CN112812484A - Antibacterial moisturizing degradable porous gel preservative film and preparation method thereof - Google Patents
Antibacterial moisturizing degradable porous gel preservative film and preparation method thereof Download PDFInfo
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Abstract
The invention discloses an antibacterial moisturizing degradable porous gel preservative film and a preparation method thereof. (1) Placing a methacrylic acid monomer in deionized water, and adding double-long-chain methyl tertiary amine and cuprous bromide to obtain a component A solution; (2) dispersing ferulic acid in ethanol solution, and adding 3, 4-vinyl dioxythiophene to obtain component B solution; (3) dissolving chitosan in an acetic acid solution, and adding the component A solution, the component B solution and chloroethanol to obtain preservative film slurry; (4) heating the preservative film slurry, and adding L-cysteine to obtain porous gel preservative film slurry; (5) preparing the porous gel preservative film. The porous gel preservative film prepared by the invention has the advantages of simple principle, safe components and good bacteriostatic effect, solves the problem of poor mechanical property of the preservative film which can be taken as a main material by Kotahe, has high degradation rate, is safe and environment-friendly, can realize industrial production, and has strong market popularization value.
Description
Technical Field
The invention relates to the technical field of food preservation, in particular to an antibacterial moisturizing degradable porous gel preservative film and a preparation method thereof.
Background
People pay more attention to the food fresh-keeping safety problem along with the improvement of living standard. In order to keep the freshness of food as much as possible and avoid the problems of food spoilage and mildewing, people often use a preservative film to preserve the freshness of food. However, most of the traditional preservative films are made of materials such as polyvinyl chloride (PVC), polypropylene (PP), Polyethylene (PE), polyester and the like. The materials have low cost, convenient processing and good fresh-keeping effect, and are very popular with people. However, the traditional plastic preservative film often contains chemical substances such as a phthalate, di (2-ethyl) hexyl adipate and the like, and the substances have certain carcinogenic risks, so that the plastic preservative film can cause harm to human health after being used for a long time. Moreover, the plastic preservative film is difficult to degrade, and can cause harm to the environment regardless of incineration or landfill treatment; therefore, the problem to be solved urgently is to develop a preservative film which is safe, environment-friendly and high in degradation rate.
Chitosan, as a natural high molecular polysaccharide, has excellent degradability and film-forming property, and also has certain antibacterial and bactericidal effects, and is receiving more and more attention from people. Chinese patent (CN 109825017A) discloses an antibacterial preservative film for cooked food in bulk and a preparation method thereof, which mainly uses chitosan as a base material and is assisted by starch-based polyvinyl alcohol, glutinous rice flour, Prussian blue polysaccharide gel and other components to prepare the antibacterial preservative film; although the preservative film has certain bacteriostatic and preservative effects, the problems of poor inherent mechanical strength and narrow bacteriostatic range of the chitosan cannot be avoided.
In order to solve the above problems, an antibacterial moisture-keeping degradable porous gel preservative film and a preparation process thereof are needed to solve the problems suggested in the background.
Disclosure of Invention
The invention aims to provide an antibacterial moisturizing degradable porous gel preservative film and a preparation method thereof, and aims to solve the problems in the background art.
The preparation method of the antibacterial moisturizing degradable porous gel preservative film comprises the following steps
(1) Preparing a component A solution: placing a methacrylic acid monomer in deionized water, and sequentially adding double-long-chain methyl tertiary amine and cuprous bromide to obtain a uniform and stable component A solution; because the molecules of the methacrylic acid monomer contain a large amount of carboxyl, and the double-long-chain methyl tertiary amine contains a large amount of amino, the invention utilizes the reaction of the methacrylic acid monomer and the double-long-chain methyl tertiary amine to form amide, and then the double-long-chain methyl tertiary amine is modified on the molecules of the methacrylic acid monomer to obtain the component A solution;
(2) preparing a component B solution: placing ferulic acid in ethanol solution, stirring and dispersing, and adding 3, 4-vinyl dioxythiophene to obtain uniform and stable component B solution; and because the 3, 4-vinyl dioxythiophene is a polymerization monomer with positive charges, the polymerization monomer reacts with ferulic acid, an electrostatic self-assembly reaction occurs between an anionic group contained in the ferulic acid and the 3, 4-vinyl dioxythiophene, and the ferulic acid is modified on a 3, 4-vinyl dioxythiophene monomer molecule to obtain a component B solution.
(3) Synthesizing fresh-keeping slurry: placing chitosan in an acetic acid solution, stirring and dissolving, adding the component A solution and the component B solution into the chitosan solution while stirring, and adding chloroethanol to obtain preservative film slurry; the addition of the component A solution and the component B solution is beneficial to the uniform dispersion of the component A solution and the component B solution in the chitosan solution while stirring.
According to the invention, chloroethanol is further added into the reaction system in the step (3), and the chloroethanol can be subjected to a complex reaction by the double-long-chain methyl tertiary amine in the component A solution to generate the double-long-chain methyl quaternary ammonium salt. The quaternary ammonium salt prepared by the adding method of the invention has more uniform and stable dispersibility in a reaction system.
(4) Heating the preservative film slurry: heating the preservative film slurry, adding L-cysteine, stirring, standing, and vacuum degassing to obtain porous gel preservative film slurry;
the component A solution and the component B solution are polymerized under the heating condition, and because molecules of the component A solution and molecules of the component B solution have opposite charges, molecules of the component A solution and molecules of the component B solution are polymerized and subjected to electrostatic assembly, so that a compact and stable network structure is formed in the chitosan solution; due to the long chain length of the double-long-chain methyl quaternary ammonium salt molecules in the reaction system, the double-long-chain methyl quaternary ammonium salt molecules can be continuously entangled with a high-molecular polymer network, so that the polymer network is further compact and stable; due to the existence of negative sulfydryl, the L-cysteine can be electrostatically assembled with double-long-chain methyl quaternary ammonium salt in preservative film slurry, and then is modified in a polymer network structure in the porous gel preservative film slurry.
(5) Preparing a porous gel preservative film: pouring the porous gel preservative film slurry obtained in the step (4) into a mould, performing casting film forming, naturally cooling to room temperature, and removing the film to obtain the porous gel preservative film.
Further, the specific operation process of the step (1) is as follows: weighing 60-100 parts of methacrylic acid monomer, placing the methacrylic acid monomer in 100-130 parts of deionized water, stirring and dissolving, sequentially adding 30-40 parts of double-long-chain methyl tertiary amine and 1-3 parts of cuprous bromide, and stirring and reacting for 20-30min at the temperature of 22-28 ℃ to obtain a component A solution; .
Further, the specific operation process of the step (2) is as follows: weighing 20-40 parts of ferulic acid, placing the ferulic acid in 60-80 parts of ethanol solution, stirring and dispersing, adding 15-25 parts of 3, 4-vinyl dioxythiophene, and stirring and reacting at 22-28 ℃ for 60-90min to obtain a component B solution.
Further, the specific operation process of the step (3) is as follows: and (2) putting 40-50 parts of chitosan into 50-60 parts of acetic acid solution, stirring and dissolving, adding 45-55 parts of the component A solution and 25-35 parts of the component B solution into the chitosan solution while stirring, and after the addition is finished, adding 10-15 parts of chloroethanol at the adding speed of V1 to obtain the preservative film slurry.
Further, the addition rate V1 was 8 to 15 ml/min.
Further, the mass percent of the chloroethanol is 12-18%.
Further, the specific operation method of the step (4) is as follows: heating the preservative film slurry at a low temperature, adding L-cysteine while heating, stirring and reacting at the rotating speed of 100-.
Further, the steps (1) to (4) need to be carried out under a high-purity nitrogen atmosphere with the purity of more than or equal to 99.99 percent; avoiding the influence of impurity gas in the air on the reaction.
Further, the low-temperature heating condition is 30-60 ℃; the high-temperature heating condition is 80-130 ℃; the invention adopts a sectional heating method, the reaction process is easier to control, and the problem of implosion of preservative film slurry and the influence on the quality of the preservative film can be effectively prevented; under the sectional type heating mode, the polymer network structure formed in the preservative film slurry is more uniform and stable, and the mechanical property is better.
A preservative film prepared by the method for preparing the antibacterial, moisture-keeping and degradable porous gel preservative film according to any one of claims 1 to 9.
Compared with the prior art, the invention has the following beneficial effects:
1. according to the invention, the double-long-chain methyl tertiary amine is modified on a methacrylic acid monomer, ferulic acid is modified on 3, 4-vinyl dioxythiophene, the two are mixed with a chitosan solution, under the heating condition, the double-long-chain methyl tertiary amine is modified on the methacrylic acid monomer and the ferulic acid modified 3, 4-vinyl dioxythiophene to polymerize, and molecular chain entanglement and self-assembly occur among the methyl acrylic acid monomer and the ferulic acid modified 3, 4-vinyl dioxythiophene, so that a compact and stable network structure is formed in the gel slurry of the porous preservative film, and the mechanical property of the gel preservative film is improved.
2. According to the method, the component A solution is uniformly dispersed in the chitosan solution, and then the tertiary amine in the component A solution reacts with chloroethanol to generate the double-long-chain methyl tertiary amine to react to generate the double-long-chain methyl quaternary ammonium salt; the fine pores in the network structure can automatically adjust gas components in the film, and the storage period of food is prolonged. The long-chain molecules contained in the double-long-chain methyl quaternary ammonium salt can be entangled with polymer network molecular chains, so that the mechanical property of the preservative film is enhanced, and the later-stage complexing of L-cysteine is facilitated to further improve the comprehensive property of the preservative film.
3. The L-cysteine specially added in the invention contains a large amount of sulfydryl with a reducing effect, can effectively inhibit the activity of polyphenol oxidase in fruits and vegetables, relieves the problem of color change of the fruits and vegetables in the storage process, and keeps the luster of food. The L-cysteine also has excellent bacteriostatic effect, can expand the bacteriostatic range of the chitosan and strengthen the bacteriostatic action of the preservative film.
4. Because L-cysteine belongs to micromolecular amino acid components, the aqueous solution of the L-cysteine is difficult to stay on the surface of food, the L-cysteine is assembled in a preservative film high molecular polymer network structure in an electrostatic self-assembly mode, the stability of the cysteine can be kept, the loss of the L-cysteine is avoided, the mechanical property of the porous gel preservative film is improved, and the bacteriostatic and antioxidant effects of the porous gel preservative film are enhanced.
5. Ferulic acid is a natural component extracted from important materials such as ferula asafetida, angelica sinensis, spina date seeds and the like, can eliminate free radicals, and has excellent antioxidant performance.
6. The porous gel preservative film contains a large number of hydrophilic functional groups, can adsorb excessive water in the preservative film, keeps water-vapor balance in the preservative film, inhibits the respiration of food, and reduces the breeding of bacteria.
7. The porous gel preservative film prepared by the invention has the advantages of simple principle, safe components and good bacteriostatic effect, solves the problem of poor mechanical property of the preservative film which can be taken as a main material by Kotahe, has high degradation rate, is safe and environment-friendly, can realize industrial production, and has strong market popularization value.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
(1) Preparing a component A solution: weighing 60 parts of methacrylic acid monomer, placing the methacrylic acid monomer into 100 parts of deionized water, stirring and dissolving, sequentially adding 30 parts of double-long-chain methyl tertiary amine and 1 part of cuprous bromide, and stirring and reacting for 20min at 22 ℃ to obtain a component A solution;
(2) preparing a component B solution: weighing 20 parts of ferulic acid, placing the ferulic acid into 60 parts of ethanol solution, stirring and dispersing, adding 15 parts of 3, 4-vinyl dioxythiophene, and stirring and reacting for 60min at 22 ℃ to obtain a component B solution;
(3) synthesizing fresh-keeping slurry: placing 40 parts of chitosan into 50 parts of acetic acid solution, stirring and dissolving, adding 45 parts of component A solution and 25 parts of component B solution into the chitosan solution while stirring, and after the addition is finished, adding 10 parts of chloroethanol at the adding speed of V1 to obtain preservative film slurry;
(4) heating the preservative film slurry: heating the preservative film slurry at low temperature, adding L-cysteine while heating, stirring at the rotating speed of 100r/min for reaction for 20min, then heating at high temperature, stirring at the rotating speed of 300r/min for reaction for 5h, standing for 10min, and degassing in vacuum for 32min to obtain the porous gel preservative film slurry.
(5) Preparing a porous gel preservative film: pouring the porous gel preservative film slurry obtained in the step (4) into a mould, performing casting film forming, naturally cooling to room temperature, and removing the film to obtain the porous gel preservative film.
The addition rate V1 was 8 ml/min.
The mass percent of the chloroethanol is 12%.
The steps (1) to (4) need to be carried out under a high-purity nitrogen atmosphere with the purity of more than or equal to 99.99 percent.
The low-temperature heating condition is 30 ℃; the high-temperature heating condition is 80 ℃.
Example 2
(1) Preparing a component A solution: weighing 75 parts of methacrylic acid monomer, placing the methacrylic acid monomer into 110 parts of deionized water, stirring and dissolving, sequentially adding 34 parts of double-long-chain methyl tertiary amine and 2 parts of cuprous bromide, and stirring and reacting for 23min at 24 ℃ to obtain a component A solution;
(2) preparing a component B solution: weighing 25 parts of ferulic acid, placing the ferulic acid into 65 parts of ethanol solution, stirring and dispersing, adding 18 parts of 3, 4-vinyl dioxythiophene, and stirring and reacting at 25 ℃ for 65min to obtain a component B solution;
(3) synthesizing fresh-keeping slurry: putting 43 parts of chitosan into 53 parts of acetic acid solution, stirring and dissolving, adding 48 parts of component A solution and 28 parts of component B solution into the chitosan solution while stirring, and after the addition is finished, adding 11 parts of chloroethanol at the adding speed of V1 to obtain preservative film slurry;
(4) heating the preservative film slurry: heating the preservative film slurry at a low temperature, adding L-cysteine while heating, stirring at a rotating speed of 130r/min for reacting for 23min, then heating at a high temperature, stirring at a rotating speed of 350r/min for reacting for 7h, standing for 13min, and degassing in vacuum for 34min to obtain the porous gel preservative film slurry.
(5) Preparing a porous gel preservative film: pouring the porous gel preservative film slurry obtained in the step (4) into a mould, performing casting film forming, naturally cooling to room temperature, and removing the film to obtain the porous gel preservative film.
The addition rate V1 was 10 ml/min.
The mass percent of the chloroethanol is 13%.
The steps (1) to (4) need to be carried out under a high-purity nitrogen atmosphere with the purity of more than or equal to 99.99 percent.
The low-temperature heating condition is 38 ℃; the high-temperature heating condition is 90 ℃.
Example 3
(1) Preparing a component A solution: weighing 90 parts of methacrylic acid monomer, placing the methacrylic acid monomer in 110 parts of deionized water, stirring and dissolving, sequentially adding 36 parts of double-long-chain methyl tertiary amine and 2 parts of cuprous bromide, and stirring and reacting for 26min at 27 ℃ to obtain a component A solution;
(2) preparing a component B solution: weighing 30 parts of ferulic acid, placing the ferulic acid into 72 parts of ethanol solution, stirring and dispersing, adding 23 parts of 3, 4-vinyl dioxythiophene, and stirring and reacting at 25 ℃ for 72min to obtain a component B solution;
(3) synthesizing fresh-keeping slurry: putting 46 parts of chitosan into 56 parts of acetic acid solution, stirring and dissolving, adding 52 parts of component A solution and 32 parts of component B solution into the chitosan solution while stirring, and after the addition is finished, adding 13 parts of chloroethanol at the adding speed of V1 to obtain preservative film slurry;
(4) heating the preservative film slurry: heating the preservative film slurry at low temperature, adding L-cysteine while heating, stirring at the rotating speed of 160r/min for reaction for 26min, heating at high temperature, stirring at the rotating speed of 430r/min for reaction for 7h, standing for 16min, and vacuum degassing for 36min to obtain the porous gel preservative film slurry.
5) Preparing a porous gel preservative film: pouring the porous gel preservative film slurry obtained in the step (4) into a mould, performing casting film forming, naturally cooling to room temperature, and removing the film to obtain the porous gel preservative film.
The addition rate V1 was 12 ml/min.
The mass percent of the chloroethanol is 16%.
The steps (1) to (4) need to be carried out under a high-purity nitrogen atmosphere with the purity of more than or equal to 99.99 percent.
The low-temperature heating condition is 55 ℃; the high-temperature heating condition is 110 ℃.
Example 4
(1) Preparing a component A solution: weighing 100 parts of methacrylic acid monomer, placing the methacrylic acid monomer into 130 parts of deionized water, stirring and dissolving, sequentially adding 40 parts of double-long-chain methyl tertiary amine and 3 parts of cuprous bromide, and stirring and reacting for 30min at the temperature of 28 ℃ to obtain a component A solution;
(2) preparing a component B solution: weighing 40 parts of ferulic acid, placing the ferulic acid into 80 parts of ethanol solution, stirring and dispersing, adding 25 parts of 3, 4-vinyl dioxythiophene, stirring and reacting for 90min at the temperature of 28 ℃ to obtain a component B solution;
(3) synthesizing fresh-keeping slurry: placing 50 parts of chitosan into 60 parts of acetic acid solution, stirring and dissolving, adding 55 parts of component A solution and 35 parts of component B solution into the chitosan solution while stirring, and after the addition is finished, adding 15 parts of chloroethanol at the adding speed of V1 to obtain preservative film slurry;
(4) heating the preservative film slurry: heating the preservative film slurry at a low temperature, adding L-cysteine while heating, stirring at a rotating speed of 200r/min for reaction for 30min, then heating at a high temperature, stirring at a rotating speed of 500r/min for reaction for 10h, standing for 20min, and vacuum degassing for 38min to obtain the porous gel preservative film slurry.
(5) Preparing a porous gel preservative film: pouring the porous gel preservative film slurry obtained in the step (4) into a mould, performing casting film forming, naturally cooling to room temperature, and removing the film to obtain the porous gel preservative film.
The addition rate V1 was 15 ml/min.
The mass percent of the chloroethanol is 18%.
The steps (1) to (4) need to be carried out under a high-purity nitrogen atmosphere with the purity of more than or equal to 99.99 percent.
The low-temperature heating condition is 60 ℃; the high-temperature heating condition is 130 ℃.
Example 5
(1) Preparing a component A solution: weighing 100 parts of methacrylic acid monomer, placing the methacrylic acid monomer into 130 parts of deionized water, stirring and dissolving, sequentially adding 40 parts of double-long-chain methyl tertiary amine and 3 parts of cuprous bromide, and stirring and reacting for 30min at the temperature of 28 ℃ to obtain a component A solution;
(2) synthesizing fresh-keeping slurry: placing 50 parts of chitosan into 60 parts of acetic acid solution, stirring and dissolving, adding 55 parts of the component A solution into the chitosan solution while stirring, and after the addition is finished, adding 15 parts of chloroethanol at the adding speed of V1 to obtain preservative film slurry;
(3) heating the preservative film slurry: heating the preservative film slurry at a low temperature, adding L-cysteine while heating, stirring at a rotating speed of 200r/min for reaction for 30min, then heating at a high temperature, stirring at a rotating speed of 500r/min for reaction for 10h, standing for 20min, and vacuum degassing for 38min to obtain the porous gel preservative film slurry.
(4) Preparing a porous gel preservative film: pouring the porous gel preservative film slurry obtained in the step (3) into a mould, performing casting film forming, naturally cooling to room temperature, and removing the film to obtain the porous gel preservative film.
The addition rate V1 was 15 ml/min.
The mass percent of the chloroethanol is 18%.
The steps (1) to (3) need to be carried out under a high-purity nitrogen atmosphere with the purity of more than or equal to 99.99 percent.
The low-temperature heating condition is 60 ℃; the high-temperature heating condition is 130 ℃.
The present application differs from example 4 in that no component a solution is added.
Example 6
(1) Preparing a component B solution: weighing 40 parts of ferulic acid, placing the ferulic acid into 80 parts of ethanol solution, stirring and dispersing, adding 25 parts of 3, 4-vinyl dioxythiophene, stirring and reacting for 90min at the temperature of 28 ℃ to obtain a component B solution;
(2) synthesizing fresh-keeping slurry: placing 50 parts of chitosan into 60 parts of acetic acid solution, stirring and dissolving, adding 35 parts of the component B solution into the chitosan solution while stirring, and after the addition is finished, adding 15 parts of chloroethanol at the adding speed of V1 to obtain preservative film slurry;
(3) heating the preservative film slurry: heating the preservative film slurry at a low temperature, adding L-cysteine while heating, stirring at a rotating speed of 200r/min for reaction for 30min, then heating at a high temperature, stirring at a rotating speed of 500r/min for reaction for 10h, standing for 20min, and vacuum degassing for 38min to obtain the porous gel preservative film slurry.
(4) Preparing a porous gel preservative film: pouring the porous gel preservative film slurry obtained in the step (4) into a mould, performing casting film forming, naturally cooling to room temperature, and removing the film to obtain the porous gel preservative film.
The addition rate V1 was 15 ml/min.
The mass percent of the chloroethanol is 18%.
The steps (1) to (3) need to be carried out under a high-purity nitrogen atmosphere with the purity of more than or equal to 99.99 percent.
The low-temperature heating condition is 60 ℃; the high-temperature heating condition is 130 ℃.
The present application differs from example 4 in that no B-component solution is added.
Example 7
(1) Preparing a component A solution: weighing 100 parts of methacrylic acid monomer, placing the methacrylic acid monomer into 130 parts of deionized water, stirring and dissolving, sequentially adding 40 parts of double-long-chain methyl tertiary amine and 3 parts of cuprous bromide, and stirring and reacting for 30min at the temperature of 28 ℃ to obtain a component A solution;
(2) preparing a component B solution: weighing 40 parts of ferulic acid, placing the ferulic acid into 80 parts of ethanol solution, stirring and dispersing, adding 25 parts of 3, 4-vinyl dioxythiophene, stirring and reacting for 90min at the temperature of 28 ℃ to obtain a component B solution;
(3) synthesizing fresh-keeping slurry: placing 50 parts of chitosan into 60 parts of acetic acid solution, stirring and dissolving, adding 55 parts of component A solution and 35 parts of component B solution into the chitosan solution while stirring, and after the addition is finished, adding 15 parts of chloroethanol at the adding speed of V1 to obtain preservative film slurry;
(4) heating the preservative film slurry: adding L-cysteine into the preservative film slurry, stirring and reacting at the rotating speed of 200r/min for 30min, heating at the high temperature of 130 ℃, stirring and reacting at the rotating speed of 500r/min for 10h, standing for 20min, and vacuum degassing for 38min to obtain the porous gel preservative film slurry.
(5) Preparing a porous gel preservative film: pouring the porous gel preservative film slurry obtained in the step (4) into a mould, performing casting film forming, naturally cooling to room temperature, and removing the film to obtain the porous gel preservative film.
The addition rate V1 was 15 ml/min.
The mass percent of the chloroethanol is 18%.
The steps (1) to (4) need to be carried out under a high-purity nitrogen atmosphere with the purity of more than or equal to 99.99 percent.
The present application is different from example 4 in that the present application does not use a stepwise heating method, but directly uses a high temperature of 130 ℃.
Comparative example 1: a porous gel preservative film with chitosan as a main component is randomly purchased in the market.
Comparative example 2: common PE preservative film.
Test one:
(1) and (3) testing mechanical properties: the tensile strength and the elongation at break of the preservative film are measured according to the standard of GB13022-91 'test method for tensile property of plastic film', and the test speed is 20 mm/min.
(2) Biodegradability test: the soil is naturally degraded by utilizing soil microorganisms, and the pH value of the soil is 7.62, the organic matter is 46.57g/kg, the alkaline hydrolysis nitrogen is 24.89mg/100g, and the quick-acting phosphorus is 32.88 g/kg. The preservative film samples prepared in the embodiments 1 to 8 of the invention are buried in soil 15cm and exuded, and the test, observation and recording are carried out on the 15 th day.
The results of the mechanical property test and the biodegradation rate test of the preservative film samples prepared in examples 1 to 7 and comparative examples are shown in Table 1:
according to the data in the table 1, the biodegradation rates of the preservative film samples prepared in the embodiments 1-4 of the invention are all more than 95%, and are far higher than that of the preservative film made of the common PE material, and the preservative film samples are high in biodegradation rate, safe and environment-friendly. The tensile strength of the cling film samples described in examples 1-4 is greatly improved over the conventional porous gel cling film sample of comparative example 1.
Experiment two: the strawberry fruits are bright red, soft and juicy, and are extremely easy to be damaged and rotten and deteriorated due to microorganism infection, so the strawberries are selected as test objects; the test results of the fresh-keeping effect and the bacteriostasis rate are shown in the table 2;
(1) and (3) testing the preservation effect: 20g of the same strawberry is taken and placed in the preservative film sample prepared in the embodiment 1-8 of the invention, the fresh-keeping film sample is wrapped and tied by a rope, the fresh-keeping film sample is placed in a refrigerated cabinet at 4 ℃ for 7 days and 14 days respectively, and the malonaldehyde content of the strawberry sample in the refrigerated cabinet for 7 days and 14 days is measured respectively. Malondialdehyde is a cytotoxic lipid peroxide, reflecting the degree of lipid peroxidation in the matrix, and indirectly also the degree of cell damage.
(2) And (3) antibacterial property test: the test is carried out according to GB/T2591-2003, and the test index is Escherichia coli.
Preparing a culture medium: dissolving peptone in distilled water, heating and stirring for dissolving to obtain liquid culture medium, adding a certain amount of agar into the liquid culture medium, heating and stirring to obtain solid culture medium, wherein the peptone and the used distilled water are subjected to high-temperature steam sterilization treatment at 120 ℃.
The operation process is as follows: taking a certain amount of fresh escherichia coli from a solid culture medium by using an inoculating loop, adding the fresh escherichia coli into a liquid culture medium, and then diluting the liquid culture medium by using distilled water by 10 times, wherein the dilution concentration of the escherichia coli is 8.9 multiplied by 106 cfu/mL; 1mL of the bacterial solutions were respectively dropped on the surfaces of the strawberry samples prepared in examples 1 to 8, covered with a sterile cover film, cultured for 24 hours at 37 ℃ under a humidity of more than 90%, the cover film and the strawberry sample were repeatedly washed with 24mL of eluent, then 0.2mL of the eluent was dropped on a solid agar medium, cultured for 48 hours at 37 ℃, and then viable bacteria were counted to determine the number of viable bacteria. The antibacterial ratio was calculated and the results are shown in Table 1.
According to the data in the table 2, the antibacterial effect of the porous gel preservative film samples prepared in the embodiments 1 to 4 is as high as more than 99%, the antibacterial effect is obvious, and the antibacterial effect is not reduced to an obvious degree after the strawberry samples are placed for 14 days, which shows that the preservative film has a long antibacterial effect and can realize a long-acting antibacterial effect on food. The content of the propanedione measured in the preservative film samples in the embodiments 1-4 of the invention is far lower than that in the comparative examples 1 and 2, the preservative film has obvious antioxidant effect, can effectively inhibit food deterioration, and prolongs the storage period of the food.
According to the data in the table, it can be seen that: in the example 5, because the solution of the component A is lacked, the densification degree of the prepared porous gel preservative film sample is reduced to a certain extent compared with that of the example 4, the mechanical property of the preservative film is obviously reduced, oxygen in the air gradually permeates into the film, the oxidative decay process of the strawberry is accelerated by the respiration action of the strawberry, and the preservation effect is reduced to a certain extent compared with that of the example 4. In example 6, due to the lack of the solution of the component A, the densification degree of the prepared porous gel preservative film sample is reduced to a certain extent compared with that of example 4, the mechanical property of the preservative film is obviously reduced, oxygen in the air gradually permeates into the film, the oxidative decay process of the strawberry is accelerated by the respiration effect of the strawberry, and the preservation effect is reduced to a certain extent compared with that of example 4. The polymer network structure in the porous gel preservative film in the example 7 has a implosion phenomenon, the formed polymer network is not uniform and stable enough, and the mechanical property is insufficient compared with the example 4.
From the above data and experiments, we can conclude that: 1. according to the invention, the double-long-chain methyl tertiary amine is modified on a methacrylic acid monomer, ferulic acid is modified on 3, 4-vinyl dioxythiophene, the two are mixed with a chitosan solution, under the heating condition, the double-long-chain methyl tertiary amine is modified on the methacrylic acid monomer and the ferulic acid modified 3, 4-vinyl dioxythiophene to polymerize, and molecular chain entanglement and self-assembly occur among the methyl acrylic acid monomer and the ferulic acid modified 3, 4-vinyl dioxythiophene, so that a compact and stable network structure is formed in the gel slurry of the porous preservative film, and the mechanical property of the gel preservative film is improved.
2. According to the method, the component A solution is uniformly dispersed in the chitosan solution, and then the tertiary amine in the component A solution reacts with chloroethanol to generate the double-long-chain methyl tertiary amine to react to generate the double-long-chain methyl quaternary ammonium salt; the fine pores in the network structure can automatically adjust gas components in the film, and the storage period of food is prolonged. The long-chain molecules contained in the double-long-chain methyl quaternary ammonium salt can be entangled with polymer network molecular chains, so that the mechanical property of the preservative film is enhanced, and the later-stage complexing of L-cysteine is facilitated to further improve the comprehensive property of the preservative film.
3. The L-cysteine specially added in the invention contains a large amount of sulfydryl with a reducing effect, can effectively inhibit the activity of polyphenol oxidase in fruits and vegetables, relieves the problem of color change of the fruits and vegetables in the storage process, and keeps the luster of food. The L-cysteine also has excellent bacteriostatic effect, can expand the bacteriostatic range of the chitosan and strengthen the bacteriostatic action of the preservative film.
4. Because L-cysteine belongs to micromolecular amino acid components, the aqueous solution of the L-cysteine is difficult to stay on the surface of food, the L-cysteine is assembled in a preservative film high molecular polymer network structure in an electrostatic self-assembly mode, the stability of the cysteine can be kept, the loss of the L-cysteine is avoided, the mechanical property of the porous gel preservative film is improved, and the bacteriostatic and antioxidant effects of the porous gel preservative film are enhanced.
5. Ferulic acid is a natural component extracted from important materials such as ferula asafetida, angelica sinensis, spina date seeds and the like, can eliminate free radicals, and has excellent antioxidant performance.
6. The porous gel preservative film contains a large number of hydrophilic functional groups, can adsorb excessive water in the preservative film, keeps water-vapor balance in the preservative film, inhibits the respiration of food, and reduces the breeding of bacteria.
7. The porous gel preservative film prepared by the invention has the advantages of simple principle, safe components and good bacteriostatic effect, solves the problem of poor mechanical property of the preservative film which can be taken as a main material by Kotahe, has high degradation rate, is safe and environment-friendly, can realize industrial production, and has strong market popularization value.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A preparation method of an antibacterial moisturizing degradable porous gel preservative film is characterized by comprising the following steps: comprises the following steps
(1) Preparing a component A solution: placing a methacrylic acid monomer in deionized water, and sequentially adding double-long-chain methyl tertiary amine and cuprous bromide to obtain a component A solution;
(2) preparing a component B solution: placing ferulic acid in ethanol solution, stirring and dispersing, and adding 3, 4-vinyl dioxythiophene to obtain component B solution;
(3) synthesizing fresh-keeping slurry: placing chitosan in an acetic acid solution, stirring and dissolving, adding the component A solution and the component B solution into the chitosan solution while stirring, and adding chloroethanol to obtain preservative film slurry;
(4) heating the preservative film slurry: heating the preservative film slurry, adding L-cysteine, stirring, standing, and vacuum degassing to obtain porous gel preservative film slurry;
(5) preparing a porous gel preservative film: pouring the porous gel preservative film slurry obtained in the step (4) into a mould, performing casting film forming, naturally cooling to room temperature, and removing the film to obtain the porous gel preservative film.
2. The preparation method of the antibacterial moisturizing degradable porous gel preservative film according to claim 1, characterized in that: the specific operation process of the step (1) is as follows: weighing 60-100 parts of methacrylic acid monomer, placing the methacrylic acid monomer into 100-130 parts of deionized water, stirring and dissolving, sequentially adding 30-40 parts of double-long-chain methyl tertiary amine and 1-3 parts of cuprous bromide, and stirring and reacting for 20-30min at the temperature of 22-28 ℃ to obtain the component A solution.
3. The preparation method of the antibacterial moisturizing degradable porous gel preservative film according to claim 1, characterized in that: the specific operation process of the step (2) is as follows: weighing 20-40 parts of ferulic acid, placing the ferulic acid in 60-80 parts of ethanol solution, stirring and dispersing, adding 15-25 parts of 3, 4-vinyl dioxythiophene, and stirring and reacting at 22-28 ℃ for 60-90min to obtain a component B solution.
4. The preparation method of the antibacterial moisturizing degradable porous gel preservative film according to claim 1, characterized in that: the specific operation process of the step (3) is as follows: and (2) putting 40-50 parts of chitosan into 50-60 parts of acetic acid solution, stirring and dissolving, adding 45-55 parts of the component A solution and 25-35 parts of the component B solution into the chitosan solution while stirring, and after the addition is finished, adding 10-15 parts of chloroethanol at the adding speed of V1 to obtain the preservative film slurry.
5. The preparation method of the antibacterial moisture-keeping degradable porous gel preservative film according to claim 4, which is characterized in that: the addition rate V1 is 8-15 ml/min.
6. The preparation method of the antibacterial moisture-keeping degradable porous gel preservative film according to claim 4, which is characterized in that: the mass percent of the chloroethanol is 12-18%.
7. The preparation method of the antibacterial moisturizing degradable porous gel preservative film according to claim 1, characterized in that: the specific operation method of the step (4) comprises the following steps: heating the preservative film slurry at a low temperature, adding L-cysteine while heating, stirring and reacting at the rotating speed of 100-.
8. The preparation method of the antibacterial moisturizing degradable porous gel preservative film according to claim 1, characterized in that: the steps (1) to (4) need to be carried out under a high-purity nitrogen atmosphere with the purity of more than or equal to 99.99 percent.
9. The preparation method of the antibacterial moisturizing degradable porous gel preservative film according to claim 1, characterized in that: the low-temperature heating condition is 30-60 ℃; the high-temperature heating condition is 80-130 ℃.
10. A preservative film prepared by the method for preparing the antibacterial, moisture-keeping and degradable porous gel preservative film according to any one of claims 1 to 9.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116535546A (en) * | 2023-05-19 | 2023-08-04 | 贵州省材料产业技术研究院 | Preparation method of polyvinyl alcohol film and product thereof |
| CN117357692A (en) * | 2023-12-06 | 2024-01-09 | 成都中医药大学 | In-situ curing forming hydrogel and preparation method and application thereof |
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| CN116535546A (en) * | 2023-05-19 | 2023-08-04 | 贵州省材料产业技术研究院 | Preparation method of polyvinyl alcohol film and product thereof |
| CN116535546B (en) * | 2023-05-19 | 2024-04-12 | 贵州省材料产业技术研究院 | Preparation method of polyvinyl alcohol film and product thereof |
| CN117357692A (en) * | 2023-12-06 | 2024-01-09 | 成都中医药大学 | In-situ curing forming hydrogel and preparation method and application thereof |
| CN117357692B (en) * | 2023-12-06 | 2024-02-02 | 成都中医药大学 | In-situ curing forming hydrogel and preparation method and application thereof |
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Application publication date: 20210518 |