Plant essential oil-sodium alginate composite film and preparation method thereof

Abstract

The invention discloses a plant essential oil-sodium alginate composite film and a preparation method thereof, and belongs to the technical field of composite film preparation and essential oil inclusion. The method comprises the following steps: 1, emulsifying and homogenizing: mixing gelatin, plant essential oil and water, and then homogenizing and emulsifying to prepare an essential oil emulsion; 2, forming a film: adding the essential oil emulsion into the sodium alginate-gelatin solution, then adding glycerol, stirring in a water bath at 40-45 DEG C for 20-30 minutes to obtain a film-forming solution, then pouring the film-forming solution into a mold, drying, cooling, and uncovering the film to obtain the plant essential oil composite film. According to the method, the composite film can load more essential oil, meanwhile, the slow-release effect is better, and the maximum effect of the essential oil can be achieved.

Description

Technical Field

[0001] This invention relates to the field of composite membrane preparation and essential oil encapsulation technology, specifically to a plant essential oil-sodium alginate composite membrane and its preparation method. Background Technology

[0002] With increasing emphasis on environmental protection and food safety, research on natural edible films has garnered significant attention. However, it remains in its early stages, and edible films have many shortcomings, failing to meet the requirements of food packaging films. Current edible films primarily focus on the properties of the film itself, with considerable room for improvement in their application to specific foods and their antibacterial and preservative properties. Studies have shown that essential oils possess strong antimicrobial, antibacterial, and antioxidant activities, making them potential preservatives for perishable foods and leading to their widespread use in food preservation.

[0003] While plant essential oils hold great promise for food packaging and preservation, they also face several challenges and limitations. First, the stability and solubility of plant essential oils need further improvement to ensure their durability and effectiveness in food packaging. Second, the relatively high cost of plant essential oils necessitates cost reduction to enhance their competitiveness in food packaging. Furthermore, the dosage and application methods of plant essential oils require further research and optimization to ensure their safety and effectiveness in food packaging. Summary of the Invention

[0004] To address the above problems, this invention provides a method for preparing a plant essential oil composite film, comprising the following steps:

[0005] 1. Emulsification and homogenization: Mix gelatin, plant essential oil and water, and then homogenize and emulsify to obtain an essential oil emulsion;

[0006] 2. Film formation: Add the essential oil emulsion to the sodium alginate-gelatin solution, then add glycerin, stir in a water bath at 40-45℃ for 20-30 minutes to obtain a film-forming solution, then pour the film-forming solution into a mold, dry it, cool it and peel off the film to obtain a plant essential oil composite film.

[0007] Furthermore, in step 1, the mass fraction of gelatin in the essential oil emulsion is 0.4–0.5%, w / v.

[0008] Furthermore, in step 1, the mass fraction of plant essential oil in the essential oil emulsion is 0.8–1%, w / v.

[0009] Furthermore, the plant essential oils in step 1 include benzyl isothiocyanate, eugenol, carvacrol, cinnamaldehyde, and turmeric essential oil.

[0010] Preferably, the plant essential oil in step 1 is eugenol.

[0011] Furthermore, in step 2, the concentration of sodium alginate in the sodium alginate-gelatin solution is 1.5–2%, w / v.

[0012] Furthermore, in step 2, the concentration of gelatin in the sodium alginate-gelatin solution is 0.4–0.5%, w / v.

[0013] Furthermore, in step 2, the volume ratio of the essential oil emulsion to the sodium alginate-gelatin solution is 1:4 to 5.

[0014] Furthermore, in step 2, the concentration of glycerol in the film-forming solution is 0.4–0.5%, w / v.

[0015] The present invention provides a plant essential oil composite film prepared according to the above method.

[0016] The application of the plant essential oil composite film provided by this invention in the field of food packaging.

[0017] The beneficial effects of this invention are:

[0018] This invention reveals that the edible composite membrane prepared by emulsification and homogenization of plant essential oils, sodium alginate, and gelatin is superior to that prepared by blending and stirring. After emulsification and homogenization, the release efficiency decreases while the loading rate increases, allowing the composite membrane to carry more essential oils and achieve a better sustained-release effect, thus maximizing the effect of the essential oils. Consequently, the composite membrane exhibits a more significant antibacterial effect, broadening the application of plant essential oil composite membranes. Attached Figure Description

[0019] Figure 1 The release rate results are for Examples 1 and 2;

[0020] Figure 2 The release rate results are for Examples 3 and 4;

[0021] Figure 3 The load rate results are for Examples 1 and 2;

[0022] Figure 4 The load rate results are for Examples 3 and 4;

[0023] Figure 5 This is a scanning electron microscope image;

[0024] Figure 6 Infrared spectrum;

[0025] Figure 7 The changes in the appearance and morphology of cherries during storage;

[0026] Figure 8 The rate of decay of cherries stored at 4℃;

[0027] Figure 9 The weight loss rate of cherries stored at 4℃;

[0028] Among them, SA-G is sodium alginate-gelatin film; A is benzyl isothiocyanate / sodium alginate / gelatin edible composite film; B is eugenol / sodium alginate / gelatin edible composite film; C is carvacrol / sodium alginate / gelatin edible composite film; D is cinnamaldehyde / sodium alginate / gelatin edible composite film; and E is turmeric essential oil / sodium alginate / gelatin edible composite film. Detailed Implementation

[0029] Example 1

[0030] 1. Blending and stirring: Add 0.2g of eugenol essential oil to 100mL of sodium alginate-gelatin solution (sodium alginate concentration 1.5g / L, gelatin concentration 0.5g / L), and stir for 30min under water bath heating at 45℃ to fully dissolve it and obtain sodium alginate gelatinized solution.

[0031] 2. Film formation: Then, add 0.5g of plasticizer glycerin to the sodium alginate gelatinization solution, stir in a water bath at 45℃ for 30 minutes to fully dissolve it and obtain the film-forming solution. Then, pour the film-forming solution into a mold and place it in a 45℃ oven to dry. After drying, take it out, cool it and peel off the film to obtain the plant essential oil composite film.

[0032] Example 2

[0033] According to the method described in Example 1, except that the essential oils are replaced with equal amounts of benzyl isothiocyanate (BITC), carvacrol, cinnamaldehyde, and turmeric essential oil, while other operations remain unchanged, four other plant essential oil composite films are prepared.

[0034] Example 3

[0035] 1. Emulsification and homogenization: 0.1g gelatin, 0.2g eugenol essential oil and 20mL water are put into a 50mL centrifuge tube and homogenized and emulsified in a homogenizer for 2min to obtain essential oil emulsion;

[0036] 2. Film formation: Add the essential oil emulsion to the sodium alginate-gelatin solution (80mL, sodium alginate 1.5g, gelatin 0.4g), then add 0.5g of plasticizer glycerin, stir in a water bath at 45℃ for 30min to fully dissolve and obtain the film-forming solution. Then pour the film-forming solution into a mold and place it in a 45℃ oven to dry. After drying, remove it, cool and peel off the film to obtain the plant essential oil composite film.

[0037] Example 4

[0038] According to the method described in Example 3, except that the essential oils are replaced with equal amounts of benzyl isothiocyanate (BITC), carvacrol, cinnamaldehyde, and turmeric essential oil, while other operations remain unchanged, four other plant essential oil composite films are prepared.

[0039] Example 5

[0040] The release rate of the plant essential oil composite membranes prepared in Examples 1-4 was tested. The testing procedure was as follows:

[0041] Using n-hexane as a food simulant, a membrane sample (2cm × 2cm) was immersed in 10mL of the simulant solution at 25°C with gentle stirring on a shaker. 3mL of the solution was pipetted and the absorbance was measured. The measurement was repeated three times. The amount of essential oil released into the food simulant was calculated using the following formula:

[0042] Release rate (%) = Mt / M0 × 100%

[0043] Where Mt corresponds to the content of essential oil in the food simulant at any given time, and M0 corresponds to the initial content of essential oil in the film.

[0044] The test results of Examples 1 and 2 are as follows Figure 1 As shown in Table 1, the results of Examples 3 and 4 are as follows: Figure 2 As shown in Table 1.

[0045] Table 1 Release rate data of composite membrane

[0046] Group A B C D E Blending 64.62％ 52.28％ 61.82％ 54.74％ 81.28％ Emulsification and homogenization 55.89％ 42.45％ 52.92％ 45.11％ 75.88％

[0047] Among them, A is an edible composite film of benzyl isothiocyanate / sodium alginate / gelatin, B is an edible composite film of eugenol / sodium alginate / gelatin, C is an edible composite film of carvacrol / sodium alginate / gelatin, D is an edible composite film of cinnamaldehyde / sodium alginate / gelatin, and E is an edible composite film of turmeric oil / sodium alginate / gelatin.

[0048] As shown in Table 1 above, there are significant differences in the release efficiency of essential oils in edible composite films prepared by different methods. The films prepared by emulsification and homogenization generally have a lower release rate than the films prepared by blending and stirring, indicating that the films prepared by emulsification and homogenization have a better sustained-release effect.

[0049] Depend on Figure 1 and Figure 2 It is evident that during the measurement period, there were significant differences in the release efficiency of different essential oils in the edible composite film.

[0050] Example 6

[0051] The plant essential oil composite membranes prepared in Examples 1-4 were subjected to loading rate testing. The testing procedure was as follows:

[0052] The final essential oil content in the film after the casting / evaporation process was determined by UV-Vis spectrophotometry. Fresh film samples (2 cm × 2 cm) were swollen in a test tube containing 25 mL of deionized water at 25 °C for 5 minutes. Next, 25 mL of n-hexane was added, and the test tube was vigorously shaken to extract the essential oil. After separation, the n-hexane was centrifuged at 10000 g for 5 minutes. The essential oil concentration in the supernatant was determined by measuring the absorbance on a UV spectrophotometer. The results are expressed as follows:

[0053] Load factor (%) = Cf / Ci × 100%

[0054] Ci and Cf represent the essential oil concentrations in the base film solution and dry film, respectively.

[0055] The test results of Examples 1 and 2 are as follows Figure 3 As shown in Table 2, the results of Examples 3 and 4 are as follows: Figure 4 As shown in Table 2.

[0056] Table 2 Loading rate data of composite membranes

[0057] Group A B C D E Blending 43.67％ 45.27％ 43.53％ 49.27％ 45.27％ Emulsification and homogenization 69.86％ 68.5％ 66.77％ 65.83％ 64.87％

[0058] Among them, A is an edible composite film of benzyl isothiocyanate / sodium alginate / gelatin, B is an edible composite film of eugenol / sodium alginate / gelatin, C is an edible composite film of carvacrol / sodium alginate / gelatin, D is an edible composite film of cinnamaldehyde / sodium alginate / gelatin, and E is an edible composite film of turmeric oil / sodium alginate / gelatin.

[0059] As shown in Table 2 above, the loading rate of essential oil in the edible composite membrane prepared by the emulsification homogenization process is significantly higher than that in the blending process. This indicates that the emulsification homogenization process can enable the composite membrane to load more essential oil, thereby further improving the functionality of the composite membrane.

[0060] Example 7

[0061] The edible composite films prepared in Examples 3-4 (benzyl isothiocyanate / sodium alginate / gelatin, eugenol / sodium alginate / gelatin, and carvacrol / sodium alginate / gelatin) were subjected to brittle fracture in liquid nitrogen. The composite films were then sputter-coated with gold, and their surface and cross-sections were analyzed using a scanning electron microscope. The results are as follows: Figure 6 As shown.

[0062] Using Fourier transform infrared spectroscopy, an appropriate amount of the lyophilized composite membrane powder was mixed with potassium chloride powder, ground, and compressed into tablets. The gel was then scanned at room temperature. The results are as follows: Figure 7 As shown.

[0063] Scanning electron microscopy and infrared spectroscopy showed that different plant essential oils have good compatibility with sodium alginate gelatin.

[0064] Example 8

[0065] Ordinary commercially available fresh cherries were soaked in the film-forming solution prepared according to Examples 2-3 for 1 minute, then removed and dried to obtain groups A-E. Following the preparation process of Example 3, the addition of essential oils was omitted to prepare a sodium alginate-gelatin film-forming solution, which was then used to soak cherries to obtain groups SA-G. A blank control group (Air), i.e., cherries without any treatment, and a PE group, i.e., fresh cherries wrapped in plastic wrap, were also set up.

[0066] Then, each group of cherries was placed in the same cool, shaded environment, and photos were taken and data recorded every 3 days. The results are as follows: Figures 7-9 As shown in the figure, the cherries in group B had a lower weight loss rate and a lower rot rate after 15 days of storage, indicating that the eugenol / sodium alginate / gelatin edible composite film prepared in this invention is a good antibacterial preservation film.

[0067] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for preparing a plant essential oil composite film, characterized in that, Includes the following steps:

1. Emulsification and homogenization: Mix gelatin, plant essential oil and water, and then homogenize and emulsify to obtain an essential oil emulsion; 2. Film formation: Add the essential oil emulsion to the sodium alginate-gelatin solution, then add glycerin, stir in a water bath at 40-45℃ for 20-30 minutes to obtain a film-forming solution, then pour the film-forming solution into a mold, dry it, cool it and peel off the film to obtain a plant essential oil composite film.

2. The preparation method according to claim 1, characterized in that, In step 1, the mass fraction of gelatin in the essential oil emulsion is 0.4-0.5%, w / v.

3. The preparation method according to claim 1, characterized in that, In step 1, the mass fraction of plant essential oil in the essential oil emulsion is 0.8-1%, w / v.

4. The preparation method according to claim 1, characterized in that, The plant essential oils in step 1 include benzyl isothiocyanate, eugenol, carvacrol, cinnamaldehyde, and turmeric essential oil.

5. The preparation method according to claim 1, characterized in that, The plant essential oil in step 1 is eugenol.

6. The preparation method according to claim 1, characterized in that, In step 2, the concentration of sodium alginate in the sodium alginate-gelatin solution is 1.5–2%, w / v.

7. The preparation method according to claim 1, characterized in that, In step 2, the concentration of gelatin in the sodium alginate-gelatin solution is 0.4-0.5%, w / v.

8. The preparation method according to claim 1, characterized in that, In step 2, the volume ratio of the essential oil emulsion to the sodium alginate-gelatin solution is 1:4 to 5.

9. The preparation method according to claim 1, characterized in that, In step 2, the concentration of glycerol in the film-forming solution is 0.4-0.5%, w / v.

10. A plant essential oil composite film prepared by the method according to any one of claims 1 to 9.

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