Crushed starch microspheres with high digestion resistance as well as preparation method and application thereof

Abstract

The invention relates to the technical field of starch microspheres, in particular to fragmented starch microspheres with high digestion resistance and a preparation method and application thereof, and the preparation method comprises the following steps: preparing short amylose from native starch; the method comprises the following steps: mixing short amylose and gellan gum, dispersing the mixture in deionized water to obtain a pre-gelatinizing solution, injecting the pre-gelatinizing solution into a dispersed phase channel of a microfluidic device, injecting a calcium chloride solution into a continuous phase channel of the microfluidic device, and enabling the pre-gelatinizing solution to form uniform liquid drops in the calcium chloride solution; transferring the liquid drops into a calcium chloride solution, standing, cross-linking and curing to obtain short amylose-gellan gum resistant starch beads; and performing gradient crushing after freezing, and sieving after unfreezing to obtain the crushed starch microspheres. By adopting the steps and adopting a freezing-crushing combined technology, the RS content of resistant starch of the obtained high-crushing type starch microspheres still reaches 14.63%, and the traditional cognition that crushing can cause damage to a starch anti-digestion structure and the RS content is suddenly reduced is thoroughly broken through.

Description

Technical Field

[0001] This invention relates to the field of starch microsphere technology, and in particular to a highly digestible, fragmented starch microsphere, its preparation method, and its application. Background Technology

[0002] Resistant starch (RS), a functional starch component that is difficult to digest and absorb in the human small intestine but can be fermented and utilized by microorganisms in the large intestine, possesses physiological functions such as regulating intestinal flora balance, reducing postprandial glycemic response, and delaying fat accumulation. It has significant application value and broad market prospects in low-GI foods, dietary fiber-fortified foods, and functional health products. Currently, the main technical means to improve the resistance to digestion of starch focus on two main directions: starch modification and carrier encapsulation. To further enhance the resistance to digestion of short-chain amylose, carrier encapsulation technology is widely used. Among these, polysaccharide carriers, due to their good biocompatibility and ability to form stable gel networks through ionic cross-linking, have become the preferred carriers for encapsulating starch-based substances.

[0003] However, the research and application of existing starch-polysaccharide composite gel resistant starch products still face significant technical bottlenecks, specifically in the following two aspects: Limited application scenarios and reliance on crushing processes: Existing technologies produce starch-polysaccharide composite gels primarily in the form of millimeter-sized intact gel beads. These particles are relatively large and poorly dispersed, making them unsuitable for food systems requiring high raw material dispersion, such as baked goods, beverages, and sauces. To expand application areas, the intact gel beads must be crushed into fine particles or microspheres to improve their mixing uniformity and mouthfeel compatibility in food matrices. However, the impact of crushing processes on the digestibility structure of the gel beads is not considered—due to the high water content and flexible outer shell of starch-polysaccharide composite gel beads, traditional mechanical crushing easily leads to gel shell rupture, exposure of the internal starch network, and even structural damage. Whether the digestibility of the product can still be maintained after crushing, and what crushing method can achieve uniform crushing while retaining high digestibility, are questions that have no relevant research reports or technical insights in the existing technology. This has led to a technical contradiction between "expanding application scenarios through crushing" and "retaining high digestibility", which is difficult to balance. This has seriously limited the application scope of starch-polysaccharide composite gel resistant starch products.

[0004] In summary, there is an urgent need to develop a technical solution that can achieve uniform crushing of starch-polysaccharide composite gel beads, and ensure that the crushed product still has high resistance to digestion, so as to promote the large-scale application of resistant starch in more functional food fields. Summary of the Invention

[0005] The purpose of this invention is to provide a highly digestible, fragmented starch microsphere, its preparation method, and its application. By using a freeze-crushing combined technology to process short-chain amylose-gellan gum resistant starch beads, even highly fragmented starch microspheres still have an RS content of 14.63%, completely breaking through the traditional understanding that crushing leads to the destruction of the starch's digestibility structure and a sharp drop in RS content.

[0006] To achieve the above objectives, the present invention provides a method for preparing highly digestible, fragmented starch microspheres, comprising the following steps: S1. Disperse the original starch in water, decrystallize at high temperature to obtain starch paste solution, cool and adjust the pH to 3-5.5, add pullulanase for enzymatic hydrolysis at constant temperature and then inactivate at high temperature, concentrate under reduced pressure to obtain concentrated solution. S2. Add anhydrous ethanol to the concentrated solution obtained in S1 for alcohol extraction. After standing, filter and collect the precipitate. Dry with hot air to obtain short-chain starch. S3. Mix the short-chain starch and gellan gum from S2 and disperse them in deionized water. Stir the mixture in a constant temperature water bath until completely dissolved to obtain a pregel solution. S4. Inject the pregel solution obtained in S3 into the dispersed phase channel of the microfluidic device, inject the calcium chloride solution into the continuous phase channel of the microfluidic device, and start the injection pump to form uniform droplets of the pregel solution in the dispersed phase channel into the calcium chloride solution in the continuous phase channel. S5. Transfer the droplets obtained in S4 to a calcium chloride solution, allow them to stand and cross-link and solidify to obtain short-chain starch-gellan gum resistant starch beads. S6. The short-chain starch-gellan gum resistant starch beads obtained in S5 are frozen and then subjected to gradient crushing. After thawing, they are sieved to obtain crushed starch microspheres.

[0007] Preferably, in S1, the high-temperature decrystallization is carried out by stirring at 90-110°C for 30-40 minutes, with a stirring rate of 200-300 r / min and a cooling temperature of 55-60°C.

[0008] Preferably, in S1, the amount of pullulanase added is 0.1-0.5% of the starch mass, and the enzyme activity of pullulanase is ≥1000U / g.

[0009] Preferably, in S2, the solid content in the concentrate is 30-40%, the hot air drying temperature is 40-45℃, and the hot air drying time is 12-16h.

[0010] Preferably, in S3, the mass ratio of short-chain starch to gellan gum is 8-10:1, the temperature of the constant temperature water bath is 75-80℃, the stirring speed is 300-400 r / min, and the stirring time is 10-40 min.

[0011] Preferably, in S4, the inner diameter of the dispersed phase channel is 0.5-0.8 mm, the flow rate of the dispersed phase is 0.5-1.0 mL / min, the inner diameter of the continuous phase channel is 1.5-2.0 mm, and the flow rate of the continuous phase is 5-8 mL / min.

[0012] Preferably, in S5, the cross-linking curing temperature is 20-30℃ and the cross-linking curing time is 2-3h.

[0013] Preferably, in S6, the freezing temperature is -20℃ to -15℃, the freezing time is 4-6h, the gradient crushing is one of low crushing degree, medium crushing degree and high crushing degree, the gradient crushing temperature is -10℃ to -5℃, and the thawing temperature is 40-50℃.

[0014] The fragmented starch microspheres were prepared using the above-described method for preparing highly resistant to digestion. The fragmented starch microspheres are one of the following: low-fragmentation starch microspheres, medium-fragmentation starch microspheres, and high-fragmentation starch microspheres.

[0015] The aforementioned highly resistant, brittle starch microspheres are used in food processing.

[0016] Therefore, the present invention employs the above-mentioned highly digestible broken starch microspheres, their preparation method, and their application, and its beneficial effects are as follows: 1. The preparation method provided by the present invention uses a freeze-crushing combined technology to process short amylose-gellan gum resistant starch beads. Even for highly crushed starch microspheres, the RS content still reaches 14.63%, which is much higher than that of short amylose, native starch and pregel solution. This completely breaks through the traditional understanding that crushing will lead to the destruction of starch digestibility structure and a sharp drop in RS content. 2. This invention has prepared starch microspheres with different degrees of fragmentation, which have high resistant starch content. The resistant starch RS of low fragmentation starch microspheres reaches 22.16%, and the resistant starch RS of medium fragmentation starch microspheres reaches 21.74%. Furthermore, the fragmentation process improves dispersibility and can be flexibly adapted to low-GI foods, dietary fiber fortified foods, and other applications. 3. In the broken starch microspheres prepared by this invention, gellan gum and calcium ions undergo multi-point chelation and cross-linking to form a dense gel network. This ensures that the broken starch microspheres obtained by the breaking treatment still retain the core anti-digestion structure of short amylose encapsulated by the gellan gum cross-linking skeleton, thus ensuring the stability of RS content.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is an SEM image of the low-fragmentation starch microspheres in Example 1 of the present invention, magnified 80 times. Figure 2 This is a 1000x magnified SEM image of the low-fragmentation starch microspheres in Example 1 of this invention; Figure 3 This is a 40x magnified SEM image of the broken starch microspheres in Example 2 of the present invention; Figure 4 This is a 1000x magnified SEM image of the broken starch microspheres in Embodiment 2 of the present invention; Figure 5 This is a 50x magnified SEM image of the highly fragmented starch microspheres in Example 3 of this invention; Figure 6 This is a 1000x magnified SEM image of the highly fragmented starch microspheres in Example 3 of this invention; Figure 7 This is a 50x magnified SEM image of the short amylose-gellan gum resistant starch beads in Comparative Example 1 of this invention. Figure 8 This is a 1000x magnified SEM image of the short-chain amylose-gellan gum resistant starch beads in Comparative Example 1 of this invention. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0020] This invention provides a method for preparing highly digestible, fragmented starch microspheres, comprising the following steps: S1. Disperse native starch in water and decrystallize at high temperature to obtain a starch paste solution. After cooling, adjust the pH to 3-5.5, add pullulanase for isothermal enzymatic hydrolysis, followed by high-temperature inactivation, and concentrate under reduced pressure to obtain a concentrated solution. Pullulanase selectively cleaves the α-1,6 glycosidic bonds of starch molecules to generate short-chain amylose. Due to their moderate chain length, short-chain amylose is more likely to arrange itself through intermolecular hydrogen bonds to form a digestible crystalline structure (B-type or V-type crystals), which is the basis for increasing the content of resistant starch (RS).

[0021] S2. Add anhydrous ethanol to the concentrated solution obtained in S1 for alcohol extraction. After standing, filter and collect the precipitate. Dry with hot air to obtain short-chain starch. S3. Mix the short-chain starch and gellan gum from S2 and disperse them in deionized water. Stir the mixture in a constant temperature water bath until completely dissolved to obtain a pregel solution. S4. Inject the pregel solution obtained in S3 into the dispersed phase channel of the microfluidic device, inject the calcium chloride solution into the continuous phase channel of the microfluidic device, and start the injection pump to form uniform droplets of the pregel solution in the dispersed phase channel into the calcium chloride solution in the continuous phase channel. S5. Transfer the droplets obtained in S4 to a calcium chloride solution, allow them to stand and cross-link, and solidify to obtain short-chain starch-gellan gum resistant starch beads. This allows the gellan gum to fully chelate with calcium ions, forming a three-dimensional gel network that encapsulates the internal short-chain starch. Gellan gum is an anionic polysaccharide, and its carboxyl groups (-COO-) - ) and Ca 2+ A chelating structure is formed to construct a dense gel shell, locking the short-chain starch within the gel network and preventing its structure from loosening during subsequent processing.

[0022] S6. The short-chain amylose-gellan gum-resistant starch beads obtained in S5 are frozen and then subjected to gradient crushing. After thawing, they are sieved to obtain crushed starch microspheres. Low-temperature freezing causes the internal moisture of the short-chain amylose-gellan gum-resistant starch beads to form small ice crystals. The expansion of the ice crystals can slightly disrupt the density of the gellan gum gel network, but does not destroy the chemical cross-linking points and the overall encapsulation structure, laying the foundation for subsequent uniform crushing, while avoiding starch gelatinization caused by high-temperature crushing.

[0023] In some embodiments of the present invention, in S1, the native starch is one or more of waxy corn starch, potato starch, and cassava starch.

[0024] In some embodiments of the present invention, in S1, high-temperature decrystallization involves stirring at 90-110°C for 30-40 minutes at a stirring rate of 200-300 r / min, and cooling at 55-60°C. This thoroughly destroys the crystalline regions (Type A crystals) of the starch granules, allowing them to fully hydrate and swell, thus making them accessible to the enzyme.

[0025] In some embodiments of the present invention, in S1, the amount of pullulanase added is 0.1-0.5% of the starch mass, and the enzyme activity of pullulanase is ≥1000U / g.

[0026] In some embodiments of the present invention, in step S2, the solid content in the concentrate is 30-40%, the hot air drying temperature is 40-45°C, and the hot air drying time is 12-16 hours. Alcohol precipitation utilizes ethanol to reduce the polarity of the aqueous phase, causing short-chain starch to precipitate due to decreased solubility. Hot air drying avoids excessive starch retrogradation or thermal degradation.

[0027] In some embodiments of the present invention, in S3, the mass ratio of short-chain starch to gellan gum is 8-10:1, the temperature of the constant temperature water bath is 75-80℃, the stirring rate is 300-400 r / min, and the stirring time is 10-40 min.

[0028] In some embodiments of the present invention, in step S4, the inner diameter of the dispersed phase channel is 0.5-0.8 mm, the flow rate of the dispersed phase is 0.5-1.0 mL / min, the inner diameter of the continuous phase channel is 1.5-2.0 mm, and the flow rate of the continuous phase is 5-8 mL / min. By adjusting the flow rate ratio of the two phases and the channel size, monodisperse droplets are formed using shear force and interfacial tension.

[0029] In some embodiments of the present invention, in step S5, the cross-linking curing temperature is 20-30°C and the cross-linking curing time is 2-3 hours.

[0030] In some embodiments of the present invention, in step S6, the freezing temperature is -20°C to -15°C, the freezing time is 4-6 hours, the gradient crushing is one of low, medium, and high crushing degrees, the gradient crushing temperature is -10°C to -5°C, and the thawing temperature is 40-50°C. Mechanical crushing is performed below the starch gelatinization temperature (approximately -5°C) to avoid thermal effects that could cause starch gelatinization or gel melting, thus ensuring that the crystalline structure of short-chain starch is preserved.

[0031] In some embodiments of the present invention, fragmented starch microspheres are prepared using the above-described method for preparing highly digestible fragmented starch microspheres. The fragmented starch microspheres are one of three types: low-fragmentation starch microspheres (fragmentation frequency of 5 times), medium-fragmentation starch microspheres (fragmentation frequency of 10 times), and high-fragmentation starch microspheres (fragmentation frequency of 20 times). By controlling the fragmentation frequency (5 / 10 / 20 times), a fracture energy input gradient is achieved, thereby controlling the fragment size distribution and realizing controllable particle size.

[0032] In some embodiments of the present invention, the above-mentioned highly resistant, fragmented starch microspheres are applied in food processing, such as in low-GI foods (e.g., low-GI bread, biscuits), dietary fiber-fortified foods (e.g., meal replacement shakes, foods for the elderly), and functional beverages.

[0033] Example 1 S1. Disperse 8% starch (waxy corn starch with amylopectin content ≥95%) in water, and decrystallize at 100℃ with stirring for 30 min at a stirring rate of 240 r / min to obtain a starch paste solution. After cooling to 55℃, add phosphate buffer to adjust the pH to 4.8, add pullulanase (enzyme activity ≥1000 U / g), and perform enzymatic hydrolysis at isothermal followed by high-temperature inactivation. The amount of pullulanase added is 0.15% of the starch mass. After concentration under reduced pressure, obtain a concentrated solution.

[0034] S2. Add 3 times the volume of anhydrous ethanol to the concentrate obtained in S1 for alcohol extraction. The solid content in the concentrate is 30%. After standing for 2 hours, filter and collect the precipitate. Dry it with hot air at 45°C for 12 hours to obtain short amylose.

[0035] S3. Mix the short-chain starch and gellan gum from S2 at a mass ratio of 8:1 and disperse them in deionized water. Stir the mixture in a constant temperature water bath at 80°C at a stirring rate of 300 r / min for 30 min until completely dissolved to obtain a pregel solution.

[0036] S4. Inject the pregel solution obtained in S3 into the dispersed phase channel of the microfluidic device. The inner diameter of the dispersed phase channel is 0.5 mm, and the flow rate of the dispersed phase is 0.5 mL / min. Inject the calcium chloride solution into the continuous phase channel of the microfluidic device. The inner diameter of the continuous phase channel is 1.5 mm, and the flow rate of the continuous phase is 5 mL / min. Start the syringe pump to form uniform droplets of the pregel solution in the dispersed phase channel into the calcium chloride solution in the continuous phase channel.

[0037] S5. Transfer the droplets obtained in S4 to a calcium chloride solution and allow them to stand for cross-linking and curing. The cross-linking and curing temperature is 25℃ and the cross-linking and curing time is 2h to obtain short-chain starch-gellan gum resistant starch beads.

[0038] S6. The short-chain starch-gellan gum resistant starch beads obtained in S5 were spread in a single layer in a stainless steel tray and frozen at -18℃ for 6 hours. After freezing, they were crushed at -10℃ for 5 times. After thawing at 40℃, they were sieved to obtain low-crushing starch microspheres with a particle size of 1000μm.

[0039] Example 2 S1. Disperse 15% starch (waxy corn starch with amylopectin content ≥95%) in water, and decrystallize at 95℃ with stirring for 30 min at a stirring rate of 200 r / min to obtain a starch paste solution. After cooling to 55℃, add phosphate buffer to adjust the pH to 5.0, add pullulanase (enzyme activity ≥1000 U / g), and perform enzymatic hydrolysis at isothermal followed by high-temperature inactivation. The amount of pullulanase added is 0.2% of the starch mass. Concentrate under reduced pressure to obtain a concentrated solution.

[0040] S2. Add 3 times the volume of anhydrous ethanol to the concentrate obtained in S1 for alcohol extraction. The solid content in the concentrate is 35%. After standing for 2.5 hours, filter and collect the precipitate. Dry it with hot air at 40°C for 12 hours to obtain short amylose.

[0041] S3. Mix the short-chain starch and gellan gum from S2 at a mass ratio of 9:1 and disperse them in deionized water. Stir the mixture in a constant temperature water bath at 80°C at a stirring rate of 400 r / min for 40 min until completely dissolved to obtain a pregel solution.

[0042] S4. Inject the pregel solution obtained in S3 into the dispersed phase channel of the microfluidic device. The inner diameter of the dispersed phase channel is 0.6 mm, and the flow rate of the dispersed phase is 0.9 mL / min. Inject the calcium chloride solution into the continuous phase channel of the microfluidic device. The inner diameter of the continuous phase channel is 1.8 mm, and the flow rate of the continuous phase is 6 mL / min. Start the syringe pump to form uniform droplets of the pregel solution in the dispersed phase channel into the calcium chloride solution in the continuous phase channel.

[0043] S5. Transfer the droplets obtained in S4 to a calcium chloride solution and allow them to stand for cross-linking and curing. The cross-linking and curing temperature is 30℃ and the cross-linking and curing time is 2.5h to obtain short-chain starch-gellan gum resistant starch beads.

[0044] S6. The short-chain starch-gellan gum resistant starch beads obtained in S5 were spread in a single layer in a stainless steel tray and frozen at -15℃ for 6 hours. After freezing, they were crushed at -8℃ for 10 times. After thawing at 50℃, they were sieved to obtain medium-crushed starch microspheres with a particle size of 800μm.

[0045] Example 3 S1. Disperse 20% starch (waxy corn starch with amylopectin content ≥95%) in water, and decrystallize at 95℃ with stirring at a rate of 300 r / min for 40 min to obtain a starch paste solution. After cooling to 55℃, add phosphate buffer to adjust the pH to 4.7, add pullulanase (enzyme activity ≥1000 U / g), and perform enzymatic hydrolysis at isothermal followed by high-temperature inactivation. The amount of pullulanase added is 0.3% of the starch mass. Concentrate under reduced pressure to obtain a concentrated solution.

[0046] S2. Add 3 times the volume of anhydrous ethanol to the concentrate obtained in S1 for alcohol extraction. The solid content in the concentrate is 35%. After standing for 3 hours, filter and collect the precipitate. Dry it with hot air at 45°C for 16 hours to obtain short amylose.

[0047] S3. Mix the short-chain starch and gellan gum from S2 at a mass ratio of 10:1 and disperse them in deionized water. Stir the mixture in a constant temperature water bath at 75-80℃ at a stirring rate of 400 r / min for 10 min until completely dissolved to obtain a pregel solution.

[0048] S4. Inject the pregel solution obtained in S3 into the dispersed phase channel of the microfluidic device. The inner diameter of the dispersed phase channel is 0.7 mm, and the flow rate of the dispersed phase is 0.8 mL / min. Inject the calcium chloride solution into the continuous phase channel of the microfluidic device. The inner diameter of the continuous phase channel is 1.6 mm, and the flow rate of the continuous phase is 5.5 mL / min. Start the syringe pump to form uniform droplets of the pregel solution in the dispersed phase channel into the calcium chloride solution in the continuous phase channel.

[0049] S5. Transfer the droplets obtained in S4 to a calcium chloride solution and allow them to stand for cross-linking and curing. The cross-linking and curing temperature is 25℃ and the cross-linking and curing time is 2h to obtain short-chain starch-gellan gum resistant starch beads.

[0050] S6. The short-chain starch-gellan gum resistant starch beads obtained in S5 were spread in a single layer in a stainless steel tray and frozen at -20℃ for 6 hours. After freezing, they were crushed at -10℃ for 20 times. After thawing at 50℃, they were sieved to obtain highly crushable starch microspheres with a particle size of 260μm.

[0051] Comparative Example 1 The difference between this comparative example and Example 1 is that step S6 was not performed, while the rest of the steps were the same as in Example 1, resulting in complete short-chain starch-gellan gum resistant starch beads.

[0052] Comparative Example 2 Waxy corn starch with a branched-chain starch content ≥95%.

[0053] Comparative Example 3 The difference between this comparative example and Example 1 is that steps S3-S6 were not performed, while the rest were the same as in Example 1, resulting in short amylose.

[0054] Comparative Example 4 The difference between this comparative example and Example 1 is that steps S4-S6 were not performed; the rest of the steps are the same as in Example 1, resulting in a pre-gel solution.

[0055] Performance testing a. SEM tests were performed on the fragmented starch microspheres obtained in Examples 1-3 and the short-chain amylose-gellan gum-resistant starch beads obtained in the comparative example. The results are as follows: Figure 1-8 As shown, in Examples 1-3, the multi-point chelation crosslinking of gellan gum and calcium ions forms a dense gel network. Combined with the moderate destruction (rather than complete rupture) of the gel structure by the freezing pretreatment, although the spherical structure of the starch microspheres is completely destroyed after the starch microspheres are broken to different degrees in Examples 1-3, the surface of the broken starch microspheres still has the broken shell of gellan gum, and the core anti-digestion structure of short amylose wrapped by the crosslinked skeleton of gellan gum is still retained inside the broken starch microspheres.

[0056] b. In vitro digestion tests were performed on the fragmented starch microspheres obtained in Examples 1-3 and the waxy corn starch, short amylose, and pregel solutions in Comparative Examples 2-4. 0.2 g of sample was placed in 18 mL of sodium acetate buffer, 6-8 glass beads were added, the mixture was incubated in a boiling water bath for 30 min, cooled to 37°C, and 2 mL of enzyme solution (trypsin and glucoamylase) was added. 0.1 mL of sample solution was taken at 0 min, 20 min, and 120 min, and 0.9 mL of 90% ethanol solution was added. After centrifugation at 7710 rpm, 0.1 mL of the supernatant was taken and 3 mL of GOPOD solution was added. The mixture was reacted at 45°C in the dark for 20 min, and the absorbance was measured at 510 nm. The contents of rapidly digestible starch, slowly digestible starch, and resistant starch in the samples are shown in Table 1.

[0057] Table 1 Performance data of Examples 1-3 and Comparative Examples 2-4

[0058] As shown in Table 1, the broken starch microspheres in Examples 1-3 still exhibited good resistance to digestion compared to the original short-chain starch after chewing. The resistance gradually decreased with increasing chewing frequency, indicating that this simulated chewing method is meaningful and can achieve the effect of simulating chewing to a certain extent. This provides experimental evidence for the preparation of low-GI foods to meet the needs of diabetic patients.

[0059] Therefore, this invention employs the above-mentioned highly digestible broken starch microspheres, their preparation method, and their application. By using a freeze-breakage combined technology to process short-chain amylose-gellan gum resistant starch beads, even highly broken starch microspheres still achieve an RS content of 14.63%, completely breaking through the traditional understanding that breakage leads to the destruction of the starch's digestibility structure and a sharp drop in RS content.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing highly digestible, fragmented starch microspheres, characterized in that: Includes the following steps: S1. Disperse starch in water, decrystallize at high temperature to obtain starch paste solution, cool and adjust pH to 3-5.5, add pullulanase for enzymatic hydrolysis at constant temperature and then inactivate at high temperature, concentrate under reduced pressure to obtain concentrated solution. S2. Add anhydrous ethanol to the concentrated solution obtained in S1 for alcohol extraction. After standing, filter and collect the precipitate. Dry with hot air to obtain short-chain starch. S3. Mix the short-chain starch and gellan gum from S2 and disperse them in deionized water. Stir the mixture in a constant temperature water bath until completely dissolved to obtain a pregel solution. S4. Inject the pregel solution obtained in S3 into the dispersed phase channel of the microfluidic device, inject the calcium chloride solution into the continuous phase channel of the microfluidic device, and start the injection pump to form uniform droplets of the pregel solution in the dispersed phase channel into the calcium chloride solution in the continuous phase channel. S5. Transfer the droplets obtained in S4 to a calcium chloride solution, allow them to stand and cross-link and solidify to obtain short-chain starch-gellan gum resistant starch beads. S6. The short-chain starch-gellan gum resistant starch beads obtained in S5 are frozen and then subjected to gradient crushing. After thawing, they are sieved to obtain crushed starch microspheres.

2. The method for preparing highly digestible, fragmented starch microspheres according to claim 1, characterized in that: In S1, high-temperature decrystallization involves stirring at 90-110℃ for 30-40 minutes at a stirring rate of 200-300 r / min and cooling at 55-60℃.

3. The method for preparing highly digestible, fragmented starch microspheres according to claim 1, characterized in that: In S1, pullulanase is added at a rate of 0.1-0.5% of starch mass, and the enzyme activity of pullulanase is ≥1000U / g.

4. The method for preparing highly digestible, fragmented starch microspheres according to claim 1, characterized in that: In S2, the solid content in the concentrate is 30-40%, the hot air drying temperature is 40-45℃, and the hot air drying time is 12-16h.

5. The method for preparing highly digestible, fragmented starch microspheres according to claim 1, characterized in that: In S3, the mass ratio of short-chain starch to gellan gum is 8-10:1, the temperature of the constant temperature water bath is 75-80℃, the stirring speed is 300-400 r / min, and the stirring time is 10-40 min.

6. The method for preparing highly digestible, fragmented starch microspheres according to claim 1, characterized in that: In S4, the inner diameter of the dispersed phase channel is 0.5-0.8 mm, the flow rate of the dispersed phase is 0.5-1.0 mL / min, the inner diameter of the continuous phase channel is 1.5-2.0 mm, and the flow rate of the continuous phase is 5-8 mL / min.

7. The method for preparing highly digestible, fragmented starch microspheres according to claim 1, characterized in that: In S5, the cross-linking curing temperature is 20-30℃, and the cross-linking curing time is 2-3h.

8. The method for preparing highly digestible, fragmented starch microspheres according to claim 1, characterized in that: In S6, the freezing temperature is -20℃ to -15℃, the freezing time is 4-6h, the gradient crushing is one of low crushing degree, medium crushing degree and high crushing degree, the gradient crushing temperature is -10℃ to -5℃, and the thawing temperature is 40-50℃.

9. A highly resistant, brittle starch microsphere, characterized in that: The microspheres are prepared using the method for preparing highly digestible broken starch microspheres as described in any one of claims 1-8, wherein the broken starch microspheres are one of low-broken starch microspheres, medium-broken starch microspheres, and high-broken starch microspheres.

10. The application of a highly digestible, fragmented starch microsphere, characterized in that: The highly digestible, fragmented starch microspheres as described in claim 9 are applied in food processing.

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