Composite gel based on hydrogen bond reconstruction and directional crosslinking as well as preparation method and application of composite gel

Abstract

The invention discloses composite gel based on hydrogen bond reconstruction and directional crosslinking as well as a preparation method and application of the composite gel, and relates to the technical field of gel preparation. The preparation method comprises the following steps: mixing a sodium alginate solution with a cyclodextrin solution to obtain a mixed solution; the mixed solution is added into a first container, the first container is placed in a second container, and the bottom of the first container is provided with a cation exchange membrane communicated with the second container; a D-(+)-gluconic acid-delta-lactone solution and a nano calcium carbonate solution are added into the second container until the D-(+)-gluconic acid-delta-lactone solution and the nano calcium carbonate solution submerge the cation exchange membrane, calcium ions generated by the reaction of the D-(+)-gluconic acid-delta-lactone solution and the nano calcium carbonate solution enter the first container through the cation exchange membrane to react with the mixed solution, and the composite gel is obtained. Compared with common gel prepared by mixing, the bottom section of the composite gel prepared based on hydrogen bond reconstruction and directional crosslinking presents a more uniform and compact adsorption pore structure, and efficient adsorption of EGCG molecules is facilitated.

Description

Technical Field

[0001] This invention relates to the field of gel preparation technology, specifically to a composite gel based on hydrogen bond reconstruction and directional crosslinking, its preparation method, and its application. Background Technology

[0002] Epigallocatechin gallate (EGCG), the main active polyphenol in green tea, is easily oxidized and deactivated, and has low bioavailability. It needs to be stably loaded and controlled released through carrier materials. At the same time, its bitter taste is obvious, which is difficult for consumers to accept.

[0003] Currently, existing technologies typically use sodium alginate gel or cyclodextrin gel alone to encapsulate polyphenols. Sodium alginate is a natural polysaccharide compound extracted from kelp or seaweed, possessing good biocompatibility, biodegradability, and adsorption properties. Its molecular chain contains abundant hydroxyl and carboxyl groups, enabling it to effectively adsorb polyphenols through mechanisms such as ion exchange and coordination. Furthermore, sodium alginate forms a gel at low pH values, exhibiting thermal irreversibility, making it suitable for preparing stable adsorbent materials. It can be combined with other materials to improve its adsorption performance and mechanical strength. Cyclodextrin is a cyclic oligosaccharide composed of glucose units, possessing a unique "externally hydrophilic and internally hydrophobic" structure. It can form inclusion complexes with various organic molecules through host-guest interactions, thereby improving its solubility, stability, and selective adsorption capacity. Its structure is a hollow cylindrical shape; α-, β-, and γ-cyclodextrins are composed of 6, 7, and 8 glucose units, respectively, exhibiting different cavity sizes and solubilities. While sodium alginate gel or cyclodextrin gel can encapsulate polyphenols, sodium alginate gel suffers from drawbacks such as weak mechanical strength, uncontrollable degradation in physiological environments, and uncontrollable cross-linking rates, resulting in uneven gel formation and an inability to mask the bitterness of polyphenols. Using cyclodextrin gels to encapsulate polyphenols may lead to mismatched cavity sizes and low encapsulation rates. Therefore, existing gel technologies cannot meet the requirements for loading and controlled release of active polyphenols, nor can they effectively mask the bitterness of polyphenols. Summary of the Invention

[0004] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a composite gel based on hydrogen bond reconstruction and directional crosslinking, its preparation method and application, specifically a composite gel based on hydrogen bond reconstruction and directional crosslinking, its preparation method and application, and more specifically an EGCG bitterness-shielding gel based on hydrogen bond reconstruction and directional crosslinking and its preparation method.

[0005] This invention addresses the limitations of existing carrier materials in masking the bitterness of polyphenols and the defects in the structural design of adsorption carriers by proposing a sodium alginate composite gel carrier and its preparation method. By adding glycerol, sodium alginate and cyclodextrin undergo a dynamic reconstruction of the hydrogen bond network through "breaking strong hydrogen bonds → exposing hydroxyl groups → bridging and recombination," intensifying protonation and forming "molecular bridges." This results in a more robust network structure in the composite gel, thereby improving its ability to capture and load polyphenol (e.g., EGCG) molecules. Simultaneously, a directional permeation migration device effectively controls the gel crosslinking rate, resulting in more uniform crosslinking of the prepared gel and facilitating the formation of "bottom-up" adsorption channels, effectively enhancing the adsorption effect of polyphenols (e.g., EGCG). This technology can provide theoretical and technical reference for the resource utilization of industrial waste tea water.

[0006] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a method for preparing a composite gel, comprising the following steps: S1. Sodium alginate is added to water to prepare a sodium alginate solution; cyclodextrin is added to water to prepare a cyclodextrin solution; the sodium alginate solution and the cyclodextrin solution are mixed to obtain a mixed solution; S2. The mixed solution is added to a first container, wherein the first container is placed in a second container, and the bottom of the first container has a cation exchange membrane communicating with the second container; S3. D-(+)-gluconic acid-δ-lactone is added to water to prepare a D-(+)-gluconic acid-δ-lactone solution; nano-calcium carbonate is added to the nano-calcium carbonate solution in water; the D-(+)-gluconic acid-δ-lactone solution and the nano-calcium carbonate solution are added to the second container until they cover the cation exchange membrane. The calcium ions generated by the reaction of the D-(+)-gluconic acid-δ-lactone solution and the nano-calcium carbonate solution enter the first container through the cation exchange membrane and react with the mixed solution to obtain a composite gel.

[0007] Optionally, the molar ratio of sodium alginate to cyclodextrin is 1~2:1~2.

[0008] Optionally, the molar ratio of calcium ions in the nano-calcium carbonate to carboxyl groups in the sodium alginate is 1.5~2.5:1, and the molar ratio of nano-calcium carbonate to D-(+)-gluconic acid-δ-lactone is 4~6:3.

[0009] Optionally, step S1 further includes adding a glycerol solution. When adding a glycerol solution, step S1 includes the following specific steps: A sodium alginate solution was prepared by adding sodium alginate to water; a cyclodextrin solution was prepared by adding cyclodextrin to water; a glycerol solution was prepared by adding glycerol to water; the sodium alginate solution, the cyclodextrin solution, and the glycerol solution were mixed to obtain a mixed solution.

[0010] Optionally, the ratio of sodium alginate to glycerol is 2g~3g:1.3mL~2.3mL.

[0011] Optionally, step S3 includes the following specific steps: D-(+)-gluconic acid-δ-lactone was added to water to prepare a D-(+)-gluconic acid-δ-lactone solution; nano-calcium carbonate was added to water to prepare a nano-calcium carbonate solution; Add the nano-calcium carbonate solution to the second container until it covers the cation exchange membrane but does not cover the top of the first container; The D-(+)-gluconic acid-δ-lactone solution is slowly added to the second container at a rate of 0.05 mL / min to 0.15 mL / min. The calcium ions generated by the reaction of the D-(+)-gluconic acid-δ-lactone solution and the nano calcium carbonate solution in the second container enter the first container through the cation exchange membrane and react with the mixed solution to obtain a composite gel.

[0012] Secondly, the present invention provides a composite gel based on hydrogen bond reconstruction and directional crosslinking, which is obtained by the preparation method described above.

[0013] Preferably, the composite gel has adsorption channels extending from the bottom to the top of the composite gel.

[0014] Thirdly, the present invention provides a composite gel obtained by the preparation method described above, or the application of the composite gel described above in the adsorption and / or loading and / or controlled release of polyphenols.

[0015] Preferably, the application includes using the composite gel to adsorb epigallocatechin gallate in industrial waste tea water. The composite gel achieves an adsorption rate of 91.09 ± 3.20% for epigallocatechin gallate within 24 hours and can mask the bitterness of epigallocatechin gallate.

[0016] This invention has at least one of the following beneficial effects: 1. This invention uses sodium alginate and cyclodextrin as raw materials to prepare a composite gel. Specifically, it optimizes the size of the cyclodextrin cavity to better shield the bitterness of polyphenols such as EGCG, taking into account their structural characteristics. Furthermore, by placing a cation exchange membrane at the bottom of a first container, calcium ions are generated through the reaction of D-(+)-gluconic acid-δ-lactone solution and the nano-calcium carbonate solution. These calcium ions pass through the cation exchange membrane and undergo directional cross-linking with sodium alginate and cyclodextrin. Therefore, this specially designed gel formation method with directional migration solves the problem of uneven preparation caused by excessively rapid gel cross-linking in traditional methods. It forms ordered pores with a "bottom-up" orientation within the gel, significantly improving the adsorption efficiency for polyphenols such as EGCG molecules. Compared to gels prepared by ordinary mixing, its bottom cross-section exhibits a more uniform and dense adsorption pore structure, which is conducive to the efficient adsorption of EGCG molecules, achieving an adsorption efficiency of 91.09 ± 3.20%. In oral simulated digestion experiments, it was found that this composite gel can effectively shield the bitterness of EGCG in the oral environment, showing promising application prospects. This technology can be further applied to the adsorption and enrichment of polyphenols such as EGCG in industrial waste tea water, realizing the secondary utilization of resources.

[0017] 2. This invention further incorporates glycerol as a raw material. The core innovation of this technology lies in using glycerol to treat the sodium alginate-cyclodextrin composite solution. Through a three-step mechanism of breaking strong hydrogen bonds → exposing hydroxyl groups → bridging and recombination, the hydrogen bond network between sodium alginate and cyclodextrin is enhanced. Glycerol competitively binds to break the original hydroxyl bonds, stretches the molecular chain structure, and uses its multi-hydroxyl structure to bridge and form a hydrogen bond recombination network again, thereby improving the adsorption effect of the composite gel on polyphenols such as EGCG and enhancing the shielding effect on the bitterness of EGCG. Attached Figure Description

[0018] Figure 1 The image shows the infrared spectrum of the composite gel prepared in this embodiment of the invention.

[0019] Figure 2 This is a radar image of the bitterness intensity detected by an electronic tongue after simulated oral digestion of the composite gel prepared in this embodiment of the invention.

[0020] Figure 3 This is a comparison chart of the adsorption efficiency of the composite gel prepared in the embodiments of the present invention for EGCG.

[0021] Figure 4The images shown are bottom cross-sectional SEM images of the composite gels prepared in the comparative examples and embodiments of the present invention. (A) is a bottom cross-sectional SEM image of SA-Gel prepared in Comparative Example 1; (B) is a bottom cross-section of G-SA-γ-CD-Gel prepared in Example 6 (wherein the specific amount of γ-cyclodextrin added is 0.0519 g); and (C) is a bottom oblique cross-sectional SEM image of G-SA-γ-CD-Gel prepared in Example 6 (wherein the specific amount of γ-cyclodextrin added is 0.0519 g). Detailed Implementation

[0022] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0023] An embodiment of the present invention provides a method for preparing a composite gel based on hydrogen bond reconstruction and directional crosslinking, comprising the following steps: S1. Sodium alginate is added to water to prepare a sodium alginate solution; cyclodextrin is added to water to prepare a cyclodextrin solution; the sodium alginate solution and the cyclodextrin solution are mixed to obtain a mixed solution; S2. The mixed solution is added to a first container, wherein the first container is placed in a second container, and the bottom of the first container has a cation exchange membrane communicating with the second container; S3. D-(+)-gluconic acid-δ-lactone is added to water to prepare a D-(+)-gluconic acid-δ-lactone solution; nano-calcium carbonate is added to the nano-calcium carbonate solution in water; the D-(+)-gluconic acid-δ-lactone solution and the nano-calcium carbonate solution are added to the second container until they cover the cation exchange membrane. The calcium ions generated by the reaction of the D-(+)-gluconic acid-δ-lactone solution and the nano-calcium carbonate solution enter the first container through the cation exchange membrane and react with the mixed solution to obtain a composite gel.

[0024] This invention optimizes the size of the cyclodextrin cavity to better mask the bitterness of EGCG, taking advantage of its structural characteristics. Furthermore, a specially designed gel-forming directional migration device is employed, solving the problem of uneven preparation caused by excessively rapid gel cross-linking in traditional methods. This device creates ordered pores within the gel with a bottom-up orientation, significantly improving the adsorption efficiency of EGCG molecules. This technology can be further applied to the adsorption and enrichment of EGCG in industrial waste tea water, achieving secondary utilization of the resource.

[0025] In some embodiments, the molar ratio of sodium alginate to cyclodextrin is 1~2:1~2; preferably 1:1~2, specifically 1:2, 1:1 or 2:1.

[0026] In some embodiments, the molar ratio of calcium ions in the nano-calcium carbonate to carboxyl groups in the sodium alginate is 1.5~2.5:1, and the molar ratio of nano-calcium carbonate to D-(+)-gluconic acid-δ-lactone is 4~6:3. Preferably, the molar ratio of calcium ions in the nano-calcium carbonate to carboxyl groups in the sodium alginate is 1.8~2.2:1, and the molar ratio of nano-calcium carbonate to D-(+)-gluconic acid-δ-lactone is 4.5~5.5:3. More preferably, the molar ratio of calcium ions in the nano-calcium carbonate to carboxyl groups in the sodium alginate is 2:1, and the molar ratio of nano-calcium carbonate to D-(+)-gluconic acid-δ-lactone is 5:3.

[0027] In some embodiments, step S1 further includes adding a glycerol solution. When adding a glycerol solution, step S1 includes the following specific steps: A sodium alginate solution was prepared by adding sodium alginate to water; a cyclodextrin solution was prepared by adding cyclodextrin to water; a glycerol solution was prepared by adding glycerol to water; the sodium alginate solution, the cyclodextrin solution, and the glycerol solution were mixed to obtain a mixed solution.

[0028] In some embodiments, the ratio of sodium alginate to glycerol is 2g~3g:1.3mL~2.3mL.

[0029] In some embodiments, step S3 includes the following specific steps: D-(+)-gluconic acid-δ-lactone was added to water to prepare a D-(+)-gluconic acid-δ-lactone solution; nano-calcium carbonate was added to water to prepare a nano-calcium carbonate solution; Add the nano-calcium carbonate solution to the second container until it covers the cation exchange membrane but does not cover the top of the first container; The D-(+)-gluconic acid-δ-lactone solution is slowly added to the second container at a rate of 0.05 mL / min to 0.15 mL / min. The calcium ions generated by the reaction of the D-(+)-gluconic acid-δ-lactone solution and the nano calcium carbonate solution in the second container enter the first container through the cation exchange membrane and react with the mixed solution to obtain a composite gel.

[0030] In some embodiments, the specific process for preparing a composite gel is as follows: (1) Add sodium alginate to water to prepare a sodium alginate solution with a mass fraction of 2.4%; add cyclodextrin to water according to the molar ratio of cyclodextrin (α, β, γ) to sodium alginate of 1:1, 1:2, 2:1 respectively, heat to prepare a cyclodextrin solution; add glycerol to water to prepare a glycerol solution with a volume fraction of 1.8%; after all solutions are completely dissolved by magnetic stirring, place them in beakers for later use.

[0031] (2) Place the tubing into the solution in step (1) and equip the tubing into a constant flow pump device. Set the flow rate to 0.5 mL / min and process for 30 min to the raw material mixing tube. Sodium alginate, glycerol and cyclodextrin are mixed in the raw material mixing tube to obtain a mixed solution.

[0032] (3) Turn on the ultrasonic generator and perform online ultrasonic mixing and defoaming treatment on the mixed solution in step (2).

[0033] (4) Open the twelve-way pressure start valve and simultaneously and evenly inject the mixed solution after step (3) into the silica gel mold (first container) with the bottom of the cation exchange membrane. After the liquid level is even, close the start valve.

[0034] (5) A glass device (second container) with a top opening is set below the cation exchange membrane. A nano-calcium carbonate solution is placed in the glass device in advance according to the molar ratio of calcium ions in nano-calcium carbonate to carboxyl groups in sodium alginate of 2:1.

[0035] (6) Using ice-pure water (-20 ℃), prepare D-(+)-gluconic acid-δ-lactone solution according to the molar ratio of calcium ions to D-(+)-gluconic acid-δ-lactone of 5:3. Draw 10 mL of D-(+)-gluconic acid-δ-lactone solution with a syringe, place it on the injection pump, and set the injection speed to 0.1 mL / min to inject D-(+)-gluconic acid-δ-lactone solution into the glass device in step (5).

[0036] (7) Immerse the cation exchange membrane at the bottom of the silicone mold completely into the nano calcium carbonate solution prepared in step (6), but at the same time keep the nano calcium carbonate solution from completely submerging the silicone mold. The calcium ions generated by the reaction of D-(+)-gluconic acid-δ-lactone solution with nano calcium carbonate enter the silicone mold through the cation exchange membrane and react with the mixed solution, and the gel begins to crosslink. (8) Form 12 bite-sized gels, each measuring 1.5 cm × 1.5 cm × 1.5 cm, in a silicone mold.

[0037] Another embodiment of the present invention provides a composite gel obtained by the preparation method described above.

[0038] The composite gel prepared by this invention has a good adsorption effect on polyphenols such as EGCG and a shielding effect on the bitterness of EGCG.

[0039] In some embodiments, the composite gel has adsorption channels extending from the bottom to the top of the composite gel.

[0040] Another embodiment of the present invention provides a composite gel obtained by the preparation method described above, or the application of the composite gel described above in the adsorption and / or loading and / or controlled release of polyphenols.

[0041] The composite gel of this invention can be used for the adsorption, loading and controlled release of active polyphenols, with an adsorption efficiency of 91.09 ± 3.20% for EGCG. In oral simulated digestion experiments, it was found that the composite gel can effectively shield the bitter taste of EGCG in the oral environment, showing good application prospects.

[0042] In some embodiments, the application includes using the composite gel to adsorb epigallocatechin gallate from industrial waste tea water. The composite gel achieves an adsorption rate of 91.09 ± 3.20% for epigallocatechin gallate within 24 hours and can mask the bitterness of epigallocatechin gallate.

[0043] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited to the following specific embodiments.

[0044] (-)-Epigallocatechin gallate (95%, Aladdin Reagent Shanghai Co., Ltd.), α, β, γ cyclodextrin (Beijing Solarbio Technology Co., Ltd.), nano calcium carbonate (Shanghai Maclean Biotech Co., Ltd.), D-(+)-glucono-δ-lactone (Aladdin Reagent Shanghai Co., Ltd.), sodium alginate (30 kJ, M:G=1:2, Shanghai Maclean Biotech Co., Ltd.), glycerol (Shanghai Maclean Biotech Co., Ltd.).

[0045] Example 1 This embodiment provides a method for preparing a composite gel, specifically a method for preparing a sodium alginate-α-cyclodextrin composite gel (SA-α-Gel), comprising the following steps: Weigh 1.6 g of sodium alginate and dissolve it in 100 mL of ultrapure water. Stir on a magnetic stirrer at 500 rpm and 40 ℃ for 2 hours until completely dissolved. Set aside. Weigh 0.0518 g, 0.0260 g, and 0.1038 g of α-cyclodextrin respectively and dissolve them in 100 mL of ultrapure water. Stir on a magnetic stirrer (500 rpm, 40 ℃) until completely dissolved. Set aside separately. Introduce the sodium alginate solution and α-cyclodextrin solution into a constant flow pump device through tubing. Set the flow rate to 0.5 mL / min and process for 30 min to ensure thorough mixing of the raw materials in the mixing tube. Then, turn on the ultrasonic generator to perform online ultrasonic mixing and defoaming treatment of the mixture. Open the 12-port pressure start valve and simultaneously and evenly inject the mixture into a silica gel mold with a cation exchange membrane at the bottom. After the liquid level is reached, close the start valve. 0.2024 g of nano-calcium carbonate was weighed and dissolved in 100 mL of ultrapure water. The solution was stirred until homogeneous and then transferred to a glass apparatus. 10 g of D-(+)-gluconic acid-δ-lactone powder was weighed and dissolved in 100 mL of ice-cold ultrapure water (-20 ℃) ​​to prepare a D-(+)-gluconic acid-δ-lactone solution. 10 mL of the D-(+)-gluconic acid-δ-lactone solution was drawn using a syringe and placed on a syringe pump with an injection rate of 0.1 mL / min. The cation exchange membrane at the bottom of the silicone mold was completely immersed in the nano-calcium carbonate solution, but the silicone mold itself was not completely submerged. The D-(+)-gluconic acid-δ-lactone solution reacted with the nano-calcium carbonate, and the generated calcium ions entered the mixed liquid through the cation exchange membrane, initiating gel cross-linking and forming "bottom-up" adsorption channels inside the gel. Ultimately, twelve 1.5 cm × 1.5 cm × 1.5 cm single-serving composite gels were formed in the silicone mold.

[0046] To test the adsorption rate of the composite gel for EGCG and its effect on masking bitterness, the following experiments were conducted: Adsorption efficiency: The mold was removed, the bottom cation exchange membrane was removed, and the composite gel was immersed in an EGCG aqueous solution with an initial concentration of 3 mg / mL for 24 hours for adsorption. After adsorption, the EGCG aqueous solution was collected, centrifuged and filtered to remove impurities, and the remaining concentration was determined at 274 nm (y = 25.536x + 0.0268, R² = 0.999) using a standard curve. The adsorption efficiency was calculated using the formula (initial concentration - remaining concentration) / remaining concentration × 100%.

[0047] Bitterness Response Value: The bitterness response value of EGCG was tested using an electronic tongue method. EGCG solutions without gel adsorption and EGCG aqueous solutions adsorbed with different composite gels (after simulated oral digestion) were sequentially injected into the test cell. Detection parameters were set (sampling time: 120 s, signal acquisition frequency: 1 Hz, temperature: 25℃). The sensor response signal was recorded, and the sensor was rinsed with deionized water between tests until the baseline stabilized. The characteristic peak signal value of bitterness was extracted, and the bitterness response intensity was calculated using a tasteless blank solution as a reference.

[0048] Experimental results showed that when the molar ratio of sodium alginate to α-cyclodextrin was 1:1, 1:2, and 2:1, the adsorption rates of the composite gel for EGCG within 24 hours reached 33.28 ± 0.28%, 38.58 ± 1.25%, and 30.24 ± 2.23%, respectively. After simulated oral digestion, the bitter taste response values ​​of EGCG detected by the electronic tongue were 0.35, 0.30, and 0.43, respectively, which were reduced by 77.0%, 80.3%, and 71.7% compared with EGCG without gel adsorption.

[0049] Example 2 This embodiment provides a method for preparing a composite gel, specifically a method for preparing a sodium alginate-β-cyclodextrin composite gel (hereinafter referred to as "SA-β-Gel"). The difference from Example 1 is that α-cyclodextrin in Example 1 is replaced with β-cyclodextrin, while the other processes are basically the same as in Example 1.

[0050] The specific steps of Example 2 are as follows: Weigh 1.6 g of sodium alginate and dissolve it in 100 mL of ultrapure water. Stir on a magnetic stirrer at 500 rpm and 40 ℃ for 2 hours until completely dissolved. Set aside. Weigh 0.0606 g, 0.0302 g, and 0.1212 g of β-cyclodextrin respectively and dissolve them in 100 mL of ultrapure water. Stir on a magnetic stirrer (500 rpm, 40 ℃) until completely dissolved. Set aside separately. Introduce the sodium alginate solution and β-cyclodextrin solution into a constant flow pump device through tubing. Set the flow rate to 0.5 mL / min and process for 30 min to ensure thorough mixing of the raw materials in the mixing tube. Then, turn on the ultrasonic generator to perform online ultrasonic mixing and defoaming treatment of the mixture. Open the 12-port pressure start valve and simultaneously and evenly inject the mixture into a silica gel mold with a cation exchange membrane at the bottom. After the liquid level is reached, close the start valve. Weigh 0.2024 g of nano-calcium carbonate and dissolve it in 100 mL of ultrapure water, stirring until the solution is homogeneous. Transfer the solution to a glass apparatus. Weigh 10 g of D-(+)-gluconic acid-δ-lactone powder and dissolve it in 100 mL of ice-cold ultrapure water (-20 ℃) ​​to prepare a D-(+)-gluconic acid-δ-lactone solution. Draw 10 mL of the D-(+)-gluconic acid-δ-lactone solution into a syringe and place it on a syringe pump, setting the injection rate to 0.1 mL / min. Completely immerse the cation exchange membrane at the bottom of the silicone mold in the nano-calcium carbonate solution, but do not completely submerge the silicone mold. The D-(+)-gluconic acid-δ-lactone solution reacts with the nano-calcium carbonate, and the generated calcium ions enter the mixed liquid through the cation exchange membrane, initiating gel cross-linking and forming "bottom-up" adsorption channels inside the gel. Finally, 12 bite-sized gels, each 1.5 cm × 1.5 cm × 1.5 cm, are formed in the silicone mold.

[0051] Experimental results showed that when the molar ratio of sodium alginate to β-cyclodextrin was 1:1, 1:2, and 2:1, the adsorption rates of EGCG by the composite gel within 24 hours reached 45.40 ± 1.70%, 52.40 ± 2.71%, and 40.40 ± 1.90%, respectively. After oral simulated digestion, the bitter taste response values ​​of the EGCG aqueous solution adsorbed by the composite gel were 0.15, 0.11, and 0.21, respectively, as detected by the electronic tongue. Compared with EGCG without gel adsorption, the bitter taste response was reduced by 90.1%, 92.8%, and 86.2%, respectively.

[0052] Comparing the results with those of Example 1, it can be seen that the composite gel prepared in Example 2 has a significantly increased adsorption rate for EGCG, while the bitterness response value is also significantly reduced. Therefore, compared with the composite gel prepared by sodium alginate and α-cyclodextrin, the composite gel prepared by sodium alginate and β-cyclodextrin has a higher adsorption rate for EGCG and a better effect on blocking bitterness.

[0053] Example 3 This embodiment provides a method for preparing a composite gel, specifically a method for preparing a sodium alginate-γ-cyclodextrin composite gel (hereinafter referred to as "SA-γ-Gel"). The difference from Example 1 is that the α-cyclodextrin in Example 1 is replaced with γ-cyclodextrin, while the other processes are basically the same as in Example 1.

[0054] The specific steps of Example 3 are as follows: Weigh 1.6 g of sodium alginate and dissolve it in 100 mL of ultrapure water. Stir the solution on a magnetic stirrer at 500 rpm and 40 ℃ for 2 hours until completely dissolved. Set aside. Weigh 0.0692 g, 0.0346 g, and 0.1384 g of γ-cyclodextrin, respectively, and dissolve them in 100 mL of ultrapure water. Stir the solutions on a magnetic stirrer (500 rpm, 40 ℃) until completely dissolved. Set aside separately. Introduce the sodium alginate solution and γ-cyclodextrin solution into a constant flow pump device through tubing. Set the flow rate to 0.5 mL / min and process for 30 min to ensure thorough mixing of the raw materials in the mixing tube. Then, turn on the ultrasonic generator to perform online ultrasonic mixing and defoaming of the mixture. Open the 12-port pressure start valve and simultaneously and evenly inject the mixture into a silica gel mold with a cation exchange membrane at the bottom. After the liquid level is reached, close the start valve. 0.2024 g of nano-calcium carbonate was weighed and dissolved in 100 mL of ultrapure water. The solution was stirred until homogeneous and then transferred to a glass apparatus. 10 g of D-(+)-gluconic acid-δ-lactone powder was weighed and dissolved in 100 mL of ice-cold ultrapure water (-20 ℃) ​​to prepare a D-(+)-gluconic acid-δ-lactone solution. 10 mL of the D-(+)-gluconic acid-δ-lactone solution was drawn using a syringe and placed on a syringe pump with an injection rate of 0.1 mL / min. The cation exchange membrane at the bottom of the silicone mold was completely immersed in the nano-calcium carbonate solution, but the silicone mold itself was not completely submerged. The D-(+)-gluconic acid-δ-lactone solution reacted with the nano-calcium carbonate, and the generated calcium ions entered the mixed liquid through the cation exchange membrane, initiating gel cross-linking and forming "bottom-up" adsorption channels inside the gel. Ultimately, twelve 1.5 cm × 1.5 cm × 1.5 cm bite-sized gels were formed in the silicone mold. Remove the mold, remove the bottom cation exchange membrane, and immerse it in a 3 mg / mL EGCG aqueous solution for adsorption for 24 hours.

[0055] Experimental results showed that when the molar ratios of sodium alginate to γ-cyclodextrin were 1:1, 1:2, and 2:1, the adsorption rates reached 62.09 ± 2.50%, 68.09 ± 1.54%, and 60.00 ± 1.00% respectively within 24 hours. After oral simulated digestion, the EGCG aqueous solution adsorbed by the composite gel showed bitterness response values ​​of -0.02, -0.05, and -0.01 detected by the electronic tongue, proving that bitterness was completely blocked.

[0056] Comparing the results with those of Examples 1 and 2, it can be seen that the adsorption rate of EGCG by the composite gel prepared in Example 3 is significantly better than that of Examples 1 and 2. At the same time, the bitterness response value is also significantly lower than that of Examples 1 and 2. Therefore, compared with α-cyclodextrin and β-cyclodextrin, the composite gel prepared by γ-cyclodextrin and sodium alginate has a higher adsorption rate of EGCG and a better effect on blocking bitterness, and can completely block bitterness.

[0057] Therefore, as can be seen from Examples 1 to 3, all three cyclodextrins—α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin—can be combined with sodium alginate to prepare composite gels with good adsorption effects and the ability to mask bitterness. In comparison, the composite gel prepared by γ-cyclodextrin and sodium alginate has the best effect, followed by β-cyclodextrin, and lastly α-cyclodextrin.

[0058] Example 4 This embodiment provides a method for preparing a composite gel, specifically a method for preparing a glycerol-sodium alginate-α-cyclodextrin composite gel (referred to as "G-SA-α-Gel"). The difference from Example 1 is that glycerol is added in addition to the method in Example 1, while the other processes are basically the same as in Example 1.

[0059] The specific steps of Example 4 are as follows: Weigh 2.4 g of sodium alginate and dissolve it in 100 mL of ultrapure water. Stir the solution on a magnetic stirrer at 500 rpm and 40 °C for 2 hours until completely dissolved. Set aside. Weigh 0.0777 g, 0.0390 g, and 0.1557 g of α-cyclodextrin, respectively, and dissolve them in 100 mL of ultrapure water. Stir the solutions on a magnetic stirrer at 500 rpm and 40 °C until completely dissolved. Set aside. Add 1.8 mL of glycerol to 98.2 mL of ultrapure water and stir magnetically until homogeneous. Set aside. Introduce the sodium alginate, α-cyclodextrin, and glycerol solutions into a constant flow pump via tubing. Set the flow rate to 0.5 mL / min and process for 30 min to ensure thorough mixing of the materials in the mixing tube. Then, turn on the ultrasonic generator to perform online ultrasonic mixing and defoaming of the mixture. Next, open the 12-port pressure start valve to evenly inject the mixed liquid into the silica gel mold with the cation exchange membrane at the bottom. Once the liquid level is even, close the start valve. Separately, dissolve 0.2024 g of nano-calcium carbonate in 100 mL of ultrapure water, stir until the solution is homogeneous, and then transfer it to a glass apparatus. Weigh 10 g of D-(+)-gluconic acid-δ-lactone powder and dissolve it in 100 mL of ice-cold ultrapure water (-20 ℃) ​​to prepare a 100 mg / mL D-(+)-gluconic acid-δ-lactone solution. Draw 10 mL of this solution using a syringe, place it on a syringe pump, and set the injection rate to 0.1 mL / min. Completely immerse the cation exchange membrane at the bottom of the silica gel mold in the nano-calcium carbonate solution, but ensure the silica gel mold is not completely submerged. At this point, the D-(+)-gluconic acid-δ-lactone solution reacts with nano-calcium carbonate, and the generated calcium ions enter the mixed liquid through the cation exchange membrane, initiating gel cross-linking and forming "bottom-up" adsorption channels inside the gel. Ultimately, twelve 1.5 cm × 1.5 cm × 1.5 cm bite-sized gels are formed in the silica gel mold. After removing the mold and the bottom cation exchange membrane, the gels are immersed in a 3 mg / mL EGCG aqueous solution for 24 hours for adsorption.

[0060] Experimental results showed that when the molar ratio of sodium alginate to α-cyclodextrin was 1:1, 1:2, and 2:1, the adsorption rates of EGCG by the composite gel within 24 hours reached 44.31 ± 1.50%, 48.58 ± 1.80%, and 42.21 ± 0.89%, respectively. After oral simulated digestion experiments, the bitterness response values ​​of the EGCG aqueous solution adsorbed by the composite gel were measured to be 0.22, 0.16, and 0.34 in electronic tongue detection, respectively. Compared with EGCG without gel adsorption, the bitterness response values ​​were reduced by 85.5%, 89.5%, and 77.6%, respectively.

[0061] Comparing the results with those of Example 1, it can be seen that the adsorption rate of EGCG in the composite gel prepared by adding glycerol in Example 4 is significantly increased, while the bitterness response value is also significantly reduced. Therefore, compared with the sodium alginate-cyclodextrin composite gel, the glycerol-sodium alginate-cyclodextrin composite gel has a higher adsorption rate of EGCG and a better effect on blocking bitterness.

[0062] Example 5 This embodiment provides a method for preparing a composite gel, specifically a method for preparing a glycerol-sodium alginate-β-cyclodextrin composite gel (referred to as "G-SA-β-Gel"). The difference from Example 2 is that glycerol is added in addition to the method in Example 2, while the other processes are basically the same as in Example 2.

[0063] The specific steps of Example 5 are as follows: Weigh 2.4 g of sodium alginate and dissolve it in 100 mL of ultrapure water. Stir the solution on a magnetic stirrer at 500 rpm and 40 °C for 2 hours until completely dissolved. Set aside. Weigh 0.0909 g, 0.0453 g, and 0.1818 g of β-cyclodextrin, respectively, and dissolve them in 100 mL of ultrapure water. Stir the solutions on a magnetic stirrer at 500 rpm and 40 °C until completely dissolved. Set aside. Add 1.8 mL of glycerol to 98.2 mL of ultrapure water and stir magnetically until homogeneous. Set aside. Introduce the sodium alginate, β-cyclodextrin, and glycerol solutions into a constant flow pump via tubing. Set the flow rate to 0.5 mL / min and process for 30 min to ensure thorough mixing of the materials in the mixing tube. Then, turn on the ultrasonic generator to perform online ultrasonic mixing and defoaming of the mixture. Next, open the 12-port pressure start valve to evenly inject the mixed liquid into the silica gel mold with the cation exchange membrane at the bottom. Once the liquid level is even, close the start valve. Separately, dissolve 0.2024 g of nano-calcium carbonate in 100 mL of ultrapure water, stir until the solution is homogeneous, and then transfer it to a glass apparatus. Weigh 10 g of D-(+)-gluconic acid-δ-lactone powder and dissolve it in 100 mL of ice-cold ultrapure water (-20 ℃) ​​to prepare a 100 mg / mL D-(+)-gluconic acid-δ-lactone solution. Draw 10 mL of this solution using a syringe, place it on a syringe pump, and set the injection rate to 0.1 mL / min. Completely immerse the cation exchange membrane at the bottom of the silica gel mold in the nano-calcium carbonate solution, but ensure the silica gel mold is not completely submerged. At this point, the D-(+)-gluconic acid-δ-lactone solution reacts with nano-calcium carbonate, and the generated calcium ions enter the mixed liquid through the cation exchange membrane, initiating gel cross-linking and forming "bottom-up" adsorption channels inside the gel. Ultimately, twelve 1.5 cm × 1.5 cm × 1.5 cm bite-sized gels are formed in the silica gel mold. After removing the mold and the bottom cation exchange membrane, the gels are immersed in a 3 mg / mL EGCG aqueous solution for 24 hours for adsorption.

[0064] Experimental results showed that when the molar ratio of sodium alginate to β-cyclodextrin was 1:1, 1:2, and 2:1, the adsorption rates of EGCG by the composite gel within 24 hours reached 65.73 ± 1.89%, 70.40 ± 2.01%, and 62.00 ± 2.80%, respectively. After oral simulated digestion experiments, the bitterness response values ​​of the EGCG aqueous solution adsorbed by the composite gel were measured to be 0.08, 0.03, and 0.12 in electronic tongue detection, respectively. Compared with EGCG without gel adsorption, the bitterness response values ​​were reduced by 94.7%, 98.0%, and 92.1%, respectively.

[0065] Comparing the results with those of Example 2, it can be seen that the adsorption rate of EGCG in the composite gel prepared by adding glycerol in Example 5 is significantly increased, while the bitterness response value is also significantly reduced. Therefore, compared with the sodium alginate-cyclodextrin composite gel, the glycerol-sodium alginate-cyclodextrin composite gel has a higher adsorption rate of EGCG and a better effect on blocking bitterness.

[0066] Example 6 This embodiment provides a method for preparing a composite gel, specifically a method for preparing a glycerol-sodium alginate-γ-cyclodextrin composite gel (referred to as "G-SA-γ-Gel"). The difference from Example 3 is that glycerol is added in addition to the method in Example 3, while the other processes are basically the same as in Example 3.

[0067] The specific steps of Example 6 are as follows: Weigh 2.4 g of sodium alginate and dissolve it in 100 mL of ultrapure water. Stir the solution on a magnetic stirrer at 500 rpm and 40 °C for 2 hours until completely dissolved. Set aside. Weigh 0.1038 g, 0.0519 g, and 0.2076 g of γ-cyclodextrin, respectively, and dissolve them in 100 mL of ultrapure water. Stir the solutions on a magnetic stirrer at 500 rpm and 40 °C until completely dissolved. Set aside. Add 1.8 mL of glycerol to 98.2 mL of ultrapure water and stir magnetically until homogeneous. Set aside. Introduce the sodium alginate, γ-cyclodextrin, and glycerol solutions into a constant flow pump via tubing. Set the flow rate to 0.5 mL / min and process for 30 min to ensure thorough mixing of the materials in the mixing tube. Then, turn on the ultrasonic generator to perform online ultrasonic mixing and defoaming of the mixture. Next, open the 12-port pressure start valve to evenly inject the mixed liquid into the silica gel mold with the cation exchange membrane at the bottom. Once the liquid level is even, close the start valve. Separately, dissolve 0.2024 g of nano-calcium carbonate in 100 mL of ultrapure water, stir until the solution is homogeneous, and then transfer it to a glass apparatus. Weigh 10 g of D-(+)-gluconic acid-δ-lactone powder and dissolve it in 100 mL of ice-cold ultrapure water (-20 ℃) ​​to prepare a 100 mg / mL D-(+)-gluconic acid-δ-lactone solution. Draw 10 mL of this solution using a syringe, place it on a syringe pump, and set the injection rate to 0.1 mL / min. Completely immerse the cation exchange membrane at the bottom of the silica gel mold in the nano-calcium carbonate solution, but ensure the silica gel mold is not completely submerged. At this point, the D-(+)-gluconic acid-δ-lactone solution reacts with nano-calcium carbonate, and the generated calcium ions enter the mixed liquid through the cation exchange membrane, initiating gel cross-linking and forming "bottom-up" adsorption channels inside the gel. Ultimately, twelve 1.5 cm × 1.5 cm × 1.5 cm bite-sized gels are formed in the silica gel mold. After removing the mold and the bottom cation exchange membrane, the gels are immersed in a 3 mg / mL EGCG aqueous solution for 24 hours for adsorption.

[0068] Experimental results showed that when the molar ratio of sodium alginate to γ-cyclodextrin was 1:1, 1:2, and 2:1, the adsorption rates of the composite gel for EGCG within 24 hours reached 87.94 ± 2.73%, 91.09 ± 3.20%, and 82.11 ± 3.92%, respectively. After oral simulated digestion experiments, the bitter taste response values ​​of EGCG in the EGCG aqueous solution adsorbed by the composite gel were measured in electronic tongue detection to be -0.04, -0.10, and -0.03, respectively. This indicates that the composite gel has a complete masking effect on the bitter taste of EGCG.

[0069] Comparing the results with those of Example 3, it can be seen that the adsorption rate of EGCG in the composite gel prepared by adding glycerol in Example 6 is significantly increased, while the bitterness response value is also significantly reduced. Therefore, compared with the sodium alginate-cyclodextrin composite gel, the glycerol-sodium alginate-cyclodextrin composite gel has a higher adsorption rate of EGCG and a better effect on blocking bitterness.

[0070] Therefore, as can be seen from Examples 4 to 6, after the addition of glycerol, the composite gels prepared by α-cyclodextrin, β-cyclodextrin and γ-cyclodextrin with sodium alginate all have better adsorption performance and better bitterness shielding effect than the composite gels prepared without the addition of glycerol.

[0071] Comparative Example 1 This comparative example provides a method for preparing sodium alginate gel (SA-Gel), which differs from Example 1 in that no cyclodextrin is added.

[0072] The specific steps for Comparative Example 1 are as follows: 0.8 g of sodium alginate was dissolved in 100 mL of ultrapure water and stirred at 500 rpm and 40 °C for 2 hours on a magnetic stirrer until completely dissolved. Then, 0.2024 g of nano-calcium carbonate was added to the solution, and stirring continued to obtain a sodium alginate mixture. Separately, 10 g of D-(+)-gluconic acid-δ-lactone powder was dissolved in 100 mL of ice-cold ultrapure water (-20 °C) to prepare a 100 mg / mL D-(+)-gluconic acid-δ-lactone solution. This solution was added to the sodium alginate mixture, stirred for 5 minutes, and allowed to stand to form a gel. The resulting gel was cut into 1.5 cm × 1.5 cm × 1.5 cm pieces and then immersed in a 3 mg / mL EGCG aqueous solution for 24 hours for adsorption.

[0073] Experimental results showed that the composite gel in Comparative Example 1 achieved an EGCG adsorption rate of 21.91 ± 0.4%. After a simulated oral digestion experiment, the gel showed a bitterness response value of 0.36 for EGCG in an electronic tongue test, which was 76.3% lower than that of EGCG without gel adsorption.

[0074] Comparative Example 2 This comparative example provides a method for preparing a composite gel, which differs from Example 1 in that: instead of using the cation exchange membrane in Example 1, D-(+)-gluconic acid-δ-lactone solution and nano-calcium carbonate are directly added to the mixed liquid.

[0075] The specific steps for Comparative Example 2 are as follows: Weigh 1.6 g of sodium alginate and dissolve it in 100 mL of ultrapure water. Stir on a magnetic stirrer at 500 rpm and 40 ℃ for 2 hours until completely dissolved. Set aside. Weigh 0.0260 g of α-cyclodextrin separately and dissolve it in 100 mL of ultrapure water. Stir on the solution at 500 rpm and 40 ℃ until completely dissolved. Set aside separately. Introduce the sodium alginate solution and α-cyclodextrin solution separately into a constant flow pump device through tubing. Set the flow rate to 0.5 mL / min and process for 30 min to ensure thorough mixing of the raw materials in the mixing tube. Then, turn on the ultrasonic generator to perform online ultrasonic mixing and defoaming treatment on the mixture. Open the 12-port pressure start valve and simultaneously and evenly inject the mixture into the silicone mold. After the liquid level is reached, close the start valve. Weigh 0.2024 g of nano-calcium carbonate and continue stirring in 100 mL of ultrapure water until the solution is homogeneous to obtain a nano-calcium carbonate solution. 10 g of D-(+)-gluconic acid-δ-lactone powder was dissolved in 100 mL of ice-cold ultrapure water (-20 ℃) ​​to prepare a D-(+)-gluconic acid-δ-lactone solution. A silica gel mold without a cation exchange membrane was directly immersed in the D-(+)-gluconic acid-δ-lactone solution and the nano-calcium carbonate solution to finally generate a composite gel.

[0076] Experimental results showed that the composite gel in Comparative Example 2 achieved an EGCG adsorption rate of 23.16 ± 1.5%. After a simulated oral digestion experiment, the EGCG aqueous solution adsorbed by the composite gel was measured to have a bitter taste response value of 0.34 in an electronic tongue test, which was 79.6% lower than that of EGCG without gel adsorption.

[0077] Compared with Example 1, it can be seen that the adsorption rate of EGCG in Comparative Example 2 is lower than that in Example 1, and the bitterness shielding effect is worse than that in Example 1. This is because Comparative Example 2 does not use a cation exchange membrane, so it cannot achieve directional cross-linking and cannot form a "bottom-up" adsorption channel inside the gel. As a result, the adsorption of EGCG and the bitterness shielding effect of the prepared gel are worse.

[0078] Comparative Example 3 This comparative example provides a method for preparing a composite gel, which differs from Example 1 in that D-(+)-gluconic acid-δ-lactone is replaced with hydrochloric acid.

[0079] The specific steps for Comparative Example 3 are as follows: Weigh 1.6 g of sodium alginate and dissolve it in 100 mL of ultrapure water. Stir on a magnetic stirrer at 500 rpm and 40 ℃ for 2 hours until completely dissolved. Set aside. Weigh 0.0260 g of α-cyclodextrin separately and dissolve it in 100 mL of ultrapure water. Stir on the solution at 500 rpm and 40 ℃ until completely dissolved. Set aside separately. Introduce the sodium alginate solution and α-cyclodextrin solution separately into a constant flow pump device through tubing. Set the flow rate to 0.5 mL / min and process for 30 min to ensure thorough mixing of the raw materials in the mixing tube. Then turn on the ultrasonic generator to perform online ultrasonic mixing and defoaming treatment on the mixture. Open the 12-port pressure start valve and simultaneously and evenly inject the mixture into the silicone mold. Close the start valve after the liquid level is reached. Weigh 0.2024 g of nano-calcium carbonate and continue stirring in 100 mL of ultrapure water until the solution is homogeneous to obtain a nano-calcium carbonate solution. Dissolve and prepare a 0.1M solution. The cation exchange membrane at the bottom of the silicone mold is completely immersed in a mixture of nano-calcium carbonate solution and hydrochloric acid solution, but the silicone mold is not completely submerged.

[0080] Experimental results showed that the composite gel in Comparative Example 3 achieved an EGCG adsorption rate of 22.16 ± 0.4%. After oral simulated digestion experiments, the EGCG aqueous solution adsorbed by the composite gel showed a bitterness response value of 0.75 in electronic tongue detection, which was 42.4% lower than that of EGCG without gel adsorption.

[0081] Compared with Example 1, it can be seen that the adsorption rate of EGCG in Comparative Example 3 is lower than that in Example 1, and the bitterness shielding effect is worse than that in Example 1. This is because a strong inorganic acid was added to Comparative Example 3, which completely ionizes in water and releases hydrogen ions instantaneously. The gel is only locally cross-linked and saturated, with a loose structure, and it is also unable to form an ordered adsorption channel inside the gel, resulting in a poorer adsorption of EGCG and bitterness shielding effect of the prepared gel.

[0082] Testing and Results Analysis: The present invention also conducted infrared spectroscopy tests on sodium alginate (SA), SA-Gel prepared in Comparative Example 1, SA-γ-CD-Gel prepared in Example 3 (in which the specific amount of γ-cyclodextrin added was 0.0346 g), and G-SA-γ-CD-Gel prepared in Example 6 (in which the specific amount of γ-cyclodextrin added was 0.0519 g).

[0083] The results are as follows Figure 1 As shown in the infrared spectrum, after glycerol treatment, the OH bonds of sodium alginate-γ-cyclodextrin changed from 3340 cm⁻¹ to 3340 cm⁻¹. -1 Redshifted to 3280 cm -1This indicates that glycerol competitively breaks the original hydroxyl bonds, stretches the molecular chain structure, and uses its multi-hydroxyl structure to bridge and form a hydrogen bond recombination network.

[0084] Figure 2 The bitterness-masking effect of the composite gels prepared in Examples 1-6 with molar ratios of sodium alginate to cyclodextrin of 1:1, 1:2, and 2:1, and the sodium alginate gel prepared in Comparative Example 1, is determined by... Figure 2 It can be seen that the sodium alginate gel with the addition of cyclodextrin can significantly improve the bitterness shielding effect of EGCG, and the bitterness shielding effect is further increased after the addition of glycerol, indicating that glycerol can significantly enhance the network structure of the gel.

[0085] Figure 3 This is a comparison of the adsorption efficiency of EGCG by the composite gels prepared in Examples 1-6 and the sodium alginate gel prepared in Comparative Example 1. Figure 3 It can be seen that the composite gels prepared in Examples 4-6 have better adsorption efficiency for EGCG than those prepared in Examples 1-3. This is because glycerol was added in Examples 4-6. Furthermore, regardless of whether glycerol was added in Examples 1-3 (without glycerol) or Examples 4-6 (with glycerol), the composite gel prepared with a sodium alginate to cyclodextrin molar ratio of 1:2 had a higher adsorption efficiency than the composite gels prepared with molar ratios of 1:1 and 2:1. This indicates that a 1:2 molar ratio of sodium alginate to cyclodextrin is more conducive to preparing composite gels with good adsorption performance.

[0086] Figure 4 (A) is a scanning electron microscope image of the bottom cross section of SA-Gel prepared in Comparative Example 1. The scanning electron microscope results show that the gel has an irregularly sized pore structure inside, and the pore direction is disordered. Figure 4 Images (B) and (C) in the image are scanning electron microscope (SEM) images of the bottom cross section and the bottom oblique cross section of G-SA-γ-CD-Gel prepared in Example 6 (where the specific amount of γ-cyclodextrin added was 0.0519 g), respectively. Figure 4 (B) The scanning electron microscopy results from the bottom cross section of the gel show that, compared with ordinary sodium alginate gel, the gel treated with cyclodextrin and glycerol has more pores with neat and orderly orientation, which is conducive to the adsorption of EGCG molecules. Figure 4 The scanning electron microscopy results of (C) show that the gel forms ordered pores from bottom to top.

[0087] Example 7 The gel with the best effect among the composite gels prepared in Examples 1 to 6 (i.e., the molar ratio of sodium alginate to cyclodextrin is 1:2) and the gels prepared in Comparative Examples 1 to 3 were used to adsorb EGCG in industrial waste tea water. The specific method was as follows: 100 g of gel was immersed in 1 L of industrial waste tea water for 24 hours for adsorption, and the adsorption efficiency of the gel was tested.

[0088] To verify the adsorption effect, the EGCG content in industrial waste tea water and the bitterness response value after gel simulated digestion were detected by ultraviolet spectrophotometry and electronic tongue method in existing technologies, and compared with the adsorption results of the gel prepared in this invention.

[0089] The results are shown in Table 1.

[0090] Table 1 As shown in Table 1, the results of Examples 1-6 indicate that the adsorption capacity and adsorption efficiency of the composite gel prepared in this invention for EGCG in industrial waste tea water are similar, proving that its adsorption capacity is not affected by other interfering substances in the waste tea water. Furthermore, after simulated oral digestion, the bitterness response value of the gel-adsorbed sample was significantly lower than that of the industrial waste tea water before adsorption, demonstrating that the gel can effectively shield the bitterness of the waste tea water.

[0091] Comparing the results of Examples 1 to 6 with those of Comparative Examples 1 to 3, it can be seen that the adsorption efficiency and the effect of shielding the bitterness of waste tea water in Comparative Examples 1 to 3 are significantly lower than those of Examples 1 to 6. Therefore, whether it is waste tea water or the prepared EGCG solution, the composite gel prepared by Comparative Examples 1 to 3 has a worse effect on EGCG adsorption and bitterness shielding due to changes in raw materials or preparation process.

[0092] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a composite gel based on hydrogen bond reconstruction and directional crosslinking, characterized in that, Includes the following steps: S1. Sodium alginate was added to water to prepare a sodium alginate solution; cyclodextrin was added to water to prepare a cyclodextrin solution; The sodium alginate solution and the cyclodextrin solution are mixed to obtain a mixed solution; S2. The mixed solution is added to a first container, wherein the first container is placed in a second container, and the bottom of the first container has a cation exchange membrane communicating with the second container; S3. D-(+)-gluconic acid-δ-lactone is added to water to prepare a D-(+)-gluconic acid-δ-lactone solution; nano-calcium carbonate is added to the nano-calcium carbonate solution in water; the D-(+)-gluconic acid-δ-lactone solution and the nano-calcium carbonate solution are added to the second container until they cover the cation exchange membrane. The calcium ions generated by the reaction of the D-(+)-gluconic acid-δ-lactone solution and the nano-calcium carbonate solution enter the first container through the cation exchange membrane and react with the mixed solution to obtain a composite gel.

2. The preparation method according to claim 1, characterized in that, The molar ratio of sodium alginate to cyclodextrin is 1-2:1-2.

3. The preparation method according to claim 1, characterized in that, The molar ratio of calcium ions in the nano-calcium carbonate to carboxyl groups in the sodium alginate is 1.5–2.5:1, and the molar ratio of nano-calcium carbonate to D-(+)-gluconic acid-δ-lactone is 4–6:

3.

4. The preparation method according to claim 1, characterized in that, Step S1 also includes adding a glycerol solution. When adding the glycerol solution, step S1 includes the following specific steps: A sodium alginate solution was prepared by adding sodium alginate to water; a cyclodextrin solution was prepared by adding cyclodextrin to water; a glycerol solution was prepared by adding glycerol to water; the sodium alginate solution, the cyclodextrin solution, and the glycerol solution were mixed to obtain a mixed solution.

5. The preparation method according to claim 4, characterized in that, The ratio of sodium alginate to glycerol is 2g-3g: 1.3mL-2.3mL.

6. The preparation method according to claim 1 or 4, characterized in that, Step S3 includes the following specific steps: D-(+)-gluconic acid-δ-lactone was added to water to prepare a D-(+)-gluconic acid-δ-lactone solution; nano-calcium carbonate was added to water to prepare a nano-calcium carbonate solution; Add the nano-calcium carbonate solution to the second container until it covers the cation exchange membrane but does not cover the top of the first container; The D-(+)-gluconic acid-δ-lactone solution is slowly added to the second container at a rate of 0.05 mL / min to 0.15 mL / min. The calcium ions generated by the reaction of the D-(+)-gluconic acid-δ-lactone solution and the nano calcium carbonate solution in the second container enter the first container through the cation exchange membrane and react with the mixed solution to obtain a composite gel.

7. A composite gel based on hydrogen bond reconstruction and directional crosslinking, characterized in that, It is obtained by the preparation method described in any one of claims 1 to 6.

8. The composite gel according to claim 7, characterized in that, The composite gel has adsorption channels extending from the bottom to the top of the composite gel.

9. The composite gel obtained by the preparation method according to any one of claims 1 to 6, or the composite gel according to any one of claims 7 to 8, is used in the adsorption and / or loading and / or controlled release of polyphenols.

10. The application according to claim 9, characterized in that, The application includes using the composite gel to adsorb epigallocatechin gallate from industrial waste tea water. The composite gel achieves an adsorption rate of 91.09±3.20% for epigallocatechin gallate within 24 hours and can mask the bitterness of epigallocatechin gallate.

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