High-amylose corn starch, preparation method thereof and application of high-amylose corn starch in low-GI food

Abstract

The invention belongs to the technical field of food, and discloses a preparation method of high-amylose corn starch and application of the high-amylose corn starch in low-GI food. According to the high-amylose corn starch, high-amylose corn kernels are pretreated mainly through enzymatic softening, high-amylose corn starch slurry obtained through enzymatic soaking is subjected to high-pressure homogenization-enzymatic extraction, and the high-amylose corn starch is obtained. The low-GI bread is prepared by fermenting and baking the following raw materials in percentage by weight: 20%-50% of high amylose corn starch, 10%-30% of high gluten flour, 10%-25% of eggs, 1%-5% of sugar, 1%-4% of a leavening agent, 0.2%-1% of table salt, 2%-9% of a mixed plant extract and the balance of water. The invention further discloses a preparation method of the low-GI bread, the GI value of the prepared bread is 42.68, and the requirement (GI is smaller than or equal to 55) of low-GI food is met.

Description

Technical Field

[0001] The invention belongs to the technical field of food, and in particular relates to a high-amylose corn starch and a preparation method thereof and application thereof in low-GI food. Background Art

[0002] The bread we use in daily life is mainly made of refined wheat flour. If refined grains are consumed for a long time, it will not only lead to nutritional imbalance in the human body, but also the glycemic index (GI) value of refined wheat flour is relatively high.

[0003] High amylose corn starch is a very good source of resistant starch (HACS). Resistant starch mainly acts in the large intestine and can be fermented to produce various short-chain fatty acids, which are beneficial to improving the health and function of the human intestine. Studies have found that Cornus officinalis, Eucommia ulmoides leaves, mulberry leaves, and peony flowers all have hypoglycemic effects. Therefore, HACS can be used as the main raw material of functional foods, and a low GI healthy food can be developed by combining Cornus officinalis, Eucommia ulmoides leaves, mulberry leaves, and peony flowers.

[0004] China has now cultivated high-amylose corn varieties with independent intellectual property rights, but the current problems faced in the extraction of high-amylose corn starch include the difficulty in separating starch and protein, resulting in low yield and low purity. It has not yet been put into large-scale commercial production, resulting in increased costs and limited product applications. Therefore, it is of great significance to explore an extraction process that can effectively improve the yield and purity of high-amylose corn starch and provide laboratory data support for the industrial production of high-amylose corn starch. Summary of the invention

[0005] In view of the problems and shortcomings in the prior art, the present invention provides a high-amylose corn starch and a preparation method thereof and application thereof in low GI foods.

[0006] Based on the above purpose, the present invention adopts the following technical solution:

[0007] The first aspect of the present invention provides a method for preparing high-amylose corn starch, comprising the following steps:

[0008] (1) Enzyme soaking

[0009] S101: soaking high-amylose corn seeds in water, grinding them, sieving them to remove part of the seed coat and embryo, and filtering and separating the soaking liquid and the roughly ground high-amylose corn particles;

[0010] S102: Soaking high-amylose corn kernels in NaCl solution, removing embryos, and washing with water;

[0011] S103: adding a composite enzyme preparation A to a NaHSO3 solution, wherein the composite enzyme preparation A is composed of cellulase and acid protease in a mass ratio of (0.8-2.0): (0.1-1.2), and then adding the high-amylose corn particles washed in step S102, soaking, filtering, and crushing to obtain a high-amylose corn starch slurry; the mass ratio of the composite enzyme preparation A to the high-amylose corn kernels is (0.1-2.5):100;

[0012] (2) High-pressure homogenization-enzymatic extraction

[0013] S201: homogenizing the high amylose corn starch slurry obtained in step (1) at 40-120 MPa for 8-12 times;

[0014] S202: after homogenization, adding compound enzyme preparation B, performing enzymolysis, inactivating enzymes, cooling, filtering, and collecting filtrate; the mass ratio of the compound enzyme preparation B to the high straight-chain corn seeds in step (1) is (0.2-3):100, and the compound enzyme preparation B is composed of neutral protease and alkaline protease in a mass ratio of (0.5-1.5):(1.5-2.5);

[0015] S203: The obtained filtrate is mixed with the soaking liquid obtained in step (1), and then centrifuged to discard the supernatant. The precipitate is washed with water, and then centrifuged again to discard the supernatant. The obtained precipitate is dried to obtain high-amylose corn starch.

[0016] Preferably, the ratio of high-amylose corn kernels to water in step S101 is 1:(0.5-3); more preferably, the ratio of high-amylose corn kernels to water in step S101 is 1:2.

[0017] Preferably, the mass ratio of the complex enzyme preparation A in step S103 to the high-linear corn seeds in step S101 is 0.9:50.

[0018] Preferably, in step S103, the mass ratio of cellulase to acid protease is 1.05:0.67.

[0019] Preferably, the mass ratio of the complex enzyme preparation B in step S202 to the high-linear corn seeds in step S101 is 2.5:100.

[0020] Preferably, in step S202, the mass ratio of neutral protease to alkaline protease is 1.2:2.

[0021] Preferably, the concentration of the NaCl solution in step S102 is 0.5-4 mol / L; more preferably, the concentration of the NaCl solution in step S102 is 2 mol / L.

[0022] Preferably, the concentration of the NaHSO3 solution in step S103 is 0.1-1.7 g / L, and the solid-liquid ratio with the high-linear corn seeds in step S101 is (1-3):(3-8); more preferably, the concentration of the NaHSO3 solution in step S103 is 0.8 g / L, and the solid-liquid ratio with the high-linear corn seeds in step S101 is 1:3.

[0023] Preferably, the mesh number of filtration in step S202 is 50-200 mesh; more preferably, the mesh number of filtration in step S202 is 100 mesh.

[0024] Preferably, the centrifugal speed in step S203 is 1000-7000 rpm, and the centrifugal time is 10-25 min; more preferably, the centrifugal speed in step S203 is 4000 rpm, and the centrifugal time is 25 min.

[0025] Preferably, the drying temperature in step S203 is 20-80° C., and the drying time is 5-19 hours; more preferably, the drying temperature in step S203 is 55° C., and the drying time is 12 hours.

[0026] The second aspect of the present invention provides the use of high-amylose corn starch prepared by the method described in the first aspect in low GI food.

[0027] The third aspect of the present invention provides a low GI bread, which is fermented and baked from the following raw materials in weight percentage: 20%-50% high-amylose corn starch prepared by the method described in the first aspect, 10%-30% high-gluten flour, 10%-25% eggs, 1%-5% sugar, 1%-4% leavening agent, 0.2%-1% salt, 2%-9% mixed plant extract, and the balance is water, wherein the mixed plant extract is prepared by mixing, water-extracting and concentrating eucommia leaf powder, cornus officinalis powder, mulberry leaf powder and peony pollen in a mass ratio of (1.3-2.4):(1.0-1.8):(1.2-2.0):(0.8-1.9).

[0028] Preferably, the low GI bread is fermented and baked from the following raw materials in weight percentage: 30% high-amylose corn starch, 16% high-gluten flour, 15% eggs, 1.5% sugar, 2.4% leavening agent, 0.8% salt, 5% mixed plant extract, and the balance is water.

[0029] Preferably, the mixed plant extract is prepared by mixing, water extracting and concentrating Eucommia leaf powder, Cornus officinalis powder, mulberry leaf powder and peony pollen in a mass ratio of 2:1.5:1.7:1.2.

[0030] The fourth aspect of the present invention provides a method for preparing the low GI bread according to the third aspect, characterized in that the method comprises the following steps:

[0031] (1) mixing high amylose corn starch, high gluten flour, eggs, sugar, leavening agent, salt, mixed plant extract and water into dough;

[0032] (2) leaving the dough to rest for 5-40 minutes at an ambient temperature of 25° C. to 28° C. and a humidity of 55% to 90% for resting, and then fermenting for the first time until the dough expands to 2-3 times its original size;

[0033] (3) cutting the fermented dough into pieces, rolling them into balls, and performing secondary fermentation at a temperature of 35° C. to 38° C. and a humidity of 80% to 85% until the dough is 2 to 3 times larger;

[0034] (4) The dough that has been fermented twice is baked to obtain low GI bread.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The present invention uses enzymatic softening to pre-treat high-amylose corn kernels, and utilizes the degradation and modification of proteins wrapped outside starch molecules by proteases, so that large molecular proteins are converted into small molecular peptides, thereby effectively separating proteins from starch; the high-amylose corn starch slurry obtained by enzymatic soaking is subjected to high-pressure homogenization-enzymatic extraction of high-amylose corn starch, and under the efficient catalytic action of the enzyme and the strong shearing, impact, vibration and cavitation generated during the high-pressure homogenization process, the mechanical strength of the high-amylose corn kernels is reduced, and their toughness and elasticity are changed, thereby better separating the cortex, germ and endosperm, breaking chemical bonds such as hydrogen bonds and disulfide bonds inside the protein, thereby destroying the protein matrix, so that the corn starch can be better released from the protein matrix.

[0037] (2) The high-amylose corn starch of the present invention has a simple preparation process, low cost, no chemical additives are used in the preparation process, no pollution to the environment and human body, and good safety.

[0038] (3) The mixed extract of Eucommia leaf powder, Cornus officinalis powder, mulberry leaf powder and peony pollen prepared by the present invention has an α-amylase inhibition rate of 71.2% and an α-glucosidase inhibition rate of 96.3%, and has a good in vitro hypoglycemic effect.

[0039] (4) The bread prepared by the present invention uses high-amylose corn starch and a mixed extract of eucommia leaf powder, cornus officinalis powder, mulberry leaf powder and peony pollen as main raw materials, wherein the mixed extract of eucommia leaf, cornus officinalis, mulberry leaf and peony flower is extracted from raw materials of medicine and food and new food. The bread prepared with the mixed extract is green, healthy and safe, and the GI value of the bread is 42.68, which meets the requirements of low GI food (GI<55). BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The starch hydrolysis rate curve of bread obtained for Example 3;

[0041] Figure 2 The starch hydrolysis rate curve of bread obtained for Example 4;

[0042] Figure 3 The starch hydrolysis rate curve of bread obtained for Example 5;

[0043] Figure 4 The starch hydrolysis rate curve of bread was obtained for Comparative Example 1;

[0044] Figure 5 The starch hydrolysis rate curve of bread was obtained for Comparative Example 2. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail by way of embodiments below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0046] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below in conjunction with the embodiments.

[0047] Example 1

[0048] This embodiment provides a high-amylose corn starch, and the preparation method thereof is as follows:

[0049] (1) Enzyme soaking

[0050] S1: Add 200 ml of pure water to 100 g of high-amylase corn seeds, soak in a water bath at 55° C. for 10 h, coarsely grind the soaked high-amylase corn kernels using a food-grade tissue crusher in low gear mode for 1-2 min, sieve to remove part of the seed coat and embryo, filter out the soaking liquid and the coarsely ground corn kernels for later use;

[0051] S2: Add a 2 mol / L NaCl solution to the coarsely ground high-amylose corn kernels and soak them for 1-3 hours (the NaCl solution is sufficient to submerge the corn kernels), remove the embryos floating on the kernels with a sieve, and rinse the high-amylose corn kernels with tap water after removing most of the embryos to remove residual NaCl. The washed high-amylose corn kernels are then set aside;

[0052] S3: Accurately weigh 0.24g NaHSO3, dissolve it in 300mL water, adjust the pH of the NaHSO3 solution to 4.5 with dilute hydrochloric acid, then accurately weigh and add 1.8g of complex enzyme preparation A (complex enzyme preparation A consists of cellulase and acid protease in a mass ratio of 1.05:0.67), stir evenly and add the above-mentioned cleaned high-amylose corn particles, adjust the pH to 4.5 with dilute hydrochloric acid again, then soak at 50°C for 8h, filter out the soaking liquid, pour the solids into the crusher, stir in high-end mode to obtain high-amylose corn starch slurry.

[0053] (2) High-pressure homogenization-enzymatic extraction

[0054] S1: After the high-linear corn slurry obtained in step (1) is stirred evenly, it is poured into a high-pressure homogenizer and homogenized 10 times at 100 MPa;

[0055] S2: After homogenization, add 2.5g of compound enzyme preparation B (compound enzyme preparation B consists of neutral protease and alkaline protease in a mass ratio of 1.2:2), put it in a constant temperature water bath for enzymolysis at 45℃, adjust the pH to 6.8 with dilute hydrochloric acid, and the enzymolysis time is 4h. After the enzymolysis is completed, inactivate the enzyme in a 98℃ water bath for 10min, cool it, filter it with 100-mesh gauze, collect the filtrate, wash the filtered residue with water, filter it, collect the filtrate, repeat 3 times, and mix the obtained filtrates;

[0056] S3: The obtained filtrate is mixed with the soaking liquid obtained in step (1), allowed to stand, and then centrifuged in a centrifuge at a speed of 4000 rpm for 15 min, the supernatant is discarded, and the precipitate is washed with distilled water. In order to collect the starch cleanly, the precipitate is washed with water three times and then centrifuged again. Finally, the starch precipitate is dried in an oven at 55° C. for 12 h to obtain high-amylose corn starch.

[0057] Example 2

[0058] This embodiment provides a mixed plant extract and a preparation method thereof, and detects the α-amylase inhibition rate and α-glucosidase inhibition rate of the extract.

[0059] The preparation method of the mixed plant extract is as follows: the crushed and sieved Eucommia leaf powder, Cornus officinalis powder, mulberry leaf powder and peony pollen are mixed evenly in a mass ratio of 2:1.5:1.7:1.2, water with a solid-liquid ratio of 1:30 is added, and then the mixture is extracted in a water bath at a temperature of 80°C for 3 hours, the extracted mixture extract is filtered, the filtrate is collected, and the reduced pressure concentration is carried out under the conditions of a pressure of 100mba, a speed of 50r / min and a temperature of 70°C until the water extract is dry. The obtained extract is stored in a dryer for later use.

[0060] The detection method of α-amylase inhibition rate is as follows: take 0.5mL sample extract, add 0.5mL α-amylase (0.02mg / mL), and place in a water bath at 37℃ for 5min, add 0.5mL 1% starch solution, react at 37℃ for 15min, add 0.5mL DNS reagent, mix the solution, place in a boiling water bath for 5min, cool to room temperature, set to 25mL, and measure the absorbance at a wavelength of 540nm. For details on the addition of each group of reagents, please refer to the following:

[0061] Blank group: 0.5 mL distilled water + 0.5 mL α-amylase + 0.5 ml 1% starch solution + 0.5 ml DNS reagent;

[0062] Blank control: 0.5 mL distilled water + 0.5 mL distilled water + 0.5 mL 1% starch solution + 0.5 mL DNS reagent;

[0063] Sample group: 0.5 mL extract + 0.5 mL α-amylase + 0.5 mL 1% starch solution + 0.5 mL DNS reagent;

[0064] Sample control: 0.5 mL of extract + 0.5 mL of distilled water + 0.5 mL of 1% starch solution + 0.5 mL of DNS reagent.

[0065] The α-glucosidase inhibition rate detection method is as follows: take 0.1mL of extract and add 0.1mL (0.01mg / mL) α-glucosidase, mix, water bath at 37℃ for 20min, add 0.1mL 10mmol / LPNPG, mix well, water bath at 37℃ for 30min, then add 5mL 0.1moL / LNa2CO3, terminate the reaction, and measure the absorbance at 405nm. For details on the addition of each group of reagents, please refer to the following.

[0066] Blank group: 0.1mL distilled water + 0.1mL α-glucosidase + 0.1mL 10mmol / L PNPG + 5mL 0.1mol / LNa2CO3;

[0067] Blank control: 0.1mL distilled water + 0.1mL distilled water + 0.1mL 10mmol / LPNPG + 5mL 0.1mol / LNa2CO3;

[0068] Sample group: 0.1mL extract + 0.1mL α-glucosidase + 0.1mL 10mmol / L PNPG + 5mL 0.1mol / LNa2CO3;

[0069] Sample control: 0.1 mL extract + 0.1 mL distilled water + 0.1 mL 10 mmol / LPNPG + 5 mL 0.1 mol / LNa2CO3.

[0070] The calculation formulas for α-amylase inhibition rate and α-glucosidase inhibition rate are as follows:

[0071]

[0072] Through calculation, it was found that the α-amylase inhibition rate of the mixed plant extract extracted from eucommia leaf powder, cornus officinalis powder, mulberry leaf powder and peony pollen was 71.2%, and the α-glucosidase inhibition rate was 96.3%. The results showed that the mixed plant extract extracted from eucommia leaf powder, cornus officinalis powder, mulberry leaf powder and peony pollen had a good in vitro hypoglycemic effect.

[0073] Example 3

[0074] This embodiment provides a low GI bread, which is made from the following raw materials in mass ratio: 30% high amylose corn starch obtained in Example 1, 16% high gluten flour, 15% eggs, 1.5% sugar, 2.4% leavening agent, 0.8% salt, 5% mixed plant extract obtained in Example 2, and the balance is water. The preparation method of the low GI bread is as follows:

[0075] Put the raw materials in the above mass ratio into a dough mixer, mix for 15-20 minutes to form a uniform dough, let the dough stand and relax for 20 minutes, let it rest in an environment with a temperature of 25°C-28°C and a humidity of about 75%, ferment it for the first time after resting, wait for the dough to expand to 2-3 times of its original size, cut the fermented dough into dough of an average size of 70g, roll it into balls, ferment the cut dough for the second time, control the temperature at 35°C-38°C and the humidity at 80%-85%, ferment it to 2-3 times of its size, evenly place the fermented dough on a tray, put the tray into an oven, and take it out after baking; cool the baked bread naturally to a temperature below 32°C and then package it.

[0076] Example 4

[0077] The present embodiment provides a low GI bread, which is made of the following raw materials in mass ratio: 40% of the high-amylose corn starch obtained in Example 1, 10% of high-gluten flour, 25% of eggs, 1% of sugar, 1% of a leavening agent, 0.2% of salt, 9% of the mixed plant extract obtained in Example 2, and the balance being water.

[0078] The preparation method of the low GI bread is the same as that of Example 3.

[0079] Example 5

[0080] The present embodiment provides a low GI bread, which is made of the following raw materials in mass ratio: 20% of high-amylose corn starch obtained in Example 1, 30% of high-gluten flour, 15% of eggs, 1.5% of sugar, 2.4% of leavening agent, 1% of salt, 2% of the mixed plant extract obtained in Example 2, and the balance is water.

[0081] The preparation method of the low GI bread is the same as that of Example 3.

[0082] Comparative Example 1

[0083] The present embodiment provides a bread prepared with common corn starch (commercially available), which is made of the following raw materials in mass ratio: 30% corn starch (commercially available), 16% high-gluten flour, 15% eggs, 1.5% sugar, 2.4% leavening agent, 0.8% salt, 5% mixed plant extract obtained in Example 2, and the balance is water.

[0084] The preparation method of the above-mentioned ordinary corn starch (commercially available) bread is the same as that of Example 3.

[0085] Comparative Example 2

[0086] The present embodiment provides a common bread, which is made of the following raw materials in mass ratio: 51% high-gluten flour, 15% eggs, 1.5% sugar, 2.4% leavening agent, 0.8% salt, and the balance is water, without adding high-amylose corn starch and mixed plant extracts.

[0087] The preparation method of the above ordinary bread is the same as that of Example 3.

[0088] Example 6

[0089] In this example, the sensory scoring standard and texture analyzer shown in Table 1 were used to perform sensory characteristic analysis and texture analysis on the bread obtained from Examples 3 to 5 and Comparative Examples 1 to 2. The results are shown in Tables 2 and 3.

[0090] Among them, the method for determining the texture of low GI bread is as follows: after the bread is cooled, take a cube located in the center of the bread with a length of 1cm×1cm×1cm for testing. Each sample is measured three times on average. Parameter settings: texture analyzer P / 50 column probe, sensor range 500N, starting test 0.3N, test speed 60mm / min, strain during test 60.00%, pre-test speed 2.00mm / s, pre-test rate 1.0 mm / s, test rate 1.0 mm / s, post-test rate 1.0mm / s.

[0091] Table 1 Sensory scoring criteria for low GI bread

[0092]

[0093] Table 2 Sensory characteristics analysis results

[0094] Example No. form organize Color Taste and mouthfeel Impurities Total score Example 3 20 20 19 19 19 97 Example 4 19 18 17 18 18 90 Example 5 18 17 17 18 18 88 Comparative Example 1 15 15 17 15 17 79 Comparative Example 2 18 16 17 17 18 86

[0095] Table 3 Bread texture analysis results (n=3)

[0096]

[0097] The results of the sensory characteristics analysis of bread are shown in Table 2. It can be seen that the bread with the addition of high-amylose corn starch and mixed extracts has good sensory quality. Example 4 increases the content of high-amylose corn starch and mixed extracts, and the sensory quality is reduced. The reason may be that the high-amylose corn starch is increased, the dietary fiber content is increased, the protein content in the dough is reduced, and the dough cannot be fully proofed, which affects the sensory score. Example 5 reduces the content of high-amylose corn starch and mixed extracts, the sensory quality is reduced, and its shape, taste and taste are poor. Comparative Example 1 uses ordinary corn starch instead of high-amylose corn starch, and the resulting bread has a lower sensory score. Comparative Example 2 does not add high-amylose corn starch and mixed plant extracts, and its flavor and shape are poor.

[0098] The results showed that the addition of high-amylose corn starch played an important role in the sensory evaluation of bread.

[0099] The texture analysis results of the bread are shown in Table 3. It can be seen that the bread in Example 3 with the addition of high-amylose corn starch and mixed extracts has good texture characteristics. Example 4 increases the content of high-amylose corn starch and mixed extracts, reduces the proportion of protein in the dough, and makes it difficult to form a gluten network structure. The CO2 gas produced by fermentation cannot be completely filled in the gluten network structure, resulting in increased hardness, insufficient elasticity, and poor texture characteristics. The hardness and other qualities of bread are mainly affected by the protein content in the flour. Example 5 reduces the content of high-amylose corn starch and mixed extracts, reduces the proportion of protein, and makes the bread hard enough and has poor adhesiveness. Comparative Example 1 uses ordinary corn starch instead of high-amylose corn starch to increase elasticity, and reduce hardness, adhesiveness and chewiness. Comparative Example 2 does not add high-amylose corn starch and mixed plant extracts, and the hardness of the bread is reduced. The addition of high-amylose corn starch partially replaces the high-gluten flour in the bread formula, which reduces the proportion of gluten protein in the bread, thereby reducing the pore structure formed during the fermentation process, which can increase the hardness of the bread, and the adhesiveness and chewiness are worse than those of Comparative Example 1.

[0100] The results showed that the addition of high amylose corn starch and mixed extracts could give bread better textural properties.

[0101] Example 7

[0102] In this example, the starch hydrolysis rate of bread obtained by testing examples 3 to 4 and comparative examples 1 to 2 was used to calculate the GI value, and white bread (commercially available) was used as a reference sample. The results are shown in Table 4. Figures 1 to 5 .

[0103] GI value detection method: soak 10g sample bread in 100mL distilled water, homogenize, then take 100mg homogenate in a conical flask, add acetate buffer (10mL, pH5.2), keep the temperature in a water bath to 37℃, add 1mL mixed enzyme solution (porcine pancreatic enzyme: amyloglucosidase = 120:80U / mL) also kept at 37℃, enzymolysis at 37℃ for 180min to obtain digestive solution. Within 0-180min, remove the digestive solution every 20min, inactivate the enzyme in a water bath at 100℃ water for 5min, and then use 3,5-dinitrosalicylic acid (DNS) method to detect the starch hydrolysis rate. Draw a hydrolysis curve with hydrolysis time as the horizontal axis and starch hydrolysis rate as the vertical axis, and calculate the area under the starch hydrolysis curve (area under the curve, AUC) of the sample within 0-180min (AUC sample and AUC reference). The results are as follows: Figure 1 shown.

[0104] The hydrolysis index (HI) and GI value of bread starch were calculated according to formula (1) and (2), respectively.

[0105]

[0106] GI = 8.1981 + 0.862 × HI (2).

[0107] Table 4 GI value of bread

[0108] Example No. GI value Whether it meets the requirements of low GI food (GI≤55) Example 3 42.68 yes Example 4 48.91 yes Example 5 51.43 yes Comparative Example 1 54.07 yes Comparative Example 2 70.25 no

[0109] It can be seen from Table 4 that the GI value of the bread obtained in Example 3 is 42.68, which meets the requirements of low GI food; the GI value of the bread obtained in Example 4 is 48.91, which meets the requirements of low GI food; the GI value of the bread obtained in Example 5 is 51.43, which meets the requirements of low GI food; the GI value of the bread obtained in Comparative Example 1 is 54.07, which meets the requirements of low GI food, but the overall GI value is higher than the bread added with high amylose corn starch; the GI value of the bread measured in Comparative Example 2 is 70.25, which does not meet the requirements of low GI food.

[0110] In summary, the above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above technical content as inspiration to make changes or modifications. This is an equivalent embodiment of equivalent changes. However, any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical concept of the present invention still fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing high-amylose corn starch, characterized in that: The following steps are involved: (1) Enzyme soaking S101: soaking high-amylose corn seeds in water, grinding them, sieving them to remove part of the seed coat and embryo, and filtering and separating the soaking liquid and the roughly ground high-amylose corn particles; S102: Soaking high-amylose corn kernels in NaCl solution, removing embryos, and washing with water; S103: adding a composite enzyme preparation A to a NaHSO3 solution, wherein the composite enzyme preparation A is composed of cellulase and acid protease in a mass ratio of (0.8-2.0): (0.1-1.2), and then adding the high-amylose corn particles washed in step S102, soaking, filtering, and crushing to obtain a high-amylose corn starch slurry; the mass ratio of the composite enzyme preparation A to the high-amylose corn kernels is (0.1-2.5):100; (2) High-pressure homogenization-enzymatic extraction S201: homogenizing the high amylose corn starch slurry obtained in step (1) at 40-120 MPa for 8-12 times; S202: after homogenization, adding compound enzyme preparation B, performing enzymolysis, inactivating enzymes, cooling, filtering, and collecting filtrate; the mass ratio of the compound enzyme preparation B to the high straight-chain corn seeds in step (1) is (0.2-3):100, and the compound enzyme preparation B is composed of neutral protease and alkaline protease in a mass ratio of (0.5-1.5):(1.5-2.5); S203: The obtained filtrate is mixed with the soaking liquid obtained in step (1), and then centrifuged to discard the supernatant. The precipitate is washed with water, and then centrifuged again to discard the supernatant. The obtained precipitate is dried to obtain high-amylose corn starch.

2. The method for preparing high amylose corn starch according to claim 1, characterized in that: In step S101, the liquid ratio of high-amylose corn seeds to water is 1:(0.5-3).

3. The method for preparing high amylose corn starch according to claim 1, characterized in that: The concentration of the NaCl solution in step S102 is 0.5-4 mol / L.

4. The method for preparing high amylose corn starch according to claim 1, characterized in that: The concentration of the NaHSO3 solution in step S103 is 0.1-1.7 g / L, and the material-liquid ratio to the high-linear corn kernels is (1-3): (3-8).

5. The method for preparing high amylose corn starch according to claim 1, characterized in that: The mesh size of the filtration in step S202 is 50-200 mesh; the centrifugal speed in step S203 is 1000-7000 rpm, the time is 10-25 min, and the drying temperature is 20° C.-80° C., and the time is 5-19 h.

6. Use of high-amylose corn starch prepared by the method of claims 1-5 in low GI food.

7. A low GI bread, characterized in that: The invention is prepared by fermenting and baking the following raw materials in weight percentage: 20%-50% high-amylose corn starch prepared by the method according to claims 1-5, 10%-30% high-gluten flour, 10%-25% eggs, 1%-5% sugar, 1%-4% leavening agent, 0.2%-1% salt, 2%-9% mixed plant extract, and the balance is water. The mixed plant extract is prepared by mixing, water-extracting and concentrating eucommia leaf powder, cornus officinalis powder, mulberry leaf powder and peony pollen in a mass ratio of (1.3-2.4):(1.0-1.8):(1.2-2.0):(0.8-1.9).

8. The low GI bread according to claim 7, characterized in that The product is fermented and baked from the following raw materials in percentage by weight: 30% high-amylose corn starch, 16% high-gluten flour, 15% eggs, 1.5% sugar, 2.4% leavening agent, 0.8% salt, 5% mixed plant extract, and the balance is water.

9. The low GI bread according to claim 8, characterized in that The mixed plant extract is prepared by mixing, water extracting and concentrating eucommia leaf powder, cornus officinalis powder, mulberry leaf powder and peony pollen in a mass ratio of 2:1.5:1.7:1.

2.

10. The method for preparing low GI bread according to any one of claims 7 to 9, characterized in that: The specific steps include: (1) mixing high amylose corn starch, high gluten flour, eggs, sugar, leavening agent, salt, mixed plant extract and water into dough; (2) leaving the dough to rest for 5-40 minutes at an ambient temperature of 25° C. to 28° C. and a humidity of 55% to 90% for resting, and then fermenting for the first time until the dough expands to 2-3 times its original size; (3) cutting the fermented dough into pieces, rolling them into balls, and performing secondary fermentation at a temperature of 35° C. to 38° C. and a humidity of 80% to 85% until the dough is 2 to 3 times larger; (4) The dough that has been fermented twice is baked to obtain low GI bread.

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