Resistant starch and a method for its preparation

Abstract

The application belongs to the technical field of food processing, and particularly relates to a resistant starch and a preparation method thereof. The preparation method mainly comprises the following steps: soaking, grinding, removing protein, gelatinization, acidolysis, debranching, temperature rising, resuscitation and purification. The preparation method is innovatively improved on the basis of the original traditional preparation method, a microwave-infrared heating method is introduced, and a physical method, a chemical method and an enzyme method are combined, so that the prepared resistant starch of red dates has the characteristics of high resistant content, low impurity content, uniform color, good quality, and good heat resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of food processing, and particularly relates to a resistant starch and a preparation method thereof. BACKGROUND

[0002] Resistant starch (RS) refers to a type of starch that cannot be digested and absorbed in the stomach and small intestine, but can be fermented and decomposed by intestinal bacteria in the colon to produce short-chain fatty acids and play a probiotic role. It is also called anti-enzymatic starch. According to the properties of RS, RS classification covers five types of RS1 (physically embedded starch), RS2 (resistant starch granules), RS3 (aged retrograded starch), RS4 (chemically modified starch), and RS5 (starch-lipid complex). RS1 and RS2 are easily destroyed after heat treatment, so their anti-enzymatic properties are weak. RS3 is formed by aging and recrystallization of amylose in starch molecules, such as during the cooling process of gelatinized starch, so it has very high stability in a hot environment. RS4 is a type of starch whose molecular structure is changed by esterification, etherification or crosslinking, and its safety needs to be verified. RS5 is formed by the complexation between amylose and lipids, but the production cost is higher after the introduction of lipids, and the yield is unstable.

[0003] Among them, RS3 resistant starch has broad application prospects due to its safety and high efficiency. It can improve intestinal health, promote the growth of beneficial bacteria, enhance intestinal peristalsis, prevent constipation and intestinal diseases. It can also help control blood sugar, slow down the rate of postprandial blood sugar rise, and is beneficial to diabetic patients. At the same time, it increases satiety, helps control appetite and weight. In addition, RS3 resistant starch also has certain lipid-lowering effect, can reduce the level of cholesterol in the blood, thereby reducing the risk of cardiovascular diseases.

[0004] Red dates are a widely cultivated crop in China. At present, the processing products of red dates are mainly primary processing, such as red date powder and red date dry. With the growth of market demand and the progress of technology, the processing and utilization level of red dates is expected to be further improved. At present, there are limited types of resistant starch products available for commercialization on the market in China, while red dates contain a high content of starch, about 80 grams of starch per 100 grams of red dates, so it is a good raw material for preparing resistant starch.

[0005] In order to solve the problems of "few varieties, low purity and poor heat resistance" existing in the extraction of resistant starch, the technical scheme of the present application is proposed. SUMMARY

[0006] In order to solve the problems in the prior art, the present application uses red dates as raw materials, introduces a microwave-infrared heating method, and provides a preparation process combining physical, chemical and enzymatic methods, so that the purity of resistant starch is improved without changing the structure of starch, the types of domestic resistant starch are widened, and the heat resistance of resistant starch is improved

[0007] The scheme of the present application is to provide a preparation method of resistant starch, which comprises the following steps:

[0008] (1) soaking: after the fresh red dates are pitted, they are soaked in water, washed with water, and impurities are removed to obtain clean red dates;

[0009] (2) grinding: after the clean red dates are cut into small pieces, water is added for grinding, and a first slurry is collected and obtained;

[0010] (3) sugar removal: yeast is added to the first slurry, air is introduced and continuously stirred to remove the sugar in the first slurry, and the slurry after sugar removal is a second slurry;

[0011] (4) protein removal: the pH of the second slurry is adjusted to neutral, and neutral protease is added to remove protein, and then the slurry is centrifuged to obtain a precipitate; the precipitate is washed, dried, crushed and sieved in sequence to obtain red date starch;

[0012] (5) gelatinization: the red date starch is added to water, and gelatinization is carried out under ultrasonic and high temperature and high pressure conditions;

[0013] (6) acid hydrolysis: then, hydrochloric acid-acetic acid solution is added to adjust the pH to be acidic, and potassium hydrogen phthalate-sodium hydroxide buffer solution is added, and after being fully stirred, a gelatinized acid hydrolyzed starch milk is obtained;

[0014] (7) debranching: alkali, pullulanase and mesophilic alpha-amylase are added to the gelatinized acid hydrolyzed starch milk for debranching, and after completion, the enzyme is inactivated to obtain a debranched starch milk;

[0015] (8) temperature rising and regeneration: the debranched starch milk is subjected to microwave-infrared heating treatment, and then is left to stand for aging and regeneration to obtain a regenerated starch milk;

[0016] (9) purification: glucosidase is added to the regenerated starch milk to enzymatically hydrolyze non-resistant starch, and then centrifugation is performed and the supernatant is discarded, and the precipitate is washed, dried and sieved in sequence to obtain red date resistant starch.

[0017] Preferably, in step (1), the soaking time is 4-24h.

[0018] Preferably, in step (2), the mass of water added is 5-10 times the mass of the clean red dates.

[0019] Preferably, in step (3), the yeast is added in an amount of 2% to 5% of the mass of the red dates.

[0020] Preferably, in step (4), the neutral protease is added in an amount of 200 to 1200 U / g;

[0021] And / or, after the addition of the neutral protease, the temperature of the slurry is maintained at 37 to 50°C during the process of removing the protein;

[0022] And / or, the centrifugation is performed at a speed of 3000 to 3500 r / min for 15 to 20 min;

[0023] And / or, the drying is performed at a temperature of 50 to 55°C;

[0024] And / or, the sieving is performed through a 100 to 120 mesh screen.

[0025] Preferably, in step (5), the red date starch is added to water to maintain a concentration of 10 to 35 wt%;

[0026] And / or, the ultrasonic and high temperature and high pressure conditions are as follows: the ultrasonic power is 80 to 240 W, the high temperature is 121°C, and the high pressure is 1.0 to 1.2 MPa;

[0027] And / or, the gelatinization is performed for 15 to 90 min.

[0028] Preferably, in step (6), the concentration of the hydrochloric acid-acetic acid solution is 25 to 75 wt%;

[0029] And / or, the pH is adjusted to 3 to 5 by adding the hydrochloric acid-acetic acid solution, and the pH is maintained at less than 5 during the acid hydrolysis process.

[0030] Preferably, in step (7), the alkali solution is a mixture of 1 wt% NaOH solution and 0.5 wt% KOH solution;

[0031] And / or, the addition amount of the pullulanase is 50 to 300 U / g;

[0032] And / or, the addition amount of the mesophilic α-amylase is 10 to 35 U / g;

[0033] And / or, the debranching is performed at a temperature of 50 to 60°C for 4 h.

[0034] Preferably, in step (8), the microwave heating power is 300 to 900 W;

[0035] And / or, the wavelength of the infrared heating is 2 to 10 μm, and the power of the infrared heating is 200 to 1200 W;

[0036] and / or, the time of microwave-infrared heating is 2-12 min;

[0037] and / or, the temperature of aging and regeneration is 4℃, and the time is 18-48 h.

[0038] Preferably, in step (9), the added amount of the glucosidase is 50-300 U / g.

[0039] and / or, the centrifugal speed is 3000-3500 r / min, and the centrifugal time is 15-20 min.

[0040] and / or, the drying temperature is 60-65℃.

[0041] and / or, the sieving is 100-120 mesh.

[0042] Based on the same technical concept, another aspect of the present application provides a resistant starch prepared by the preparation method.

[0043] The present application has the following advantages:

[0044] (1) The preparation method has the advantages of using hydrochloric acid and acetic acid acidolysis to prepare jujube resistant starch, which can enhance the acidolysis effect, improve the yield and purity of resistant starch through synergistic effect, and reduce the use amount and potential side effects of single acid to a certain extent.

[0045] (2) The preparation method has the advantages of using microwave-infrared heating method to prepare jujube resistant starch, which is energy-saving and can accurately control the heating temperature, so that the starch molecules can reach the reaction condition in a short time, and the heat loss is reduced, and the preparation efficiency and product quality are improved.

[0046] (3) The preparation method has the advantages of using glucosidase to prepare jujube resistant starch, which can specifically act on starch molecules, efficiently remove impurities, improve the purity and quality of resistant starch, and maintain its natural structure and health value.

[0047] (4) The preparation method has the advantages of preparing jujube resistant starch with high resistant content, low impurity content, uniform color, good quality, and good heat resistance, which can be used in the food industry. BRIEF DESCRIPTION OF DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below only illustrate some of the embodiments of the present application, and all other embodiments obtained by those of ordinary skill in the art without creative effort based on these drawings belong to the protection scope of the present application.

[0049] Figure 1 is a process flow diagram of the present application.

[0050] Figure 2 is a structural schematic diagram of a microwave-infrared heating device.

[0051] Figure 3 is a scanning electron microscope graph of jujube starch before treatment under different magnifications (from left to right: x500, x1000, x5000).

[0052] Figure 4 is a scanning electron microscope graph of jujube resistant starch obtained in Example 6 under different magnifications (from left to right: x500, x1000, x5000).

[0053] Figure 5 is an XRD graph of jujube starch and jujube resistant starch.

[0054] Figure 6 is an FTIR graph of jujube starch and jujube resistant starch.

[0055] Figure 7 is a DSC graph of jujube starch and jujube resistant starch.

[0056] Figure 8 is the expansion degree of jujube starch and jujube resistant starch at different temperatures.

[0057] In the drawings, the reference signs are:

[0058] 1-magnetic stirrer; 2-infrared heater; 3-starch container; 4-microwave heater. DETAILED DESCRIPTION

[0059] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described in detail below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the protection scope of the present application.

[0060] Example 1

[0061] The embodiment provides a preparation method of resistant starch, and the preparation method comprises the following steps:

[0062] (1) soaking: after the fresh red dates are treated by removing the cores, the red dates are soaked in water for 4 hours, washed with water, and impurities are removed to obtain clean red dates;

[0063] (2) grinding: after the clean red dates are cut into small pieces, 5 times the amount of water is added to perform 3 times of grinding, and a first slurry is collected;

[0064] (3) sugar removal: yeast bacteria with a mass fraction of 2% of the red dates is added to the first slurry, air is introduced, and stirring is continuously performed to remove sugar in the first slurry, and the slurry after the sugar is removed is a second slurry;

[0065] (4) protein removal: the pH of the second slurry is adjusted to neutral, and 200 U / g of neutral protease is added to remove proteins (the temperature is kept at 37 DEG C), then the slurry is centrifuged at 3000 r / min for 20 min to obtain a precipitate; the precipitate is washed with distilled water for 3 times, then is sequentially dried in a 50 DEG C oven, crushed, and passed through a 100-mesh screen to obtain red date starch;

[0066] (5) gelatinization: the red date starch is added to water, the concentration is controlled to be 10 wt%, and the red date starch is fully gelatinized in an ultrasonic high-pressure pot at 80 W and 121 DEG C for 15 min;

[0067] (6) acid hydrolysis: then, a 25 wt% hydrochloric acid-acetic acid solution is added to adjust the pH to 5.0, and a potassium hydrogen phthalate-sodium hydroxide buffer solution is added, and after fully stirring, a gelatinized acid hydrolysis starch milk is obtained;

[0068] (7) debranching: the gelatinized acid hydrolysis starch milk is placed in a 50 DEG C constant-temperature water bath, a mixed solution of 1 wt% NaOH solution and 0.5 wt% KOH solution is added to adjust the pH to 6.0, 50 U / g of pullulanase and 10 U / g of mesophilic alpha-amylase are added to fully debranch for 4 h, and after completion, enzyme is inactivated by boiling water bath, and a debranched starch milk is obtained;

[0069] (8) temperature rising and resuscitation: the debranched starch milk is heated for 2 min under the conditions of a microwave power of 300 W and an infrared heating power of 200 W, and stirring is performed while heating; then, the debranched starch milk is aged and resuscitated at 4 DEG C for 18 h, and a resuscitated starch milk is obtained;

[0070] (9) purification: 50 U / g of glucosidase is added to the resuscitated starch milk to enzymatically hydrolyze non-resistant starch, then the resuscitated starch milk is centrifuged at 3000 r / min for 20 min and the supernatant is discarded, the precipitate is washed with anhydrous ethanol for 3 times, and is placed in a 60 DEG C oven to be dried, and is passed through a 100-mesh screen, and red date resistant starch is obtained (encapsulated and stored in a desiccator).

[0071] The process flow chart is shown as Figure 1

[0072] It is emphasized that in step (8), a microwave-infrared heating device is needed, the schematic diagram of which is shown as Figure 2

[0073] Example 2

[0074] The present embodiment provides a preparation method of resistant starch, comprising the following steps:

[0075] (1) Soaking: after the fresh red dates are pitted, they are soaked in water for 8h, washed with water, and impurities are removed to obtain clean red dates;

[0076] (2) Pulping: after the clean red dates are cut into small pieces, 10 times the amount of water is added for pulping for 3 times, and the first slurry is collected;

[0077] (3) Sugar removal: yeast bacteria with a mass fraction of 5% of the red dates is added to the first slurry, air is introduced and stirred continuously to remove the sugar in the first slurry, and the slurry after the sugar is removed is the second slurry;

[0078] (4) Protein removal: the pH of the second slurry is adjusted to neutral, and 400 U / g of neutral protease is added to remove the protein (the temperature is kept at 37℃), and then the slurry is centrifuged at 3500 r / min for 15 min to obtain a precipitate; the precipitate is washed with distilled water for 3 times, and then is sequentially dried in a 50℃ oven, crushed, and passed through a 120 mesh screen to obtain red date starch;

[0079] (5) Gelatinization: the red date starch is added to water, the concentration is controlled to be 15wt%, and is fully gelatinized in an ultrasonic pressure cooker at 240W power and 121℃ for 30min;

[0080] (6) Acidolysis: then a 25wt% hydrochloric acid-acetic acid solution is added to adjust the pH to 5.0, a potassium hydrogen phthalate-sodium hydroxide buffer solution is added, and after fully stirring, a gelatinized acidolysis starch milk is obtained;

[0081] (7) Debranching: the gelatinized acidolysis starch milk is placed in a 50℃ constant temperature water bath, a mixture of 1wt% NaOH solution and 0.5wt% KOH solution is added to adjust the pH to 6.0, 100 U / g of pullulanase and 15 U / g of mesophilic α-amylase are added for fully debranching for 4h, and after completion, the enzyme is inactivated in a boiling water bath to obtain a debranched starch milk;

[0082] ​​(8) heating and regeneration: the debranched starch milk is heated for 4 min under microwave power of 300 W and infrared heating power of 400 W, and stirring is performed while heating; then, the debranched starch milk is aged and regenerated at 4°C for 24 h, to obtain regenerated starch milk;

[0083] (9) purification: 100 U / g of glucosidase is added to the regenerated starch milk to enzymatically hydrolyze non-resistant starch, then the mixture is centrifuged at 3500 r / min for 15 min, and the supernatant is discarded; the precipitate is washed with anhydrous ethanol for 3 times, and is dried in a 60°C oven; the dried product is sieved through a 120-mesh screen, to obtain jujube resistant starch (which is packaged and stored in a desiccator).

[0084] Example 3

[0085] The present embodiment provides a preparation method of resistant starch, which comprises the following steps:

[0086] (1) soaking: fresh jujubes are pitted, soaked in water for 12 h, washed with water, and impurities are removed, to obtain clean jujubes;

[0087] (2) pulping: the clean jujubes are cut into small pieces, and 6 times the amount of water is added to perform pulping for 3 times, and a first slurry is collected;

[0088] (3) sugar removal: 4% of the mass of the jujubes of yeast is added to the first slurry, air is introduced, and stirring is continuously performed to remove sugar in the first slurry; the slurry from which the sugar is removed is a second slurry;

[0089] (4) protein removal: the pH of the second slurry is adjusted to neutral, and 600 U / g of neutral protease is added to remove protein (the temperature is maintained at 45°C); then, the slurry is centrifuged at 3500 r / min for 15 min, to obtain a precipitate; the precipitate is washed with distilled water for 3 times, and is sequentially dried in a 50°C oven, crushed, and sieved through a 100-mesh screen, to obtain jujube starch;

[0090] (5) gelatinization: the jujube starch is added to water, and the concentration is controlled to be 20 wt%; the mixture is fully gelatinized in an ultrasonic pressure cooker at 120 W power and 121°C for 45 min;

[0091] (6) acid hydrolysis: then, a 50 wt% hydrochloric acid-acetic acid solution is added to adjust the pH to 4.0, and a potassium hydrogen phthalate-sodium hydroxide buffer solution is added; after fully stirring, a gelatinized acid-hydrolyzed starch milk is obtained;

[0092] (7) Debranching: the gelatinized acid-thinned starch milk is placed in a 55°C constant temperature water bath, and a mixed solution of 1wt% NaOH solution and 0.5wt% KOH solution is added to adjust the pH to 6.0, then 150U / g of pullulanase and 20U / g of medium-temperature α-amylase are added for sufficient debranching for 4h, and after completion, a boiling water bath is used to kill the enzymes to obtain debranched starch milk;

[0093] (8) Temperature rising and resuscitation: the debranched starch milk is heated for 6min under microwave power of 600W and infrared heating power of 600W, and stirred while heating; then it is aged and resuscitated at 4°C for 30h to obtain resuscitated starch milk;

[0094] (9) Purification: 150U / g of glucosidase is added to the resuscitated starch milk to enzymatically hydrolyze non-resistant starch, then it is centrifuged at 3500r / min for 15min and the supernatant is discarded, the precipitate is washed with anhydrous ethanol for 3 times, and then dried in a 60°C oven, and passed through a 100-mesh screen to obtain red jujube resistant starch (packaged and stored in a desiccator).

[0095] Example 4

[0096] The embodiment provides a preparation method of resistant starch, and the preparation method comprises the following steps:

[0097] (1) Soaking: fresh red dates are pitted, soaked in water for 16h, washed with water, and impurities are removed to obtain clean red dates;

[0098] (2) Pulping: the clean red dates are cut into small pieces, and 9 times the amount of water is added for pulping for 3 times, and a first slurry is collected;

[0099] (3) Sugar removal: 3% of the mass of the red dates of yeast is added to the first slurry, air is introduced, and the slurry is continuously stirred to remove sugar in the first slurry, and the slurry after the sugar is removed is a second slurry;

[0100] (4) Protein removal: the pH of the second slurry is adjusted to neutral, and 800U / g of neutral protease is added to remove protein (the temperature is kept at 45°C), then the slurry is centrifuged at 3500r / min for 15min to obtain a precipitate; the precipitate is washed with distilled water for 3 times, and then sequentially dried in a 50°C oven, crushed, and passed through a 120-mesh screen to obtain red date starch;

[0101] (5) Gelatinization: the red date starch is added to water, the concentration is controlled to be 25wt%, and the gelatinization is performed in an ultrasonic pressure cooker at 80W power and 121°C for 60min;

[0102] (6) Acidolysis: Then, a 50wt% hydrochloric acid-acetic acid solution is added to adjust the pH to 4.0, and a potassium hydrogen phthalate-sodium hydroxide buffer solution is added, and after being fully stirred, a gelatinized acidolysis starch milk is obtained;

[0103] (7) Debranching: The gelatinized acidolysis starch milk is placed in a 60℃ constant temperature water bath, and a mixture of 1wt% NaOH solution and 0.5wt% KOH solution is added to adjust the pH to 6.0, and then 200U / g of pullulanase and 25U / g of mesophilic α-amylase are added for sufficient debranching for 4h, and after completion, a boiling water bath is used to kill the enzymes, and a debranched starch milk is obtained;

[0104] (8) Heating and resuscitation: The debranched starch milk is heated for 8min under microwave power of 600W and infrared heating power of 800W, and stirred while heating; then, it is placed at 4℃ for 36h for aging and resuscitation, and a resuscitated starch milk is obtained;

[0105] (9) Purification: 200U / g of glucosidase is added to the resuscitated starch milk to enzymatically hydrolyze non-resistant starch, and then centrifuged at 3500r / min for 15min and the supernatant is discarded, the precipitate is washed with anhydrous ethanol for 3 times, and then dried in a 60℃ oven, and then sieved through a 120 mesh screen, and a red jujube resistant starch is obtained (packaged and stored in a desiccator).

[0106] Example 5

[0107] The embodiment provides a preparation method of resistant starch, and the preparation method comprises the following steps:

[0108] (1) Soaking: After being pitted, fresh red dates are soaked in water for 20h, washed with water, and impurities are removed, and a clean red date is obtained;

[0109] (2) Pulping: The clean red date is cut into small pieces, and 5 times the amount of water is added for pulping 3 times, and a first slurry is collected and obtained;

[0110] (3) Sugar removal: 5% of the mass of the red date of yeast is added to the first slurry, air is introduced, and the slurry is continuously stirred to remove the sugar in the first slurry, and the slurry after the sugar is removed is a second slurry;

[0111] (4) Protein removal: The pH of the second slurry is adjusted to neutral, and 1000U / g of neutral protease is added to remove the protein (the temperature is kept at 50℃), and then the slurry is centrifuged at 3500r / min for 15min, and a precipitate is obtained; the precipitate is washed with distilled water for 3 times, and then sequentially dried in a 50℃ oven, crushed, and sieved through a 100 mesh screen, and a red date starch is obtained;

[0112] (5) Pasting: the jujube starch is added into water, the concentration is controlled to be 30wt%, and the pasting is performed in an ultrasonic pressure cooker under the condition of 120W power and 121℃ for 75min;

[0113] (6) Acidolysis: then, a 75wt% hydrochloric acid-acetic acid solution is added to adjust the pH to 3.0, and a potassium hydrogen phthalate-sodium hydroxide buffer solution is added, and the pasting acidolysis starch milk is obtained after fully stirring;

[0114] (7) Debranching: the pasting acidolysis starch milk is placed in a 60℃ constant temperature water bath, a mixed solution of 1wt% NaOH solution and 0.5wt% KOH solution is added to adjust the pH to 6.0, 250U / g of pullulanase and 30U / g of medium temperature α-amylase are added for fully debranching for 4h, and the enzyme is inactivated by boiling water bath after completion, and the debranched starch milk is obtained;

[0115] (8) Heating and resuscitation: the debranched starch milk is heated for 10min under the condition of microwave power of 900W and infrared heating power of 1000W, and the heating is stirred; then, the resuscitation is performed at 4℃ for 42h for aging, and the resuscitated starch milk is obtained;

[0116] (9) Purification: 250U / g of glucosidase is added to the resuscitated starch milk for enzymatic hydrolysis of non-resistant starch, then centrifugation is performed at 3500r / min for 15min, and the supernatant is discarded, the precipitate is washed with anhydrous ethanol for 3 times, and is placed in a 60℃ oven for drying and drying, and is passed through a 100 mesh screen, and the jujube resistant starch is obtained (encapsulated and stored in a desiccator).

[0117] Example 6

[0118] The embodiment provides a preparation method of resistant starch, and the preparation method comprises the following steps:

[0119] (1) Soaking: after the fresh jujube is pitted, the jujube is soaked in water for 24h, washed with water, and impurities are removed, and the clean jujube is obtained;

[0120] (2) Pulping: the clean jujube is cut into small pieces, 5 times the amount of water is added, and pulping is performed for 3 times, and the first slurry is collected and obtained;

[0121] (3) Sugar removal: 3.5% of the mass of the jujube is added to the first slurry as yeast, air is introduced, and the slurry is continuously stirred to remove the sugar in the first slurry, and the slurry after the sugar is removed is the second slurry;

[0122] (4) Protein removal: the pH of the second slurry is adjusted to neutral, and 1200 U / g of neutral protease is added to remove proteins (the temperature is kept at 50°C), and then the slurry is centrifuged at 3500 r / min for 15 min to obtain a precipitate; the precipitate is washed with distilled water for 3 times, and then is sequentially dried in a 50°C oven, crushed, and passed through a 100-mesh screen to obtain jujube starch;

[0123] (5) Gelatinization: the jujube starch is added to water, the concentration is controlled to be 35 wt%, and is fully gelatinized in an ultrasonic pressure cooker at 80W power and 121°C for 90 min;

[0124] (6) Acidolysis: then a 75 wt% hydrochloric acid-acetic acid solution is added to adjust the pH to 3.0, and a potassium hydrogen phthalate-sodium hydroxide buffer solution is added, and after being fully stirred, a gelatinized acidolysis starch milk is obtained;

[0125] (7) Debranching: the gelatinized acidolysis starch milk is placed in a 60°C constant temperature water bath, and a mixture of 1 wt% NaOH solution and 0.5 wt% KOH solution is added to adjust the pH to 6.0, and then 300 U / g of pullulanase and 35 U / g of medium-temperature α-amylase are added for fully debranching for 4 h, and after completion, enzyme is inactivated in a boiling water bath to obtain a debranched starch milk;

[0126] (8) Heating and resuscitation: the debranched starch milk is heated at a microwave power of 900W and an infrared heating power of 1200W for 12 min, and is stirred while heating; then is placed at 4°C for 48 h for aging and resuscitation to obtain a resuscitated starch milk;

[0127] (9) Purification: 300 U / g of glucosidase is added to the resuscitated starch milk to enzymatically hydrolyze non-resistant starch, and then is centrifuged at 3500 r / min for 15 min and the supernatant is discarded, the precipitate is washed with anhydrous ethanol for 3 times, and is placed in a 60°C oven for drying, and is passed through a 100-mesh screen to obtain jujube resistant starch (encapsulated and placed in a desiccator for storage).

[0128] Verification example

[0129] The jujube resistant starch prepared in Examples 1-6 is detected for RDS (fast digestible starch), SDS (slow digestible starch) and RS (resistant starch) content:

[0130] 200 mg of the prepared jujube resistant starch is taken in a 15 mL round-bottom centrifuge tube, 4 mL of deionized water and 4 mL of a sodium acetate buffer solution with a pH of 5.2 are added, and a magnetic stirrer is added. The mixture is placed in a 37°C water bath and continuously oscillated for 30 minutes.

[0131] Add 2 mL of the enzyme mixture to the above mixed solution. The enzyme mixture was prepared as follows: Dissolve 4.5 g of trypsin (A3176, ≥5 U / mg) in 40 mL of deionized water and centrifuge at 5000 r / min for 10 min. Take 27 mL of the supernatant and mix it with 3.2 mL of amylase (10115, ≥70 U / mg).

[0132] Subsequently, 0.1 mL aliquots were taken from the mixture and added to the ethanol solution at mins 0, 20, and 120. The mixture was centrifuged, and the absorbance of the supernatant at 510 nm was measured using the Megazyme GOPOD kit. The RDS, SDS, and RS contents were calculated using the following formulas:

[0133] RDS (%) = (G 20 -G0)×0.9 / W

[0134] SDS (%) = (G 120 -G 20 )×0.9 / W

[0135] RS (%) = 100% - RDS% - SDS%

[0136] Among them, G0, G 20 and G 120 The absorbance at 510 nm represents the absorbance at min 0, 20 and 120 respectively, and W represents the weight of the starch sample.

[0137] Table 1 shows the contents of RDS, SDS and RS of resistant starch obtained from jujubes in Examples 1 to 6.

[0138] Table 1

[0139]

[0140] As shown in Table 1, the raw material ratio and processing parameters were appropriate in Example 6, resulting in the highest content of resistant starch.

[0141] Commercially available product 1: Manufacturer: Hebei Qiansheng Biotechnology Co., Ltd., Product name: Resistant Starch

[0142] Commercially available product 2: Manufacturer: Xi'an Kangnuo Chemical Co., Ltd., Product name: Resistant Starch

[0143] Furthermore, further detection and characterization were performed using Example 6 as an example, as detailed below:

[0144] Depend on Figure 3 It can be seen that the surface of jujube starch granules is relatively smooth and the shape is relatively regular.

[0145] Depend on Figure 4It can be seen that: compared with jujube starch granules, resistant starch granules of jujube also have relatively complete and larger granules, but the surface becomes rough, with small bumps, and the shape becomes irregular.

[0146] Depend on Figure 5 It can be seen that jujube resistant starch has a diffraction peak around 17°, and jujube starch has diffraction peaks around 6°, 14°, 17°, 20°, 21° and 24°. This shows that jujube resistant starch has a high degree of crystallinity and a more stable crystal structure, which increases the stability of the double helix structure.

[0147] Depend on Figure 6 It can be seen that: resistant starch from jujubes and jujube starch at a wavelength of 3500 cm⁻¹ -1 2800cm -1 1680cm -1 Both contain hydroxyl groups, carbon-carbon bonds, and carbonyl bonds. The chemical structures of jujube resistant starch and jujube starch are identical, indicating that they are the same substance.

[0148] Depend on Figure 7 It can be seen that resistant starch from jujubes is less prone to thermal decomposition than jujube starch, which is consistent with the characteristic of high crystallinity of resistant starch.

[0149] Depend on Figure 8 It can be seen that the swelling rate of resistant starch from jujubes is lower than that of jujube starch.

[0150] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for producing resistant starch, characterized by, The preparation method comprises the following steps: (1) soaking: after the fresh red dates are pitted, they are soaked in water, washed with water, and impurities are removed to obtain clean red dates; wherein: the soaking time is 4-24 h; (2) grinding: after the clean red dates are cut into small pieces, water is added for grinding, and a first slurry is collected and obtained; wherein: the added water is 5-10 times the mass of the clean red dates; (3) sugar removal: yeast is added to the first slurry, air is introduced, and stirring is continuously performed to remove sugar in the first slurry, and the slurry after the sugar is removed is a second slurry; wherein: the added amount of the yeast is 2-5% of the mass of the red dates; (4) protein removal: the pH of the second slurry is adjusted to neutral, and neutral protease is added to remove proteins, and then the slurry is centrifuged to obtain a precipitate; the precipitate is sequentially washed, dried, crushed, and sieved to obtain red date starch; wherein: the added amount of the neutral protease is 200-1200 U / g; and / or, after the neutral protease is added, the temperature of the slurry is maintained at 37-50°C during the removal of the proteins; and / or, the centrifugation is performed at a speed of 3000-3500 r / min for 15-20 min; and / or, the drying is performed at a temperature of 50-55°C; and / or, the sieving is performed through a 100-120 mesh screen; (5) gelatinization: the red date starch is added to water, and is gelatinized under ultrasonic and high-temperature and high-pressure conditions; wherein: the red date starch is added to water, and the concentration of the red date starch is maintained at 10-35 wt%; and / or, the ultrasonic and high-temperature and high-pressure conditions are as follows: the ultrasonic power is 80-240 W, the high-temperature is 121°C, and the high-pressure is 1.0-1.2 MPa; and / or, the gelatinization is performed for 15-90 min; (6) acid hydrolysis: then, a hydrochloric acid-acetic acid solution is added to adjust the pH to be acidic, and a potassium hydrogen phthalate-sodium hydroxide buffer solution is added, and a gelatinized acid-hydrolyzed starch milk is obtained after sufficient stirring; wherein: the concentration of the hydrochloric acid-acetic acid solution is 25-75 wt%; and / or, the pH is adjusted to 3-5 by adding the hydrochloric acid-acetic acid solution, and the pH is maintained to be less than 5 during the acid hydrolysis; (7) debranching: alkali, pullulanase, and mesophilic α-amylase are added to the gelatinized acid-hydrolyzed starch milk for debranching, and after completion, the enzyme is inactivated to obtain a debranched starch milk; wherein: the alkali is a mixture of 1 wt% NaOH solution and 0.5 wt% KOH solution; and / or, the added amount of the pullulanase is 50-300 U / g; and / or, the added amount of the mesophilic α-amylase is 10-35 U / g; and / or, the debranching is performed at a temperature of 50-60°C for 4 h; (8) temperature rising and retrogradation: the debranched starch milk is subjected to microwave-infrared heating treatment, and then is left to stand for aging and retrogradation to obtain a retrograded starch milk; wherein: the microwave heating power is 300-900 W; and / or, the infrared heating wavelength is 2-10 μm, and the infrared heating power is 200-1200 W. And / or, the time of microwave-infrared heating is 2-12 min; And / or, the temperature of aging retrogradation is 4℃, and the time is 18-48 h; (9) Purification: adding glucosidase to the retrograded starch milk to enzymatically hydrolyze non-resistant starch, then centrifuging, discarding the supernatant, and sequentially washing, drying and sieving the precipitate to obtain red jujube resistant starch; wherein: The addition amount of the glucosidase is 50-300 U / g; And / or, the centrifugal speed is 3000-3500 r / min, and the centrifugal time is 15-20 min; And / or, the drying temperature is 60-65℃; And / or, the sieving is through 100-120 mesh screen; The resistant starch has RDS content of 7.28%, SDS content of 3.79% and RS content of 88.93%; The resistant starch has diffraction peak at 17°. Said resistant starch has hydroxyl groups, carbon-carbon bonds, carbonyl bonds at wavelengths 3500 cm -1 , 2800 cm -1 , 1680 cm -1 .

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