A low-GI fermented rice product and its preparation method

Abstract

This invention provides a low-GI fermented rice product and its preparation method, belonging to the field of food processing technology. The method includes the following steps: (1) Preparing a rice flour-rice bran dietary fiber mixture: Rice is ground into flour and mixed with rice bran dietary fiber (RBDF) to obtain a mixture; (2) Preparing a microbial fermentation broth: Lactobacillus paracasei undergoes a three-stage activation culture to obtain an activated microbial fermentation broth; (3) Fermentation: The fermentation broth obtained in step (2) is inoculated into a mixture of the mixture and water from step (1), and fermented at 35-37℃ for 20-24 hours to obtain the fermented rice flour product. This invention, through the synergistic fermentation of Lactobacillus paracasei and rice bran dietary fiber, significantly reduces the glycemic index (GI) of the resulting rice biscuit to 53.64, while increasing its resistant starch (RS) content to 21.22%. Furthermore, it is superior to control products that are fermented alone or have only dietary fiber added, in terms of texture, sensory evaluation, and processing performance.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, specifically to a low-GI fermented rice product and its preparation method. Background Technology

[0002] In recent years, the global prevalence of type 2 diabetes has continued to rise, making dietary intervention a crucial strategy for diabetes risk management. Rice products, as a traditional staple food, may increase metabolic risks for long-term consumers due to their high glycemic index (GI). Studies have shown that lactic acid bacteria fermentation and dietary fiber fortification can regulate starch digestibility and lower the GI value of foods. Low-GI foods (GI < 55) release glucose slowly, maintaining stable blood sugar levels, making them suitable for diabetic patients and those requiring blood sugar control. However, traditional rice products (such as rice and rice crackers) have high GI values ​​(typically 70-90), and long-term consumption can easily lead to blood sugar fluctuations. Therefore, developing low-GI rice products has become an important direction for the food industry.

[0003] Rice flour, as one of the most important grain products globally, especially in Asia, is a major source of carbohydrates in people's diets. As an important food ingredient, rice flour has a wide range of applications. In traditional foods, it is used to make rice noodles, rice cakes, and rice pancakes. In modern food industry, it is used to make baby food, baked goods, and ready-to-eat foods. However, rice products can rapidly raise blood sugar levels, and long-term consumption may increase the risk of hyperglycemia. The starches in rice flour, such as rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS), affect the body's digestion and absorption to varying degrees.

[0004] Lactic acid bacteria, belonging to the Gram-positive bacteria, play a crucial role in the food industry. On one hand, they rapidly acidify raw materials; on the other hand, they generate metabolites such as ethanol, organic acids, extracellular polysaccharides, and bacteriocins. Lactic acid bacteria fermentation can significantly alter the digestibility and glycemic index of rice flour, directly influencing starch digestibility through the fermentation substrate and its metabolites. Lactic acid bacteria fermentation has been proven to improve the digestibility of rice flour and produce various metabolites, such as organic acids, polysaccharides, and specific enzyme systems, providing a more solid theoretical basis for developing functional foods with low digestibility. Lactic acid bacteria have extremely wide and crucial applications in fermented grain products, such as fermented grain bread, beverages, and functional grain foods, which not only improve the sensory characteristics of these products but also significantly enhance their nutritional value and functionality.

[0005] Rice bran, a byproduct of rice processing, has high nutritional value. Although it only accounts for 5%-7% of rice weight, it is an excellent source of dietary fiber. Rice bran dietary fiber (RBDF) is one of the main components of rice bran and shows potential application value in various fields such as food and medicine. RBDF not only helps improve digestive function, lower cholesterol, and control blood sugar, but also has antioxidant, anti-inflammatory, and immune-boosting effects. In terms of applications, RBDF is widely used in the food industry due to its water-holding, swelling, and adsorption properties to improve the texture, taste, and nutritional characteristics of products. It can be added as a functional ingredient to foods such as bread, biscuits, noodles, and breakfast cereals to increase their dietary fiber content and is used to develop low-calorie, high-fiber health foods.

[0006] In recent years, against the backdrop of increased global consumer health awareness and the rising incidence of chronic diseases, low-GI foods have seen explosive growth in market demand as a superior choice for healthy eating. Low-GI foods effectively control the rate of post-meal blood sugar rise and reduce blood sugar fluctuations, making them an important dietary choice for diabetics to stabilize blood sugar levels and reduce the risk of complications. For obese individuals, low-GI foods provide a longer-lasting feeling of fullness, reducing food intake and thus helping to control weight and avoid calorie accumulation caused by excessive consumption of high-GI foods. In terms of market prospects, in addition to traditional staple foods and snacks, a large number of low-GI products are now emerging in the beverage and meal replacement sectors.

[0007] Existing research on reducing the GI value of rice products mainly focuses on the following directions, and has obvious limitations: 1. Single lactic acid bacteria fermentation technology Existing research indicates that lactic acid bacteria fermentation can regulate starch structure and reduce digestibility by producing metabolites such as organic acids and extracellular polysaccharides (EPS). Fermenting rice flour with Lactobacillus plantarum and Lactobacillus rhamnosus can lower the GI value from around 82 to 71-76, but the GI-lowering effect is limited, remaining within the medium-high GI range (55-70), and not meeting the low-GI food standard (<55). Furthermore, single fermentation may result in an excessively sour taste and has a weak effect on improving the texture of rice crackers, easily leading to problems such as a hard or crumbly texture.

[0008] 2. Single dietary fiber fortification technology Rice bran dietary fiber (RBDF), as a natural functional component, lowers the glycemic index (GI). While existing technologies that directly add RBDF to rice flour can reduce digestibility to some extent, they have significant drawbacks: When the amount of RBDF added exceeds 5%, it will cause a significant increase in the hardness of the rice dough, making the rice biscuits rough in texture and poor in chewiness; the poor compatibility between dietary fiber and starch will easily lead to an increase in the product baking loss rate, affecting the product shape and yield.

[0009] 3. Co-fermentation of lactic acid bacteria and dietary fiber Some studies have attempted to combine lactic acid bacteria with dietary fiber, but no systematic process has been developed. The optimal synergistic ratio between the strain and RBDF is not clearly defined, and most fermentation is carried out with mixed strains, which leads to unstable metabolites and large fluctuations in GI values ​​(58-69). Therefore, this invention utilizes Lactobacillus paracasei in conjunction with rice bran dietary fiber (RBDF) fermentation to produce low-GI rice biscuits, which effectively slows down carbohydrate absorption, stabilizes postprandial blood sugar, provides a suitable dietary choice for people with diabetes and other individuals who need to control their blood sugar, and makes full use of rice bran by-products, thereby increasing the added value of grain processing, meeting the market demand for low-GI foods, and has broad application prospects. Summary of the Invention

[0010] The technical objective of this invention is to construct a starch digestion barrier through the synergistic fermentation of Lactobacillus paracasei and rice bran dietary fiber, thereby significantly reducing the glycemic index (GI value) of rice biscuits to below the low GI food standard (<55), while improving the product texture and taste, in order to solve the problem that traditional rice products are not suitable for people with blood sugar control due to their high GI value.

[0011] To achieve the above-mentioned objectives of this invention, the following technical solution is adopted: A method for preparing a low-GI fermented rice product includes the following steps: (1) Preparation of rice flour-rice bran dietary fiber mixed powder: Rice is ground into powder and mixed with rice bran dietary fiber (RBDF) to obtain mixed powder; (2) Preparation of bacterial fermentation broth: Lactobacillus paracasei was subjected to three-stage activation culture to obtain activated bacterial fermentation broth; (3) Fermentation: The fermentation liquid obtained in step (2) is inoculated into the mixture of mixed powder and water in step (1), and fermented at 35-37℃ for 20-24 hours to obtain fermented rice flour products; (4) Baking: After the above fermented rice product is shaped, it is baked for 12-13 minutes at top and bottom heat temperatures of 160℃ and 170℃ respectively to obtain the low-GI rice biscuit.

[0012] Preferably, in step (1), the mass ratio of rice flour to rice bran dietary fiber is 200g: (16-20)g, that is, the addition ratio of RBDF is 8%-10%.

[0013] Preferably, the preferred addition ratio of the rice bran dietary fiber (RBDF) is 8%, that is, the mass ratio of rice flour to RBDF is 200g:16g.

[0014] Preferably, in step (2), the three-stage activation culture conditions for *Lactobacillus paracasei* are as follows: *Lactobacillus paracasei* strain is first activated in liquid culture medium to obtain a first activated culture solution; the first activated culture solution is inoculated into liquid culture medium for a second activation culture to obtain a second activated culture solution; the second activated culture solution is inoculated into liquid culture medium for a third activation culture to obtain a third activated culture solution. During the first activation culture, the volume ratio of *Lactobacillus paracasei* strain to liquid culture medium is 1:100; the first activation culture condition is 37℃ for 24 h. During the second activation culture, the volume ratio of the first activated culture solution to liquid culture medium is 1:100; the second activation culture condition is 37℃ for 24 h. During the third activation culture, the volume ratio of the second activated culture solution to liquid culture medium is 1:100; the third activation culture condition is 37℃ for 24 h.

[0015] Further preferred, the fermented fiber liquid is freeze-dried to produce fermented fiber powder, which is used to prepare low-GI rice crackers.

[0016] Preferably, in step (3), the inoculation amount of the fermentation broth is 5% of the mass of the mixed powder.

[0017] Preferably, in step (3), the mass ratio of water to mixed powder is 3:1.

[0018] This invention also provides a low-GI rice biscuit, wherein the glycemic index (GI) of the rice biscuit is below 55. The resistant starch (RS) content of the rice biscuit is not less than 21.22%. The specific method for making the low-GI rice biscuit is as follows: Ingredients: butter, granulated sugar, baking powder, whole egg liquid; Steps: Soften the butter at room temperature until it becomes toothpaste-like, then beat it with an electric mixer until smooth. Gradually add the granulated sugar and baking powder, mixing well after each addition. Continue beating the butter until it turns white and increases in volume. Gradually add the beaten egg, continuing to beat until fluffy. Sift in the baking powder, fold it in with a spatula, and continue mixing until the dough is formed. Place the dough in a mold, shape it, refrigerate it, and after it sets, cut it into thin, even slices and place them on a baking tray. Preheat the oven and bake.

[0019] The fermented fiber powder prepared by this invention can be used to prepare low-GI rice crackers. The rice crackers prepared using this fermented fiber powder have high sensory scores, low GI and HI values, good digestibility and water retention, and can improve blood sugar control, regulate immunity and maintain intestinal barrier function.

[0020] Compared with the prior art, the present invention achieves the following technical effects: 1. Solve the problem of excessively high GI value in traditional rice crackers In existing technologies, rice biscuits are mostly made from unprocessed rice flour, whose starch structure is loose and easily digested, resulting in a GI value generally higher than 70. These are considered high-GI foods, and long-term consumption can cause rapid fluctuations in blood sugar, making them unsuitable for diabetics and those needing to control their blood sugar. This invention utilizes the synergistic fermentation of *Lactobacillus paracasei* and RBDF to construct a starch digestion barrier, significantly reducing the GI value of rice biscuits to below 55, meeting low-GI standards.

[0021] 2. Overcome the limitations of single fermentation or single addition of dietary fiber In existing technologies, while single-lactic acid bacteria fermentation can lower the GI value, the effect is limited. Using *Lactobacillus paracasei* alone for fermentation reduced the GI value from 84.44 to 72.32; however, simply adding RBDF leads to a harder texture and a rougher mouthfeel. This invention achieves both a lower GI value and improved texture through the synergistic effect of fermentation and dietary fiber, solving the problem of balancing functionality and taste.

[0022] 3. Optimize the functional components and processing performance of rice biscuits Existing rice crackers have low resistant starch (RS) content (typically below 10%) and are prone to aging during processing. This invention increases the RS content to 21.22% through synergistic fermentation, while reducing starch retrogradation value and enhancing anti-aging ability, thus solving the problems of traditional rice crackers having limited functionality and short shelf life.

[0023] 4. Provide low-GI rice biscuit production process This invention clarifies the optimal inoculum amount (5%) of Lactobacillus paracasei, the RBDF addition ratio (8%), fermentation conditions (37℃, 24h), and baking parameters (160 / 170℃, 12-13min for both top and bottom heat), thus solving the problems of ambiguous parameters and poor product stability in the production of low-GI rice biscuits.

[0024] This invention provides a method for making rice biscuits that combines low GI characteristics, excellent texture, and functional activity through component improvement (synergistic effect of Lactobacillus paracasei and RBDF) and process innovation (optimization of fermentation and baking parameters), thus meeting the market demand for health foods. Attached Figure Description

[0025] For ease of explanation, the present invention will be described in detail below with reference to specific embodiments and accompanying drawings.

[0026] Figure 1 A flowchart of a process for producing rice biscuits using Lactobacillus paracasei in synergistic fermentation with rice bran dietary fiber (RBDF).

[0027] Figure 2 Schematic diagram of the effect of Lactobacillus paracasei synergistic fermentation with RBDF on the starch hydrolysis rate of rice crackers.

[0028] Figure 3 A schematic diagram illustrating the effect of Lactobacillus paracasei synergistic fermentation with RBDF on the baking loss rate of rice crackers. The values ​​of different letters in the diagram represent statistically significant differences. P <0.05) Figure 4 Images of rice crackers made from four different ingredients: (a): RF; (b): G-RF; (c): RF-RBDF; (d): G-RF-RBDF.

[0029] Figure 5 A schematic diagram illustrating the effect of different lactic acid bacteria fermentation on the digestibility of rice flour.

[0030] Figure 6 Schematic diagram of the effect of Lactobacillus paracasei synergistically with RBDF on the starch hydrolysis rate of rice flour.

[0031] Figure 7 Schematic diagram of infrared spectral analysis of rice flour fermented with Lactobacillus paracasei and RBDF.

[0032] Figure 8 This is a schematic diagram illustrating the effect of Lactobacillus paracasei synergistic fermentation with RBDF on the crystal structure of rice flour. In the figure: (a): RF; (b): G-RF; (c): RF-RBDF; (d): G-RF-RBDF.

[0033] Figure 9 The microscopic morphology of starch granules in rice products under different treatment conditions. Detailed Implementation

[0034] The following are specific embodiments of the present invention, described in conjunction with the accompanying drawings, to further illustrate the technical solutions of the present invention. However, the present invention is not limited to these embodiments. Specific details, such as particular configurations, are provided in the following description merely to aid in a comprehensive understanding of the embodiments of the present invention. Therefore, those skilled in the art should understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present invention.

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0036] This invention utilizes Lactobacillus paracasei in conjunction with rice bran dietary fiber (RBDF) fermentation to produce rice biscuits, and compares four groups of rice biscuits: pure rice flour (RF), fermented rice flour (G-RF), fiber mixture powder (RF-RBDF), and fermented fiber mixture powder (G-RF-RBDF).

[0037] The preparation methods for the four groups of rice biscuits are as follows: 1. Beat 40g of butter at room temperature with an electric mixer until smooth and softened to a toothpaste-like consistency. 2. Gradually add 5g of granulated sugar and 1g of baking powder, mixing well after each addition. Continue beating the butter until it turns white and increases in volume. 3. Gradually add 30g of beaten eggs, continuing to beat until fluffy. 4. Sift in 100g of rice flour or mixed flour (add the corresponding flour product for each group), and fold in with a spatula until well combined. Continue mixing until a dough forms. 5. Shape the dough in a mold, refrigerate for 1 hour to set, then slice into evenly thin pieces and place on a baking sheet. 6. Preheat the oven to 160℃ (top heat) and 170℃ (bottom heat), and bake for 12-13 minutes.

[0038] Example 1 Determination of the digestibility, HI value, and GI value of fermented fiber biscuits Determination of digestibility: A standard glucose curve was plotted. 0.2 g of fermented fiber powder was dispersed in 10.0 mL of sodium acetate buffer solution. Then, 5 mL of preheated enzyme solution (37℃) was added, followed by a water bath with continuous shaking. After digestion, 1 mL of the hydrolysis product was collected and mixed with 5 mL of anhydrous ethanol to inactivate the enzyme. The mixture was centrifuged, and the supernatant was collected. DNS reagent was added, the mixture was heated in boiling water, cooled under running water, and then water was added. After mixing, the absorbance was measured at 540 nm. The hydrolysis rate was calculated.

[0039] Determination of HI and GI values: Using white biscuits as a control, the hydrolysis index (HI) and glycemic index (eGI) values ​​of the samples were calculated based on the curve of digestive characteristics determination.

[0040] Table 1. Effects of Lactobacillus paracasei synergistic fermentation with RBDF on the HI and GI values ​​of rice crackers.

[0041] The effect of Lactobacillus paracasei synergistic fermentation with RBDF on the starch digestibility of rice crackers in Example 1 is shown in the figure below. Figure 2 Table 1.

[0042] from Figure 2 As can be seen, the starch digestibility of G-RF, RF-RBDF and G-RF-RBDF is significantly lower than that of RF, showing the effect of reducing the digestibility of RF, among which G-RF-RBDF has the most obvious effect.

[0043] As shown in Table 1, compared with RF, the HI and GI values ​​of G-RF, RF-RBDF, and G-RF-RBDF were all significantly reduced. G-RF-RBDF had the most significant effect, reducing the HI and GI values ​​by 68.8% and 36.48%, respectively.

[0044] Example 2 Determination of RDS, SDS, and RS content in fermented fiber biscuits Determination of RDS, SDS, and RS content: Based on the determination of digestibility in Example 1, the contents of rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) were calculated.

[0045] Table 2. Effects of Lactobacillus paracasei synergistic fermentation with RBDF on RDS, SDS, and RS content in rice crackers.

[0046] Note: The numerical values ​​of different letters represent significant differences (P<0.05). The effects of Lactobacillus paracasei synergistic fermentation with RBDF on the RDS, SDS, and RS content of rice crackers in Example 2 are shown in Table 2.

[0047] As shown in Table 2, compared to RF, the RDS content of G-RF, RF-RBDF, and G-RF-RBDF was significantly reduced, while the SDS and RS contents were significantly increased (P<0.05). G-RF-RBDF had the lowest RDS content, decreasing by 32.84% compared to RF, while the SDS and RS contents increased significantly, by 16.10% and 153.83%, respectively. The RS content increased in the presence of RBDF. Adding RBDF alone also significantly reduced the RDS content of the rice crackers, with G-RF-RBDF showing the most significant reduction.

[0048] Example 3 Determination of textural properties of fermented fiber biscuits Determination of textural properties: The rice biscuit was cut into 2cm×2cm×2cm square pieces using a mold. In TPA mode, a P / 25 probe was used with the following parameters set: speed before, during and after the test: 1.0mm / s; compression degree: 40%; contact force: 5g; pressing distance: 7mm; probe pressure was maintained for 5s after pressing; compression was repeated twice with an interval of 5s between the two compressions.

[0049] Table 3. Effects of Lactobacillus paracasei synergistic fermentation with RBDF on the textural properties of rice crackers.

[0050] The effects of Lactobacillus paracasei synergistic fermentation with RBDF on the textural properties of rice crackers in Example 3 are shown in Table 3.

[0051] As can be seen from Table 3, the hardness and chewiness of the rice biscuits decreased significantly after fermentation, while their elasticity, cohesion, and resilience increased significantly. P<0.05). Hardness decreased by 37.73%, chewiness decreased by 26.55%, and elasticity, cohesion, and resilience increased by 24.53%, 21.67%, and 26.83%, respectively. Compared with RF, the addition of RBDF significantly increased the hardness and chewiness of rice crackers, while significantly decreasing elasticity, cohesion, and resilience. Hardness increased by 162.21%, chewiness increased by 176.45%, and elasticity, cohesion, and resilience decreased by 32.08%, 45.00%, and 29.27%, respectively. Compared with RF, G-RF-RBDF increased hardness by 56.76%, chewiness increased by 36.91%, and elasticity, cohesion, and resilience decreased by 15.09%, 10%, and 12.2%, respectively. Compared with RF-RBDF, G-RF-RBDF improved hardness, elasticity, chewiness, cohesion, and resilience.

[0052] Example 4 Determination of baking loss rate of fermented fiber biscuits Determination of baking loss rate: The baked rice biscuits were cooled at room temperature for 1 hour and their mass was measured. The baking loss rate was calculated based on the difference between the mass of the fresh dough and the mass of the baked biscuits.

[0053] The effect of Lactobacillus paracasei synergistic fermentation with RBDF on the baking loss rate of rice crackers in Example 4 is shown in the figure below. Figure 3 .

[0054] from Figure 3 As can be seen, the baking loss rate of G-RF is significantly lower than that of RF. Among the four types of rice biscuits, G-RF-RBDF has the lowest baking loss rate. The fermented RBDF has a more loose and porous microstructure and smaller particle size. This structural change helps to improve the dough structure of the mixed flours, making it more stable during baking and reducing moisture loss and volume shrinkage caused by loose structure.

[0055] Example 5 Determining the color difference of fermented fiber biscuits Color difference determination: The color of the rice dough and rice biscuits was measured using a colorimeter. The kneaded dough was rolled into a circular sheet with a thickness of 1 mm and a diameter of 4 mm, and air bubbles were removed from the surface. Color difference was measured on the dough at two different locations on both the dough and the biscuits to obtain the color difference index. L*, a*, b* value.

[0056] Table 4. Effects of Lactobacillus paracasei synergistic fermentation with RBDF on the color value of rice crackers.

[0057] The effects of Lactobacillus paracasei synergistic fermentation with RBDF on the color value of rice crackers in Example 5 are shown in Table 4 and . Figure 4 .

[0058] From Table 4 and Figure 4 As can be seen, lactic acid bacteria fermentation significantly alters the color value of rice crackers, making the rice crackers... L* The value decreased by 5.09%. a* Value and b* The values ​​increased by 36.77% and 1.20%. After adding RBDF, the rice biscuits... L* The value decreased by 18.06%. a* Value and b* The values ​​increased by 36.77% and 13.00%. G-RF-RBDF L* The value was significantly higher than that of RF-RBDF. L* The value increased by 10.37%. a* The value decreased by 27.6%, and b* The value decreased by 6.31%.

[0059] Example 6 Determining the sensory characteristics of fermented fiber biscuits Sensory characteristics were determined as follows: Ten cookies of uniform size and thickness were selected, baked, cooled, and placed on a plate for tasting. A sensory evaluation panel of ten professionally trained experts was formed, and the final result was the arithmetic mean of the scores from all experts. Cookies made from four different ingredients were tasted and scored on seven sensory indicators.

[0060] Table 5. Effects of Lactobacillus paracasei synergistic fermentation with RBDF on sensory properties of rice crackers

[0061] Note: The numerical values ​​of different letters represent significant differences. P <0.05) The effect of Lactobacillus paracasei synergistic fermentation with RBDF on the color value of rice crackers in Example 6 is shown in Table 5.

[0062] From Table 5 and Figure 4As can be seen, the co-fermented sample (G-RF-RBDF) achieved a comprehensive improvement in sensory evaluations, including aroma and taste, compared to the unfermented sample (RF-RBDF). Specifically, in terms of aroma, the score significantly increased from 10.14 to 16.52, an increase of 63.1%. This indicates that the mellow aroma and slightly acidic flavor produced by Lactobacillus paracasei fermentation effectively neutralized the raw bran taste of rice bran dietary fiber (RBDF), adding fragrance to the product. In terms of taste, the score jumped from 19.16 to 27.53, an increase of 43.7%. This suggests that the organic acids and amino acids produced during fermentation harmonized the taste defects caused by the single fiber, making the overall taste more mellow and harmonious. In addition, the taste score of G-RF-RBDF increased significantly by 96.8% (from 9.28 to 18.26), and the scores for texture and appearance also showed significant improvement, ultimately leading to an overall acceptance score soaring from 5.38 to 9.24. RF-RBDF received the lowest sensory score and had poor overall acceptability. Because RBDF itself is dark in color and has a certain grainy texture, it may result in a darker surface color and a rough, grainy texture on the biscuit, reducing its smoothness and affecting the sensory score of appearance. The total score of G-RF-RBDF increased by 20.43% and 55.83% compared to RF and RF-RBDF, respectively. This data fully demonstrates that the co-fermentation of Lactobacillus paracasei not only did not affect the flavor of the product due to the addition of RBDF, but also significantly improved the sensory quality of the rice biscuits through biotransformation.

[0063] Example 7 The effect of different lactic acid bacteria fermentation on the digestibility of rice flour Depend on Figure 5 As shown in Table 6, the starch hydrolysis rates of Q-RF, R-RF, S-RF, Z-RF, and G-RF were significantly reduced to varying degrees compared to before fermentation. G-RF showed the most significant reduction, with a 24.54% decrease in starch hydrolysis rate compared to RF at 180 min. Table 6 also shows that after fermentation, the HI value of G-RF decreased by 26.07% and the GI value decreased by 13.49% compared to RF, demonstrating a significantly higher GI reduction effect than the other four lactic acid bacteria.

[0064] (WB: White bread, RF: Rice flour, Z-RF: Lactobacillus plantarum fermented rice flour, Q-RF: Lactobacillus sakei fermented rice flour, S-RF: Lactobacillus rhamnosus fermented rice flour, G-RF: Lactobacillus paracasei fermented rice flour, R-RF: Lactococcus lactis fermented rice flour) Table 6. HI and GI values ​​of rice flour fermented with different lactic acid bacteria

[0065] Note: Values ​​with different letters in the same column represent significant differences. P <0.05) Example 8 Effect of RBDF addition on the digestibility of Lactobacillus paracasei fermented mixed rice flour The synergistic fermentation of lactic acid bacteria and RBDF significantly reduced the digestibility of rice flour. Figure 6 Table 7 shows that without the addition of RBDF, the GI value of RF-RBDF is close to that of a medium-GI food, but still falls within the high-GI range. When RBDF is added at 2%, 4%, and 6% and fermented with rice flour, the rice flour reaches a medium-GI range (56 < GI value < 69). When the addition reaches 8% and 10%, the rice flour reaches a low-GI range (GI value < 55). With the addition of RBDF, the GI value shows a gradual decreasing trend.

[0066] Table 7. Effects of Lactobacillus paracasei synergistic with RBDF on HI and GI values ​​of rice flour.

[0067] Note: The numerical values ​​of different letters represent significant differences. P <0.05) Example 9 Influence of Lactobacillus paracasei synergistic with RBDF fermentation on the infrared spectrum of rice flour Depend on Figure 7 It can be known that 2930 cm -1 and 1653 cm -1 The presence of absorption peaks at 2930 cm⁻¹ indicates the presence of starch-lipid complexes in the sample. This is further confirmed by fermentation, the addition of RBDF, and synergistic effects. -1 and 1653 cm -1 The increased absorption peak intensity at this point indicates an increase in the complex, which can reduce digestibility. The concentration at 1147 cm⁻¹ after fermentation, addition of RBDF, and synergistic effects... -1 1010cm -1 and 1073 cm -1 The increased peak intensity of the COC stretching vibration and the increased peak intensity of the COC stretching vibration indicate that the two, along with their synergistic effect, increased the glycosidic bonds in starch. This may be due to metabolic acids and enzymes promoting rearrangement or the formation of new cross-linked structures in starch molecules, thereby enhancing the absorption peak of the COC bond. This could allow starch molecular chains to reconnect through glycosidic bonds, leading to an increase in chain length, an increase in the degree of polymerization of starch molecular chains, and the formation of a more ordered structure.

[0068] Example 10 Effects of Lactobacillus paracasei synergistic fermentation with RBDF on the crystal structure of rice flour like Figure 8As shown, diffraction peaks at 15°, 17°, 18°, 20° (2θ), and 23° were present in all samples, indicating the presence of A+V hybrid crystal structures in all samples. This suggests that the characteristic peak positions of starch remained unchanged under the combined effects of lactic acid bacteria fermentation, the addition of RBDF, and the synergistic effect of both, and did not significantly affect the starch crystal structure. The relative crystallinity of G-RF and G-RF-RBDF increased by 19.96% and 26.38% respectively compared to RF, representing increases 3.35 times and 4.43 times that of RF-RBDF. The significant increase in relative crystallinity of G-RF-RBDF compared to G-RF is attributed to RBDF providing a fermentation substrate for Lactobacillus paracasei, leading to an increase in its metabolites, particularly short-chain amylopectin, thus significantly increasing the crystalline region. The structure of fermented RBDF becomes looser, and the formation of starch-lipid complexes and polysaccharide-starch complexes by amylose and lipids easily fills the loose structure of RBDF, making the G-RF-RBDF structure more compact and thus significantly increasing its relative crystallinity.

[0069] Example 11 Microstructure of rice flour fermented with Lactobacillus paracasei and RBDF Unfermented starch granules have a smooth surface, regular shape, clear edges, and are evenly dispersed without obvious cracks or damage. Rice flour granules are loosely piled together, such as... Figure 9 As shown in (a), after fermentation, the starch granules become irregular in shape, with blurred edges, and their structure is altered, as shown in [the diagram]. Figure 9 As shown in (b). After the addition of RBDF, the starch granules adhere to the fibrous material, intertwining with or adhering to the surface of the original rice flour granules, as shown in [example]. Figure 9 As shown in (c). Figure 9 As shown in (d), when lactic acid bacteria fermentation and RBDF work synergistically, starch granules aggregate more tightly, forming larger aggregates. The fibrous structure of RBDF may bind tightly to starch granules through physical entanglement or electrostatic interactions and hydrogen bonds, forming a uniform composite system. The overall microstructure becomes more compact, reducing the hydrolytic effect of enzymes on starch and increasing the content of SDS and RS.

[0070] Those skilled in the art to which this application pertains may modify or supplement the specific embodiments described or use similar methods to replace them, but without departing from the inventive concept of this application or exceeding the scope defined by the appended claims.

Claims

1. A method for preparing a low-GI fermented rice product, characterized in that, Includes the following steps: (1) Preparation of rice flour-rice bran dietary fiber mixed powder: Rice is ground into powder and mixed with rice bran dietary fiber (RBDF) to obtain mixed powder; (2) Preparation of bacterial fermentation broth: Lactobacillus paracasei was subjected to three-stage activation culture to obtain activated bacterial fermentation broth; (3) Fermentation: The fermentation liquid obtained in step (2) is inoculated into the mixture of mixed powder and water in step (1), and fermented at 35-37℃ for 20-24 hours to obtain fermented rice products.

2. The method according to claim 1, characterized in that, It also includes a baking step: after shaping the fermented dough, bake it for 12-13 minutes at top and bottom heat temperatures of 160℃ and 170℃ respectively to obtain fermented rice flour food.

3. The method according to claim 1, characterized in that, In step (1), the mass ratio of rice flour to rice bran dietary fiber is 200g: (16-20)g.

4. The method according to claim 3, characterized in that, The proportion of added rice bran dietary fiber is 8%, which means the mass ratio of rice flour to RBDF is 200g: 16g.

5. The method according to claim 1, characterized in that, In step (2), the three-stage activation culture conditions for the Lactobacillus paracasei are: cultured in liquid culture medium at 37°C for 24 hours; and the inoculum amount for each activation stage is 1:100 by volume.

6. The method according to claim 1, characterized in that, In step (3), the inoculation amount of the fermentation broth is 5% of the mass of the mixed powder.

7. The method according to claim 1, characterized in that, In step (3), the mass ratio of water to mixed powder is 3:

1.

8. A low-GI rice biscuit prepared by the method according to any one of claims 1-7, characterized in that, The rice biscuits have a glycemic index (GI) value of less than 55.

9. The low-GI rice biscuit according to claim 7, characterized in that, The resistant starch (RS) content of the rice biscuits is not less than 21.22%.

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