Alkali treatment sensitization acetic acid response anthocyanin intelligent packaging film and preparation method thereof

Abstract

The invention belongs to the field of food packaging materials, and discloses an alkali treatment sensitization acetic acid response anthocyanin intelligent packaging film and a preparation method thereof. The method comprises the following steps: uniformly dispensing alkali liquor on the surface of an original anthocyanin film, and drying to obtain the alkali treatment sensitization acetic acid response anthocyanin intelligent packaging film. The packaging film disclosed by the invention can enhance the precision of monitoring the freshness of fruits and vegetables in real time, and also has the advantages of low cost, simple process, convenience in operation and high universality.

Description

Technical Field

[0001] The present invention belongs to the field of food packaging materials, and more specifically, relates to an anthocyanin intelligent packaging film with alkali treatment to enhance acetic acid response and a preparation method thereof. Background Art

[0002] With people's increasing attention to food safety issues and the rapid development of food packaging technology, traditional food packaging materials can no longer meet people's needs. Smart packaging films that can monitor food freshness in real time have received widespread attention.

[0003] During food storage, microbial growth or metabolism can produce substances that alter the pH of the food packaging environment. For example, livestock and poultry meat / aquatic products produce alkaline substances such as volatile basic nitrogen (such as ammonia) during storage, causing the pH of the packaging environment to increase; while fruits and vegetables produce acidic substances such as acetic acid during storage, causing the pH of the packaging environment to decrease. By embedding pH-sensitive indicator materials that respond to metabolites such as ammonia and acetic acid in the packaging material, the freshness of the food can be monitored in real time by observing the color change of the indicator material. Anthocyanins are natural pigments from various plants and fruits and vegetables. They are natural, non-toxic, safe, and biodegradable, and have obvious color reactions at different pH values. Therefore, the preparation of anthocyanin freshness indicator films has become a key research topic for many scholars.

[0004] Previously reported anthocyanin freshness indicator films have primarily been used for monitoring the freshness of livestock, poultry, and aquatic products, using ammonia as a color-changing agent. However, reports on anthocyanin-based smart packaging films that use acetic acid as a color-changing agent, suitable for monitoring the freshness of fruits and vegetables, are limited. Furthermore, further research is needed to improve the color response of anthocyanin indicator films used for monitoring the freshness of fruits and vegetables to acetic acid. Summary of the Invention

[0005] The present invention addresses the shortcomings of existing technologies by providing an intelligent anthocyanin packaging film with alkali-treated, acetic acid-sensitized responsiveness and a preparation method. This packaging film enhances the accuracy of real-time monitoring of fruit and vegetable freshness while offering the advantages of low cost, simple processing, convenient operation, and broad applicability.

[0006] In order to achieve the above-mentioned purpose, the present invention provides a method for preparing anthocyanin smart packaging film with alkali treatment sensitized to acetic acid response, the method comprising: evenly applying alkali solution on the surface of the original anthocyanin film, drying, and obtaining the anthocyanin smart packaging film with alkali treatment sensitized to acetic acid response.

[0007] In the present invention, "intelligent" means that the packaging film of the present invention can monitor the freshness of fruits and vegetables in real time.

[0008] According to the present invention, preferably, the drying temperature is 25-35° C., and the drying time is 10 min-2 h.

[0009] In the present invention, the alkali solution is a non-volatile alkali solution. According to the present invention, preferably, the alkali solution is at least one of a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, a sodium carbonate aqueous solution, a potassium carbonate aqueous solution, a sodium bicarbonate aqueous solution and a potassium bicarbonate aqueous solution.

[0010] According to the present invention, preferably, the usage ratio of the alkali solution to the original anthocyanin film is (3-4): 1 mL / g.

[0011] According to the present invention, preferably, the concentration of the alkali solution is 0.05-0.6 mol / L.

[0012] According to the present invention, preferably, the method for preparing the original anthocyanin film comprises the following steps:

[0013] S1: mixing chitosan with an aqueous acetic acid solution to obtain a chitosan solution; mixing polyvinyl alcohol with water to obtain a polyvinyl alcohol solution;

[0014] S2: uniformly mixing the chitosan solution and the polyvinyl alcohol solution to obtain a mixed solution; mixing glycerol with the mixed solution to obtain a film-forming matrix mixed solution;

[0015] S3: mixing anthocyanin with the film-forming matrix mixed solution to obtain a film-forming solution;

[0016] S4: The film-forming solution is sequentially stirred, allowed to stand for defoaming, cast into a film, dried, and allowed to stand at a constant temperature and humidity to obtain the original anthocyanin film.

[0017] According to the present invention, preferably, the mass fraction of acetic acid in the acetic acid aqueous solution is 0.5-1.5 wt.%, based on the total weight of the acetic acid aqueous solution.

[0018] According to the present invention, preferably, the mass fraction of chitosan in the chitosan solution is 0.5-1.5 wt.%, based on the total weight of the chitosan solution.

[0019] According to the present invention, preferably, based on the total weight of the polyvinyl alcohol solution, the mass fraction of the polyvinyl alcohol in the polyvinyl alcohol solution is 0.5-1.5 wt.%.

[0020] According to the present invention, preferably, the mass ratio of the chitosan solution to the polyvinyl alcohol solution is (6.5-7.5): (2.5-3.5).

[0021] According to the present invention, preferably, the mass fraction of glycerol in the film-forming matrix mixed solution is 0.15-0.25 wt.%, based on the total weight of the film-forming matrix mixed solution.

[0022] According to the present invention, preferably, the concentration of the anthocyanin in the film-forming solution is 0.15-0.25 mg / mL.

[0023] According to the present invention, preferably, the anthocyanin is at least one of grape skin anthocyanin, purple potato anthocyanin and blueberry anthocyanin.

[0024] According to the present invention, preferably, the rotation speed of the stirring treatment is 350-450 rpm, and the time is 1.5-2.5 h.

[0025] According to the present invention, preferably, the time for the static defoaming treatment is 1.5-2.5 hours.

[0026] According to the present invention, preferably, the drying temperature is 30-35° C. and the drying time is 22-26 hours.

[0027] According to the present invention, preferably, the constant temperature and humidity static treatment is performed at a temperature of 24-26° C., a humidity of 50-60%, and a time of 22-26 hours.

[0028] Another aspect of the present invention provides the method for preparing the anthocyanin smart packaging film with enhanced acetic acid response through alkali treatment, and the obtained anthocyanin smart packaging film with enhanced acetic acid response through alkali treatment.

[0029] The beneficial effects of the technical solution of the present invention are as follows: the packaging film of the present invention can enhance the accuracy of real-time monitoring of the freshness of fruits and vegetables, and also has the advantages of low cost, simple process, convenient operation, and strong universality. Specifically:

[0030] (1) The present invention can directionally change the structure of grape skin anthocyanin in the grape skin anthocyanin film through alkali treatment and regulate the initial color of the grape skin anthocyanin film, thereby significantly enhancing its color responsiveness to acetic acid. The highly sensitive acetic acid-responsive anthocyanin smart packaging film of the present invention has broad application prospects in real-time monitoring of the freshness of fruits and vegetables.

[0031] (2) The preparation process of the present invention is simple, the conditions are mild, and the operation is easy. The effect of improving the sensitivity of acetic acid is not limited to grape skin anthocyanin membranes, but can be used for other types of anthocyanin membranes, and has good universality.

[0032] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0034] Figure 1 The process flow chart of the preparation method of an anthocyanin smart packaging film with acetic acid response enhanced by alkali treatment provided in Example 1 of the present invention is shown.

[0035] Figure 2 The color response of the packaging films prepared under the process conditions of Examples 1-6 of the present invention and the comparative example to acetic acid is shown. DETAILED DESCRIPTION

[0036] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. Instead, these embodiments are provided to make the present invention more thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0037] In the following examples and comparative examples,

[0038] The chitosan was purchased from Qingdao Hehai Biotechnology Co., Ltd.

[0039] The polyvinyl alcohol was purchased from Shanghai Sinopharm Chemical Reagent Co., Ltd.

[0040] The sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate and potassium bicarbonate were all purchased from Shanghai Sinopharm Chemical Reagent Co., Ltd.

[0041] Grape skin anthocyanins (purity: 25%) were purchased from Yunnan Tonghai Yang's Natural Products Co., Ltd.

[0042] Example 1

[0043] This embodiment provides a method for preparing anthocyanin smart packaging film with enhanced acetic acid response by alkali treatment, such as Figure 1 As shown, the following steps are included:

[0044] S1: mixing chitosan with a 1 wt.% aqueous acetic acid solution to obtain a 1 wt.% chitosan solution; and mixing polyvinyl alcohol with water to obtain a 1 wt.% polyvinyl alcohol solution;

[0045] S2: uniformly mixing the chitosan solution and the polyvinyl alcohol solution in a mass ratio of 7:3 to obtain a mixed solution; mixing glycerol with the mixed solution to obtain a film-forming matrix mixed solution; the mass fraction of glycerol in the film-forming matrix mixed solution is 0.2 wt.% based on the total weight of the film-forming matrix mixed solution;

[0046] S3: Mixing grape skin anthocyanidins with the film-forming matrix mixed solution to obtain a film-forming solution (i.e. Figure 1The concentration of the grape skin anthocyanins in the film-forming solution is 0.2 mg / mL;

[0047] S4: The film-forming solution was stirred at 400 rpm for 2 h, then allowed to stand for 2 h to defoam, poured into a culture dish, and cast into a film. The film was dried at 30° C. for 24 h, and then placed in a constant temperature and humidity chamber (temperature 25° C., humidity 55%) for 24 h to obtain the original anthocyanin film (i.e., grape skin anthocyanin film);

[0048] S5: Evenly apply a 0.05 mol / L sodium hydroxide aqueous solution to the surface of the original anthocyanin film and dry it at 30°C for 1 hour to obtain the anthocyanin smart packaging film with alkali-treated sensitized acetic acid response. The ratio of the sodium hydroxide aqueous solution to the original anthocyanin film is 3.8:1 mL / g.

[0049] Example 2

[0050] This embodiment provides a method for preparing anthocyanin smart packaging film with enhanced acetic acid response through alkali treatment. The only difference between this embodiment and Example 1 is that the alkali solution used is a 0.1 mol / L potassium hydroxide aqueous solution.

[0051] Example 3

[0052] This embodiment provides a method for preparing anthocyanin smart packaging film with enhanced acetic acid response through alkali treatment. The only difference between this embodiment and Example 1 is that the alkali solution used is a 0.5 mol / L sodium carbonate aqueous solution.

[0053] Example 4

[0054] This embodiment provides a method for preparing anthocyanin smart packaging film with enhanced acetic acid response through alkali treatment. The only difference between this embodiment and Example 1 is that the alkali solution used is a 0.5 mol / L potassium carbonate aqueous solution.

[0055] Example 5

[0056] This embodiment provides a method for preparing anthocyanin smart packaging film with enhanced acetic acid response through alkali treatment. The only difference between this embodiment and Example 1 is that the alkali solution used is a 0.5 mol / L sodium bicarbonate aqueous solution.

[0057] Example 6

[0058] This embodiment provides a method for preparing anthocyanin smart packaging film with enhanced acetic acid response through alkali treatment. The only difference between this embodiment and Example 1 is that the alkali solution used is a 0.5 mol / L potassium bicarbonate aqueous solution.

[0059] Comparative Example

[0060] This comparative example provides a method for preparing anthocyanin intelligent packaging film, comprising the following steps:

[0061] S1: mixing chitosan with a 1 wt.% aqueous acetic acid solution to obtain a 1 wt.% chitosan solution; and mixing polyvinyl alcohol with water to obtain a 1 wt.% polyvinyl alcohol solution;

[0062] S2: uniformly mixing the chitosan solution and the polyvinyl alcohol solution in a mass ratio of 7:3 to obtain a mixed solution; mixing glycerol with the mixed solution to obtain a film-forming matrix mixed solution; the mass fraction of glycerol in the film-forming matrix mixed solution is 0.2 wt.% based on the total weight of the film-forming matrix mixed solution;

[0063] S3: mixing grape skin anthocyanidins with the film-forming matrix mixed solution to obtain a film-forming solution; the concentration of the grape skin anthocyanidins in the film-forming solution is 0.2 mg / mL;

[0064] S4: The film-forming solution was stirred at 400 rpm for 2 hours, then allowed to stand for 2 hours to defoam, and then poured into a culture dish to form a film. The film was dried at 30°C for 24 hours, and then placed in a constant temperature and humidity chamber (temperature 25°C, humidity 55%) for 24 hours to obtain a grape skin anthocyanin film, i.e., anthocyanin smart packaging film.

[0065] Test Case

[0066] This test example tests the color response of the packaging films prepared under the process conditions of Examples 1-6 and the comparative example to acetic acid.

[0067] The test method is as follows: the packaging film is exposed to a conical flask containing 10 mL of acetic acid aqueous solution (purity: 36%) for 30 minutes. The color parameters (L, a, b) of the packaging film are recorded using a handheld colorimeter (SR-64, Shenzhen Sanenshi Technology Co., Ltd.) under the same lighting conditions and at the same position. The color difference (ΔE) of the film before and after the acetic acid response is then calculated.

[0068] Table 1 Total color difference (ΔE) of packaging film before and after acetic acid

[0069] sample Chromatic Aberration Comparative Example 4.56 Example 1 8.38 Example 2 8.44 Example 3 5.71 Example 4 5.55 Example 5 6.61 Example 6 5.60

[0070] The color response results of the packaging films prepared under the process conditions of Examples 1-6 and Comparative Examples to acetic acid are shown in Tables 1 and Figure 2 As shown in Table 1, the color difference (ΔE) of the packaging film prepared in the comparative example before and after the acetic acid response is small, while the color difference (ΔE) of the packaging film prepared in Examples 1-6 before and after the acetic acid response is significantly larger than that of the comparative example (see Table 1), and is easier to identify with the naked eye (see Figure 2), it can be seen that the packaging film prepared by the present invention can enhance the accuracy of real-time monitoring of the freshness of fruits and vegetables.

[0071] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for preparing anthocyanin smart packaging film with alkali treatment sensitized to acetic acid response, characterized in that: The method comprises: uniformly applying alkali solution to the surface of the original anthocyanin film, and drying the film to obtain the anthocyanin intelligent packaging film with alkali treatment and enhanced acetic acid response.

2. The method for preparing anthocyanin intelligent packaging film with alkali treatment sensitized to acetic acid response according to claim 1, wherein: The drying temperature is 25-35℃ and the drying time is 10min-2h.

3. The method for preparing anthocyanin intelligent packaging film with alkali treatment sensitized to acetic acid response according to claim 1, wherein: The alkali solution is at least one of a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, a sodium carbonate aqueous solution, a potassium carbonate aqueous solution, a sodium bicarbonate aqueous solution and a potassium bicarbonate aqueous solution; The usage ratio of the alkali solution to the original anthocyanin film is (3-4): 1 mL / g; The concentration of the alkali solution is 0.05-0.6 mol / L.

4. The method for preparing anthocyanin intelligent packaging film with alkali treatment sensitized to acetic acid response according to claim 1, wherein: The preparation method of the original anthocyanin film comprises the following steps: S1: mixing chitosan with an aqueous acetic acid solution to obtain a chitosan solution; mixing polyvinyl alcohol with water to obtain a polyvinyl alcohol solution; S2: uniformly mixing the chitosan solution and the polyvinyl alcohol solution to obtain a mixed solution; mixing glycerol with the mixed solution to obtain a film-forming matrix mixed solution; S3: mixing anthocyanin with the film-forming matrix mixed solution to obtain a film-forming solution; S4: The film-forming solution is sequentially stirred, allowed to stand for defoaming, cast into a film, dried, and allowed to stand at a constant temperature and humidity to obtain the original anthocyanin film.

5. The method for preparing anthocyanin intelligent packaging film with alkali treatment sensitized to acetic acid response according to claim 4, wherein: The mass fraction of acetic acid in the acetic acid aqueous solution is 0.5-1.5 wt.% based on the total weight of the acetic acid aqueous solution; The mass fraction of chitosan in the chitosan solution is 0.5-1.5 wt.% based on the total weight of the chitosan solution; Based on the total weight of the polyvinyl alcohol solution, the mass fraction of the polyvinyl alcohol in the polyvinyl alcohol solution is 0.5-1.5 wt.%.

6. The method for preparing anthocyanin intelligent packaging film with alkali treatment sensitized to acetic acid response according to claim 4, wherein: The mass ratio of the chitosan solution to the polyvinyl alcohol solution is (6.5-7.5): (2.5-3.5).

7. The method for preparing anthocyanin intelligent packaging film with alkali treatment sensitized to acetic acid response according to claim 4, wherein: Based on the total weight of the film-forming matrix mixed solution, the mass fraction of glycerol in the film-forming matrix mixed solution is 0.15-0.25 wt.%.

8. The method for preparing anthocyanin intelligent packaging film with alkali treatment sensitized to acetic acid response according to claim 4, wherein: The concentration of anthocyanin in the film-forming solution is 0.15-0.25 mg / mL; The anthocyanin is at least one of grape skin anthocyanin, purple sweet potato anthocyanin and blueberry anthocyanin.

9. The method for preparing anthocyanin intelligent packaging film with alkali treatment sensitized to acetic acid response according to claim 4, wherein: The stirring process is performed at a speed of 350-450 rpm and for a time of 1.5-2.5 h; The time for the static defoaming treatment is 1.5-2.5h; The drying temperature is 30-35°C and the drying time is 22-26 hours; The constant temperature and humidity static treatment is performed at a temperature of 24-26° C., a humidity of 50-60%, and a time of 22-26 hours.

10. Anthocyanin smart packaging film with enhanced acetic acid response by alkali treatment, prepared by the method for preparing the anthocyanin smart packaging film with enhanced acetic acid response by alkali treatment according to any one of claims 1 to 9.

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