Non-woven fabric packaging bag with fresh-keeping and bacteriostatic effects and application

Abstract

The invention belongs to the technical field of fruit and vegetable fresh-keeping, and particularly relates to a fresh-keeping antibacterial material and a preparation method thereof. The non-woven fabric packaging bag with the preservation and bacteriostasis functions is characterized in that a dry modified non-woven fabric serves as a base layer of the packaging bag, a film coating solution A is firstly coated on the non-woven fabric, then a ClO2 powder layer is evenly scattered on the non-woven fabric, and finally a film coating solution B is coated on the non-woven fabric. According to the packaging bag, the surface of the packaging bag is coated with the film with the preservation and bacteriostasis effects, the film does not make direct contact with the fruits, the acceptability of consumers is improved, the complex and tedious process of direct coating operation on the fruits is avoided, and continuous sterilization in the fruit storage and transportation process is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of fruit and vegetable preservation, and particularly relates to a non-woven packaging bag with preservation and antibacterial functions and an application thereof. Background Art

[0002] According to the prior art, a common method for preserving fruits and vegetables is to coat the surface of fruits and vegetables with one or more layers of fresh-keeping and antibacterial films. The above method can achieve longer-term preservation and better antibacterial effect on fruits and vegetables. However, the above method has the following disadvantages: (1) It is difficult to apply it on a large scale. Farmers or individual retailers need to first purchase the corresponding coating solution, and then coat the fruits one by one and dry them. In addition, the coating amount is difficult to control during the coating process. If the coating thickness is not enough, the preservation effect will be compromised. If the coating thickness is too thick, the coating solution will be wasted and it may also affect the normal respiration and metabolism of fruits and vegetables. (2) In the perception of most consumers, even if the ingredients of plastic wrap are relatively safe, they may still think that the plastic wrap contains unknown chemical ingredients and its safety is difficult to guarantee. Therefore, for most fruits, the method of coating with preservatives is difficult to promote in actual application.

[0003] The inventor has found that there are also cases of using non-woven fabrics to preserve oranges. For example, there is a document that discloses: after the navel oranges are soaked in fennel extract and air-dried, they are packaged individually in non-woven fabric fresh-keeping bags treated with hydroxypropyl methylcellulose. This can reduce the weight loss rate and decay rate of the navel oranges and extend the shelf life of the navel oranges.

[0004] However, the above document discloses that the non-woven bag is treated with hydroxypropyl methylcellulose, and its main function is to form a micro-atmosphere environment, reduce the respiration rate of navel oranges, and maintain quality, rather than directly coating the antibacterial film on the non-woven fabric. If the antibacterial film is directly coated on the non-woven fabric, what is its antibacterial effect? ​​Whether the active ingredients therein can evaporate to achieve the antibacterial effect on fruit preservation is also a problem to be solved. If the antibacterial ingredients can be coated on the non-woven packaging bag without direct contact with the fruit, it will not only make preservation more convenient, but also greatly improve consumer acceptance, which is conducive to the promotion and large-scale application of this technology. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a non-woven packaging bag with fresh-keeping and antibacterial effects. The packaging bag is based on a modified non-woven fabric, and then a coating solution A is coated on the base layer, a ClO2 powder layer is evenly spread, and finally a coating solution B is coated.

[0006] A non-woven packaging bag with fresh-keeping and antibacterial effects, the packaging bag uses a dry modified non-woven fabric as a base, first coated with a coating solution A, then evenly sprinkled with a ClO2 powder layer, and finally coated with a coating solution B; The coating solution A mainly includes the following components: 1.5~2.0% chitosan by mass and 1.0~1.5% glacial acetic acid by volume; the chitosan deacetylation degree is greater than 95% and the viscosity is 100~200 mpa.s; the balance is distilled water; a higher chitosan deacetylation degree will enhance its inhibitory effect on bacteria and fungi, and highly deacetylated chitosan forms colloids in water. When the deacetylation degree is ≥95%, the solubility and viscosity of chitosan will increase significantly; chitosan with a viscosity in the range of 100~200 mpa.s usually has a higher molecular weight and has higher viscosity and gel ability. When the deacetylated viscosity is less than 95%, its solubility in dilute acid also decreases. When it is less than 70%, it cannot be completely dissolved in dilute acid or dissolves extremely slowly; when the viscosity is lower than 100~200 mpa.s, its viscosity and gel forming ability will be relatively reduced.

[0007] The coating solution B mainly includes the following components: 1.0-2.0% carboxymethyl cellulose by mass percentage; 1.0-2.0% plant essential oil and 0.5-0.8% surfactant by volume, and the balance is distilled water; the surfactant in the coating solution B is selected from at least one of Tween-80, Tween-20 and Sorbitol-20.

[0008] Preferably, the plant essential oil in the coating solution B is selected from at least one of cinnamaldehyde and lemon essential oil.

[0009] According to the specification of the modified non-woven fabric of 30cm×21cm, the coating amount of the coating solution A and the coating solution B are both 10-12mL; the amount of the ClO2 powder layer is 0.5g.

[0010] The modified nonwoven fabric is obtained by modification through the following steps: (1) Preparation of polyvinyl alcohol mother solution: Place polyvinyl alcohol particles in distilled water and stir to remove impurities. Take out the polyvinyl alcohol particles after impurities are removed and dry them at 70° C. for 12 h. The dried polyvinyl alcohol particles are added to deionized water at a solid-liquid ratio of 1:9, and swelled at a constant temperature of 65°C for 2 h, and then a plasticizer is added until its mass fraction reaches 1.5%, and then stirred at a constant temperature of 95°C for 4 h, and the stirring is stopped when the polyvinyl alcohol is completely melted, and finally degassed at -0.1MPa for 1 h to obtain a polyvinyl alcohol mother liquid; the plasticizer is preferably glycerol; (2) Pretreatment of non-woven fabric: soak the non-woven fabric in anhydrous ethanol, shake it to remove impurities, rinse it with deionized water to remove the anhydrous ethanol, and dry it; (3) Modification of non-woven fabric: Fix the pre-treated non-woven fabric and evenly apply the polyvinyl alcohol mother liquid on the non-woven fabric to modify it, so as to obtain modified non-woven fabric; the amount of polyvinyl alcohol mother liquid applied to each non-woven fabric with a size of 30 cm × 21 cm is 10-12 mL.

[0011] The application of the above-mentioned non-woven packaging bag with fresh-keeping and antibacterial effects in the preservation and antibacterial of fruits and vegetables is also the key content to be protected by the present invention.

[0012] The application method of the non-woven packaging bag with fresh-keeping and antibacterial effects comprises the following steps: (1) Take two pieces of nonwoven fabrics prepared by the above method, with the coated surface as the inner surface and the opposite surface as the outer surface, and press them into the shape of a cloth bag by a heat sealing machine, leaving an opening in the cloth bag for placing fruits inside; the cloth bag can be a rectangular bag, of course, it can also be a cloth bag of other shapes; generally speaking, the cloth bag is mostly rectangular, with a specification of 30 cm × 21 cm; (2) Place the fruits to be preserved in the heat-sealed non-woven packaging bags in (1); put 200-300g of fruits, such as blueberries or cherries, in each bag. Of course, you can also put a corresponding amount of fruits according to the size of the fruits according to the specific situation; (3) Place the non-woven bag containing the fruit in a fresh-keeping box and store it at room temperature or at a low temperature, such as -2~2℃ or 3~7℃.

[0013] Preferably, the surfactant is selected from at least one of Tween-80, polyoxyethylene (20) sorbitan monolaurate (also known as Tween-20) and sorbitan monolaurate (also known as Span-20).

[0014] The packaging bag of the present invention is coated with three layers of film, namely, the coating solution A, the ClO2 powder layer and the coating solution B, because the chitosan in the coating solution A has good film-forming property, biocompatibility and degradability, and plays a role of a physical barrier. The carboxymethyl cellulose in the coating solution B has good solubility and film-forming property, and has a certain water absorption, and can adjust the humidity of the coating layer, thus making up for the deficiency of the chitosan film.

[0015] In order to further improve the antibacterial and fresh-keeping effects, a ClO2 powder layer and cinnamaldehyde are also added in the present application, which have a more obvious effect on improving the antibacterial and fresh-keeping effects.

[0016] In addition, the new antibacterial film formed by the two layers of coating solution A and coating solution B through electrostatic deposition has improved uniformity, stability, and mechanical properties. The combined use of the two provides a better dispersion and carrying environment for the antibacterial component chlorine dioxide between the two layers of the film and the antibacterial component cinnamaldehyde and other active antibacterial agents in the coating solution B, thereby delaying the release rate of volatile bactericidal substances and achieving the effect of continuous sterilization during the storage and logistics of fruits and vegetables.

[0017] Therefore, the present invention first modifies the non-woven fabric to improve its surface hydrophilicity, strength and durability, etc., and then uses coating solution A, ClO2 and coating solution B to treat the modified non-woven fabric respectively to form a fresh-keeping and antibacterial material with different levels. The hierarchical order of coating solution A, ClO2 powder coating and coating solution B is coating solution A, ClO2 powder coating and coating solution B, respectively. The principle of their action is analyzed as above, and their hierarchical order cannot be changed, otherwise it will affect the antibacterial effect.

[0018] The present invention also seeks to protect the use of the non-woven packaging bag with fresh-keeping and antibacterial effects prepared by the above method in the fresh-keeping and antibacterial effects of fruits and vegetables. The above-mentioned fruits and vegetables may be blueberries, figs, strawberries, cherries, or other fruits, such as apples, citrus, etc.

[0019] The beneficial effects of the present invention are: (1) The biggest improvement of the present invention is that it breaks through the traditional solution of coating the fresh-keeping and antibacterial agent on the surface of the fruit. Instead, the film with fresh-keeping and antibacterial effects is coated on the inner surface of the packaging bag, which does not directly contact the fruit. On the one hand, it improves consumer acceptance. On the other hand, it utilizes the slow-release effect of the fresh-keeping bag embedded with volatile fungicides to achieve continuous sterilization during the storage and transportation of fruits. Through large-scale production and preparation of active packaging bags, the decay loss of fruits and vegetables during the storage and transportation after harvest is reduced; (2) In order to make the effective ingredients in the coating on the non-woven fabric volatilize continuously and play the role of antibacterial preservation, the present invention uses a double-layer membrane of chitosan and carboxymethyl cellulose. There can be electrostatic interaction between the two to enhance the stability and integrity of the coating, provide a better dispersion and carrying environment for active antibacterial agents such as chlorine dioxide and cinnamaldehyde, and delay the release rate of volatile bactericidal substances, thereby achieving a continuous sterilization effect during the storage and logistics of fruits and vegetables; (3) The non-woven packaging bag in this application is more convenient than the technical solution of coating on the surface of fruits. It avoids the complicated and tedious process of directly coating the fruits. Only the coated packaging bags are needed to achieve the effect of preserving and inhibiting bacteria on the fruits. There is no need to coat the fruits one by one. It is suitable for large-scale production and promotion. Compared with the traditional technology of coating the surface of fruits, this is a significant improvement. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the coating sequence when preparing a packaging bag in Example 1; Figure 2 The modified nonwoven fabric after coating in Example 1; Figure 3 The packaging effect diagram of blueberries using the packaging material obtained in Comparative Example 1, wherein left: Comparative Example 1 is stored for 0 days; middle: Comparative Example 1 is refrigerated for 6 days; right: Comparative Example 1 is refrigerated for 6 days + shelf for 3 days; Figure 4 The effect diagram of packaging blueberries using the packaging material obtained in Example 1, wherein left: Example 1 is stored for 0 days; middle: Example 2 is refrigerated for 6 days; right: Example 1 is refrigerated for 6 days + shelf for 3 days; Figure 5 The colony plates of various embodiments and comparative examples are shown in FIG.

[0021] Figure 6 It is the total number of colonies of each embodiment and comparative example. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in conjunction with specific implementation methods.

[0023] ClO2 powder layer, i.e. chlorine dioxide effervescent tablets, Beijing Hualong Xingyu Technology Development Co., Ltd.), can be crushed when used; Other raw materials not mentioned are common commercially available products.

[0024] Example 1 The steps for preparing non-woven bags are as follows: (1) Pretreatment of non-woven fabrics The non-woven fabric was cut into pieces of 30 cm × 21 cm, soaked in anhydrous ethanol for 4 h, then shaken in an oscillator for 2 h to remove impurities, then rinsed with deionized water several times to wash away the anhydrous ethanol, and finally dried at 60 ° C for 6 h until the non-woven fabric was completely dry and set aside; (2) Preparation of non-woven fabric modification solution The polyvinyl alcohol particles were placed in distilled water and stirred to remove impurities. The polyvinyl alcohol particles after impurities were taken out and dried in a drying oven at 70°C for 12 hours. The ratio of polyvinyl alcohol particles to deionized water was 1:9. The particles were swelled at a constant temperature of 65°C for 2 hours. Then, a plasticizer was added until its mass fraction reached 1.5%. The particles were stirred at a constant temperature of 95°C for 4 hours. The stirring was stopped when the polyvinyl alcohol was completely melted. The particles were then degassed at -0.1MPa for 1 hour to obtain a polyvinyl alcohol mother liquor. (3) Modification of non-woven fabrics Take about 12 mL of the polyvinyl alcohol mother solution in (2) and coat it on the non-woven fabric (specification: 30 cm × 21 cm) that has been pretreated in (1) using a wire rod. The coating process should be slow to keep the coating uniform and smooth. After coating, the modified non-woven fabric is obtained and dried at 65°C for 15 min. (4) Preparation of coating solution Preparation of coating solution A: 1.5 g of chitosan and glacial acetic acid were dissolved in distilled water to make the mass percentage of chitosan 1.5% and the volume percentage of glacial acetic acid 1.5%, and stirred at room temperature overnight to obtain chitosan coating solution A; the deacetylation degree of chitosan was greater than 95%, and the viscosity was 100-200 mpa.s; Preparation of coating solution B: 1.5 g of carboxymethyl cellulose was slowly added to distilled water while stirring to prevent the carboxymethyl cellulose from forming a film on the surface during the dissolution process, which increases the difficulty of dissolution. After the carboxymethyl cellulose was completely dissolved, cinnamaldehyde was added, followed by Tween-80. Distilled water was added to make the mass percentage of carboxymethyl cellulose 1.5%, the volume percentage of cinnamaldehyde 1%, and the volume percentage of Tween-80 0.8%. Stirring was continued until a stable emulsion was formed to obtain coating solution B (the coating sequence is as shown in the attached figure). Figure 1 shown); (5) Apply antibacterial film on modified non-woven fabric 12 mL of coating solution A was applied to the modified and dried non-woven fabric in (3), and then dried at 65°C for 10 min; then 0.5 g of ClO2 powder was evenly sprinkled on it; finally 12 mL of coating solution B was applied, and dried at 65°C for 15 min; a non-woven fabric with antibacterial and fresh-keeping effects was formed (the non-woven fabric after coating is as shown in the attached Figure 2 shown); Take two pieces of nonwoven fabric of the same size as in (5), with the coated surface as the inner surface and the opposite surface as the outer surface, and use a heat sealing machine to make a rectangular packaging bag with three sides closed and one side open.

[0025] The following are other embodiments and comparative examples. In each embodiment and comparative examples 1-8, the nonwoven fabric is cut into the same specifications as in embodiment 1, and the steps not specifically described are the same as those in embodiment 1.

[0026] Example 2 The difference from Example 1 is that in the coating solution A, the mass percentage of chitosan is 1.5%, and the volume percentage of glacial acetic acid is 1.5%; In the coating solution B, the mass percentage of carboxymethyl cellulose is 1.2%; the volume percentages are 1.0% of lemon essential oil and 0.6% of Tween-20.

[0027] Example 3 In the coating solution B, the mass percentage of carboxymethyl cellulose is 1.8%; the volume percentages are 1.5% of lemon essential oil and 0.6% of sorbitan-20.

[0028] Example 4 In the coating solution A, the mass percentage of chitosan is 2%, and the volume percentage of glacial acetic acid is 2%.

[0029] Comparative Example 1 The difference from Example 1 is that the nonwoven fabric is not treated, specifically as follows: Soak in ethanol solution for 4 hours, then shake in an oscillator for 2 hours to remove impurities from the non-woven fabric, rinse with deionized water several times to remove the ethanol, and dry at 60°C; then use a heat sealer to make a rectangular packaging bag. That is, ordinary non-woven bags are only pre-treated and not coated with an antibacterial film layer.

[0030] Comparative Example 2 The difference from Example 1 is that the non-woven fabric is not treated with ClO2, and the coating solution B does not contain cinnamaldehyde, as follows: (4) Preparation of coating solution B: 1.5 g of carboxymethyl cellulose was slowly added to distilled water while stirring to prevent the carboxymethyl cellulose from forming a film on the surface during the dissolution process, which would increase the difficulty of dissolution. After the carboxymethyl cellulose was completely dissolved, Tween-80 was added, and distilled water was added to make the mass percentage of carboxymethyl cellulose 1.5% and the volume percentage of Tween-80 0.8%. The mixture was stirred continuously until a stable emulsion was formed to obtain coating solution B. (5) Apply antibacterial film on modified non-woven fabric 12 mL of coating solution A was applied to the modified and dried non-woven fabric in (3), and then dried at 65°C for 10 min; then 12 mL of coating solution B was applied, and dried at 65°C for 15 min; thus, a non-woven fabric having antibacterial and fresh-keeping effects was formed.

[0031] Comparative Example 3 The difference from Example 1 is that the non-woven fabric is not treated with ClO2, and the volume concentration of cinnamaldehyde in the coating solution B is 1.5%, as follows: (4) Preparation of coating solution B: 1.5 g of carboxymethyl cellulose was slowly added to distilled water while stirring. After the carboxymethyl cellulose was completely dissolved, cinnamaldehyde was added, followed by Tween-80. Additional distilled water was added to make the mass percentage of carboxymethyl cellulose 1.5%, the volume percentage of cinnamaldehyde 1.5%, and the volume percentage of Tween-80 0.8%. The mixture was stirred continuously until a stable emulsion was formed to obtain coating solution B. (5) Apply antibacterial film on modified non-woven fabric 12 mL of coating solution A was applied to the modified and dried non-woven fabric in (3), and then dried at 65°C for 10 min; finally, 12 mL of coating solution B was applied and dried at 65°C for 15 min; thus, a non-woven fabric having antibacterial and fresh-keeping effects was formed.

[0032] Comparative Example 4 The difference from Example 1 is that the coating solution B does not contain cinnamaldehyde, as follows: (4) Preparation of coating solution B: Take 1.5 g of carboxymethyl cellulose and slowly add it into distilled water while stirring to prevent the carboxymethyl cellulose from forming a film on the surface during the dissolution process, which increases the difficulty of dissolution. After the carboxymethyl cellulose is completely dissolved, add Tween-80 and additional distilled water to make the mass percentage of carboxymethyl cellulose 1.5%, thereby obtaining coating solution B.

[0033] Comparative Example 5 The difference from Example 1 is that the coating order of the modified non-woven fabric is different, first coating B, then sprinkling the ClO2 powder layer, and finally coating A, as follows: 12 mL of coating solution B was applied on the modified and dried non-woven fabric in (3), and then dried at 65°C for 10 min; then 0.5 g of ClO2 powder layer was evenly sprinkled on it; finally 12 mL of coating solution A was applied, and dried at 65°C for 15 min; thus, a non-woven fabric with antibacterial and fresh-keeping effects was formed.

[0034] Comparative Example 6 The difference from Example 1 is that the coating order of the modified non-woven fabric is different, first coating A, then coating B, and finally coating the ClO2 powder layer, as follows: 12 mL of coating solution A was applied on the modified and dried non-woven fabric in (3), and then dried at 65°C for 10 min; then 12 mL of coating solution B was applied, and finally 0.5 g of ClO2 powder layer was evenly sprinkled on it, and dried at 65°C for 15 min; thus, a non-woven fabric with antibacterial and fresh-keeping effects was formed.

[0035] Comparative Example 7 The difference from Example 1 is that the modified nonwoven fabric is not treated with the coating solution A, specifically as follows: A 0.5 g ClO2 powder layer was evenly sprinkled on the non-woven fabric modified and dried in (3); finally, 12 mL of coating solution B was applied and dried at 65°C for 15 min; thus, a non-woven fabric with antibacterial and fresh-keeping effects was formed.

[0036] Comparative Example 8 The difference from Example 1 is that the modified nonwoven fabric is not treated with the coating solution B, as follows: 12 mL of coating solution A was applied to the modified and dried non-woven fabric in (3), and then dried at 65°C for 10 min; then 0.5 g of ClO2 powder layer was evenly sprinkled on it, and dried at 65°C for 15 min; thus, a non-woven fabric with antibacterial and fresh-keeping effects was formed.

[0037] Test Example 1: Testing of the effect of packaging materials on the preservation of blueberries after harvest (1) Select blueberries that are fresh, free of external injuries, diseases and insect pests, and record the appearance of the tested fruits; (2) After selection, the blueberries were placed in the packaging bags prepared in the embodiment and the comparative example, with 30 blueberries in each group, and the fruit quality indicators were recorded and tested; (3) Store at 4-6°C for 6 days and then place at shelf temperature for 3 days to test the decay index, weight loss rate and hardness of the fruit.

[0038] The detection method is as follows: (1) Determination of hardness The fruit hardness was measured using a GY-2 hardness tester. Three fruits were randomly selected from each group and the average value of the test results was taken in kg·cm 2 ; (2) Determination of weight loss rate Fruit mass loss rate = (fruit mass before storage - fruit mass after storage) / fruit mass before storage × 100%; (3) Determination of the corruption index The blueberries were divided into five levels based on the area of ​​corruption, with 0 points for no corruption, 2 points for corruption area between 0 and 1 / 4 of the blueberries, 2 points for corruption area between 1 / 4 and 1 / 2 of the blueberries, 3 points for corruption area between 1 / 2 and 3 / 4 of the blueberries, 4 points for corruption area between 3 / 4 of the blueberries and the entire blueberries, and 5 points for corruption area of ​​the entire blueberries.

[0039] Corruption index = number of blueberries of each grade × grade score ÷ (5 × total number of experimental measurements) × 100%; Before the experiment, the blueberries were full, disease-free, and had an average hardness of 0.99 kg / cm 2 The quality indexes of blueberry fruits packaged in the packaging bags prepared in the embodiments and comparative examples are shown in Table 1: Table 1 Fruit quality indexes name <![CDATA[Hardness kg / cm 2 > Weight loss rate / % Decay index / % Example 1 0.94±0.07 7.68±0.67 16.9±1.09 Example 2 0.92±0.04 7.46±0.13 17.0±0.95 Example 3 0.95±0.02 7.53±0.29 16.8±1.21 Example 4 0.94±0.05 7.61±0.44 17.0±1.16 Comparative Example 1 0.68±0.03 7.83±0.61 44.76±2.18 Comparative Example 2 0.73±0.05 7.21±0.65 17.62±1.80 Comparative Example 3 0.94±0.14 7.86±0.55 19.76±0.82 Comparative Example 4 0.94±0.07 7.8±0.73 41.43±2.15 Comparative Example 5 0.93±0.03 7.64±0.17 18.34±1.07 Comparative Example 6 0.90±0.04 7.80±0.15 25.35±4.24 Comparative Example 7 0.77±0.06 7.63±0.33 24.72±1.15 Comparative Example 8 0.89±0.04 7.71±0.31 22.05±1.06 As shown in Table 1, the decay index of Examples 1-4 is greatly reduced compared with Comparative Examples 1-8, and is between 16-17%, while the decay index is higher in Comparative Examples 1 and 4. In terms of fruit hardness and weight loss rate, Example 1 has the best preservation effect on the fruit, followed by Examples 2-4.

[0040] As attached Figure 3 , 4 As shown, the effect of using the packaging material of the embodiment to package and preserve blueberries at different shelf lives is far better than that of using the solution of the comparative example. Figure 5 , 6 From the above, it can be seen that the total number of colonies in the packaging and preservation method in this application is lower than that in the control example.

[0041] Test Example 2 Mechanical properties test of non-woven bags Test Example 2-1 Water absorption performance Refer to GB / T1034-2008 test of plastic water absorption. Testing the performance of non-woven bags is actually testing the mechanical properties of the non-woven fabric blocks used to make the bags. Therefore, take the non-woven fabric after coating prepared by the method in Example 1 (the non-woven fabric obtained in step (5)). In the following tests, the above non-woven fabric is taken as the sample to be tested, with a size of 50mm×50mm. Put it in an oven and adjust the temperature to 50°C. Measure the weight of the sample regularly until the sample reaches constant weight, then put it in distilled water (500ml, 24°C) and soak it for 24 hours. Carefully take out the sample, gently absorb the moisture on the surface of the sample with filter paper, and weigh it. Calculate the water absorption rate according to the following formula: η=(m1-m0) / m0×100%, Among them, m0 is the mass of the initial composite membrane, and m1 is the mass of the composite membrane after absorbing water.

[0042] Test Example 2-2 Mechanical properties of non-woven bags The mechanical properties of the sample, tensile strength F and elongation at break β, were measured using an intelligent electronic tensile testing machine. The nonwoven fabric (size 10×1.5 cm) in step (5) of Example 1 was taken. The stretching rate was 300 mm / min, the clamping distance was 80 mm, the ambient temperature was 25°C, the relative humidity of the sample environment was controlled to be 50%, and three samples were taken in parallel. The results were expressed as the mean.

[0043] Test Example 2-3 Thickness of nonwoven fabric Vernier caliper measurement was used, and at least three different positions of each sample were measured, and the results were averaged.

[0044] Test Example 2-4 Water Vapor Transmission Rate The film samples were cut into squares, weighed to record the original mass, and used to seal a weighing cup (4 cm in diameter, 4 cm in depth) containing 3 g of CaCl2; the cup was then placed in a desiccator containing saturated potassium iodide (20°C, RH = 70% relative humidity).

[0045] Weigh the cup every 6 hours for 2 days until the weight is constant. Record the time t to constant weight, the mass difference M before and after weighing, and calculate the water vapor transmission rate (WVP) according to the following formula: Water vapor permeability = (M×x) / (t×A×Δp), Where x is the membrane thickness (m), A is the membrane permeation area (m 2 ), Δp is the vapor pressure difference of the permeation area (2339 Pa at 20°C), and t is the permeation time (s).

[0046] The results are shown in Table 2: Table 2 Packaging material performance test name Water absorption performance / % Water vapor transmission rate / % Thickness / mm Elongation / % Tensile strength / MPa Example 1 52.56±5.84 3.56±0.38 0.61±0.03 115.83±8.3 4.68±0.15 Comparative Example 1 27.25±6.26 3.88±0.2 0.44±0.02 108.66±10.35 4.16±0.05 Comparative Example 2 16±5.55 5.5±1.46 0.55±0.02 106.91±6.29 4.42±0.21 Comparative Example 3 27.96±4.97 2.92±2.45 0.53±0.01 107.08±11.36 4.19±0.19 Comparative Example 4 61.04±11.26 3.33±0.4 0.56±0.02 107.16±0.82 4.33±0.13 As shown in Table 2, the water absorption performance of the packaging bag of Example 1 is improved by 0.9, 2.2 and 0.9 times respectively compared with Comparative Examples 1, 2 and 3; the water vapor permeability of Example 1 is reduced by 35.3% compared with Comparative Example 2, and it can effectively reduce the loss of water during fruit storage as a fresh-keeping packaging for fruits and vegetables; the tensile strength of Example 1 is increased compared with Comparative Examples 1, 2, 3 and 4, which are increased by 12.5%, 5.9%, 11.7% and 8.1% respectively.

Claims

1. A non-woven packaging bag with fresh-keeping and antibacterial effects, characterized in that: The packaging bag is based on a dry modified non-woven fabric, which is first coated with a coating solution A, then evenly sprinkled with a ClO2 powder layer, and finally coated with a coating solution B; The coating solution A mainly includes the following components: 1.5-2.0% chitosan by mass, 1.0-1.5% glacial acetic acid by volume; the chitosan deacetylation degree is greater than 95%, and the viscosity is 100-200 mpa.s; the balance is distilled water; The coating solution B mainly includes the following components: 1.0-2.0% by mass of carboxymethyl cellulose; The volume percentage is 1.0~2.0% plant essential oil and 0.5~0.8% surfactant, and the balance is distilled water; According to the specifications of the modified non-woven fabric of 30cm×21cm, the coating amount of the coating solution A and the coating solution B are both 10-12mL; the amount of the ClO2 powder layer is 0.5g.

2. The non-woven packaging bag with fresh-keeping and antibacterial effects as claimed in claim 1, characterized in that: The modified nonwoven fabric is obtained by the following steps: (1) Preparation of polyvinyl alcohol mother solution: Place polyvinyl alcohol particles in distilled water and stir to remove impurities. Take out the polyvinyl alcohol particles after impurities are removed and dry them at 70°C for 12 hours. The dried polyvinyl alcohol particles were added into deionized water at a material-liquid ratio of 1:9, and swelled at a constant temperature of 65°C for 2 h. Then, a plasticizer was added until its mass fraction reached 1.5%, and then stirred at a constant temperature of 95°C for 4 h. Stirring was stopped when the polyvinyl alcohol was completely melted, and finally, degassed at -0.1 MPa for 1 h to obtain a polyvinyl alcohol mother liquor. (2) Pretreatment of non-woven fabric: soak the non-woven fabric in anhydrous ethanol, shake it to remove impurities, rinse it with deionized water to remove the anhydrous ethanol, and dry it; (3) Modification of non-woven fabric: Fix the pre-treated non-woven fabric and apply polyvinyl alcohol mother liquor, evenly apply it on the non-woven fabric to modify it, and obtain modified non-woven fabric; the amount of polyvinyl alcohol mother liquor applied to each non-woven fabric with a size of 30 cm × 21 cm is 10-12 mL.

3. The non-woven packaging bag with freshness-preserving and antibacterial effects as claimed in claim 1, characterized in that: The surfactant in the coating solution B is selected from at least one of Tween-80, Tween-20 and Sorbitol-20.

4. The non-woven packaging bag with fresh-keeping and antibacterial effects as claimed in claim 1, characterized in that: The plant essential oil in the coating solution B is selected from at least one of cinnamaldehyde and lemon essential oil.

5. The non-woven packaging bag with freshness-preserving and antibacterial effects as claimed in claim 2, characterized in that: The plasticizer is glycerol.

6. Use of the non-woven packaging bag with fresh-keeping and antibacterial effects as claimed in claim 1 in the preservation and antibacterial effects of fruits and vegetables.

7. The method for applying the non-woven packaging bag with fresh-keeping and antibacterial effects as claimed in claim 1 comprises the following steps: (1) Take two pieces of nonwoven fabrics according to claim 1, with the surfaces coated with the coating as the inner surfaces and the surfaces opposite to them as the outer surfaces; and press them into the shape of a bag using a heat sealing machine; (2) Put the fruit to be preserved in the non-woven packaging bag heat-sealed in (1); (3) Place the non-woven bag containing the fruit in a fresh-keeping box and store it at room temperature or at -2 to 7°C.

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