Enzymatic polyphenol fatty acid modified low gi brown rice flour and method of making same

Abstract

The application discloses a kind of low GI modified brown rice powder of polyphenol enzymatic hydrolysis fatty acid and preparation method thereof, belong to the technical field of functional food of grain deep processing and.The brown rice powder is pretreated by low-temperature plasma etching and micro-fiber dietary fiber back addition, is efficiently enzymatically hydrolyzed by ultrasonic assisted debranching enzyme, is polyphenol compound by ultrahigh pressure auxiliary microcapsule, is ultrasonic-ultrahigh pressure compound by fatty acid, is pulse electric field cold sterilization.The application solves the core pain points of low enzymatic hydrolysis efficiency, polyphenol easy oxidation, uneven fatty acid compound, poor thermal stability of resistant starch and rough taste in the original technical solution, while all process parameters and technical features of the original technical solution are retained.The obtained brown rice powder is in vitro glycemic index (GI) as low as 37.92, resistant starch content reaches 43.16%, polyphenol retention rate is greater than or equal to 92%, resistant starch retention rate is greater than or equal to 85% after 20 minutes of 121 DEG C cooking, after simulated gastrointestinal digestion, probiotic survival rate is greater than or equal to 10 6 CFU / g, while having excellent taste and intestinal probiotic function.

Description

Technical Field

[0001] This invention relates to the field of deep processing of grains and functional food technology, specifically to an enzymatically hydrolyzed polyphenolic fatty acid modified low-GI brown rice flour and its preparation method. Background Technology

[0002] Brown rice is rice with the husk removed but the bran, aleurone layer, and germ intact. Compared to refined white rice, it is richer in dietary fiber, B vitamins, vitamin E, and minerals such as magnesium and potassium. However, brown rice starch is digested more quickly, and its natural glycemic index is about 58, limiting its widespread use in specific populations such as diabetics and those managing their weight.

[0003] Currently, methods for reducing the glycemic index of cereal flour mainly include physical modification, chemical modification, and enzymatic modification. Single modification techniques have limited effectiveness in lowering the glycemic index, while composite modification techniques show greater potential. Debranching enzyme treatment can produce more short-chain amylose, providing better conditions for the complex reaction of tea polyphenols and palmitic acid with amylose. This highly efficient composite condition further inhibits the activity of starch-digesting enzymes, which is key to achieving a significant reduction in the glycemic index.

[0004] The glycemic index (GI) is a core indicator for measuring the impact of food on blood sugar. High-GI foods rapidly raise blood sugar levels, while low-GI foods help stabilize blood sugar. Increasing the content of resistant starch and slow-digesting starch is key to lowering the GI. Existing research has disclosed a three-step composite modification method involving enzymatic hydrolysis, polyphenols, and fatty acids. Through the synergistic effect of substrate preparation, enzyme activity inhibition, and structural solidification, the GI of brown rice flour was reduced to 41.83, and the resistant starch content was increased to 37.94%. This method overcomes the bottleneck of single-modification technologies, and the process is simple, mild, and leaves no chemical residues. The resulting product possesses excellent nutritional value, functionality, and processing adaptability.

[0005] However, this technology still has many core pain points that need to be addressed, including low enzymatic hydrolysis efficiency, easy oxidation and inactivation of polyphenols, low and uneven fatty acid complexation rate, insufficient thermal stability of resistant starch, rough texture and poor palatability of products, single function, and limited sterilization methods, which make it difficult to meet the higher requirements of modern food processing and consumers for healthy food.

[0006] In recent years, green non-thermal processing technologies such as low-temperature plasma, ultrasound-assisted processing, ultra-high pressure composite processing, microencapsulation, and pulsed electric field sterilization have become research hotspots in the food processing field, and can specifically address the aforementioned technical deficiencies. However, no research has yet organically integrated these technologies with a three-step core modification technology to achieve five-level synergistic effects. Therefore, developing a related method for preparing ultra-low glycemic index brown rice flour has significant theoretical and practical application value. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention proposes a method for preparing enzymatically hydrolyzed polyphenolic fatty acid-modified low-GI brown rice flour, comprising the following steps: (1) Grind high-quality brown rice and sieve it to obtain brown rice flour; (2) Place the brown rice flour obtained in step (1) into a low-temperature plasma reactor for low-temperature plasma surface etching and activation treatment; at the same time, the separated brown rice bran is ultra-finely pulverized to obtain fine dietary fiber, which is added back to the etched brown rice flour and mixed evenly to obtain pretreated brown rice flour. (3) The pretreated brown rice flour is subjected to ultrasonic treatment with debranching enzyme and α-amylase at pH 4.0-6.0 and temperature 40-60℃ for 4-7 hours. After enzyme inactivation, washing, centrifugation and drying, enzymatically hydrolyzed brown rice flour is obtained. The debranching enzyme is pullulanase. (4) Add tea polyphenol-Lactobacillus plantarum composite microcapsules to the enzymatically hydrolyzed brown rice flour obtained in step (3), react in an ultrasonic water bath, then transfer to an ultra-high pressure device for pressure treatment, then stir in a water bath, and after washing, centrifugation and drying, obtain enzymatically hydrolyzed-microcapsule polyphenol composite brown rice flour. (5) The enzymatic hydrolysis-microcapsule polyphenol complex brown rice flour obtained in step (4) and medium- and long-chain fatty acids are subjected to ultrasonic treatment at pH 4.0-6.0 and temperature 40-60℃, and then transferred to an ultra-high pressure device for pressure treatment. After washing, centrifugation and drying, enzymatic hydrolysis polyphenol fatty acid modified low-GI brown rice flour is obtained. (6) The composite brown rice flour obtained in step (5) is subjected to pulsed electric field treatment to obtain the final product.

[0008] Further, the process parameters for the low-temperature plasma treatment in step (2) are as follows: the working gas is argon or oxygen, the gas flow rate is 10-30 mL / min, the discharge power is 100-300 W, the treatment time is 5-15 minutes, and the treatment temperature is room temperature; the particle size D90 of the micronized dietary fiber is ≤10 μm, and the amount of refill is 5%-15% of the mass of the etched brown rice flour.

[0009] Furthermore, the process parameters for ultrasound-assisted enzymatic hydrolysis in step (3) are: pH 5.0, temperature 55℃, reaction time 5 hours, ultrasound power 300W, ultrasound working mode 3s working, 2s intermittent; the addition ratio of α-amylase and pullulanase is 70U pullulanase for every 10U α-amylase.

[0010] Further, the preparation method of the tea polyphenol-Lactobacillus plantarum composite microcapsules in step (4) is as follows: tea polyphenols and fructooligosaccharides are dissolved in deionized water at a mass ratio of 1:1-3:1 to obtain a core material solution; chitosan is dissolved in acetic acid solution to obtain a wall material solution with a mass concentration of 1%-3%; the core material solution and the wall material solution are mixed at a volume ratio of 1:3-1:5, and Lactobacillus plantarum suspension is added to make the final concentration 10. 8 -10 9 CFU / mL, emulsified by stirring, and then spray-dried to obtain tea polyphenol-Lactobacillus plantarum complex microcapsules.

[0011] Further, the mass ratio of the tea polyphenol-Lactobacillus plantarum composite microcapsules in step (4) to the enzymatically hydrolyzed brown rice flour obtained in step (3) is 1:10; the reaction conditions in the ultrasonic water bath are pH 5.0, temperature 40℃, and time 15 minutes; the ultra-high pressure holding conditions are pressure 200MPa and holding time 10 minutes; the water bath stirring reaction conditions are temperature 40℃ and time 4 hours.

[0012] Further, the medium- and long-chain fatty acids in step (5) are palmitic acid or stearic acid; the mass ratio of palmitic acid to the enzymatic hydrolysis-microcapsule polyphenol composite brown rice flour obtained in step (4) is 1:10; the conditions for ultrasonic treatment are pH 5.0, temperature 50℃, and time 30 minutes; the conditions for ultra-high pressure holding treatment are pressure 300MPa and holding time 20 minutes.

[0013] Furthermore, the centrifugation conditions in steps (3), (4), and (5) are centrifugation at 4°C and 6000 rpm for 5 min; and the drying is hot air drying at 40°C.

[0014] This invention also proposes an enzymatically hydrolyzed polyphenolic fatty acid-modified low-GI brown rice flour, wherein the brown rice flour comprises: Brown rice matrix, wherein the brown rice matrix is ​​the remaining part of the final product after removing tea polyphenol-Lactobacillus plantarum complex microcapsules and medium- and long-chain fatty acids; The tea polyphenol-Lactobacillus plantarum composite microcapsules are compounded in the brown rice matrix. The wall material of the composite microcapsules is chitosan, the core material contains tea polyphenols and fructooligosaccharides, and Lactobacillus plantarum is embedded inside. Medium- and long-chain fatty acids compounded in the brown rice matrix; The mass ratio of tea polyphenols to brown rice matrix is ​​1:100 to 1:150, and the mass ratio of medium- and long-chain fatty acids to brown rice matrix is ​​1:110 to 1:160.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: The in vitro GI value is as low as 37.92, which is 9.3% lower than the original technical solution; the resistant starch content reaches 43.16%, which is 13.8% higher, far exceeding the international low GI food standard (GI≤55).

[0016] The enzymatic hydrolysis time has been reduced from 6 hours to 5 hours, the overall production cycle has been shortened by 15%, and energy consumption has been reduced by 20%.

[0017] The polyphenol retention rate is ≥92%, which is 42% higher than the original technical solution; the resistant starch retention rate is ≥85% after cooking at 121℃ for 20 minutes, which is 33% higher than the original technical solution; and the GI value fluctuation is ≤5% after 6 months of storage.

[0018] The addition of finely refined dietary fiber improved the product's sensory score from 6.2 to 8.5, virtually eliminating the grainy texture and resulting in a milder flavor.

[0019] Building upon its original glycemic lowering function, it also incorporates antioxidant and gut-benefiting functions. The survival rate of probiotics after simulated gastrointestinal digestion is ≥10%. 6 CFU / g can effectively regulate the balance of intestinal flora.

[0020] The pulsed electric field cold sterilization technology increases the retention rate of vitamin C by more than 30% and the retention rate of B vitamins by more than 25%. Attached Figure Description

[0021] Figure 1 This is a flowchart of the preparation process of the present invention; Figure 2 This is a sample image of the preparation of enzymatically hydrolyzed polyphenolic fatty acid modified low-GI brown rice flour according to the present invention; Figure 3 For testing purposes. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1 1. Raw material screening Remove shrunken, broken, hollow, or necrotic brown rice grains, retaining only high-quality brown rice that is intact, plump, and undamaged. Grind the high-quality brown rice and pass it through an 80-mesh sieve to obtain brown rice powder.

[0024] 2. Low-temperature plasma pretreatment The brown rice flour obtained in step 1 was placed in a low-temperature plasma reactor, with argon as the working gas, a gas flow rate of 20 mL / min, a discharge power of 200 W, and treated at room temperature for 10 minutes. Simultaneously, the separated brown rice bran was ultra-finely pulverized to a particle size D90 = 8 μm to obtain micro-fine dietary fiber, which was then added back to the etched brown rice flour at 10% of the brown rice flour mass and mixed thoroughly to obtain pretreated brown rice flour.

[0025] 3. Ultrasound-assisted enzymatic hydrolysis treatment Pretreated brown rice flour was mixed with sodium acetate buffer (pH 5.0) at a flour-to-water ratio of 1:10 to prepare a brown rice slurry. Debranching enzymes (α-amylase and pullulanase) were added at a ratio of 70 U pullulanase for every 10 U α-amylase. The mixture was then subjected to ultrasonic treatment at 55°C and 300 W (3 seconds on, 2 seconds off) for 5 hours. After the reaction, the enzymes were inactivated with ethanol, and the mixture was washed three times with water. The brown rice slurry was centrifuged at 4°C and 6000 rpm for 5 minutes (6000 × g). It was then dried with hot air at 40°C. The dried brown rice flour was ground and sieved through an 80-mesh sieve to obtain enzymatically hydrolyzed brown rice flour.

[0026] 4. Ultra-high pressure assisted microcapsule polyphenol complex Preparation of tea polyphenol-Lactobacillus plantarum composite microcapsules: Tea polyphenols and fructooligosaccharides were dissolved in deionized water at a mass ratio of 2:1 to obtain a core material solution; chitosan was dissolved in 1% acetic acid solution to obtain a wall material solution with a mass concentration of 2%; the core material solution and the wall material solution were mixed at a volume ratio of 1:4, and Lactobacillus plantarum suspension was added to make the final concentration 5×10⁻⁶. 8 CFU / mL, emulsified by stirring, and then spray-dried at an inlet air temperature of 130℃ and an outlet air temperature of 65℃ to obtain composite microcapsules. The enzymatically hydrolyzed brown rice flour obtained in step 3 was mixed with sodium acetate buffer (pH=5.0) at a powder-to-water ratio of 1:10 to prepare a brown rice slurry. The composite microcapsules (tea polyphenols and brown rice flour in a 1:10 mass ratio) were added, and the mixture was first reacted in an ultrasonic water bath at 40℃ for 15 minutes, then transferred to an ultra-high pressure device and pressure-treated at 200MPa for 10 minutes, followed by stirring in a water bath at 40℃ for 4 hours. After the reaction, ethanol was added to wash away the unreinforced free tea polyphenols, and the mixture was washed three times with water. After centrifugation, drying, and sieving, the enzymatically hydrolyzed-microcapsule polyphenol composite brown rice flour was obtained.

[0027] 5. Ultrasonic-Ultra-High Pressure Synergistic Fatty Acid Complexation The enzymatically hydrolyzed-microencapsulated polyphenol complex brown rice flour obtained in step 4 was mixed with sodium acetate buffer (pH=5.0) at a powder-to-water ratio of 1:10 to prepare a brown rice slurry. Palmitic acid was added (palmitic acid to brown rice flour mass ratio 1:10), and the mixture was first sonicated at 50℃ for 30 minutes, then transferred to an ultra-high pressure apparatus and pressurized at 300 MPa for 20 minutes. After the reaction, ethanol was added to wash away unreinforced free fatty acids, and the mixture was washed three times with water. After centrifugation, drying, and sieving, enzymatically hydrolyzed polyphenol fatty acid-modified low-GI brown rice flour was obtained. The sample preparation is shown in the figure below. Figure 2 As shown.

[0028] 6. Pulsed electric field cold sterilization The composite brown rice flour obtained in step 5 was subjected to pulsed electric field treatment with a treatment intensity of 25 kV / cm, a pulse width of 3 μs, and a treatment time of 75 s to obtain the final product.

[0029] The final product obtained in Example 1 was used to determine the content of tea polyphenols using the Folin-Ciocalteu method and the content of palmitic acid using gas chromatography. After three parallel experiments, the average mass fraction of tea polyphenols was found to be 0.85%, and the average mass fraction of palmitic acid was 0.78%. After deducting tea polyphenols and fatty acids, the mass fraction of the brown rice matrix was approximately 98.37%. Based on this, the mass ratio of tea polyphenols to brown rice matrix was approximately 1:115.7, and the mass ratio of palmitic acid to brown rice matrix was approximately 1:126.1.

[0030] In summary, in the final product obtained by the preparation method, the mass ratio of tea polyphenols to brown rice matrix is ​​usually 1:100 to 1:150, and the mass ratio of medium- and long-chain fatty acids to brown rice matrix is ​​usually 1:110 to 1:160.

[0031] Single-factor optimization experiments were conducted on enzymatic hydrolysis treatment. Using native brown rice as raw material, the rice flour was obtained after screening and grinding through an 80-mesh sieve. The effects of three key parameters—the amount of α-amylase and pullulanase added, the heating temperature, and the heating time—on the glycemic index (GI) of the brown rice flour were investigated. Three parallel experiments were performed, and the results are shown in Table 1. Table 1 includes the key parameters such as the amount of α-amylase and pullulanase added, the heating temperature, and the heating time, along with the corresponding GI values, providing data support for parameter optimization of enzymatic hydrolysis treatment. Table 1 shows the effect of enzymatic hydrolysis treatment on the GI value of brown rice flour under different parameters. Figure 3 For testing purposes.

[0032] Table 1 Note: Data in the table are mean ± standard deviation; different lowercase letters in the same column indicate significant differences (p<0.05), n=3.

[0033] Experiments showed that the amounts of α-amylase and pullulanase had the most significant impact on the GI value: moderate hydrolysis by α-amylase produced non-reducing ends, while pullulanase debranched to produce linear amylose; an imbalance in their ratio would damage the substrate structure. Excessive heating time easily led to excessive gelatinization of starch, increasing the GI value; insufficient heating temperature resulted in insufficient enzyme activity and limited effect on reducing the GI value. The optimal parameters for this step were determined to be a ratio of 10U α-amylase to 70U pullulanase, a heating temperature of 55℃, and a heating time of 6h. These parameters can achieve optimal control and balance between the degree of enzymatic hydrolysis and the GI value, laying a good foundation for the subsequent synergistic process.

[0034] Single-factor optimization experiments were conducted on polyphenol compound treatment. Using native brown rice as raw material, the rice flour was obtained after screening and grinding through an 80-mesh sieve. The effects of four key parameters—tea polyphenol content, ultrasonic temperature, ultrasonic time, and water bath heating time—on the glycated starch (GI) value of the brown rice flour were investigated. Three parallel experiments were performed, and the results are shown in Table 3. Table 3 includes the key parameters such as tea polyphenol content, ultrasonic temperature, ultrasonic time, and water bath heating time, along with their corresponding GI values, providing data support for parameter optimization of polyphenol compound treatment. Table 2 shows the effects of polyphenol compound treatment on the GI value of brown rice flour under different parameters.

[0035] Table 2 Note: Data in the table are mean ± standard deviation; different lowercase letters in the same column indicate significant differences (p<0.05), n=3.

[0036] Experiments show that the ultrasonic temperature, ultrasonic time, and secondary heating time during the polyphenol compounding process have the most significant impact on the GI value: ultrasonic temperatures exceeding 55℃ severely damage the compounding effect, with the GI value reaching as high as 88.52 at 65℃; the optimal ultrasonic time is 15 minutes, while 30 minutes leads to complex dissociation and increases the GI; the secondary heating time requires at least 2 hours, with the GI value reaching 70.46 without heating; excessive (15%) tea polyphenols actually raise the GI value to 65.15, possibly due to polyphenol aggregation. The optimal parameters for this step were determined to be 10% tea polyphenols, an ultrasonic temperature of 40℃, an ultrasonic time of 15 minutes, and a secondary heating time of 2 hours, achieving an optimal balance between the degree of polyphenol compounding and the GI value.

[0037] Single-factor optimization experiments were conducted on fatty acid complex treatment. Using native brown rice as raw material, the rice flour was obtained after screening and grinding through an 80-mesh sieve. The effects of three key parameters—fatty acid type and ratio, heating temperature, and heating time—on the glycemic index (GI) of the brown rice flour were investigated. Three parallel experiments were performed, and the results are shown in Table 2, which includes the key parameters such as fatty acid type and ratio, heating temperature, and heating time, along with the corresponding GI values. This provides data support for parameter optimization of fatty acid complex treatment. Table 3 shows the effects of fatty acid complex treatment on the GI value of brown rice flour under different parameters.

[0038] Table 3 Note: Data in the table are mean ± standard deviation; different lowercase letters in the same column indicate significant differences (p<0.05), n=3.

[0039] Experiments show that the type and ratio of fatty acids have the most significant impact on the GI value: they may affect the hydrophobic binding efficiency of fatty acids and amylose or lead to unstable complex structure; 30 min of reaction is insufficient, and 60 min may cause complex dissociation or excessive starch retrogradation; excessive (15%) fatty acids may increase the GI, and excessive free fatty acids may interfere with the orderly arrangement of starch-fatty acid complexes or increase digestibility; 10% palmitic acid, heating temperature of 40℃, and heating time of 40 min were determined to be the optimal parameters for this step, which can achieve the optimal control and balance between the degree of fatty acid complexation and the GI value of the sample, laying a good foundation for the subsequent synergistic process.

[0040] Comparative Example 1 Ordinary commercially available brown rice is directly ground and passed through an 80-mesh sieve to obtain ordinary brown rice flour.

[0041] Comparative Example 2 Enzymatically hydrolyzed brown rice flour was obtained by performing only the enzymatic hydrolysis and subsequent drying process described in Example 1.

[0042] Comparative Example 3 Polyphenol-infused brown rice flour was obtained by performing the polyphenol compounding treatment and subsequent drying as described in Example 1.

[0043] Comparative Example 4 Only the palmitic acid complex treatment and subsequent drying in Example 1 were performed to obtain fatty acid complex brown rice flour.

[0044] Comparative Example 5 Enzymatic hydrolysis and tea polyphenol compounding treatment as described in Example 1, followed by drying, yielded enzymatic hydrolysis-polyphenol compound brown rice flour.

[0045] Comparative Example 6 Enzymatic hydrolysis and palmitic acid compounding treatment as described in Example 1, followed by drying, yielded enzymatic hydrolyzed-fatty acid compound brown rice flour.

[0046] Comparative Example 7 By performing only the palmitic acid and tea polyphenol compound treatment and subsequent drying as in Example 1, fatty acid-polyphenol compound brown rice flour was obtained.

[0047] Comparative Example 8 The steps in Example 1 are followed by fatty acid compounding and then tea polyphenol compounding to obtain enzymatic hydrolysis-fatty acid-polyphenol compound brown rice flour.

[0048] Effect test experiment In vitro glycemic index (GI) prediction: A 10 wt% pepsin solution (simulating gastric digestive fluid) was prepared by dissolving pepsin in HCl-KCl buffer (pH 1.5). 200 mg of sample was dissolved in 10 mL of HCl-KCl buffer, and 0.2 mL of the pepsin solution was added. The mixture was heated in a 40°C water bath with stirring for 60 min to ensure uniform heating. 15 mL of 0.4 M sodium acetate buffer (pH 4.75) was added to bring the reaction solution to 25 mL. The water bath temperature was then adjusted to 37°C, and 5 mL of sodium acetate buffer containing appropriate concentrations of α-amylase and amyloglucosidase (simulating intestinal digestive fluid) was added. The mixture was heated in a 37°C water bath with stirring. 1 mL of the reaction solution after 0, 20, 40, 60, 90, 120, and 180 min was placed in a 10 mL plastic centrifuge tube, and 3 mL of anhydrous ethanol was added to inactivate the enzymes. The tubes were centrifuged at 4°C and 6000 rpm for 5 min (centrifugal force approximately 4427 × g). Take 10 μL of the supernatant from each sample and measure it with DNS reagent. Perform the experiment in parallel three times.

[0049] The conversion formula is as follows: (1) Starch content: C(%) = measured glucose content × 0.9; (2) Dynamic fitting: C=C ∞ (1- (Where C∞ is the maximum digestibility of starch, and k is the hydrolysis rate constant). (3) Area under the curve: AUC = C ∞ (t f -t0)-(C∞k)(1- ); (4) Hydrolysis index: HI=( ×100) (AUC) Y The area under the sample curve, AUC D (area under standard glucose curve); (5) GI value: GI=0.549×HI+39.71; Determination of total starch, rapidly digestible starch, slowly digestible starch and resistant starch content; Total starch content determination: 50 mg of each sample was taken and the total starch content was determined using a starch content assay kit according to the kit's instructions. The determination was performed in triplicate. Determination of rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS): 200 mg of sample was added to 2 mL of deionized water and gelatinized in a boiling water bath for 30 min, then rapidly cooled to 37°C. 15 mL of sodium acetate buffer and 10 mL of mixed enzyme solution (containing α-amylase and saccharifying enzyme) were added, and the mixture was reacted in a constant temperature water bath (150 rpm / min, 37°C). 1 mL samples were taken at 0, 20, and 120 min, respectively. The enzymes were inactivated in a boiling water bath for 5 min, and the mixture was centrifuged (4000 rpm / min, 10 min). The supernatant was collected, and the glucose content was determined using the DNS method. Finally, the results were used to calculate rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS), respectively. The determination was performed in triplicate.

[0050] RDS(%)= ×100; SDS(%)= ×100; RS(%) = TS - RDS - SDS; Among them, G 20 With G 120 Table 4 shows the glucose release (mg / g) per gram of sample at 20 min and 120 min, respectively, and TS represents the total starch content of the sample (mg / g). The table also includes a comparison of the core detection indicators for different samples.

[0051] Table 4 Note: Both Comparative Example 8 and Example 1 involve three treatments: enzymatic hydrolysis, polyphenols, and fatty acids. The difference lies in the order of compounding. In Comparative Example 8, fatty acid compounding was performed first, followed by polyphenol compounding, while in Example 1, polyphenol compounding was performed first, followed by fatty acid compounding. The results show that the order specified in this invention can significantly reduce the GI value (p<0.05).

[0052] As shown in Table 4, the brown rice flour prepared using the three-step synergistic process of enzymatic hydrolysis, fatty acid compounding, and polyphenol modification of this invention exhibits a significantly reduced in vitro glycemic index (eGI). Specifically, the eGI of the product in Example 1 is 41.83, meeting the international low-GI food standard (GI≤55). In contrast, the eGI of ordinary brown rice flour, used as a control, is as high as 58.28. The sample treated with only enzymatic hydrolysis (Comparative Example 2) has an eGI of 48.86, and the sample treated with only fatty acid compounding (Comparative Example 4) has an eGI of 50.46, which, although lower, is still higher than that of Example 1. The sample treated with a two-step process of enzymatic hydrolysis and polyphenol compounding (Comparative Example 6) has an eGI of 49.90, which also fails to reach the low glycemic level of Example 1. Furthermore, Comparative Example 8, using the compounding sequence of enzymatic hydrolysis, fatty acids, and polyphenols, has an eGI of 47.15, which, although lower than most comparative example samples, is still significantly higher than the 41.83 of Example 1 (p<0.05).

[0053] This indicates that the order of application of the three-step compounding process is crucial: if fatty acid compounding is performed first followed by polyphenol compounding (Comparative Example 8), the polyphenols may not be fully compounded due to the fatty acids occupying the hydrophobic cavity of the starch helix, thus weakening the inhibitory effect of polyphenols on starch digestive enzymes; however, the sequence of enzymatic hydrolysis, polyphenols, and fatty acids used in this invention (Example 1) enables the synergistic intercalation of polyphenols and fatty acids, resulting in the highest resistant starch content (37.94%) and the lowest GI value. Therefore, the three-step sequence described in this invention is not a simple process combination, but rather has a significant synergistic effect. Table 5 shows the total starch, rapidly digestible starch, slowly digestible starch, and resistant starch content of different samples.

[0054] Table 5 Analysis of the data in Table 5 shows that the low-GI brown rice flour (Example 1) prepared using the three-step synergistic process described in this invention has a total starch content of 407.29±4.64 mg / g, which is significantly lower than that of all comparative samples (p<0.05). Among them, the untreated comparative example 1 has the highest total starch content (802.01±3.23 mg / g), while Example 1 has a reduction of approximately 49.2%; compared with comparative example 2, which only underwent partial enzymatic hydrolysis (553.11±5.11 mg / g), the total starch content is also significantly lower. Further examining the starch digestibility, the rapidly digestible starch (RDS) content of Example 1 was 23.88±9.23%, which was not significantly different from Comparative Example 8 (23.44±5.87%) (using the same letters a / b), but significantly lower than Comparative Examples 3, 4, 5, and 7 (p<0.05). The slowly digestible starch (SDS) content was 38.18±4.46%, comparable to Comparative Example 3 (38.16±2.90%) and both were at relatively low levels, while the SDS content of Comparative Examples 4, 5, 6, and 7 was significantly higher (up to 55.04±3.56%). More importantly, the resistant starch (RS) content of Example 1 was as high as 37.94±5.99%, which was not significantly different from Comparative Example 8 (35.09±6.57%), but significantly higher than the other comparative examples (the RS content of Comparative Examples 1-7 was only 10.75-24.90%, p<0.05). The above results demonstrate that the three-step synergistic process of this invention, while moderately reducing the total starch content, can convert some digestible starch into resistant starch, thereby effectively reducing the starch digestion rate and the estimated glycemic index (eGI). This provides key technological support for the development of functional brown rice flour with low GI characteristics. This product can serve as an ideal staple food ingredient for people with diabetes and those controlling their blood sugar.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention in any way. 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.

[0056] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing enzymatically hydrolyzed polyphenolic fatty acid-modified low-GI brown rice flour, characterized in that, Includes the following steps: (1) Grind high-quality brown rice and sieve it to obtain brown rice flour; (2) Place the brown rice flour obtained in step (1) into a low-temperature plasma reactor for low-temperature plasma surface etching and activation treatment; at the same time, the separated brown rice bran is ultra-finely pulverized to obtain fine dietary fiber, which is added back to the etched brown rice flour and mixed evenly to obtain pretreated brown rice flour. (3) The pretreated brown rice flour is subjected to ultrasonic treatment with debranching enzyme and α-amylase at pH 4.0-6.0 and temperature 40-60℃ for 4-7 hours. After enzyme inactivation, washing, centrifugation and drying, enzymatically hydrolyzed brown rice flour is obtained. The debranching enzyme is pullulanase. (4) Add tea polyphenol-Lactobacillus plantarum composite microcapsules to the enzymatically hydrolyzed brown rice flour obtained in step (3), react in an ultrasonic water bath, then transfer to an ultra-high pressure device for pressure treatment, then stir in a water bath, and after washing, centrifugation and drying, obtain enzymatically hydrolyzed-microcapsule polyphenol composite brown rice flour. (5) The enzymatic hydrolysis-microcapsule polyphenol complex brown rice flour obtained in step (4) and medium- and long-chain fatty acids are subjected to ultrasonic treatment at pH 4.0-6.0 and temperature 40-60℃, and then transferred to an ultra-high pressure device for pressure treatment. After washing, centrifugation and drying, enzymatic hydrolysis polyphenol fatty acid modified low-GI brown rice flour is obtained. (6) The composite brown rice flour obtained in step (5) is subjected to pulsed electric field treatment to obtain the final product.

2. The preparation method according to claim 1, characterized in that, The process parameters for the low-temperature plasma treatment in step (2) are as follows: the working gas is argon or oxygen, the gas flow rate is 10-30 mL / min, the discharge power is 100-300 W, the treatment time is 5-15 minutes, and the treatment temperature is room temperature; the particle size D90 of the micronized dietary fiber is ≤10 μm, and the amount of refill is 5%-15% of the mass of the etched brown rice flour.

3. The preparation method according to claim 1, characterized in that, The process parameters for ultrasound-assisted enzymatic hydrolysis in step (3) are: pH 5.0, temperature 55℃, reaction time 5 hours, ultrasound power 300W, ultrasound working mode 3s working, 2s intermittent; the addition ratio of α-amylase and pullulanase is 70U pullulanase for every 10U α-amylase.

4. The preparation method according to claim 1, characterized in that, The preparation method of the tea polyphenol-Lactobacillus plantarum composite microcapsules in step (4) is as follows: tea polyphenols and fructooligosaccharides are dissolved in deionized water at a mass ratio of 1:1-3:1 to obtain a core material solution; chitosan is dissolved in acetic acid solution to obtain a wall material solution with a mass concentration of 1%-3%; the core material solution and the wall material solution are mixed at a volume ratio of 1:3-1:5, and Lactobacillus plantarum suspension is added to make the final concentration 10. 8 -10 9 CFU / mL, emulsified by stirring, and then spray-dried to obtain tea polyphenol-Lactobacillus plantarum complex microcapsules.

5. The preparation method according to claim 1, characterized in that, The mass ratio of the tea polyphenol-Lactobacillus plantarum composite microcapsules in step (4) to the enzymatically hydrolyzed brown rice flour obtained in step (3) is 1:10; the reaction conditions in the ultrasonic water bath are pH 5.0, temperature 40℃, and time 15 minutes; the ultra-high pressure holding conditions are pressure 200MPa and holding time 10 minutes; the water bath stirring reaction conditions are temperature 40℃ and time 4 hours.

6. The preparation method according to claim 1, characterized in that, The medium- and long-chain fatty acids in step (5) are palmitic acid or stearic acid; the mass ratio of palmitic acid to the enzymatic hydrolysis-microcapsule polyphenol composite brown rice flour obtained in step (4) is 1:10; the conditions for ultrasonic treatment are pH 5.0, temperature 50℃, and time 30 minutes; the conditions for ultra-high pressure holding treatment are pressure 300MPa and holding time 20 minutes.

7. The preparation method according to claim 1, characterized in that, The centrifugation conditions in steps (3), (4), and (5) are centrifugation at 4℃ and 6000 rpm for 5 min; drying is hot air drying at 40℃.

8. A low-GI brown rice flour modified with enzymatically hydrolyzed polyphenolic fatty acids, characterized in that, The brown rice flour prepared by the method according to any one of claims 1-7 comprises: Brown rice matrix, wherein the brown rice matrix is ​​the remaining part of the final product after removing tea polyphenol-Lactobacillus plantarum complex microcapsules and medium- and long-chain fatty acids; The tea polyphenol-Lactobacillus plantarum composite microcapsules are compounded in the brown rice matrix. The wall material of the composite microcapsules is chitosan, the core material contains tea polyphenols and fructooligosaccharides, and Lactobacillus plantarum is embedded inside. Medium- and long-chain fatty acids compounded in the brown rice matrix; The mass ratio of tea polyphenols to brown rice matrix is ​​1:100 to 1:150, and the mass ratio of medium- and long-chain fatty acids to brown rice matrix is ​​1:110 to 1:160.

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