Porous starch as well as preparation method and application thereof

Abstract

The invention discloses porous starch and a preparation method and application thereof, and the preparation method comprises the following steps: (1) starch pretreatment: taking corn starch as a raw material, fully mixing the corn starch with a calcium chloride solution, performing magnetic stirring for shelling and gelatinization treatment, after the shelling and gelatinization are stopped, centrifuging to take precipitate, washing and drying to obtain shelled starch; (2) enzymolysis treatment: preheating the shelled starch and a citric acid-disodium hydrogen phosphate buffer solution in a constant-temperature water bath to obtain a starch suspension; and adding a compound enzyme into the starch suspension for enzymolysis, centrifuging after enzymolysis is stopped, taking precipitate, drying, and crushing to obtain the porous starch. Compared with the prior art, the specific solution volume and oil absorption rate of the porous starch obtained by the method are obviously increased, and the dissolution rate of the porous starch in water is also obviously increased.

Description

Technical Field

[0001] The invention relates to the technical field, and in particular to porous starch and a preparation method and application thereof. Background Art

[0002] Porous starch is a safe, non-toxic modified starch with good adsorption performance. It has a large number of micropores extending from the surface to the inside of the starch granules. The diameter of the pores covering the surface of the granules is about 1μm, and its volume accounts for about half of the starch granules. It has a high porosity and specific surface area, and has encapsulation, sustained release and adsorption properties, which has attracted widespread attention. It has been used as an active ingredient stabilizer, drug sustained release agent and pollutant adsorbent. Therefore, the preparation and application research of porous starch has far-reaching significance.

[0003] At present, porous starch can be prepared by physical, chemical, and enzymatic methods. Enzymatic preparation refers to the hydrolysis of starch with an enzyme with amylase activity under conditions below the gelatinization temperature of starch. It is widely used because of its safety and green advantages. The amorphous area on the surface of starch granules is first hydrolyzed by saccharifying enzymes along the non-reducing ends of the molecules. Due to the swelling of starch by water absorption, the interior of the starch granules is penetrated by α-amylase, and the starch chains are randomly incised, and new non-reducing ends appear, so that the hydrolysis action continuously enters the interior of the starch molecules. Finally, the starch is in a porous state and forms a hollow structure inside. Although the preparation of porous starch by enzymatic hydrolysis has certain advantages over physical and chemical methods, natural starch has a dense granular structure and a tight double helix molecular structure, high crystallinity, poor solubility, and weak enzyme binding ability. Therefore, the efficiency of preparing porous starch by enzymatic hydrolysis using native starch as a substrate is low, and the solubility of the obtained porous starch in water is poor, resulting in certain limitations on its application.

[0004] Starch exists in the form of semi-crystalline aggregates organized in the form of granules. The granular structure of starch can be divided into four levels: molecules, bodies, shells and granules. Studies have shown that there are two types of bodies in starch granules. "Normal bodies" are mainly composed of amylopectin molecules, and the reducing ends of amylopectin molecules in the bodies may be close to the umbilicus of starch granules; "defective bodies" are formed by the participation of amylose molecules, and their loose binding form will form small holes on the surface of starch granules. The content of amylose and amylopectin is the most important factor determining the properties of starch. Amylose has good gel properties, and the strength of the gel formed increases with its content. Amylopectin has good freeze-thaw stability, swelling, water absorption, anti-aging properties and thickening effects. The shell structure of starch granules is formed by alternating crystalline and amorphous regions. The thickness becomes thinner and the hardness becomes larger from the inside to the outside, and the surface of the granule is a hard shell layer. Studies have shown that the corpuscles are the building blocks of the shell structure. The smaller corpuscle structures are densely compacted to form a harder outer shell structure, while the larger corpuscles are loosely stacked to form an inner shell. Therefore, the corpuscles are the key structures for amylase to enter the starch granules and react effectively during the starch modification process. How effectively amylase can penetrate the outer shell structure of starch and evenly hydrolyze the corpuscle molecules inside the starch granules directly determines the reaction efficiency and functional properties of porous starch preparation. In the process of porous starch preparation, how to safely and effectively activate starch granules and improve their enzymatic hydrolysis efficiency is currently a research hotspot in the preparation of porous starch. Summary of the invention

[0005] In order to overcome the shortcomings and deficiencies of the prior art, the purpose of the present invention is to provide a method for preparing porous starch, wherein corn starch is pretreated by gelatinization and shelling with a calcium chloride solution by a chemical method, and then the porous starch prepared by enzymatic hydrolysis has significantly increased specific solubility, oil absorption rate and solubility.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for preparing porous starch comprises the following steps:

[0008] (1) Starch pretreatment: corn starch is used as raw material, corn starch is fully mixed with calcium chloride solution, and shelling and gelatinization are performed by magnetic stirring. After shelling and gelatinization are stopped, centrifugation is performed to obtain a precipitate, washing, and drying to obtain shelled starch;

[0009] (2) Enzymatic hydrolysis: preheat the dehulled starch and citric acid-disodium hydrogen phosphate buffer in a constant temperature water bath to obtain a starch suspension; add a complex enzyme to the starch suspension for enzymatic hydrolysis, stop the enzymatic hydrolysis, centrifuge to obtain a precipitate, dry it, and crush it to obtain porous starch.

[0010] Preferably, in step (1), the molar concentration of the calcium chloride solution is 2-5 mol / L; and the mass volume ratio of the corn starch to the calcium chloride solution is 1 g:5-10 mL.

[0011] Preferably, in step (1), the dehulling and gelatinization treatment is carried out for 30-50 min at a temperature of 20-30° C. and the magnetic stirring speed is 100-500 r / min.

[0012] Preferably, in step (1), the method of stopping the shelling and gelatinization is to use ice water to stop the gelatinization immediately after the shelling and gelatinization process.

[0013] Preferably, in step (2), the pH value of the citric acid-disodium hydrogen phosphate buffer is 4-5; the temperature of the constant temperature water bath is 40-45° C., and the preheating time is 8-15 min.

[0014] Preferably, in step (2), the complex enzyme is a complex enzyme composed of saccharifying enzyme and α-amylase in a mass ratio of 2-4:1.

[0015] Preferably, in step (2), the enzymatic hydrolysis temperature is 40-45°C, and the enzymatic hydrolysis time is 10-24h.

[0016] The present invention also provides a porous starch prepared by the above-mentioned preparation method. The porous starch provided by the present invention has a higher specific solubility and oil absorption rate, and its solubility rate and swelling degree in water are also significantly improved.

[0017] The present invention also provides a method for preparing fisetin inclusion compound using the porous starch, comprising the following steps:

[0018] S1: dissolving fisetin in anhydrous ethanol to obtain a fisetin stock solution;

[0019] S2: Mix the porous starch and ethanol solution, add the fisetin stock solution drop by drop slowly while ultrasonicating, seal the mixture, ultrasonicate the mixture at room temperature, filter, dry, grind and sieve to obtain the fisetin inclusion complex.

[0020] The invention adopts ultrasound to encapsulate fisetin in porous starch, and greatly improves the encapsulation rate of porous starch through process optimization.

[0021] Preferably, in step S2, the mass ratio of fisetin to porous starch is 1:14-20; the volume concentration of the ethanol solution is 5%-15%; and the ultrasonic time is 20-40 min.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention pre-treats corn starch by dehulling and gelatinizing with calcium chloride, and then uses a composite enzyme to perform enzymatic hydrolysis to prepare porous starch. Dehulling and gelatinizing pre-treatment can hydrolyze the outer shell structure of starch, so that starch particles can achieve limited swelling, partial gelatinization occurs, and the gelatinization and dispersion of internal small bodies are promoted, thereby forming internal and external passages on the surface of starch particles, allowing amylase to enter the interior of starch particles, increasing the sensitivity of amylase and improving its enzymatic hydrolysis efficiency. Compared with the prior art, the specific solubility and oil absorption rate of the porous starch obtained by this method are significantly increased, and the solubility rate in water is also significantly improved.

[0024] (2) The present invention utilizes the obtained porous starch to encapsulate fisetin. Through process optimization, this method can improve the encapsulation rate and encapsulation amount of the porous starch to a certain extent, and has the advantages of good accuracy, simple operation, stability and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The electron microscope scanning images of the microscopic morphology of dehulled starch (1, 2, and 3 are images at resolutions of 50, 20, and 5 μm, respectively);

[0026] Figure 2 The electron microscope scanning images of the microscopic morphology of porous starch (1, 2, and 3 are images at resolutions of 50, 20, and 5 μm, respectively);

[0027] Figure 3 The effect of different amounts of porous starch added on the encapsulation of fisetin in porous starch;

[0028] Figure 4 The effect of different ultrasound time on the encapsulation of fisetin in porous starch;

[0029] Figure 5 The effect of different ethanol concentrations on the encapsulation of fisetin in porous starch. DETAILED DESCRIPTION

[0030] The present invention is further described below by means of specific implementation methods. The following examples are preferred implementation methods of the present invention, but the implementation methods of the present invention are not limited to the following examples.

[0031] Embodiment 1:

[0032] A method for preparing porous starch, comprising the following steps:

[0033] (1) Starch pretreatment: 20 g of starch was dispersed in 150 mL of 4 mol / L CaCl2 solution, and the solution was subjected to magnetic stirring for shelling and gelatinization at 300 r / min for 40 min at a temperature of 30°C. After obtaining the shelled and gelatinized starch solution, 1200 mL of ice water (0°C) was immediately added to stop the gelatinization process, and the solution was centrifuged at 3000 r / min for 10 min. The supernatant was discarded and the precipitate was washed twice with 2 L of distilled water to remove residual CaCl2. The collected precipitate sample was then resuspended in 300 mL of distilled water, crushed and stirred in a wall breaking machine for 10 min, and the sample was then centrifuged at 3000 r / min for 5 min. The supernatant was discarded and the precipitate was collected. The process was repeated several times until the supernatant was transparent and colorless. The obtained starch granules were washed twice with anhydrous ethanol and dried in an oven at 40°C for 48 h to obtain shelled starch.

[0034] Figure 1 The electron microscope scanning image of the microscopic morphology of shelled starch is shown. Corn starch is in the form of large polygonal particles and small round particles. After shelling and gelatinization, the surface of the starch particles is damaged, and the edges and corners of the polygonal starch gradually disappear, and the shape gradually becomes spherical.

[0035] (2) Enzymatic hydrolysis: 15 g of dehulled starch was weighed and placed in a 500 mL conical flask. 100 mL of pH 4.2 citric acid-sodium hydrogen phosphate buffer solution was measured and added to the conical flask and placed in a constant temperature water bath at 42°C for preheating for 10 min. Then, a certain amount of α-amylase and saccharifying enzyme (saccharifying enzyme: α-amylase = 3:1) was weighed according to the specific gravity (mass fraction 2%), and the enzyme solution (volume fraction 2%) was prepared with the buffer solution. The enzyme solution was added to the starch suspension, mixed thoroughly, and placed on a constant temperature shaker at 42°C (120 r / min) for enzymatic hydrolysis for 20 h. 5 ml of NaOH (40 g / L) solution was added to terminate the reaction. The suspension was centrifuged at 3000 r / min for 5 min, and the precipitate was washed three times with distilled water and dried at 45°C. After being crushed and passed through a 100-mesh sieve, it was set aside to obtain porous starch.

[0036] Figure 2 The electron microscope scanning image of the microscopic morphology of porous starch is shown. After the corn starch is dehulled and gelatinized, more adsorption sites are added for the amylase in the enzymatic hydrolysis reaction, increasing the enzyme sensitivity. After further enzymatic hydrolysis, regular circular holes of varying depths appear on the starch surface, while the overall granular shape of the starch does not change.

[0037] Embodiment 2:

[0038] A method for preparing porous starch, comprising the following steps:

[0039] (1) Starch pretreatment: 20 g of starch was dispersed in 100 mL of 5 mol / L CaCl2 solution, and the mixture was subjected to magnetic stirring dehulling and gelatinization treatment at 400 r / min for 30 min at a temperature of 25°C. After obtaining the dehulled and gelatinized starch solution, 1000 mL of ice water (0°C) was immediately added to stop the gelatinization process, and the mixture was centrifuged at 3000 r / min for 10 min. The supernatant was discarded, and the precipitate was washed twice with 2 L of distilled water to remove residual CaCl2. The collected precipitate sample was then resuspended in 300 mL of distilled water, crushed and stirred in a wall breaking machine for 10 min, and the sample was then centrifuged at 3000 r / min for 5 min. The supernatant was discarded and the precipitate was collected. The process was repeated several times until the supernatant was transparent and colorless. The obtained starch granules were washed twice with anhydrous ethanol and dried in an oven at 40°C for 48 h to obtain dehulled starch.

[0040] (2) Enzymatic hydrolysis: 15 g of dehulled starch was weighed and placed in a 500 mL conical flask. 100 mL of pH 4.2 citric acid-sodium hydrogen phosphate buffer solution was measured and added to the conical flask and placed in a constant temperature water bath at 45°C for preheating for 12 min. Then, a certain amount of α-amylase and saccharifying enzyme (saccharifying enzyme: α-amylase = 2.5:1) was weighed according to the specific gravity (mass fraction 2%), and the enzyme solution (volume fraction 2%) was prepared with the buffer solution. The enzyme solution was added to the starch suspension, mixed thoroughly, and placed on a constant temperature shaker at 45°C (120 r / min) for enzymatic hydrolysis for 18 h. 5 mL of NaOH (40 g / L) solution was added to terminate the reaction. The suspension was centrifuged at 3000 r / min for 5 min, and the precipitate was washed three times with distilled water and dried at 45°C. It was crushed and passed through a 100-mesh sieve for later use, thereby obtaining porous starch.

[0041] Embodiment 3:

[0042] A method for preparing porous starch, comprising the following steps:

[0043] (1) Starch pretreatment: 20 g of starch was dispersed in 200 mL of 3 mol / L CaCl2 solution, and the solution was dehulled and gelatinized by magnetic stirring at 350 r / min for 50 min at a temperature of 20°C. After obtaining the dehulled and gelatinized starch solution, 1200 mL of ice water (0°C) was immediately added to stop the gelatinization process, and the solution was centrifuged at 3000 r / min for 10 min. The supernatant was discarded and the precipitate was washed twice with 2 L of distilled water to remove residual CaCl2. The collected precipitate sample was then resuspended in 300 mL of distilled water, crushed and stirred in a wall breaking machine for 10 min, and the sample was then centrifuged at 3000 r / min for 5 min. The supernatant was discarded and the precipitate was collected. The process was repeated several times until the supernatant was transparent and colorless. The obtained starch granules were washed twice with anhydrous ethanol and dried in an oven at 40°C for 48 h to obtain dehulled starch.

[0044] (2) Enzymatic hydrolysis: 15 g of dehulled starch was weighed and placed in a 500 mL conical flask. 100 mL of pH 4.2 citric acid-sodium hydrogen phosphate buffer solution was measured and added to the conical flask and placed in a constant temperature water bath at 42°C for preheating for 15 min. Then, a certain amount of α-amylase and saccharifying enzyme (saccharifying enzyme: α-amylase = 3.5:1) was weighed according to the specific gravity (mass fraction 2%), and the enzyme solution (volume fraction 2%) was prepared with the buffer solution. The enzyme solution was added to the starch suspension, mixed thoroughly, and placed on a constant temperature shaker at 42°C (120 r / min) for enzymatic hydrolysis for 20 h. 5 mL of NaOH (40 g / L) solution was added to terminate the reaction. The suspension was centrifuged at 3000 r / min for 5 min, and the precipitate was washed three times with distilled water and dried at 45°C. It was crushed and passed through a 100-mesh sieve for later use, thereby obtaining porous starch.

[0045] Comparative Example 1:

[0046] A method for preparing porous starch, comprising the following steps:

[0047] Weigh 15g corn starch and place it in a 500ml conical flask, measure 100mL pH4.2 citric acid-disodium hydrogen phosphate buffer solution, add it to the conical flask and place it in a constant temperature water bath at 42°C for preheating for 10min, then weigh a certain amount of α-amylase and saccharifying enzyme (saccharifying enzyme: α-amylase = 3:1) according to specific gravity (mass fraction 2%), use buffer to prepare enzyme solution (volume fraction 2%), add the enzyme solution to the starch suspension, mix well and place it on a 42°C constant temperature shaker (120r / min) for enzymolysis reaction for 20h, add 5mL of NaOH (40g / L) solution to terminate the reaction; centrifuge the suspension at 3000r for 5min, wash the precipitate three times with distilled water, dry it at 45°C, crush it through a 100-mesh sieve for use, and then obtain porous starch.

[0048] The porous starch prepared in Examples 1-3 and Comparative Example 1 was subjected to performance tests, and the results are shown in Table 1:

[0049] Table 1

[0050] Enzyme sensitivity (%) Specific solubility (mL / g) Oil absorption rate (%) Dissolution rate (%) Expansion rate (%) Example 1 23.85 3.69 1.78 1.98 10.82 Example 2 23.38 3.65 1.56 1.78 10.59 Example 3 24.97 3.70 1.58 2.09 13.35 Comparative Example 1 4.13 1.94 1.34 1.23 7.46

[0051] From the results in Table 1, it can be seen that enzymatic hydrolysis of corn starch after dehulling and gelatinization can significantly improve the sensitivity of amylase and its enzymatic hydrolysis efficiency. The specific solubility and oil absorption rate of the porous starch obtained are significantly increased, and the solubility rate and swelling rate in water are also significantly improved.

[0052] Example 4: Optimization process of starch pretreatment process

[0053] 1. Optimization of shelling and gelatinization time

[0054] 20g starch was dispersed in 150mL 4 mol / L CaCl2 solution, and the shelling and gelatinization treatment was carried out at 30°C with magnetic stirring at a speed of 300r / min. The shelling and gelatinization time was selected from 0 to 80min. The effect of shelling and gelatinization time on porous starch was optimized. The performance results are shown in Table 2:

[0055] Table 2

[0056]

[0057] As shown in Table 2, with the increase of dehulling and gelatinization time, the degree of starch dehulling increases significantly. Compared with the original starch, the enzyme sensitivity of the dehulled starch increases significantly. Compared with the original starch, the starch granules after gelatinization are more susceptible to degradation by enzymes such as amylase, because part of its crystal structure is destroyed and the molecular structure is more open, and amylase can more easily bind to it and promote its degradation. Therefore, the higher the degree of starch dehulling, the stronger its enzyme sensitivity is, and it is easier to be degraded by enzymes. In addition, with the increase of starch dehulling degree, the specific volume of the prepared porous starch shows a trend of first increasing and then decreasing. With the increase of dehulling degree, starch granules begin to form more pore structures, so the volume of porous starch increases. However, when the starch dehulling degree reaches a certain degree, excessive gelatinization will cause starch granules to aggregate, the pore structure to be destroyed, and the originally formed pore structure to be partially filled or destroyed, thereby reducing the specific volume of porous starch. Similar to the specific volume, the oil absorption rate of porous starch increases with the increase of starch dehulling degree, and the increase in surface area enhances the adsorption of oil. However, when the shelling degree is large enough, the pore structure is destroyed, resulting in a gradual decrease in the oil absorption rate.

[0058] The solubility rate indicates the mass fraction of starch dissolved at a certain temperature, and the swelling rate indicates the mass fraction of water absorbed per kilogram of sample at a certain temperature. The solubility rate and swelling rate of starch can reflect the interaction strength between starch and water molecules to a certain extent. Factors such as the size and morphology of starch granules and the composition of starch can affect the solubility rate and swelling rate of starch. The solubility rate and swelling performance of starch are important factors affecting the processing properties of starch and product texture. Finally, the solubility rate and swelling rate of porous starch prepared with starch with different dehulling rates were determined. The results showed that the solubility rate increased with the increase of starch dehulling degree, and the swelling rate increased first and then decreased. This is because the morphology and size of starch granules can affect the solubility rate and swelling rate of starch. Water molecules combine with the hydroxyl groups of starch molecules to form hydrogen bonds. After forming porous, the structural strength of starch granules is weakened under the action of enzymes, and water molecules easily invade the interior of starch granules, resulting in an increase in the solubility of starch granules. After starch is hydrolyzed into pores, the structural strength of starch is reduced, and water molecules are more likely to enter the interior of starch and combine with the hydroxyl groups in starch molecules by hydrogen bonds, resulting in an increase in the solubility rate and swelling rate of starch. Taking all the properties into consideration, the preferred shelling and gelatinization time of the present invention is 30-50 min.

[0059] 1. Optimization of shelling and gelatinization temperature

[0060] 20g starch was dispersed in 150mL 4 mol / L CaCl2 solution, and the shelling and gelatinization treatment was carried out at a speed of 300r / min for 40min by magnetic stirring. The shelling and gelatinization temperature was selected from 0-50℃. The effect of shelling and gelatinization temperature on porous starch was optimized. The performance results are shown in Table 3:

[0061] Table 3

[0062]

[0063] It can be seen from the results in Table 3 that with the increase of the dehulling and gelatinization temperature, the starch dehulling degree increases significantly. Compared with the original starch, the enzyme sensitivity of the dehulled starch increases significantly. In addition, with the increase of the starch dehulling degree, the specific volume of the prepared porous starch shows a trend of first increasing and then decreasing. With the increase of the dehulling degree, the starch granules begin to form more pore structures, so the volume of the porous starch increases. However, when the starch dehulling degree reaches a certain level, excessive gelatinization will cause the starch granules to aggregate and the pore structure to be destroyed, so that the originally formed pore structure is partially filled or destroyed, thereby reducing the specific volume of the porous starch. Similar to the specific volume, the oil absorption rate of the porous starch increases with the increase of the starch dehulling degree, and the increase in surface area enhances the adsorption of oil. However, when the dehulling degree is large enough, the pore structure is destroyed, resulting in a gradual decrease in the oil absorption rate. The solubility rate shows an upward trend with the increase of the starch dehulling degree, and the swelling rate shows a trend of first increasing and then decreasing. Comprehensively considering various properties, the preferred dehulling and gelatinization temperature of the present invention is 20-30°C.

[0064] Embodiment 5:

[0065] A method for preparing fisetin inclusion compound using the porous starch prepared in Example 1 comprises the following steps:

[0066] Accurately weigh 400 mg of fisetin and dilute to 100 mL with anhydrous ethanol to prepare a 4 mg / mL fisetin stock solution;

[0067] Mix 400 mg of porous starch with 40 mL of 10% ethanol solution, add 6 mL of fisetin stock solution drop by drop while ultrasonicating, seal and treat with ultrasonic at room temperature for 40 min; filter and dry at 40°C, grind and pass through a 100-mesh sieve, and store the prepared fisetin inclusion complex at 4°C in a light-proof and sealed state for later use.

[0068] The optimization process of porous starch encapsulation of fisetin is as follows:

[0069] 1. Selection of the amount of porous starch added: Weigh 240mg, 320mg, 400mg, 480mg and 560mg of porous starch respectively and place them in 250mL conical flasks, mark them, add 40mL of 10% ethanol solution respectively, repeat the ultrasonic treatment three times while slowly adding 6mL of 4mg / mL fisetin dropwise, seal and ultrasonicate at room temperature for 30min. According to the test results, the porous starch fisetin encapsulation curves with different amounts of porous starch added were drawn. The results are as follows: Figure 3 shown.

[0070] Depend on Figure 3 As a result, it can be seen that when the amount of porous starch added increases from 240mg to 400mg, the encapsulation amount and encapsulation rate of the fisetin inclusion complex prepared by ultrasonic method have a significant growth trend. With the increase of the content of porous starch in the system, the chance of collision and bonding between fisetin and porous starch increases, so the encapsulation amount and encapsulation rate have a significant increase. When the amount of porous starch added is from 400mg to 560mg, the encapsulation amount and encapsulation rate of the fisetin inclusion complex prepared by ultrasonic method both show a downward trend, which is due to the excessive porous starch, resulting in a decrease in encapsulation capacity. Therefore, the preferred mass ratio of fisetin to porous starch in the present invention is 1:14-20.

[0071] 2. Selection of ultrasonic time: Accurately weigh 400 mg of porous starch and place them in 250 mL conical flasks, mark them, add 40 mL of 10% ethanol solution to each flask, slowly add 6 mL of fisetin stock solution drop by drop while ultrasonicating, seal them and ultrasonicate them at room temperature for 10 min, 20 min, 30 min, 40 min, and 50 min. Conduct 3 parallel experiments. Draw the fisetin encapsulation curve of porous starch at different ultrasonic times based on the test results. The results are shown in the figure. Figure 4 shown.

[0072] Depend on Figure 4 The results show that when the ultrasonic time increases from 10 min to 30 min, the encapsulation amount and encapsulation rate of porous starch for fisetin increase significantly with the increase of ultrasonic time. When the ultrasonic time reaches 30 min, the encapsulation amount and encapsulation rate basically begin to decline, indicating that they reach a peak after 40 min of ultrasound, so the ultrasonic time is selected as 20-40 min.

[0073] 3. Selection of ethanol concentration: Accurately weigh 400 mg of porous starch and place them in 250 mL conical flasks, mark them, and add 40 ml of 5%, 10%, 15%, 20%, and 25% ethanol solutions respectively. While ultrasonicating, slowly add 6 mL of fisetin stock solution drop by drop. After sealing, ultrasonicate at room temperature for 30 minutes. Carry out three parallel experiments. According to the test results, draw the fisetin encapsulation curve of porous starch at different ethanol concentrations. The results are as follows Figure 5 shown.

[0074] Depend on Figure 5 It can be seen that fisetin can be dissolved in ethanol solution, so ethanol will have a certain inhibitory effect on the embedding of fisetin. The higher the ethanol concentration, the more obvious the inhibitory effect. When the ethanol concentration is 5-15%, the encapsulation amount and encapsulation rate reach the optimal value.

[0075] 4. Orthogonal test

[0076] According to the single factor results, the three factors of ethanol concentration (A), ultrasonic time (B), and amount of porous starch added (C) were subjected to orthogonal test. The experiment was conducted three times in parallel, and the encapsulation rate of fisetin encapsulated by ultrasonic porous starch was averaged. The results are shown in Tables 4-6.

[0077] Table 4 Intuitive analysis of orthogonal test on the encapsulation efficiency of fisetin in porous starch by ultrasound

[0078] Serial number A: Ethanol concentration (%) B: Ultrasonic time (min) C: Addition amount of starch (mg) D Packing rate (%) 1 1 1 1 1 41.52 2 1 2 2 2 6.91 3 1 3 3 3 2.69 4 2 1 2 3 28.35 5 2 2 3 2 7.48 6 2 3 1 1 2.98 7 3 1 3 2 33.14 8 3 2 1 3 5.04 9 3 3 2 1 3.36 K1 17.040 34.339 17.455 17.455 K2 12.937 6.475 14.342 14.342 K3 13.847 14.438 12.027 12.027 R 4.103 31.328 3.640 5.428

[0079] Table 5 Analysis of variance of orthogonal test

[0080]

[0081]

[0082] Table 6 Results of orthogonal test on the encapsulation efficiency of fisetin in porous starch by ultrasound

[0083] serial number Packing rate (%) Mean(%) RSD value (%) 1 41.523 2 41.432 41.527±0.097 0.233 3 41.626

[0084] Through the intuitive analysis of the R value in the orthogonal test of the encapsulation rate of porous starch encapsulated with fisetin by ultrasound, it can be seen that the order of influence of each factor on the encapsulation of fisetin is: ultrasound time > ethanol concentration > amount of porous starch added. Since group D is a blank column, this group can be used as the error column of variance analysis. The results are shown in Table 5. According to the results of variance analysis, P < 0.05 for factor A (ethanol concentration), factor B (ultrasound time), and factor C (amount of porous starch added) are all significantly different. According to the single factor results, it is known that the amount of porous starch added has little effect on the process of porous starch encapsulation of fisetin.

[0085] According to the orthogonal test results in Table 6, the best process combination for the encapsulation rate of fisetin in ultrasonic porous starch is A1B1C1, the amount of porous starch added is 320 mg, the ultrasonic time is 20 min, and the concentration of ethanol is 5%. According to the best process combination A1B1C1, three encapsulations were performed to calculate the average encapsulation rate of fisetin. The encapsulation rate of porous starch is 41.53%, RSD = 0.233%, and the encapsulation rate of the optimized porous starch has a certain stability. Therefore, the orthogonal best process group selects A1B1C1, that is, the amount of porous starch added is 320 mg, the ultrasonic time is 20 min, and the concentration of ethanol is 5%.

Claims

1. A method for preparing porous starch, Features: The steps include: (1) Starch pretreatment: corn starch is used as raw material, corn starch is fully mixed with calcium chloride solution, and dehulling and gelatinization is performed by magnetic stirring. After dehulling and gelatinization are stopped, centrifugation is performed to obtain the precipitate, washing, and drying to obtain dehulled starch; (2) Enzymatic hydrolysis: preheat the dehulled starch and citric acid-disodium hydrogen phosphate buffer in a constant temperature water bath to obtain a starch suspension; add a complex enzyme to the starch suspension for enzymatic hydrolysis, stop the enzymatic hydrolysis, centrifuge to obtain the precipitate, dry it, and crush it to obtain porous starch.

2. The method for preparing porous starch according to claim 1, Features: In step (1), the molar concentration of the calcium chloride solution is 2-5 mol / L; the mass volume ratio of the corn starch to the calcium chloride solution is 1 g: 5-10 mL.

3. The method for preparing porous starch according to claim 1, Features: In step (1), the dehulling and gelatinization treatment is carried out for 30-50 minutes at a temperature of 20-30° C. and at a speed of 100-500 r / min.

4. The method for preparing porous starch according to claim 1, Features: In step (1), the method of stopping the shelling and gelatinization is to use ice water to stop the gelatinization immediately after the shelling and gelatinization process.

5. The method for preparing porous starch according to claim 1, Features: In step (2), the pH value of the citric acid-disodium hydrogen phosphate buffer is 4-5; the temperature of the constant temperature water bath is 40-45° C., and the preheating time is 8-15 min.

6. The method for preparing porous starch according to claim 1, Features: In step (2), the complex enzyme is a complex enzyme composed of saccharifying enzyme and α-amylase in a mass ratio of 2-4:

1.

7. The method for preparing porous starch according to claim 1, Features: In step (2), the enzymatic hydrolysis temperature is 40-45°C and the enzymatic hydrolysis time is 10-24h.

8. A porous starch prepared by the preparation method according to any one of claims 1 to 7.

9. A method for preparing fisetin inclusion compound using the porous starch according to claim 8, It is characterized in that The steps include: S1: dissolving fisetin in anhydrous ethanol to obtain a fisetin stock solution; S2: Mix the porous starch and ethanol solution, add the fisetin stock solution drop by drop slowly while ultrasonicating, seal the mixture, ultrasonicate the mixture at room temperature, filter, dry, grind and sieve to obtain the fisetin inclusion complex.

10. The method according to claim 9, It is characterized in that In step S2, the mass ratio of fisetin to porous starch is 1:14-20; the volume concentration of the ethanol solution is 5%-15%; and the ultrasonic time is 20-40 min.

Images