High-hydrophobicity surface deacetylated chitin nanocrystal package and preparation method and application thereof

Abstract

The invention discloses a high-hydrophobicity surface deacetylated chitin nanocrystal package as well as a preparation method and application thereof, and relates to the technical field of materials. A preparation method of a high-hydrophobicity surface-deacetylated chitin nanocrystalline package comprises the following steps: pouring a surface-deacetylated chitin nanocrystalline solution into a culture dish, and slowly drying to obtain a surface-deacetylated chitin nanocrystalline film; and casting a layer of protein solution on the dried film until the surface of the film is immersed, placing a culture dish on an electric turntable, rotating at a constant rotating speed until the protein solution is uniformly diffused on the surface of the film, and drying the protein solution to obtain the high-hydrophobicity surface deacetylated chitin nanocrystal package. The film prepared by the method provided by the invention is simple to operate, the raw materials are all natural substances, no chemical residue exists, the film is healthier and suitable for food packaging, the research on the electrostatic self-assembly of the protein and the deacetylated chitin nanocrystals is less, and the electrostatic self-assembly market of the chitin nanocrystals can be impacted.

Description

Technical Field

[0001] The invention relates to the technical field of materials, and in particular to a highly hydrophobic surface chitosan nanocrystal package and a preparation method and application thereof. Background Art

[0002] Chitin nanocrystals (ChNCs) are the product obtained by acid hydrolysis of natural chitin. They are green and environmentally friendly, have high crystallinity and good dispersion stability, and show good application prospects in the field of food packaging. The surface deacetylated chitin nanocrystals (D-ChNCs) prepared by partial deacetylation of natural chitin combined with acid hydrolysis have good film-forming properties and obvious antibacterial activity.

[0003] Compared with natural chitin nanocrystals, deacetylated chitin nanocrystals show a higher water contact angle (WCA), but still exhibit hydrophilic properties (WCA < 90°). Generally speaking, the high hydrophilicity of food polysaccharide packaging is a common problem that limits its practical application. The reason is that highly hydrophilic packaging is easily affected by moisture, resulting in a decrease in packaging mechanical properties and barrier properties, which directly has an adverse effect on subsequent food packaging applications. In the study of improving the hydrophobic properties of chitin nanocrystals, the approach of introducing hydrophobic functional groups on the surface of chitin nanocrystals is currently widely used. Although this method can greatly improve the hydrophobicity of chitin nanocrystals, the chemical modification method often involves various chemical reagents, expensive instruments or complex processes, so its application in the field of food packaging is still limited. The widely used deposition method, although it can achieve the deposition of materials to a certain extent, has the disadvantages of difficulty in controlling the precipitation position, poor repeatability, difficult process control, and uneven particle deposition. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a highly hydrophobic surface chitosan nanocrystal package and a preparation method and application thereof.

[0005] The objective of the present invention is achieved through the following technical solutions: A preparation method of a highly hydrophobic surface chitosan nanocrystal package comprises the following steps: pouring a surface chitosan nanocrystal solution into a culture dish, and slowly drying the solution to obtain a surface chitosan nanocrystal film; casting a layer of protein solution on the dried film until the film surface is immersed, placing the culture dish on an electric turntable and rotating it at a constant speed until the protein solution is evenly diffused on the film surface, and obtaining a highly hydrophobic surface chitosan nanocrystal package after the protein solution is dried.

[0006] The surface deacetylated chitin nanocrystals are prepared by an alkali treatment method.

[0007] The alkali treatment method is specifically as follows: dispersing chitin powder in a sodium hydroxide solution for reaction, treating the sample after the reaction to neutrality, and drying to obtain deacetylated chitin powder; taking the deacetylated chitin powder, adding it to a hydrochloric acid solution for reaction, adding distilled water after the reaction to repeat centrifugation, ultrasonicating the obtained sample, and then centrifuging to remove impurities to obtain surface deacetylated chitin nanocrystals.

[0008] The mass concentration of the surface chitosan nanocrystal solution was 0.6%, and the liquid level in the culture dish reached 0.5 cm. The depth of the polytetrafluoroethylene culture dish was about 1 cm, and the liquid height did not exceed two-thirds of it.

[0009] The culture dish is made of polytetrafluoroethylene. The protein solution is zein solution, and the mass concentration of the protein solution is 1%.

[0010] The rotation speed of the electric turntable is 10s / turn, and the whole device is placed in a 37°C oven for low-temperature drying.

[0011] The second aspect of the present invention provides a highly hydrophobic surface chitosan nanocrystal package.

[0012] The third aspect of the present invention provides an application of a highly hydrophobic surface chitosan nanocrystal package in food packaging.

[0013] This method is based on the principle of electrostatic interaction between food macromolecules, with electrostatic self-assembly technology as the core entry point, to improve the hydrophobicity of surface deacetylated chitin nanocrystal packaging, while retaining the original antibacterial activity, and can be used for food preservation. The spin coating deposition technology is used to make the liquid evenly distributed in the culture dish at a low speed without large fluctuations, so that the overall thickness of the film is uniform, the surface is smoother, and the internal structure is more uniform and dense.

[0014] The beneficial effects of the present invention are: The film prepared by the method provided by the present invention is easy to operate, and the raw materials are all natural substances, which are healthier without chemical residues and are suitable for food packaging. There are few studies on the electrostatic self-assembly of protein and deacetylated chitin nanocrystals, and the film can impact the market of electrostatic self-assembly of chitin nanocrystals. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a SEM comparison picture; Figure 2 This is the AFM comparison picture; Figure 3 It is a contact angle comparison chart; Figure 4 This is the change diagram of TVB-N during pork storage; Figure 5 This is a graph showing the changes in TBA during pork storage; Figure 6 This is a graph showing the changes in the total colony count during pork storage. DETAILED DESCRIPTION

[0016] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention. Example

[0017] A method for preparing a highly hydrophobic surface chitosan nanocrystal package: 1. Preparation of surface deacetylated chitin nanocrystals: 50 g of purified natural chitin was dispersed in 1000 mL of 33% NaOH solution and reacted at 90 °C for 8 hours. After the reaction, it was washed with deionized water until neutral, and then vacuum freeze-dried to obtain surface deacetylated chitin. Subsequently, 40 g of surface deacetylated chitin was suspended in 1000 mL of 3.5 mol / L HCl solution and reacted at 95 °C for 1.5 hours. After the suspension was restored to neutrality by repeated centrifugation and washing, highly dispersed surface deacetylated chitin nanocrystals (D-ChNCs) were obtained by ultrasonic treatment.

[0018] 2. Preparation of hydrophobic film of chitosan nanocrystal / zein: First, pour the surface chitosan nanocrystal (0.6wt%) into a polytetrafluoroethylene culture dish (so that the liquid level reaches 0.5cm), and then slowly dry it at 25℃ for 8 hours to obtain a surface chitosan nanocrystal film. Then cast a layer of 1% zein solution on the film until the surface is immersed, place the culture dish on an electric turntable and rotate it at a constant speed until the zein is evenly diffused on the surface of the film, and place the whole in a 37℃ oven for low-temperature drying. After the solvent is completely evaporated, a highly hydrophobic surface chitosan nanocrystal package (D-ChNCs / Zein) can be obtained.

[0019] Comparative Example Compared with the preparation in the example, the comparative example does not include the step of adding zein.

[0020] The comparative example and the finished product prepared in the comparative example were subjected to SEM scanning, and the scanning images are as follows Figure 1 As shown, it can be seen from SEM that the deacetylated chitin nanocrystal / zein film (D-ChNCs / Zein) has an additional protein film on the surface compared with the deacetylated chitin nanocrystal film (D-ChNCs), and zein has been electrostatically deposited on the surface of the deacetylated chitin nanocrystals.

[0021] The surface morphology analysis and contact angle measurement of the comparative example and the finished product prepared in the comparative example are shown in the AFM comparison diagram. Figure 2 , contact angle comparison Figure 3 . As can be seen from the figure, the chitosan nanocrystal / zein film has a higher water contact angle than the chitosan nanocrystal film, and is greater than 90°, which has been modified to be hydrophobic. According to the AFM comparison of the two films, the surface of the chitosan nanocrystal / zein film is significantly smoother than that of the chitosan nanocrystal film, and the surface defects are reduced, which has a positive effect on improving the hydrophobicity.

[0022] application The finished product prepared in the embodiment is applied to pork packaging.

[0023] Take fresh pork with uniform appearance and texture, cut the beef into 3cm×3cm×1cm blocks on a sterile operating table for later use, and place the prepared highly hydrophobic surface deacetylated chitin nanocrystal package in a sterile operating room and irradiate it with an ultraviolet lamp for 30 minutes for later use. Cover the surface of the pork with the sterilized highly hydrophobic surface deacetylated chitin nanocrystal package, and use the package treatment prepared in the comparative example as the control group. The two groups of samples were refrigerated at 4°C for 10 days, and the various indicators of the beef (TVB-N, TBA, total colony count) were measured regularly.

[0024] Volatile basic nitrogen (TVB-N) can reflect the degree of protein decomposition in fresh pork. Due to the action of microorganisms and enzymes, the protein in beef is decomposed into alkaline nitrogen-containing substances accompanied by an unpleasant odor. The determination results are as follows: Figure 4 .Depend on Figure 4 It can be seen that the volatile basic nitrogen of the samples increased with the extension of storage time, and the ChNCs-Zein group was lower than the control group. The TVB-N value of fresh pork is generally lower than 15 mg / 100 g. Figure 4 It can be seen that the ChNCs-Zein group can significantly delay the deterioration of pork during the 7-day storage period.

[0025] Among them, malondialdehyde (TBA) is a compound produced during the oxidation process. Testing the malondialdehyde value of pork can determine the degree of oxidation of pork. Figure 5 It is the change of TBA in pork during storage. The initial TBA value of pork is 0.11 mg / kg. On the seventh day, the TBA value of the sample increased significantly, among which the blank control group significantly exceeded the TBA range of fresh pork.

[0026] The growth and reproduction of microorganisms is one of the main factors for the spoilage of meat. During storage, the growth of microorganisms will have adverse effects on the sensory quality, color and other indicators of meat. D-ChNCs / Zein is applied to fresh pork in the hope of reducing the growth and reproduction of microorganisms during storage. Figure 6 is the change in total bacterial count during pork storage, Figure 6 It can be seen that with the increase of storage time, the total number of microorganisms showed a gradual upward trend. Compared with the control group, the increasing trend of the D-ChNCs / Zein group was slow, and on the seventh day it did not exceed the total number of fresh meat bacteria specified by the national standard.

[0027] It can be seen from the above experimental data that the hydrophobic packaging provided by the present invention is improved on the basis of D-ChNCs, which significantly improves the preservation effect on meat. While retaining the antibacterial properties of D-ChNCs, its hydrophobicity, mechanical properties and surface smoothness are all improved.

[0028] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a highly hydrophobic surface chitosan nanocrystal package, characterized in that: The method comprises the following steps: pouring a surface deacetylated chitin nanocrystal solution into a culture dish, and slowly drying the solution to obtain a surface deacetylated chitin nanocrystal film; casting a layer of protein solution on the dried film until the surface of the film is immersed, placing the culture dish on an electric turntable and rotating it at a constant speed until the protein solution is evenly diffused on the surface of the film, and obtaining a highly hydrophobic surface deacetylated chitin nanocrystal package after the protein solution is dried.

2. The preparation method according to claim 1, characterized in that: The surface deacetylated chitin nanocrystals are prepared by an alkali treatment method.

3. The preparation method according to claim 2, characterized in that: The alkali treatment method specifically comprises: dispersing chitin powder in a sodium hydroxide solution for reaction, treating the sample after the reaction to be neutral, and drying to obtain deacetylated chitin powder; taking the deacetylated chitin powder, adding it to a hydrochloric acid solution for reaction, adding distilled water after the reaction to perform repeated centrifugation, ultrasonicating the obtained sample, and then centrifuging to remove impurities to obtain surface deacetylated chitin nanocrystals.

4. The preparation method according to claim 1, characterized in that: The mass concentration of the surface deacetylated chitin nanocrystal solution is 0.6%, and the height of the liquid level in the culture dish reaches 0.5 cm.

5. The preparation method according to claim 1, characterized in that: The culture dish is made of polytetrafluoroethylene.

6. The preparation method according to claim 1, characterized in that: The protein solution is zein solution.

7. The preparation method according to claim 1, characterized in that: The mass concentration of the protein solution is 1%.

8. The preparation method according to claim 1, characterized in that: The rotation speed of the electric turntable is 10s / turn, and the whole device is placed in a 37°C oven for low-temperature drying.

9. A highly hydrophobic surface chitosan nanocrystal package, characterized in that: The method is prepared by any one of claims 1 to 8.

10. Use of the highly hydrophobic surface deacetylated chitin nanocrystal packaging as claimed in claim 9 in food packaging.

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