阅读说明：本技术 一种没食子酸交联的壳聚糖-明胶活性复合膜的制备方法 (Preparation method of gallic acid crosslinked chitosan-gelatin active composite membrane ) 是由 张长才 石吉勇 邹小波 李志华 黄晓玮 郭志明 于江 刘凯 翟晓东 申婷婷 于 2020-12-30 设计创作，主要内容包括：本发明属于包装材料技术领域,具体涉及一种没食子酸交联的壳聚糖-明胶活性复合膜的制备方法。制备步骤为：将壳聚糖溶液和明胶溶液混合,搅拌均匀后得到壳聚糖-明胶共混溶液；然后配制没食子酸水溶液,将没食子酸水溶液加入壳聚糖-明胶共混溶液中,充分搅拌、反应后得到成膜液；再将成膜液倒在平板中,烘干成膜后将膜从平板中轻轻剥离,得到活性复合膜。壳聚糖-明胶-没食子酸活性复合膜以壳聚糖和明胶共混溶液作为膜基质,没食子酸作为天然交联剂和活性物质加入后制备而成。该活性膜具有机械性能好、抗氧化和抗菌能力强等特点,并且对人体无毒害作用,安全环保；可以作为食品包装材料,能够有效延缓食品的腐败过程,从而延长食品的货架期。(The invention belongs to the technical field of packaging materials, and particularly relates to a preparation method of a gallic acid crosslinked chitosan-gelatin active composite membrane. The preparation steps are as follows: mixing the chitosan solution and the gelatin solution, and uniformly stirring to obtain a chitosan-gelatin blending solution; then preparing a gallic acid aqueous solution, adding the gallic acid aqueous solution into the chitosan-gelatin blended solution, fully stirring and reacting to obtain a film forming solution; and pouring the film-forming solution into a flat plate, drying to form a film, and slightly stripping the film from the flat plate to obtain the active composite film. The chitosan-gelatin-gallic acid active composite membrane is prepared by using a chitosan and gelatin blended solution as a membrane matrix and adding gallic acid as a natural cross-linking agent and an active substance. The active membrane has the characteristics of good mechanical property, strong oxidation resistance and antibacterial capacity and the like, has no toxic action on human bodies, and is safe and environment-friendly; can be used as food packaging material, and can effectively delay the putrefaction process of food, thereby prolonging the shelf life of food.)

1. A preparation method of a gallic acid crosslinked chitosan-gelatin active composite membrane is characterized by comprising the following steps:

(1) preparing a chitosan-gelatin blending solution;

s1, weighing a certain amount of chitosan, dissolving the chitosan in an acetic acid aqueous solution, and reacting at a certain temperature to obtain a chitosan solution;

s2, weighing a certain amount of gelatin, dissolving the gelatin in water, and reacting at a certain temperature to obtain a gelatin solution;

s3, mixing the chitosan solution and the gelatin solution, and stirring and reacting at a certain temperature to obtain a chitosan-gelatin blending solution;

(2) adding gallic acid powder into water, and performing ultrasonic treatment to obtain gallic acid water solution; then adding the gallic acid aqueous solution into the chitosan-gelatin blending solution, stirring and reacting under a certain temperature condition to obtain a film forming solution.

(3) And (3) pouring the film-forming solution obtained in the step (2) into a plastic flat plate, then drying the flat plate filled with the film-forming solution, and slightly peeling the film from the flat plate after drying and film forming to obtain the active composite film.

2. The method for preparing a gallic acid crosslinked chitosan-gelatin active composite membrane according to claim 1, wherein the mass concentration of chitosan in the chitosan solution in step S1 is 1% -3%, and the mass concentration of acetic acid is 1% -5%; the certain temperature condition is 50-80 ℃, and the reaction time is 1-3 h.

3. The method for preparing a gallic acid crosslinked chitosan-gelatin active composite membrane according to claim 1, wherein the mass concentration of gelatin in the gelatin solution in step S2 is 1% -3%; the certain temperature condition is 30-80 ℃, and the reaction time is 1-2 h.

4. The method for preparing a gallic acid crosslinked chitosan-gelatin active composite membrane according to claim 1, wherein the volume ratio of the chitosan solution and the gelatin solution when mixing in step S2 is 1: 1.

5. The method for preparing a gallic acid crosslinked chitosan-gelatin active composite membrane according to claim 1, wherein the certain temperature condition in step S2 is 50-80 ℃, and the stirring reaction time is 2-3 h.

6. The method for preparing a gallic acid crosslinked chitosan-gelatin active composite membrane according to claim 1, wherein the dosage ratio of gallic acid powder to water in step (2) is 0.1 g: 4-10 ml; the ultrasonic treatment time is 3-5 min.

7. The method for preparing a gallic acid crosslinked chitosan-gelatin active composite membrane according to claim 1, wherein the gallic acid powder in step (2) accounts for 0.02-0.08% of the chitosan-gelatin blended solution by mass; the certain temperature condition is 50-80 ℃, and the stirring reaction time is 2-3 h.

8. The method for preparing a gallic acid crosslinked chitosan-gelatin active composite membrane according to claim 1, wherein the thickness of the deposition solution poured into the flat plate in step (3) is 3-5 mm.

9. The method for preparing a gallic acid crosslinked chitosan-gelatin active composite membrane according to claim 1, wherein the drying temperature in step (3) is 30-80 ℃, and the drying time is 20-30 h.

10. Use of the gallic acid crosslinked chitosan-gelatin activated composite membrane prepared according to the method of any one of claims 1-9 for food packaging and food spoilage delay.

Technical Field

The invention belongs to the technical field of packaging materials, and particularly relates to a preparation method of a gallic acid crosslinked chitosan-gelatin active composite membrane.

Background

At present, inert packaging materials mainly made of plastics have already occupied a large share of the food packaging market by virtue of the advantages of low cost, simplicity, convenience and the like, and are favored by merchants and consumers. However, the problems of excessive use of petroleum-based materials and difficult degradation of plastic packaging have placed a significant burden on the natural environment. With the development of the food industry, new requirements are also put forward on food packaging, namely, the packaging material is required to meet the basic requirements of maintaining the food quality through physical barrier, and the packaging material is required to have the functional properties of prolonging the shelf life of the food and relieving the putrefaction process of the food. This therefore presents new challenges for food packaging materials.

In recent years, bio-based active packaging has emerged in the background of this era. The bio-based active package is a packaging material prepared by loading active ingredients on a natural biological base material, and has the characteristics of no toxicity, easy degradation and the like. The food packaging bag can also automatically adjust the internal environmental conditions of the package, create a 'microenvironment' suitable for food storage and fresh keeping, and prolong the shelf life of the food. The active packages can be classified into antibacterial, uvioresistant, antioxidant, etc. according to their functional properties. However, the existing bio-based active package has the problems of poor mechanical property, and the like, and the bioactivity needs to be further improved.

Gallic acid is a polyphenol compound widely existing in nature, and has antibacterial, antiinflammatory, and antioxidant effects. It is also called a natural cross-linking agent because it can produce strong cross-linking action with protein and polysaccharide. However, no researchers have added gallic acid to biofilms as both a cross-linking agent and an active substance to improve their mechanical and functional properties.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to overcome the technical defects in the prior art, and provides a preparation method of an active packaging material for food packaging. The packaging material is prepared using a chitosan and gelatin blend solution as a film matrix, and gallic acid as a natural cross-linking agent and an active substance added to the film matrix. The chitosan-gelatin-gallic acid active composite membrane has the characteristics of good mechanical property, strong oxidation resistance and antibacterial capacity and the like, is expected to better maintain the food quality, prolong the shelf life, has no toxic action on human bodies, and is safe and environment-friendly.

The present invention achieves the above-described object by the following technical means.

A preparation method of a gallic acid crosslinked chitosan-gelatin active composite membrane comprises the following steps:

(1) preparing a chitosan-gelatin blending solution;

s1, weighing a certain amount of chitosan, dissolving the chitosan in an acetic acid aqueous solution, and reacting at a certain temperature to obtain a chitosan solution;

s2, weighing a certain amount of gelatin, dissolving the gelatin in water, and reacting at a certain temperature to obtain a gelatin solution;

s3, mixing the chitosan solution and the gelatin solution, and stirring and reacting at a certain temperature to obtain a chitosan-gelatin blending solution;

(2) adding gallic acid powder into water, and performing ultrasonic treatment to obtain gallic acid water solution; then adding the gallic acid aqueous solution into the chitosan-gelatin blending solution, and stirring and reacting under a certain temperature condition to obtain a film forming solution.

(3) And (3) pouring the film-forming solution obtained in the step (2) into a flat plate, drying the flat plate filled with the film-forming solution, drying to form a film, and slightly stripping the film from the flat plate to obtain the active composite film.

Preferably, in the step S1, the mass concentration of chitosan in the chitosan solution is 1% to 3%, and the mass concentration of acetic acid is 1% to 5%; the certain temperature condition is 50-80 ℃, and the reaction time is 1-3 h.

Preferably, the mass concentration of gelatin in the gelatin solution in the step S2 is 1% to 3%; the certain temperature condition is 30-80 ℃, and the reaction time is 1-2 h.

Preferably, the volume ratio of the chitosan solution and the gelatin solution in the step S2 is 1: 1.

Preferably, the certain temperature condition in the step S2 is 50-80 ℃, and the stirring reaction time is 2-3 hours.

Preferably, the ratio of the gallic acid powder to water in step (2) is 0.1 g: 4-10 ml; the ultrasonic treatment time is 3-5 min.

Preferably, the gallic acid powder in the step (2) accounts for 0.02-0.08% of the weight of the chitosan-gelatin blending solution.

Preferably, the certain temperature condition in the step (2) is 50-80 ℃, and the stirring reaction time is 2-3 hours.

Preferably, the thickness of the deposition solution poured into the plastic flat plate in step (3) is 3-5 mm.

Preferably, the drying temperature in the step (3) is 30-80 ℃, and the drying time is 20-30 h.

The invention has the advantages and technical effects that:

(1) the active composite membrane is prepared by taking natural substances of chitosan, gelatin and gallic acid as raw materials, is green and environment-friendly, can be naturally degraded, cannot damage the nature, and accords with the sustainable development strategy.

(2) The invention adopts the curtain coating drying method to prepare the active composite membrane, the preparation process is simple, the production efficiency is high, and the composite membrane has complete and smooth appearance, consistent thickness and stable performance.

(3) The active composite film has better mechanical property and meets the basic requirements of food packaging; has excellent antioxidant and antibacterial abilities, and can effectively delay the putrefaction process of food and finally prolong the shelf life of food.

Drawings

FIG. 1 shows the results of mechanical property tests of an active composite membrane;

FIG. 2 shows DPPH radical scavenging ability of an active composite membrane;

FIG. 3 shows the antibacterial activity of the active composite membrane against Escherichia coli, Staphylococcus aureus and Bacillus subtilis;

wherein different lower case letters in the figure indicate significant differences (P < 0.05).

Detailed Description

The invention is further illustrated by the following examples.

Example 1:

a preparation method of a chitosan-gelatin-gallic acid cross-linked active composite membrane comprises the following steps:

(1) weighing chitosan, dissolving the chitosan in an acetic acid aqueous solution, wherein the mass concentration of the chitosan is 2%, and the mass concentration of the acetic acid is 2%, and reacting for 2 hours at 65 ℃ to obtain a chitosan solution;

weighing gelatin, dissolving the gelatin in water, wherein the mass concentration of the gelatin is 2%, reacting for 1.5h at the temperature of 60 ℃, and obtaining a gelatin solution after reaction;

mixing chitosan solution and gelatin solution at a ratio of 1:1, reacting at 60 deg.C for 2h, continuously stirring to mix them thoroughly to obtain chitosan-gelatin blended solution;

(2) weighing gallic acid powder according to 0.04% of the weight of the chitosan-gelatin blending solution, and then dissolving the gallic acid powder in water, wherein the dosage ratio of the gallic acid powder to the water is 0.1 g: 4ml, and ultrasonic treatment is carried out for 5min to fully dissolve the materials; then slowly adding the gallic acid water solution into the chitosan-gelatin blended solution by using a rubber head dropper, and continuously stirring, wherein the whole process is carried out at 60 ℃, and the stirring time is 3 h.

(3) Finally preparing the active composite membrane by using a tape casting drying method;

pouring the film-forming solution into a plastic flat plate, wherein the thickness of the film-forming solution poured into the flat plate is 3 mm; then, the flat plate filled with the film forming solution is moved into an oven to be dried, the temperature of the oven is set to be 35 ℃, and the drying time is 24 hours; and (3) after drying and film forming, slightly stripping the film from the flat plate to obtain the active composite film.

Example 2:

a preparation method of a chitosan-gelatin-gallic acid cross-linked active composite membrane comprises the following steps:

(1) weighing chitosan, dissolving the chitosan in an acetic acid aqueous solution, wherein the mass concentration of the chitosan is 2%, and the mass concentration of the acetic acid is 2%, and reacting for 2 hours at 65 ℃ to obtain a chitosan solution;

weighing gelatin, dissolving the gelatin in water, wherein the mass concentration of the gelatin is 2%, reacting for 1.5h at the temperature of 60 ℃, and obtaining a gelatin solution after reaction;

mixing chitosan solution and gelatin solution at a ratio of 1:1, reacting at 60 deg.C for 2h, continuously stirring to mix them thoroughly to obtain chitosan-gelatin blended solution;

(2) weighing gallic acid powder according to 0.08% of the weight of the chitosan-gelatin blending solution, and then dissolving the gallic acid powder in water, wherein the dosage ratio of the gallic acid powder to the water is 0.1 g: 5ml, and ultrasonic treatment is carried out for 5min to ensure that the mixture is fully dissolved; then slowly adding the gallic acid water solution into the chitosan-gelatin blended solution by using a rubber head dropper, and continuously stirring, wherein the whole process is carried out at 60 ℃, and the stirring time is 3 h.

(3) Finally preparing the active composite membrane by using a tape casting drying method;

pouring the film-forming solution into a plastic flat plate, wherein the thickness of the film-forming solution poured into the flat plate is 3 mm; then, the flat plate filled with the film forming solution is moved into an oven to be dried, the temperature of the oven is set to be 35 ℃, and the drying time is 24 hours; and (3) after drying and film forming, slightly stripping the film from the flat plate to obtain the active composite film.

Comparison: the preparation method is the same as example 2, except that no gallic acid is added.

The mechanical property of the active composite membrane prepared by the invention is measured, and the specific steps are as follows:

the tensile strength and elongation at break of the film were measured using a physical property tester. All films were cut into 60mm long, 20mm wide strips prior to testing. During testing, the film sample is fixed at two ends of a tensile grab handle, the initial grab handle distance is 40mm, and the tensile speed is 0.06mm s^-1Each film sample was tested 5 times.

FIG. 1 is a graph showing the mechanical properties of the active composite films prepared in examples 1 and 2 (A is tensile strength, B is elongation at break, and the control is a chitosan-gelatin blend film prepared without adding gallic acid);

the results show that the tensile strength of the active composite membranes prepared in examples 1 and 2 is significantly improved compared to the control group, because the gallic acid forms a dense cross-linked network structure with the membrane matrix after being added, and the mechanical properties of the membranes are enhanced. Although the elongation at break of the film is somewhat reduced, the degree of reduction is not great and the flexibility of the film is within an acceptable range.

The oxidation resistance of the active composite membrane prepared by the invention is tested, and the specific steps are as follows:

the antioxidant capacity of the active composite membrane was tested using DPPH free radical scavenging. The membrane sample (20mg) was placed in a solution of DPPH in methanol (4mL, 0.25. mu.M), and the mixture was reacted in a dark room at 20 ℃ for 1 h. After the reaction was completed, the supernatant was extracted, and then the absorbance thereof was measured at 517 nm. All experiments were repeated 3 times. FIG. 2 shows the DPPH radical scavenging ability of the active composite membranes prepared in examples 1 and 2 (control group is chitosan-gelatin blend membrane without gallic acid). The results show that the antioxidant capacity of the active composite membrane is in a direct proportional relationship with the concentration of gallic acid.

The antibacterial ability test of the active composite membrane prepared by the invention comprises the following specific steps:

the antibacterial ability of the composite membrane to escherichia coli, staphylococcus aureus and bacillus subtilis was evaluated by an agar diffusion method. The membrane samples were first cut into disks (6 mm diameter) and placed on agar plates containing the corresponding bacteria. The plate was then incubated in an incubation chamber at 37 ℃ for 24 hours. And finally, measuring the diameter of the inhibition region by using a vernier caliper, and evaluating the antibacterial capacity of the composite membrane according to the size of the inhibition region. All experiments were repeated three times. Fig. 3 is a graph showing the antibacterial ability of the active composite membranes prepared in examples 1 and 2 (control group is chitosan-gelatin blend membrane without gallic acid). The result shows that the diameter of the inhibition zone of the composite membrane containing the gallic acid is obviously increased, which indicates that the antibacterial performance of the composite membrane is improved by adding the gallic acid.

In summary, the preparation method of the chitosan-gelatin-gallic acid active composite membrane of the invention comprises the steps of firstly mixing chitosan and gelatin to obtain a blending solution, then adding gallic acid for crosslinking, and finally adopting a tape casting drying method to obtain the active composite membrane. The active composite membrane has complete and smooth appearance and consistent thickness. Has better mechanical property and excellent oxidation resistance and antibacterial capacity, can effectively delay the putrefaction process of food, and finally prolongs the shelf life of the food.

Description of the drawings: the above embodiments are only used to illustrate the present invention and do not limit the technical solutions described in the present invention; thus, while the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted; all such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims.