Preparation method and application of low-GI whole wheat flour

Abstract

The invention discloses a preparation method and application of low-GI whole wheat flour, and the preparation method comprises the following steps: step (1), grinding wheat to respectively obtain flour and wheat bran; (2) performing steam explosion modification treatment on wheat bran, and drying after the modification treatment is finished to obtain modified wheat bran; and (3) grinding the modified wheat bran into wheat bran powder, adding the wheat bran powder into the flour obtained in the step (1), and uniformly mixing to obtain the low-GI whole wheat flour. The low-GI whole wheat flour is used for making low-GI whole wheat food. The low-GI wholewheat food can solve the technical problems of low nutritional quality and poor sensory quality of the existing low-GI wholewheat food.

Description

Technical Field

[0001] The present invention relates to the technical field of low GI foods, in particular to a preparation method and application of low GI whole wheat flour. Background Art

[0002] Wheat bran is a key byproduct of wheat flour processing. Its main components include the aleurone layer, nucellus layer, pericarp, seed coat, and some residual endosperm, which together account for approximately 15% of the total kernel weight. Wheat bran is rich in nutrients, including protein, dietary fiber, starch, polysaccharides, and phenolic compounds, accounting for approximately 60%-70% of wheat's total nutrients. Wheat bran polysaccharides have excellent water-binding properties and viscosity, making them suitable for use as food additives such as thickeners. Phenolic compounds in wheat bran primarily include ferulic acid, lignans, flavonoids, and alkylresorcinols (ARs). These compounds have been shown to improve human physiological functions, including antioxidant, anti-aging, and cardiovascular disease prevention. Dietary fiber, a polysaccharide primarily found in wheat bran, accounts for approximately 40%-50% of the total kernel weight. It is neither digested nor absorbed by the intestines nor does it produce energy. It is a special nutrient, recognized by nutritionists as a Category 7 nutrient. Studies have shown that dietary fiber is significantly effective in reducing the risk of hypertension, diabetes, obesity, and some intestinal diseases.

[0003] The glycemic index (GI) generally refers to the degree of blood sugar response after consuming a certain type of food. It reflects the food's ability to raise blood sugar in the body and the change in blood sugar concentration after consumption. The Food and Agriculture Organization of the United Nations (FAO) has established a standard based on the ratio of the area under the postprandial blood sugar response curve for a 50g meal of the same human-usable carbohydrates to that of a standard food (GI = 100). Research has shown that the GI plays an important role in health management.

[0004] Currently, low-GI foods are receiving widespread attention and are a hot topic in food research and development. Research on developing low-GI foods by adding wheat bran has been reported, but the amount of wheat bran added has been low and the taste has been poor. Ling Bin et al. added puffed wheat bran to dried noodles to investigate its effect on noodle quality. The results showed that puffed wheat bran increased the dietary fiber content and reduced color. Noodles containing a small amount of wheat bran had better elasticity than those without wheat bran, with the optimal wheat bran addition being 3%. Wang Chongchong et al. compared steamed bread made with different amounts of wheat bran to investigate the effect of different wheat bran addition levels on its quality. The results showed that lower amounts of dietary fiber improved dough toughness and prolonged stability, but reduced gas retention and shortened fermentation time. The optimal wheat bran addition level was 5%, and exceeding 10% had adverse effects on frozen dough. Martijn et al. added wheat bran to white flour to prepare whole-wheat bread and found that the addition of wheat bran negatively affected both the mixing properties of the dough and the quality of the bread. Cui Xibin added fermented bran back into flour and found that steamed bread made with fermented bran had higher sensory and edible qualities than those made with raw bran. Liu Jiao et al. compared whole-wheat noodles made with raw bran and bran treated with xylanase. They found that the whole-wheat noodles with enzyme-treated bran had increased dry matter loss, decreased cooking weight gain, and improved nutritional quality, indicating that the addition of modified bran can improve noodle quality compared to whole-wheat noodles with raw bran.

[0005] The nutritional quality and sensory quality of existing low GI whole wheat foods still have much room for improvement, and it is necessary to further improve the preparation method of low GI whole wheat flour. Summary of the Invention

[0006] To this end, the technical problem to be solved by the present invention is to provide a preparation method and application of low GI whole wheat flour, so as to solve the technical problems of low nutritional quality and poor sensory quality of existing low GI whole wheat foods.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] A method for preparing low GI whole wheat flour comprises the following steps:

[0009] Step (1), grinding the wheat to obtain flour and wheat bran respectively;

[0010] Step (2), subjecting the wheat bran to a steam explosion modification treatment, and drying the resulting product after the modification treatment to obtain modified wheat bran;

[0011] Step (3), grinding the modified wheat bran into wheat bran powder and adding the powder to the flour obtained in step (1), mixing evenly, and obtaining low GI whole wheat flour.

[0012] To improve the nutritional and sensory qualities of low-GI whole-wheat foods, the present invention uses steam explosion (SE) technology to modify wheat bran. During the steam explosion modification process of the present invention, steam has a strong penetrating force and penetrates into the internal structure of the wheat bran. The explosive decompression causes most of the steam to expand rapidly, affecting the internal structure of the material, and ultimately forming pores on the surface when the steam rushes out. In addition, the steam explosion modification process can hydrolyze the glycosidic bonds of cellulose, hemicellulose, and lignin, producing some organic acids, which are degraded into small molecules, making the biomass loose and porous. Utilizing steam explosion technology can change the nutrient content in the wheat bran and loosen its structure, which is more conducive to improving the quality of low-GI whole-wheat products.

[0013] In the above-mentioned method for preparing low-GI whole-wheat flour, in step (2), the conditions for the steam explosion modification treatment are: a pressure of 0.9 to 1.5 MPa and a pressure maintenance time of 120 to 180 seconds. The modified wheat bran powder obtained by the steam explosion modification treatment has a significantly increased content of total phenols and soluble dietary fiber, which is beneficial for slowing down the absorption rate of glucose and reducing the GI value; and the appropriate Maillard reaction can produce a toasted aroma and a caramel aroma to improve the flavor of the wheat bran, and the browning reaction that occurs at the same time can enhance the attractiveness of the product. If the pressure and pressure maintenance time of the steam explosion modification treatment exceed the above range, the wheat bran Maillard reaction may be excessive, resulting in an unpleasant burnt bitter taste, and the excessively dark color may also affect the aesthetics of the product.

[0014] In the above-mentioned method for preparing low GI whole wheat flour, in step (2), the conditions for the steam explosion modification treatment are: a pressure of 1.5 MPa and a pressure maintenance time of 180 s.

[0015] In the method for preparing the low GI whole wheat flour, in step (2), the drying temperature is 40-60° C. and the drying time is 12-36 hours. When the modified wheat bran flour is dried, a uniform pore structure is formed on its surface after modification, and the surface area is increased. If the drying temperature is too high, the Maillard reaction may continue to occur, affecting the appearance and nutritional content of the product. Too high a temperature may make the fibers compact, which is not conducive to subsequent processing. Too low a temperature may extend the drying time, which not only wastes resources but may also cause the growth of microorganisms.

[0016] In the preparation method of the above-mentioned low GI whole wheat flour, in step (2), the drying temperature is 50° C. and the drying time is 24 hours.

[0017] The method for preparing the low GI whole wheat flour comprises the following steps: in step (3), the wheat bran flour is passed through a 100-mesh sieve; the mass fraction of the wheat bran flour in the low GI whole wheat flour is 10-30 wt%; if the particle size of the wheat bran flour is too large, the dough formed by the whole wheat flour will absorb water unevenly, and the noodles produced will have a poor taste and a foreign body sensation, which is not conducive to product quality; if the particle size of the wheat bran flour is too small, the wheat bran flour will increase the water absorption rate of the dough when it is interspersed between the gluten protein networks, which is not conducive to the formation of the dough, and the noodles produced will be severely adhered and easily broken.

[0018] In the preparation method of the low GI whole wheat flour, in step (3), the wheat bran powder is passed through a 100-mesh sieve; and the mass fraction of the wheat bran powder in the low GI whole wheat flour is 25wt%.

[0019] The preparation method of the low GI whole wheat flour is as follows: in step (2), the conditions of the steam explosion modification treatment are: a pressure of 1.5 MPa, a pressure maintenance time of 180 s; a drying temperature of 50° C., and a drying time of 24 h; in step (3), the wheat bran powder is passed through a 100-mesh sieve; and the mass fraction of the wheat bran powder in the low GI whole wheat flour is 25 wt %.

[0020] The invention discloses an application of low GI whole wheat flour, wherein the low GI whole wheat flour is used to prepare low GI whole wheat food.

[0021] The low GI whole wheat flour is used as a low GI whole wheat food, and the low GI whole wheat food is low GI noodles. The low GI noodles are prepared by the following method: 55 to 65 parts by weight of low GI whole wheat flour, 20 to 30 parts by weight of buckwheat flour and 5 to 15 parts by weight of gluten are uniformly mixed to form a mixed flour; the mixed flour is poured into a dough mixer, 37 to 41 parts by weight of water is added, stirred until flocculent, poured out, kneaded into dough, and proofed for 20 to 30 minutes; the proofed dough is repeatedly folded and rolled to obtain dough sheets, and the dough sheets are cut into strips using a noodle machine to obtain low GI noodles. When preparing low-GI noodles, the present invention adds buckwheat flour, which can reduce the digestion rate of the noodles by utilizing its lower hydrolysis rate than flour; and there is a synergistic effect between the buckwheat flour in the above ratio and the modified wheat bran in the whole wheat flour. Compared with wheat flour itself, buckwheat flour has a higher content of slowly digestible starch and resistant starch, and the modified wheat bran has a higher soluble dietary fiber, which can further reduce the digestibility of the composite flour (low-GI noodle flour) and thus reduce the GI value; the addition of wheat gluten can promote the formation of gluten protein, making the dough easy to shape and not broken into strips. The present invention adjusts the ratio of low GI whole wheat flour, buckwheat flour and gluten flour so that the modified wheat bran flour in the low GI whole wheat flour can be fully connected with gliadin and gluten in the gluten flour as macromolecules (the connection is mainly achieved by adsorbing gliadin and glutenin through the moderately sized and evenly distributed pore structure on the surface of the wheat bran flour particles), forming a strong, orderly and stable network structure, thereby effectively reducing the adverse effects of the addition of buckwheat flour on the viscosity and formability of the dough, and facilitating the processing and production of low GI noodles.

[0022] The technical solution of the present invention achieves the following beneficial technical effects:

[0023] 1. The method for preparing low-GI whole-wheat flour of the present invention selects the optimal treatment conditions by comparing the changes in the nutrient content of wheat bran under different steam explosion conditions, thereby significantly increasing the total phenols and soluble dietary fiber contents in the modified wheat bran obtained by treatment and reducing the GI value of the whole-wheat flour. More importantly, buckwheat flour itself has the characteristics of low viscosity and difficulty in agglomeration. As the amount of buckwheat flour added increases, the viscosity of the dough decreases significantly, making the dough difficult to shape. The steam explosion treatment conditions of the present invention can make the wheat bran structure loose, with surface pores of moderate size and uniform distribution, which are conducive to accommodating gliadin and glutenin in gluten to form a more solid and orderly network structure, thereby improving the viscoelasticity and extensibility of the whole-wheat flour dough, making it easy to agglomerate even when a high amount of buckwheat flour is added.

[0024] 2. The whole wheat flour prepared by the modified wheat bran of the present invention and having good gelatinization and rheological properties is mixed with buckwheat flour and gluten in a specific ratio to obtain a mixed noodle flour, which can produce a high-quality low-GI whole wheat noodle product. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Effects of different steam explosion treatment conditions on ARs content in wheat bran in the embodiments of the present invention;

[0026] Figure 2 Effects of different steam explosion treatment conditions on the total phenol content in wheat bran in the embodiments of the present invention;

[0027] Figure 3 Effects of different steam explosion treatment conditions on the soluble dietary fiber content in wheat bran in the embodiments of the present invention;

[0028] Figure 4 Cluster analysis results of steam explosion treatment conditions in an embodiment of the present invention;

[0029] Figure 5 The principal component analysis results of steam explosion treatment conditions in the embodiment of the present invention;

[0030] Figure 6 Scanning results of elastic modulus (G') of whole wheat dough with different whole wheat flours in the embodiment of the present invention;

[0031] Figure 7 Scanning results of the viscosity modulus (G") of whole-wheat dough with different whole-wheat flours in the embodiment of the present invention;

[0032] Figure 8 Scanning results of the loss angle (tan δ) of whole wheat dough made with different whole wheat flours in the embodiments of the present invention;

[0033] Figure 9 A comparison of the hardness of noodles made from different whole wheat flours according to the present invention;

[0034] Figure 10 Comparison of the viscosity of noodles made from different whole wheat flours in the embodiments of the present invention;

[0035] Figure 11 Comparison of the elasticity of noodles made from different whole wheat flours in the embodiments of the present invention;

[0036] Figure 12 A comparison of the chewiness of noodles made from different whole wheat flours according to the present invention;

[0037] Figure 13 Comparative diagram of hydrolysis rates of noodles made from different whole wheat flours according to the present invention;

[0038] Figure 14 Comparison of the eGI of noodles made from different whole wheat flours according to the present invention;

[0039] Figure 15 Comparison of sensory quality scores of noodles made from different whole-wheat flours in the embodiments of the present invention. DETAILED DESCRIPTION

[0040] 1. Effects of different steam explosion treatments on the contents of phenols and soluble dietary fiber in wheat bran

[0041] The blasting treatment was performed at pressures of 0.9 MPa, 1.2 MPa, and 1.5 MPa and pressure holding times of 120 s and 180 s, respectively. Unblasted wheat bran was used as a control. The treated bran was dried at 50° C., pulverized, and passed through a 60-mesh sieve, sealed, and used for standby use. The wheat used in the examples of the present invention was purchased from Jiangsu Golden Land Seed Industry Co., Ltd.

[0042] (1) Determination of alkylresorcinol (ARs) content and analysis of results

[0043] 1 g of ground wheat bran powder, passed through a 60-mesh sieve, was mixed with 40 mL of ethyl acetate and stirred continuously at room temperature for 24 hours using a magnetic stirrer. The ethyl acetate in the supernatant was removed using a rotary evaporator and then redissolved in 40 mL of methanol to obtain a crude extract of wheat ARs. Fast Blue RR was dissolved in methanol (5:10,000). 100 μL of the methanol solution and 10 μL of the ARs extract were added, along with 10 μL of a 10% potassium carbonate solution and 100 μL of the Fast Blue-methanol solution. The mixture was incubated at 37°C in the dark for 15 minutes, and the absorbance at 490 nm was measured using a microplate reader. Olive alcohol was used as the standard to construct a standard curve, and the ARs content was calculated based on the absorbance.

[0044] The ARs content of wheat bran after steam explosion under different conditions is as follows Figure 1 As shown. Figure 1 It can be seen that the ARs content of unmodified wheat bran is 1022.5ug / g, and the ARs content of modified wheat bran increases. Among them, the ARs content of wheat bran treated under 1.5MPa 180s conditions is the highest, reaching 1086.39ug / g, but none of them reached a significant level, which suggests that the ARs functional components are very stable and are basically not affected by the processing process.

[0045] (2) Determination of total phenol content and analysis of results

[0046] Accurately weigh 1.00 g of sample into a 50 mL plastic centrifuge tube. Add 20 mL of 80% methanol and ultrasonically extract (40°C, 100 W, 30 min). Centrifuge (3500 rpm for 10 min) and collect the supernatant. Repeat this process once, and combine the supernatants. Determine the soluble polyphenol content using the Folin-Ciocalteu method: 125 μL of sample solution or standard solution is mixed with 125 μL of Folin-phenol reagent and 0.5 mL of ultrapure water for 6 min. Then, 1.25 mL of 7% (m / V) Na₂CO₃ solution and 1 mL of distilled water are added. After reacting at room temperature for 2 hours, the absorbance is measured at 765 nm using a microplate reader.

[0047] The total phenol content of wheat bran after steam explosion under different conditions is as follows: Figure 2 As shown in the figure, the total phenol content of unmodified wheat bran is 2.93 mg GAE / g, and the total phenol content of wheat bran treated with different modifications is significantly higher than that of untreated bran. Under the same blasting pressure conditions, the longer the blasting time, the higher the total phenol content. The total phenol content of wheat bran treated with 1.2 MPa for 120 seconds is 4.91 mg GAE / g, and the total phenol content of wheat bran treated with 1.2 MPa for 180 seconds reaches 6.88 mg GAE / g, an increase of about 40%. The total phenol content of wheat bran treated with 1.5 MPa for 120 seconds is 7.38 mg GAE / g, and the total phenol content of wheat bran treated with 1.5 MPa for 180 seconds reaches 10.16 mg GAE / g, an increase of about 38%. Under different pressure conditions, keeping the time consistent, the total phenol content of wheat bran at 1.5 MPa for 180 seconds is the highest, at 10.16 mg GAE / g, about 3.6 times that of the untreated bran.

[0048] (3) Determination of soluble dietary fiber content and analysis of results

[0049] The method for determining the soluble dietary fiber content in wheat bran in this embodiment refers to GB 5009.88-2023 "National Food Safety Standard - Determination of Dietary Fiber in Foods".

[0050] After steam explosion treatment under different conditions, the soluble dietary fiber content is as follows Figure 3 As shown. Figure 3 It can be seen that the unmodified wheat bran content is 2.95g / 100g, and the soluble dietary fiber content of the wheat brans treated with different modifications is significantly higher than that of the untreated wheat bran. The soluble dietary fiber content increases with the increase of blasting pressure and pressure maintenance time. Among them, the wheat bran treated under 1.5MPa 120s has the highest soluble dietary fiber content, reaching 10.54g / 100g, which is about 3.5 times that of the untreated sample. At this time, the soluble dietary fiber content decreases with the extension of time. This may be because the high pressure causes the cellulose and lignin in the wheat bran to degrade into smaller molecules. These molecules cannot be precipitated by alcohol, resulting in a decrease in the extraction rate of soluble dietary fiber. Therefore, 1.5MPa 120s is the best treatment condition for increasing soluble dietary fiber.

[0051] According to the content of main nutrients (ARs, total phenols, soluble dietary fiber) in whole wheat after modification, cluster analysis and principal component analysis (such as Figure 4 、 Figure 5 , Table 1). The above results show that the samples can be divided into two categories at the k = 10 level. Principal component analysis and scoring indicate that samples treated with blasting at 1.5 MPa for 180 s have better quality. Therefore, 1.5 MPa for 180 s was selected as the optimal wheat bran modification condition.

[0052] Table 1 Principal component analysis of different modification treatments

[0053]

[0054]

[0055] 2. Effects of different modified wheat bran powder addition amounts on the gelatinization and rheological properties of whole wheat flour

[0056] Wheat bran modified by steam explosion at a pressure of 1.5 MPa for 180 seconds was dried at 50°C and ground through a 100-mesh sieve to obtain modified wheat bran powder. The original and modified wheat bran powders, which had passed through a 100-mesh sieve, were then added to flour and mixed to obtain whole-wheat flour. The addition amounts of the original and modified wheat bran powders were adjusted to achieve mass fractions of 15, 20, and 25% by weight, respectively, in the whole-wheat flour. Flour without wheat bran addition served as a control.

[0057] (1) Gelatinization properties of whole wheat flour with different amounts of wheat bran added before and after modification

[0058] Gelatinization properties were determined using a rapid viscometer. 2.61g of sample was weighed and added to 27g of distilled water to prepare a flour emulsion. The mixture was stirred thoroughly before testing. The test procedure was as follows: the stirrer speed was set at 960 rpm for the first 10 seconds, then maintained at 160 rpm. The temperature was initially set at 50°C for 1 minute, then increased to 95°C at a rate of 12°C / minute and held for 2.5 minutes, then decreased to 50°C and held for 2 minutes. The gelatinization curve and related gelatinization parameters were obtained.

[0059] Table 2 Effect of wheat bran before and after modification on the viscosity of whole wheat flour

[0060]

[0061] The results in Table 2 show that the addition of wheat bran significantly decreased the peak viscosity, minimum viscosity, final viscosity, and retrogradation value of whole-wheat flour, while the gelatinization temperature slightly increased compared to the control (P < 0.05). Modified wheat bran exhibited lower viscosity and retrogradation values ​​compared to original wheat bran. The addition of wheat bran also decreased starch content, impacting these parameters. This is due to the higher water absorption of dietary fiber compared to starch. Furthermore, gluten, which absorbs water and forms fibrous or globular structures, comes into contact with starch, impacting starch gelatinization, resulting in a decrease in gelatinization viscosity and an increase in gelatinization temperature. Another possible explanation is that the modified wheat bran contains more hydrophilic groups that interact with starch, altering the arrangement of starch molecules and limiting starch dissolution and coagulation, reducing starch retrogradation and thus reducing the retrogradation value of whole-wheat flour. This decrease in viscosity indicates enhanced thermal stability of whole-wheat flour, and the addition of modified wheat bran further enhances the thermal stability of whole-wheat flour.

[0062] (2) Rheological properties of whole wheat flour with different amounts of wheat bran added before and after modification

[0063] Dynamic rheological properties were measured by mixing whole wheat flour and water in a mass ratio of 10 / 7 (w / w = 10 / 7) to form a dough, wrapping it in plastic wrap and letting it rest at 37°C for 30 minutes. An appropriate amount of dough was placed on the plate of the dynamic rheometer. Excess dough was scraped off with a plastic sheet. Then, an appropriate amount of silicone oil was evenly applied to the edges of the dough to prevent evaporation. The dynamic rheometer was first subjected to a strain sweep within the range of 0.001% to 10% to determine the linear viscoelastic range of the dough. A frequency sweep was then performed to measure the dynamic rheological properties of the dough. The frequency test conditions for the dynamic rheometer were: a test temperature of 25°C, a fixed strain of 0.1%, and a frequency range of 0.1 to 100 rad / s. The test results include the elastic modulus (G'), the viscous modulus (G"), and the loss angle (tan δ), where the loss angle is the ratio of the viscous modulus to the elastic modulus.

[0064] Figures 6 to 8Obvious viscoelastic curves were observed in the dough of whole wheat flour with different contents of wheat bran. As can be seen from the figure, the elastic modulus (G') and viscous modulus (G") of the dough continue to increase with the increase of oscillation frequency, and G' is greater than G". At the same time, G' and G" increase with the increase of the amount of wheat bran added; this shows that wheat bran can connect some macromolecular chains in the dough, forming a more solid and orderly network structure, reducing the fluidity and viscosity of the dough, and vice versa, increasing the elasticity. Compared with the original wheat bran, the addition of modified wheat bran can increase the elastic modulus (G') and viscous modulus (G") of the dough; however, the inherent rheological properties of the dough have not changed, and it still has the same G'>G". Figure 8 As can be seen, the tanδ values ​​of all doughs first decrease and then increase with increasing frequency, and tanδ values ​​< 1, indicating that the inherent characteristics of the dough are weak gels, with elasticity being the dominant factor. Furthermore, at the same wheat bran addition level, the tanδ values ​​of the doughs containing modified wheat bran are lower, indicating that the addition of modified wheat bran enhances the elasticity of the dough, decreases its viscosity, weakens its fluidity, and strengthens the gluten network structure. Based on these analyses, the addition of modified wheat bran can improve the viscoelastic properties of wheat dough.

[0065] 3. Effects of different modified wheat bran flour addition amounts on the cooking characteristics, texture characteristics, in vitro digestibility and sensory evaluation of noodles made from whole wheat flour

[0066] Wheat bran modified by steam explosion at a pressure of 1.5 MPa and a holding time of 180 s was dried at 50 ° C and pulverized through a 100 mesh sieve to obtain modified wheat bran powder. 60 g of whole wheat flour with a mass fraction of 0, 15 wt%, 20 wt% or 25 wt% of modified wheat bran powder was mixed with 30 g of buckwheat flour and 10 g of gluten flour to prepare a mixed flour; the mixed flour was poured into a dough mixer, 39 g of distilled water was added in batches, stirred until flocculent, poured out, kneaded into a ball, and proofed for 30 min; the proofed dough was repeatedly folded and rolled to obtain fully rolled dough sheets; finally, the dough sheets were cut into strips using a noodle machine to obtain fresh noodles. The buckwheat flour and gluten flour used in this embodiment are both commercially available. Buckwheat flour was purchased from Shangqiu Wanzhu Miscellaneous Grains Flour Co., Ltd., and gluten was purchased from Xintai Food Technology Co., Ltd., with a protein content of 85 wt%.

[0067] Noodles made from whole wheat flour with modified wheat bran flour mass fractions of 0, 15wt%, 20wt% and 25wt% were recorded as control group, group A, group B and group C, respectively.

[0068] (1) Steaming and cooking characteristics of noodles

[0069] Test method: Take 20 noodles, each 200 mm long, weigh them, and place them in 500 mL of boiling water for 5 minutes. After 5 minutes, remove the noodles, rinse them with cold water for 10 seconds, and spread them flat on filter paper to cool for 5 minutes. Observe the number of broken noodles and calculate the breakage rate of the alkaline noodles according to formula (1). Weigh the cooled noodles again and calculate the dry matter water absorption rate of the alkaline noodles according to formula (2). After cooling, pour all the remaining noodle soup from the previous cooking into a volumetric flask and make the volume up to 500 mL. Shake well and take out 100 mL from it and transfer it to a small beaker with constant weight. First, place it on an electric stove to dry until it is almost dry, then place it in an oven at 105°C to continue drying until constant weight. Calculate the dry matter loss rate according to formula (3).

[0070] Broken strip rate (%) = number of broken strips / 20 × 100 (1);

[0071]

[0072] Where m1 represents the mass of fresh noodles, g; m2 represents the mass of fresh noodles after cooking, g; m3 represents the mass of dry matter after drying, g; and w represents the moisture content of fresh noodles, %.

[0073] Table 3 Effect of modified wheat bran addition on noodle cooking characteristics

[0074]

[0075] Table 3 shows that as the amount of modified wheat bran increases, the dry matter water absorption of noodles gradually decreases. The control group had the highest water absorption, at 171.01%, while Group C had the lowest, at 161.84%. This may be because increasing the amount of wheat bran added increases the protein content in the noodles. During the cooking process, more hydrophobic groups of the protein are exposed, reducing the water absorption and water-holding capacity of the gluten network. This may be because the dietary fiber in the wheat bran is not tightly bound to the gluten protein, making it easier to overflow into the water during cooking. Furthermore, the rough surface of the wheat bran easily disrupts the gluten network, making it easier for flour to diffuse outward, resulting in a significant increase in the cooking loss rate. The breakage rate remained unchanged with increasing wheat bran addition.

[0076] (2) Texture characteristics of noodles

[0077] Test Method: Three strands of cooked noodles of uniform length were laid flat on the stage of a texture analyzer. TPA texture analysis was used to measure the noodles' hardness, stickiness, springiness, and chewiness. Test parameters were: probe model TA3 / 100, deformation of 70%, trigger point load of 5g, and test speed of 0.80mm / s.

[0078] Depend on Figures 9 to 12As shown, with increasing amounts of modified wheat bran added, the hardness, stickiness, and chewiness of the noodles significantly improved (P < 0.05); however, there was no significant change in elasticity. This may be because the dietary fiber in the wheat bran binds with the gluten protein, absorbing more water, thereby increasing the hardness and chewiness of the noodles. The presence of dietary fiber hinders the contact between starch and gluten protein, reducing the structural strength of the gluten network, resulting in no significant difference in elasticity values. The increase in stickiness may be due to increased cooking loss, resulting in more gelatinized starch precipitating and adsorbing on the noodle surface.

[0079] (3) In vitro digestibility of noodles

[0080] Pancreatic α-amylase (250 mg, 9 U / mg) was suspended in 7.5 mL of sodium acetate buffer (0.02 M, pH 5.4) and magnetically stirred for 30 minutes. Before use, it was mixed with 0.865 mL of amyloglucosidase (260 U / mL). A noodle sample containing 100 mg of starch was weighed, 10 mL of sodium acetate buffer (0.02 M, pH 5.4) was added, and equilibrated at 37°C for 10 minutes, followed by the addition of 0.75 mL of a mixture of pancreatic α-amylase and amyloglucosidase. Aliquots (0.1 mL) were removed at specific intervals during the digestion process. Each aliquot was then mixed with anhydrous ethanol (0.9 mL) to inhibit the enzyme and centrifuged at 6000 × g for 10 minutes. Subsequently, the glucose concentration of the incubation mixture was measured using a GOPOD glucose assay kit. The starch hydrolysis rate was calculated using the following formula:

[0081] Starch hydrolysis rate (%) = (Gh*0.9) / Si*100%

[0082] Where Gh represents the amount of glucose sampled at each time point (mg); Si represents the initial starch content (mg). The area under the hydrolysis curve was calculated by integration, and the hydrolysis index (HI) was calculated using glucose as the reference standard. The estimated glycemic index (eGI) was calculated using the following formula.

[0083] HI = area under the digestion curve (0-120 min) × 100 / area under the digestion curve of standard substance (0-120 min); eGI = 0.862HI + 8.198.

[0084] The results of in vitro simulated digestion of noodles with different amounts of modified wheat bran are as follows: Figure 13 and Figure 14As shown in the figure, the eGI of noodles decreased with increasing wheat bran addition. The eGI values ​​of whole-wheat noodles in Groups B and C were significantly lower than those in the control group, both below 55. This may be due to the increased dietary fiber content in whole-wheat noodles after the addition of modified wheat bran, which slows starch digestion. Furthermore, the presence of phenolic compounds in wheat bran can inhibit amylase activity, reducing the rate of starch digestion.

[0085] (4) Sensory quality evaluation of noodles

[0086] The sensory quality of noodles was evaluated with reference to the method in GB / T35875-2018 "Grain and Oil Inspection - Evaluation of Wheat Flour Noodle Processing Quality". The scoring criteria are shown in the table below.

[0087] Table 4

[0088]

[0089]

[0090] like Figure 15 As shown, modified wheat bran affects the color, surface texture, firmness, taste, smoothness, and elasticity of whole-wheat noodles. Sensory scores were ranked as follows: Group A > Group B > Group C. The eGI value of Group B whole-wheat noodles was significantly lower (P < 0.05) than the control group, reaching 51.85, making it a low-GI whole-wheat product.

[0091] In summary, the noodles prepared in this embodiment are low GI whole wheat products, which are digested slowly and have little effect on blood sugar. They can improve postprandial blood sugar levels and help regulate and control blood sugar stability.

[0092] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the claims of this patent application.

Claims

1. A method for preparing low GI whole wheat flour, characterized in that: The steps include: Step (1), grinding the wheat to obtain flour and wheat bran respectively; Step (2), subjecting the wheat bran to a steam explosion modification treatment, and drying the resulting product after the modification treatment to obtain modified wheat bran; Step (3), grinding the modified wheat bran into wheat bran powder and adding the powder to the flour obtained in step (1), mixing evenly, and obtaining low GI whole wheat flour.

2. The method for preparing low GI whole wheat flour according to claim 1, wherein In step (2), the conditions for the steam explosion modification treatment are: a pressure of 0.9 to 1.5 MPa, and a pressure maintenance time of 120 to 180 s.

3. The method for preparing low GI whole wheat flour according to claim 2, wherein In step (2), the conditions for the steam explosion modification treatment are: a pressure of 1.5 MPa and a pressure maintenance time of 180 s.

4. The method for preparing low GI whole wheat flour according to claim 1, wherein In step (2), the drying temperature is 40-60° C. and the drying time is 12-36 hours.

5. The method for preparing low GI whole wheat flour according to claim 1, wherein In step (2), the drying temperature is 50° C. and the drying time is 24 h.

6. The method for preparing low GI whole wheat flour according to claim 1, wherein In step (3), the wheat bran powder is passed through a 100-mesh sieve; and the mass fraction of the wheat bran powder in the low GI whole wheat flour is 10 to 30 wt%.

7. The method for preparing low GI whole wheat flour according to claim 6, wherein In step (3), the wheat bran powder is passed through a 100-mesh sieve; the mass fraction of the wheat bran powder in the low GI whole wheat flour is 25 wt%.

8. The method for preparing low GI whole wheat flour according to claim 1, wherein In step (2), the conditions of the steam explosion modification treatment are: a pressure of 1.5 MPa, a pressure maintenance time of 180 s; a drying temperature of 50° C., and a drying time of 24 h; in step (3), the wheat bran powder is passed through a 100-mesh sieve; and the mass fraction of the wheat bran powder in the low GI whole wheat flour is 25 wt %.

9. An application of low GI whole wheat flour, characterized in that: The low GI whole wheat flour according to any one of claims 1 to 8 is used to prepare low GI whole wheat food.

10. The use of the low GI whole wheat flour according to claim 9, characterized in that The low GI whole-wheat food is low-GI noodles. The preparation method of the low-GI noodles comprises the following steps: uniformly mixing 55-65 parts by weight of low-GI whole-wheat flour, 20-30 parts by weight of buckwheat flour and 5-15 parts by weight of gluten to prepare a mixed flour; pouring the mixed flour into a dough mixer, adding 37-41 parts by weight of water, stirring until flocculent, pouring out, kneading into dough, and proofing the dough for 20-30 minutes; repeatedly folding and rolling the proofed dough to obtain dough sheets, and cutting the dough sheets into strips using a noodle machine to obtain low-GI noodles.

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