A coating preservative containing natural antibacterial polysaccharide and its preparation method and application

Abstract

The application discloses a kind of natural antibacterial polysaccharide-containing film coating preservative and its preparation method and application, specifically related to fruit and vegetable preservation technical field.The preservative includes chitosan solution, speed joy β-glucan solution and trivalent iron ion solution.The application is based on a new antibacterial anionic natural polysaccharide (speed joy β-glucan) first discovered, first utilizes the electrostatic interaction between chitosan and speed joy β-glucan to obtain a new composite coating, then carries out the micro-ionization of coating by the coordination between speed joy β-glucan and metal ions, and then obtains a green and safe, antibacterial performance and mechanical performance excellent new preservative coating.

Description

Technical Field

[0001] This invention relates to the field of fruit and vegetable preservation technology, specifically to a coating preservative containing natural antibacterial polysaccharides, its preparation method, and its application. Background Technology

[0002] my country is a major producer of bamboo shoots, ranking first in the world in bamboo shoot production. However, since bamboo shoots are mainly grown in mountainous areas, the harvesting season is concentrated in the hot and humid spring and summer. After harvesting, bamboo shoots, due to their high water content and vigorous respiration, consume a large amount of nutrients through metabolism, making them prone to dehydration and aging. In particular, changes in the physiological environment after harvesting accelerate their lignification process. Furthermore, phenolic substances (tannins, tyrosine, etc.) in bamboo shoots oxidize into quinones, causing the shoot flesh to turn brown. At room temperature, they lose their commercial and edible value within 2-3 days. Therefore, the development of preservation technologies is particularly important.

[0003] Extensive research has been conducted both domestically and internationally on bamboo shoot preservation. Existing literature reports physical methods including modified atmosphere packaging, ozone, microwave, ultrasound, irradiation, ultra-high pressure, depressurization, ultraviolet light, and quick-freezing. While these methods have shown some effectiveness, they are complex to operate and costly, making them unsuitable for implementation at harvest sites and thus difficult to promote. Chemical preservation methods, with their advantages of low investment, simplicity, and good preservation effects, are widely used for agricultural product preservation. However, chemical preservatives and hormones typically have strict requirements regarding usage conditions and concentrations, pose certain food safety risks, and have poor consumer acceptance. Therefore, biological preservatives, such as natural plant and animal extracts and microbial metabolites with antibacterial properties, are increasingly attracting widespread attention from researchers.

[0004] Chitosan, a positively charged natural polysaccharide with antibacterial properties, is widely used in preservative coating technology for agricultural products. However, the film-forming properties, air permeability, and mechanical properties of single chitosan are not ideal. Therefore, composite coating technology has become a research hotspot and innovative direction in this field. Suleke β-glucan is an extracellular soluble β-glucan secreted by Agrobacterium ZX09 (Chinese patent, CN 201010146371.2), which was approved as a new food ingredient in China in 2021. It has high biosafety and better water solubility compared to β-glucan from other sources. Its production cost is low, the cycle is short, and it is not limited by region or season. Furthermore, it possesses good rheological properties and film-forming properties, and appropriate use can have a good effect on lowering blood sugar and lipids, promoting bowel movement, and relieving constipation. However, there are no reports on how to apply it to biological preservation. Summary of the Invention

[0005] Therefore, the present invention provides a coating preservative containing natural antibacterial polysaccharides, its preparation method and application, to solve the problems in the prior art.

[0006] Previous research in this invention revealed that Suleco β-glucan is an anionic polysaccharide with good antibacterial properties. This characteristic suggests that the β-glucan can form a composite antibacterial film through electrostatic interaction with chitosan. Studies have shown that dynamically reversible organometallic coordination exhibits unique advantages in improving the mechanical tensile properties of materials. It not only avoids the use of toxic organic crosslinking agents but also simplifies the process, making it particularly suitable for solving the problem of bamboo shoot preservation in mountainous areas. Previous research also found that this β-glucan can rapidly crosslink with ferric ions to form a gel (Chinese Patent CN202110661463.2). Therefore, this invention, based on the dual gelation effect of Suleco β-glucan, designs a novel bamboo shoot coating preservation technology that is green, easy to operate, and possesses excellent antibacterial and mechanical properties.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] According to a first aspect of the present invention, a coating preservative containing natural antibacterial polysaccharides is provided, the preservative comprising chitosan solution, sulphuric acid β-glucan solution and ferric ion solution.

[0009] Furthermore, the preservative comprises: a chitosan solution with a concentration of 0.5% to 2%, a Suleke β-glucan with a concentration of 0.5% to 2%, and a ferric ion solution with a concentration of 0.01 to 0.05 mol / L.

[0010] Furthermore, the aforementioned Suleke β-glucan is a novel natural anionic polysaccharide with antibacterial activity; it is an extracellular polysaccharide secreted by Agrobacterium ZX09, and its molecular structure is a chain-like structure of repeating units connected by 7 β-1,3-glucose and 2 α-1,3-glucose, as shown in Formula I. It is a natural anionic polysaccharide with a novel structure.

[0011]

[0012] The second aspect of the present invention provides the application of a coating preservative containing natural antibacterial polysaccharides in the preservation of fruits and vegetables.

[0013] Furthermore, the fruit and vegetable in question is bamboo shoots.

[0014] A method for preserving fruits and vegetables using a coating preservative containing natural antibacterial polysaccharides, provided by a third aspect of the present invention, includes:

[0015] First, soak fresh fruits and vegetables in a chitosan solution. After soaking, remove them and soak them in a β-glucan solution. A first composite film will form on the surface of the fruits and vegetables. Then, remove the fruits and vegetables with the first composite film and soak them again in a solution containing ferric ions to micro-ionize the composite film. After that, take them out and let them air dry naturally.

[0016] Furthermore, the fresh fruits and vegetables mentioned are fresh bamboo shoots.

[0017] Furthermore, the soaking times are as follows: 4-6 minutes in chitosan solution; 4-6 minutes in β-glucan solution; and 0.5-1.5 minutes in ferric ion solution.

[0018] The present invention has the following advantages:

[0019] This invention is based on a novel antibacterial anionic natural polysaccharide (Suleco β-glucan) that was discovered for the first time. It utilizes the electrostatic interaction between chitosan and Suleco β-glucan to obtain a novel composite coating. Then, by combining the coordination between Suleco β-glucan and metal ions, the coating is micro-ionized, thereby obtaining a novel preservation coating that is green, safe, and has excellent antibacterial and mechanical properties.

[0020] The components of the coating preservative of this invention are all safe, non-toxic, and non-irritating to the human body. They are safe to eat, inexpensive, and readily available. Compared with existing bamboo shoot preservation technologies, this invention effectively avoids the addition and residue of toxic and harmful substances while ensuring the preservation effect of bamboo shoots. It also has a high nutrient retention rate, which is beneficial to human health.

[0021] This invention provides a novel green and edible bamboo shoot coating preservative with low equipment investment, a green and environmentally friendly preparation process, easy operation, safety and efficiency. It can effectively prevent the lignification of bamboo shoots in a short period of time, greatly reducing the cost of bamboo shoot preservation. It is suitable for large-scale production and application, especially for large-scale promotion and application in remote mountainous areas. Moreover, the antibacterial effect and mechanical properties of the coating are enhanced. Attached Figure Description

[0022] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0023] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0024] Figure 1 The potential values ​​of the Suleco β-glucan solution provided in Example 1 of this invention at different pH values;

[0025] Figure 2 The different components provided in Experimental Example 2 of this invention exhibit antibacterial effects against Staphylococcus aureus and Escherichia coli;

[0026] Figure 3 This is a comparison image of coated bamboo shoots and ordinary bamboo shoots after 5 days of storage, provided in Experimental Example 2 of the present invention.

[0027] Figure 4 This is a comparison chart showing the mass loss rate, hardness, lignin content, and POD activity of bamboo shoots with different coating treatments provided in Experimental Example 2 of the present invention. Detailed Implementation

[0028] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] The film-forming principle of this invention: Sulex β-glucan is a novel natural anionic polysaccharide with antibacterial activity. It forms a composite film by utilizing the electrostatic interaction between it and chitosan and the coordination interaction between Sulex β-glucan and metal ions.

[0030] Example 1

[0031] The pH of the Suleco β-glucan solution was adjusted to 3–8 using 0.1M hydrochloric acid or sodium hydroxide solution. A suitable amount was placed in the measuring cell, and the potential values ​​of the Suleco β-glucan solution at different pH values ​​were measured using a Zeta potential nanoparticle size analyzer. The results are as follows: Figure 1 As shown, within the measured pH range, the potential values ​​of the Suleke β-glucan solution are all negative, indicating that it is an anionic polysaccharide.

[0032] Structural diagram of Suleco-β-glucan:

[0033]

[0034] Example 2

[0035] This embodiment provides a method for using a composite natural polysaccharide coating for preserving bamboo shoots:

[0036] (1) Prepare 2% Suleco β-glucan and 2% chitosan solutions respectively; (2) Soak fresh bamboo shoots in chitosan solution for 5 minutes; (3) Soak the bamboo shoots in Suleco β-glucan solution for 5 minutes; the two polysaccharides form a first composite membrane due to electrostatic interaction; (4) Soak the bamboo shoots in 0.05mol / L ferric ion solution, and micro-ionize the composite membrane through coordination between Suleco β-glucan and ferric ions. After 1 minute, take them out and air dry them naturally to obtain bamboo shoots with chitosan-Suleco-ferric ion composite membrane.

[0037] Example 3

[0038] This embodiment provides a method for using a composite natural polysaccharide coating for preserving bamboo shoots:

[0039] (1) Prepare 0.5% Suleco β-glucan and 2% chitosan solutions respectively; (2) Soak fresh bamboo shoots in chitosan solution for 5 minutes; (3) Soak the bamboo shoots in Suleco β-glucan solution for 5 minutes, and the two polysaccharides form a first composite film due to electrostatic interaction; (4) Soak the bamboo shoots in 0.05mol / L ferric ion solution, and micro-ionize the composite film through coordination between Suleco β-glucan and ferric ions. After 1 minute, take them out and air dry them naturally to obtain bamboo shoots with chitosan-Suleco-ferric ion composite film.

[0040] Example 4

[0041] This embodiment provides a method for using a composite natural polysaccharide coating for preserving bamboo shoots:

[0042] (1) Prepare 1% Suleco β-glucan and 2% chitosan solutions respectively; (2) Soak fresh bamboo shoots in chitosan solution for 5 minutes; (3) Soak the bamboo shoots in Suleco β-glucan solution for 5 minutes, and the two polysaccharides form a first composite film due to electrostatic interaction; (4) Soak the bamboo shoots in 0.03mol / L ferric ion solution, and micro-ionize the composite film through coordination between Suleco β-glucan and ferric ions. After 1 minute, take them out and air dry them naturally to obtain bamboo shoots with chitosan-Suleco-ferric ion composite film.

[0043] Example 5

[0044] This embodiment provides a method for using a composite natural polysaccharide coating for preserving bamboo shoots:

[0045] (1) Prepare 2% Suleco β-glucan and 2% chitosan solutions respectively; (2) Soak fresh bamboo shoots in Suleco β-glucan solution for 5 minutes; (3) Soak the bamboo shoots in chitosan solution for 5 minutes, and the two polysaccharides form a first composite film due to electrostatic interaction; (4) Soak the bamboo shoots in 0.01mol / L ferric ion solution, and micro-ionize the composite film through coordination between Suleco β-glucan and ferric ions. After 1 minute, take them out and air dry them naturally to obtain bamboo shoots with chitosan-Suleco-ferric ion composite film.

[0046] Example 6

[0047] This embodiment provides a method for using a composite natural polysaccharide coating for preserving bamboo shoots:

[0048] (1) Prepare 2% Suleco β-glucan and 0.5% chitosan solutions respectively; (2) Soak fresh bamboo shoots in chitosan solution for 5 minutes; (3) Soak the bamboo shoots in Suleco β-glucan solution for 5 minutes, and the two polysaccharides form a first composite film due to electrostatic interaction; (4) Soak the bamboo shoots in 0.05mol / L ferric ion solution, and micro-ionize the composite film through coordination between Suleco β-glucan and ferric ions. After 1 minute, take them out and air dry them naturally to obtain bamboo shoots with chitosan-Suleco-ferric ion composite film.

[0049] Example 7

[0050] This embodiment provides a method for using a composite natural polysaccharide coating for preserving bamboo shoots:

[0051] (1) Prepare 1% Suleco β-glucan and 1% chitosan solutions respectively; (2) Soak fresh bamboo shoots in chitosan solution for 5 minutes; (3) Soak the bamboo shoots in Suleco β-glucan solution for 5 minutes, and the two polysaccharides form a first composite film due to electrostatic interaction; (4) Soak the bamboo shoots in 0.04mol / L ferric ion solution, and micro-ionize the composite film through coordination between Suleco β-glucan and ferric ions. After 1 minute, take them out and air dry them naturally to obtain bamboo shoots with chitosan-Suleco-ferric ion composite film.

[0052] Example 8

[0053] This embodiment provides a method for using a composite natural polysaccharide coating for preserving bamboo shoots:

[0054] (1) Prepare 1.5% Suleco β-glucan and 1.5% chitosan solutions respectively; (2) Soak fresh bamboo shoots in chitosan solution for 5 minutes; (3) Soak the bamboo shoots in Suleco β-glucan solution for 5 minutes, and the two polysaccharides form a first composite film due to electrostatic interaction; (4) Soak the bamboo shoots in 0.03mol / L ferric ion solution, and the composite film is micro-ionized through the coordination between Suleco β-glucan and ferric ions. After 1 minute, take them out and air dry them naturally to obtain bamboo shoots with chitosan-Suleco-ferric ion composite film.

[0055] Comparative Example 1

[0056] Bamboo shoots are soaked in a 1.5% chitosan solution for 5 minutes, then removed and air-dried to obtain bamboo shoots with a chitosan single-layer coating.

[0057] Comparative Example 2

[0058] Fresh bamboo shoots are soaked in a 1.5% chitosan solution for 5 minutes, and then soaked in a 1.5% sucralose β-glucan solution for another 5 minutes. Due to electrostatic interaction, a composite film is formed between the two polysaccharides, resulting in bamboo shoots with a chitosan-sucralose composite coating.

[0059] Comparative Example 3

[0060] Fresh bamboo shoots were soaked in a 1.5% chitosan solution for 5 minutes, and then soaked in a 1.5% β-glucan solution for another 5 minutes. After soaking, the bamboo shoots were removed and placed back into the chitosan solution to obtain bamboo shoots with a chitosan-suleco-chitosan composite coating.

[0061] Comparative Example 4

[0062] No action will be taken.

[0063] Experimental Example

[0064] This experimental example uses the film-forming bamboo shoots from Example 2 for subsequent experiments:

[0065] Chitosan, Suleco β-glucan, and the composite film (12 mg) on ​​the surface of dried bamboo shoots from Example 2 were respectively placed in a suspension of Staphylococcus aureus and Escherichia coli (1×10⁻⁶). 8 After incubation in (CFU / mL) for 24 hours, plate counting was performed. Figure 2 It is evident that, compared to the control group, the number of colonies in both the chitosan and composite membrane groups was reduced, and the antibacterial properties of the composite membrane group were superior to those of the chitosan and β-glucan groups alone.

[0066] After placing the coated bamboo shoots from Example 2 into a plastic bag and storing them for 5 days, compared with the uncoated bamboo shoots (see...), the results showed that... Figure 3The bamboo shoots showed significant improvements in color and morphology. Further analysis was conducted on the mass loss rate, hardness, lignin content, and POD activity of bamboo shoots treated with different coatings (Example 2 and Comparative Examples 1-4). Figure 4 The results showed that the chitosan-Sulex-iron ion coating had the best effect.

[0067] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A coating preservative containing natural antibacterial polysaccharides, characterized in that, The preservatives include chitosan solution, Suleke β-glucan solution and ferric ion solution; The preservative forms a multi-layer composite film on the surface of fruits and vegetables, including: a first composite film formed by the electrostatic combination of chitosan and seleno-β-glucan; and a micro-ionized layer formed by the coordination of ferric ions with seleno-β-glucan in the first composite film. Methods for preserving fruits and vegetables using coating preservatives containing natural antibacterial polysaccharides include: First, soak fresh fruits and vegetables in a chitosan solution. After soaking, remove them and soak them in a β-glucan solution. A first composite film will form on the surface of the fruits and vegetables. Then, remove the fruits and vegetables with the first composite film and soak them again in a solution containing ferric ions to micro-ionize the composite film. After that, take them out and let them air dry naturally.

2. The coating preservative containing natural antibacterial polysaccharides according to claim 1, characterized in that, The preservative comprises: a chitosan solution with a concentration of 0.5% to 2%, a β-glucan solution with a concentration of 0.5% to 2%, and a ferric ion solution with a concentration of 0.01 to 0.05 mol / L.

3. The coating preservative containing natural antibacterial polysaccharides according to claim 1, characterized in that, The aforementioned Suleke β-glucan is a novel natural anionic polysaccharide with antibacterial activity; it is an extracellular polysaccharide secreted by Agrobacterium ZX09, and its molecular structure is a chain-like structure of repeating units connected by 7 β-1,3-glucose and 2 α-1,3-glucose, as shown in Formula I. It is a natural anionic polysaccharide with a completely new structure. Formula I.

4. A coating preservative containing natural antibacterial polysaccharides according to claim 1, characterized in that, The fresh fruits and vegetables mentioned are fresh bamboo shoots.

5. A coating preservative containing natural antibacterial polysaccharides according to claim 1, characterized in that, The soaking times are as follows: 4-6 minutes in chitosan solution; 4-6 minutes in β-glucan solution; and 0.5-1.5 minutes in ferric ion solution.

6. The application of the coating preservative containing natural antibacterial polysaccharides as described in claim 1 in the preservation of fruits and vegetables.

7. The application according to claim 6, characterized in that, The fruit and vegetable in question is bamboo shoots.

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