A method for preparing RS3 resistant starch by "extrusion-debranching"

Abstract

The present invention discloses a method for preparing RS3 type resistant starch by an "extrusion debranching" method, and belongs to the technical field of functional foods. The method for preparing RS3 type resistant starch by an "extrusion debranching" method of the present invention comprises the following steps: adding a starch raw material to a twin-screw extruder, performing a primary extrusion, collecting the extruded gelatinized and degraded starch, and drying and crushing the starch; fully mixing the crushed gelatinized starch with pullulanase, adding the starch to a twin-screw extruder, performing a secondary extrusion, collecting the debranched starch after extrusion, and recrystallizing the starch, followed by centrifugal washing, collecting the precipitate, and drying to obtain RS3 type resistant starch. The method achieves rapid and efficient debranching of high substrate starch concentration, increases the content of RS3 type resistant starch, solves the problem of low output efficiency of RS3 type resistant starch, and provides a theoretical basis and practical guidance for the continuous industrial production of resistant starch.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional foods, and specifically relates to a method for preparing RS3 resistant starch by an "extrusion-debranching" method. Background Art

[0002] Based on the digestion rate, starch can be divided into rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS). Eating rapidly digestible starch will cause a rapid increase in blood sugar levels after a meal, while slowly digestible starch is digested more slowly, resulting in relatively low blood sugar levels after consumption. Resistant starch cannot be digested in the small intestine, but is fermented and degraded by intestinal flora in the colon, producing short-chain fatty acids and gas. Resistant starch plays a key role in promoting a variety of beneficial health effects, including lowering blood sugar and cholesterol, inhibiting body fat accumulation, increasing mineral absorption, reducing digestive tract cancer and preventing gallstone formation. With the increasing threat of diabetes to human health, the development of resistant starch is of great significance to obese patients and diabetics. However, the current level of industrialization of resistant starch is low, and there are few commercially available resistant starch products.

[0003] Resistant starch is generally divided into five types: RS1, RS2, RS3, RS4 and RS5. Among them, RS3 has received special attention due to its thermal stability during the cooking process and its safety when consumed. RS3 mainly refers to recrystallized amylose, so the amylose content is the main factor affecting the formation and content of RS3. However, the amylose content in ordinary starch is low (<30%). At present, pullulanase debranching is a commonly used method to increase the amylose content. However, debranching needs to be carried out after starch gelatinization. Due to the high viscosity of gelatinized starch, the debranching reaction needs to be carried out in a high liquid phase system. The starch concentration is usually low (<15wt%) and the enzymatic hydrolysis time is long. The Chinese patent "A method for preparing high-amylose mung bean resistant starch" (application number 202111157414.1) discloses a method for preparing mung bean resistant starch by ultrasonic combined enzymatic method, wherein the ratio of mung bean starch to water is 1:15 1:25 (w / v), and the pullulanase hydrolysis time is 10.0 14.0h; the Chinese patent "A method for preparing glutinous wheat resistant starch" (application number 202111651682.9) discloses a composite enzyme technology using the synergistic action of pullulanase and branching enzyme to prepare glutinous wheat resistant starch, the mass concentration of starch milk is 4% 8%, and the pullulanase hydrolysis time is 4-6h. The low substrate concentration and long hydrolysis time limit the efficiency of enzyme debranching to increase the amylose content, and cannot meet the needs of industrial production of amylose.

[0004] Therefore, discovering new strategies to improve the efficiency of starch debranching to obtain amylose is of great significance for the industrial production of resistant starch. Summary of the Invention

[0005] In view of the technical defects existing in the prior art, the purpose of the present invention is to solve the problem of low output efficiency of amylose and type III resistant starch (RS3), and for this purpose, an extrusion-debranching means is proposed to realize efficient and continuous industrial production of amylose and RS3 type resistant starch. Extrusion is a temperature-controlled, strong shear, short-time, low-cost industrial continuous thermomechanical production technology with the advantages of versatility and high yield. The present application realizes the full gelatinization, degradation and viscosity reduction of starch by the first extrusion, and the second extrusion and the cooperation of the debranching enzyme to realize the rapid and efficient debranching of high-concentration starch, thereby obtaining amylose, and obtaining a high content of resistant starch after recrystallization.

[0006] The object of the present invention is to provide a method for preparing RS3 resistant starch by an "extrusion-debranching" method, the method comprising the following steps:

[0007] (1) adding starch raw material into a twin-screw extruder, performing one extrusion, collecting the starch after extrusion gelatinization and degradation, and drying and crushing;

[0008] (2) The gelatinized starch crushed in step (1) is mixed with pullulanase, added to a twin-screw extruder, and extruded for a second time. The debranched starch after extrusion is collected and recrystallized, and then washed with water, centrifuged, and the precipitate is collected and dried to obtain RS3 type resistant starch; the rotation speed of the twin-screw extruder is 100-250 rpm; the temperature of the six temperature zones of the extruder is increased sequentially to 35-100° C.; the water content of the material in the extruder is 40-60wt%, and the starch mass concentration is 40-60%.

[0009] In one embodiment, the rotation speed of the twin-screw extruder in step (1) is 100-250 rpm; the temperature of the six temperature zones of the extruder is increased sequentially to 35-120° C.; and the moisture content of the material is 30-60 wt %.

[0010] In one embodiment, the starch in step (1) includes one or more of ordinary starch and waxy starch.

[0011] In one embodiment, the drying in step (1) can be carried out in conventional drying equipment at a drying temperature of 40-50°C, preferably 45°C.

[0012] In one embodiment, the temperature of the first five temperature zones of the twin-screw extruder in step (2) is 35-70°C, and the temperature of the last temperature zone is 95-100°C; preferably, the temperatures of the first five temperature zones are 35, 45, 55, 60, and 65°C, respectively, and the temperature of the last temperature zone is 95°C.

[0013] In one embodiment, the amount of pullulanase added in step (2) is 20-100 U / g (based on dry starch), preferably 80 U / g.

[0014] In one embodiment, the recrystallization conditions in step (2) are: temperature of 2-25°C, time of 10-36h; preferably 4°C, time of 24h.

[0015] In one embodiment, the centrifugal force in step (2) is 2000-5000 g, and the time is 5 to 20 minutes.

[0016] In one embodiment, the drying in step (2) can be carried out in conventional drying equipment at a drying temperature of 40-50°C, preferably 45°C.

[0017] Another object of the present invention is to provide an RS3 resistant starch prepared by the above method.

[0018] The third object of the present invention is to provide an application of the above method in the field of food preparation.

[0019] Beneficial effects of the present invention:

[0020] (1) The present invention discloses a method for efficiently preparing RS3 resistant starch using an "extrusion-debranching" method. This method utilizes the synergistic effect of extrusion technology and pullulanase to obtain high-content amylose and resistant starch through two extrusions, significantly reducing the digestibility of the starch. This method is simple and efficient, and can achieve rapid and efficient debranching of high-concentration starch. It overcomes the problems of the prior art in which the substrate starch content (less than 15 wt%) cannot be too high and the debranching time is long, and can achieve industrialized continuous production.

[0021] (2) The optimal pH range for pullulanase is 4.2-4.8. When starch is debranched, hydrochloric acid is usually added or the starch is dispersed in a buffered salt solution to adjust the pH. In an extrusion system, due to the buffering specificity of the starch matrix, the high concentration of starch allows pullulanase to have a wider optimal pH range than in a liquid system. The present invention uses a high starch concentration extrusion debranching method to reduce the pH dependence of pullulanase and simplify the production process.

[0022] (3) The present invention will provide a theoretical basis and practical guidance for the continuous industrial production of amylose, and provide feasible strategies and methods for the industrial production of resistant starch and the development of low glycemic index foods. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] Example 1

[0025] A method for preparing RS3 resistant starch by an "extrusion-debranching" method, the method specifically comprising the following steps:

[0026] (1) Adding ordinary corn starch to the feeding end of a twin-screw extruder, setting the material moisture content to 40 wt%, the screw speed to 150 rpm, and the temperatures of zones I, II, III, IV, V, and VI of the extruder (ZE-16) to 35, 45, 60, 80, 100, and 120°C, respectively, and starting extrusion. Collect the fully gelatinized corn starch, dry it at 45°C, and then grind it;

[0027] (2) The corn starch gelatinized in step (1) was mixed with 20 U / g of pullulanase (based on the dry matter weight of ordinary corn starch) and added to the feeding end of a twin-screw extruder, and the moisture content of the material was set to 60 wt% and the mass concentration of corn starch was 40%; the temperatures of zones I, II, III, IV, V, and VI of the extruder were set to 35, 45, 55, 60, 65, and 95° C., respectively, and the screw speed was 150 rpm, and extrusion was started. The debranched corn starch was collected and recrystallized at 4° C. for 24 h, and centrifuged and washed at 4000 g for 10 min to remove the soluble short chains therein. The precipitate was collected and dried at 45° C. to obtain resistant starch.

[0028] When the pullulanase content was 20 U / g, the amylose content in the sample was determined to be 71.53% using the Megazyme amylose and amylopectin assay kit, and the resistant starch content in the sample was determined to be 26.49% using the Englyst in vitro simulated digestion method, as shown in Tables 1 and 2, respectively.

[0029] Example 2

[0030] A method for preparing RS3 resistant starch by an "extrusion-debranching" method, the method specifically comprising the following steps:

[0031] (1) Adding ordinary corn starch to the feeding end of a twin-screw extruder, setting the material moisture content to 40 wt%, the screw speed to 150 rpm, and the temperatures of zones I, II, III, IV, V, and VI of the extruder (ZE-16) to 35, 45, 60, 80, 100, and 120°C, respectively, and starting extrusion. Collect the fully gelatinized corn starch, dry it at 45°C, and then grind it;

[0032] (2) The corn starch gelatinized in step (1) was mixed with 40 U / g of pullulanase (based on the dry matter weight of ordinary corn starch) and added to the feeding end of a twin-screw extruder, and the moisture content of the material was set to 60 wt% and the mass concentration of corn starch was 40%; the temperatures of zones I, II, III, IV, V, and VI of the extruder were set to 35, 45, 55, 60, 65, and 95° C., respectively, the screw speed was 150 rpm, and extrusion was started. The debranched corn starch was collected and recrystallized at 4° C. for 24 h, and centrifuged and washed at 4000 g for 10 min to remove the soluble short chains therein. The precipitate was collected and dried at 45° C. to obtain resistant starch.

[0033] When the pullulanase content was 40 U / g, the amylose content in the sample was determined to be 75.34% using the Megazyme amylose and amylopectin assay kit, and the resistant starch content in the sample was determined to be 29.67% using the Englyst in vitro simulated digestion method, as shown in Tables 1 and 2, respectively.

[0034] Example 3

[0035] A method for preparing RS3 resistant starch by an "extrusion-debranching" method, the method specifically comprising the following steps:

[0036] (1) Adding ordinary corn starch to the feeding end of a twin-screw extruder, setting the material moisture content to 40 wt%, the screw speed to 150 rpm, and the extruder (ZE-16) zones I, II, III, IV, V, and VI to 35, 45, 60, 80, 100, and 120°C, respectively, and starting extrusion. Collect the fully gelatinized corn starch, dry it at 45°C, and then grind it;

[0037] (2) The corn starch gelatinized in step (1) was mixed with 60 U / g of pullulanase (based on the dry matter weight of ordinary corn starch) and added to the feeding end of a twin-screw extruder, and the moisture content of the material was set to 60 wt% and the mass concentration of corn starch was 40%; the temperatures of zones I, II, III, IV, V, and VI of the extruder were set to 35, 45, 55, 60, 65, and 95° C., respectively, the screw speed was 150 rpm, and extrusion was started. The debranched corn starch was collected and recrystallized at 4° C. for 24 h, and centrifuged and washed at 4000 g for 10 min to remove the soluble short chains therein. The precipitate was collected and dried at 45° C. to obtain resistant starch.

[0038] When the pullulanase content was 60 U / g, the amylose content in the sample was determined to be 80.70% using the Megazyme amylose and amylopectin assay kit, and the resistant starch content in the sample was determined to be 35.31% using the Englyst in vitro simulated digestion method, as shown in Tables 1 and 2, respectively.

[0039] Example 4

[0040] A method for preparing RS3 resistant starch by an "extrusion-debranching" method, the method specifically comprising the following steps:

[0041] (1) Adding ordinary corn starch to the feeding end of a twin-screw extruder, setting the material moisture content to 40 wt%, the screw speed to 150 rpm, and the extruder (ZE-16) zones I, II, III, IV, V, and VI to 35, 45, 60, 80, 100, and 120°C, respectively, and starting extrusion. Collect the fully gelatinized corn starch, dry it at 45°C, and then grind it;

[0042] (2) The corn starch gelatinized in step (1) was mixed with 80 U / g of pullulanase (based on the dry matter weight of ordinary corn starch) and added to the feeding end of a twin-screw extruder, and the moisture content of the material was set to 60 wt% and the mass concentration of corn starch was 40%; the temperatures of zones I, II, III, IV, V, and VI of the extruder were set to 35, 45, 55, 60, 65, and 95° C., respectively, the screw speed was 150 rpm, and extrusion was started. The debranched corn starch was collected and recrystallized at 4° C. for 24 h, and centrifuged and washed at 4000 g for 10 min to remove the soluble short chains therein. The precipitate was collected and dried at 45° C. to obtain resistant starch.

[0043] When the pullulanase content was 80 U / g, the amylose content in the sample was determined to be 85.27% using the Megazyme amylose and amylopectin assay kit, and the resistant starch content in the sample was determined to be 40.39% using the Englyst in vitro simulated digestion method, as shown in Tables 1 and 2, respectively.

[0044] Example 5

[0045] A method for preparing RS3 resistant starch by an "extrusion-debranching" method, the method specifically comprising the following steps:

[0046] (1) Adding ordinary corn starch to the feeding end of a twin-screw extruder, setting the material moisture content to 40 wt%, the screw speed to 150 rpm, and the extruder (ZE-16) zones I, II, III, IV, V, and VI to 35, 45, 60, 80, 100, and 120°C, respectively, and starting extrusion. Collect the fully gelatinized corn starch, dry it at 45°C, and then grind it;

[0047] (2) The corn starch gelatinized in step (1) was mixed with 100 U / g pullulanase (based on the dry matter weight of ordinary corn starch) and added to the feeding end of a twin-screw extruder, and the moisture content of the material was set to 60 wt% and the mass concentration of corn starch was 40%; the temperatures of zones I, II, III, IV, V, and VI of the extruder were set to 35, 45, 55, 60, 65, and 95° C., respectively, the screw speed was 150 rpm, and extrusion was started. The debranched corn starch was collected and recrystallized at 4° C. for 24 h, and centrifuged and washed at 4000 g for 10 min to remove the soluble short chains therein. The precipitate was collected and dried at 45° C. to obtain resistant starch.

[0048] When the pullulanase content was 100 U / g, the amylose content in the sample was determined to be 90.21% using the Megazyme amylose and amylopectin assay kit, and the resistant starch content in the sample was determined to be 41.50% using the Englyst in vitro simulated digestion method, as shown in Tables 1 and 2, respectively.

[0049] Example 6

[0050] A method for preparing RS3 resistant starch by an "extrusion-debranching" method, the method specifically comprising the following steps:

[0051] (1) Adding ordinary corn starch to the feeding end of a twin-screw extruder, setting the material moisture content to 40 wt%, the screw speed to 150 rpm, and the temperatures of zones I, II, III, IV, V, and VI of the extruder (ZE-16) to 35, 45, 60, 80, 100, and 120°C, respectively, and starting extrusion. Collect the fully gelatinized corn starch, dry it at 45°C, and then grind it;

[0052] (2) The corn starch gelatinized in step (1) was mixed with 80 U / g of pullulanase (based on the dry matter weight of ordinary corn starch) and added to the feeding end of a twin-screw extruder. The moisture content of the material was adjusted to 40 wt% and the mass concentration of corn starch was adjusted to 60%. The temperatures of zones I, II, III, IV, V, and VI of the extruder were set to 35, 45, 55, 60, 65, and 95° C., respectively, and the screw speed was 150 rpm. Extrusion was started, the debranched corn starch was collected and recrystallized at 4° C. for 24 h, and the soluble short chains were removed by centrifugation and water washing at 4000 g for 10 min. The precipitate was collected and dried at 45° C. to obtain resistant starch.

[0053] When the corn starch mass concentration was 60%, the amylose content in the sample was determined to be 74.94% using the Megazyme amylose and amylopectin assay kit, and the resistant starch content in the sample was determined to be 29.78% using the Englyst in vitro simulated digestion method, as shown in Tables 1 and 2, respectively.

[0054] Comparative Example 1

[0055] Ordinary corn starch was added to the feeding end of a twin-screw extruder, the moisture content was set to 40 wt%, the screw speed was set to 150 rpm, the temperatures of zones I, II, III, IV, V, and VI of the extruder (ZE-16) were set to 35, 45, 60, 80, 100, and 120°C, respectively, and extrusion was started. The fully gelatinized corn starch was collected, dried at 45°C, and then crushed.

[0056] The amylose content in Comparative Example 1 was determined to be 29.52% using the Megazyme amylose and amylopectin assay kit, and the resistant starch content in the sample was determined to be 5.61% using the Englyst in vitro simulated digestion method, as shown in Tables 1 and 2, respectively.

[0057] Comparative Example 2

[0058] (1) Adding ordinary corn starch to the feeding end of a twin-screw extruder, setting the moisture content to 40 wt%, the screw speed to 150 rpm, and the temperatures of zones I, II, III, IV, V, and VI of the extruder (ZE-16) to 35, 45, 60, 80, 100, and 120°C, respectively, and starting extrusion. Collect the fully gelatinized corn starch, dry it at 45°C, and then grind it;

[0059] (2) Gelatinized corn starch was added to the feeding end of a twin-screw extruder, the moisture content was set to 60 wt%, the temperatures of zones I, II, III, IV, V, and VI of the extruder were set to 35, 45, 55, 60, 65, and 95 °C, respectively, the screw speed was 150 rpm, and extrusion was started. The extrudate was collected and recrystallized at 4 °C for 24 h, and then dried at 45 °C.

[0060] The amylose content in Comparative Example 2 was determined to be 31.61% using the Megazyme amylose and amylopectin assay kit, and the resistant starch content in the sample was determined to be 8.16% using the Englyst in vitro simulated digestion method, as shown in Tables 1 and 2, respectively.

[0061] Table 1 Amylose content of samples

[0062]

[0063] (Note: Different letters in abcdef indicate significant differences between the data groups, p<0.05)

[0064] Table 2 Contents of rapidly digestible starch, slowly digestible starch and resistant starch in samples

[0065]

[0066]

[0067] (Note: Different letters in abcdef indicate significant differences between the data groups, p<0.05)

[0068] The present invention's method for preparing RS3 resistant starch utilizes extrusion-debranching to achieve efficient debranching of starch at high starch substrate concentrations and in a short time, providing a feasible approach for the industrial production of amylose and resistant starch. After extrusion-debranching, the starch can have an amylose content as high as 90.21% and a resistant starch content as high as 41.50%. This method is simple to operate, highly efficient, and suitable for industrial continuous production.

[0069] The above embodiments are described to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing RS3 resistant starch by "extrusion-debranching" method, characterized in that: The method comprises the following steps: (1) Starch raw material was added to a twin-screw extruder and extruded once. The gelatinized and degraded starch was collected and dried and crushed. The speed of the twin-screw extruder was 150 rpm. The temperature of the six temperature zones of the extruder was increased successively to 35, 45, 60, 80, 100 and 120 °C. The moisture content of the material was 40 wt%. (2) The gelatinized starch crushed in step (1) is fully mixed with pullulanase, added to a twin-screw extruder, and extruded for a second time. The debranched starch after extrusion is collected and recrystallized, and then washed with water, centrifuged, and the precipitate is collected and dried to obtain RS3 resistant starch; the speed of the twin-screw extruder is 150 rpm, and the temperatures of the six temperature zones of the extruder are increased sequentially, wherein the temperatures of the first five temperature zones are 35, 45, 55, 60 and 65 °C, and the temperature of the last temperature zone is 95 °C; The moisture content of the material in the extruder is 60wt%, and the starch mass concentration is 40-60%; the amount of pullulanase added is 20-100 U / g based on the dry starch basis; The recrystallization conditions are: temperature of 2-25°C and time of 10-36 h; The drying is carried out in conventional drying equipment at a drying temperature of 40-50°C.

2. The method for preparing RS3 resistant starch by the "extrusion-debranching" method according to claim 1, characterized in that: The starch in step (1) includes one or more of ordinary starch and waxy starch.

3. The method for preparing RS3 resistant starch by the "extrusion-debranching" method according to claim 1, characterized in that: Step (1) drying is carried out in conventional drying equipment at a drying temperature of 40-50°C.

4. The method for preparing RS3 resistant starch by the "extrusion-debranching" method according to claim 1, characterized in that: The centrifugal force in step (2) is 2000-5000 g, and the time is 5-20 min.

5. Use of the method for preparing RS3 resistant starch by the "extrusion-debranching" method according to any one of claims 1 to 4 in the field of food preparation.

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