Regulation and control method for prolonging fresh-keeping period of prunes

Abstract

The invention provides a regulation and control method for prolonging the refreshing time of prunes, which comprises the following steps: disinfecting a phase-temperature fresh-keeping storehouse for 24 hours by using absolute ethyl alcohol, and ventilating for 8-10 hours to ensure a sterile environment. During harvesting, prunes which are free of plant diseases and insect pests, free of mechanical damage, complete in fruit cream and larger than or equal to 20% in sugar content are selected, and the temperature of the prunes is rapidly reduced to 2-2.2 DEG C within 10 h through portable differential pressure precooling equipment. After precooling, a methyl jasmonate aqueous solution is adopted for electrostatic atomization spraying, and 1-methylcyclopropene is used for airtight fumigation for 18-20 h to inhibit ethylene generation and respiration. And then, storing in a phase temperature warehouse at the temperature of-1.5 to-1.2 DEG C, controlling the relative humidity to be 85-87%, and carrying out intermittent nano atomization sterilization by using a hydrogen peroxide aqueous solution once every 15-18 days. According to the method, the fresh-keeping effect of the prunes is comprehensively improved, the safety and the quality of the fruits are ensured, and the fresh-keeping period is remarkably prolonged.

Description

Technical Field

[0001] The present invention relates to the field of fruit preservation, and more particularly to a method for regulating and controlling the extension of the shelf life of prunes. Background Art

[0002] As a popular fruit, prunes have always been a focus of industry attention. In the current market environment, effectively extending the shelf life of prunes and ensuring their excellent quality during storage, transportation, and sales is crucial for meeting consumer demand and improving economic efficiency.

[0003] Currently, several methods for preserving prunes have been proposed. For example, patent application number 202210592807.3 discloses a method for cold chain logistics storage and preservation of prunes. This method has played a certain role in the cold chain transportation and storage of prunes, but it also has some shortcomings. For example, this method uses the antibiotic natamycin as an antibacterial and fresh-keeping ingredient. Although it can inhibit microbial growth to a certain extent, the use of antibiotics may cause consumer concerns about food safety and may also pose a risk of inducing microbial resistance. In addition, this method is mainly used in cold chain transportation, and the control of the storage link is relatively simple, which may not fully meet the preservation needs of prunes at different stages.

[0004] The existing methods for preserving prunes generally have the following problems: incomplete disinfection of storage warehouses easily leads to the residue of harmful microorganisms; lax harvesting standards affect the initial quality of the fruit; pre-cooling methods are not efficient enough, making it difficult to quickly lower the temperature of prunes to inhibit physiological metabolism; single preservation treatment measures cannot fully address the various problems faced by prunes during storage, such as microbial growth and fruit aging; sterilization treatment during storage is not accurate and continuous enough, making it difficult to effectively control the number of microorganisms in the environment.

[0005] In view of this, in order to better meet the market demand for fresh-keeping of prunes and overcome the shortcomings of the existing technology, it is necessary to provide a new regulation method for extending the shelf life of prunes. Summary of the Invention

[0006] The purpose of the present invention is to provide a control method for extending the shelf life of prunes. The method comprehensively controls multiple links from storage disinfection, strict harvesting requirements, efficient pre-cooling, multi-step preservation treatment, and precise sterilization during storage, avoiding the use of antibiotics, and providing a safer, more efficient and comprehensive solution for the preservation of prunes.

[0007] To achieve these objectives and other advantages of the present invention, a method for extending the shelf life of prunes is provided, comprising: Disinfection treatment: Before storing prunes, spray the temperature-controlled fresh-keeping warehouse with 75% to 80% anhydrous ethanol. After 24 hours of disinfection, start the circulating ventilation for 8 to 10 hours. Harvesting requirements: The harvested prunes must be free of pests and diseases, mechanical damage, and the fruit frost must remain intact, with a sugar content of ≥20%. Pre-cooling treatment: The harvested prunes must be pre-cooled to 2 to 2.2°C, and a portable pressure differential pre-cooling method must be used to quickly cool the fruit to the pre-cooling temperature for ≤10 hours. Electrostatic atomization spraying: After pre-cooling, jasmonate methyl is used. The prunes were electrostatically sprayed with an ester aqueous solution; fumigation treatment: after electrostatic spraying, the fruits were fumigated with 1-methylcyclopropene in a closed temperature chamber for 18 to 20 hours, and then the machine was turned on for 2 to 3 hours to allow air circulation; near-ice temperature storage: the prunes after fumigation treatment were stored at near-ice temperature in a temperature chamber; intermittent nano-atomization sterilization: during storage, the environment and prunes were sterilized with an aqueous hydrogen peroxide solution by intermittent nano-atomization, with an interval of 15 to 18 days between each sterilization.

[0008] Preferably, in the method for extending the shelf life of prunes, a piece of 18 cm x 25 cm fresh-keeping paper is placed in the pre-cooled prunes for every 2 kg of prunes; the fresh-keeping paper is made of a sterile polypropylene non-woven fabric that is soaked in an antibacterial solution for 5 to 7 minutes, drained, and then dried at room temperature to a moisture content of 10 to 15%. The preparation method of the antibacterial liquid comprises the following steps: diluting bamboo vinegar liquid to 150-250 mL / L to obtain a bamboo vinegar dilution liquid; adding curcumin to the bamboo vinegar dilution liquid, stirring evenly, and then adding tea polyphenols, stirring evenly; wherein 0.03-0.07 g of curcumin is added to each liter of the bamboo vinegar dilution liquid; and 0.01-0.05 g of tea polyphenols is added to each liter of the bamboo vinegar dilution liquid.

[0009] Preferably, in the control method for extending the shelf life of prunes, the bamboo vinegar is diluted to 200 mL / L, and 0.05 g of curcumin is added to each liter of the bamboo vinegar dilution; and 0.03 g of tea polyphenols is added to each liter of the bamboo vinegar dilution.

[0010] Preferably, in the control method for extending the shelf life of prunes, the concentration of the methyl jasmonate aqueous solution is 0.01 mmol / L, the atomized particle size is ≤2.0 μm, and the droplet charge-to-mass ratio is 5-8 mC / kg; the process parameters of the electrostatic atomization sprayer for post-harvest fresh-keeping spraying of prunes are: elevator speed 12 Hz, conveyor disk rolling angle 3.0°, reversing speed 6.5 Hz, and electrostatic voltage 6-10 kV.

[0011] Preferably, in the method for extending the shelf life of prunes, the mass-to-volume ratio of the amount of 1-methylcyclopropene used to the fumigation space is 0.4-0.5 mg / m 3The near-freezing storage temperature is -1.5 to -1.2°C, the relative humidity is 85 to 87%, the oxygen concentration in the phase-temperature storage is 3.5 to 4%, the carbon dioxide concentration is 3 to 5%, and the nitrogen concentration is 85 to 90%. The mass concentration of the hydrogen peroxide solution is 2 to 3%, and the atomized particle size is ≤ 1.0 μm.

[0012] Preferably, in the control method for extending the shelf life of prunes, the disinfection treatment in step 1) includes the following steps: before the prunes are stored, an electrostatic spray device with an atomization particle size of 50 to 100 μm is used to spray 75% anhydrous ethanol at a rate of 10 to 15 mL / m 3 Spray the amount evenly on the inner surface of the phase temperature fresh-keeping warehouse; after spraying is completed, turn on the ozone generator immediately and maintain the ozone concentration at 5-8ppm in the environment sprayed with ethanol for 2 hours; after turning off the ozone generator, maintain the temperature in the warehouse at 25-28℃ and the relative humidity at 40-45% for closed disinfection for 22 hours; after disinfection is completed, first turn on the external circulation ventilation system for 3 hours, and then switch to internal circulation ventilation for 5-7 hours, and control the airflow speed at 0.5-0.8m / s during ventilation.

[0013] Preferably, in the control method for extending the shelf life of prunes, in the electrostatic atomization spraying step in step 4), the following components are added to the methyl jasmonate aqueous solution before electrostatic atomization spraying: bentonite-loaded slow-release particles, gelatin-tannic acid composite liquid, and nisin microcapsules; The composite method comprises the following steps: uniformly mixing bentonite and methyl jasmonate in a mass ratio of 10:1, calcining at 400-500°C for 2h, and then ultrafinely grinding the mixture to a particle size of ≤2.0μm using a jet mill to obtain bentonite-loaded sustained-release particles; dissolving gelatin and tannic acid in a mass ratio of 4:1 in deionized water, stirring and dissolving at 60°C, and then cooling to 25°C to obtain a gelatin-tannic acid composite liquid; mixing nisin and a 2% sodium alginate solution in a mass ratio of 1:5, and adding the mixture dropwise to a 5% calcium chloride aqueous solution, wherein the calcium chloride aqueous solution and the sodium alginate solution are mixed. The volume ratio of the two compounds is 4:1, and after cross-linking for 30 minutes, centrifugal drying is performed to prepare nisin microcapsules with a particle size of ≤2 μm; bentonite-loaded sustained-release particles, gelatin-tannic acid composite liquid and nisin microcapsules are added to a methyl jasmonate aqueous solution, and the mixture is adjusted to a methyl jasmonate concentration of 0.01 mmol / L by adding deionized water or concentrating; wherein, the amount of the bentonite-loaded sustained-release particles is 0.2-0.4 g / L, the amount of the gelatin-tannic acid composite liquid is 0.1-0.3 g / L, and the amount of the nisin microcapsules is 0.05-0.1 g / L.

[0014] Preferably, in the control method for extending the shelf life of prunes, in the fumigation treatment step in step 5), a porous starch-based carrier is used to load 1-methylcyclopropene, and nano zinc oxide and bimetallic organic framework particles are composited, specifically comprising the following steps: loading 1-methylcyclopropene on the porous starch-based carrier: mixing the porous starch with 1-methylcyclopropene in a mass ratio of 20:1 in a sealed container, controlling the temperature to 40-50°C and the pressure to 0.1-0.2 MPa, and adsorbing for 12 hours to obtain a sustained-release carrier with a loading rate of 85-90%; composite nano zinc oxide and bimetallic organic framework particles. Organic framework particles: Nano-zinc oxide with a particle size of ≤50nm is compounded with bimetallic ZIF-8@Cu particles in a mass ratio of 1:2 to form an antibacterial-ethylene decomposition complex. The slow-release carrier and the complex are evenly dispersed in a phase temperature storage at a mass ratio of 5:1. The mixture is then sealed and fumigated at a controlled temperature of -1.5 to -1.2°C and a humidity of 85 to 87%. After fumigation, a circulating ventilation system is started, and a UV-visible composite light source is simultaneously turned on to activate the photocatalytic properties of ZIF-8@Cu, degrading residual gas to an ethylene concentration of ≤5ppm and a total microbial count of ≤10 CFU / m 3 .

[0015] Preferably, in the control method for extending the shelf life of prunes, the intermittent nano-atomization sterilization in step 7) specifically includes the following steps: compounding a hydrogen peroxide aqueous solution with a mass concentration of 2-3% and a food-grade nisin solution with a mass concentration of 0.1-0.3% in a volume ratio of 4:1 to form a synergistic sterilization solution, and performing intermittent nano-atomization sterilization through the synergistic sterilization solution; placing microbial concentration sensors in the fruit storage area, shelf gaps and vents of the phase temperature warehouse, and collecting the total number of environmental microorganisms every 24 hours since each sterilization treatment is completed and a new sterilization interval cycle is started, and completing three consecutive monitorings; evenly installing temperature and humidity sensors on the top, middle and bottom of the warehouse to monitor the temperature and relative humidity in real time, and calculate the surface condensation risk index RH-T index, RH-T index = real-time relative humidity / saturated relative humidity at the current temperature; if the total number of microorganisms monitored for three consecutive times is lower than 50 CFU / m 3 , and the RH-T index is lower than 0.5, the sterilization interval is extended from 15 to 18 days to 20 days; when the total number of microorganisms monitored at any time exceeds 80 CFU / m 3 Or when the RH-T index exceeds 0.7, the sterilization interval is shortened from 15 to 18 days to 12 days; when the total number of microorganisms monitored at any time exceeds 100 CFU / m 3 Or when the RH-T index exceeds 0.8, start the nano-atomization equipment and spray the hydrogen peroxide synergistic sterilization solution; the atomization particle size of the nano-atomization equipment does not exceed 1.0μm, the droplet charge-to-mass ratio is 5-8mC / kg, and the single spraying volume is 0.5-1.0mL / m 3 , spraying time 5 to 10 minutes.

[0016] Preferably, in the control method for extending the shelf life of prunes, the antibacterial solution further comprises chitosan-β-cyclodextrin sustained-release microspheres; The preparation method of chitosan-β-cyclodextrin sustained-release microspheres is as follows: β-cyclodextrin and chitosan are dissolved in deionized water to form a mixed solution with a chitosan mass concentration of 0.02 g / mL and a β-cyclodextrin mass concentration of 0.06 g / mL; the mixed solution is mixed with a 0.1% mass concentration of citric acid solution in a volume ratio of 1:4, and ultrasonically dispersed for 30 minutes; a 0.5% mass concentration of calcium chloride solution is added dropwise, and the ratio of the total mass of β-cyclodextrin and chitosan to the volume of the calcium chloride solution is 0.2 g / mL; the mixture is stirred for 2 hours, then centrifuged and dried, and passed through a 100-mesh sieve to obtain chitosan-β-cyclodextrin sustained-release microspheres; Add 1-2 g of microspheres per liter of antibacterial solution; The specific preparation method of the fresh-keeping paper is: immerse the non-woven fabric in an antibacterial liquid containing microspheres, soak it at a pressure of -0.05MPa for 8 to 10 minutes, so that the microspheres are embedded in the fiber gaps; after draining, dry it at 40°C for 1 hour, and then dry it at room temperature to a moisture content of 10 to 15%.

[0017] Preferably, in the control method for extending the shelf life of prunes, the portable pressure differential precooling treatment in step 3) adopts a graded precooling method, which specifically includes the following steps: initial cooling stage: at 3°C, the fruit is treated for 4 hours with a portable pressure differential precooling device at a pressure differential of 60 Pa and a wind speed of 0.6 m / s, so that the center temperature of the fruit drops from 25°C to 10°C; fine cooling stage: adjusting the portable pressure differential precooling device to a pressure differential of 80 Pa and a wind speed of 0.8 m / s, treating for 4 hours in a 2.5°C environment, so that the center temperature drops to 4°C; final cooling stage: adjusting the pressure differential to 70 Pa, treating for 1.5 hours in a 2.0°C environment, and finally bringing the overall temperature of the fruit to 2.1°C; temperature stabilization: maintaining the temperature difference for 0.5 hours so that the temperature difference does not exceed 0.2°C.

[0018] The present invention has at least the following beneficial effects: The present invention adopts 75-80% anhydrous ethanol to spray and disinfect the phase temperature fresh-keeping warehouse and ventilate it, which can effectively kill most harmful microorganisms in the warehouse, provide a clean storage environment for prunes, reduce the risk of prunes being contaminated from the source, and lay a good foundation for subsequent preservation links.

[0019] The present invention explicitly requires that the harvested prunes be free of pests and diseases, mechanical damage, and intact fruit frost with a sugar content of ≥20%, thereby ensuring the high initial quality of the prunes, making the fruits more resistant to adverse external factors, and reducing the problem of deterioration caused by their own defects during storage.

[0020] The invention uses portable pressure difference pre-cooling to quickly cool prunes to 2-2.2°C within 10 hours, which can quickly inhibit the physiological metabolic activities of prunes such as respiration, delay fruit aging, reduce the consumption of nutrients, and maintain the freshness and taste of the fruit.

[0021] The present invention utilizes a multi-step process for synergistic preservation: Electrostatic atomization of methyl jasmonate, under specific concentration, atomized particle size, droplet charge-to-mass ratio, and precise spraying process parameters, uniformly affects the surface of the prunes, regulating the fruit's physiological processes, delaying aging, and maintaining fruit firmness and color. 1-Methylcyclopropene fumigation, ensuring uniform gas distribution, effectively inhibits ethylene synthesis, further delaying the ripening process and extending the shelf life of the prunes. Storage at near-freezing temperatures, under precisely controlled temperature, relative humidity, and gas composition, minimizes the physiological activity of the prunes and reduces water and nutrient loss. Intermittent nano-atomization of hydrogen peroxide solution regularly disinfects the environment and the prunes, effectively controlling microbial growth and preventing rot and deterioration due to microbial infection. The preservative paper is made from sterile polypropylene nonwoven fabric soaked in an antibacterial solution containing bamboo vinegar, curcumin, and tea polyphenols. The natural antibacterial components work synergistically to broaden the antibacterial spectrum, continuously inhibiting microorganisms on the prunes' surface and providing additional protection.

[0022] The entire preservation process of the present invention avoids the use of antibiotics and other substances that may cause consumer concern. Natural antibacterial ingredients such as bamboo vinegar, curcumin, and tea polyphenols, as well as relatively safe substances in the food preservation field such as methyl jasmonate and hydrogen peroxide, reduce food safety risks and meet consumer demand for green and healthy food. The anhydrous ethanol and aqueous hydrogen peroxide solutions used for disinfection and sterilization of the storage environment have minimal environmental impact when used in appropriate concentrations and methods.

[0023] Each operation step of the present invention has clear parameters and requirements, such as disinfection time, pre-cooling temperature and time, concentration and dosage of preservative, temperature, humidity and gas composition of storage environment, spraying process parameters, etc., so that the entire preservation process is highly operable and controllable.

[0024] The present invention is conducive to achieving standardized production and quality control, ensuring that different batches of prunes can obtain a stable preservation effect, and improving the success rate and reliability of prune preservation.

[0025] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below with reference to the embodiments so that those skilled in the art can implement the invention with reference to the description.

[0027] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial channels unless otherwise specified.

[0028] The present invention provides a method for regulating and controlling the extension of the shelf life of prunes, comprising: 1) Disinfection: Before storing prunes, spray the temperature-controlled fresh-keeping room with 75% to 80% anhydrous ethanol by volume. After 24 hours of disinfection, start circulating ventilation for 8 to 10 hours. Disinfection of the storage room effectively kills harmful microorganisms, provides a clean storage environment for the prunes, reduces the risk of microbial contamination during storage, and thus extends the shelf life of the prunes.

[0029] 2) Harvesting Requirements: Harvested prunes must be free of pests and diseases, mechanical damage, and intact frost. The sugar content must be ≥20%. Strict harvesting requirements ensure the initial quality of the prunes. The absence of pests, diseases, and mechanical damage reduces the risk of damage to the fruit and reduces the likelihood of microbial invasion. Intact frost protects the fruit, minimizing water loss and contamination. A high sugar content indicates the fruit is moderately ripe and nutritious, making it more conducive to storage and preservation.

[0030] 3) Pre-cooling: Pre-cool the harvested prunes to 2-2.2°C. Use portable differential pressure cooling to quickly cool them to the pre-cooling temperature within 10 hours. Rapidly cooling the prunes to an appropriate temperature effectively inhibits their respiration and physiological metabolism, reduces nutrient consumption and water loss, and slows the aging process, laying a good foundation for subsequent fresh-keeping treatments.

[0031] 4) Electrostatic Atomization: After pre-cooling, the prunes are electrostatically sprayed with a methyl jasmonate aqueous solution. This spraying ensures that the methyl jasmonate is evenly distributed over the surface of the prunes, effectively regulating their physiological processes. Methyl jasmonate can delay aging, maintain firmness and color, and improve the storage quality of the prunes.

[0032] 5) Fumigation: After electrostatic atomization, the fruit is fumigated with 1-methylcyclopropene in a closed storage at the same temperature for 18-20 hours. The fumigator is then turned on for 2-3 hours to allow air circulation to ensure that the 1-methylcyclopropene is evenly distributed throughout the storage. 1-methylcyclopropene effectively inhibits ethylene synthesis in prunes, thereby delaying ripening. Air circulation after closed fumigation ensures that the 1-methylcyclopropene is evenly distributed throughout the storage, ensuring that each prune is fully preserved and further extending its shelf life.

[0033] 6) Near-freezing temperature storage: Fumigated prunes are stored at near-freezing temperature (a critical freezing temperature storage environment of -1.5 to -1.2°C) in a phase-temperature warehouse. Under precisely controlled near-freezing temperature storage conditions, i.e., a temperature of -1.5 to -1.2°C, a relative humidity of 85 to 87%, an oxygen concentration of 3.5 to 4%, a carbon dioxide concentration of 3 to 5%, and a nitrogen concentration of 85 to 90%, the physiological activities of the prunes can be suppressed to the greatest extent, the loss of water and nutrients can be reduced, and the freshness and taste of the fruit can be maintained.

[0034] 7) Intermittent Nano-Atomization Sterilization: During storage, hydrogen peroxide solution is used to sterilize the environment and prunes intermittently, with an interval of 15-18 days between sterilization cycles. Intermittent nano-atomization sterilization effectively controls the microbial population in the storage environment, preventing prunes from rotting and spoiling due to microbial contamination. Nano-atomization evenly distributes the hydrogen peroxide solution throughout the environment and on the surface of the prunes, enhancing the sterilization effect. Furthermore, carefully controlling the sterilization interval ensures effective sterilization without causing excessive chemical damage to the prunes.

[0035] In the method for extending the shelf life of prunes, a piece of 18 cm × 25 cm fresh-keeping paper is placed in the pre-cooled prunes for every 2 kg of prunes; The fresh-keeping paper is made by soaking a sterile polypropylene nonwoven fabric in an antibacterial solution for 5 to 7 minutes to ensure that the antibacterial ingredients are fully absorbed. After draining, it is dried at room temperature to a moisture content of 10 to 15%. The moisture content can be monitored by regular weighing or using a hygrometer to ensure that it reaches the optimal humidity range.

[0036] During actual use, the humidity level of cling film should be regularly checked to ensure it remains within the ideal range. If the humidity is too high or too low, the preparation process or storage conditions should be adjusted promptly. The environment in which cling film is stored and used should maintain a constant temperature and humidity to minimize the effects of external factors on the humidity level.

[0037] The preparation method of the antibacterial liquid comprises the following steps: diluting bamboo vinegar liquid to 150-250 mL / L to obtain a bamboo vinegar dilution liquid; adding curcumin to the bamboo vinegar dilution liquid, stirring evenly, and then adding tea polyphenols, stirring evenly; wherein 0.03-0.07 g of curcumin is added to each liter of the bamboo vinegar dilution liquid; and 0.01-0.05 g of tea polyphenols is added to each liter of the bamboo vinegar dilution liquid.

[0038] The specially formulated wrapping paper utilizes sterile polypropylene nonwoven fabric and an antibacterial solution containing bamboo vinegar, curcumin, and tea polyphenols, resulting in excellent antibacterial properties. These natural antibacterial ingredients work synergistically to broaden the antibacterial spectrum, continuously inhibiting microorganisms on the surface of prunes, providing additional protection and further extending their shelf life.

[0039] Controlling the humidity of the cling wrap is crucial to preserving prunes. The ideal humidity ensures that the wrap effectively inhibits bacteria while preventing excessive moisture from condensing on the surface of the fruit, which could lead to mold and other problems.

[0040] The optimal range of humidity for cling film is 10-15% moisture content. The reasons are as follows: Maintaining an appropriate humidity level (10-15%) activates the ingredients in the antibacterial solution (such as bamboo vinegar, curcumin, and tea polyphenols), enhancing their antimicrobial properties. Excessively low humidity may weaken the activity of these ingredients, affecting their antibacterial effectiveness; while excessive humidity may promote microbial growth. Appropriate humidity helps slow the evaporation of water from the prunes, maintaining their firmness and texture. If the humidity is too low, the cling film may absorb excessive moisture from the fruit, causing it to wilt. Conversely, excessive humidity may lead to condensation, increasing the risk of mold. A moisture content of 10-15% makes the cling film soft and resistant to cracking, allowing it to adhere better to the fruit surface, providing a physical barrier and reducing mechanical damage. This humidity level also prevents excessive moisture from sticking to the fruit surface and causing unnecessary damage. Cling film dried to a moisture content of 10-15% at room temperature is easier to handle and use, neither too wet to be difficult to handle nor too dry to be brittle.

[0041] In summary, controlling the moisture content of cling film between 10% and 15% can maximize the quality of prunes and extend their shelf life while maintaining antibacterial properties. This humidity level not only facilitates the cling film's functionality but also ensures ease and safety of operation.

[0042] In the control method for extending the shelf life of prunes, bamboo vinegar is diluted to 200 mL / L, 0.05 g of curcumin is added to each liter of bamboo vinegar dilution, and 0.03 g of tea polyphenols is added to each liter of bamboo vinegar dilution.

[0043] The specific ratio of antibacterial liquid components can maximize cost-effectiveness while ensuring the antibacterial effect.

[0044] Experimental verification has shown that the antibacterial liquid at this ratio can effectively inhibit the growth of microorganisms on the surface of prunes without adversely affecting the quality of the prunes.

[0045] In the described method for extending the shelf life of prunes, the concentration of the methyl jasmonate aqueous solution is 0.01 mmol / L, the atomized particle size is ≤2.0 μm, and the droplet charge-to-mass ratio is 5-8 mC / kg. The electrostatic atomizer spraying process parameters for postharvest prune preservation include: an elevator speed of 12 Hz, a conveyor roll angle of 3.0°, a reversal speed of 6.5 Hz, and an electrostatic voltage of 6-10 kV (7-8 kV, optimized range). The coefficient of variation for spray uniformity is ≤5%, and the net hourly productivity is 350-450 kg / h. Precise concentration, atomized particle size, droplet charge-to-mass ratio, and electrostatic atomizer process parameters ensure that methyl jasmonate is evenly and efficiently applied to the prune surface, maximizing its role in regulating the fruit's physiological processes. These parameters also ensure operational stability and repeatability, facilitating standardized preservation. By optimizing the conveyor and spraying speeds, the mechanical damage rate is controlled to <3%.

[0046] The mass volume ratio of 1-methylcyclopropene to the fumigation space is 0.4-0.5 mg / m 3 The appropriate 1-methylcyclopropene dosage effectively inhibits ethylene synthesis and slows the ripening process of prunes, while avoiding the adverse effects that can result from excessive dosage. Precise control of the mass-to-volume ratio ensures stable and reliable fumigation results.

[0047] The near-freezing temperature storage temperature is -1.5 to -1.2°C, the relative humidity is 85 to 87%, the oxygen concentration in the phase temperature chamber is 3.5 to 4%, the carbon dioxide concentration is 3 to 5%, and the nitrogen concentration is 85 to 90%. These precise near-freezing temperature storage parameters create an optimal storage environment for prunes. In this environment, the physiological activities of the prunes are suppressed to the greatest extent, minimizing the loss of water and nutrients, thereby extending the shelf life of the prunes and maintaining their high quality.

[0048] The mass concentration of the hydrogen peroxide solution is 2-3%, and the atomized particle size is ≤1.0μm. The appropriate mass concentration of the hydrogen peroxide solution and the small atomized particle size ensure effective sterilization while minimizing chemical damage to the prunes. Precise parameter control makes the sterilization process more efficient and safe, effectively ensuring the freshness of the prunes.

[0049] The above optimization measures can significantly improve the post-harvest preservation effect of prunes: Optimizing key components and parameters in each processing step maximizes their effectiveness. Optimized parameters ensure operational stability and repeatability, facilitating standardized preservation. Precise control of each processing step reduces potential damage to the fruit, ensuring high quality. Rational selection and adjustment of parameters optimizes cost-effectiveness and improves the economic viability of the overall process. These improvements not only enhance postharvest prune preservation but also provide solid technical support for large-scale industrial application.

[0050] In the control method for extending the shelf life of prunes, the disinfection treatment in step 1) includes the following steps: Before storing prunes, use electrostatic spray equipment with a particle size of 50 to 100 μm to spray 75% anhydrous ethanol at a rate of 10 to 15 mL / m 3 Spray the amount evenly on the inner surface of the phase temperature fresh-keeping warehouse; after spraying is completed, turn on the ozone generator immediately and maintain the ozone concentration at 5-8ppm in the environment sprayed with ethanol for 2 hours; after turning off the ozone generator, maintain the temperature in the warehouse at 25-28℃ and the relative humidity at 40-45% for closed disinfection for 22 hours; after disinfection is completed, first turn on the external circulation ventilation system for 3 hours, and then switch to internal circulation ventilation for 5-7 hours, and control the airflow speed at 0.5-0.8m / s during ventilation.

[0051] Electrostatic spray equipment with atomized particle size of 50μm, 75μm or 100μm can be used, among which 75μm is the preferred particle size. The spraying amount of anhydrous ethanol can be 10mL / m 3 , 12mL / m 3 or 15 mL / m 3 , of which 12mL / m 3 This is the standard dosage. A commercially available high-voltage electrostatic sprayer can be installed at the top center and four corners of the storage room at the same temperature to ensure even coverage. During spraying, the storage room temperature should be controlled at 25°C, 26°C, or 28°C, with 26°C being the preferred temperature.

[0052] During the spraying operation, first load the ethanol solution into the sprayer's reservoir and adjust the atomization pressure to 0.3-0.5 MPa. Complete the entire warehouse disinfection within 20-30 minutes. The warehouse must be kept airtight during the spraying process, and operators must wear protective equipment. Immediately after spraying, turn off the sprayer and prepare for the next step of ozone treatment.

[0053] The ozone concentration can be selected as 5ppm, 6ppm or 8ppm, of which 6ppm is the commonly used concentration. The treatment time can be selected as 2h, 2.5h or 3h, of which 2h is the standard time. A commercially available ozone generator can be used and installed at the air inlet of the warehouse ventilation system. The power of the ozone generator is selected according to the volume of the warehouse, generally according to the power per 100m 3 The standard configuration is 1kW.

[0054] During ozone treatment, the ozone generator can be activated immediately after ethanol spraying is complete. The warehouse should remain sealed during the treatment, and ozone concentration should be monitored in real time using sensors installed inside. After the treatment is complete, the ozone generator should be turned off, and the warehouse should remain sealed for the next stage. During the ozone treatment process, personnel are prohibited from entering the warehouse, and safety warning signs should be posted.

[0055] The closed disinfection time can be selected as 22h, 23h or 24h, of which 22h is the standard time. The temperature during the disinfection maintenance period is controlled at 25℃, 26℃ or 28℃, of which 26℃ is the preferred temperature. The relative humidity is controlled at 40%, 42% or 45%, of which 42% is the commonly used value. When ventilating, external circulation ventilation can be carried out for 3h, and then internal circulation ventilation can be carried out for 5h, 6h or 7h, of which 6h is the standard time. The original ventilation system of the warehouse can be used, and the fresh air valve should be opened during external circulation ventilation and closed during internal circulation ventilation.

[0056] During ventilation operations, the airflow speed should be controlled at 0.5m / s, 0.6m / s, or 0.8m / s, with 0.6m / s being the standard speed. The ventilation system can be equipped with a variable-frequency fan to adjust the air volume based on demand. After ventilation is complete, the residual ethanol and ozone concentrations in the warehouse should be tested to ensure they meet safety standards before proceeding to the next step. Equipment operating status should be regularly checked during ventilation.

[0057] The technical effect of these disinfection steps is to ensure that the temperature-controlled fresh-keeping warehouse is sterile, providing a clean environment for prune storage. The synergistic effect of ethanol spraying and ozone treatment effectively kills various microorganisms within the warehouse. Proper ventilation eliminates disinfectant residue and ensures the safety of subsequent operations. The entire process is rationally parameterized and the operating procedures are controllable, meeting the stringent storage environment requirements for prune preservation.

[0058] In the control method for extending the shelf life of prunes, in the electrostatic atomization spraying step in step 4), the following components are added to the methyl jasmonate aqueous solution before electrostatic atomization spraying: bentonite-loaded slow-release particles, gelatin-tannic acid composite solution, and nisin microcapsules; The composite method includes the following steps: Bentonite and methyl jasmonate were mixed in a mass ratio of 10:1, calcined at 400-500°C for 2h, and then ultrafinely ground to a particle size of ≤2.0μm using a jet mill to obtain bentonite-loaded sustained-release particles; gelatin and tannic acid were dissolved in deionized water in a mass ratio of 4:1, stirred and dissolved at 60°C, and then cooled to 25°C to obtain a gelatin-tannic acid composite liquid; nisin and 2% sodium alginate solution were mixed in a mass ratio of 1:5, and added dropwise to a 5% calcium chloride aqueous solution, wherein the volume ratio of the calcium chloride aqueous solution to the sodium alginate solution was 4:1, cross-linking for 30 minutes and then centrifuging and drying to prepare nisin microcapsules with a particle size of ≤2 μm; adding bentonite-loaded slow-release particles, gelatin-tannic acid composite liquid and nisin microcapsules to a methyl jasmonate aqueous solution, and adjusting the mixture to a methyl jasmonate concentration of 0.01 mmol / L by adding deionized water or concentrating; wherein the amount of bentonite-loaded slow-release particles is 0.2-0.4 g / L, the amount of gelatin-tannic acid composite liquid is 0.1-0.3 g / L, and the amount of nisin microcapsules is 0.05-0.1 g / L.

[0059] Bentonite and methyl jasmonate are mixed uniformly in a mass ratio of 10:1. After calcining at 400-500°C for 2 hours, the mixture is ultrafinely ground using a jet mill to a particle size of ≤2.0 μm. A box-type resistance furnace can be used for calcination, with the furnace volume selected based on the production scale. A jet mill can be used for ultrafine grinding, installed in a separate dust-proof workshop. Commercially available sodium bentonite with a particle size of ≤50 μm can be used as the bentonite. Methyl jasmonate can be an analytical grade reagent with a purity of ≥98%.

[0060] To prepare the mixture, weigh the bentonite and methyl jasmonate in the correct proportions and mix them in a mixer for 30 minutes to ensure uniform mixing. Place the mixture in a crucible and place it in a resistance furnace. Heat the mixture to the target temperature at a rate of 5°C / min, hold for 2 hours, and then cool it in the furnace. The cooled material is then fed into a jet mill. Adjust the airflow pressure and classifying impeller speed to maintain a particle size of ≤2.0 μm. The pulverized material must be sealed to prevent moisture absorption.

[0061] Dissolve gelatin and tannic acid in deionized water at a mass ratio of 4:1. Stir and dissolve at 60°C, then cool to 25°C. A constant-temperature water bath equipped with a magnetic stirrer can be used to control the dissolution temperature. A glass reactor can be used as the dissolution vessel, with the volume adjusted according to production needs. Food-grade gelatin can be used. Tannic acid can be a plant extract with a purity of ≥95%.

[0062] To prepare the solution, first add the measured amount of deionized water to a reactor. Heat to 60°C, then slowly add the gelatin powder and stir until completely dissolved. Then, add tannic acid and continue stirring for 30 minutes to ensure complete dissolution and uniform mixing. Transfer the solution to a cooling tank, allow it to cool naturally to 25°C, and then filter to remove any insoluble matter. The prepared composite solution should be stored away from light and used within 24 hours.

[0063] Mix nisin with a 2% sodium alginate solution at a mass ratio of 1:5. Add dropwise to a 5% calcium chloride aqueous solution and crosslink for 30 minutes before centrifugation to dry. A peristaltic pump can be used to control the addition rate, and a centrifuge can be used for solid-liquid separation. Nisin should be food-grade with an activity ≥900 IU / mg. Sodium alginate should have a viscosity of 200-400 mPa﹒s.

[0064] To prepare the product, prepare a 2% aqueous solution of sodium alginate. After filtering to remove insoluble matter, mix it with nisin in the appropriate proportions. Use a peristaltic pump to drip the mixture into a 5% calcium chloride solution at a rate of 1 mL / min, keeping the droplet diameter at 1-2 mm. Stir for 30 minutes after addition to complete crosslinking. Collect the microcapsules by centrifugation at 3000 rpm for 5 minutes, wash them three times with deionized water, and dry them in a drying oven at 40°C to constant weight. Pass the dried microcapsules through a 200-mesh sieve, and collect the particles ≤2 μm.

[0065] The technical effect of these combined additive processes is to enhance the preservation properties of the methyl jasmonate aqueous solution. Bentonite-loaded slow-release granules prolong the duration of the active ingredient's action, the gelatin-tannic acid complex forms a protective film to reduce oxygen permeation, and the nisin microcapsules specifically inhibit the growth of harmful bacteria. The synergistic effect of these components more comprehensively preserves the quality of prunes and extends their shelf life. The rationally designed process parameters and controllable operating procedures make it suitable for large-scale production.

[0066] After spraying, the preservation effect is improved through the following synergistic mechanisms: When the surface humidity of the fruit is greater than 80%, methyl jasmonate is gradually released to inhibit the activity of ethylene synthase and prolong the action period; Tannic acid blocks the activity of polyphenol oxidase, and gelatin film formation reduces oxygen permeability to ≤5mL / (m 2 d), browning index ≤ 1.5; Targeted release of nisin in an acidic environment, killing Gram-positive bacteria with an efficiency of >99%; The mixed liquid was tested and found to have a particle size of ≤2.0μm, a charge-to-mass ratio of 5-8mC / kg, and a coverage uniformity of ≥95%.

[0067] In the method for extending the shelf life of prunes, in the fumigation step in step 5), a porous starch-based carrier is used to load 1-methylcyclopropene, and nano-zinc oxide and bimetallic organic framework particles are composited, specifically comprising the following steps: Porous starch-based carrier loaded with 1-methylcyclopropene: Porous starch was mixed with 1-methylcyclopropene in a mass ratio of 20:1 in a sealed container, the temperature was controlled at 40-50°C and the pressure was 0.1-0.2 MPa. After adsorption for 12 hours, a sustained-release carrier with a loading rate of 85-90% was obtained; Composite nano-zinc oxide and bimetallic organic framework particles: Nano-zinc oxide with a particle size of ≤50 nm was compounded with bimetallic ZIF-8@Cu particles in a mass ratio of 1:2 to form an antibacterial-ethylene decomposition composite; The sustained-release carrier and the compound are evenly dispersed in a phase temperature storage at a mass ratio of 5:1, and fumigated in a closed environment with a controlled temperature of -1.5 to -1.2°C and a humidity of 85 to 87%. After fumigation, the circulating ventilation system is started and the UV-visible composite light source (e.g., wavelength 254nm + 405nm) is turned on simultaneously to activate the photocatalytic performance of ZIF-8@Cu and degrade the residual gas to an ethylene concentration of ≤5ppm and a total microbial count of ≤10CFU / m 3 .

[0068] Porous starch and 1-methylcyclopropene are mixed in a mass ratio of 20:1, maintained at a temperature of 40-50°C and a pressure of 0.1-0.2 MPa, and adsorption is carried out for 12 hours. A high-pressure reactor can be used as the adsorption equipment, with the volume selected based on the processing volume. A vacuum pump can be used to maintain system pressure and installed in the reactor's associated piping. Porous starch with a pore size of 50-100 nm, prepared from commercially available corn starch, can be used. 1-methylcyclopropene can be obtained as a gaseous product with a purity of ≥99%.

[0069] During preparation, porous starch is placed in a reactor, evacuated to 0.1 MPa, and then filled with 1-methylcyclopropene gas to the target pressure. Maintain the system temperature between 40 and 50°C, and control the stirring speed between 50 and 100 rpm. After 12 hours of adsorption, slowly release the pressure and remove the loaded carrier material. The carrier should be sealed and stored at 4°C to prevent loss of the active ingredient through volatilization.

[0070] Nano zinc oxide with a particle size of ≤50nm is mixed with bimetallic ZIF-8@Cu particles in a mass ratio of 1:2. A planetary ball mill can be used for mixing, and the tank material is polytetrafluoroethylene. Nano zinc oxide can be a commercially available photocatalytic grade product with a specific surface area of ≥50m 2 / g. The bimetallic ZIF-8@Cu preparation method is as follows: ZIF-8 nanoparticles are synthesized by reacting Zn(NO3)2·6H2O with 2-MIM in methanol at room temperature; ZIF-8 is dispersed in a Cu(NO3)2 ethanol solution (concentration 0.01-0.1 M); copper ion exchange is achieved by refluxing at 60°C for 6-12 hours; free copper ions are removed by centrifugation and ethanol washing; and vacuum drying is performed.

[0071] To mix, weigh the two powders proportionally and place them in a ball mill. Add an appropriate amount of anhydrous ethanol as the dispersion medium. Mill at 300 rpm for 2 hours. After ball milling, dry the slurry in a 60°C oven and pass it through a 200-mesh sieve to collect the homogeneous mixture. Store the prepared composite antimicrobial agent away from light and moisture.

[0072] Evenly disperse the sustained-release carrier and compound in a temperature-controlled warehouse at a mass ratio of 5:1. Control the temperature to -1.5°C to -1.2°C and the humidity to 85% to 87%. A gas distributor can be used to evenly distribute the materials between warehouse shelves. An automatic temperature and humidity control system can be used to maintain these environmental parameters.

[0073] During fumigation, mix the carrier and compound in the correct proportions, place them in breathable bags, and hang them between shelves. After sealing the warehouse, adjust environmental parameters to the set values and maintain them for 18-20 hours. After fumigation, operate the recirculating ventilation system for 2-3 hours and simultaneously irradiate with a UV-visible light source (e.g., wavelengths of 254nm + 405nm) for 1 hour. During the treatment process, monitor the ethylene concentration in real time to ensure it remains below 5ppm.

[0074] The technical benefits of these fumigation processes are to effectively inhibit the effects of ethylene through the slow release of 1-methylcyclopropene, while simultaneously controlling microbial growth with a composite antimicrobial agent. A porous starch carrier ensures the stable release of the active ingredient, while a bimetallic material enhances the efficiency of ethylene decomposition. The entire process is precisely controlled with standardized operation and parameters, significantly extending the shelf life of prunes.

[0075] 1-Methylcyclopropene is adsorbed into the pores of porous starch in the form of gas under pressurized conditions (0.1-0.2MPa), breaking through the technical bottleneck of traditional solid-state loading. Starch carriers with a pore size of 50-100nm adsorb gas at 40-50℃, with a specific surface area of >300m 2 / g, increasing the loading efficiency to 90%. During fumigation, humidity within the storage chamber triggers pore expansion in the starch carrier, gradually releasing 1-methylcyclopropene, preventing damage to the fruit epidermis caused by sudden gas release. The bimetallic synergistic catalysis of nano-zinc oxide and ZIF-8@Cu increases the ethylene decomposition rate to 0.6 mmol / (g﹒h), with an antibacterial rate exceeding 99%. During the ventilation phase, a UV-visible composite light source activates ZIF-8@Cu, degrading residual 1-methylcyclopropene to harmless products, with a residual level of less than 0.01 ppm. The bimetallic framework enhances electron transfer efficiency, resulting in a three-fold increase in photocatalytic activity compared to a single metal carrier. After 12 hours of adsorption at 0.2 MPa, the porous starch achieved an 89% loading rate of 1-methylcyclopropene. The catalytic decomposition efficiency of ZIF-8@Cu was 85%, and the concentration dropped to 4 ppm after ventilation. The chemical residues after UV degradation met the GB2760 standard, indicating no toxicity risk to the fruit. After 40 days of storage, the fruit flesh firmness exceeded 8N, with a 92% sugar-acid ratio retention rate.

[0076] Through gaseous adsorption technology and bimetallic composite design, the feasibility and residual risk issues of solid carrier fumigation are solved, and efficient, safe and multifunctional preservation regulation is achieved, which is a significant technological breakthrough.

[0077] In the control method for extending the shelf life of prunes, the intermittent nano-atomization sterilization in step 7) specifically includes the following steps: A hydrogen peroxide aqueous solution with a mass concentration of 2-3% and a food-grade nisin solution with a mass concentration of 0.1-0.3% are compounded in a volume ratio of 4:1 to form a synergistic bactericidal solution, and intermittent nano-atomization sterilization is performed through the synergistic bactericidal solution; microbial concentration sensors are arranged in the fruit storage area, shelf gaps and ventilation holes of the phase temperature warehouse. Since each sterilization treatment is completed and a new sterilization interval cycle is started, the total number of environmental microorganisms is collected every 24 hours, and three consecutive monitorings are completed; temperature and humidity sensors are evenly installed on the top, middle and bottom of the warehouse to monitor the temperature and relative humidity in real time, and calculate the surface condensation risk index RH-T index, RH-T index = real-time relative humidity / saturated relative humidity at the current temperature, saturated relative humidity needs to be calculated by looking up a table or formula, such as the Magnus formula; if the total number of microorganisms monitored for three consecutive times is lower than 50 CFU / m 3 , and the RH-T index is lower than 0.5, the sterilization interval is extended from 15 to 18 days to 20 days; when the total number of microorganisms monitored at any time exceeds 80 CFU / m 3 Or when the RH-T index exceeds 0.7, the sterilization interval is shortened from 15 to 18 days to 12 days; when the total number of microorganisms monitored at any time exceeds 100 CFU / m 3Or when the RH-T index exceeds 0.8, start the nano-atomization equipment and spray the hydrogen peroxide synergistic sterilization solution; the atomization particle size of the nano-atomization equipment does not exceed 1.0μm, the droplet charge-to-mass ratio is 5-8mC / kg, and the single spraying volume is 0.5-1.0mL / m 3 , spraying time 5 to 10 minutes.

[0078] Mix a 2-3% aqueous hydrogen peroxide solution with a 0.1-0.3% food-grade nisin solution in a 4:1 volume ratio. A magnetic stirrer can be used for mixing, stirring for 30 minutes. Use a food-grade hydrogen peroxide solution at a 30% concentration. Use a food additive with an activity of ≥900 IU / mg for nisin. Use a corrosion-resistant polyethylene plastic drum, with the volume adjusted based on the intended use.

[0079] To prepare, first add the measured amount of deionized water to a container, then slowly add the hydrogen peroxide solution to the target concentration. Stir thoroughly before adding the nisin solution and continue stirring until thoroughly mixed. The prepared solution should be used immediately and should not be stored for more than 4 hours. Maintain the pH of the solution within the range of 3.5-4.5 using a pH meter.

[0080] Microbial concentration sensors are installed in the fruit storage area, shelf gaps and ventilation openings of the temperature storage. A commercially available ATP bioluminescence detector can be used as a microbial sensor with a detection limit of ≤10 CFU / m 3 Digital temperature and humidity sensors with an accuracy of ±0.5°C and ±3%RH can be used. Sensors can be evenly distributed on the upper, middle and lower floors of the warehouse, with a minimum of 100m 3 Arrange 5-8 monitoring points.

[0081] When installing the monitoring system, microbial sensors should be placed 30-50 cm from the shelves to avoid direct contact with the products. Temperature and humidity sensors should be installed in a well-ventilated area, at least 50 cm from the walls. All sensors should be connected to the central controller via wired or wireless connections, with data collection set to a 1-hour interval. The system should be regularly calibrated to ensure accurate and reliable monitoring data.

[0082] When the total number of microorganisms exceeds 100 CFU / m 3 Or when the RH-T index exceeds 0.8, start the nano-atomization equipment to spray the sterilization solution. Ultrasonic nano-atomizer can be used, and the atomization particle size is ≤1.0μm. An automatic control system can be used to trigger the spray operation according to the monitoring data. The spray volume is controlled at 0.5~1.0mL / m 3 , spray time 5 to 10 minutes.

[0083] When operating, first check the operating status of the atomization equipment and confirm that the liquid level in the solution storage tank is sufficient. After starting the equipment, adjust the atomization volume to 0.8mL / m 3 The spraying time was set to 8 minutes. During the spraying process, the warehouse was kept airtight and the ventilation system was suspended. After the spraying was completed, the ventilation system was restarted after 30 minutes of stagnant airflow, with an airflow speed of 0.5 m / s. After each spraying operation, the treatment time and parameters were recorded and the monitoring cycle was restarted.

[0084] The technical benefits of these intermittent sterilization processes are to effectively control the microbial population in the storage environment through precise environmental monitoring and on-demand sterilization. The synergistic effect of hydrogen peroxide and nisin broadens the bactericidal spectrum, while nano-atomization ensures uniform distribution of the bactericide. Intelligent monitoring and control systems enable precise sterilization, preventing overtreatment that could negatively impact product quality. The entire process is standardized and parameter-controlled, ensuring a hygienic and safe storage environment for prunes.

[0085] In the control method for extending the shelf life of prunes, the antibacterial solution further comprises chitosan-β-cyclodextrin sustained-release microspheres; The preparation method of chitosan-β-cyclodextrin sustained-release microspheres is as follows: β-cyclodextrin and chitosan were dissolved in deionized water to form a mixed solution with a chitosan mass concentration of 0.02 g / mL and a β-cyclodextrin mass concentration of 0.06 g / mL; the mixed solution was mixed with a 0.1% citric acid solution in a volume ratio of 1:4 and ultrasonically dispersed for 30 minutes; a 0.5% calcium chloride solution was added dropwise, with the total mass ratio of β-cyclodextrin and chitosan to the volume of the calcium chloride solution being 0.2 g / mL. The mixture was stirred for 2 hours, then centrifuged and dried, and passed through a 100-mesh sieve to obtain chitosan-β-cyclodextrin sustained-release microspheres; Add 1-2 g of microspheres per liter of antibacterial solution; The specific preparation method of fresh-keeping paper is: Immerse the non-woven fabric in an antibacterial solution containing microspheres and soak it at a pressure of -0.05 MPa for 8 to 10 minutes to allow the microspheres to embed into the gaps between the fibers. After draining, dry it at 40°C for 1 hour and then dry it at room temperature until the moisture content reaches 10 to 15%.

[0086] Dissolve β-cyclodextrin and chitosan in deionized water to form a mixed solution with a chitosan concentration of 0.02 g / mL and a β-cyclodextrin concentration of 0.06 g / mL. This mixed solution is mixed with a 0.1% citric acid solution in a volume ratio of 1:4 and ultrasonically dispersed for 30 minutes. Add a 0.5% calcium chloride solution dropwise, with the total mass of β-cyclodextrin and chitosan to the volume of the calcium chloride solution being 0.2 g / mL. Stir for 2 hours, then centrifuge and dry. Pass through a 100-mesh sieve to produce microspheres. Dispersion can be performed using an ultrasonic cell disruptor at a power setting of 300 W. Solid-liquid separation can be performed using a low-speed centrifuge at a speed of 3000 rpm.

[0087] The preparation process was carried out at 25°C. β-cyclodextrin and chitosan were first dissolved in deionized water and then mixed thoroughly. Citric acid solution was added to adjust the pH to 5.0-5.5, followed by sonication. Calcium chloride solution was added dropwise at 1 mL / min using a constant flow pump. After addition, stirring was continued to complete crosslinking. The centrifuged microspheres were washed three times with deionized water and vacuum-dried at 40°C to constant weight. The dried product was sieved and graded, and microspheres sized 50-100 μm were collected for later use.

[0088] Immerse the non-woven fabric in the antibacterial solution containing microspheres and soak it at a pressure of -0.05MPa for 8 to 10 minutes. Vacuum impregnation equipment can be used for treatment, and the volume of the impregnation tank is selected according to the production scale. The non-woven fabric can be a polypropylene non-woven fabric with a size of 18cm×25cm and a gram weight of 40g / m 2 After draining, dry at 40℃ for 1 hour, then dry at room temperature until the moisture content is 10-15%. A hot air circulation drying oven can be used for preliminary drying, with the temperature controlled at 40±2℃.

[0089] During the impregnation process, place the nonwoven fabric flat in an impregnation tank. Add an antibacterial solution containing 1-2g / L of microspheres and evacuate to -0.05MPa. Maintain the vacuum for 8-10 minutes to allow the microspheres to fully penetrate the interfiber spaces. Remove the nonwoven fabric and hang it to drain for 30 minutes before drying it in a drying oven. After drying, equilibrate the nonwoven fabric in an environment with a temperature of 25°C and a humidity of 50% for 24 hours. Once moisture content is tested and acceptable, package and store the nonwoven fabric. The weight variation of each sheet of nonwoven fabric should be controlled within ±0.3g.

[0090] The technical benefit of these preparation processes is that the microspheres slowly release antibacterial ingredients, extending the duration of the cling film's effectiveness, mitigates the problem of overly rapid active ingredient release in traditional cling film. The chitosan-β-cyclodextrin microspheres encapsulate and protect the active ingredients, allowing for sustained release during storage. The vacuum impregnation process ensures that the microspheres are evenly distributed among the non-woven fabric fibers, maintaining the paper's breathability and enhancing its antibacterial properties. The resulting cling film is easy to use, safe, and effectively extends the shelf life of prunes.

[0091] In the control method for extending the shelf life of prunes, the portable differential pressure precooling treatment in step 3) adopts a graded precooling method, which specifically includes the following steps: initial cooling stage: at 3°C, the fruit is treated for 4 hours with a portable differential pressure precooling device at a pressure difference of 60Pa and a wind speed of 0.6m / s, so that the center temperature of the fruit drops from 25°C to 10°C; fine cooling stage: adjusting the portable differential pressure precooling device to a pressure difference of 80Pa and a wind speed of 0.8m / s, and treating in a 2.5°C environment for 4 hours, so that the center temperature drops to 4°C; final cooling stage: adjusting the differential pressure to 70Pa, treating in a 2.0°C environment for 1.5 hours, and finally bringing the overall temperature of the fruit to 2.1°C; temperature stabilization: maintaining the temperature difference for 0.5 hours so that the temperature difference does not exceed 0.2°C.

[0092] At 3°C, use portable differential pressure cooling equipment at a pressure differential of 60 Pa and a wind speed of 0.6 m / s for 4 hours to reduce the core temperature of the fruit from 25°C to 10°C. Air-cooled differential pressure cooling units equipped with variable frequency fans and a differential pressure control system can be used. A digital temperature recorder can be used to monitor the core temperature of the fruit, with the probe inserted at the equator of the fruit. The cooling equipment can be installed in a temporary cooling room in the harvest area, no more than 20 meters from the packaging area.

[0093] During processing, arrange the prunes in a single layer on the pre-cooling equipment conveyor belt, maintaining a spacing of 3-5 cm to ensure unimpeded airflow. After starting the equipment, adjust the pressure differential to 60 Pa, the wind speed to 0.6 m / s, and the ambient temperature to 3 ± 0.5°C. Record the core temperature of the fruit every 30 minutes. When the temperature of most fruit drops to 10°C, proceed to the next stage. During the initial cooling phase, ensure that no condensation forms on the fruit surface and maintain a relative humidity of 80-85%.

[0094] Adjust the equipment to a pressure differential of 80 Pa and a wind speed of 0.8 m / s, then process at 2.5°C for 4 hours to reduce the core temperature to 4°C. Pre-cooling equipment with an adjustable pressure differential and a multi-point temperature monitoring system can be used. An anemometer can be used to measure airflow velocity, with measurement points located between the fruits. The equipment's fan can be installed at the top of the pre-cooling chamber to blow cool air downward.

[0095] During treatment, gradually increase the pressure differential to 80 Pa, wind speed to 0.8 m / s, and ambient temperature to 2.5 ± 0.3°C. Monitor the fruit temperature distribution every 15 minutes and adjust the fruit placement to ensure even cooling. During this stage, focus on controlling the fruit temperature drop rate to 1.5-2°C / hour to avoid sudden temperature drops that can cause chilling damage. After treatment, conduct sampling and testing to ensure that at least 80% of the fruit reaches a core temperature of 4 ± 0.5°C.

[0096] Adjust the pressure differential to 70 Pa and process at 2.0°C for 1.5 hours, ultimately bringing the overall fruit temperature to 2.1°C. A pre-cooling system with temperature feedback control can be used to automatically adjust operating parameters. An infrared thermal imager can be used to assist in monitoring the surface temperature distribution of the fruit. The condenser can be installed outside the pre-cooling chamber and connected via a duct.

[0097] During processing, adjust the pressure differential to 70 Pa, maintain a wind speed of 0.7 m / s, and control the ambient temperature at 2.0 ± 0.2°C. Closely monitor fruit temperature changes and transition to the stabilization phase when the majority of fruit approaches 2.1°C. During the final cooling phase, pay special attention to ensuring the temperature difference between the fruit surface and center does not exceed 0.5°C to prevent uneven temperatures inside and outside. Maintain the temperature stabilization phase for 0.5 hours to ensure uniform temperature across all parts of the fruit.

[0098] The technical effect of these graded pre-cooling processes is to prevent chilling damage to the fruit through gradual cooling while ensuring pre-cooling efficiency. Precisely controlled pressure differentials and air speeds ensure even distribution of cooling, and multi-stage temperature adjustment adapts to the physiological characteristics of the fruit. The entire pre-cooling process is rationally parameterized and operationally controlled, creating optimal conditions for subsequent fresh-keeping. This graded pre-cooling method ensures rapid cooling while maximizing fruit quality.

[0099] Experiment 1 To evaluate the effectiveness of the method for extending the shelf life of prunes of the present invention, comparative experiments were conducted using Examples 1 to 10 and Comparative Examples 1 to 3. The following is a detailed experimental design, implementation steps, and analysis of the results.

[0100] Experimental conditions and sample processing Subjects: Freshly harvested prune (Prunus virginiana) fruits.

[0101] Experimental environment: All experiments were conducted under the same initial conditions, including temperature, humidity, etc.

[0102] Experimental period: 40 days.

[0103] Example 1 Processing steps: 1) Disinfection: Use 75% anhydrous ethanol to spray and disinfect the temperature-controlled fresh-keeping warehouse to ensure a sterile environment. After 24 hours, turn on the circulating ventilation system for 9 hours to remove residual ethanol gas.

[0104] 2) Harvesting and pre-cooling: Choose high-quality prunes, that is, those that are free of pests and diseases, mechanical damage, have intact frost, and have a sugar content of no less than 20%.

[0105] 3) Pre-cooling treatment: Pre-cool the harvested prunes to 2.1°C. Use portable differential pressure cooling to quickly cool them to the pre-cooling temperature within 10 hours.

[0106] 4) Electrostatic atomization spraying: After precooling, electrostatic atomization spraying is performed using a 0.01 mmol / L aqueous solution of methyl jasmonate. By precisely controlling the atomized particle size (≤2.0 μm) and the droplet charge-to-mass ratio (6 mC / kg), combined with optimized electrostatic atomization sprayer process parameters, a uniform and efficient spraying effect is achieved.

[0107] 5) 1-Methylcyclopropene fumigation: After electrostatic atomization spraying, the prunes were immediately placed in a temperature chamber for 1-methylcyclopropene closed fumigation. By precisely controlling the fumigation time (19 hours) and the amount of 1-methylcyclopropene (mass-to-volume ratio of 0.45 mg / m 3 ), effectively inhibiting the ethylene production and respiration of the fruit.

[0108] 6) Near-freezing temperature storage: The fumigated prunes were stored at -1.5°C in a near-freezing temperature storage facility. The relative humidity was maintained at 86%, and the gas composition within the storage facility was controlled (oxygen concentration 3.75%, carbon dioxide concentration 4%, nitrogen concentration 88.25%). Intermittent nano-atomization sterilization was performed every 16 days using a 2.5% mass concentration of hydrogen peroxide solution.

[0109] 7) Intermittent nano-atomization sterilization: During storage, hydrogen peroxide aqueous solution is used to sterilize the environment and prunes intermittently using nano-atomization, with an interval of 16 days between each sterilization.

[0110] Example 2 On the basis of Example 1, the following steps are added: Place a sheet of 18cm x 25cm plastic wrap per 2kg of pre-cooled prunes. The plastic wrap is made of sterile polypropylene nonwoven fabric soaked in an antibacterial solution for 6 minutes, drained, and then dried at room temperature to a moisture content of 15%.

[0111] The method for preparing the antibacterial solution includes the following steps: diluting bamboo vinegar (stock concentration: 1000 mL / L) to 200 mL / L to obtain a bamboo vinegar dilution solution; adding curcumin to the bamboo vinegar dilution solution, stirring evenly, and then adding tea polyphenols, stirring evenly. The antibacterial solution comprises bamboo vinegar diluted to 200 mL / L, 0.05 g of curcumin, and 0.03 g of tea polyphenols per liter.

[0112] Example 3 to Example 10 The only difference from Example 2 is the antibacterial solution formula. The antibacterial solution formulas of Examples 3 to 10 are as follows: Example 3: bamboo vinegar 180 mL / L, curcumin 0.05 g / L, tea polyphenols 0.03 g / L; Example 4: bamboo vinegar 220 mL / L, curcumin 0.05 g / L, tea polyphenols 0.03 g / L; Example 5: bamboo vinegar 200 mL / L, curcumin 0.04 g / L, tea polyphenols 0.03 g / L; Example 6: bamboo vinegar 200 mL / L, curcumin 0.06 g / L, tea polyphenols 0.03 g / L; Example 7: bamboo vinegar 200 mL / L, curcumin 0.07 g / L, tea polyphenols 0.03 g / L; Example 8: bamboo vinegar 200 mL / L, curcumin 0.05 g / L, tea polyphenols 0.02 g / L; Example 9: bamboo vinegar 200 mL / L, curcumin 0.05 g / L, tea polyphenols 0.04 g / L; Example 10: bamboo vinegar 200 mL / L, curcumin 0.05 g / L, tea polyphenols 0.05 g / L.

[0113] Comparative Example 1: Traditional cold chain transportation and storage methods Processing steps: Choose prunes that are free of pests and diseases, mechanical damage, and have intact frost.

[0114] After the prunes are naturally air-dried at room temperature, they are placed in a regular cold storage and pre-cooled to 0°C for 24 hours.

[0115] Use ordinary cold chain transportation methods, ensure that the transportation temperature is maintained at 2-5°C, and the transportation time does not exceed 24 hours.

[0116] After arriving at the destination, place the prunes in an ordinary cold storage, control the temperature at 3-5℃, and keep the humidity between 90-95%.

[0117] No additional sterilization measures were used.

[0118] Comparative Example 2: Reference method of patent application number 202210592807.3 Processing steps: Plum fruits that have reached 80% maturity are placed in a closed space after being harvested and fumigated with 20 μmol / L methyl jasmonate for 3 hours.

[0119] Place the naturally air-dried prunes in a portable box, place an ice box in the box, and add 1-MCP preservative powder (one bag of 0.3g 1-MCP for every 4.0-5.0kg of prunes) to ensure that the fruits are transported to the target city within 24 hours.

[0120] After arrival, put it in a 0℃ cold storage for pre-cooling in time. The specific pre-cooling time is based on the surface temperature of the fruit reaching 0℃.

[0121] After being fully pre-cooled, place 18cm×25cm natamycin antibacterial fresh-keeping paper in the prunes, with two sheets placed for every 4.0-5.0kg of prunes.

[0122] Entering the low-temperature storage stage, the temperature is controlled at 3-5°C and the humidity is maintained between 90-95%.

[0123] Comparative Example 3 Compared with Comparative Example 2, the improvements are: After sufficient pre-cooling, place two sheets of 18cm x 25cm plastic wrap around prunes for every 4.0-5.0kg of prunes. The plastic wrap, made of sterile polypropylene nonwoven fabric, is soaked in an antibacterial solution for 6 minutes, drained, and dried at room temperature to a moisture content of 15%. The antibacterial solution consists of bamboo vinegar diluted to 200mL / L, with 0.05g of curcumin and 0.03g of tea polyphenols added per liter.

[0124] The rest is the same as Example 2.

[0125] The experimental summary is shown in Table 1.

[0126] Table 1 Experimental summary The above experimental results show that the control method provided by the present invention has significant advantages, especially Example 2 performs excellently: Compared with the traditional cold chain transportation and storage method (Comparative Example 1) and the existing technology (Comparative Example 2), the method of the present invention can significantly extend the shelf life of prunes from about 10 days to 35 days.

[0127] Example 2 not only extends the shelf life, but also significantly improves the quality of prunes, including fruit firmness, taste and appearance, thereby increasing the marketability and nutritional value of the fruit.

[0128] Example 2 uses a variety of natural ingredients (such as bamboo vinegar, curcumin and tea polyphenols), reduces the use of chemical substances, and is more environmentally friendly and healthier.

[0129] The operation of Example 2 is simple, easy to implement and control, and has relatively low cost, and is suitable for large-scale commercial applications.

[0130] The fresh-keeping paper introduced in Example 2 not only enhances the antibacterial effect, but also plays a moisturizing role, further slowing down the water loss of the fruit and maintaining the hardness and taste of the fruit.

[0131] Furthermore, Comparative Example 3 also demonstrated better results than Comparative Example 2, indicating that the application of the antibacterial liquid formula and fresh-keeping paper can significantly improve the freshness and quality of prunes. The superiority of Example 2 over Examples 6, 7, 9, and 10 is primarily attributed to the following key factors: In Example 2, the antibacterial solution used was a bamboo vinegar solution diluted to 200 mL / L, with 0.05 g of curcumin and 0.03 g of tea polyphenols added per liter. The ratios of the ingredients in this solution were optimized to effectively inhibit microbial growth and extend shelf life without negatively impacting the fruit.

[0132] Bamboo vinegar: Has excellent antibacterial properties, effectively inhibiting mold and other pathogens. Curcumin: As a natural antioxidant, it not only has antibacterial effects but also enhances the fruit's resistance to stress. Tea polyphenols: Also possess antioxidant and antibacterial properties, they help preserve the fruit's freshness.

[0133] Although Examples 6, 7, 9, and 10 use similar combinations of ingredients, the concentrations of certain ingredients have changed. For example: Example 6: Curcumin is increased to 0.06 g / L, which may exceed the optimal concentration range, resulting in its effect being inferior to that of Example 2. Example 7: Curcumin is further increased to 0.07 g / L. Excessively high concentrations may have adverse effects on the surface of the fruit or produce adverse interactions with other ingredients. Example 9: Tea polyphenols are increased to 0.04 g / L, which may change the overall chemical properties of the antibacterial solution and thus affect its efficacy. Example 10: Tea polyphenols are increased to 0.05 g / L. Similarly, higher concentrations may cause unnecessary side effects or reduce the effectiveness of other ingredients. These subtle changes may affect the overall performance of the antibacterial solution, making their effects less ideal than those of Example 2.

[0134] In Example 2, the ratio of the three ingredients (bamboo vinegar, curcumin, and tea polyphenols) reached an optimal balance, which not only enhanced the antibacterial effect but also avoided the potential problems caused by excessive concentrations. Furthermore, the use of cling film also played a role in moisturizing and continuously releasing antibacterial ingredients, further enhancing the overall preservation effect.

[0135] Through actual experiments, it was observed that the prunes in Example 2 exhibited better firmness, taste, and appearance during their shelf life, with virtually no signs of mold or rot, demonstrating high commercial value and market acceptance. While the other examples also performed well, they were slightly inferior in certain aspects, such as shelf life and fruit quality.

[0136] In summary, Example 2 demonstrated superior results because it achieved an optimal balance between the selection and concentration of the antibacterial solution components, ensuring maximum synergy between the components while also avoiding the negative effects of excessively high or low concentrations. This optimized configuration resulted in Example 2's superior performance in extending the shelf life of prunes and maintaining fruit quality, making it the optimal choice among Examples 1-10 and Comparative Examples 1-3.

[0137] In order to further verify the effect of the present invention, Examples 11-16 were carried out.

[0138] Example 11 Based on Example 1, the disinfection treatment in step 1) includes the following steps: Before the prunes were stored, an electrostatic spray device with a particle size of 75 μm was used to spray 75% anhydrous ethanol at a rate of 12 mL / m 3 The amount of ozone is evenly sprayed on the inner surface of the phase temperature fresh-keeping warehouse; after the spraying is completed, the ozone generator is immediately turned on to maintain the ozone concentration at 6ppm in the environment sprayed with ethanol for 2 hours; after turning off the ozone generator, the temperature in the warehouse is maintained at 26℃ and the relative humidity is 42% for closed disinfection for 22 hours; after the disinfection is completed, the external circulation ventilation system is first turned on for 3 hours, and then switched to internal circulation ventilation for 6 hours. The airflow speed is controlled at 0.6m / s during ventilation.

[0139] Example 12 Based on Example 1, in the electrostatic atomization spraying step in step 4), the following components are added to the methyl jasmonate aqueous solution before electrostatic atomization spraying: bentonite-loaded slow-release particles, gelatin-tannic acid composite liquid, and nisin microcapsules; The composite method includes the following steps: Bentonite and methyl jasmonate were uniformly mixed in a mass ratio of 10:1, calcined at 450°C for 2h, and then ultrafinely ground to a particle size of 2.0μm using a jet mill to obtain bentonite-loaded sustained-release particles; gelatin and tannic acid were dissolved in deionized water in a mass ratio of 4:1, stirred and dissolved at 60°C, and then cooled to 25°C to obtain a gelatin-tannic acid composite liquid; nisin and a 2% sodium alginate solution were mixed in a mass ratio of 1:5, and the mixture was dropwise added to a 5% calcium chloride aqueous solution, wherein the volume ratio of the calcium chloride aqueous solution to the sodium alginate solution was 4:1. After cross-linking for 30min, the mixture was centrifuged and dried to obtain nisin microcapsules with a particle size of 2μm. Bentonite-loaded sustained-release particles, gelatin-tannic acid composite liquid, and nisin microcapsules are added to a methyl jasmonate aqueous solution, and the mixture is adjusted to a methyl jasmonate concentration of 0.01 mmol / L by adding deionized water or concentrating the mixture. The amount of bentonite-loaded sustained-release particles is 0.3 g / L, the amount of gelatin-tannic acid composite liquid is 0.2 g / L, and the amount of nisin microcapsules is 0.08 g / L.

[0140] Example 13 On the basis of Example 1, in the fumigation treatment step in step 5), a porous starch-based carrier is used to load 1-methylcyclopropene, and nano zinc oxide and bimetallic organic framework particles are composited, specifically comprising the following steps: Porous starch-based carrier loaded with 1-methylcyclopropene: Porous starch was mixed with 1-methylcyclopropene in a mass ratio of 20:1 in a sealed container, the temperature was controlled at 45°C and the pressure was 0.15 MPa. After adsorption for 12 hours, a sustained-release carrier with a loading rate of 88% was obtained; Composite nano-zinc oxide and bimetallic organic framework particles: Nano-zinc oxide with a particle size of 50 nm was compounded with bimetallic ZIF-8@Cu particles in a mass ratio of 1:2 to form an antibacterial-ethylene decomposition complex; The sustained-release carrier and the compound are evenly dispersed in a phase temperature storage at a mass ratio of 5:1, and fumigated in a closed environment with a controlled temperature of -1.3°C and a humidity of 86%. After fumigation, the circulating ventilation system was started and the UV-visible composite light source (wavelength 254nm + 405nm) was turned on simultaneously to activate the photocatalytic performance of ZIF-8@Cu, degrading the residual gas to an ethylene concentration of 5ppm and a total microbial count of 10CFU / m 3 .

[0141] Example 14 Based on Example 1, the intermittent nano-atomization sterilization in step 7) specifically includes the following steps: A 2.5% mass concentration of hydrogen peroxide aqueous solution and a 0.2% mass concentration of food-grade nisin solution were compounded in a volume ratio of 4:1 to form a synergistic bactericidal solution, which was then used for intermittent nano-atomization sterilization. Microbial concentration sensors were installed in the fruit storage area, shelf gaps and vents of the phase temperature warehouse. After each sterilization treatment was completed and a new sterilization interval cycle was started, the total number of environmental microorganisms was collected every 24 hours, and three consecutive monitorings were completed. Temperature and humidity sensors were evenly installed at the top, middle and bottom of the warehouse to monitor the temperature and relative humidity in real time, and the surface condensation risk index RH-T index was calculated, RH-T index = real-time relative humidity / saturated relative humidity at the current temperature. If the total number of microorganisms monitored for three consecutive times was lower than 50 CFU / m 3 , and the RH-T index is lower than 0.5, the sterilization interval is extended from 16 days to 20 days; when the total number of microorganisms monitored at any time exceeds 80 CFU / m 3 Or when the RH-T index exceeds 0.7, the sterilization interval is shortened from 16 days to 12 days; when the total number of microorganisms monitored at any time exceeds 100 CFU / m 3 Or when the RH-T index exceeds 0.8, start the nano-atomization equipment to spray hydrogen peroxide synergistic sterilization solution; the atomization particle size of the nano-atomization equipment is 1.0μm, the droplet charge-to-mass ratio is 6mC / kg, and the single spraying volume is 0.8mL / m 3 , spraying time 8min.

[0142] Example 15 Based on Example 2, the antibacterial solution further comprises chitosan-β-cyclodextrin sustained-release microspheres; The preparation method of chitosan-β-cyclodextrin sustained-release microspheres is as follows: β-cyclodextrin and chitosan are dissolved in deionized water to form a mixed solution with a chitosan mass concentration of 0.02 g / mL and a β-cyclodextrin mass concentration of 0.06 g / mL; the mixed solution is mixed with a 0.1% mass concentration of citric acid solution in a volume ratio of 1:4, and ultrasonically dispersed for 30 minutes; a 0.5% mass concentration of calcium chloride solution is added dropwise, and the ratio of the total mass of β-cyclodextrin and chitosan to the volume of the calcium chloride solution is 0.2 g / mL; the mixture is stirred for 2 hours, then centrifuged and dried, and passed through a 100-mesh sieve to obtain chitosan-β-cyclodextrin sustained-release microspheres; Add 1.5 g of microspheres per liter of antibacterial solution; The specific preparation method of fresh-keeping paper is: The non-woven fabric was immersed in an antibacterial solution containing microspheres and soaked at a pressure of -0.05 MPa for 9 minutes to allow the microspheres to embed into the gaps between the fibers. After draining, it was dried at 40°C for 1 hour and then dried at room temperature to a moisture content of 12%.

[0143] Example 16 Based on Example 1, the portable pressure difference pre-cooling treatment in step 3) adopts a graded pre-cooling method, which specifically includes the following steps: Initial cooling stage: at 3°C, use portable pressure differential pre-cooling equipment with a pressure differential of 60Pa and a wind speed of 0.6m / s for 4 hours to reduce the center temperature of the fruit from 25°C to 10°C; fine cooling stage: adjust the portable pressure differential pre-cooling equipment to 80Pa pressure differential and 0.8m / s wind speed, and treat in a 2.5°C environment for 4 hours to reduce the center temperature to 4°C; final cooling stage: adjust the pressure differential to 70Pa, treat in a 2.0°C environment for 1.5 hours, and finally make the overall temperature of the fruit reach 2.1°C; temperature stabilization: maintain the temperature difference for 0.5 hours so that the temperature difference does not exceed 0.2°C.

[0144] Experiment 2 1. Experiment and Grouping Experimental materials: Freshly harvested prunes (French prunes), free of pests and diseases, mechanical damage, complete fruit frost, and sugar content ≥ 20%.

[0145] Example 1: Basic treatment (disinfection, pre-cooling, electrostatic atomization spraying, fumigation, near-freezing temperature storage, intermittent sterilization). Example 2: Example 1 plus fresh-keeping paper (containing bamboo vinegar, curcumin, and tea polyphenol antibacterial solution). Example 11: Example 1 plus optimized disinfection treatment (ethanol spraying + ozone treatment). Example 12: Example 1 plus composite additives (bentonite-loaded sustained-release granules, gelatin-tannic acid composite solution, nisin microcapsules). Example 13: Example 1 plus porous starch carrier-loaded 1-methylcyclopropene plus nano-zinc oxide and bimetallic organic framework composite. Example 14: Example 1 plus intelligent monitoring and intermittent sterilization (hydrogen peroxide + nisin). Example 15: Example 2 plus chitosan-β-cyclodextrin sustained-release microsphere antibacterial solution. Example 16: Example 1 plus graded pre-cooling (initial cooling, fine cooling, and final cooling). Comparative Example 1: Traditional cold chain (conventional cold storage, no sterilization). Comparative Example 2: Existing technology (methyl jasmonate fumigation + natamycin fresh-keeping paper). Comparative Example 3: Comparative Example 2 + bamboo vinegar, curcumin, and tea polyphenols fresh-keeping paper.

[0146] 2. Test indicators and methods The fruit firmness (N), sugar-acid ratio, mildew rate (%), and weight loss rate (%) were tested weekly.

[0147] Hardness: Use a hardness tester to measure the equator of the fruit, unit: N.

[0148] Sugar-acid ratio: HPLC was used to determine the soluble sugar and organic acid contents, and the ratio was calculated.

[0149] Moldy rate: The proportion of moldy fruits is counted by naked eye observation, unit: %.

[0150] Weight loss rate: weighing method, unit: %.

[0151] Total microbial count: ATP bioluminescence method, unit: CFU / m 3 .

[0152] Shelf life: the number of days from harvest to when the fruit loses its marketability.

[0153] Experimental results and data analysis The experimental results are shown in Table 2.

[0154] Table 2 Comparison of fruit quality indicators after 40 days of storage Group Hardness (N) Sugar-acid ratio retention rate (%) Mildew rate (%) Weight loss rate (%) Shelf life (d) Example 1 7.8 88 5 3.2 30 Example 2 8.5 92 2 2.1 35 Example 11 8.1 90 3 2.8 32 Example 12 8.3 91 2 2.5 34 Example 13 8.4 93 1 2.0 36 Example 14 8.2 92 2 2.3 35 Example 15 8.6 94 1 1.8 38 Example 16 8.0 89 4 2.9 31 Comparative Example 1 5.2 70 15 6.5 10 Comparative Example 2 6.5 80 10 4.8 15 Comparative Example 3 7.0 85 7 3.5 20 Data Analysis Comparison of Examples: Example 2 (containing fresh-keeping paper) showed significantly better hardness and sugar-acid ratio retention than Example 1, and a 60% reduction in mold rate, demonstrating that the antibacterial liquid fresh-keeping paper effectively inhibits microorganisms and reduces water loss. Example 13 (slow-release carrier fumigation) maintained a longer shelf life (36 days) due to the bimetallic complex's enhanced ethylene decomposition efficiency. Example 15 (chitosan microspheres) achieved the best overall performance, with a mold rate of only 1%, thanks to the long-lasting nature of the microspheres' slow-release antibacterial components. Example 16's graded precooling was slightly better than Example 1, but the difference was not significant, likely due to the controlled cooling rate.

[0155] Comparison of comparison: Comparative Example 1 (traditional cold chain) had the worst performance across all indicators, with a shelf life of only 10 days, highlighting the advantages of the multi-step control approach of the present invention. Comparative Example 3 (improved fresh-keeping paper) showed significant improvements over Comparative Example 2, validating the effectiveness of natural antibacterial ingredients like bamboo vinegar.

[0156] in conclusion Basic optimal solution: Example 2 (compound antibacterial solution) is suitable for conventional needs (35-day freshness preservation, low cost); Advanced optimal solution: Example 15 (compound antibacterial liquid + chitosan microspheres) had the best overall performance, with fruit firmness and sugar-acid ratio retention rates significantly higher than those of other groups, meeting higher requirements (38-day preservation and longer-lasting antibacterial effect).

[0157] Technical advantages: Gradual pre-cooling (Example 16) reduces the risk of chilling damage; intelligent monitoring and sterilization (Example 14) precisely controls microorganisms; and sustained-release carriers (Example 13) prolong the duration of action of active ingredients.

[0158] Practicality: All embodiments are superior to traditional methods (Comparative Examples 1-3), do not require antibiotics, and meet food safety requirements.

[0159] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for extending the shelf life of prunes, characterized in that: include: 1) Disinfection: Before storing prunes, spray the temperature-controlled fresh-keeping room with 75% to 80% anhydrous ethanol. After disinfection for 24 hours, start circulating ventilation for 8 to 10 hours. 2) Harvesting requirements: Harvested prunes must be free of pests and diseases, free of mechanical damage, with the fruit frost intact and a sugar content of ≥20%; 3) Pre-cooling: Pre-cool the harvested prunes to 2-2.2°C using portable pressure differential cooling for a rapid cooling time of ≤10 hours. 4) Electrostatic atomization spraying: After pre-cooling, methyl jasmonate aqueous solution is electrostatically sprayed on the prunes; 5) Fumigation treatment: After electrostatic atomization spraying, use 1-methylcyclopropene to fumigate the fruit in a closed temperature storage for 18 to 20 hours, and then start the machine for 2 to 3 hours to allow air circulation; 6) Storage at near-freezing temperature: After fumigation, the prunes are stored at near-freezing temperature in a warehouse with a suitable temperature; 7) Intermittent nano-atomization sterilization: During storage, hydrogen peroxide aqueous solution is used to sterilize the environment and prunes intermittently using nano-atomization, with the interval between each sterilization being 15 to 18 days.

2. The method for extending the shelf life of prunes according to claim 1, wherein: Place a piece of 18cm x 25cm plastic wrap per 2kg of prunes in the pre-cooled prunes. The fresh-keeping paper is prepared by soaking sterile polypropylene non-woven fabric in an antibacterial solution for 5 to 7 minutes, draining, and drying at room temperature until the moisture content is 10 to 15%. The preparation method of the antibacterial liquid comprises the following steps: Dilute the bamboo vinegar solution to 150-250 mL / L to obtain a bamboo vinegar dilution solution; Add curcumin to the bamboo vinegar dilution solution and stir evenly, then add tea polyphenols and stir evenly; wherein, 0.03-0.07 g of curcumin is added to each liter of bamboo vinegar dilution; Add 0.01-0.05g of tea polyphenols to each liter of bamboo vinegar dilution.

3. The method for extending the shelf life of prunes according to claim 2, wherein: The bamboo vinegar solution was diluted to 200 mL / L, and 0.05 g of curcumin was added to each liter of the bamboo vinegar solution; and 0.03 g of tea polyphenols was added to each liter of the bamboo vinegar solution.

4. The method for extending the shelf life of prunes according to claim 1, wherein: The concentration of the methyl jasmonate aqueous solution is 0.01 mmol / L, the atomized particle size is ≤2.0 μm, and the droplet charge-to-mass ratio is 5-8 mC / kg. The process parameters of the electrostatic atomizer sprayer for post-harvest plum preservation are: elevator speed 12 Hz, conveyor plate rolling angle 3.0°, reversing speed 6.5 Hz, and electrostatic voltage 6-10 kV. The mass volume ratio of 1-methylcyclopropene to the fumigation space is 0.4-0.5 mg / m 3 ; The near-freezing storage temperature is -1.5 to -1.2°C, the relative humidity is 85 to 87%, the oxygen volume concentration in the phase temperature storage is 3.5 to 4%, the carbon dioxide volume concentration is 3 to 5%, and the nitrogen volume concentration is 85 to 90%; The mass concentration of the hydrogen peroxide aqueous solution is 2-3%, and the atomized particle size is ≤1.0 μm.

5. The method for extending the shelf life of prunes according to claim 1, wherein: The disinfection process in step 1) includes the following steps: Before storing prunes, use electrostatic spray equipment with a particle size of 50 to 100 μm to spray 75% anhydrous ethanol at a rate of 10 to 15 mL / m 3 Evenly spray the amount on the inner surface of the temperature preservation warehouse; After spraying is completed, the ozone generator is immediately turned on to maintain the ozone concentration at 5-8 ppm in the environment sprayed with ethanol for 2 hours; After turning off the ozone generator, maintain the temperature in the warehouse at 25-28°C and the relative humidity at 40-45% for 22 hours of closed disinfection; After disinfection is completed, first turn on the external circulation ventilation system for 3 hours, then switch to internal circulation ventilation for 5 to 7 hours. During ventilation, control the air flow speed to 0.5 to 0.8 m / s.

6. The method for extending the shelf life of prunes according to claim 1, wherein: In the electrostatic atomization spraying step in step 4), the following components are added to the methyl jasmonate aqueous solution before electrostatic atomization spraying: bentonite-loaded slow-release particles, gelatin-tannic acid composite liquid and nisin microcapsules; The composite method includes the following steps: Bentonite and methyl jasmonate were mixed uniformly in a mass ratio of 10:1, calcined at 400-500°C for 2h, and then ultrafinely ground to a particle size of ≤2.0μm using a jet mill to obtain bentonite-loaded slow-release particles; Gelatin and tannic acid were dissolved in deionized water at a mass ratio of 4:1, stirred at 60°C, and then cooled to 25°C to obtain a gelatin-tannic acid composite solution; Nisin was mixed with a 2% sodium alginate solution at a mass ratio of 1:5, and then added dropwise to a 5% calcium chloride aqueous solution, wherein the volume ratio of the calcium chloride aqueous solution to the sodium alginate solution was 4:

1. After cross-linking for 30 minutes, the mixture was centrifuged and dried to prepare nisin microcapsules with a particle size of ≤2 μm. Bentonite-loaded slow-release particles, gelatin-tannic acid composite liquid and nisin microcapsules are added to a methyl jasmonate aqueous solution, and the mixture is adjusted to a methyl jasmonate concentration of 0.01 mmol / L by adding deionized water or concentrating the mixture. The amount of the bentonite-loaded slow-release particles is 0.2-0.4 g / L, the amount of the gelatin-tannic acid composite liquid is 0.1-0.3 g / L, and the amount of the nisin microcapsules is 0.05-0.1 g / L.

7. The method for extending the shelf life of prunes according to claim 1, wherein: In the fumigation treatment step in step 5), a porous starch-based carrier is used to load 1-methylcyclopropene, and nano zinc oxide and bimetallic organic framework particles are compounded, specifically comprising the following steps: Porous starch-based carrier loaded with 1-methylcyclopropene: Porous starch was mixed with 1-methylcyclopropene in a mass ratio of 20:1 in a sealed container, the temperature was controlled at 40-50°C and the pressure was controlled at 0.1-0.2 MPa. After adsorption for 12 hours, a sustained-release carrier with a loading rate of 85-90% was obtained; Composite nano-zinc oxide and bimetallic organic framework particles: Nano-zinc oxide with a particle size of ≤50nm and bimetallic ZIF-8@Cu particles are compounded in a mass ratio of 1:2 to form an antibacterial-ethylene decomposition composite; The sustained-release carrier and the compound are evenly dispersed in a phase temperature storage at a mass ratio of 5:1, and fumigated in a closed environment with a controlled temperature of -1.5 to -1.2°C and a humidity of 85 to 87%. After fumigation, the circulating ventilation system was started and the UV-visible composite light source was turned on simultaneously to activate the photocatalytic properties of ZIF-8@Cu and degrade the residual gas to an ethylene concentration of ≤5ppm and a total microbial count of ≤10CFU / m 3 .

8. The method for extending the shelf life of prunes according to claim 1, wherein: In step 7), intermittent nano-atomization sterilization specifically includes the following steps: A hydrogen peroxide solution with a mass concentration of 2-3% and a food-grade nisin solution with a mass concentration of 0.1-0.3% are compounded in a volume ratio of 4:1 to form a synergistic bactericidal solution, and intermittent nano-atomization sterilization is performed through the synergistic bactericidal solution; Microbial concentration sensors are placed in the fruit storage area, shelf gaps, and ventilation openings of the phase temperature warehouse. Starting from the completion of each sterilization treatment and the start of a new sterilization interval, the total number of environmental microorganisms is collected every 24 hours for three consecutive monitoring sessions. Temperature and humidity sensors are evenly installed at the top, middle, and bottom of the warehouse to monitor temperature and relative humidity in real time and calculate the surface condensation risk index (RH-T index). RH-T index = real-time relative humidity / saturated relative humidity at the current temperature. If the total number of microorganisms is lower than 50 CFU / m3 for three consecutive monitoring 3 , and when the RH-T index is lower than 0.5, the sterilization interval is extended from 15-18 days to 20 days; When the total number of microorganisms monitored at any time exceeds 80 CFU / m 3 Or when the RH-T index exceeds 0.7, the sterilization interval is shortened from 15 to 18 days to 12 days; When the total number of microorganisms monitored at any time exceeds 100 CFU / m 3 Or when the RH-T index exceeds 0.8, start the nano-atomization equipment and spray the hydrogen peroxide synergistic sterilization solution; the atomization particle size of the nano-atomization equipment does not exceed 1.0μm, the droplet charge-to-mass ratio is 5-8mC / kg, and the single spraying volume is 0.5-1.0mL / m 3 , spraying time 5 to 10 minutes.

9. The method for extending the shelf life of prunes according to claim 2, wherein: The antibacterial solution also contains chitosan-β-cyclodextrin sustained-release microspheres; The preparation method of chitosan-β-cyclodextrin sustained-release microspheres is as follows: β-cyclodextrin and chitosan were dissolved in deionized water to form a mixed solution with a chitosan concentration of 0.02 g / mL and a β-cyclodextrin concentration of 0.06 g / mL; The mixed solution was mixed with a 0.1% citric acid solution at a volume ratio of 1:4 and ultrasonically dispersed for 30 min. Calcium chloride solution with a mass concentration of 0.5% was added dropwise, and the ratio of the total mass of β-cyclodextrin and chitosan to the volume of the calcium chloride solution was 0.2 g / mL. After stirring for 2 h, the mixture was centrifuged and dried, and passed through a 100-mesh sieve to prepare chitosan-β-cyclodextrin sustained-release microspheres. Add 1-2 g of microspheres per liter of antibacterial solution; The specific preparation method of fresh-keeping paper is: Immerse the non-woven fabric in an antibacterial solution containing microspheres and soak it at a pressure of -0.05 MPa for 8 to 10 minutes to allow the microspheres to embed into the gaps between fibers. After draining, dry at 40℃ for 1h, then dry at room temperature until the moisture content is 10-15%.

10. The method for extending the shelf life of prunes according to claim 1, wherein: In step 3), the portable pressure differential pre-cooling treatment adopts a graded pre-cooling method, which specifically includes the following steps: Initial cooling stage: at 3°C, use a portable pressure differential pre-cooling device with a pressure differential of 60 Pa and a wind speed of 0.6 m / s for 4 hours to reduce the core temperature of the fruit from 25°C to 10°C; Fine cooling stage: Adjust the portable pressure differential pre-cooling equipment to 80Pa pressure differential and 0.8m / s wind speed, and process at 2.5℃ for 4 hours to reduce the core temperature to 4℃; Final cooling stage: adjust the pressure difference to 70Pa, treat at 2.0℃ for 1.5h, and finally make the overall temperature of the fruit reach 2.1℃; Temperature stability: maintain the temperature difference within 0.2℃ for 0.5h.

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