A method for making starch resistant to digestion and for increasing the resistance of starch to digestion

Abstract

The present application aims to provide a kind of resistant digestion starch and the method for improving the resistance of starch digestion.The waxy starch with high amylopectin content is used as raw material, and after high temperature pre-gelatinization, enzymatic debranching and alcohol fractionation, the low temperature assisted molecular chain ordering of starch is used, and the perfect structure of starch recrystallization is further improved based on magnetic induction effect, so that the resistant digestion starch is obtained.The obtained resistant digestion starch is typical A type crystal, and the relative crystallinity is more than 70%, the content of slow digestion starch and resistant starch can reach 30% and more than 55%.

Description

Technical Field

[0001] This invention belongs to the field of starch refining technology, specifically relating to a resistant starch and a method for improving the resistantness of starch to digestion. Background Technology

[0002] my country's annual starch production exceeds 20 million tons, making the starch industry a vital part of the national economy. Resistant starch is an important starch derivative, and its large-scale production is crucial for increasing the added value of starch and promoting the development of the starch deep processing industry. In 2019, the global market value of resistant starch reached 1.5 billion yuan, and it is projected to grow to 2.2 billion yuan by 2026. However, the development of domestic resistant starch brands in my country has been slow, with most products suffering from poor taste, low resistance, and susceptibility to enzymatic hydrolysis upon heating. Therefore, exploring safe and high-quality resistant starch structural design schemes and mechanisms is a critical bottleneck issue that urgently needs to be addressed to ensure the high-quality development of my country's starch deep processing industry.

[0003] Meanwhile, with socio-economic development, the demand for high-quality healthy foods is increasing. However, under modern dietary patterns, the prevalence of metabolic syndromes such as diabetes is constantly rising. Surveys indicate that the prevalence of type II diabetes in my country is as high as 12%, a serious trend. Resistant starch does not cause a rapid rise in blood sugar after ingestion and plays a beneficial role in improving blood lipid and blood sugar levels, controlling weight, and promoting gut health. Resistant starches, represented by brands like Hi.Maize and Novelose, are widely used as low-energy health and nutritional ingredients in foods such as bread, breakfast cereals, and noodles; these low-glycemic health foods are very popular with consumers. Therefore, developing the resistant starch industry is also an important way to enhance the market competitiveness of traditional staple food products.

[0004] Starch granules are polycrystalline aggregates containing amorphous and crystalline regions, formed by the orderly arrangement of amylose and amylopectin molecules. From the perspective of novel food processing, starch structure regulation is divided into a two-way strategy: from aggregate to molecule (top-down) and from molecule to aggregate (bottom-up). Currently, the preparation of resistant starch mostly adopts traditional top-down processing methods such as wet heating, extrusion, ultrasound, and hydrolysis to destroy the amorphous regions of raw starch granules and improve their crystallinity. However, these methods suffer from problems such as high randomness in the processing, uncontrollable product structure, disordered crystalline regions, and poor thermal stability. Therefore, this invention aims to achieve uniform distribution and quality improvement of resistant starch crystals through precise bottom-up structural design. Summary of the Invention

[0005] To solve all or part of the above-mentioned technical problems, the present invention provides the following technical solutions:

[0006] One objective of this invention is to provide a method for improving the digestibility of starch, comprising:

[0007] Starch is pregelatinized to obtain pregelatinized starch;

[0008] The pregelatinized starch was subjected to enzymatic debranching to obtain debranched starch hydrolysate;

[0009] The debranched starch enzymatic hydrolysate was subjected to a first alcohol precipitation fractionation and a second alcohol precipitation fractionation in sequence, wherein the alcohol content used in the second alcohol precipitation fractionation was higher than that used in the first alcohol precipitation fractionation, to obtain graded debranched starch.

[0010] The graded debranched starch was recrystallized to obtain recrystallized starch.

[0011] The recrystallized starch was subjected to magnetic induction treatment at a temperature below the starch gelatinization temperature to obtain digestible starch.

[0012] In the preparation method, after pregelatinization, the original starch granules absorb water, swell, and disintegrate, and the starch chains are in a disordered state, which is conducive to subsequent enzymatic debranching. Pullulanase is used to hydrolyze the α-1,6 glycosidic bonds of the starch chains to obtain linear starch chains. Compared with unbranched starch chains, linear starch chains have less steric hindrance, which is conducive to the subsequent recrystallization process. The purpose of using two alcohol precipitation fractionation is to remove molecular chains with larger and smaller molecular weights in the system by gradually increasing the alcohol concentration, so as to obtain medium-length starch chains with moderate molecular weight and relatively concentrated distribution. Long starch chains are not easy to rearrange and crystallize, which is not conducive to improving the digestibility of starch, while short starch chains will interfere with the integrity of crystallization and reduce the thermal stability of crystallization. Alternating magnetic flux induction is used to perform magnetic induction treatment below the starch gelatinization temperature. The electrical and thermal effects generated by magnetic induction drive the rearrangement of imperfect crystals in the recrystallized starch, further improving the digestibility of recrystallized starch.

[0013] In some embodiments, the pregelatinization process includes: dispersing starch in a phosphate buffer solution, stirring and preheating for 5 to 15 minutes, and then stirring continuously for 30 to 60 minutes at a heating temperature of 85 to 120°C to partially or completely gelatinize the starch, thereby obtaining pregelatinized starch.

[0014] Furthermore, the starch includes waxy cereal starch. Preferably, it includes waxy corn starch and / or waxy rice starch.

[0015] Furthermore, the pH of the phosphate buffer is 4.5–6.5;

[0016] Furthermore, the preheating time is 8–12 minutes;

[0017] Furthermore, the heating temperature is 90–100°C;

[0018] Furthermore, the continuous stirring time is 40–50 minutes.

[0019] In some embodiments, the enzymatic debranching method includes: uniformly mixing the pregelatinized starch with pullulanase at 1000-3000 npun / g, and sealing and insulating the mixture at a reaction temperature of 40-65°C for 12-36 h. After the reaction is completed, enzyme inactivation treatment is performed to obtain the mixed defatted starch enzymatic hydrolysate.

[0020] Furthermore, the pullulanase activity is 1500–2000 npun / g;

[0021] Furthermore, the reaction temperature for the enzymatic debranching is 55–60°C;

[0022] Furthermore, the reaction time for the enzymatic debranching is 18–24 hours.

[0023] In some embodiments, the first alcohol precipitation fractionation includes: uniformly mixing the debranched starch enzymatic hydrolysate with alcohol at a volume ratio of 1:0.4 to 1:0.7, allowing it to stand, and then separating the supernatant; the second alcohol precipitation fractionation includes: uniformly mixing the supernatant with alcohol at a volume ratio of 1:0.8 to 1:1.6, allowing it to stand, and then separating to obtain the fractionated debranched starch. It should be noted that the "alcohol" mentioned in this invention refers to an alcohol with a concentration of 100% or approximately 100%, and the volume ratio is calculated accordingly; of course, the alcohol used can also be an alcohol solution of other concentrations, and when using an alcohol solution of other concentrations, the volume ratio can be calculated based on the concentration of the alcohol solution.

[0024] Furthermore, in the first alcohol precipitation fractionation, the volume ratio of the debranched starch hydrolysate to alcohol is 1:0.5 to 1:0.6.

[0025] Furthermore, in the first alcohol precipitation fractionation, the settling time is 20-60 minutes to ensure that the starch molecular chains are fully precipitated at the current alcohol concentration.

[0026] Furthermore, in the second alcohol precipitation fractionation, the volume ratio of the supernatant to alcohol is 1:0.9 to 1:1.2.

[0027] Furthermore, in the second alcohol precipitation fractionation, the settling time is 20-60 minutes to ensure that the starch molecular chains are fully precipitated at the current alcohol concentration.

[0028] Furthermore, the alcohol is typically a lower alcohol and / or polyethylene glycol. The lower alcohol preferably includes at least one of methanol, ethanol, and isopropanol, more preferably ethanol.

[0029] In some embodiments, the recrystallization temperature is 0–8°C.

[0030] In some embodiments, the recrystallization time is 12-48 hours. More preferably, the recrystallization time is 18-24 hours.

[0031] In some embodiments, prior to recrystallization, the debranched starch is dried, then dispersed in water and subjected to high-temperature treatment at 80-120°C for 20-60 minutes to obtain a debranched starch dispersion, followed by low-temperature recrystallization. During high-temperature treatment, the starch molecular chains are in a disordered state; under the low-temperature conditions, the starch molecular chains rearrange themselves in an ordered manner to form recrystallized starch.

[0032] Furthermore, the high-temperature treatment time is preferably 30 to 40 minutes.

[0033] Furthermore, the preferred temperature for the high-temperature treatment is 90–100 min.

[0034] Furthermore, the recrystallization temperature is preferably 4-6°C.

[0035] In some embodiments, the method for improving the digestibility of starch further includes: before performing the magnetic induction treatment, dispersing the recrystallized starch in water to obtain a recrystallized starch dispersion, adjusting the conductivity of the recrystallized starch dispersion to above 200 μS / cm, and then performing the magnetic induction treatment.

[0036] Furthermore, it is preferable to adjust the electrical conductivity of the recrystallized starch to 200-400 μS / cm before performing the magnetic induction treatment to ensure that sufficient ionic current is generated in the system. If the ionic current is too low, the resulting thermal effect will be too low, making it difficult to induce starch annealing and thus difficult to improve the perfection of crystallization. If the ionic current is too high, it will lead to the destruction of starch crystallization.

[0037] Furthermore, the excitation voltage of the magnetic induction treatment is 100-400V, preferably 200-300V, to ensure that a sufficiently strong induced voltage and ionic current are induced in the recrystallized starch dispersion.

[0038] Furthermore, the excitation frequency of the magnetic induction treatment is 20-60kHz, preferably 35-50kHz, to ensure that a sufficiently strong induced voltage and ionic current are induced in the recrystallized starch dispersion.

[0039] Furthermore, the alternating magnetic flux intensity of the magnetic induction treatment is 330-500MT, preferably 380-420MT, to ensure that a sufficiently strong induced voltage and ionic current are induced in the recrystallized starch dispersion.

[0040] Furthermore, the temperature of the magnetic induction treatment is 45-60℃, preferably 48-55℃, to ensure starch annealing occurs, thereby promoting perfect starch crystallization.

[0041] Furthermore, the magnetic induction treatment time is 12-48 hours, preferably 18-24 hours, to ensure that the starch chains have enough time to rearrange, thereby enhancing the perfection of the original crystals.

[0042] A second object of the present invention is to provide a digestible starch obtained according to any of the above methods.

[0043] In some embodiments, the resistant starch has a starch chain length DP≥37 accounting for less than 5%, DP25~36 accounting for more than 22%, DP13~24 accounting for more than 56%, and DP6~12 accounting for less than 15%.

[0044] In some embodiments, the digestible starch is type A cereal starch crystal form, and type A cereal starch has a more dense crystalline arrangement.

[0045] In some embodiments, the relative crystallinity of the resistant starch is 70% or higher.

[0046] In some embodiments, the resistant starch comprises more than 30% slow-digesting starch and more than 55% resistant starch.

[0047] Compared with the prior art, the present invention has at least the following beneficial effects:

[0048] (1) The method for improving the digestibility of starch provided by the present invention is to induce the starch molecular chain to combine from bottom to top to form digestible starch crystals. Compared with the traditional top-down methods such as extrusion, ultrasound, and hydrolysis, the starch product structure obtained by this method is more controllable and easier to design target products. This method can not only provide starch products with good digestibility, but also flexibly control the starch structure to meet the needs of different consumer groups.

[0049] (2) This invention combines pregelatinization, enzymatic debranching and alcohol precipitation fractionation to debranch multi-branched starch to obtain linear molecular chains. Based on the difference in polarity of starch chains with different molecular weights, alcohol is added step by step to effectively increase the proportion of medium and short chains and medium and long chains in the linear starch chain combination, which is conducive to the subsequent formation of stable and uniformly distributed starch crystals.

[0050] (3) This invention utilizes low temperature to induce starch chains to recrystallize from disorder to order, and further utilizes the dual effects of thermal and electrical effects generated by magnetic induction to drive the cell arrangement and orientation during recrystallization, thereby improving the crystallization perfection of recrystallized starch and realizing the preparation of digestible starch.

[0051] (4) The method provided by the present invention uses pure starch as raw material and does not require the introduction of emulsifiers or other chemical reagents, resulting in a green and healthy product.

[0052] (5) The resistant starch product obtained by the above method is a densely arranged type A cereal starch crystal with a relative crystallinity of over 70%; the slow-digesting starch content is over 30% and the resistant starch content is over 55%. This resistant starch product can be used as an ingredient in low glycemic index foods and has physiological functions such as improving intestinal health, preventing diabetes, and controlling weight. Attached Figure Description

[0053] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0054] Figure 1 This is a flowchart of a method for improving starch digestibility in one embodiment of the present invention; Detailed Implementation

[0055] The technical solutions of the present invention will be described in detail below with reference to specific embodiments, so that those skilled in the art can better understand and implement the technical solutions of the present invention. The specific functional details disclosed herein should not be construed as limiting, but are merely intended to form the basis of the claims and to teach those skilled in the art to employ the representative basis of the invention in different ways in any suitable detailed embodiment.

[0056] The starch and chemical reagents used in the following examples are all commercially available general products.

[0057] Example 1

[0058] This embodiment provides a method for improving the digestibility of starch and its resistance to digestion. Figure 1 As shown, the method includes:

[0059] Waxy corn starch was dispersed in a phosphate buffer solution with a pH of 5.5, stirred and preheated for 10 min, and then heated and stirred continuously for 40 min at a temperature of 95℃ to obtain pregelatinized starch.

[0060] The pregelatinized starch was cooled to 58°C, and then 2000 npun / g pullulanase was added. The mixture was mixed and sealed and kept warm for 36 h for enzymatic hydrolysis. After the enzymatic hydrolysis was completed, the resulting hydrolysate was incubated in a boiling water bath for 10 min to inactivate the enzyme, and then rapidly centrifuged to obtain a transparent debranched starch hydrolysate.

[0061] Mix the enzymatic hydrolysate with anhydrous ethanol at a volume ratio of 1:0.7, let stand for 30 minutes, then centrifuge to obtain the supernatant, thus completing the first alcohol precipitation fractionation. Mix the supernatant with anhydrous ethanol at a volume ratio of 1:1.6, let stand for 30 minutes, then centrifuge to obtain the precipitate, thus completing the second alcohol precipitation fractionation, and obtaining alcohol-precipitated starch.

[0062] The obtained alcohol-precipitated and graded starch was dried, dispersed in distilled water, heated in a boiling water bath for 40 min, and then recrystallized at 4℃ for 24 h to obtain recrystallized starch.

[0063] Then, the recrystallized starch was dispersed in an aqueous solution, potassium chloride was added to adjust the conductivity to 300 μS / cm, and pumped into a magnetic induction reactor. It was treated for 24 h under the conditions of excitation voltage of 300 V, excitation frequency of 35 kHz, alternating magnetic flux intensity of 420 MT, and temperature of 50 °C to obtain digestible starch.

[0064] In this embodiment, the starch chain length distribution after alcohol precipitation, low-temperature recrystallization, and magnetic induction treatment is as follows: DP6-12 accounts for 14.21%, DP13-24 accounts for 58.34%, DP25-36 accounts for 23.63%, and DP≥37 accounts for 3.82%. The resulting resistant recrystallized starch contains 11.3% rapidly digestible starch, 30.3% slowly digestible starch, and 58.4% resistant starch.

[0065] Example 2

[0066] Waxy corn starch was dispersed in a phosphate buffer solution with a pH of 4.5, stirred and preheated for 15 min, and then heated and stirred continuously for 60 min at a temperature of 85℃ to obtain pregelatinized starch.

[0067] The pregelatinized starch was cooled to 65°C, and then 3000 npun / g pullulanase was added. The mixture was mixed and sealed and kept warm for 36 h for enzymatic hydrolysis. After the enzymatic hydrolysis was completed, the resulting hydrolysate was heated in a boiling water bath for 10 min to inactivate the enzyme, and then rapidly centrifuged to obtain a transparent debranched starch hydrolysate.

[0068] Mix the enzymatic hydrolysate with anhydrous ethanol at a volume ratio of 1:0.4, let stand for 20 minutes, then centrifuge to obtain the supernatant, thus completing the first alcohol precipitation fractionation. Mix the supernatant with anhydrous ethanol at a volume ratio of 1:0.8, let stand for 20 minutes, then centrifuge to obtain the precipitate, thus completing the second alcohol precipitation fractionation, and obtaining alcohol-precipitated starch.

[0069] The obtained alcohol-precipitated fractionated starch was dried, dispersed in distilled water, heated in a boiling water bath for 30 min, and then recrystallized at 0℃ for 12 h to obtain recrystallized starch.

[0070] Then, the recrystallized starch was dispersed in an aqueous solution, and sodium chloride was added to adjust the conductivity to 200 μS / cm. The solution was then pumped into a magnetic induction reactor and treated for 12 h at an excitation voltage of 400 V, an excitation frequency of 50 kHz, an alternating magnetic flux intensity of 500 MT, and a temperature of 60 °C to obtain digestible starch.

[0071] In this embodiment, the starch chain length distribution after alcohol precipitation, low-temperature recrystallization, and magnetic induction treatment is as follows: DP6-12 accounts for 14.54%, DP13-24 accounts for 57.54%, DP25-36 accounts for 24.22%, and DP≥37 accounts for 3.7%. The resulting resistant recrystallized starch contains 11.8% rapidly digestible starch, 31.8% slowly digestible starch, and 56.4% resistant starch.

[0072] Example 3

[0073] Waxy corn starch was dispersed in a phosphate buffer solution with a pH of 4.5, stirred and preheated for 5 minutes, and then heated and stirred continuously for 30 minutes at a temperature of 120°C to obtain pregelatinized starch.

[0074] The pregelatinized starch was cooled to 40°C, and then 1000 npun / g pullulanase was added. The mixture was mixed and sealed and kept warm for 12 h for enzymatic hydrolysis. After the enzymatic hydrolysis was completed, the resulting hydrolysate was heated in a boiling water bath for 10 min to inactivate the enzyme, and then rapidly centrifuged to obtain a transparent debranched starch hydrolysate.

[0075] Mix the enzymatic hydrolysate with anhydrous ethanol at a volume ratio of 1:0.5, let stand for 20 minutes, then centrifuge to obtain the supernatant to complete the first alcohol precipitation fractionation. Mix the supernatant with anhydrous ethanol at a volume ratio of 1:1, let stand for 20 minutes, then centrifuge to obtain the precipitate to complete the second alcohol precipitation fractionation, and obtain alcohol-precipitated starch.

[0076] The obtained alcohol-precipitated and graded starch was dried, dispersed in distilled water, heated in a boiling water bath for 60 min, and then recrystallized at 8℃ for 48 h to obtain recrystallized starch.

[0077] Then, the recrystallized starch was dispersed in an aqueous solution, sodium chloride was added to adjust the conductivity to 400 μS / cm, and the solution was pumped into a magnetic induction reactor. The solution was treated for 48 h under the conditions of excitation voltage of 100 V, excitation frequency of 20 kHz, alternating magnetic flux intensity of 330 MT, and temperature of 45 ℃ to obtain digestible starch.

[0078] In this embodiment, the starch chain length distribution after alcohol precipitation, low-temperature recrystallization, and magnetic induction treatment is as follows: DP6-12 accounts for 14.29%, DP13-24 accounts for 58.86%, DP25-36 accounts for 23.65%, and DP≥37 accounts for 3.2%. The resulting resistant recrystallized starch contains 12.4% rapidly digestible starch, 32.4% slowly digestible starch, and 55.2% resistant starch.

[0079] Comparative Example 1-1

[0080] The only difference between Comparative Example 1-1 and Example 1 is that the alcohol precipitation process only involves the first alcohol precipitation: the enzymatic hydrolysate and anhydrous ethanol are mixed evenly at a volume ratio of 1:0.7, and the second alcohol precipitation is not performed. The rest of the process is the same as in Example 1.

[0081] The starch chain length distribution in this comparative example after alcohol precipitation, low-temperature recrystallization, and magnetic induction treatment was as follows: DP6-12 accounted for 15.31%, DP13-24 accounted for 46.14%, DP25-36 accounted for 21.32%, and DP≥37 accounted for 17.23%. The obtained resistant recrystallized starch contained 62.1% rapidly digestible starch, 24.4% slowly digestible starch, and 13.5% resistant starch.

[0082] Comparative Examples 1-2

[0083] The only difference between Comparative Examples 1-2 and Example 1 is that the alcohol precipitation process is performed only once: the enzymatic hydrolysate and anhydrous ethanol are mixed evenly at a volume ratio of 1:3.0 to precipitate all the enzymatically debranched starch.

[0084] The starch chain length distribution after alcohol precipitation fractionation, low-temperature recrystallization, and magnetic induction treatment in this comparative example was as follows: DP6-12 accounted for 19.65%, DP13-24 accounted for 49.45%, DP25-36 accounted for 18.54%, and DP≥37 accounted for 12.36%. The obtained resistant recrystallized starch contained 52.3% rapidly digestible starch, 24.6% slowly digestible starch, and 23.1% resistant starch.

[0085] Comparative Examples 1-3

[0086] The only difference from Example 1 is that in the first alcohol precipitation fractionation, the enzymatic hydrolysate and anhydrous ethanol are mixed evenly at a volume ratio of 1:0.4; in the second alcohol precipitation fractionation, the supernatant and anhydrous ethanol are mixed evenly at a volume ratio of 1:1.6. The rest of the process is the same as in Example 1.

[0087] The starch chain length distribution after alcohol precipitation, low-temperature recrystallization, and magnetic induction treatment in this comparative example was as follows: DP6-12 accounted for 14.58%, DP13-24 accounted for 53.32%, DP25-36 accounted for 21.52%, and DP≥37 accounted for 10.58%. The obtained resistant recrystallized starch contained 22.4% rapidly digestible starch, 35.3% slowly digestible starch, and 42.3% resistant starch.

[0088] Comparative Examples 1-4

[0089] The only difference from Example 1 is that in the first alcohol precipitation fractionation, the enzymatic hydrolysate and anhydrous ethanol are mixed evenly at a volume ratio of 1:0.7; and in the second alcohol precipitation fractionation, the supernatant and anhydrous ethanol are mixed evenly at a volume ratio of 1:3.0.

[0090] The starch chain length distribution in this comparative example after alcohol precipitation, low-temperature recrystallization, and magnetic induction treatment was as follows: DP6-12 accounted for 21.36%, DP13-24 accounted for 54.34%, DP25-36 accounted for 17.63%, and DP≥37 accounted for 6.67%. The obtained resistant recrystallized starch contained 30.2% rapidly digestible starch, 30.1% slowly digestible starch, and 39.7% resistant starch.

[0091] Comparative Examples 1-5

[0092] The only difference from Example 1 is that the alcohol precipitate powder is not subjected to magnetic induction treatment after low-temperature recrystallization.

[0093] The starch chain length distribution after alcohol precipitation fractionation and low-temperature recrystallization in this comparative example was as follows: DP6-12 accounted for 14.21%, DP13-24 accounted for 58.34%, DP25-36 accounted for 23.63%, and DP≥37 accounted for 3.82%. The obtained resistant recrystallized starch contained 24.3% rapidly digestible starch, 31.2% slowly digestible starch, and 44.5% resistant starch.

[0094] Comparative Example 2-1

[0095] The only difference from Example 2 is that the alcohol precipitation process is performed only once: the enzymatic hydrolysate and anhydrous ethanol are mixed evenly at a volume ratio of 1:0.8, and the rest is the same as in Example 2.

[0096] The starch chain length distribution after alcohol precipitation fractionation, low-temperature recrystallization, and magnetic induction treatment in this comparative example was as follows: DP6-12 accounted for 15.42%, DP13-24 accounted for 45.42%, DP25-36 accounted for 21.85%, and DP≥37 accounted for 17.31%. The obtained resistant recrystallized starch contained 53.3% rapidly digestible starch, 23.1% slowly digestible starch, and 23.6% resistant starch.

[0097] Comparative Example 2-2

[0098] The only difference from Example 2 is that the alcohol precipitate powder is not subjected to magnetic induction treatment after low-temperature recrystallization.

[0099] The starch chain length distribution after alcohol precipitation fractionation and low-temperature recrystallization in this comparative example was as follows: DP6-12 accounted for 14.54%, DP13-24 accounted for 57.54%, DP25-36 accounted for 24.22%, and DP≥37 accounted for 3.7%. The obtained resistant recrystallized starch contained 23.6% rapidly digestible starch, 32.2% slowly digestible starch, and 44.2% resistant starch.

[0100] Comparative Example 3-1

[0101] The only difference from Example 3 is that after amylase debranching, 3 times the volume of ethanol is added directly to precipitate and separate all the debranched starch.

[0102] The starch chain length distribution after alcohol precipitation in this comparative example was as follows: DP6-12 accounted for 21.34%, DP13-24 accounted for 52.84%, DP25-36 accounted for 17.43%, and DP≥37 accounted for 8.39%. The obtained resistant recrystallized starch contained 23.2% rapidly digestible starch, 36.1% slowly digestible starch, and 40.7% resistant starch.

[0103] Comparative Example 3-2

[0104] The only difference from Example 3 is that the alcohol precipitate powder is not subjected to magnetic induction treatment after low-temperature recrystallization.

[0105] The starch chain length distribution after alcohol precipitation fractionation and low-temperature recrystallization in this comparative example was as follows: DP6-12 accounted for 14.29%, DP13-24 accounted for 58.86%, DP25-36 accounted for 23.65%, and DP≥37 accounted for 3.2%. The obtained resistant recrystallized starch contained 24.2% rapidly digestible starch, 35.6% slowly digestible starch, and 40.2% resistant starch.

[0106] The digestibility of the starch products in the examples and comparative examples was determined, and the results are shown in Table 2. The resistant starch obtained by the method provided by the present invention has a higher proportion of slow-digesting starch and resistant starch, while the starch product obtained in the comparative example has a higher proportion of fast-digesting starch, indicating that the method provided by the present invention can improve the digestibility of starch products.

[0107] Table 1. Starch digestibility results in the examples and comparative examples.

[0108] Rapidly digestible starch (%) Slow-digesting starch (%) Resistant starch (%) Example 1 11.3 30.3 58.4 Example 2 11.8 31.8 56.4 Example 3 12.4 32.4 55.2 Comparative Example 1-1 62.1 24.4 13.5 Comparative Examples 1-2 52.3 24.6 23.1 Comparative Examples 1-3 22.4 35.3 42.3 Comparative Examples 1-4 30.2 30.1 39.7 Comparative Examples 1-5 24.3 31.2 44.5 Comparative Example 2-1 53.3 23.1 23.6 Comparative Example 2-2 23.6 32.2 44.2 Comparative Example 3-1 23.2 36.1 40.7 Comparative Example 3-2 24.2 35.6 40.2

[0109] To further illustrate the effects achieved by the stepwise alcohol precipitation fractionation of the present invention, the starch chain lengths after alcohol precipitation fractionation in Examples 1 and Comparative Examples 1-1 to 1-4, Examples 2 and Comparative Examples 2-1, and Examples 3 and Comparative Examples 3-1 were measured, and the results are shown in Table 2. Table 2 shows that the starch chain lengths obtained using the two-step alcohol precipitation fractionation method provided by the present invention are more concentrated in the DP13-24 and DP25-36 chain length ranges. Starch chains within this range are more likely to rearrange to form stable recrystallized starch. In contrast, single-step alcohol precipitation fractionation, or no fractionation, leads to the appearance of more short chains (DP6-12) and long chains (DP≥37), affecting the starch recrystallization process and resulting in crystal form transformation or a decrease in relative crystallinity.

[0110] Table 2. Distribution of starch chain length (degree of polymerization, DP) in alcohol precipitation fractionation in the examples and comparative examples.

[0111]

[0112]

[0113] To further illustrate the effect achieved by the magnetic induction treatment of the present invention, the starch crystallinity in the examples and comparative examples was measured, and the results are shown in Table 3. The starch chain length distribution significantly affects the starch recrystallization process; the presence of long chains leads to the formation of more unstable A+B type crystals, while the relative crystallinity and R... 1044 / 1022 Significant decrease; the presence of short chains also leads to the existence of imperfect regions in starch crystallization, affecting relative crystallinity and R. 1044 / 1022 Decrease. Magnetic induction can induce thermal and polarization effects. At temperatures below the starch gelatinization temperature, it can induce starch annealing while simultaneously polarizing the orientation of starch chains through electro-induction, thereby improving the arrangement and orientation of unit cells in recrystallized starch. This leads to an increase in the short-range and long-range crystallization order of starch, which in turn helps to improve the digestibility of recrystallized starch.

[0114] Table 3 shows the results of short-range and long-range crystallization order of the products in the examples and comparative examples.

[0115]

[0116] The methods for determining the in vitro digestibility of starch, measuring starch chain length, and analyzing the short-range and long-range crystallization order of starch are as follows:

[0117] The in vitro digestion characteristics assay was performed as follows: Before the assay, 0.5 mol / L sodium acetate buffer (pH 5.2) and mixed enzyme solution were prepared. 6.8 g of trypsin was dispersed in 18 mL of deionized water, vortexed, and centrifuged at 5000 rpm for 10 min after shaking in a 37°C water bath. 0.006 g of glucoamylase was added to a centrifuge tube containing 2 mL of deionized water, vortexed, and centrifuged at 37°C for 10 min. 1 mL of glucoamylase was added to 10 mL of trypsin supernatant, mixed, and incubated at 37°C. 100 mg of sample was weighed and placed in a centrifuge tube, 2 mL of deionized water was added, mixed, and incubated in a boiling water bath for 20 min. After cooling to 37°C, 2 mL of acetate buffer was added, mixed, and 1 mL of mixed enzyme solution was added. The mixture was then incubated at 37°C with shaking. At reaction times of 0, 20, 60, 90, 120, and 180 min, 0.5 mL of the enzymatic hydrolysate was taken and placed in centrifuge tubes containing 4.5 mL of anhydrous ethanol. The supernatant was obtained by centrifugation at 10,000 rpm for 5 min. The reducing sugar content in the supernatant was determined at 540 nm using the 3,5-dinitrosalicylic acid colorimetric method. The determination was repeated three times, and the average value was taken. The slow-digested starch content was calculated using the following formula:

[0118]

[0119] In the formula: G20 is the mass of reducing sugar released after starch is hydrolyzed by enzyme for 20 min / g; G120 is the mass of reducing sugar released after starch is hydrolyzed by enzyme for 120 min / g; W is the total mass of the test sample / g.

[0120] Starch chain length assay: Weigh 10 mg of starch, add 5 mL of ultrapure water, boil in a water bath for 60 min, and vortex intermittently to mix. Add 50 μL of sodium acetate buffer (0.6 M, pH 4.4), 10 μL of sodium azide (2%, w / v), and 10 μL of isoamylase (1400 U), and incubate at 37 °C for 24 h. After incubation, add sodium borohydride solution (0.5%, w / v), vortex to mix, and let stand for 20 h. Take 600 μL of the sample into a centrifuge tube, dry under nitrogen at room temperature, dissolve in 30 μL of sodium hydroxide, dilute with 570 μL of ultrapure water, centrifuge at 12000 rpm for 5 min, and collect the supernatant for analysis. The chain length distribution of the starch sample was determined using high-performance ion exchange chromatography (HPAEC-PAD) equipped with a pulsed amperometric detection system. Test conditions: chromatographic column, Dionex. TM CarboPac TMPA200 (250*4.0mm, 10μm); column temperature, 30℃; flow rate, 0.4mL / min; elution gradient: 0min A / B (90:10V / V), 10min A / B (90:10V / V), 30min A / B (40:60V / V), 50min A / B (40:60V / V); 50.1min A / B (90:10V / V); 60min A / B (90:10V / V). Oligosaccharides DP 4–7 were used as standards.

[0121] The short-range crystallization order analysis method was as follows: Fourier transform infrared spectroscopy (FTIR) was used to determine the short-range crystallization structure of the sample. 1 mg of the sample and 100 mg of dry potassium bromide powder were weighed, thoroughly ground in an agate mortar, and then pressed into a pellet for testing. The parameters were as follows: wavelength range 400–4000 cm⁻¹. -1 Scan resolution 4cm -1 The scan was performed 64 times. Automatic baseline calibration and Fourier deconvolution were performed on the original spectra, with a deconvolution half-width of 20 cm⁻¹. -1 Enhancement factor 3.0, calculated at 1044 and 1022 cm⁻¹. -1 The ratio of absorbance at point R 1044 / 1022 .

[0122] The long-range crystallization order analysis method was as follows: X-ray diffraction was used to determine the semi-crystalline structure of starch samples. After equilibrating the sample in a desiccator containing saturated saline solution for 3 days, the sample was evenly spread in the center of the sample trough and compacted with a glass slide. The sample stage was then placed in an XRD chamber for measurement. The test conditions were: Cu-Kα rays, scanning speed 5° / min, measurement range (2θ) 4°~45°, power 1600W, tube voltage 40kV, and tube current 40mA. The crystal form of starch was analyzed and the relative crystallinity was calculated using Jade 6.0 software. The calculation formula is as follows:

[0123]

[0124] In the formula: Rc is the relative crystallinity; Ac is the area of ​​the crystalline region; Aa is the area of ​​the amorphous region.

[0125] All aspects, embodiments, features, and examples of this invention are to be regarded as illustrative in all respects and are not intended to limit the invention, the scope of which is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0126] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0127] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated otherwise, any use of the terms first, second, etc., does not indicate any order or importance, but is used to distinguish one element from another.

Claims

1. A method of increasing the resistance to digestion of starch, characterized in that, The method comprises the following steps: pre-gelatinization treatment is performed on starch to obtain pre-gelatinized starch; enzymatic debranching is performed on the pre-gelatinized starch to obtain a debranched starch enzymatic hydrolysate; first alcohol precipitation fractionation and second alcohol precipitation fractionation are sequentially performed on the debranched starch enzymatic hydrolysate, wherein, according to an alcohol concentration of 100%, the first alcohol precipitation fractionation comprises: uniformly mixing the debranched starch enzymatic hydrolysate with alcohol at a volume ratio of 1:0.4-1:0.7, and separating supernatant after standing for 20-60 min; the second alcohol precipitation fractionation comprises: uniformly mixing the supernatant with alcohol at a volume ratio of 1:0.8-1:1.6, and separating after standing for 20-60 min to obtain fractionated debranched starch; recrystallization is performed on the fractionated debranched starch to obtain recrystallized starch; magnetic induction treatment is performed on the recrystallized starch under conditions lower than starch gelatinization temperature, the magnetic induction treatment has an excitation voltage of 100-400 V, an excitation frequency of 20-60 kHz, an alternating magnetic flux intensity of 330-500 MT, and a temperature of 45-60 ℃, to obtain digestion-resistant starch; wherein the digestion-resistant starch is in a crystal form of A type cereal starch, contains more than 30% slow-digestible starch, and contains more than 55% resistant starch.

2. The method of increasing the resistance to digestion of starch according to claim 1, characterized in that, The pre-gelatinization treatment comprises: starch is dispersed in a phosphate buffer, stirred, and preheated for 5-15 min, and then continuously stirred at a heating temperature of 85-120 ℃ for 30-60 min to partially or completely gelatinize the starch, to obtain pre-gelatinized starch.

3. The method of increasing the resistance to digestion of starch according to claim 2, characterized in that: The starch comprises waxy cereal starch.

4. The method of increasing the resistance to digestion of starch according to claim 3, characterized in that: The starch comprises waxy corn starch and / or waxy rice starch.

5. The method of increasing the resistance to digestion of starch according to claim 2, characterized in that: The phosphate buffer has a pH of 4.5-6.

5.

6. The method of increasing the resistance to digestion of starch according to claim 2, characterized in that: The preheating time is 8-12 min.

7. The method of increasing the resistance to digestion of starch according to claim 2, characterized in that: The heating temperature is 90-100 ℃.

8. The method of increasing the resistance to digestion of starch according to claim 2, characterized in that: The continuous stirring time is 40-50 min.

9. The method of increasing the resistance to digestion of starch according to claim 1, characterized in that, The enzymatic debranching comprises: uniformly mixing the pre-gelatinized starch with 1000-3000 npun / g of pullulanase, and sealing and incubating for reaction at a reaction temperature of 40-65 ℃ for 12-36 h, and performing enzyme inactivation treatment after the reaction is completed, to obtain the debranched starch enzymatic hydrolysate.

10. The method of increasing the resistance to digestion of starch according to claim 9, characterized in that: The pullulanase activity is 1500-2000 npun / g; and / or, the reaction temperature is 55-60 ℃; and / or, the reaction time is 18-24 h.

11. The method of increasing the resistance to digestion of starch according to claim 1, characterized in that: In the first alcohol precipitation fractionation, the volume ratio of the debranched starch enzymatic hydrolysate to alcohol is 1:0.5-1:0.

6.

12. The method of increasing the resistance to digestion of starch according to claim 1, characterized in that: In the second alcohol precipitation fractionation, the volume ratio of the supernatant to alcohol is 1:0.9-1:1.

2.

13. The method of increasing the resistance to digestion of starch according to claim 1, characterized in that: The alcohol comprises a lower alcohol and / or polyethylene glycol.

14. The method of increasing the resistance to digestion of starch according to claim 13, characterized in that: The alcohol comprises at least one of methanol, ethanol, and isopropyl alcohol.

15. The method of increasing the resistance to digestion of starch according to claim 14, characterized in that: The alcohol comprises ethanol.

16. The method of increasing the resistance to digestion of starch according to claim 1, characterized in that: The recrystallization temperature is 0-8 ℃; and / or, the recrystallization time is 12-48 h.

17. The method of increasing the resistance to digestion of starch according to claim 16, characterized in that: The recrystallization temperature is 4-6 ℃, and / or the recrystallization time is 18-24 h.

18. The method of increasing the resistance to digestion of starch according to claim 1, characterized in that: Before the recrystallization, the debranched starch is also subjected to a drying treatment, and then the dried debranched starch is dispersed in water and subjected to a high-temperature treatment at a temperature of 80-120℃ for 20-60min to obtain a debranched starch dispersion, and then the recrystallization is performed.

19. The method of increasing the resistance of starch to digestion according to claim 18, characterized in that: The high-temperature treatment is performed for 30-40min, and / or the high-temperature treatment is performed at a temperature of 90-100℃.

20. The method of increasing the resistance to digestion of starch according to claim 1, characterized in that, Also included are: Before the magnetic induction treatment, the recrystallized starch is dispersed in water to obtain a recrystallized starch dispersion, and the conductivity of the recrystallized starch dispersion is adjusted to 200μS / cm or higher, and then the magnetic induction treatment is performed.

21. The method of increasing the resistance of starch to digestion according to claim 20, characterized in that: The conductivity of the recrystallized starch is adjusted to 200-400μS / cm, and then the magnetic induction treatment is performed. And / or, an inorganic salt is added to the recrystallized starch dispersion to adjust the conductivity.

22. The method of increasing the resistance to digestion of starch according to claim 1, characterized in that: The magnetic induction treatment is performed for 12-48h.

23. The method of increasing the resistance to digestion of starch according to claim 1, characterized in that: The excitation voltage is 200-300V, and / or the excitation frequency is 35-50kHz, and / or the alternating magnetic flux intensity is 380-420MT, and / or the temperature of the magnetic induction treatment is 48-55℃, and / or the time of the magnetic induction treatment is 18-24h.

24. The digestion-resistant starch obtained by the method according to any one of claims 1-23.

25. The digestion resistant starch according to claim 24, characterized in that: In the digestion-resistant starch, the starch chains with a length DP≥37 account for 5% or less, the starch chains with a length DP25-36 account for 22% or more, the starch chains with a length DP13-24 account for 56% or more, and the starch chains with a length DP6-12 account for 15% or less.

26. The digestion resistant starch of claim 24, wherein: The relative crystallinity of the digestion-resistant starch is 70% or more.

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