Method for increasing content of resistant starch in starch and application thereof

Abstract

The invention relates to a method for increasing the content of resistant starch in starch and application of the method, and the method comprises the following steps: carrying out autoclaving treatment, enzymolysis treatment and crystallization on the starch, then carrying out microwave drying, cooling and then carrying out hot air drying so as to increase the content of the resistant starch in the starch. According to the method, microwave drying and hot air drying are combined, so that the content of resistant starch is effectively increased, the product color is improved, and meanwhile, the energy consumption is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of resistant starch, and in particular to a method for increasing the content of resistant starch in starch and an application thereof. Background Art

[0002] Resistant starch (RS) is widely used in food and medicine due to its low glycemic index and improved gut health. With rising public health awareness and a growing demand for healthy foods, RS is being used in health foods and special medical foods, particularly for those suffering from obesity, diabetes, hyperlipidemia, and constipation.

[0003] After enzymatic hydrolysis and crystallization, RS3 resistant starch requires drying, typically using hot air convection drying or conduction drying. However, low-temperature conduction drying results in low resistant starch content and poor product quality. High-temperature drying allows the starch molecules to rearrange and crystallize at high moisture content, forming a more stable crystalline structure. 1 However, traditional high-temperature conduction drying is inefficient and can easily lead to surface hardening and coking of starch granules. Due to the bulk of the material, hot air convection drying presents challenges in industrial production, including difficult feeding and uneven heating.

[0004] CN103918872A discloses a method for preparing rice resistant starch. The method comprises gelatinizing, debranching, and crystallizing the rice starch, and then drying the extracted rice resistant starch to obtain the rice resistant starch. The debranching treatment increases the amylose content in the rice starch. The drying temperature is 50-70°C, which is not conducive to increasing the resistant starch content.

[0005] Therefore, it is very necessary to provide a method for increasing the resistant starch content in starch while reducing energy consumption. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a method for increasing the resistant starch content in starch and its application. The present invention combines microwave drying and hot air drying to effectively increase the resistant starch content, improve the product color, and reduce energy consumption.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for increasing the content of resistant starch in starch, the method comprising: subjecting the starch to autoclaving, enzymatic hydrolysis and crystallization, followed by microwave drying, cooling and then hot air drying, so as to increase the content of resistant starch in the starch.

[0009] In the present invention, the water content of the material obtained after heat-pressure treatment, enzymatic hydrolysis treatment and crystallization of starch is 70-80%, mainly free water. During the microwave drying process, the material gelatinizes and molecular bonds break. During the cooling process, some of the leached amylose molecules rearrange to form a tight crystal structure, and it is also possible to form a relatively large amount of starch-water-oxygen bond gel network structure. These structures reduce the sensitivity of digestive enzymes to starch, thereby increasing the content of resistant starch and slowly digestible starch.

[0010] Microwave drying is a new drying method with the advantages of short time, high thermal efficiency, low energy consumption, and good retention of product color. By combining microwave drying and hot air drying, the present invention effectively improves the production efficiency and quality of the product, and at the same time reduces energy consumption.

[0011] Preferably, the starch includes any one or a combination of at least two of corn starch, cassava starch, potato starch, wheat starch or rice starch.

[0012] Preferably, the power of the microwave drying is 100-1000W (for example, it can be 100W, 200W, 300W, 400W, 500W, 600W, 700W, 750W, 800W, 850W, 900W, 950W, 1000W, etc.), and the time is 10-180s (for example, it can be 10s, 40s, 80s, 100s, 140s, 160s, 180s, etc.).

[0013] Preferably, the power of the microwave drying is 300-500W, and the time is 10-30s.

[0014] In the present invention, the microwave power, microwave time and resistant starch content are not positively correlated. As the microwave power and time increase, the degree of damage to the starch granule structure becomes severe and the resistant starch content decreases. The present invention effectively increases the content of resistant starch by reasonably limiting the microwave power and microwave time.

[0015] Preferably, the cooling is to a temperature of 20-30°C (for example, it can be 20°C, 22°C, 24°C, 26°C, 28°C, 30°C, etc.).

[0016] Preferably, the temperature of the hot air drying is 90-105°C (for example, it can be 90°C, 92°C, 95°C, 98°C, 100°C, 102°C, 105°C, etc.), and the hot air drying is until the mass content of the product moisture ≤ 10% (for example, it can be 2%, 4%, 6%, 8%, 10%, etc.).

[0017] In the present invention, if the temperature of hot air drying is too low, the content of resistant starch will decrease; if the temperature is too high, the product is likely to turn yellow. The quality of the product can be effectively guaranteed within the above-defined range.

[0018] Preferably, before the pressure heat treatment, it further includes heating and gelatinizing the mixture of starch and water.

[0019] Preferably, the temperature of the heating and gelatinizing is 90 - 110 °C (such as 90 °C, 95 °C, 100 °C, 105 °C, 110 °C, etc.), and the time is 20 - 40 min (such as 20 min, 25 min, 30 min, 35 min, 40 min, etc.).

[0020] Preferably, the pressure of the pressure heat treatment is 0.1 - 0.25 MPa (such as 0.1 MPa, 0.15 MPa, 0.2 MPa, 0.25 MPa, etc.), the temperature is 100 - 121 °C (such as 100 °C, 105 °C, 110 °C, 115 °C, 121 °C, etc.), and the time is 0.5 - 1 h (such as 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1 h, etc.).

[0021] Preferably, the enzyme used in the enzymatic hydrolysis treatment includes pullulanase.

[0022] Preferably, the dosage of the enzyme in the enzymatic hydrolysis treatment is 1.5 - 2.5% of the mass of the system (such as 1.5%, 1.8%, 2%, 2.2%, 2.5%, etc.).

[0023] Preferably, the pH of the enzymatic hydrolysis is 4 - 6 (such as 4, 4.5, 5, 5.5, 6, etc.), the temperature is 50 - 60 °C (such as 50 °C, 52 °C, 55 °C, 58 °C, 60 °C, etc.), and the time is 2.5 - 3.5 h (such as 2.5 h, 2.8 h, 3 h, 3.2 h, 3.5 h, etc.).

[0024] Preferably, the temperature of the crystallization is 4 - 50 °C (such as 4 °C, 6 °C, 8 °C, 10 °C, 15 °C, 20 °C, 30 °C, 40 °C, 50 °C, etc.), and the time is 16 - 32 h (such as 16 h, 20 h, 24 h, 28 h, 32 h, etc.).

[0025] Preferably, after the crystallization, it further includes a solid-liquid separation step, and the obtained solid product is dried by microwave.

[0026] In the second aspect, the present invention provides a preparation method of a starch product, and the starch product is prepared by the method described in the first aspect.

[0027] Thirdly, the present invention provides a model for predicting the resistant starch content in the starch product prepared by the preparation method described in the second aspect. The model is as follows:

[0028] y = A - Bx1 - Cx2 - Dx1 2 + Ex1x2

[0029] Wherein, y is the mass percentage content of resistant starch in the starch product obtained by subjecting the starch to autoclaving treatment, enzymatic hydrolysis treatment, crystallization, followed by microwave drying, and then hot air drying after cooling; x1 is the time of microwave drying, in units of s; x2 is the power of microwave drying, in units of W; A, B, C, D, and E are all constants. A ranges from 65 to 75 (for example, it can be 65, 68, 69, 70, 71, 72, 75, etc.), B ranges from 0.12 to 0.22 (for example, it can be 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, etc.), C ranges from 0.01 to 0.1 (for example, it can be 0.01, 0.02, 0.04, 0.06, 0.08, 0.1, etc.), D ranges from 0.001 to 0.002 (for example, it can be 0.001, 0.0012, 0.0014, 0.0016, 0.0018, 0.002, etc.), and E ranges from 0.0001 to 0.001 (for example, it can be 0.0001, 0.0002, 0.0004, 0.0006, 0.0008, 0.001, etc.).

[0030] There is no positive correlation between the power and time of microwave drying and the mass percentage content of resistant starch. By constructing a mathematical model of the resistant starch content with the microwave power and time, the present invention can effectively predict the product quality under specific microwave parameters, providing a guiding basis for accurately controlling the drying parameters, improving the product quality, and reducing the production energy consumption.

[0031] Preferably, A ranges from 68 to 72, B ranges from 0.14 to 0.2, C ranges from 0.04 to 0.08, D ranges from 0.0014 to 0.0018, and E ranges from 0.0004 to 0.0008.

[0032] Preferably, the temperature of the hot air drying is 100 - 105 °C (for example, it can be 100 °C, 101 °C, 102 °C, 103 °C, 104 °C, 105 °C, etc.), and the hot air drying is carried out until the mass content of the product moisture is 8 - 10% (for example, it can be 8%, 8.5%, 9%, 9.5%, 10%, etc.).

[0033] Compared with the prior art, the present invention has at least the following beneficial effects:

[0034] (1) The present invention adopts a drying method combining microwave drying and hot air drying, effectively increasing the content of resistant starch in starch, reducing production energy consumption, avoiding the defect of product yellowing, and improving the industrial production efficiency.

[0035] (2) The prediction model of the resistant starch content during the drying process constructed by the present invention has a high correlation coefficient R 2 and a low P value, and can effectively predict the resistant starch content under specific microwave parameters, providing a guiding basis for accurately regulating drying parameters, improving product quality, and reducing production energy consumption. Description of the Drawings

[0036] Figure 1 It is a comparison chart of the product colors of Example 1 and Comparative Example 1. Detailed Embodiments

[0037] The technical solutions of the present invention will be further described below with reference to the drawings and through specific embodiments. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the patent protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0038] Preparation Example 1

[0039] Accurately weigh 100.00 g of corn starch, add 900 mL of distilled water to prepare a starch milk, stir evenly, pre-gelatinize in a boiling water bath for 30 min, then put it into an autoclave at 121 °C and keep warm for 1 h; after the heat treatment, add acetic acid to adjust the system pH to 4.5, add 2% (mass ratio) of pullulanase, put it into a reaction kettle at 200 rpm and 55 °C for enzymatic hydrolysis for 3 h; after the enzymatic hydrolysis treatment, the starch is cooled and crystallized, stirred and crystallized at 50 - 4 °C for 24 h, the crystallization rotation speed is 50 rpm, and the crystallization temperature is as shown in the following table; after the crystallization is completed, discharge the material, and centrifuge the crystallization liquid (6000 r / min, 6 min) to obtain starch solids (yield 79.10%).

[0040] Temperature (°C) Retention time (h) 50 19 40 1 30 1 20 1 10 1 4 1

[0041] Preparation Example 2

[0042] Accurately weigh 100.00 g of cassava starch, add 900 mL of distilled water to prepare a starch milk, stir evenly, pre-gelatinize in a boiling water bath for 30 min, then put it into an autoclave at 121 °C and keep warm for 1 h; after the heat treatment, add acetic acid to adjust the system pH to 4.5, add 2% (mass ratio) of pullulanase, put it into a reaction kettle at 200 rpm and 55 °C for enzymatic hydrolysis for 3 h; after the enzymatic hydrolysis treatment, the starch is cooled and crystallized, stirred and crystallized at 50 - 4 °C for 24 h, the crystallization rotation speed is 50 rpm, and the crystallization temperature refers to Preparation Example 1; after the crystallization is completed, discharge the material, and centrifuge the crystallization liquid (6000 r / min, 6 min) to obtain starch solids.

[0043] Preparation Example 3

[0044] Accurately weigh 100.00 of wheat starch, add 900 mL of distilled water to prepare a starch milk, stir evenly, pre-gelatinize in a boiling water bath for 30 min, then put it into an autoclave at 121 °C and keep warm for 1 h; after the heat pressing is completed, add acetic acid to adjust the pH of the system to 4.5, add 2% (mass ratio) of pullulanase, put it into a reaction kettle at 200 rpm and 55 °C for enzymatic hydrolysis for 3 h; after enzymatic hydrolysis treatment, the starch is cooled and crystallized, stirred and crystallized at 50 - 4 °C for 24 h, the crystallization rotation speed is 50 rpm, and the crystallization temperature refers to Preparation Example 1; after crystallization is completed, discharge the material, and centrifuge the crystallization liquid (6000 r / min, 6 min) to obtain starch solids.

[0045] Example 1

[0046] This example provides a method for increasing the content of resistant starch in starch: The starch solids (provided by Preparation Example 1) are dried at 700 W for 50 s, then cooled to 25 °C, and then dried by hot air at 105 °C until the water content of the product is 10%, and after pulverization and sieving treatment, a starch product is obtained.

[0047] Examples 2 - 9

[0048] The above examples respectively provide a method for increasing the content of resistant starch in starch, and the difference from Example 1 is only the different microwave power and microwave time. The specific parameters are shown in Table 1, and the others refer to Example 1.

[0049] Example 10

[0050] This example provides a method for increasing the content of resistant starch in starch: The starch solids (provided by Preparation Example 2) are dried at 1000 W for 120 s, then cooled to 25 °C, and then dried by hot air at 90 °C until the water content of the product is 4%, and after pulverization and sieving treatment, a starch product is obtained.

[0051] Example 11

[0052] This example provides a method for increasing the content of resistant starch in starch: The starch solids (provided by Preparation Example 3) are dried at 1000 W for 60 s, then cooled to 20 °C, and then dried by hot air at 100 °C until the water content of the product is 8%, and after pulverization and sieving treatment, a starch product is obtained.

[0053] Comparative Example 1

[0054] This comparative example provides a method for increasing the content of resistant starch in starch, and the difference from Example 1 is only that microwave drying is not carried out and hot air drying is directly carried out to obtain a starch product.

[0055] Comparative Example 2

[0056] This comparative example provides a method for increasing the content of resistant starch in starch. The only difference from Example 1 is that microwave drying and hot air drying are carried out simultaneously: the starch solid is dried under the action of 700 W microwave and 105 °C hot air until the water content of the product is 10%, and after being crushed and sieved, a starch product is obtained.

[0057] Test Example 1

[0058] The K-DSTRS kit method was used to test the resistant starch content of the starch products obtained in the above examples and comparative examples respectively, and the energy consumption was calculated at the same time. The total energy consumption = microwave power × time + hot air drying power × time. The summary is shown in Table 1. The color comparison diagrams of the products obtained in Example 1 and Comparative Example 1 are as Figure 1 shown.

[0059] Table 1

[0060]

[0061] It can be seen from the test results that:

[0062] (1) It can be seen from Examples 1 to 11 that by combining microwave drying and hot air drying, the present invention can achieve the technical effect of increasing the content of resistant starch in starch.

[0063] (2) It can be seen from the comparison between Example 1 and Comparative Example 1 that when microwave treatment is not used and only hot air drying is carried out, due to low efficiency, the surface of starch granules is prone to hardening and coking, and the product is significantly yellowish ( Figure 1 ), and the energy consumption during the treatment process is relatively high.

[0064] It can be seen from the comparison between Example 1 and Comparative Example 2 that when microwave and hot air treatments are carried out simultaneously, due to the absence of the retrogradation and recrystallization process, the content of resistant starch decreases.

[0065] Test Example 2

[0066] Taking the microwave time obtained in Examples 1-9 as the variable x1, the microwave power as the variable x2, and the resistant starch content as y for data correlation analysis, the results show that the P values of x1, x2 and y are less than the significant level of 0.01, indicating that both x1 and x2 have a very significant statistical relationship with y.

[0067] Based on the data of microwave time x1, microwave power x2, and resistant starch content y obtained in Examples 1-9, a prediction model of resistant starch content y based on microwave time x1 and microwave power x2 was established, and the regression equation obtained is as follows:

[0068] y = 70.09 - 0.1785x1 - 0.0577x2 - 0.001617x12 +0.000592x1x2(R 2 = 94.27, P = 0.003);

[0069] The above equations were respectively used to predict the resistant starch content, and the results were compared with the actual values (the microwave parameters refer to Table 2, and other operations refer to Example 1). The results are summarized in Table 2 as follows.

[0070] Table 2

[0071]

[0072]

[0073] The results show that the prediction model for resistant starch content provided by the present invention can accurately predict the resistant starch content, providing guidance for precisely regulating the drying parameters, minimizing energy consumption while ensuring product quality, and improving the industrial production efficiency.

[0074] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for increasing the content of resistant starch in starch, characterized in that, The method includes: after the starch is subjected to pressure heat treatment, enzymatic hydrolysis treatment and crystallization, it is subjected to microwave drying, and then hot air drying after cooling, so as to increase the content of resistant starch in the starch.

2. The method according to claim 1, characterized in that, The starch includes any one or a combination of at least two of corn starch, cassava starch, potato starch, wheat starch or rice starch; Preferably, the power of the microwave drying is 100 - 1000W, and the time is 10 - 180s; Preferably, the power of the microwave drying is 300 - 500W, and the time is 10 - 30s; Preferably, the cooling is to a temperature of 20 - 30°C.

3. The method according to claim 1 or 2, characterized in that, The temperature of the hot air drying is 90 - 105°C, and the hot air drying is carried out until the mass content of the product moisture ≤ 10%.

4. The method according to any one of claims 1 to 3, characterized in that, Before the pressure heat treatment, it also includes heating and gelatinizing the mixture of starch and water; Preferably, the temperature of the heating and gelatinizing is 90 - 110°C, and the time is 20 - 40min.

5. The method according to any one of claims 1-4, characterized in that, The pressure of the pressure heat treatment is 0.1 - 0.25MPa, the temperature is 100 - 121°C, and the time is 0.5 - 1h.

6. The method according to any one of claims 1-5, characterized in that, The enzyme used in the enzymatic hydrolysis treatment includes pullulanase; Preferably, the dosage of the enzyme in the enzymatic hydrolysis treatment is 1.5 - 2.5% of the system mass; Preferably, the pH of the enzymatic hydrolysis is 4 - 6, the temperature is 50 - 60°C, and the time is 2.5 - 3.5h; Preferably, the temperature of the crystallization is 4 - 50°C, and the time is 16 - 32h; Preferably, after the crystallization, it also includes a solid-liquid separation step, and the obtained solid product is subjected to microwave drying.

7. A method for preparing a starch product, characterized in that, The starch product is prepared by the method according to any one of claims 1 - 6.

8. A model for predicting the resistant starch content in a starch product prepared by the preparation method described in claim 8, characterized in that, The model is: y = A - Bx1 - Cx2 - Dx1 2 + Ex1x2 Wherein, y is the mass percentage content of resistant starch in the starch product obtained by subjecting the starch to pressure heat treatment, enzymatic hydrolysis treatment and crystallization, then microwave drying, and then hot air drying after cooling; x1 is the time of microwave drying, in units of s; x2 is the power of microwave drying, in units of W; A, B, C, D, E are all constants, A takes values of 65 - 75, B takes values of 0.12 - 0.22, C takes values of 0.01 - 0.1, D takes values of 0.001 - 0.002, and E takes values of 0.0001 - 0.

001.

9. The model according to claim 8, characterized in that, A takes values of 68 - 72, B takes values of 0.14 - 0.2, C takes values of 0.04 - 0.08, D takes values of 0.0014 - 0.0018, and E takes values of 0.0004 - 0.0008.

10. The model according to claim 8 or 9, characterized in that, The temperature of the hot air drying is 100 - 105°C, and the hot air drying is carried out until the mass content of the product moisture is 8 - 10%.

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