An efficient method for A-type starch crystallization

Abstract

The present invention discloses an efficient method for A-type starch crystallization, belonging to the field of starch crystallization. In the present invention, starch is gelatinized and enzymatically debranched to obtain an amylolytic solution; then solvent vapor (ethanol, n-butanol, acetone, etc.) is pumped into the amylolytic solution to induce starch crystallization, followed by centrifugation and drying to obtain A-type crystalline starch. The method of the present invention improves the efficiency of A-type starch crystallization, simplifies the preparation process of resistant starch, and shortens the preparation time. The content of resistant starch in the A-type crystalline starch prepared by the present invention reaches more than 68%, and the crystallinity is more than 75%.

Description

Technical Field

[0001] The present invention relates to an efficient method for crystallizing type A starch, belonging to the field of starch crystallization. Background Art

[0002] Resistant starch refers to starch that resists enzymatic hydrolysis by digestive enzymes, has dietary fiber characteristics, cannot be digested and absorbed in the human small intestine, but can be fermented in the large intestine to produce short-chain fatty acids and metabolites beneficial to the human body, helps regulate intestinal health, and causes little blood sugar fluctuation after being ingested by the human body. The content of resistant starch in most common natural starches is low, and only starches extracted from some special varieties of plants have a high content of resistant starch. However, such starches usually have a high cost and still need further processing to meet the application requirements of their resistant starch content.

[0003] Generally speaking, the content of resistant starch in starch is closely related to the crystalline region of starch. Promoting the formation of the crystalline structure of common natural starch through recrystallization means is the key technology for the industrial processing of resistant starch. Starch crystallization can be divided into type A, type B, type V, and amorphous. Among them, the crystal cell arrangement of type A crystallization is the most compact and has the strongest anti-digestibility.

[0004] At present, the conventional methods for preparing crystalline starch have problems such as cumbersome processes, high costs, non-green environmental protection, and room for improvement in crystallization effects. Moreover, the prepared crystalline starch is not type A, but more of type B, type V, and amorphous. For example:

[0005] Patent CN115011652B discloses a method for preparing resistant starch using fan-shaped by-products. It prepares resistant starch by enzymatic hydrolysis and then recrystallization. The recrystallization time requires at least 12 hours, and the crystal type of the product is type B. After recrystallization, toughening treatment is still required to improve the crystallinity of the product.

[0006] Patent CN117099942A discloses a resistant starch nanoparticle and its preparation method. It mixes and disperses a short amylose mixed solution with konjac gum, gelatinizes it to obtain a gelatinized short amylose-konjac gum molecular solution, and then induces the gelatinized short amylose-konjac gum molecular solution to recrystallize at -18~25°C to obtain recrystallized starch particles, namely resistant starch nanoparticles. Patent CN115181772A discloses a method for preparing RS5 type resistant starch using waxy starch and α-linolenic acid as raw materials. It disperses branched-chain extended starch with an alkaline solution, combines it with an α-linolenic acid solution to prepare a starch-fat composite, and then prepares RS5 type resistant starch. Both of these two patents improve the content of resistant starch in the recrystallized product by introducing other functional components (konjac gum, α-linolenic acid, etc.) into the starch system. However, the recrystallized product is mainly in the form of type B and type V crystalline structures, and the introduction of functional components greatly increases the processing cost, which is not conducive to the industrial production of resistant starch.

[0007] Moreover, the existing technologies for the conventional preparation of crystalline starch usually need to be further supplemented with treatment means such as annealing (CN117099942A, CN117643381A), toughening (CN115011652B), and magnetic induction (CN117327203A) to improve the starch crystal structure and thus increase the content of resistant starch in the product, or to protect the starch from enzymatic hydrolysis by introducing other dietary fiber molecules to embed the starch (CN117683248A). This time-consuming and complex preparation process greatly affects the production efficiency of resistant starch.

[0008] In addition, the literature (Liu Yanqi, Yu Jiugao, Sun Xiuping. Preparation and characterization of A-type starch spherulites [J]. Journal of the Chinese Cereals and Oils Association, 2004. DOI: CNKI:SUN:ZLYX.0.2004-01-008.) discloses that through the mild acidolysis of hydrochloric acid, the amorphous region of corn starch granules is hydrolyzed to obtain acid-hydrolyzed starch with a higher crystallinity. After dissolving the acid-hydrolyzed starch and performing freeze recrystallization, B-type spherulites are prepared, and on this basis, further recrystallization is carried out to obtain A-type starch spherulites. However, its operation is complex and the crystallization time is long, which is not suitable for industrial production.

[0009] Therefore, finding a rapid and efficient method for preparing A-type crystalline starch is a technical problem that urgently needs to be solved to promote the industrial production of resistant starch. Summary of the Invention

[0010] [Technical Problem]

[0011] The conventional methods for preparing crystalline starch have problems such as cumbersome processes, high costs, lack of environmental friendliness, and room for improvement in crystallization effects. Moreover, the prepared crystalline starch is not of type A, but more of type B, type V, and amorphous.

[0012] The methods for preparing A-type crystalline starch have complex operations, long crystallization times, and are not suitable for industrial production.

[0013] [Technical Solution]

[0014] To solve the above problems, the present invention provides an efficient method for A-type starch crystallization. Specifically, the present invention gelatinizes starch and performs enzymatic debranching to obtain an amylolytic solution; then, solvent vapor (ethanol, n-butanol, acetone, etc.) is pumped into the amylolytic solution to induce starch crystallization, followed by centrifugation and drying to obtain A-type crystalline starch. The method of the present invention improves the efficiency of A-type starch crystallization, simplifies the preparation process of resistant starch, and shortens the preparation time.

[0015] The first object of the present invention is to provide an efficient method for A-type starch crystallization, comprising the following steps:

[0016] (1) Starch gelatinization:

[0017] Disperse starch in water and gelatinize it to obtain a gelatinized starch solution;

[0018] (2) Enzymatic debranching:

[0019] Add pullulanase to the gelatinized starch solution and carry out enzymatic hydrolysis to obtain an enzymatic hydrolysate;

[0020] (3) Inducing crystallization:

[0021] Pump solvent vapor into the enzymatic hydrolysate at a rate of 80 - 120 mL / h to induce crystallization. After crystallization is completed, centrifuge to obtain a precipitate, and dry it to obtain A-type crystalline starch powder;

[0022] Among them, the solvent is one or more of ethanol, n-butanol, and acetone.

[0023] In an embodiment of the present invention, the starch in step (1) is waxy corn starch.

[0024] In an embodiment of the present invention, the dosage ratio of starch to water in step (1) is 5 - 15 g: 100 mL.

[0025] In an embodiment of the present invention, the gelatinization in step (1) is gelatinization by stirring in a boiling water bath, specifically stirring and gelatinizing at 90 - 100 °C in a water bath and 100 - 500 rpm for 5 - 40 min.

[0026] In an embodiment of the present invention, after gelatinization in step (1), it is cooled to 50 - 60 °C.

[0027] In an embodiment of the present invention, the dosage ratio of starch in step (1) to pullulanase in step (2) is 10 g: 1 - 2 mL.

[0028] In an embodiment of the present invention, the enzyme activity of pullulanase in step (2) ≥ 1000 NPUN / g.

[0029] In an embodiment of the present invention, the enzymatic hydrolysis in step (2) is an enzymatic hydrolysis reaction at 50 - 60 °C for 6 - 10 h, and further preferably a reaction at 58 °C for 8 h.

[0030] In an embodiment of the present invention, the pumping of solvent vapor in step (3) can inactivate the enzyme, so no additional enzyme inactivation step is required.

[0031] In an embodiment of the present invention, the dosage ratio of starch in step (1) to solvent in step (3) is 10 g: 200 - 350 mL.

[0032] In one embodiment of the present invention, in step (3), the solvent vapor is obtained by evaporating a liquid solvent to form vapor.

[0033] In one embodiment of the present invention, in step (3), the temperature for inducing crystallization is 40 - 80 °C, and crystallization is completed when the solvent addition is finished.

[0034] In one embodiment of the present invention, in step (3), centrifugation is carried out at 2000 - 5000 rpm for 10 - 40 min.

[0035] In one embodiment of the present invention, in step (3), drying is carried out at 40 - 50 °C for 4 - 20 h.

[0036] The second object of the present invention is the A-type crystalline starch prepared by the method of the present invention.

[0037] In one embodiment of the present invention, the resistant starch content in the A-type crystalline starch reaches more than 68%, and the crystallinity is more than 75%.

[0038] The third object of the present invention is the application of the A-type crystalline starch of the present invention in the fields of food processing and drug preparation.

[0039] In one embodiment of the present invention, the food processing field includes the fields of preparing low-sugar foods, weight-loss foods, snack foods, foods for special medical purposes, food additives, etc.

[0040] In one embodiment of the present invention, the drug preparation field includes being used as a carrier for biochemical drugs.

[0041] The fourth object of the present invention is a method for enhancing the anti-digestibility of resistant starch, which uses the A-type crystalline starch of the present invention.

[0042] [Beneficial effects]

[0043] (1) The method of the present invention simplifies the starch crystallization process and improves the preparation efficiency of resistant starch.

[0044] (2) The crystalline starch prepared by the present invention is of type A and has better anti-digestibility.

[0045] (3) The resistant starch content in the A-type crystalline starch prepared by the present invention reaches more than 68%, and the crystallinity is more than 75%. Description of the drawings

[0046] Figure 1 Crystalline structures of the starches prepared in Examples 1 - 3 and Comparative Examples 1 - 8. Detailed implementation manners

[0047] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explaining the present invention and are not used to limit the present invention.

[0048] Test method:

[0049] 1. Use XRD to characterize the crystal form and crystallinity of recrystallized starch

[0050] Collect the XRD pattern of the sample to be tested under the conditions of a 2θ scanning range of 4 - 40°, a scanning step size of 0.05°, and a scanning speed of 2° / min.

[0051] 2. Use the Englyst in vitro digestion simulation to test the resistant starch content in recrystallized starch

[0052] Disperse 600 mg of crystalline starch in 20 mL of sodium acetate buffer solution. After preheating to 37°C, add 5 mL of a mixed enzyme solution containing trypsin and amyloglucosidase (prepared by dispersing 18 g of trypsin in 120 mL of water, fully mixing, and then taking 90 mL of the supernatant and mixing it with 4 mL of amyloglucosidase). Start digestion at 37°C. When digestion proceeds to 120 min, use a GOPOD kit to measure the glucose content G120 released in the digestion solution, and then calculate the resistant starch (RS) content in the product according to the following formula.

[0053]

[0054] Where M is the total mass of the starch.

[0055] Raw materials used in the examples:

[0056] Waxy corn starch: Purchased from Shandong Fuyang Biotechnology;

[0057] Pullulanase: Enzyme activity ≥ 1000 NPUN / g, purchased from sigma - aldrich;

[0058] Ethanol: 100%, purchased from Tianjin Zhiyuan;

[0059] n - Butanol: 99.5%, purchased from Shanghai Experiment Reagent Co., Ltd. of Sinopharm Chemical Reagent Co., Ltd.;

[0060] Acetone: 99.5%, purchased from Shanghai Experiment Reagent Co., Ltd. of Sinopharm Chemical Reagent Co., Ltd.

[0061] Example 1

[0062] A method for preparing A - type crystalline starch, comprising the following steps:

[0063] (1) Starch gelatinization:

[0064] Disperse 10 g of waxy corn starch in 100 mL of water, stir and gelatinize it in a boiling water bath (100 °C) at 300 rpm for 30 min, and cool it to 58 °C to obtain a gelatinized starch solution;

[0065] (2) Enzymatic debranching:

[0066] Add 1 mL of pullulanase to the gelatinized starch solution and enzymatically hydrolyze it at 58 °C for 8 h to obtain an enzyme-hydrolyzed solution;

[0067] (3) Induced crystallization:

[0068] Evaporate 300 mL of ethanol to obtain ethanol vapor;

[0069] Pump the ethanol vapor into the enzyme-hydrolyzed solution at a rate of 100 mL / h and induce crystallization at 58 °C for 3 h; after crystallization, centrifuge at 4000 rpm for 10 min to obtain a precipitate, and dry it at 45 °C for 12 h to obtain A-type crystalline starch powder.

[0070] Example 2

[0071] Adjust the ethanol in step (3) of Example 1 to n-butanol, and keep the others the same as in Example 1 to obtain A-type crystalline starch powder.

[0072] Example 3

[0073] Adjust the ethanol in step (3) of Example 1 to acetone, and keep the others the same as in Example 1 to obtain A-type crystalline starch powder.

[0074] Comparative Example 1

[0075] A method for preparing crystalline starch, comprising the following steps:

[0076] (1) Starch gelatinization:

[0077] Disperse 10 g of waxy corn starch in 100 mL of water, stir and gelatinize it in a boiling water bath (100 °C) at 300 rpm for 30 min, and cool it to 58 °C to obtain a gelatinized starch solution;

[0078] (2) Enzymatic debranching:

[0079] Add 1 mL of pullulanase to the gelatinized starch solution and enzymatically hydrolyze it at 58 °C for 8 h to obtain an enzyme-hydrolyzed solution; place the enzyme-hydrolyzed solution in a boiling water bath for 10 min to inactivate the enzyme, and then centrifuge at 4500 rpm for 10 min to collect the supernatant;

[0080] (3) Crystallization:

[0081] Recrystallize the supernatant at 4 °C for 24 h; after the crystallization is completed, centrifuge at 4000 rpm for 10 min to obtain the precipitate, and dry at 45 °C for 12 h to obtain crystalline starch.

[0082] Comparative Example 2

[0083] Adjust the ethanol in step (3) of Example 1 to dimethyl sulfoxide, and keep the others the same as in Example 1 to obtain crystalline starch powder.

[0084] Comparative Example 3

[0085] Adjust the amount of ethanol in step (3) of Example 1 to 50 mL, and keep the others the same as in Example 1 to obtain crystalline starch powder.

[0086] Comparative Example 4

[0087] Adjust the addition method of ethanol vapor in step (3) of Example 1 to:

[0088] Directly add 300 mL of ethanol to the amylolytic solution to induce crystallization, and keep the others the same as in Example 1 to obtain crystalline starch powder.

[0089] Comparative Example 5

[0090] Adjust step (3) of Example 1 to:

[0091] Evaporate 300 mL of ethanol to obtain ethanol vapor;

[0092] After cooling the amylolytic solution to 25 °C, pump the ethanol vapor into the amylolytic solution at a rate of 100 mL / h to induce crystallization. After the crystallization is completed, centrifuge at 4000 rpm for 10 min to obtain the precipitate, and dry at 45 °C for 12 h to obtain crystalline starch powder.

[0093] Comparative Example 6

[0094] Adjust the speed of ethanol vapor in step (3) of Example 1 to 200 mL / h, and keep the others the same as in Example 1 to obtain crystalline starch powder.

[0095] Comparative Example 7

[0096] Adjust the speed of ethanol vapor in step (3) of Example 1 to 50 mL / h, and keep the others the same as in Example 1 to obtain crystalline starch powder.

[0097] Comparative Example 8

[0098] Adjust the amount of ethanol in step (3) of Example 1 to 400 mL, and keep the others the same as in Example 1 to obtain crystalline starch powder.

[0099] The obtained crystalline starch was subjected to performance tests, and the test results are as follows:

[0100] Figure 1 Crystalline structures of starches prepared in Examples 1-3 and Comparative Examples 1-8. From Figure 1 it can be seen that:

[0101] (1) The crystalline starches prepared in Examples 1-3 and Comparative Examples 3-8 have sharp diffraction peaks at 15°, 17°, 18°, and 23°, indicating that their crystal type is A-type;

[0102] (2) The crystalline starch prepared in Comparative Example 1 has diffraction peaks at 17°, 22°, and 24°, indicating that its crystal type is B-type;

[0103] (3) The crystalline starch prepared in Comparative Example 2 has an amorphous crystalline structure, and no obvious crystal diffraction peaks are observed.

[0104] Table 1 shows the yield, relative crystallinity, and resistant starch content of the crystalline starch.

[0105] From Table 1, it can be seen that:

[0106] (1) The relative crystallinity of the A-type crystalline starches prepared in Examples 1-3 is above 75%; the yield of the starch crystallization products is above 80%, and the resistant starch content (RS%) in the products is above 68%; that is, the crystalline starches prepared in Examples 1-3 have a high resistant starch content, with a simple preparation process, short preparation time, and high preparation efficiency, and can meet the industrial application requirements of resistant starch.

[0107] (2) The relative crystallinity of the crystalline starch prepared in Comparative Example 1 is only 13.5%, with a low crystallinity. The yield of the crystallization product is 73.6%, but the resistant starch content (RS%) is only 24.7%, which does not meet the industrial application requirements of resistant starch;

[0108] (3) The relative crystallinity of the crystalline starch prepared in Comparative Example 2 is only 5.3%, the yield of the crystallization product is 74.8%, and the resistant starch content (RS%) in the product is only 1.9%, and it cannot be used as resistant starch;

[0109] (4) The crystallinity, yield, and resistant starch content of the crystalline starches prepared in Comparative Examples 3-5 are all low, and they cannot meet the industrial application requirements of resistant starch;

[0110] (5) In Comparative Example 6, the too-fast steam flow rate results in a relatively low relative crystallinity (22.5%) and a relatively low resistant starch content (12.6%) of the product;

[0111] (6) The yield, crystallinity, and resistant starch content of the product in Comparative Example 7 were comparable to those in Example 1. However, the steam flow rate was too slow, resulting in a significant extension of the crystallization time to 6 h, which was not conducive to high-efficiency industrial production.

[0112] (7) The yield, crystallinity, and resistant starch content of the product in Comparative Example 8 were comparable to those in Example 1. However, the increase in the amount of ethanol not only prolonged the crystallization time but also increased the raw material cost, which was not conducive to high-efficiency industrial production.

[0113] Table 1 Yield, relative crystallinity, and resistant starch content of recrystallized starch

[0114]

[0115] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the claims.

Claims

1. An efficient method for crystallizing type A starch, characterized in that: The steps include: (1) Starch gelatinization: Dispersing starch in water and gelatinizing it to obtain a gelatinized starch solution; (2) Enzymatic debranching: Adding pullulanase to the gelatinized starch solution for enzymolysis to obtain a starch hydrolyzate; (3) Induced crystallization: Pumping solvent vapor into the starch hydrolysate at a rate of 80-120 mL / h to induce crystallization; after the crystallization is completed, centrifuging to obtain the precipitate, drying, and obtaining type A crystalline starch powder; Wherein, the solvent is one or more of ethanol, n-butanol and acetone.

2. The method for crystallizing type A starch according to claim 1, characterized in that: The dosage ratio of starch to water in step (1) is 5-15 g:100 mL.

3. The method for crystallizing type A starch according to claim 1, characterized in that: The dosage ratio of starch in step (1) and pullulanase in step (2) is 10 g:1-2 mL.

4. The method for crystallizing type A starch according to claim 1, characterized in that: The usage ratio of starch in step (1) to the solvent in step (3) is 10 g: 200-350 mL.

5. The method for crystallizing type A starch according to claim 1, characterized in that: The temperature for inducing crystallization in step (3) is 40-80°C, and crystallization is completed when the solvent is added.

6. The method for crystallizing type A starch according to claim 1, characterized in that: In step (2), the enzymatic hydrolysis is carried out at 50-60°C for 6-10 hours.

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