[0008] In a further improvement, in step S2, the moisture content is adjusted to 12.5-14%, and a planetary mixer is used to stir at a speed of 300-400 r / min for 15-20 min, followed by standing conditioning at 25-30℃ for 25-35 min.

[0009] In a further improvement, in step S3, the conditioned mixed raw materials are fed into a drum-type pregelatinizer, and the drum temperature is controlled at 50-60℃, the drum speed at 15-20 r / min, and the material layer thickness at 2-3 mm. The pregelatinizes the material for 10-15 minutes in a closed environment with a humidity of 75-80% to achieve a starch gelatinization degree of 30-40%.

[0010] In a further improvement, in step S4, the pregelatinized raw material is evenly spread on a microwave conveyor belt with a thickness of 1-2 cm, and then fed into a tunnel microwave device. The device output power is controlled at 320-380W, the cavity temperature at 62-72℃, and the conveyor belt speed at 0.8-1.2 m / min, corresponding to a pre-expansion time of 1.6-2.6 min, so that initial micropores with a pore size of 30-60 μm are formed inside the raw material.

[0011] In a further improvement, in step S5, the microwave-pre-expanded raw material is transferred into the vacuum expansion tank within ≤30s using a sealed rapid transfer device. After closing the tank door, the vacuum pump is started to rapidly achieve a vacuum level of -0.085~-0.095MPa inside the tank, while simultaneously raising the temperature to 86-92℃ and holding the expansion for 4.5-6.5min. During this period, the vacuum level fluctuation is adjusted every 1min with a fluctuation range of ≤±0.005MPa.

[0012] In a further improvement, in step S6, the expanded product is transferred into a vacuum cooling tank, the vacuum pump is started to make the vacuum degree inside the tank reach -0.05~-0.06MPa, and at the same time, cooling air at 25-30℃ is introduced, the wind speed is controlled at 0.3-0.5m / s, and cooling is continued for 8-12 minutes to reduce the product temperature to 35-40℃.

[0013] In a further improvement, in step S7, the antioxidant is tea polyphenols, which are sprayed using a high-pressure atomization spraying device. The spraying amount is 0.04-0.06% of the product mass. After spraying, the product is screened by a 10-20 mesh vibrating screen to remove fragments with a particle size ≤0.5cm. Finally, the product is vacuum packaged using a vacuum packaging machine.

[0014] Compared with the prior art, the beneficial effects of the rice product preparation method of the present invention are as follows: Addressing the issue of extremely low utilization rates of rice processing byproducts such as rice bran and broken rice in traditional processes, this invention improves rice bran processing performance through a customized pretreatment process. This eliminates the off-odors caused by easy oxidation and overcomes processing barriers posed by the dense fibrous structure, transforming previously discarded byproducts into core raw materials. Simultaneously, through the scientific blending of refined rice and functional components, the raw material system is upgraded from a single starch matrix to a complex system of basic nutrients, dietary fiber, and prebiotics, meeting the diverse needs of modern consumers for healthy foods.

[0015] Abandoning the traditional, extensive high-temperature extrusion method, we have developed a refined process involving low-temperature pretreatment, segmented puffing, and vacuum synergistic processing. Through precise matching of equipment selection and operating procedures at each stage, we avoid the destruction of natural nutrients in the raw materials by high temperatures, thus fully preserving the active ingredients of the raw materials.

[0016] Traditional rice bran-added products often suffer from a rough texture and excessive hardness. This invention addresses these issues by modifying rice bran fibers and controlling starch gelatinization, resulting in a crispy texture without a hard core and eliminating the roughness caused by the fibers. The synergistic effect of vacuum cooling and tea polyphenol spraying significantly delays moisture absorption, softening, and oxidative odor during storage, solving the problems of short shelf life and easy spoilage in traditional puffed foods. The product features a natural grain flavor with no added large amounts of oil, aligning with contemporary healthy eating trends. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the present invention. Figure 2 This is a schematic diagram of the specific process of step S1 of the present invention. Detailed Implementation

[0018] The following is a description of the embodiments and appendices. Figure 1 Appendix Figure 2 The technical solution of the present invention will be further described below.

[0019] I. Raw Material Preparation Refined rice: Commercially available japonica rice with a starch content of ≥78%; Rice bran: a by-product of rice processing, with a dietary fiber content of ≥32% and a crude fat content of ≥20%; Broken rice: Commercially available rice processed into broken rice, with a starch content ≥72%; Modified starch: acetylated starch (degree of substitution 0.06-0.12), hydroxypropyl starch phosphate (degree of substitution 0.05-0.09); Fructooligosaccharides: food grade, purity ≥95%; Xanthan gum: food grade, viscosity (2% aqueous solution, 25℃) ≥1500mPa·s; Phytase: Food grade, enzyme activity ≥5000U / g; Tea polyphenols: food grade, purity ≥98%; Equipment: Low-temperature screw press, constant temperature water bath, freeze dryer, microwave modification equipment, air jet mill, planetary mixer, drum pregelatinizer, tunnel microwave equipment, sealed rapid transfer device, vacuum expansion tank, vacuum cooling tank, high-pressure atomizing spraying equipment, vibrating screen, vacuum packaging machine.

[0020] III. Examples Example 1 A method for preparing a rice product includes the following steps: Rice bran pretreatment (S1): S11 Low-Temperature Degreasing: Feed rice bran into a low-temperature screw press, control the pressing temperature at 60℃ and the pressing pressure at 1.0MPa, and press continuously for 25 minutes; S12 enzymatic hydrolysis: Add deionized water to defatted rice bran, adjust the material-to-liquid ratio to 1:6 (g / mL), then add 0.25% phytase by dry weight of rice bran, adjust the pH of the system to 5.2, place in a constant temperature water bath, and enzymatically hydrolyze at 58℃ for 35 min. After enzymatic hydrolysis, raise the temperature to 90℃ and keep warm for 10 min to inactivate phytase. S13 Microwave Modification: The enzymatically hydrolyzed rice bran is freeze-dried to a moisture content of 6%, pulverized to 110 mesh, and then fed into a microwave modification device. A fixed frequency microwave of 2450MHz is used, the power is controlled at 280W, and the process is carried out for 30 seconds, during which the bran is turned over once every 5 seconds. S14 Ultrafine Grinding: Microwave-modified rice bran is fed into an airflow mill, and the grinding pressure is controlled at 0.7 MPa and the feeding speed is 12 kg / h. The rice bran is ground to 220 mesh to obtain pretreated rice bran.

[0021] 2. Raw material mixing and conditioning (S2): Take 60% refined rice, 20% pretreated rice bran, 12% broken rice, 5% acetylated starch, 2% fructooligosaccharides, and 0.3% xanthan gum by weight percentage, and mix them evenly. Add deionized water to the mixed raw materials to adjust the moisture content to 13.2%. Stir with a planetary mixer at 350 r / min for 18 min, and then let it stand at 28℃ for 30 min to condition.

[0022] 3. Low-temperature pregelatinization (S3): The conditioned raw materials are fed into a drum-type pregelatinizer. The drum temperature is controlled at 55℃, the drum speed at 18r / min, and the material layer thickness at 2.5mm. Pregelatinize for 12 minutes in a closed environment with 78% humidity, and the starch gelatinization degree reaches 35%.

[0023] 4. Microwave pre-expansion (S4): The pre-gelatinized raw material is evenly spread on a microwave conveyor belt with a thickness of 1.5cm and sent into a tunnel microwave device. The device output power is controlled at 350W, the internal temperature of the cavity is 68℃, the conveyor belt speed is 1.0m / min, and the pre-expansion time is 2.0min. Initial micropores with a pore size of 45μm are formed inside the raw material.

[0024] 5. Vacuum low-temperature expansion (S5): The microwave pre-expanded raw material is transferred into the vacuum expansion tank within 28 seconds through a sealed rapid transfer device. After the tank door is closed, the vacuum pump is started to quickly bring the vacuum degree inside the tank to -0.09MPa. At the same time, the temperature is raised to 89℃ and held for expansion for 5.0min. During this period, the temperature is adjusted once every 1min, and the vacuum degree fluctuation range is ≤±0.003MPa.

[0025] 6. Vacuum cooling (S6): Transfer the expanded product into a vacuum cooling tank, start the vacuum pump to make the vacuum degree inside the tank reach -0.055MPa, and at the same time introduce cooling air at 28℃, control the air speed at 0.4m / s, and continue cooling for 10 minutes until the product temperature drops to 38℃.

[0026] 7. Post-processing (S7): Tea polyphenols are sprayed using high-pressure atomization spraying equipment, with a spraying amount of 0.05% of the product mass. After spraying, the product is screened through a 15-mesh vibrating screen to remove fragments with a particle size ≤0.5cm. Vacuum packaging is then performed using a vacuum packaging machine.

[0027] Example 2 A method for preparing a rice product, the core steps of which are the same as in Example 1, with only the parameters adjusted as follows: 1. Rice bran pretreatment (S1): S11 Low-Temperature Degreasing: Temperature 62℃, Pressure 1.2MPa, Pressing for 30 minutes; S12 enzymatic hydrolysis: material-to-liquid ratio 1:8 (g / mL), phytase addition 0.3%, pH 5.5, enzymatic hydrolysis at 60℃ for 40 min, inactivation at 90℃ for 10 min; S13 Microwave Modification: Freeze-dry to 7% moisture content, pulverize to 120 mesh, microwave power 300W, process for 35s, turning every 5s; S14 Ultrafine Grinding: Airflow mill with a pressure of 0.8MPa and a feeding speed of 15kg / h, grinding to 250 mesh.

[0028] 2. Raw material mixing and conditioning (S2): 55% refined rice, 25% pretreated rice bran, 13% broken rice, 5% hydroxypropyl starch phosphate, 1.5% fructooligosaccharides, and 0.5% xanthan gum; adjust the moisture content to 14%, mix with a planetary mixer at 400r / min for 20min, and let it stand at 29℃ for 35min to condition.

[0029] 3. Low-temperature pregelatinization (S3): Drum temperature 60℃, rotation speed 20r / min, material layer thickness 3mm, humidity 80%, pregelatinization for 15min, starch gelatinization degree 40%.

[0030] 4. Microwave pre-expansion (S4): Spread thickness 2cm, microwave power 380W, temperature 72℃, conveyor belt speed 0.8m / min, pre-expansion 2.6min, initial micropore diameter 60μm.

[0031] 5. Vacuum low-temperature expansion (S5): Transfer to a vacuum tank within 25s, vacuum degree -0.095MPa, temperature 92℃, expansion for 6.5min, vacuum degree fluctuation ≤±0.005MPa.

[0032] 6. Vacuum cooling (S6): Vacuum degree -0.06MPa, cooling air 30℃, wind speed 0.5m / s, cooling for 12min, product temperature drops to 35℃.

[0033] 7. Post-treatment (S7): Tea polyphenols sprayed at 0.06%, screened on a 20-mesh vibrating sieve, and vacuum packaged.

[0034] Example 3 A method for preparing a rice product, the core steps of which are the same as in Example 1, with only the parameters adjusted as follows: 1. Rice bran pretreatment (S1): S11 Low-Temperature Degreasing: Temperature 60℃, Pressure 0.8MPa, Pressing for 20 minutes; S12 enzymatic hydrolysis: material-to-liquid ratio 1:5 (g / mL), phytase addition 0.2%, pH 5.0, 55℃ enzymatic hydrolysis for 30 min, 90℃ inactivation for 10 min; S13 Microwave Modification: Freeze-dry to 8% moisture content, grind to 100 mesh, microwave power 250W, process for 25s, turning every 5s; S14 Ultrafine Grinding: Airflow mill with a pressure of 0.6MPa and a feeding speed of 10kg / h, grinding to 200 mesh.

[0035] 2. Raw material mixing and conditioning (S2): 65% refined rice, 18% pretreated rice bran, 10% broken rice, 6% acetylated starch, 0.8% fructooligosaccharides, and 0.2% xanthan gum; adjust the moisture content to 12.5%, mix with a planetary mixer at 300r / min for 15min, and let it stand at 25℃ for 25min to condition.

[0036] 3. Low-temperature pregelatinization (S3): Drum temperature 50℃, rotation speed 15r / min, material layer thickness 2mm, humidity 75%, pregelatinization for 10min, starch gelatinization degree 30%.

[0037] 4. Microwave pre-expansion (S4): Spread thickness 1cm, microwave power 320W, temperature 62℃, conveyor belt speed 1.2m / min, pre-expansion 1.6min, initial micropore diameter 30μm.

[0038] 5. Vacuum low-temperature expansion (S5): Transfer to a vacuum tank within 30s, vacuum degree -0.085MPa, temperature 86℃, expansion for 4.5min, vacuum degree fluctuation ≤±0.004MPa.

[0039] 6. Vacuum cooling (S6): Vacuum degree -0.05MPa, cooling air 25℃, wind speed 0.3m / s, cooling for 8min, product temperature drops to 40℃.

[0040] 7. Post-treatment (S7): Tea polyphenols sprayed at 0.04%, screened on a 10-mesh vibrating sieve, and vacuum packaged.

[0041] Example 4 A method for preparing rice products, wherein the rice bran pretreatment steps are the same as in Example 1, and the remaining parameters are adjusted as follows: 1. Raw material mixing and conditioning (S2): The mixture consists of 58% refined rice, 22% pretreated rice bran, 15% broken rice, 3% acetylated starch, 1.7% fructooligosaccharides, and 0.3% xanthan gum. The moisture content is adjusted to 13.5%. The mixture is stirred in a planetary mixer at 380 rpm for 19 minutes and then allowed to stand at 27°C for 32 minutes to condition.

[0042] 2. Low-temperature pregelatinization (S3): Drum temperature 56℃, rotation speed 17r / min, material layer thickness 2.8mm, humidity 79%, pregelatinization for 13min, starch gelatinization degree 37%.

[0043] 3. Microwave pre-expansion (S4): Spread thickness 1.8cm, microwave power 360W, temperature 70℃, conveyor belt speed 0.9m / min, pre-expansion 2.2min, initial micropore diameter 50μm.

[0044] 4. Vacuum low-temperature expansion (S5): Transfer to a vacuum tank within 27s, vacuum degree -0.092MPa, temperature 90℃, expansion for 5.5min, vacuum degree fluctuation ≤±0.003MPa.

[0045] 5. Vacuum cooling (S6): Vacuum degree -0.058MPa, cooling air 29℃, wind speed 0.45m / s, cooling for 11min, product temperature drops to 36℃.

[0046] 6. Post-treatment (S7): Tea polyphenols sprayed at 0.055%, screened on an 18-mesh vibrating sieve, and vacuum packaged.

[0047] (iv) Comparative Example Comparative Example 1 (Traditional process + no rice bran / functional ingredients) 1. Raw material mixing: Take 95% refined rice and 5% corn starch by weight percentage (total 100%), and mix them evenly; 2. Extrusion puffing: A traditional twin-screw extruder is used, with an extrusion temperature of 175℃ and a screw speed of 320 r / min; 3. Drying: After extrusion, dry with hot air (85℃, 25min); 4. Post-processing: Spray with 12% edible oil, screen with a 15-mesh sieve, and then package as usual.

[0048] Comparative Example 2 (rice bran not pretreated according to the present invention + no prebiotics / xanthan gum) 1. Rice bran processing: Directly pulverize to 220 mesh, without low-temperature defatting, enzymatic hydrolysis, or microwave modification steps; 2. Raw material mixing and conditioning: Same as step 2 in Example 1; 3. Subsequent steps (3-7): Same as steps 3-7 in Example 1.

[0049] Comparative Example 3 (with rice bran pretreatment + microwave-free - vacuum synergistic puffing) 1. Rice bran pretreatment: Same as step 1 in Example 1; 2. Raw material mixing and conditioning: Same as step 2 in Example 1; 3. Extrusion puffing: A traditional twin-screw extruder is used, with a temperature of 165℃ and a speed of 350r / min; 4. Drying: Hot air drying (80℃, 20min); 5. Post-processing: Spray with 0.05% tea polyphenols, sieve through a 15-mesh screen and vacuum package; no low-temperature pregelatinization, microwave pre-expansion, vacuum low-temperature expansion, or vacuum cooling steps.

[0050] Comparative Example 4 (with deep pretreatment + synergistic process + no fructooligosaccharides / xanthan gum) 1. Rice bran pretreatment: Same as step 1 in Example 1; 2. Raw material mixing and conditioning: Based on a total weight percentage of 100%, take 62% refined rice, 20% pretreated rice bran, 12% broken rice, and 6% acetylated starch. The remaining parameters are the same as in step 2 of Example 1. 3. Subsequent steps (3-7): Same as steps 3-7 in Example 1.

[0051] Comparative Example 5 (with deep pretreatment + without low-temperature pregelatinization step) 1. Rice bran pretreatment: Same as step 1 in Example 1; 2. Raw material mixing and conditioning: Same as step 2 in Example 1; 3. Direct microwave pre-expansion: Skip the low-temperature pre-gelatinization step and directly feed the conditioned raw material into the microwave equipment with parameters consistent with step 4 of Example 1; Subsequent steps (4-7): Same as steps 4-7 in Example 1.

[0052] V. Performance Test Results Table 1. Performance test results of the examples and comparative examples. 1) The overall performance of Examples 1-4 is the best: the puffing rate, nutrient retention rate, crispness and sensory score of the four examples are significantly better than those of the comparative examples, and the mold blockage rate is ≤3% and the shelf life is ≥12 months, which verifies the feasibility and superiority of the "deep pretreatment of rice bran + low temperature synergistic puffing" technical solution of the present invention.

[0053] (2) Comparative Example 1 highlights the defects of traditional process: its oil content (17.2%) is more than 4 times that of Example 1, its moisture absorption rate (10.5%) is more than 3 times that of Example 1, and it has no dietary fiber and functional ingredients. Its sensory score is only 73 points, which proves the effect of the "raw material compound + low temperature process" of the present invention on improving the health attributes and quality of the product.

[0054] (3) Comparative Example 2 confirms the necessity of rice bran pretreatment: its phytic acid removal rate is only 12.5% ​​(72.3% in Example 1), the mold blockage rate is as high as 18.3%, and the crispness (26.5N) far exceeds the qualified standard (≤21N). This shows that the residual anti-nutritional factors and fiber entanglement of untreated rice bran will directly lead to processing obstruction and quality decline. The "degreasing-enzymatic hydrolysis-modification" pretreatment of this invention is the core innovation.

[0055] (4) Comparative Example 3 verifies the core value of synergistic puffing: After the "microwave pre-puffing-vacuum low-temperature puffing" step was omitted, the oryzanol retention rate (60.2%) decreased by 30 percentage points compared with Example 1, and the oil content (13.5%) increased significantly, proving that the low-temperature synergistic puffing process is the key to retaining nutrients and reducing oil content.

[0056] (5) Comparative Examples 4 and 5 demonstrate the integrity of the formula and process: Comparative Example 4 has a poorer moisture absorption rate and crispness due to the lack of oligofructose and xanthan gum; Comparative Example 5 skipped the low temperature pregelatinization step, and the mold blockage rate increased to 10.5% and the expansion rate decreased, indicating that the formula combination and the whole process of the present invention are indispensable, and each link works together to ensure product quality.

[0057] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for preparing rice products, characterized in that, Includes the following steps: S1: The rice bran is pretreated by passing it through low-temperature defatting, enzymatic removal of anti-nutritional factors, microwave modification and ultra-fine grinding in sequence for later use. S2: Take refined rice, pretreated rice bran prepared in step S1, broken rice, modified starch, fructooligosaccharides and xanthan gum in a total weight percentage of 100%, mix them evenly, add deionized water to adjust the moisture content, stir and let stand to condition; the modified starch is at least one of acetylated starch and hydroxypropyl starch phosphate. S3: Pregelatinize the conditioned mixed raw materials under set temperature and humidity conditions; S4: The pregelatinized raw material is fed into a tunnel microwave equipment for pre-expansion; S5: Quickly transfer the microwave-pre-expanded raw material into a vacuum expansion tank and expand it under set vacuum and temperature conditions; S6: Transfer the puffed product into a vacuum cooling tank for cooling; S7: Spray the cooled product with an antioxidant, screen it, and then vacuum pack it.

2. The method for preparing rice products according to claim 1, characterized in that, Step S1 specifically includes the following steps: S11: Feed the rice bran into a low-temperature screw press, control the pressing temperature at 60-65℃ and the pressing pressure at 0.8-1.2MPa, and press continuously for 20-30 minutes; S12: Add deionized water to defatted rice bran, adjust the material-to-liquid ratio to 1:5-1:8 (g / mL), then add 0.2-0.3% phytase by dry weight of rice bran, adjust the pH of the system to 5.0-5.5, place in a constant temperature water bath, and enzymatically hydrolyze at 55-60℃ for 30-40 min. After enzymatic hydrolysis, raise the temperature to 90℃ and keep warm for 10 min to inactivate phytase. S13: After enzymatic hydrolysis, rice bran is freeze-dried to a moisture content of ≤8%, pulverized to 100-120 mesh, and then fed into a microwave modification device. A fixed frequency microwave of 2450MHz is used, the power is controlled at 250-300W, and the process is continued for 25-35 seconds, during which the bran is turned over once every 5 seconds. S14: Feed the microwave-modified rice bran into an air jet mill, control the milling pressure to be 0.6-0.8MPa and the feeding speed to be 10-15kg / h, and mill it to 200-250 mesh.

3. The method for preparing rice products according to claim 1, characterized in that, In step S2, the raw materials, in terms of total weight percentage of 100%, are: 50-65% refined rice, 18-25% pretreated rice bran, 10-15% broken rice, 3-6% modified starch, 1-3% fructooligosaccharides, and 0.1-0.5% xanthan gum.

4. The method for preparing rice products according to claim 1, characterized in that, In step S2, the moisture content is adjusted to 12.5-14%, and the mixture is stirred for 15-20 minutes at a speed of 300-400 r / min using a planetary mixer. Then, it is allowed to stand and condition for 25-35 minutes at 25-30℃.

5. The method for preparing rice products according to claim 1, characterized in that, In step S3, the conditioned mixed raw materials are fed into a drum-type pregelatinizer. The drum temperature is controlled at 50-60℃, the drum speed at 15-20 r / min, and the material layer thickness at 2-3 mm. The pregelatinizer is pre-gelatinized for 10-15 minutes in a closed environment with a humidity of 75-80% to achieve a starch gelatinization degree of 30-40%.

6. The method for preparing rice products according to claim 1, characterized in that, In step S4, the pregelatinized raw material is evenly spread on a microwave conveyor belt with a thickness of 1-2 cm, and then fed into a tunnel microwave device. The device output power is controlled at 320-380W, the internal temperature of the cavity is 62-72℃, and the conveyor belt speed is 0.8-1.2m / min, corresponding to a pre-expansion time of 1.6-2.6min, so that initial micropores with a pore size of 30-60μm are formed inside the raw material.

7. The method for preparing rice products according to claim 1, characterized in that, In step S5, the microwave-pre-expanded raw material is transferred into the vacuum expansion tank within ≤30s using a sealed rapid transfer device. After closing the tank door, the vacuum pump is started to rapidly achieve a vacuum level of -0.085~-0.095MPa inside the tank, while simultaneously raising the temperature to 86-92℃ and holding the expansion for 4.5-6.5min. During this period, the vacuum level fluctuation is adjusted every 1min with a fluctuation range of ≤±0.005MPa.

8. The method for preparing rice products according to claim 1, characterized in that, In step S6, the puffed product is transferred into a vacuum cooling tank. The vacuum pump is started to make the vacuum degree inside the tank reach -0.05~-0.06MPa. At the same time, cooling air at 25-30℃ is introduced and the air speed is controlled at 0.3-0.5m / s. The cooling is continued for 8-12 minutes to reduce the product temperature to 35-40℃.

9. The method for preparing rice products according to claim 1, characterized in that, In step S7, the antioxidant is tea polyphenol, which is sprayed using a high-pressure atomization spraying device. The spraying amount is 0.04-0.06% of the product mass. After spraying, it is screened by a 10-20 mesh vibrating screen to remove fragments with a particle size ≤0.5cm. Finally, it is vacuum packaged using a vacuum packaging machine.

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