Low-GI fermented puffed rice bar and preparation method thereof

Abstract

The invention relates to the technical field of food processing, in particular to a preparation method and quality characteristics of a low-GI fermented puffed rice stick, and the preparation method comprises the following steps: by taking black rice No. 3 as a raw material, comparing the influences of different processing modes (primary processing (ultrasonic wave, microwave, extrusion recombination and fermentation) and deep processing (puffing, baking and cooking)) on the GI value of the rice; the low-GI fermented puffed rice bar is prepared by adopting a low-GI value'primary processing + deep processing 'mode, and the optimal process conditions are determined; according to the method for preparing the optimized fermented puffed rice bar formula, compared with unprocessed raw materials, the low-GI fermented puffed rice bar with the optimal formula is subjected to physicochemical property and nutritional ingredient detection so as to comprehensively evaluate the quality of the product.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, and more particularly to a convenient and healthy food with low glycemic index (GI) and its preparation method. Background Technology

[0002] Currently, the development of low glycemic index (GI) rice foods mainly relies on physical processing techniques and the compounding of functional ingredients. Chinese invention patent (CN102805315A) discloses a "method for preparing puffed snack foods using rice." This method optimizes the screw speed (250-300 r / min) and puffing temperature (122±2℃), combined with the addition of flour adjuvants (30-50%) and emulsifiers (sucrose fatty acid esters, 0.2-0.5%), to achieve starch structure reorganization, reducing the product's GI value to below 55.

[0003] However, the shortcomings of the existing technologies are as follows: their core processes rely on sodium bicarbonate soaking pretreatment and single extrusion puffing technology, failing to effectively utilize the deep degradation of starch molecules by microbial fermentation, resulting in a limited reduction in the product's GI value (only 10-15%). Furthermore, existing methods rely on post-seasoning for flavor improvement, failing to introduce natural sweeteners (such as mogrosides) into the formulation to balance the need for blood sugar reduction with the taste experience. In addition, the selection of auxiliary materials is limited to flour blends, neglecting the addition of micron-sized rice bran and its synergistic effect with the fermentation process, thus failing to leverage the synergistic blood sugar-reducing value of dietary fiber and micronutrients. Therefore, there is an urgent need to develop a composite process integrating bio-fermentation, precise formulation, and extrusion puffing to overcome the current technological bottlenecks. Summary of the Invention

[0004] To address the shortcomings of existing low-GI rice products, which rely on a single extrusion puffing technology, lack microbial fermentation leading to limited blood sugar-lowering efficiency, and lack of synergistic effects from natural sweeteners and functional excipients, this invention proposes a low-GI fermented puffed rice bar and its preparation method that integrates bio-fermentation and extrusion puffing processes. By deeply regulating starch structure through microbial fermentation and combining precise formula design, the product's nutrition, flavor, and blood sugar-lowering performance are simultaneously optimized.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0006] In a first aspect, the present invention provides a method for preparing low-GI fermented puffed rice sticks, characterized by comprising the following steps:

[0007] (1) Rice flour preparation: threshing rice to obtain brown rice, grinding it through a 100-mesh sieve to obtain rice flour with uniform particle size;

[0008] (2) Fermentation process: Weigh rice flour, add 10-25% (preferably 15%) of micronized bran and 0.01-0.04% (preferably 0.03%) of mogroside, and adjust the moisture content to 13-16% (preferably 15%); use Lactobacillus plantarum as a starter culture, adding 0.5-2% (preferably 1%), and ferment at 37℃ for 3-12 hours (preferably 6 hours) to obtain fermented rice flour with deep starch degradation;

[0009] (3) Extrusion process: Adjust the moisture content of fermented rice flour to 16%, and extrude it using a twin-screw extruder with a barrel temperature of 110-140℃ (preferably 120℃) and a screw speed of 200-230r / min (preferably 220r / min). The resulting extruded rice sticks are dried at 45℃ for 12 hours until the moisture content is ≤14%, and then passed through a 100-mesh sieve.

[0010] Secondly, this invention provides a low-GI fermented puffed rice stick, characterized by being prepared using the aforementioned method. Through fermentation with *Lactobacillus plantarum*, starch molecules are deeply degraded (e.g., increasing β-sheet structure and reducing β-turn content), combined with the puffing process to disrupt the ordered structure of starch. Compared to the unfermented puffing process, the GI value is reduced by more than 30%. Micronized bran provides dietary fiber and γ-oryzanol, while mogrosides replace synthetic sweeteners, improving palatability and nutritional value while lowering blood sugar. The fermentation temperature (37℃), time (3-12h), and puffing parameters (temperature 110-140℃, rotation speed 200-230r / min) form a wide-range adjustable process window, suitable for large-scale production.

[0011] Through the above technical solutions, this invention establishes a systematic process path from microbial fermentation regulation and starch structure recombination to synergistic optimization of nutrition and flavor. It can effectively achieve deep degradation and structural recombination of starch molecules, and elucidate the mechanism by which the synergistic effect of fermentation and puffing enhances the blood sugar reduction performance. This provides a new process paradigm for the industrial production of low-GI rice products that combines high blood sugar reduction efficiency, excellent palatability, and nutritional balance. Attached Figure Description

[0012] Figure 1 GI values ​​of rice samples under different processing methods;

[0013] Figure 2 The results of single-factor optimization of the fermentation and puffing rice stick process;

[0014] Figure 3 Response surface plots and contour plots of the interaction between various factors for process optimization and the overall score;

[0015] Figure 4 Single-factor results for optimizing the fermented puffed rice stick formula;

[0016] Figure 5Response surface plots and contour plots of the interaction of various factors in formula optimization on the overall score;

[0017] Figure 6 FTIR images of fermented puffed rice sticks and unprocessed original samples;

[0018] Figure 7 The gelatinization characteristics of fermented puffed rice sticks and unprocessed original samples;

[0019] Figure 8 The rheological properties of fermented puffed rice sticks and unprocessed samples were compared. Detailed Implementation

[0020] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0021] The raw material used in this invention is rice flour. By comparing the effects of different processing methods on the GI value of rice, the most suitable process conditions were selected. The co-processing method of fermentation and puffing was used to optimize the processing conditions of fermented puffed rice sticks by considering the effects of the amount of starter culture, fermentation time, puffing screw speed, and puffing temperature on the GI value. The influence of ultra-micron bran, mogrosides, and moisture content in the fermented puffed rice stick formula on the overall score was also analyzed to optimize the formula, which helps in the development of functional foods and improves resource utilization efficiency. The results show that the fermented puffed rice sticks prepared by this invention using a combined "primary processing + deep processing" method have the advantage of a lower GI value compared to single processing methods.

[0022] In this invention, unless otherwise specified, the experimental reagents and materials used are all conventional experimental reagents and materials in the art, which can be obtained commercially or prepared using conventional methods. Unless otherwise specified, the experimental methods used in this invention are all conventional experimental methods in the art.

[0023] In this invention, the "Yanghei No. 3" black rice was purchased from Qingyang Town, Shangzhi City, Heilongjiang Province, and is of food grade.

[0024] The experimental equipment involved in this invention is as follows: a centrifuge, model LH-300M, purchased from Qingdao Yijin Biotechnology Co., Ltd.; and a Fourier transform infrared spectrometer, model PerkinElmer UATR Two.

[0025] The following instruments were purchased from PerkinElmer Enterprise Management (Shanghai) Co., Ltd.: Automatic Kjeldahl nitrogen analyzer, model K9840, from Shandong Haineng Scientific Instruments Co., Ltd.; Rheometer, model MCR302e, from Anton Paasche Trading Co., Ltd.; Centrifugal thresher, model LH-300M, from Qingdao Yijin Biotechnology Co., Ltd.; Halogen moisture analyzer, model SN-SH-10A, from Shanghai Shangpu Instrument Equipment Co., Ltd.; Laser diffraction particle size analyzer, model S3500, from Macchiato Inc. (USA); Ultrasonic cleaner, model SB-5200D, from Ningbo Xinzhi Biotechnology Co., Ltd.; Twin-screw extruder, model LW-35, from Shandong Liwei Microwave Equipment Co., Ltd.; Microwave oven, model WD800G, from Foshan Shunde Galanz Microwave Oven Appliances Co., Ltd.; Electric oven, model T3-L326B, from Guangdong Midea Kitchen Appliances Manufacturing Co., Ltd.

[0026] The following is a description through specific embodiments.

[0027] Example 1

[0028] This embodiment compares the effects of fermentation puffing technology on the GI value of rice with traditional processing methods (ultrasound, microwave, extrusion, etc.), verifying the technical advantages of fermentation puffing technology in deeply regulating starch structure and significantly reducing GI value, thus providing data support for the industrial application of low-GI fermented puffed rice bars. The specific steps are as follows:

[0029] 1.1 Sample Preparation

[0030] Preparation of rice flour: The rice sample was threshed to obtain brown rice. The brown rice sample was then ground using a grinder and passed through a 100-mesh sieve to obtain rice flour with uniform particle size. The prepared rice flour sample was placed in a sealed bag and stored at -20℃, labeled Y3-0, for subsequent processing.

[0031] 1.2 Experimental methods for different rice processing methods

[0032] (1) Ultrasonic processing includes the following steps: Weigh 100g of rice flour and mix it with 250mL of distilled water. After thorough stirring, seal and let stand (25℃, 10min). Then, perform ultrasonic treatment (25℃, 240W, 30min), stirring every 15min and changing the cooling water to maintain a constant temperature. After treatment, the suspension is centrifuged (4000r / min, 10min) to collect the precipitate, frozen for 24h, and then freeze-dried. The final sample is ground into powder, labeled Y3-1-U, and stored at 4℃ for later use.

[0033] (2) Microwave processing includes the following steps: Weigh 500g of rice flour and pour it into a beaker. Microwave at 3.0kW for 60s. After cooling to room temperature, grind it again through a 100-mesh sieve, put it into a sealed bag, label it Y3-1-M, and store it at 4℃ for later use.

[0034] (3) The extrusion and reorganization process includes the following steps: extrusion and reorganization are carried out using a twin-screw extruder with a moisture content of 22%, a barrel temperature of 80℃, and a screw speed of 220 r / min. The extruded reorganized rice is aged at room temperature for 2 hours, then placed in a 45℃ oven for 12 hours to dry until the moisture content is below 14%. It is then ground through a 100-mesh sieve, packed into sealed bags, labeled Y3-1-CZ, and stored at 4℃ for later use.

[0035] (4) The fermentation process includes the following steps: Select Lactobacillus plantarum as the starter culture, add 2% starter culture, and ferment at 37°C. Ferment rice flour: Weigh 100g of rice flour, mix it with water at a ratio of 1:2, add 2% starter culture, ferment at 37°C for 12 hours, air dry for 2 days, grind it through a 100-mesh sieve, pack it into a sealed bag, label it as Y3-1-FJ, and store it at 4°C for later use.

[0036] (5) The puffing process includes the following steps: puffing is carried out using a twin-screw extruder with a moisture content of 16%, a barrel temperature of 120℃, and a screw speed of 200 r / min. The extruded puffed rice sticks are placed in a 45℃ oven and dried for 12 hours until the moisture content is below 14%. They are then ground through a 100-mesh sieve, packed into sealed bags, labeled Y3-2-PH, and stored at 4℃ for later use.

[0037] (6) The baking process includes the following steps: Spread the rice flour sample evenly on a metal baking tray covered with aluminum foil, controlling the thickness of the spread to 2 mm. Use top and bottom heating mode, set the baking temperature to 180℃ and preheat for 3 minutes. Then place the sample in the middle rack of the oven and bake for 10 minutes, stirring every 2 minutes to ensure even heating. After baking, allow it to cool naturally to room temperature, grind it through a 100-mesh sieve, seal and store it. The sample number is Y3-2-BK, and it should be stored at 4℃ for later use.

[0038] (7) The steaming and cooking process includes the following steps: Accurately weigh 100g of rice flour sample, add 1.5 times its weight of distilled water, pregelatinize at 95℃ for 10min, and steam in a steamer for 15min. Transfer to a petri dish, seal with plastic wrap, freeze for 24h, and freeze-dry. Grind the dried sample into powder using a mortar and pestle, seal in a self-sealing bag, label it as Y3-2-ZZ, and store at 4℃ for later use.

[0039] 1.3 Determination of GI value of rice processed by different methods

[0040] The specific experimental steps are as follows: Accurately weigh 0.200g of rice sample and white bread control sample, mix with 5mL of sodium acetate buffer (pH 7.0), and heat in a 95℃ constant temperature water bath for 20min to allow for complete gelatinization. After naturally cooling to room temperature, add α-amylase and saccharifying enzyme sequentially to concentrations of 300U / mL and 20U / mL, respectively, and carry out enzymatic hydrolysis under a 37℃ constant temperature shaking water bath. Maintain uniform shaking during the reaction to ensure complete enzymatic hydrolysis. The 3,5-dinitrosalicylic acid (DNS) method was used to determine the glucose equivalent (DE) at different time points (0, 10, 20, 30, 60, 90, 120, and 180min). The specific operation is as follows: Centrifuge the enzymatically hydrolyzed mixture at 5000rpm for 5min, take the supernatant and react it with DNS chromogenic reagent, place it in a 100℃ boiling water bath for color development, and heat in a boiling water bath for 10min. After color development, the absorbance of the solution was immediately measured at a characteristic wavelength of 510 nm using a UV-Vis spectrophotometer

[74] , and the DE value was calculated. A hydrolysis kinetic curve was established, and the area under the curve (AUC) was obtained by integral method to determine the hydrolysis index (HI). Finally, the GI value of the sample was calculated based on the established mathematical model. To ensure the reliability of the experimental results, all samples were measured three times.

[0041] The calculation formula is as follows:

[0042] HI = AUC 样品 / AUC 参考 ×100% Formula (1)

[0043] GI = 39.71 + 0.549 × HI (Formula 2)

[0044] In the formula: HI is the hydrolysis index; AUC is the area under the curve calculated from the sample hydrolysis rate curve; GI is the glycemic index; 39.71 and 0.549 are constants and coefficients for calculating the GI value.

[0045] 1.4 Analysis of GI values ​​of rice under different processing methods

[0046] The GI values ​​of rice under different processing methods are as follows: Figure 1 As shown, microwave treatment and fermentation treatment in primary processing significantly reduced the GI value of rice (p<0.01), while puffing treatment was the processing method with the lowest GI value among the three deep processing methods.

[0047] Example 2

[0048] 2.1 Experimental Methods

[0049] Fermentation and puffing rice stick process

[0050] Fermented rice flour: Weigh rice flour, select Lactobacillus plantarum as the starter culture, ferment at 37℃, select a certain amount of starter culture and fermentation time to ferment the rice flour to obtain fermented rice flour, grind it through a 100-mesh sieve, put it into a sealed bag and store at 4℃ for later use.

[0051] Extrusion: Extrusion is carried out using a twin-screw extruder. The moisture content of the fermented rice flour is adjusted to 16%, and a certain barrel temperature and screw speed are set to obtain fermented and extruded rice sticks.

[0052] 2.2 Data Processing and Analysis

[0053] Experimental results are expressed as mean ± standard deviation. All experiments were repeated three times under the same conditions. Excel 2016 was used for data analysis, Design Expert 13.0 was used for response surface methodology, Origin 2024 was used for plotting, and SPSS 26.0 was used for analysis of variance.

[0054] 2.3 Single-factor experimental design and results analysis

[0055] (1) Effect of fermentation time on the GI value of fermented puffed rice sticks

[0056] With a fixed inoculum concentration of 2%, the screw speed during the puffing process was set to 200 r / min, and the puffing temperature was set to 120℃. The effects of different fermentation times (3h, 6h, 9h, 12h) on the GI value of fermented puffed rice sticks were investigated.

[0057] (2) Effect of inoculum concentration on the GI value of fermented puffed rice sticks

[0058] The fermentation time was fixed at 6 hours, the screw speed during the puffing process was set at 200 r / min, and the puffing temperature was set at 120℃. The effects of different inoculum concentrations (0.5%, 1%, 1.5%, and 2%) on the GI value of fermented puffed rice sticks were investigated.

[0059] (3) Effect of screw speed on the GI value of fermented puffed rice sticks

[0060] The fermentation time was fixed at 6 hours, the inoculum concentration was 1%, and the puffing temperature was set at 120℃. The effects of different screw speeds (200, 210, 220, 230 r / min) on the GI value of fermented puffed rice sticks were investigated.

[0061] (4) Effect of extrusion temperature on the GI value of fermented puffed rice sticks

[0062] The fermentation time was fixed at 6 hours, the inoculum concentration was 1%, and the screw speed during the puffing process was set at 200 r / min. The effect of different extrusion temperatures (110, 120, 130, 140℃) on the GI value of fermented puffed rice sticks was investigated.

[0063] (5) Univariate results analysis

[0064] The effects of fermentation time, inoculum concentration, puffing screw speed, and puffing temperature on the GI value of fermented puffed rice sticks are as follows: Figure 2 As shown, the fermentation time was 6 hours. Figure 2 (a) Fermentation agent addition amount 1.0% ( Figure 2 (b) Screw speed 220 r / min Figure 2 (c) Expansion temperature 120℃ Figure 2 (d) represents the best single-factor result for fermented puffed rice sticks, with a GI value of 41.94 ± 0.03.

[0065] To further explore the optimal process conditions for fermented puffed rice sticks, response surface methodology was conducted using fermentation time (5, 6, 7 h), inoculum concentration (0.8, 1.0, 1.2%), screw speed (210, 220, 230 r / min), and extrusion temperature (125, 130, 135 ℃) as factors.

[0066] Based on the results of the single-factor experiments, the optimal parameter ranges were selected as follows: fermentation time, optimally 6 hours; yeast addition amount, optimally 1.0%; screw speed, optimally 220 r / min; and extrusion temperature, optimally 120℃.

[0067] 2.4 Response Surface Optimization Experimental Design and Result Analysis

[0068] (1) Process optimization Box-Behnken experimental design and results

[0069] Based on the results of the single-factor experiments, the GI value was selected as the response value. Then, the effects of fermentation time (A), inoculum concentration (B), puffing screw speed (C), and puffing temperature (D) on fermented puffed rice sticks were investigated. The experimental results are shown in Table 1.

[0070] Table 1. Box-Behnken Experimental Design and Results for Process Optimization

[0071]

[0072] (2) Establishment of regression model and significance analysis

[0073] Using GI as the response value, the response surface methodology was used to perform regression fitting on Table 1, resulting in the quadratic polynomial regression equation GI = 42.33 + 0.69A + 1.17B - 1.05C - 1.54D + 0.305AB + 0.515AC - 0.2AD - 1.08BC - 0.575BD + 0.6825CD + 4.32A² + 2.88B² + 3.46C² + 3.08D².

[0074] The significance of the model was tested, and the results of the analysis of variance are shown in Table 2.

[0075] Table 2 Regression Model and Analysis of Variance

[0076]

[0077]

[0078] Note: * indicates a significant difference (P < 0.05); ** indicates a highly significant difference (P < 0.01).

[0079] Table 2 shows that the model P < 0.0001, indicating a highly significant difference; the lack-of-fit term P = 0.224 > 0.05 in the regression equation, indicating no significant difference; R² = 0.9916, with a good fit > 90%, indicating that the model can explain the changes in response values ​​well, the theoretical values ​​and actual values ​​have a good fit, the experimental error is small, the correlation is high, and the data is authentic. Therefore, this equation can be used to analyze the experimental results. The order of influence on the comprehensive score is D > B > C > A. The significance of the interaction of each factor on the comprehensive score is BC > CD > BD > AC > AB > AD; A, B, C, D, BC, BD, and CD have highly significant effects, AC has a significant effect, and AB and AD have no significant effects.

[0080] To further verify the mechanism of the interaction terms among the influencing factors, the contour lines and response surfaces obtained from the quadratic model can be used to evaluate the strength of the interaction between the experimental factors and determine the optimal level range for each factor. The contour lines and response surfaces illustrating the interaction of each factor are shown below. Figure 3 As shown.

[0081] (3) Determining the optimal conditions and validating the regression model

[0082] The optimal conditions for this model were obtained using Design Expert software: fermentation time 5.9924 h, inoculum concentration 0.9686%, screw speed 221.111 r / min, and puffing temperature 131.1℃, with a predicted GI value of 41.986. Considering the limitations of actual operating conditions, the optimal conditions were modified to a fermentation time of 6 h, inoculum concentration of 0.97%, screw speed 220 r / min, and puffing temperature 131℃. Under these conditions, the overall score of the fermented puffed rice sticks produced was 41.89 ± 0.25, which is close to the 41.986 predicted by the established regression model. This indicates that the model can predict the GI value of fermented puffed rice sticks well, the mathematical model is reliable, has high credibility, and is feasible to a certain extent.

[0083] Example 3

[0084] Using rice flour, mogrosides, and ultra-micronized bran as raw materials, fermented rice flour was prepared according to the process optimization results in Example 2, with a fermentation time of 6 hours, a starter culture concentration of 1%, a puffing screw speed of 220 r / min, and a puffing temperature of 130°C. Then, puffed rice sticks were prepared. The optimal fermented puffed rice stick formula was determined by comprehensive scoring and determination of nutritional components.

[0085] 3.1 Sample Preparation

[0086] The rice bran obtained by dehulling "Yanghei No. 3" rice is pulverized into ultra-micro bran and passed through a 300-mesh sieve.

[0087] Fermented rice flour was prepared according to the process optimization results. The moisture content of the fermented rice flour was adjusted with mogroside solution and distilled water to achieve the expected proportion of mogroside. Ultra-micron bran was added in proportion.

[0088] The fermented rice flour was puffed using a twin-screw extruder, with the moisture content adjusted to 14%. The barrel temperature and screw speed were set according to the process optimization results. The extruded fermented rice sticks were dried in a 45℃ oven for 12 hours, ground through a 100-mesh sieve, packaged in sealed bags, labeled, and stored at 4℃ for later use.

[0089] 3.2 Data Processing and Analysis

[0090] Experimental results are expressed as mean ± standard deviation. All experiments were repeated three times under the same conditions. Excel 2016 was used for data analysis, Design Expert 13.0 was used for response surface methodology, Origin 2024 was used for plotting, and SPSS 26.0 was used for analysis of variance.

[0091] 3.3 Single-factor experimental design and results analysis of fermented puffed rice stick formulation

[0092] (1) Effect of ultra-micron bran addition on the overall score of fermented puffed rice sticks:

[0093] The moisture content of the fermented rice flour was fixed at 14%, and the amount of mogroside added was 0.02%. The effect of the amount of ultra-micron bran added (10%, 15%, 20%, 25%) on the overall score of fermented puffed rice sticks was investigated.

[0094] (2) Effect of mogroside addition on the overall score of fermented puffed rice sticks:

[0095] The moisture content of the fermented rice flour was fixed at 14%, and the amount of ultra-micron bran added was 15%. The effects of different amounts of mogroside added (0.01%, 0.02%, 0.03%, and 0.04%) on the overall score of the fermented puffed rice sticks were investigated.

[0096] (3) Effect of moisture content on the overall score of fermented puffed rice sticks:

[0097] With a fixed amount of mogroside added at 0.03% and an amount of ultra-micronized bran added at 15%, the effects of different moisture contents (13%, 14%, 15%, and 16%) on the overall score of fermented puffed rice sticks were investigated.

[0098] The comprehensive scoring criteria are shown in Table 3. Ten food science students (male to female ratio of 1:1) were randomly selected as comprehensive evaluation evaluators to evaluate the products.

[0099] Table 3 Comprehensive Evaluation Table

[0100]

[0101] (4) Univariate results analysis

[0102] The effects of ultra-micron bran addition, mogroside addition, and moisture content on the overall score of fermented puffed rice sticks are as follows: Figure 4 As shown in the figure. Analysis shows that the optimal single-factor results for the fermented puffed rice stick formula are 15% ultrafine bran addition, 0.03% mogroside addition, and 15% moisture content, with a comprehensive score of 85.82±0.78. To further explore the optimal formula conditions for fermented puffed rice sticks, the addition amounts of ultrafine bran (14%, 15%, 16%), mogroside addition (0.025%, 0.03%, 0.035%), and moisture content (14.5%, 15.0%, 15.5%) were selected as factors for corresponding surface experiments.

[0103] 3.4 Response Surface Optimization Experimental Design and Result Analysis

[0104] (1) Process optimization Box-Behnken experimental design and results

[0105] Based on the results of the single-factor experiments, the comprehensive score was selected as the response value (Y) to investigate the effects of the amount of ultra-micron bran added (A), the amount of mogroside added (B), and the moisture content (C) on fermented puffed rice sticks. The experimental results are shown in Table 4.

[0106] Table 4. Box-Behnken Experimental Design and Results for Formulation Optimization

[0107]

[0108] (2) Establishment of regression model and significance analysis

[0109] Using the comprehensive score (Y) as the response value, the response surface methodology was used to perform regression fitting on Table 4, resulting in the quadratic polynomial regression equation Y = 88.1 + 1.1125A + 1.8125B + 0.775C - 0.8AB + 0.525AC + 0.975BC - 5.125A² - 2.925B² - 4.25C².

[0110] The significance of the model was tested, and the results of the analysis of variance are shown in Table 5.

[0111] Table 5 Regression Model and Analysis of Variance

[0112]

[0113]

[0114] Note: * indicates a significant difference (P < 0.05); ** indicates a highly significant difference (P < 0.01).

[0115] Table 5 shows that the model P < 0.0001, indicating a highly significant difference; the lack-of-fit term P = 0.5438 > 0.05 in the regression equation indicates no significant difference; R² = 0.9913, with a good fit > 90%, indicating that the model can explain the changes in response values ​​well, the theoretical values ​​and actual values ​​have a good fit, the experimental error is small, the correlation is high, and the data is authentic. Therefore, this equation can be used to analyze the experimental results. The order of influence on the comprehensive score is B > A > C, and the significance of the interaction of factors on the comprehensive score is BC > AB > AC; the effects of A, B, and C are highly significant, the effects of AB and BC are significant, and the effect of AC is not significant.

[0116] To further verify the mechanism of the interaction terms among the influencing factors, the contour lines and response surfaces obtained from the quadratic model can be used to evaluate the strength of the interaction between the experimental factors and determine the optimal level range for each factor. The contour lines and response surfaces illustrating the interaction of each factor are shown below. Figure 5 As shown.

[0117] (3) Determination of the optimal formulation and validation of the regression model

[0118] The optimal conditions for this model were obtained using Design Expert software: 15.09% ultrafine rice bran, 0.032% mogroside, and 15.07% moisture content, with a predicted comprehensive score of 88.492. Considering the limitations of actual operating conditions, the optimal conditions were modified to 15.1% ultrafine rice bran, 0.032% mogroside, and 15.1% moisture content. Under these conditions, the comprehensive score of the fermented puffed rice sticks produced was 88.47 ± 0.3, which is close to the sensory score of 88.492 predicted by the established regression model. This indicates that the model can predict the comprehensive score of fermented puffed rice sticks well, the mathematical model is reliable, has high credibility, and is feasible to a certain extent.

[0119] 3.5 Quality determination of fermented rice sticks

[0120] (1) FTIR determination of fermented puffed rice sticks

[0121] Take 0.5-2.0 mg of starch sample and mix it evenly with KBr powder. Place it in a Fourier transform infrared spectrometer for full-band scanning. The infrared spectrometer scanning range is 4000-450 cm-1, and the scanning rate is 4 cm-1. The absorbance values ​​at 1047 cm-1, 1022 cm-1 and 995 cm-1 are obtained after baseline correction and deconvolution.

[0122] (2) Determination of gelatinization characteristics of fermented puffed rice sticks

[0123] A starch solution (12%, w / v) was prepared. The torque was measured at 700 cmg. The heating program was used to heat the solution from 50°C to 95°C at a rate of 10°C / min, hold for 3 min, and then cool it to 50°C at the same heating rate, hold for 2 min. The peak viscosity (PV), trough viscosity (TV), breakdown viscosity (BDV), final viscosity (FV), setback viscosity (SBV), peak time (PT), and peak temperature (Tp) were measured.

[0124] (3) Determination of rheological properties of fermented puffed rice sticks

[0125] The samples were placed on the MCR rheometer testing platform for rheological frequency scanning analysis to determine gel strength. A PP50 probe was used, with a pre-test speed of 0.5 mm / s, a test speed of 5.0 mm / s, a compression distance of 1.00 mm, a trigger force of 5.0 g, and a compression interval of 2 s. The ratios of G′ and G″ to the frequency were collected.

[0126] (4) Determination of nutritional composition of fermented puffed rice sticks

[0127] Energy detection shall be performed in accordance with GB / Z 21922-2008;

[0128] Protein content was determined according to Method I of GB 5009.5-2016;

[0129] Fat content was determined according to Method II of GB 5009.6-2016;

[0130] Carbohydrate content is referenced to GB / Z 21922-2008;

[0131] Sodium content testing shall be performed in accordance with GB 5009.91-2017, Method III.

[0132] 3.6 Quality Results and Analysis of Fermented Rice Sticks

[0133] (1) FTIR results analysis of fermented puffed rice sticks:

[0134] Table 6 Secondary structural composition of fermented puffed rice sticks and unprocessed original samples

[0135]

[0136] surface Figure 6 As shown in Table 6, after fermentation and puffing treatment, the β-sheet content of fermented puffed rice sticks increased (41.75% → 46.14%), while the β-turn content decreased (21.96% → 15.37%). Therefore, it can be inferred that the fermentation and puffing rice stick processing method can reduce the GI value of rice, resulting in rice products with the lowest GI.

[0137] (2) Analysis of the gelatinization characteristics of fermented puffed rice sticks:

[0138] A comparison of the gelatinization characteristics of fermented puffed rice sticks and unprocessed rice sticks, along with relevant data, is shown in Table 7. Figure 7 As shown in the figure. The results indicate that fermented puffed rice sticks significantly reduced the peak viscosity of rice flour, loosened the starch granule structure, reduced the orderliness of the starch structure, and lowered the GI value.

[0139] Table 7 Gelatinization characteristics of fermented puffed rice sticks and unprocessed rice sticks

[0140]

[0141] (3) Determination of rheological properties of fermented puffed rice sticks

[0142] The rheological properties of fermented puffed rice sticks and unprocessed rice sticks are as follows: Figure 8 As shown. Figure 8It can be seen that the internal interaction forces of the low-GI fermented puffed rice stick sample are weakened, indicating that the fermentation and puffing processing methods affect the crystal structure of rice starch granules, and the decomposition of large molecular particles into small molecular particles, resulting in a weakening of the internal interaction forces of the sample and a loose internal structure of rice. This reduces the formation of aggregates of starch, protein and fat, and further lowers the GI value of the original sample.

[0143] (4) Nutritional composition of fermented puffed rice sticks

[0144] The results of the optimization through response surface methodology were as follows: fermentation time of 6 h, inoculum concentration of 0.97%, screw speed of 220 r / min, puffing temperature of 131℃, ultra-micron bran addition of 15.1%, mogroside addition of 0.032%, and moisture content of 15.1%. Fermented puffed rice sticks were then produced, and the basic nutritional components of the finished product were tested. The data are shown in Table 8.

[0145] Table 8 Nutritional composition of fermented puffed rice sticks

[0146]

[0147] The significance of producing fermented puffed rice sticks lies in obtaining low-GI processed rice foods. Therefore, the GI value of the finished product was tested and compared with unprocessed rice samples. The GI value of unprocessed rice was 49.19±3.48, while the GI value of the low-GI fermented puffed rice sticks produced using the optimal process and formula obtained through response surface methodology was reduced to 42.09±3.31 (<55), a decrease of 7.1 compared to unprocessed rice. This effectively lowered the GI value, meeting the standards for low-GI foods, and thus can be called low-GI fermented puffed food, providing a scientific basis for the development of low-GI foods.

[0148] In summary, the fermented puffed rice sticks prepared using the "primary processing + deep processing" method with a low GI value have a low GI value.

[0149] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing low-GI fermented puffed rice sticks, characterized in that, Includes the following steps: (1) Preparation of rice flour: The rice sample was threshed to obtain brown rice sample; then, the brown rice sample was ground using a grinder and passed through a 100-mesh sieve to obtain rice flour with uniform particle size. (2) Preparation of fermented puffed rice sticks: Fermented rice flour: Weigh rice flour, add 10-25% micronized bran, add 0.01-0.04% mogroside, and adjust the moisture content to 13-16%. Use Lactobacillus plantarum as the starter culture, ferment at 37℃, add 0.5-2% starter culture, and ferment for 3-12 hours to obtain fermented rice flour; Extrusion: Extrusion is carried out using a twin-screw extruder. The moisture content of the fermented rice flour is adjusted to 16%, and the barrel temperature is set to 110-140℃, and the screw speed is set to 200-230 r / min. The extruded fermented rice sticks are placed in a 45℃ oven and dried for 12 hours until the moisture content is below 14%, and then ground through a 100-mesh sieve.

2. The method for preparing low-GI fermented puffed rice sticks according to claim 1, characterized in that, The amount of micronized bran added is 15%.

3. The method for preparing low-GI fermented puffed rice sticks according to claim 2, characterized in that, The amount of mogroside added is 0.03%.

4. The method for preparing low-GI fermented puffed rice sticks according to claim 3, characterized in that, The moisture content is 15%.

5. The method for preparing low-GI fermented puffed rice sticks according to claim 4, characterized in that, The fermentation time is 6 hours.

6. The method for preparing low-GI fermented puffed rice sticks according to claim 5, characterized in that, The amount of fermenting agent added is 1.0%.

7. The method for preparing low-GI fermented puffed rice sticks according to claim 6, characterized in that, The screw speed is 220 r / min.

8. The method for preparing low-GI fermented puffed rice sticks according to claim 7, characterized in that, The barrel temperature is 120°C.

9. A low-GI fermented puffed rice stick, characterized in that, Prepared using the preparation method described in any one of claims 1-8.

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