1. A preparation method of a high-strength edible antibacterial packaging film, which takes chitosan and carboxymethyl cellulose as film matrixes and utilizes hydrogen bond acting force between hydroxyl groups of the chitosan and the carboxymethyl cellulose to prepare the high-strength edible antibacterial packaging film, and is characterized by comprising the following steps:

preparing a chitosan acetic acid aqueous solution containing a plasticizer, a cross-linking agent and an antioxidant;

preparing a carboxymethyl cellulose aqueous solution containing a plasticizer, an antioxidant and an antibacterial agent;

respectively dissolving chitosan acetic acid aqueous solution and carboxymethyl cellulose aqueous solution, filtering, defoaming filtrate, and respectively obtaining chitosan membrane solution and carboxymethyl cellulose membrane solution;

sequentially or alternatively forming films on the chitosan film solution or the carboxymethyl cellulose film solution to obtain the high-strength edible antibacterial packaging film.

2. The method for preparing a high-strength edible antibacterial packaging film according to claim 1, wherein one of the chitosan film solution or the carboxymethyl cellulose film solution is coated to form a film, and then the other film solution is coated on the formed film to obtain the high-strength edible antibacterial packaging film, and in the process of coating one of the chitosan film solution or the carboxymethyl cellulose film solution to form a film, a solution casting method is adopted for multilayer composite film formation; or the like, or, alternatively,

and (3) forming a film by multilayer compounding of the chitosan film solution and the carboxymethyl cellulose film solution by adopting an alternative solution tape casting method to obtain the high-strength edible antibacterial packaging film.

3. The method for preparing a high-strength edible antibacterial packaging film according to claim 1, wherein the method for preparing the chitosan acetic acid aqueous solution containing the plasticizer, the cross-linking agent and the antioxidant comprises the following steps:

firstly preparing a chitosan acetic acid aqueous solution, and then adding a plasticizer, a cross-linking agent and an antioxidant into the chitosan acetic acid aqueous solution to obtain the chitosan acetic acid aqueous solution containing the plasticizer, the cross-linking agent and the antioxidant.

4. The method for preparing a high-strength edible antibacterial packaging film according to claim 3, wherein the chitosan deacetylation degree is 80-95%, and the mass fraction of chitosan in the chitosan acetic acid aqueous solution is 2-4%.

5. The method for preparing a high-strength edible antibacterial packaging film according to claim 1 or 3, wherein in the chitosan acetic acid aqueous solution containing the plasticizer, the cross-linking agent and the antioxidant, the plasticizer is glycerol, and the addition amount of the plasticizer is 5-30% of the mass of the chitosan, preferably 15-20%;

in a chitosan acetic acid aqueous solution containing a plasticizer, a cross-linking agent and an antioxidant, the cross-linking agent is citric acid, and the addition amount of the cross-linking agent is 2-20% of the mass of chitosan, preferably 5-15%, and most preferably 6-10%;

in the chitosan acetic acid aqueous solution containing the plasticizer, the cross-linking agent and the antioxidant, the antioxidant is vitamin C, and the addition amount of the antioxidant is 5-40% of the mass of the chitosan, preferably 5-20%, more preferably 5-15%, and most preferably 5-10%.

6. The method for preparing a high-strength edible antibacterial packaging film according to claim 1, wherein the method for preparing the carboxymethyl cellulose aqueous solution containing the plasticizer, the antioxidant and the antibacterial agent comprises the following steps:

the method comprises the steps of preparing a carboxymethyl cellulose aqueous solution, and then adding a plasticizer, an antioxidant and an antibacterial agent into the carboxymethyl cellulose aqueous solution to obtain the carboxymethyl cellulose aqueous solution containing the plasticizer, the antioxidant and the antibacterial agent.

7. The method for preparing a high-strength edible antibacterial packaging film according to claim 1 or 6, wherein the viscosity of the carboxymethyl cellulose is 300-800 mpa.s, and the mass fraction of the carboxymethyl cellulose in the carboxymethyl cellulose aqueous solution is 1-3%.

8. The preparation method of the high-strength edible antibacterial packaging film according to claim 1 or 6, wherein in the carboxymethyl cellulose aqueous solution containing the plasticizer, the antioxidant and the antibacterial agent, the plasticizer is glycerol, and the addition amount of the plasticizer is 10-30% of the mass of the carboxymethyl cellulose, preferably 15-20%;

in the carboxymethyl cellulose aqueous solution containing the plasticizer, the antioxidant and the antibacterial agent, the antioxidant is selected from vitamin C, and the addition amount of the antioxidant is 5-40% of the mass of the carboxymethyl cellulose, preferably 5-20%, more preferably 5-15%, and most preferably 5-10%;

in the aqueous solution of carboxymethyl cellulose containing a plasticizer, an antioxidant and an antibacterial agent, the antibacterial agent is one or a composition of more of chitosan oligosaccharide, carvacrol or catechol, and the addition amount of the antibacterial agent is 0.5-9.5% of the mass of the carboxymethyl cellulose.

9. The method for preparing a high-strength edible antibacterial packaging film according to claim 1, wherein in the film forming process, after the solution is cast into a film, the film is formed after being placed in an environment with the temperature of 35-60 ℃ and the humidity of 25-60% RH for 10-14 hours.

10. The high-strength edible antibacterial packaging film prepared by the preparation method of any one of claims 1 to 9.

Background

The preservative film is a food packaging material widely applied in daily life, and is very common in occasions of microwave oven food heating, refrigerator food preservation, fresh and cooked food packaging and the like. Because the traditional plastic preservative film is difficult to degrade in natural environment and has great pollution to the environment, the treatment of plastic preservative film garbage becomes a current difficult problem. In addition, the food is very easy to be affected by microorganism invasion, oxidation and the like to generate acidification and putrefaction in the production, storage, transportation and sale processes, thereby not only damaging the nutritional value of the food, but also seriously threatening the safety of consumers. The plastic preservative film lacks active antibacterial and antioxidant properties, cannot protect the contents actively, and needs to be added with an antiseptic. Although some chemical anticorrosion products on the market have strong anticorrosion and fresh-keeping effects, the chemical anticorrosion products also bring negative effects to human health and social environment.

The edible preservative film is a film formed by interaction among different molecules in natural edible substances (such as polysaccharides, proteins, cellulose and derivatives thereof and the like), has the advantages of natural degradation, no environmental pollution and the like compared with an artificially synthesized preservative film, also has better physical properties, can prevent the permeation and the migration of moisture, oxygen, solutes and the like, can be used as a carrier of a flavoring agent, a nutrition enhancer, an antioxidant, a preservative and the like, can ensure the safety of food, and has good application prospect. The properties of edible films are usually evaluated by some important film properties, such as mechanical strength (TS-tensile strength, YM-Young's modulus and EAB-elongation at break), which is crucial for protecting the contained food from external loads. Unplasticized edible films have mechanical strength inferior to petroleum-derived plastics. But the tensile strength of the common edible preservative film at present is mostly not more than 60 MPa.

Chinese patent CN109261087A discloses a hollow microcapsule, a preparation method and application thereof, which mainly uses mesoporous silica as a template, alternately coats carboxymethyl cellulose and chitosan for layer-by-layer self-assembly, and finally uses hydrofluoric acid to remove the template to obtain the hollow microcapsule. However, during the process of removing the template, the great osmotic pressure generated when the template material permeates from the inside to the outside can cause the deformation of the microcapsule; and the low concentration of hydrofluoric acid can influence the removal effect, and the high concentration can destroy the structure of chitosan, and has risk in the preparation process.

Chinese patent CN111499929A discloses a graphene-nano silver modified chitosan-cellulose antibacterial film, which is prepared into a film by mainly using nano silver loaded modified graphene, chitosan, glutaraldehyde, carboxymethyl cellulose, tetraethylenepentamine, graphene oxide and the like. Although the composite film has good barrier property and excellent antibacterial property, glutaraldehyde has high toxicity and is harmful to the environment; and it can increase the water vapor transmission rate of the film, which is not good for food preservation.

Disclosure of Invention

In order to solve the current situation that the tensile strength of the edible packaging film is not high in the prior art, the invention provides a high-strength edible antibacterial packaging film and a preparation method thereof.

The invention takes chitosan and carboxymethyl cellulose as film matrixes, and prepares the edible packaging film with high mechanical strength by using hydrogen bond acting force between two natural polymer hydroxyls in a film forming mode of multilayer compounding and the like.

The purpose of the invention can be realized by the following technical scheme:

the invention provides a preparation method of a high-strength edible antibacterial packaging film, which is characterized in that chitosan and carboxymethyl cellulose are used as film matrixes, and the high-strength edible antibacterial packaging film is prepared by using hydrogen bond acting force between hydroxyl groups of the chitosan and the carboxymethyl cellulose in film forming modes such as solution blending, multilayer compounding and the like.

In one embodiment of the present invention, a method for preparing a high-strength edible antimicrobial packaging film includes the steps of:

preparing a chitosan acetic acid aqueous solution containing a plasticizer, a cross-linking agent and an antioxidant;

preparing a carboxymethyl cellulose aqueous solution containing a plasticizer, an antioxidant and an antibacterial agent;

respectively dissolving chitosan acetic acid aqueous solution and carboxymethyl cellulose aqueous solution, filtering, defoaming filtrate, and respectively obtaining chitosan membrane solution and carboxymethyl cellulose membrane solution;

sequentially or alternatively forming films on the chitosan film solution or the carboxymethyl cellulose film solution to obtain the high-strength edible antibacterial packaging film.

In one embodiment of the invention, one of the chitosan film solution and the carboxymethyl cellulose film solution is coated to form a film, and then the other film solution is coated on the formed film, so that the high-strength edible antibacterial packaging film is obtained.

In one embodiment of the present invention, a chitosan membrane is formed first, and then a carboxymethyl cellulose membrane is coated on the basis of the chitosan membrane. For example, the film forming method is a solution casting method for multilayer compounding, wherein chitosan film forming is performed on a glass plate, and then carboxymethyl cellulose film liquid is coated on the basis of the chitosan film.

In one embodiment of the invention, in the process of coating one of the chitosan membrane solution or the carboxymethyl cellulose membrane solution to form a membrane, a solution casting method is adopted to form a multilayer composite membrane.

In one embodiment of the invention, the chitosan film solution and the carboxymethyl cellulose film solution are subjected to multilayer composite film formation by adopting an alternative solution casting method to obtain the high-strength edible antibacterial packaging film.

In one embodiment of the present invention, the method for preparing the aqueous chitosan acetic acid solution containing the plasticizer, the crosslinking agent and the antioxidant comprises the following steps:

firstly preparing a chitosan acetic acid aqueous solution, and then adding a plasticizer, a cross-linking agent and an antioxidant into the chitosan acetic acid aqueous solution to obtain the chitosan acetic acid aqueous solution containing the plasticizer, the cross-linking agent and the antioxidant.

In one embodiment of the present invention, the degree of deacetylation of chitosan is 80 to 95%.

In one embodiment of the invention, the mass fraction of chitosan in the chitosan acetic acid aqueous solution is 2-4%.

In one embodiment of the present invention, the volume concentration of acetic acid in the acetic acid aqueous solution is 0.5% to 2%.

In one embodiment of the present invention, the aqueous solution of chitosan acetate is prepared by stirring at room temperature for 18 to 36 hours (e.g., 24 hours) to sufficiently dissolve chitosan.

In one embodiment of the present invention, the plasticizer is glycerin in the aqueous chitosan acetic acid solution containing the plasticizer, the crosslinking agent, and the antioxidant.

In one embodiment of the present invention, the amount of the plasticizer added to the aqueous chitosan acetate solution containing the plasticizer, the crosslinking agent and the antioxidant is 5 to 30%, preferably 15 to 20% by mass of the chitosan.

In one embodiment of the invention, the cross-linking agent is citric acid in the aqueous chitosan acetic acid solution containing the plasticizer, the cross-linking agent and the antioxidant. Compared with glutaraldehyde, the crosslinked film with the same content of citric acid has the advantages of higher tensile strength, higher elongation at break, higher water holding rate, no toxicity and environmental protection.

In one embodiment of the present invention, the amount of the crosslinking agent added to the aqueous chitosan acetate solution containing the plasticizer, the crosslinking agent and the antioxidant is 2 to 20%, preferably 5 to 15%, and most preferably 6 to 10% by mass of the chitosan.

In one embodiment of the invention, in the aqueous chitosan acetate solution containing the plasticizer, the crosslinking agent and the antioxidant, the antioxidant is selected from vitamin C.

In one embodiment of the present invention, the amount of the antioxidant added to the aqueous chitosan acetate solution containing the plasticizer, the crosslinking agent and the antioxidant is 5 to 40% by mass, preferably 5 to 20% by mass, more preferably 5 to 15% by mass, and most preferably 5 to 10% by mass of the chitosan.

In one embodiment of the present invention, a method for preparing an aqueous solution of carboxymethyl cellulose containing a plasticizer, an antioxidant, and an antibacterial agent comprises:

the method comprises the steps of preparing a carboxymethyl cellulose aqueous solution, and then adding a plasticizer, an antioxidant and an antibacterial agent into the carboxymethyl cellulose aqueous solution to obtain the carboxymethyl cellulose aqueous solution containing the plasticizer, the antioxidant and the antibacterial agent.

In one embodiment of the invention, the carboxymethyl cellulose has a viscosity of 300 to 800 mpa.s.

In one embodiment of the present invention, the mass fraction of carboxymethyl cellulose in the carboxymethyl cellulose aqueous solution is 1 to 3%.

In one embodiment of the present invention, the carboxymethyl cellulose is sufficiently dissolved by stirring at room temperature for 18 to 36 hours (e.g., 24 hours) when preparing the aqueous carboxymethyl cellulose solution.

In one embodiment of the present invention, the plasticizer is glycerin in an aqueous solution of carboxymethyl cellulose containing a plasticizer, an antioxidant, and an antibacterial agent.

In one embodiment of the present invention, the amount of the plasticizer added to the aqueous solution of carboxymethyl cellulose containing a plasticizer, an antioxidant and an antibacterial agent is 10 to 30% by mass, preferably 15 to 20% by mass, of the carboxymethyl cellulose.

In one embodiment of the present invention, in the aqueous solution of carboxymethyl cellulose containing a plasticizer, an antioxidant and an antibacterial agent, the antioxidant is selected from vitamin C.

In one embodiment of the present invention, the amount of the antioxidant added to the aqueous solution of carboxymethyl cellulose containing a plasticizer, an antioxidant and an antibacterial agent is 5 to 40% by mass, preferably 5 to 20% by mass, more preferably 5 to 15% by mass, and most preferably 5 to 10% by mass of carboxymethyl cellulose.

In one embodiment of the invention, in the carboxymethyl cellulose aqueous solution containing the plasticizer, the antioxidant and the antibacterial agent, the antibacterial agent is one or a combination of chitosan oligosaccharide, carvacrol and catechol.

In one embodiment of the invention, in the carboxymethyl cellulose aqueous solution containing the plasticizer, the antioxidant and the antibacterial agent, the addition amount of the antibacterial agent is 0.5-9.5% of the mass of the carboxymethyl cellulose, and the optimal addition concentration is 0.5-2% of chitosan oligosaccharide, 1-5% of carvacrol and 2-4% of catechol.

In one embodiment of the present invention, the film formation process is performed on a substrate.

In one embodiment of the present invention, the substrate is a glass plate.

In one embodiment of the present invention, in the film formation process, after the solution is cast into a film, the film is formed after being placed in an environment at a temperature of 35 to 60 ℃ and a humidity of 25 to 60% RH for 10 to 14 hours (for example, 12 hours).

In one embodiment of the present invention, the optimum film forming conditions in the film forming process are an environment having a temperature of 35 ℃ and a humidity of 55% RH.

In one embodiment of the invention, after film formation is complete, the film is removed and the hood is placed in a volatile solvent.

In one embodiment of the present invention, there is provided a specific method for preparing a high-strength edible antimicrobial packaging film, comprising the steps of:

(1) preparing a chitosan acetic acid aqueous solution with the mass fraction of 2-4%, and stirring for 24 hours at room temperature to fully dissolve to obtain a mixed solution 1.

(2) Preparing a carboxymethyl cellulose aqueous solution with the mass concentration of 1-3%, and stirring for 24 hours at room temperature to fully dissolve the carboxymethyl cellulose aqueous solution to obtain a mixed solution 2.

(3) In the mixed solution 1, glycerol is added as a plasticizer in an amount of 10-30% by mass of chitosan, citric acid is added as a crosslinking agent in an amount of 5-15% by mass of chitosan, and vitamin C is added as an antioxidant in an amount of 10-40% by mass of chitosan, to obtain a mixed solution 3.

(4) In the mixed solution 2, glycerol is added as a plasticizer in an amount of 5-15% by mass of the carboxymethyl cellulose, vitamin C is added as an antioxidant in an amount of 10-20% by mass of the carboxymethyl cellulose, and chitosan oligosaccharide, carvacrol, catechol or a combination thereof is added as an antibacterial agent in an amount of 0.5-9.5% by mass of the carboxymethyl cellulose, to obtain a mixed solution 4.

(5) And (4) respectively and fully dissolving the mixed solution obtained in the steps (3) and (4) at room temperature, filtering, taking the filtrate, standing for 24h, and defoaming to respectively obtain chitosan membrane solution and carboxymethyl cellulose membrane solution.

(6) And uniformly coating the defoamed chitosan film liquid on a glass plate, and drying in a constant temperature and humidity box for 12 hours and then taking out.

(7) And (3) uniformly coating the defoamed carboxymethyl cellulose membrane liquid on the chitosan membrane obtained in the step (6), drying in a constant temperature and humidity cabinet for 12h, taking out, uncovering the membrane, and standing in a fume hood for 7 days to volatilize the residual solvent, thus obtaining the high-strength edible antibacterial packaging membrane.

The invention also provides the high-strength edible antibacterial packaging film prepared based on the method.

The tensile strength of the high-strength edible antibacterial packaging film is up to 270MPa, and the high-strength edible antibacterial packaging film has an important application value in the field of food packaging.

In one embodiment of the present invention, the packaging film is a wrap film.

Chitosan and carboxymethyl cellulose are used as a green, nontoxic and harmless high polymer material and are widely applied to the aspects of film materials, packaging materials and the like. The composite film obtained from common chitosan and carboxymethyl cellulose has low water molecule barrier property and poor tensile strength and antibacterial property, and limits the practicability and application of the chitosan and cellulose composite material. In order to improve the performance of the composite membrane, glycerol and citric acid are used as a plasticizer and a cross-linking agent to improve the tensile strength and water molecule barrier property of the composite membrane, and one or a composition of more of chitosan oligosaccharide, carvacrol or catechol is added to improve the antibacterial property. Wherein the added citric acid molecules ionize to form COO^-And H⁺Can protonate amino on the macromolecular chain of chitosan into NH³⁺So as to generate electrostatic interaction with the chitosan and generate ion crosslinking, and a chitosan-citric acid complex is formed. At this time, the complex is positively charged, and the carboxymethyl cellulose has a large number of carboxyl groups to have a certain negative charge, so that the carboxymethyl cellulose and the carboxymethyl cellulose can generate a certain electrostatic interaction to form the hydrogel. Further, the tensile strength of the film is further improved. The added glycerol can weaken hydrogen bonds between carboxymethyl cellulose and chitosan molecules, so that the mutual sliding action of the molecules is enhanced, the distance between molecular chains is increased, the crystalline structure of the composite film is changed, the breaking elongation of the film is increased, and the plasticizing effect is achieved.

The invention utilizes carboxymethyl cellulose and chitosan to prepare the composite film, and finds that the composite film is obviously improved in the aspects of permeability, toughness and the like compared with a single chitosan film. The carboxymethyl cellulose contains a large amount of functional groups such as carboxyl, hydroxyl and the like, and the strong hydrogen bond effect is formed between the carboxymethyl cellulose and the hydroxyl in the chitosan at the interface of a film matrix during multilayer coating, so that the mechanical strength is greatly improved and can reach hundreds of megapascals, and the carboxymethyl cellulose is far beyond most products on the market.

In addition, the invention also adds a trace amount of phenolic substances as bacteriostat, which has inhibitory effect on various bacteria and fungi and is an excellent antioxidant. The antibacterial property of the substance and chitosan is combined to achieve the synergistic effect, and the edible antibacterial packaging film with high mechanical strength is prepared. And the composite membrane material of carboxymethyl cellulose and chitosan is degradable, and has no pollution to the environment.

Compared with the prior art, the edible packaging film with high mechanical strength is prepared by using chitosan and carboxymethyl cellulose as film matrixes and utilizing the hydrogen bond acting force between two natural polymer hydroxyls in film forming modes such as solution blending, multilayer compounding and the like. Vitamin C, glycerol, citric acid and the like are added into the film matrix to serve as an antioxidant, a plasticizer and a cross-linking agent, and chitosan oligosaccharide, carvacrol, catechol and the like are added to serve as antibacterial agents, so that the durability and the antibacterial property of the edible preservative film are effectively improved. The film prepared by the method has excellent mechanical property and antibacterial property, the tensile strength is up to 270MPa, and the film has important application value in the field of food packaging.

Drawings

FIG. 1 is a process flow for obtaining a thin film by the method

FIG. 2 is an infrared spectrum of the film of example 3.

(a) The IR spectrum of the chitosan single film of example 3 was regarded as the IR spectrum of the chitosan single film having a mass fraction of 4%. (b) The infrared spectrum of the high-strength edible antibacterial preservative film obtained in example 3 was shown.

Detailed Description

The invention provides a preparation method of a high-strength edible antibacterial packaging film, which comprises the following steps:

preparing a chitosan acetic acid aqueous solution containing a plasticizer, a cross-linking agent and an antioxidant;

preparing a carboxymethyl cellulose aqueous solution containing a plasticizer, an antioxidant and an antibacterial agent;

respectively dissolving chitosan acetic acid aqueous solution and carboxymethyl cellulose aqueous solution, filtering, defoaming filtrate, and respectively obtaining chitosan membrane solution and carboxymethyl cellulose membrane solution;

sequentially or alternatively forming films on the chitosan film solution or the carboxymethyl cellulose film solution to obtain the high-strength edible antibacterial packaging film.

In one embodiment of the invention, one of the chitosan film solution and the carboxymethyl cellulose film solution is coated to form a film, and then the other film solution is coated on the formed film, so that the high-strength edible antibacterial packaging film is obtained.

In one embodiment of the present invention, a chitosan membrane is formed first, and then a carboxymethyl cellulose membrane is coated on the basis of the chitosan membrane. For example, the film forming method is a solution casting method for multilayer compounding, wherein chitosan film forming is performed on a glass plate, and then carboxymethyl cellulose film liquid is coated on the basis of the chitosan film.

In one embodiment of the invention, in the process of coating one of the chitosan membrane solution or the carboxymethyl cellulose membrane solution to form a membrane, a solution casting method is adopted to form a multilayer composite membrane.

In one embodiment of the invention, the chitosan film solution and the carboxymethyl cellulose film solution are subjected to multilayer composite film formation by adopting an alternative solution casting method to obtain the high-strength edible antibacterial packaging film.

In one embodiment of the present invention, the method for preparing the aqueous chitosan acetic acid solution containing the plasticizer, the crosslinking agent and the antioxidant comprises the following steps:

firstly preparing a chitosan acetic acid aqueous solution, and then adding a plasticizer, a cross-linking agent and an antioxidant into the chitosan acetic acid aqueous solution to obtain the chitosan acetic acid aqueous solution containing the plasticizer, the cross-linking agent and the antioxidant.

In one embodiment of the present invention, the degree of deacetylation of chitosan is 80 to 95%. The mass fraction of chitosan in the chitosan acetic acid aqueous solution is 2-4%. The volume concentration of acetic acid in the acetic acid aqueous solution is 0.5-2%. When preparing the aqueous solution of chitosan acetic acid, the mixture is stirred at room temperature for 18 to 36 hours (for example, 24 hours) to fully dissolve the chitosan.

In one embodiment of the present invention, the plasticizer is glycerin in the aqueous chitosan acetic acid solution containing the plasticizer, the crosslinking agent, and the antioxidant. The addition amount of the plasticizer is 5-30% of the mass of the chitosan, and preferably 15-20%. The cross-linking agent is citric acid. The addition amount of the cross-linking agent is 2-20% of the mass of the chitosan, preferably 5-15%, and most preferably 6-10%. The antioxidant is selected from vitamin C. The addition amount of the antioxidant is 5 to 40% by mass of the chitosan, preferably 5 to 20%, more preferably 5 to 15%, and most preferably 5 to 10%.

In one embodiment of the present invention, a method for preparing an aqueous solution of carboxymethyl cellulose containing a plasticizer, an antioxidant, and an antibacterial agent comprises:

the method comprises the steps of preparing a carboxymethyl cellulose aqueous solution, and then adding a plasticizer, an antioxidant and an antibacterial agent into the carboxymethyl cellulose aqueous solution to obtain the carboxymethyl cellulose aqueous solution containing the plasticizer, the antioxidant and the antibacterial agent.

In one embodiment of the invention, the carboxymethyl cellulose has a viscosity of 300 to 800 mpa.s. The mass fraction of the carboxymethyl cellulose in the carboxymethyl cellulose aqueous solution is 1-3%. When the aqueous solution of carboxymethyl cellulose is prepared, the solution is stirred at room temperature for 18 to 36 hours (for example, 24 hours) to sufficiently dissolve the carboxymethyl cellulose.

In one embodiment of the present invention, the plasticizer is glycerin in an aqueous solution of carboxymethyl cellulose containing a plasticizer, an antioxidant, and an antibacterial agent. The addition amount of the plasticizer is 10-30% of the mass of the carboxymethyl cellulose, and preferably 15-20%. The antioxidant is selected from vitamin C. The amount of the antioxidant added is 5 to 40% by mass of the carboxymethylcellulose, preferably 5 to 20%, more preferably 5 to 15%, and most preferably 5 to 10%. The antibacterial agent is one or more of chitosan oligosaccharide, carvacrol and catechol. The addition amount of the antibacterial agent is 0.5-9.5% of the mass of the carboxymethyl cellulose, and the optimal addition concentration of the antibacterial agent is 0.5-2% of chitosan oligosaccharide, 1-5% of carvacrol and 2-4% of catechol.

In one embodiment of the invention, the film formation process is performed on a glass plate. In the film forming process, after the solution is cast into a film, the film is formed after being placed in an environment with the temperature of 35-60 ℃ and the humidity of 25-60% RH for 10-14 hours (for example, 12 hours). The optimum film forming conditions are 35 ℃ temperature and 55% RH humidity. And after the film forming is finished, uncovering the film, and placing the volatilized residual solvent in a fume hood.

The invention is described in detail below with reference to the figures and specific embodiments.

Example 1

Referring to fig. 1, there is provided a method for preparing a high-strength edible antibacterial preservative film, comprising the steps of:

(1) preparing a chitosan acetic acid aqueous solution with the mass fraction of 2%, and stirring for 24 hours at room temperature to fully dissolve to obtain a mixed solution 1.

(2) Preparing a carboxymethyl cellulose aqueous solution with the mass concentration of 1%, and stirring for 24 hours at room temperature to fully dissolve the carboxymethyl cellulose aqueous solution to obtain a mixed solution 2.

(3) In the mixed solution 1, glycerin was added as a plasticizer in an amount of 10% by mass of chitosan, citric acid was added as a crosslinking agent in an amount of 5% by mass of chitosan, and vitamin C was added as an antioxidant in an amount of 10% by mass of chitosan, to obtain a mixed solution 3.

(4) In the mixed solution 2, 15% by mass of carboxymethyl cellulose is added with glycerol as a plasticizer, 20% by mass of carboxymethyl cellulose is added with vitamin C as an antioxidant, and 9.5% by mass of carboxymethyl cellulose is added with chitosan oligosaccharide, carvacrol, catechol or a combination thereof as an antibacterial agent to obtain a mixed solution 4.

(5) And (4) respectively and fully dissolving the mixed solution obtained in the steps (3) and (4) at room temperature, filtering, taking the filtrate, standing for 24h, and defoaming to respectively obtain chitosan membrane solution and carboxymethyl cellulose membrane solution.

(6) And uniformly coating the defoamed chitosan film liquid on a glass plate, and drying in a constant temperature and humidity box for 12 hours and then taking out.

(7) And (3) uniformly coating the defoamed carboxymethyl cellulose membrane liquid on the chitosan membrane obtained in the step (6), drying in a constant temperature and humidity cabinet with 60 ℃ and 50% RH for 12h, taking out, uncovering the membrane, and placing in a fume hood for 7 days to volatilize the residual solvent, thus obtaining the high-strength edible antibacterial preservative membrane.

Example 2

Referring to fig. 1, there is provided a method for preparing a high-strength edible antibacterial preservative film, comprising the steps of:

(1) preparing a chitosan acetic acid aqueous solution with the mass fraction of 3%, and stirring for 24 hours at room temperature to fully dissolve to obtain a mixed solution 1.

(2) Preparing a carboxymethyl cellulose aqueous solution with the mass concentration of 2%, and stirring for 24 hours at room temperature to fully dissolve the carboxymethyl cellulose aqueous solution to obtain a mixed solution 2.

(3) In the mixed solution 1, glycerin as a plasticizer was added in an amount of 20% by mass of chitosan, citric acid as a crosslinking agent was added in an amount of 10% by mass of chitosan, and vitamin C as an antioxidant was added in an amount of 25% by mass of chitosan, to obtain a mixed solution 3.

(4) In the mixed solution 2, glycerin is added as a plasticizer in an amount of 10% by mass of the carboxymethyl cellulose, vitamin C is added as an antioxidant in an amount of 15% by mass of the carboxymethyl cellulose, and chitosan oligosaccharide, carvacrol, catechol, or a combination thereof is added as an antibacterial agent in an amount of 15% by mass of the carboxymethyl cellulose, to obtain a mixed solution 4.

(5) And (4) respectively and fully dissolving the mixed solution obtained in the steps (3) and (4) at room temperature, filtering, taking the filtrate, standing for 24h, and defoaming to respectively obtain chitosan membrane solution and carboxymethyl cellulose membrane solution.

(6) And uniformly coating the defoamed chitosan film liquid on a glass plate, and drying in a constant temperature and humidity box for 12 hours and then taking out.

(7) And (3) uniformly coating the defoamed carboxymethyl cellulose membrane liquid on the chitosan membrane obtained in the step (6), drying in a constant temperature and humidity cabinet with 60 ℃ and 50% RH for 12h, taking out, uncovering the membrane, and placing in a fume hood for 7 days to volatilize the residual solvent, thus obtaining the high-strength edible antibacterial preservative membrane.

Example 3

Referring to fig. 1, there is provided a method for preparing a high-strength edible antibacterial preservative film, comprising the steps of:

(1) preparing a chitosan acetic acid aqueous solution with the mass fraction of 4%, and stirring for 24 hours at room temperature to fully dissolve to obtain a mixed solution 1.

(2) Preparing a carboxymethyl cellulose aqueous solution with the mass concentration of 3%, and stirring for 24 hours at room temperature to fully dissolve the carboxymethyl cellulose aqueous solution to obtain a mixed solution 2.

(3) In the mixed solution 1, 30% by mass of chitosan was added glycerol as a plasticizer, 15% by mass of chitosan was added citric acid as a crosslinking agent, and 40% by mass of chitosan was added vitamin C as an antioxidant to obtain a mixed solution 3.

(4) In the mixed solution 2, glycerin is added as a plasticizer in an amount of 5% by mass of the carboxymethyl cellulose, vitamin C is added as an antioxidant in an amount of 10% by mass of the carboxymethyl cellulose, and chitosan oligosaccharide, carvacrol, catechol, or a combination thereof is added as an antibacterial agent in an amount of 0.5% by mass of the carboxymethyl cellulose, to obtain a mixed solution 4.

(5) And (4) respectively and fully dissolving the mixed solution obtained in the steps (3) and (4) at room temperature, filtering, taking the filtrate, standing for 24h, and defoaming to respectively obtain chitosan membrane solution and carboxymethyl cellulose membrane solution.

(6) And uniformly coating the defoamed chitosan film liquid on a glass plate, and drying in a constant temperature and humidity box for 12 hours and then taking out.

(7) And (3) uniformly coating the defoamed carboxymethyl cellulose membrane liquid on the chitosan membrane obtained in the step (6), drying in a constant temperature and humidity cabinet with 60 ℃ and 50% RH for 12h, taking out, uncovering the membrane, and placing in a fume hood for 7 days to volatilize the residual solvent, thus obtaining the high-strength edible antibacterial preservative membrane.

The infrared spectrum of the chitosan single film obtained in the step (6) of example 3 is shown in (a) of fig. 2, and the infrared spectrum of the high-strength edible antibacterial preservative film obtained after the step (7) is shown in (b) of fig. 2.

The composite preservative film obtained in the above examples was subjected to the following performance tests, and the results of the performance tests are shown in table 1.

Tensile strength and elongation at break, measured according to GB/T13022-1991;

the water vapor transmission amount and the water vapor transmission coefficient are measured according to GB/T2679.2-2015;

infrared spectroscopy, as determined by YBB 00262004-

The light transmittance is measured according to GB/T2410-

Sensory evaluation the oxidation resistance of the analytical films.

The antibacterial activity was measured in accordance with QB-T2591-2003.

The parameters of the wrap films prepared in examples 1-3 above are shown in Table 1.

TABLE 1 parameters of the cling films obtained in examples 1-3

It can be seen that the increase in chitosan in the film significantly improves the tensile strength and elastic modulus of the film. Mixing carboxymethyl cellulose according to a certain proportion to form a film, and finding that the performance of the edible film is obviously improved. Along with the increase of the content of the chitosan and the antibacterial agent, the bacteriostasis rate of the film is also obviously improved.

The film is exposed in the air, the film has no peculiar smell for a long time, keeps normal luster, has flat and smooth surface, no shrinkage and good plasticity, and the film is proved to have good oxidation resistance.

The film prepared by the method has excellent mechanical property and antibacterial property, the tensile strength can reach 270MPa, and the film has important application value in the field of food packaging.

Example 4

Referring to fig. 1, there is provided a method for preparing a high-strength edible antibacterial preservative film, comprising the steps of:

(1) preparing a chitosan acetic acid aqueous solution with the mass fraction of 4%, and stirring for 24 hours at room temperature to fully dissolve to obtain a mixed solution 1.

(2) Preparing a carboxymethyl cellulose aqueous solution with the mass concentration of 3%, and stirring for 24 hours at room temperature to fully dissolve the carboxymethyl cellulose aqueous solution to obtain a mixed solution 2.

(3) In the mixed solution 1, 30% by mass of chitosan was added glycerol as a plasticizer, 15% by mass of chitosan was added citric acid as a crosslinking agent, and 40% by mass of chitosan was added vitamin C as an antioxidant to obtain a mixed solution 3.

(4) In the mixed solution 2, glycerin is added as a plasticizer in an amount of 5% by mass of the carboxymethyl cellulose, vitamin C is added as an antioxidant in an amount of 10% by mass of the carboxymethyl cellulose, and chitosan oligosaccharide, carvacrol, catechol, or a combination thereof is added as an antibacterial agent in an amount of 0.5% by mass of the carboxymethyl cellulose, to obtain a mixed solution 4.

(5) And (4) respectively and fully dissolving the mixed solution obtained in the steps (3) and (4) at room temperature, filtering, taking the filtrate, standing for 24h, and defoaming to respectively obtain chitosan membrane solution and carboxymethyl cellulose membrane solution.

(6) Soaking fresh oranges in the prepared chitosan membrane solution at 15 ℃ in lmin, taking out the oranges, putting the oranges in a constant-temperature constant-humidity box at the temperature of 25 ℃ and the relative humidity of 50%, air-drying the oranges for 12 hours, and taking out the oranges to form chitosan membranes on the surfaces of the oranges;

(7) and (3) soaking the oranges with the chitosan films formed in the step (6) in the prepared carboxymethyl cellulose film liquid at 15 ℃ in lmin, taking out the oranges, putting the oranges in a constant-temperature constant-humidity box with the temperature of 25 ℃ and the relative humidity of 50% for air drying for 12h, and taking out the oranges to obtain the high-strength edible antibacterial preservative films on the surfaces of the oranges.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.