Making method of coarse cereal mixed nutritional rice with low GI value

Abstract

The invention discloses a preparation method of low-GI-value coarse cereal mixed nutritional rice in the field of functional food processing. The method comprises the following steps: mixing polished round-grained rice flour, whole wheat flour, chenopodium quinoa flour, chickpea flour, oat bran and a special synergistic digestion-resistant starch protein fiber compound, tempering, adding water, stirring, carrying out extrusion forming in a certain temperature interval through a double-screw extruder, cutting, and carrying out segmented drying treatment to finally obtain the finished product. The core lies in preparation of a compound, and the compound is prepared by the following steps: firstly, carrying out moist heat pretreatment on corn starch under the assistance of ultrasonic waves and in the presence of sodium citrate, then carrying out branching modification on the starch for a long time under a mild condition by utilizing glycogen branching enzyme, then compounding with pea protein and inulin, and carrying out spray drying. And finally, embedding with an Arabic gum solution fluidized bed. The method is simple in process, and the prepared nutritional rice is low in glycemic index, good in sensory quality and suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of functional food processing technology, specifically relating to a method for producing a low-GI mixed grain nutritional rice. Background Technology

[0002] With the changing dietary structure of modern society and the significant increase in the global incidence of metabolic syndromes such as diabetes and obesity, the public has placed unprecedentedly high demands on the health attributes of their daily staple foods. Traditional refined rice, as a staple food in most regions, often causes a rapid rise in postprandial blood glucose due to its starch composition and structural characteristics, exhibiting a high glycemic index (GI). Long-term consumption of refined rice is detrimental to stable blood glucose management. Therefore, developing low-GI staple food products that can effectively delay starch digestion and stabilize postprandial blood glucose responses has become a core issue of common concern in functional food research and the food processing industry. Currently, low-GI rice products and related technologies on the market mainly focus on exploration and practice through raw material compounding, physical processing, and biological modification, aiming to intervene in the enzymatic hydrolysis process of starch through various means.

[0003] A common approach in existing technologies combines raw material blending with extrusion recombination. Specifically, high-glycemic index rice is mixed with natural grains, legumes, and functional ingredients rich in dietary fiber, protein, or slow-digesting carbohydrates. This utilizes the physical barrier effect of dietary fiber, the competitive inhibition of digestive enzymes by protein, and the interactions between different starch sources to reduce the overall digestibility of the mixture. Subsequently, modern extrusion molding technology is used to give the mixture a shape and texture similar to natural rice grains. Another common approach is to physically modify the raw starch, for example, using processing techniques such as wet heat treatment, microwave, or ultrasound to change the ratio of crystalline to amorphous regions of the starch granules, or to create micropores on the surface, thereby increasing enzymatic resistance and reducing digestion speed. Furthermore, some studies have explored using bio-enzymes such as glycogen branching enzymes to structurally modify starch molecules, directly increasing the content of resistant starch at the molecular level. However, these existing solutions all have certain limitations: the raw material compounding method often requires the addition of a high proportion of excipients, which may have a negative impact on the texture and flavor of the final product; the effect of single physical modification is highly unstable and has a limited range of control over the glycemic index; while enzymatic modification is precise, it is costly and complex, making it difficult to apply directly to the industrial production of staple foods.

[0004] In summary, there is an urgent need in the current technological field for an innovative solution that can overcome the shortcomings of the aforementioned methods while meeting the stringent requirements of industrial production for process simplicity, cost control, and product stability. An ideal solution should include a highly efficient and multifunctional core material that can significantly regulate the digestibility of the product with only a small amount added, thereby allowing the main production process to remain as simple and efficient as possible. This invention has emerged in this context, aiming to provide a low glycemic index mixed grain nutritional rice based on a novel functional material and its preparation method. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for producing a low-GI mixed grain nutritional rice.

[0006] A first aspect of the present invention provides a method for preparing a low-GI mixed grain nutritional rice, comprising the following steps: S1. By weight, add 30-50 parts of japonica rice flour, 20-30 parts of whole wheat flour, 10-20 parts of quinoa flour, 8-15 parts of chickpea flour, 3-8 parts of oat bran and 1-5 parts of synergistic resistant starch-protein-fiber complex into a mixer and mix at room temperature to obtain a mixture. S2. Transfer the mixture to a conditioning tank, add purified water, stir, and obtain the conditioned material. S3. The conditioned material is fed into a twin-screw extruder. The five temperature sections of the extruder from the feeding zone to the die zone are set to 68-72℃, 88-92℃, 108-112℃, 98-102℃, and 84-86℃, respectively. The material is extruded from the die to obtain long strips of rice grains. S4. Cut the long strips of rice grains to obtain the cut wet rice grains; dry the cut wet rice grains in stages: dry them in hot air at 78-82℃, and then dry them at 54-56℃; after drying, cool them to room temperature.

[0007] In this invention, the synergistic resistant starch-protein-fiber complex is applied to the preparation of a low glycemic index mixed grain rice. The reaction mechanism mainly manifests in the interaction between components, structural reorganization, and the final expression of the complex's function during extrusion molding and drying. The entire process is a continuous structuring process driven by heat, mechanical shear, and moisture. When the conditioned mixture enters a twin-screw extruder, under a set temperature gradient and screw shearing action, the system undergoes a series of complex physicochemical changes. First, starch granules from various sources begin to absorb water and swell. As the temperature rises, their crystalline structure melts, gelatinizes, and amylose molecules dissolve, forming a complex melt with the dissolved amylopectin, coexisting moisture, and added complex, protein, and fiber components. In this melt, the synergistic resistant starch-protein-fiber complex added in this invention plays a crucial role. Its pre-formed porous and branched structure is retained, becoming a "digestion resistance island" within the melt. Simultaneously, the pea protein fragments, inulin, and gum arabic released from the complex intertwine with the proteins and fibers naturally present in the base formula, such as whole wheat flour and chickpea flour. Under heat and shear stress, the proteins denature, and the unfolded peptide chains, along with gelatinized starch and dietary fiber, form a new, pervasive three-dimensional network structure through hydrogen bonds and hydrophobic interactions. This network not only imparts the rice product with its inherent elasticity and resilience, but more importantly, it effectively encapsulates, separates, and fixes the rapidly digestible starch components, reducing their chance of contact with digestive enzymes. The functional components in the complex further strengthen this network and provide sustained-release effects. After extrusion through a die and cooling, starch molecules recrystallize. Due to the presence of highly branched starch in the complex and interference from the protein fiber network, this process results in more imperfect, resistant crystal types. The subsequent segmented drying process first rapidly removes surface moisture at a higher temperature to set the shape and prevent rice grains from sticking together, then slowly removes internal bound water at a lower temperature. This process avoids damage to the already formed resistant structure caused by high temperatures, ensuring the stability of the product's function. Ultimately, the microstructure of the finished nutritional rice is a multiphase system consisting of a protein fiber network encapsulated and supported by numerous resistant and slow-digesting starch units. Upon entering the digestive tract, its exterior first forms a viscous barrier layer upon contact with water, slowing enzyme penetration; the dense internal network and resistant components further delay the enzymatic hydrolysis of starch, resulting in a gradual and sustained release of glucose, thus achieving a stable and significant low glycemic index effect. Although the entire preparation method is simple in steps, the pre-design and introduction of the core functional complex triggers a synergistic response from the microscopic molecular level to the macroscopic texture in the final product, which is the key mechanism for achieving complex functions with a simple process.

[0008] According to a preferred embodiment of the present invention, in step S1, the mixing time at room temperature is 30-40 minutes.

[0009] According to a preferred embodiment of the present invention, in step S2, the stirring time is 20-40 min.

[0010] According to a preferred embodiment of the present invention, in step S3, the screw speed of the twin-screw extruder is 110-130 rpm.

[0011] According to a preferred embodiment of the present invention, in step S4, the drying time under hot air at 78-82°C is 15-20 minutes.

[0012] According to a preferred embodiment of the present invention, the preparation steps of the synergistic resistant starch-protein-cellulose complex include: A1. By weight, place 80-120 parts of corn starch in a reactor, add distilled water containing 0.8-1.2 parts of sodium citrate, and sonicate to obtain a suspension; heat the suspension to 64-66℃ for treatment, and after treatment, cool to 24-26℃ and filter to obtain a wet filter cake. A2. Redisperse the wet filter cake in phosphate buffer solution at pH 6.4-6.6, add 0.4-0.6 parts of glycogen branching enzyme to obtain a mixture, place the mixture in a constant temperature shaking water bath and react at 56-60℃ to obtain a reaction solution; heat the reaction solution to 94-96℃ and maintain it, then cool and centrifuge to obtain a precipitate, wash the precipitate with deionized water, centrifuge again to obtain modified wet starch; A3. Premix the modified wet starch with 14-16 parts of pea protein and 8-12 parts of inulin to obtain a premix; spray dry the premix to obtain a dry composite powder. A4. Place the dried composite powder in a fluidized bed, add 4-6 parts of an aqueous solution of gum arabic, and dry.

[0013] In this invention, the preparation process of the synergistic anti-digestion starch-protein-fiber complex is a precisely controlled, multi-step, multi-scale synergistic modification process, aiming to construct a novel food ingredient with multiple digestive inhibitory functions from the molecular, supramolecular, and particle scales. The first step, a combined ultrasonic and hydrothermal treatment, is crucial for the pre-modification of the physical structure. The strong cavitation effect generated by ultrasound in the liquid phase can create micropores and cracks on the surface and inside of corn starch granules, significantly increasing the specific surface area and internal accessibility of the starch granules. Simultaneously, the hydrothermal treatment within a specific temperature range enhances the molecular chain segment movement in the amorphous region of the starch granules in a partially gelatinized state, causing partial unwinding of the double helix structure and limited disruption of the integrity of the crystalline region; this is known as partial pregelatinization. This synergistic treatment not only disrupts the dense structure of the starch granules but, more importantly, provides numerous previously encapsulated sites for subsequent enzyme adsorption and action, laying the physical foundation for reaction accessibility. The subsequent enzymatic branching modification is the core of molecular structure reconstruction. In a mild reaction system below the starch gelatinization temperature, glycogen branching enzymes are specifically activated. This enzyme possesses dual activities of hydrolysis and transglycosylation. It first selectively cleaves the longer glucose chains surrounding the straight and branched starch chains. Then, using these cleaved short chains as donors, it catalyzes the formation of new alpha glycosidic bonds, attaching them to other chains, thereby introducing numerous new, short branched structures within the starch molecule. This molecular-level reshaping significantly increases the complexity and branching density of the starch molecule, fundamentally altering its digestible properties: the highly branched short-chain structure is more prone to forming tight, resistant local conformations, while the efficiency of digestive enzymes acting on linear segments decreases significantly due to shorter chain lengths and increased steric hindrance. Ultimately, this results in a fundamentally improved ratio of slowly digestible starch to resistant starch in the modified starch. Subsequent compounding with pea protein and inulin, as well as encapsulation with gum arabic, represents the final step in functional integration and stabilization. The spray-drying process causes the modified porous starch granules, pea protein, and inulin to physically entangle and bind under high-temperature instantaneous action. Inulin, as a soluble dietary fiber, interacts with starch and protein through hydrogen bonds, forming a complex. Finally, a dense hydrophilic film was formed on the surface of the composite powder using a fluidized bed with an aqueous solution of gum arabic. This film not only improves the dispersion stability of the composite, but also hydrates first during digestion to form a viscous colloidal barrier, further delaying the diffusion and contact of digestive enzymes into the internal starch matrix.

[0014] According to a preferred embodiment of the present invention, in step A1, the suspension is heated to 64-66°C for 30-60 minutes.

[0015] According to a preferred embodiment of the present invention, in step A2, the reaction time at 56-60°C is 12-14 hours.

[0016] According to a preferred embodiment of the present invention, in step A3, the inlet temperature of the spray dryer is 178-182°C, and the outlet temperature of the spray dryer is 84-86°C.

[0017] According to a preferred embodiment of the present invention, in step A4, the mass concentration of the aqueous solution of gum arabic is 10-12%.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The method for producing low glycemic index mixed grain nutritional rice provided by this invention introduces an innovatively designed synergistic resistant starch-protein-fiber complex combined with an optimized and simplified process, resulting in significant and multifaceted comprehensive technical effects. Its core effect is primarily reflected in its ability to stably and effectively regulate the product's glycemic index. This method does not rely on a single approach but integrates multiple glycemic index-lowering mechanisms through the synergistic effect of the functional complex and the basic formula. The complex undergoes a fundamental structural transformation through ultrasonic moist heat pretreatment, precise modification of glycogen branching enzymes, and functional compounding with pea protein and inulin. This allows it to simultaneously function as a physical barrier, regulate enzyme activity, and remodel the starch digestion pathway in the final product. This results in the final nutritional rice exhibiting a significant reduction in rapidly digestible starch content and a significant increase in the ratio of slowly digestible starch and resistant starch in an in vitro digestion model, thereby ensuring that the predicted glycemic index value of the product can be stably controlled within the standard range for low glycemic index foods. This powerful regulatory ability allows for the achievement of excellent glycemic index targets with only a small amount of this complex added to basic whole grain formulas, avoiding the taste and cost problems that may result from the overuse of functional ingredients in pursuit of a low glycemic index.

[0019] Secondly, the technical advantages of this invention are prominently reflected in the simplicity, stability, and excellent adaptability to industrial production of the production process. The final product preparation process includes only four core steps: material mixing, conditioning, extrusion molding, and segmented drying. The equipment used in each step is conventional in the food processing field, and the process parameter window is clear and broad. From the time control of mixing and conditioning, to the temperature settings and screw speeds of each zone of the twin-screw extruder, and then to the specific temperature and time of segmented drying, all key operating points are given clear range guidance. This makes the entire production process easy to standardize and control, highly repeatable, and able to maintain good process stability for different batches of raw materials. More importantly, by pre-positioning and solidifying the complex modification technology and functional construction process into an independent compound preparation step, the final nutritional rice production line can maintain maximum simplicity and efficiency, greatly reducing production complexity and energy consumption. It is very suitable for large-scale continuous industrial manufacturing and effectively solves the common problems of cumbersome processes, difficult quality control, and limited production capacity often encountered in the production of functional staple food products.

[0020] Finally, the technical benefits of this invention extend to the overall quality and practical value of the final product. This method not only focuses on the glycemic index, a core health indicator, but also ensures nutritional balance through a scientifically proportioned blend of grains, providing abundant dietary fiber, protein, and trace elements. Simultaneously, precisely controlled extrusion and drying processes guarantee a good texture and particle shape, resulting in an appearance, taste, and chewiness similar to natural rice after cooking, significantly improving consumer acceptance. This combination of health attributes and a pleasant sensory experience makes the nutritious rice prepared by this invention not merely a special dietary food, but a readily integrated staple food choice that can be easily incorporated into daily meals, providing the public with a convenient and effective dietary solution for blood sugar management, possessing broad market application prospects and social value. Detailed Implementation

[0021] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0022] Example 1

[0023] This embodiment provides a method for preparing a low-GI mixed grain nutritional rice, including the following steps: Preparation of synergistic resistant starch-protein-cellulose complex: A1. Weigh 100.0g of corn starch and place it in a reactor equipped with heating and ultrasonic functions. Add 300.0mL of distilled water, in which 1.0g of sodium citrate is pre-dissolved. Turn on the ultrasonic generator, setting the power to 300W and the frequency to 28kHz. Under continuous ultrasonic treatment, heat the suspension to 65.0℃ and maintain this temperature for 45.0min. After treatment, immediately cool the suspension to 25.0℃, and then perform vacuum filtration using a Buchner funnel and filter paper to obtain a wet filter cake.

[0024] A2. Transfer the obtained wet filter cake to a beaker, add 0.02 mol / L phosphate buffer (pH 6.5), and bring the volume to 400.0 mL to prepare a homogeneous suspension. Accurately add 0.5 g of glycogen branching enzyme to this suspension, place in a constant temperature shaking water bath at 58.0 °C and 150 rpm, and react for 13.0 h. After the reaction, transfer the reaction solution to a water bath and heat to 95.0 °C for 12.0 min. Then cool the reaction solution to room temperature and centrifuge at 4000 rpm for 15.0 min, discarding the supernatant. Add 200.0 mL of deionized water to the precipitate, stir with a glass rod, and centrifuge again under the same conditions. Repeat this washing process twice to obtain the modified wet starch.

[0025] A3. The modified wet starch (100.0g on a dry basis), 15.0g pea protein, and 10.0g inulin were placed together in a high-speed mixer and premixed at 1000rpm for 5.0min to obtain a premix. The premix was then spray-dried at a feed rate of 15mL / min, an inlet air temperature of 180.0℃, and an outlet air temperature of 85.0℃ to obtain a dried composite powder.

[0026] A4. Place 95.0g of dried composite powder in a fluidized bed granulator, set the inlet air temperature to 60.0℃, dissolve 5.0g of gum arabic in 45.0g of deionized water to prepare a 10.0% aqueous solution, and spray it into the fluidized bed at a rate of 3.0mL / min for encapsulation. After encapsulation, continue drying at 60.0℃ for 20.0min, and pass through a 100-mesh sieve to obtain the synergistic resistant starch-protein-cellulose complex.

[0027] Preparation of low-GI mixed grain nutritional rice: S1. Accurately weigh 400.0g of japonica rice flour, 250.0g of whole wheat flour, 150.0g of quinoa flour, 120.0g of chickpea flour, 50.0g of oat bran, and 30.0g of the synergistic resistant starch-protein-fiber complex prepared above according to the formula. Put all the powdered raw materials into a three-dimensional motion mixer, set the speed to 20 rpm, and mix for 35.0 min at room temperature of 25.0℃ to obtain a uniformly colored mixture.

[0028] S2. Transfer the mixture to a conditioning tank equipped with a stirring paddle. Turn on the stirring and set the speed to 60 rpm. Simultaneously, slowly and evenly spray in purified water at a rate of 26.0% of the total mass of the mixture, i.e., 260.0 g. After adding the water, continue stirring for 30.0 min to obtain a loosely conditioned material with uniform moisture distribution.

[0029] S3. The conditioned material is fed into a co-rotating twin-screw extruder via a feeder. The main feed rate is set to 12.0 kg / h, and the screw speed is set to 120 rpm. The temperatures of the five independent temperature control zones from the feeding zone to the die zone are set to 70.0℃, 90.0℃, 110.0℃, 100.0℃, and 85.0℃, respectively. After being melted and sheared at high temperature, the material is extruded from the die with rice-grain-shaped holes to form continuous long strips of rice grains.

[0030] S4. Using a rotating cutter synchronized with the die head, cut the extruded rice strips into wet rice grains approximately 5.0 mm in length. Spread the wet rice grains evenly on the conveyor belt of a mesh belt dryer, and first dry them in hot air at 80.0℃ for 18.0 min. Then adjust the temperature to 55.0℃ and continue drying for 45.0 min. After drying, transfer the rice grains to a cooling box and cool them to room temperature of 25.0℃. After sieving to remove debris, the finished low-GI mixed grain nutritional rice is obtained.

[0031] Example 2

[0032] The difference between this embodiment and Example 1 lies in the preparation of the synergistic resistant starch-protein-cellulose complex: A1. Weigh 90.0g of corn starch and place it in a reactor. Add 270.0mL of distilled water, in which 0.9g of sodium citrate has been pre-dissolved. Turn on the ultrasonic generator, setting the power to 290W and the frequency to 27kHz. Under continuous ultrasonic treatment, heat the suspension to 64.0℃ and maintain this temperature for 50.0min. After treatment, cool the suspension to 24.0℃, and then perform vacuum filtration to obtain a wet filter cake.

[0033] A2. Disperse the wet filter cake in phosphate buffer (pH 6.4) and bring the volume to a final volume of 360.0 mL. Accurately add 0.45 g of glycogen branching enzyme to the suspension, place in a constant-temperature shaking water bath at 57.0 °C and a shaking speed of 145 rpm, and react for 12.5 h. After the reaction is complete, heat the reaction solution to 94.0 °C and maintain this temperature for 15.0 min. After cooling, centrifuge at 4000 rpm for 15.0 min, discard the supernatant, and wash the precipitate twice with deionized water to obtain the modified wet starch.

[0034] A3. 90.0g of modified wet starch (dry basis), 13.0g of pea protein, and 9.0g of inulin were placed together in a high-speed mixer and premixed at 950rpm for 6.0min. The premix was then spray-dried at an inlet air temperature of 179.0℃ and an outlet air temperature of 84.0℃ to obtain a dried composite powder.

[0035] A4. Place approximately 91.0g of dried composite powder in a fluidized bed and set the inlet air temperature to 58.0℃. Dissolve 4.5g of gum arabic in 40.9g of deionized water to prepare an 11.0% aqueous solution, spray it into the fluidized bed for encapsulation and drying, and after sieving, obtain approximately 95.0g of synergistic resistant starch-protein-cellulose complex.

[0036] Preparation of low-GI mixed grain nutritional rice: S1. Accurately weigh 350.0g of japonica rice flour, 280.0g of whole wheat flour, 180.0g of quinoa flour, 100.0g of chickpea flour, 40.0g of oat bran, and 50.0g of the prepared complex. Put them into a three-dimensional motion mixer and mix at 20 rpm for 32.0 min at room temperature of 25.0℃.

[0037] S2. Transfer the mixture to a conditioning tank, turn on the agitator and spray in purified water. The amount of water added is 25.0% of the total mass of the mixture, i.e., 250.0g. Continue to stir at 60rpm for 25.0min.

[0038] S3. Feed the material into the twin-screw extruder, setting the main feed rate to 11.5 kg / h and the screw speed to 115 rpm. Set the temperatures of the five temperature control zones to 69.0℃, 89.0℃, 109.0℃, 99.0℃, and 84.0℃ respectively. Extrude rice grains.

[0039] S4. After cutting the rice grains, dry them first at 79.0℃ hot air for 16.0 min, and then at 54.0℃ for 50.0 min. After cooling and sieving, the finished product is obtained.

[0040] Example 3

[0041] The difference between this embodiment and Example 1 lies in the preparation of the synergistic resistant starch-protein-cellulose complex: A1. Weigh 110.0g of corn starch and place it in a reactor. Add 330.0mL of distilled water, in which 1.1g of sodium citrate has been pre-dissolved. Turn on the ultrasonic generator, setting the power to 310W and the frequency to 29kHz. Under continuous ultrasonic treatment, heat the suspension to 66.0℃ and maintain this temperature for 35.0min. After treatment, cool the suspension to 26.0℃, and then perform vacuum filtration to obtain a wet filter cake.

[0042] A2. Disperse the wet filter cake in phosphate buffer (pH 6.6) and bring the volume to 440.0 mL. Accurately add 0.55 g of glycogen branching enzyme to the suspension, place in a constant-temperature shaking water bath at 59.0 °C and 155 rpm, and react for 13.5 h. After the reaction is complete, heat the reaction solution to 96.0 °C and maintain for 10.0 min. After cooling, centrifuge, and wash the precipitate twice with deionized water to obtain the modified wet starch.

[0043] A3. 110.0g of modified wet starch (dry basis), 16.0g of pea protein, and 11.0g of inulin were placed together in a high-speed mixer and premixed at 1050rpm for 4.5min. The premix was then spray-dried at an inlet air temperature of 181.0℃ and an outlet air temperature of 86.0℃ to obtain a dried composite powder.

[0044] A4. Place approximately 104.0g of dried composite powder in a fluidized bed and set the inlet air temperature to 62.0℃. Dissolve 6.0g of gum arabic in 44.0g of deionized water to prepare a 12.0% aqueous solution, spray it into the fluidized bed for encapsulation and drying, and then sieve to obtain the synergistic resistant starch-protein-cellulose complex.

[0045] Preparation of low-GI mixed grain nutritional rice: S1. Accurately weigh 450.0g of japonica rice flour, 220.0g of whole wheat flour, 120.0g of quinoa flour, 140.0g of chickpea flour, 70.0g of oat bran, and 20.0g of the prepared complex. Place them into a three-dimensional motion mixer and mix at 20 rpm for 38.0 min at room temperature of 25.0℃.

[0046] S2. Transfer the mixture to a conditioning tank, turn on the agitator and spray in purified water. The amount of water added is 27.0% of the total mass of the mixture, i.e., 270.0g. Continue stirring at 60rpm for 35.0min.

[0047] S3. Feed the material into the twin-screw extruder, setting the main feed rate to 12.5 kg / h and the screw speed to 125 rpm. Set the temperatures of the five temperature control zones to 71.0℃, 91.0℃, 111.0℃, 101.0℃, and 86.0℃ respectively. Extrude rice grains.

[0048] S4. After cutting the rice grains, dry them first at 81.0℃ hot air for 19.0 min, and then at 56.0℃ for 40.0 min. After cooling and sieving, the finished product is obtained.

[0049] Comparative Example 1

[0050] The difference between this comparative example and Example 1 lies in the preparation of the low-GI mixed grain nutritional rice: S1. Accurately weigh 430.0g of rice flour, 250.0g of whole wheat flour, 150.0g of quinoa flour, 120.0g of chickpea flour, and 50.0g of oat bran. Put them into a three-dimensional motion mixer and mix at 20 rpm for 35.0 min at room temperature of 25.0℃.

[0051] S2. Transfer the mixture to a conditioning tank, turn on the agitator and spray in purified water. The amount of water added is 26.0% of the total mass of the mixture, i.e., 260.0g. Continue stirring at 60rpm for 30.0min.

[0052] S3. Feed the material into the twin-screw extruder, setting the main feed rate to 12.0 kg / h and the screw speed to 120 rpm. Set the temperatures of the five temperature control zones to 70.0℃, 90.0℃, 110.0℃, 100.0℃, and 85.0℃ respectively. Extrude rice grains.

[0053] S4. After cutting the rice grains, dry them first at 80.0℃ hot air for 18.0 min, and then at 55.0℃ for 45.0 min. After cooling and sieving, obtain the comparison product.

[0054] Comparative Example 2

[0055] The difference between this comparative example and Example 1 lies in the preparation of the low-GI mixed grain nutritional rice: S1. Accurately weigh 400.0g of japonica rice flour, 250.0g of whole wheat flour, 150.0g of quinoa flour, 120.0g of chickpea flour, 50.0g of oat bran, and 30.0g of ordinary pregelatinized corn starch. Put them into a three-dimensional motion mixer and mix at 20 rpm for 35.0 min at room temperature of 25.0℃.

[0056] S2. Transfer the mixture to a conditioning tank, start the agitator and spray in purified water at a rate of 26.0% of the total mass of the mixture, i.e., 260.0g. Continue stirring at 60 rpm for 30.0 min. All subsequent extrusion, cutting, drying, and cooling process parameters and conditions are completely consistent with those in Example 1, yielding a comparative product.

[0057] Comparative Example 3

[0058] The difference between this comparative example and Example 1 lies in the preparation of the low-GI mixed grain nutritional rice: S1. Accurately weigh 400.0g of japonica rice flour, 250.0g of whole wheat flour, 150.0g of quinoa flour, 120.0g of chickpea flour, 50.0g of oat bran, and 30.0g of unmodified ordinary corn starch. Put them into a three-dimensional motion mixer and mix at 20 rpm for 35.0 min at room temperature of 25.0℃.

[0059] S2. Transfer the mixture to a conditioning tank, start the agitator and spray in purified water at a rate of 26.0% of the total mass of the mixture, i.e., 260.0g. Continue stirring at 60 rpm for 30.0 min. All subsequent extrusion, cutting, drying, and cooling process parameters and conditions are completely consistent with those in Example 1, yielding a comparative product.

[0060] In accordance with national and industry standard testing specifications, the performance tests of this invention were conducted on the low-GI mixed grain nutritional rice prepared in Examples 1-3 and Comparative Examples 1-3. The performance tests were based on three aspects: in vitro starch digestion kinetics, texture profile analysis, and sensory evaluation. All tests were performed in triplicate, and the results are expressed as mean ± standard deviation.

[0061] The in vitro starch digestion test is used to determine the content of rapidly digestible starch, slowly digestible starch, and resistant starch, and to predict the glycemic index. Accurately weigh 200.0 mg (dry basis) of sample powder, pulverized through an 80-mesh sieve, and place it in a 50 mL Erlenmeyer flask. Add 15.0 mL of 0.05 mol / L sodium acetate buffer solution (pH 5.2). Incubate at 37.0℃ with shaking for 10.0 min. Then add 5.0 mL of simulated gastric juice containing 1.0 mg / mL pepsin (dissolved in 0.05 mol / L HCl). React at 37.0℃ and 100 rpm for 30.0 min. After reaction, adjust the pH of the mixture to neutral with 0.5 mol / L NaOH solution. Immediately add 10... Digestion was initiated with a 0.0 mL mixed enzyme solution containing pancreatic α-amylase (activity not less than 10 U / mL) and glucoamylase (activity not less than 15 U / mL). At 0, 20, 60, 90, 120 and 180 min of digestion, 0.5 mL of hydrolysate was accurately pipetted into 4.0 mL of anhydrous ethanol to terminate the reaction. After centrifugation, the supernatant was collected, and the glucose concentration was determined using the glucose oxidase-peroxidase method. The starch hydrolysis rate at each time point was calculated with the completely hydrolyzed sample as a reference. The hydrolysis curve was plotted and the hydrolysis index was calculated. The glycemic index was predicted according to the formula = 39.71 + (0.549 × hydrolysis index) and the eGI value was calculated. The percentage content of rapidly digested starch, slowly digested starch and resistant starch was calculated based on the 120 min digestion data.

[0062] Texture profile analysis was used to determine hardness, adhesion, and elasticity. Using a texture analyzer, approximately 20.0g of cooked rice (rice to water ratio 1:1.5) was evenly filled into a test container. Two compression tests were performed using a cylindrical probe. Parameters were set as follows: pre-test speed 2.0mm / s, test speed 1.0mm / s, return speed 1.0mm / s, compression deformation 50%, interval between compressions 5.0s, trigger force 5.0g. Hardness, adhesion, and elasticity values ​​were directly obtained from the force-time curve. Sensory overall acceptability evaluation was conducted by 10 trained evaluators in a standard sensory laboratory. After cooking, samples were randomly coded with three-digit numbers and presented randomly. Evaluators independently rated the samples using a 9-point preference scale, where 1 point represents "strongly dislike," 5 points represent "neither like nor dislike," and 9 points represent "strongly like." Rinsing with water was provided during the evaluation process, and the average score was calculated.

[0063] The performance test data above are shown in Table 1.

[0064] Table 1 Performance Test Results

[0065] As can be seen from the above, the technical solutions of the present invention represented by Examples 1-3, compared with Comparative Examples 1-3, systematically solve the three major technical problems that are common in the development of existing low glycemic index staple food products.

[0066] First, this invention has achieved a breakthrough in core health function indicators. Comparative Example 1, which uses only conventional mixed grains, still has a predicted glycemic index as high as 68.8, which is within the medium glycemic index range, and its effect on lowering the glycemic index is significantly insufficient. Comparative Example 2, which uses ordinary pregelatinized starch, and Comparative Example 3, which uses unmodified starch, have predicted glycemic index values ​​that further increase to 72.5 and 82.1, respectively, indicating that simple physical mixing or the use of ordinary starch as a substitute cannot effectively regulate the digestion rate.

[0067] In contrast, the embodiments of this invention show that the predicted glycemic index (GI) values ​​remain stable between 52.9 and 55.8, all strictly below the international low GI threshold of 55, achieving a fundamental leap from "medium-high GI" to "low GI." This remarkable effect is directly attributed to the introduction of the synergistic resistant starch-protein fiber complex, which, through its unique structural design, significantly reshapes the starch digestibility profile of the product: the rapidly digestible starch content of the product in the embodiments is reduced by an average of approximately 15-25 percentage points compared to the comparative example, while the content of slowly digestible starch and resistant starch is correspondingly significantly increased. This demonstrates that this invention successfully transforms the starch digestibility mode from "rapid concentrated release" to "slow and stable release," fundamentally solving the key problems of insufficient efficacy and unstable effects in lowering the GI of existing mixed grain compound technologies.

[0068] Secondly, while achieving excellent glycemic index reduction, this invention successfully avoids the "trade-off" dilemma often faced by functional foods, where health attributes are enhanced at the expense of sensory and edible quality. Test data shows that Comparative Example 1, despite not adding any functional materials, had an overall sensory acceptability score of only 6.9, indicating that the basic whole grain formula itself presents a challenge in terms of taste harmony. Comparative Example 2, after adding ordinary pregelatinized starch, saw its sensory score further drop to 6.5, suggesting that inappropriate functional ingredients may negatively impact taste. However, the sensory scores of all embodiments of this invention remained consistently above 7.1, reaching a maximum of 7.4, significantly better than all comparative examples. This confirms that the complex does not sacrifice taste for function, but rather achieves a synergistic benefit in both health and flavor.

[0069] In terms of texture, the product in the example exhibits suitable hardness, low adhesiveness (a smaller absolute negative value indicates less stickiness), and good elasticity. Its overall textural characteristics are closer to consumers' expectations of high-quality rice. This solves the technical bottleneck that often resulted in products with a rough texture, hard or sticky mouthfeel from the addition of large amounts of functional ingredients such as bran and resistant starch.

[0070] Finally, this invention resolves the contradiction between process complexity and reliability in industrial production. The results of Comparative Examples 2 and 3 clearly demonstrate that simply replacing or adding ordinary starch (whether pregelatinized or native) to the final formulation does not fundamentally improve the digestibility of the product compared to ordinary mixed grain rice, and may even worsen it. This highlights the ineffectiveness of functional ingredients without specific structural design. This invention focuses its core technical complexity and innovation on the preparation of the composite material. Once prepared, this material only needs to be simply mixed with other conventional raw materials at a ratio of 1-5% during final product production, and then shaped using a standard extrusion process.

[0071] Examples 1-3 demonstrate that low glycemic index products can be stably produced using different amounts and batches of the complex, with consistent textural and sensory properties, proving the reliability and process adaptability of the proposed method. Therefore, this invention successfully transforms a complex nutritional regulation target into a simple addition step easily implemented on existing food processing lines, solving the core pain points of difficulty in scaling up processes and controlling quality encountered when functional staple food products move from the laboratory to large-scale industrial production.

Claims

1. A method for producing a low GI value mixed nutrient coarse grain rice, characterized by comprising the steps of: Includes the following steps: ​ S1. By weight, add 30-50 parts of japonica rice flour, 20-30 parts of whole wheat flour, 10-20 parts of quinoa flour, 8-15 parts of chickpea flour, 3-8 parts of oat bran and 1-5 parts of synergistic resistant starch-protein-fiber complex into a mixer and mix at room temperature to obtain a mixture. S2. Transfer the mixture to a conditioning tank, add purified water, stir, and obtain the conditioned material. S3. The conditioned material is fed into a twin-screw extruder. The five temperature sections of the extruder from the feeding zone to the die zone are set to 68-72℃, 88-92℃, 108-112℃, 98-102℃, and 84-86℃, respectively. The material is extruded from the die to obtain long strips of rice grains. S4. Cut the long strips of rice grains to obtain the cut wet rice grains; dry the cut wet rice grains in stages: dry them in hot air at 78-82℃, and then dry them at 54-56℃; after drying, cool them to room temperature.

2. The method of claim 1, wherein the low GI value mixed nutrient millet is characterized by, In step S1, the mixing time at room temperature is 30-40 minutes.

3. The method of claim 1, wherein the low GI value mixed nutrient millet is prepared by mixing 30 to 70% of the millet and 70 to 30% of the legume. In step S2, the stirring time is 20-40 minutes.

4. The method for preparing low-GI mixed grain nutritional rice according to claim 1, characterized in that, In step S3, the screw speed of the twin-screw extruder is 110-130 rpm.

5. The method for preparing low-GI mixed grain nutritional rice according to claim 1, characterized in that, In step S4, the drying time under hot air at 78-82℃ is 15-20 minutes.

6. The method for preparing low-GI mixed grain nutritional rice according to any one of claims 1-5, characterized in that, The preparation steps of the synergistic resistant starch-protein-fiber complex include: A1. By weight, place 80-120 parts of corn starch in a reactor, add distilled water containing 0.8-1.2 parts of sodium citrate, and sonicate to obtain a suspension; heat the suspension to 64-66℃ for treatment, and after treatment, cool to 24-26℃, filter, and obtain a wet filter cake. A2. Redisperse the wet filter cake in phosphate buffer solution at pH 6.4-6.6, add 0.4-0.6 parts of glycogen branching enzyme to obtain a mixture, place the mixture in a constant temperature shaking water bath and react at 56-60℃ to obtain a reaction solution; heat the reaction solution to 94-96℃ and maintain it, then cool and centrifuge to obtain a precipitate, wash the precipitate with deionized water, centrifuge again to obtain modified wet starch; A3. Premix the modified wet starch with 14-16 parts of pea protein and 8-12 parts of inulin to obtain a premix; spray dry the premix to obtain a dry composite powder. A4. Place the dried composite powder in a fluidized bed, add 4-6 parts of an aqueous solution of gum arabic, and dry.

7. The method for preparing low-GI mixed grain nutritional rice according to claim 6, characterized in that, In step A1, the suspension is heated to 64-66℃ for 30-60 minutes.

8. The method for preparing low-GI mixed grain nutritional rice according to claim 6, characterized in that, In step A2, the reaction time is 12-14 hours at 56-60℃.

9. The method for preparing low-GI mixed grain nutritional rice according to claim 6, characterized in that, In step A3, the inlet temperature of the spray dryer is 178-182℃, and the outlet temperature of the spray dryer is 84-86℃.

10. The method for preparing low-GI mixed grain nutritional rice according to claim 6, characterized in that, In step A4, the mass concentration of the aqueous solution of gum arabic is 10-12%.

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