CN117304559A - Preparation method and application of antibacterial fresh-keeping composite sponge - Google Patents
Preparation method and application of antibacterial fresh-keeping composite sponge Download PDFInfo
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- CN117304559A CN117304559A CN202311408969.8A CN202311408969A CN117304559A CN 117304559 A CN117304559 A CN 117304559A CN 202311408969 A CN202311408969 A CN 202311408969A CN 117304559 A CN117304559 A CN 117304559A
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- 239000002131 composite material Substances 0.000 title claims abstract description 79
- 230000000844 anti-bacterial effect Effects 0.000 title claims abstract description 57
- 238000002360 preparation method Methods 0.000 title claims abstract description 21
- 229920002678 cellulose Polymers 0.000 claims abstract description 85
- 239000001913 cellulose Substances 0.000 claims abstract description 85
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims abstract description 78
- 150000003242 quaternary ammonium salts Chemical class 0.000 claims abstract description 78
- 239000000243 solution Substances 0.000 claims abstract description 76
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- 238000006243 chemical reaction Methods 0.000 claims abstract description 45
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims abstract description 40
- 239000004202 carbamide Substances 0.000 claims abstract description 40
- 238000000502 dialysis Methods 0.000 claims abstract description 25
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- 235000012055 fruits and vegetables Nutrition 0.000 claims abstract description 19
- 238000000034 method Methods 0.000 claims abstract description 19
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonium chloride Substances [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 claims abstract description 16
- PLKATZNSTYDYJW-UHFFFAOYSA-N azane silver Chemical compound N.[Ag] PLKATZNSTYDYJW-UHFFFAOYSA-N 0.000 claims abstract description 16
- 238000004132 cross linking Methods 0.000 claims abstract description 13
- 238000004108 freeze drying Methods 0.000 claims abstract description 13
- 235000011114 ammonium hydroxide Nutrition 0.000 claims abstract description 12
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- 238000007493 shaping process Methods 0.000 claims abstract description 3
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- 238000004090 dissolution Methods 0.000 claims description 6
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Classifications
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/28—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D65/00—Wrappers or flexible covers; Packaging materials of special type or form
- B65D65/38—Packaging materials of special type or form
- B65D65/44—Applications of resilient shock-absorbing materials, e.g. foamed plastics material, honeycomb material
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2305/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2301/00 or C08J2303/00
- C08J2305/08—Chitin; Chondroitin sulfate; Hyaluronic acid; Derivatives thereof
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2329/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
- C08J2329/02—Homopolymers or copolymers of unsaturated alcohols
- C08J2329/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2405/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2401/00 or C08J2403/00
- C08J2405/08—Chitin; Chondroitin sulfate; Hyaluronic acid; Derivatives thereof
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2429/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
- C08J2429/02—Homopolymers or copolymers of unsaturated alcohols
- C08J2429/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/02—Elements
- C08K3/08—Metals
- C08K2003/0806—Silver
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K2201/00—Specific properties of additives
- C08K2201/011—Nanostructured additives
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K9/00—Use of pretreated ingredients
- C08K9/12—Adsorbed ingredients, e.g. ingredients on carriers
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W90/00—Enabling technologies or technologies with a potential or indirect contribution to greenhouse gas [GHG] emissions mitigation
- Y02W90/10—Bio-packaging, e.g. packing containers made from renewable resources or bio-plastics
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- Chemical & Material Sciences (AREA)
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- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
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Abstract
The invention discloses a preparation method and application of an antibacterial fresh-keeping composite sponge, and belongs to the technical field of functional materials. The method comprises the following steps: dissolving cellulose into an alkali urea solution, then adding a silver ammonia solution, reacting under the condition of microwave heating, and dialyzing after the reaction is finished to obtain a cellulose solution loaded with nano silver; dissolving chitin quaternary ammonium salt into alkali urea solution, adding the cellulose solution and polyvinyl alcohol solution loaded with nano silver, adding epoxy chloropropane, performing a crosslinking reaction, placing the obtained mixed solution into a mould after the reaction is finished, and performing shaping, dialysis and freeze drying to obtain the cellulose/chitin quaternary ammonium salt/polyvinyl alcohol composite sponge loaded with nano silver, namely the antibacterial fresh-keeping composite sponge. The preparation method is environment-friendly and efficient, and the prepared composite sponge has excellent antibacterial and fresh-keeping properties, can buffer and resist extrusion deformation, is biodegradable, and is suitable for packaging and transportation of picked fruits and vegetables.
Description
Technical Field
The invention relates to the technical field of functional materials, in particular to a preparation method and application of an antibacterial fresh-keeping composite sponge.
Background
The picked fruits and vegetables are still in a living state, and the fruits and vegetables are easy to age and invade by diseases and microorganisms, and the quality is also reduced due to mechanical damage in the picking and transporting processes. Provides a proper preservation environment, kills internal and external pathogenic bacteria, reduces mechanical damage, and is a key technology for prolonging the service life and quality of the picked fruits and vegetables. Although the traditional preservative film material can keep the freshness of fruits and vegetables to a certain extent, the preservative film material is generally prepared from petroleum-based products, has certain environmental pollution and difficult degradability, and the preservative film often has no anti-buffering performance and cannot give certain protection effect to the fruits and vegetables in transportation. In addition, the traditional film material has no antibacterial property, can not actively kill microorganisms such as bacteria and the like, can not reduce the problems of decay and deterioration, and can cause a large amount of loss in the long-time transportation, storage and sales process. Therefore, the food and fruit and vegetable packaging material needs to have the fresh-keeping function, the antibacterial and buffer protection functions, and a green, environment-friendly and efficient method is needed to develop the novel packaging material, so that the packaging effect of the food and fruit and vegetable is integrally improved. Therefore, it is necessary to find a green, environment-friendly and efficient preparation method for the food, fruit and vegetable packaging material with the functions of fresh keeping, antibiosis and buffer protection.
Disclosure of Invention
The invention aims to provide a preparation method and application of an antibacterial fresh-keeping composite sponge, which are used for solving the problems in the prior art. The preparation method is environment-friendly and efficient, and the prepared composite sponge has excellent antibacterial and fresh-keeping properties, can buffer and resist extrusion deformation, is biodegradable, and is suitable for packaging and transportation of picked fruits and vegetables.
In order to achieve the above object, the present invention provides the following solutions:
one of the technical schemes of the invention is as follows: the preparation method of the antibacterial fresh-keeping composite sponge comprises the following steps: dissolving cellulose into an alkali urea solution, then adding a silver ammonia solution, reacting under the condition of microwave heating, and dialyzing after the reaction is finished to obtain a cellulose solution loaded with nano silver; dissolving chitin quaternary ammonium salt into alkali urea solution, adding the cellulose solution and polyvinyl alcohol solution loaded with nano silver, adding epoxy chloropropane, performing a crosslinking reaction, placing the obtained mixed solution into a mould after the reaction is finished, and performing shaping, dialysis and freeze drying to obtain the cellulose/chitin quaternary ammonium salt/polyvinyl alcohol composite sponge loaded with nano silver, namely the antibacterial fresh-keeping composite sponge.
Further, the dissolution is low-temperature dissolution, and the temperature of the low-temperature dissolution is-20 ℃.
Further, the alkali urea solution is a mixed aqueous solution of NaOH and urea; the concentration of NaOH in the alkali urea solution is 5-7 wt.%, and the concentration of urea is 12-14 wt.%; the concentration of the silver ammonia solution is 0.025M-0.3M; the concentration of the polyvinyl alcohol solution is 5-8 wt.%; the substitution degree of the quaternary ammonium salt of the chitin quaternary ammonium salt is 92-94%.
Further, the solid-to-liquid ratio of the cellulose to the alkali urea solution to the silver ammonia solution is 1-5 g:100mL: 5-10 mL; the solid-to-liquid ratio of the chitin quaternary ammonium salt to the alkali urea solution, the cellulose solution loaded with nano silver, the polyvinyl alcohol solution and the epichlorohydrin is 1-5 g:100mL: 50-100 mL: 10-50 mL: 15-20 mL.
Further, adding the silver-ammonia solution, stirring uniformly, fully and uniformly mixing cellulose and the silver-ammonia solution, and reacting under the condition of microwave heating.
Further, the microwave power of the reaction under the condition of microwave heating is 500-900W, the heating temperature is 50-90 ℃, and the reaction time is 30-90 min. The reaction is carried out under stirring.
Further, the dialysis time in the process of obtaining the cellulose solution loaded with nano silver by dialysis after the reaction is finished is 24-72 hours (ensuring that unreacted silver-ammonia solution is completely separated out).
Further, after the chitin quaternary ammonium salt is dissolved into the alkali urea solution, stirring for 5-10 min by using a homogenizer until the chitin quaternary ammonium salt is completely dissolved, and then adding the cellulose solution and the polyvinyl alcohol solution loaded with nano silver.
Further, the temperature of the crosslinking reaction is 0-4 ℃ and the time is 60-90 min. The specific operation is as follows: adding epichlorohydrin, stirring uniformly, and then placing into a water bath with the temperature of 0-4 ℃ to carry out crosslinking reaction for 60-90 min.
Further, the molding temperature is 0-4 ℃ and the molding time is 24-72 h. The mixed solution forms a hydrogel during the molding process.
Further, after the reaction is finished, the obtained mixed solution is placed in a mould, and then the dialysis in the cellulose/chitin quaternary ammonium salt/polyvinyl alcohol composite sponge loaded with nano silver is obtained after molding, dialysis and freeze drying, namely, the hydrogel formed after molding is placed in water for dialysis, and the dialysis time is 5-7 d.
Further, the freeze drying temperature is between-20 and 0 ℃ and the time is between 24 and 72 hours.
The second technical scheme of the invention is as follows: the antibacterial fresh-keeping compound sponge prepared by the preparation method is provided.
The third technical scheme of the invention: an application of the antibacterial fresh-keeping compound sponge in antibacterial fresh-keeping packaging of fruits and vegetables.
Further, the fruits and vegetables include, but are not limited to, strawberries, litchis, grapes, bananas, cherry tomatoes, lettuce, cabbages and cucumbers.
The invention is characterized in that:
chitin is a polysaccharide compound obtained from shrimp and crab shells, insect shells and other wastes, and has certain film forming property. The functional material prepared from the chitin has the advantages of low cost, wide source, environmental protection, degradability and the like, and has the potential of preparing the fruit and vegetable packaging material. And the antibacterial property of the chitin can be obviously improved through quaternization modification. Nano silver is a nano-level metallic silver simple substance, has the characteristic of broad-spectrum physical antibacterial property, and has the inhibiting and killing effects on more than 40 common pathogenic microorganisms such as staphylococcus aureus, escherichia coli, pseudomonas aeruginosa and the like. Cellulose is a green, renewable and environment-friendly biomass resource, and the molecular chain of the cellulose contains a large amount of reducing functional groups, so that nano silver can be prepared in a green and efficient reduction mode and is loaded among fibers under the condition that a chemical reducing agent is not added. The cellulose loaded with nano silver can be compounded with chitin quaternary ammonium salt through dynamic hydrogen bonds, so that the physical properties of the pure chitin quaternary ammonium salt sponge, such as antibacterial property, flexibility and the like, can be improved, and the strength property of the sponge can be improved by combining the reinforcing effect of polyvinyl alcohol. Therefore, the invention firstly uses cellulose as a reducing agent, a stabilizing agent and an immobilizing agent to prepare nano silver, loads the nano silver into fibers to obtain nano silver loaded cellulose, and then utilizes the nano silver loaded cellulose, the chitin quaternary ammonium salt and the polyvinyl alcohol to prepare the antibacterial fresh-keeping composite sponge. The composite sponge prepared by the method has the advantages of low cost, simple operation and environmental protection, can reduce and load nano silver in a green way, and can improve the antibacterial property and the physical property of the chitin quaternary ammonium salt sponge.
The invention discloses the following technical effects:
(1) The invention firstly uses cellulose as a reducing agent, a stabilizing agent and an immobilizing agent to prepare nano silver, loads the nano silver into fibers to obtain nano silver loaded cellulose, and then uses the nano silver loaded cellulose, chitin quaternary ammonium salt and polyvinyl alcohol to prepare the antibacterial fresh-keeping composite sponge. The cellulose loaded with nano silver and the chitin quaternary ammonium salt are compounded to form a sponge material with a three-dimensional network structure, so that the fixing effect of the nano silver is further improved, the secondary fixing of the nano silver is realized, the excessively rapid release of the nano silver is reduced, and the accumulated toxicity problem of the nano silver is solved. The addition of the polyvinyl alcohol has an enhancement effect on the sponge, and can improve the physical strength of the sponge, so that the composite sponge has good buffering and extrusion deformation resistance. Meanwhile, the chitin quaternary ammonium salt has good antibacterial performance, and the nano silver has broad-spectrum antibacterial performance, and the nano silver have synergistic effect, so that the composite sponge has excellent antibacterial and fresh-keeping performances.
(2) According to the invention, the film forming property of chitin is utilized, the antibacterial property of the chitin is improved on the basis of quaternization modification, and the cellulose and polyvinyl alcohol loaded with nano silver are used for improving the antibacterial property of the chitin, so that the antibacterial property of the chitin is further improved, and meanwhile, the flexibility and strength of the chitin are improved, so that the multifunctional composite sponge is formed, and the composite sponge is applied to the field of antibacterial and fresh-keeping of fruits and vegetables.
(3) The raw materials such as cellulose, chitin quaternary ammonium salt and the like utilized by the invention are derived from agricultural, forestry and ocean wastes, and have the advantages of wide sources, low cost, environmental friendliness and sustainability.
(4) The invention uses cellulose as reducing agent, stabilizing agent and immobilizing agent to prepare nano silver, and loads nano silver between fibers, so as to reduce the release rate of nano silver, and no chemical reducing agent or stabilizing agent is added, thus the preparation method is simple, green, high in reduction efficiency, low in cost, safe and nontoxic; the microwave-assisted preparation method has high catalytic efficiency and low energy consumption.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a graph showing the effect of nano-silver loaded cellulose/chitosan quaternary ammonium salt/polyvinyl alcohol composite sponge prepared in example 1, cellulose/chitosan quaternary ammonium salt composite sponge prepared in comparative example 3, chitosan quaternary ammonium salt sponge prepared in comparative example 4 and common PU preservative film on inhibition zones of staphylococcus aureus (left) and escherichia coli (right);
FIG. 2 is a graph (a-c) showing the compression process and stress-strain curves (d) of the nano-silver-loaded cellulose/chitosan quaternary ammonium salt/polyvinyl alcohol composite sponge prepared in example 1, the cellulose/chitosan quaternary ammonium salt composite sponge prepared in comparative example 3, and the chitosan quaternary ammonium salt sponge prepared in comparative example 4;
FIG. 3 is an electron microscope image of nano silver on the nano silver loaded cellulose/chitin quaternary ammonium salt/polyvinyl alcohol composite sponge prepared in example 1;
FIG. 4 is a graph showing the degradation effects of the nano-silver loaded cellulose/chitosan quaternary ammonium salt/polyvinyl alcohol composite sponge prepared in example 1, the cellulose/chitosan quaternary ammonium salt composite sponge prepared in comparative example 3, the chitosan quaternary ammonium salt sponge prepared in comparative example 4 and the common PU fresh-keeping film in a simulated environment;
fig. 5 is a graph showing the preservation effect of the nano-silver loaded cellulose/chitosan quaternary ammonium salt/polyvinyl alcohol composite sponge, blank set (naturally placed) and common PU preservative film prepared in example 1 on strawberries in a simulated environment.
Detailed Description
Various exemplary embodiments of the invention will now be described in detail, which should not be considered as limiting the invention, but rather as more detailed descriptions of certain aspects, features and embodiments of the invention.
It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In addition, for numerical ranges in this disclosure, it is understood that each intermediate value between the upper and lower limits of the ranges is also specifically disclosed. Every smaller range between any stated value or stated range, and any other stated value or intermediate value within the stated range, is also encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.
It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the invention described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from consideration of the specification of the present invention. The specification and examples are exemplary only.
As used herein, the terms "comprising," "including," "having," "containing," and the like are intended to be inclusive and mean an inclusion, but not limited to.
The invention provides a preparation method of an antibacterial fresh-keeping composite sponge, which comprises the following steps: dissolving cellulose into an alkali urea solution (mixed aqueous solution with NaOH concentration of 5-7 wt% and urea concentration of 12-14 wt%), then adding silver-ammonia solution (0.025-0.3M), stirring uniformly, stirring for reaction under the condition of microwave heating (microwave power of 500-900W, heating temperature of 50-90 ℃ and reaction time of 30-90 min), and dialyzing (24-72 h) after the reaction is finished to obtain a cellulose solution loaded with nano silver; dissolving chitin quaternary ammonium salt (with the substitution degree of 92-94%) into alkali urea solution, stirring for 5-10 min by using a homogenizer until the chitin quaternary ammonium salt is completely dissolved, then adding the cellulose solution loaded with nano silver and polyvinyl alcohol solution (5-8 wt.%), adding epichlorohydrin, stirring uniformly, then placing the mixture into a water bath with the temperature of 0-4 ℃ for crosslinking reaction for 60-90 min, placing the obtained mixed solution into a mould after the reaction is finished, forming hydrogel by molding (with the temperature of 0-4 ℃ for 24-72 h), placing the hydrogel into water for dialysis for 5-7 d, and then freeze-drying (with the temperature of-20-0 ℃ for 24-72 h) to obtain the cellulose/chitin quaternary ammonium salt/polyvinyl alcohol composite sponge loaded with nano silver, namely the antibacterial fresh-keeping composite sponge.
Further, the solid-to-liquid ratio of the cellulose to the alkali urea solution to the silver ammonia solution is 1-5 g:100mL: 5-10 mL; the solid-to-liquid ratio of the chitin quaternary ammonium salt to the alkali urea solution, the cellulose solution loaded with nano silver, the polyvinyl alcohol solution and the epichlorohydrin is 1-5 g:100mL: 50-100 mL: 10-50 mL: 15-20 mL.
The invention also provides the antibacterial fresh-keeping composite sponge prepared by the preparation method.
The invention also provides application of the antibacterial fresh-keeping composite sponge in antibacterial fresh-keeping packaging of fruits and vegetables.
Further, the fruits and vegetables include, but are not limited to, strawberries, litchis, grapes, bananas, cherry tomatoes, lettuce, cabbages and cucumbers.
The invention is further illustrated by the following examples:
the cellulose used in the following examples is conventional cellulose extracted from biomass by conventional methods; the alkali urea solution used is a mixed aqueous solution of NaOH and urea (urea), wherein the concentration of NaOH is 7wt.%, the concentration of urea is 12wt.%, and the solution is called 7%/12% NaOH/urea solution for short; the quaternary ammonium salt substitution degree of the chitin quaternary ammonium salt is 92%, and the chitin quaternary ammonium salt is purchased from Shanghai Meilin Biochemical technology Co.
Example 1
The preparation of the antibacterial fresh-keeping composite sponge (nano silver loaded cellulose/chitin quaternary ammonium salt/polyvinyl alcohol composite sponge) comprises the following steps:
(1) 1g of cellulose is dissolved into 100mL of 7%/12% NaOH/urea solution at low temperature (-20 ℃), then 5mL of 0.025M silver ammonia solution is added, the mixture is stirred uniformly by using a glass rod, the mixture is placed into a microwave reaction kettle, the mixture is stirred mechanically at the power of 500W and the temperature of 50 ℃ for 30min, after the reaction is completed, the unreacted silver ions are removed by using a dialysis bag of mw10000 for dialysis for 24h, and the cellulose solution loaded with nano silver is obtained.
(2) Dissolving 1g of chitin quaternary ammonium salt into 100mL of 7%/12% NaOH/urea solution at low temperature (-20 ℃), stirring for 5min to completely dissolve by using a homogenizer, then adding 50mL of cellulose solution loaded with nano silver and 10mL of 5wt.% polyvinyl alcohol solution prepared in the step (1), then adding 15mL of epichlorohydrin, stirring, then placing into a water bath at 0 ℃ for crosslinking reaction for 60min, placing the mixed solution into a mold after the reaction is completed, forming hydrogel after molding (the temperature is 0 ℃ for 24 h), placing the molded hydrogel into water for dialysis for 5d, and then freeze-drying (the temperature is 0 ℃ for 24 h) to obtain the cellulose/chitin quaternary ammonium salt/polyvinyl alcohol composite sponge loaded with nano silver.
Example 2
The preparation of the antibacterial fresh-keeping composite sponge (nano silver loaded cellulose/chitin quaternary ammonium salt/polyvinyl alcohol composite sponge) comprises the following steps:
(1) 2g of cellulose is dissolved into 100mL of 7%/12% NaOH/urea solution at low temperature (-20 ℃), then 7mL of 0.05M silver ammonia solution is added, the mixture is stirred uniformly by using a glass rod, the mixture is placed into a microwave reaction kettle, the mixture is stirred mechanically at the power of 600W and the temperature of 70 ℃ for reaction for 60min, after the reaction is completed, unreacted silver ions are removed by using a dialysis bag of mw10000 for dialysis for 48h, and the cellulose solution loaded with nano silver is obtained.
(2) Dissolving 2g of chitin quaternary ammonium salt into 100mL of 7%/12% NaOH/urea solution at low temperature (-20 ℃), stirring for 5min to completely dissolve by using a homogenizer, then adding 50mL of cellulose solution loaded with nano silver and 20mL of polyvinyl alcohol solution with 5wt.% prepared in the step (1), then adding 15mL of epichlorohydrin, stirring, then placing into a water bath with 0 ℃ for crosslinking reaction for 60min, placing the mixed solution into a mold after the reaction is completed, forming hydrogel after molding (the temperature is 0 ℃ for 48 h), placing the molded hydrogel into water for dialysis for 5d, and then freeze-drying (the temperature is 0 ℃ for 24 h) to obtain the cellulose/chitin quaternary ammonium salt/polyvinyl alcohol composite sponge loaded with nano silver.
Example 3
The preparation of the antibacterial fresh-keeping composite sponge (nano silver loaded cellulose/chitin quaternary ammonium salt/polyvinyl alcohol composite sponge) comprises the following steps:
(1) 3g of cellulose is dissolved into 100mL of 7%/12% NaOH/urea solution at low temperature (-20 ℃), then 10mL of 0.1M silver ammonia solution is added, the mixture is stirred uniformly by using a glass rod, the mixture is placed into a microwave reaction kettle, the mixture is stirred mechanically at the power of 800W and the temperature of 80 ℃ for reaction for 60min, after the reaction is completed, unreacted silver ions are removed by using a dialysis bag of mw10000 for dialysis for 72h, and the cellulose solution loaded with nano silver is obtained.
(2) Dissolving 3g of chitin quaternary ammonium salt into 100mL of 7%/12% NaOH/urea solution at low temperature (-20 ℃), stirring for 5min to completely dissolve by using a homogenizer, then adding 100mL of cellulose solution loaded with nano silver and 30mL of polyvinyl alcohol solution with 5wt.% prepared in the step (1), then adding 20mL of epichlorohydrin, stirring, then placing into a water bath with 0 ℃ for crosslinking reaction for 60min, placing the mixed solution into a mold after the reaction is completed, forming hydrogel after molding (the temperature is 2 ℃ for 72 h), placing the formed hydrogel into water for dialysis for 7d, and then freeze-drying (the temperature is 0 ℃ for 24 h) to obtain the cellulose/chitin quaternary ammonium salt/polyvinyl alcohol composite sponge loaded with nano silver.
Example 4
The preparation of the antibacterial fresh-keeping composite sponge (nano silver loaded cellulose/chitin quaternary ammonium salt/polyvinyl alcohol composite sponge) comprises the following steps:
(1) 5g of cellulose is dissolved into 100mL of 7%/12% NaOH/urea solution at low temperature (-20 ℃), then 10mL of 0.3M silver ammonia solution is added, the mixture is stirred uniformly by using a glass rod, the mixture is placed into a microwave reaction kettle, the mixture is stirred mechanically at the power of 900W and the temperature of 90 ℃ for reaction for 90min, after the reaction is completed, unreacted silver ions are removed by using a dialysis bag of mw10000 for dialysis for 72h, and the cellulose solution loaded with nano silver is obtained.
(2) Dissolving 5g of chitin quaternary ammonium salt into 100mL of 7%/12% NaOH/urea solution at low temperature (-20 ℃), stirring for 5min to completely dissolve by using a homogenizer, then adding 100mL of cellulose solution loaded with nano silver and 50mL of polyvinyl alcohol solution with 5wt.% prepared in the step (1), then adding 20mL of epichlorohydrin, stirring, then placing into a water bath with 0 ℃ for crosslinking reaction for 60min, placing the mixed solution into a mold after the reaction is completed, forming hydrogel after molding (the temperature is 4 ℃ for 72 h), placing the molded hydrogel into water for dialysis for 7d, and then freeze-drying (the temperature is 0 ℃ for 24 h) to obtain the cellulose/chitin quaternary ammonium salt/polyvinyl alcohol composite sponge loaded with nano silver.
Comparative example 1
The difference from example 1 is only that the chitin quaternary ammonium salt is replaced by the common chitin which is not modified by quaternary ammonium salt and has the same quality. The obtained composite sponge is cellulose/chitin/polyvinyl alcohol composite sponge loaded with nano silver.
Comparative example 2
The only difference from example 1 is that the addition of the polyvinyl alcohol solution was omitted. The obtained sponge is cellulose/chitin quaternary ammonium salt composite sponge loaded with nano silver.
Comparative example 3
The preparation of the antibacterial fresh-keeping compound sponge (cellulose/chitin quaternary ammonium salt compound sponge) comprises the following steps:
(1) 2g of cellulose was dissolved at low temperature (-20 ℃) into 100mL of a 7%/12% NaOH/urea solution to obtain a cellulose solution.
(2) Dissolving 2g of chitin quaternary ammonium salt into 100mL of 7%/12% NaOH/urea solution at low temperature (-20 ℃), stirring for 5min to completely dissolve by using a homogenizer, adding 50mL of cellulose solution prepared in the step (1), then adding 15mL of epichlorohydrin, stirring, then placing into a water bath at 0 ℃ for crosslinking reaction for 60min, placing the mixed solution into a mold after the reaction is completed, forming hydrogel through molding (the temperature is 0 ℃ for 24 h), dialyzing the molded hydrogel in water for 5d, and freeze-drying (the temperature is 0 ℃ for 24 h) to obtain the cellulose/chitin quaternary ammonium salt composite sponge.
Comparative example 4
2g of chitin quaternary ammonium salt is dissolved into 100mL of 7%/12% NaOH/urea solution at low temperature (-20 ℃), stirred by a homogenizer for 5min until the chitin quaternary ammonium salt is completely dissolved, then 15mL of epichlorohydrin is added, stirred, then the mixture is placed into a water bath at 0 ℃ for crosslinking reaction for 60min, the mixed solution is placed into a mould after the reaction is finished, hydrogel is formed after molding (the temperature is 0 ℃ for 24 h), the molded hydrogel is placed into water for dialysis for 5d, and then freeze-drying (the temperature is 0 ℃ for 24 h) is carried out, so that the chitin quaternary ammonium salt sponge is obtained.
Effect verification
According to the requirements of the antibacterial fresh-keeping sponge material for final fruit and vegetable packaging, the antibacterial performance (taking the antibacterial effect on staphylococcus aureus and escherichia coli as an example), the buffering anti-extrusion performance (taking the compression rebound effect of the sponge as an example), the degradation performance (taking the common PU fresh-keeping film as an example) and the fresh-keeping performance (taking the common PU fresh-keeping film as an example) of the composite sponge are mainly detected. The common PU preservative films used in the following effect verification are common commercial PU preservative films, and are purchased from local supermarkets (brand: golden sunlight, heat-resistant temperature 100 ℃ C., cold-resistant temperature-40 ℃ C.), and the specification and the size are 30m multiplied by 30cm (length multiplied by width). The specific detection is as follows.
1. Antibacterial property
The bacteriostasis circle test adopts the existing methods in the industry, and concretely refers to the following papers:
(1)https://doi.org/10.1016/j.indcrop.2020.112987；
(2)https://doi.org/10.1016/j.cej.2021.129815；
(3)https://doi.org/10.1016/j.msec.2020.111012。
fig. 1 is a graph showing the effect of the nano silver-loaded cellulose/chitosan quaternary ammonium salt/polyvinyl alcohol composite sponge (QCH/tcnf@agnps/PVA, QCH for chitosan quaternary ammonium salt, tcnf@agnps for nano silver-loaded cellulose, PVA for polyvinyl alcohol) prepared in example 1, the cellulose/chitosan quaternary ammonium salt composite sponge (QCH/TCNF) prepared in comparative example 3, the effect of the chitosan quaternary ammonium salt sponge (QCH) prepared in comparative example 4 and a common PU preservative film (control group) on the inhibition zone of staphylococcus aureus and escherichia coli, wherein the left graph shows the inhibition zone effect of each sponge sample on staphylococcus aureus, and the right graph shows the inhibition zone effect of each sponge sample on escherichia coli. As can be seen from fig. 1, the nano-silver loaded cellulose/chitosan quaternary ammonium salt/polyvinyl alcohol composite sponge prepared in example 1 has an obvious inhibition effect on two bacteria, and an obvious inhibition zone is generated.
The test results of the inhibition zone of the composite sponge prepared in each example and comparative example are shown in table 1:
TABLE 1
As can be seen from Table 1, the composite sponges prepared in examples 1 to 4 of the present invention have good inhibitory properties against Staphylococcus aureus and against Escherichia coli. Comparison of the data of example 1 and comparative example 1 shows that the antibacterial effect of example 1 using chitin quaternary ammonium salt is better than that of comparative example 1 using chitin, which indicates that quaternization modification can improve the antibacterial performance of chitin and that the antibacterial performance of chitin quaternary ammonium salt is better.
2. Buffer anti-extrusion performance
The anti-extrusion performance is measured by a universal tensile machine, the composite sponge is placed on a platform, compression is carried out according to different pressures and cycle numbers, the compression is carried out, and a stress-strain curve and a compression picture are recorded.
Fig. 2 is a graph (a-c) showing compression process and stress strain curves (d) of the nano silver-loaded cellulose/chitosan quaternary ammonium salt/polyvinyl alcohol composite sponge (QCH/tcnf@agnps/PVA) prepared in example 1, the cellulose/chitosan quaternary ammonium salt composite sponge (QCH/TCNF) prepared in comparative example 3, and the chitosan quaternary ammonium salt sponge (QCH) prepared in comparative example 4, from which it can be seen that the composite sponge prepared in example 1 has good compression retraction elastic properties.
3. Electronic mirror image
Fig. 3 is an electron microscope image of nano silver on the nano silver loaded cellulose/chitin quaternary ammonium salt/polyvinyl alcohol composite sponge prepared in example 1, and it can be seen that the particle size of the prepared nano silver is relatively uniform, about 20 nm.
4. Degradation properties
The degradation performance testing method comprises the following steps:
the degradation test of the material was performed in phosphate buffer (pH 7.4) containing lysozyme (. Gtoreq.20000U/mg). The same mass material is put into the solution, after a fixed time, the sample is taken out of the phosphate buffer solution, washed with ultrapure water, dried and weighed. The degradation rate in different time periods can be calculated from the quality difference before and after the sample.
Fig. 4 is a graph showing degradation effects of the nano silver-loaded cellulose/chitosan quaternary ammonium salt/polyvinyl alcohol composite sponge (QCH/tcnf@agnps/PVA) prepared in example 1, the cellulose/chitosan quaternary ammonium salt composite sponge (QCH/TCNF) prepared in comparative example 3, the chitosan quaternary ammonium salt sponge (QCH) prepared in comparative example 4, and the common PU preservative film (comparative group) in a simulated environment, from which it can be seen that the composite sponge prepared in example 1 has good degradation performance in the simulated environment. With the time, the composite sponge is mostly degraded.
4. Fresh-keeping property of fruits and vegetables
The fresh-keeping effect of the sponge is compared between a blank group, a common PU fresh-keeping film group and a cellulose/chitin quaternary ammonium salt/polyvinyl alcohol composite sponge (QCH/TCNF@AgNPS/PVA) loaded with nano silver, wherein the selected fresh-keeping object is strawberries which are not easy to store, the blank group is not packaged by any material and is naturally placed in a container, the common PU fresh-keeping film group is respectively provided with a PU fresh-keeping film at the bottom and the top (surface) of the strawberries, and the cellulose/chitin quaternary ammonium salt/polyvinyl alcohol composite sponge group loaded with nano silver is respectively provided with a composite sponge with the same area as the PU fresh-keeping film at the bottom and the top (surface) of the strawberries. The fresh-keeping result is shown in fig. 5 (for convenience in photographing, fresh-keeping materials on the tops of the strawberries of the common PU fresh-keeping film group and the composite sponge group are temporarily taken off), and as can be seen from fig. 5, the strawberries of the blank group start to rot on the 2 nd day, a large amount of strawberries rot on the 4 th day, and a large amount of mould grows until the strawberries completely rot on the 6 th day; the PU group also shows mould on the 2 nd day, more mould on the 4 th day, and a large amount of mould grows up to the 6 th day; the cellulose/chitin quaternary ammonium salt/polyvinyl alcohol composite sponge (QCH/TCNF@AgNPS/PVA) loaded with nano silver only has a small amount of mould on the 4 th day, and can be ignored, and on the 6 th day, the individual strawberries have a small amount of mould, so that the fresh-keeping effect is obvious compared with the first two materials.
The above embodiments are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope defined by the claims of the present invention without departing from the design spirit of the present invention.
Claims (10)
1. The preparation method of the antibacterial fresh-keeping composite sponge is characterized by comprising the following steps of: dissolving cellulose into an alkali urea solution, then adding a silver ammonia solution, reacting under the condition of microwave heating, and dialyzing after the reaction is finished to obtain a cellulose solution loaded with nano silver; dissolving chitin quaternary ammonium salt into alkali urea solution, adding the cellulose solution and polyvinyl alcohol solution loaded with nano silver, adding epoxy chloropropane, performing a crosslinking reaction, placing the obtained mixed solution into a mould after the reaction is finished, and performing shaping, dialysis and freeze drying to obtain the cellulose/chitin quaternary ammonium salt/polyvinyl alcohol composite sponge loaded with nano silver, namely the antibacterial fresh-keeping composite sponge.
2. The method for preparing the antibacterial fresh-keeping compound sponge according to claim 1, wherein the dissolution is low-temperature dissolution, and the temperature of the low-temperature dissolution is-20 ℃.
3. The method for preparing the antibacterial fresh-keeping composite sponge according to claim 1, wherein the alkali urea solution is a mixed aqueous solution of NaOH and urea; the concentration of NaOH in the alkali urea solution is 5-7 wt.%, and the concentration of urea is 12-14 wt.%; the concentration of the silver ammonia solution is 0.025M-0.3M; the concentration of the polyvinyl alcohol solution is 5-8 wt.%; the substitution degree of the quaternary ammonium salt of the chitin quaternary ammonium salt is 92-94%.
4. The method for preparing the antibacterial fresh-keeping composite sponge according to claim 3, wherein the solid-to-liquid ratio of the cellulose to the alkali urea solution to the silver ammonia solution is 1-5 g:100mL: 5-10 mL; the solid-to-liquid ratio of the chitin quaternary ammonium salt to the alkali urea solution, the cellulose solution loaded with nano silver, the polyvinyl alcohol solution and the epichlorohydrin is 1-5 g:100mL: 50-100 mL: 10-50 mL: 15-20 mL.
5. The method for preparing the antibacterial fresh-keeping composite sponge according to claim 1, wherein the microwave power of the reaction under the condition of microwave heating is 500-900W, the heating temperature is 50-90 ℃, and the reaction time is 30-90 min.
6. The method for preparing the antibacterial fresh-keeping composite sponge according to claim 1, wherein the dialysis time in the process of obtaining the nano silver loaded cellulose solution by dialysis after the reaction is finished is 24-72 h.
7. The method for preparing the antibacterial fresh-keeping composite sponge according to claim 1, wherein the temperature of the crosslinking reaction is 0-4 ℃ and the time is 60-90 min.
8. The method for preparing the antibacterial fresh-keeping composite sponge according to claim 1, wherein the temperature of freeze drying is-20-0 ℃ and the time is 24-72 h.
9. An antibacterial fresh-keeping composite sponge prepared by the preparation method according to any one of claims 1 to 8.
10. Use of the antibacterial fresh-keeping compound sponge according to claim 9 in antibacterial fresh-keeping packaging of fruits and vegetables.
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