Digestion-resistant chestnut starch and preparation method thereof

Abstract

The present invention provides a digestion-resistant chestnut starch and a preparation method thereof, the preparation method comprising the following steps: preparing chestnut wet starch by alkali extraction; sieving the chestnut wet starch to a quick-freeze solid form in liquid nitrogen, and then performing vacuum freeze drying to obtain freeze-dried starch; re-dissolving the freeze-dried starch in water, adding a phenolic compound, dispersing evenly, standing, and filtering to obtain a precipitate, and performing wet pressing and heat-induced assembly of the precipitate to obtain a self-assembled starch; cooling the self-assembled starch, heating it up again, and cooling it down again to obtain a starch complex; placing the starch complex under human body temperature conditions to react, and as a whole, digestion-resistant chestnut starch with a higher RS ​​content can be obtained. At the same time, the digestion-resistant chestnut starch prepared by the present invention has stable rheological properties, has application effects such as low calories, inhibiting blood sugar, and easing swallowing, and is convenient for application in food and health products.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of digestion-resistant starch, and in particular to digestion-resistant chestnut starch and a preparation method thereof. Background Art

[0002] Starch is the most common energy source for human energy supplementation. Most starches have the advantages of fast digestion, wide sources, and high universality. With the improvement of living standards, people are no longer limited to satisfying food and clothing, but pay more attention to nutrition and health. Studies have found that the digestion process of conventional starch in the body is accompanied by the production of high calories and high blood sugar, which increases the risk of obesity.

[0003] There have been some studies on improving the digestibility of starch to meet the future demand for food processing base materials. However, the digestibility modification effect of resistant starch still needs to be improved. Summary of the invention

[0004] Based on this, it is necessary to provide a digestion-resistant chestnut starch and a preparation method and application thereof.

[0005] The present invention adopts the following technical solution:

[0006] The invention discloses a method for preparing digestion-resistant chestnut starch, comprising the following steps: preparing chestnut wet starch by alkali extraction; sieving the chestnut wet starch to a quick-freeze solid form in liquid nitrogen, and then performing vacuum freeze drying to obtain freeze-dried starch; re-dissolving the freeze-dried starch in water, adding a phenolic compound, dispersing evenly, standing, and filtering to obtain a precipitate, and performing wet pressing and heat-induced assembly on the precipitate, wherein the process parameters are: controlling the humidity to be 15-20%, the pressure to be 0.3-0.5MPa, the temperature to be 100-110°C, and the time to be 4-6h to obtain self-assembled starch; cooling the self-assembled starch to 0-4°C to obtain a starch complex; and placing the starch complex at a human-like temperature of 36-38°C for reaction for 3-6h to obtain the digestion-resistant starch.

[0007] In some of the embodiments, the starch complex preparation process also includes a programmed temperature rise and fall step: the self-assembled starch is cooled to 0-4°C, then heated to 30-40°C and maintained for 30 min, then cooled to -20°C to -18°C and maintained for 30 min, the cycle is repeated 2 to 5 times, and then placed at 0-4°C to obtain the starch complex.

[0008] In some of the embodiments, the chestnut wet starch can be prepared by an alkali extraction method, the alkali solution of the alkali extraction is preferably 0.1-0.5% food grade sodium hydroxide solution, the temperature of the alkali solution extraction is 0-4°C, and the time is 18-30h.

[0009] In some embodiments, the process parameters of the vacuum freeze drying are: vacuum degree <5Pa, cooling from room temperature to -40°C at a cooling rate of 15-25°C / min, then cooling to -50°C at a cooling rate of 0.5-2°C / min, and maintaining for 40-60h. Preferably, the process parameters of the vacuum freeze drying are: vacuum degree <5Pa, cooling from room temperature to -40°C at a cooling rate of 20°C / min, then cooling to -50°C at a cooling rate of 1°C / min, and maintaining for 48h.

[0010] In some of the embodiments, freeze-dried starch is redissolved in water, a phenolic compound is added, and the mixture is dispersed evenly using a high-speed disperser. The mixture is allowed to stand, the supernatant is removed, and the precipitate is filtered to remove part of the water.

[0011] In some embodiments, the phenolic compound is selected from at least one of resveratrol, magnolol, quercetin, catechin, epicatechin, caffeic acid, epicatechin gallate, ferulic acid, chlorogenic acid, and gallic acid.

[0012] In some of the embodiments, the method for preparing the digestion-resistant chestnut starch also includes the step of passing the wet starch through a 60-mesh sieve (screening into liquid nitrogen can achieve the effect of dispersion without agglomeration, which is conducive to constructing porous, large-surface-area starch adsorption particles) and / or the step of passing the starch complex through an 80-mesh sieve.

[0013] In some of the embodiments, the method for preparing the digestion-resistant chestnut starch also includes the step of packaging the digestion-resistant chestnut starch in a three-layer composite eight-side sealed zipper bag, the inner layer of the three-layer composite eight-side sealed zipper bag is made of CPP (polypropylene) material to lock in fragrance, the middle layer is made of soft BOPP (biaxially oriented polypropylene film) for moisture-proofing, and the outer layer is made of PE (polyethylene) composite nylon material for oxygen isolation and tear resistance, thereby achieving a better packaging effect.

[0014] The digestion-resistant chestnut starch prepared by the above-mentioned preparation method has a RS content of not less than 50%.

[0015] Compared with the prior art, the core beneficial effects of the present invention are:

[0016] The present invention extracts wet chestnut starch and sieves it into a quick-freeze solid form in liquid nitrogen, vacuum freeze-drying, adding phenol wet pressing heat-induced assembly, program-controlled gradient temperature rise and fall, and human body temperature 36-38°C conditions, so that digestion-resistant chestnut starch with a high RS content (up to 50% or more) can be obtained as a whole. At the same time, the digestion-resistant chestnut starch prepared by the present invention has stable rheological properties, has the application effects of low calories, inhibiting blood sugar, easing swallowing, etc., and is easy to be used in food and health products. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1This is the temperature-rheology test diagram of the digestion-resistant starch prepared in Experimental Example 4.

[0018] Figure 2 Effect of drying temperatures on the rheological properties of prefabricated starch.

[0019] Figure 3 This is the X-ray diffraction test pattern of chestnut starch prepared with different amounts of resveratrol (Res) added. DETAILED DESCRIPTION

[0020] Terminology explanation:

[0021] According to the digestion characteristics of starch, it can generally be divided into rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS). Among them, RDS will be quickly digested and absorbed in the upper small intestine, causing blood sugar levels to rise rapidly, and then the pancreas will secrete insulin into the blood to lower blood sugar levels as quickly as possible. SDS will be slowly digested throughout the small intestine to continuously release glucose, so the rise in blood sugar levels is slower. RS cannot be digested in the small intestine, but it will be fermented by microorganisms in the large intestine (colon) to produce short-chain fatty acids, including butyrate, which is beneficial to colon health.

[0022] Resistant starch (RS), also known as resistant starch and indigestible starch, cannot be enzymatically hydrolyzed in the small intestine, but can undergo fermentation reaction with volatile fatty acids in the human gastrointestinal colon. This starch is more difficult to degrade than other starches, is digested slowly in the body, and is absorbed and enters the blood slowly. The technical concept of the present invention is to provide a digestion-resistant chestnut starch with a high RS content.

[0023] The present invention is further described in detail below in conjunction with specific embodiments so that those skilled in the art can understand the present invention more clearly. The following embodiments are only used to illustrate the present invention, but are not only used to limit the scope of the present invention. Based on the specific embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without creative work belong to the protection scope of the present invention. In the embodiments of the present invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art; in the embodiments of the present invention, if not specifically specified, the technical means used are conventional means well known to those skilled in the art.

[0024] Determination of starch composition and degree of polymerization: The absorbance test method was used. References: Zhang Bin. Study on the preparation, properties and formation mechanism of slowly digestible starch [D]. South China University of Technology, 2011. and Banks W, Greenwood CT, Khan KM. The interaction of linear, amylose oligomers with iodine [J]. Carbohydrate Research, 1971, 17(1): 25-33.

[0025] Particle size determination: Mastersizer 2000 laser particle size distribution analyzer (Malvern, UK) was used to evaluate the particle size. Distilled water was used as a dispersant. When the shading rate reached 8-15%, three measurements were taken and the average value was taken.

[0026] Determination of digestion-resistant starch content: Determined according to the Englyst method (reference Englyst KN, Englyst H.N., Hudson GJ, et al. Rapidly available glucose in foods: An in vitro measurement that reflects the glycemic response [J]. American Journal of Clinical Nutrition, 1999, 69: 448-454, or Englyst HN, Kingman SM, Cummings, JH Classification and measurement of nutritionally important starch fractions [J]. European Journal of Clinical Nutrition, 1992, 46: S33-S50.).

[0027] Rheological properties were determined using a DHR2 rheometer (TA, USA) for temperature and frequency scanning.

[0028] X-ray diffraction measurement: using monochromatic Cu-Ka rays with a wavelength of 0.1542nm, the test tube voltage is 40KV, the tube current is 40mA, the starting angle is 5°, the ending angle is 45°, the step length is 0.02°, the scanning speed is 5° / min, and the scanning is continuous.

[0029] Test Example 1

[0030] This test example provides a method for preparing digestion-resistant chestnut starch, comprising the following steps:

[0031] S1, extraction and preparation of wet starch:

[0032] The chestnuts were shelled and peeled, chopped and pulped, immersed in 0.2% food-grade sodium hydroxide solution at a solid-liquid ratio of 1:2 (w / w), and extracted at 4°C for 24 hours to obtain an alkaline extract.

[0033] The alkaline extract was passed through a 100-mesh sieve to remove the residue, the filtrate was centrifuged at 4500 rpm for 5 minutes, the supernatant was removed, the centrifugal precipitate was washed three times with tap water, allowed to stand, and the precipitate was retained to obtain wet starch.

[0034] S2, preparation of freeze-dried starch:

[0035] The wet starch obtained in step S1 was passed through a 60-mesh sieve and sieved to a quick-frozen solid form in liquid nitrogen. The solid was taken out and placed in a material tray of a desktop vacuum freeze dryer. The cold trap temperature was set to rapidly drop from room temperature to -40°C at a cooling rate of 20°C / min, and then dropped to -50°C at a cooling rate of 1°C / min, and maintained for 48 hours to obtain freeze-dried starch.

[0036] S3, preparation of self-assembled starch:

[0037] The freeze-dried starch obtained in step S2 is redissolved in water at a solid-liquid ratio of 1:2 (w / w) to form a freeze-dried starch solution; resveratrol accounting for 5% of the dry weight of the freeze-dried starch is dissolved in a small amount of anhydrous ethanol, and then added to the freeze-dried starch solution, and dispersed for 5 seconds under the condition of a high-speed disperser adjusted to 300 rpm, and allowed to stand at room temperature for 30 minutes, the supernatant is removed, and most of the water is removed from the precipitate by suction filtration, and hot air drying at 55° C. is performed to obtain a self-assembled starch.

[0038] S4, program-controlled gradient temperature rise and fall to prepare starch composites:

[0039] The self-assembled starch obtained in step S3 was heated and cooled by program-controlled gradient heating and cooling: cooled to 4°C at a cooling rate of 10°C / min and maintained for 1 hour, then heated to 40°C at 2°C / min and maintained for 30 minutes, cooled to -18°C at 2°C / min and maintained for 30 minutes, cycled 3 times, and then maintained at 4°C for 1 hour to form a starch complex.

[0040] S5, obtain digestion-resistant starch:

[0041] The starch complex obtained in step S4 is taken out, passed through an 80-mesh sieve, the material is evenly dispersed, and loaded into a disposable tray with a material thickness of 3 to 5 mm, and the human body temperature is set to 36 to 37° C., and the digestion-resistant prefabricated starch is obtained after reacting for 3 to 6 hours. The prefabricated starch is sealed and packaged in a three-layer composite eight-side sealed zipper bag.

[0042] Test Example 2

[0043] This test example provides a method for preparing digestion-resistant chestnut starch, comprising the following steps:

[0044] S1, extraction and preparation of wet starch:

[0045] The chestnuts are shelled and peeled, chopped and pulped, immersed in 0.2% food-grade sodium hydroxide solution at a solid-liquid ratio of 1:2 (w / w), and extracted at 4°C for 24 hours to obtain an alkaline extract; the alkaline extract is sieved through a 100-mesh sieve to remove the filter residue, the filtrate is centrifuged at 4500rpm for 5 minutes, the supernatant is removed, the centrifugal precipitate is washed three times with tap water, and allowed to stand, and the precipitate is retained to obtain wet starch.

[0046] S2, preparation of freeze-dried starch:

[0047] The wet starch obtained in step S1 was passed through a 60-mesh sieve and sieved to a quick-frozen solid form in liquid nitrogen. The solid was taken out and placed in a material tray of a desktop vacuum freeze dryer. The cold trap temperature was set to rapidly drop from room temperature to -40°C at a cooling rate of 20°C / min, and then dropped to -50°C at a cooling rate of 1°C / min, and maintained for 48 hours to obtain freeze-dried starch.

[0048] S3, preparation of self-assembled starch:

[0049] The freeze-dried starch obtained in step S2 is redissolved in water at a solid-liquid ratio of 1:2 (w / w) to form a freeze-dried starch solution; resveratrol accounting for 5% of the dry weight of the freeze-dried starch is dissolved in a small amount of anhydrous ethanol and added to the freeze-dried starch solution, and dispersed for 5 seconds under the condition of a high-speed disperser adjusted to 300 rpm, and allowed to stand at room temperature for 30 minutes, the supernatant is removed, and most of the water is removed from the precipitate by suction filtration, and then it is transferred to a closed environment to control the humidity to 20%, the pressure to 0.4 MPa, the temperature to 105±5°C, and the reaction time to 4 hours to obtain self-assembled starch.

[0050] S4, preparation of starch complex:

[0051] The self-assembled starch obtained in step S3 was cooled to 25° C. at a cooling rate of 10° C. / min and maintained for 5 hours to form a starch complex.

[0052] S5, obtain digestion-resistant starch:

[0053] The starch complex obtained in step S4 is taken out, passed through an 80-mesh sieve, the material is evenly dispersed, and loaded into a disposable tray with a material thickness of 3 to 5 mm, and the human body temperature is set to 36 to 37° C., and the digestion-resistant prefabricated starch is obtained after reacting for 3 to 6 hours. The prefabricated starch is sealed and packaged in a three-layer composite eight-side sealed zipper bag.

[0054] Test Example 3

[0055] This test example provides a method for preparing digestion-resistant chestnut starch, comprising the following steps:

[0056] S1, extraction and preparation of wet starch:

[0057] The chestnuts are shelled and peeled, chopped and pulped, immersed in 0.2% food-grade sodium hydroxide solution at a solid-liquid ratio of 1:2 (w / w), and extracted at 4°C for 24 hours to obtain an alkaline extract; the alkaline extract is sieved through a 100-mesh sieve to remove the filter residue, the filtrate is centrifuged at 4500rpm for 5 minutes, the supernatant is removed, the centrifugal precipitate is washed three times with tap water, and allowed to stand, and the precipitate is retained to obtain wet starch.

[0058] S2, preparation of freeze-dried starch:

[0059] The wet starch obtained in step S1 was passed through a 60-mesh sieve and sieved to a quick-frozen solid form in liquid nitrogen. The solid was taken out and placed in a material tray of a desktop vacuum freeze dryer. The cold trap temperature was set to rapidly drop from room temperature to -40°C at a cooling rate of 20°C / min, and then dropped to -50°C at a cooling rate of 1°C / min, and maintained for 48 hours to obtain freeze-dried starch.

[0060] S3, preparation of self-assembled starch:

[0061] The freeze-dried starch obtained in step S2 is redissolved in water at a solid-liquid ratio of 1:2 (w / w) to form a freeze-dried starch solution; resveratrol accounting for 5% of the dry weight of the freeze-dried starch is dissolved in a small amount of anhydrous ethanol and added to the freeze-dried starch solution, and dispersed for 5 seconds under the condition of a high-speed disperser adjusted to 300 rpm, and allowed to stand at room temperature for 30 minutes, the supernatant is removed, and most of the water is removed from the precipitate by suction filtration, and then it is transferred to a closed environment to control the humidity to 20%, the pressure to 0.4 MPa, the temperature to 105±5°C, and the reaction time to 4 hours to obtain self-assembled starch.

[0062] S4, preparation of starch complex:

[0063] The self-assembled starch obtained in step S3 was cooled to 4°C at a cooling rate of 10°C / min and maintained for 6 hours to form a starch complex.

[0064] S5, obtain digestion-resistant starch:

[0065] The starch complex obtained in step S4 is taken out, passed through an 80-mesh sieve, the material is evenly dispersed, and loaded into a disposable tray with a material thickness of 3 to 5 mm, and the human body temperature is set to 36 to 37° C., and the digestion-resistant prefabricated starch is obtained after reacting for 3 to 6 hours. The prefabricated starch is sealed and packaged in a three-layer composite eight-side sealed zipper bag.

[0066] Test Example 4

[0067] This test example provides a method for preparing digestion-resistant chestnut starch, comprising the following steps:

[0068] S1, preparing wet starch:

[0069] The chestnuts are shelled and peeled, chopped and pulped, immersed in 0.2% food-grade sodium hydroxide solution at a solid-liquid ratio of 1:2 (w / w), and extracted at 4°C for 24 hours to obtain an alkaline extract; the alkaline extract is sieved through a 100-mesh sieve to remove the filter residue, the filtrate is centrifuged at 4500rpm for 5 minutes, the supernatant is removed, the centrifugal precipitate is washed three times with tap water, and allowed to stand, and the precipitate is retained to obtain wet starch.

[0070] S2, preparation of freeze-dried starch:

[0071] The wet starch obtained in step S1 is passed through a 60-mesh sieve and sieved into liquid nitrogen (which can disperse and prevent agglomeration, and is conducive to the construction of porous, large-surface-area starch particles for adsorption), and the solidified material is quickly frozen. The solidified material is taken out and placed in a material tray of a desktop vacuum freeze dryer. The cold trap temperature is set to drop rapidly from room temperature to -40°C at a cooling rate of 20°C / min, and then to -50°C at a cooling rate of 1°C / min, and maintained for 48 hours to obtain freeze-dried starch.

[0072] S3, preparation of self-assembled starch:

[0073] The freeze-dried starch obtained in step S2 is redissolved in water at a solid-liquid ratio of 1:2 (w / w) to form a freeze-dried starch solution; resveratrol accounting for 5% of the dry weight of the freeze-dried starch is dissolved in a small amount of anhydrous ethanol and added to the freeze-dried starch solution, and dispersed for 5 seconds under the condition of a high-speed disperser adjusted to 300 rpm, and allowed to stand at room temperature for 30 minutes, the supernatant is removed, and most of the water is removed from the precipitate by suction filtration, and then it is transferred to a closed environment to control the humidity to 20%, the pressure to 0.4 MPa, the temperature to 105±5°C, and the reaction time to 4 hours to obtain self-assembled starch.

[0074] S4, program-controlled gradient temperature rise and fall to prepare starch composites:

[0075] The self-assembled starch obtained in step S3 was heated and cooled by a program-controlled gradient: cooled to 4°C at a cooling rate of 10°C / min and maintained for 1 hour, then heated to 30°C-40°C at 2°C / min and maintained for 30 minutes, cooled to -18°C at 2°C / min and maintained for 30 minutes, cycled 3 times, and then maintained at 4°C for 1 hour to form a starch complex.

[0076] S5, obtain digestion-resistant starch:

[0077] The starch complex obtained in step S4 is taken out, passed through an 80-mesh sieve, the material is evenly dispersed, and loaded into a disposable tray with a material thickness of 3 to 5 mm, and the human body temperature is set to 36 to 37° C., and the digestion-resistant prefabricated starch is obtained after reacting for 3 to 6 hours. The prefabricated starch is sealed and packaged in a three-layer composite eight-side sealed zipper bag.

[0078] Test Example 5

[0079] This test example provides a method for preparing chestnut starch, and the method steps are basically the same as those in Test Example 4, except that:

[0080] In the process step of extracting and preparing wet starch in step S1, 0.45% food-grade sodium metabisulfite aqueous solution is used to replace 0.2% food-grade sodium hydroxide solution.

[0081] Compared with the alkaline extraction method using 0.2% food-grade sodium hydroxide aqueous solution, the acid extraction process using 0.45% sodium pyrosulfite requires more reagents, has a lower total starch yield, a lower average degree of polymerization of starch, and a weakened ability to self-assemble with polyphenol compounds in the later stage.

[0082] Test Example 6

[0083] This test example provides a method for preparing chestnut starch, and the method steps are basically the same as those in Test Example 4, except that:

[0084] The process step of preparing freeze-dried starch in step S2 is replaced by hot air drying (hot air drying at 55° C. for 48 hours).

[0085] Test Example 7

[0086] This comparative example provides a method for preparing chestnut starch, and the method steps are basically the same as those in Experimental Example 4, except that:

[0087] In step S3, resveratrol (Res) is added in an amount of 10% or 20% instead of 5%.

[0088] like Figure 3 As shown, when the amount of resveratrol (Res) added reaches 20%, the characteristic peak of polyphenols is obvious. After testing and comparison, it is found that when the amount of resveratrol added is too much, the characteristic peak of polyphenols is obvious, and starch and polyphenols do not self-assemble to form a complex, but exist in a free state.

[0089] The chestnut starch prepared in the above test examples was subjected to particle size test, digestion-resistant starch content test and rheological property test.

[0090] The statistical data of the effects of different extraction processes on the components and particle size of the prepared alkali-extracted starch or acid-extracted starch in Experimental Examples 4 and 5 are shown in the following table:

[0091]

[0092] The test results in the table above show that the chestnuts are fully hydrolyzed during the alkali extraction process, and the total starch content obtained is higher than that of acid extraction, and the proportion of amylose is high, the average degree of polymerization is large, and the subsequent self-assembly space size is large and the number is large, which is conducive to the later self-assembly of the host and guest with polyphenol compounds. At the same time, the average surface area and volume particle size of the wet starch test of alkali-extracted chestnuts are large. During the wet pressing and heat-induced treatment process, polyphenols or amylose can realize self-assembly in the amorphous area of ​​starch through the micropores on the surface of the swollen starch particles.

[0093] Among them, the alkali-extracted starch prepared in step S1 of Test Example 4 was used as a control, and the test results of the content of the final product chestnut starch prepared in each test example were statistically shown in the following table:

[0094] Statistical table of chestnut starch content test

[0095]

[0096]

[0097] Further, referring to the preparation method of Experimental Example 4, the inventor team actually also specifically explored the effects of different temperature treatments in step S5 (room temperature 25°C, simulated human body temperature 37°C, conventional drying temperature 55°C, critical temperature 70°C and high temperature 90°C) on the rheological properties of the obtained chestnut starch. The results are statistically shown as follows: Figure 1 and 2 shown.

[0098] The test results of rheological properties show that different shear frequencies have the least effect on the products treated at 37°C.

[0099] Furthermore, referring to the preparation method of Experimental Example 4, the inventor team actually also specifically explored the effect of adding polyphenol reagents (resveratrol, magnolol, quercetin, catechin, epicatechin, caffeic acid, epicatechin gallate, ferulic acid, chlorogenic acid, gallic acid) accounting for 5% of the dry weight of freeze-dried starch in step S3 on the anti-digestive properties of the finally prepared chestnut starch.

[0100] Taking the alkali-extracted starch prepared in step S1 of Experimental Example 4 as a control, the test results of the content of the final product chestnut starch prepared by using various polyphenol reagents are shown in the following table:

[0101] Statistics of chestnut starch content test

[0102]

[0103]

[0104] It is worth noting that the amount of the polyphenol reagent in step S3 of the preparation method of the present invention should not be too much. If it exceeds 20% of the dry weight of the freeze-dried starch, it will cause the polyphenol assembly to fail.

[0105] At the same time, in the preparation step of the self-assembled starch of specific polyphenol compounds, the humidity in the closed environment is controlled to be 15-20%, the pressure is 0.3-0.5 MPa, the temperature is 105±5°C, the reaction time is 4-6h, and then it is further treated by cooling (program-controlled gradient heating and cooling) and human body temperature to ensure that the RS content in the digestion-resistant chestnut starch is not less than 50% as a whole.

[0106] It is necessary to point out that the above embodiments are limited to further elaboration and explanation of the technical solution of the present invention, and are not further limitations of the technical solution of the present invention. The method of the present invention is only a preferred implementation scheme, and is not used to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing digestion-resistant chestnut starch, characterized in that: The steps include: Preparation of chestnut wet starch by alkali extraction; The wet chestnut starch is sieved to a quick-freeze solid form in liquid nitrogen, and then vacuum freeze-dried to obtain freeze-dried starch; The freeze-dried starch was redissolved in water, phenolic compounds were added, dispersed evenly, allowed to stand, and precipitates were obtained by suction filtration. The precipitates were subjected to wet pressing and heat-induced assembly. The process parameters were: humidity was controlled at 15-20%, pressure was 0.3-0.5 MPa, temperature was 100-110°C, and time was 4-6 hours to obtain self-assembled starch. The self-assembled starch was cooled to 0-4°C, then heated to 30-40°C and maintained for 30 min, then cooled to -20°C--18°C and maintained for 30 min, the cycle was repeated 2-5 times, and then placed at 0-4°C to obtain a starch composite; The starch complex is placed in a human body temperature of 36-38°C for reaction for 3-6 hours to obtain digestion-resistant starch; The phenolic compound is resveratrol.

2. The method for preparing digestion-resistant chestnut starch according to claim 1, characterized in that: The method also includes the step of screening the wet starch with a 60-mesh sieve. The process parameters of the vacuum freeze-drying are: vacuum degree <5 Pa, cooling from room temperature to -40°C at a cooling rate of 15-25°C / min, and then cooling to -50°C at a cooling rate of 0.5-2°C / min, and maintaining for 40-60 hours.

3. The method for preparing digestion-resistant chestnut starch according to claim 2, characterized in that: The process parameters of the vacuum freeze drying are: vacuum degree <5 Pa, cooling from room temperature to -40°C at a cooling rate of 20°C / min, and then cooling to -50°C at a cooling rate of 1°C / min, and maintaining for 48 hours.

4. The method for preparing digestion-resistant chestnut starch according to claim 1, characterized in that: The method further comprises the step of passing the wet starch through a 60-mesh sieve and / or the step of passing the starch complex through an 80-mesh sieve.

5. The method for preparing digestion-resistant chestnut starch according to claim 1, characterized in that: The method also includes the step of packaging the digestion-resistant chestnut starch in a three-layer composite eight-side sealed zipper bag, wherein the inner layer of the three-layer composite eight-side sealed zipper bag is made of CPP material, the middle layer is made of soft BOPP, and the outer layer is made of PE composite nylon material.

6. Digestion-resistant chestnut starch prepared by the preparation method according to any one of claims 1 to 5.

7. The digestion-resistant chestnut starch according to claim 6, wherein the RS content is not less than 50%.

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