Degradable electrostatic spinning slow-release antibacterial fiber membrane as well as preparation method and application thereof

Abstract

The invention relates to a degradable electrostatic spinning slow-release antibacterial fiber membrane as well as a preparation method and application thereof. According to the degradable electrostatic spinning slow-release antibacterial fiber membrane, a non-woven fabric layer serves as a supporting layer, an active thin film layer is arranged on the surface of the supporting layer, and the active thin film layer is prepared from a mixture of a slow-release rosemary extract and a high-molecular polymer through electrostatic spinning. By reasonably designing a material formula, an electrostatic spinning process and a laminated composite structure, the fiber membrane can continuously and stably release antibacterial substances, inhibit the growth and reproduction of microorganisms on the surfaces of fruits and vegetables and reduce the respiration intensity and water loss of the fruits and vegetables, so that the shelf life of the fruits and vegetables is remarkably prolonged; and an innovative efficient solution is provided for fresh-keeping packaging of fruits and vegetables.

Description

Technical Field

[0001] The invention relates to the technical field of fruit and vegetable preservation, and in particular to a degradable electrostatically spun slow-release antibacterial fiber membrane and a preparation method and application thereof. Background Art

[0002] Rot and deterioration caused by microbial contamination is considered to be an important factor leading to postharvest losses of fruits and vegetables. Traditional packaging materials for fruit and vegetable preservation mainly include plastic films, paper packaging, etc. Although plastic films have certain barrier properties, most of them are non-degradable and will cause environmental pollution. Although paper packaging is degradable, its preservation performance is limited and it is difficult to effectively inhibit microbial growth and physiological metabolism of fruits and vegetables. Rosemary extract is a safe and effective natural antibacterial agent with excellent antioxidant, anti-inflammatory and antibacterial activities. Its powerful functional properties make it a promising antibacterial substance that can replace chemical fungicides. However, the strong flavor of rosemary extract may affect the flavor of food, which limits its direct application as an antibacterial additive in food. In addition, the practical application of rosemary extract in food is often limited by its poor stability, low water solubility, high reactivity (potential interaction with other food ingredients), and uncontrolled release characteristics, which greatly reduces its bioavailability.

[0003] Electrospinning is considered a promising technology for encapsulating rosemary extract. In addition, electrospinning fiber materials allow high loading of active ingredients, and their higher specific surface area improves the response to surrounding conditions and allows timely release of active ingredients, which means that it is possible to reduce the amount of antimicrobial active ingredients added to achieve extended shelf life; and the smaller gaps between fibers also provide a barrier to bacterial entry.

[0004] Chinese patent CN117988107A discloses a slow-release antibacterial zein fiber membrane, which has good antioxidant and antibacterial activities. However, glutaraldehyde cross-linking is used to enhance structural stability during the preparation process, which results in poor film flexibility and possible glutaraldehyde residue on the fiber membrane. Therefore, it is difficult to take into account the mechanical properties, antibacterial properties and slow-release properties of this type of biodegradable material electrospun fiber membrane at the same time.

[0005] Chinese patent CN202410981382.4 discloses a starch-polyvinyl alcohol-based film with sustained-release antibacterial effect. The film has excellent antibacterial properties and antioxidant properties, but starch and polyvinyl alcohol are both prepared by a water-soluble method. After film formation, they have strong hygroscopicity and are easy to precipitate after adding glycerol. When used as a food preservative material, there may be a problem of plasticizer migration to the surface of fruits and vegetables, causing food safety hazards. Summary of the invention

[0006] In order to solve the technical problems of microbial contamination and short shelf life in the process of fruit and vegetable preservation in the prior art. The present invention provides a degradable electrospun slow-release antibacterial fiber membrane and its preparation method and application. The present invention reasonably designs the material formula, electrospinning process and layered composite structure, so that the fiber membrane can continuously and stably release antibacterial substances, inhibit the growth and reproduction of microorganisms on the surface of fruits and vegetables, reduce the respiration intensity and water loss of fruits and vegetables, thereby significantly extending the shelf life of fruits and vegetables, and providing an innovative and efficient solution for fruit and vegetable preservation packaging.

[0007] The first object of the present invention is to provide a method for preparing a degradable electrospun sustained-release antibacterial fiber membrane, comprising the following steps:

[0008] (1) mixing a polybutylene terephthalate adipate (PBAT) solution and a polylactic acid (PLA) solution to obtain a polymer mixture;

[0009] (2) mixing rosemary extract, alkali solution and epichlorohydrin, heating and reacting to obtain rosemary extract-based epoxy resin;

[0010] (3) mixing the β-cyclodextrin solution with the rosemary extract-based epoxy resin, heating for reaction, and performing solid-liquid separation to obtain a solid phase, wherein the solid phase is a sustained-release rosemary extract;

[0011] (4) mixing the polymer mixture obtained in step (1) with the sustained-release rosemary extract to form an electrospinning solution; and electrospinning the electrospinning solution to obtain a PBAT / PLA film loaded with the sustained-release rosemary extract;

[0012] (5) Using non-woven fabric as a support layer, the PBAT / PLA film loaded with sustained-release rosemary extract is laminated and compounded with the non-woven fabric to obtain the degradable electrospun sustained-release antibacterial fiber membrane.

[0013] In some embodiments of the present invention, in step (1), the concentration of the polybutylene terephthalate-adipate solution is 10-30.wt%;

[0014] The concentration of the polylactic acid solution is 10-30.wt%;

[0015] The mass ratio of polybutylene terephthalate-adipate PBAT and polylactic acid is (1:3)-(3:1).

[0016] In some embodiments of the present invention, in step (2), the mass ratio of rosemary extract to epichlorohydrin is (1-5): (5-15);

[0017] The mass volume ratio of the rosemary extract to the alkali solution is 1-5:5-40 g / mL;

[0018] The heating reaction temperature is 50-90°C and the time is 30min-2h;

[0019] The alkali solution is selected from sodium hydroxide solution and / or potassium hydroxide solution.

[0020] In some embodiments of the present invention, in step (3), the solvent of the β-cyclodextrin solution is sodium hydroxide solution and / or potassium hydroxide solution; the concentration of the β-cyclodextrin solution is 2-8 g / mL;

[0021] The heating reaction temperature is 40-70°C and the time is 2-6 hours.

[0022] In some embodiments of the present invention, in step (4), the mass fraction of the sustained-release rosemary extract is 5%-20%.

[0023] In some embodiments of the present invention, in step (4), the parameters of electrospinning are: voltage of 15-30 kV, receiving distance of 10-20 cm, and solution flow rate of 0.5-2 ml / h.

[0024] In some embodiments of the present invention, in step (5), the lamination is performed by hot pressing or adhesive bonding.

[0025] In some embodiments of the present invention, the hot pressing temperature of the hot pressing compound is 80-120° C. and the pressure is 0.5-2 MPa;

[0026] The amount of adhesive used in the adhesive compound is 5-15 g / m 2 ;

[0027] The adhesive is selected from one or more of polyurethane, acrylic acid, natural rubber and epoxy resin.

[0028] The second object of the present invention is to provide a degradable electrospun sustained-release antibacterial fiber membrane prepared by the above-mentioned preparation method; the degradable electrospun sustained-release antibacterial fiber membrane uses a non-woven fabric layer as a support layer, and an active film layer is arranged on the surface of the support layer, and the active film layer is prepared by electrospinning a mixture of sustained-release rosemary extract and a high molecular polymer.

[0029] In some embodiments of the present invention, the high molecular polymer includes polybutylene terephthalate-adipate and polylactic acid; and the sustained-release rosemary extract is composed of rosemary extract, sodium hydroxide and β-cyclodextrin.

[0030] The innovative design of the present invention:

[0031] (1) Innovation in material combination: By compounding PBAT and PLA, the biodegradable properties of both are fully utilized, and electrospinning technology is used to make them into a thin film structure, providing a good carrier for the subsequent loading of rosemary extract.

[0032] (2) Implementation of sustained-release antibacterial function: A special sustained-release rosemary extract preparation process is adopted to enable it to be evenly dispersed in the PBAT / PLA film and slowly released over a certain period of time, thereby continuously exerting its antibacterial effect, effectively solving the problem of microbial contamination of fruits and vegetables during storage, and extending the shelf life of fruits and vegetables.

[0033] (3) Layered composite structure design: The PBAT / PL film loaded with sustained-release rosemary extract is layered with PLA non-woven fabric. On the one hand, the good air permeability and mechanical properties of the non-woven fabric are utilized to enhance the overall strength and practicality of the fiber membrane; on the other hand, the release environment and rate of the rosemary extract are further optimized through the composite structure, thereby improving the antibacterial and fresh-keeping effects.

[0034] The above technical solution of the present invention has the following advantages compared with the prior art:

[0035] (1) The sustained-release rosemary extract loaded in the fiber membrane of the present invention can continuously and slowly release antioxidant components such as carnosin and rosmarinol, thereby effectively extending the shelf life of fruits and vegetables.

[0036] (2) The fiber membrane of the present invention is composed of biodegradable materials PBAT and PLA, which are gradually decomposed into harmless substances such as water and carbon dioxide under the action of microorganisms, effectively solving the white pollution problem caused by packaging waste to the environment and helping to promote the sustainable development of the packaging industry.

[0037] (3) The present invention uses rosemary extract as an antibacterial agent, which is naturally derived and has higher safety than chemically synthesized antibacterial agents. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0039] Figure 1 This is the antioxidant performance of the PBAT / PLA / rosemary a film obtained in Example 1 of the present invention.

[0040] Figure 2 This is the antioxidant performance of the PBAT / PLA / rosemary b film obtained in Example 2 of the present invention.

[0041] Figure 3 This is the antioxidant performance of the PBAT / PLA / rosemary c film obtained in Example 3 of the present invention.

[0042] Figure 4 These are the broccoli preservation test results of the PBAT / PLA / rosemary films prepared in the examples and comparative examples of the present invention. DETAILED DESCRIPTION

[0043] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0044] Example 1

[0045] This embodiment provides a method for preparing a degradable electrospun sustained-release antibacterial fiber membrane, and the specific steps are as follows:

[0046] 1. Preparation of sustained-release rosemary extract:

[0047] (1) PBAT is dissolved in chloroform and dimethyl sulfoxide at a concentration of 10 wt% to obtain a PBAT solution, and PLA is dissolved in dichloromethane or tetrahydrofuran at a concentration of 20 wt% to obtain a PLA solution. The treated PBAT solution and PLA solution are mixed in a mass ratio of 1:2 to form a uniform spinning solution.

[0048] (2) The rosemary extract is made into a sustained-release type by using a reaction process of β-cyclodextrin and epichlorohydrin with the rosemary extract to achieve its slow release in the fiber membrane. The specific steps are as follows:

[0049] S1. Weigh 5 g of rosemary extract, add 30 mL of 15 wt% NaOH solution as solvent and as reaction catalyst, add 10 g of epichlorohydrin at room temperature, stir well, gradually heat to 90° C., react for 2 h, vacuum filter the product to dryness, wash the solid product with benzene, wash with water until neutral, and place at 40° C. to vacuum dry for 24 h to obtain rosemary extract-based epoxy resin.

[0050] S2. Dissolve 15 g of β-cyclodextrin in 70 mL of 15 wt% NaOH solution, add the solution to the rosemary extract-based epoxy resin synthesized in step S1, stir thoroughly, gradually raise the temperature to 60° C., react for 3 h, filter, wash the filter cake with distilled water until neutral, and vacuum dry at 40° C. for 24 h to obtain a yellow powder product, which is a sustained-release rosemary extract.

[0051] 2. Electrospinning:

[0052] (1) Add 5 wt% of sustained-release rosemary extract to the spinning solution obtained in step (1), and stir evenly to form an electrospinning solution.

[0053] (2) The electrospinning solution was placed in an electrospinning device, the voltage was set to 15 kV, the receiving distance was 15 cm, the solution flow rate was 2 ml / h, and an electrospinning operation was performed to obtain a PBAT / PLA film loaded with sustained-release rosemary extract.

[0054] 3. Layered Composite:

[0055] Prepare PLA non-woven fabric as the support layer, and laminate the PBAT / PLA film and PLA non-woven fabric by hot pressing or adhesive lamination. When hot pressing, the hot pressing temperature is 120℃ and the pressure is 2MPa; when adhesive polyurethane is used for lamination, the amount of adhesive is 15g / m 2 , thereby obtaining a biodegradable electrospun sustained-release antibacterial fiber membrane, namely PBAT / PLA / rosemary a film.

[0056] Example 2

[0057] Similar to Example 1, the difference is that in step 2, electrospinning is performed with a mass fraction of 10 wt% of sustained-release rosemary extract, and finally a PBAT / PLA / rosemary b film is obtained.

[0058] Example 3

[0059] Similar to Example 1, the difference is that in step 2, electrospinning is performed with a mass fraction of 15 wt% of sustained-release rosemary extract, and finally a PBAT / PLA / rosemary c film is obtained.

[0060] Example 4

[0061] Similar to Example 1, the difference is that in step 2, electrospinning is performed with a mass fraction of 15 wt% of sustained-release rosemary extract, and finally a PBAT / PLA / rosemary d film is obtained.

[0062] Comparative Example 1 (PBAT / PLA)

[0063] Similar to Example 1, the difference is that no rosemary extract is added in step 2.

[0064] Performance Testing

[0065] The fiber membranes obtained in Example 1 and Comparative Example 1 were subjected to performance tests such as tensile strength, elongation at break, and free radical scavenging ability:

[0066] (1) Test method for tensile strength: According to the method of GB / T1040.3-2006, the tensile strength and elongation at break of the composite film were tested. The four film samples were cut into strips of 100 mm in length and 15 mm in width using a cutting knife. The tensile strength (TS), elongation at break and other mechanical properties of the film were tested using an intelligent electronic tensile testing machine at a temperature of 25°C and a relative humidity of 60% RH. During the test, the strip film was clamped and aligned up and down; the initial clamping distance of the test was set to 50 mm; the tensile test rate was 300 mm / min. The experimental results are shown in Table 1.

[0067] (2) Test of sustained release performance: Rosemary extract absorbent (alcohol and phosphate buffered saline solution 1:5, v / v) was prepared, and samples were taken every 4 days for 16 consecutive days. The absorbance was measured at a wavelength of 273.5 nm using a UV-visible spectrophotometer, and the absorbance was calculated based on the rosemary extract standard curve. The cumulative release of the rosemary extract was calculated using a specific formula. The experimental results are shown in Table 2.

[0068] (3) Antioxidant activity: DPPH is a free radical scavenger that can be used for the photometric determination of phenols. It has a fixed absorption peak at 515 nm by ultraviolet spectral scanning. It absorbs free radicals and then reduces them. At this time, the absorption peak at 515 nm decreases or disappears. In view of this feature, the DPPH free radical scavenging method is widely used to evaluate the free radical scavenging activity of natural antioxidants. The sample film is cut into pieces and immersed in methanol. It is left to stand at room temperature for 24 hours. The supernatant is collected and mixed with a methanol solution of DPPH in a 1:1 ratio. Finally, the resulting mixed solution is kept in a dark place for 60 minutes, and the absorption band intensity of DPPH at 515 nm is measured on a UV spectrophotometer. Methanol is used as a blank, and the DPPH / methanol solution is set as a negative control. The antioxidant activity is expressed as the DPPH free radical scavenging ability (RSA). The RSA calculation formula is shown in Eq. (1):

[0069]

[0070] A sample Refers to the ultraviolet absorption of the sample at 515nm, A control Refers to the UV absorption of 25mg / mL DPPH / methanol solution at 515nm. The experimental results are shown in Figure 1-Figure 3 .

[0071] (4) Broccoli preservation test: Select broccoli that is suitable for harvesting with dense flowers, uniform color, and free of pests and diseases. Then cut the selected broccoli samples into uniform-sized flower balls with a sharp knife, divide them into experimental components, and put them into different biodegradable fresh-keeping bags (15cm×20cm, thickness (20±3)μm), seal them and refrigerate them. Take samples for testing every day. When the broccoli rots or turns yellow, stop storing it. The experimental results are shown in Figure 4 .

[0072] Table 1 Tensile strength, elongation at break and oxidation resistance (RSA) of the films

[0073]

[0074] As shown in Table 1, compared with Comparative Example 2, the film strength does not change much after adding rosemary a / c / d, and the elongation at break decreases, indicating that the rosemary extract has a negative effect on the toughness of the film itself. The tensile strength of Example 2 increases, and the elongation at break decreases. Compared with Comparative Example 2, the tensile strength of b increases, the toughness decreases, and the free radical scavenging ability is as high as 91%. This result shows that the PBAT / PLA / rosemary extract electrospun fiber film has certain antioxidant properties (free radical scavenging rate is 53.2% to 91), and has the potential to be used in food packaging.

[0075] Table 2 Cumulative release of rosemary from composite films

[0076]

[0077]

[0078] As shown in Table 2, the release of the rosemary extract sample of the unencapsulated control group no longer increased after the 8th day. The release amount and rate of the film encapsulated with β-cyclodextrin and rosemary extract for sustained release decreased, which had a better protective effect on the rosemary extract. By the 16th day, the cumulative release reached 6.65-9.30%, and the cumulative release showed a slowly increasing trend, indicating that the composite film has the characteristics of slowly releasing rosemary extract and having long-term stable performance.

[0079] Depend on Figure 4It can be seen that the fiber film made of PBAT / PLA / rosemary extract was used to wrap fruits and vegetables to test its preservation effect. As the number of cold storage days increased, the chlorophyll content of broccoli continued to decrease, and then wilted and yellowed. On the 7th day of storage, the surface of the broccoli head wrapped in PE plastic wrap withered, oxidized and yellowed, and began to fall off naturally. The leaves of broccoli wrapped in PBAT / PLA and PBAT / PLA / rosemary extract a film turned black. On the 9th day of storage, the broccoli in the PE plastic wrap group produced a sour smell due to anaerobic respiration and acid production, and began to lose its edible value, and storage was terminated. In contrast, the film packaging with natural antioxidant BD can effectively inhibit the loss of leaf green. The color is light green and the fragrance remains within the first 9 days of storage, and it still has commercial value. The release of antioxidant components in the film significantly delays the degradation of chlorophyll in fresh-cut broccoli, and its effect is significantly better than that of other groups of films. Compared with PE bags, the shelf life of broccoli packaged in PBAT / PLA with rosemary extract is extended by more than 2 times.

[0080] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A method for preparing a degradable electrospun sustained-release antibacterial fiber membrane, characterized in that: The following steps are involved: (1) Mixing a polybutylene terephthalate (PBAT) solution and a polylactic acid (PLA) solution to obtain a polymer mixture; (2) mixing rosemary extract, alkali solution and epichlorohydrin, heating and reacting to obtain rosemary extract-based epoxy resin; (3) mixing the β-cyclodextrin solution with the rosemary extract-based epoxy resin, heating for reaction, and performing solid-liquid separation to obtain a solid phase, wherein the solid phase is a sustained-release rosemary extract; (4) mixing the polymer mixture obtained in step (1) with the sustained-release rosemary extract to form an electrospinning solution; and electrospinning the electrospinning solution to obtain a PBAT / PLA film loaded with the sustained-release rosemary extract; (5) Using non-woven fabric as a support layer, the PBAT / PLA film loaded with sustained-release rosemary extract is laminated and compounded with the non-woven fabric to obtain the degradable electrospun sustained-release antibacterial fiber membrane.

2. The preparation method according to claim 1, characterized in that: In step (1), the concentration of the polybutylene terephthalate-adipate solution is 10-30wt%; The concentration of the polylactic acid solution is 10-30wt%; The mass ratio of polybutylene terephthalate-adipate PBAT and polylactic acid is (1:3)-(3:1); The alkali solution is selected from sodium hydroxide and / or potassium hydroxide.

3. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of rosemary extract to epichlorohydrin is (1-5): (5-15); The mass volume ratio of the rosemary extract to the alkali solution is (1-5): (5-40) g / mL; The heating reaction temperature is 50-90°C and the time is 30min-2h.

4. The preparation method according to claim 1, characterized in that: In step (3), the solvent of the β-cyclodextrin solution is sodium hydroxide solution or potassium hydroxide solution; the concentration of the β-cyclodextrin solution is 2-8 g / mL; The heating reaction temperature is 40-70°C and the time is 2-6 hours.

5. The preparation method according to claim 1, characterized in that: In step (4), the mass fraction of the sustained-release rosemary extract is 5%-20%.

6. The preparation method according to claim 1, characterized in that: In step (4), the parameters of electrospinning are: voltage of 15-30 kV, receiving distance of 10-20 cm, and solution flow rate of 0.5-2 ml / h.

7. The preparation method according to claim 1, characterized in that: In step (5), the lamination is performed by hot pressing or adhesive bonding.

8. The preparation method according to claim 6, characterized in that: The hot pressing temperature of the hot pressing compound is 80-120°C and the pressure is 0.5-2MPa; The amount of adhesive used in the adhesive compound is 5-15 g / m 2 ; The adhesive is selected from one or more of polyurethane, acrylic acid, natural rubber and epoxy resin.

9. A degradable electrospun slow-release antibacterial fiber membrane, characterized in that: Prepared by the preparation method described in any one of claims 1 to 8; the degradable electrospun sustained-release antibacterial fiber membrane uses a non-woven fabric layer as a support layer, and an active film layer is arranged on the surface of the support layer, and the active film layer is prepared by electrospinning a mixture of sustained-release rosemary extract and a high molecular polymer.

10. The degradable electrospun sustained-release antibacterial fiber membrane according to claim 9, characterized in that: The high molecular polymer comprises polybutylene terephthalate-adipate and polylactic acid; and the sustained-release rosemary extract consists of rosemary extract, alkali and beta-cyclodextrin.

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