Preparation method of bacteriostatic one-way moisture conducting and preserving pad for livestock and poultry fresh meat

Abstract

The application belongs to the field of food fresh-keeping packaging materials, and particularly relates to a preparation method of a bacteriostatic one-way moisture-conducting fresh-keeping pad for livestock and poultry fresh meat, which comprises the following steps: preparing a water-locking layer of sodium alginate / gelatin fibers by wet spinning, preparing a water-absorbing layer of polyvinyl alcohol / chitosan fibers on the upper surface of the water-locking layer by electrospinning, and preparing a hydrophobic layer of linalool-containing poly-caprolactone fibers on the upper surface of the water-absorbing layer by electrospinning. The prepared bacteriostatic one-way moisture-conducting fresh-keeping pad has excellent one-way moisture conductivity, and can quickly and directionally transport fresh blood water from the top of the fresh-keeping pad to the bottom of the pad; the fresh-keeping pad has a water-absorbing layer and a water-locking layer, which can avoid liquid accumulation at the bottom of the fresh meat, and the top layer releases the bacteriostatic agent linalool to prolong the shelf life of the meat; and the electrospun materials used are non-toxic and safe and easy to degrade.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of food preservation packaging materials, and particularly relates to a preparation method of a bacteriostatic one-way moisture guiding preservation pad for livestock and poultry fresh meat. BACKGROUND

[0002] Livestock and poultry fresh meat is often packaged in a tray with good display effect during storage and sales. The fresh meat is directly placed in a plastic tray and covered with a preservation film for sales. However, the tissue fluid such as blood water in the livestock and poultry fresh meat will gradually seep out to the surface of the meat and accumulate at the bottom of the tray. The nutrient-rich meat and the blood water environment provide nutrients and living conditions for the growth and reproduction of spoilage bacteria, which aggravates the spoilage of the fresh meat, shortens the shelf life, and in addition, the accumulation of blood water at the bottom of the tray damages the appearance of the product and reduces the willingness of consumers to purchase. In view of the problem of seepage of tissue fluid of fresh meat during storage, a bacteriostatic water-absorbing pad is placed at the bottom of the tray packaging to absorb the seepage to maintain the quality of the fresh meat and prolong the shelf life.

[0003] Most of the water-absorbing pads on the market are made of non-woven fabric. Such water-absorbing pads have weak preservation effect: first, the water-absorbing capacity of the pad material is low; second, the pad material is single and has no water barrier capacity. The lower part of the fresh meat is attached to the water-absorbed pad, and the meat is wet, which is easy for spoilage bacteria to proliferate; third, the pad has no bacteriostatic effect. Therefore, it is of great significance to solve the problem of tissue fluid pollution of fresh livestock and poultry meat.

[0004] The preservation pad is endowed with one-way moisture guiding function for the blood water tissue fluid seeping out of the meat to improve the preservation effect. The transmission mode of tissue fluid on the pad fabric mainly includes three processes of absorption, diffusion and evaporation. One-way moisture guiding means that the absorption, diffusion and evaporation of water can only be transmitted from one side of the fabric to the other side, and cannot be transmitted reversely, and the transmission has directionality. The mechanism of one-way moisture guiding is that the difference in wettability between the two sides of the pad will form an additional pressure difference. When the water is in the hydrophobic layer, it can penetrate into the hydrophilic layer along the vertical surface direction capillary; when the water reaches the hydrophilic layer, it will diffuse along the horizontal capillary and will not penetrate into the hydrophobic layer, realizing one-way moisture guiding of the pad. In this way, the meat and the seeping blood water can be separated.

[0005] The preparation process of the cushion material affects the safety of the food it packages. The main preparation methods of one-way moisture transfer composite material are structure design method, chemical finishing method, direct forming method and electrospinning method. The first three methods have the limitations of complex process, environmental pollution and poor durability, while electrospinning has the advantages of simple operation and high efficiency. The fabric cushion made of nanofibers by electrospinning has a higher specific surface area, which is beneficial to capillary action and one-way moisture transfer, and has active substance packaging capacity. Electrospinning is used to prepare nanofiber materials, including hydrophobic fibers (such as polyurethane, polystyrene, polyvinylidene fluoride, polylactic acid, etc.) and hydrophilic fibers, and the organic solvents used for hydrophobic fiber spinning are N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, dimethyl sulfoxide, acetone, etc. These organic solvents may remain in the prepared spinning fibers, and may cause food contamination after contacting with the packaged food. Therefore, it is the key to realize the safety of meat cushion material to avoid using harmful organic solvents in the electrospinning process to prepare harmless spinning materials. SUMMARY

[0006]

Technical problems

[0007] The water absorption capacity of the water absorption cushion on the market is insufficient, it has no water isolation capacity, lacks bacteriostatic effect, and has weak fresh-keeping effect on fresh products. It is necessary to develop a water absorption cushion with water isolation capacity to inhibit bacterial proliferation. Electrospinning technology can prepare nanofiber fabric with higher specific surface area and active substance packaging capacity, and has the advantage of simple process. Electrospinning can prepare hydrophobic fibers for one-way moisture transfer material, and the hydrophobic raw materials need to be dissolved with organic solvents, but most of the organic solvents are harmful to health, which limits their application in food packaging field.

[0008]

Technical solutions

[0009] In order to overcome the above problems, the application develops a preparation method of bacteriostatic one-way moisture transfer fresh-keeping pad for livestock and poultry fresh meat. First of all, the application has excellent one-way moisture transfer performance, the exuded blood water can be quickly transferred from the surface of the meat to the inside of the fresh-keeping pad, isolating the contact between the blood water and the fresh meat, and solving the problem of blood water pollution. Secondly, the bacteriostatic agent in the fresh-keeping pad can inhibit the growth of microorganisms in the meat, prolonging the shelf life of fresh meat. Finally, the application uses biodegradable polyvinyl alcohol and polycaprolactone as the base material, and uses water and acetic acid as the electrospinning solvent, without using toxic and harmful organic solvents, on the one hand, the functionality of the base material is maintained, on the other hand, the safety of the packaged food and the harm to the production and use environment are avoided.

[0010] The application provides a bacteriostatic one-way moisture-conducting fresh-keeping pad, which is composed of three layers from bottom to top, namely a water-locking layer (sodium alginate / gelatin fiber), a water-absorbing layer (polyvinyl alcohol / chitosan fiber) and a bacteriostatic hydrophobic layer (poly-caprolactone fiber loaded with linalool). The structural schematic diagram of the fresh-keeping pad is shown in the accompanying Figure 1

[0011] The application also provides a preparation method of the above-mentioned bacteriostatic one-way moisture-conducting fresh-keeping pad, which comprises the following steps.

[0012] S1, preparing the water-locking layer by wet spinning technology through sodium alginate / gelatin spinning solution;

[0013] S2, preparing the water-absorbing layer on the upper surface of the water-locking layer by electrospinning technology through polyvinyl alcohol / chitosan spinning solution;

[0014] S3, preparing the hydrophobic layer on the upper surface of the water-absorbing layer by electrospinning technology through poly-caprolactone spinning solution loaded with linalool, so as to obtain the bacteriostatic one-way moisture-conducting fresh-keeping pad.

[0015] In an embodiment of the application, step S1 comprises the following steps.

[0016] 1) mixing sodium alginate solution and gelatin solution to prepare wet spinning solution I;

[0017] 2) wet spinning the wet spinning solution I and solidifying and forming in a calcium chloride coagulation bath to prepare sodium alginate / gelatin fiber;

[0018] 3) cutting the sodium alginate / gelatin fiber, laying it on a screen, freezing at-60 to-20 DEG C for 12 to 36 h, and freeze-drying at a pressure of 1 to 50 Pa and a temperature of-50 to-40 DEG C for 36 to 60 h to prepare the water-locking layer.

[0019] Further, in an embodiment of the application, in step S1 1), the concentration of the sodium alginate solution is 1.5 to 4 g / 100 g, the concentration of the gelatin solution is 1.5 to 4 g / 100 g, and the mixing volume ratio of the sodium alginate solution to the gelatin solution is 1:1 to 4:1; in step S1 2), the concentration of the calcium chloride coagulation bath is 2 to 4 g / 100 g, and the solidifying and forming condition is 20 to 30 DEG C for 0.5 to 1.5 h.

[0020] Further, in an embodiment of the application, step S1 comprises the following steps.

[0021] ​1) Spinning solution preparation: prepare a sodium alginate solution with a concentration of 1.5-4.0 g / 100 g and a gelatin solution with a concentration of 1.5-4 g / 100 g, and adjust the pH value of the gelatin solution to 8-9 with triethanolamine, mix the sodium alginate solution and the gelatin solution at a volume ratio of 1:1-4:1, and add 1-5 mL / 100 mL of glycerol to the mixed solution to obtain a wet spinning solution I;

[0022] 2) Spinning forming: wet spinning of the wet spinning solution I, solidification forming in a calcium chloride coagulation bath with a concentration of 2-4 g / 100 g, standing in the coagulation bath for 0.5-1.5 h for sufficient crosslinking, washing, and obtaining a sodium alginate / gelatin fiber;

[0023] 3) Post-processing: cutting the sodium alginate / gelatin fiber, laying it on a screen, freezing at -60 to -20°C for 12-36 h, freeze-drying at a pressure of 1-50 Pa and a temperature of -50 to -40°C for 36-60 h to form a water-locking layer, and obtaining a single-layer fiber membrane.

[0024] Further, in an embodiment of the present application, step S1 comprises the following steps:

[0025] 1) Spinning solution preparation: adding sodium alginate powder to deionized water while stirring, standing for 2-4 h, and continuing to stir for 1-3 h after the sodium alginate is fully swollen to obtain a sodium alginate solution with a concentration of 1.5-4 g / 100 g; adding gelatin to deionized water, stirring at 40-50°C for 1-3 h, adjusting the pH value of the gelatin solution to 8-9 with triethanolamine, and obtaining a gelatin solution with a concentration of 1.5-4 g / 100 g; mixing the sodium alginate solution and the gelatin solution at a volume ratio of 1:1-4:1, adding 1-5% of glycerol to the mixed solution, stirring at 20-30°C for 3-5 h, and obtaining a wet spinning solution I after ultrasonic defoaming;

[0026] 2) Spinning forming: injecting the wet spinning solution I into a syringe, and advancing the syringe pump at a speed of 0.5-1.5 mL / min, and the spinning solution is solidified and formed in a calcium chloride coagulation bath with a concentration of 2-4 g / 100 g through a needle with an inner diameter of 0.2-0.3 mm, standing in the coagulation bath for 0.5-1.5 h for sufficient crosslinking, and washing with deionized water three times to obtain a sodium alginate / gelatin fiber;

[0027] 3) Post-processing: cutting the sodium alginate / gelatin fiber, laying it on a screen with a pore size of 0.1-0.2 mm, freezing at -60 to -20°C for 12-36 h, and placing it in a freeze-drying machine for treatment at a pressure of 1-50 Pa and a temperature of -50 to -40°C for 36-60 h to form a water-locking layer, and obtaining a single-layer fiber membrane.

[0028] In an embodiment of the present application, step S2 comprises the following steps:

[0029] 1) mixing polyvinyl alcohol aqueous solution and chitosan acetic acid aqueous solution to prepare mixed spinning solution II;

[0030] 2) electrospinning the mixed spinning solution II onto the upper surface of the water-locking layer to prepare polyvinyl alcohol / chitosan fiber membrane;

[0031] 3) sealing the polyvinyl alcohol / chitosan fiber membrane with glutaraldehyde hydrochloric acid aqueous solution for 18-30 h, heating at 30-60℃ for 20-40 min after the reaction, and preparing the water-absorbing layer from the polyvinyl alcohol / chitosan fiber membrane which is insoluble in water.

[0032] Further, in one embodiment of the present application, in step S21), the concentration of the polyvinyl alcohol aqueous solution is 5-10 g / 100 g, the concentration of chitosan in the chitosan acetic acid aqueous solution is 3-8 g / 100 g, the concentration of acetic acid is 4-6 mL / 100 mL, and the volume ratio of the polyvinyl alcohol aqueous solution to the chitosan acetic acid aqueous solution is 1:1-4:1; in step S22), the spinning temperature is 30-35℃, and the spinning humidity is 15%-25%; and in step S23), the glutaraldehyde hydrochloric acid aqueous solution is prepared by mixing glutaraldehyde aqueous solution and hydrochloric acid aqueous solution, the volume ratio of the glutaraldehyde aqueous solution to the hydrochloric acid aqueous solution is 8:1-12:1, the concentration of the glutaraldehyde aqueous solution is 20-30 g / 100 g, and the concentration of the hydrochloric acid aqueous solution is 30-42 g / 100 g.

[0033] Further, in one embodiment of the present application, step S2 comprises the following steps:

[0034] 1) Spinning solution preparation: preparing polyvinyl alcohol aqueous solution with a concentration of 5-10 g / 100 g, preparing chitosan acetic acid aqueous solution with a chitosan concentration of 3-8 g / 100 g and an acetic acid concentration of 4-6 mL / 100 mL, mixing the polyvinyl alcohol aqueous solution and the chitosan acetic acid aqueous solution at a volume ratio of 1:1-4:1, and removing insoluble substances to obtain mixed spinning solution II;

[0035] 2) Spinning forming: electrospinning the mixed spinning solution II onto the upper surface of the water-locking layer under the condition of a spinning temperature of 30-35℃ and a humidity of 15%-25% to prepare polyvinyl alcohol / chitosan fiber membrane;

[0036] 3) Post-treatment: mixing 20-30 g / 100 g of glutaraldehyde aqueous solution and 30-42 g / 100 g of hydrochloric acid aqueous solution at a volume ratio of 8:1-12:1 to obtain glutaraldehyde hydrochloric acid aqueous solution, reacting the polyvinyl alcohol / chitosan fiber membrane with the glutaraldehyde hydrochloric acid aqueous solution in a closed drying dish at 20-30℃ for 18-30 h, placing the reaction product in an oven at 30-60℃ for 20-40 min after the reaction, preparing the water-absorbing layer from the polyvinyl alcohol / chitosan fiber membrane which is insoluble in water, and obtaining the double-layer fiber membrane with the water-locking layer and the water-absorbing layer.

[0037] Further, in one embodiment of the present application, step S2 comprises the following steps:

[0038] 1) Spinning solution preparation: polyvinyl alcohol (CAS: 9002-89-5) with molecular weight Mw = 195000 is dissolved in deionized water, stirred at 90-98℃ for 7-10h at 100-300r / min, to obtain a polyvinyl alcohol aqueous solution with a concentration of 5-10g / 100g; chitosan (CAS: 9012-76-4) is dissolved in an aqueous acetic acid solution with a concentration of 4-6mL / 100mL, stirred at 55-75℃ for 7-10h at 100-300r / min, to obtain a chitosan acetic acid aqueous solution with a chitosan concentration of 3-8g / 100g, the polyvinyl alcohol aqueous solution and the chitosan acetic acid aqueous solution are mixed uniformly at a volume ratio of 1:1-4:1, then centrifuged at 800-1500r / min for 5-15min, and the insoluble matter is discarded, to obtain a mixed spinning solution II of polyvinyl alcohol and chitosan;

[0039] 2) Spinning forming: using an electrospinning device, under the conditions of a spinning temperature of 30-35℃, a humidity of 15%-25%, a spinning voltage of 12-20kV, a pushing speed of 0.4-0.6mL / h, an inner diameter of the needle of 0.4-0.8mm, a rotating speed of the receiving drum of 15-25r / min, and a distance from the needle to the receiver of 10-20cm, the mixed spinning solution II is electrospun onto the upper surface of the water-locking layer, and the spinning time is 2-4h, to prepare a polyvinyl alcohol / chitosan fiber membrane;

[0040] 3) Post-processing: 20-30g / 100g of a glutaraldehyde aqueous solution and 30-42g / 100g of a hydrochloric acid aqueous solution are mixed at a volume ratio of 8:1-12:1 to obtain a glutaraldehyde hydrochloric acid solution, and the polyvinyl alcohol / chitosan fiber membrane is subjected to steam reaction with the glutaraldehyde hydrochloric acid aqueous solution in a closed drying dish at 20-30℃ for 18-30h, and then heated in an oven at 30-60℃ for 20-40min, to obtain a water-absorbing layer which is insoluble in water, thereby obtaining a double-layer fiber membrane with a water-locking layer and a water-absorbing layer.

[0041] In one embodiment of the present application, step S3 comprises the following steps:

[0042] 1) An aqueous acetic acid solution containing polycaprolactone and linalool is prepared to obtain a mixed spinning solution III;

[0043] 2) The mixed spinning solution III is electrospun onto the upper surface of the water-absorbing layer to obtain a bacteriostatic one-way moisture-conducting fresh-keeping pad.

[0044] Further, in one embodiment of the present application, in step S3 1), the acetic acid concentration of the mixed spinning solution III is 50-82 mL / 100 mL, the polycaprolactone concentration is 40-60 g / 100 g, and the linalool concentration is 10-40 mL / 100 mL; in step S3 2), the ambient temperature is 15-30℃, and the relative humidity is 40%-60%.

[0045] Further, in one embodiment of the present application, step S3 includes the following steps:

[0046] 1) Spinning solution preparation: an aqueous solution with an acetic acid concentration of 50-82 mL / 100 mL, a polycaprolactone concentration of 40-60 g / 100 g, and a linalool concentration of 10-40 mL / 100 mL is prepared to obtain a mixed spinning solution III;

[0047] 2) Spinning forming: the mixed spinning solution III is electrospun onto the upper surface of the water-absorbing layer of the two-layer fiber membrane under the condition that the ambient temperature is 15-30℃ and the relative humidity is 40%-60%, and the spinning time is 10-30 min to obtain a three-layer fiber membrane with a hydrophobic layer, a water-locking layer, and a water-absorbing layer.

[0048] Further, in one embodiment of the present application, step S3 includes the following steps:

[0049] 1) Spinning solution preparation: polycaprolactone (CAS: 24980-41-4) with a molecular weight Mn of 80000 and linalool are dissolved in an aqueous solution with an acetic acid concentration of 90 mL / 100 mL, stirred at 20-30℃ at 300-500 r / min for 18-30 h, and a mixed spinning solution III with a polycaprolactone concentration of 40-60 g / 100 g and a linalool concentration of 10-40 mL / 100 mL is obtained;

[0050] 2) Spinning forming: the mixed spinning solution III is electrospun onto the upper surface of the water-absorbing layer of the two-layer fiber membrane using an electrospinning device under the condition that the ambient temperature is 15-30℃, the relative humidity is 40%-60%, the spinning voltage is 10-15 kV, the pushing speed is 1.0-1.8 mL / h, the inner diameter of the needle is 0.4-0.8 mm, the rotating speed of the receiving drum is 15-25 r / min, and the distance between the needle and the receiver is 10-20 cm, and the spinning time is 10-30 min to obtain a three-layer fiber membrane with a hydrophobic layer, a water-locking layer, and a water-absorbing layer.

[0051] The present application also provides the application of the above-mentioned bacteriostatic one-way moisture-conducting fresh-keeping pad in the field of fresh meat preservation of livestock and poultry.

[0052]

Advantages

[0053] The present application has the following advantages:

[0054] (1) The bacteriostatic one-way wetting fresh-keeping pad prepared by the present application has excellent one-way wetting property, and water is transferred from the top layer to the bottom layer within 10s, and cannot be transferred reversely, so as to achieve the purpose of isolating blood water from contacting with meat, and the blood water is absorbed and fixed by the water-locking layer. The bacteriostatic one-way wetting fresh-keeping pad can realize the functions of quickly removing water exuded from meat and reducing liquid accumulation at the contact position between meat and the fresh-keeping pad.

[0055] (2) The bacteriostatic one-way wetting fresh-keeping pad prepared by the present application uses linalool as a bacteriostatic agent, has excellent bacteriostatic property, and the bacteriostatic fresh-keeping performance is better than that of the non-woven fabric water-absorbing pad on the market, so that the freshness of fresh chicken can be maintained, including reducing total number of colonies and volatile base nitrogen content.

[0056] (3) The electrospinning solution base material used in the present application adopts polyvinyl alcohol, chitosan and polycaprolactone, and the obtained fibers have the advantages of safety, non-toxicity and easy degradation, and will not cause long-term pollution to the environment after use.

[0057] (4) The electrospinning solution used in the present application uses water and acetic acid as solvents, and does not use toxic organic solvents, so as to avoid the problems of environmental pollution and residue in the pad product caused by organic solvents in the production of the pad. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 It is a structural schematic diagram of the bacteriostatic one-way wetting fresh meat fresh-keeping pad.

[0059] Figure 2 It is a scanning electron microscope image and its diameter distribution diagram of the comparative example 1 (polyvinyl alcohol / chitosan nanofiber, A), the comparative example 2 (polycaprolactone nanofiber, B) and the comparative example 3 (polycaprolactone nanofiber carrying linalool, C).

[0060] Figure 3 It is a hydrophilic and hydrophobic relationship of the comparative example 3 (polycaprolactone nanofiber carrying linalool, PCL / LL) and the comparative example 1 (polyvinyl alcohol / chitosan nanofiber, PVA / CS), and a one-way wetting effect diagram of the comparative example 4 (double-layer composite fiber of PCL / LL and PVA / CS).

[0061] Figure 4 It is a total number of colonies (TVC) change diagram of fresh chicken in 4℃ storage of the example 2 (bacteriostatic one-way wetting pad, experimental group), the comparative example 6 (without pad, blank group) and the comparative example 5 (commercial non-woven fabric pad, control group).

[0062] Figure 5 It is a volatile base nitrogen (TVB-N) change diagram of fresh chicken in 4℃ storage of the example 2 (bacteriostatic one-way wetting pad, experimental group), the comparative example 6 (without pad, blank group) and the comparative example 5 (commercial non-woven fabric pad, control group). DETAILED DESCRIPTION

[0063] Test method:

[0064] Diameter distribution test method: Put Comparative Example 1, Comparative Example 2 and Comparative Example 3 on the conductive silica gel, and after gold spraying treatment, use a Japanese Hitachi S4800 field emission scanning electron microscope to determine the surface morphology of Comparative Example 1, Comparative Example 2 and Comparative Example 3, use the ruler tool of Image J 1.32 software to randomly intercept 100 fibers in the picture, calculate the fiber diameter and draw the fiber diameter distribution graph.

[0065] Contact angle test method: Comparative Example 1, Comparative Example 3 and Comparative Example 4 are evenly fixed on a glass slide, and the water contact angle is measured using a surface contact angle tester OCA15EC, 1 μL of deionized water is released on the surface of Comparative Example 1, Comparative Example 3 and Comparative Example 4 respectively using a microsyringe, and images are collected at 0, 1, 5, 10 and 30 seconds, and the angle between the droplet and the fiber surface is analyzed using SCA-20 software.

[0066] Bacteriostatic performance test method: refer to GB 4789.2-2016 "Food Microbiology Test Determination of Total Number of Colonies", under sterile conditions, chicken is beaten and mixed in sterile physiological saline, and the sample solution is diluted by 10 times, the appropriate gradient of diluent is mixed with sterile medium, after the agar is coagulated, it is cultured in a 37℃±1℃ incubator for 48h±2h, and the total number of colonies is calculated.

[0067] Test method for volatile nitrogen: refer to GB 5009.228-2016 "National Food Safety Standard Determination of Volatile Nitrogen in Food" for determination of TVB-N content of chicken sample by semi-micro nitrogen determination method. The unit is mg / 100g sample.

[0068] Example 1

[0069] A preparation method of a bacteriostatic one-way moisture-conducting three-layer fiber film, the steps are as follows:

[0070] S1, preparation of water-locking layer:

[0071] 1) Preparation of spinning solution: take 2g of sodium alginate, add sodium alginate powder into 100mL of deionized water while stirring, stand for 3h, after the sodium alginate is fully swollen, continue to stir for 2h, prepare a 2g / 100g sodium alginate solution; take 2g of gelatin, add 100mL of deionized water, stir at 45℃ for 2h, adjust the pH value of the gelatin solution to 8.2 with triethanolamine, prepare a gelatin solution with a concentration of 2g / 100g; mix 70mL of sodium alginate solution with 30mL of gelatin solution, add 1mL of glycerol, mix and stir at room temperature for 4h, and then ultrasonic defoaming to obtain a wet spinning solution I;

[0072] 2) Spinning: wet spinning solution I was injected into a syringe, the injection pump pushing speed was 1 mL / min, wet spinning solution I was solidified into the calcium chloride concentration of 3 g / 100 g coagulation bath through the syringe needle with an inner diameter of 0.25 mm, and was placed in the coagulation bath for 1 h to be fully cross-linked, then washed with deionized water for three times to obtain sodium alginate / gelatin fiber;

[0073] 3) Post-processing: sodium alginate / gelatin fiber was cut into pieces, laid on a sieve with a pore size of 0.154 mm, frozen at-40℃ for 24 h, and then placed in a freeze dryer, treated at a pressure of 30 Pa and a temperature of-45℃ for 48 h to obtain a single-layer fiber membrane of the water-locking layer.

[0074] S2, Preparation of the water-absorbing layer:

[0075] 1) Spinning solution preparation: 0.6 g of polyvinyl alcohol (CAS: 9002-89-5) with a molecular weight Mw = 195000 was dissolved in 10 mL of deionized water, stirred at 95℃ and 200 r / min for 8 h to obtain a polyvinyl alcohol aqueous solution with a concentration of 6 g / 100 g; 0.4 g of chitosan (CAS: 9012-76-4) was dissolved in 10 mL of 5 mL / 100 mL acetic acid aqueous solution, stirred at 65℃ and 200 r / min for 8 h to obtain a chitosan acetic acid aqueous solution with a chitosan concentration of 4 g / 100 g, the polyvinyl alcohol aqueous solution and the chitosan acetic acid aqueous solution were mixed at a volume ratio of 7:3, stirred at 65℃ and 200 r / min for 4 h, centrifuged at 1000 r / min for 10 min, and the insoluble matter was discarded to obtain a mixed spinning solution II of polyvinyl alcohol and chitosan;

[0076] 2) Spinning: using an electrospinning device, under the conditions of a spinning temperature of 30℃, a humidity of 20%, a spinning voltage of 15 kV, a pushing speed of 0.5 mL / h, a needle inner diameter of 0.6 mm, a receiving drum rotating speed of 20 r / min, and a needle-to-receiver distance of 15 cm, the mixed spinning solution II was electrospun onto the upper surface of the water-locking layer, and the spinning time was 3 h to prepare a polyvinyl alcohol / chitosan fiber membrane;

[0077] 3) Post-processing: 25 g / 100 g glutaraldehyde aqueous solution and 36 g / 100 g hydrochloric acid aqueous solution were mixed at a volume ratio of 10:1 to obtain a glutaraldehyde hydrochloric acid aqueous solution, and the polyvinyl alcohol / chitosan fiber membrane was subjected to glutaraldehyde hydrochloric acid aqueous solution vapor reaction in a closed dry dish at room temperature for 24 h, then was placed in a 45℃ oven for heating for 30 min to remove residual glutaraldehyde hydrochloric acid gas, and the polyvinyl alcohol / chitosan fiber membrane was made into a water-insoluble water-absorbing layer to obtain a double-layer fiber membrane with a water-locking layer and a water-absorbing layer.

[0078] S3, Preparation of the hydrophobic layer

[0079] 1) Spinning solution preparation: 3 g of polycaprolactone with a molecular weight Mn = 80000 (CAS: 24980-41-4) and 2 ml of linalool were dissolved in 5 mL of a 90 mL / 100 mL aqueous solution of acetic acid, stirred at 400 r / min at 25°C for 24 h, and a mixed spinning solution III was obtained;

[0080] 2) Spinning forming: using an electrospinning device, under the conditions of ambient temperature 25°C, humidity 50%, spinning voltage 12 kV, pushing speed 1.4 mL / h, needle inner diameter 0.6 mm, receiving drum rotating speed 20 r / min, and needle to receiver 15 cm, the mixed spinning solution III was electrospun onto the upper surface of the water-absorbing layer of the two-layer fiber membrane, and the spinning time was 10 min, to obtain a three-layer fiber membrane with a hydrophobic layer, a water-locking layer, and a water-absorbing layer.

[0081] Example 2

[0082] The antibacterial one-way moisture management pad was applied to the packaging of chilled fresh chicken, and the preservation effect on the chilled fresh chicken was tested:

[0083] 150 g of fresh chicken was placed on the antibacterial one-way moisture management pad prepared in Example 1, placed in a plastic tray and sealed with a preservative film, and stored in a 4°C refrigerator. The total number of colonies and the value of total volatile basic nitrogen of the chicken were tested at 0, 2, 4, 7, and 10 days of storage.

[0084] Comparative Example 1

[0085] Polyvinyl alcohol / chitosan fiber (PVA / CS) was prepared as follows:

[0086] 1) Spinning solution preparation: 0.6 g of polyvinyl alcohol with a molecular weight Mw = 195000 (CAS: 9002-89-5) was dissolved in 10 mL of deionized water, stirred at 200 r / min at 95°C for 8 h, and a polyvinyl alcohol aqueous solution with a concentration of 6 g / 100 g was obtained. 0.4 g of chitosan (CAS: 9012-76-4) was dissolved in 10 mL of a 5 mL / 100 mL aqueous solution of acetic acid, stirred at 200 r / min at 65°C for 8 h, and a chitosan acetic acid solution with a chitosan concentration of 4 g / 100 g was obtained. The polyvinyl alcohol aqueous solution and the chitosan acetic acid solution were mixed in a volume ratio of 7:3, stirred at 200 r / min at 65°C for 4 h, centrifuged at 1000 r / min for 10 min, and the insoluble material was discarded, to obtain a mixed spinning solution II of polyvinyl alcohol and chitosan;

[0087] 2) Spinning: using electrospinning equipment, under the conditions of a spinning temperature of 30°C, a humidity of 20%, a spinning voltage of 15 kV, a pushing speed of 0.5 mL / h, a needle inner diameter of 0.6 mm, a receiving drum rotating speed of 20 r / min, and a needle-to-receiver distance of 15 cm, the mixed spinning solution II was electrospun for 3 h to prepare a polyvinyl alcohol / chitosan fiber membrane;

[0088] 3) Post-processing: 25 g / 100 g of a glutaraldehyde aqueous solution and 36 g / 100 g of a hydrochloric acid aqueous solution were mixed at a volume ratio of 10:1 to obtain a glutaraldehyde hydrochloric acid solution, and the polyvinyl alcohol / chitosan fiber membrane was subjected to a glutaraldehyde hydrochloric acid solution vapor reaction in a closed dry dish at room temperature for 24 h, and then was placed in an oven at 45°C for heating for 30 min to remove residual glutaraldehyde hydrochloric acid gas, thereby preparing a water-insoluble polyvinyl alcohol / chitosan fiber membrane.

[0089] Comparative Example 2

[0090] Poly caprolactone nanofiber (PCL), prepared as follows:

[0091] 1) Spinning solution preparation: 3 g of poly caprolactone (CAS: 24980-41-4) with a molecular weight Mn = 80000 and 5 mL of an acetic acid aqueous solution with a concentration of 90 mL / 100 mL were stirred at 25°C at 400 r / min for 24 h to obtain a poly caprolactone spinning solution III with a concentration of 60 g / 100 g;

[0092] 2) Spinning: using electrospinning equipment, under the conditions of an ambient temperature of 25°C, a humidity of 50%, a spinning voltage of 12 kV, a pushing speed of 1.4 mL / h, a needle inner diameter of 0.6 mm, a receiving drum rotating speed of 20 r / min, and a needle-to-receiver distance of 15 cm, the spinning solution III was electrospun for 10 min to prepare a poly caprolactone nanofiber (PCL).

[0093] Comparative Example 3

[0094] Linalool-containing poly caprolactone nanofiber (PCL / LL), prepared as follows:

[0095] 1) Spinning solution preparation: 3 g of poly caprolactone (CAS: 24980-41-4) with a molecular weight Mn = 80000 and 2 mL of linalool were dissolved in 5 mL of an acetic acid aqueous solution with a concentration of 90 mL / 100 mL, and the mixture was stirred at 25°C at 400 r / min for 24 h to obtain a mixed spinning solution III with a poly caprolactone concentration of 60 g / 100 g and a linalool concentration of 40 mL / 100 mL;

[0096] 2) Spinning forming: using electrostatic spinning equipment, under the conditions of ambient temperature 25℃, relative humidity 50%, spinning voltage 12kV, propelling speed 1.4mL / h, needle inner diameter 0.6mm, receiving roller rotating speed 20r / min and needle to receiver distance 15cm, the mixed spinning solution III is electrospun, the spinning time is 10min, to obtain a three-layer fiber membrane with a hydrophobic layer, a water-locking layer and a water-absorbing layer.

[0097] Comparative Example 4

[0098] A double-layer fiber membrane with a hydrophobic layer and a water-absorbing layer is prepared as follows:

[0099] The difference from Example 1 is that no water-locking layer is prepared.

[0100] Comparative Example 5

[0101] A commercially available non-woven fabric pad is applied to the packaging of chilled fresh chicken, and the fresh-keeping effect on the chilled fresh chicken is tested:

[0102] The difference from Example 2 is that the antibacterial one-way moisture transfer pad is replaced by a commercially available non-woven fabric pad.

[0103] Comparative Example 6

[0104] The fresh-keeping ability of chilled fresh chicken is tested:

[0105] The difference from Example 2 is that no antibacterial one-way moisture transfer pad is used.

[0106] Comparative Example 7

[0107] A preparation method of an antibacterial one-way moisture transfer fresh-keeping pad is as follows:

[0108] The difference from Example 1 is that in step S3 2), the spinning time is 30min.

[0109] Comparative Example 8

[0110] A preparation method of an antibacterial one-way moisture transfer fresh-keeping pad is as follows:

[0111] The difference from Example 1 is that in step S3 2), the spinning time is 1h.

[0112] Comparative Example 9

[0113] Polyvinyl alcohol / chitosan fiber (PVA / CS) is prepared as follows:

[0114] The difference from Comparative Example 1 is that in step 2), the spinning temperature is 25℃ and the spinning humidity is 40%.

[0115] Comparative Example 10

[0116] Polyvinyl alcohol / chitosan fiber (PVA / CS) was prepared by the following method:

[0117] The difference between the present example and Comparative Example 1 is that the spinning temperature is 25℃ and the spinning humidity is 50% in step 2).

[0118] Figure 2 For the scanning electron microscope images, it can be seen that the fiber morphology and fiber diameter distribution of PVA / CS (Comparative Example 1), PCL (Comparative Example 2) and PCL / LL (Comparative Example 3) are shown in FIG. 1, FIG. 2 and FIG. 3, respectively. Figure 2 It can be seen that the three fiber structures are stable, smooth and have no beading and broken filament phenomenon, indicating that the concentration of each component in the spinning solution is appropriate and uniform stretching in the electrospinning process. Figure 2 It can be seen from FIG. 4A that the PVA / CS fiber diameter distribution is between 38.01-292.88 nm. Figure 2 It can be seen from FIG. 4B that the PCL fiber diameter distribution is between 74.54-437.54 nm. Figure 2 It can be seen from FIG. 4C that the PCL / LL fiber diameter distribution is between 102.54-890.04 nm. Compared with the PCL fiber, the PCL / LL fiber diameter distribution increases, and the increase in fiber diameter indicates that the antibacterial agent linalool LL is successfully encapsulated into the base material PCL fiber. Thus, the scanning electron microscope images show that the electrospinning technology successfully obtains nanofibers PVA / CS and functional nanofibers PCL / LL.

[0119] Figure 3 The water contact angle experiment results are shown in Table 1. The test method is to release the same volume of water droplets above the test material. Due to the presence of surface tension, the water droplets and the test material form a certain angle, which is the water contact angle. The water contact angle shows the hydrophilic or hydrophobic nature of the test material. If the angle is less than 90°, the material is a hydrophilic material, otherwise it is a hydrophobic material. Figure 3 It can be seen that the water contact angle on the PCL / LL fiber (Comparative Example 3) is 125° after the water droplets are stable for 30s, indicating that PCL / LL is a hydrophobic material. On the PVA / CS fiber (Comparative Example 1), the water droplets are absorbed within 1s and the water contact angle is stable at 0°, indicating that PVA / CS is a superhydrophilic material. On the double-layer composite fiber (Comparative Example 4) with hydrophobic material PCL / LL as the surface layer and superhydrophilic material PVA / CS as the bottom layer, the same volume of water droplets is released. The water contact angle is 122° at 1s, which is a hydrophobic angle. The water contact angle is 84° at 5s, which is a hydrophilic angle. Within 10s, the water droplets are absorbed from the hydrophobic surface layer side to the bottom layer and disappear in the hydrophobic surface layer. The water contact experiment results of Comparative Example 4 show that the antibacterial one-way moisture management pad has one-way moisture management, which is achieved by two asymmetric fiber membranes with significantly different wetting properties. The hydrophobic layer is changed in nature after the hydrophilic layer is compounded at the bottom of the hydrophobic layer.

[0120] The unidirectional wetting property of the antibacterial unidirectional wetting and preserving pad is also related to the capillary force. When the water droplet is on the PVA / CS fiber, in addition to the gravity of the water droplet itself, the water droplet is also subjected to the capillary force provided by PVA / CS. The capillary force is affected by the fiber pore, and PVA / CS provides strong capillary force and specific surface area, so that the water droplet is quickly and uniformly dispersed and absorbed on PVA / CS. When the water droplet is on the PCL / LL fiber, in addition to the gravity of the water droplet itself, the water droplet is also subjected to the hydrophobic force and capillary force provided by PCL / LL. Because the hydrophobic force is greater than the gravity of the water droplet, the liquid droplet does not disperse and maintains a larger hydrophobic angle on the surface of PCL / LL. When the water droplet is released on the double-layer composite fiber of Comparative Example 4, similarly, the water droplet is subjected to its own gravity, hydrophobic force and capillary force. The gravity and the hydrophobic force are two opposite forces, which make the water droplet initially present a hydrophobic angle. Unlike the single PCL / LL fiber, the capillary force of the composite fiber of Comparative Example 4 is changed. The PVA / CS of the bottom layer has a finer fiber diameter and smaller pore. Under the action of gravity, the water droplet is in full contact with the nanofiber with high specific surface area. Once the water droplet contacts the PVA / CS fiber of the bottom layer, the strong capillary force will quickly attract the water droplet. Under the action of gravity and capillary force, the water droplet overcomes the hydrophobic force and is absorbed from the top to the bottom. The capillary force makes it quickly spread in the hydrophilic bottom, realizes the transfer of moisture, and achieves the effect of unidirectional wetting.

[0121] Figure 4 The change of TVC of chilled chicken during storage packaged with the antibacterial unidirectional wetting pad (Example 2, experimental group), commercially available non-woven cloth pad (Comparative Example 5, control group) and without using pad (Comparative Example 6, blank group) is shown. TVC is one of the key indicators for evaluating the health and safety of meat quality. The judgment standard for the freshness of chilled meat is as follows: when the TVC of meat is greater than 6Lg (CFU / g), the meat is considered to be deteriorated. From the figure, it can be seen that the TVC of the experimental group is the lowest, and the TVC of the control group is the highest. The TVC of the blank group is between the experimental group and the control group. The antibacterial unidirectional wetting pad can effectively inhibit the growth of bacteria, and the antibacterial effect is better than that of the commercially available non-woven cloth pad. The antibacterial unidirectional wetting pad can effectively inhibit the growth of bacteria, and the antibacterial effect is better than that of the commercially available non-woven cloth pad. Figure 4It can be seen that TVC showed a positive correlation trend with the extension of storage time. TVC of Comparative Example 5 increased the fastest, followed by Comparative Example 6, and the growth of microorganisms in Example 2 was slow. During the storage period of 0-7d, the TVC of Comparative Example 5 and Comparative Example 6 increased significantly (P<0.05), while the TVC of Example 2 did not increase significantly (P>0.05). Among them, on the 7th day, the TVC of Example 2 was 5.54Lg(CFU / g), which did not exceed the spoilage limit, while the TVC of Comparative Example 6 was 6.18Lg(CFU / g) and the TVC of Comparative Example 5 was 6.73Lg(CFU / g), both of which exceeded the limit. This shows that the fresh-keeping pad of the application can inhibit the growth of microorganisms and prolong the storage period of chilled chicken. This is because the chicken is in direct contact with the PCL / LL fiber, and the antibacterial agent linalool in the fiber is continuously released, which inhibits the proliferation of microorganisms in the chicken. At the same time, the one-way moisture management function prevents the chicken surface from being infiltrated by blood water and other tissue fluids, maintaining a dry state and being not conducive to the proliferation of microorganisms. On the contrary, the commercially available non-woven fabric has a larger diameter, a smaller specific surface area, and no antibacterial effect, resulting in a significant increase in TVC of the comparative example, and the antibacterial and fresh-keeping effect is lower than that of Comparative Example 6 and Example 2.

[0122] Figure 5 The change of TVB-N content of chilled chicken packaged with antibacterial one-way moisture management pad (Example 2, experimental group), commercially available non-woven fabric pad (Comparative Example 5, control group) and no pad (Comparative Example 6, blank group) during storage is shown. According to GB 2707-2016 "National Food Safety Standard Fresh (Frozen) Livestock and Poultry Products", the TVB-N value of fresh livestock and poultry meat should not exceed 15mg / 100g. From Figure 5 It can be seen that Example 2 can significantly delay the release of volatile basic nitrogen in chilled chicken. The TVB-N value of Comparative Example 5 increased the fastest, followed by Comparative Example 6, and the TVB-N value of Example 2 was significantly inhibited. Among them, on the 4th day of storage, the TVB-N value of Example 2 was 9.82mg / 100g, which was significantly lower than that of Comparative Example 6 (11.08mg / 100g) and Comparative Example 5 (11.69mg / 100g) (P<0.05). On the 4th day of storage, the TVB-N value of the chicken of Example 2 was significantly lower than the TVB-N value of the initial fresh chicken (10.71mg / 100g) (P<0.05), which shows that the chicken treated by Example 2 can still maintain the freshness of the initial chicken after 4 days of storage in terms of protein decomposition. On the 10th day of storage, the TVB-N value of Example 2 was 13.02mg / 100g, which did not exceed the spoilage limit, and was significantly lower than the TVB-N value of Comparative Example 6 (15.73mg / 100g) and Comparative Example 5 (28.7mg / 100g) which exceeded the spoilage limit (P<0.05). This shows the fresh-keeping effect of the application on chilled chicken, which further confirms the antibacterial effect and one-way moisture management effect of the fresh-keeping pad of the application.

[0123] Example 1 differs from Comparative Example 4 in that Example 1 has a water-locking layer. Although Comparative Example 4 has excellent one-way moisture transfer performance, its double-layer nanofiber layer is too thin to absorb enough liquid, resulting in difficulty in separating fresh food and liquid and failing to achieve fresh food preservation. The water-absorbing capacity of the water-locking layer of sodium alginate / gelatin fibers is 11.3 g / g, so Example 1 not only has excellent one-way moisture transfer performance, but also can absorb and fix the exudate of fresh meat, separate fresh food and liquid, and thus maintain the freshness of fresh food.

[0124] The spinning time of the hydrophobic layer of Example 1 is 10 min, that of Comparative Example 7 is 30 min, and that of Comparative Example 8 is 1 h. Due to the prolonged spinning time of the hydrophobic layer of Comparative Examples 7 and 8, the thickness of the polycaprolactone fibers increases, the hydrophobicity is enhanced, and the contact of water with the water-absorbing layer is hindered, resulting in poor one-way moisture transfer performance of the three-layer fiber membrane. After the liquid droplet is released on the hydrophobic side, Example 1 can complete the transport of the liquid droplet from the hydrophobic layer to the hydrophilic layer within 10 s, while Comparative Example 7 needs 46.3 s. The water contact angle of Comparative Example 8 is 131°, the hydrophobicity is strong, and it is difficult to complete the transport of water from the hydrophobic layer to the water-absorbing layer.

[0125] Comparative Examples 1, 9, and 10 differ in that the spinning temperature and humidity of the PVA / CS fibers are different. Comparative Example 9 forms PVA / CS fibers with beads by electrostatic spraying, indicating that the fiber stretching is uneven. Comparative Example 9 forms a granular structure instead of a fiber membrane structure. This results in a decrease in the specific surface area of the PVA / CS fibers prepared in Comparative Examples 9 and 10, which is not conducive to the generation of capillary action and one-way moisture transfer. The reason is that the solvent of the PVA / CS spinning solution is water, and water molecules need to evaporate from the solution to the air at a lower humidity and a higher temperature. If the solvent water molecules fail to completely evaporate and separate from the solute PVA / CS during the movement of the charged jet, the fiber cannot be well solidified, and a beaded structure or a granular structure is formed.

[0126] The above provided examples are not intended to limit the scope covered by the present application, and the described steps are not intended to limit the execution order. Those skilled in the art can make obvious improvements to the present application in combination with existing common knowledge, which also falls within the protection scope defined by the claims of the present application.

Claims

1. A method for preparing a bacteriostatic one-way moisture management preservative pad, characterized in that, Comprising the following steps: S1, preparing a water-locking layer: 1) Spinning solution preparation: prepare a sodium alginate solution with a concentration of 1.5-4.0 g / 100 g and a gelatin solution with a concentration of 1.5-4 g / 100 g, and adjust the pH value of the gelatin solution to 8-9 with triethanolamine, mix the sodium alginate solution and the gelatin solution at a volume ratio of 1:1-4:1, add 1-5 mL / 100 mL of glycerol to the mixed solution to obtain a wet spinning solution I; 2) Spinning forming: wet spinning of the wet spinning solution I, coagulation forming in a calcium chloride coagulation bath of 2-4 g / 100 g, standing in the coagulation bath for 0.5-1.5 h for sufficient crosslinking, washing to obtain a sodium alginate / gelatin fiber; 3) Post-treatment: cut the sodium alginate / gelatin fiber, lay it flat on a screen, freeze and freeze-dry to prepare the water-locking layer; S2, preparing a water-absorbing layer on the upper surface of the water-locking layer: 1) Spinning solution preparation: mix a polyvinyl alcohol aqueous solution and a chitosan acetic acid aqueous solution to prepare a mixed spinning solution II; the polyvinyl alcohol aqueous solution has a concentration of 5-10 g / 100 g, the chitosan acetic acid aqueous solution has a chitosan concentration of 3-8 g / 100 g and an acetic acid concentration of 4-6% v / v, and the mixed volume ratio of the polyvinyl alcohol aqueous solution to the chitosan acetic acid aqueous solution is 1:1-4:1; 2) Spinning forming: electrospinning the mixed spinning solution II onto the upper surface of the water-locking layer to prepare a polyvinyl alcohol / chitosan fiber membrane; the spinning temperature is 30-35 ℃, and the spinning relative humidity is 15%-25%; 3) Post-treatment: steam reaction of the polyvinyl alcohol / chitosan fiber membrane with a glutaraldehyde hydrochloric acid aqueous solution in a closed state for 18-30 h, heating at 30-60 ℃ for 20-40 min after the reaction to prepare a water-insoluble water-absorbing layer; the glutaraldehyde hydrochloric acid aqueous solution is prepared by mixing a glutaraldehyde aqueous solution and a hydrochloric acid aqueous solution, the volume ratio of the glutaraldehyde aqueous solution to the hydrochloric acid aqueous solution is 8:1-12:1, the glutaraldehyde aqueous solution has a concentration of 20-30 g / 100 g, and the hydrochloric acid aqueous solution has a concentration of 30-42 g / 100 g; S3, preparing a hydrophobic layer on the upper surface of the water-absorbing layer to prepare the antibacterial one-way moisture management fresh-keeping pad: 1) Spinning solution preparation: prepare an aqueous solution of acetic acid with a concentration of 50-82 mL / 100 mL, polycaprolactone with a concentration of 40-60 g / 100 g, and linalool with a concentration of 10-40 mL / 100 mL to obtain a mixed spinning solution III; 2) Spinning forming: electrospinning the mixed spinning solution III onto the upper surface of the water-absorbing layer of the two-layer fiber membrane under the condition that the ambient temperature is 15-30 ℃ and the relative humidity is 40-60%, and the spinning time is 10-30 min.

2. The production method according to claim 1, characterized by, In step S13), the freezing temperature is -60 to -20 ℃, the freezing time is 12-36 h; the freeze-drying pressure is 1-50 Pa, the freeze-drying temperature is -50 to -40 ℃, and the freeze-drying time is 36-60 h.

3. The preparation method according to claim 1, characterized in that, Step S1 comprises the following steps: 1) Spinning solution preparation: sodium alginate powder is added to deionized water while stirring, and is left to stand for 2-4 h. After the sodium alginate is fully swollen, continue stirring for 1-3 h to prepare a 1.5-4 g / 100 g sodium alginate solution. Gelatin is added to deionized water, and is stirred at 40-50 ℃ for 1-3 h. The pH value of the gelatin solution is adjusted to 8-9 using triethanolamine to obtain a gelatin solution with a concentration of 1.5-4 g / 100 g. The sodium alginate solution and the gelatin solution are mixed at a volume ratio of 1:1-4:1, and 1-5% of the volume of the mixed solution is added to glycerol. The mixture is stirred at 20-30 ℃ for 3-5 h, and is ultrasonically degassed to obtain a wet spinning solution I; 2) Spinning and forming: the wet spinning solution I is injected into a syringe, and the injection pump is advanced at a speed of 0.5-1.5 mL / min. The spinning solution is solidified into a calcium chloride coagulation bath with a concentration of 2-4 g / 100 g through a needle with an inner diameter of 0.2-0.3 mm. The fibers are left to stand in the coagulation bath for 0.5-1.5 h to allow them to be fully crosslinked, and are then washed three times with deionized water to obtain sodium alginate / gelatin fibers; 3) Post-processing: the sodium alginate / gelatin fibers are cut into small pieces, and are laid flat on a screen with a pore size of 0.1-0.2 mm. After being frozen at -60 to -20 ℃ for 12-36 h, the fibers are placed in a freeze dryer and are treated at a pressure of 1-50 Pa and a temperature of -50 to -40 ℃ for 36-60 h to form a water-locking layer, thereby obtaining a single-layer fiber membrane.

4. The preparation method according to claim 1, characterized in that, Step S2 includes the following steps: 1) Spinning solution preparation: polyvinyl alcohol with a molecular weight Mw=195000 is dissolved in deionized water, and is stirred at 100-300 r / min at 90-98 ℃ for 7-10 h to obtain a polyvinyl alcohol aqueous solution with a concentration of 5-10 g / 100 g. Chitosan is dissolved in an aqueous acetic acid solution with a concentration of 4-6 mL / 100 mL, and is stirred at 100-300 r / min at 55-75 ℃ for 7-10 h to obtain a chitosan acetic acid aqueous solution with a chitosan concentration of 3-8 g / 100 g. The polyvinyl alcohol aqueous solution and the chitosan acetic acid aqueous solution are mixed at a volume ratio of 1:1-4:1, and are centrifuged at 800-1500 r / min for 5-15 min. The insoluble matter is discarded to obtain a mixed spinning solution II of polyvinyl alcohol and chitosan; 2) Spinning and forming: using an electrospinning device, the mixed spinning solution II is electrospun onto the upper surface of the water-locking layer under the following conditions: a spinning temperature of 30-35 ℃, a humidity of 15%-25%, a spinning voltage of 12-20 kV, an advancing speed of 0.4-0.6 mL / h, a needle inner diameter of 0.4-0.8 mm, a receiving drum rotating speed of 15-25 r / min, and a needle-to-receiver distance of 10-20 cm. The spinning time is 2-4 h to prepare a polyvinyl alcohol / chitosan fiber membrane; 3) Post-processing: 20-30 g / 100 g glutaraldehyde aqueous solution and 30-42 g / 100 g hydrochloric acid aqueous solution are mixed in a volume ratio of 8:1-12:1 to obtain a glutaraldehyde hydrochloric acid solution. The polyvinyl alcohol / chitosan fiber membrane is subjected to glutaraldehyde hydrochloric acid aqueous vapor reaction in a closed dry dish at 20-30 °C for 18-30 h. After reaction, the polyvinyl alcohol / chitosan fiber membrane is placed in an oven at 30-60 °C for 20-40 min to make the water-absorbing layer insoluble in water, obtaining a double-layer fiber membrane with a water-locking layer and a water-absorbing layer.

5. The preparation method according to claim 1, characterized in that, Step S3 comprises the following steps: 1) Spinning solution preparation: polycaprolactone (CAS: 24980-41-4) with a molecular weight Mn=80000 and linalool are dissolved in an aqueous solution of acetic acid with a concentration of 90 mL / 100 mL, stirred at 20-30 °C at 300-500 r / min for 18-30 h, to obtain a mixed spinning solution III with a polycaprolactone concentration of 40-60 g / 100 g and a linalool concentration of 10-40 mL / 100 mL; 2) Spinning forming: using an electrospinning device, under the conditions of ambient temperature 15-30 °C, relative humidity 40-60%, spinning voltage 10-15 kV, pushing speed 1.0-1.8 mL / h, needle inner diameter 0.4-0.8 mm, receiving drum rotating speed 15-25 r / min, and needle to receiver distance 10-20 cm, the mixed spinning solution III is electrospun onto the upper surface of the water-absorbing layer of the two-layer fiber membrane, and the spinning time is 10-30 min, obtaining a three-layer fiber membrane with a hydrophobic layer, a water-locking layer and a water-absorbing layer.

6. The antibacterial one-way moisture-permeable fresh-keeping pad prepared by the preparation method of any one of claims 1-5.

7. The application of the antibacterial one-way moisture-permeable fresh-keeping pad of claim 6 in the field of fresh meat preservation of livestock and poultry.

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