Method for preparing preservative film from cinnamon essential oil and waste polylactic acid

Abstract

The invention provides a method for preparing a preservative film from cinnamon essential oil and waste polylactic acid. The preparation method comprises the following steps: firstly measuring the minimum inhibitory concentration MIC of PLA, then taking chitosan as a raw material, and adding polylactic acid-base degradation liquid with the concentration of 1 / 4 MIC and cinnamon essential oil to prepare the biological fresh-keeping film. And it is verified that the compound has a good antibacterial effect on escherichia coli and staphylococcus aureus. The invention provides a preservative film with relatively good antibacterial activity, which can be used for biological food preservation and aims to reduce white pollution.

Description

Technical Field

[0001] This invention belongs to the field of recycling organic waste, specifically relating to a method for making plastic wrap using cinnamon essential oil and waste polylactic acid. Background Technology

[0002] Cinnamon (Cinnamomum cassia Presl) is an evergreen tree belonging to the genus Cinnamomum in the family Lauraceae. Its bark, branches, leaves, and fruits can all be used in medicine or to extract essential oils. It has a strong spicy aroma and extensive medicinal, edible, and industrial value.

[0003] Polylactic acid (PLA) is a biodegradable plastic made from renewable resources (such as corn starch) and is widely used in food packaging. However, its recycling faces the following challenges: Recycling technology bottlenecks: Existing physical recycling methods (such as mechanical crushing and remolding) easily lead to a decline in material properties; chemical recycling methods (such as depolymerization and repolymerization) are costly and complex. Waste PLA degrades slowly in the natural environment, and the degradation products are carbon dioxide and water, making resource recycling impossible. Achieving efficient PLA recycling through technological improvements can reduce production costs and environmental pollution. Therefore, it is necessary to develop a biodegradable antibacterial food preservation film using waste PLA materials combined with cinnamon essential oil. Summary of the Invention

[0004] This invention addresses the reuse of waste polylactic acid (PLA) and the antibacterial activity of cinnamon essential oil, disclosing a method for producing a biodegradable antibacterial food preservation film using waste PLA combined with cinnamon essential oil. This invention belongs to the field of organic waste recycling, specifically relating to a method for producing a bio-preservative film from plant secondary metabolites and waste PLA.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The first objective of this invention is to provide a method for making plastic wrap using cinnamon essential oil and waste polylactic acid, comprising the following steps: determining the antibacterial activity and minimum inhibitory concentration (MIC) of PLA, and adding PLA, cinnamon essential oil and chitosan at a concentration of 1 / 4 to 1 / 3 of the MIC during the production of the plastic wrap.

[0007] Preferably, the concentration of PLA is 1 / 4 MIC.

[0008] Preferably, the bacteria are Escherichia coli and / or Staphylococcus aureus, and the minimum inhibitory concentration (MIC) is 200 mg / mL.

[0009] Preferably, the process includes the following steps: mixing chitosan with 1% acetic acid until homogeneous, stirring for 1-2 h, then adding glycerol and stirring for 30-40 min, adding PLA at 1 / 4 MIC concentration and stirring for 10-20 min, adding cinnamon oil, pouring into a mold, and drying at 45-50℃ for 48-50 h.

[0010] Preferably, 100 mL of 1% acetic acid and 0.5 mL of glycerol are added for every 2.5 g of chitosan.

[0011] Preferably, the cinnamon essential oil is extracted from cinnamon bark and leaves using steam distillation.

[0012] Preferably, the concentration of the cinnamon essential oil is 1% by volume.

[0013] Preferably, the PLA is prepared by collecting waste polylactic acid straws, grinding them into powder, dissolving them with NaOH at high temperature, and adjusting the pH to neutral.

[0014] Preferably, the specific steps are as follows: 2.5 g of chitosan is mixed with 100 mL of 1% acetic acid and stirred for 1 h at 50℃ and 900 r / min using a magnetic stirrer. Then, 0.5 mL of glycerol is added and stirred for 30 min. A 1 / 4 MIC concentration of PLA degradation solution is added to the membrane solution, followed by 1% (v / v) cinnamon essential oil. The mixture is magnetically stirred for 10 min to prepare a membrane solution with a degradation solution addition of 1 / 4 MIC + chitosan + MIC cinnamon essential oil. 20 mL of this solution is poured into a membrane container and placed in a 45℃ oven for 48 h.

[0015] A second objective of this invention is to provide a food preservation film prepared by the above method.

[0016] This invention provides a method for preparing a bio-preservative film using cinnamon essential oil and waste polylactic acid (PLA). Cinnamon essential oil is extracted from cinnamon bark and branches, and an inhibition zone experiment is conducted. It exhibits strong antibacterial activity against Staphylococcus aureus (Gram-positive bacteria) and Escherichia coli (Gram-negative bacteria), with the minimum inhibitory concentrations (MICs) further determined to be 1% and 1%, respectively. Waste PLA is degraded using NaOH at high temperature, and the pH is adjusted to neutral; the MIC for both is further determined to be 20%. Finally, using chitosan as a raw material, PLA alkaline degradation solution and cinnamon essential oil are added to prepare the bio-preservative film. Its good antibacterial effect against both Escherichia coli and Staphylococcus aureus is verified. This invention also provides a preservative film with good antibacterial activity, which can be used for the preservation of biological food, aiming to reduce white pollution. Attached Figure Description

[0017] Figure 1This is a graph showing the antibacterial effect of cinnamon essential oil-polylactic acid (PLA) plastic wrap. CK represents the bacterial growth without the film; +1 / 4MIC represents the bacterial growth with the film containing chitosan and 1 / 4MIC PLA alkaline degradation solution; +1 / 4MIC+cinnamon essential oil represents the bacterial growth with the film containing chitosan, 1% cinnamon essential oil (by volume), and 1 / 4MIC PLA alkaline degradation solution. Detailed Implementation

[0018] The following embodiments are further illustrations of the present invention, but not limitations thereof.

[0019] Example 1:

[0020] Cinnamon essential oil was extracted from cinnamon bark and leaves using steam distillation.

[0021] Preparation method of PLA degradation solution: Collect waste polylactic acid pipettes, grind them into powder, and dissolve them with 0.5 mol / L NaOH at high temperature with a solid-liquid ratio of 1 g: 10 mL. Stir at 180℃ for 2 h until completely dissolved. Filter while hot to remove insoluble impurities and obtain clear PLA alkaline hydrolysis solution. After cooling to room temperature in an ice-water bath, add 1 mol / L HCl dropwise while stirring to adjust the pH to neutral (6.5-7.0) to obtain PLA degradation solution. Store in a sealed container at 4℃ for later use.

[0022] 10 μL of Staphylococcus aureus and Escherichia coli suspension (OD) 600 =1) The PLA was added to 96-well plates containing different concentrations of degradation solution diluted using the double-soup method. After incubation at 37 °C for 24 h, the lowest concentration of PLA and essential oil at which no visible bacterial growth was observed was defined as the minimum inhibitory concentration (MIC). The MIC of the PLA degradation solution against Escherichia coli and Staphylococcus aureus was 20% (200 mg / mL). The MIC of cinnamon essential oil against Escherichia coli and Staphylococcus aureus was 1% (v / v).

[0023] Mix 2.5 g of chitosan with 100 mL of 1% acetic acid and dissolve at 50 °C. Stir at 900 r / min for 1 h. Then add 0.5 mL of glycerol and stir for 30 min. Add 1 / 4 MIC concentration (final concentration 5%, i.e. 50 mg / mL) of PLA degradation solution and a certain amount of cinnamon essential oil (final concentration 1% by volume). Stir for 10 min. As a control, take 20 mL of PLA degradation solution with 1 / 4 MIC concentration but no cinnamon essential oil added and put it into a film container and bake in a 45 °C oven for 48 h to obtain the biological preservation film.

[0024] Test of the antibacterial ability of bio-preservation film: The bio-preservation film was sterilized under ultraviolet light for 1 hour, and 0.8 g of film was added to a solution containing 10 mL of OD... 600 In a 0.3% concentration of either *E. coli* or *Staphylococcus aureus* bacterial suspension, the bacterial solution without biological preservation film served as the control (CK). The mixture was incubated with shaking at 37°C for 4 hours, and then diluted 10⁻⁶ times. 4 Then, 50 μL was placed on an LB agar plate and incubated at 37°C for 24 h to observe the colony density.

[0025] like Figure 1 Chitosan plastic wrap containing cinnamon essential oil and 1 / 4 MIC concentration of PLA has the best antibacterial effect, followed by chitosan plastic wrap containing only 1 / 4 MIC concentration of PLA degradation solution.

[0026] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple modifications, changes or equivalent substitutions made within the spirit and principle of the present invention should still be considered to fall within the protection scope of the present invention.

Claims

1. A method for producing plastic wrap using cinnamon essential oil and waste polylactic acid, characterized in that, The process includes the following steps: determining the antibacterial activity and minimum inhibitory concentration (MIC) of PLA, and adding PLA, cinnamon oil, and chitosan at 1 / 4 to 1 / 3 of the MIC concentration during the preparation of the plastic wrap.

2. The method according to claim 1, characterized in that, The concentration of PLA is 1 / 4 MIC.

3. The method according to claim 1, characterized in that, The bacteria are Escherichia coli and / or Staphylococcus aureus, and the minimum inhibitory concentration (MIC) is 200 mg / mL.

4. The method according to claim 1, characterized in that, The process includes the following steps: mix chitosan with 1% acetic acid evenly and stir for 1-2 hours. Then add glycerol and stir for 30-40 minutes. Add PLA with a concentration of 1 / 4 MIC and stir for 10-20 minutes. Add cinnamon oil and pour into a mold. Bake at 45-50°C for 48-50 hours.

5. The method according to claim 4, characterized in that, For every 2.5 g of chitosan, add 100 mL of 1% acetic acid and 0.5 mL of glycerol.

6. The method according to claim 4, characterized in that, The cinnamon essential oil is extracted from cinnamon bark and leaves using steam distillation.

7. The method according to claim 4, characterized in that, The bacteria are Escherichia coli and / or Staphylococcus aureus, and the minimum inhibitory concentration (MIC) of the cinnamon essential oil is 1% by volume.

8. The method according to claim 4, characterized in that, The PLA is prepared by collecting waste polylactic acid straws, grinding them into powder, dissolving them with NaOH at high temperature, and adjusting the pH to neutral.

9. The method according to claim 1, characterized in that, The specific steps are as follows: 2.5 g of chitosan is mixed with 100 mL of 1% acetic acid and stirred for 1 h at 50℃ and 900 r / min in a magnetic stirrer. Then, 0.5 mL of glycerol is added and stirred for 30 min. 1 / 4 MIC concentration of PLA degradation solution and 1% volume fraction of cinnamon essential oil are added to the membrane solution and magnetically stirred for 10 min. 20 mL is taken and poured into a mold and placed in an oven at 45℃ for 48 h to make a plastic wrap.

10. The food preservation film prepared by the method according to any one of claims 1-9.

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