CN110541240A - A nano-preservation film with intelligent response and antibacterial function and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of food preservation, and relates to a nano preservative film with intelligent response and antibacterial functions and a preparation method thereof, wherein the preservative film is superfine fiber with a core-shell structure; the core-shell structure takes polylactic acid-glycolic acid copolymer and ethylene-vinyl alcohol copolymer compound as shells and thymol as a core. The polylactic acid-glycolic acid copolymer is used as a degradable framework material, the ethylene-vinyl alcohol copolymer is a material with high barrier property, and the ethylene-vinyl alcohol copolymer is used as a shell, so that oxygen in the air can be isolated, and volatilization of thymol can be effectively inhibited. Under the condition of improving the humidity, the molecular gap of the shell material is enlarged, the isolation performance is reduced, and the antibacterial agent thymol wrapped in the core-shell nano-fiber can slowly volatilize into the environment for storing fruits and vegetables. The film is applied to storage of fruits and vegetables, and can intelligently and spontaneously realize response release of thymol essential oil along with change of environmental humidity, so that the storage period of the fruits and vegetables is prolonged.

Description

A nano-preservation film with intelligent response and antibacterial function and preparation method thereof

technical field

The invention relates to the technical field of food preservation, in particular to a nano-preservation film with intelligent response and antibacterial function and a preparation method thereof.

Background technique

Food packaging is an important part of food. It has the characteristics of protecting food from damage by foreign biological, chemical and physical factors, and maintaining stable food quality. With the strengthening of consumer safety awareness and government supervision, food packaging safety has also been raised to the same level of supervision. In order to meet the strategic requirements of sustainable development, the development of new, green and safe multi-functional food packaging and materials is the direction of food packaging development in the future.

The main function of food packaging is to protect the product, so the packaging design must be safe and protective, and at the same time, it must be convenient for production and transportation, and it should be conducive to sales, and it should also reflect the cultural value and artistic characteristics of the product. In food packaging design, the selected materials should also meet the needs of the product and meet the concept of sustainable development. Packaging materials should have appropriate barrier properties, sufficient mechanical strength, good chemical stability, high temperature resistance and optical properties. In addition, food packaging should also have multiple functions (moisture resistance, waterproof, sterilization, anticorrosion, oil resistance, acid resistance, etc.) to meet the packaging requirements of various foods.

Active packaging and smart packaging are two types of new packaging forms, they can make food packaging have functional characteristics that cannot be obtained by traditional packaging, and meet consumers' requirements for food quality and safety. This is a new concept for future food packaging design, and it is also The development trend of food packaging.

Electrospinning technology is a spinning method that uses polymer solution or melt to stretch under the action of electrostatic repulsion to obtain continuous fibers. Under the action of high-voltage static electricity, the spinning solution forms a Taylor cone on the needle. With the charge enrichment, the electric field force acting on the Taylor cone increases continuously. A jet is formed when the electric field force is greater than the surface tension of the spinning solution at the needle end. The jet moves in a straight line at the beginning, and stretches continuously in a spiral form in the later stage. During the process of drawing and elongating, the solvent evaporates or cools, and is collected in the receiving device to solidify to form nanofibers. The coaxial electrospinning technology is developed from the traditional electrospinning technology, and its main feature is to replace the single-hole spinneret in the traditional electrospinning with a coaxial composite spinneret. The coaxial electrospinning technology not only solves the limitation that the traditional electrospinning stock solution must be uniform and has a viscoelastic mixed system, but also expands the scope of application, and can also be used to prepare nanofibers with various shapes, such as ribbons fiber, hollow fiber, tube-in-wire nanofiber, etc.

The core/shell nanofibers prepared by coaxial electrospinning have a wide range of applications in biomedicine and other fields, for example, drug storage, controlled release of drugs, surface modification, etc. Studies have shown that the fluorescent label is bovine serum albumin (BSA) and PEG dissolved in trifluoroethanol as the core layer material, and PCL is dissolved in trifluoroethanol as the shell material for coaxial electrospinning, wrapped in the core layer. The sustained release of BSA from the layer material can last up to five months. However, the fibers obtained by blending BSA, PEG and PCL showed a burst release phenomenon. There are also researchers who directly use the small molecule drug gentamicin aqueous solution and resveratrol ethanol solution as the core layer solution, and use PCL dissolved in chloroform/ethanol solution as the shell layer solution. Axial fibers can achieve sustained release of two drugs at the same time, avoiding drug burst release.

Contents of the invention

The invention provides a nano fresh-keeping film with intelligent response and antibacterial function and a preparation method thereof. The material is a nanofiber material prepared by a coaxial electrospinning method. Among them, thymol loaded in the nuclear layer, as a natural plant antibacterial agent, has a broad-spectrum antibacterial effect. The EVOH in the shell layer has high barrier properties and changes with humidity. Therefore, under different humidity conditions, the rate of release of essential oils from the nanofiber membranes is also different. Finally, the controlled release of thymol essential oils can be achieved, so it can prolong the life of fruits and vegetables. storage period.

To achieve the above object, the present invention adopts the following technical solutions:

A preparation method of a nano-preservative film with intelligent response and antibacterial function, said method adopts coaxial electrospinning technology, comprising the steps of:

S1) Prepare shell solution: mix polylactic acid-glycolic acid copolymer, ethylene-vinyl alcohol copolymer, N,N-dimethylacetamide and ethanol to obtain a uniform solution;

S2) Prepare the nuclear layer solution: dissolve thymol in absolute ethanol, and stir at room temperature until thymol and absolute ethanol are completely soluble in each other to obtain a uniform solution;

S3) The solution obtained in S1) and the solution obtained in S2) are prepared by coaxial electrospinning technology to produce a core-shell double-layer microfiber film, that is, a nano-preservation film.

Further, the volume ratio of N,N-dimethylacetamide to ethanol in S1) is 1:1-1:6. The mass ratio of polylactic acid-glycolic acid copolymer to ethylene-vinyl alcohol copolymer is 9:1-1:1. The mass percent of ethylene in the ethylene-vinyl alcohol copolymer is 32%-44%, and the ratio of the polylactic acid-glycolic acid copolymer to ethanol is 1:1-1:3.

Further, the mass ratio of thymol and absolute ethanol in S2) is 1:1-3:1.

Further, the electrospinning process parameters described in S3) are: the voltage applied by the high-voltage power supply is 14-20kV, the receiving distance is 10-18cm, the core layer solution advance rate is 0.1-0.5ml/h, and the shell layer solution advances The rate is 0.8-1.2ml/h, the relative humidity is 30%-70%, and the propelling rate of the shell layer solution is usually greater than that of the core layer solution. The inner and outer diameters of the coaxial composite needle used were 0.34 and 0.63 nm, respectively, and the inner and outer diameters of the outer needle were 1.12 and 1.48 nm, respectively.

Further, the nanofiber membrane has a dual structure of a core material and a shell material, wherein the shell material is wrapped around the core material; the core material is made of EVOH, and the core material contains thymol.

Further, the permeability of the microfiber membrane will change under different humidity conditions, thereby affecting the release rate of the encapsulated thymol essential oil, thereby affecting the storage period of fruits and vegetables, and is suitable for use as a packaging material for fruits and vegetables.

The intentional effect of the present invention is: owing to adopt above-mentioned technical scheme, the present invention has following characteristics:

1. The double-structure plastic wrap has the characteristics of antibacterial and intelligent humidity response. The plastic wrap does not release antibacterial agent when it is not in use, but only releases it when fruits and vegetables are kept fresh, avoiding the loss of active ingredients and extending the validity period;

2. The barrier property of the plastic wrap changes with the change of humidity, and releases gas antibacterial agent under high humidity conditions. During the storage of fruits and vegetables, the humidity of the storage environment will change, and the plastic wrap will automatically release antibacterial agents, which is a smart packaging material. Moreover, the released gas antibacterial agent makes all points in the packaging system effectively antibacterial and has a good fresh-keeping effect;

3. The shell material is green and degradable, and the wrapped thymol is a natural plant antibacterial agent, which is also of great significance to food safety and environmental protection, and has good economic and social benefits.

Description of drawings

Figure 1 is a scanning electron micrograph of a coaxial double-layer electrospun nanofiber membrane used in the method of the present invention.

Fig. 2 is the strawberry that uses nano-preservative film of the present invention to use different preservative films three days after effect contrast figure; Fig. 2 (a) uses antibacterial humidity response preservative film, Fig. 2 (b) uses common polyethylene preservative film.

Detailed ways

Below in conjunction with specific embodiment, further set forth the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

The present invention is a nano-preservation film with intelligent response and antibacterial function, wherein the nano-preservation film is a superfine fiber film with a double structure; the superfine fiber film with a double structure is a core-shell structure;

Among them, the shell material is a compound of polylactic acid-glycolic acid copolymer and ethylene-vinyl alcohol copolymer, accounting for 60-80% of the total mass; polylactic acid-glycolic acid copolymer is a degradable skeleton material, and ethylene-ethylene Alcohol copolymer acts as a barrier;

The core layer material is thymol, accounting for 20-40% of the total mass.

Further, the mass ratio of the polylactic acid-glycolic acid copolymer and the ethylene-vinyl alcohol copolymer of the shell material is 9:1-1:1.

Further, the mass percent of ethylene in the ethylene-vinyl alcohol copolymer is 32%-44%.

Another object of the present invention is to provide a kind of preparation method of above-mentioned nano preservative film, described preparation method comprises the steps:

S1) Prepare shell solution: mix polylactic acid-glycolic acid copolymer, ethylene-vinyl alcohol copolymer, N,N-dimethylacetamide and ethanol to obtain a uniform solution;

S2) Prepare the nuclear layer solution: dissolve thymol in absolute ethanol, and stir at room temperature until thymol and absolute ethanol are completely soluble in each other to obtain a uniform solution;

S3) The solution obtained in S1) and the solution obtained in S2) are prepared by coaxial electrospinning technology to produce a core-shell double-layer microfiber film, that is, a nano-preservation film.

Further, the volume ratio of N,N-dimethylacetamide to ethanol in S1) is 1:1-1:6.

Further, the ratio of polylactic acid-glycolic acid copolymer and ethanol in S1) is 1:1-1:3.

Further, the mass ratio of thymol and absolute ethanol in S2) is 1:1-3:1.

Further, the electrospinning process parameters of S3) are: the voltage applied by the high-voltage power supply is 14-20kV, the receiving distance is 10-18cm, the advancing rate of the shell solution is greater than that of the nuclear solution, and the relative humidity is 30%-70% .

Further, it is characterized in that the propelling rate of the core layer solution is 0.1-0.5ml/h, and the propelling rate of the shell layer solution is 0.8-1.2ml/h.

When the temperature of the nano-preservation film is 25°C and the humidity is less than 30%, the core layer material thymol of the nano-preservation film is not released; when it is used for fruit and vegetable preservation, as the humidity increases, the core layer material thymol of the nano-preservation film Accelerated release, antibacterial efficiency greater than 99%.

Example 1:

Weighed 3g EVOH (32% ethylene content) into 27g DMAc with an electronic balance, stirred magnetically at 90°C until completely dissolved, and obtained a shell solution with a mass fraction of 10%.

Place the reagent bottle containing the above-mentioned shell solution in an ultrasonic cleaning device, and ultrasonicate for half an hour, in order to remove air bubbles in the electrospinning solution.

Electronic balance weighs 5g thymol, joins in the ethanol of 5g that has been weighed, puts into the shaker and vibrates and shakes well, dissolves completely in ethanol until thymol, obtains the thymol solution that mass fraction is 50%, and this solution is used as Core layer solution for coaxial electrospinning.

Carry out coaxial electrospinning, the voltage applied by the high-voltage power supply is 14kV, the flow rate of the shell layer solution is set to 0.8ml/h, the flow rate of the core layer solution is 0.3ml/h, and the distance from the needle to the receiving plate is 18cm, the obtained nanofibers The scanning electron microscope image of the film is shown in Figure 1.

The diameter of the prepared ultrafine fiber is about 350nm. When the humidity is less than 30%, there is no obvious release. Under the condition of 95% humidity, the release rate of essential oil is accelerated. The release amount of essential oil is about 50% in 48 hours, and the antibacterial (bacteria, fungus, yeast) efficiency is greater than 95%.

Example 2:

Electronic balance weighed 6g EVOH (36% ethylene content respectively) and added it to 34g DMAc, and magnetically stirred at 90°C until completely dissolved to obtain a shell solution with a mass fraction of 15%.

Place the reagent bottle containing the above-mentioned shell solution in an ultrasonic cleaning device, and ultrasonicate for half an hour, in order to remove air bubbles in the electrospinning solution.

Electronic balance weighs 8g thymol, joins in the ethanol of 8g that has been weighed, puts into the shaker and vibrates and shakes well, dissolves completely in ethanol to thymol, obtains the thymol solution that mass fraction is 50%, and this solution is used as Core layer solution for coaxial electrospinning.

For coaxial electrospinning, the voltage applied by the high-voltage power supply is 16kV, the flow rate of the shell solution is 1.0ml/h, the flow rate of the core solution is 0.5ml/h, and the distance from the needle to the receiving plate is 15cm.

The diameter of the prepared ultrafine fiber is about 380nm. When the humidity is less than 30%, there is no obvious release. Under the condition of 95% humidity, the release rate of essential oil is accelerated, and the release amount of essential oil is about 40% in 48 hours, and the antibacterial (bacteria, fungus, yeast) efficiency is greater than 95%.

Example 3:

Electronic balance weighed 6g EVOH (44% ethylene content) into 24g DMAc, and magnetically stirred at 90°C until completely dissolved to obtain a shell solution with a mass fraction of 20%.

Place the reagent bottle containing the above-mentioned shell solution in an ultrasonic cleaning device, and ultrasonicate for half an hour, in order to remove air bubbles in the electrospinning solution.

Electronic balance weighs 6g thymol, joins in the ethanol of 6g that has been weighed, puts into the shaker and vibrates and shakes well, dissolves completely in ethanol until thymol, obtains the thymol solution that mass fraction is 50%, and this solution is used as Core layer solution for coaxial electrospinning.

For coaxial electrospinning, the voltage applied by the high-voltage power supply is 20kV, the flow rate of the shell solution is set to 1.2ml/h, the flow rate of the core solution is 0.6ml/h, and the distance from the needle to the receiving plate is 18cm.

The diameter of the prepared ultrafine fiber is about 410nm. When the humidity is less than 30%, there is no obvious release. Under the condition of 95% humidity, the release rate of essential oil is accelerated, and the release amount of essential oil is about 36% in 48 hours, and the antibacterial (bacteria, fungus, yeast) efficiency is greater than 95%. Fig. 2 is the strawberry that uses nano-preservative film of the present invention to use different preservative film effect comparison figure after three days; Fig. 2 (a) uses antibacterial humidity response nano-preservative film, and the fresh-keeping effect of strawberry is good, does not go bad; Fig. 2 (b) uses Ordinary polyethylene plastic wrap, some strawberries have deteriorated.

Although several embodiments of the present invention have been given herein, those skilled in the art should understand that the embodiments herein can be changed without departing from the spirit of the present invention. The above-mentioned embodiments are only exemplary, and the embodiments herein should not be used as limitations on the scope of rights of the present invention.

Claims (10)

1. a nanometer preservative film with intelligent response and antibacterial functions is characterized in that the nanometer preservative film is a superfine fiber film with a double-structure; the superfine fiber membrane with the double structure is of a core-shell structure;

Wherein, the shell material is a compound of polylactic acid-glycolic acid copolymer and ethylene-vinyl alcohol copolymer, accounting for 60-80% of the total mass; the polylactic acid-glycolic acid copolymer is a degradable framework material, and the ethylene-vinyl alcohol copolymer plays a role in blocking;

the core layer material is thymol and accounts for 20-40% of the total mass.

2. the nano preservative film according to claim 1, wherein the mass ratio of the polylactic acid-glycolic acid copolymer to the ethylene-vinyl alcohol copolymer of the shell material is 9:1-1: 1.

3. The nano preservative film according to claim 2, wherein the ethylene content in the ethylene-vinyl alcohol copolymer is 32-44% by mass.

4. A method for preparing the nano preservative film according to any one of claims 1 to 3, wherein the method comprises the following steps:

S1) preparing a shell solution: mixing polylactic acid-glycolic acid copolymer, ethylene-vinyl alcohol copolymer, N-dimethylacetamide and ethanol to obtain uniform solution;

S2) preparing a core layer solution: dissolving thymol in absolute ethyl alcohol, and stirring at normal temperature until the thymol and the absolute ethyl alcohol are completely mutually dissolved to obtain a uniform solution;

S3) preparing the superfine fiber film with the core-shell double-layer structure, namely the nanometer preservative film, from the solution obtained in S1) and the solution obtained in S2) by adopting a coaxial electrostatic spinning technology.

5. The preparation method according to claim 4, wherein the volume ratio of N, N-dimethylacetamide to ethanol in S1) is: 1:1-1:6.

6. The method according to claim 4, wherein the ratio of the polylactic acid-glycolic acid copolymer to the ethanol in S1) is 1:1-1: 3.

7. The preparation method according to claim 4, wherein the mass ratio of thymol to absolute ethyl alcohol in S2) is 1:1-3: 1.

8. The preparation method according to claim 4, wherein the electrospinning process parameters of S3) are as follows: the voltage applied by a high-voltage power supply is 14-20kV, the receiving distance is 10-18cm, the advancing speed of the shell layer solution is greater than that of the nuclear layer solution, and the relative humidity is 30% -70%.

9. The method of claim 8, wherein the core layer solution advancing rate is 0.1 to 0.5ml/h and the shell layer solution advancing rate is 0.8 to 1.2 ml/h.

10. The preparation method of claim 4, wherein the core layer material thymol of the nano preservative film is not released when the temperature of the nano preservative film is 25 ℃ and the humidity is less than 30%; when the nano preservative film is used for preserving fruits and vegetables, the core layer material thymol of the nano preservative film is released in an accelerated manner along with the increase of humidity, and the antibacterial efficiency is more than 99%.