Efficient antibacterial full-degradable preservative film and preparation method thereof

Abstract

The invention discloses an efficient antibacterial full-degradable preservative film and a preparation method thereof, and belongs to the field of preservative films. The preparation method comprises the following steps: dissolving chitosan and an acetic acid aqueous solution to prepare a chitosan solution, adding polyvinyl alcohol, heating in a water bath, stirring and dissolving, finally adding menthol and Tween 80, and emulsifying to obtain a film forming solution; and centrifuging the film-forming liquid, pouring into a mold, and drying to form the film. The preservative film has a remarkable inhibiting effect on staphylococcus aureus and escherichia coli by adding a bacteriostatic agent menthol, so that the preservation effect is enhanced; the chitosan, the polyvinyl alcohol and the menthol which are selected as the raw materials for preparing the efficient antibacterial full-degradable preservative film can be naturally degraded, so that the preservative film is environment-friendly and conforms to the green development concept.

Description

Technical Field

[0001] The invention belongs to the field of cling film, and in particular relates to a high-efficiency antibacterial and fully degradable cling film and a preparation method thereof. Background Art

[0002] In the current market, plastic cling film is widely used in various life scenarios such as homes and supermarkets because of its low price and convenient use. According to the material, it is mainly divided into three categories: polyethylene, polyvinyl chloride, and polyvinylidene chloride. They work by blocking gases.

[0003] Plastic cling film has poor preservation effect, cannot keep food fresh for a long time, and cannot be naturally degraded. The accumulated plastic debris has caused serious white pollution to the ecological environment. Therefore, it is very necessary to develop a new type of biodegradable cling film with high antibacterial properties. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a highly efficient antibacterial and fully degradable cling film and a preparation method thereof, thereby solving the problems in the prior art.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing an antibacterial and fully degradable cling film comprises the following steps:

[0007] Dissolve chitosan and acetic acid aqueous solution to prepare chitosan solution, then add polyvinyl alcohol, heat in a water bath and stir to dissolve, finally add menthol and Tween 80, and emulsify to obtain a film-forming solution;

[0008] The film-forming liquid is centrifuged and poured into a mold, and dried to form a film.

[0009] Furthermore, the mass ratio of chitosan to polyvinyl alcohol is (0.6122-1.0204):(1.9148-3.1914).

[0010] Furthermore, the concentration of the acetic acid aqueous solution is 1vt%.

[0011] Furthermore, in the film-forming solution, the mass fraction of menthol is 2-10%.

[0012] Furthermore, the water bath heating temperature is 85°C.

[0013] Furthermore, the rotation speed of the membrane-forming liquid during centrifugation is 11000 r / min, and the centrifugation time is 20 min.

[0014] Furthermore, the emulsification adopts a high-speed homogenizer with a rotation speed of 15000r / min and an emulsification time of 10min.

[0015] Furthermore, the drying temperature is 25-45°C.

[0016] An antibacterial and fully degradable cling film is prepared by using the above-mentioned method for preparing the antibacterial and fully degradable cling film.

[0017] Application of the above-mentioned antibacterial and fully degradable cling film in fruit preservation.

[0018] Beneficial effects of the present invention:

[0019] 1. The invention adds the antibacterial agent menthol to enable the cling film to have a significant inhibitory effect on Staphylococcus aureus and Escherichia coli, thereby enhancing the preservation effect.

[0020] 2. The raw materials chitosan, polyvinyl alcohol and menthol selected for preparing the high-efficiency antibacterial and fully degradable cling film of the present invention are all naturally degradable, environmentally friendly and in line with the concept of green development. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 It is an indication diagram of the mechanical properties of the fresh-keeping film prepared with different volumes of film-forming liquid of the present invention;

[0023] Figure 2 This is a graph indicating the mechanical properties of the cling film prepared with different glycerol contents of the present invention;

[0024] Figure 3 It is the mechanical property indicator diagram of the cling film prepared at different drying temperatures of the present invention;

[0025] Figure 4 Any three infrared characterization spectra of the 2% menthol high-efficiency antibacterial and fully degradable cling film of the present invention;

[0026] Figure 5 This is a graph showing the growth inhibition of Escherichia coli by the cling film prepared with different menthol concentrations of the present invention;

[0027] Figure 6 This is a graph showing the growth inhibition of Staphylococcus aureus by the cling film prepared with different menthol concentrations of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The technical scheme of the present invention is described below by the following examples and comparative examples; the sources of the raw materials involved in the examples and comparative examples are as follows:

[0030] Chitosan, deacylation degree ≥ 95%, viscosity 100-200 mPa.s, CAS: 9012-76-4, from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0031] Polyvinyl alcohol, 1788 low viscosity type, alcoholysis degree: 87.0~89.0mol / mol, CAS: 9002-89-5, from Sinopharm Chemical Reagent Co., Ltd.;

[0032] Glycerol, CAS: 56-81-5, was obtained from Sinopharm Chemical Reagent Co., Ltd.;

[0033] Menthol, CAS: 2216-51-5, from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0034] Tween 80, CAS: 9005-65-6, was sourced from Sinopharm Chemical Reagent Co., Ltd.

[0035] Comparative Example 1

[0036] A method for preparing chitosan-polyvinyl alcohol fresh-keeping film comprises the following steps:

[0037] S1, weigh 0.6122g of chitosan, add 30ml of 1vt% acetic acid aqueous solution, stir magnetically to dissolve, and prepare a 2% chitosan solution; then add 1.9148g of polyvinyl alcohol, stir magnetically and heat to dissolve in a water bath at 85°C to obtain a film-forming solution.

[0038] S2. Pour the prepared film-forming liquid into centrifuge tubes and balance them. Centrifuge them in a centrifuge at 11000r / min for 20min until the bubbles disappear completely. Finally, pour them into a mold and dry them at 25℃ to form a film.

[0039] Comparative Example 2

[0040] A method for preparing chitosan-polyvinyl alcohol fresh-keeping film comprises the following steps:

[0041] S1, weigh 0.6122g of chitosan, add 30ml of 1vt% acetic acid aqueous solution, stir magnetically to dissolve, and prepare a 2% chitosan solution; then add 1.9148g of polyvinyl alcohol, stir magnetically and heat to dissolve in a 85℃ water bath, then add 300μl of glycerol, continue to dissolve, and obtain a film-forming solution.

[0042] S2. Pour the prepared film-forming liquid into centrifuge tubes and balance them. Centrifuge them in a centrifuge at 11000r / min for 20min until the bubbles disappear completely. Finally, pour them into a mold and dry them at 25℃ to form a film.

[0043] Comparative Example 3

[0044] A method for preparing chitosan-polyvinyl alcohol fresh-keeping film comprises the following steps:

[0045] S1, weigh 0.6122g of chitosan, add 30ml of 1vt% acetic acid aqueous solution, stir magnetically to dissolve, and prepare a 2% chitosan solution; then add 1.9148g of polyvinyl alcohol, stir magnetically and heat to dissolve in a 85℃ water bath, then add 600μl of glycerol, continue to dissolve, and obtain a film-forming solution.

[0046] S2. Pour the prepared film-forming liquid into centrifuge tubes and balance them. Centrifuge them in a centrifuge at 11000r / min for 20min until the bubbles disappear completely. Finally, pour them into a mold and dry them at 25℃ to form a film.

[0047] Comparative Example 4

[0048] A method for preparing chitosan-polyvinyl alcohol fresh-keeping film comprises the following steps:

[0049] S1, weigh 0.6122g of chitosan, add 30ml of 1vt% acetic acid aqueous solution, stir magnetically to dissolve, and prepare a 2% chitosan solution; then add 1.9148g of polyvinyl alcohol, stir magnetically and heat to dissolve in a water bath at 85°C to obtain a film-forming solution.

[0050] S2, pour the prepared film-forming liquid into centrifuge tubes and balance them, centrifuge them in a centrifuge at 11000r / min for 20min until the bubbles disappear completely, and finally pour them into a mold and dry them at 45℃ to form a film.

[0051] Comparative Example 5

[0052] A method for preparing chitosan-polyvinyl alcohol fresh-keeping film comprises the following steps:

[0053] S1, weigh 0.6122g of chitosan, add 30ml of 1vt% acetic acid aqueous solution, stir magnetically to dissolve, and prepare a 2% chitosan solution; then add 1.9148g of polyvinyl alcohol, stir magnetically and heat to dissolve in a 85℃ water bath, then add 300μl of glycerol, continue to dissolve, and obtain a film-forming solution.

[0054] S2, pour the prepared film-forming liquid into centrifuge tubes and balance them, centrifuge them in a centrifuge at 11000r / min for 20min until the bubbles disappear completely, and finally pour them into a mold and dry them at 45℃ to form a film.

[0055] Comparative Example 6

[0056] A method for preparing chitosan-polyvinyl alcohol fresh-keeping film comprises the following steps:

[0057] S1, weigh 0.6122g of chitosan, add 30ml of 1vt% acetic acid aqueous solution, stir magnetically to dissolve, and prepare a 2% chitosan solution; then add 1.9148g of polyvinyl alcohol, stir magnetically and heat to dissolve in a 85℃ water bath, then add 600μl of glycerol, continue to dissolve, and obtain a film-forming solution.

[0058] S2, pour the prepared film-forming liquid into centrifuge tubes and balance them, centrifuge them in a centrifuge at 11000r / min for 20min until the bubbles disappear completely, and finally pour them into a mold and dry them at 45℃ to form a film.

[0059] Comparative Example 7

[0060] A method for preparing chitosan-polyvinyl alcohol fresh-keeping film comprises the following steps:

[0061] S1, weigh 1.0204g of chitosan, add 50ml of 1vt% acetic acid aqueous solution, stir magnetically to dissolve, prepare a 2% chitosan solution, then add 3.1914g of polyvinyl alcohol, stir magnetically and heat to dissolve in a water bath at 85℃ to obtain a membrane-forming solution.

[0062] S2. Pour the prepared film-forming liquid into centrifuge tubes and balance them. Centrifuge them in a centrifuge at 11000r / min for 20min until the bubbles disappear completely. Finally, pour them into a mold and dry them at 25℃ to form a film.

[0063] Comparative Example 8

[0064] A method for preparing chitosan-polyvinyl alcohol fresh-keeping film comprises the following steps:

[0065] S1, weigh 1.0204g of chitosan, add 50ml of 1vt% acetic acid aqueous solution, stir magnetically to dissolve, and prepare a 2% chitosan solution; then add 3.1914g of polyvinyl alcohol, stir magnetically and heat to dissolve in a 85℃ water bath, then add 500μl of glycerol, continue to dissolve, and obtain a film-forming solution.

[0066] S2. Pour the prepared film-forming liquid into centrifuge tubes and balance them. Centrifuge them in a centrifuge at 11000r / min for 20min until the bubbles disappear completely. Finally, pour them into a mold and dry them at 25℃ to form a film.

[0067] Comparative Example 9

[0068] A method for preparing chitosan-polyvinyl alcohol fresh-keeping film comprises the following steps:

[0069] S1, weigh 1.0204g of chitosan, add 50ml of 1vt% acetic acid aqueous solution, stir magnetically to dissolve, and prepare a 2% chitosan solution; then add 3.1914g of polyvinyl alcohol, stir magnetically and heat to dissolve in a 85℃ water bath, then add 1000μl of glycerol, continue to dissolve, and obtain a film-forming solution.

[0070] S2. Pour the prepared film-forming liquid into centrifuge tubes and balance them. Centrifuge them in a centrifuge at 11000r / min for 20min until the bubbles disappear completely. Finally, pour them into a mold and dry them at 25℃ to form a film.

[0071] Comparative Example 10

[0072] A method for preparing chitosan-polyvinyl alcohol fresh-keeping film comprises the following steps:

[0073] S1, weigh 1.0204g of chitosan, add 50ml of 1vt% acetic acid aqueous solution, stir magnetically to dissolve, and prepare a 2% chitosan solution; then add 3.1914g of polyvinyl alcohol, stir magnetically and heat to dissolve in a water bath at 85°C to obtain a film-forming solution.

[0074] S2, pour the prepared film-forming liquid into centrifuge tubes and balance them, centrifuge them in a centrifuge at 11000r / min for 20min until the bubbles disappear completely, and finally pour them into a mold and dry them at 45℃ to form a film.

[0075] Comparative Example 11

[0076] A method for preparing chitosan-polyvinyl alcohol fresh-keeping film comprises the following steps:

[0077] S1, weigh 1.0204g of chitosan, add 50ml of 1vt% acetic acid aqueous solution, stir magnetically to dissolve, and prepare a 2% chitosan solution; then add 3.1914g of polyvinyl alcohol, stir magnetically and heat to dissolve in a 85℃ water bath, then add 500μl of glycerol, continue to dissolve, and obtain a film-forming solution.

[0078] S2, pour the prepared film-forming liquid into centrifuge tubes and balance them, centrifuge them in a centrifuge at 11000r / min for 20min until the bubbles disappear completely, and finally pour them into a mold and dry them at 45℃ to form a film.

[0079] Comparative Example 12

[0080] A method for preparing chitosan-polyvinyl alcohol fresh-keeping film comprises the following steps:

[0081] S1, weigh 1.0204g of chitosan, add 50ml of 1vt% acetic acid aqueous solution, stir magnetically to dissolve, and prepare a 2% chitosan solution; then add 3.1914g of polyvinyl alcohol, stir magnetically and heat to dissolve in a 85℃ water bath, then add 1000μl of glycerol, continue to dissolve, and obtain a film-forming solution.

[0082] S2, pour the prepared film-forming liquid into centrifuge tubes and balance them, centrifuge them in a centrifuge at 11000r / min for 20min until the bubbles disappear completely, and finally pour them into a mold and dry them at 45℃ to form a film.

[0083] Example 1

[0084] A method for preparing a chitosan-polyvinyl alcohol-menthol fresh-keeping film comprises the following steps:

[0085] S1, weigh 1.0204g of chitosan, add 50ml of 1vt% acetic acid aqueous solution, stir magnetically to dissolve, prepare a 2% chitosan solution, then add 3.1914g of polyvinyl alcohol, stir magnetically to dissolve in a water bath at 85°C, then add menthol and 0.5vt% Tween 80, emulsify for 10min under a high-speed homogenizer at 15000r / min to obtain a film-forming solution; wherein, in the film-forming solution, the mass fraction of menthol is 2%.

[0086] S2, pour the prepared film-forming liquid into centrifuge tubes and balance them, centrifuge them in a centrifuge at 11000r / min for 20min until the bubbles disappear completely, and finally pour them into a mold and dry them at 45℃ to form a film.

[0087] Example 2

[0088] The only difference between this embodiment and embodiment 1 is that the mass fraction of menthol in the film-forming liquid is 4%.

[0089] Example 3

[0090] The only difference between this embodiment and embodiment 1 is that the mass fraction of menthol in the film-forming liquid is 6%.

[0091] Example 4

[0092] The only difference between this embodiment and embodiment 1 is that the mass fraction of menthol in the film-forming liquid is 8%.

[0093] Example 5

[0094] The only difference between this embodiment and embodiment 1 is that the mass fraction of menthol in the film-forming liquid is 10%.

[0095] Experimental testing

[0096] 1) Mechanical properties testing

[0097] The elongation at break and tensile strength of chitosan-polyvinyl alcohol cling films prepared with different film-forming liquid volumes, different glycerol contents and different drying temperatures were tested.

[0098] Figure 1 It shows that the mechanical properties of the cling film prepared with different film-forming liquid volumes (Comparative Example 3 and Comparative Example 9)

[0099] Figure 2 It shows that the mechanical properties of cling film prepared with different glycerol contents (Comparative Example 1, Comparative Example 2 and Comparative Example 3)

[0100] Figure 3 It shows that the mechanical properties of the cling film prepared at different drying temperatures (Comparative Example 3 and Comparative Example 6)

[0101] Depend on Figure 1 , 2 3 It can be seen that when the volume of the acetic acid aqueous solution is 50 ml, the glycerol content is 0, and the drying temperature is 45 °C, the prepared cling film has greater elongation at break and tensile strength, and better mechanical properties, which is the optimal film-making process.

[0102] 2) Infrared characterization:

[0103] The infrared characterization of any three parts of the chitosan-polyvinyl alcohol-menthol cling film was carried out, and the cling film prepared by adding 2% menthol (Example 1) was used as an example to illustrate. Figure 4 It can be seen that the three peaks have the same shape, indicating that the prepared plastic wrap is uniform and the menthol is well dispersed.

[0104] 3) Antibacterial experiment:

[0105] Step 1: Dissolve the freeze-dried powder of Gram-negative bacteria-Escherichia coli and Gram-positive bacteria-Staphylococcus aureus in 5-10 ml of liquid culture medium, and transfer to plate nutrient agar medium twice for activation.

[0106] Step 2: Prepare bacterial suspension: Take a small amount of activated bacteria and add it to sterile water, and make ten-fold dilutions in turn. -6 -10 -7 The diluted bacterial suspension was inoculated into the nutrient agar medium, and a blank control was added. After culturing at 37°C for 48 h, the colonies were counted. The concentration of 10 7 ~10 8 CFU / ml of bacterial suspension.

[0107] Step 3: Take 200 μl of the bacterial suspension and add it to the sterilized agar medium. Cut the plastic wrap and the wrap containing 2wt%-10wt% menthol (Example 1-Example 5) into several discs with a diameter of 6 mm, stick them in the middle of the above-mentioned bacterial plate with sterile tweezers, and culture them at a constant temperature of 37°C for 24 hours.

[0108] Step 4: Count the colonies respectively and calculate the antibacterial rate. The formula is: R% = (BC) / B*100, where R is the antibacterial rate, B is the number of colonies on the plastic cling film, and C is the number of colonies on the antibacterial cling film containing different concentrations of menthol.

[0109] The results are as follows Figure 5 and Figure 6 As shown, when the menthol concentration is 8%, the inhibition rates of Escherichia coli and Staphylococcus aureus are both >95%, 95.15% and 99.23% respectively. Even when the menthol concentration reaches 10%, both bacteria are completely inhibited, with an inhibition rate of 100%, and the antibacterial effect is significant.

[0110] 4) Degradability test:

[0111] The high-efficiency antibacterial and fully degradable cling film of Example 1 was cut into 7 cm*7 cm size, buried about 10 cm deep in the soil, and observed for a continuous period of time to test the degradability of the film. The results showed that after three weeks, the chitosan-polyvinyl alcohol-menthol cling film could be completely degraded.

[0112] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0113] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for preparing an antibacterial and fully degradable cling film, characterized in that: The following steps are involved: Dissolve chitosan and acetic acid aqueous solution to prepare chitosan solution, then add polyvinyl alcohol, heat in a water bath and stir to dissolve, finally add menthol and Tween 80, and emulsify to obtain a film-forming solution; The film-forming liquid is centrifuged and poured into a mold, and dried to form a film.

2. The method for preparing an antibacterial and fully degradable cling film according to claim 1, characterized in that: The mass ratio of chitosan to polyvinyl alcohol is (0.6122-1.0204):(1.9148-3.1914).

3. The method for preparing an antibacterial and fully degradable cling film according to claim 1, characterized in that: The concentration of the acetic acid aqueous solution is 1 vt%.

4. The method for preparing an antibacterial and fully degradable cling film according to claim 1, characterized in that: In the film-forming liquid, the mass fraction of menthol is 2-10%.

5. The method for preparing an antibacterial and fully degradable cling film according to claim 1, characterized in that: The water bath heating temperature is 85°C.

6. The method for preparing an antibacterial and fully degradable cling film according to claim 1, characterized in that: The rotation speed of the membrane-forming liquid during centrifugation is 11000 r / min, and the centrifugation time is 20 min.

7. The method for preparing an antibacterial and fully degradable cling film according to claim 1, characterized in that: The emulsification was performed using a high-speed homogenizer with a rotation speed of 15000 r / min and an emulsification time of 10 min.

8. The method for preparing an antibacterial and fully degradable cling film according to claim 1, characterized in that: The drying temperature is 25-45°C.

9. An antibacterial and fully degradable cling film, characterized in that: The antibacterial and fully degradable cling film is prepared using the method for preparing the antibacterial and fully degradable cling film described in any one of claims 1 to 8.

10. Use of the antibacterial and fully degradable cling film according to claim 9 in fruit preservation.

Images