Efficient A-type starch crystallization method

Abstract

The invention discloses an efficient A-type starch crystallization method, and belongs to the field of starch crystallization. The preparation method comprises the following steps: gelatinizing starch, and carrying out enzymolysis debranching to obtain starch enzymatic hydrolysate; and pumping solvent steam (ethanol, n-butyl alcohol, acetone and the like) into the starch enzymatic hydrolysate to induce starch crystallization, centrifuging and drying to obtain the A-type crystalline starch. According to the method, the crystallization efficiency of the A-type starch is improved, the preparation process of the resistant starch is simplified, and the preparation time is shortened. The content of resistant starch in the A type crystalline starch prepared by the method reaches 68% or above, and the crystallinity is 75% or above.

Description

Technical Field

[0001] The invention relates to an efficient A-type starch crystallization method and belongs to the field of starch crystallization. Background Art

[0002] Resistant starch refers to starch that is resistant to digestion by digestive enzymes and has the characteristics of dietary fiber. It cannot be digested and absorbed in the human small intestine, but it can be fermented in the large intestine to produce short-chain fatty acids and metabolites that are beneficial to the human body, which helps regulate intestinal health and causes little blood sugar fluctuations after being ingested by the human body. Most common natural starches have a low content of resistant starch. Only starch extracted from some special varieties of plants has a high content of resistant starch, but this type of starch is usually more expensive and still needs further processing to make its resistant starch content meet application requirements.

[0003] Generally speaking, the content of resistant starch in starch is closely related to the crystallization area of ​​starch. Promoting the formation of common natural starch crystal structure by recrystallization is the key technology for the industrial processing of resistant starch. Starch crystals can be divided into type A, type B, type V and amorphous, among which type A crystals have the most compact arrangement of unit cells and the strongest resistance to digestion.

[0004] At present, the conventional method of preparing crystalline starch has problems such as complicated process, high cost, not green and environmentally friendly, and the crystallization effect still needs to be improved. In addition, the prepared crystalline starch is not type A, but more of type B, type V and amorphous. For example: Patent CN115011652B discloses a method for preparing resistant starch using vermicelli by-products, which involves enzymatic hydrolysis of starch followed by recrystallization to prepare resistant starch. The recrystallization time requires at least 12 hours, and the product crystal type is type B. After recrystallization, toughening treatment is still required to increase the crystallinity of the product.

[0005] Patent CN117099942A discloses a resistant starch nanoparticle and a preparation method thereof, wherein a short-amylose mixed dispersion is mixed with konjac gum, gelatinized to obtain a gelatinized short-amylose-konjac gum molecular solution, and then the gelatinized short-amylose-konjac gum molecular solution is induced to recrystallize at -18 to 25°C to obtain recrystallized starch particles, i.e., resistant starch nanoparticles; Patent CN115181772A discloses a method for preparing RS5 resistant starch using waxy starch and α-linolenic acid as raw materials, wherein branched extended starch is dispersed with an alkaline solution, and then compounded with an α-linolenic acid solution to prepare a starch-fat composite, and then RS5 resistant starch is prepared; Both patents increase the resistant starch content of the recrystallized product by introducing other functional ingredients (konjac gum, α-linolenic acid, etc.) into the starch system, but the recrystallized product is mainly B-type and V-type crystalline structures, and the introduction of functional ingredients greatly increases the processing cost, which is not conducive to the industrial production of resistant starch.

[0006] Moreover, conventional existing technologies for preparing crystalline starch usually require further treatment methods such as annealing (CN117099942A, CN117643381A), toughening (CN115011652B), and magnetic induction (CN117327203A) to improve the starch crystal structure and thereby increase the resistant starch content in the product, or to introduce other dietary fiber molecules to embed the starch to protect it from enzymatic hydrolysis (CN117683248A). This time-consuming and complicated preparation process greatly affects the production efficiency of resistant starch.

[0007] 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 the amorphous regions of corn starch granules are hydrolyzed by mild acid hydrolysis with hydrochloric acid to obtain acid-degraded starch with high crystallinity. The acid-degraded starch is dissolved and then frozen and recrystallized to prepare B-type spherulites, and on this basis, A-type starch spherulites are prepared by further recrystallization. However, the operation is complicated and the crystallization time is long, which is not suitable for industrial production.

[0008] Therefore, finding a fast and efficient method to prepare type A crystalline starch is a technical problem that needs to be solved urgently to promote the industrial production of resistant starch. Summary of the invention

[0009] [Technical issues] The conventional method for preparing crystalline starch has problems such as complicated process, high cost, not being green and environmentally friendly, and there is still room for improvement in crystallization effect. In addition, the prepared crystalline starch is not type A, but more of type B, type V and amorphous.

[0010] The method for preparing type A crystalline starch is complicated to operate and takes a long time to crystallize, and is not suitable for industrial production.

[0011] [Technical solution] In order to solve the above problems, the present invention provides an efficient method for crystallizing type A starch. Specifically, the present invention gelatinizes starch and debranches it by enzymatic means to obtain a starch hydrolysate; then, solvent vapor (ethanol, n-butanol, acetone, etc.) is pumped into the starch hydrolysate to induce starch crystallization, centrifuge, and dry to obtain type A crystalline starch. The method of the present invention improves the efficiency of type A starch crystallization, simplifies the preparation process of resistant starch, and shortens the preparation time.

[0012] The first object of the present invention is to provide an efficient method for crystallizing type A starch, comprising the following steps: (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: The solvent vapor is pumped into the starch hydrolysate at a rate of 80-120 mL / h to induce crystallization. After the crystallization is completed, the precipitate is obtained by centrifugation and dried to obtain type A crystalline starch powder; Wherein, the solvent is one or more of ethanol, n-butanol and acetone.

[0013] In one embodiment of the present invention, the starch in step (1) is waxy corn starch.

[0014] In one embodiment of the present invention, the ratio of starch to water in step (1) is 5-15 g:100 mL.

[0015] In one embodiment of the present invention, the gelatinization in step (1) is gelatinization with stirring in a boiling water bath, specifically, gelatinization with stirring in a water bath at 90-100° C. and 100-500 rpm for 5-40 min.

[0016] In one embodiment of the present invention, after gelatinization in step (1), the mixture is cooled to 50-60°C.

[0017] In one embodiment of the present invention, the dosage ratio of starch in step (1) to pullulanase in step (2) is 10 g: 1-2 mL.

[0018] In one embodiment of the present invention, the enzymatic activity of the pullulanase in step (2) is ≥1000 NPUN / g.

[0019] In one embodiment of the present invention, the enzymatic hydrolysis in step (2) is carried out at 50-60°C for 6-10 hours, more preferably at 58°C for 8 hours.

[0020] In one 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.

[0021] In one embodiment of the present invention, the usage ratio of starch in step (1) to the solvent in step (3) is 10 g: 200-350 mL.

[0022] In one embodiment of the present invention, the solvent vapor in step (3) is obtained by evaporating a liquid solvent.

[0023] In one embodiment of the present invention, the temperature for inducing crystallization in step (3) is 40-80° C., and crystallization is completed when the solvent is added.

[0024] In one embodiment of the present invention, the centrifugation in step (3) is performed at 2000-5000 rpm for 10-40 min.

[0025] In one embodiment of the present invention, the drying in step (3) is performed at 40-50° C. for 4-20 h.

[0026] The second object of the present invention is the type A crystalline starch prepared by the method described in the present invention.

[0027] In one embodiment of the present invention, the resistant starch content in the A-type crystalline starch is above 68%, and the crystallinity is above 75%.

[0028] The third object of the present invention is to use the type A crystalline starch of the present invention in the fields of food processing and drug preparation.

[0029] In one embodiment of the present invention, the field of food processing includes the fields of preparing low-sugar foods, weight-loss foods, snack foods, foods for special medical purposes, food additives, etc.

[0030] In one embodiment of the present invention, the field of drug preparation includes use as a biochemical drug carrier.

[0031] The fourth object of the present invention is a method for improving the digestibility resistance of resistant starch, which uses the A-type crystalline starch described in the present invention.

[0032] [Beneficial Effects] (1) The method of the present invention simplifies the starch crystallization process and improves the efficiency of preparing resistant starch.

[0033] (2) The crystalline starch prepared by the present invention is type A, which has better digestibility.

[0034] (3) The resistant starch content in the type A crystalline starch prepared by the present invention is above 68%, and the crystallinity is above 75%. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The crystalline structures of the starches prepared in Examples 1-3 and Comparative Examples 1-8. DETAILED DESCRIPTION

[0036] 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.

[0037] Test method: 1. Characterization of the crystal form and crystallinity of recrystallized starch by XRD The XRD spectrum of the sample to be tested was collected under the conditions of a 2θ scanning range of 4-40°, a scanning step of 0.05°, and a scanning speed of 2° / min.

[0038] 2. Using Englyst in vitro digestion simulation to test the resistant starch content in recrystallized starch Disperse 600 mg of crystalline starch in 20 mL of sodium acetate buffer, preheat to 37°C, add 5 mL of a mixed enzyme solution containing pancreatic enzyme and amyloglucosidase (disperse 18 g of pancreatic enzyme in 120 mL of water, mix thoroughly, take 90 mL of supernatant and mix with 4 mL of amyloglucosidase), start digestion at 37°C, and use the GOPOD kit to measure the glucose content G120 released in the digestion solution when the digestion is carried out for 120 min, and then calculate the resistant starch (RS) content in the product according to the following formula.

[0039]

[0040] Where M is the total mass of starch.

[0041] The raw materials used in the examples are: Waxy corn starch: purchased from Shandong Fuyang Biological; Pullulanase: enzyme activity ≥1000 NPUN / g, purchased from Sigma-Aldrich; Ethanol: 100%, purchased from Tianjin Zhiyuan; n-Butanol: 99.5%, purchased from Sinopharm Shanghai Test; Acetone: 99.5%, purchased from Sinopharm Shanghai Test.

[0042] Example 1 A method for preparing type A crystalline starch comprises the following steps: (1) Starch gelatinization: 10 g of waxy corn starch was dispersed in 100 mL of water in a boiling water bath (100°C) and stirred at 300 rpm for 30 min, and then cooled to 58°C to obtain a gelatinized starch solution; (2) Enzymatic debranching: 1 mL of pullulanase was added to the gelatinized starch solution, and the solution was enzymolyzed at 58°C for 8 h to obtain a starch hydrolyzate. (3) Induced crystallization: Evaporate 300 mL of ethanol to obtain ethanol vapor; Ethanol vapor was pumped into the starch hydrolysate at a rate of 100 mL / h, and crystallization was induced at 58°C for 3 h. After the crystallization, the precipitate was obtained by centrifugation at 4000 rpm for 10 min, and dried at 45°C for 12 h to obtain type A crystalline starch powder.

[0043] Example 2 The ethanol in step (3) of Example 1 was adjusted to n-butanol, and the other steps were kept the same as in Example 1 to obtain type A crystalline starch powder.

[0044] Example 3 The ethanol in step (3) of Example 1 was adjusted to acetone, and the other steps were kept the same as in Example 1 to obtain type A crystalline starch powder.

[0045] Comparative Example 1 A method for preparing crystalline starch comprises the following steps: (1) Starch gelatinization: 10 g of waxy corn starch was dispersed in 100 mL of water in a boiling water bath (100°C) and stirred at 300 rpm for 30 min, and then cooled to 58°C to obtain a gelatinized starch solution; (2) Enzymatic debranching: 1 mL of pullulanase was added to the gelatinized starch solution, and the starch hydrolyzate was hydrolyzed at 58°C for 8 hours to obtain a starch hydrolyzate; the starch hydrolyzate was placed in a boiling water bath for 10 minutes to inactivate the enzyme, and then centrifuged at 4500 rpm for 10 minutes to collect the supernatant; (3) Crystallization: The supernatant was recrystallized at 4°C for 24 h. After the crystallization, the precipitate was obtained by centrifugation at 4000 rpm for 10 min and dried at 45°C for 12 h to obtain crystalline starch.

[0046] Comparative Example 2 The ethanol in step (3) of Example 1 was adjusted to dimethyl sulfoxide, and the other steps were kept the same as in Example 1 to obtain crystalline starch powder.

[0047] Comparative Example 3 The amount of ethanol in step (3) of Example 1 was adjusted to 50 mL, and the other conditions were kept the same as in Example 1 to obtain crystalline starch powder.

[0048] Comparative Example 4 The method of adding ethanol vapor in step (3) of Example 1 is adjusted as follows: 300 mL of ethanol was directly added to the starch hydrolysate to induce crystallization, and the other steps were kept consistent with those in Example 1 to obtain crystalline starch powder.

[0049] Comparative Example 5 Adjust step (3) of Example 1 to: Evaporate 300 mL of ethanol to obtain ethanol vapor; After the starch hydrolysate was cooled to 25°C, ethanol vapor was pumped into the starch hydrolysate at a rate of 100 mL / h to induce crystallization. After the crystallization was completed, the precipitate was obtained by centrifugation at 4000 rpm for 10 min, and dried at 45°C for 12 h to obtain crystalline starch powder.

[0050] Comparative Example 6 The rate of ethanol vapor in step (3) of Example 1 was adjusted to 200 mL / h, and the other steps were kept the same as in Example 1 to obtain crystalline starch powder.

[0051] Comparative Example 7 The rate of ethanol vapor in step (3) of Example 1 was adjusted to 50 mL / h, and the other steps were kept the same as in Example 1 to obtain crystalline starch powder.

[0052] Comparative Example 8 The amount of ethanol in step (3) of Example 1 was adjusted to 400 mL, and the other steps were kept consistent with Example 1 to obtain crystalline starch powder.

[0053] The obtained crystalline starch was subjected to performance tests, and the test results are as follows: Figure 1 The crystalline structure of the starch prepared in Examples 1-3 and Comparative Examples 1-8. Figure 1 It can be seen that: (1) The crystalline starch prepared in Examples 1-3 and Comparative Examples 3-8 has sharp diffraction peaks at 15°, 17°, 18° and 23°, indicating that its crystal type is type A; (2) The crystalline starch prepared in Comparative Example 1 has diffraction peaks at 17°, 22° and 24°, indicating that its crystal type is type B; (3) The crystalline starch prepared in Comparative Example 2 has an amorphous crystalline structure, and no obvious crystal diffraction peak is observed.

[0054] Table 1 shows the yield, relative crystallinity and resistant starch content of crystalline starch.

[0055] From Table 1 we can see that: (1) The relative crystallinity of the type A crystalline starch prepared in Examples 1-3 is above 75%; the yield of the starch crystallization product is above 80%, and the resistant starch content (RS%) in the product is above 68%; that is, the crystalline starch prepared in Examples 1-3 has a high resistant starch content, a simple preparation process, a short preparation time, and a high preparation efficiency, and can meet the application requirements of industrial resistant starch.

[0056] (2) The relative crystallinity of the crystalline starch prepared in Comparative Example 1 was only 13.5%, which was relatively low. The yield of the crystalline product was 73.6%, but the resistant starch content (RS%) was only 24.7%, which did not meet the application requirements of industrial resistant starch; (3) The relative crystallinity of the crystalline starch prepared in Comparative Example 2 was only 5.3%, the yield of the crystalline product was 74.8%, and the resistant starch content (RS%) in the product was only 1.9%, which could not be used as resistant starch; (4) The crystallinity, yield and resistant starch content of the crystalline starch prepared in Comparative Examples 3-5 were all low, and could not meet the application requirements of industrial resistant starch; (5) In Comparative Example 6, the steam flow rate was too fast, resulting in a low relative crystallinity (22.5%) and a low resistant starch content (12.6%) of the product; (6) The yield, crystallinity and resistant starch content of the product in Comparative Example 7 were comparable to those in Example 1, but the slow steam flow rate significantly prolonged the crystallization time to 6 h, which was not conducive to industrial and efficient production.

[0057] (7) The yield, crystallinity and resistant starch content of the product in Comparative Example 8 are comparable to those in Example 1. However, the increase in the amount of ethanol not only prolongs the crystallization time but also increases the raw material cost, which is not conducive to industrial and efficient production.

[0058] Table 1 Yield, relative crystallinity and resistant starch content of recrystallized starch

[0059] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of 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; The usage ratio of starch in step (1) to the solvent in step (3) is 10 g: 200-350 mL.

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 solvent vapor in step (3) is obtained by evaporating a liquid solvent. The amount ratio of the 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.

7. A-type crystalline starch prepared by the A-type starch crystallization method according to any one of claims 1 to 6.

8. The A-type crystalline starch according to claim 7, characterized in that The resistant starch content in type A crystalline starch is over 68%, and the crystallinity is over 75%.

9. Use of the type A crystalline starch according to claim 7 in the field of food processing or drug preparation.

10. A method for improving the digestibility of resistant starch, characterized in that: It uses the type A crystalline starch described in claim 7.

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