Preparation method of agar-chitosan double-layer film with high barrier property and antibacterial property

Abstract

The invention discloses an agar-chitosan double-layer film with high barrier property and antibacterial property and a preparation method of the agar-chitosan double-layer film. The double-layer film is characterized in that the double-layer film is prepared by taking agar and chitosan as substrates, taking nano zinc oxide as a functional substance and adding glycerol as a plasticizer. The preparation method of the double-layer film comprises the following steps: firstly, respectively preparing an agar film-forming solution, chitosan and a functional component film-forming solution, and then obtaining the agar-chitosan double-layer film by adopting a layer-by-layer casting film-forming method. The double-layer film is compounded and tightly combined through synchronous casting, due to the special structural design and intermolecular reaction, the double-layer film has better tensile resistance than a single-layer film, and the chitosan layer in the double-layer film further improves the barrier property and the mechanical property of the film by using functional substances, so that the antibacterial property of the double-layer film is enhanced. The packaging film can be applied to the field of food packaging, and the shelf life and shelf life of food are prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of edible packaging films, and in particular relates to a method for preparing an agar-chitosan double-layer film with high barrier properties and antibacterial properties. Background Art

[0002] Agar is a colloidal polysaccharide extracted from marine red algae. It has good film-forming ability and has been widely used in food packaging films. In order to improve the preservation effect of bio-based degradable packaging films, a variety of active compounds and ingredients are added to the film to prepare active films. Chitosan is a macromolecular polysaccharide extracted from the shells of crustaceans. Due to its good antibacterial activity and excellent film-forming ability, it is widely selected as a film material. However, its poor water vapor barrier performance and severe brittleness limit its direct application in food packaging.

[0003] In order to further improve the barrier and antibacterial properties of the material, adding inorganic particles to the matrix is ​​an effective method. Nano zinc oxide is an ideal material because it is non-toxic, low-cost, has strong thermal stability and antibacterial activity. At the same time, nano zinc oxide has been approved as a food additive by the state.

[0004] In the prior art, the use of a single-layer film cannot meet the mechanical properties and barrier properties required by specific foods, so it is an important means to improve its performance through a multi-layer film structure or blending modification. The present invention uses agar and chitosan, two polysaccharides with good film-forming ability, to prepare a double-layer film, and adds metal oxide nanoparticles to the film to further improve the tensile properties, barrier properties and antibacterial properties of the double-layer film. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing an agar-chitosan double-layer film with high barrier and antibacterial properties, and to prepare a double-layer film with strong mechanical properties, high barrier properties, and excellent antibacterial properties. It provides a new preparation method for the research of multi-layer degradable packaging materials, and also provides a certain reference for the research and development of new low-cost degradable packaging materials, and promotes the application of more composite films in the field of food packaging in the future.

[0006] The technical solution of the present invention is as follows:

[0007] (1) Preparation of agar coating liquid: agar is dissolved in water to prepare an agar solution, a plasticizer is added thereto, and the solution is stirred and dissolved under certain temperature conditions to obtain an agar coating liquid.

[0008] (2) Pour the agar coating liquid prepared in step (1) into a plastic plate, cool it at room temperature to form a hydrogel, and then dry it in an oven to form a film for later use.

[0009] (3) Preparation of chitosan coating liquid: Add nano zinc oxide to a weak organic acid solution, disperse it by ultrasonic, then add chitosan and plasticizer to the dispersion, and stir and dissolve them under certain temperature conditions to obtain a chitosan coating liquid.

[0010] (4) Pour the prepared chitosan film liquid evenly onto the agar film dried in step (2), and place it in an oven to dry into a double-layer film.

[0011] Preferably, the concentration of the agar solution in step (1) is 1 g to 6 g / 100 mL.

[0012] Preferably, in step (3), the concentration of nano zinc oxide is 0.01-0.2%, the ultrasonic power is 300 W, the time is 10 min, and the chitosan concentration is 1 g-8 g / 100 mL.

[0013] Preferably, the plasticizers in steps (1) and (3) are both glycerol, and the mass ratio of glycerol to agar or chitosan is 1 / 8 to 1 / 2.

[0014] Preferably, the stirring time in steps (1) and (3) is 0.5 to 3 hours, and the stirring temperature is 70 to 90° C.

[0015] Preferably, the drying temperature in step (4) is 40-60° C., and the drying time is 3-7 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a flow chart of the preparation method of the double-layer membrane.

[0017] Figure 2 Graphs showing the anti-ultraviolet properties of different embodiments.

[0018] Figure 3 Graphs showing water vapor permeability of different embodiments.

[0019] Figure 4 This is a diagram showing the effects of different embodiments on Staphylococcus aureus.

[0020] Figure 5 The microstructure diagram of some embodiments. Example

[0021] Embodiment 1:

[0022] Step 1: Preparation of agar monolayer

[0023] (1) Add 1-6 g agar to 100 mL aqueous solution, add glycerol to the agar aqueous solution at a ratio of 1:8-1:2 (glycerol / agar), and stir the mixture in a constant temperature stirring water bath at 70-90°C for 0.5-3 h.

[0024] (2) Take 20 mL of the film-forming solution and cast it on a plastic plate. Then place it in an oven at 40 to 60 °C and dry it for 3 to 7 h to form a film.

[0025] (3) After the membrane is dry, place it in a constant temperature and humidity incubator at 20-25°C and 55% relative humidity for 48 hours and use it as the bottom layer.

[0026] Step 2: Preparation of chitosan membrane solution

[0027] (1) Dissolve 1-8 g of chitosan in a weak organic acid solution to obtain a chitosan aqueous solution, add glycerol in a ratio of 1:8-1:2 (glycerol / chitosan) to the chitosan aqueous solution, and stir the mixture in a constant temperature stirring water bath at 70-90 °C for 0.5-3 h to obtain a chitosan membrane solution.

[0028] Step 3: Preparation of agar-chitosan bilayer membrane

[0029] (1) Cast 15 mL of the prepared chitosan film liquid onto a dried agar film plastic plate, and then place it in a 60°C oven for 3 to 7 h to dry the film liquid.

[0030] (2) After the membrane is dry and cooled, remove the membrane and place it in a constant temperature and humidity incubator at 20-25°C and 55% relative humidity for 48 h for membrane performance testing.

[0031] Embodiment 2:

[0032] Step 1: Preparation of agar monolayer

[0033] (1) Add 1-6 g agar to 100 mL aqueous solution, add glycerol to the agar aqueous solution at a ratio of 1:8-1:2 (glycerol / agar), and stir the mixture in a constant temperature stirring water bath at 70-90°C for 0.5-3 h.

[0034] (2) Take 20 mL of the film-forming solution and cast it on a plastic plate. Then place it in an oven at 40 to 60 °C and dry it for 3 to 7 h to form a film.

[0035] (3) After the membrane is dry, place it in a constant temperature and humidity incubator at 20-25°C and 55% relative humidity for 48 hours and use it as the bottom layer.

[0036] Step 2: Preparation of chitosan membrane solution.

[0037] (1) Dissolve 0.01-0.05 g of nano zinc oxide in a weak organic acid solution, then disperse it in an ice water bath under an ultrasonic power of 300 W for 10 min and set aside.

[0038] (2) Dissolve 1-8 g of chitosan in the chitosan aqueous solution obtained in step 2 (1), add glycerol in a ratio of 1:8-1:2 (glycerol / chitosan) to the chitosan aqueous solution, and stir the mixture in a constant temperature stirring water bath at 70-90°C for 0.5-3 h to obtain a chitosan membrane solution.

[0039] Step 3: Preparation of agar-chitosan bilayer membrane.

[0040] (1) Cast 15 mL of the prepared chitosan film liquid onto a dried agar film plastic plate, and then place it in a 60°C oven for 3 to 7 h to dry the film liquid.

[0041] (2) After the membrane is dry and cooled, remove the membrane and place it in a constant temperature and humidity incubator at 20-25°C and 55% relative humidity for 48 hours for membrane performance testing.

[0042] Embodiment 3:

[0043] Step 1: Preparation of agar monolayer

[0044] (1) Add 1-6 g agar to 100 mL aqueous solution, add glycerol to the agar aqueous solution at a ratio of 1:8-1:2 (glycerol / agar), and stir the mixture in a constant temperature stirring water bath at 70-90°C for 0.5-3 h.

[0045] (2) Take 20 mL of the film-forming solution and cast it on a plastic plate. Then place it in an oven at 40 to 60 °C and dry it for 3 to 7 h to form a film.

[0046] (3) After the membrane is dry, place it in a constant temperature and humidity incubator at 20-25°C and 55% relative humidity for 48 hours and use it as the bottom layer.

[0047] Step 2: Preparation of chitosan membrane solution

[0048] (1) Dissolve 0.06-0.1 g of nano zinc oxide in a weak organic acid solution, then disperse it in an ice water bath under an ultrasonic power of 300 W for 10 min and set aside.

[0049] (2) Dissolve 1-8 g of chitosan in the chitosan aqueous solution obtained in step 2 (1), add glycerol in a ratio of 1:8-1:2 (glycerol / chitosan) to the chitosan aqueous solution, and stir the mixture in a constant temperature stirring water bath at 70-90°C for 0.5-3 h to obtain a chitosan membrane solution.

[0050] Step 3: Preparation of agar-chitosan bilayer membrane

[0051] (1) Cast 15 mL of the prepared chitosan film liquid onto a dried agar film plastic plate, and then place it in a 60°C oven for 3 to 7 h to dry the film liquid.

[0052] (2) After the membrane is dry and cooled, remove the membrane and place it in a constant temperature and humidity incubator at 20-25°C and 55% relative humidity for 48 hours for membrane performance testing.

[0053] Embodiment 4:

[0054] Step 1: Preparation of agar monolayer

[0055] (1) Add 1-6 g agar to 100 mL aqueous solution, add glycerol to the agar aqueous solution at a ratio of 1:8-1:2 (glycerol / agar), and stir the mixture in a constant temperature stirring water bath at 70-90°C for 0.5-3 h.

[0056] (2) Take 20 mL of the film-forming solution and cast it on a plastic plate. Then place it in an oven at 40 to 60 °C and dry it for 3 to 7 h to form a film.

[0057] (3) After the membrane is dry, place it in a constant temperature and humidity incubator at 20-25°C and 55% relative humidity for 48 hours and use it as the bottom layer.

[0058] Step 2: Preparation of chitosan membrane solution

[0059] (1) Dissolve 0.11-0.15 g of nano zinc oxide in a weak organic acid solution, then disperse it in an ice water bath under an ultrasonic power of 300 W for 10 min and set aside.

[0060] (2) Dissolve 1-8 g of chitosan in the chitosan aqueous solution obtained in step 2 (1), add glycerol in a ratio of 1:8-1:2 (glycerol / chitosan) to the chitosan aqueous solution, and stir the mixture in a constant temperature stirring water bath at 70-90°C for 0.5-3 h to obtain a chitosan membrane solution.

[0061] Step 3: Preparation of agar-chitosan bilayer membrane.

[0062] (1) Cast 15 mL of the prepared chitosan film liquid onto a dried agar film plastic plate, and then place it in a 60°C oven for 3 to 7 h to dry the film liquid.

[0063] (2) After the membrane is dry and cooled, remove the membrane and place it in a constant temperature and humidity incubator at 20-25°C and 55% relative humidity for 48 hours for membrane performance testing.

[0064] Embodiment 5:

[0065] Step 1: Preparation of agar monolayer.

[0066] (1) Add 1-6 g agar to 100 mL aqueous solution, add glycerol to the agar aqueous solution at a ratio of 1:8-1:2 (glycerol / agar), and stir the mixture in a constant temperature stirring water bath at 70-90°C for 0.5-3 h.

[0067] (2) Take 20 mL of the film-forming solution and cast it on a plastic plate. Then place it in an oven at 40 to 60 °C and dry it for 3 to 7 h to form a film.

[0068] (3) After the membrane is dry, place it in a constant temperature and humidity incubator at 20-25°C and 55% relative humidity for 48 hours and use it as the bottom layer.

[0069] Step 2: Preparation of chitosan membrane solution

[0070] (1) Dissolve 0.16-0.2 g of nano zinc oxide in a weak organic acid solution, then disperse it in an ice water bath under an ultrasonic power of 300 W for 10 min and set aside.

[0071] (2) Dissolve 1-8 g of chitosan in the chitosan aqueous solution obtained in step 2 (1), add glycerol in a ratio of 1:8-1:2 (glycerol / chitosan) to the chitosan aqueous solution, and stir the mixture in a constant temperature stirring water bath at 70-90°C for 0.5-3 h to obtain a chitosan membrane solution.

[0072] Step 3: Preparation of agar-chitosan bilayer membrane

[0073] (1) Cast 15 mL of the prepared chitosan film liquid onto a dried agar film plastic plate, and then place it in a 60°C oven for 3 to 7 h to dry the film liquid.

[0074] (2) After the membrane is dry and cooled, remove the membrane and place it in a constant temperature and humidity incubator at 20-25°C and 55% relative humidity for 48 h for membrane performance testing.

Claims

1. A method for preparing an agar-chitosan double-layer membrane with high barrier properties and antibacterial properties, characterized in that: At least the following steps are included: Step 1: Preparation of agar monolayer (1) Add 1-6 g agar to the aqueous solution, add glycerol to the agar aqueous solution, the mass ratio of glycerol to agar is 1:8-1:2, and stir the mixture in a constant temperature stirring water bath at 70-90°C for 0.5-3 h; (2) Take the film-forming solution and cast it on a plastic plate. The casting amount of the film-forming solution is 0.3 mL / cm 2 , and then place it in a 40~60℃ oven to dry for 3~7 hours to dry the membrane liquid; (3) After the membrane is dry, remove the membrane and place it in a constant temperature and humidity incubator at 20-25°C and 55% relative humidity for 48 hours for membrane performance testing. Step 2: Preparation of chitosan membrane solution (1) Dissolve nano zinc oxide in a weak organic acid solution to obtain a 0.01% to 0.2% solution, and then disperse it in an ice water bath under an ultrasonic power of 300 W for 10 min for later use; (2) dissolving 1-8 g of chitosan in the chitosan aqueous solution obtained in step 2 (1), adding glycerol to the chitosan aqueous solution, wherein the mass ratio of glycerol to chitosan is 1:8-1:2, and stirring the mixture in a constant temperature stirring water bath at 70-90°C for 0.5-3 h to obtain a chitosan film solution; Step 3: Preparation of agar-chitosan bilayer membrane (1) The prepared chitosan film liquid was cast onto a dried agar film plastic plate, where the film-forming liquid casting volume was 0.2 mL / cm 2 , and then place it in a 40~60℃ oven to dry for 3~7 hours to dry the membrane liquid; (2) After the membrane is dry and cooled, remove the membrane and place it in a constant temperature and humidity incubator at 20-25°C and 55% relative humidity for 48 h for membrane performance testing.

2. The method for preparing the agar-chitosan double-layer membrane with high barrier and antibacterial properties according to claim 1, characterized in that: The mass concentration w / v of the agar aqueous solution described in step (1) is 1% to 6%.

3. The method for preparing the agar-chitosan double-layer membrane with high barrier and antibacterial properties according to claim 1, characterized in that: In step 2 (1), the solvent for dissolving chitosan and plasticizer is acetic acid; in step 2 (2), the solvent for dissolving chitosan and plasticizer is a weak organic acid solution with a solute mass percentage of 1% to 8%.

4. The method for preparing the agar-chitosan double-layer membrane with high barrier and antibacterial properties according to claim 1, characterized in that: It comprises a first film-forming layer and a second film-forming layer, and there is no significant difference in thickness between the first film-forming layer and the second film-forming layer.

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