A debittered, low-GI quinoa starch, its preparation method and application

Abstract

This invention relates to a debittered, low-GI quinoa starch, its preparation method, and its applications, belonging to the field of modified starch processing technology. To reduce the GI value of quinoa starch and effectively remove its bitter components, this invention employs a synergistic process of "blanching-enzymatic hydrolysis-heat treatment" to prepare quinoa starch. The composite enzymatic hydrolysis technology significantly improves the removal efficiency of saponins while optimizing the starch structure; the heat treatment process further regulates the digestibility of the starch and reduces its glycemic index. The modified quinoa starch obtained by this invention has the characteristics of low bitterness, good taste, and strong resistance to digestive enzyme interference, making it suitable for developing low-glycemic index foods, diabetes-friendly diets, and functional health foods.

Description

Technical Field

[0001] This invention belongs to the field of modified starch processing technology, specifically relating to a debittered low-GI quinoa starch, its preparation method, and its application. Background Technology

[0002] Quinoa (Chenopodium quinoa Willd.), a "super grain" native to South America, has garnered significant attention due to its rich content of nine essential amino acids, high-quality protein (12-18%), and various minerals. While quinoa itself has a glycemic index (GI) of around 35, processed quinoa starch has a GI of approximately 50-60, classifying it as a medium GI. This difference primarily stems from the composition of quinoa starch: resistant starch accounts for only 1%-3%, slow-digesting starch comprises 18%-19%, and fast-digesting starch is excessively high. Therefore, after removing polyphenols, peptides, and dietary fiber—substances with hypoglycemic activity—from quinoa, the GI value of quinoa starch increases significantly. Currently, domestic and international research on whole grains largely focuses on modifying high-GI staple foods like rice and wheat through blending with other grains or active ingredients, as well as processing methods such as steaming, frying, and baking. Some studies focus on further processing finished staple foods to obtain lower-GI staple foods with improved taste.

[0003] Furthermore, quinoa bran contains 0.1-5% triterpenoid saponins, which not only produce a distinct bitter taste but may also cause digestive discomfort if consumed in excess. Studies have shown that triterpenoid saponins have a structure that binds to bitter taste receptor molecules, activating α-taste receptors and thus triggering bitter taste transmission; therefore, triterpenoid saponins typically have a strong bitter taste. Given that quinoa saponins are abundant in the bran and outer shell, the most common quinoa saponification technique in pre-processing is the peeling and hulling method. Traditional physical cleaning methods (such as soaking and rubbing) have limited efficiency in removing saponins, easily leading to residual bitter substances that affect starch quality; mechanical peeling methods have a high breakage rate, and some saponins may be mixed into subsequent processed products, which is detrimental to the processing and utilization of quinoa. Considering the physiological characteristics of quinoa, post-processing methods such as germination and fermentation are also used to remove saponins, but these methods have long processing cycles, which are not conducive to commercial production. Patent CN213315132U discloses a method combining mechanical and wet saponin removal, in which quinoa is sequentially passed through a vibrating screen, a huller, a destoner, a turbine washer, a dehydrator, and an air dryer. While this saponin removal system effectively removes saponins, it suffers from drawbacks such as high water consumption in the wet process, high energy consumption in subsequent drying, potential nutrient loss or mechanical damage to the quinoa, and complex and costly maintenance due to the multiple devices connected in series. Patent application CN119432952A discloses a method for preparing low-GI corn starch through dual enzymatic hydrolysis. This method increases the content of resistant starch in corn starch and reduces its digestibility by adding branched enzymes twice for enzymatic hydrolysis. Although this preparation method effectively reduces the GI value of corn starch, it suffers from drawbacks such as cumbersome process steps, the need for multiple pH adjustments, the consumption of large amounts of solvents and potential starch loss during enzymatic hydrolysis, alcohol washing, and water washing, high drying energy consumption, and high production costs.

[0004] Therefore, improving saponin removal technology and combining it with starch modification to reduce the GI value is a key research direction for improving the processing quality and functional properties of quinoa. Summary of the Invention

[0005] To reduce the glycemic index (GI) of quinoa starch and effectively remove its bitter components, this invention employs a synergistic process of blanching, enzymatic hydrolysis, and heat treatment to prepare quinoa starch. The combined enzymatic hydrolysis technology significantly improves the removal efficiency of saponins while optimizing the starch structure. The heat treatment process further regulates the digestible properties of the starch, reducing its glycemic index. The modified quinoa starch obtained by this invention features low bitterness, excellent taste, and strong resistance to digestive enzyme interference, making it suitable for developing low-glycemic index foods, diabetes-friendly diets, and functional health foods.

[0006] To solve the above-mentioned technical problems and achieve the corresponding technical effects, the present invention provides the following technical solution:

[0007] The first objective of this invention is to provide a method for preparing debittered, low-GI quinoa starch, the method comprising the following steps:

[0008] S1. Place the washed quinoa in a 70-90℃ water bath and stir for 1-5 minutes. Drain the water to obtain blanched quinoa.

[0009] S2. Grind the blanched quinoa into a slurry, add one or more of pectinase, cellulase and β-glucosidase for enzymatic hydrolysis, with each enzyme added at a rate of 500 U / g. After centrifugation to remove the supernatant, dry the quinoa to obtain enzymatically modified quinoa powder.

[0010] S3. Dissolve the enzymatically modified quinoa powder in water, equilibrate at 4°C for 24 h, perform heat treatment for modification, extract the modified quinoa powder with sodium hydroxide solution, centrifuge to obtain a precipitate, wash the precipitate with water 2-3 times, and freeze-dry the precipitate to obtain modified quinoa starch; the heat treatment is 600 W infrared treatment for 150 s, 600 W microwave treatment for 15 s, 170°C steam treatment for 4 min, or 110°C hot and humid treatment for 3 h.

[0011] In one embodiment of the present invention, S1 involves placing the washed quinoa in an 80°C water bath and stirring for 3 minutes.

[0012] In one embodiment of the present invention, S2 involves adding 500 U / g pectinase, 500 U / g cellulase, and 500 U / g β-glucosidase for enzymatic hydrolysis under the conditions of 40°C and pH 5.0 for 2 hours.

[0013] In one embodiment of the present invention, the heat treatment in S3 is a hot and humid treatment at 110°C for 3 hours.

[0014] In one embodiment of the present invention, step S3 involves adding water to adjust the moisture content of the enzymatically modified quinoa powder to 30%, equilibrating at 4°C for 24 h, performing heat treatment for modification, and extracting with a 0.2% sodium hydroxide solution. The sodium hydroxide solution is added at a liquid-to-solid ratio of 16 mL:1 g, and after extraction for 14 h, the pH is adjusted to 7.0, followed by centrifugation.

[0015] In one embodiment of the present invention, the grinding in S2 is performed using a high-speed blender at 30,000 rpm for 1 min.

[0016] In one embodiment of the present invention, the drying in step S2 is drying at 50°C for 4 hours.

[0017] A second object of the present invention is to provide quinoa starch obtained by the above preparation method.

[0018] A third objective of this invention is to provide the application of the above-mentioned quinoa starch in the processing of low glycemic index foods.

[0019] The fourth objective of this invention is to provide the application of the above-mentioned quinoa starch in the preparation of health foods that help lower blood sugar.

[0020] The fifth objective of this invention is to provide a low glycemic index food containing the aforementioned quinoa starch.

[0021] The sixth objective of this invention is to provide a health food containing the above-mentioned quinoa starch that helps lower blood sugar.

[0022] The beneficial effects of this invention are:

[0023] (1) This invention addresses the problem of high saponin content in quinoa by employing a compound enzymatic hydrolysis method to specifically degrade saponins in quinoa slurry. This enzymatic hydrolysis process significantly improves the removal efficiency of saponins, effectively eliminates the bitterness of quinoa products, and improves the taste and processing performance of the products.

[0024] (2) This invention addresses the problems of low resistant starch content and high glycemic index in quinoa by using heat treatment to restructure quinoa starch. This process, through precise control of temperature and time parameters, effectively promotes the rearrangement of starch molecular structure, significantly increases the content of resistant starch, and significantly reduces the glycemic index of the final product. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be noted that the embodiments mentioned below are only for explaining this invention and are not intended to limit the scope of this invention. The embodiments mentioned below are only some embodiments of this invention, not all embodiments. Those skilled in the art can refer to the content of this document and appropriately improve the process parameters to achieve the desired results. It should be particularly pointed out that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments, and those skilled in the art can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content and scope of this invention to realize and apply the technology of this invention. In the art, any embodiments obtained by other skilled personnel without creative effort are protected by this invention.

[0026] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials, reagents and instruments used are conventional materials, reagents and instruments in the art, which can be obtained by those skilled in the art through commercial channels.

[0027] The reagents used in the following embodiments of the present invention are as follows:

[0028] Cellulase, pectinase, β-glucosidase, pepsin, α-amylase, trypsin and lipase were purchased from Shanghai Yuanye Biotechnology Co., Ltd.

[0029] Oleanolic acid was purchased from Macklin Ltd.;

[0030] Quinoa was purchased from Golmud Gelifu Agricultural Development Co., Ltd.

[0031] The detection method involved in this invention is as follows:

[0032] 1. Extraction and determination of saponins

[0033] (1) Preparation of standard solutions

[0034] Accurately weigh 10.01 mg of oleanolic acid standard, place it in a 50 mL volumetric flask, dissolve it in methanol and dilute to volume to prepare a standard stock solution with a concentration of 0.202 mg / mL.

[0035] (2) Drawing the standard curve

[0036] Accurately measure 0, 50, 100, 200, and 400 μL of the standard stock solution into dry, stoppered test tubes. Evaporate to dryness at 60 °C, remove and cool. Add 0.2 mL of 5% vanillin-glacial acetic acid and 0.8 mL of perchloric acid sequentially, and shake well. Incubate in a 60 °C water bath for 15 min, then remove and cool in an ice-water bath for 10 min. Add 4 mL of glacial acetic acid and shake well. Measure the absorbance A of each standard solution at 420 nm. Plot a standard curve with absorbance A as the ordinate and the corresponding standard concentration (mg / mL) as the abscissa.

[0037] (3) Determination of quinoa samples

[0038] The sample was passed through a 60-mesh sieve, and 1 g was weighed and placed in an Erlenmeyer flask. 70% ethanol solution was added at a solid-liquid ratio of 1:30 (g / mL). Extraction was carried out at 50℃ with shaking for 24 h. The filtrate obtained was the test solution. 400 μL of the test solution was processed in the same manner as the standard, and the absorbance was measured at 420 nm. The saponin content of the sample was calculated based on the standard curve. The formula for calculating the saponin content is as follows:

[0039] Saponin content (mg / g) = mV / Mv;

[0040] In the formula, m is the saponin content in the sample solution, in mg; v is the volume of the test solution, in mL; M is the total mass of the sample, 5 g; and V is the sample volume of the test sample, 400 μL.

[0041] 2. Determination of in vitro digestibility

[0042] Each group of samples underwent three parallel digestion simulations, ensuring the experimental system temperature remained constant at 37℃. The specific operating steps are as follows:

[0043] Weigh 1 g of starch sample, add pepsin (100 U / mL), adjust the pH of the digestion solution to 3.0 with HCl (1 mol / L), and digest in a constant temperature water bath with shaking for 0.5 h. After simulated gastric digestion, add α-amylase (10 U / mL), trypsin (5 U / mL), and lipase (10 U / mL) to the gastric digestion solution, and adjust the pH of the digestion solution to 7.0 with NaOH (1 mol / L). During digestion, at 0, 10, 20, 40, 60, 90, 120, and 180 min, respectively, dehydrate 100 μL of the digestion solution, add 900 μL of anhydrous ethanol, and determine its reducing sugar content. Calculate the starch hydrolysis rate according to the following formula:

[0044] .

[0045] Plot hydrolysis curves with hydrolysis time on the x-axis and starch hydrolysis rate on the y-axis. Calculate the area under the starch hydrolysis curves for each sample and the reference sample (glucose) during the 0-180 min period.

[0046] Hydrolysis curves were plotted with hydrolysis time on the x-axis and starch hydrolysis rate on the y-axis. The area under the starch hydrolysis curve for each sample and the reference sample (white bread) was calculated during the 0-180 min period. Based on the nonlinear model established by Goñi et al., the area under the hydrolysis curve (AUC) was calculated using a first-order equation:

[0047] ;

[0048] In the formula: t f The final time is 180 min; t0 is the initial time of 0 min; C∞ is the time of t. f The concentration of glucose at time t; k is the kinetic constant.

[0049] The HI and eGI values ​​are calculated using the following formulas:

[0050] ;

[0051] eGI = 39.71 + 0.549HI.

[0052] Example 1: Effects of blanching temperature and time on saponin content and eGI value in quinoa starch

[0053] To investigate the effects of different blanching temperatures and times on the saponin content and eGI value of quinoa starch, modified quinoa was blanched, and modified quinoa starch was extracted. The following control standards were prepared for a control experiment:

[0054] Control 1: Quinoa was washed with clean water and stirred in a 70℃ water bath at 300 rpm for 1, 3, and 5 min respectively. After draining the water, blanched quinoa was obtained. The blanched quinoa was ground into a slurry using a high-speed blender (30,000 rpm, 1 min). A 0.2% sodium hydroxide solution was added for extraction. The ratio of sodium hydroxide solution to quinoa was 16 mL:1 g. The extraction was carried out for 14 h. The pH was then adjusted to 7.0. After centrifugation, the precipitate was washed three times with water. The precipitate was then freeze-dried to obtain modified quinoa starch.

[0055] Control 2: Quinoa was washed with clean water and stirred in an 80℃ water bath at 300 rpm for 1, 3, and 5 min respectively. After draining the water, blanched quinoa was obtained. The blanched quinoa was ground into a slurry using a high-speed blender (30,000 rpm, 1 min). A 0.2% sodium hydroxide solution was added for extraction. The ratio of sodium hydroxide solution to quinoa was 16 mL:1 g. The extraction was carried out for 14 h. The pH was then adjusted to 7.0. After centrifugation, the precipitate was washed three times with water. The precipitate was then freeze-dried to obtain modified quinoa starch.

[0056] Control 3: Quinoa was washed with clean water and stirred in a 90℃ water bath at 300 rpm for 1, 3, and 5 min respectively. After draining the water, blanched quinoa was obtained. The blanched quinoa was ground into a slurry using a high-speed blender (30,000 rpm, 1 min). A 0.2% sodium hydroxide solution was added for extraction. The ratio of sodium hydroxide solution to quinoa was 16 mL:1 g. The extraction was carried out for 14 h. The pH was then adjusted to 7.0. After centrifugation, the precipitate was washed three times with water. The precipitate was then freeze-dried to obtain modified quinoa starch.

[0057] The saponin content and eGI value of the quinoa starch prepared by the above method were detected, and the results are shown in Table 1.

[0058] Table 1. Effects of blanching temperature and time on saponin content and eGI value in quinoa starch.

[0059]

[0060] Note: Lowercase letters (ac) indicate that the blanching temperature has a significant effect on the saponin content and eGI value of quinoa flour.

[0061] As shown in Table 1, the eGI value of quinoa starch was lowest (57.8) when blanched at 80℃ for 3 min, significantly better than other treatment conditions. While increasing the blanching temperature to 90℃ further reduced the saponin content to 0.59%, it also led to an increase in the eGI value (59.1). Treatment at 80℃ for 3 min effectively degraded saponins (0.79%) while achieving optimal starch digestibility, indicating that this condition achieved the best balance between saponin removal and starch quality maintenance. The shorter 3-min treatment time avoided excessive starch gelatinization, while the moderate temperature of 80℃ disrupted cell structure to promote saponin dissolution without significantly altering the starch molecular structure. Therefore, the optimal blanching temperature was determined to be 80℃, and the optimal blanching time was determined to be 3 min.

[0062] Example 2: Effect of a single enzyme on saponin content and eGI value in quinoa starch

[0063] To investigate the effects of different enzymes on the saponin content and eGI value of quinoa starch, quinoa was blanched under the optimal blanching conditions obtained in Example 1. After blanching, the quinoa was ground into a slurry, and the quinoa slurry was enzymatically hydrolyzed using different enzymes to extract modified quinoa starch. The following control standards were prepared for the control experiment:

[0064] Control 1: Quinoa was washed with clean water and stirred at 300 rpm for 3 min in an 80℃ water bath. After draining, blanched quinoa was obtained. The blanched quinoa was ground into a slurry using a high-speed blender (30000 rpm, 1 min). Cellulase (500 U / g) was added and enzymatically hydrolyzed at 40℃ and pH 5.0 for 2 h. Then, the slurry was centrifuged at 9000 rpm for 10 min at 4℃, the supernatant was discarded, and the quinoa was dried at 50℃ for 4 h to obtain enzymatically modified quinoa powder. The enzymatically modified quinoa powder was extracted with a 0.2% sodium hydroxide solution at a liquid-to-solid ratio of 16 mL:1 g for 14 h. The pH was then adjusted to 7.0, and the precipitate was obtained by centrifugation. The precipitate was washed three times with water and then freeze-dried to obtain modified quinoa starch.

[0065] Control 2: Quinoa was washed with clean water and stirred at 300 rpm for 3 min in an 80℃ water bath. After draining, blanched quinoa was obtained. The blanched quinoa was ground into a slurry using a high-speed blender (30,000 rpm, 1 min). Pectinase (500 U / g) was added and enzymatically hydrolyzed at 40℃ and pH 5.0 for 2 h. Then, the quinoa was centrifuged at 9,000 rpm for 10 min at 4℃, the supernatant was discarded, and the quinoa was dried at 50℃ for 4 h to obtain enzymatically modified quinoa powder. The enzymatically modified quinoa powder was extracted with a 0.2% sodium hydroxide solution at a liquid-to-solid ratio of 16 mL:1 g for 14 h. The pH was then adjusted to 7.0, and the precipitate was obtained by centrifugation. The precipitate was washed three times with water and then freeze-dried to obtain modified quinoa starch.

[0066] Control 3: Quinoa was washed with clean water and stirred at 300 rpm for 3 min in an 80℃ water bath. After draining, blanched quinoa was obtained. The blanched quinoa was ground into a slurry using a high-speed blender (30,000 rpm, 1 min). β-glucosidase (500 U / g) was added and enzymatically hydrolyzed at 40℃ and pH 5.0 for 2 h. Subsequently, the quinoa was centrifuged at 9,000 rpm for 10 min at 4℃, the supernatant was discarded, and the quinoa was dried at 50℃ for 4 h to obtain enzymatically modified quinoa powder. The enzymatically modified quinoa powder was extracted with a 0.2% sodium hydroxide solution at a liquid-to-solid ratio of 16 mL:1 g for 14 h. The pH was then adjusted to 7.0, and the precipitate was obtained by centrifugation. The precipitate was washed three times with water and then freeze-dried to obtain modified quinoa starch.

[0067] The saponin content and eGI value of the quinoa starch prepared by the above method were detected, and the results are shown in Table 2.

[0068] Table 2. Effects of different enzymes on saponin content and eGI value in quinoa starch.

[0069]

[0070] Note: Lowercase letters (ab) indicate that different enzymes have significantly different effects on the saponin content and eGI value of quinoa starch.

[0071] As shown in Table 2, the three enzyme treatments had significant differences in their effects on the saponin content of quinoa starch. The β-glucosidase treatment group had the lowest saponin content (0.35%), significantly lower than the pectinase treatment group (0.45%), demonstrating a specific degradation advantage for saponins. Regarding starch digestibility, the eGI values ​​after the three enzyme treatments varied within a narrow range (58.6-57.9), indicating that the enzyme treatment had a limited impact on starch digestibility. This phenomenon may be due to the fact that enzyme treatment mainly acts on the cell wall and saponin components, with less impact on the starch molecular structure. Furthermore, the homogenization effect of the subsequent alkali extraction process further weakened the differences brought about by enzyme treatment. In summary, β-glucosidase performed best in reducing saponin content, but its effect on improving starch digestibility was not significant.

[0072] Example 3: Effect of the composition of the complex enzyme on the saponin content and eGI value of quinoa starch

[0073] To investigate the effect of the composition of the complex enzyme on the saponin content and eGI value of quinoa starch, quinoa was blanched under the optimal blanching conditions obtained in Example 1. After blanching, the quinoa was ground into a slurry, and the quinoa slurry was enzymatically hydrolyzed using complex enzymes with different compositions. Modified quinoa starch was then extracted, and the following control standards were prepared for the control experiment:

[0074] Control 1: Quinoa was washed with clean water and stirred at 300 rpm for 3 min in an 80℃ water bath. After draining, blanched quinoa was obtained. The blanched quinoa was ground into a slurry using a high-speed blender (30,000 rpm, 1 min). Cellulase (500 U / g) and β-glucosidase (500 U / g) were added, and the mixture was enzymatically hydrolyzed for 2 h at 40℃ and pH 5.0. Subsequently, the mixture was centrifuged at 9,000 rpm for 10 min at 4℃, the supernatant was discarded, and the mixture was dried at 50℃ for 4 h to obtain enzymatically modified quinoa powder. The enzymatically modified quinoa powder was extracted with a 0.2% sodium hydroxide solution at a liquid-to-solid ratio of 16 mL:1 g for 14 h. The pH was then adjusted to 7.0, and the precipitate was obtained by centrifugation. The precipitate was washed three times with water and then freeze-dried to obtain modified quinoa starch.

[0075] Control 2: Quinoa was washed with clean water and stirred at 300 rpm for 3 min in an 80℃ water bath. After draining, blanched quinoa was obtained. The blanched quinoa was ground into a slurry using a high-speed blender (30,000 rpm, 1 min). Pectinase (500 U / g) and β-glucosidase (500 U / g) were added, and the mixture was enzymatically hydrolyzed for 2 h at 40℃ and pH 5.0. Subsequently, the mixture was centrifuged at 9,000 rpm for 10 min at 4℃, the supernatant was discarded, and the mixture was dried at 50℃ for 4 h to obtain enzymatically modified quinoa powder. The enzymatically modified quinoa powder was extracted with a 0.2% sodium hydroxide solution at a liquid-to-solid ratio of 16 mL:1 g for 14 h. The pH was then adjusted to 7.0, and the precipitate was obtained by centrifugation. The precipitate was washed three times with water and then freeze-dried to obtain modified quinoa starch.

[0076] Control 3: Quinoa was washed with clean water and stirred at 300 rpm for 3 min in an 80℃ water bath. The water was drained to obtain blanched quinoa. The blanched quinoa was ground into a slurry using a high-speed blender (30000 rpm, 1 min). Cellulase (500 U / g) and pectinase (500 U / g) were added, and the mixture was enzymatically hydrolyzed for 2 h at 40℃ and pH 5.0. Subsequently, the mixture was centrifuged at 9000 rpm for 10 min at 4℃, the supernatant was discarded, and the mixture was dried at 50℃ for 4 h to obtain enzymatically modified quinoa powder. The enzymatically modified quinoa powder was extracted with a 0.2% sodium hydroxide solution at a liquid-to-solid ratio of 16 mL:1 g for 14 h. The pH was then adjusted to 7.0, and the precipitate was obtained by centrifugation. The precipitate was washed three times with water and then freeze-dried to obtain modified quinoa starch.

[0077] Control 4: Quinoa was washed with clean water and stirred at 300 rpm for 3 min in an 80℃ water bath. The water was drained to obtain blanched quinoa. The blanched quinoa was ground into a slurry using a high-speed blender (30000 rpm, 1 min). Cellulase (500 U / g), pectinase (500 U / g), and β-glucosidase (500 U / g) were added and enzymatically hydrolyzed at 40℃ and pH 5.0 for 2 h. Then, it was centrifuged at 9000 rpm for 10 min at 4℃, the supernatant was discarded, and it was dried at 50℃ for 4 h to obtain enzymatically modified quinoa powder. The enzymatically modified quinoa powder was extracted with a 0.2% sodium hydroxide solution at a liquid-to-solid ratio of 16 mL:1 g for 14 h. The pH was then adjusted to 7.0, and the precipitate was obtained by centrifugation. The precipitate was washed three times with water and then freeze-dried to obtain modified quinoa starch.

[0078] The saponin content and eGI value of the quinoa starch prepared by the above method were detected, and the results are shown in Table 3.

[0079] Table 3. Effects of complex enzyme composition on saponin content and eGI value in quinoa starch.

[0080]

[0081] Note: Lowercase letters (ad) indicate that the composition of the complex enzyme has a significant effect on the saponin content and eGI value of quinoa flour.

[0082] As shown in Table 3, the effects of compound enzyme treatment on the saponin content and eGI value of quinoa flour varied significantly. The three-enzyme compound treatment group (cellulase + pectinase + β-glucosidase) had the lowest saponin content (0.07%), significantly better than other treatment groups, demonstrating the best synergistic degradation effect. Notably, the saponin content of the compound treatment groups containing β-glucosidase (cellulase + β-glucosidase and pectinase + β-glucosidase) was significantly lower than that of the cellulase + pectinase group (0.22%), confirming the key role of β-glucosidase in saponin degradation.

[0083] Regarding starch digestibility, the pectinase + β-glucosidase treatment group had the lowest eGI value (56.5), while the cellulase + pectinase group had the highest eGI value (59.0). The eGI values ​​of each combined enzyme treatment group (56.5-59.0) showed relatively small variations compared to the single enzyme treatment groups (57.8-58.6). This result indicates that although different enzyme combinations showed significant differences in saponin degradation effects, these enzymes primarily act on cell wall components and saponin molecules, having a relatively small impact on starch structure, thus limiting their improvement on starch digestibility.

[0084] Example 4: Determination of the optimal heat treatment scheme for quinoa starch

[0085] To investigate the effect of heat treatment on the saponin content and eGI value of quinoa starch, quinoa was blanched under the optimal blanching conditions obtained in Example 1. After blanching, the quinoa was ground into a slurry, and then enzymatically hydrolyzed using a complex enzyme combination containing three enzymes as described in Example 3 to obtain enzymatically modified quinoa flour. After water equilibration, the flour was heat-treated using different methods to extract modified quinoa starch. The specific methods are as follows:

[0086] Quinoa was washed with clean water and stirred at 300 rpm for 3 minutes in an 80℃ water bath. The water was then drained to obtain blanched quinoa. The blanched quinoa was ground into a slurry using a high-speed blender (30,000 rpm, 1 minute). Pectinase (500 U / g), cellulase (500 U / g), and β-glucosidase (500 U / g) were added, and the mixture was enzymatically hydrolyzed at 40℃ and pH 5.0 for 2 hours. Subsequently, the mixture was centrifuged at 9,000 rpm for 10 minutes at 4℃, the supernatant was discarded, and the quinoa was dried at 50℃ for 4 hours to obtain enzymatically modified quinoa powder. Water was added to adjust the moisture content of the enzymatically modified quinoa powder to 30%, and the moisture was equilibrated at 4℃ for 24 hours. The powder was then subjected to 30% of the following treatments: infrared treatment at 600 W for 150 seconds, microwave treatment at 600 W for 15 seconds, steam treatment at 170℃ for 4 minutes, and hot and humid treatment at 110℃ for 3 minutes. h; Extraction was performed using a 0.2% sodium hydroxide solution with a liquid-to-solid ratio of 16 mL:1 g for 14 h. The pH was then adjusted to 7.0, centrifuged to obtain a precipitate, which was then washed three times with water. The precipitate was then freeze-dried to obtain modified quinoa starch.

[0087] The saponin content and eGI value of the quinoa starch prepared by the above method were detected, and the results are shown in Table 4.

[0088] Table 4. Effects of different heat treatment methods on quinoa starch saponin content and eGI value.

[0089]

[0090] Note: Lowercase letters (ad) indicate that different heat treatment methods have significantly different effects on the eGI value of quinoa starch.

[0091] As shown in Table 4, different heat treatment methods significantly affected the saponin removal and eGI value improvement of quinoa starch. The hot-wet treatment (110℃, 3 h) exhibited the best overall effect, with the lowest eGI value (49.2), significantly lower than other treatment groups (p<0.05), and the saponin content (0.009%) was only slightly higher than that of the superheated steam treatment (0.003%). It is noteworthy that although the superheated steam treatment showed the best saponin degradation effect, its eGI value (54.2) was significantly higher than that of the hot-wet treatment, indicating that simple high-temperature short-time treatment had limited effect on improving starch digestibility. In contrast, the hot-wet treatment, through the synergistic effect of heat and moisture, not only effectively degraded saponins but also significantly altered the starch molecular structure, forming more anti-digestive components.

[0092] The contents not described in detail in this specification are well-known to those skilled in the art. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A process for the preparation of debittered low GI value quinoa starch, characterized by, Comprising the following steps: S1, the washed quinoa is placed in 80℃ water bath condition under stirring for 3 min, and then drained to obtain blanched quinoa; S2, the blanched quinoa is ground into slurry, and then a combination of pectinase, cellulase and β-glucosidase is added for enzymatic hydrolysis, the addition amount of each enzyme is 500 U / g, after centrifugation to remove the supernatant, the enzymatic hydrolysis modified quinoa powder is obtained by drying; S3, the enzymatic hydrolysis modified quinoa powder is dissolved by adding water, and then balanced at 4℃ for 24 h, and then modified by heat treatment, and then the modified quinoa powder is extracted by sodium hydroxide solution, and then the precipitate is obtained by centrifugation, and then washed 2-3 times, and then the precipitate is freeze-dried to obtain modified quinoa starch; the heat treatment is hot and humid treatment at 110℃ for 3 h.

2. The production method according to claim 1, characterized by, The enzymatic hydrolysis conditions in S2 are 40℃, pH 5.0, and enzymatic hydrolysis for 2 h.

3. The production method according to claim 1, characterized by, In S3, the water content of the enzymatic hydrolysis modified quinoa powder is adjusted to 30% by adding water, and then balanced at 4℃ for 24 h, and then modified by heat treatment, and then extracted by 0.2% sodium hydroxide solution, and then the sodium hydroxide solution is added according to the liquid-solid ratio of 16 mL:1 g, and then the pH is adjusted to 7.0 after 14 h of extraction, and then centrifuged.

4. The quinoa starch obtained by the preparation method of any one of claims 1-3.

5. The application of the quinoa starch of claim 4 in processing low glycemic index food.

6. The application of the quinoa starch of claim 4 in preparing health food for assisting blood sugar reduction.

7. A low glycemic index food containing the quinoa starch of claim 4.

8. A health food for assisting blood sugar reduction containing the quinoa starch of claim 4.

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