A berry fresh-keeping product and a preparation method and application thereof

Abstract

The application discloses a berry fresh-keeping product and a preparation method and application thereof. The product comprises a carrier barrier layer, a bacteriostatic active ingredient layer, a breathable and moisture-permeable layer and a moisture-retaining buffer layer. The carrier barrier layer is a microporous LDPE film bag. The bacteriostatic active ingredient layer is a ternary core material coated on the lower surface of the microporous LDPE film bag, and comprises micro-acid electrolytic water freeze-dried powder, chitosan oligosaccharide, 1-MCP inclusion compound, glycerol and a bacteriostatic additive. The bacteriostatic additive is any one of nano-TiO2, sodium metabisulfite, sodium bisulfite and sodium sulfite. The breathable and moisture-permeable layer is an electrostatic nanofiber non-woven fabric. The moisture-retaining buffer layer is humidity buffer microbeads sprayed on the surface thereof. The three functional active ingredients of bacteriostasis, respiration inhibition and film formation protection are integrated in the same active layer, and are released in a synergistic manner, thereby avoiding step-by-step operation and rapid release. Meanwhile, the microporous LDPE film is used to adjust the gas composition in the package, and the humidity buffer microbeads are used to maintain humidity, so that the berry mildew rate and mechanical damage are effectively reduced, and the cold chain shelf life is prolonged.

Description

Technical Field

[0001] This invention relates to the field of fruit and vegetable preservation technology, and in particular to a berry preservation product, its preparation method, and its application. Background Technology

[0002] Berries have thin, juicy skins that are easily damaged. They also have high respiration and metabolism after harvest, and their shelf life at room temperature is usually only 12-24 hours. During storage and transportation, the mold rate can be as high as 30% or more, resulting in extremely high loss rates, which seriously restricts their commercial circulation and e-commerce development.

[0003] In existing berry preservation technologies, fumigation treatment with 1-methylcyclopropene (1-MCP) is used. 1-MCP inhibits fruit respiration metabolism by irreversibly binding to ethylene receptors, delaying ripening and senescence. However, conventional 1-MCP tablets or powders release too quickly, with over 80% of the total amount released in the first 6 hours. This leads to excessively high concentrations in the early stages of treatment, easily causing phytotoxicity, while the concentration rapidly declines below the effective threshold in the later stages, resulting in respiratory rebound and failing to achieve long-term preservation. Chitosan oligosaccharide coating treatment is another option. Chitosan oligosaccharides can form a semi-permeable edible film on the fruit surface, playing a role in micro-modified atmosphere, antibacterial activity, and inducing disease resistance. However, existing chitosan oligosaccharide coating processes usually require hot air drying to accelerate film formation, which increases fruit surface temperature and accelerates berry browning, thus reducing fruit quality. Slightly acidic electrolyzed water (SAEW) is used for sterilization. Slightly acidic electrolyzed water has broad-spectrum bactericidal capabilities and has a good killing effect on pathogenic bacteria on the fruit surface. However, its active ingredient, available chlorine (ACC), decays rapidly, with a half-life of less than 2 hours at 25°C, failing to provide long-lasting antibacterial protection. The above preservation methods are implemented in steps: fumigation, coating, and sterilization—a three-step process. This method is cumbersome, requiring repeated manual handling of the fruit, increasing the risk of mechanical damage and cross-contamination. Furthermore, the lack of synergy between the preservatives used in each step makes it difficult to achieve simultaneous, integrated control over post-harvest respiration suppression, pathogen inhibition, and mold prevention of the berries.

[0004] Furthermore, in existing food preservation packaging, the preservation pads or preservatives are usually placed in direct contact with the fruit, which can easily cause damage due to excessively high local concentrations or direct contact. At the same time, the lack of effective humidity control within the packaging makes condensation prone to occur, further exacerbating the risk of mold growth.

[0005] Therefore, it is necessary to propose a solution to improve one or more problems existing in the above-mentioned related technical solutions.

[0006] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0007] The purpose of this disclosure is to provide a berry preservation product, its preparation method, and its application, thereby overcoming, at least to some extent, one or more problems caused by the limitations and defects of related technologies.

[0008] A berry preservation product provided according to a first aspect of the present disclosure includes a carrier barrier layer, an antibacterial active ingredient layer, an air-permeable and moisture-permeable layer, and a moisture-retaining buffer layer. The carrier barrier layer is composed of a microporous LDPE membrane bag; The antibacterial active ingredient layer is a ternary core material coated on the lower surface of the microporous LDPE film bag; The breathable and moisture-permeable layer is an electrostatic nanofiber nonwoven fabric. The moisturizing buffer layer consists of moisture-buffering microbeads sprayed onto the surface of the electrospun nanofiber pad. The ternary core material includes slightly acidic electrolyzed water freeze-dried micro powder, chitosan oligosaccharide, 1-MCP inclusion complex, glycerol, and antibacterial additives. The antibacterial additives are any one of nano TiO2, sodium metabisulfite, sodium bisulfite, and sodium sulfite.

[0009] In an exemplary embodiment of this application, the microporous LDPE membrane bag has an oxygen permeability of 3000 cm³ / m² / day, a carbon dioxide permeability of 12000 cm³ / m² / day, a micropore diameter of 0.8 μm, and a thickness of 50 μm.

[0010] In an exemplary embodiment of this application, the electrospun nanofiber pad is made of PA6, has a specific surface area of ​​15m² / g, a fiber diameter of 200nm-400nm, a thickness of 0.3mm, and a unit mass of 0.8g.

[0011] In an exemplary embodiment of this application, the mass composition of the ternary core material is as follows: The mixture comprises 30-50 parts of slightly acidic electrolyzed water freeze-dried micro powder, 20-30 parts of chitosan oligosaccharide, 10-20 parts of 1-MCP inclusion complex, 5 parts of food-grade glycerol, and 1 part of antibacterial additive, wherein the antibacterial additive is any one of nano TiO2, sodium metabisulfite, sodium bisulfite, and sodium sulfite.

[0012] In an exemplary embodiment of this application, the effective chlorine content of the slightly acidic electrolyzed water freeze-dried micropowder is 150 ppm and the pH value is 5.8; the degree of deacetylation of the chitosan oligosaccharide is ≥95% and the molecular weight is 1kDa–3kDa; the 1-MCP inclusion complex is α-cyclodextrin-1-MCP with a molar encapsulation rate of 68%; and the nano-TiO2 is anatase nano-TiO2 with a particle size <20nm.

[0013] In one exemplary embodiment of this application, the humidity buffer microbeads are SAP superabsorbent resin microbeads with a particle size of 100 μm and a distilled water absorption capacity of 200 g·g. - ¹, used to absorb moisture when RH>95% and release moisture when RH<85%, maintaining the humidity inside the chamber at 90±5%.

[0014] In an exemplary embodiment of this application, the upper surface of the microporous LDPE film bag is provided with a self-adhesive hanging wing composed of two food-grade silicone self-adhesive wings, which is used to attach the berry preservation product to the lid of a fruit basket or the top wall of a courier box.

[0015] A second aspect of this disclosure provides a method for preparing the above-mentioned berry preservation product, comprising the following steps: A microporous LDPE membrane with a thickness of 50 μm and a micropore diameter of 0.8 μm was selected. Weigh each component of the ternary core material according to the mass fraction to prepare the slurry, and evenly coat it on the lower surface of the LDPE film bag; PA6 electrostatic nanofiber nonwoven fabric is laminated with coated LDPE film bag by thermal bonding or food-grade adhesive, so that the antibacterial active ingredient layer is located between the two. SAP superabsorbent resin microbeads are suspended in ethanol or water and uniformly sprayed onto the outer surface of electrostatic nanofiber nonwoven fabric. Food-grade silicone adhesive wings are attached to both sides of the upper surface of the LDPE film bag. The bag is then cut to size and sealed to protect it from light.

[0016] A third aspect of this disclosure provides the application of the berry preservation product as described above or the berry preservation product prepared by the above preparation method in berry preservation, wherein the product is placed or attached to a sealed packaging container of berries to be preserved, and transported or stored in a cold chain environment at 0-10°C.

[0017] In one exemplary embodiment of this application, the berry is any one of blueberry, raspberry, strawberry, and mulberry.

[0018] This application proposes a berry preservation product, its preparation method, and its application, which can include the following beneficial effects: On the one hand, through a four-layer composite structure, combined with freeze-dried micro-powder containing slightly acidic electrolyzed water, chitosan oligosaccharide, and 1 The synergistic effect of MCP inclusion complex and antibacterial additives in ternary core materials solves the problem of existing 1 The solution addresses several issues, including the rapid release of MCP which can cause phytotoxicity, the need for drying chitosan oligosaccharide coatings which accelerates browning, the rapid decay of effective chlorine in freeze-dried micropowders from slightly acidic electrolyzed water which does not provide long-lasting antibacterial protection, and the cumbersome step-by-step preservation process. It achieves integrated control over berry respiration inhibition, pathogen inhibition, and mold prevention. Furthermore, it utilizes microporous LDPE film bags to regulate gas permeability, electrospun electrostatic nanofiber nonwoven fabrics to ensure air and moisture permeability, and SAP humidity buffer microbeads to dynamically regulate humidity, maintaining a stable microenvironment within the packaging, preventing condensation from exacerbating mold growth, reducing berry storage and transportation losses, and effectively extending shelf life. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0020] Figure 1 This illustration shows a schematic diagram of a berry-based preservation product according to an exemplary embodiment of this application; Figure 2 The diagram illustrates the steps of a method for producing berry-based preservative products in an exemplary embodiment of this application. Figure 3 This document shows a comparison of experimental results in Exemplary Example 3 of this application; Figure 4 A comparison diagram of experimental results in Exemplary Example 4 of this application is shown. Detailed Implementation

[0021] To provide a more detailed description of the present invention, the following embodiments are provided for further explanation. The specific embodiments described below are for illustrative purposes only and should not be construed as limiting the scope of protection of this application. Those skilled in the art can make non-essential improvements and adjustments to this application based on the above description.

[0022] The first aspect of this exemplary implementation provides a berry-based preservation product, such as... Figure 1 As shown, it includes a carrier barrier layer, an antibacterial active ingredient layer, a breathable and moisture-permeable layer, and a moisturizing buffer layer. The carrier barrier layer is composed of a microporous LDPE membrane bag; The antibacterial active ingredient layer is a ternary core material coated on the lower surface of the microporous LDPE film bag; The breathable and moisture-permeable layer is an electrostatic nanofiber nonwoven fabric. The moisturizing buffer layer consists of moisture-buffering microbeads sprayed onto the surface of the electrospun nanofiber pad. The ternary core material includes slightly acidic electrolyzed water freeze-dried micro powder, chitosan oligosaccharide, 1-MCP inclusion complex, glycerol, and antibacterial additives. The antibacterial additives are any one of nano TiO2, sodium metabisulfite, sodium bisulfite, and sodium sulfite.

[0023] It's important to understand that in existing technologies, 1-MCP fumigation requires rapid release in a sealed environment to achieve an effective fumigation concentration, while chitosan oligosaccharide coating requires an open environment for hot air drying to form a film. These two preservation methods have a fundamental contradiction in their operational timing and cannot be implemented simultaneously within the same package. The four-layer structure, through the control of humidity permeation rate by the microporous LDPE membrane, establishes a release sequence. In the initial stage of packaging sealing, the microporous LDPE membrane allows a small amount of water vapor to slowly permeate into the inner layer, triggering the preferential release of the 1-MCP inclusion complex. 1-MCP is released at a gradual and continuous rate for approximately 120 hours, effectively inhibiting the fruit's respiration peak and ripening process. Simultaneously, the moisturizing effect of the nanofiber pad maintains a suitable water activity in the local environment, allowing the chitosan oligosaccharide to slowly dissolve under the cold chain high-humidity environment. Once 1-MCP has completed its primary function of inhibiting respiration, the fruit's respiration intensity has significantly decreased. At this point, the chitosan oligosaccharide fully dissolves from the nanofiber pad and forms a protective film on the fruit surface. This sequential control of first suppressing respiration and then forming a protective film allows 1-MCP and chitosan oligosaccharide, two preservation technologies that are contradictory in traditional processes, to coexist harmoniously and enhance each other in the same system.

[0024] With the aid of nanofiber pads, chitosan oligosaccharides form a dense, positively charged edible film on the fruit surface. This film not only acts as a physical barrier in the traditional sense, preventing the invasion of external pathogens and reducing water evaporation, but more importantly, its gel layer acts as a molecular sieve, firmly adsorbing negatively charged, slightly acidic electrolyzed water chlorine molecules onto the fruit peel surface through electrostatic adsorption. This significantly extends the bactericidal concentration of available chlorine from less than two hours to over seventy-two hours. This is not due to the effect of the slightly acidic electrolyzed water formed by the freeze-dried micropowder, but rather the function acquired by the chitosan oligosaccharide film within this specific four-layer structure.

[0025] Traditionally, anatase nano-titanium dioxide is considered solely as a photocatalytic bactericide, generating reactive oxygen species to kill microorganisms under ultraviolet or visible light irradiation. However, due to the low oxygen concentration regulated by the microporous LDPE membrane, the photocatalytic activity of nano-titanium dioxide is significantly suppressed. Nevertheless, the initial burst release of 1-MCP is significantly reduced compared to the absence of nano-titanium dioxide. Nano-titanium dioxide, with its extremely high specific surface area and surface adsorption activity, primarily functions to adsorb and stabilize 1-MCP molecules in a low-oxygen environment, temporarily binding the molecules to its surface and delaying its rapid release upon contact with moisture, thus acting as a physical slow-release agent. This further slows down the release of 1-MCP, avoiding the risk of phytotoxicity caused by excessively high initial concentrations.

[0026] When sodium metabisulfite is selected as the antibacterial additive, it can be replaced with sodium bisulfite or sodium sulfite. Its mechanism of action differs from that of nano-titanium dioxide, but it still synergizes with the four-layer structure. Sodium metabisulfite, upon contact with moisture, can slowly release low concentrations of sulfur dioxide gas at a controllable rate. Sulfur dioxide is a broad-spectrum and highly effective fungicide, effectively inhibiting spore germination and mycelial growth of major post-harvest pathogens of berries such as gray mold and anthracnose. The SO2 released by sodium metabisulfite does not simply diffuse into the packaging space, but is adsorbed by the positively charged chitosan oligosaccharide edible membrane. A reversible weak interaction forms between the amino groups on the chitosan oligosaccharide molecular chain and SO2, maintaining a continuous and stable low-concentration antibacterial microenvironment on the fruit surface. This avoids the drawbacks of traditional SO2 slow-release agents, such as excessively rapid initial release leading to bleaching damage to the fruit peel and insufficient concentration in the later stages causing ineffectiveness. Meanwhile, SO2 also possesses antioxidant activity, inhibiting the activity of polyphenol oxidase during post-harvest senescence of berries, slowing down peel browning, and scavenging free radicals produced by fruit respiration metabolism, thus better preserving the color and quality of the berries. Furthermore, the release of SO2 gas can form a relay-effect antibacterial effect with slightly acidic electrolyzed water. The available chlorine in the slightly acidic electrolyzed water first rapidly sterilizes the fruit surface, removing existing mold biofilms, while the slowly released SO2 from sodium metabisulfite continuously inhibits the germination of new spores, together forming a dual bactericidal barrier of rapid removal and long-term inhibition.

[0027] The four-layer structure works synergistically in both temporal and spatial dimensions. Temporally, the humidity permeation control of the microporous LDPE membrane and the slow-release effect of the nanofiber pads achieve precise timing control of the sequence, first inhibiting respiration and then forming a protective film. Spatially, the porous template effect of the nanofiber pads and the moisture-regulating effect of the SAP microbeads create a microenvironment on the fruit peel surface conducive to film formation and continuous sterilization. This cannot be explained by a simple superposition of the ingredients' effects.

[0028] This application proposes a berry preservation product, its preparation method, and its application, which can include the following beneficial effects: On the one hand, through a four-layer composite structure, combined with freeze-dried micro-powder containing slightly acidic electrolyzed water, chitosan oligosaccharide, and 1 The synergistic effect of MCP inclusion complex and antibacterial additives in ternary core materials solves the problem of existing 1 The solution addresses several issues, including the rapid release of MCP which can cause phytotoxicity, the need for drying chitosan oligosaccharide coatings which accelerates browning, the rapid decay of effective chlorine in slightly acidic electrolyzed water which does not provide long-lasting antibacterial protection, and the cumbersome step-by-step preservation process. It achieves integrated control over berry respiration inhibition, pathogen inhibition, and mold prevention. Furthermore, it utilizes microporous LDPE film bags to regulate gas permeability, electrospun electrostatic nanofiber nonwoven fabric to ensure air and moisture permeability, and SAP humidity buffer microbeads to dynamically regulate humidity, maintaining a stable microenvironment within the packaging, preventing condensation from exacerbating mold growth, reducing berry storage and transportation losses, and effectively extending shelf life.

[0029] The following detailed embodiments are only used to further illustrate this application and should not be construed as limiting the scope of protection of this application. Those skilled in the art can make some non-essential improvements and adjustments to this application based on the above application content.

[0030] In one embodiment, the microporous LDPE film bag has an oxygen permeability of 3000 cm³ / m² / day, a carbon dioxide permeability of 12000 cm³ / m² / day, a micropore size of 0.8 μm, and a thickness of 50 μm. It should be understood that the oxygen permeability of the microporous LDPE film bag is set at 3000 cubic centimeters per square meter per day, and the carbon dioxide permeability is 12000 cubic centimeters per square meter per day. The ratio of oxygen to carbon dioxide permeability is 1:4. Berries continue to undergo vigorous respiration and metabolism after harvest, constantly consuming oxygen and releasing carbon dioxide. An appropriate oxygen permeability can prevent the oxygen inside the packaging from being depleted too quickly, leading to anaerobic respiration and producing odors; while a higher carbon dioxide permeability helps to promptly remove excess carbon dioxide produced by fruit respiration, preventing excessive carbon dioxide accumulation that could damage the fruit. By setting the permeability value of the microporous LDPE film bag, a stable micro-modified atmosphere can be spontaneously formed inside the sealed packaging container, that is, the oxygen concentration is moderately reduced and the carbon dioxide concentration is moderately increased, thereby effectively inhibiting the respiration intensity of the berries, delaying their aging process, and avoiding adverse physiological reactions caused by poor gas exchange.

[0031] The microporous LDPE film bag has a pore size of 0.8 micrometers and a thickness of 50 micrometers. The pore size determines the film bag's permeability to gases and water vapor. The 0.8-micrometer pore size ensures sufficient oxygen and carbon dioxide permeability while effectively blocking dust and some microorganisms from entering the packaging, acting as a physical barrier. The 50-micrometer thickness provides sufficient mechanical strength and flexibility, allowing it to stably support the coated antibacterial active ingredients when used as a carrier barrier layer, and preventing damage during subsequent lamination, cutting, and use. This thickness, combined with the pore size, ensures uniform and stable air and moisture permeability. The microporous LDPE film bag not only serves as the outermost structural support for the product but, more importantly, acts as a precise gas regulator, providing fundamental protection for the slow release of antibacterial active ingredients and the dynamic balance of humidity within the packaging. The specific numerical range is based on the actual needs of berry preservation and represents the optimal technical solution derived through extensive experimental verification.

[0032] In one embodiment, the electrospun nanofiber mat is made of PA6, with a specific surface area of ​​15 m² / g, a fiber diameter of 200 nm-400 nm, a thickness of 0.3 mm, and a unit mass of 0.8 g. It should be understood that the electrostatic nanofiber nonwoven fabric is made of PA6, also known as polyamide 6. PA6 possesses excellent mechanical strength, chemical stability, and fiber-forming properties. Through electrospinning, it can form extremely fine fibers, resulting in a nonwoven fabric structure with a high specific surface area and high porosity, ensuring effective permeability of gases and water vapor. Specifically, the specific surface area of ​​the electrostatic nanofiber nonwoven fabric is set at 15 m² / g. The large surface area per unit mass of fiber material allows for the uniform and slow release of antibacterial active ingredients, avoiding localized accumulation or excessively rapid release. Simultaneously, the fiber diameter of this nonwoven fabric is set within the range of 200 nm to 400 nm. The nanoscale fiber diameter is achieved through electrospinning technology. The extremely fine fibers intertwine to form a three-dimensional network structure, giving the nonwoven fabric extremely high porosity and making the fiber pad soft, dense, and permeable. This allows it to effectively trap and carry micron- or nanoscale functional particles without hindering gas exchange. Furthermore, the electrostatic nanofiber nonwoven fabric is set at a thickness of 0.3 mm and a unit mass of 0.8 g, reflecting the pad's lightweight characteristics. This ensures that the entire preservation product maintains sufficient mechanical strength and load-bearing capacity without increasing the packaging volume and weight, making it convenient for use in fruit baskets or express delivery boxes. The thinner thickness also facilitates the rapid passage of water vapor and active gas molecules through the fiber pad, achieving efficient exchange with the antibacterial active ingredient layer and the moisture-retaining buffer layer. The parameters of the electrostatic nanofiber nonwoven fabric are set to give it a suitable pore structure and breathable and moisture-permeable properties, allowing it to act as a physical barrier layer to prevent antibacterial ingredients from directly contacting the berry surface, and as a controlled-release medium to regulate the release rate of moisture and active substances. If the fiber diameter is too large or the specific surface area is too small, it will result in insufficient loading or uneven distribution of active ingredients, thereby weakening the preservation effect; while if the thickness is too large or the unit mass is too high, it will reduce the air and moisture permeability, and disrupt the carefully maintained micro-atmosphere environment and humidity balance inside the packaging.

[0033] In one embodiment, the ternary core material comprises: 30-50 parts of slightly acidic electrolyzed water freeze-dried micropowder, 20-30 parts of chitosan oligosaccharide, 10-20 parts of 1-MCP inclusion complex, 5 parts of food-grade glycerol, and 1 part of antibacterial additive. The antibacterial additive is any one of nano-TiO2, sodium metabisulfite, sodium bisulfite, and sodium sulfite. The slightly acidic electrolyzed water freeze-dried micropowder has an effective chlorine content of 150 ppm and a pH of 5.8; the chitosan oligosaccharide has a degree of deacetylation ≥95% and a molecular weight of 1 kDa-3 kDa; the 1-MCP inclusion complex is α-cyclodextrin-1-MCP with a molar encapsulation rate of 68%; and the nano-TiO2 is anatase nano-TiO2 with a particle size <20 nm. It should be understood that sodium metabisulfite, sodium bisulfite, and sodium sulfite are all food-grade, and the ternary core material's mass ratio is fundamental to achieving the synergistic effect of antibacterial activity, film formation, and respiratory inhibition. For slightly acidic electrolyzed water freeze-dried micropowder, the available chlorine content is limited to 150 ppm and the pH value is 5.8. The available chlorine content directly determines its broad-spectrum bactericidal ability. 150 ppm is a proven optimal concentration that can effectively kill common pathogens on the surface of berries without damaging the fruit skin. The slightly acidic environment of pH 5.8 not only helps maintain the stability of available chlorine but also matches the slightly acidic environment of the berry surface, avoiding fruit irritation. For chitosan oligosaccharides, the degree of deacetylation is limited to not less than 95%, and the molecular weight is limited to 1 kDa to 3 kDa. The high degree of deacetylation exposes more amino groups on the chitosan oligosaccharide molecular chain, giving it a stronger positive charge, which is beneficial for binding to the negatively charged microbial cell membrane and exerting an antibacterial effect. The low molecular weight range of 1kDa to 3kDa ensures good water solubility and permeability, allowing it to gradually dissolve from the nanofiber pad under cold chain conditions of low temperature and high humidity, rapidly forming a uniform, thin, edible film on the berry surface without the need for hot air drying. The 1-MCP inclusion complex is an inclusion complex formed by α-cyclodextrin and 1-MCP, with a molar encapsulation rate of 68%. α-cyclodextrin is the main molecule forming the 1-MCP inclusion complex, effectively encapsulating and stabilizing 1-MCP gas, preventing premature release during storage and transportation. The 68% molar encapsulation rate represents a high inclusion efficiency, ensuring that each unit mass of the inclusion complex contains sufficient active 1-MCP, allowing for controlled release for up to 120 hours when exposed to moisture within the packaging, avoiding the problems of initial burst release and insufficient concentration in the later stages common in traditional tablets. The nano-TiO2 is anatase and has a particle size of less than 20 nanometers.In the four-layer structure of this application, because the oxygen concentration is regulated to a low level by the microporous LDPE membrane, the photocatalytic activity of nano-TiO2 is significantly suppressed. Instead, due to its extremely high specific surface area and surface adsorption activity, it mainly plays the role of adsorbing and stabilizing 1-MCP molecules, temporarily binding 1-MCP molecules on its surface, delaying its rapid release upon contact with moisture, thus acting as a physical slow-release agent and avoiding the risk of phytotoxicity caused by excessively high concentrations in the early stages. The ultrafine particle size of less than 20 nanometers endows it with extremely high specific surface area and dispersibility, enabling it to be uniformly distributed in the ternary core material and fully exert its physical slow-release effect. Food-grade glycerin, as a plasticizer, plays a specific role in regulating the adhesion and flexibility of the slurry in the overall formulation, ensuring that the ternary core material can be uniformly and firmly coated on the lower surface of the microporous LDPE membrane bag without cracking. All parameters work together to ensure that the ternary core material can be released in the expected sequence in a cold chain high-humidity environment. 1-MCP is released first to inhibit respiration, chitosan oligosaccharides gradually dissolve to form a protective film, and slightly acidic electrolyzed water continuously provides antibacterial activity with the assistance of nano-TiO2. All three are indispensable and enhance each other, ultimately achieving a long-lasting, broad-spectrum, and low-damage berry preservation effect that cannot be achieved by a single component or a combination of two components.

[0034] In one embodiment, the humidity-buffered microspheres are SAP superabsorbent resin microspheres with a particle size of 100 μm and a distilled water absorption capacity of 200 g·g. -¹ This material is used to absorb moisture when RH > 95% and release moisture when RH < 85%, maintaining the humidity inside the chamber at 90 ± 5%. It's important to understand that the humidity-absorbing microbeads are made of SAP (Super Absorbent Polymer) resin. SAP is a type of functional polymer material with a three-dimensional network structure capable of absorbing and retaining hundreds of times its own weight in water. The particle size of these humidity-absorbing microbeads is 100 micrometers. On one hand, the 100-micrometer microbeads can be uniformly attached to the surface of the electrostatic nanofiber nonwoven fabric through a spraying process, forming a densely distributed moisturizing buffer layer without significantly increasing the product thickness. On the other hand, this prevents clogging of the pores of the electrostatic nanofiber nonwoven fabric, ensuring that the gas exchange function of the breathable and moisture-permeable layer is not affected. The distilled water absorption rate of the SAP super absorbent resin microbeads is limited to 200 grams per gram, meaning that each gram of microbeads can absorb and retain 200 grams of distilled water. This high humidity regulation capacity allows the microbeads to quickly absorb excess moisture when the relative humidity inside the packaging exceeds 95%, effectively preventing condensation on the surface of berries in high-humidity environments. Condensation is one of the main causes of berry mold and rot, as condensed water droplets form a liquid film on the fruit surface, providing an ideal environment for the germination and growth of mold spores. When the relative humidity inside the packaging drops below 85%, these microbeads can slowly release the stored moisture, preventing the environment from becoming too dry and causing the berries to wilt. Through this two-way moisture absorption and release behavior, SAP humidity buffer microbeads can stably maintain the relative humidity inside the sealed packaging container within a range of 90% ± 5%. This humidity range is the optimal humidity range for berry preservation, determined through extensive experiments. Below the lower limit of this range (relative humidity below 85%), transpiration of the berries intensifies, weight loss increases significantly, the fruit skin wrinkles, and the commercial value decreases. Above the upper limit of this range (relative humidity exceeding 95%), a large amount of free water exists, and the risk of mold growth increases sharply. The humidity range of 90% ± 5% can both inhibit fruit moisture evaporation, maintaining the plump and bright texture of the berries, and effectively prevent free water condensation, thus destroying the growth conditions for mold. The moisture-retaining buffer layer is an adaptive humidity control system that can automatically maintain the optimal humidity environment inside the packaging without external energy or human intervention. It complements the modified atmosphere function of the carrier barrier layer and the bactericidal function of the antibacterial active ingredient layer, further reducing the post-harvest loss rate of berries through humidity control.

[0035] In one embodiment, the upper surface of the microporous LDPE film bag is provided with self-adhesive hanging wings consisting of two food-grade silicone adhesive wings, used to attach the berry preservation product to the lid of a fruit basket or the top wall of a courier box. It should be understood that in the prior art, preservation pads or preservatives are usually placed directly under the berries or stored mixed with them. This method easily leads to two problems: first, the preservation pad is in direct contact with the berries, which may cause chemical damage or physical indentation to the fruit peel due to excessively high local concentrations of active ingredients; second, the preservation pad is located at the bottom of the fruit and is often soaked in juice or blocked by the fruit, affecting its normal air and moisture permeability. The self-adhesive hanging wings change the preservation product from a pad form to a hanging form. Specifically, two food-grade silicone adhesive wings are set on the upper surface of the microporous LDPE film bag, i.e., connected to the carrier barrier layer. Silicone material has excellent food safety and moderate adhesive strength, which can reliably adhere to the inside of the fruit basket lid or the top wall of the courier box, and can be easily peeled off after use without leaving adhesive residue. Self-adhesive hanging wings ensure the entire preserved product remains level and stable during transportation and storage. This hanging installation method allows berry-type preserved products to be suspended and fixed inside the top wall of the sealed packaging container, maintaining a certain distance from the berries below. This completely avoids direct physical contact between the preserved product and the berry surface, eliminating the risk of mechanical damage and localized pesticide poisoning. The suspended state allows the gaseous active substances released from the antibacterial active ingredient layer to diffuse evenly from top to bottom within the packaging, creating a uniform protective atmosphere around the berries without being blocked by the fruit or becoming ineffective due to sap accumulation. The breathable and moisture-permeable layer and the moisture-retaining buffer layer, while suspended, face towards the berries but do not contact them. This effectively senses changes in humidity and gas within the packaging and allows any small amounts of water that may condense to drip off directly without accumulating on the functional layer surface, thus maintaining the continuity of the humidity regulation function. In addition, the self-adhesive suspension wing simplifies the operation process. Users do not need to perform complicated steps such as tearing the film, placing or positioning. They can simply peel off the release paper and press it with one hand to complete the installation, achieving zero-touch delivery and reducing the risk of secondary contamination and mechanical damage to the berries caused by manual operation.

[0036] The second aspect of this exemplary embodiment provides a method for preparing the above-mentioned berry-based preservative products, such as... Figure 2 As shown, it includes the following steps: Step S101: Select a microporous LDPE membrane that meets the parameters, with a thickness of 50 μm and a micropore diameter of 0.8 μm; Step S102: Weigh each component of the ternary core material according to the mass fraction, prepare a slurry, and evenly coat it on the lower surface of the LDPE film bag; Step S103: The PA6 electrostatic nanofiber nonwoven fabric is laminated with the coated LDPE film bag by thermal bonding or food-grade adhesive, so that the antibacterial active ingredient layer is located between the two. Step S104: Suspend SAP superabsorbent resin microbeads in ethanol or water and spray them evenly onto the outer surface of electrostatic nanofiber nonwoven fabric. Step S105: Attach food-grade silicone self-adhesive wings to both sides of the upper surface of the LDPE film bag, cut it to specifications, and seal it for light protection.

[0037] Example 1: Preparation of a four-layer structured preservation product A microporous LDPE membrane bag with a thickness of 50 μm and a micropore diameter of 0.8 μm was selected as the carrier barrier layer. Its oxygen permeability was 3000 cm³ / m² / day and its carbon dioxide permeability was 12000 cm³ / m² / day.

[0038] Weigh out the following ternary core materials by weight: 40 parts of slightly acidic electrolyzed water freeze-dried micro powder (with an effective chlorine content of 150 ppm and a pH of 5.8); 25 parts of chitosan oligosaccharide (with a degree of deacetylation ≥95% and a molecular weight of 2 kDa); 15 parts of 1-MCP inclusion complex (α-cyclodextrin-1-MCP with a molar encapsulation rate of 68%); 5 parts of food-grade glycerol; and 1 part of nano-TiO2 (anatase-type nano-TiO2 with a particle size <20 nm). Mix these materials to form a slurry, which is then uniformly coated onto the lower surface of the LDPE film bag.

[0039] An electrostatic nanofiber nonwoven fabric with PA6 material, specific surface area of ​​15m² / g, fiber diameter of 300nm, thickness of 0.3mm, and unit mass of 0.8g is used as a breathable and moisture-permeable layer. It is then laminated with a coated LDPE film bag using a food-grade adhesive, so that the antibacterial active ingredient layer is located between the two.

[0040] SAP superabsorbent polymer (SAP) microspheres with a particle size of 100 μm and a distilled water absorption capacity of 200 g / g were suspended in ethanol and uniformly sprayed onto the outer surface of electrostatic nanofiber nonwoven fabric to form a moisturizing buffer layer.

[0041] Food-grade silicone adhesive wings are attached to both sides of the upper surface of the LDPE film bag. After cutting, it is sealed and packaged in a light-proof manner to obtain the product.

[0042] Example 2: Preparation of a four-layer structured preservation product Replace 1 part of nano TiO2 in Example 1 with 1 part of sodium metabisulfite.

[0043] This example embodiment, in its third aspect, provides the application of the berry preservation product described above, or the berry preservation product prepared by the above method, in berry preservation. The product is placed or adhered inside a sealed packaging container of berries to be preserved, and transported or stored in a cold chain environment at 0-10°C. The berries are any one of blueberries, raspberries, strawberries, and mulberries.

[0044] It's important to understand that using self-adhesive hanging wings allows for non-contact hanging installation of the preserved products by attaching them to the inside of the fruit basket lid or the top wall of the express delivery box. Placing the preserved products in a sealed environment ensures that the release of the slightly acidic electrolyzed water freeze-dried micropowder, chitosan oligosaccharides, and 1-MCP inclusion complexes in the ternary core material depends on the gradually accumulating humidity and atmosphere within the packaging. A sealed environment ensures that the active ingredients remain within their effective concentration range for a longer period. Simultaneously, the ambient temperature is between 0 and 10 degrees Celsius, i.e., a cold chain environment. The physiological metabolism of berries slows down at low temperatures, reducing ethylene release and respiration intensity, providing more favorable conditions for 1-MCP to inhibit ethylene receptors. While the release rate of chitosan oligosaccharides is relatively slow under low temperature and high humidity conditions, it allows for a more uniform formation of a thin film on the fruit surface, avoiding the uneven film formation that might occur with rapid film formation at room temperature. The slightly acidic electrolyzed water freeze-dried micropowder exhibits a further reduced decay rate of effective chlorine at 0 to 10 degrees Celsius, and combined with the photocatalytic regeneration effect of nano-TiO2, this allows the antibacterial activity to persist for an even longer period. The cold chain environment is perfectly compatible with existing operating procedures in e-commerce logistics and supermarket retail, requiring no additional equipment or changes to existing processes. Blueberries, raspberries, strawberries, and mulberries are all susceptible to spoilage. These four berries share common characteristics: thin skin, high juiciness, easy perishability after harvest, and rapid metabolism (either climacteric or non-climacteric respiration). Furthermore, they suffer from high loss rates in current commercial distribution. Blueberries have a natural bloom layer, making them sensitive to humidity and mechanical damage; raspberries are aggregate fruits, and their internal cavities are prone to mold growth; strawberries lack an outer skin, making them highly susceptible to gray mold; and mulberries have delicate tissue that softens rapidly after harvest. This application's preservation product addresses the common problems and individual characteristics of these berries. Through the synergistic antibacterial and antirespiratory effects of the ternary core material, the humidity and gas regulation effects of the four-layer structure, and stable performance under a 0-10°C cold chain, it can extend the shelf life of these berries from the conventional 2-3 days to over 8 days, controlling the mold rate to below 3% and the weight loss rate to below 5%. When using this product, you only need to use one leaf per 500 grams of berries. It is easy to use, inexpensive, and the product itself is environmentally friendly and biodegradable, and can be recycled along with the packaging.

[0045] The following specific application examples and comparative experiments further illustrate the effects of the present invention and the synergistic effect between its components.

[0046] Example 3: Experiments on the application of the three-layer structure preservation pad and the four-layer structure berry preservation pad in Example 1 to raspberries.

[0047] Fresh raspberries were harvested, selecting those of uniform size and ripeness, free from disease and mechanical damage. The raspberries were packed into 10cm*10cm PET boxes lined with 8cm*8cm protective pads, 125g per box. The boxes were then sealed and stored at a low temperature (0-2℃). Random sampling was conducted every two days to determine the percentage of good-quality raspberries under different treatments. The experiment included four treatments, with three replicates for each treatment.

[0048] The corresponding preservation pads for each process are as follows: Treatment Group 1: The three-layer structure food preservation pad consists of a breathable and moisture-permeable layer, an antibacterial active ingredient layer, and a carrier barrier layer; it includes an LDPE film, a ternary core material, and a nanofiber pad; it does not contain SAP humidity buffer microbeads.

[0049] Treatment Group 2: The three-layer structure food preservation pad consists of a moisturizing buffer layer, an antibacterial active ingredient layer, and a carrier barrier layer; it includes LDPE film, ternary core material, and SAP microbeads; it does not contain nanofiber pads.

[0050] Treatment Group 3: The four-layer berry preservation pad consists of a moisturizing buffer layer, a breathable and moisture-permeable layer, an antibacterial active ingredient layer, and a carrier barrier layer. The four-layer structure is the preservation product in Example 1.

[0051] Treatment group 4: Blank control (CK).

[0052] The test results are as follows Figure 3 As shown in the figure, statistical analysis showed that the raspberries in the blank control group began to mold and rot on the 15th day of storage, with a rot rate of 40%. The fruits in treatment groups 1 and 2 also showed some mold on the 17th day of storage, with a rot rate of 3% in treatment group 1 and 5% in treatment group 2. By the 20th day of storage, the rot rate in the blank control group was 60%, the rot rate in treatment group 1 was 22%, and the rot rate in treatment group 2 was 31%. The raspberries in treatment group 3 remained fresh and did not develop any microbial diseases.

[0053] In this invention, the four-layer structure exhibits functional synergy between each layer and the ternary core material. Compared to treatment group 1 and treatment group 3, treatment group 1 lacks a moisture-retaining buffer layer. Without SAP humidity-retaining microbeads, the moisture content within the packaging cannot be effectively controlled. Moisture generated by raspberry respiration accumulates continuously in the sealed environment, and when the relative humidity exceeds 95%, significant condensation appears on the fruit surface. The condensed liquid water film provides an ideal environment for the germination and growth of mold spores. Simultaneously, the liquid water washes away the newly formed chitosan oligosaccharide film on the fruit surface, accelerating its loss and causing excessive dilution of the effective chlorine released by the slightly acidic electrolyzed water, rendering it ineffective in sterilization. Therefore, even though treatment group 1 still contains the complete ternary core material components, its preservation effect is significantly reduced, with the spoilage rate climbing to 22% by day 20. While the moisture-retaining buffer layer itself does not contain any antibacterial components, it maintains an optimal humidity range of 90 ± 5%, creating the necessary working environment for the uniform film formation of chitosan oligosaccharides and the sustained sterilization effect of the slightly acidic electrolyzed water.

[0054] Treatment group 2 lacked a breathable and moisture-permeable layer, namely a nanofiber pad. Without the nanofiber pad, the ternary core material was directly coated onto the surface of the microporous LDPE membrane. The loss of the slow-release function of the three-dimensional nanofiber network as a microscopic reservoir led to an uncontrolled release rate of the antibacterial active ingredients. On the one hand, the 1-MCP inclusion complex was rapidly and massively released upon initial exposure to moisture, potentially causing excessively high concentrations in the early stages, leading to fruit phytotoxicity. Simultaneously, the concentration rapidly decreased to below the effective threshold in the later stages, causing a respiration rebound. On the other hand, without the porous template of nanofibers, chitosan oligosaccharides could not dissolve uniformly and slowly in a cold-chain, high-humidity environment to form a complete and dense edible film on the fruit surface. The film-forming process of chitosan oligosaccharides became uncontrollable; either film formation failed, or the formed film was uneven in thickness and defective, failing to effectively block external pathogens or provide anchoring points for the effective chlorine in slightly acidic electrolyzed water. The preservation effect of treatment group 2 was worse than that of treatment group 1, with a rot rate as high as 31% by day 20. Nanofiber pads are not only physical isolation layers, but also functional layers that enable precise controlled release of active ingredients and cold field film formation of chitosan oligosaccharides. Without them, the two core advantages of the ternary core material, namely sustained release and film formation, will be lost.

[0055] In treatment group 3, 1-MCP was preferentially and slowly released from the nanofiber pads. It first bound to the ethylene receptors on raspberries, inhibiting the fruit's respiratory climacteric and ripening processes at the source, reducing the overall metabolic intensity and transpiration of the fruit, and keeping the waxy layer on the peel intact, providing a substrate for the subsequent attachment of chitosan oligosaccharides. Under the stable high-humidity environment maintained by the SAP microbeads and the cold chain low-temperature conditions, chitosan oligosaccharides were uniformly dissolved from the three-dimensional porous structure of the nanofibers, forming a dense, positively charged edible film on the raspberry fruit surface. This film not only has a physical barrier and induces disease resistance, but more importantly, its positive charge can anchor negatively charged, slightly acidic electrolyzed water chlorine molecules firmly to the fruit surface through electrostatic adsorption, significantly extending the bactericidal concentration maintenance time of available chlorine from less than 2 hours to over 72 hours. The freeze-dried micropowder in slightly acidic electrolyzed water, upon activation by moisture, releases available chlorine that first removes existing mold spores and bacterial biofilms from the fruit peel surface, eliminating the physical barrier between chitosan oligosaccharides and the peel. Simultaneously, with the aid of the slow-release effect of nano-titanium dioxide, 1-MCP is released smoothly, avoiding the risk of phytotoxicity. The three components work in perfect synergy across the temporal and spatial dimensions created by the four-layer structure: 1-MCP regulates internal metabolism, chitosan oligosaccharides build a physical barrier and anchor available chlorine, and slightly acidic electrolyzed water continuously eliminates external pathogens, resulting in a high rate of high-quality fruit.

[0056] Comparing the effects of treatment groups 1 and 2 with those of treatment group 3 yields a clear conclusion: the breathable and moisture-permeable layer and the moisturizing buffer layer in the four-layer structure of this invention are not optional auxiliary layers, but rather essential functional carriers for the synergistic effect of the various components of the ternary core material. Without the nanofiber pad, the ternary core material loses its slow-release and film-forming support; without SAP microbeads, the ternary core material loses its stable working humidity and effective environment. It is precisely the organic integration of these four layers that upgrades the three preservative components in the ternary core material from simple physical coexistence to a dynamic synergy with temporal coordination and functional mutual promotion.

[0057] Example 4: Experiments on the application of the three-layer structure preservation pad and the four-layer structure berry preservation pad in Example 2 on blueberries.

[0058] Fresh blueberries were harvested, selecting those of uniform size and ripeness, free from disease and mechanical damage. 125g of blueberries were placed in 10cm x 10cm PET boxes lined with 8cm x 8cm berry preservation pads, then packed into cardboard boxes (12 PET boxes per box) and sealed. The boxes were then stored at a low temperature (5-7℃). Random sampling was conducted every 5 days to determine the percentage of good-quality blueberries under different treatments. The experiment included three treatments, with three replicates for each treatment.

[0059] Treatment Group 5: An 8cm*8cm three-layer preservation mat was placed under each PET box, then blueberries were added, and the boxes were packed into cardboard boxes (12 boxes per box), sealed, and stored at low temperature. The three-layer preservation mat consists of a moisture-retaining buffer layer, a breathable and moisture-permeable layer, and a carrier barrier layer. It includes LDPE film, nanofiber pads, and SAP microbeads; it does not include ternary core material. In Treatment Group 5, some blueberries began to show mold and a sour smell after 30 days of storage, with a spoilage rate of 31%.

[0060] Treatment Group 6: Blueberries were placed in PET boxes with an 8cm*8cm four-layer berry preservation pad underneath. The PET boxes were then packed into cardboard boxes (12 boxes per box), sealed, and stored at low temperature. The four-layer structure was the preservation product from Example 2. The four-layer berry preservation pad consisted of a moisture-retaining buffer layer, a breathable and moisture-permeable layer, an antibacterial active ingredient layer, and a carrier barrier layer. The blueberries in Treatment Group 6 remained fresh from the early stage of storage to day 30, with no microbial diseases occurring.

[0061] Treatment Group 7: Blank Control (CK) Blueberries were directly packed into PET boxes, then into cardboard boxes, sealed, and stored at low temperature. The blank control group blueberries showed signs of mold and rot on the 15th day of storage, with a sour smell and a spoilage rate of 39%. By the 30th day of storage, the spoilage rate reached 85%.

[0062] The test results are as follows Figure 4As shown in the figure, statistical analysis revealed that, when stored at 5-7℃, the blueberries in the blank control group began to show significant microbial diseases after 15 days of storage, with a disease rate of 39%, resulting in mold, rot, and a bland taste. In treatment group 5, the blueberries treated with the three-layer preservation pad showed no obvious diseases for the first 20 days of storage, but microbial diseases could not be suppressed in the later stages of storage, with a spoilage rate reaching 31% by day 30. In treatment group 6, the blueberries treated with the berry preservation pad remained fresh and disease-free throughout the entire 30-day storage process.

[0063] Although treatment group 5 included a three-layer structure of microporous LDPE membrane, nanofiber pad, and SAP superabsorbent polymer (SAP) microbeads, its preservation effect was extremely limited due to the lack of an antibacterial active ingredient layer coated with a ternary core material. By day 30, the spoilage rate reached 31%, which, while better than the 85% in the blank control group, was far worse than treatment group 6. The nanofiber pad and SAP microbeads themselves do not possess antibacterial or respiration-inhibiting functions; they are merely functional carriers and microenvironment regulators. While the LDPE membrane can regulate the oxygen and carbon dioxide ratio within the packaging to create a micro-modified atmosphere, this passive modified atmosphere itself has very limited inhibitory effect on mold. Although the nanofiber pad has a high specific surface area and porous structure, without an active ingredient load, it is merely an ordinary insulating cloth. While the SAP microbeads can intelligently regulate humidity to prevent condensation, simply controlling humidity without killing existing pathogens cannot prevent mold growth. Therefore, treatment group 5 still showed mold and a sour smell after day 15, and by day 30, nearly one-third of the fruit had rotted.

[0064] In treatment group 6, the microporous LDPE membrane, acting as a carrier barrier layer, was located on the outermost layer. Its specific oxygen permeability of 3,000 cubic centimeters per square meter per day and carbon dioxide permeability of 12,000 cubic centimeters per square meter per day created a micro-controlled atmosphere within the sealed packaging, characterized by a moderately reduced oxygen concentration and a moderately increased carbon dioxide concentration. This environment directly inhibited the respiration intensity of the blueberry fruit, reducing the production of endogenous ethylene and providing a more favorable physiological background for the 1-MCP inclusion complex to function. Simultaneously, the microporous LDPE membrane, by precisely controlling the rate at which external moisture enters the inner layer, prevented a sudden and excessive release of active ingredients from the inner layer due to excessive humidity, thus achieving the first barrier for slow release.

[0065] The ternary core material is coated on the lower surface of the microporous LDPE membrane, in which the 1-MCP inclusion complex is preferentially released upon contact with moisture. The 1-MCP molecule irreversibly binds to the ethylene receptors on blueberry fruit, fundamentally blocking the ethylene signaling pathway and significantly delaying the ripening and senescence process of the fruit. This respiration inhibition not only maintains the firmness and color of the fruit, but more importantly, it reduces the transpiration rate, allowing the natural waxy layer on the peel surface to be intact, providing a physical substrate for the subsequent attachment of chitosan oligosaccharides.

[0066] The breathable and moisture-permeable layer, namely the PA6 electrospun nanofiber pad, is located between the antibacterial active ingredient layer and the moisturizing buffer layer. It has a specific surface area of ​​15 square meters per gram, with fiber diameters ranging from 200 to 400 nanometers, forming a dense three-dimensional porous network structure. This structure acts as a microscopic reservoir, uniformly fixing the ternary core material. When ambient humidity slowly permeates into this layer, the humidity-responsive chitosan oligosaccharides undergo gradient swelling, forming a dynamic gel layer on the nanofiber surface. This gel layer acts as a second controlled-release barrier, further hindering the rapid diffusion of moisture into the core material. This restricts the activation and release of 1-MCP and slightly acidic electrolyzed water to a stable and continuous rate, achieving a constant-rate release with near-zero-order kinetics. Under low-temperature, high-humidity conditions (5-7 degrees Celsius), the chitosan oligosaccharides dissolve uniformly from the nanofiber pad and, with the aid of the porous template effect of the nanofibers, form a positively charged, dense, edible film on the surface of the blueberry fruit. This membrane not only acts as a physical barrier to prevent the invasion of external pathogens and reduce water evaporation, but more importantly, its positive charge can anchor the negatively charged, slightly acidic electrolyzed water chlorine molecules firmly to the surface of the fruit peel through electrostatic adsorption, thus greatly extending the bactericidal concentration of effective chlorine from less than two hours to more than seventy-two hours.

[0067] The freeze-dried micropowder, activated by slightly acidic electrolyzed water upon contact with moisture, releases effective chlorine for rapid, broad-spectrum sterilization. This eliminates pathogenic microorganisms such as gray mold already present on the surface of blueberries, removing the physical barriers of mold spores and bacterial biofilms that prevent direct contact between chitosan oligosaccharide molecules and the fruit peel. This allows the chitosan oligosaccharide to form a denser and more complete protective film. Simultaneously, sodium metabisulfite is used as the antibacterial additive. It's important to note that sodium bisulfite or sodium sulfite can also be used as the antibacterial additive. Upon contact with moisture, these additives slowly release low concentrations of sulfur dioxide gas at a controlled rate. The sulfur dioxide is adsorbed by the positively charged edible film of the chitosan oligosaccharide. A reversible weak interaction forms between the amino groups on the chitosan oligosaccharide molecular chain and SO2, maintaining a continuous and stable low-concentration antibacterial microenvironment on the fruit surface. SO2 not only further inhibits residual and newly formed mold spores but also possesses antioxidant activity, inhibiting polyphenol oxidase activity, slowing down peel browning, and scavenging free radicals generated by fruit respiration metabolism, thus better preserving the color and quality of blueberries. The release of SO2 and the slightly acidic electrolyzed water form a relay-like antibacterial effect: the available chlorine first performs rapid sterilization, and then SO2 continuously inhibits the germination of new spores, together forming a dual sterilization barrier of rapid removal and long-term inhibition.

[0068] The moisturizing buffer layer, consisting of SAP superabsorbent polymer (SAP) microspheres sprayed onto the outer surface of the nanofiber pad, has a particle size of 100 micrometers and an absorption rate of 200 grams of distilled water per gram. These microspheres rapidly absorb excess moisture to prevent condensation when the relative humidity inside the packaging exceeds 95%, and slowly release stored moisture to prevent fruit dehydration and wilting when the relative humidity is below 85%, dynamically maintaining the humidity within the chamber at an optimal range of 90% ± 5%. This humidity-regulating effect provides the most suitable environmental humidity for the uniform dissolution and film formation of chitosan oligosaccharides and the stable release of slightly acidic electrolyzed water, while simultaneously preventing liquid water from eroding the chitosan oligosaccharide film and diluting the available chlorine.

[0069] Comparing treatment group 6 and treatment group 5 reveals that even with its three-layer structure of LDPE film, nanofiber pad, and SAP microspheres, treatment group 5, lacking the ternary core material, exhibits extremely limited preservation effects. In contrast, treatment group 6 achieved excellent results with minimal disease under the same conditions. The complementary functions of the slightly acidic electrolyzed water's broad-spectrum sterilization, the film-forming properties of chitosan oligosaccharides, and the respiration-inhibiting effects of 1-MCP in the ternary core material, combined with the modified atmosphere control of the microporous LDPE film, the slow-release film formation of the nanofiber pad, and the humidity-regulating structure of the SAP microspheres, constitute a dynamic and synergistic preservation process that inhibits internal growth, blocks external growth, and kills surface pathogens. This results in excellent preservation of blueberries with no disease occurrence during a 30-day storage period.

[0070] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Other embodiments of this application will readily conceive of by those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein.

Claims

1. A berry-based preservation product, characterized in that, It includes a carrier barrier layer, an antibacterial active ingredient layer, a breathable and moisture-permeable layer, and a moisturizing buffer layer; The carrier barrier layer is composed of a microporous LDPE membrane bag; The antibacterial active ingredient layer is a ternary core material coated on the lower surface of the microporous LDPE film bag; The breathable and moisture-permeable layer is an electrostatic nanofiber nonwoven fabric. The moisturizing buffer layer consists of moisture-buffering microbeads sprayed onto the surface of the electrospun nanofiber pad. The ternary core material includes slightly acidic electrolyzed water freeze-dried micro powder, chitosan oligosaccharide, 1-MCP inclusion complex, glycerol, and antibacterial additives. The antibacterial additives are any one of nano TiO2, sodium metabisulfite, sodium bisulfite, and sodium sulfite.

2. The berry preservation product according to claim 1, characterized in that, The microporous LDPE membrane bag has an oxygen permeability of 3000 cm³ / m² / day, a carbon dioxide permeability of 12000 cm³ / m² / day, a micropore diameter of 0.8 μm, and a thickness of 50 μm.

3. The berry preservation product according to claim 1, characterized in that, The electrospun nanofiber pad is made of PA6, with a specific surface area of ​​15m² / g, a fiber diameter of 200nm-400nm, a thickness of 0.3mm, and a unit mass of 0.8g.

4. The berry preservation product according to claim 1, characterized in that, The mass composition of the ternary core material is as follows: The mixture comprises 30-50 parts of slightly acidic electrolyzed water freeze-dried micro powder, 20-30 parts of chitosan oligosaccharide, 10-20 parts of 1-MCP inclusion complex, 5 parts of food-grade glycerol, and 1 part of antibacterial additive, wherein the antibacterial additive is any one of nano TiO2, sodium metabisulfite, sodium bisulfite, and sodium sulfite.

5. The berry preservation product according to claim 4, characterized in that, The slightly acidic electrolyzed water freeze-dried micro powder has an effective chlorine content of 150 ppm and a pH value of 5.8; the chitosan oligosaccharide has a degree of deacetylation ≥95% and a molecular weight of 1 kDa-3 kDa; the 1-MCP inclusion complex is α-cyclodextrin-1-MCP with a molar encapsulation rate of 68%; and the nano-TiO2 is anatase nano-TiO2 with a particle size <20 nm.

6. The berry preservation product according to claim 1, characterized in that, The humidity buffer microspheres are SAP superabsorbent resin microspheres with a particle size of 100 μm and a distilled water absorption capacity of 200 g·g. - ¹, used to absorb moisture when RH>95% and release moisture when RH<85%, maintaining the humidity inside the chamber at 90±5%.

7. The berry preservation product according to claim 1, characterized in that, The upper surface of the microporous LDPE film bag is provided with a self-adhesive hanging wing composed of two food-grade silicone self-adhesive wings, which is used to attach the berry preservation products to the lid of the fruit basket or the top wall of the express box.

8. A method for preparing a berry-based preservative product as described in any one of claims 1-7, characterized in that, Includes the following steps: A microporous LDPE membrane with a thickness of 50 μm and a micropore diameter of 0.8 μm was selected. Weigh each component of the ternary core material according to the mass fraction to prepare the slurry, and evenly coat it on the lower surface of the LDPE film bag; PA6 electrostatic nanofiber nonwoven fabric is laminated with coated LDPE film bag by thermal bonding or food-grade adhesive, so that the antibacterial active ingredient layer is located between the two. SAP superabsorbent resin microbeads are suspended in ethanol or water and uniformly sprayed onto the outer surface of electrostatic nanofiber nonwoven fabric. Food-grade silicone adhesive wings are attached to both sides of the upper surface of the LDPE film bag. The bag is then cut to size and sealed to protect it from light.

9. The application of a berry preservation product as described in any one of claims 1 to 7 in berry preservation, characterized in that, Place or attach it to a sealed container of berries to be preserved, and transport or store it in a cold chain environment at 0-10℃.

10. The application according to claim 9, characterized in that, The berries are any one of blueberries, raspberries, strawberries, and mulberries.

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