Slow-release chitosan / sodium alginate gel film as well as preparation method and application thereof
By preparing a chitosan/sodium alginate-based gel membrane, chlorine dioxide is generated by reacting citric acid and sodium chlorite, and a gel network structure is formed through electrostatic deposition technology. This solves the problems of instability of chlorine dioxide and poor mechanical properties of chitosan, achieving a safe and stable sustained-release effect and expanding its application in fruit and vegetable preservation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SANYA INSTITUTE OF NANJING AGRICULTURAL UNIVERSITY
- Filing Date
- 2025-12-17
- Publication Date
- 2026-04-17
AI Technical Summary
The instability, volatility, and high toxicity of chlorine dioxide limit its widespread application in fruit and vegetable preservation. Traditional chitosan materials have low antibacterial activity and poor mechanical properties, making it difficult to meet the needs of modern food storage and preservation.
By preparing a chitosan/sodium alginate-based gel membrane, chlorine dioxide is generated by reacting citric acid and sodium chlorite as precursors, and a gel network structure is formed by electrostatic deposition technology to slow down the release rate of chlorine dioxide and improve the mechanical properties of chitosan and sodium alginate.
It achieves safe, stable, and slow release of chlorine dioxide, prolongs the preservation effect of fruits and vegetables, improves the antibacterial and mechanical properties of chitosan/sodium alginate-based materials, and expands their application in the field of fruit and vegetable storage and preservation.
Smart Images
Figure CN121867274A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of fruit and vegetable preservation, specifically to chitosan / sodium alginate gel membrane and its preparation method, and the application of the gel membrane in the postharvest room temperature storage and preservation of vegetable soybeans. Background Technology
[0002] Chlorine dioxide is an inorganic compound that, under normal temperature and pressure, is a yellowish-green to orange-yellow gas with a pungent odor. It possesses strong oxidizing properties and is recognized both domestically and internationally as a highly efficient, low-toxicity, rapid-acting, and broad-spectrum green disinfectant. However, ClO2 is unstable; concentrations exceeding 10% in the air pose an explosion hazard, and it is easily decomposed or oxidized by heat and light. Direct application makes concentration control difficult, which can negatively impact the sensory quality of fruits and vegetables, thus limiting the widespread use of chlorine dioxide in the storage and preservation of agricultural products.
[0003] With the continuous improvement of people's living standards, the field of fruit and vegetable preservation has developed rapidly. Traditional physical and chemical preservation methods cannot meet the needs of modern food storage and preservation. Therefore, it is imperative to develop a new type of antibacterial preservation material for fruits and vegetables with slow-release chlorine dioxide to achieve long-term preservation.
[0004] Polysaccharides are macromolecular polymers whose functional groups endow them with diverse biological activities. Chitosan is a natural polysaccharide with good film-forming properties, is non-toxic, and biodegradable, and can be widely used in food storage and preservation through coating, soaking, and other methods. However, chitosan itself has low antibacterial activity, limited functionality, and poor mechanical properties, which cannot meet the needs of modern active food packaging materials, thus restricting its application. Summary of the Invention
[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a chitosan / sodium alginate-based gel membrane for postharvest storage and preservation of vegetable soybeans. Specifically, it is a method for preserving vegetable soybeans at room temperature by delaying the release of chlorine dioxide within the national standard range, reducing browning and delaying aging of vegetable soybeans.
[0006] The present invention also aims to provide a method for preparing a chitosan / sodium alginate-based gel membrane by producing chlorine dioxide through a precursor reaction and delaying the release of chlorine dioxide by forming a gel network structure using a matrix. This preparation method uses chitosan as a matrix, embedding citric acid, and mixing it with a sodium alginate solution containing sodium chlorite to prepare the chitosan / sodium alginate-based gel membrane.
[0007] The objective of this invention is achieved through the following technical solution.
[0008] A method for preparing a sustained-release chitosan / sodium alginate gel membrane, the method comprising the following steps:
[0009] (1) Add citric acid to the chitosan acetate solution and dissolve it completely to obtain a chitosan-citric acid solution;
[0010] (2) Add sodium chlorite to the sodium alginate solution and dissolve it completely to obtain a sodium alginate-sodium chlorite solution;
[0011] (3) After removing the solvent from the chitosan-citric acid solution, the sodium alginate-sodium chlorite solution was poured into it using a layered electrostatic deposition technique. The solution was allowed to stand at room temperature and the solvent was removed to obtain a chitosan-citric acid / sodium alginate-sodium chlorite composite gel membrane.
[0012] In the above preparation method, in step (1), the chitosan volume concentration in the chitosan acetic acid solution is 5~15 g / L, and the acetic acid volume concentration is 0.5~1.5%; the mass fraction ratio of citric acid to chitosan is 1:15~30.
[0013] In the above preparation method, in step (1), the molecular weight of the chitosan is 20~40 kDa; the temperature for complete dissolution is 70℃~90℃, and the time is 12-24h.
[0014] In the above preparation method, in step (2), the molecular weight of sodium alginate is 100~300 kDa; the mass ratio of sodium chlorite to sodium alginate is 1:20~40; the temperature for complete dissolution is 40℃~60℃, and the time is 12-24h.
[0015] In the above preparation method, in step (2), the mass-volume concentration of sodium alginate in the sodium alginate solution is 5~15g / L.
[0016] In the above preparation method, in step (3), the volume ratio of chitosan-citric acid solution and sodium alginate-sodium chlorite solution is 3~5:2~4;
[0017] In step (3), the temperature for removing the solvent and removing the solvent again is 20~35℃, and the time is 24~36h.
[0018] A sustained-release chitosan / sodium alginate-based gel membrane was prepared using the method described above.
[0019] In this invention, the slow-release chitosan / sodium alginate-based gel membrane prepared by the method is used for vegetable preservation. In some preferred embodiments, the vegetables are grouped and packaged using the slow-release chitosan / sodium alginate-based gel membrane. Furthermore, the vegetable in question is soybean.
[0020] The concept of this invention is as follows:
[0021] The method for preparing a controlled-release chitosan / sodium alginate-based gel membrane provided by this invention delays the release rate of chlorine dioxide by utilizing the reaction of precursor substances to generate chlorine dioxide and the gel network structure of the matrix, thus exhibiting safe and efficient delayed release characteristics.
[0022] This invention utilizes a matrix to encapsulate citric acid and sodium chlorite as precursors to generate chlorine dioxide, solving problems such as instability and limited encapsulation space of chlorine dioxide. It leverages the encapsulation properties of chitosan and sodium alginate to encapsulate chlorine dioxide, slowing its release rate and ensuring long-lasting antibacterial effects while addressing the issue of rapid chlorine dioxide release leading to decreased preservation. The electrostatic interaction between sodium alginate and chitosan improves the weak mechanical strength of chitosan and the high hygroscopicity of sodium alginate. Chlorine dioxide is used as a long-lasting antibacterial preservative, addressing the weak and unstable antibacterial activity of chitosan / sodium alginate-based packaging materials. Chlorine dioxide is used as an encapsulating core material, overcoming its strong odor, high volatility, and heat sensitivity. This results in a composite gel film with excellent antibacterial properties, expanding the application of chitosan / sodium alginate-based materials in the field of biodegradable antibacterial packaging.
[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:
[0024] (1) The preparation method provided by the present invention uses citric acid and sodium chlorite, which are stable and safe. The chlorine dioxide generated by the reaction has good safety in use. It will not react with organic matter or produce toxic substances like other chlorine disinfectants during use. It is inexpensive, widely available, and has antioxidant and antibacterial activities.
[0025] (2) The preparation method provided by the present invention uses electrostatic deposition technology to encapsulate citric acid and sodium chlorite with chitosan and sodium alginate respectively, which cleverly slows down the volatilization of chlorine dioxide and does not introduce other substances. It is green and safe, and expands its application in the field of fruit and vegetable storage and preservation.
[0026] (3) The preparation method provided by the present invention mixes chitosan and sodium alginate matrix, thereby improving the mechanical properties of chitosan and sodium alginate;
[0027] (4) The preparation method of the present invention is simple, easy to operate, and has a wide range of raw material sources, which is conducive to large-scale industrial production;
[0028] (5) The preservation method provided by the present invention uses a chitosan / sodium alginate-based gel membrane, which is simple to operate and solves the problems of easy residue and unsafety of chemical preservation methods;
[0029] (6) The preservation method provided by the present invention utilizes chitosan / sodium alginate-based gel membrane to effectively delay the aging of post-harvest vegetable soybeans and extend the storage period. Attached Figure Description
[0030] Figure 1 This is a graph showing the release rate data of chlorine dioxide obtained in Example 2 under matrix-free conditions;
[0031] Figure 2 This is a graph showing the release rate of chlorine dioxide in the chitosan / sodium alginate-based gel membrane obtained in Example 2 under different temperature conditions.
[0032] Figure 3 This is a graph showing the release rate of chlorine dioxide in the chitosan / sodium alginate-based gel membrane obtained in Example 2, under the same temperature conditions but with different concentrations but in the same proportion.
[0033] Figure 4 This is a graph showing the release rate data of chlorine dioxide in the chitosan / sodium alginate-based gel membrane obtained in Example 2 at different ratios under the same temperature conditions;
[0034] Figure 5 This is a scanning electron microscope image of the chitosan / sodium alginate-based gel membrane obtained in Example 3 during the chlorine dioxide release process;
[0035] Figure 6 This is a graph showing the growth inhibition data of the chitosan / sodium alginate-based gel membrane obtained in Example 3 against Escherichia coli, Staphylococcus aureus, Alternaria alternata, Rhizopus spp., and Bacillus anthracis. Detailed Implementation
[0036] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings, but the embodiments and protection scope of the present invention are not limited thereto.
[0037] Example 1
[0038] The specific steps for preserving soybeans at room temperature after harvest are as follows:
[0039] (1) Using chitosan and citric acid monohydrate as raw materials, chitosan was added to acetic acid solution and dissolved completely to obtain chitosan acetic acid solution. Then, citric acid was added under stirring to obtain chitosan-citric acid solution (where the molecular weight of chitosan is 30 kDa, the mass volume concentration of chitosan in chitosan acetic acid solution is 10 g / L, the volume concentration of acetic acid is 1%, the mass ratio of citric acid to chitosan is 1:25, and the mixture was stirred at 70 °C for 20 h at a stirring speed of 800 r / min).
[0040] (2) Under stirring conditions, sodium chlorite was added to the sodium alginate solution to obtain a sodium alginate-sodium chlorite solution (wherein the sodium alginate has a molecular weight of 200 kDa, a sodium alginate mass-volume concentration of 10 g / L, and a mass ratio of sodium chlorite to sodium alginate of 1:30, and the mixture was stirred at 50°C for 20 h at a stirring speed of 800 r / min).
[0041] (3) Remove the solvent from the chitosan-citric acid solution (temperature 35℃, time 30h), then pour in the sodium alginate-sodium chlorite solution (volume ratio of chitosan-citric acid solution and sodium alginate-sodium chlorite solution is 4:3) using a layered electrostatic deposition technique, incubate at low temperature overnight, and remove the solvent (temperature 35℃, time 30h). A chitosan-citric acid / sodium alginate-sodium chlorite composite gel membrane is obtained.
[0042] (4) Preparation of raw soybeans for vegetable use: Select soybeans that are uniform in size and color, without obvious mechanical damage or pests and diseases, and of the same weight.
[0043] (5) Gel membrane treatment of vegetable soybeans: The prepared gel membrane was used for treatment;
[0044] (6) Storage of vegetable soybeans: The dried vegetable soybeans were placed in a constant temperature box at 20 ℃±1 ℃ for 8 days (the experimental time was set to 8 days).
[0045] Example 2
[0046] The specific steps for preserving soybeans at room temperature after harvest are as follows:
[0047] (1) Using chitosan and citric acid monohydrate as raw materials, chitosan was added to acetic acid solution and dissolved completely to obtain chitosan acetic acid solution. Then, citric acid was added under stirring to obtain chitosan-citric acid solution (where the molecular weight of chitosan is 30 kDa, the mass volume concentration of chitosan in chitosan acetic acid solution is 10 g / L, the volume concentration of acetic acid is 1%, the mass ratio of citric acid to chitosan is 1:25, and the mixture was stirred at 70 °C for 20 h at a stirring speed of 800 r / min).
[0048] (2) Under stirring conditions, sodium chlorite was added to the sodium alginate solution to obtain a sodium alginate-sodium chlorite solution (wherein the sodium alginate has a molecular weight of 200 kDa, a sodium alginate mass-volume concentration of 10 g / L, and a mass ratio of sodium chlorite to sodium alginate of 1:20, and the mixture was stirred at 50°C for 20 h at a stirring speed of 800 r / min).
[0049] (3) Remove the solvent from the chitosan-citric acid solution (temperature 35℃, time 30h), then pour in the sodium alginate-sodium chlorite solution (volume ratio of chitosan-citric acid solution and sodium alginate-sodium chlorite solution is 4:3) using a layered electrostatic deposition technique, incubate at low temperature overnight, and remove the solvent (temperature 35℃, time 30h). A chitosan-citric acid / sodium alginate-sodium chlorite composite gel membrane is obtained.
[0050] (4) Preparation of raw soybeans for vegetable use: Select soybeans that are uniform in size and color, without obvious mechanical damage or pests and diseases, and of the same weight.
[0051] (5) Gel membrane treatment of vegetable soybeans: The prepared gel membrane was used for treatment;
[0052] (6) Storage of vegetable soybeans: The dried vegetable soybeans were placed in a constant temperature box at 20 ℃±1 ℃ for 8 days (the experimental time was set to 8 days).
[0053] The release rate of chlorine dioxide in the prepared chitosan / sodium alginate-based gel membrane is as follows: Figure 1 As shown. By Figure 1 It was found that at a temperature of 25 ℃, the release rate of ClO2 decreased with increasing time. During the first 36 hours of release, the release rate of ClO2 in the composite gel membrane did not show a significant increasing trend; however, the release rate of ClO2 without matrix encapsulation increased rapidly, and the release rate of ClO2 without matrix encapsulation was significantly higher than that of ClO2 with matrix encapsulation. Furthermore, during the release period, the change in the ClO2 release rate was relatively gradual, while the release rate of ClO2 without matrix encapsulation decreased significantly. This indicates that improving the encapsulation of precursor substances in the composite gel membrane can effectively delay the formation of ClO2, thereby improving the efficiency of ClO2 action and prolonging the action time.
[0054] The release rates of chlorine dioxide in the prepared chitosan / sodium alginate-based gel membrane under different temperature conditions are as follows: Figure 2 As shown. By Figure 2 It was found that the release rate of ClO2 from the composite gel membrane decreased with increasing time within the temperature range of 4 ℃ to 25 ℃. The release rate of the composite gel membrane at 4 ℃ did not show a significant increasing trend; however, at 15 ℃ and 25 ℃, the ClO2 release rate increased rapidly, and the release rate of the composite liposomes at 25 ℃ was higher than that at 25 ℃. This indicates that the composite gel membrane allows for the on-demand, controllable release of ClO2 under different temperature conditions, thereby improving the efficiency of ClO2 action and prolonging the action time.
[0055] The release rates of chlorine dioxide in the prepared chitosan / sodium alginate-based gel membrane at the same temperature and with different concentrations and proportions are as follows: Figure 3 and Figure 4 As shown in the figure above, the ClO2 release rate in the composite gel membrane slows down with increasing time, while the ClO2 release rate rapidly increases when the concentrations of citric acid and sodium chlorite are high. This indicates that the composite gel membrane allows for the controlled release of ClO2 by adjusting the concentration and ratio of citric acid and sodium chlorite as needed, thereby improving the efficiency of ClO2 action and prolonging the action time.
[0056] Scanning electron microscopy (SEM) images of the prepared chitosan / sodium alginate-based gel membrane during the ClO2 release process are shown below. Figure 5 As shown. By Figure 5 It can be seen that the composite gel membrane has a dense, uniform, and smooth structure, indicating the successful synthesis of the composite gel membrane.
[0057] The prepared chitosan / sodium alginate-based gel membrane exhibits the following inhibitory effects on the growth of Escherichia coli, Staphylococcus aureus, Alternaria alternata, Rhizopus spp., and Bacillus anthracis: Figure 6 As shown. By Figure 6 It can be seen that the composite gel membrane has a significant inhibitory effect on the above-mentioned bacterial species, indicating that the composite gel membrane has excellent antibacterial properties.
[0058] Example 3
[0059] The specific steps for preserving soybeans at room temperature after harvest are as follows:
[0060] (1) Using chitosan and citric acid monohydrate as raw materials, chitosan was added to acetic acid solution and dissolved completely to obtain chitosan acetic acid solution. Then, citric acid was added under stirring to obtain chitosan-citric acid solution (where the molecular weight of chitosan is 30 kDa, the mass volume concentration of chitosan in chitosan acetic acid solution is 10 g / L, the volume concentration of acetic acid is 1%, the mass ratio of citric acid to chitosan is 1:15, and the mixture was stirred at 70 °C for 20 h at a stirring speed of 800 r / min).
[0061] (2) Under stirring conditions, sodium chlorite was added to the sodium alginate solution to obtain a sodium alginate-sodium chlorite solution (wherein the sodium alginate has a molecular weight of 200 kDa, a sodium alginate mass-volume concentration of 10 g / L, and a mass ratio of sodium chlorite to sodium alginate of 1:20, and the mixture was stirred at 50°C for 20 h at a stirring speed of 800 r / min).
[0062] (3) Remove the solvent from the chitosan-citric acid solution (temperature 35℃, time 30h), then pour in the sodium alginate-sodium chlorite solution (volume ratio of chitosan-citric acid solution and sodium alginate-sodium chlorite solution is 4:3) using a layered electrostatic deposition technique, incubate at low temperature overnight, and remove the solvent (temperature 35℃, time 30h). A chitosan-citric acid / sodium alginate-sodium chlorite composite gel membrane is obtained.
[0063] (4) Preparation of raw soybeans for vegetable use: Select soybeans that are uniform in size and color, without obvious mechanical damage or pests and diseases, and of the same weight.
[0064] (5) Gel membrane treatment of vegetable soybeans: The prepared gel membrane was used for treatment;
[0065] (6) Storage of vegetable soybeans: The dried vegetable soybeans were placed in a constant temperature box at 20 ℃±1 ℃ for 8 days (the experimental time was set to 8 days).
[0066] The above embodiments are merely preferred embodiments of the present invention and are only used to explain the present invention, not to limit the present invention. Any changes, substitutions, modifications, etc., made by those skilled in the art without departing from the spirit and essence of the present invention should be within the protection scope of the present invention.
Claims
1. A method for preparing a sustained-release chitosan / sodium alginate gel membrane, characterized in that, The preparation method includes the following steps: (1) Add citric acid to the chitosan acetate solution and dissolve it completely to obtain a chitosan-citric acid solution; (2) Add sodium chlorite to the sodium alginate solution and dissolve it completely to obtain a sodium alginate-sodium chlorite solution; (3) After removing the solvent from the chitosan-citric acid solution, the sodium alginate-sodium chlorite solution was poured into it using a layered electrostatic deposition technique. The solution was allowed to stand at room temperature, and the solvent was removed again to obtain a chitosan-citric acid / sodium alginate-sodium chlorite composite gel membrane.
2. The preparation method according to claim 1, characterized in that, In step (1), the chitosan volume concentration in the chitosan acetic acid solution is 5~15 g / L, and the acetic acid volume concentration is 0.5~1.5%; the mass fraction ratio of citric acid to chitosan is 1:15~30.
3. The preparation method according to claim 1, characterized in that, In step (1), the molecular weight of the chitosan is 20~40 kDa; the temperature for complete dissolution is 70℃~90℃, and the time is 12-24h.
4. The preparation method according to claim 1, characterized in that, In step (2), the molecular weight of sodium alginate is 100~300 kDa; the mass ratio of sodium chlorite to sodium alginate is 1:20~40; the temperature for complete dissolution is 40℃~60℃, and the time is 12-24h.
5. The preparation method according to claim 1, characterized in that, In step (2), the mass-volume concentration of sodium alginate in the sodium alginate solution is 5~15 g / L.
6. The preparation method according to claim 1, characterized in that, In step (3), the volume ratio of chitosan-citric acid solution and sodium alginate-sodium chlorite solution is 3~5:2~4; In step (3), the temperature for removing the solvent and removing the solvent again is 20~35℃, and the time is 24~36h.
7. A sustained-release chitosan / sodium alginate-based gel membrane, characterized in that, It is prepared by any one of the methods described in claims 1 to 6.
8. The application of the sustained-release chitosan / sodium alginate-based gel membrane prepared by the method of claim 1 in vegetable preservation.
9. The application according to claim 8, characterized in that, Vegetables are grouped and packaged using a slow-release chitosan / sodium alginate-based gel membrane.
10. The application according to claim 9, characterized in that... The vegetable in question is soybean for vegetable use.