A nanofiber membrane and its preparation method and application

Abstract

The present invention belongs to the technical field of membrane materials, and specifically relates to a nanofiber membrane and a preparation method and application thereof. The present invention provides a nanofiber membrane, the nanofiber membrane comprises modified polylactic acid; the modified polylactic acid is perillaldehyde cross-linked polylactic acid; the mass ratio of perillaldehyde to polylactic acid in the perillaldehyde cross-linked polylactic acid is 0.01 to 0.02:1. The nanofiber membrane provided by the present invention has good biodegradability and reduces environmental pollution. In the present invention, perillaldehyde has good antibacterial properties. The present invention cross-links polylactic acid and perillaldehyde, improves the stability of perillaldehyde in the nanofiber membrane, avoids the free leakage and volatilization of perillaldehyde, and thus improves the freshness-keeping performance of the nanofiber membrane.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane materials, and in particular relates to a nanofiber membrane and a preparation method and application thereof. Background Art

[0002] Meat is an important component of human daily diet and an important source of nutrients needed by the human body. In recent years, due to the outbreak of animal diseases and changes in consumer consumption concepts, fresh meat has gradually become the main meat consumption for the public. In the production, transportation and sales process, microbial contamination is the main factor causing the quality decline and economic losses of fresh meat. How to extend the shelf life of fresh meat has become a key challenge currently faced.

[0003] At present, packaging based on biodegradable materials is a hot topic in research. It has the characteristics of avoiding environmental white pollution and good biocompatibility, and can inhibit microbial growth and delay food spoilage by loading antibacterial substances. Therefore, the development of biodegradable packaging materials with antibacterial activity is an important way to ensure the quality and hygiene of fresh food and extend its shelf life. Summary of the invention

[0004] In view of this, the present invention provides a nanofiber membrane and a preparation method and application thereof. The nanofiber membrane provided by the present invention has degradable properties and good freshness-preserving and antibacterial properties.

[0005] In order to solve the above technical problems, the present invention provides a nanofiber membrane, which includes modified polylactic acid; the modified polylactic acid is perillaldehyde cross-linked polylactic acid; the mass ratio of perillaldehyde to polylactic acid in the perillaldehyde cross-linked polylactic acid is 0.01-0.02:1.

[0006] The present invention also provides a method for preparing the nanofiber membrane described in the above technical solution, comprising the following steps:

[0007] dissolving polylactic acid in an organic solvent to obtain a polylactic acid solution;

[0008] The polylactic acid solution, perillaldehyde and a cross-linking agent are mixed to carry out a cross-linking reaction to obtain a spinning solution;

[0009] The spinning solution is subjected to electrostatic spinning to obtain the nanofiber membrane.

[0010] Preferably, the mass ratio of the polylactic acid to perillaldehyde is 3g:40-60mg;

[0011] The cross-linking agent is Amiao-PEG4-Amine, and the mass ratio of the polylactic acid to the cross-linking agent is 1:0.01-0.02.

[0012] Preferably, the mixing comprises stirring mixing and ultrasonic mixing performed sequentially.

[0013] Preferably, the temperature of the cross-linking reaction is 40-50° C., and the time of the cross-linking reaction is 25-35 min.

[0014] Preferably, the organic solvent is a mixture of N,N-dimethylformamide and dichloromethane;

[0015] The volume ratio of N,N-dimethylformamide to dichloromethane in the mixed liquid of N,N-dimethylformamide and dichloromethane is 2.8-3.2:7.

[0016] Preferably, the dissolution temperature is 48-52° C., and the dissolution time is 28-32 min.

[0017] Preferably, the voltage of the electrospinning is 18-22 kV, and the injection speed of the electrospinning is 0.0048-0.0052 mm / s.

[0018] The present invention also provides the use of the nanofiber membrane described in the above technical solution or the nanofiber membrane prepared by the preparation method described in the above technical solution in the preservation of fresh cold meat.

[0019] Preferably, the chilled fresh meat includes chilled fresh mutton.

[0020] The present invention provides a nanofiber membrane, the nanofiber membrane comprises modified polylactic acid; the modified polylactic acid is perillaldehyde cross-linked polylactic acid; the mass ratio of perillaldehyde to polylactic acid in the perillaldehyde cross-linked polylactic acid is 0.01-0.02:1. The nanofiber membrane provided by the present invention has good biodegradability and reduces environmental pollution. In the present invention, perillaldehyde has good antibacterial properties. The present invention cross-links polylactic acid and perillaldehyde, improves the stability of perillaldehyde in the nanofiber membrane, avoids the free leakage and volatilization of perillaldehyde, and thus improves the freshness-keeping performance of the nanofiber membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The SEM images and nanofiber diameter distribution images of the nanofiber membranes prepared in Examples 1 to 2 and Comparative Examples 1 to 3, wherein a is the result image of the nanofiber membrane prepared in Comparative Example 1, b is the result image of the nanofiber membrane prepared in Comparative Example 2, c is the result image of the nanofiber membrane prepared in Comparative Example 3, e is the result image of the nanofiber membrane prepared in Example 1, and f is the result image of the nanofiber membrane prepared in Comparative Example 4;

[0022] Figure 2 The XRD patterns of the nanofiber membranes prepared in Example 1 and Comparative Examples 1 to 4;

[0023] Figure 3The dot-line graph is the pH value of fresh mutton packaged with different nanofiber membranes after different storage times;

[0024] Figure 4 The dot-line graph of the total bacterial count of fresh mutton packaged with different nanofiber films after different storage times;

[0025] Figure 5 This is a dot-line graph of TVB-N of fresh mutton packaged with different nanofiber films after different storage times. DETAILED DESCRIPTION

[0026] The present invention provides a nanofiber membrane, which comprises modified polylactic acid; the modified polylactic acid is perillaldehyde cross-linked polylactic acid; the mass ratio of perillaldehyde to polylactic acid in the perillaldehyde cross-linked polylactic acid is 0.01-0.02:1, preferably 0.016-0.017:1.

[0027] In the present invention, the thickness of the nanofiber membrane is preferably 38-42 μm, more preferably 40 μm.

[0028] When the nanofiber membrane provided by the present invention contacts the surface of fresh meat, the water on the surface of the fresh meat enters the interior of the nanofiber membrane under the action of osmotic pressure, and at the same time, the H + The acidic hydrolysis effect causes perillaldehyde to be continuously released from the nanofiber membrane to the membrane surface. Perillaldehyde has high antibacterial and antioxidant properties, and has good preservation properties for meat products. Low concentrations of perillaldehyde will damage the structure of spoilage bacteria, leak macromolecules such as biological activity, and even cause death. The polylactic acid membrane loaded with perillaldehyde responds to the pH stimulation of the meat environment and gradually releases the active substance perillaldehyde to achieve the purpose of antibacterial preservation.

[0029] The present invention also provides a method for preparing the nanofiber membrane described in the above technical solution, comprising the following steps:

[0030] dissolving polylactic acid in an organic solvent to obtain a polylactic acid solution;

[0031] The polylactic acid solution, perillaldehyde and a cross-linking agent are mixed to carry out a cross-linking reaction to obtain a spinning solution;

[0032] The spinning solution is subjected to electrostatic spinning to obtain the nanofiber membrane.

[0033] The present invention dissolves polylactic acid in an organic solvent to obtain a polylactic acid solution. In the present invention, the organic solvent is preferably a mixture of N,N-dimethylformamide and dichloromethane; the volume ratio of N,N-dimethylformamide and dichloromethane in the mixture of N,N-dimethylformamide and dichloromethane is preferably 2.8-3.2:7, more preferably 3:7. In the present invention, the mass concentration of the polylactic acid (PLA) solution is preferably 0.1-0.2g / mL, more preferably 0.15g / mL. The present invention uses a mixture of N,N-dimethylformamide and dichloromethane as an organic solvent to better dissolve polylactic acid particles and obtain a uniform and stable electrospinning membrane solution.

[0034] In the present invention, the dissolution temperature is preferably 48 to 52° C., more preferably 50° C.; the dissolution time is preferably 28 to 32 min, more preferably 30 min.

[0035] After obtaining the polylactic acid solution, the present invention mixes the polylactic acid solution, perillaldehyde and a cross-linking agent to perform a cross-linking reaction to obtain a spinning solution. In the present invention, the cross-linking agent is preferably Amiao-PEG4-Amine. In the present invention, the mass ratio of the polylactic acid (PLA) to perillaldehyde (PAE) is preferably 3g:40-60mg, more preferably 3g:50mg. In the present invention, the mass ratio of the polylactic acid to the cross-linking agent is preferably 1:0.01-0.02, more preferably 1:0.016-0.017.

[0036] In the present invention, the mixing preferably includes stirring and mixing and ultrasonic mixing performed in sequence. In the present invention, the speed of the stirring and mixing is preferably 400-600 r / min, more preferably 450-500 r / min; the time of the stirring and mixing is preferably 10-14 h, more preferably 12 h; the power of the ultrasonic mixing is preferably 450-500 W, more preferably 16-480 W; the time of the ultrasonic mixing is preferably 25-35 min, more preferably 30 min.

[0037] In the present invention, the temperature of the cross-linking reaction is preferably 40-50° C., more preferably 45° C.; the time of the cross-linking reaction is preferably 25-35 min, more preferably 30 min.

[0038] In the present invention, Amiao-PEG4-Amine is used as a diamino coupling agent to achieve effective cross-linking of polylactic acid and perillaldehyde, forming a stable core-shell polymer with perillaldehyde as the core and polylactic acid as the shell, thereby avoiding the free leakage and volatilization of perillaldehyde under weak binding force conditions, and also avoiding the problem of decreased freshness preservation effect of the nanofiber membrane during use.

[0039] After obtaining the spinning solution, the present invention electrospins the spinning solution to obtain the nanofiber membrane. The present invention preferably transfers the electrospinning solution to a syringe for electrospinning solution, and fixes the syringe on an electrospinning platform for electrospinning. In the present invention, the steel needle of the electrospinning installation is preferably a No. 18 steel needle. In the present invention, the distance between the syringe and the receiver is preferably 8 to 12 cm, more preferably 10 cm.

[0040] In the present invention, the voltage of the electrospinning is preferably 18-22 kV, more preferably 20 kV; the injection speed of the electrospinning is preferably 0.0048-0.0052 mm / s, more preferably 0.005 mm / s. In the present invention, the temperature of the electrospinning environment is preferably 20-30 ° C, more preferably 25 ° C; the relative humidity of the electrospinning environment is preferably 48-52%, more preferably 50%.

[0041] The present invention also provides the use of the nanofiber membrane described in the above technical solution or the nanofiber membrane prepared by the preparation method described in the above technical solution in the preservation of chilled fresh meat. In the present invention, the chilled fresh meat preferably includes chilled fresh mutton.

[0042] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0043] Sources of raw materials and instruments in the embodiments of the present invention: polylactic acid, biological grade, purchased from Shanghai MacLean Biological Co., Ltd.; N,N-dimethylformamide, analytical grade, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; dichloromethane, analytical grade, purchased from Beijing Sinopharm Group; perillaldehyde, biological grade, purchased from Shanghai Yuanye Biotechnology Co., Ltd.; plate count agar (PCA) medium, analytical grade, purchased from Beijing Luqiao Biological Company; cold fresh mutton, purchased from Meitong Market, Yuquan District, Hohhot City;

[0044] JY5002 electronic balance, Shanghai Liangping Instrument Co., Ltd.; DFS-001 high-voltage electrospinning machine, Beijing Xinkaiwei Technology Co., Ltd.; EVO-LS10 scanning electron microscope, Carl Zeiss, Germany; electronic universal testing machine, Shanghai Zhujin Analytical Instrument Co., Ltd.

[0045] Example 1

[0046] 3 g of PLA was dissolved (30 min) at 50°C in 20 mL of a mixture of N,N-dimethylformamide and dichloromethane in a volume ratio of 3:7 to obtain a polylactic acid solution;

[0047] The polylactic acid solution, 50 mg of perillaldehyde (PAE) and 50 mg of Amiao-PEG4-Amine were stirred at a speed of 500 r / min for 12 h, ultrasonicated at a power of 480 W for 30 min, and cross-linked at 45°C for 30 min to obtain an electrospinning solution;

[0048] Electrospinning was performed using a DFS-001 high-voltage electrospinning machine. 5 mL of electrospinning solution was injected into a syringe and then fixed on the electrospinning platform. An 18-gauge steel needle was installed. Electrospinning was performed at an injection speed of 0.005 mm / s, a voltage of 20 kV, a distance of 10 cm between the syringe and the receiver, an ambient temperature of 25°C, and an ambient relative humidity of 50% to obtain a nanofiber membrane, which was labeled PAE-50.

[0049] Comparative Example 1

[0050] A nanofiber membrane was prepared according to the method of Example 1, except that the amount of perillaldehyde added was 0 mg. The obtained nanofiber membrane was labeled PAE-0.

[0051] Comparative Example 2

[0052] A nanofiber membrane was prepared according to the method of Example 1, except that the amount of perillaldehyde added was 12.5 mg. The obtained nanofiber membrane was labeled PAE-12.5.

[0053] Comparative Example 3

[0054] A nanofiber membrane was prepared according to the method of Example 1, except that the amount of perillaldehyde added was 25 mg. The obtained nanofiber membrane was labeled PAE-25.

[0055] Comparative Example 4

[0056] A nanofiber membrane was prepared according to the method of Example 1, except that the amount of perillaldehyde added was 100 mg. The obtained nanofiber membrane was labeled as PAE-100.

[0057] The morphology of the nanofiber membranes prepared in Examples 1 to 2 and Comparative Examples 1 to 4 was detected using an EVO-LS10 scanning electron microscope to obtain SEM images, and the images were analyzed using Image J to obtain a distribution diagram of the diameters of the nanofibers in the nanofiber membranes, as shown in FIG. Figure 1As shown; wherein, a is the result diagram of the nanofiber membrane prepared in Comparative Example 1, b is the result diagram of the nanofiber membrane prepared in Comparative Example 2, c is the result diagram of the nanofiber membrane prepared in Comparative Example 3, e is the result diagram of the nanofiber membrane prepared in Example 1, and f is the result diagram of the nanofiber membrane prepared in Comparative Example 4. According to the Image J analysis results, it can be seen that the average diameter of the nanofibers in PAE-0 is 137.91±41.97nm, the average diameter of the nanofibers in PAE-12.5 is 107.16±41.71nm, the average diameter of the nanofibers in PAE-25 is 91.41±25.33nm, the average diameter of the nanofibers in PAE-50 is 114.65±31.99nm, and the average diameter of the nanofibers in PAE-100 is 91.43±31.89nm.

[0058] Depend on Figure 1 It can be seen that with the increase of perillaldehyde loading, the diameter of the nanofibers in the nanofiber membrane shows a trend of first decreasing, then increasing, and then decreasing, and the fiber morphology gradually becomes regular. When the perillaldehyde loading is between 0 and 50 mg, the diameter of the polylactic acid nanofiber membrane first decreases and then increases with the increase of the loading, but is smaller than the fiber diameter of the control group (137.91 nm), which indicates that the addition of PAE may change the particle size of the polylactic acid biomacromolecules, thereby significantly changing the fiber diameter. Among them, the nanofiber diameter of the PAE-50 group is the largest, which is 114.65 nm, and the nanofiber morphology is better; when the PAE loading is greater than or less than 50 mg, the nanofibers show the phenomenon of nanofiber curling. This is because the loading of different concentrations of perillaldehyde affects the surface charge density of the electrospinning solution, and the nanofibers collected in the receiver will merge as the surface charge density decreases, thereby changing the fiber diameter. At the same time, with the increase of PAE loading concentration, the distribution of nanofibers gradually changed from irregular to a state of good morphology and no broken fibers; when the addition amount of PAE reached 100 mg / 20 mL of electrospinning solution, the fiber membrane showed broken fibers and formed nanoparticles, which shows that PLA has a certain limit to its PAE loading capacity.

[0059] The nanofiber diameters in the nanofiber membrane provided by the present invention are discrete, indicating that the nanofiber membrane provided by the present invention has good mechanical properties.

[0060] The nanofiber membranes prepared in Examples 1 to 2 and Comparative Examples 1 to 3 were tested using a Bruker D8 Advance X-ray diffraction analyzer to obtain XRD patterns, as shown in FIG. Figure 2 The test conditions are: voltage 20kV, current 5mA, Kα The scanning rate was 4° / min, the step length was 0.02°, and the scanning range was 5° to 60°.

[0061] Depend on Figure 2 It can be seen that the control group, PAE-12.5, PAE-25, PAE-50, and PAE-100 nanofiber membranes all have two wide characteristic diffraction peaks at 17° and 31°. The peak intensity difference between the groups is not obvious, and the peak height is lower than the peak width. This is because the rapid evaporation of the solvent during the electrospinning process hinders the formation of the lattice; the similar peak position also shows that the addition of PAE does not change the original crystal structure of PLA, and also shows that PLA and PAE have good compatibility, which helps to improve the stability of the PLA film.

[0062] Mechanical properties test:

[0063] The PLA-PAE film was cut into 0.5 cm × 3 cm samples, and the thickness of the sample at multiple different positions was measured using a vernier caliper. Based on the average thickness, the tensile strength and elongation at break of the PLA-PAE nanofiber membrane were analyzed using an electronic universal testing machine, and the results are listed in Table 1. The test conditions were: initial gap distance 2.0 cm, test speed 50 mm / min.

[0064] Table 1 Elongation and tensile strength of the nanofiber membranes prepared in Examples 1 to 2 and Comparative Examples 1 to 3

[0065]

[0066] Note: Different capital letters in the same row indicate significant differences (P<0.05), while the same capital letters indicate no significant differences (P>0.05).

[0067] Good mechanical properties are important indicators for measuring the service life of nanofiber membrane materials and reducing costs and resource losses. With the increase of PAE loading, the elongation and tensile strength of the nanofiber membrane showed a trend of increasing first and then decreasing. When the PAE loading was 50 mg, the elongation and tensile strength of the nanofiber membrane reached the highest, 68.72% and 1.80 MPa, respectively. Table 1 shows that the elongation of the PAE-50 group membrane was 15.17% higher than that of the PAE-0 group, and the tensile strength was 24.13% higher than that of the PAE-0 group. This is because the addition of a certain concentration of perillaldehyde improves the uniformity of the polylactic acid electrospinning solution, increases the interaction between perillaldehyde and polylactic acid molecules, makes the PAE-PLA membrane network structure more compact, and improves the tensile strength of the membrane; at the same time, it increases the fluidity of the polymer chain, improves the toughness of the composite membrane, and increases the elongation of the membrane. Therefore, loading an appropriate concentration of PAE is an important choice for improving the mechanical properties of PLA membranes.

[0068] Lamb storage

[0069] In a sterile environment, after removing the fascia on the surface of mutton, the meat samples were cut into 30g cubes, and then packaged using the films prepared in Examples 1 to 2 and Comparative Examples 2 to 3, with unpackaged samples used as controls; the samples were stored in a 4°C refrigerator for 0, 3, 6, 9, and 12 days, and freshness-keeping tests were performed to evaluate the results.

[0070] The pH values ​​of mutton samples at different preservation stages were measured with reference to GB 5009.237-2016 “National Food Safety Standard for Determination of pH Value of Foods”, and the results are listed in Table 2.

[0071] Table 2 pH values ​​of fresh mutton packaged with nanofiber membrane after different storage times

[0072]

[0073] Note: Different uppercase (lowercase) letters in the same row (column) indicate significant differences (P<0.05), while the same letters indicate insignificant differences (P>0.05).

[0074] According to Table 1, a dot-line graph of the pH values ​​of fresh mutton packaged with different nanofiber membranes after different storage times was drawn. Figure 3 shown.

[0075] During the storage of fresh meat, the oxidative decomposition of fat and protein is an important sign of meat deterioration. As the degree of oxidative decomposition increases, the protein in the meat is decomposed into small molecular ammonia and other alkaline substances, which gradually accumulate and cause the pH value of the meat to rise. Therefore, pH value is a key indicator for evaluating the freshness and quality deterioration of fresh meat. Figure 3 It can be seen that during the storage process, the pH value of fresh mutton showed different trends with the difference in PAE loading concentration. With the extension of storage time, the pH value of fresh mutton increased at an increasing rate after 6 days, indicating that the activity of microorganisms or endogenous enzymes in decomposing meat protein into alkaline substances such as ammonia and amines increased, causing the mutton to show a tendency to spoil at this time. Compared with the control group, when the perillaldehyde loading was 12.5-50 mg, the pH rising trend slowed down with the increase of perillaldehyde loading, indicating that the increase in PAE concentration had a cumulative inhibitory effect on spoilage bacteria. When the perillaldehyde loading was 100 mg, there was no significant difference in pH between the PAE-100 and PAE-50 groups at 6 and 12 days. This is due to the weak molecular interaction between PLA and PAE, which caused the excess PAE to be free and volatilized during the electrospinning process, reducing the effective loading rate of the PLA film, resulting in a similar preservation effect to the PAE-50 group. After 12 days of storage, the pH value of the PAE-50 group was the lowest in the group, at 6.50. The comparison shows that PAE-50 nanofiber membrane can effectively delay the spoilage of mutton.

[0076] The colorimeter was used to measure the brightness L* value, redness a* value and yellowness b* value of the mutton samples. Before use, the matching blackboard and whiteboard were used for calibration. Three different positions were selected for each sample and the results were averaged to ensure the uniformity of sampling. The results are listed in Table 3.

[0077] Table 3 Effect of nanofiber membrane on the color of fresh mutton during storage

[0078]

[0079] Note: Different uppercase (lowercase) letters in the same row (column) indicate significant differences (P<0.05), and the same letters indicate no significant differences (P>0.05).

[0080] Color is an important indicator for evaluating the sensory characteristics of meat and an important basis for consumers to judge the freshness of meat. Among them, a* represents the redness of meat, b* represents the yellowness, and L* represents the brightness. As shown in Table 3, the L* values ​​of the control group and the PAE-50 group on the 6th day were significantly lower than those on the 12th day (P<0.05), and the L* values ​​of the PAE-12.5 and PAE-25 groups on the 6th day were not significantly different from those on the 12th day (P>0.05). The L* value of the PAE-100 group on the 12th day was significantly lower than that on the 6th day. On the 12th day, the L* value of the control group was significantly lower than that of the PAE-50 group, and significantly higher than that of the PAE-25 and PAE-100 groups (P<0.05). Compared with the L* value of the PAE-12.5 group, there was no significant difference (P>0.05). At the beginning of storage, the change trend of a* value in the experimental group and the control group was generally consistent. In the late storage period, the a* values ​​of the PAE-50 and PAE-100 groups were significantly higher than those of the control, PAE-12.5, and PAE-25 groups. During storage, the b* value of the experimental group did not change significantly (P>0.05), while the b* value of the control group changed significantly in the late storage period (P<0.05). Comparing the changes in a* and b* values ​​of the control group and the experimental group at 12 days, it can be seen that the nanofiber membrane helps to delay the spoilage of mutton and extend the shelf life.

[0081] Total colony count determination

[0082] Refer to GB / T 4789.2-2016 "National Food Safety Standard for Microbiological Examination of Foods - Determination of Total Colony Count" and make slight changes. Weigh 5g of meat sample into a sterile conical flask containing 45mL of 0.95% saline, mix thoroughly on a shaker at 4℃, and wait for testing. Place the coated plate in a 37℃ constant temperature incubator, incubate for 24h, and count the colonies. The results are listed in Table 4.

[0083] Table 4 Colony counts of fresh mutton packaged with nanofiber membranes after different storage times

[0084]

[0085] Note: Different uppercase (lowercase) letters in the same row (column) indicate significant differences (P<0.05), and the same letters indicate no significant differences (P>0.05).

[0086] According to Table 4, a dot-line graph of the total number of bacterial colonies of fresh mutton packaged with different nanofiber films after different storage times was drawn. Figure 4 shown.

[0087] The change in the number of microbial colonies is an important indicator for measuring the degree of meat spoilage. The degree of meat spoilage is positively correlated with the number of microorganisms. When the number of viable bacteria is higher than 1×10 6 Log(CFU / g) indicates that it has entered the spoilage stage, with protein and fat oxidative denaturation accompanied by the generation of undesirable decomposition metabolites, and the degree of meat deterioration will gradually increase. Figure 4 It can be seen that the total number of viable bacteria gradually increased with the extension of storage time; with the increase of PAE loading in the nanofiber membrane, the increase of the number of viable bacteria in the test group gradually slowed down; compared with other groups, the increase in the PAE-50 group was smaller. After 6 days of storage, the total number of viable bacteria in the control group reached 5.90Log (CFU / g), close to the critical freshness of meat products, and significantly higher than the PLA nanofiber membrane packaging group loaded with different concentrations of PAE (P<0.05). After 12 days of storage, the total number of viable bacteria in the PAE-12.5, PAE-25, and PAE-50 groups were 7.44Log (CFU / g), 7.29Log (CFU / g), and 5.56Log (CFU / g), respectively, indicating that the cumulative inhibitory effect of PAE on spoilage bacteria in meat increased with the increase of PAE loading concentration. At the end of storage, the total bacterial count in the mutton of the PAE-100 group was 6.46Log (CFU / g), which was higher than that of the PAE-50 group. This may further confirm that PLA has a limited loading capacity for PAE, resulting in excess PAE not being well bound and causing volatilization loss, causing the effective loading amount of PAE in the PAE-100 membrane to be lower than that of PAE-50. It also shows that PAE-50 nanofiber membrane will be a potential meat preservation packaging material.

[0088] TVB-N determination

[0089] The numerical determination was carried out according to the microdiffusion method in GB 5009.228-2016 "National Food Safety Standard Determination of Volatile Basic Nitrogen in Foods", with slight modifications. Weigh 5g of meat sample and add it to a centrifuge tube filled with 25mL of distilled water and shake it from time to time. The sample was homogenized in an ice bath for 30s, and then filtered after immersion for 30min. The filtrate was tested.

[0090] Excel and SPSS 19.0 were used to perform statistical and variance analysis on the experimental data, and the results were expressed as mean ± standard deviation.

[0091] Table 5 TVB-N of fresh mutton packaged with nanofiber membrane after different storage time

[0092]

[0093]

[0094] Note: Different uppercase (lowercase) letters in the same row (column) indicate significant differences (P<0.05), and the same letters indicate no significant differences (P>0.05).

[0095] According to Table 5, a dot-line graph of TVB-N of fresh mutton packaged with different nanofiber films after different storage times is drawn, as shown in Figure 5 shown.

[0096] Volatile basic nitrogen is mainly alkaline substances such as ammonia and amines. Its content is positively correlated with the degree of protein destruction and is one of the important indicators for measuring the freshness of meat products. my country's domestic livestock and fresh meat hygiene standards stipulate that the TVB-N content of fresh poultry meat should not exceed 15 mg / 100 g. Figure 5 It can be seen that the TVB-N content in mutton gradually increases with the extension of storage time, which is mainly caused by the decomposition of protein by spoilage bacteria. As the PAE load content increases, the increase in TVB-N content in mutton slows down. After 6 days of storage, the control group reached 17.50 mg / 100g, and the TVB-N content of cold fresh mutton packaged with nanofiber membrane increased relatively slowly. The TVB-N content of the four groups of mutton was not higher than 10 mg / 100g. At the end of 12 days of storage, the TVB-N content of the PAE-50 group was the lowest, at 12.55 mg / 100g. Therefore, PAE-50 nanofiber membrane will have good and potential application prospects in the field of fresh-keeping packaging.

[0097] The PAE-loaded PLA nanofiber packaging film was prepared by electrospinning technology. Based on SEM, XRD, mechanical properties characterization and preservation test evaluation, PLA and PAE improved the state and stability of PLA nanofibers through chemical coupling. The PAE-loaded PLA nanofiber film showed good fiber arrangement and spatial network structure, thereby improving the mechanical properties of the PLA film. PLA showed a certain load on PAE, and the appropriate load amount helped to show the preservation properties of the PLA film.

[0098] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. Application of a nanofiber membrane in the preservation of cold fresh meat, wherein the nanofiber membrane comprises modified polylactic acid; The modified polylactic acid is perillaldehyde cross-linked polylactic acid; The mass ratio of perillaldehyde to polylactic acid in the perillaldehyde cross-linked polylactic acid is 0.01-0.02:1; The method for preparing the nanofiber membrane comprises the following steps: dissolving polylactic acid in an organic solvent to obtain a polylactic acid solution; The polylactic acid solution, perillaldehyde and a cross-linking agent are mixed to carry out a cross-linking reaction to obtain a spinning solution; Electrospinning the spinning solution to obtain the nanofiber membrane; The mass ratio of the polylactic acid to perillaldehyde is 3g:40-60mg; The cross-linking agent is Amiao-PEG4-Amine, and the mass ratio of the polylactic acid to the cross-linking agent is 1:0.01-0.02; The mixing includes stirring mixing and ultrasonic mixing performed sequentially; The temperature of the cross-linking reaction is 40-50°C, and the time of the cross-linking reaction is 25-35 minutes; The organic solvent is a mixture of N,N-dimethylformamide and dichloromethane; The volume ratio of N,N-dimethylformamide to dichloromethane in the mixed solution of N,N-dimethylformamide and dichloromethane is 2.8-3.2:7; The dissolution temperature is 48-52°C, and the dissolution time is 28-32 minutes; The voltage of the electrospinning is 18-22 kV, and the injection speed of the electrospinning is 0.0048-0.0052 mm / s; The chilled fresh meat is chilled fresh mutton.

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