Polyvinyl alcohol film as well as preparation method and application thereof in preservation of edible mushrooms

Abstract

The invention discloses a polyvinyl alcohol film as well as a preparation method and application thereof in preservation of edible mushrooms, aiming at the problem that edible mushrooms (especially white mushrooms) are easy to brown after being picked and influence the appearance and the eating quality, nano particles (mesoporous silica) are used as a carrier to enhance the antioxidant activity of hericium erinaceus polysaccharide, and metal ion chelating modification is combined, so that the anti-oxidation activity of hericium erinaceus polysaccharide is enhanced. The PVA packaging film is prepared through tape casting, so that easily-oxidized components in polysaccharide are protected, the PVA film material is endowed with antioxidant and antibacterial activity, the possibility of enzymatic browning and microorganism invasion after edible fungi are harvested is reduced, the browning phenomenon is reduced from the two aspects of internal causes and external causes, the quality of the harvested edible fungi is improved, and the preservation period of the edible fungi is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of food preservation film preparation technology, specifically relating to a polyvinyl alcohol film, its preparation method, and its application in the preservation of edible fungi. Background Technology

[0002] Edible fungi are a healthy food sourced from high-protein, low-fat ingredients rich in bioactive components. However, their high water content and strong post-harvest respiration make them prone to browning, dehydration, textural changes, and autolysis, thus shortening their storage and transportation lifespan and reducing their commercial and edible value. Browning, in particular, has a more significant impact on the appearance and post-harvest quality of white mushrooms such as king oyster mushrooms and button mushrooms.

[0003] Studies have confirmed that the browning mechanism of edible fungi has a dual nature: internally, phenolic compounds contained in the fungus undergo enzymatic reactions catalyzed by polyphenol oxidase and peroxidase, generating brown polymers; externally, microbial invasion (such as Pseudomonas and yeast) disrupts cell membrane integrity, accelerating the release of intracellular phenolic substances and further intensifying the browning process through metabolic products. To address this issue, the industry has developed various preservation technologies, such as low-temperature storage and modified atmosphere packaging. However, low-temperature storage requires continuous energy consumption, resulting in high costs and difficulty in covering the entire distribution process; traditional modified atmosphere packaging requires high precision in gas ratio control and cannot simultaneously address the synergistic hazards of microbial contamination and enzymatic browning, limiting its application scenarios.

[0004] Film preservation technology has become an important development direction for post-harvest preservation of edible fungi due to its ease of operation, controllable cost, and ability to specifically regulate the gas environment. This technology can suppress respiration intensity and reduce ethylene production by regulating the oxygen and carbon dioxide concentrations inside the packaging, while simultaneously blocking the invasion of external microorganisms and delaying quality deterioration. Polyvinyl alcohol (PVA), as a commonly used packaging substrate, has excellent film-forming properties, transparency, and mechanical properties, but it also has significant drawbacks. It has poor water resistance and is prone to swelling and deformation in high-humidity storage environments, resulting in loss of packaging integrity. Furthermore, it lacks antioxidant and antibacterial activity and cannot function effectively against the dual mechanisms of browning in edible fungi, thus its preservation effect is limited when used alone.

[0005] Hericium erinaceus (monkey head mushroom) has high edible and medicinal value, and hericium polysaccharide (HEP) is its main active substance. HEP can enhance the body's ability to resist oxidative stress and reduce the degree of cell damage caused by free radical attack and cell membrane damage, exhibiting strong antioxidant capacity. However, its bioavailability is low and the effective components are severely lost during use. Therefore, appropriate modification of HEP, such as altering its spatial structure, the type, number, and position of substituents, is necessary to fully realize its biological activity.

[0006] CN 110051647 B discloses a method for preparing Hericium erinaceus polysaccharide chelated zinc microcapsules. Using a polysaccharide-zinc chelate as the core material and carrageenan:chitosan:β-cyclodextrin as the wall material, microcapsules are formed through homogenization, emulsification, and spray drying. This method enhances the stability and antioxidant activity of the polysaccharide. Although this method improves the stability and antioxidant activity of HEP (Heric Emulsion Extract), the microcapsules exhibit poor dispersibility in the film substrate, are prone to aggregation, and are difficult to fully exert their effects. CN 109045308 B discloses a method for preparing chitosan / carbon nanotube / Heicium erinaceus polysaccharide, loading Hericium erinaceus polysaccharide onto chitosan-carboxylated multi-walled carbon nanotubes, enhancing the drug loading capacity and encapsulation efficiency of the carbon nanotubes. However, carbon nanotubes suffer from poor biocompatibility and high production costs, limiting their large-scale application in the food packaging field. Summary of the Invention

[0007] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0008] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0009] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing polyvinyl alcohol film.

[0010] To solve the above-mentioned technical problems, the present invention provides the following technical solution: including, Hericium erinaceus polysaccharide solution was mixed with ZnSO4 solution and heated to react, followed by dialysis and freeze-drying to obtain Hericium erinaceus polysaccharide chelated zinc ions; Hericium erinaceus polysaccharide chelated zinc ion solution was ultrasonically mixed and dispersed with mesoporous silica nanoparticles, then magnetically stirred, and freeze-dried to obtain mesoporous silica-loaded Hericium erinaceus polysaccharide. After heating the PVA solution until it is completely dissolved, cool it down, add mesoporous silica-supported Hericium erinaceus polysaccharide, and continue stirring the reaction to obtain the coating solution. After ultrasonic degassing, the coating solution is scraped and dried by heating before peeling off to obtain a polyvinyl alcohol film.

[0011] In a preferred embodiment of the method for preparing the polyvinyl alcohol film of the present invention, the concentration of the Hericium erinaceus polysaccharide solution is 12-14 mg / ml.

[0012] In a preferred embodiment of the method for preparing the polyvinyl alcohol film of the present invention, the concentration of the ZnSO4 solution is 0.35~0.45 mol / L.

[0013] In a preferred embodiment of the method for preparing the polyvinyl alcohol film of the present invention, the reaction temperature of the mixture of Hericium erinaceus polysaccharide solution and ZnSO4 solution is 30~50℃ and the reaction time is 3~5h.

[0014] In a preferred embodiment of the method for preparing the polyvinyl alcohol film of the present invention, the specific surface area of ​​the mesoporous silica nanoparticles is >700 cm². 3 ·g -1 Aperture < 5nm.

[0015] In a preferred embodiment of the method for preparing the polyvinyl alcohol film of the present invention, the hericium erinaceus polysaccharide chelated zinc ion solution and mesoporous silica nanoparticles are ultrasonically mixed and dispersed and then magnetically stirred, wherein the mass ratio of the hericium erinaceus polysaccharide chelated zinc ions to the mesoporous silica nanoparticles is 1:1.

[0016] In a preferred embodiment of the method for preparing the polyvinyl alcohol film of the present invention, the amount of mesoporous silica-supported Hericium erinaceus polysaccharide added is 2-3 wt% compared to the amount of PVA solution.

[0017] In a preferred embodiment of the method for preparing the polyvinyl alcohol film according to the present invention, the method for preparing the mesoporous silicon nanoparticles includes, 0.6-0.8 g of hexadecyltrimethylammonium bromide and 0.2-0.4 g of gelatin were poured into a mixture of 220-240 mL of deionized water and 60-80 mL of isopropanol. Then, 0.2-0.3 g of KCl, 10-15 mL of ammonia, and 1.4-1.7 mL of mesitylene were added sequentially. The mixture was heated to 60-65 °C and stirred for 0.5-1 h. Then, 18-20 mL of a mixture of tetraethyl orthosilicate and methanol in a volume ratio of 1:1-2 was added dropwise. The mixture was stirred and reacted for 2-3 h. After aging for 2-3 h, the mixture was cooled, filtered, washed, and vacuum dried at 30-40 °C for 10-12 h. The resulting powder was calcined at 500-550 °C for 12-14 h to obtain mesoporous silica nanoparticles.

[0018] Another object of the present invention is to provide a polyvinyl alcohol film having a contact angle of 50-60° and a free radical scavenging rate of >60%.

[0019] Another object of the present invention is to provide an application of polyvinyl alcohol film in the preservation of edible fungi, including mushrooms called twin mushrooms.

[0020] Beneficial effects of this invention: This invention addresses the issue of browning in edible fungi (especially white mushrooms) after harvest, which affects their appearance and edible quality. It provides a polyvinyl alcohol (PVA) film for preservation packaging of edible fungi, slowing down browning during storage. This invention uses nanoparticles (mesoporous silica) as a carrier to enhance the antioxidant activity of Hericium erinaceus polysaccharides, combined with metal ion chelation modification, and then casts the PVA packaging film. This protects the easily oxidized components in the polysaccharides, endowing the PVA film material with antioxidant and antibacterial activities, reducing the likelihood of enzymatic browning and microbial invasion after harvest. By addressing both internal and external factors, this invention reduces browning, improves the post-harvest quality of edible fungi, and extends their shelf life. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a transmission electron microscope (TEM) image of mesoporous silicon (MS) nanoparticles prepared in Example 1 of the present invention.

[0022] Figure 2 The nitrogen adsorption-desorption curves of mesoporous silica (MS) nanoparticles prepared in Example 1 of this invention are shown.

[0023] Figure 3 To compare the preservation effects of different films on button mushrooms.

[0024] Figure 4 This is a transmission electron microscope (TEM) image of commercially available mesoporous SiO2 used in Comparative Example 2 of this invention.

[0025] Figure 5 The nitrogen adsorption-desorption curves of commercially available mesoporous SiO2 used in Comparative Example 2 of this invention are shown. Detailed Implementation

[0026] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0027] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0028] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0029] Unless otherwise specified, all raw materials used in this invention are commercially available in the field. Among them, Hericium erinaceus polysaccharide was purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number S28439. The performance of the polyvinyl alcohol film in this invention is as follows: (1) The water contact angle of the thin film was tested using a contact angle meter (DSA25, Krüger GmbH, Germany). The water droplet content was 3 μL, and the surface wettability of the membrane material was measured by the contact angle size at 120 s.

[0030] (2) Evaluation of the antioxidant capacity of the film by DPPH free radical scavenging rate. Prepare 0.02 mmol / L DPPH ethanol solution, weigh 0.1 g of sample and cut it into small pieces, add it to 4 mL of DPPH ethanol solution, and measure the absorbance at 517 nm after standing in the dark for 30 min.

[0031] DPPH free radical scavenging rate / % = (A C -A B ) / A C ×100% Among them, A C and A B The absorbance values ​​are for the control group and the sample group, respectively.

[0032] (3) The storage time is determined based on the color, smell, texture and deterioration of the twin mushrooms. When the twin mushrooms produce a putrid smell, mold, autolysis, severe browning and shrinkage, they are considered to have reached the shelf life.

[0033] Example 1 This embodiment provides a method for preparing a polyvinyl alcohol film using mesoporous silica as a carrier, specifically: 1) Preparation of mesoporous silica (MS) nanoparticles: Weigh 0.6g CTAB and 0.4g gelatin, pour them into a mixture of 240mL deionized water and 80mL isopropanol, add 0.3g KCl, 10mL ammonia, and 1.7mL mesitylene in sequence, heat to 65℃, stir for 0.5h, add dropwise a mixture of 18mL tetraethyl orthosilicate and methanol (volume ratio 1:2), continue stirring and react for 3h, age for 2h, cool, filter, wash, and vacuum dry at 40℃ for 12h. The resulting powder is calcined at 550℃ for 12h to obtain MS.

[0034] Figure 1 The transmission electron microscope (TEM) image of the mesoporous silica (MS) nanoparticles prepared in this step is shown. Figure 2 The nitrogen adsorption-desorption curves for mesoporous silica (MS) nanoparticles show that the nanoparticles prepared in this step possess small size, porous structure, and a large specific surface area (759.15 cm²). 3 ·g -1 (Aperture 4.1 nm).

[0035] 2) Preparation of Hericium erinaceus polysaccharide chelated zinc ions (HEP-Zn): Using deionized water as a solvent, 12 mg / mL HEP solution and 0.45 mol / L ZnSO4 solution were prepared and reacted at 40 °C for 3 h to ensure thorough mixing. The mixture was then dialyzed and freeze-dried to obtain HEP-Zn.

[0036] 3) Preparation of Hericium erinaceus polysaccharide supported on mesoporous silica (HEP-MS): A 1 mg / mL HEP-Zn solution was prepared, and MS of the same mass as HEP-Zn was added (i.e., the mass ratio of HEP-Zn to MS was 1:1). The mixture was ultrasonically mixed and dispersed for 20 min, and then magnetically stirred at 40 °C for 12 h. The mixed solution was freeze-dried to obtain MS-HEP.

[0037] 4) Preparation of polyvinyl alcohol composite film (PVA / MS-HEP): A 14wt% PVA solution was prepared by adding PVA (1799) to deionized water. The solution was reacted at 95°C for 2 hours until completely dissolved. The temperature was then lowered to 40°C, and 2wt% HEP-MS was added. The mixture was stirred and reacted for another 3 hours to obtain a coating solution. After degassing under 500W ultrasonic power, the coating solution was poured onto a coating machine and a film was formed with a thickness of approximately 0.06 mm. The film was dried at 30°C and then peeled off, which is the PVA / MS-HEP film of this embodiment.

[0038] The preservation effect of the film prepared in Example 1 on button mushrooms was determined and compared with that of pure PVA. The results are as follows: Figure 3 And as shown in Table 1.

[0039] Table 1

[0040] from Figure 3It can be seen that the button mushrooms in the blank control group showed severe mold and browning after 3 days of storage, and the button mushrooms packaged with pure PVA film shrank severely on the 3rd day, accompanied by browning; while the button mushrooms packaged with PVA / MS-HEP film prepared in this example did not show mold after 4 days of storage, and the fruits were plump. Although the fruits were oxidized, the degree of browning was lower than that of the blank control group, indicating that PVA / MS-HEP film can effectively improve the browning and mold phenomena during storage and extend the shelf life of button mushrooms.

[0041] As can be seen from the data in Table 1, the polyvinyl alcohol preservation film prepared in this application has antioxidant and antibacterial activities. It reduces microbial contamination by inhibiting enzymatic reactions. The combined effect of these two factors can effectively improve the browning phenomenon in edible fungi during post-harvest packaging and storage, enhance the preservation time of edible fungi, and expand the application scope of polyvinyl alcohol as a packaging material.

[0042] Furthermore, the small size effect and large specific surface area of ​​nanoparticles in this application not only effectively increase the loading of Hericium erinaceus polysaccharides, but also help improve the strong hydrophilicity of polyvinyl alcohol film, thus meeting actual packaging requirements.

[0043] Example 2 The difference between this embodiment and Example 1 is that the mass ratio of HEP-Zn to MS in step 3) is adjusted to 1:2 or 2:1. The remaining steps are the same as in Example 1. The PVA / MS-HEP film of this embodiment is obtained, and the relevant properties are measured and compared with the 1:1 ratio of Example 1. The results are shown in Table 2.

[0044] Table 2

[0045] As shown in Table 2, when the mass ratio of HEP-Zn to MS is 1:1, the polyvinyl alcohol composite film has a high DPPH free radical scavenging rate, extending the storage time of button mushrooms to 5 days. Adjusting the mass ratio of HEP-Zn to MS, when the proportion of MS in the composite film increases, the free radical scavenging rate of the composite film decreases, making the button mushrooms more susceptible to oxidation during storage and shortening the storage time. When the proportion of HEP-Zn in the composite film increases, the contact angle of the composite film decreases, i.e., the water resistance is poor, and the film easily absorbs water during storage, damaging the membrane structure and hindering practical applications.

[0046] Example 3 The difference between this embodiment and Example 1 is that the amount of HEP-MS added to the PVA solution in step 4) was adjusted to 1wt%, 3wt%, and 4wt%, respectively. The remaining steps and processes were the same as in Example 1. The PVA / MS-HEP film of this embodiment was obtained, and the relevant properties were measured and compared with 2wt% in Example 1. The results are shown in Table 3.

[0047] Table 3

[0048] As shown in Table 3, when the MS-HEP content in the composite film is too low, the antioxidant effect is weak, and the mushrooms are prone to browning, which shortens the storage time and fails to meet the preservation requirements. With the increase of MS-HEP addition, the scavenging rate of DPPH free radicals of the polyvinyl alcohol composite film increases, but excessive MS-HEP is prone to agglomeration, which leads to poor air permeability of the composite film and causes swelling and condensation during storage, thus shortening the storage time.

[0049] Comparative Example 1 The difference between this comparative example and Example 1 is that the preparation of MS in step 1) is omitted, and the MS used in subsequent steps is replaced with commercially available solid SiO2 (purchased from Hefei Qianguo New Material Technology Co., Ltd.). The remaining steps are the same as in Example 1, and the plastic wrap of this comparative example is obtained.

[0050] Comparative Example 2 The difference between this comparative example and Example 1 is that the preparation of MS in step 1) is omitted, and the MS used in subsequent steps is replaced with commercially available mesoporous SiO2 (purchased from Hefei Qianguo New Material Technology Co., Ltd.). The remaining steps are the same as in Example 1, and the plastic wrap of this comparative example is obtained.

[0051] Figure 4 This is a transmission electron microscope (TEM) image of commercially available mesoporous SiO2 used in this comparative example. Figure 5 The nitrogen adsorption-desorption curves of commercially available mesoporous SiO2 used in this comparative example show that its specific surface area is 138.33 cm². 3 ·g -1 The pore size is relatively large (>18nm) and the distribution is uneven.

[0052] The relevant properties of the plastic wrap prepared in Comparative Examples 1 and 2 were measured and compared with those in Example 1. The results are shown in Table 4.

[0053] Table 4

[0054] Table 4 shows that using commercially available mesoporous SiO2 as a carrier to prepare polyvinyl alcohol composite membrane materials resulted in a decreased free radical scavenging rate of DPPH and a shortened storage time for *Agaricus bisporus*. Comparative TEM tests revealed that MS exhibited continuous worm-like channels, while the commercially available mesoporous SiO2 showed discontinuous channels with uneven pore size distribution. This affects the loading and release of HEP-Zn by the carrier, leading to a decrease in the film's antioxidant properties and packaging performance.

[0055] Example 4 The difference between this embodiment and Example 1 is that the amount of mesitylene added in step 1) of preparing mesoporous silica (MS) nanoparticles was adjusted to 0~2mL. The remaining steps were the same as in Example 1. The PVA / MS-HEP film of this embodiment was obtained and the relevant properties were measured. The results are shown in Table 5.

[0056] Table 5

[0057] Table 5 shows that by changing the TMB content, the prepared mesoporous silica exhibits different pore sizes. This larger pore size structure is beneficial for loading larger active molecules, enhancing the bioactivity of the composite membrane. When the TMB addition amount is 1.7 mL, the silica carrier exhibits higher activity in the fixation of HEP-Zn, thus the composite membrane material has stronger antioxidant and antibacterial properties, better protecting *Agaricus bisporus* from browning and rotting. When excessive TMB is added, the ordered assembly structure of CTAB micelles is disrupted, resulting in smaller MS pore sizes, affecting the enrichment and immobilization of macromolecules, leading to a decrease in the free radical scavenging performance of the composite membrane material, thereby shortening its packaging performance for *Agaricus bisporus*.

[0058] Example 5 The difference between this embodiment and Example 1 is that the concentration of the HEP solution in step 2) of preparing zinc ions by chelating Hericium erinaceus polysaccharide is adjusted to 10~16 mol / mL. The remaining steps are the same as in Example 1. The PVA / MS-HEP film of this embodiment was obtained and the relevant properties were measured. The results are shown in Table 6.

[0059] Table 6

[0060] Table 6 shows that the DPPH radical scavenging effect of the polyvinyl alcohol composite film increases with increasing HEP concentration, achieving optimal preservation of button mushrooms at concentrations of 12 mg / mL and 14 mg / mL. However, further increasing the HEP concentration leads to a decrease in the DPPH radical scavenging rate of the film and a shortening of the preservation time of the button mushrooms. Therefore, 12 mg / mL was selected as the optimal HEP concentration.

[0061] Example 6 The difference between this embodiment and Example 1 is that the concentration of the ZnSO4 solution in the preparation process of zinc ion chelation by Hericium erinaceus polysaccharide in step 2) is adjusted to 0.25~0.55mol / L. The remaining steps are the same as in Example 1. The PVA / MS-HEP film of this embodiment was obtained, and the relevant properties were measured. The results are shown in Table 7.

[0062] Table 7

[0063] Table 7 shows that the concentration of ZnSO4 solution has no significant effect on the DPPH radical scavenging rate of polyvinyl alcohol (PVA) film. However, due to the good antibacterial properties of Zn ions, low concentrations of ZnSO4 solution make the film susceptible to microbial attack, and *Hypericum bisporus* (button mushrooms) are prone to mold growth, reaching their shelf life in just 3 days. As the concentration of ZnSO4 solution increases, more Zn ions react with HEP, and the film can better inhibit browning and mold growth, extending the storage time of *Hypericum bisporus* to 5 days. However, excessively high concentrations of ZnSO4 solution weaken the electrostatic attraction between the negative charge of HEP and the Zn ion, reducing their binding efficiency and stability, which is detrimental to storage and packaging.

[0064] Comparative Example 3 The difference between this comparative example and Example 1 is that Hericium erinaceus polysaccharide is replaced with Trametes versicolor polysaccharide, while the remaining steps and processes are the same as in Example 1, resulting in the composite membrane of this comparative example.

[0065] Comparative Example 4 The difference between this comparative example and Example 1 is that the Hericium erinaceus polysaccharide does not chelate zinc ions and is directly loaded onto mesoporous silica. The remaining steps and processes are the same as in Example 1, resulting in the composite membrane of this comparative example.

[0066] The performance of the composite membranes prepared by Comparative Example 3 (CVPS-Zn) and Comparative Example 4 (HEP) was measured and compared with that of Example 1 (HEP-Zn). The results are shown in Table 8.

[0067] Table 8

[0068] Table 8 shows that the polyvinyl alcohol composite membrane prepared with *Trametes versicolor* polysaccharide exhibited lower DPPH radical scavenging rate and shorter storage time for *Agaricus bisporus* than the polyvinyl alcohol composite membrane prepared with *Hericium erinaceus* polysaccharide. This indicates that the combination of *Hericium erinaceus* polysaccharide with other components in this application system has superior antioxidant and antibacterial effects, thereby improving browning and spoilage. Direct loading of HEP onto MS had little effect on the antioxidant effect of the composite membrane, but *Agaricus bisporus* reached its storage limit on day 4. This suggests that HEP chelation of Zn ions helps extend the storage time of *Agaricus bisporus*. This may be because the synergistic antibacterial effect of Zn ions and HEP further prevents microbial contamination and spoilage of *Agaricus bisporus* during storage.

[0069] In summary, this application utilizes the small size effect and large specific surface area of ​​nanoparticles to effectively increase the loading of Hericium erinaceus polysaccharides and improve the strong hydrophilicity of polyvinyl alcohol (PVA) films, meeting practical packaging requirements. The prepared PVA preservation film exhibits antioxidant and antibacterial activities, reducing microbial contamination while inhibiting enzymatic reactions. The combined effect of these two factors effectively improves browning during post-harvest packaging and storage of edible fungi, enhances their shelf life, and expands the application scope of PVA as a packaging material.

[0070] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A process for the production of a polyvinyl alcohol film, characterized by: Comprising, The monkey head mushroom polysaccharide solution is mixed with the ZnSO4 solution and heated to react, and then dialyzed and freeze-dried to obtain monkey head mushroom polysaccharide chelated zinc ions; The monkey head mushroom polysaccharide chelated zinc ion solution is mixed with the mesoporous silica nanoparticles under ultrasonic dispersion and then magnetically stirred, and then freeze-dried to obtain mesoporous silica loaded monkey head mushroom polysaccharide; The PVA solution is heated to complete dissolution, cooled, and then the mesoporous silica loaded monkey head mushroom polysaccharide is added and continuously stirred to react to obtain a coating solution. The coating solution is deaerated by ultrasonic, and then a film is scraped and dried to obtain a polyvinyl alcohol film.

2. The method of producing a polyvinyl alcohol film according to claim 1, characterized by: The concentration of the monkey head mushroom polysaccharide solution is 12-14 mg / ml.

3. The method of producing a polyvinyl alcohol film according to claim 1, characterized by: The concentration of the ZnSO4 solution is 0.35-0.45 mol / L.

4. The process for the production of polyvinyl alcohol films according to any one of claims 2 or 3, characterized in that: The reaction temperature of the monkey head mushroom polysaccharide solution mixed with the ZnSO4 solution and heated to react is 30-50°C, and the reaction time is 3-5 h.

5. The method of producing a polyvinyl alcohol film according to claim 1, characterized by: The mesoporous silica nanoparticles have a specific surface area > 700 cm 3 ·g -1 , and a pore size < 5 nm.

6. The method of producing a polyvinyl alcohol film according to claim 5, characterized by: The monkey head mushroom polysaccharide chelated zinc ion solution is mixed with the mesoporous silica nanoparticles under ultrasonic dispersion and then magnetically stirred, and the mass ratio of the monkey head mushroom polysaccharide chelated zinc ion to the mesoporous silica nanoparticles is 1:

1.

7. The method of producing a polyvinyl alcohol film according to claim 4, characterized by: The addition amount of the mesoporous silica loaded monkey head mushroom polysaccharide compared to the PVA solution is 2-3 wt%.

8. The method of producing a polyvinyl alcohol film according to claim 5, characterized by: The preparation method of the mesoporous silica nanoparticles comprises, 0.6-0.8 g of cetyltrimethylammonium bromide and 0.2-0.4 g of gelatin are poured into a mixture of 220-240 mL of deionized water and 60-80 mL of isopropyl alcohol, and then 0.2-0.3 g of KCl, 10-15 mL of ammonia water, and 1.4-1.7 mL of mesitylene are sequentially added, the temperature is raised to 60-65°C, and the mixture is stirred for 0.5-1 h, 18-20 mL of a mixture of n-silicate and methanol with a volume ratio of 1:1-2 is added dropwise, the stirring is continued for 2-3 h, and the mixture is aged for 2-3 h, then filtered, washed, and dried in a vacuum at 30-40°C for 10-12 h, and the obtained powder is calcined at a high temperature of 500-550°C for 12-14 h to obtain the mesoporous silica nanoparticles.

9. The polyvinyl alcohol film prepared by the production method according to any one of claims 1 to 3, 5 to 8, characterized by: The contact angle of the polyvinyl alcohol film is 50-60°, and the free radical scavenging rate is >60%.

10. The polyvinyl alcohol film according to claim 9 for use in the preservation of edible mushrooms, characterized in that: The edible fungus comprises a double-belly mushroom.

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