Preparation method and application method of multi-effect fruit and vegetable preservative solution

Abstract

This invention discloses a method for preparing and applying a multifunctional fruit and vegetable preservative solution. The preservative is made from the following raw materials in the indicated mass fractions: 0.5-0.8% organic acid, 0.2-1.0% polyethylene glycol, 0.2-0.5% glycerol, 0.4-1.5% sodium benzoate, 0.3-1.5% potassium sorbate, with the remainder being water. The application method involves evenly spraying the preservative solution onto the surface of fruits and vegetables. In summer, spray every 25-30 minutes; in winter… Spray every 30-45 minutes; for perishable fruits and vegetables, soak for 1-10 minutes, drain, and then spray. The polyethylene glycol in this invention is rich in ether bonds, providing acid buffering and spreading effects, as well as synergistic water-retention with hydroxyl-containing glycerol. It forms a colorless protective layer on the surface of fruits and vegetables and synergistically enhances the antibacterial effects of sodium benzoate and potassium sorbate under acidic conditions, achieving multiple functions including water retention to prevent wilting, rot prevention, color protection, anti-oxidation and anti-fading, and washing away pesticide residues from the surface of fruits and vegetables. This invention has a simple preparation process, low cost, and is suitable for preserving fruits and vegetables on open shelves in supermarkets and farmers' markets.

Description

Technical Field

[0001] This invention relates to the field of fruit and vegetable storage and preservation technology, and in particular to a method for preparing a multifunctional fruit and vegetable preservative solution. Background Technology

[0002] my country is a major producer and consumer of fruits and vegetables. However, due to improper preservation techniques or a lack of efficient and low-cost preservatives, the losses of fruits and vegetables during post-harvest distribution are staggering. According to reports, due to the lack of preservation technology, the average rate of water loss and rot in my country's fruits and vegetables is over 7%, resulting in losses of hundreds of billions of yuan annually for farmers, vendors, and supermarkets. Especially in summer, supermarkets and farmers' markets lack safe preservatives that simultaneously retain moisture and prevent decay, leading to wilting and rot rates of fresh fruits and vegetables exceeding 15%, causing severe economic losses for businesses. An ideal preservative for fresh fruits and vegetables needs to possess three core characteristics: (1) safety, meaning that the ingredients must strictly comply with national food safety regulations and standards, and have no toxic side effects on the human body after treatment; (2) water retention, meaning that it can inhibit the evaporation of water from fruits and vegetables and prevent wilting; and (3) antiseptic properties, meaning that it can effectively inhibit the growth of microorganisms and prevent spoilage. However, existing preservation technologies and products have many insurmountable defects: First, existing mainstream products are outdated, have high barriers to entry, and are ineffective. Currently, commercially available preservatives have limited ingredients, such as benzoic acid, sodium benzoate, sorbic acid, or potassium sorbate, and are mostly sold in solid form. Because these preservatives require acidic conditions to be effective, and their concentration is typically below 1.5%, it is extremely difficult for ordinary farmers and vendors to accurately control the concentration, dissolution method, and pH adjustment. This results in highly unstable performance of these solid powders in practical applications, hindering their widespread adoption. Furthermore, while there are occasional cases of using disinfectants such as chlorine dioxide and hypochlorite for preservation, these substances only have bactericidal properties and do not retain moisture or prevent evaporation, thus failing to address the problem of fruit and vegetable wilting due to dehydration. Secondly, existing patented technologies are complex in composition and expensive, making them difficult to commercialize. Many published patent documents reveal preservative formulations that often contain numerous components and involve cumbersome preparation processes. For example, patent application CN201710933424.7 discloses a preservative containing nine ingredients, including extracts from 12 kinds of traditional Chinese herbs; patent application CN201810849181.3 contains as many as 12 ingredients. Such complex formulations not only increase production costs but also raise the difficulty of industrial production. Some patented technologies involve high-cost ingredients, such as "p-coumaric acid ester" used in authorization publication number CN107927149B. Whether naturally extracted or chemically synthesized, its cost is extremely high, making large-scale promotion in the agricultural trade sector economically unfeasible. Third, the overuse and illegal use of pesticides pose serious food safety risks. This is currently the most severe problem in the fruit and vegetable preservation industry. Many existing technologies directly contain pesticides such as thiamethoxam, prochloraz, imazalil, 2,4-D, and bacitracin in their formulations. According to national food safety regulations, these pesticides are mainly used in pre-harvest agricultural production and are strictly restricted or prohibited in post-harvest processing of fruits and vegetables. However, according to investigations, more than 10,000 citrus fruit sorting plants across the country generally operate illegally, adding large amounts of the aforementioned pesticides to the fruit washing tanks for sterilization and preservation, resulting in excessive pesticide residues in agricultural products. For example, in 2024, excessive levels of prochloraz were detected in many places, seriously hindering export trade and threatening public health. In addition, incidents such as the illegal use of unregulated sweeteners to soak bayberries in Zhangzhou, Fujian in May 2026, as well as the illegal use of borax and formaldehyde, all expose the industry's need for safe and compliant preservatives. Fourth, existing technologies often suffer from limited functionality and significant side effects. Many formulations lack water-retention capabilities, failing to prevent rapid water loss from fruits and vegetables on open shelves. Some formulations cannot prevent the oxidation and fading of natural pigments in fruits and vegetables. For example, patent CN201810849181.3 uses starch as a film-forming agent, which can cause milky white spots to form on the surface of fruits and vegetables, severely reducing the product's appearance. Furthermore, certain bioactive components, such as allicin and lysozyme, are extremely unstable in formulations, easily degraded and inactivated, and require stringent storage and transportation conditions, making them unsuitable for grassroots vendors. In other words, existing technologies have the following technical problems: ordinary fruit and vegetable preservatives cannot simultaneously meet the requirements of safety and compliance, low cost, simple process, and basic functions such as water retention, anti-corrosion, and color protection. Therefore, to address the above problems, this invention proposes a method for preparing a multifunctional fruit and vegetable preservative solution and its application method. Summary of the Invention

[0003] This application provides a method for preparing a multifunctional fruit and vegetable preservative solution to address the problem that existing common fruit and vegetable preservatives cannot simultaneously meet the requirements of safety and compliance, low cost, simple process, water retention, corrosion prevention, and color protection. According to one aspect of this application, a method for preparing a multifunctional fruit and vegetable preservative solution is provided, comprising the following steps: 1. Material preparation: Prepare the following raw materials according to the following mass fraction ratio: organic acid 0.5~0.8%, polyethylene glycol 0.2~1.0%, glycerol 0.2~0.5%, sodium benzoate 0.4~1.5%, potassium sorbate 0.3~1.5%, and the balance is water; the organic acid is selected from one or a combination of two of citric acid, malic acid, and maleic acid; 2. Acidification: Add the organic acid to water and stir until completely dissolved to obtain an acidic aqueous solution; 3. Hydration: Add polyethylene glycol to the acidic aqueous solution, stir until completely dissolved, and let stand for 5 minutes to allow the polyethylene glycol to fully form hydrogen bonds with water and hydrate, thus obtaining a hydrated solution; 4. Solubilization: Add glycerol to the hydrated solution and stir until completely dissolved, so that glycerol can fully form hydrogen bonds with polyethylene glycol and water and hydrate to obtain a solubilized solution; 5. Preservative compounding: Sodium benzoate and potassium sorbate are added sequentially to the solubilizing solution and stirred until completely dissolved to obtain the multifunctional fruit and vegetable preservative solution; The pH value of the preservative solution is controlled between 1.8 and 2.8 by adding organic acids and the acidic stabilizing effect of polyethylene glycol. Furthermore, the preservation treatment of fruits or vegetables using the preservative solution prepared by the method of preparing multifunctional fruit and vegetable preservative solution includes the following steps: The prepared preservative solution is sprayed evenly onto the surface of fruits or vegetables, or fruits or vegetables are soaked in the preservative solution. In summer, spray once every 25 to 30 minutes, and in winter, spray once every 30 to 45 minutes. Furthermore, the molecular weight of the polyethylene glycol in step 1 is 2000~6000. Further, the organic acid in step 1 is citric acid; the mass fraction of the citric acid is 0.5%. Further, the mass fraction ratio of the raw materials in step 1 is: citric acid 0.5%, polyethylene glycol 0.2%, glycerol 0.2%, sodium benzoate 0.4%, potassium sorbate 0.3%, and the balance is water. Further, the mass fraction ratio of the raw materials in step 1 is: malic acid 0.65%, polyethylene glycol 0.75%, glycerol 0.35%, sodium benzoate 1.0%, potassium sorbate 0.9%, and the balance is water. Further, the mass fraction ratio of the raw materials in step 1 is: maleic acid 0.8%, polyethylene glycol 1.0%, glycerol 0.5%, sodium benzoate 1.5%, potassium sorbate 1.5%, and the balance is water. Furthermore, the soaking step is for perishable fruits and vegetables, and the soaking time is 1 to 10 minutes; after soaking and draining, the preservative solution is sprayed again according to the spraying frequency corresponding to the season. Furthermore, the preservative solution is stored in the dark at room temperature. Furthermore, the polyethylene glycol rich in ether bonds and glycerol containing hydroxyl groups in the preservative solution work synergistically to form a moisturizing barrier layer on the surface of fruits or vegetables, which is used to block the oxidation of pigments in fruits or vegetables and reduce the evaporation of water from fruits or vegetables. The advantages and innovations of this invention are: 1. This invention has high food safety. After the human body ingests appropriate amounts of polyethylene glycol, its large molecular weight prevents it from being absorbed by the digestive system and it is excreted in feces. Glycerol is an intermediate product of human carbohydrate metabolism and can therefore be consumed in large quantities. Citric acid, malic acid, and maleic acid are commonly used food additives with no toxic side effects on the human body. Benzoate and sorbate have been used for food preservation and freshness preservation internationally for more than 70 years. After the human body ingests appropriate amounts of sodium benzoate, it can be metabolized into hippuric acid and excreted from the body, thus having no toxic side effects on the human body. After the human body ingests appropriate amounts of potassium sorbate, it can be metabolized into carbon dioxide and water and is harmless to the human body. 2. All ingredients used in this invention are permitted food additives, and their concentrations are strictly controlled within the national standard range, thus avoiding the problem of excessive pesticide residues caused by the illegal use of pesticide preservatives. 3. This invention utilizes the synergistic effect of organic acids and polyethylene glycol to control the pH value of the preservative solution within a moderately acidic range of 1.8 to 2.8. This acidic condition falls within the normal range of human gastric acid, ensuring safety and non-toxicity. It also ensures that sodium benzoate and potassium sorbate remain entirely in their ionic state in the solution, avoiding the crystallization and precipitation problems that occur under neutral or alkaline conditions. This enhances the stability and antibacterial effect of the preservative. Therefore, polyethylene glycol acts as an acid buffer and stabilizer in this invention. 4. This invention is the first to utilize the synergistic effect of organic molecules rich in ether bonds and organic molecules rich in hydroxyl groups to form strong hydrogen bonds with water molecules in the preservative solution, ensuring the preservative has water-locking, water-retaining, and moisturizing effects. Polyethylene glycol (PEG) molecules are rich in ether bonds, enabling them to form strong hydrogen bonds with water molecules in the preservative solution. In addition, PEG has a large molecular weight and is not easily volatile. These characteristics allow PEG to greatly reduce water evaporation, thus exhibiting significant water-locking, water-retaining, and moisturizing effects. Glycerol molecules contain three hydroxyl groups, which can form strong hydrogen bonds with water and PEG molecules in the solution. Glycerol is also not easily volatile and is currently recognized as one of the most effective water-retaining and moisturizing agents. Therefore, this invention overcomes the shortcoming of commonly used preservatives that lack water-retaining properties. 5. The organic acids and glycerol used in this invention have strong antioxidant capabilities, and polyethylene glycol also has a certain antioxidant capability. In addition, these substances are not easily volatilized or decomposed. The resulting preservative solution can form a protective film on the surface of fruits and vegetables, preventing the pigments of fruits and vegetables from being oxidized. Therefore, the preservative prepared by this invention has excellent color protection and freshness preservation effects. 6. This invention can maintain the appearance quality of fruits and vegetables and avoid sensory degradation. Unlike the existing technology that uses starch as a film-forming agent, which easily leads to milky white spots on the surface of fruits and vegetables and reduces the appearance quality of the product, the substance selected in this invention forms a colorless and transparent moisturizing layer on the surface of fruits and vegetables, without producing color spots or powder spots. Combined with its color protection function, it can significantly improve the freshness and commercial value of fruits and vegetables during the shelf life. 7. The polyethylene glycol and glycerol molecules used in this invention have high kinematic viscosity and can form strong surface tension, which enhances the "adhesion" of the preservative solution to the surface of fruits and vegetables, acts as a spreading agent, and enhances the overall efficacy of the preservative. 8. The polyethylene glycol and glycerol used in this invention are amphoteric solvents with strong washing effects on organic compounds, which can wash off the organic pesticide residues on the surface of fruits and vegetables, thus enhancing the safety benefits of this invention. 9. The preparation process and raw material costs of this invention are low, and it has the potential for large-scale market application. The selected raw materials are all common food additives that are mass-produced in the industry and are inexpensive. At the same time, this invention eliminates complex reaction or extraction steps, is easy to operate, does not require special equipment, and has the advantage of low cost. 10. The application of this invention is flexible and efficient, and it is suitable for high-frequency operation scenarios in supermarkets and farmers' markets. Attached Figure Description To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 This is a schematic diagram of the preservation effect of spinach in the experimental group of Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the effect of the spinach control group in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the preservation effect of the Spring Snow Peach experimental group in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the effect of the control group of Spring Snow Peach in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the preservation effect of red amaranth in the experimental group of Embodiment 2 of the present invention; Figure 6 This is a schematic diagram of the effect of the red amaranth control group in Embodiment 2 of the present invention; Figure 7 This is a schematic diagram of the preservation effect of lychee in the experimental group of Embodiment 2 of the present invention; Figure 8 This is a schematic diagram of the effect of the litchi control group in Example 2 of the present invention; Figure 9 This is a schematic diagram of the preservation effect of water spinach in the experimental group of Embodiment 3 of the present invention; Figure 10 This is a schematic diagram of the effect of the water spinach control group in Embodiment 3 of the present invention; Figure 11 This is a schematic diagram of the preservation effect of dragon fruit in the experimental group of Embodiment 3 of the present invention; Figure 12 This is a schematic diagram of the effect of the dragon fruit control group in Example 3 of the present invention; Figure 13 This is a schematic diagram of the preparation method of a multifunctional fruit and vegetable preservative solution according to an embodiment of the present invention. Detailed Implementation To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention. Please see Figure 13 As shown, a method for preparing a multifunctional fruit and vegetable preservative solution includes the following steps: (1) Preparation of raw materials: Prepare the following raw materials according to the mass fraction ratio: organic acid 0.5~0.8%, polyethylene glycol 0.2~1.0%, glycerol 0.2~0.5%, sodium benzoate 0.4~1.5%, potassium sorbate 0.3~1.5%, and the balance is water; the organic acid is selected from one or a combination of two of citric acid, malic acid and maleic acid; (2) Acidification: Add organic acid to water and stir until completely dissolved to obtain an acidic aqueous solution; (3) Hydration: Add polyethylene glycol to the acidic aqueous solution, stir until completely dissolved, and let stand for 5 minutes to allow polyethylene glycol to fully form hydrogen bonds with water and hydrate, thus obtaining a hydrated solution; (4) Solubilization: Add glycerol to the hydrated solution and stir until completely dissolved, so that glycerol can fully form hydrogen bonds with water and polyethylene glycol molecules and hydrate to obtain a solubilized solution; (5) Preservative compounding: Sodium benzoate and potassium sorbate are added sequentially to the solubilizing solution and stirred until completely dissolved to obtain the multifunctional fruit and vegetable preservative solution. Furthermore, the preservation treatment of fruits or vegetables using the preservative solution prepared by the method of preparing multifunctional fruit and vegetable preservative solution includes the following steps: The prepared preservative solution is sprayed evenly onto the surface of fruits or vegetables, or fruits or vegetables are soaked in the preservative solution. In summer, spray every 25-30 minutes; in winter, spray every 30-45 minutes. Before implementing specific embodiments, it is necessary to understand the synergistic mechanism of the components of this invention during the preparation process: First, by adding organic acids in conjunction with the acidic stabilizer properties of polyethylene glycol, this invention controls the pH value of the preservative solution between 1.8 and 2.8. This pH range is within the normal range of human stomach acid, ensuring food safety. More importantly, sodium benzoate and potassium sorbate are prone to crystallization in neutral or alkaline solutions, but in the moderately acidic environment constructed by this invention, these two preservatives can remain in a completely ionic state, significantly enhancing their antibacterial effect. At the same time, the organic acids not only provide an acidic environment but also possess significant antioxidant, preservative, and color-protecting effects. Secondly, polyethylene glycol (PEG) not only has a strong water-retaining and moisturizing effect in this system, but also has a strong hydrogen bonding ability due to the many ether bonds it contains. The step of letting it stand for 5 minutes after stirring and dissolving is to ensure that it is fully hydrated with water molecules. This process makes PEG also act as an "acid buffer" to maintain the stability of the solution pH. At the same time, as an amphoteric solvent of inorganic and organic, it promotes the dissolution of sodium benzoate and potassium sorbate and enhances their stability. In addition, polyethylene glycol has a large molecular weight and is not easily volatile. Its kinematic viscosity gives the solution good affinity to the surface of fruits and vegetables, acting as a "spreading agent" and enhancing the antibacterial and water-retaining effects. Furthermore, its stable structure and reputation as an inert molecule mean it does not react with oxygen at room temperature, forming an isolation layer on the surface of fruits and vegetables to prevent pigment oxidation. Finally, glycerol, as an intermediate product of human carbohydrate metabolism, synergistically forms a dual water-retaining and moisturizing system with polyethylene glycol. Glycerol itself has water-retaining, moisturizing, antioxidant, and color-protecting effects. It is worth mentioning that polyethylene glycol and glycerol, as amphoteric solvents, have a strong washing effect on organic compounds and can wash off residual organic pesticides on the surface of fruits and vegetables. This is an additional safety benefit of this invention. Example 1: This embodiment provides a multifunctional fruit and vegetable preservative solution and its application on spinach and peaches. The multifunctional fruit and vegetable preservative solution contains the following components by mass fraction: citric acid 0.5%, polyethylene glycol 0.2%, glycerol 0.2%, sodium benzoate 0.4%, potassium sorbate 0.3%, and water 98.4%. To prepare 20 kg of the multifunctional fruit and vegetable preservative solution, the specific steps include the following: A. Preparation: Accurately weigh 100g of citric acid, 40g of polyethylene glycol, 40g of glycerol, 80g of sodium benzoate, 60g of potassium sorbate, and 19680g of water, and place them in clean containers. B. Acidification: Add the weighed citric acid to a container filled with water and stir continuously until the citric acid crystals are completely dissolved, forming a uniform acidic aqueous solution. At this point, the pH value of the solution is measured to be within the target range. C. Hydration: Add 40 g of polyethylene glycol to the above acidic aqueous solution and stir until the polyethylene glycol is completely dissolved. Then, stop stirring and let stand for 5 minutes. As described in the aforementioned mechanism, this step is to enable the long-chain molecules of polyethylene glycol to fully form hydrogen bonds with water molecules, complete the hydration process, and fully exert their functions as an "acid buffer" and "spreading agent," laying the foundation for the subsequent preservative solution to have the functions of water retention and oxygen barrier. D. Solubilization: Add 40 grams of glycerol to the hydrated solution and stir until completely dissolved. At this point, the solution system is more homogeneous and stable. E. Preservative compounding: Add 80g of sodium benzoate and 60g of potassium sorbate to the mixed solution in sequence, and stir until the two preservatives are completely dissolved and there are no visible particles. F. The resulting mixed solution is the preservative solution of this embodiment. After testing, its pH value is 2.3, which meets the design requirements. The solution is transferred to a light-proof container and stored at room temperature for later use. Application method and efficacy verification of the multifunctional fruit and vegetable preservative solution: A. Freshly harvested "Huabo No. 1" spinach and "Chunxue Peach" were selected as experimental subjects. Experimental group: The preservative solution prepared above was injected into a manual spray bottle and evenly sprayed onto the surface of spinach leaves and peach fruits, ensuring the formation of a uniform liquid film without dripping. Spraying was performed every 30 minutes in a summer room temperature environment. This high-frequency spraying strategy was designed to address the rapid evaporation of moisture from fruits and vegetables under high temperature and humidity conditions in summer, and to continuously replenish the moisturizing layer on the surface of fruits and vegetables. Control group: No preservatives were used; the food was simply left to stand naturally. B. Result Observation: After 36 hours of storage, such as Figure 1 and Figure 2 As shown, the spinach in the experimental group, "Huabo No. 1", remained bright green with upright leaves and showed no signs of wilting or rotting; while the spinach in the control group had faded significantly and the leaves had shriveled and rotted after 36 hours. After 72 hours of storage, such as Figure 3 and Figure 4As shown, the "Spring Snow Peach" in the experimental group was plump, brightly colored, and showed no signs of wilting; the peaches in the control group showed obvious skin wrinkling, dehydration, and wilting after 72 hours, and began to rot, subsequently attracting fruit flies and accelerating the decay process. Once peaches and other fruits begin to rot, the microorganisms within them ferment and produce acetic acid and lactic acid. Combined with the sweetness of the fruit, this attracts small insects such as fruit flies to feed on them, accelerating the decay process. This invention effectively breaks this vicious cycle by inhibiting the growth of microorganisms. This embodiment demonstrates that the preservative effectively blocks water evaporation by forming a water-retaining and color-protecting protective layer on the surface of fruits and vegetables, and greatly inhibits microbial growth in an acidic environment by utilizing preservatives, thus maintaining the freshness of fruits and vegetables. Example 2: This embodiment provides a multifunctional fruit and vegetable preservative solution and its application on red amaranth and lychee. The multifunctional fruit and vegetable preservative solution is composed of the following raw materials by mass fraction: malic acid 0.65%, polyethylene glycol 0.75%, glycerol 0.35%, sodium benzoate 1.0%, potassium sorbate 0.9%, and water 96.35%. The specific steps for preparing 20 kg of the multifunctional fruit and vegetable preservative solution are as follows: A. Preparation of materials: Weigh out 130g malic acid, 150g polyethylene glycol, 70g glycerol, 200g sodium benzoate, 180g potassium sorbate, and 19270g water. B. Acidification: Add malic acid to water and stir to dissolve. C. Hydration: Add polyethylene glycol, stir to dissolve, and let stand for 5 minutes to promote hydrogen bonding and hydration. Because the polyethylene glycol used in this example has a relatively large molecular weight, as the molecular weight of polyethylene glycol increases, the network structure formed by its hydration becomes more compact, and its ability to block oxygen is correspondingly enhanced. D. Solubilization: Add glycerol and stir until homogeneous. E. Antiseptic compound: Add sodium benzoate and potassium sorbate in sequence and stir until completely dissolved. F. The pH value of the resulting solution is stable at around 2.55. Store it in the dark at room temperature. Application method and efficacy verification of the multifunctional fruit and vegetable preservative solution: A. Select "Jingyi Nuo Amaranth" and "Red Shell" lychee as experimental subjects. Experimental group: The fruits and vegetables in the experimental group were evenly sprayed using a spray bottle, once every 30 minutes. For lychees, in addition to spraying, an auxiliary soaking treatment was also performed, with a soaking time of about 5 minutes. After draining, they were sprayed again. For lychees, a fruit whose skin is extremely prone to browning and mold growth, the soaking treatment can wash away pesticide residues on the surface of the peel, while allowing the preservative to fully penetrate the crevices, forming a three-dimensional protection in conjunction with the subsequent spraying. Control group: placed naturally. B. Results observation, see reference. Figure 5 and Figure 6 As shown, after 36 hours, the red amaranth in the experimental group remained deep purplish-red, with fresh leaves and no wilting; while the red amaranth in the control group showed severe discoloration and wilting. For lychee, see [link / reference] Figure 7 and Figure 8 As shown, the fruit shells of the experimental group remained bright red after 72 hours, without browning or mold growth; while the fruit shells of the control group began to brown after 18 hours, and by 72 hours they were severely moldy and spoiled. This embodiment verifies the significant effect of the synergistic effect of polyethylene glycol and glycerol in color protection, especially for red amaranth rich in anthocyanins and lychee which is prone to browning, its ability to isolate oxygen and prevent pigment oxidation is particularly outstanding. Example 3: This embodiment provides a multifunctional fruit and vegetable preservative solution and its application on water spinach and dragon fruit. The multifunctional fruit and vegetable preservative solution is composed of the following raw materials by mass fraction: maleic acid 0.8%, polyethylene glycol 1.0%, glycerol 0.5%, sodium benzoate 1.5%, potassium sorbate 1.5%, and water 93.7%. The specific steps for preparing 20 kg of the multifunctional fruit and vegetable preservative solution are as follows: A. Preparation of materials: Weigh out 160g maleic acid, 200g polyethylene glycol, 100g glycerol, 300g sodium benzoate, 300g potassium sorbate, and 18740g water. B. Acidification: Add maleic acid to water and stir to dissolve. The strong acidity provided by maleic acid further enhances the anti-corrosion basis of the system. C. Hydration: Adding high molecular weight polyethylene glycol (PEG) is crucial. Due to its longer molecular chains, the step of stirring and allowing it to stand for 5 minutes after dissolving is even more critical to ensure full hydration and the formation of a high-viscosity moisturizing network structure. High molecular weight PEG has greater viscosity and acts as a better "spreading agent," adhering more effectively to the surface of fruits and vegetables and reducing runoff loss. D. Solubilization: Glycerol is added to further enhance the moisturizing properties of the system. E. Antiseptic compound: Add sodium benzoate and potassium sorbate in sequence and stir to dissolve. F. The pH of the resulting solution is 2.2. Store in the dark at room temperature. Application method and efficacy verification of the multifunctional fruit and vegetable preservative solution: A. Select "Green-stemmed Long-leaf Water Spinach" and "Red Crystal" dragon fruit as experimental subjects. Experimental group: The surface of fruits and vegetables was sprayed evenly every 30 minutes. For dragon fruit, the same combined treatment method of soaking followed by spraying was used. Dragon fruit is a tropical fruit and is very sensitive to mold. Its skin is also prone to water loss and wrinkling. This combined treatment method can effectively extend its shelf life. Control group: placed naturally. B. Results observation, see reference. Figure 9 and Figure 10 As shown, after 36 hours, the water spinach leaves in the experimental group were fully expanded and remained bright green and fresh; the water spinach in the control group had severely wilted and the leaf edges were curled. See after 72 hours. Figure 11 and Figure 12 As shown, the "Red Crystal" dragon fruit in the experimental group had no mold spots on its skin and a normal color; while the dragon fruit in the control group showed obvious wilting and mold. This embodiment demonstrates the ability of high molecular weight polyethylene glycol to construct physical barrier layers and prevent moisture evaporation, making it particularly suitable for tropical fruits such as dragon fruit that are susceptible to microbial contamination. In summary, by adjusting the type of organic acid and the molecular weight and amount of polyethylene glycol, this invention can flexibly meet the preservation needs of different types and characteristics of fruits and vegetables, especially the functions of high molecular weight polyethylene glycol in constructing physical barrier layers, preventing moisture evaporation, anti-oxidation, and color protection. In its application, the present invention offers high flexibility in its methods: Specifically, a combination of spraying and soaking can be used. For example, for fruits and vegetables such as spinach, lychee, and dragon fruit that are prone to water loss or rotting, it is recommended to use a "soaking combined with high-frequency spraying" method. Soaking time is usually 1 to 10 minutes. This not only quickly replenishes moisture but also utilizes the amphoteric solvent properties of polyethylene glycol and glycerol to effectively wash away residual organic pesticides on the surface of fruits and vegetables, such as imazalil and acetamiprid. Afterward, drain the water and perform high-frequency spraying to maintain the protective layer. It can also be adjusted according to the season. Due to the influence of temperature and humidity on the rate of water evaporation, the spraying frequency is set to once every 25 to 30 minutes during the high temperature of summer; and once every 30 to 45 minutes during the low temperature of winter when water evaporation slows down. This dynamic adjustment method is very suitable for the management of open shelves in farmers' markets and supermarkets. Meanwhile, all components of this invention are nationally approved food additives; Among them, sodium benzoate and potassium sorbate are used in low-volume, high-efficiency conditions under acidic conditions, ensuring food safety; polyethylene glycol is not absorbed by the human digestive tract due to its large molecular weight, and glycerol is an intermediate product of human metabolism; citric acid, malic acid, and maleic acid are three commonly used preservatives, and appropriate intake can be absorbed and decomposed by the human body without toxic side effects; therefore, the design of this invention ensures safety for long-term use. This is fundamentally different from the current practice of illegally using borax, formaldehyde, or pesticide-based preservatives in the market, and it solves the food safety hazards caused by the illegal use of pesticides for preservation in places such as fruit and vegetable sorting centers. The advantages and innovations of this invention are: 1. This invention has high food safety. After the human body ingests appropriate amounts of polyethylene glycol, its large molecular weight prevents it from being absorbed by the digestive system and it is excreted in feces. Glycerol is an intermediate product of human carbohydrate metabolism and can therefore be consumed in large quantities. Citric acid, malic acid, and maleic acid are commonly used food additives with no toxic side effects on the human body. Benzoate and sorbate have been used for food preservation and freshness preservation internationally for more than 70 years. After the human body ingests appropriate amounts of sodium benzoate, it can be metabolized into hippuric acid and excreted from the body, thus having no toxic side effects on the human body. After the human body ingests appropriate amounts of potassium sorbate, it can be metabolized into carbon dioxide and water and is harmless to the human body. 2. All ingredients used in this invention are permitted food additives, and their concentrations are strictly controlled within the national standard range, thus avoiding the problem of excessive pesticide residues caused by the illegal use of pesticide preservatives. 3. This invention utilizes the synergistic effect of organic acids and polyethylene glycol to control the pH value of the preservative solution within a moderately acidic range of 1.8 to 2.8. This acidic condition falls within the normal range of human stomach acid, ensuring safety and non-toxicity. It also ensures that sodium benzoate and potassium sorbate remain entirely in their ionic state in the solution, preventing the crystallization and precipitation of sodium benzoate and potassium sorbate under neutral or alkaline conditions. This enhances the stability and antibacterial effect of the preservative. Therefore, polyethylene glycol acts as an acid buffer and stabilizer in this invention. 4. The polyethylene glycol (PEG) molecules of this invention are rich in ether bonds, exhibiting strong hydrogen bonding capabilities. Combined with its large molecular weight and low volatility, these characteristics allow PEG to significantly reduce water evaporation, thus providing remarkable water retention and moisturizing effects. Glycerol molecules contain three hydroxyl groups, enabling them to form strong hydrogen bonds with water and PEG molecules in solution. Glycerol is also not easily volatile and is currently recognized as one of the most effective water-retaining and moisturizing agents. Therefore, this invention overcomes the shortcomings of commonly used preservatives that lack water-retaining properties. 5. The organic acids and glycerol used in this invention have strong antioxidant capabilities, and polyethylene glycol also has a certain antioxidant capability. In addition, these substances are not easily volatilized or decomposed. The resulting preservative solution can form a protective film on the surface of fruits and vegetables, preventing the pigments of fruits and vegetables from being oxidized. Therefore, the preservative prepared by this invention has excellent color protection and freshness preservation effects. 6. This invention can maintain the appearance quality of fruits and vegetables and avoid sensory degradation. Unlike the existing technology that uses starch as a film-forming agent, which easily leads to milky white spots on the surface of fruits and vegetables and reduces the appearance quality of the product, the substance selected in this invention forms a colorless and transparent moisturizing layer on the surface of fruits and vegetables, without producing color spots or powder spots. Combined with its color protection function, it can significantly improve the freshness and commercial value of fruits and vegetables during the shelf life. 7. The polyethylene glycol and glycerol used in this invention are amphoteric solvents with strong washing effects on organic compounds, which can wash off the organic pesticide residues on the surface of fruits and vegetables, thus enhancing the safety benefits of this invention. 8. The polyethylene glycol and glycerol molecules used in this invention have high kinematic viscosity and can form strong surface tension, which enhances the "adhesion" of the preservative solution to the surface of fruits and vegetables, acts as a spreading agent, and enhances the overall efficacy of the preservative. 9. The preparation process and raw material costs of this invention are low, and it has the potential for large-scale market application. The selected raw materials are all common food additives that are mass-produced in the industry and are inexpensive. At the same time, this invention eliminates complex reaction or extraction steps, is easy to operate, does not require special equipment, and has the advantage of low cost. 10. The application of this invention is flexible and efficient, and it is suitable for high-frequency operation scenarios in supermarkets and farmers' markets. The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a multifunctional fruit and vegetable preservative solution, characterized in that, Includes the following steps: (1) Preparation of raw materials: Prepare the following raw materials according to the mass fraction ratio: organic acid 0.5~0.8%, polyethylene glycol 0.2~1.0%, glycerol 0.2~0.5%, sodium benzoate 0.4~1.5%, potassium sorbate 0.3~1.5%, and the balance is water; the organic acid is selected from one or a combination of two of citric acid, malic acid and maleic acid; (2) Acidification: Add organic acid to water and stir until completely dissolved to obtain an acidic aqueous solution; (3) Hydration: Add polyethylene glycol to the acidic aqueous solution, stir until completely dissolved, and let stand for 5 minutes to allow polyethylene glycol to fully form hydrogen bonds with water and hydrate, thus obtaining a hydrated solution; (4) Solubilization: Add glycerol to the hydrated solution and stir until completely dissolved, so that glycerol can fully form hydrogen bonds with polyethylene glycol and water and hydrate to obtain a solubilized solution; (5) Preservative compounding: Sodium benzoate and potassium sorbate are added sequentially to the solubilizing solution and stirred until completely dissolved to obtain the multifunctional fruit and vegetable preservative solution; The pH value of the preservative solution is controlled between 1.8 and 2.8 by adding organic acids and the acidic stabilizing effect of polyethylene glycol.

2. A method for applying a multi-functional fruit and vegetable preservative solution, characterized in that, The method for preparing the multifunctional fruit and vegetable preservative solution according to claim 1 is used to preserve fruits or vegetables, comprising the following steps: The prepared preservative solution is sprayed evenly onto the surface of fruits or vegetables, or fruits or vegetables are soaked in the preservative solution before spraying. In summer, spray once every 25 to 30 minutes, and in winter, spray once every 30 to 45 minutes.

3. The method for preparing the multifunctional fruit and vegetable preservative solution according to claim 1, characterized in that, The molecular weight of the polyethylene glycol in step (1) is 2000~6000.

4. The method for preparing the multifunctional fruit and vegetable preservative solution according to claim 1, characterized in that, The organic acid in step (1) is citric acid; the mass fraction of the citric acid is 0.5%.

5. The method for preparing the multifunctional fruit and vegetable preservative solution according to claim 1, characterized in that, The mass fraction ratio of the raw materials in step (1) is: citric acid 0.5%, polyethylene glycol 0.2%, glycerol 0.2%, sodium benzoate 0.4%, potassium sorbate 0.3%, and the remainder is water.

6. The method for preparing the multifunctional fruit and vegetable preservative solution according to claim 1, characterized in that, The mass fraction ratio of the raw materials in step (1) is: malic acid 0.65%, polyethylene glycol 0.75%, glycerol 0.35%, sodium benzoate 1.0%, potassium sorbate 0.9%, and the remainder is water.

7. The method for preparing the multifunctional fruit and vegetable preservative solution according to claim 1, characterized in that, The mass fraction ratio of the raw materials in step (1) is: maleic acid 0.8%, polyethylene glycol 1.0%, glycerol 0.5%, sodium benzoate 1.5%, potassium sorbate 1.5%, and the remainder is water.

8. The application method of the multi-functional fruit and vegetable preservative solution according to claim 2, characterized in that, The soaking step is for perishable fruits and vegetables, and the soaking time is 1 to 10 minutes; after soaking and draining, the preservative solution is sprayed again according to the spraying frequency corresponding to the season.

9. The application method of the multi-functional fruit and vegetable preservative solution according to claim 2, characterized in that, The preservative solution should be stored away from light and at room temperature.

10. The application method of the multifunctional fruit and vegetable preservative solution according to claim 2, characterized in that, The preservative solution contains polyethylene glycol rich in ether bonds and glycerol containing hydroxyl groups, which work synergistically to form a moisturizing barrier layer on the surface of fruits or vegetables, thereby blocking the oxidation of fruit and vegetable pigments and reducing water evaporation.

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