A slow-release label for preserving fruits, vegetables, and edible fungi, its preparation method, and its application.

Abstract

This invention belongs to the technical field of agricultural product preservation materials. It discloses a slow-release label paper for preserving fruits and vegetables / edible fungi, its preparation method, and its application. The slow-release label paper includes an antibacterial layer (1), a preservation-inducing layer (2), a self-absorbent layer (3), and an ethylene adsorption color-developing printing layer (4). The antibacterial layer (1), the preservation-inducing layer (2), the self-absorbent layer (3), and the ethylene adsorption color-developing printing layer (4) are tightly bonded together from the inside out. This invention provides a label material with preservation effects on agricultural products, especially fruits, vegetables, and edible fungi. It can be applied to fruit and vegetable preservation. Compared with existing technologies, the label of this invention uses natural plant-derived active ingredients (Sichuan pepper extract) to replace chemically synthesized substances, inhibiting the main factors causing fruit and vegetable spoilage at the source, thereby significantly extending the shelf life and maintaining quality.

Description

Technical Field

[0001] This invention belongs to the field of agricultural product preservation materials technology, and in particular to a slow-release label paper for preserving fruits and vegetables / edible fungi, its preparation method and its application. Background Technology

[0002] Fruits and vegetables are highly susceptible to spoilage and decay after harvest due to microbial growth and respiration, resulting in resource waste and significant economic losses. Traditional preservation methods are insufficient to meet the demands for long-term, efficient preservation, necessitating innovative technologies. Slow-release fruit and vegetable labels can extend shelf life by releasing preservative components and provide visual information about the condition of fruits and vegetables, meeting consumer needs. Therefore, the development potential of slow-release fruit and vegetable labels is vast.

[0003] 1-MCP, as an ethylene inhibitor, has multiple functions, including delaying fruit ripening and postharvest softening, reducing chilling injury, and improving disease resistance. Currently, the 1-MCP used for fruit and vegetable storage is mainly a powder form encapsulated with α-cyclodextrin. Its application method involves dissolving α-cyclodextrin in water to release the 1-MCP gas for fumigation. This method requires precise calculation of the dosage before use and a long fumigation time in a sealed space, making the process extremely cumbersome. Furthermore, studies have found that even after 1-MCP fumigation, ethylene levels in some fruits and vegetables gradually recover during long-term storage, causing the ethylene-induced ripening process to restart and failing to achieve good preservation results.

[0004] The role of sodium nitroprusside in fruit and vegetable preservation primarily stems from its characteristic as a nitric oxide (NO) donor. It exerts multiple preservation mechanisms by releasing NO, with its core function being to significantly delay fruit and vegetable senescence. NO effectively inhibits ethylene biosynthesis and also regulates respiratory metabolism, reducing respiration intensity and minimizing energy and substrate consumption. Furthermore, the NO released by sodium nitroprusside enhances the antioxidant defense system of fruits and vegetables, maintaining cell membrane and cell wall integrity, and preserving firmness and freshness. NO also induces disease resistance, activating plant defense responses, promoting the synthesis of antimicrobial substances, and directly inhibiting the growth of certain pathogens at certain concentrations, thus reducing post-harvest decay. For cold-sensitive fruits and vegetables, sodium nitroprusside treatment can also alleviate chilling injury by stabilizing cell membranes and enhancing stress resistance to mitigate damage caused by low temperatures.

[0005] Chinese patent publication CN109527081A discloses "a 1-methylcyclopropene sustained-release adhesive and its preparation method and application". The method uses cyclodextrin, gelatin and other materials to encapsulate 1-methylcyclopropene for sustained release of 1-MCP. The product is an adhesive, which needs to be applied to the inside of the fruit packaging when used. The operation is relatively complicated. At the same time, after application, it will stick to the fruits and vegetables, which will reduce consumers' desire to buy to some extent.

[0006] Chinese patent publication CN112878105A discloses a "slow-release 1-MCP preservation paper for Xinjiang white apricots and its application." This preservation paper is made by coating 1-MCP onto kraft paper using ethyl cellulose (EC) and polyacrylic acid (PAA), followed by high-temperature drying. The paper base of this invention is kraft paper, which has almost no antibacterial effect. PAA, one of the raw materials, is a Group 3 carcinogen, posing a certain risk to human health. Furthermore, the PAA-based paper absorbs water and can stick to fruits and vegetables, causing damage. While this preservation paper can achieve slow release of 1-MCP gas, its ease of use is poor, hindering its market promotion.

[0007] By comparison, the present invention patent application is fundamentally different from the aforementioned patent publications. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a slow-release label paper for preserving fruits and vegetables / edible fungi, its preparation method and its application.

[0009] The technical solution adopted by this invention to solve its technical problem is:

[0010] A slow-release label for preserving fruits, vegetables, and edible fungi includes an antibacterial layer, a preservation-inducing layer, a self-absorbent layer, and an ethylene-adsorbent color-developing printing layer. These layers are sequentially and tightly adhered together from the inside out. The antibacterial layer is located on the inside, and its layers self-adsorb onto the ethylene-adsorbent color-developing printing layer, forming a slow-release label that delays post-harvest softening and other quality maintenance effects of fruits, vegetables, and edible fungi, thus extending their shelf life.

[0011] The method for preparing the slow-release label paper as described above involves sequentially and tightly arranging the antibacterial layer, the preservation and inducing layer, the self-absorbent layer, and the ethylene adsorption and color development printing layer together from the inside out.

[0012] Furthermore, the method for preparing the antibacterial layer includes the following steps:

[0013] Nanocellulose (CNF) was diluted to a concentration of 0.2-0.5 wt% and magnetically stirred at 200-1000 rpm for 1-4 hours until a uniform gel state was obtained, yielding a CNF suspension with a concentration of 0.2-0.5 wt%. Powdered Sichuan peppercorns were mixed with anhydrous ethanol at a ratio of 1:10-1:30 (g:ml). The mixture was placed in an ultrasonic cleaner and sonicated at 40-60℃ and 150-300W for 20-50 minutes. After filtration through five layers of gauze, the filtrate was collected and concentrated under reduced pressure using a rotary evaporator at 30-50℃ to recover the ethanol, yielding the Sichuan peppercorn extract. The Sichuan peppercorn extract was then added to a 0.2-0.5 wt% CNF suspension. In the CNF suspension, the mass ratio of Sichuan pepper extract to CNF suspension is 1:4-1:20. The mixture is magnetically stirred at 300-800 rpm for 0.5-2 hours until homogeneous. The mixed solution is poured into a Buchner funnel and vacuumed to form a wet film. It is then dried at room temperature for 12 hours to form a gel network framework. The mixture is then transferred to a constant temperature and humidity chamber at 30℃ and 50% RH. When the moisture content reaches 40%, it is placed in a 40℃ oven for 1-3 hours. Then, the temperature is raised to 60℃ and dried for 1-4 hours until the final moisture content is 8-10%, thus obtaining the antibacterial layer.

[0014] Furthermore, the method of setting the preservation-inducing layer on the antibacterial layer includes the following steps:

[0015] Polyvinylpyrrolidone (PVP) and ethyl cellulose (EC) were added to anhydrous ethanol and stirred, then sonicated until fully mixed to prepare a slow-release agent. 1-MCP powder and sodium nitroprusside were added to the prepared slow-release agent, stirred, and sonicated again to form a homogenate with the 1-MCP powder and sodium nitroprusside. The homogenate was evenly coated onto the outer surface of the antibacterial layer, so that the paper base contained 1-MCP powder and sodium nitroprusside. After coating, the semi-finished label with the homogenate was placed in an oven to dry, allowing the solvent to evaporate completely. Finally, a natural adhesive starch glue was brushed onto the inner surface of the antibacterial layer, and a polytetrafluoroethylene (PTFE) film was attached to facilitate adhesion to the surface of fruits and vegetables, resulting in an antibacterial layer and a preservation-inducing layer set together.

[0016] Furthermore, the mass ratio of polyvinylpyrrolidone (PVP) to ethyl cellulose (EC) is 1:0 to 4:1, and the amount of anhydrous ethanol added is 8 to 10 times the total mass of PVP and EC.

[0017] Alternatively, the sustained-release agent is prepared at a stirring temperature of 20–40°C, an ultrasonic power of 100W–300W, and an ultrasonic time of 2–10 min.

[0018] The 1-MCP powder is a powder-type 1-MCP encapsulated with α-cyclodextrin, and the ratio of polyvinylpyrrolidone: 1-MCP powder: sodium nitroprusside (g:g:mg) is 50:4:25 to 70:4:25.

[0019] Alternatively, add 1-MCP powder and sodium nitroprusside, and after stirring, sonicate again for 5-10 minutes, at a temperature of 20-35°C, with an ultrasonic power of 100W-300W and a sonication time of 3-15 minutes.

[0020] Alternatively, the coating amount of the homogenate is 0.1–0.4 ml / cm². 2 Ensure that the antibacterial layer contains 0.05–0.24 g of 1-MCP and 5 μM to 200 μM sodium nitroprusside powder, and the coating speed is 1–5 m / min.

[0021] Alternatively, the drying temperature of the oven is 40–80°C, and the drying time is 6–16 hours.

[0022] Furthermore, the method for preparing the self-absorbing water layer includes the following steps:

[0023] Citric acid powder was dissolved in deionized water to prepare a 3-6 wt% citric acid solution. CNF powder and the citric acid solution were mixed at a material-to-liquid ratio of 1:40-1:60 (g:ml). After thorough mixing, the mixture was placed in a thermostatic magnetic stirrer at 70-90℃ and reacted continuously at 600-1000 rpm for 3-5 hours. After the reaction, the mixture was immediately cooled to room temperature. The resulting mixture was then added to 10 times its volume of deionized water and centrifuged at 8000-10000 rpm for 5-15 minutes. The precipitate was collected and repeatedly washed with deionized water. The washed precipitate was then added to deionized water to form a suspension. The suspension was then placed in a dialysis bag and dialyzed for 3-5 days. The dialysis bag must be completely submerged in deionized water. The external deionized water was changed every 5-9 hours. The final product was obtained... Carboxylated CNF suspension was placed in a dialysis bag; the carboxylated CNF suspension was concentrated to a final mass concentration of 0.5-2.0 wt%, and 0.02-0.2 wt% polyvinyl alcohol (PVA) was added. The mixture was magnetically stirred at 300-1000 rpm for 1-3 hours to form a homogeneous sol. This sol was poured onto a polytetrafluoroethylene (PTFE) plate and frozen at -20°C for 1-3 hours, followed by freezing at -80°C for 5-12 hours to obtain a membrane. The crosslinking solution, a mixed aqueous solution consisting of 1-8 wt% citric acid, 0.5-2.5 wt% NaH2PO4, and water, was atomized and sprayed onto the membrane. Finally, plasma treatment was performed under the conditions of O2:Ar=3:1, power 100W, and treatment time 90s to obtain a nanoscale three-dimensional network + hydrophilic groups + microporous capillary effect active water-absorbing membrane, thus obtaining a self-absorbing water layer.

[0024] Furthermore, the preparation method of the ethylene adsorption color-developing printing layer includes the following steps:

[0025] Zeolite particles were immersed in a 20% KMnO4 aqueous solution (g:mL ratio of zeolite particles to KMnO4 aqueous solution was 5-20:25-100), ultrasonically vibrated for 20-60 min, and then rotary evaporated under reduced pressure at 60℃ to dryness, followed by vacuum drying at 80℃ for 4 h to obtain purplish-red loaded particles. The particles were passed through a 200-mesh sieve, and particles with a diameter ≤75μm were selected for later use. The loaded particles were placed in a fluidized bed and coated with a 5%-10% gelatin aqueous solution as a binder to form a dense release film, resulting in gelatin-coated particles. Bromocresol purple (BCP) powder was dissolved in ethanol, and then 1-3% chitosan acetic acid solution was added (bromocresol purple:1-3% chitosan acetic acid solution ratio was...). Example g:mL ratio 1:900, magnetic stirring for 2 h, to obtain purple BCP-chitosan mixture; in fluidized bed, spray gelatin-coated particles with BCP-chitosan mixture, control the inlet air temperature at 40℃, to complete the second coating layer, to obtain microcapsules; immerse the above microcapsules in 1%-4% sodium alginate solution, stir slowly for 5-30 min; transfer the coated particles to 2-6% CaCl2 solution, let stand for crosslinking for 10-40 min to form a gel outer layer; filter the coated particles and wash 3 times with deionized water; vacuum dry the obtained particles at 40℃ for 12 h to obtain the final ethylene adsorption colorimetric microcapsule particles;

[0026] The preparation steps of the 1-3% chitosan acetic acid solution are as follows: prepare a 1% acetic acid aqueous solution by mixing chitosan powder and 1% acetic acid aqueous solution at a material-liquid ratio of 1:100-3:100 (g:mL).

[0027] Nanocellulose (CNF) was diluted to a final concentration of 0.2-0.5 wt%, and magnetically stirred at 200-1000 rpm for 1-4 hours until a homogeneous gel state was achieved. The solution was poured into a Buchner funnel, and vacuum-sealed to form a wet film. The film was dried at room temperature for 12 hours to form a gel network framework. It was then transferred to a constant temperature and humidity chamber at 30°C and 50% RH. When the moisture content reached 40%, it was placed in a 40°C oven for 1-3 hours, and then dried at 60°C for 1-4 hours until the final moisture content was 8-10%, yielding an ethylene adsorption color-developing printing layer paper base. A coating of 0.025-0.225 ml / cm² was then applied to the inner side of the paper base. 2 The ethylene adsorption color-developing microcapsule particles are adhered to the ethylene adsorption color-developing printing layer paper base with the starch adhesive side brushed on. Label information can be printed on the outside of the paper base, and the ethylene adsorption color-developing printing layer is prepared.

[0028] Furthermore, the starch adhesive is a natural adhesive made from starch as a base material, characterized by its abundant source, low price, ease of use, and non-toxicity. The coating amount is 0.025–0.225 ml / cm². 2 .

[0029] The application of slow-release label paper for fruit and vegetable / edible fungi preservation as described above.

[0030] The application of the slow-release label paper for preserving fruits and vegetables / edible fungi as described above in delaying the softening properties of fruits and vegetables and / or edible fungi.

[0031] The advantages and positive effects of this invention are as follows:

[0032] 1. This invention provides a label material that preserves agricultural products, especially fruits, vegetables and edible fungi. It can be used in the preservation of fruits and vegetables. Compared with existing technologies, the label of this invention uses natural plant-derived active ingredients (Sichuan pepper extract) to replace chemically synthesized substances, thereby inhibiting the main factors that cause fruits and vegetables to rot and deteriorate at the source, thus significantly extending the shelf life and maintaining the quality.

[0033] 2. The 1-MCP in the label paper of this invention is an ethylene inhibitor with a higher affinity for ethylene. This makes 1-MCP more likely to preferentially and irreversibly bind to ethylene receptor proteins, thereby preventing the normal binding of ethylene to its receptor and hindering the transmission and expression of ethylene action signals. Polyvinylpyrrolidone (PVP) acts as a water-absorbing agent, a sustained-release agent, and an adhesive. Its adhesive properties improve the stability of the 1-MCP / α-cyclodextrin complex on the paper base. Its water-absorbing properties absorb moisture generated during the respiration of fruits and vegetables, thus achieving controlled release of 1-MCP. After water absorption, 1-MCP begins to be released, and PVP acts as a sustained-release agent to simultaneously control the slow release of 1-MCP. Ethyl cellulose (EC), as another sustained-release agent, can be combined with PVP to achieve sustained release of 1-MCP. By combining different controlled-release and sustained-release raw materials to exert a synergistic effect, the excellent performance of the 1-MCP sustained-release label is improved.

[0034] 3. The sodium nitroprusside in the label paper of this invention can slowly release NO upon contact with water. NO is an important gaseous signaling molecule that can inhibit ethylene biosynthesis and signal transduction, and reduce the accumulation of reactive oxygen species (ROS). Utilizing the multiple physiological regulatory functions of NO gas molecules, it can precisely regulate the stress resistance potential of fruits and vegetables by delaying aging, enhancing disease resistance, and alleviating chilling injury, reducing dependence on external intervention and achieving "inside-out" preservation. In the ethylene adsorption printing layer of the label, MnO4 is released slowly through microcapsules, targeting the oxidation of ethylene, reducing the concentration of ethylene in the environment, while inhibiting the activity of ACC oxidase in fruits and vegetables, maintaining cell structure, and delaying fruit softening.

[0035] 4. In the self-absorbing layer of the label paper of this invention, carboxyl groups strongly bind water molecules through hydrogen bonds and electrostatic interactions. The vertical through-pores constructed by freezing generate Laplace negative pressure, driving water to permeate in seconds (<0.3s). Cellulose nanofibers (3-5nm) form multi-level pores (porosity >83%), locking in moisture through nano-confinement. This layer achieves ultrafast intelligent response, and the material is safe and biodegradable.

[0036] 5. The preservation paper, i.e., the label paper of this invention, consists of four layers. The innermost layer is an antibacterial layer of antibacterial cellulose paper base containing Sichuan pepper extract. The paper base surface is coated with starch glue (non-toxic adhesive) and covered with polytetrafluoroethylene (PTFE). When in use, the label can be directly attached to fruits or edible fungi after tearing off the PTFE layer. The second layer is the core functional layer, which is a core component with anti-inducing preservation effects, such as polyvinylpyrrolidone (PVP) coupled with ethyl cellulose (EC), 1-MCP, and sodium nitroprusside. The core component complex and the slow-release homogenate constructed by PVP and EC are evenly coated on the paper base. The third layer is a nano-scale three-dimensional network + hydrophilic groups + microporous capillary effect active water absorption membrane adhered on the homogenate of the second layer. The fourth layer is a double-embedded potassium permanganate microcapsule (KMnO4) ethylene adsorption color development printing layer. Starch glue is brushed on the surface of the cellulose paper base, so that the double-embedded potassium permanganate color development microcapsule particles are evenly distributed on the paper base. The color change of bromocresol purple indicator shows the degree of ethylene adsorption. The outermost ethylene adsorption printing layer absorbs ethylene produced by fruits, vegetables, and fungi. When the bromocresol purple indicator turns yellow, it indicates that the ethylene adsorption in this layer has reached saturation. The third layer actively absorbs moisture produced by the respiration of fruits, vegetables, and fungi. When moisture is encountered, the 1-MCP and sodium nitroprusside in the second layer begin to be released, slowing down the deterioration process of fruits, vegetables, and edible fungi. The innermost layer is an antibacterial layer, effectively inhibiting fungal damage to fruits, vegetables, and edible fungi. The slow-release packaging label produced by this invention improves the preservation effectiveness, practicality, and convenience of slow-release labels.

[0037] 6. The label paper of this invention can delay the softening of fruits, vegetables and edible fungi after harvest, maintain their quality and extend their shelf life, improve the convenience of fruit and vegetable / edible fungi preservation paper, and effectively inhibit the respiration of fruits, vegetables and edible fungi, thereby delaying the softening of fruits and vegetables and extending their shelf life.

[0038] 7. In the method of this invention, a polytetrafluoroethylene (PTFE) membrane is selected. PTFE is a high-molecular polymer polymerized from tetrafluoroethylene as a monomer. It is stable at room temperature and pressure, has the lowest surface tension among solid materials, and does not adhere to any substance. Therefore, PTFE membrane is selected as the protective film for the adhesive. Attached Figure Description

[0039] Figure 1 The effect of the 4-layer label on the weight loss rate of hardy kiwifruit in Example 1 of this invention;

[0040] Figure 2This is a graph showing the effect of the 4-layer label on the rot rate of hardy kiwifruit according to Example 1 of the present invention;

[0041] Figure 3 This is a diagram showing the effect of the 4-layer label of Embodiment 1 of the present invention on the hardness of hardy kiwifruit;

[0042] Figure 4 This is a diagram showing the effect of the four-layer label on the brightness of the hardy kiwifruit according to Embodiment 1 of the present invention.

[0043] Figure 5 This is a diagram illustrating the effect of the four-layer label on the total color difference of the hardy kiwifruit in Embodiment 1 of the present invention.

[0044] Figure 6 This is a graph showing the effect of the 4-layer label of Example 1 of the present invention on the TSS content of hardy kiwifruit;

[0045] Figure 7 This is a graph showing the effect of the 4-layer label of Embodiment 1 of the present invention on the respiration intensity of hardy kiwifruit;

[0046] Figure 8 This is a graph showing the effect of the four-layer label of Example 1 of the present invention on the ethylene release of hardy kiwifruit;

[0047] Figure 9 This is a diagram showing the effect of the 4-layer label of Embodiment 1 of the present invention on the characterization of hardy kiwifruit;

[0048] Figure 10 This is a graph showing the effect of the four-layer label on the sensory score of shiitake mushrooms in Embodiment 1 of the present invention;

[0049] Figure 11 This is a graph showing the effect of the 4-layer label on the weight loss rate of shiitake mushrooms in Embodiment 1 of the present invention;

[0050] Figure 12 This is a graph showing the effect of the four-layer label on the rot rate of shiitake mushrooms in Example 1 of the present invention;

[0051] Figure 13 This is a diagram showing the effect of the four-layer label on the hardness of shiitake mushrooms in Embodiment 1 of the present invention;

[0052] Figure 14 This is a graph showing the effect of the four-layer label of Example 1 of the present invention on the soluble protein content of shiitake mushrooms;

[0053] Figure 15 This is a graph showing the effect of the four-layer label on the reducing sugar content of shiitake mushrooms in Example 1 of the present invention;

[0054] Figure 16 This is a graph showing the effect of the four-layer label on the vitamin C content of shiitake mushrooms in Example 1 of the present invention;

[0055] Figure 17This is a graph showing the effect of the four-layer label on the total phenolic content of shiitake mushrooms in Example 1 of the present invention;

[0056] Figure 18 This is a diagram showing the effect of the four-layer label on the characterization of shiitake mushrooms in Embodiment 1 of the present invention;

[0057] Figure 19 This is a schematic diagram of the structural connection of a slow-release label paper for preserving fruits, vegetables, and edible fungi in this invention;

[0058] Figure 20 This is a schematic diagram of the preparation process of the slow-release label paper for preserving fruits, vegetables, and edible fungi according to the present invention. Detailed Implementation

[0059] The present invention will be further described below with reference to the embodiments. The following embodiments are descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0060] The various experimental operations involved in the specific embodiments are all conventional techniques in the art. For parts not specifically annotated herein, those skilled in the art can refer to various commonly used reference books, scientific and technological literature, or related instructions and manuals prior to the filing date of this invention for implementation. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art, and the raw materials used are all commercially available products.

[0061] A slow-release label for preserving fruits, vegetables, and edible fungi includes an antibacterial layer 1, a preservation-inducing layer 2, a self-absorbent layer 3, and an ethylene-adsorbent color-developing printing layer 4. These layers are tightly adhered together from the inside out. The antibacterial layer 1 is positioned on the inside, self-adsorbing layer onto the ethylene-adsorbent color-developing printing layer 4, forming a slow-release label that delays post-harvest softening and other quality maintenance effects of fruits, vegetables, and edible fungi, thus extending their shelf life.

[0062] The method for preparing the slow-release label paper as described above involves sequentially and tightly arranging the antibacterial layer 1, the preservation and inducing layer 2, the self-absorbent layer 3, and the ethylene adsorption and color development printing layer 4 together from the inside out.

[0063] Preferably, the method for preparing the antibacterial layer 1 includes the following steps:

[0064] Nanocellulose (CNF) was diluted to a concentration of 0.2-0.5 wt% and magnetically stirred at 200-1000 rpm for 1-4 hours until a uniform gel state was obtained, yielding a CNF suspension with a concentration of 0.2-0.5 wt%. Powdered Sichuan peppercorns were mixed with anhydrous ethanol at a ratio of 1:10-1:30 (g:ml). The mixture was placed in an ultrasonic cleaner and sonicated at 40-60℃ and 150-300W for 20-50 minutes. After filtration through five layers of gauze, the filtrate was collected and concentrated under reduced pressure using a rotary evaporator at 30-50℃ to recover the ethanol, yielding the Sichuan peppercorn extract. The Sichuan peppercorn extract was then added to a 0.2-0.5 wt% CNF suspension. In the CNF suspension, the mass ratio of Sichuan pepper extract to CNF suspension is 1:4-1:20. The mixture is magnetically stirred at 300-800 rpm for 0.5-2 hours until homogeneous. The mixed solution is poured into a Buchner funnel and vacuumed to form a wet film. It is then dried at room temperature for 12 hours to form a gel network skeleton. The solution is then transferred to a constant temperature and humidity chamber at 30°C and 50% RH. When the moisture content reaches 40%, it is placed in a 40°C oven for 1-3 hours. The temperature is then raised to 60°C and dried for 1-4 hours until the final moisture content is 8-10%, thus obtaining antibacterial layer 1.

[0065] Preferably, the method of setting the preservation-inducing layer 2 on the antibacterial layer 1 includes the following steps:

[0066] Polyvinylpyrrolidone (PVP) and ethyl cellulose (EC) were added to anhydrous ethanol and stirred, then sonicated until fully mixed to prepare a slow-release agent. 1-MCP powder and sodium nitroprusside were added to the prepared slow-release agent, stirred, and sonicated again to form a homogenate with the 1-MCP powder and sodium nitroprusside. The homogenate was evenly coated onto the outer surface of the antibacterial layer 1, so that the paper base contained 1-MCP powder and sodium nitroprusside. After coating, the semi-finished label with the homogenate was placed in an oven to dry, allowing the solvent to evaporate completely. Finally, natural adhesive starch glue 6 was brushed onto the inner surface of the antibacterial layer 1, and a polytetrafluoroethylene (PTFE) film 5 was attached to facilitate adhesion to the surface of fruits and vegetables, resulting in the antibacterial layer 1 and the preservation-inducing layer 2 set together.

[0067] Preferably, the mass ratio of polyvinylpyrrolidone (PVP) to ethyl cellulose (EC) is 1:0 to 4:1, and the amount of anhydrous ethanol added is 8 to 10 times the total mass of PVP and EC.

[0068] Alternatively, the sustained-release agent is prepared at a stirring temperature of 20–40°C, an ultrasonic power of 100W–300W, and an ultrasonic time of 2–10 min.

[0069] The 1-MCP powder is a powder-type 1-MCP encapsulated with α-cyclodextrin, and the ratio of polyvinylpyrrolidone:1-MCP powder:sodium nitroprusside (g:g:mg) is 50:4:25 to 70:4:25.

[0070] Alternatively, add 1-MCP powder and sodium nitroprusside, and after stirring, sonicate again for 5-10 minutes, at a temperature of 20-35°C, with an ultrasonic power of 100W-300W and a sonication time of 3-15 minutes.

[0071] Alternatively, the coating amount of the homogenate is 0.1–0.4 ml / cm². 2 Ensure that the antibacterial layer 1 contains 0.05–0.24 g of 1-MCP and 5 μM to 200 μM sodium nitroprusside powder, and the coating speed is 1–5 m / min.

[0072] Alternatively, the drying temperature of the oven is 40–80°C, and the drying time is 6–16 hours.

[0073] Preferably, the method for preparing the self-absorbing water layer 3 includes the following steps:

[0074] Citric acid powder was dissolved in deionized water to prepare a 3-6 wt% citric acid solution. CNF powder and the citric acid solution were mixed at a material-to-liquid ratio of 1:40-1:60 (g:ml). After thorough mixing, the mixture was placed in a thermostatic magnetic stirrer at 70-90℃ and reacted continuously at 600-1000 rpm for 3-5 hours. After the reaction, the mixture was immediately cooled to room temperature. The resulting mixture was then added to 10 times its volume of deionized water and centrifuged at 8000-10000 rpm for 5-15 minutes. The precipitate was collected and repeatedly washed with deionized water. The washed precipitate was then added to deionized water to form a suspension. The suspension was then placed in a dialysis bag and dialyzed for 3-5 days. The dialysis bag must be completely submerged in deionized water. The external deionized water was changed every 5-9 hours. The final product was obtained... Carboxylated CNF suspension was placed in a dialysis bag; the carboxylated CNF suspension was concentrated to a final mass concentration of 0.5-2.0 wt%, and 0.02-0.2 wt% polyvinyl alcohol (PVA) was added. The mixture was magnetically stirred at 300-1000 rpm for 1-3 hours to form a homogeneous sol. The sol was poured onto a polytetrafluoroethylene plate and frozen at -20°C for 1-3 hours, followed by freezing at -80°C for 5-12 hours to obtain a membrane. The crosslinking solution, a mixed aqueous solution consisting of 1-8 wt% citric acid, 0.5-2.5 wt% NaH2PO4, and water, was atomized and sprayed onto the membrane. Finally, plasma treatment was performed under the conditions of O2:Ar=3:1, power 100W, and treatment time 90s to obtain a nanoscale three-dimensional network + hydrophilic groups + microporous capillary effect active water-absorbing membrane, resulting in a self-absorbing water layer 3.

[0075] Preferably, the preparation method of the ethylene adsorption color-developing printing layer 4 includes the following steps:

[0076] Zeolite particles were immersed in a 20% KMnO4 aqueous solution (g:mL ratio of zeolite particles to KMnO4 aqueous solution was 5-20:25-100), ultrasonically vibrated for 20-60 min, and then rotary evaporated under reduced pressure at 60℃ to dryness, followed by vacuum drying at 80℃ for 4 h to obtain purplish-red loaded particles. The particles were passed through a 200-mesh sieve, and particles with a diameter ≤75μm were selected for later use. The loaded particles were placed in a fluidized bed and coated with a 5%-10% gelatin aqueous solution as a binder to form a dense release film, resulting in gelatin-coated particles. Bromocresol purple (BCP) powder was dissolved in ethanol, and then 1-3% chitosan acetic acid solution was added (bromocresol purple:1-3% chitosan acetic acid solution ratio was...). Example g:mL ratio 1:900, magnetic stirring for 2h yields a purple BCP-chitosan mixture; in a fluidized bed, the gelatin-coated particles are sprayed with the BCP-chitosan mixture, the inlet air temperature is controlled at 40℃, to complete the second coating layer and obtain microcapsules; the above microcapsules are immersed in a 1%-4% sodium alginate solution and slowly stirred for 5-30min; the coated particles are transferred to a 2-6% CaCl2 solution and allowed to stand for crosslinking for 10-40min to form a gel outer layer; the coated particles are filtered and rinsed 3 times with deionized water; the obtained particles are vacuum dried at 40℃ for 12h to obtain the final ethylene adsorption colorimetric microcapsule particles 7;

[0077] The preparation steps of the 1-3% chitosan acetic acid solution are as follows: prepare a 1% acetic acid aqueous solution by mixing chitosan powder and 1% acetic acid aqueous solution at a material-liquid ratio of 1:100-3:100 (g:mL).

[0078] Nanocellulose (CNF) was diluted to a final concentration of 0.2-0.5 wt%, and magnetically stirred at 200-1000 rpm for 1-4 hours until a homogeneous gel state was achieved. The solution was poured into a Buchner funnel, and vacuum-sealed to form a wet film. The film was dried at room temperature for 12 hours to form a gel network framework. It was then transferred to a constant temperature and humidity chamber at 30°C and 50% RH. When the moisture content reached 40%, it was placed in a 40°C oven for 1-3 hours, and then dried at 60°C for 1-4 hours until the final moisture content was 8-10%, yielding an ethylene adsorption color-developing printing layer paper base. A coating of 0.025-0.225 ml / cm² was then applied to the inner side of the paper base. 2 The natural adhesive starch glue 6 is used to adhere the above-mentioned ethylene adsorption color-developing microcapsule particles 7 to the ethylene adsorption color-developing printing layer paper base coated with starch glue 6. Label information can be printed on the outside of the paper base, and the ethylene adsorption color-developing printing layer 4 is completed.

[0079] Preferably, the starch adhesive 6 is a natural adhesive made from starch as a base material, which is characterized by abundant supply, low price, ease of use, and non-toxicity. The coating amount is 0.025–0.225 ml / cm². 2 .

[0080] The application of slow-release label paper for fruit and vegetable / edible fungi preservation as described above.

[0081] The application of the slow-release label paper for preserving fruits and vegetables / edible fungi as described above in delaying the softening properties of fruits and vegetables and / or edible fungi.

[0082] Specifically, the relevant preparation and testing methods are as follows:

[0083] Example 1

[0084] A type of slow-release label paper for preserving fruits, vegetables, and edible fungi, such as Figure 19 As shown, the slow-release label paper includes an antibacterial layer 1, a freshness-preserving inducing layer 2, a self-absorbent layer 3, and an ethylene adsorption color-developing printing layer 4. The antibacterial layer 1, freshness-preserving inducing layer 2, self-absorbent layer 3, and ethylene adsorption color-developing printing layer 4 are tightly adhered together from the inside out. The antibacterial layer 1 is located on the inside, and it self-adsorbs layer by layer onto the ethylene adsorption color-developing printing layer 4, forming a slow-release label that delays post-harvest softening of fruits, vegetables, and edible fungi, maintaining their quality and extending their shelf life.

[0085] The above-mentioned method for preparing slow-release packaging paper for fruits, vegetables, and edible fungi can be as follows: Figure 20 As shown, it includes the following steps:

[0086] S1. Dilute nanocellulose (CNF) to a mass concentration of 0.25 wt%, and magnetically stir at 600 rpm for 2 hours until a uniform gel state is obtained, yielding a CNF suspension with a mass concentration of 0.2-0.5 wt%. Mix pulverized Sichuan pepper powder with anhydrous ethanol at a material-to-liquid ratio of 1:20 (g / ml). Place the mixture in an ultrasonic cleaner and sonicate at 50℃ and 200W for 30 minutes. Filter through five layers of gauze and collect the filtrate. Then, concentrate the filtrate under reduced pressure in a rotary evaporator at 40℃ to recover the ethanol, obtaining Sichuan pepper extract. Pour 5g of Sichuan pepper extract into a 0.2 wt% CNF solution. In a 0.5wt% CNF suspension, the mass ratio of Sichuan pepper extract to CNF suspension was 1:8. The mixture was magnetically stirred at 800 rpm for 2 hours until homogeneous. The mixture was poured into a Buchner funnel and vacuumed until a wet film was formed. It was dried at room temperature for 12 hours to form a gel network framework. Then it was transferred to a constant temperature and humidity chamber at 30℃ and 50% RH. When the moisture content was 40%, it was placed in a 40℃ oven for 2 hours. Then the temperature was raised to 60℃ and dried for 3 hours until the final moisture content was 8%, thus obtaining antibacterial layer 1.

[0087] S2. Add 8g of polyvinylpyrrolidone (PVP) and 2g of ethyl cellulose (EC) to anhydrous ethanol and stir. Then sonicate (250W, 5min) until fully mixed to prepare a sustained-release agent. Add 0.48g of 1-MCP powder and 200μM sodium nitroprusside to the prepared sustained-release agent, stir, and sonicate again to form a homogenate with the 1-MCP powder and sodium nitroprusside. Coat the homogenate evenly onto antibacterial layer 1, so that the paper base contains 0.2g of 1-MCP powder and 100μM sodium nitroprusside. After coating, place the semi-finished label with the homogenate in a 50℃ oven and dry for 8h to allow the solvent to evaporate completely. Finally, brush 0.25 ml / cm onto the bottom paper base. 2 Starch adhesive 6 (a non-toxic adhesive) is attached with a polytetrafluoroethylene (PTFE) film 5 to facilitate adhesion to the surface of fruits and vegetables, resulting in an antibacterial layer 1 and a preservation-inducing layer 2 set together.

[0088] S3. Dissolve citric acid powder in deionized water to prepare a 5wt% citric acid solution. Mix CNF powder and citric acid solution at a ratio of 1:50 (g / ml). After mixing evenly, place the mixture in a 90℃ heated magnetic stirrer and react at 800 rpm for 5 hours. After the reaction, immediately cool to room temperature. Add 10 times the mass of deionized water to the mixture and centrifuge at 10000 rpm for 10 minutes. Collect the precipitate and wash it repeatedly with deionized water. Add the washed precipitate to deionized water to form a suspension. Then place the suspension in a dialysis bag and dialyze for 5 days. The dialysis bag must be completely immersed in a large beaker containing only deionized water. Change the external deionized water every 8 hours to finally obtain a carboxylated CNF suspension in the dialysis bag. The carboxylated CNF suspension was concentrated to a mass concentration of 0.5 wt%, and 0.1 wt% polyvinyl alcohol (PVA) was added. The mixture was magnetically stirred at 600 rpm for 2 hours to form a homogeneous sol. This sol was poured onto a polytetrafluoroethylene plate and frozen at -20°C for 2 hours, followed by freezing at -80°C for 8 hours. The crosslinking solution, a mixed aqueous solution consisting of 4 wt% citric acid, 1.5 wt% NaH2PO4, and water, was atomized and sprayed onto the membrane. Finally, plasma treatment was performed under the conditions of O2:Ar = 3:1, power 100W, and treatment time 90s to obtain a nanoscale three-dimensional network + hydrophilic groups + microporous capillary effect active water-absorbing membrane, namely the self-absorbing water layer 3.

[0089] S4. Immerse 10g of zeolite particles in 50mL of a 20% KMnO4 aqueous solution, sonicate for 30min, evaporate to dryness under reduced pressure at 60℃, and then vacuum dry at 80℃ for 4h to obtain purplish-red loaded particles; pass the particles through a 200-mesh sieve and take particles with a particle size ≤75μm for later use; place the loaded particles in a fluidized bed and use a 5% gelatin aqueous solution as a binder for primer coating to form a dense isolation film, obtaining gelatin-coated particles; dissolve 0.1g of bromocresol purple (BCP) powder in 10mL of ethanol, and then add 90mL of 2% chitosan acetic acid solution. mL (to prepare a 1% acetic acid aqueous solution, chitosan powder and 1% acetic acid aqueous solution were mixed evenly at a material-to-liquid ratio of 1:50 g:mL to obtain a chitosan-acetic acid solution), and magnetically stirred for 2 h to obtain a purple BCP-chitosan mixture; in a fluidized bed, the gelatin-coated particles were sprayed with the BCP-chitosan mixture, and the inlet air temperature was controlled at 40℃ to complete the second coating layer and obtain capsules; the above microcapsules were immersed in a 2% sodium alginate solution and slowly stirred for 15 min; the coated particles were transferred to a 2% CaCl2 solution and allowed to stand for crosslinking for 10 min to form a gel outer layer. The coated particles were filtered and rinsed 3 times with deionized water. The obtained particles were vacuum dried at 40℃ for 12 h to obtain the final ethylene adsorption colorimetric microcapsule particles 7; nanocellulose (CNF) was diluted to a final mass concentration of 0.25 wt%, magnetically stirred (600 rpm, 3 h) until a uniform gel state was reached, the solution was poured into a Buchner funnel, vacuumed to form a wet film, and dried at room temperature for 12 h to form a gel network framework, then transferred to a constant temperature and humidity chamber (30℃, RH 50%), and dried to a moisture content of 40% in a 40℃ oven for 2 h, then heated to 60℃ and dried for 3 h to achieve a final moisture content of 8%, thus obtaining the ethylene adsorption colorimetric printing layer paper base; 0.2 ml / cm was brushed onto the inner side of the paper base. 2 Natural adhesive starch glue 6 is used to adhere the above-mentioned ethylene adsorption color development microcapsule particles 7 to the inner side of the ethylene adsorption color development printing layer paper base, and label information can be printed on the outer side of the paper base to obtain ethylene adsorption color development printing layer 4.

[0090] S5. On the outer surface of the antibacterial layer 1 and the preservation inducing layer 2, which are arranged in close sequence from the inside to the outside, the self-absorbent layer 3, the ethylene adsorption color development printing layer 4, are obtained as a slow-release label paper for preserving fruits and vegetables / edible fungi.

[0091] Example 2

[0092] Application of the slow-release packaging paper for fruits and vegetables / edible fungi prepared in Example 1 in the preservation of hardy kiwifruit.

[0093] 1. Application of the above-mentioned slow-release packaging paper for fruits and vegetables / edible fungi in the preservation of hardy kiwifruit:

[0094] Fresh, pre-cooled hardy kiwifruit were selected, accurately weighed, and divided into three groups of 15 kg each. Each group was packaged and labeled as: control (CK), 1-MCP fumigation treatment (1-MCP), and slow-release packaging paper treatment for fruits and vegetables / edible fungi (4 layers of labeling). During the selection process, operators ensured gentle handling, holding the fruit by the stem and avoiding touching the fruit with fingers as much as possible to reduce mechanical damage, extend the storage period of the hardy kiwifruit, and ensure its edible and commercial value.

[0095] (1) Control (CK): Select fruits with similar maturity, uniform size, no mechanical damage or pest infestation, and randomly divide them into 1 group for storage and observation in an environment of 0±1℃.

[0096] (2) 1-MCP fumigation treatment (1-MCP): The fruits were placed in boxes with inner diameters of 44 cm, 32 cm and 15 cm respectively. They were fumigated with 1 μL / L 1-MCP for 24 h in a closed environment. The whole process was carried out in a closed environment at a temperature of 0±1℃. After fumigation, the fruits were stored and observed in an environment of 0±1℃.

[0097] (3) Treatment of slow-release packaging paper for fruits and vegetables / edible fungi (4-layer label): The bottom polytetrafluoroethylene film of the 4-layer label prepared in Example 1, namely the slow-release label paper for the preservation of fruits and vegetables / edible fungi (the same below), is peeled off and pasted into the preservation box containing kiwifruit and stored in a sealed environment at 0±1℃.

[0098] Quality parameters of the jujube kiwifruit were measured on days 5, 10, 15, 20, 25, 30, 45, and 60 during storage to observe quality changes. The tests were repeated three times.

[0099] 2. Determination and methods of quality indicators of hardy kiwifruit

[0100] (1) Determination of weight loss rate

[0101] The weight loss rate of hardy kiwifruit was determined by weighing. Specifically, three boxes of fruit were randomly selected from each treatment group, marked and weighed, and the initial mass of each box of fruit was recorded. In each measurement cycle, the mass of each previously marked box of hardy kiwifruit was measured and recorded.

[0102] The calculation formula is as follows:

[0103]

[0104] (2) Determination of decay rate

[0105] Each storage period of hardy kiwifruit was used for characterization and observation. 100 samples were randomly selected each time and measured 3 times. The occurrence of fruit cracking, browning of the skin, and mold was observed and recorded.

[0106] The calculation formula is as follows:

[0107]

[0108] (3) Hardness measurement

[0109] The hardness of hardy kiwifruit was measured using a hardness tester (GY-4) with a P / 100 probe. The compression percentage was set to 60%. The probe compression rate during the test was 4 mm / s, and the probe lifting rate after the test was 2 mm / s. The time interval between two probe compressions was 2 s. The sample to be tested was placed in the center of the stage on the base. Three points at equal distances were selected at the equator of the fruit. Before the test, the probe descent rate was 5 mm / s. Five fruits were used for each parallel treatment. Hardness was expressed as the maximum force required to penetrate the hardy kiwifruit, in N.

[0110] (4) Determination of soluble solids (TSS)

[0111] The determination was performed using a portable PAL-1 handheld refractometer. The kiwifruit was wrapped in gauze, and the squeezed juice was dripped onto the detection well. Three measurements were taken for each group, and the average value was recorded. The instrument was zeroed with distilled water before each measurement. The digital display showed the soluble solids content, expressed as a percentage (%).

[0112] (5) Determination of color

[0113] The L value of the hardy kiwifruit sample was measured using a precision colorimeter and recorded. a and b For each treatment, select 5 fruits and sample from two symmetrical sides of the middle of the fruit, avoiding the top and bottom edges.

[0114] The calculation formula is as follows:

[0115]

[0116] In the formula, ΔE is the total color difference, and L The brightness of the hardy kiwifruit fruit, a b represents the red-green value of the hardy kiwi fruit. The yellow-blue value represents the color of the hardy kiwifruit.

[0117] (6) Measurement of respiratory rate

[0118] The respiration rate of hardy kiwifruit was measured using a fruit and vegetable respiration meter (GXH-3051H). Three fresh hardy kiwifruit fruits were randomly weighed, and three parallel sets were set up for each measurement. The machine was zeroed before the measurement. The hardy kiwifruit fruits were placed in the gas chamber of the respiration meter, and the change in CO2 production before and after measurement was measured at 2-minute intervals. The initial values ​​were recorded.

[0119] The calculation formula is as follows:

[0120]

[0121] In the formula: C1 is the total amount of CO2 in the post-breathing canister, %; C2 is the total amount of CO2 in the pre-breathing canister, %; V is the volume of the breathing canister, L; M is the relative molar mass of CO2 gas, g·mol⁻¹ -1 V0 is the actual molar volume of CO2 gas at the measured temperature, in L·mol⁻¹. -1 m is the mass of the fruit at the time of measurement, in g; t is the time (h) for measuring the respiration rate of the fruit and vegetables.

[0122] (7) Determination of ethylene release

[0123] Four fresh hardy kiwifruit were randomly weighed from each group and placed in a sealed bottle for 3 hours. Then, 1 mL of gas was extracted from the top of the bottle, and the ethylene release from the hardy kiwifruit was determined using an Agilent 7890 zone gas chromatograph. The parameters were: column oven temperature increased from 35℃ to 60℃, injection port temperature was 60℃, and detector temperature was 240℃. The flow rates of hydrogen, air, and make-up nitrogen were 30 mL / min, 300 mL / min, and 25 mL / min, respectively. The ethylene generation rate is expressed in μL / (kg·h).

[0124] 3. Results and analysis of quality indicators of hardy kiwifruit:

[0125] (1) Effect of 4-layer label on weight loss rate of hardy kiwifruit

[0126] The loss of water and the consumption of nutrients in fruits and vegetables will cause the fruit to shrink more quickly, resulting in a decrease in fruit weight. Therefore, the weight loss rate is an important indicator for judging the quality of fruits during storage. Figure 1The figure shows the changes in weight loss rate of hardy kiwifruit treated with different methods after 60 days of storage at 0±1℃. As can be seen from the figure, the weight loss rate of the control group (CK) was significantly higher than that of other treatment groups throughout the 60-day storage period (P<0.05), with the most significant effects observed on days 45 and 60. Among the treatment groups, the weight loss rate of the 4-layer label group was generally lower than that of the 1-MCP group. On day 60, the highest weight loss rate was observed in the CK group at 15.16%, while the 1-MCP group and the 4-layer label group had rates of 7.33% and 4.73%, respectively. Therefore, the 4-layer label treatment group showed the best results.

[0127] (2) Effect of 4-layer labeling on the rot rate of hardy kiwifruit

[0128] Hardy kiwifruit is prone to softening, rotting, and spoilage during storage, thus losing its edible value. The changes in the rotting rate of hardy kiwifruit in three different treatment groups after 60 days of storage at 0±1℃ are shown below. Figure 2 As shown in the figure, no rotting occurred in any of the treatment groups during the first 15 days of storage. After 15 days, rotting began, and the rotting rate was positively correlated with storage time. On day 20, the control group (CK) began to rot, with a rotting rate of 0.67%. On day 25, rotting occurred in both the 4-layer label group and the 1-MCP group, but the rotting rate was low. On day 45, the rotting rate in the CK group increased, and the rotting rates in both treatment groups were significantly lower than those in the CK group (P<0.05). Towards the end of storage, the rotting rate in the CK group increased significantly, reaching 28.33%, while the rotting rate in the 4-layer label group was only 6.67%, significantly lower than that in the CK group. This indicates that the 4-layer label treatment effectively slowed down the quality deterioration of the hardy kiwifruit during storage, greatly maintaining its economic value.

[0129] (3) Effect of 4-layer label on the hardness of hardy kiwifruit

[0130] Firmness, as a key textural parameter in the postharvest maturity evaluation system for fruits and vegetables, is closely related to the cell wall metabolism of the fruit. At fresh harvest, the firmness of hardy kiwifruit remains around 30 N, which is directly related to the high content of protopectin and amylose in the cell wall. Figure 3 As shown, compared with the control group (CK), both the 1-MCP group and the 4-layer label group significantly regulated the hardness decay process of the hardy kiwifruit (P<0.05). At 60 days of storage, the hardness was 19.92 N for the 4-layer label group, 16.81 N for the 1-MCP group, and only 9.97 N for the CK group. The 4-layer label group showed the best effect during the 60-day storage period, indicating that this treatment effectively slowed down the softening process of the hardy kiwifruit.

[0131] (4) The effect of 4-layer label on the color of hardy kiwifruit

[0132] Depend on Figure 9 It is evident that the 4-layer label treatment group effectively extended the storage period of the hardy kiwifruit and maintained its excellent quality. The control group (CK) showed significant shrinkage and moisture loss after 30 days of storage. On day 60, the CK group developed mold spots, softening, and rotting, while the 1-MCP group showed extensive discoloration of the peel. The 4-layer label group outperformed both the CK and 1-MCP groups, exhibiting only slight softening while preserving its unique flavor and bioactivity. This result is consistent with the observed changes in physiological indicators.

[0133] L The size of the surface of the hardy kiwifruit reflects its brightness; the higher the brightness, the better. The larger the size, the better. The effects of different treatment methods on hardy kiwifruit are as follows: Figure 4 As shown, within 60 days of storage, the skin of the hardy kiwifruit in the three treatment groups gradually changed from greenish-blue to dark green with increasing storage time, accompanied by a decrease in brightness. Therefore, L The values ​​all showed a gradually decreasing trend. At 60 days, the L values ​​of the CK group, 1-MCP group, and 4-layer label group were... The percentages were reduced by 24.24%, 21.01%, and 19.03%, respectively. This result indicates that the four-layer labeling treatment of hardy kiwifruit played an important role in delaying the decrease in fruit brightness during low-temperature storage, thus better ensuring the quality of hardy kiwifruit.

[0134] ΔE is calculated using a formula based on the fruit brightness value, peel red-green value, and yellow-blue value. It represents the total color difference of the peel, and its value is positively correlated with the color difference of the hardy kiwifruit peel during storage; that is, the larger the value, the worse the color of the hardy kiwifruit. For example... Figure 5 As shown, the ΔE value of the hardy kiwifruit gradually increased during the process of changing from green to dark green. During storage, the ΔE value of the CK group was significantly higher (P<0.05) than that of other treatment groups. After 60 days of storage, the total color difference of the CK group was as high as 17.42, the 1-MCP group was 14.01, while the 4-label group was only 11.86. In conclusion, the 4-label treatment of hardy kiwifruit better maintained the ΔE value and delayed the deterioration of fruit quality.

[0135] (5) Effect of 4-layer label on TSS content of hardy kiwifruit

[0136] Soluble solids (TSS) can be used to determine changes in the composition of nutrients in fruit and is one of the standards for judging fruit quality. For example... Figure 6As shown, except for the control group (CK), the soluble solids content of the two treatment groups (excluding the control group) gradually increased during storage. The soluble solids content of the 4-layer label treatment group was significantly lower than that of the 1-MCP treatment group throughout the storage period. After 60 days of storage, the soluble solids content of the 4-layer label group was 13.13% and that of the 1-MCP group was 15.17%, both significantly lower than that of the control group (CK). These results indicate that the 4-layer label treatment group inhibited the increase in soluble solids content in the soluble solids content of the soluble solids in ...

[0137] (6) Effect of 4-layer label on respiration intensity of hardy kiwifruit

[0138] The respiration rate of the hardy kiwi fruit is as follows Figure 7 As shown, the fruit exhibited a typical respiratory dynamic pattern during storage: the respiratory intensity of each treatment group initially increased and then decreased with prolonged storage time, with peak respiratory values ​​appearing at different times. The intensity of transpiration in plant cells was significantly positively correlated with respiratory metabolism, increasing the consumption of water and nutrients in the fruit. The figure shows that the peak respiratory rate in the 1-MCP group occurred on day 20 after storage, while the peak respiratory rate in the 4-layer label group occurred on day 25 after storage, 15 days later than the peak in the CK group (10 days). This indicates that treating the hardy kiwifruit with 4 layers of labels can minimize the consumption of nutrients in the fruit and maintain its quality.

[0139] (7) Effect of 4-layer label on ethylene release from hardy kiwifruit

[0140] Ethylene production occurs alongside the ripening of fruits and vegetables; therefore, inhibiting ethylene synthesis can effectively slow down the post-harvest aging process. Ethylene is also released during the storage of hardy kiwifruit, and the large release and accumulation of ethylene is one of the reasons for the deterioration of its quality during storage. Figure 8 In summary, the ethylene release trends across all treatment groups were similar, initially increasing and then decreasing, with the peak ethylene levels occurring at different times for each group. The CK group peaked on day 15, the 1-MCP group on day 25, and the 4-layer label group on day 30, representing decreases of 31.08% and 29.60% respectively compared to the CK group, significantly (P<0.05) improving fruit quality. This indicates that the 4-layer label treatment can effectively slow down ethylene release from hardy kiwifruit during storage, thus playing a better role in preserving the fruit.

[0141] Example 3

[0142] Application of the slow-release packaging paper for fruits and vegetables / edible fungi prepared in Example 1 in the preservation of shiitake mushrooms:

[0143] Fresh shiitake mushrooms that have undergone pre-cooling were selected, accurately weighed, and divided into three groups of 10 kg each. Each group was then packaged and labeled as follows: control (CK), 1-MCP slow-release label treatment (label), and 4-layer slow-release label treatment (the 4-layer label refers to slow-release label paper used for preserving fruits, vegetables, and edible fungi). During the selection process, operators ensured gentle handling to minimize mechanical damage, extend the shelf life of the shiitake mushrooms, and preserve their edible and commercial value.

[0144] (1) Control (CK): Select shiitake mushrooms with similar maturity, uniform size, and no mechanical damage or pest infestation. Randomly divided into 1 group, they were stored and observed in an environment of 0±1℃.

[0145] (2) 1-MCP sustained-release label treatment (label): The prepared 1-MCP sustained-release label is peeled off the polytetrafluoroethylene film and attached to the inside of the mushroom preservation box, and stored in a sealed environment at 0±1℃.

[0146] The preparation method of 1-MCP sustained-release label is as follows:

[0147] S1. Add 10g of polyvinylpyrrolidone (PVP) and ethyl cellulose (EC) in a mass ratio of 4:1 to 10 mL of anhydrous ethanol, and sonicate for 5 min to mix them thoroughly to prepare a sustained-release agent.

[0148] S2. Add 0.48 g of 1-MCP powder to the sustained-release agent, use an ultrasonic power of 250W and an ultrasonic time of 5min to form a homogenate of 1-MCP powder and sustained-release agent, and set aside.

[0149] S3. Take 5.00 mL of homogenate and evenly coat it onto a 4 cm × 6 cm cellulose paper base (dilute nanocellulose CNF to a mass concentration of 0.3 wt%, magnetically stir at 800 rpm for 3 h until a uniform gel state is reached, pour the CNF suspension into a Buchner funnel, vacuum to form a wet film, dry at room temperature for 12 h to form a gel network framework, then transfer to a constant temperature and humidity chamber at 30℃ and RH 50%, dry to a moisture content of 40%, then place in a 40℃ oven for 3 h, then raise the temperature to 60℃ and dry for 2 h, so that the final moisture content is 8%, to obtain the cellulose paper base). This will result in the paper base containing 0.12 g of 1-MCP powder. After coating, place the semi-finished label with the homogenate in a 60℃ oven and dry for 12 h to allow the solvent to completely evaporate.

[0150] S4. A layer of cellulose paper containing Sichuan pepper extract is adhered to the top of the homogenate. (The nanocellulose (CNF) is diluted to a mass concentration of 0.3 wt%, magnetically stirred at 800 rpm for 3 hours until a uniform gel state is reached; the pulverized Sichuan pepper powder is mixed with anhydrous ethanol at a material-to-liquid ratio of 1:20 (g / ml), and the mixture is placed in an ultrasonic cleaner and ultrasonically cleaned at 50℃ and 250W for 40 minutes. After filtration through five layers of gauze, the filtrate is collected. The filtrate is then concentrated under reduced pressure in a rotary evaporator at 50℃ to recover the ethanol, yielding the Sichuan pepper extract; 3 g of the Sichuan pepper extract is added to a 0.3 wt% CNF suspension. The Sichuan pepper extract and CNF suspension...) The liquid-to-mass ratio was 1:8, and the mixture was magnetically stirred at 600 rpm for 1.5 hours until homogeneous. The mixture was poured into a Buchner funnel, evacuated to form a wet film, and dried at room temperature for 12 hours to form a gel network skeleton. Then it was transferred to a constant temperature and humidity chamber at 30°C and 50% RH. When the moisture content was 40%, it was placed in a 40°C oven for 3 hours, and then the temperature was raised to 60°C for 2 hours to make the final moisture content 8%, thus obtaining a cellulose paper base containing Sichuan pepper extract for subsequent printing. Finally, 3 ml of starch glue (non-toxic adhesive) was brushed onto the bottom paper base surface, and a polytetrafluoroethylene (PTFE) film was attached to make the 1-MCP slow-release packaging label finished product.

[0151] (3) Treatment of slow-release packaging paper for fruits and vegetables / edible fungi (4-layer label): The polytetrafluoroethylene film of the 4-layer slow-release label prepared in Example 1, namely the slow-release label paper for the preservation of fruits and vegetables / edible fungi (the same below), is peeled off and pasted into the mushroom preservation box and stored in a sealed environment at 0±1℃.

[0152] Quality parameters of shiitake mushrooms were measured on days 6, 12, 18, 24, and 30 during storage to observe quality changes. The tests were repeated three times.

[0153] 2. Determination and methods of quality indicators for shiitake mushrooms

[0154] (1) Sensory evaluation

[0155] Sensory evaluation of stored shiitake mushrooms was conducted using color, aroma, degree of cap opening, texture, and whether they were sticky as evaluation indicators. The scoring criteria are shown in Table 1. Whether the shiitake mushroom cap has opened is one of the important indicators for evaluating the maturity and quality of shiitake mushrooms; the more mature the shiitake mushroom, the easier it is for the cap to open.

[0156] Table 1 Sensory Quality Scoring Criteria for Shiitake Mushrooms

[0157]

[0158] (2) Determination of weight loss rate

[0159] The weight loss rate of shiitake mushrooms was determined by weighing. Specifically, three boxes of shiitake mushrooms were randomly selected from each treatment group, marked, weighed, and the initial mass of each box was recorded. In each measurement cycle, the mass of each previously marked box of shiitake mushrooms was measured and recorded.

[0160] The calculation formula is as follows:

[0161]

[0162] (3) Determination of decay rate

[0163] Shiitake mushrooms from each storage period were taken out for characterization and observation. 30 samples were randomly selected each time and measured 3 times. The occurrence of cap opening, browning of the skin, and mold was observed and recorded.

[0164] The calculation formula is as follows:

[0165]

[0166] (4) Hardness measurement

[0167] Hardness was measured using a hardness tester (GY-4) with a P / 100 probe. The compression percentage was set to 60%. The probe compression rate during the test was 4 mm / s, and the probe lift rate after the test was 2 mm / s. The time interval between two probe compressions was 2 seconds. The sample to be tested was placed in the center of the stage on the base, with three equidistant points selected. The probe descent rate before the test was 5 mm / s. Five fruits were used for each parallel treatment. Hardness was expressed as the maximum force required to penetrate the shiitake mushroom, in N.

[0168] (5) Determination of soluble protein content

[0169] The protein content in shiitake mushrooms was determined using the Coomassie Brilliant Blue method. Shiitake mushrooms were homogenized in 5 mL of deionized water and centrifuged at 10000 × g for 20 min. The supernatant was diluted 20-fold and reacted with Coomassie Brilliant Blue G-250. The absorbance was then recorded at 595 nm. The standard curve for bovine serum albumin was calculated as y = 0.0038x + 0.5325, R0. 2 = 0.9975. The result is expressed as the mass of soluble protein per gram of shiitake mushroom tissue, in mg / g.

[0170]

[0171] In the formula: m' is the protein mass calculated from the reference curve, μg; V is the total volume of the sample extract, mL; N is the dilution factor; VS is the volume of the sample extract taken during the determination, mL; m is the sample mass, g.

[0172] (6) Determination of reducing sugar content

[0173] Reducing sugars were determined using the 3,5-dinitrosalicylic acid (DNS) method. A suitable amount of shiitake mushrooms was ground with distilled water and incubated at 80 ℃ for 30 min to extract the reducing sugars. After centrifugation, 2 mL of the supernatant was added to 1.5 mL of DNS, mixed, and then boiled in a water bath for 5 min. The glucose standard curve was measured at 540 nm. The standard curve for glucose was y = 2.0578x + 0.0126, R0. 2 =0.9979. The result is expressed as the mass of reducing sugar contained in each gram of shiitake mushroom tissue, in mg / g.

[0174] (7) Determination of Vitamin C content

[0175] Vitamin C content was determined using a spectrophotometer. A standard curve was plotted using ascorbic acid: y = 0.0179x + 0.1566, R0 2 = 0.9975. Shiitake mushrooms were ground into a paste in 50 g / L trichloroacetic acid solution and then centrifuged at 10000×g for 10 min. 1 mL of the supernatant was taken and added sequentially to 50 g / L trichloroacetic acid (1 mL), 0.4% (v / v, volume concentration) phosphoric acid-ethanol solution (1 mL), 5 g / L phenanthroline-ethanol solution (1 mL), and 0.3 g / L FeCl3-ethanol solution (0.5 mL), and mixed thoroughly. The absorbance of the mixture was measured at 534 nm. Vitamin C content is expressed as the mass of vitamin C contained in 100 g of shiitake mushrooms (fresh weight), in mg / 100g.

[0176] (8) Determination of total phenol content

[0177] Total phenols were determined using the Folin-Ciocalteu colorimetric method. 1.0 g of shiitake mushroom was weighed and added to 5 mL of 80% ethanol, then extracted in a 60 ℃ water bath for 30 min. After centrifugation, 0.5 mL of the supernatant was collected, and 0.5 mL of Folin-Ciocalteu colorimetric reagent and 4 mL of 7% (w / v) sodium carbonate solution were added sequentially. The mixture was then diluted to 10 mL with water and reacted in the dark for 1 h. Colorimetric analysis was performed at 760 nm. A series of standard solutions of 0-200 mg / L were prepared using gallic acid and treated using the same method as the samples. The total phenol content in shiitake mushrooms is expressed as the mass of gallic acid per gram of shiitake mushroom tissue, in mg / g.

[0178] 3. Results and analysis of the quality indicators of shiitake mushrooms:

[0179] (1) Sensory evaluation

[0180] from Figure 18It can be seen that the four-layer labeling treatment has a significant effect on the appearance quality of shiitake mushrooms. The control group (CK) shiitake mushrooms showed obvious softening and browning on day 18 of storage, and mold appeared on day 24. In contrast, the samples treated with the four-layer labeling maintained good appearance quality throughout the entire storage period, without showing obvious softening, browning, or mold. This result indicates that the four-layer labeling treatment can effectively delay the deterioration of the appearance of shiitake mushrooms during storage.

[0181] Sensory evaluation is typically characterized by color, aroma, and texture. The effects of different treatment groups on the sensory evaluation of shiitake mushrooms are shown in [reference needed]. Figure 10 As shown in the figure, the sensory scores of all three treatment groups decreased with prolonged storage time, but the sensory score of the 4-layer label group was significantly higher than that of the control group and the label group. This is because, with prolonged storage, the respiration and transpiration of the shiitake mushrooms, as well as the activity of microorganisms, caused severe browning on their surface, resulting in a sticky texture, a distinct musty smell, and autolysis, thus leading to a decrease in the sensory score. The 4-layer label group reduced the activity of microbial cells and enzymes, inhibiting respiration and transpiration to a certain extent. Therefore, the 4-layer label treatment can effectively inhibit the deterioration of the color and texture of fresh shiitake mushrooms and improve their sensory score during storage.

[0182] (2) Effect of 4-layer label on the weight loss rate of shiitake mushrooms

[0183] The loss of water and the consumption of nutrients in fruits and vegetables will cause the fruit to shrink more quickly, resulting in a decrease in fruit weight. Therefore, the weight loss rate is an important indicator for judging the quality of fruits during storage. Figure 11 The figure shows the changes in weight loss rate of shiitake mushrooms treated with different methods after 30 days of storage at 0±1℃. As can be seen from the figure, the weight loss rate of the control group (CK) was significantly higher than that of other treatment groups throughout the 30-day storage period (P<0.05), with the most significant effects observed on days 24 and 30. Among the treatment groups, the weight loss rate of the label group was generally higher than that of the four-layer label group. On day 30, the highest weight loss rate was observed in the CK group at 24.57%, while the label group and the four-layer label group had rates of 17.60% and 10.56%, respectively. Therefore, the four-layer label treatment group showed the best results.

[0184] (3) Effect of 4-layer label on the rot rate of shiitake mushrooms

[0185] Shiitake mushrooms are prone to softening, rotting, and spoilage during storage, thus losing their edible value. The changes in the rotting rate of shiitake mushrooms in three different treatment groups after 30 days of storage at 0±1℃ are shown below. Figure 12As shown in the figure, no rotting occurred in any of the treatment groups during the first 6 days of storage. Rotting began after 12 days, and the rotting rate was positively correlated with storage time. On day 18, rotting occurred in both the label group and the 4-layer label group, but the rotting rate was low. Towards the end of storage, the rotting rate in the control group (CK) increased significantly to 30.33%, while the rotting rates in the label group and the 4-layer label group were only 13.31% and 5.98%, respectively, significantly lower than the CK group. This indicates that the 4-layer label treatment effectively slowed down the quality deterioration of the shiitake mushrooms during storage, greatly maintaining their economic value.

[0186] (4) Effect of 4-layer label on the firmness of shiitake mushrooms

[0187] Firmness, as one of the key texture parameters in the postharvest maturity evaluation system for fruits and vegetables, is closely related to the cell wall metabolism of the fruit. The changes in the decay rate of shiitake mushrooms under different treatment groups after 30 days of storage at 0±1 ℃ are shown below. Figure 13 As shown, compared with the control group, both the label group and the 4-layer label group significantly regulated the hardness decay process of shiitake mushrooms (P<0.05). After 30 days of storage, the hardness of both the label group and the 4-layer label group was higher than that of the control group, with the 4-layer label group reaching a hardness of 7.43 N, while the control group was only 3.07 N, indicating that the 4-layer label treatment had the most significant effect on maintaining hardness.

[0188] (5) Effect of 4-layer label on the soluble protein content of shiitake mushrooms

[0189] Soluble protein, an important functional component of shiitake mushrooms, not only participates in cellular metabolic regulation but also serves as the structural basis for many enzymes. Its dynamic changes directly affect the physiological activity and nutritional quality of post-harvest shiitake mushrooms. The changes in soluble protein content in shiitake mushrooms from different treatment groups after 30 days of storage at 0±1 ℃ are shown below. Figure 14 As shown, the soluble protein content of the samples in each treatment group exhibited a change from initial increase to decrease. At the beginning of storage (0 day), the soluble protein content was 4.23 mg / g in the CK group, 4.61 mg / g in the tag group, and 6.96 mg / g in the 4-layer tag group. Subsequently, the soluble protein levels of the tag and 4-layer tag treatment groups remained higher than those of the CK group throughout the entire storage period. On day 30 of storage, the 4-layer tag treatment group was 1.06 mg / g higher than the CK group. The results indicate that the 4-layer tag treatment can effectively delay the catabolism of soluble protein, thereby maintaining the textural properties and nutritional functions of shiitake mushrooms.

[0190] (6) Effect of 4-layer label on reducing sugar content of shiitake mushrooms

[0191] Reducing sugars are important respiratory substrates for fruits and vegetables after harvest, and their content gradually decreases with prolonged storage. The changes in reducing sugar content in shiitake mushrooms under different treatment groups after 30 days of storage at 0±1 ℃ are shown below. Figure 15As shown, the reducing sugar content of shiitake mushrooms gradually decreased with prolonged storage. Compared with the control group (CK), the label and 4-layer label treatment groups significantly increased the reducing sugar content of shiitake mushrooms, with the 4-layer label group exhibiting the highest reducing sugar content. On day 30 of storage, the reducing sugar content of the CK group was only 0.79 mg / g; while the reducing sugar content after 4-layer label treatment remained at 2.68 mg / g, significantly higher than that of the CK group, indicating that the 4-layer label treatment can effectively inhibit the degradation of reducing sugars during the storage of shiitake mushrooms.

[0192] (7) Effect of 4-layer label on vitamin C content of shiitake mushrooms

[0193] Vitamin C, an important endogenous antioxidant in plants, reflects postharvest maturity and senescence processes through its dynamic content. The changes in reducing sugar content in shiitake mushrooms under different treatment groups after 30 days of storage at 0±1 ℃ are shown below. Figure 16 As shown, the vitamin C content of shiitake mushrooms gradually decreased during storage. On day 30 of storage, compared with the control (CK), the label treatment and the four-layer label treatment significantly increased the vitamin C content of shiitake mushrooms, with the four-layer label treatment group having the highest vitamin C content, reaching 0.104 mg / g. This indicates that the four-layer label treatment group can effectively reduce the loss of vitamin C content in shiitake mushrooms.

[0194] (8) Effect of 4-layer label on total phenolic content of shiitake mushrooms

[0195] Total phenols are substances related to the antioxidant properties of shiitake mushrooms. The oxidation of phenolic substances leads to browning of the mushroom color, affecting its commercial value. The changes in total phenol content of shiitake mushrooms in different treatment groups after 30 days of storage at 0±1 ℃ are shown below. Figure 17 As shown, the total phenolic content of shiitake mushrooms decreased with prolonged storage time. Compared with the control group (CK), the label treatment and the 4-layer label treatment significantly increased the total phenolic content of shiitake mushrooms, with the 4-layer label treatment group exhibiting the highest total phenolic content. After 30 days of storage, the total phenolic content of the CK group was only 0.035 mg / g, while the total phenolic content of the 4-layer label treatment group reached 0.201 mg / g, indicating that the 4-layer label treatment can inhibit the oxidative deterioration of phenolic substances during shiitake mushroom storage, thus preserving the nutritional and commercial value of the shiitake mushrooms.

[0196] Although embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the scope of the invention is not limited to the contents disclosed in the embodiments.

Claims

1. A slow-release label paper for preserving fruits and vegetables, characterized in that: The slow-release label paper includes an antibacterial layer (1), a freshness-preserving inducing layer (2), a self-absorbent layer (3), and an ethylene adsorption color-developing printing layer (4). The antibacterial layer (1), the freshness-preserving inducing layer (2), the self-absorbent layer (3), and the ethylene adsorption color-developing printing layer (4) are tightly pasted together from the inside out. The method for preparing the self-absorbing water layer (3) includes the following steps: Citric acid powder was dissolved in deionized water to prepare a 3-6 wt% citric acid solution. CNF powder and the citric acid solution were mixed at a material-to-liquid ratio of 1:40-1:60 (g:ml). After thorough mixing, the mixture was placed in a thermostatic magnetic stirrer at 70-90℃ and reacted continuously at 600-1000 rpm for 3-5 hours. After the reaction, the mixture was immediately cooled to room temperature. The resulting mixture was then added to 10 times its volume of deionized water and centrifuged at 8000-10000 rpm for 5-15 minutes. The precipitate was collected and repeatedly washed with deionized water. The washed precipitate was then added to deionized water to form a suspension. The suspension was then placed in a dialysis bag and dialyzed for 3-5 days. The dialysis bag must be completely submerged in deionized water. Dialysis was performed every 5-9 hours. Replace the external deionized water once to finally obtain the carboxylated CNF suspension in the dialysis bag; concentrate the carboxylated CNF suspension to a final mass concentration of 0.5-2.0wt%, add 0.02-0.2wt% polyvinyl alcohol (PVA), and magnetically stir at 300-1000rpm for 1-3h to form a homogeneous sol. Pour it onto a polytetrafluoroethylene plate, freeze at -20℃ for 1-3h, and then freeze at -80℃ for 5-12h to obtain a membrane; atomize the crosslinking solution, which is a mixed aqueous solution composed of 1-8wt% citric acid, 0.5-2.5wt% NaH2PO4, and water, onto the membrane, and finally perform plasma treatment under the conditions of O2:Ar=3:1, power 100W, and treatment time 90s to obtain a self-absorbing water layer (3). The preparation method of the ethylene adsorption color development printing layer (4) includes the following steps: Zeolite particles were immersed in a 20% KMnO4 aqueous solution (g:mL ratio of zeolite particles to KMnO4 aqueous solution was 5-20:25-100), ultrasonically vibrated for 20-60 min, and then rotary evaporated under reduced pressure at 60℃ to dryness, followed by vacuum drying at 80℃ for 4 h to obtain purplish-red loaded particles. The particles were passed through a 200-mesh sieve, and particles with a diameter ≤75μm were selected for later use. These loaded particles were placed in a fluidized bed and coated with a 5%-10% gelatin aqueous solution as a binder to form a dense release film, resulting in gelatin-coated particles. Bromocresol was then added... Purple BCP powder was dissolved in ethanol, and then 1-3% chitosan acetic acid solution was added. The ratio of bromocresol purple to 1-3% chitosan acetic acid solution was 1:900 (g:mL). The mixture was magnetically stirred for 2 hours to obtain a purple BCP-chitosan mixture. In a fluidized bed, the gelatin-coated particles were sprayed with the BCP-chitosan mixture, and the inlet air temperature was controlled at 40°C to complete the second coating layer and obtain microcapsules. The microcapsules were immersed in a 1%-4% sodium alginate solution and stirred slowly for 5-30 minutes. Then, they were transferred to a 2-6% CaCl2 solution and allowed to stand for crosslinking for 10-40 minutes to form a gel outer layer. The mixture was filtered and rinsed three times with deionized water. The resulting particles were vacuum dried at 40°C for 12 hours to obtain the final ethylene adsorption colorimetric microcapsule particles (7). The preparation steps of the 1-3% chitosan acetic acid solution are as follows: prepare a 1% acetic acid aqueous solution by mixing chitosan powder and 1% acetic acid aqueous solution at a material-liquid ratio of 1:100-3:100 (g:mL). Nanocellulose (CNF) was diluted to a final concentration of 0.2-0.5 wt%, and magnetically stirred at 200-1000 rpm for 1-4 hours until a homogeneous gel state was achieved. The solution was poured into a Buchner funnel, and vacuum-sealed to form a wet film. The film was dried at room temperature for 12 hours to form a gel network framework. It was then transferred to a constant temperature and humidity chamber at 30°C and 50% RH. When the moisture content reached 40%, it was placed in a 40°C oven for 1-3 hours, and then dried at 60°C for 1-4 hours until the final moisture content was 8-10%, yielding an ethylene adsorption color-developing printing layer paper base. A coating of 0.025-0.225 ml / cm² was then applied to the inner side of the paper base. 2 The natural adhesive starch glue (6) is used to adhere the above-mentioned ethylene adsorption color-developing microcapsule particles (7) to the ethylene adsorption color-developing printing layer paper base on the side coated with starch glue (6). Label information can be printed on the outside of the paper base, and the ethylene adsorption color-developing printing layer (4) is prepared.

2. The slow-release label paper for preserving fruits and vegetables according to claim 1, characterized in that: The method for preparing the antibacterial layer (1) includes the following steps: Nanocellulose (CNF) was diluted to a concentration of 0.2-0.5 wt% and magnetically stirred at 200-1000 rpm for 1-4 hours until a uniform gel state was obtained, yielding a CNF suspension with a concentration of 0.2-0.5 wt%. Powdered Sichuan peppercorns were mixed with anhydrous ethanol at a ratio of 1:10-1:30 (g:ml). The mixture was placed in an ultrasonic cleaner and sonicated at 40-60℃ and 150-300W for 20-50 minutes. After filtration through five layers of gauze, the filtrate was collected and concentrated under reduced pressure using a rotary evaporator at 30-50℃ to recover the ethanol, yielding the Sichuan peppercorn extract. The Sichuan peppercorn extract was then added to a 0.2-0.5 wt% CNF suspension. In the CNF suspension, the mass ratio of Sichuan pepper extract to CNF suspension is 1:4-1:

20. The mixture is magnetically stirred at 300-800 rpm for 0.5-2 hours until it is homogeneous. The mixed solution is poured into a Buchner funnel, vacuumed until a wet film is formed, and dried at room temperature for 12 hours to form a gel network skeleton. Then it is transferred to a constant temperature and humidity chamber at 30℃ and RH 50%. When the moisture content is 40%, it is placed in a 40℃ oven for 1-3 hours and then heated to 60℃ for 1-4 hours to make the final moisture content 8-10%, thus obtaining the antibacterial layer (1).

3. The slow-release label paper for preserving fruits and vegetables according to claim 1, characterized in that: The method of setting the preservation-inducing layer (2) on the antibacterial layer (1) includes the following steps: Polyvinylpyrrolidone (PVP) and ethyl cellulose (EC) were added to anhydrous ethanol and stirred, then sonicated until fully mixed to prepare a slow-release agent. 1-MCP powder and sodium nitroprusside were added to the prepared slow-release agent, stirred, and sonicated again to form a homogenate with the 1-MCP powder and sodium nitroprusside. The homogenate was evenly coated on the outer surface of the antibacterial layer (1) so that the paper base contained 1-MCP powder and sodium nitroprusside. After coating, the semi-finished label with the homogenate was placed in an oven to dry so that the solvent could completely evaporate. Finally, natural adhesive starch glue (6) was brushed onto the inner surface of the antibacterial layer (1), and polytetrafluoroethylene (PTFE) film (5) was attached to facilitate adhesion to the surface of fruits and vegetables, thus obtaining the antibacterial layer (1) and the preservation inducing layer (2) set together. The mass ratio of polyvinylpyrrolidone (PVP) to ethyl cellulose (EC) is 4:1, and the amount of anhydrous ethanol added is 8 to 10 times the total mass of PVP and EC. The sustained-release agent is prepared at a stirring temperature of 20–40°C, an ultrasonic power of 100W–300W, and an ultrasonic time of 2–10 min. The 1-MCP powder is a powder-type 1-MCP encapsulated with α-cyclodextrin, and the ratio of polyvinylpyrrolidone: 1-MCP powder: sodium nitroprusside (g:g:mg) is 50:4:25 to 70:4:

25. When adding 1-MCP powder and sodium nitroprusside, the stirring time during the second ultrasonication is 5-10 min, the stirring temperature is 20-35℃, the ultrasonic power is 100W-300W, and the ultrasonication time is 3-15 min. The coating amount of the homogenate is 0.1–0.4 ml / cm². 2 Ensure that the antibacterial layer (1) contains 0.05 to 0.24 g of 1-MCP and 5 μM to 200 μM sodium nitroprusside powder, and the coating speed is 1 to 5 m / min; The drying temperature of the oven is 40–80℃, and the drying time is 6–16 hours.

4. The slow-release label paper for preserving fruits and vegetables according to claim 3, characterized in that: The starch adhesive (6) is a natural adhesive made from starch as a base material, with a coating amount of 0.025–0.225 ml / cm². 2 .

5. The application of the slow-release label paper for fruit and vegetable preservation as described in any one of claims 1 to 3 in the preservation of fruits and vegetables.

6. The application of the slow-release label paper for fruit and vegetable preservation as described in any one of claims 1 to 3 in delaying the softening of fruits and vegetables.

7. The application of the slow-release label paper for fruit and vegetable preservation as described in any one of claims 1 to 3 in delaying the softening performance of edible fungi.

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