Gradient grading preparation method of high-resistance linear dextrin

Abstract

The invention discloses a preparation method of high-resistance linear dextrin, which comprises the following steps: step 1, preparing rice starch into starch suspension, heating and cooling; adjusting the pH value of the cooled starch suspension to 5.0, and adding pullulanase to carry out enzymolysis debranching; carrying out enzyme deactivation after enzymolysis debranching, and freeze-drying to form powder, namely the linear dextrin subjected to enzymolysis debranching; and 2, grading the linear dextrin prepared in the step 1 by adopting an absolute ethyl alcohol gradient elution method, and when the concentration of absolute ethyl alcohol reaches 50%, obtaining the linear dextrin with a B-type crystal structure and the resistant starch content of 91.14%. The obtained linear dextrin can be subjected to grading treatment by using an ethanol gradient elution method, and linear dextrin with high resistant starch content corresponding to B-type crystals and A-type crystals can be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of food nutrition, in particular to a method for fractionating and preparing linear dextrin with high resistant starch content. Background Art

[0002] When exposed to heat, acidic conditions, or the action of amylase, starch's macromolecular structure gradually breaks down and hydrolyzes, forming a series of small-molecule intermediates collectively known as dextrins. Once dextrin enters the human digestive tract, it undergoes a step-by-step breakdown by various digestive enzymes, ultimately converting it into glucose, which provides the body with the necessary energy to maintain the normal functioning of various life activities. Dextrin's ability to slowly release glucose in the body helps maintain blood sugar stability. This blood sugar regulation mechanism is particularly important and beneficial for those with obesity and diabetes.

[0003] Based on the degradation mode and the conditions for controlling degradation, dextrin products can be subdivided into various types, including resistant dextrin, limit dextrin, maltodextrin, linear dextrin (LD), and cyclodextrin. Linear dextrin (LD) is composed of glucose units connected by α-(1,4)-glycosidic bonds. It can be randomly entangled in an aqueous solution system to form a single helical cavity structure with internal hydrophobicity and external hydrophilicity. This structure allows linear dextrin to be used as an embedding wall material, achieving targeted release of guest molecules in the small intestine and further digestion. In addition, linear dextrin has a certain solubility in the aqueous phase and can be more efficiently dispersed in the system. This feature has made it favored by more and more researchers.

[0004] To obtain linear dextrins, the existing technology typically uses starch as the raw material and employs isoamylase and pullulanase to cleave the α-(1,6)-glycosidic bonds of the starch molecules, thereby producing linear dextrins, which are short-chain linear oligosaccharides. Furthermore, existing technologies typically use chromatography, filtration, ultracentrifugation, and non-cosolvent precipitation methods to fractionate linear dextrins.

[0005] Although the existing technologies can quickly fractionate linear dextrins using chromatography, filtration, ultracentrifugation and non-co-solvent precipitation, these methods have high costs and safety issues and also require additional processing steps.

[0006] Compared with chromatography, filtration, ultracentrifugation, and non-cosolvent precipitation, the existing technology also has an ethanol gradient elution method for dextrin fractionation. The ethanol gradient elution method is safer and does not require additional processing steps, thereby simplifying the dextrin fractionation process. However, in the process of obtaining linear dextrins by enzymatic debranching using starch as a raw material in the existing technology, due to the insufficient penetration of the debranching enzyme into the crystalline region of the starch granules, the difficulty in controlling the enzymatic hydrolysis kinetics, and the lack of graded control of the linear starch chain length, the prepared linear dextrin has a high branching residue rate and poor product uniformity, which makes it difficult to meet high-end requirements such as sustained-release carriers. Therefore, it is difficult to obtain high-purity, specific crystal form, highly digestible linear dextrin components through the ethanol gradient elution method. Based on this, this patent proposes a gradient fractionation preparation method for highly resistant linear dextrins. Chain length fractionation is achieved by combining enzymatic debranching with gradient ethanol fractionation. After gelatinization, rice starch is uniformly dispersed in an aqueous solution, which is conducive to pullulanase cleaving the α-(1,6)-glycosidic bonds of the starch molecules. Then, fractionation is performed to obtain linear dextrins of short-chain linear oligosaccharides. In this way, crystal formation is regulated, so that the product has high resistance (RS ≥ 80%), low viscosity and strong thermal stability, achieving breakthroughs in process efficiency, environmental protection and functional integration, and providing a new path for the precise application of functional starch. Summary of the Invention

[0007] The present invention provides a gradient fractionation preparation method for highly resistant linear dextrin, so as to solve the problem in the prior art that it is difficult to obtain a highly digestion-resistant linear dextrin component with high purity and specific crystal form by an ethanol gradient elution method.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A gradient fractionation method for preparing high-resistance linear dextrin comprises the following steps:

[0010] Step 1: Add rice starch to water to prepare a starch suspension with a concentration of 10%, then heat the starch suspension at 95° C. for 30 minutes, and then cool to 60° C.;

[0011] The pH of the cooled starch suspension was then adjusted to 5.0, and pullulanase was added to the pH-adjusted starch suspension, followed by stirring at 60° C. for 6 h to perform enzymatic debranching.

[0012] After enzymatic debranching, the starch suspension was inactivated by water bath at 100°C for 15 min and finally freeze-dried into powder. The obtained powder was the enzymatically debranched linear dextrin.

[0013] Step 2: The linear dextrin prepared in step 1 is fractionated by gradient elution with anhydrous ethanol. When the concentration of anhydrous ethanol reaches 50%, a linear dextrin with a B-type crystal structure and a resistant starch content of 91.14% is obtained.

[0014] In the further step 1, the rice starch is any one of indica rice starch, japonica rice starch, and glutinous rice starch, or a combination of two or more of them in any proportion.

[0015] In the further step 2, when the concentration of anhydrous ethanol reaches 70%, linear dextrin with type A crystal structure and resistant starch content of 37.59% is obtained.

[0016] In the present invention, rice starch is used as a raw material, and the rice starch is gelatinized, pH-adjusted and pre-treated, and then enzymatically debranched, thereby obtaining linear dextrin having two crystalline structure characteristics, B type and V type.

[0017] Since the linear dextrin obtained through the above-described process of the present invention has both Type B and Type V crystal structures, when prepared as a suspension and subjected to gradient elution with anhydrous ethanol, the linear dextrin's crystal structure is effectively destroyed, and Type B and Type A crystal structures are formed at two different concentrations of anhydrous ethanol, 50% and 70%, respectively. Furthermore, the different crystal forms formed cause changes in the dextrin's microscopic morphology, increasing the difficulty of access by digestive enzymes. Consequently, when gradient elution with anhydrous ethanol is used, the present invention ultimately produces Type B linear dextrin with a resistant starch content of up to 91.14% at a 50% concentration of anhydrous ethanol, and Type A linear dextrin with a resistant starch content of up to 37.59% at a 70% concentration of anhydrous ethanol.

[0018] In summary, through the above-mentioned pretreatment of rice starch and enzymatic debranching process of the present invention, the linear dextrin obtained by the present invention has two crystalline structure characteristics of type B and type V. Therefore, the linear dextrin can be subsequently graded using an ethanol gradient elution method, and the linear dextrin with a high resistant starch content corresponding to type B crystals and type A crystals can be obtained respectively by the ethanol gradient elution method. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 XRD curves (A) and relative crystallinity (B) of dextrin samples eluted with gradient elution of different ethanol concentrations. Figure 1 In the figure, EB represents linear dextrin after enzymatic debranching, and Et50% and Et70% represent dextrin molecules eluted with 50% and 70% ethanol concentration gradients, respectively.

[0020] Figure 2 FTIR spectra (A) and deconvolution spectra (B) of dextrin samples eluted with gradient elution of different ethanol concentrations. Figure 2 In the figure, RS represents rice starch, EB represents linear dextrin after enzymatic debranching, and Et50% and Et70% represent dextrin molecules eluted with 50% and 70% ethanol concentration gradients, respectively.

[0021] Figure 3It is the DSC spectrum of dextrin samples eluted with gradient of different ethanol concentrations. Figure 3 In the figure, RS represents rice starch, EB represents linear dextrin after enzymatic debranching, and Et50% and Et70% represent dextrin molecules eluted with 50% and 70% ethanol concentration gradients, respectively.

[0022] Figure 4 This is a scanning electron micrograph of dextrin samples eluted with gradient elution using different ethanol concentrations. Figure 4 In the figure, EB represents linear dextrin after enzymatic debranching, and Et50% and Et70% represent dextrin molecules eluted with 50% and 70% ethanol concentration gradients, respectively. A1-C1 represent the micromorphologies of different dextrins under 10000× (EB, Et50%, Et70%, respectively). A2-C2 represent the micromorphologies of different dextrins under 5000× (EB, Et50%, Et70%, respectively). A3-C3 represent the micromorphologies of 1000× (EB, Et50%, Et70%, respectively). EB represents linear dextrin after enzymatic debranching, and Et50% and Et70% represent dextrin molecules eluted with 50% and 70% ethanol concentration gradients, respectively.

[0023] Figure 5 are the RDS, SDS and RS contents of dextrin samples eluted with gradient elution using different ethanol concentrations. Figure 5 In the figure, RS represents rice starch, EB represents linear dextrin after enzymatic debranching, and Et50% and Et70% represent dextrin molecules eluted with 50% and 70% ethanol concentration gradients, respectively. DETAILED DESCRIPTION

[0024] To help those skilled in the art better understand the present invention, the following detailed description of the embodiments of the present invention is provided in conjunction with the accompanying drawings and examples. This will help those skilled in the art to fully understand and implement the present invention by applying technical means to solve technical problems and achieve corresponding technical effects. The embodiments of the present invention and the various features therein may be combined with each other as long as they do not conflict with each other, and the resulting technical solutions are all within the scope of protection of the present invention.

[0025] 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 should fall within the scope of protection of the present invention.

[0026] It should be noted that the terms "include" and "have" in the specification, claims and drawings of the present invention and any variations thereof are intended to cover non-exclusive inclusions.

[0027] This embodiment discloses a gradient fractionation method for preparing high-resistance linear dextrin, comprising the following steps:

[0028] Step 1: Using rice starch as a raw material, linear starch is prepared by an enzymatic debranching method, including a pretreatment process of the rice starch and an enzymatic debranching process. The rice starch is any one of indica rice starch, japonica rice starch, and glutinous rice starch, or a combination of two or more in any proportion.

[0029] The pretreatment process of rice starch is as follows:

[0030] Rice starch was added to water to prepare a starch suspension with a concentration of 10%, and the starch suspension was heated at 95° C. for 30 minutes, cooled to 60° C. after heating, and then the pH of the cooled starch suspension was adjusted to 5.0.

[0031] The enzymatic debranching process is as follows:

[0032] Pullulanase was added to the pH-adjusted starch suspension, followed by stirring at 60°C for 6 hours to perform enzymatic debranching. The starch suspension was then inactivated in a water bath at 100°C for 15 minutes and freeze-dried to form a powder. The resulting powder was the enzymatically debranched linear dextrin, designated EB.

[0033] Step 2: Using an anhydrous ethanol gradient elution method, the linear dextrin prepared in step 1 is fractionated as follows:

[0034] The linear dextrin obtained in step 1 is added to water to prepare a suspension with a concentration of 4%, and the suspension is stirred and heated at 95° C. for 30 minutes, thereby uniformly dispersing the linear dextrin in the water.

[0035] The heated suspension was centrifuged, and then the supernatant was collected and anhydrous ethanol was added to the supernatant until the concentration of anhydrous ethanol in water reached 50%. At this time, centrifugation was performed and the precipitate was collected. The obtained precipitate was a linear dextrin with a B-type crystalline structure and a resistant starch content of 91.14%, which was recorded as Et50%.

[0036] The supernatant after centrifugation was taken and anhydrous ethanol was continued to be added to the supernatant. When the concentration of anhydrous ethanol reached 70%, centrifugation was performed and the precipitate was collected. The precipitate obtained by centrifugation was linear dextrin with type A crystalline structure and a resistant starch content of 37.59%, which was recorded as Et70%.

[0037] In this embodiment, after enzymatic debranching, linear dextrin was gradient eluted with anhydrous ethanol of different concentrations, and its crystal structure changed. Figure 1As shown. Unlike the crystalline structure of linear dextrin after enzymatic debranching, linear dextrin precipitated with 50% anhydrous ethanol exhibits characteristic peaks of type B crystals with a relative crystallinity of 27.99%, while linear dextrin precipitated with 70% anhydrous ethanol exhibits a type A crystal structure with a relative crystallinity of 51.82%. The crystal structure of rice starch undergoes reconstruction after hydrolysis, forming a new crystal form. Furthermore, dextrin precipitated with gradient elution using different anhydrous ethanol concentrations exhibits different crystal forms and digestibility. Type B crystalline linear dextrin precipitated with 50% anhydrous ethanol exhibits high digestibility.

[0038] In this embodiment, after enzymatic debranching, linear dextrin was gradient eluted with anhydrous ethanol of different concentrations, and its short-range ordered structure changed, such as Figure 2 As shown. 1047 / 1022cm of linear dextrin after enzymatic hydrolysis -1 The ratio is 0.61, and the linear dextrin precipitated by 50% anhydrous ethanol is 1047 / 1022cm -1 The ratio is 0.74, and the linear dextrin precipitated by 70% anhydrous ethanol is 1047 / 1022cm -1 The ratio is 0.69. Compared with rice starch, the short-range order of linear dextrin after enzymatic hydrolysis is reduced, while the double helical structure of linear dextrin eluted with 50% anhydrous ethanol increases, and the order is enhanced, which is conducive to the formation of B-type crystal structure and improves the digestibility of starch.

[0039] In this embodiment, linear dextrin is subjected to gradient elution using anhydrous ethanol of different concentrations after enzymatic debranching, and its thermodynamic properties are improved, such as Figure 3 As shown in Figure 2 , enzymatically hydrolyzed linear dextrins exhibit no gelatinization peak, indicating that their internal structure has been destroyed. The enthalpy of linear dextrin precipitated from 50% anhydrous ethanol was 10.29 J / g, and that from 70% anhydrous ethanol was 11.54 J / g. Compared to enzymatically debranched linear dextrins, gradient elution exhibited enhanced thermal stability.

[0040] In this embodiment, after enzymatic debranching, linear dextrin was gradient eluted with anhydrous ethanol of different concentrations, and its microscopic morphology was reconstructed, such as Figure 4 Compared to linear dextrins after enzymatic debranching, linear dextrins precipitated by 50% anhydrous ethanol reaggregate, forming small, rough spheres that aggregate together. When the anhydrous ethanol concentration is increased to 70%, the aggregated spheres gradually disperse, and the surface roughness is eliminated, resulting in a smooth surface. The new microstructure re-formed after elution with anhydrous ethanol may alter the binding sites of digestive enzymes. The surface protrusions may imprison digestive enzymes, rendering them ineffective.

[0041] In this embodiment, after enzymatic debranching, linear dextrin was gradiently eluted with anhydrous ethanol of different concentrations. The crystal type of the dextrin molecules changed, the relative crystallinity increased, the number of short-range ordered structures increased, the thermal stability was enhanced, the structure became denser, and the resistant starch content in the dextrin molecules was greatly increased. Figure 5 As shown in Table 1. Compared with rice starch, the resistant starch content of linear dextrin after enzymatic debranching is 50.56%, the resistant starch content of linear dextrin precipitated by 50% anhydrous ethanol is as high as 91.14%, and the resistant starch content of linear dextrin precipitated by 70% anhydrous ethanol is 37.59%, which greatly reduces the digestibility of linear dextrin and effectively improves its digestibility. Table 1 is as follows:

[0042] Table 1 Digestible starch content of different samples

[0043]

[0044] Note: Different letters in the same column represent significant differences (P<0.05).

[0045] The literature in the table is as follows:

[0046] [1]JIA J,DOU B,GAO M,et al.Effect of Genistein on Starch Digestion InVitro and Its Mechanism ofAction[J].Foods,2024,13(17):2809.

[0047] [2]ZHU Y,DONG C,CHI F,et al.Effects of Cactus Polysaccharide onPasting,Rheology,Structural Properties,In Vitro Digestibility,and Freeze–ThawStability of Rice Starch[J].Foods,2024,13(15):2420.

[0048] [3]WU H,WANG M,REN

[0049] [4]ZHOU

[0050] The highly resistant linear dextrin prepared in this example exhibits a different crystal type, with a higher relative crystallinity. This increases the strength of hydrogen bonds within the dextrin molecules and the number of double helical structures, reducing enzymatic digestibility. Furthermore, the linear dextrin's enthalpy increases, its thermal stability improves, and the difficulty of disrupting its molecular structure increases. Furthermore, the linear dextrin undergoes reconfiguration, forming a regular particle shape, which alters the binding sites for digestive enzymes, resulting in starch indigestibility, increasing the content of resistant starch, and enhancing the linear dextrin's anti-digestive effect.

[0051] The preferred embodiments of the present invention are described in detail above with reference to the accompanying drawings. The embodiments described in the present invention are merely descriptions of the preferred embodiments of the present invention and do not limit the concept and scope of the present invention. The various specific technical features described in the above specific embodiments can be combined in any suitable manner unless there is any contradiction. Such combinations should also be regarded as the contents disclosed in this disclosure as long as they do not violate the concept of the present invention. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0052] The present invention is not limited to the specific details of the above-mentioned embodiments. Within the scope of the technical concept of the present invention and without departing from the design concept of the present invention, various modifications and improvements made to the technical solution of the present invention by those skilled in the art should fall within the scope of protection of the present invention. The technical contents for which protection is sought in the present invention have been fully recorded in the claims.

Claims

1. A gradient fractionation method for preparing high-resistance linear dextrin, characterized in that: The following steps are involved: Step 1: Add rice starch to water to prepare a starch suspension with a concentration of 10%, then heat the starch suspension at 95° C. for 30 minutes, and then cool to 60° C.; The pH of the cooled starch suspension was then adjusted to 5.0, and pullulanase was added to the pH-adjusted starch suspension, followed by stirring at 60° C. for 6 h to perform enzymatic debranching. After enzymatic debranching, the starch suspension was inactivated by water bath at 100°C for 15 minutes and finally freeze-dried to form a powder. The obtained powder was the enzymatically debranched linear dextrin. Step 2: The linear dextrin prepared in step 1 is fractionated by gradient elution with anhydrous ethanol. When the concentration of anhydrous ethanol reaches 50%, a linear dextrin with a B-type crystal structure and a resistant starch content of 91.14% is obtained.

2. The method for preparing a high-resistance linear dextrin by gradient fractionation according to claim 1, wherein: In step 1, the rice starch is any one of indica rice starch, japonica rice starch, and glutinous rice starch, or a combination of two or more of the above in any proportion.

3. The method for preparing a high-resistance linear dextrin by gradient fractionation according to any one of claims 1 to 2, characterized in that: In step 2, when the concentration of anhydrous ethanol reaches 70%, linear dextrin with a type A crystal structure and a resistant starch content of 37.59% is obtained.

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