CN111234325A - Preparation method of food packaging film and milk packaging structure - Google Patents

Abstract

The invention discloses a preparation method of a food packaging film and a milk packaging structure, and relates to the technical field of food packaging. The preparation method of the food packaging film includes the following steps: dissolving chitosan in an acetic acid solution to form a chitosan solution; after adjusting the chitosan solution to neutrality, adding anthocyanin and stirring to form a mixed solution; After the mixed solution is defoamed, a film is laid and dried to obtain a food packaging film. The present invention aims to provide an intelligent packaging material that is environmentally safe and capable of indicating the freshness of food.

Description

Preparation method of food packaging film and milk packaging structure

technical field

The invention relates to the technical field of food packaging, in particular to a preparation method of a food packaging film and a milk packaging structure.

Background technique

At present, plastic packaging occupies a dominant position in the field of food packaging, but plastic materials are increasingly exposed to non-degradable, non-renewable and food safety characteristics, which not only bring white pollution to the environment but also endanger people's health. Moreover, when plastic materials are used for food packaging, the quality of the food can only be judged by multiple tests after removing the packaging, which makes it difficult to monitor the food during storage and transportation of perishable food such as fresh meat and milk. quality. Therefore, there is an urgent need to find a smart packaging material that is environmentally friendly, safe and can indicate the freshness of food.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to propose a preparation method of a food packaging film and a milk packaging structure, aiming to provide an intelligent packaging material that is environmentally safe and can indicate the freshness of food.

In order to achieve the above purpose, the present invention proposes a preparation method of a food packaging film, and the preparation method of the food packaging film comprises the following steps:

Dissolve chitosan in acetic acid solution to form chitosan solution;

After adjusting the chitosan solution to neutrality, add anthocyanin and stir to form a mixed solution;

After the mixed solution is defoamed, a film is laid and dried to obtain a food packaging film.

Optionally, in the step of dissolving chitosan in an acetic acid solution to form a chitosan solution, the mass fraction of chitosan in the chitosan solution is 0.8%-1.2%.

Optionally, in the step of dissolving chitosan in an acetic acid solution to form a chitosan solution, the volume fraction of acetic acid in the acetic acid solution is 0.8% to 1.2%.

Optionally, after adjusting the chitosan solution to neutrality, adding anthocyanin and stirring to form a mixed solution, the anthocyanin is tomato anthocyanin.

Optionally, after adjusting the chitosan solution to neutrality, adding anthocyanin and stirring to form a mixed solution, the mass fraction of anthocyanin in the mixed solution is 5% to 20%.

Optionally, after adjusting the chitosan solution to neutrality, adding anthocyanin, and stirring to form a mixed solution, the steps include:

After adjusting the pH of the chitosan solution to 6-7 with a sodium hydroxide solution with a concentration of 0.8-1.2 mol/L, adding anthocyanin, stirring evenly, and cooling to obtain a mixed solution.

Optionally, after the mixed solution is defoamed, a film is laid, and the steps of drying to obtain a food packaging film include:

The mixed solution is allowed to stand at 0-4° C. until the bubbles in the mixed solution are eliminated;

After the deaerated mixture is spread into a film, baked at 40 to 50° C. for 10 to 17 hours, and placed in an environment with a humidity of 45 to 55 percent for 1 to 2 days to obtain a food packaging film .

In addition, the present invention also provides a milk packaging structure, the milk packaging structure includes:

a housing having a cavity formed therein for containing the milk; and,

The inner film is arranged on the inner side wall of the casing, and the inner film includes the food packaging film prepared by the above-mentioned preparation method of the food packaging film.

Optionally, the casing is a box body or a bag body.

In the technical scheme provided by the present invention, chitosan-anthocyanin composite film is formed by using chitosan and anthocyanin as raw materials, wherein chitosan is non-toxic, transparent, biodegradable and has strong antibacterial properties, so that The prepared food packaging film not only has good film properties and bacteriostatic effect, but also is environmentally friendly and safe; Color-response to pH, enabling intelligent monitoring of the freshness of packaged foods.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only For some embodiments of the present invention, for those of ordinary skill in the art, other related drawings can also be obtained according to these drawings without creative effort.

1 is a schematic flow diagram of an embodiment of a method for preparing a food packaging film proposed by the present invention;

Fig. 2 is the change trend diagram of film properties of food packaging films under different anthocyanin mass concentrations;

Fig. 3 is the pH-dE color change curve of the food packaging film obtained in Example 1;

Fig. 4 is the pH-dL color change curve of the food packaging film obtained in Example 1;

Fig. 5 is the pH-da color change curve of the food packaging film obtained in Example 1;

6 is the pH-db color change curve of the food packaging film prepared in Example 1.

The realization, functional characteristics and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments.

Detailed ways

In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only some, but not all, embodiments of the present invention.

It should be noted that, if the specific conditions are not indicated in the examples, it is carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used without the manufacturer's indication are conventional products that can be purchased from the market. In addition, the meaning of "and/or" in the whole text includes three parallel schemes. Taking "A and/or B" as an example, it includes scheme A, scheme B, or scheme satisfying both of A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but must be based on the realization by those of ordinary skill in the art. When the combination of technical solutions is contradictory or cannot be achieved, it should be considered that the combination of technical solutions does not exist. , is not within the scope of protection required by the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

At present, plastic packaging occupies a dominant position in the field of food packaging, but plastic materials are increasingly exposed to non-degradable, non-renewable and food safety characteristics, which not only bring white pollution to the environment but also endanger people's health. Moreover, when plastic materials are used for food packaging, the quality of the food can only be judged by multiple tests after removing the packaging, which makes it difficult to monitor the food during storage and transportation of perishable food such as fresh meat and milk. quality. Therefore, there is an urgent need to find a smart packaging material that is environmentally friendly, safe and can indicate the freshness of food.

In view of this, the present invention proposes a preparation method of a food packaging film, and FIG. 1 is an embodiment of the preparation method of the food packaging film proposed by the present invention.

Please refer to Figure 1, the preparation method of the food packaging film includes the following steps:

Step S10, taking chitosan and dissolving it in an acetic acid solution to form a chitosan solution.

Chitosan, also known as chitosan, is a product obtained by removing part of the acetyl group from the natural polysaccharide chitin, which is widely present in nature. It is a polymer linear polysaccharide. Chitosan has non-toxic, transparent, good biocompatibility, biodegradability and film-forming properties, and can be made into a biodegradable edible film, and the chitosan film has good tensile strength and water resistance. Barrier properties to vapor and air. In addition, chitosan also has a certain antibacterial effect, which can inhibit the growth of bacteria and molds. Therefore, the chitosan film also has strong antibacterial properties and antioxidant properties, and is suitable for food packaging materials.

Chitosan is soluble in acetic acid, and in this example, chitosan was dissolved in an acetic acid solution to obtain a chitosan solution. Wherein, the volume fraction of acetic acid in the selected acetic acid solution is 0.8 (v/v)% to 1.2 (v/v)%, preferably 1.0 (v/v)%. In addition, in order to ensure the mixing ratio of chitosan and anthocyanin, in this embodiment, the mixing ratio of chitosan and acetic acid solution is subject to the final concentration of the formed chitosan solution, specifically, in the chitosan solution The mass fraction of chitosan is 0.8% to 1.2%, preferably 1.0%. For example, 1 g of chitosan can be weighed, 100 g of acetic acid solution is added, and stirred to dissolve, so as to obtain a chitosan solution with a mass concentration of 1.0%.

Step S20, after adjusting the chitosan solution to neutrality, add anthocyanin, and stir to form a mixed solution.

Anthocyanins are flavonoids, which are water-soluble natural pigments widely present in plants. Under the conditions of different pH values of plant cell vacuoles, petals can show colorful colors. Specifically, anthocyanins can appear in different forms at different pH values, showing red at low pH and blue at high pH. Therefore, in this example, chitosan and anthocyanin are used as the main raw materials for preparing the food packaging film, which can make the prepared food packaging film also have the pH-sensitive property of anthocyanin, so that the color can respond to pH value. When the packaged food goes rancid, the rancidity of the food will cause pH changes. After the food packaging film senses the pH change, it will show a different color. In this way, the quality inspector can avoid the need to remove the packaging film or perform multiple tests. Under the circumstance, the freshness of the food can be monitored, so that the freshness of the packaged food can be intelligently monitored.

When anthocyanins are mixed with chitosan, hydrogen bonding will occur, which will affect the film properties of food packaging films. After investigation, it was found that when the mass fraction of anthocyanin in the mixed solution increased from 0 to 50%, the tensile strength and elongation at break of the food packaging film showed the changing trend as shown in Figure 2. It can be seen from Figure 2 It can be seen that when the mass fraction of anthocyanin in the mixed solution increases from 0 to 30%, the tensile strength of the food packaging film gradually decreases, and the elongation at break increases gradually, which shows that the addition of anthocyanin makes chitosan The toughness of the membrane increases, and the ability to resist elastic deformation decreases.

In addition, anthocyanins can impart pH-responsive effects to food packaging films, but too high anthocyanin concentrations will also lead to a decrease in pH-responsive effects, resulting in food packaging films becoming less and less sensitive to the color response to pH value. Therefore, the mixing ratio of anthocyanin and chitosan needs to be controlled. After many tests, it was found that when the mass fraction of anthocyanin in the mixed solution is 5% to 20%, it can not only ensure the food packaging film It is highly responsive to pH, and can ensure that the tensile strength and elongation at break of the food packaging film remain balanced.

As a preferred embodiment of the present invention, the anthocyanin is preferably tomato anthocyanin. Compared with other anthocyanins, tomato anthocyanin has stronger antioxidant properties and has a favorable impact on the bacteriostatic effect of food packaging films.

During specific implementation, step S20 may include:

Step S21, after adjusting the pH of the chitosan solution to 6-7 with a sodium hydroxide solution with a concentration of 0.8-1.2 mol/L, adding anthocyanin, stirring evenly, and cooling to obtain a mixed solution.

Step S30, after the mixed solution is defoamed, a film is laid, and a food packaging film is obtained by drying.

In this embodiment, after the mixed solution of anthocyanin and chitosan is prepared, the mixed solution is first defoamed, and then the mixed solution is spread into a film, and after drying, a food packaging film is obtained. Among them, the defoaming treatment method can be static or ultrasonic defoaming; when paving into a film, the film can be cast on a glass plate by the casting method, or the mixed solution can be poured into a suitable mold to form a film. membrane.

Preferably, when step S30 is implemented, the following steps can be performed:

Step S31, allowing the mixed solution to stand at 0-4° C. until the bubbles in the mixed solution are eliminated;

Step S32, after the degassed mixture is spread into a film, baked at 40 to 50° C. for 10 to 17 hours, and then placed in an environment with a humidity of 45% to 55% for 1 to 2 days. Food packaging film.

In addition, the present invention also provides a milk packaging structure. The milk packaging structure includes a shell and an inner film, wherein a cavity for accommodating milk is formed inside the shell; the inner film is arranged on the inner side wall of the shell, and the inner film includes the food packaging film described above The food packaging film prepared by the preparation method. The inner film has all the technical features and technical effects of the food packaging film, which will not be repeated here.

Wherein, the housing may be a box body or a bag body, that is, the milk packaging structure may be presented as a milk packaging box or a milk packaging bag.

The technical solutions of the present invention will be described in further detail below with reference to the specific embodiments and the accompanying drawings. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

Example 1

Take chitosan, add acetic acid solution with a volume fraction of 1.0%, and stir to dissolve the chitosan to obtain a chitosan solution with a mass concentration of 1%.

After adjusting the pH of the chitosan solution to 6-7 with a sodium hydroxide solution with a concentration of 1 mol/L, adding tomato anthocyanin and stirring evenly, and then cooling to room temperature to obtain a mixed solution of chitosan and tomato anthocyanin, and The mass fraction of tomato anthocyanins in the mixture was 10%.

The mixed solution was placed in the environment of 0 to 4 °C and allowed to stand until the bubbles in the mixed solution were eliminated. Then take 70ml of the mixture and pour it into a petri dish with a diameter of 150mm. After baking at 45°C for 15 hours, put it in an environment with a humidity of 53% for 2 days, and then remove the tomato anthocyanin composite film, which is food. wrap.

Put the food packaging film under different pH value (pH3.0-pH11.0) buffer solutions, and then use a colorimeter to detect the color change of the food packaging film, and draw the color change curve pH-dE, pH-dL, pH- da, pH-db, as shown in Figures 3 to 6. It can be seen from Figure 3 to Figure 6 that with the change of pH value, the food packaging film exhibits obvious color difference changes.

Example 2

Take chitosan, add acetic acid solution with a volume fraction of 0.8%, and stir to dissolve the chitosan to obtain a chitosan solution with a mass concentration of 0.8%.

After adjusting the pH of the chitosan solution to 6-7 with a sodium hydroxide solution with a concentration of 0.8 mol/L, adding tomato anthocyanin and stirring evenly, and then cooling to room temperature to obtain a mixed solution of chitosan and tomato anthocyanin, And the mass fraction of tomato anthocyanin in the mixture is 5%.

The mixed solution was placed in the environment of 0 to 4 °C and allowed to stand until the bubbles in the mixed solution were eliminated. Then, 70 ml of the mixture was poured into a petri dish with a diameter of 150 mm, baked at 40° C. for 17 hours, placed in an environment with a humidity of 45% for 2 days, and the film was removed to obtain a food packaging film.

Example 3

Take chitosan, add acetic acid solution with a volume fraction of 1.1%, and stir to dissolve the chitosan to obtain a chitosan solution with a mass concentration of 1.1%.

After adjusting the pH of the chitosan solution to 6-7 with a sodium hydroxide solution with a concentration of 0.9 mol/L, adding tomato anthocyanin and stirring evenly, then cooling to room temperature to obtain a mixed solution of chitosan and tomato anthocyanin, And the mass fraction of tomato anthocyanin in the mixture is 8%.

The mixed solution was placed in the environment of 0 to 4 °C and allowed to stand until the bubbles in the mixed solution were eliminated. Then, 70 ml of the mixture was poured into a petri dish with a diameter of 150 mm, baked at 43° C. for 15 hours, placed in an environment with a humidity of 45% for 2 days, and the film was removed to obtain a food packaging film.

Example 4

Take chitosan, add acetic acid solution with a volume fraction of 1.0%, and stir to dissolve the chitosan to obtain a chitosan solution with a mass concentration of 1.2%.

After adjusting the pH of the chitosan solution to 6-7 with a sodium hydroxide solution with a concentration of 1.1 mol/L, adding anthocyanin and stirring evenly, and then cooling to room temperature to obtain a mixed solution of chitosan and anthocyanin, and the The mass fraction of anthocyanins in the mixture is 15%.

The mixed solution was placed in the environment of 0 to 4 °C and allowed to stand until the bubbles in the mixed solution were eliminated. Then take 70ml of the mixture and pour it into a petri dish with a diameter of 150mm, bake at 50°C for 10h, place it in an environment with a humidity of 48% for 1.5 days, and remove the film to obtain a food packaging film.

Example 5

Take chitosan, add acetic acid solution with a volume fraction of 1.2%, and stir to dissolve the chitosan to obtain a chitosan solution with a mass concentration of 0.9%.

After adjusting the pH of the chitosan solution to 6-7 with a sodium hydroxide solution with a concentration of 1.2 mol/L, adding anthocyanin and stirring evenly, and then cooling to room temperature to obtain a mixed solution of chitosan and anthocyanin, and the The mass fraction of anthocyanins in the mixture is 20%.

The mixed solution was placed in the environment of 0 to 4 °C and allowed to stand until the bubbles in the mixed solution were eliminated. Then pour 70 ml of the mixture into a petri dish with a diameter of 150 mm, bake at 48° C. for 12 hours, place it in an environment with a humidity of 52% for 2 days, and remove the film to obtain a food packaging film.

The effects of the food packaging films prepared in Examples 1 to 5 were verified.

Put 200ml of fresh milk in a 250ml beaker, wrap the food packaging film on the mouth of the beaker, and ensure the sealing between the food packaging film and the outer wall of the beaker, as the experimental group. Meanwhile, 4 control groups of chitosan films were set. The beakers of the experimental group and the control group were placed in an environment of 7 °C for 4 days, and the pH of the milk in a control group was tested every day (the control group after the test was no longer involved in the follow-up test). At the same time, the food packaging film of the experimental group was observed. The color changes were recorded in Table 1.

Table 1 Color change of food packaging film

Example 1 Example 2 Example 3 Example 4 Example 5 milk pH 0 days green green green green green 6.7 1 day green green green green green 6.0 2 days Purple Purple Purple Purple Purple 5.0 3 days Light purple Light purple Light purple Light purple Light purple 4.6 4 days pink pink pink pink pink 3.0

As can be seen from the above table, the pH of the milk in the beaker is constantly decreasing, and at the same time, the color of the food packaging films prepared in each example begins to change from green to pink, indicating that the food packaging films prepared by the preparation method of the present invention can indicate the freshness of food .

The above are only the preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of patent protection of the present invention.

Claims (9)

1. The preparation method of the food packaging film is characterized by comprising the following steps:

dissolving chitosan in an acetic acid solution to form a chitosan solution;

adjusting the chitosan solution to be neutral, adding anthocyanin, and stirring to form a mixed solution;

and (3) defoaming the mixed solution, paving a film, and drying to obtain the food packaging film.

2. The method for preparing a food packaging film according to claim 1, wherein in the step of dissolving chitosan in an acetic acid solution to form a chitosan solution, the mass fraction of chitosan in the chitosan solution is 0.8% to 1.2%.

3. The method for preparing a food packaging film according to claim 1, wherein in the step of dissolving chitosan in an acetic acid solution to form a chitosan solution, the volume fraction of acetic acid in the acetic acid solution is 0.8% to 1.2%.

4. The method for preparing a food packaging film according to claim 1, wherein the step of adding anthocyanin after adjusting the chitosan solution to be neutral and stirring to form a mixed solution is carried out, wherein the anthocyanin is tomato anthocyanin.

5. The method for producing a food packaging film according to claim 1, wherein, in the step of adjusting the chitosan solution to be neutral, adding anthocyanin and stirring to form a mixed solution, the mixed solution contains 5 to 20 mass% of anthocyanin.

6. The method for preparing a food packaging film according to claim 1, wherein the step of adding anthocyanin after adjusting the chitosan solution to be neutral and stirring to form a mixed solution comprises:

and (3) adjusting the pH of the chitosan solution to 6-7 by using a sodium hydroxide solution with the concentration of 0.8-1.2 mol/L, adding anthocyanin, uniformly stirring, and cooling to obtain a mixed solution.

7. The method for preparing a food packaging film according to claim 1, wherein the step of preparing the food packaging film by defoaming the mixed solution, laying the film and drying the film comprises the following steps:

standing the mixed solution at 0-4 ℃ until bubbles in the mixed solution are eliminated;

and spreading the mixed solution after the defoaming treatment into a film, baking the film at 40-50 ℃ for 10-17 h, and placing the film in an environment with the humidity of 45-55% for 1-2 days to obtain the food packaging film.

8. The utility model provides a milk packaging structure which characterized in that, milk packaging structure includes:

the milk container comprises a shell, a cover and a handle, wherein a cavity for containing milk is formed inside the shell; and the number of the first and second groups,

an inner film disposed on an inner sidewall of the case, the inner film comprising a food packaging film manufactured by the method of manufacturing a food packaging film according to any one of claims 1 to 7.

9. The milk packaging structure of claim 8, wherein the case is a box or a bag.

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