A high-resistant corn starch and its preparation method

Abstract

The present invention discloses a high-resistant corn starch and its preparation method and application. The preparation method includes: performing de-surface protein treatment on waxy corn starch to obtain deproteinized starch; making the deproteinized starch into a suspension and performing recrystallization treatment to obtain recrystallized starch; and performing annealing treatment on the recrystallized starch to prepare the high-resistant corn starch. The high-resistant corn starch provided by the present invention has high resistance, can slow down the release rate of glucose, provides new ideas and options for reducing the incidence risks of hyperglycemia, cardiovascular diseases, obesity, etc., and moreover, the product has good film-forming properties and has a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of food processing, and particularly relates to a high-resistant corn starch and a preparation method thereof. Background Art

[0002] Resistant starch refers to starch and its degradation products that cannot be absorbed by the small intestine of a healthy human body, and can be fermented by bacteria in the colon into short-chain fatty acids. Recrystallized resistant starch refers to the amylose recrystallization during the process of gelatinized starch being cooked, cooled or stored at low temperature, resulting in a dense crystalline structure, which causes the enzyme molecules to be unable to contact the binding sites and thus cannot be enzymatically hydrolyzed. The greatest advantage of recrystallized resistant starch, in addition to its simple preparation method, lies in its good stability and the ability to maintain its anti-enzymatic hydrolysis property during processing such as high temperature and frying. During the heat treatment process, the O-H bonds and C-O bonds between starch and protein are broken, and aromatic ring C=C bonds and C=O bonds are generated during the formation of aromatic compounds, thus generating persistent free radicals. Therefore, it is crucial to remove the surface protein of starch. Subsequently, combined modification treatment is carried out to compensate for the effects of accelerated starch hydrolysis and reduced resistant starch content caused by the removal of surface protein.

[0003] At present, the modification methods of resistant starch mainly include physical modification, chemical modification, and enzymatic modification. Chemical modification refers to treating the native starch with chemical reagents to change its molecular structure and then its properties. Generally, according to the change in the molecular weight of the modified starch, it has strong randomness, a long preparation cycle, low production efficiency, and unstable product properties. Enzymatic modification has high costs and high requirements for the production process, and is not very suitable for industrial production. Although physical modification does not cause environmental pollution and the products are safe and green, the effect of single physical modification is poor. Therefore, it is an urgent problem to provide a preparation method for high-resistant corn starch. Summary of the Invention

[0004] The main purpose of the present invention is to provide a high-resistant corn starch and a preparation method thereof to overcome the deficiencies of the prior art.

[0005] To achieve the foregoing invention purpose, the technical solutions adopted by the present invention include:

[0006] An embodiment of the present invention provides a preparation method for high-resistant corn starch, which includes:

[0007] Performing de-surface protein treatment on waxy corn starch to obtain deproteinized starch;

[0008] Preparing the deproteinized starch into a suspension and performing recrystallization treatment to obtain recrystallized starch;

[0009] And performing annealing treatment on the recrystallized starch to prepare high-resistant corn starch.

[0010] The embodiments of the present invention also provide high-resistant corn starch prepared by the aforementioned preparation method.

[0011] The embodiments of the present invention also provide the use of the aforementioned high-resistant corn starch in preparing a product for reducing the glucose release rate.

[0012] An embodiment of the present invention further provides an edible starch film, which is made from at least the aforementioned high-resistant corn starch.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] (1) The high-resistant corn starch prepared by the present invention has strong resistance to enzymatic hydrolysis and high RS content;

[0015] (2) The high-resistant corn starch prepared by the present invention has the effect of alleviating glucose release, providing new ideas and options for reducing the risks of hyperglycemia, cardiovascular diseases, obesity, etc., and the high-resistant corn starch has good film-forming properties and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1a - Figure 1b 1 is the in vitro digestibility and relative component distribution of the resistant starch prepared in Example 1 and Comparative Examples 1-3 of the present invention;

[0018] Figure 2a - Figure 2b 1 is an infrared spectrum of the resistant starch prepared in Example 1 and Comparative Examples 1-3 of the present invention;

[0019] Figure 3 1 is the XRD pattern of the resistant starch prepared in Example 1 and Comparative Examples 1-3 of the present invention;

[0020] Figure 4a - Figure 4d 1 is a TGA graph of the resistant starch prepared in Example 1 of the present invention and Comparative Examples 1-3;

[0021] Figure 5 1 is a graph showing the blood glucose levels after in vitro digestion of the resistant starch prepared in Example 1 of the present invention and Comparative Examples 1-3.

[0022] Figure 6a - Figure 6b Graph showing water absorption and solubility of the edible resistant corn starch film in Example 2 of the present invention. Detailed implementation manners

[0023] In view of the deficiencies of the prior art, through long-term research and a large number of practices, the inventors of this case have proposed the technical solution of the present invention, which mainly uses waxy corn starch as a substrate, and through surface protein removal combined with recrystallization and annealing treatment, high-resistant corn starch is prepared.

[0024] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] Specifically, as an aspect of the technical solution of the present invention, a preparation method of a high-resistant corn starch involves:

[0026] Performing surface protein removal treatment on waxy corn starch to obtain deproteinized starch;

[0027] Making the deproteinized starch into a suspension and performing recrystallization treatment to obtain recrystallized starch;

[0028] And performing annealing treatment on the recrystallized starch to prepare high-resistant corn starch.

[0029] In some preferred implementation manners, the preparation method specifically includes: mixing waxy corn starch with a sodium dodecyl sulfate solution and oscillating and reacting for 23 to 25 h, and then performing centrifugation and washing to obtain deproteinized starch.

[0030] Further, the waxy corn starch includes waxy corn starch with a branched chain content of more than 95%.

[0031] In the present invention, the amylopectin content of the used waxy corn starch exceeds 95%, and it has significantly different physical and chemical properties compared with ordinary corn starch, and has obvious improvements in aspects such as starch paste stability, transparency, and retrogradation tendency.

[0032] Further, the mass ratio of the waxy corn starch to the sodium dodecyl sulfate solution is 1:4 to 1:5.

[0033] Further, the content of sodium dodecyl sulfate in the sodium dodecyl sulfate solution is 1 to 2 wt%.

[0034] Further, the rotation speed used for the centrifugation treatment is 3600 to 3800 g, and the time is 14 to 16 min.

[0035] In some preferred implementation manners, the preparation method specifically includes:

[0036] Disperse the deproteinized starch in water to form a deproteinized starch suspension, and heat and gelatinize it at 90 - 110 °C for 18 - 22 min to obtain gelatinized starch;

[0037] And subject the gelatinized starch to retrogradation treatment at 4 - 5 °C for 94 - 98 h, and then dry and pulverize it to obtain recrystallized starch.

[0038] Furthermore, the content of deproteinized starch in the deproteinized starch suspension is 10 - 15 wt%.

[0039] In some preferred embodiments, the preparation method specifically includes: placing the recrystallized starch in a sealed device and adjusting its water content to 65 - 67 wt%, and annealing it at 54 - 56 °C for 23 - 25 h to obtain high-resistant corn starch.

[0040] In some more specific embodiments, the preparation method of the high-resistant corn starch includes:

[0041] 1) Starch deproteinization: Mix 20 g of waxy corn starch with a 1 - 2% (w / v) sodium dodecyl sulfate (SDS) solution in a ratio of 1:5, place it on a shaker (37 ± 1 °C) and shake for 24 h. After the reaction, centrifuge at room temperature (), discard the supernatant, wash the precipitate with water multiple times (5 - 6 times) until there is no foam in the supernatant. The lower solid is deproteinized starch. After collection, place it in an oven at 37 - 40 °C for 48 ± 1 h and then pass through an 80-mesh sieve for standby.

[0042] 2) 4 °C recrystallization: Prepare a 10 - 15% starch suspension from the above starch sample, heat and gelatinize it for 20 ± 2 min, subject the gelatinized starch gel to retrogradation in a refrigerator at 4 - 5 °C for 96 ± 2 h, and then dry, pulverize and sieve it in an oven at 37 ± 1 °C.

[0043] 3) Annealing: Weigh 1.0 g of the pretreated corn starch accurately into a centrifuge tube containing 2.0 mL of deionized water, and finally adjust the moisture content of the sample to reach 65 - 67%. After mixing, place the sealed centrifuge tube in a 55 ± 1 °C constant temperature water bath, seal and keep warm for 24 ± 1 h. Then place the centrifuge tube in a refrigerator at 4 - 5 °C for storage for 24 ± 1 h. For convenient and rapid drying, transfer the sample to a petri dish and spread it into a thin layer, and place it in an oven at 37 - 40 °C for drying for 24 ± 1 h.

[0044] Another aspect of the embodiments of the present invention also provides high-resistant corn starch prepared by the foregoing preparation method.

[0045] Furthermore, the content of resistant starch in the high-resistant corn starch is above 53.5 wt%.

[0046] Another aspect of the embodiments of the present invention also provides the use of the aforementioned high-resistant corn starch in the preparation of products for reducing the glucose release rate.

[0047] Another aspect of the embodiments of the present invention also provides an edible starch film, which is at least prepared from the aforementioned high-resistant corn starch.

[0048] The technical solutions of the present invention will be further described in detail below in conjunction with several preferred embodiments and the accompanying drawings. These embodiments are implemented on the premise of the technical solutions of the invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0049] In the following embodiments, the experimental materials used can be obtained from conventional biochemical reagent companies without special instructions.

[0050] Example 1

[0051] High-resistant corn starch was prepared by combining de-surface protein with recrystallization and annealing (denoted as: DPWS4℃→ANN)

[0052] (1) Starch deproteinization: 20 g of waxy corn starch was mixed with a 1.0% (w / v) sodium dodecyl sulfate (SDS) solution in a ratio of 1:5, placed on a shaker (37 °C) and shaken for 24 h. After the reaction, centrifugation was carried out at room temperature (25 °C) (3700 g, 15 min), the supernatant was discarded, and the precipitate was washed with water several times (5 - 6 times) until there was no foam in the supernatant. The lower solid was deproteinized starch, which was collected and placed in an oven at 37 °C. After 48 h, it was sieved through an 80-mesh sieve and reserved for use.

[0053] (2) 4 °C recrystallization: The above deproteinized starch sample was prepared into a 10% starch suspension and heated for gelatinization for 20 min. The gelatinized starch gel was stored in a refrigerator at 4 °C for four days and then dried and pulverized through a sieve in an oven at 37 °C.

[0054] (3) Annealing: 1.0 g of the pretreated corn starch was accurately weighed and placed in a centrifuge tube containing 2.0 mL of deionized water, and finally the moisture content of the sample was adjusted to 67%. After mixing, the sealed centrifuge tube was placed in a constant temperature water bath at 55 °C and sealed for heat preservation for 24 h. Then the centrifuge tube was placed in a refrigerator at 4 °C for storage for 24 h. For convenient and rapid drying, the sample was transferred to a petri dish and spread into a thin layer, and it was placed in an oven at 40 °C for drying for 24 h to obtain high-resistant corn starch.

[0055] Comparative Example 1

[0056] Resistant starch was prepared by combining de-surface protein with recrystallization and debranching annealing (denoted as: DPWS4℃→DB→ANN)

[0057] (1) Starch deproteinization: the method is the same as in Example 1;

[0058] (2) Recrystallization at 4°C: the same method as in Example 1;

[0059] (3) Debranching: Accurately weigh 5.0 g of the starch obtained in step (2) and disperse it in a 250 mL flat-bottom flask containing 50 mL phosphate buffer (pH 5.0, 0.1 mol / L). Stir and mix thoroughly and preheat for 5 min. Then place the flat-bottom flask in a 120 ° C heat-collecting constant temperature heating magnetic stirrer and continue heating and stirring for 20 min. After heating, transfer the flat-bottom flask containing the starch gelatinization solution to a constant temperature water bath, cool to 58 ° C, add 1 mL of pullulanase, mix thoroughly, and seal and incubate at 58 ° C for 24 h. After enzymolysis, in order to completely terminate the reaction and inactivate the enzyme, transfer the flask containing the enzymolysis solution to a boiling water bath and heat for 15 min. Then, quickly centrifuge at a centrifugal speed of 3500 g for 1 min to obtain a transparent mixed debranched starch enzymolysis solution. If recrystallization occurs and becomes turbid, microwave heating of the enzymolysis solution is required to obtain debranched starch.

[0060] (4) Annealing: The method is the same as in Example 1.

[0061] Comparative Example 2

[0062] Preparation of resistant starch by debranching annealing (denoted as: WS→DB→ANN)

[0063] (1) Debranching: Accurately weigh 5.0 g of waxy corn starch and disperse it in a 250 mL flat-bottom flask containing 50 mL of phosphate buffer (pH 5.0, 0.1 mol / L). Stir and mix thoroughly and preheat for 5 min. Then place the flat-bottom flask in a 120 °C heat-collecting constant-temperature heating magnetic stirrer and continue heating and stirring for 20 min. After heating, transfer the flat-bottom flask containing the starch gelatinization solution to a constant-temperature water bath, cool to 58 °C, add 1 mL of pullulanase, mix thoroughly, and seal and incubate at 58 °C for 24 h. After enzymatic hydrolysis, in order to completely terminate the reaction and inactivate the enzyme, transfer the flask containing the enzymatic hydrolyzate to a boiling water bath and heat for 15 min. Then, centrifuge rapidly at a speed of 3500 g for 1 min to obtain a transparent mixed debranched starch hydrolyzate. If recrystallization occurs and the solution becomes turbid, microwave heating of the hydrolyzate is required to obtain debranched starch.

[0064] (2) Annealing: The method is the same as in Example 1.

[0065] Comparative Example 3

[0066] Resistant starch was prepared by removing surface proteins and debranching annealing (denoted as: DPWS→DB→ANN)

[0067] (1) Starch deproteinization: The method is the same as in Example 1;

[0068] (2) Debranching: Accurately weigh 5.0 g of deproteinized starch and disperse it in a 250 mL flat-bottom flask containing 50 mL of phosphate buffer (pH 5.0, 0.1 mol / L). Stir and mix well and preheat for 5 min, then place the flat-bottom flask in a collecting type constant temperature heating magnetic stirrer at 120 °C and continuously heat and stir for 20 min. After heating, transfer the flat-bottom flask containing the starch gelatinization solution to a constant temperature water bath, cool to 58 °C, add 1 mL of pullulanase, mix well, and seal and incubate at 58 °C for 24 h. After enzymatic hydrolysis, in order to completely terminate the reaction and inactivate the enzyme, transfer the flask containing the enzymatic hydrolysate to a boiling water bath and heat for 15 min, then quickly centrifuge at a centrifugal speed of 3500 g for 1 min to obtain a transparent mixed debranched starch enzymatic hydrolysate. If recrystallization occurs and becomes turbid, the enzymatic hydrolysate needs to be heated by microwave to obtain debranched starch.

[0069] (3) Annealing: The method is the same as in Example 1.

[0070] Performance characterization:

[0071] 1. Effects of combined surface protein removal, recrystallization and annealing on in vitro digestion

[0072] The in vitro starch digestion of the samples in Example 1 and Comparative Examples 1-3 was measured at 37 °C. Pancreatic α-amylase (0.0225 g, 10 U / mg) was suspended in 7.5 mL of sodium acetate buffer (0.02 M, pH 5.5), magnetically stirred for 30 min, and then centrifuged at 1500 g for 5 min. The supernatant was transferred to a beaker and mixed with 0.75 mL of amyloglucosidase (300 U / mL). The starch sample (200 mg) was dispersed in a 10 mL sodium acetate buffer solution (0.02 M, pH 5.5), equilibrated at 37 °C for 10 min, and then 0.75 mL of the mixture of pancreatic α-amylase and amyloglucosidase was added. Aliquots (0.5 mL) were taken at specific intervals during digestion. Then it was mixed with absolute ethanol (4.0 mL) to inhibit the enzyme and centrifuged at 4000×g for 3 min. Then the glucose content in the supernatant was determined by the 3,5-dinitrosalicylic acid (DNS) method. A glucose standard curve was made to calculate the glucose content released from resistant starch and the relative components.

[0073] As Figure 1a - Figure 1bAs shown, the in vitro digestibility and relative component distribution of resistant corn starch obtained in different preparation processes are shown (RS: resistant starch; SDS: slowly digestible starch; RDS: rapidly digestible starch). The results show that the group of de-surface protein combined with recrystallization and annealing (DPWS4℃→ANN) releases the least amount of glucose at the digestion end point, the relative component RS accounts for the highest proportion, and the prepared resistant corn starch has the strongest anti-enzymatic hydrolysis ability. Therefore, it is determined that de-surface protein combined with recrystallization and annealing (DPWS4℃→ANN) is the preferred process for preparing high-resistant corn starch in this invention.

[0074] 2. Effect of de-surface protein combined with recrystallization and annealing on short-range ordered structure

[0075] Take appropriate powder samples from Example 1 and Comparative Examples 1-3 and evenly spread them on the middle of the ATR accessory sample stage attached to the infrared spectrometer to detect and obtain the infrared spectrogram of the sample. The collection range is 600 - 4000 cm -1 , the resolution is 4 cm -1 , the number of scans is 32 times. Before sample collection, it is necessary to collect an air background first. The obtained original infrared spectrogram is processed by automatic baseline calibration and Fourier deconvolution, where the deconvolution half-peak width is 20 cm -1 , the enhancement factor is 2.4, and finally calculate the intensity ratio R at 1049 and 1022 m -1 . 1049 / 1022 .

[0076] As Figure 2a - Figure 2b shown, the short-range ordered structure of resistant corn starch obtained in different preparation processes is shown. The results show that no new functional groups are formed during the modification process of the four groups of modified starches, only involving the reorganization between molecular chains or the change of intermolecular hydrogen bonds. The starch R in the group of de-surface protein combined with recrystallization and annealing (DPWS4℃→ANN) 1049 / 1022 is the lowest, and the orderliness of starch molecules during the short-term retrogradation process is the lowest.

[0077] 3. Effect of de-surface protein combined with recrystallization and annealing on long-range ordered structure

[0078] Use XRD to test and analyze the crystalline structure of the starch samples in Example 1 and Comparative Examples 1-3. First, evenly spread the starch samples on the central circular groove of the sample stage, and use a glass slide to press and flatten the sample surface. Then place the sample stage in the XRD for measurement. The test conditions are as follows: select Cu-Kα radiation source, set the voltage to 40 kV, the current to 30 mA, the scanning range is set to 4° - 40° (2θ), and the scanning rate is 4° / min. The relative crystallinity of the sample is calculated by Jade 6.0 software. The calculation method is as follows:

[0079]

[0080] Where Rc represents the relative crystallinity of the sample, Ac and Aa represent the areas of the crystalline and amorphous regions of the sample, respectively.

[0081] like Figure 3 The figure shows the long-range ordered structure of resistant corn starch obtained through different preparation processes. The results indicate that the starch crystal structure disappears and becomes amorphous when surface protein removal, recrystallization, and annealing (DPWS 4°C → ANN) are combined. The relative crystallinity is the lowest, and the starch molecules exhibit the lowest crystallinity during long-term retrogradation.

[0082] 4. Effect of surface protein removal combined with recrystallization and annealing on thermal stability

[0083] Approximately 3 mg of the samples from Example 1 and Comparative Examples 1-3 were weighed into a ceramic crucible with a lid. The crucibles were heated from 25°C to 600°C at a heating rate of 10°C / min and a nitrogen flow rate of 50 mL / min. The weight loss curves as a function of temperature (TG) and the derivative (DTG) were analyzed to analyze the thermal degradation temperature and process of resistant starch.

[0084] like Figure 4a - Figure 4d The results show the thermal stability of resistant corn starch obtained through different preparation processes. The results indicate that the thermal decomposition of WS→DB→ANN occurs in four stages, the thermal decomposition of DPWS→DB→ANN and DPWS4°C→DB→ANN occurs in three stages, and the thermal decomposition of DPWS4°C→ANN occurs in two stages. The weight loss rates of the four groups of samples were almost identical. However, the starch group with deproteinization combined with recrystallization and annealing (DPWS4°C→ANN) had the highest thermal decomposition temperature and the greatest thermal stability.

[0085] 5. Effect of surface protein removal combined with recrystallization and annealing on thermodynamic properties

[0086] Accurately weigh 3 mg of starch sample powder in Example 1 and Comparative Examples 1-3 and place it in an aluminum crucible. According to the starch to water mass ratio of 1:2, measure 6 μL of ultrapure water and add it to the aluminum crucible. Then use a DSC tablet press to compact and seal the aluminum crucible. Before the DSC test, the instrument was calibrated with an indium standard. Test conditions: using a sealed empty crucible as a control, the heating temperature range is 25-95°C, the heating rate is 10°C / min, and the nitrogen flow rate is 20 mL / min. The heat flow curve diagram is analyzed using the DSC built-in software to obtain the starting gelatinization temperature (To), peak gelatinization temperature (Tp), ending gelatinization temperature (Tc) and △H, as shown in Table 1.

[0087] Table 1 Initial gelatinization temperature (To), peak gelatinization temperature (Tp), final gelatinization temperature (Tc), ΔH and decomposition temperature of starch samples in Example 1 and Comparative Examples 1-3

[0088]

[0089] Table 1 shows the thermodynamic properties of the resistant corn starch obtained in different preparation processes. The results show that the gelatinization temperature (To), peak gelatinization temperature (Tp), end gelatinization temperature (Tc), and △H of the starch in the group of de-surface protein combined with recrystallization and annealing (DPWS4℃→ANN) are the highest. It indicates that the degree of order of the crystal structure of the starch in this group is the strongest, the energy required to unwind its double helix and melt is the highest, and the thermal stability is the best.

[0090] 6. Effect of de-surface protein combined with recrystallization and annealing on in vivo digestion.

[0091] Based on the mouse glucose tolerance test, the in vivo digestibility of starch was measured. During the test, after the mice were fasted for 16 h, 0.5 mL of the starch sample suspension (7.5%, w / v) in Example 1 and Comparative Examples 1-3 was used to intragastrically administer to the mice respectively. Then, blood was taken from the tail vein of the mice at different time points (0 min, 60 min, 120 min, 5 h, 12 h, 24 h), the blood glucose content in the mice was measured by a blood glucose meter, and a blood glucose level curve graph of the mice with the extension of feeding time was drawn.

[0092] As Figure 5 shown, the in vivo digestion characteristics of the resistant corn starch obtained in different preparation processes are shown. The results show that the blood glucose of the mice in the WS→DB→ANN group is always the highest during digestion. The blood glucose levels of the mice in the DPWS4℃→ANN and DPWS→DB→ANN groups are similar during the whole digestion process, and are lower than those of other groups. Moreover, the blood glucose value of the DPWS4℃→ANN group is the lowest after 24-hour digestion, indicating that the resistant corn starch prepared by de-surface protein combined with recrystallization and annealing (DPWS4℃→ANN) has the strongest resistance, which is consistent with the results of in vitro digestion.

[0093] Example 2

[0094] Preparation of high-resistant corn starch film by casting method

[0095] In this example, the resistant corn starch prepared in Example 1 and Comparative Examples 1-3 was used as the raw material, and an edible corn starch film was prepared by the casting method. The water resistance and solubility of the starch film were studied through physical and chemical experiments. The preparation method of the starch film is as follows:

[0096] The starch solution was heated in a water bath to be gelatinized into a starch gel. After the gelatinization was completed, it was cooled to room temperature. The starch gel was taken and evenly spread on a petri dish by the casting method, and then placed in an oven to dry and the film was peeled off for standby.

[0097] 1. Influence of Water Absorbency of Resistant Corn Starch Films Prepared by Different Methods

[0098] Water Resistance Performance Test: The mass increase of the film was tested to determine the water absorption rate (W A ). The film sample was dried to a constant weight at 105 °C (mass M1). At room temperature, the film sample was placed in 30 mL of distilled water until the film was completely saturated with water. The film sample was taken out, and the water droplets on the surface were blotted dry with absorbent paper. The mass of the film (M2) was measured, and the water absorption rate of the film (W A ) was calculated.

[0099] W A = (M2 - M1) / M1 × 100%

[0100] As Figure 6a shown, the starch film obtained from the resistant starch prepared by the DPWS 4 °C → ANN process has the strongest water absorbency, indicating that the water resistance of this starch film is the best. This may be due to the rearrangement of starch molecules, which restricts the tendency of starch molecules to bind to water molecules through hydrogen bonds. The starch molecules in the film system cannot bind well with water molecules, resulting in a relatively increased number of sites that can bind to water in the film system and an increase in the water absorbency of the film.

[0101] 2. Influence of Solubility of Resistant Corn Starch Films Prepared by Different Methods

[0102] Determination of the dissolution rate of the starch film: The corn starch film sample was cut into square samples to determine its initial mass (M3). The sample was mixed with 100 mL of distilled water in a conical flask and then stirred at 180 rpm at 25 °C for 6 h. The solution was filtered and dried in a forced-air drying oven for 7 h (final dry weight = M4). The dissolution rate of the corn starch film (W B ) was calculated:[[]]

[0103] W B = (M3 - M4) / M3 × 100%

[0104] As Figure 6b shown, the starch film obtained from the resistant starch prepared by the DPWS 4 °C → ANN process has the lowest solubility. This may be due to the formation of hydrogen bonds between starch molecules, which reduces the crystallinity between starch molecules, reduces the formation of crystalline regions, and thus reduces the crystallinity of the film, making the film more difficult to dissolve.

[0105] In summary, the starch film obtained from the resistant starch prepared by the DPWS 4 °C → ANN process has the most stable performance and the best performance among other groups.

[0106] Example 3

[0107] Preparation of High-Resistant Corn Starch by Combining Removal of Surface Proteins with Recrystallization and Annealing

[0108] (1) Starch deproteinization: Mix 20 g of waxy corn starch with a 2% (w / v) sodium dodecyl sulfate (SDS) solution in a ratio of 1:4, place it on a shaker (361 °C) and shake for 23 h. After the reaction, centrifuge at room temperature (3600 g, 16 min), discard the supernatant, and wash the precipitate with water multiple times (5 - 6 times) until there is no foam in the supernatant. The solid matter in the lower layer is deproteinized starch. After collection, place it in an oven at 39 °C for 49 h and then pass through an 80-mesh sieve for standby.

[0109] (2) 4 °C recrystallization: Prepare a 15% starch suspension from the above starch sample, heat and gelatinize it for 22 min. Let the gelatinized starch gel recrystallize in a 4 °C refrigerator for 98 h, then dry, crush, and sieve it in an oven at 36 °C.

[0110] (3) Annealing: Accurately weigh 1.0 g of the pretreated corn starch and place it in a centrifuge tube containing 2.0 mL of deionized water, and finally adjust the moisture content of the sample to reach 66%. After mixing, place the sealed centrifuge tube in a 54 °C constant temperature water bath, seal and keep warm for 25 h. Then place the centrifuge tube in a 5 °C refrigerator for storage for 23 h. For convenient and rapid drying, transfer the sample to a petri dish and spread it into a thin layer, and place it in an oven at 37 °C for drying for 24 h.

[0111] Example 4

[0112] Preparation of high-resistant corn starch by combining surface protein removal, recrystallization and annealing

[0113] (1) Starch deproteinization: Mix 20 g of waxy corn starch with a 1.5% (w / v) sodium dodecyl sulfate (SDS) solution in a ratio of 1:5, place it on a shaker (38 °C) and shake for 24 h. After the reaction, centrifuge at room temperature (3800 g, 14 min), discard the supernatant, and wash the precipitate with water multiple times (5 - 6 times) until there is no foam in the supernatant. The solid matter in the lower layer is deproteinized starch. After collection, place it in an oven at 40 °C for 47 h and then pass through an 80-mesh sieve for standby.

[0114] (2) 4 °C recrystallization: Prepare a 13% starch suspension from the above starch sample, heat and gelatinize it for 21 min. Let the gelatinized starch gel recrystallize in a 5 °C refrigerator for 94 h, then dry, crush, and sieve it in an oven at 38 °C.

[0115] (3) Annealing: Accurately weigh 1.0 g of the pretreated corn starch and place it in a centrifuge tube containing 2.0 mL of deionized water, and finally adjust the moisture content of the sample to reach 65%. After mixing, place the sealed centrifuge tube in a 56 °C constant temperature water bath, seal and keep warm for 23 h. Then place the centrifuge tube in a

[0116] In addition, referring to the foregoing embodiments, the inventors of this case also conducted tests using other raw materials, process operations, and process conditions described in this specification, and all obtained relatively ideal results.

[0117] It should be understood that the technical solution of the present invention is not limited to the limitations of the above specific embodiments. Any technical deformation made according to the technical solution of the present invention without departing from the gist of the present invention and the scope protected by the claims falls within the protection scope of the present invention.

Claims

1. A method for preparing high-resistant corn starch, characterized in that: include: Waxy corn starch is mixed with sodium lauryl sulfate solution and shaken for 23 to 25 hours, followed by centrifugation and washing to obtain deproteinized starch; The deproteinized starch is dispersed in water to form a deproteinized starch suspension, and heated at 90-110° C. for gelatinization for 18-22 minutes to obtain gelatinized starch; the gelatinized starch is then retrograded at 4-5° C. for 94-98 hours, and then dried and crushed to obtain recrystallized starch; Furthermore, the recrystallized starch is placed in a sealed device and its water content is adjusted to 65-67 wt %, and is annealed at 54-56° C. for 23-25 hours to obtain high-resistant corn starch.

2. The preparation method according to claim 1, wherein: The waxy corn starch comprises waxy corn starch with a branched chain content of more than 95%.

3. The preparation method according to claim 1, wherein: The mass ratio of the waxy corn starch to the sodium lauryl sulfate solution is 1:4 to 1:

5.

4. The preparation method according to claim 1, wherein: The content of sodium dodecyl sulfate in the sodium dodecyl sulfate solution is 1-2 wt %.

5. The preparation method according to claim 1, wherein: The centrifugal treatment is performed at a speed of 3600 to 3800 g and for a time of 14 to 16 minutes.

6. The preparation method according to claim 1, wherein: The content of deproteinized starch in the deproteinized starch suspension is 10-15 wt%.

7. High-resistant corn starch prepared by the preparation method according to any one of claims 1 to 6; the content of resistant starch in the high-resistant corn starch is greater than 53.5 wt%.

8. Use of the high-resistant corn starch according to claim 7 in preparing a product for reducing the glucose release rate.

9. An edible starch film, characterized in that: The edible starch film is made from at least the high-resistant corn starch according to claim 7.

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