Modified polyvinyl alcohol-based humidity-regulating antibacterial film as well as preparation method and application thereof

Abstract

The invention belongs to the field of packaging materials, and discloses a modified polyvinyl alcohol-based humidity-regulating antibacterial film and a preparation method and application thereof, and the modified polyvinyl alcohol-based humidity-regulating antibacterial film comprises the following components in parts by mass: 5-50 parts of polyvinyl alcohol, 2-8 parts of oxalic acid, 0-1 part of an antibacterial agent and 5-30 parts of a humidity regulator. The modified polyvinyl alcohol-based humidity-adjusting antibacterial film is prepared by mixing a modified film and a humidity adjusting agent, and the obtained modified polyvinyl alcohol-based humidity-adjusting antibacterial film has good humidity adjusting performance, air permeability and mechanical performance, can effectively prolong the shelf life of fruits and vegetables, can adjust the internal humidity of a package according to the moisture generated by breathing of cherry tomatoes, and can be used for packaging the fruits and vegetables. Fruit and vegetable rot caused by condensed water generated by over-high humidity is avoided, and serious water loss of fruits and vegetables caused by over-low humidity is also avoided. The preparation method of the modified polyvinyl alcohol-based humidity-regulating antibacterial film is simple, convenient to operate and suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of packaging materials, and specifically relates to a modified polyvinyl alcohol-based humidity-regulating antibacterial film and its preparation method and application. Background Art

[0002] Post-harvest preservation of fruits and vegetables is a key link to reduce resource waste and ensure food quality. For fruits and vegetable foods with high water activity, too low humidity is likely to cause the fruits and vegetables to lose water and wilt, and the texture to deteriorate; too high humidity promotes the reproduction of pathogenic microorganisms, and at the same time, condensed water is likely to form on the inner surface of the film, exacerbating the growth of microorganisms. Although existing commercial fresh-keeping films (such as polyethylene PE and polypropylene PP) can delay water evaporation through physical barrier, their moisture permeability is poor, and they cannot dynamically respond to the respiratory action of fruits and vegetables and the changes in environmental temperature and humidity, easily causing too high humidity inside the package to form condensed water. Therefore, developing a fresh-keeping film with a humidity self-adaptive adjustment function is the core challenge for achieving precise preservation.

[0003] In food packaging applications, the most commonly used humidity-regulating packaging forms include moisture-absorbing bags, moisture-absorbing trays, perforated polymer films, etc. However, the moisture absorption capacity of moisture-absorbing bags and moisture-absorbing trays is affected by their own quality. As the storage time of fruits and vegetables increases, the moisture absorption capacity reaches the upper limit and can no longer absorb water; while perforated polymer films have higher water vapor permeability and oxygen permeability, and it is necessary to adjust the perforations according to the physiological characteristics of fruits and vegetables to balance the storage atmosphere of fruits and vegetables. Moreover, the non-closed packaging environment makes it easier for microorganisms to enter the inside of the package, causing the fruits and vegetables to rot.

[0004] Due to its biodegradability, high transparency and excellent film-forming properties, polyvinyl alcohol has gradually become a research hotspot for environmentally friendly fresh-keeping materials. However, because modified polyvinyl alcohol has poor water resistance, is easy to dissolve, and has a fixed water vapor permeability, it is not suitable as a humidity-regulating packaging for fruit and vegetable products. Patent CN118725377A obtains a carboxylated MOF-type antibacterial agent by coordinating the prepared carboxyl-terminal pyridine-type ligand and / or polypyridine-type ligand with silver ions, and uses the carboxylated MOF-type antibacterial agent to crosslink and modify polyvinyl alcohol, resulting in a decrease in the water vapor barrier ability of polyvinyl alcohol, but its production method is too cumbersome. Patent CN109553940A prepares a moisture-permeable and degradable fresh-keeping film, but its mechanical properties are poor. Therefore, providing a fresh-keeping film with good water resistance, mechanical strength and water vapor permeability has broad application prospects in the green storage of high-humidity fruits and vegetables. Summary of the Invention

[0005] In order to overcome the disadvantages and deficiencies of the prior art, the primary object of the present invention is to provide a modified polyvinyl alcohol-based humidity-regulating antibacterial film.

[0006] Another object of the present invention is to provide a preparation method of a modified polyvinyl alcohol-based humidity-regulating antibacterial film.

[0007] Another object of the present invention is to provide the application of the above-mentioned modified polyvinyl alcohol humidity-regulating and antibacterial film. The obtained modified polyvinyl alcohol humidity-regulating and antibacterial film can adjust the humidity inside the package according to the moisture generated by the respiration of fruits and vegetables, and has good moisture permeability, water resistance and mechanical properties, which can effectively extend the shelf life of fruits and vegetables.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A modified polyvinyl alcohol humidity-regulating and antibacterial film, comprising the following components in parts by mass:

[0010]

[0011] Preferably, the modified polyvinyl alcohol humidity-regulating and antibacterial film comprises the following components in parts by mass:

[0012]

[0013]

[0014] Preferably, the humidity regulator is at least one of glycerol and phytic acid solution.

[0015] Preferably, the mass concentration of the phytic acid solution is 40-60%.

[0016] Preferably, the antibacterial agent is titanium dioxide nanoparticles, silver nanoparticles, zinc oxide nanoparticles.

[0017] Preferably, the molecular weight of the polyvinyl alcohol is 100,000-200,000.

[0018] Preferably, the thickness of the modified polyvinyl alcohol humidity-regulating and antibacterial film is 0.10 mm-0.20 mm, and the water vapor permeability is 1.2×10 -6 g / (m·h·Pa)-6.0×10 -6 g / (m·h·Pa), preferably 1.50×10 -6 g / (m·h·Pa)-6.0×10 -6 g / (m·h·Pa).

[0019] Preferably, the tensile strength of the modified polyvinyl alcohol humidity-regulating and antibacterial film is 20-60 MPa, and the elongation at break is 200%-370%.

[0020] A preparation method of a modified polyvinyl alcohol humidity-regulating and antibacterial film, comprising the following steps:

[0021] (1) Dissolve the antibacterial agent in water, then add polyvinyl alcohol and oxalic acid, and heat and stir to form a homogeneous solution;

[0022] (2) Add a humidity regulator to the homogeneous solution, stir, then defoam, cast into a film, and dry to obtain a modified polyvinyl alcohol moisture-regulating antibacterial film.

[0023] Preferably, in step (1), the mass part of water is 150-200 parts, the heating temperature is 70-90 °C, the stirring speed is 200-500 rpm, and the time is 2-6 h;

[0024] The antibacterial agent in step (1) is dissolved in water by homogeneous dispersion, the homogeneous speed is 6000-10000 rpm, and the time is 1-3 min.

[0025] Preferably, in step (2), the stirring speed is 200-500 rpm, and the time is 1-3 h;

[0026] The drying temperature in step (2) is 50-80 °C, and the drying time is 2-8 h.

[0027] The application of the above-mentioned modified polyvinyl alcohol moisture-regulating antibacterial film in food packaging and food preservation.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] (1) In the present invention, oxalic acid is used to modify polyvinyl alcohol for water resistance improvement, enhancing the water resistance of polyvinyl alcohol. After modification, the water-soluble polyvinyl alcohol is transformed into water-insoluble polyvinyl alcohol, avoiding the dissolution of polyvinyl alcohol by the condensed water generated due to excessive humidity inside the packaging. Through the cooperation of the modified polyvinyl alcohol-based antibacterial film and the humidity regulator, the water vapor permeability of the film is adjusted, thereby regulating the humidity inside the packaging, avoiding the generation of condensed water caused by excessive humidity, which may lead to the decay of fruits and vegetables, and also avoiding excessive water loss of fruits and vegetables due to too low humidity. The modified polyvinyl alcohol moisture-regulating antibacterial film can control the humidity inside the packaging material at 80%-90%, which is better than the humidity of 100% of commercially available PE.

[0030] (2) The water resistance and mechanical properties of the film provided by the present invention are both significantly improved.

[0031] (3) Titanium dioxide is added to the modified polyethylene film to prevent external spoilage bacteria from entering the packaging interior, achieving an antibacterial effect.

[0032] (4) The preparation method of the modified polyvinyl alcohol moisture-regulating antibacterial film provided by the present invention is simple, easy to operate, and suitable for industrial production.

[0033] (5) The cherry tomatoes packaged with the modified polyvinyl alcohol moisture-regulating antibacterial film provided by the present invention still remain in a relatively fresh state on the 7th day, which is better than commercially available PE food wrap. Description of the Drawings

[0034] Figure 1 It is a comparison chart of the water vapor permeability data of the modified polyvinyl alcohol-based humidity-regulating and antibacterial films prepared in Examples 1 to 8.

[0035] Figure 2 It is a comparison chart of the Fourier infrared data of the modified polyvinyl alcohol-based humidity-regulating and antibacterial films prepared in Examples 1 to 4.

[0036] Figure 3 It is a comparison chart of the stress-strain data of the modified polyvinyl alcohol-based humidity-regulating and antibacterial films prepared in Examples 1 to 4.

[0037] Figure 4 It is a comparison chart of the swelling rate data of the modified polyvinyl alcohol-based humidity-regulating and antibacterial films prepared in Examples 1 to 4.

[0038] Figure 5 It is a comparison chart of the water solubility data of the modified polyvinyl alcohol-based humidity-regulating and antibacterial films prepared in Examples 1 to 4.

[0039] Figure 6 It is a comparison chart of the weight loss rate of different experimental groups in the fresh-keeping experiment of the modified polyvinyl alcohol-based humidity-regulating and antibacterial films prepared in Examples 1, 3, and 4.

[0040] Figure 7 It is a comparison chart of the humidity of different experimental groups in the fresh-keeping experiment of the modified polyvinyl alcohol-based humidity-regulating and antibacterial films prepared in Examples 1, 3, and 4.

[0041] Figure 8 It is the apparent image of cherry tomatoes of different experimental groups in the fresh-keeping experiment of the modified polyvinyl alcohol-based humidity-regulating and antibacterial films prepared in Examples 1 to 4. Detailed implementation manners

[0042] The present invention will be further described in detail below in conjunction with specific embodiments, but the implementation manners of the present invention are not limited thereto. For process parameters not specifically noted, conventional techniques can be referred to.

[0043] The molecular weight of the polyvinyl alcohol used in the examples is 151,200 to 160,000.

[0044] Example 1

[0045] Step S1, weigh 20 parts of polyvinyl alcohol and dissolve it in 180 parts of distilled water, stir and dissolve at 80 °C for 4 h, and the stirring speed is 300 rpm.

[0046] Step S2, ultrasonically defoam the solution prepared in Step S1, pour it into a plastic mold, stand overnight to defoam, dry at 70 °C for 6 h, and peel off to obtain an unmodified polyvinyl alcohol film with a film thickness of 0.15 mm.

[0047] Example 2

[0048] Step S1: Weigh 0.6 parts of titanium dioxide, dissolve it in 180 parts of distilled water, and homogenize and disperse it at 8000 rpm for 1 minute to obtain a titanium dioxide dispersion;

[0049] Step S2: Weigh 20 parts of polyvinyl alcohol and 2 parts of oxalic acid, dissolve them in the titanium dioxide dispersion prepared in Step S1, and stir at 80°C for 4 hours until completely dissolved to obtain Solution A;

[0050] Step S3: Ultrasonically defoam the Solution A prepared in Step S2, pour it into a plastic mold, let it stand overnight to defoam, dry it at 70°C for 6 hours, and then peel it off to obtain a modified polyvinyl alcohol moisture-regulating antibacterial film with a film thickness of 0.15 mm.

[0051] Example 3

[0052] Step S1: Weigh 0.6 parts of titanium dioxide, dissolve it in 180 parts of distilled water, and homogenize and disperse it at 8000 rpm for 1 minute to obtain a titanium dioxide dispersion;

[0053] Step S2: Weigh 20 parts of polyvinyl alcohol and 2 parts of oxalic acid, dissolve them in the titanium dioxide dispersion prepared in Step S1, and stir at 80°C for 4 hours until completely dissolved to obtain Solution A;

[0054] Step S3: Weigh 10 parts of 50% phytic acid solution, dissolve it in Solution A prepared in Step S2, and stir at 80°C for 2 hours until completely dissolved to obtain Solution B;

[0055] Step S4: Ultrasonically defoam the Solution A prepared in Step S3, pour it into a plastic mold, let it stand overnight to defoam, dry it at 70°C for 6 hours, and then peel it off to obtain a modified polyvinyl alcohol moisture-regulating antibacterial film with a film thickness of 0.15 mm.

[0056] Example 4

[0057] Step S1: Weigh 0.6 parts of titanium dioxide, dissolve it in 180 parts of distilled water, and homogenize and disperse it at 8000 rpm for 1 minute to obtain a titanium dioxide dispersion;

[0058] Step S2: Weigh 20 parts of polyvinyl alcohol and 2 parts of oxalic acid, dissolve them in the titanium dioxide dispersion prepared in Step S1, and stir at 80°C for 4 hours until completely dissolved to obtain Solution A;

[0059] Step S3: Weigh 10 parts of glycerol solution, dissolve it in Solution A prepared in Step S2, and stir at 80°C for 2 hours until completely dissolved to obtain Solution B;

[0060] Step S4: Ultrasonically defoam the solution A prepared in step S3, pour it into a plastic mold, let it stand overnight to defoam, dry it at 70 °C for 6 h, and then peel it off to obtain a modified polyvinyl alcohol moisture-regulating antibacterial film with a film thickness of 0.15 mm.

[0061] Example 5

[0062] Step S1: Weigh 0.6 parts of titanium dioxide, dissolve it in 180 parts of distilled water, and homogenize and disperse it at 8000 rpm for 1 min to obtain a titanium dioxide dispersion.

[0063] Step S2: Weigh 20 parts of polyvinyl alcohol and 2 parts of oxalic acid, dissolve them in the titanium dioxide dispersion prepared in step S1, and stir at 80 °C for 4 h until completely dissolved to obtain solution A.

[0064] Step S3: Weigh 14 parts of 50% phytic acid solution, dissolve it in solution A prepared in step S2, and stir at 80 °C for 2 h until completely dissolved to obtain solution B.

[0065] Step S4: Ultrasonically defoam the solution A prepared in step S3, pour it into a plastic mold, let it stand overnight to defoam, dry it at 70 °C for 6 h, and then peel it off to obtain a modified polyvinyl alcohol moisture-regulating antibacterial film with a film thickness of 0.15 mm.

[0066] Example 6

[0067] Step S1: Weigh 0.6 parts of titanium dioxide, dissolve it in 180 parts of distilled water, and homogenize and disperse it at 8000 rpm for 1 min to obtain a titanium dioxide dispersion.

[0068] Step S2: Weigh 20 parts of polyvinyl alcohol and 2 parts of oxalic acid, dissolve them in the titanium dioxide dispersion prepared in step S1, and stir at 80 °C for 4 h until completely dissolved to obtain solution A.

[0069] Step S3: Weigh 20 parts of 50% phytic acid solution, dissolve it in solution A prepared in step S2, and stir at 80 °C for 2 h until completely dissolved to obtain solution B.

[0070] Step S4: Ultrasonically defoam the solution A prepared in step S3, pour it into a plastic mold, let it stand overnight to defoam, dry it at 70 °C for 6 h, and then peel it off to obtain a modified polyvinyl alcohol moisture-regulating antibacterial film with a film thickness of 0.15 mm.

[0071] Example 7

[0072] Step S1: Weigh 0.6 parts of titanium dioxide, dissolve it in 180 parts of distilled water, and homogenize and disperse it at 8000 rpm for 1 min to obtain a titanium dioxide dispersion.

[0073] Step S2: Weigh 20 parts of polyvinyl alcohol and 2 parts of oxalic acid, dissolve them in the titanium dioxide dispersion prepared in Step S1, and stir at 80 °C for 4 h until completely dissolved to obtain Solution A;

[0074] Step S3: Weigh 14 parts of glycerol solution, dissolve it in Solution A prepared in Step S2, and stir at 80 °C for 2 h until completely dissolved to obtain Solution B;

[0075] Step S4: Ultrasonically defoam the Solution A prepared in Step S3, pour it into a plastic mold, let it stand overnight to defoam, dry it at 70 °C for 6 h, and then peel it off to obtain the modified polyvinyl alcohol moisture-regulating antibacterial film with a film thickness of 0.15 mm.

[0076] Example 8

[0077] Step S1: Weigh 0.6 part of titanium dioxide, dissolve it in 180 parts of distilled water, and homogenize and disperse it at 8000 rpm for 1 min to obtain the titanium dioxide dispersion;

[0078] Step S2: Weigh 20 parts of polyvinyl alcohol and 2 parts of oxalic acid, dissolve them in the titanium dioxide dispersion prepared in Step S1, and stir at 80 °C for 4 h until completely dissolved to obtain Solution A;

[0079] Step S3: Weigh 5 parts of glycerol solution and 5 parts of 50% phytic acid, dissolve them in Solution A prepared in Step S2, and stir at 80 °C for 2 h until completely dissolved to obtain Solution B;

[0080] Step S4: Ultrasonically defoam the Solution A prepared in Step S3, pour it into a plastic mold, let it stand overnight to defoam, dry it at 70 °C for 6 h, and then peel it off to obtain the modified polyvinyl alcohol moisture-regulating antibacterial film with a film thickness of 0.15 mm.

[0081] Film performance test method

[0082] (1) Fourier transform infrared spectroscopy characterization

[0083] Test using a Fourier transform infrared spectrometer at ambient temperature. The test method selects the attenuated total reflection method with a resolution of 4 cm -1 , and the range is 400 - 4000 cm -1 .

[0084] (2) Tensile test of film mechanical properties

[0085] Cut the film into thin slices of 50 mm × 10 mm, place them in an environment of 25 °C and 57% RH to equilibrate for 48 h, and then use a servo material testing machine to measure the mechanical strength of the film. Adopt the tensile mode, set the fixture to rise at a speed of 100 mm / s until the material breaks. Use the formula to calculate the elongation at break and the tensile strength, take the elongation at break as the abscissa and the tensile strength as the ordinate, and plot the stress-strain curve.

[0086]

[0087] In the formula, F is the maximum tensile force borne when the film breaks, with the unit of N; S is the cross-sectional area of the film, with the unit of mm 2 ; L1 is the distance between the two clamps at the moment when the film breaks, with the unit of mm; L0 is the initial clamping distance, with the unit of mm.

[0088] (3) Water resistance test

[0089] Cut the film into 2 cm × 2 cm thin slices. After drying to a constant weight, place them in a beaker filled with distilled water and let them swell for 24 h, then take them out, blot the water on the surface of the film with filter paper, and weigh. Place the film that has swelled for 24 h in an oven and dry it to a constant weight, then weigh. Use the formula to calculate the swelling rate and water solubility.

[0090]

[0091] In the formula, m0 is the mass of the sample before swelling, with the unit of g; m1 is the mass of the sample after swelling, with the unit of g; m2 is the mass of the sample after swelling and drying to a constant weight, with the unit of g.

[0092] (4) Water vapor permeation test

[0093] Take 5 g of anhydrous calcium chloride and place it in a weighing dish. Cover and seal it with the film sample to be tested, weigh it, then put the weighing dish into an environment with a RH of 98%, take it out and weigh it every 24 h, and continue for one week. Use the formula to calculate the water vapor permeability.

[0094]

[0095] In the formula, Δm is the increased weight, with the unit of g; d is the thickness of the film, with the unit of m; t is the time interval of weight increase, with the unit of h; A is the area of the film through which water vapor permeates, with the unit of m 2 ; P0 is the water vapor pressure at the test temperature, with the unit of Pa; ΔRH is the relative humidity difference between the two sides of the film.

[0096] (5) Fresh-keeping effect test (taking cherry tomatoes as an example)

[0097] Put every 500 g of cherry tomatoes into a 1 L fresh-keeping box and seal it with the film. Store all the cherry tomatoes in a constant temperature incubator (LRH-70, Shanghai Hengyi Scientific Instrument Co., Ltd.) at 25 °C to simulate the room temperature environment. Record the humidity inside the package every day, measure the weight loss rate every two days, take pictures for record, and continuously measure for 8 days. Calculate the weight loss rate from the formula.

[0098]

[0099] wherein, m0 is the mass of cherry tomatoes on the 0th day, with the unit of g; m t is the mass of cherry tomatoes on the tth day after storage, with the unit of g.

[0100] The films prepared in Examples 1-8 were analyzed and compared, and the comparison results obtained through the water vapor permeation test are shown respectively as Figure 1 follows. The water vapor permeabilities of Examples 1-8 are 1.26×10 -6 g / (m·h·Pa), 1.17×10 -6 g / (m·h·Pa), 1.66×10 -6 g / (m·h·Pa), 4.81×10 -6 g / (m·h·Pa), 2.44×10 -6 g / (m·h·Pa), 2.03×10 -6 g / (m·h·Pa), 5.71×10 -6 g / (m·h·Pa), 2.50×10 -6 g / (m·h·Pa). There is no obvious difference in the water vapor permeabilities of Example 1 and Example 2. It can be seen that the addition of oxalic acid and titanium dioxide has no effect on the water vapor permeability of the film. The water vapor permeabilities of Examples 3-7 are significantly higher than those of Examples 1 and 2, indicating that the humidity regulator can improve the water vapor permeability of the film, and this change is caused by the introduced hydroxyl groups. The water vapor permeabilities of Examples 3, 5, and 6 show a trend of first increasing and then decreasing with the increase of the phytic acid addition amount, which may be due to the cross-linking of excessive phytic acid itself resulting in a decrease in the water vapor permeability. The water vapor permeability of Example 7 is higher than that of Example 4, but due to the excessive addition of glycerol, the film has too strong hydrophilicity, and water droplets condense on the film surface even in the natural environment, which is not suitable for use as food fresh-keeping packaging. Example 8 added both glycerol and phytic acid, and its water vapor permeation rate is between that of Example 3 and Example 4, balancing the water vapor permeabilities of the two.

[0101] The films prepared in Example 1, Example 2, Example 3, and Example 4 were analyzed and compared, and their infrared spectrum data are shown as Figure 2 follows. A hydroxyl characteristic peak appears at 3302 cm -1 in Example 1, which is caused by the stretching vibration of -OH between and within molecules; the absorption peak at 1731 cm -1 originates from -C=O generated by the cross-linking of hydroxyl groups within the polyvinyl alcohol molecule, and the absorption peak at 1087 cm -1 is caused by the C-OH vibration in the polyvinyl alcohol molecule. The hydroxyl peak in Example 2 redshifts from 3302 cm -1 to 3294 cm -1 , and the ester carbonyl peak redshifts from 1731 cm -1Red-shifted to 1718 cm -1 , indicating that crosslinking occurred between oxalic acid and polyvinyl alcohol. In Example 3, the characteristic peak of the hydroxyl group corresponding to 3270 cm -1 showed a red shift, and the C-OH characteristic peak at 1033 cm -1 broadened. In Example 4, the hydroxyl peak showed a red shift and the peak intensity increased, and the intensity of the C-OH characteristic peak at 1035 cm -1 increased, indicating that hydrogen bonds were generated between the compounds, and the increase in peak intensity was caused by the introduction of a large number of hydroxyl groups.

[0102] The films prepared in Example 1, Example 2, Example 3, and Example 4 were analyzed and compared. The comparison results obtained through mechanical tensile tests and water resistance tests are shown respectively as Figures 3 to 5 . The tensile strength of Example 2 was higher than that of Example 1 because the esterification reaction between oxalic acid and polyvinyl alcohol enabled Example 2 to have a more compact crosslinked network structure. The addition of phytic acid significantly increased both the tensile strength and elongation at break of Example 3, and the addition of glycerol significantly increased the elongation at break of Example 4. From Figure 4 and Figure 5 , it can be seen that Example 1 was completely dissolved in water and its swelling rate could not be measured. The water solubility of Example 2, Example 3, and Example 4 was significantly lower than that of Example 1, and the water solubility of Example 3 and Example 4 was higher than that of Example 2 because the addition of phytic acid and glycerol introduced a large number of hydroxyl groups, increasing the hydrophilicity of Example 3 and 4. In summary, the mechanical properties of the modified polyvinyl alcohol-based moisture-regulating antibacterial film proposed by the present invention were enhanced, the water resistance was significantly improved, and the water vapor transmission coefficient increased significantly.

[0103] The films prepared in Example 1, Example 3, and Example 4 were used as packaging materials to preserve cherry tomatoes. As a group, cherry tomatoes packaged with commercially available PE lids were used as the PE group, and cherry tomatoes without packaging were used as the control group. Through the preservation test, a curve graph showing the change of the weight and humidity of cherry tomatoes over time was drawn, as shown in Figure 6 , 7 , and photos were taken and recorded as shown in Figure 8 .

[0104] It can be seen from Figure 6 that the fruit weight of cherry tomatoes in both groups of packaging materials was decreasing, but the mass of cherry tomatoes packaged with the modified polyvinyl alcohol-based moisture-regulating antibacterial film decreased less than that of cherry tomatoes without packaging, indicating that the modified polyvinyl alcohol-based moisture-regulating antibacterial film had a good preservation effect on cherry tomatoes.

[0105] It can be seen from Figure 7It can be seen that the humidity inside the modified polyvinyl alcohol-based humidity-regulating and antibacterial film packaging is significantly lower than that inside the commercially available PE lid packaging. Among them, the modified polyvinyl alcohol-based humidity-regulating and antibacterial film can control the humidity inside the packaging material at 80%-90%, while the humidity inside the commercially available PE lid packaging is 100%. Excessively high humidity aggravates the decay of cherry tomatoes, indicating that the modified polyvinyl alcohol-based humidity-regulating and antibacterial film has a good fresh-keeping effect on cherry tomatoes.

[0106] It can be seen from Figure 8 It can be seen that the cherry tomatoes packaged in the commercially available PE lid were severely decayed on the 7th day, while the cherry tomatoes packaged in the modified polyvinyl alcohol-based humidity-regulating and antibacterial film were still in a relatively fresh state on the 7th day, indicating that the modified polyvinyl alcohol-based humidity-regulating and antibacterial film has a good fresh-keeping effect on cherry tomatoes.

[0107] The above experiments can prove that the modified polyvinyl alcohol-based humidity-regulating and antibacterial film prepared by using the present invention has a significant fresh-keeping effect and can extend the storage period of fruits and vegetables.

[0108] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A modified polyvinyl alcohol-based humidity-regulating and antibacterial film, characterized in that, It includes the following components by weight:

2. The modified polyvinyl alcohol humidity-regulating and antibacterial film according to claim 1, wherein The modified polyvinyl alcohol-based humidity-regulating antibacterial film comprises the following components in parts by weight:

3. The modified polyvinyl alcohol-based humidity-regulating and antibacterial film according to claim 1 or 2, wherein, The humidity regulator is at least one of glycerol and phytic acid solution.

4. The modified polyvinyl alcohol humidity-regulating and antibacterial film according to claim 3, wherein, The mass concentration of the phytic acid solution is 40-60%.

5. The moisture-adjusting and antibacterial modified polyvinyl alcohol film according to claim 1 or 2, characterized in that, The antibacterial agent is titanium dioxide nanoparticles, silver nanoparticles and zinc oxide nanoparticles.

6. The moisture-regulating antibacterial film made of modified polyvinyl alcohol according to claim 1, characterized in that, The thickness of the modified polyvinyl alcohol humidity-regulating and antibacterial film is 0.10 mm to 0.20 mm, and the water vapor permeability is 1.2×10 -6 g / (m·h·Pa) to 6.0×10 -6 g / (m·h·Pa).

7. The humidity-adjusting antibacterial film made of modified polyvinyl alcohol according to claim 1, characterized in that, The modified polyvinyl alcohol-based humidity-regulating antibacterial film has a tensile strength of 20 to 60 MPa and a breaking elongation of 200% to 370%.

8. A method for preparing the modified polyvinyl alcohol-based moisture-regulating and antibacterial film according to any one of claims 1 to 7, characterized in that, The steps include: (1) dissolving the antibacterial agent in water, adding polyvinyl alcohol and oxalic acid, heating and stirring to form a uniform solution; (2) adding a humidity regulator to the uniform solution, stirring, defoaming, casting into a film, and drying to obtain a modified polyvinyl alcohol-based humidity-regulating antibacterial film.

9. The preparation method of the modified polyvinyl alcohol-based humidity-regulating and antibacterial film according to claim 8, characterized in that, The mass fraction of water in step (1) is 150 to 200 parts, the heating temperature is 70 to 90° C., the stirring speed is 200 to 500 rpm, and the time is 2 to 6 hours; The drying temperature in step (2) is 50 to 80° C., and the drying time is 2 to 8 hours.

10. Use of the modified polyvinyl alcohol-based humidity-regulating antibacterial film according to any one of claims 1 to 7 in food packaging and food preservation.

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