An edible composite preservative solution for low-temperature refrigeration and preservation of fruits and vegetables, a preparation method and a use method thereof

Abstract

The application provides a kind of edible composite preservative solution for low temperature refrigeration of fruit and vegetable, its preparation method and use method, the edible composite preservative solution includes phosphorylated nanocellulose solution, film forming agent, plasticizing agent, biological surfactant and curcumin / cyclodextrin inclusion compound;The film forming agent includes beeswax and / or coconut oil, the plasticizing agent includes glycerol and / or potassium sorbate, and the biological surfactant includes rhamnolipid and / or sophorolipid.The preservative solution provided by the application is composed of phosphorylated nanocellulose solution, film forming agent, plasticizing agent, biological surfactant and curcumin / cyclodextrin inclusion compound.Fruit and vegetable are directly soaked in the preservative solution or the preservative solution is sprayed on the surface of fruit and vegetable, and a complete and dense preservative coating is formed on the surface of fruit and vegetable after natural air drying, the oxygen concentration on the surface of fruit and vegetable is reduced by the respiration of fruit and vegetable, the carbon dioxide concentration is increased, and the controlled atmosphere preservation of fruit and vegetable is realized.

Description

Technical Field

[0001] This invention belongs to the field of fruit and vegetable preservation technology, and relates to an edible composite preservation liquid for low-temperature cold storage and preservation of fruits and vegetables, its preparation method and usage method. Background Technology

[0002] Fresh fruits and vegetables are a popular food choice for naval crews during long voyages. They not only provide abundant vitamins, minerals, and dietary fiber, but also play a vital role in maintaining and improving appetite and promoting the health of officers and soldiers at sea. However, the preservation and storage of fresh fruits and vegetables is a crucial factor affecting their supply during long voyages. Currently, the main preservation method for ocean-going vessels is cold storage, with vegetables having a shelf life of approximately 40 days. This short shelf life and significant losses are major factors limiting the long-term supply of fresh vegetables during long voyages. Edible preservative coatings are a food preservation technology that has emerged in recent years, effectively extending the shelf life of fruits and vegetables and reducing losses in the post-harvest supply chain. Nanocellulose, due to its high strength, gas barrier properties, and excellent film-forming properties, shows great application potential in the field of edible preservative coatings. However, due to its poor water resistance and limited functionality, single-component nanocellulose cannot meet the preservation needs of fruits and vegetables. Therefore, this project focuses on the systematic research of multifunctional coating formulation design and optimization, aiming to develop a high-performance and cost-effective multifunctional fruit and vegetable preservation coating to help achieve a long-term supply of fresh fruits and vegetables on ocean-going ships.

[0003] Nanocellulose, due to its excellent film-forming properties, superior gas barrier properties, and outstanding biocompatibility, has been used as a coating matrix component in recent years to prepare fruit and vegetable preservation / packaging materials. However, the inherent hydrophilicity of nanocellulose causes the barrier performance of nanocellulose preservation coatings to deteriorate or even be destroyed under high relative humidity conditions, thus failing to perform their preservation function. Therefore, the water resistance of nanocellulose is enhanced by surface hydrophobic modification or by physical blending with soybean oil, oleic acid, silica, and sunflower oil.

[0004] Therefore, on the one hand, due to the inherent hydrophilicity of nanocellulose, few nanocellulose coatings can be used for low-temperature and high-humidity preservation; on the other hand, current coatings have poor preservation effects in low-temperature preservation and are limited to fruit preservation, with no reports on coatings for low-temperature preservation of vegetables. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide an edible composite preservative liquid for low-temperature cold storage and preservation of fruits and vegetables, its preparation method and application method. The fruits and vegetables are directly immersed in the preservative liquid or sprayed onto the surface of the fruits and vegetables. After natural drying, a complete and dense preservative coating is formed on the surface of the fruits and vegetables. The oxygen concentration on the surface of the fruits and vegetables is reduced and the carbon dioxide concentration is increased through the respiration of the fruits and vegetables, thereby achieving modified atmosphere preservation of fruits and vegetables.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides an edible composite preservative liquid for low-temperature cold storage and preservation of fruits and vegetables, the edible composite preservative liquid comprising a phosphorylated nanocellulose solution, a film-forming agent, a plasticizer, a biosurfactant, and a curcumin / cyclodextrin inclusion complex.

[0008] The film-forming agent includes beeswax and / or coconut oil, the plasticizer includes glycerin and / or potassium sorbate, and the biosurfactant includes rhamnolipid and / or sophorolipid.

[0009] This invention proposes an edible composite preservative solution for use under low-temperature and high-humidity refrigeration conditions. The preservative solution consists of a phosphorylated nanocellulose solution, a film-forming agent, a plasticizer, a biosurfactant, and a curcumin / cyclodextrin inclusion complex. Fruits and vegetables are directly immersed in the preservative solution or sprayed onto their surface and then allowed to air dry, forming a complete and dense preservative coating. This coating reduces the oxygen concentration and increases the carbon dioxide concentration on the surface of the fruits and vegetables through respiration, achieving modified atmosphere preservation.

[0010] This invention uses phosphorylated nanocellulose as the coating matrix material. The three-dimensional network structure formed by the cross-entanglement of phosphorylated nanocellulose extends the diffusion path of gas in the preservation coating, thereby reducing the gas permeability of the preservation coating, reducing the loss of moisture and nutrients on the surface and inside of fruits and vegetables, and significantly enhancing the mechanical strength of the preservation coating.

[0011] Cyclodextrin has a unique three-dimensional cyclic structure with an internal hydrophobic and external hydrophilic properties. This invention utilizes food-grade, safe, and non-toxic bio-derived cyclodextrin molecules to encapsulate curcumin, enabling curcumin and cyclodextrin to interact via non-covalent bonds. This encapsulates the poorly soluble curcumin within its hydrophobic cavity, forming a curcumin / cyclodextrin inclusion complex. This not only improves the water solubility of curcumin but also mitigates its light-sensitive decomposition, significantly enhancing its water solubility, bioavailability, and antioxidant capacity.

[0012] This invention utilizes phosphorylated nanocellulose, which possesses excellent renewability and biocompatibility, to construct a controlled-release and sustained-release preservative coating. The phosphorylated nanocellulose, with its high aspect ratio and fibrous structure, has a large specific surface area, which is beneficial for deposition and retention on the surface of fruits and vegetables. Furthermore, the large specific surface area increases the loading capacity of curcumin / cyclodextrin inclusion complexes, reducing the loss of curcumin and other active ingredients. Simultaneously, the curcumin / cyclodextrin inclusion complexes are immobilized by hydrogen bonding between the phosphorylated nanocellulose and cyclodextrin molecules, allowing them to be uniformly dispersed in the preservative solution. After coating, the curcumin within the curcumin / cyclodextrin inclusion complexes is contained within the hydrophobic cavities of the cyclodextrin molecules and gradually released, resulting in a long-lasting, sustained-release antibacterial effect.

[0013] In addition to the phosphorylated nanocellulose coating matrix material and the curcumin / cyclodextrin inclusion complex antibacterial sustained-release component, the edible composite preservative solution provided by this invention also contains film-forming agents, plasticizers, and biosurfactants to improve the wettability, film-forming properties, and integrity of the preservative coating. The selected film-forming agents, plasticizers, and biosurfactants are all edible components, posing no toxic side effects to human health, and can be eaten directly with fruits and vegetables or after washing. Specifically, this invention uses beeswax and / or coconut oil as film-forming agents. The hydrophobic properties of beeswax and coconut oil enable the preservative coating to maintain its integrity under low temperature and high humidity conditions, thus enhancing the coating's water resistance. Glycerin and / or potassium sorbate are used as plasticizers to regulate interfacial interactions between components. Rhamnollipids and / or sophorolipids are used as biosurfactants to enhance the wetting effect of the coating solution on the vegetable surface.

[0014] Untreated fruits and vegetables often have numerous cracks and wrinkles on their surfaces, providing ample oxygen permeation channels for respiration. Simultaneously, the increased surface area due to these wrinkles leads to greater effective transpiration of water vapor, resulting in rapid moisture loss. This invention, through immersion in a preservative solution, fills and smooths these cracks and wrinkles, reducing the respiration rate and transpiration area of ​​the fruits and vegetables to some extent, thus acting as a barrier between water vapor and oxygen.

[0015] The preservative liquid provided by this invention has good affinity with the surface of fruits and vegetables. During use, it adheres well to and covers the surface of fruits and vegetables, forming a preservative coating that achieves preservation effects such as blocking gases, retaining water, and preventing nutrient loss. Furthermore, compared to some waxy coatings that are difficult or even impossible to wash off, the preservative coating provided by this invention is easily soluble in water. Before consumption, the preservative coating on the surface of fruits and vegetables can be easily removed with a simple rinse of water, without affecting the taste and eliminating consumer concerns about the safety of the preservative coating. The preservative coating prepared on the surface of cucumbers and rapeseed by dipping or spraying, combined with refrigeration, can extend the shelf life of cucumbers to 30 days and the shelf life of rapeseed to 60 days.

[0016] As a preferred embodiment of the present invention, the mass fraction of the phosphorylated nanocellulose solution is 0.2-0.4 wt%, for example, it can be 0.2 wt%, 0.22 wt%, 0.24 wt%, 0.26 wt%, 0.28 wt%, 0.3 wt%, 0.32 wt%, 0.34 wt%, 0.36 wt%, 0.38 wt%, or 0.4 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0017] Fruits and vegetables release CO2 through respiration within the preservative coating, creating an atmosphere with high CO2 and low O2 content on their surface. This inhibits respiration and slows down the ripening process, achieving the purpose of modified atmosphere preservation. However, higher CO2 concentrations are not always better. For example, when preserving some leafy green vegetables, excessively high CO2 concentrations on the surface can induce anaerobic respiration, leading to the accumulation of harmful toxins and rendering the vegetables unsuitable for consumption.

[0018] The preservative solution provided by this invention can prevent external oxygen from penetrating the preservative coating and entering the interior of fruits and vegetables, while also removing, to a certain extent, excess CO2 accumulated by the fruits and vegetables due to respiration. This is because CO2 has high inductive polarity, which can generate strong intermolecular forces with nanocellulose molecules containing a large number of polar groups, resulting in high solubility of CO2 in the preservative coating and thus exhibiting high CO2 permeability, thereby effectively preventing the accumulation of toxins in fruits and vegetables due to anaerobic respiration.

[0019] Furthermore, the water vapor transmission rate of the preservative coating affects the quality loss rate of fruits and vegetables, and a suitable water vapor transmission rate is an important characteristic of the preservative coating when applied to modified atmosphere storage. This invention forms a cellulose-based preservative inner layer by coating and forming a film. This allows the prepared preservative coating to regulate O2 and CO2 transmission rates while also achieving water retention for fruits and vegetables. This is because nanocellulose molecules have a microscopic network structure with strong water retention properties; simultaneously, the nanocellulose molecular chains contain hydrophilic groups such as hydroxyl groups, giving the preservative coating a strong attraction to water molecules, which slows down water evaporation from the surface of fruits and vegetables, reducing quality loss and effectively adjusting the air humidity on the surface of fruits and vegetables. At the same time, the structure of the preservative coating after impregnation and film formation is more flexible and dense, acting as a barrier for water transport, reducing water loss from the fruit surface, effectively inhibiting water loss and respiration activity during storage, thus reducing respiration consumption and achieving a preservative effect for fruits and vegetables under low-temperature refrigeration.

[0020] This invention specifically limits the mass fraction of the phosphorylated nanocellulose solution to 0.2-0.4 wt%. When the mass fraction of the phosphorylated nanocellulose solution is less than 0.2 wt%, the viscosity of the preservative solution is too low due to the low concentration of phosphorylated nanocellulose, which affects the adhesion of the preservative solution to the surface of fruits and vegetables. Therefore, it is not easy to form a complete preservative coating on the surface of fruits and vegetables by dip coating, and the preservation effect is not achieved. When the mass fraction of the phosphorylated nanocellulose solution is higher than 0.4 wt%, the viscosity of the preservative solution is too high due to the high concentration of phosphorylated nanocellulose, and the fruit and vegetable preservative solution will gel, affecting its processing performance. It is impossible to prepare a preservative coating by dip coating, and the prepared preservative coating has uneven thickness, which affects the actual preservation effect.

[0021] As a preferred embodiment of the present invention, the amount of film-forming agent added is 20-50 wt% based on the dry weight of phosphorylated nanocellulose in the phosphorylated nanocellulose solution. For example, it can be 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, 30 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt%, 40 wt%, 42 wt%, 44 wt%, 46 wt%, 48 wt%, or 50 wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] This invention uses beeswax and coconut oil as film-forming agents. The amount of film-forming agent added directly affects the internal structure of the preservation coating, thereby affecting the comprehensive properties of the preservation coating, such as water vapor transmission rate, oxygen transmission rate, elongation at break, and tensile strength. Because beeswax and coconut oil contain fatty acids, the hydroxyl groups in the phosphorylated nanocellulose molecular chains will form hydrogen bonds and electrostatic interactions with the carboxylic acids in the fatty acids. This allows the phosphorylated nanocellulose in the preservation coating to be arranged in a tight and orderly manner, giving the preservation coating a dense network structure and improving its oxygen barrier and water retention capabilities.

[0023] This invention specifically limits the addition amount of the film-forming agent to 20-50 wt%. When the addition amount of the film-forming agent is less than 20 wt%, it cannot effectively enhance the water barrier and water resistance properties. When the addition amount of the film-forming agent exceeds 50 wt%, the hydrophobic and emulsifying effects of beeswax and coconut oil weaken the bonding between phosphorylated nanocellulose molecules, leading to a significant decrease in the tensile strength and elongation at break of the preservation coating. Simultaneously, excessive film-forming agent addition results in discontinuous crystallization within the preservation coating, disrupting the three-dimensional network formed by phosphorylated nanocellulose and deteriorating oxygen barrier properties. It also causes uneven stress distribution within the preservation coating, resulting in poor mechanical properties. Furthermore, the precipitation of some lipids reduces the smoothness of the preservation coating surface, ultimately leading to a significant decrease in the tensile strength and elongation at break of the preservation coating. This invention comprehensively considers the impact of the film-forming agent addition amount on various properties of the preservation coating and particularly optimizes the addition amount to 20-50 wt%.

[0024] In some preferred embodiments, the amount of plasticizer added is 20-50 wt% based on the dry weight of phosphorylated nanocellulose in the phosphorylated nanocellulose solution, for example, it can be 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, 30 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt%, 40 wt%, 42 wt%, 44 wt%, 46 wt%, 48 wt%, or 50 wt%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0025] This invention uses glycerol and potassium sorbate as plasticizers, and the amount of glycerol and potassium sorbate added significantly affects the performance of the preservation coating. First, since glycerol and potassium sorbate are small organic molecules, adding appropriate amounts can increase the interaction between phosphorylated nanocellulose molecules and film-forming agent molecules, and also fill the gaps in the phosphorylated nanocellulose network structure, enhancing the density of the preservation coating and making it difficult for moisture and oxygen to permeate, further improving the water retention and oxygen barrier capabilities of the coating. Second, glycerol and potassium sorbate can penetrate into the phosphorylated nanocellulose matrix, reducing the intermolecular forces between the phosphorylated nanocellulose molecular chains. The activated phosphorylated nanocellulose molecular chains are easier to slide, increasing their fluidity and thus improving the toughness and elasticity of the preservation coating. Third, the hydroxyl groups in the glycerol and potassium sorbate molecules form hydrogen bonds with the carboxyl groups on the phosphorylated nanocellulose molecular chains, enhancing the intermolecular interactions of the preservation coating and increasing its tensile strength and elongation at break.

[0026] This invention specifically limits the amount of plasticizer added to 20-50 wt%. When the amount of plasticizer added is less than 20 wt%, the brittleness of phosphorylated nanocellulose leads to cracking of the preservation coating, rendering it ineffective for preservation. When the amount of plasticizer added exceeds 50 wt%, the fluidity of the phosphorylated nanocellulose molecular chains is further enhanced, leading to increased porosity between the chains and reduced density of the preservation coating. This, in turn, promotes oxygen permeability, resulting in a decrease in the oxygen barrier capacity of the preservation coating. Furthermore, excessive plasticizer addition enhances the softening effect of the plasticizer on the preservation coating, thereby weakening its rigidity and reducing its tensile strength. Considering the combined effects of plasticizer addition on various properties of the preservation coating, this invention particularly optimizes the plasticizer addition amount to 20-50 wt%.

[0027] In some preferred embodiments, the amount of biosurfactant added is 0.02-0.12 wt% based on the total mass of the phosphorylated nanocellulose solution, for example, 0.02 wt%, 0.03 wt%, 0.04 wt%, 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt%, 0.1 wt%, 0.11 wt%, or 0.12 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0028] This invention uses rhamnolipids and sophorolipids as biosurfactants, which can effectively reduce the oil-water interfacial tension in the preservative solution. This invention specifically limits the amount of biosurfactant added to 0.02-0.12 wt%. When the amount of biosurfactant added is below 0.02 wt%, the interfacial tension of the preservative solution system is high, reducing the wettability of fruit and vegetable peels and making it difficult to form a complete preservative coating. When the amount of biosurfactant added reaches 0.12 wt%, the change in surface tension of the preservative solution has already leveled off; further addition of biosurfactants has no significant effect on reducing the surface tension of the preservative solution and may even lead to material waste.

[0029] The present invention preferably uses a compound system composed of rhamnolipin and sophorolipid to further reduce the oil-water interfacial tension in the preservative solution. When the mass ratio of rhamnolipin to sophorolipid is in the range of 1:(0.2-0.3), the oil-water interfacial tension in the preservative solution can be further reduced. Compared to single-component biosurfactants, the combination of rhamnolipids and sophorolipids can further reduce the oil-water interfacial tension in preservative solutions. This is determined by the inherent structure and properties of these two glycolipid biosurfactants. Rhamnolipids are highly hydrophilic, exhibiting significant anionic surfactant characteristics; while sophorolipids are highly hydrophobic, exhibiting significant nonionic surfactant characteristics. The resulting compound system has a suitable hydrophilic-lipophilic balance, which is conducive to oil-water emulsification. Furthermore, the anionic-nonionic composite biosurfactant has a more compact micellar structure. Specifically, the addition of nonionic sophorolipids weakens the charge repulsion effect of anionic rhamnolipids, while the presence of anionic rhamnolipids reduces the steric hindrance of nonionic sophorolipids. Therefore, through the synergistic effect between rhamnolipids and sophorolipids, the oil-water interfacial tension in preservative solutions can be effectively reduced, and the solubilizing and emulsifying activity of biosurfactants can be improved.

[0030] In some preferred embodiments, the amount of curcumin / cyclodextrin inclusion complex added is 5-10 wt% based on the dry weight of phosphorylated nanocellulose in the phosphorylated nanocellulose solution, for example, it can be 5.0 wt%, 5.5 wt%, 6.0 wt%, 6.5 wt%, 7.0 wt%, 7.5 wt%, 8.0 wt%, 8.5 wt%, 9.0 wt%, 9.5 wt%, or 10.0 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0031] Curcumin is an active ingredient extracted from the rhizomes of ginger plants. It possesses antioxidant and antibacterial properties, significantly extending the shelf life of fruits and vegetables in preservative solutions. Furthermore, curcumin has low toxicity, a low probability of allergic reactions, and no toxic side effects on human health, making it suitable for consumption. However, curcumin is a fat-soluble substance and poorly soluble in water. Therefore, it is difficult to disperse in water-based preservative systems, resulting in low utilization and hindering the full expression of its antioxidant and antibacterial capabilities.

[0032] Cyclodextrin is a water-soluble, non-reducing, white crystalline solid that is not easily hydrolyzed by acid. It is extracted from starchy raw materials such as corn or potatoes using catalytic enzymes. It is purely plant-based, non-toxic, and edible, with an extremely low risk of causing allergic reactions or other adverse effects. There are three common types of cyclodextrin: α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin, which consist of 6, 7, or 8 glucose units linked by 1,4-glycosidic bonds. The unique feature of cyclodextrin molecules is their cyclic three-dimensional structure. Their internal molecular structure can form hydrophobic cavities of specific sizes, allowing them to absorb lipophilic molecules of compatible size and shape as "guests." Their hydrophilic surface ensures the molecule's tolerance in aqueous systems.

[0033] This invention utilizes the "hydrophobic inside and hydrophilic outside" properties of cyclodextrin as a sustained-release carrier to encapsulate curcumin within its hydrophobic cavity, forming a cyclodextrin / curcumin inclusion complex. By using cyclodextrin to encapsulate curcumin, the stability and solubility of curcumin can be improved, reducing the loss of active ingredients during the production and storage of preservative solutions. Furthermore, by controlling the release time and amount of curcumin, the shelf life of fruits and vegetables can be extended, changes in their sensory characteristics can be reduced, and ultraviolet-induced spoilage and oxidation can be effectively prevented.

[0034] This invention specifically limits the addition amount of curcumin / cyclodextrin inclusion complex to 5-10 wt%. When the addition amount of curcumin / cyclodextrin inclusion complex is less than 5 wt%, the effective content of the functional component is too low, resulting in a deterioration in the antibacterial and antioxidant effects and preservation effect of the preservative coating. When the addition amount of curcumin / cyclodextrin inclusion complex is greater than 10 wt%, the cyclodextrin molecules crystallize and precipitate during the formation of the preservative coating, destroying the uniformity and integrity of the preservative coating, affecting the barrier properties of the preservative coating, and thus affecting the preservation effect. In addition, excessive curcumin addition will reduce the transparency of the preservative coating, thereby affecting consumers' acceptance of the preservative solution.

[0035] Secondly, the present invention provides a method for preparing the edible compound preservative liquid described in the first aspect, the preparation method comprising:

[0036] (I) A modified solution is obtained by mixing phosphorylation reagent, urea and deionized water. The fiber raw material is immersed in the modified solution and taken out after a period of time. It is then dried by heating and cured at high temperature to obtain phosphorylated cellulose. The phosphorylated cellulose is dispersed in deionized water to form a mixed solution. The mixed solution is homogenized under high pressure to obtain a phosphorylated nanocellulose solution.

[0037] (II) Prepare cyclodextrin solution and curcumin solution respectively. Mix the cyclodextrin solution and curcumin solution evenly, then cool and crystallize. Collect the crystallized product, filter and dry the crystallized product in sequence to obtain curcumin / cyclodextrin inclusion complex.

[0038] (III) The phosphorylated nanocellulose solution, film-forming agent, plasticizer, biosurfactant and curcumin / cyclodextrin inclusion complex are mixed in proportion and heated until the film-forming agent melts to obtain a precursor solution; then, the precursor solution is emulsified and defoamed in sequence to obtain the edible composite preservative liquid.

[0039] Compared with other physical or chemical preservation materials, the biomass material preservation liquid provided by this invention has excellent biodegradability. The preparation process requires no toxic or harmful chemical reagents, making it environmentally friendly and in line with the development concept of green chemistry. By coating the surface of fruits and vegetables with the preservation liquid through methods such as wrapping, impregnation, coating, or spraying, a preservative coating is formed on the surface, effectively extending the storage and shelf life of fruits and vegetables.

[0040] Furthermore, the preservative coating formed on the surface of fruits and vegetables can improve their mechanical strength, thereby enhancing their safety during production, storage, and transportation. This prevents damage and spoilage caused by bumps and knocks, reducing the rate of spoiled fruit. Simultaneously, the preservative liquid provided by this invention can also serve as a carrier for food additives (such as preservatives, pigments, flavorings, and antioxidants), allowing the active ingredients in these additives to exert their effects on the surface of fruits and vegetables and controlling the diffusion rate of these additives to achieve a slow-release effect.

[0041] As a preferred technical solution of the present invention, in step (I), the mass fraction of the phosphorylation reagent in the modified solution is 10-20 wt%, for example, it can be 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, or 20 wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] This invention specifically limits the mass fraction of phosphorylation reagent in the modified solution to 10-20 wt%. When the amount of phosphorylation reagent added is too low, the phosphorylation reaction is insufficient, and the cellulose surface fails to graft a sufficient number of phosphate groups, resulting in an inability to achieve an effective mechanical homogenization process. When the amount of phosphorylation reagent added is too high, although a high amount of phosphate group grafting is achieved, the high concentration of phosphorylation reagent will lead to severe degradation of cellulose, thus failing to obtain high-quality phosphorylated nanocellulose.

[0043] In some preferred embodiments, the mass fraction of urea in the modified solution is 25-40 wt%, for example, it can be 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, or 40 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0044] The present invention specifically limits the mass fraction of urea in the modified solution to 25-40 wt%. In the phosphorylation modification process, urea acts as a catalyst for the phosphorylation reaction and a protectant for cellulose raw materials. When the amount of urea added is too low, it will lead to insufficient phosphorylation reaction and cellulose degradation.

[0045] In some preferred embodiments, the phosphorylation agent includes any one or a combination of at least two of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, lithium dihydrogen phosphate, or lithium dihydrogen phosphate.

[0046] In some preferred embodiments, the soaking time is 0.5-1.5 hours, for example, 0.5 hours, 0.6 hours, 0.7 hours, 0.8 hours, 0.9 hours, 1.0 hours, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours or 1.5 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0047] In some preferred embodiments, the immersion temperature is 60-80°C, for example, 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0048] In some preferred embodiments, the high-temperature curing time is 20-30 min, for example, it can be 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0049] In some preferred embodiments, the high-temperature curing temperature is 100-200°C, for example, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C or 200°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0050] This invention specifically defines the high-temperature curing temperature as 100-200℃ and the high-temperature curing time as 20-30 min. When the curing temperature is below 100℃ or the time is less than 20 min, the phosphorylation reaction is insufficient, and the cellulose surface fails to graft a large number of phosphate groups, resulting in a low product charge and an inability to achieve an effective mechanical homogenization process. When the curing temperature is above 200℃ or the time is longer than 30 min, the cellulose loses some bound water during this process, and its structure is damaged to a certain extent, leading to a decrease in the accessibility of the phosphorylation reaction and the product charge.

[0051] In some preferred embodiments, the solid content of the mixture is 0.5-0.7 wt%, for example, it may be 0.5 wt%, 0.52 wt%, 0.54 wt%, 0.56 wt%, 0.58 wt%, 0.6 wt%, 0.62 wt%, 0.64 wt%, 0.66 wt%, 0.68 wt%, or 0.7 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0052] In some preferred embodiments, before high-pressure homogenization of the mixture, 10-30 wt% alkali solution is added to the mixture to adjust the pH value of the mixture to 9.3-9.6. The mass fraction of the alkali solution can be 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, or 30 wt%, and the pH value can be adjusted to 9.3, 9.4, 9.5, or 9.6, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0053] In some preferred embodiments, the pressure of the high-pressure homogenization is 600-1000 bar, for example, 600 bar, 650 bar, 700 bar, 750 bar, 800 bar, 850 bar, 900 bar, 950 bar or 1000 bar, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0054] In some preferred embodiments, the high-pressure homogenization is performed 3 to 6 times, for example, 3, 4, 5 or 6 times, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0055] This invention improves the dispersion stability and size uniformity of phosphorylated cellulose nanoparticles through high-pressure homogenization. With each increase in the number of high-pressure homogenization cycles, the shear force impact and cavitation generated during high-pressure treatment are enhanced, acting on both the longitudinal and transverse directions of the fibers. This results in a significant reduction in both fiber length and width, thereby improving the dispersion stability and size uniformity of the cellulose nanoparticles.

[0056] As a preferred technical solution of the present invention, in step (II), the preparation process of the cyclodextrin solution includes: dissolving cyclodextrin in deionized water at an ambient temperature of 60-70℃ to obtain the cyclodextrin solution. For example, the temperature can be 60℃, 61℃, 62℃, 63℃, 64℃, 65℃, 66℃, 67℃, 68℃, 69℃ or 70℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0057] In some preferred embodiments, the cyclodextrin solution has a mass fraction of 3-6 wt%, for example, 3.0 wt%, 3.2 wt%, 3.4 wt%, 3.6 wt%, 3.8 wt%, 4.0 wt%, 4.2 wt%, 4.4 wt%, 4.6 wt%, 4.8 wt%, 5.0 wt%, 5.2 wt%, 5.4 wt%, 5.6 wt%, 5.8 wt%, or 6.0 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0058] In some preferred embodiments, the preparation process of the curcumin solution includes: dissolving curcumin in ethanol at an ambient temperature of 60-70°C to obtain the curcumin solution. For example, the temperature may be 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, or 70°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0059] In some preferred embodiments, the concentration of the curcumin solution is 0.005-0.01 g / mL, for example, 0.005 g / mL, 0.0055 g / mL, 0.006 g / mL, 0.0065 g / mL, 0.007 g / mL, 0.0075 g / mL, 0.008 g / mL, 0.0085 g / mL, 0.009 g / mL, 0.0095 g / mL or 0.01 g / mL, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0060] In some preferred embodiments, the mixing process of the cyclodextrin solution and the curcumin solution includes: adding the curcumin solution dropwise to the cyclodextrin solution at an ambient temperature of 60-70°C; after all the curcumin solution has been added, maintaining the ambient temperature and continuing to stir for 2-4 hours; wherein the ambient temperature can be 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C or 70°C, and the stirring time can be 2.0h, 2.2h, 2.4h, 2.6h, 2.8h, 3.0h, 3.2h, 3.4h, 3.6h, 3.8h or 4.0h, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0061] This invention specifically limits the ambient temperature to 60-70℃ because ambient temperature significantly affects the solubility of curcumin. As the ambient temperature increases, the solubility of curcumin increases, molecular motion in the solution increases, the reaction rate accelerates, and thus improves the efficiency of the interaction between cyclodextrin and curcumin. However, as the temperature continues to rise, approaching the boiling point of the curcumin solution, solvent evaporation leads to material waste, poses safety hazards, and increases energy consumption.

[0062] As a preferred technical solution of the present invention, in step (II), the cooling crystallization temperature is 1-10℃, for example, it can be 1℃, 2℃, 3℃, 4℃, 5℃, 6℃, 7℃, 8℃, 9℃ or 10℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0063] In some preferred embodiments, the cooling crystallization time is 8-12 hours, for example, 8.0 hours, 8.5 hours, 9.0 hours, 9.5 hours, 10.0 hours, 10.5 hours, 11.0 hours, 11.5 hours or 12.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0064] In some preferred embodiments, the drying temperature is 40-60°C, for example, 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, 52°C, 54°C, 56°C, 58°C or 60°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0065] As a preferred technical solution of the present invention, in step (III), the heating temperature is 80-90℃, for example, it can be 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 87℃, 88℃, 89℃ or 90℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0066] In some preferred embodiments, the emulsification time is 1-10 min, for example, it can be 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0067] This invention does not impose specific requirements or limitations on the emulsification method, such as ultrasonic emulsification, homogenization, ultra-high pressure homogenization, or grinding.

[0068] Ultrasonic emulsification is performed in an ultrasonic emulsifier, utilizing the cavitation effect of ultrasound to break down, mix, and emulsify materials. Homogenization is performed in a high-pressure homogenizer, where the materials are refined under the triple action of compression, strong impact, and depressurization expansion, resulting in more uniform mixing. Ultra-high pressure homogenization is performed in a microfluidic apparatus or ultra-high pressure homogenizer, utilizing the high shear, high collision, and cavitation effects generated when fluid flows at high speed through an interactive cavity to disperse materials. Grinding is performed in a ball mill or nano-grind mill, utilizing the strong friction and impact forces generated by the speed difference between the grinding jar and the grinding balls to pulverize materials.

[0069] In some preferred embodiments, the degassing time is 5-10 min, for example, it can be 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0070] Thirdly, the present invention provides a method for using the edible compound preservative liquid described in the first aspect, the method comprising:

[0071] Soak the fruits and vegetables to be preserved in an edible compound preservative solution, or spray the edible compound preservative solution onto the surface of the fruits and vegetables to be preserved; then let the fruits and vegetables air dry naturally to form a preservative coating on the surface of the fruits and vegetables.

[0072] As a preferred technical solution of the present invention, the single soaking time is 5-60s, for example, it can be 5s, 10s, 15s, 20s, 25s, 30s, 35s, 40s, 45s, 50s, 55s or 60s, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0073] In some preferred embodiments, the number of soakings is 2 to 5 times, for example, 2, 3, 4 or 5 times, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0074] In some preferred embodiments, the spray flow rate is 5-20 mL / min, for example, it can be 5 mL / min, 6 mL / min, 7 mL / min, 8 mL / min, 9 mL / min, 10 mL / min, 11 mL / min, 12 mL / min, 13 mL / min, 14 mL / min, 15 mL / min, 16 mL / min, 17 mL / min, 18 mL / min, 19 mL / min or 20 mL / min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0075] For example, the present invention provides a method for preparing an edible composite preservative liquid for low-temperature refrigeration and preservation of fruits and vegetables, specifically including the following steps:

[0076] (1) A modified solution is prepared by mixing phosphorylation reagent, urea and deionized water. The mass fraction of phosphorylation reagent in the modified solution is 10-20 wt%, and the mass fraction of urea is 25-40 wt%. The modified solution is heated to 60-80℃. The cardboard is torn or cut into small pieces and soaked in the modified solution for 0.5-1.5 h. Then it is taken out and heated to dry. After the pulp is completely dry, it is cured at 100-200℃ for 20-30 min to obtain phosphorylated cellulose. The phosphorylated cellulose is dispersed in deionized water to form a mixture with a solid content of 0.5-0.7 wt%. The pH value of the mixture is adjusted to 9.3-9.6 with 10-30 wt% sodium hydroxide solution. Finally, the mixture is homogenized under high pressure at 600-1000 bar for 3-6 times to obtain phosphorylated nanocellulose solution.

[0077] (2) At an ambient temperature of 60-70℃, cyclodextrin was dissolved in deionized water to obtain a 3-6 wt% cyclodextrin solution; at an ambient temperature of 60-70℃, curcumin was dissolved in ethanol to obtain a 0.005-0.01 g / mL curcumin solution; at an ambient temperature of 60-70℃, the curcumin solution was added dropwise to the cyclodextrin solution. After all the addition was completed, the ambient temperature was kept constant and stirring was continued for 2-4 h; the mixture was cooled to room temperature, and then cooled and crystallized at 1-5℃ for 8-12 h. The crystallized product was filtered and dried at 40-60℃ to obtain the curcumin / cyclodextrin inclusion complex.

[0078] (3) Mix 0.2-0.4 wt% of phosphorylated nanocellulose solution, film-forming agent, plasticizer, biosurfactant and curcumin / cyclodextrin inclusion complex, wherein, based on the dry weight of phosphorylated nanocellulose in the phosphorylated nanocellulose solution, the amount of film-forming agent added is 20-50 wt%, the amount of plasticizer added is 20-50 wt%, and the amount of curcumin / cyclodextrin inclusion complex added is 5-10 wt%; based on the total mass of phosphorylated nanocellulose solution, the amount of biosurfactant added is 0.02-0.12 wt%; heat the mixture to 80-90℃ until the film-forming agent melts to obtain a precursor solution; then, emulsify the precursor solution for 1-10 min, and finally degas the precursor solution under vacuum for 5-10 min to obtain the edible composite preservative liquid.

[0079] For example, the present invention also provides a method for using an edible compound preservative liquid, which specifically includes the following steps:

[0080] Soak freshly picked fruits and vegetables in an edible compound preservative solution 2-5 times, each time for 5-60 seconds; or spray the edible compound preservative solution onto the surface of the fruits and vegetables to be preserved at a spray flow rate of 5-20 mL / min, and then remove the fruits and vegetables to air dry naturally to form a preservative coating on the surface of the fruits and vegetables.

[0081] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0082] This invention proposes an edible composite preservative solution for use under low-temperature and high-humidity refrigeration conditions. The preservative solution consists of a phosphorylated nanocellulose solution, a film-forming agent, a plasticizer, a biosurfactant, and a curcumin / cyclodextrin inclusion complex. Fruits and vegetables are directly immersed in the preservative solution or sprayed onto their surface and then allowed to air dry, forming a complete and dense preservative coating. This coating reduces the oxygen concentration and increases the carbon dioxide concentration on the surface of the fruits and vegetables through respiration, achieving modified atmosphere preservation.

[0083] This invention uses phosphorylated nanocellulose as the coating matrix material. The three-dimensional network structure formed by the cross-entanglement of phosphorylated nanocellulose extends the diffusion path of gas in the preservation coating, thereby reducing the gas permeability of the preservation coating, reducing the loss of moisture and nutrients on the surface and inside of fruits and vegetables, and significantly enhancing the mechanical strength of the preservation coating.

[0084] Cyclodextrin has a unique three-dimensional cyclic structure with an internal hydrophobic and external hydrophilic properties. This invention utilizes food-grade, safe, and non-toxic bio-derived cyclodextrin molecules to encapsulate curcumin, enabling curcumin and cyclodextrin to interact via non-covalent bonds. This encapsulates the poorly soluble curcumin within its hydrophobic cavity, forming a curcumin / cyclodextrin inclusion complex. This not only improves the water solubility of curcumin but also mitigates its light-sensitive decomposition, significantly enhancing its water solubility, bioavailability, and antioxidant capacity.

[0085] This invention utilizes phosphorylated nanocellulose, which possesses excellent renewability and biocompatibility, to construct a controlled-release and sustained-release preservative coating. The phosphorylated nanocellulose, with its high aspect ratio and fibrous structure, has a large specific surface area, which is beneficial for deposition and retention on the surface of fruits and vegetables. Furthermore, the large specific surface area increases the loading capacity of curcumin / cyclodextrin inclusion complexes, reducing the loss of curcumin and other active ingredients. Simultaneously, the curcumin / cyclodextrin inclusion complexes are immobilized by hydrogen bonding between the phosphorylated nanocellulose and cyclodextrin molecules, allowing them to be uniformly dispersed in the preservative solution. After coating, the curcumin within the curcumin / cyclodextrin inclusion complexes is contained within the hydrophobic cavities of the cyclodextrin molecules and gradually released, resulting in a long-lasting, sustained-release antibacterial effect.

[0086] In addition to the phosphorylated nanocellulose coating matrix material and the curcumin / cyclodextrin inclusion complex antibacterial sustained-release component, the edible composite preservative solution provided by this invention also contains film-forming agents, plasticizers, and biosurfactants to improve the wettability, film-forming properties, and integrity of the preservative coating. The selected film-forming agents, plasticizers, and biosurfactants are all edible components, posing no toxic side effects to human health, and can be eaten directly with fruits and vegetables or after washing. Specifically, this invention uses beeswax and / or coconut oil as film-forming agents. The hydrophobic properties of beeswax and coconut oil enable the preservative coating to maintain its integrity under low temperature and high humidity conditions, thus enhancing the coating's water resistance. Glycerin and / or potassium sorbate are used as plasticizers to regulate interfacial interactions between components. Rhamnollipids and / or sophorolipids are used as biosurfactants to enhance the wetting effect of the coating solution on the vegetable surface.

[0087] Untreated fruits and vegetables often have numerous cracks and wrinkles on their surfaces, providing ample oxygen permeation channels for respiration. Simultaneously, the increased surface area due to these wrinkles leads to greater effective transpiration of water vapor, resulting in rapid moisture loss. This invention, through immersion in a preservative solution, fills and smooths these cracks and wrinkles, reducing the respiration rate and transpiration area of ​​the fruits and vegetables to some extent, thus acting as a barrier between water vapor and oxygen.

[0088] The preservative liquid provided by this invention has good affinity with the surface of fruits and vegetables. During use, it adheres well to and covers the surface of fruits and vegetables, forming a preservative coating that achieves preservation effects such as blocking gases, retaining water, and preventing nutrient loss. Furthermore, compared to some waxy coatings that are difficult or even impossible to wash off, the preservative coating provided by this invention is easily soluble in water. Before consumption, the preservative coating on the surface of fruits and vegetables can be easily removed with a simple rinse of water, without affecting the taste and eliminating consumer concerns about the safety of the preservative coating. The preservative coating prepared on the surface of cucumbers and rapeseed by dipping or spraying, combined with refrigeration, can extend the shelf life of cucumbers to 30 days and the shelf life of rapeseed to 60 days. Attached Figure Description

[0089] Figure 1 An optical image of the emulsion droplets of the edible composite preservative liquid provided in Embodiment 1 of the present invention;

[0090] Figure 2 This is a particle size distribution diagram of the emulsion droplets of the edible composite preservative liquid provided in Embodiment 1 of the present invention;

[0091] Figure 3 These are photographs showing the appearance of rapeseed during storage and preservation tests in Example 1 and the comparative example of the present invention.

[0092] Figure 4 These are photographs showing the appearance of cucumbers during storage and preservation tests conducted in Example 1 and the comparative example of the present invention. Detailed Implementation

[0093] The technical solutions of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary, and should not be construed as limiting the implementation methods or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0094] Example 1

[0095] This embodiment provides a method for preparing an edible compound preservative liquid for low-temperature cold storage and preservation of fruits and vegetables, specifically including the following steps:

[0096] (1) A modified solution was prepared by mixing diammonium hydrogen phosphate, urea and deionized water. The mass fraction of diammonium hydrogen phosphate in the modified solution was 10 wt% and the mass fraction of urea was 25 wt%. The modified solution was heated to 60°C. The cardboard was torn or cut into small pieces and soaked in the modified solution for 1.5 h. Then it was taken out and heated to dry. After the pulp was completely dried, it was cured at 100°C for 30 min to obtain phosphorylated cellulose. The phosphorylated cellulose was dispersed in deionized water to form a mixture with a solid content of 0.5 wt%. The pH value of the mixture was adjusted to 9.3 with 10 wt% sodium hydroxide solution. Finally, the mixture was homogenized under high pressure for 6 times at 600 bar to obtain a phosphorylated nanocellulose solution.

[0097] (2) At an ambient temperature of 60°C, β-cyclodextrin was dissolved in 100g of deionized water to obtain a 3wt% β-cyclodextrin solution; at an ambient temperature of 60°C, curcumin was dissolved in 210mL of ethanol to obtain a 0.005g / mL curcumin solution; at an ambient temperature of 60°C, the curcumin solution was added dropwise to the β-cyclodextrin solution. After all the addition was completed, the ambient temperature was kept constant and stirring was continued for 2h; the mixture was cooled to room temperature and then cooled to crystallize at 1°C for 8h. The crystallized product was filtered and dried at 40°C to obtain the curcumin / cyclodextrin inclusion complex.

[0098] (3) Mix 0.2 wt% phosphorylated nanocellulose solution, beeswax, glycerol, rhamnolipid and curcumin / cyclodextrin inclusion complex, wherein, based on the dry weight of phosphorylated nanocellulose in the phosphorylated nanocellulose solution, the amount of beeswax added is 20 wt%, the amount of glycerol added is 20 wt%, and the amount of curcumin / cyclodextrin inclusion complex added is 5 wt%; based on the total mass of the phosphorylated nanocellulose solution, the amount of rhamnolipid added is 0.02 wt%; heat the mixture to 80°C until the beeswax melts to obtain a precursor solution; then, emulsify the precursor solution for 1 min, and finally vacuum degas the precursor solution for 5 min to obtain the edible composite preservative liquid.

[0099] The edible compound preservative liquid prepared in Example 1 was subjected to microscopic observation and photographed, and the results were as follows: Figure 1 The image shown is a micrograph of the emulsion; the particle size distribution of the emulsion droplets in the edible compound preservative solution was tested, and the results are as follows. Figure 2 The emulsion droplet size distribution curve shown is combined with... Figure 1 and Figure 2It can be seen that the droplet size of the emulsion in the preservation liquid prepared in this embodiment is mainly concentrated in the range of 1.5-1.8 μm.

[0100] This embodiment also provides a method for using an edible compound preservative liquid, which specifically includes the following steps:

[0101] Freshly picked fruits and vegetables are soaked in an edible compound preservative solution twice, each time for 60 seconds. Afterward, the fruits and vegetables are removed and air-dried naturally to form a preservative coating on their surface.

[0102] Example 2

[0103] This embodiment provides a method for preparing an edible compound preservative liquid for low-temperature cold storage and preservation of fruits and vegetables, specifically including the following steps:

[0104] (1) A modified solution was prepared by mixing diammonium hydrogen phosphate, urea and deionized water. The mass fraction of diammonium hydrogen phosphate in the modified solution was 12 wt% and the mass fraction of urea was 30 wt%. The modified solution was heated to 65°C. The cardboard was torn or cut into small pieces and soaked in the modified solution for 1.2 h. Then it was taken out and heated to dry. After the pulp was completely dried, it was cured at 120°C for 28 min to obtain phosphorylated cellulose. The phosphorylated cellulose was dispersed in deionized water to form a mixture with a solid content of 0.55 wt%. The pH value of the mixture was adjusted to 9.4 with 15 wt% sodium hydroxide solution. Finally, the mixture was homogenized under high pressure at 700 bar for 5 times to obtain a phosphorylated nanocellulose solution.

[0105] (2) At an ambient temperature of 62℃, β-cyclodextrin was dissolved in 100g of deionized water to obtain a 4wt% β-cyclodextrin solution; at an ambient temperature of 62℃, curcumin was dissolved in 210mL of ethanol to obtain a 0.006g / mL curcumin solution; at an ambient temperature of 62℃, the curcumin solution was added dropwise to the β-cyclodextrin solution. After all the addition was completed, the ambient temperature was kept constant and stirring was continued for 2.5h; the mixture was cooled to room temperature, and then cooled and crystallized at 3℃ for 9h. The crystallized product was filtered and dried at 45℃ to obtain the curcumin / cyclodextrin inclusion complex.

[0106] (3) Mix 0.25wt% phosphorylated nanocellulose solution, beeswax, glycerol, rhamnolipid and curcumin / cyclodextrin inclusion complex, wherein, based on the dry weight of phosphorylated nanocellulose in the phosphorylated nanocellulose solution, the amount of beeswax added is 30wt%, the amount of glycerol added is 30wt%, and the amount of curcumin / cyclodextrin inclusion complex added is 6wt%; based on the total mass of the phosphorylated nanocellulose solution, the amount of rhamnolipid added is 0.05wt%; heat the mixture to 82℃ until the beeswax melts to obtain a precursor solution; then, emulsify the precursor solution for 3min, and finally vacuum degas the precursor solution for 6min to obtain the edible composite preservative liquid.

[0107] This embodiment also provides a method for using an edible compound preservative liquid, which specifically includes the following steps:

[0108] Freshly picked fruits and vegetables are soaked in an edible compound preservative solution four times, for 30 seconds each time. Afterward, the fruits and vegetables are removed and air-dried naturally to form a preservative coating on their surface.

[0109] Example 3

[0110] This embodiment provides a method for preparing an edible compound preservative liquid for low-temperature cold storage and preservation of fruits and vegetables, specifically including the following steps:

[0111] (1) A modified solution was prepared by mixing ammonium dihydrogen phosphate, urea and deionized water. The mass fraction of ammonium dihydrogen phosphate in the modified solution was 15 wt% and the mass fraction of urea was 35 wt%. The modified solution was heated to 70°C. The cardboard was torn or cut into small pieces and soaked in the modified solution for 1 hour. Then it was taken out and heated to dry. After the pulp was completely dried, it was cured at 150°C for 25 minutes to obtain phosphorylated cellulose. The phosphorylated cellulose was dispersed in deionized water to form a mixture with a solid content of 0.6 wt%. The pH value of the mixture was adjusted to 9.5 with 20 wt% sodium hydroxide solution. Finally, the mixture was homogenized under high pressure at 800 bar for 5 times to obtain a phosphorylated nanocellulose solution.

[0112] (2) At an ambient temperature of 65°C, β-cyclodextrin was dissolved in 100g of deionized water to obtain a 5wt% β-cyclodextrin solution; at an ambient temperature of 65°C, curcumin was dissolved in 210mL of ethanol to obtain a 0.007g / mL curcumin solution; at an ambient temperature of 65°C, the curcumin solution was added dropwise to the β-cyclodextrin solution. After all the addition was completed, the ambient temperature was kept constant and stirring was continued for 3h; the mixture was cooled to room temperature, and then cooled and crystallized at 5°C for 10h. The crystallized product was filtered and dried at 50°C to obtain the curcumin / cyclodextrin inclusion complex.

[0113] (3) Mix 0.3 wt% phosphorylated nanocellulose solution, beeswax, glycerin, rhamnolipin, sophorolipid and curcumin / cyclodextrin inclusion complex, wherein, based on the dry weight of phosphorylated nanocellulose in the phosphorylated nanocellulose solution, the amount of beeswax added is 35 wt%, the amount of glycerin added is 35 wt%, and the amount of curcumin / cyclodextrin inclusion complex added is 7 wt%; based on the total mass of the phosphorylated nanocellulose solution, the total amount of rhamnolipin and sophorolipid added is 0.08 wt%, and the mass ratio of rhamnolipin and sophorolipid is 1:0.2; heat the mixture to 85°C until the beeswax melts to obtain a precursor solution; then, emulsify the precursor solution for 5 min, and finally degas the precursor solution under vacuum for 7 min to obtain the edible composite preservative liquid.

[0114] This embodiment also provides a method for using an edible compound preservative liquid, which specifically includes the following steps:

[0115] Freshly picked fruits and vegetables are soaked in an edible compound preservative solution five times, for five seconds each time. Afterward, the fruits and vegetables are removed and air-dried naturally to form a preservative coating on their surface.

[0116] Example 4

[0117] This embodiment provides a method for preparing an edible compound preservative liquid for low-temperature cold storage and preservation of fruits and vegetables, specifically including the following steps:

[0118] (1) A modified solution was prepared by mixing disodium hydrogen phosphate, urea and deionized water. The mass fraction of disodium hydrogen phosphate in the modified solution was 18 wt% and the mass fraction of urea was 35 wt%. The modified solution was heated to 75 °C. The cardboard was torn or cut into small pieces and soaked in the modified solution for 0.8 h. Then it was taken out and heated to dry. After the pulp was completely dried, it was cured at 180 °C for 22 min to obtain phosphorylated cellulose. The phosphorylated cellulose was dispersed in deionized water to form a mixture with a solid content of 0.65 wt%. The pH value of the mixture was adjusted to 9.5 with 25 wt% sodium hydroxide solution. Finally, the mixture was homogenized under high pressure at 900 bar for 4 times to obtain a phosphorylated nanocellulose solution.

[0119] (2) At an ambient temperature of 68°C, β-cyclodextrin was dissolved in 100g of deionized water to obtain a 5wt% β-cyclodextrin solution; at an ambient temperature of 68°C, curcumin was dissolved in 210mL of ethanol to obtain a 0.008g / mL curcumin solution; at an ambient temperature of 68°C, the curcumin solution was added dropwise to the β-cyclodextrin solution. After all the addition was completed, the ambient temperature was kept constant and stirring was continued for 3.5h; the mixture was cooled to room temperature and then cooled and crystallized at 7°C for 11h. The crystallized product was filtered and dried at 55°C to obtain a curcumin / cyclodextrin inclusion complex.

[0120] (3) Mix 0.35wt% of phosphorylated nanocellulose solution, coconut oil, potassium sorbate, sophorolipid and curcumin / cyclodextrin inclusion complex, wherein, based on the dry weight of phosphorylated nanocellulose in the phosphorylated nanocellulose solution, the amount of coconut oil added is 40wt%, the amount of potassium sorbate added is 40wt%, and the amount of curcumin / cyclodextrin inclusion complex added is 8wt%; based on the total mass of phosphorylated nanocellulose solution, the amount of sophorolipid added is 0.1wt%; heat the mixture to 88℃ until the coconut oil melts to obtain a precursor solution; then, emulsify the precursor solution for 7min, and finally degas the precursor solution under vacuum for 8min to obtain the edible composite preservative liquid.

[0121] This embodiment also provides a method for using an edible compound preservative liquid, which specifically includes the following steps:

[0122] The edible composite preservative liquid was sprayed onto the surface of the fruits and vegetables to be preserved at a spray flow rate of 10 mL / min. The fruits and vegetables were then removed and air-dried naturally to form a preservative coating on their surface.

[0123] Example 5

[0124] This embodiment provides a method for preparing an edible compound preservative liquid for low-temperature cold storage and preservation of fruits and vegetables, specifically including the following steps:

[0125] (1) A modified solution was prepared by mixing lithium hydrogen phosphate, urea and deionized water. The mass fraction of lithium hydrogen phosphate in the modified solution was 20 wt% and the mass fraction of urea was 40 wt%. The modified solution was heated to 80 °C. The cardboard was torn or cut into small pieces and soaked in the modified solution for 0.5 h. Then it was taken out and heated to dry. After the pulp was completely dried, it was cured at 200 °C for 20 min to obtain phosphorylated cellulose. The phosphorylated cellulose was dispersed in deionized water to form a mixture with a solid content of 0.7 wt%. The pH value of the mixture was adjusted to 9.6 with 30 wt% sodium hydroxide solution. Finally, the mixture was homogenized under high pressure at 1000 bar for 3 times to obtain a phosphorylated nanocellulose solution.

[0126] (2) At an ambient temperature of 70°C, β-cyclodextrin was dissolved in 100g of deionized water to obtain a 6wt% β-cyclodextrin solution; at an ambient temperature of 70°C, curcumin was dissolved in 210mL of ethanol to obtain a 0.01g / mL curcumin solution; at an ambient temperature of 70°C, the curcumin solution was added dropwise to the β-cyclodextrin solution. After all the addition was completed, the ambient temperature was kept constant and stirring was continued for 4h; the mixture was cooled to room temperature, and then cooled and crystallized at 10°C for 12h. The crystallized product was filtered and dried at 60°C to obtain a curcumin / cyclodextrin inclusion complex.

[0127] (3) Mix 0.4 wt% of phosphorylated nanocellulose solution, coconut oil, potassium sorbate, sophorolipid and curcumin / cyclodextrin inclusion complex, wherein, based on the dry weight of phosphorylated nanocellulose in the phosphorylated nanocellulose solution, the amount of coconut oil added is 50 wt%, the amount of potassium sorbate added is 50 wt%, and the amount of curcumin / cyclodextrin inclusion complex added is 10 wt%; based on the total mass of the phosphorylated nanocellulose solution, the amount of sophorolipid added is 0.12 wt%; heat the mixture to 90°C until the coconut oil melts to obtain a precursor solution; then, emulsify the precursor solution for 10 min, and finally degas the precursor solution under vacuum for 10 min to obtain the edible composite preservative liquid.

[0128] This embodiment also provides a method for using an edible compound preservative liquid, which specifically includes the following steps:

[0129] The edible composite preservative liquid was sprayed onto the surface of the fruits and vegetables to be preserved at a spray flow rate of 20 mL / min. The fruits and vegetables were then removed and air-dried naturally to form a preservative coating on their surface.

[0130] Example 6

[0131] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid. The difference between this method and that of Embodiment 1 is that in step (3), the mass fraction of the phosphorylated nanocellulose solution is adjusted to 0.1 wt%, while other process parameters and operating steps are exactly the same as those of Embodiment 1.

[0132] This embodiment also provides a method for using a nanocellulose-based edible preservative solution. Freshly harvested rapeseed and cucumbers are dipped in the preservative solution provided in this embodiment, and the treatment process is the same as in Example 1.

[0133] Example 7

[0134] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid. The difference between this method and that of Embodiment 1 is that in step (3), the mass fraction of the phosphorylated nanocellulose solution is adjusted to 0.6 wt%, while other process parameters and operating steps are exactly the same as those of Embodiment 1.

[0135] This embodiment also provides a method for using a nanocellulose-based edible preservative solution. Freshly harvested rapeseed and cucumbers are dipped in the preservative solution provided in this embodiment, and the treatment process is the same as in Example 1.

[0136] Example 8

[0137] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid. The difference between this method and that of Embodiment 1 is that in step (3), the amount of beeswax added is adjusted to 15wt%, while other process parameters and operating steps are exactly the same as those of Embodiment 1.

[0138] This embodiment also provides a method for using a nanocellulose-based edible preservative solution. Freshly harvested rapeseed and cucumbers are dipped in the preservative solution provided in this embodiment, and the treatment process is the same as in Example 1.

[0139] Example 9

[0140] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid. The difference between this method and that of Embodiment 1 is that in step (3), the amount of beeswax added is adjusted to 55wt%, while other process parameters and operating steps are exactly the same as those of Embodiment 1.

[0141] This embodiment also provides a method for using a nanocellulose-based edible preservative solution. Freshly harvested rapeseed and cucumbers are dipped in the preservative solution provided in this embodiment, and the treatment process is the same as in Example 1.

[0142] Example 10

[0143] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid. The difference between this method and that of Embodiment 1 is that in step (3), the amount of glycerol added is adjusted to 15wt%, while the other process parameters and operating steps are exactly the same as those of Embodiment 1.

[0144] This embodiment also provides a method for using a nanocellulose-based edible preservative solution. Freshly harvested rapeseed and cucumbers are dipped in the preservative solution provided in this embodiment, and the treatment process is the same as in Example 1.

[0145] Example 11

[0146] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid. The difference between this method and that of Embodiment 1 is that in step (3), the amount of glycerol added is adjusted to 55 wt%, while other process parameters and operating steps are exactly the same as those of Embodiment 1.

[0147] This embodiment also provides a method for using a nanocellulose-based edible preservative solution. Freshly harvested rapeseed and cucumbers are dipped in the preservative solution provided in this embodiment, and the treatment process is the same as in Example 1.

[0148] Example 12

[0149] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid. The difference between this method and that of Example 1 is that in step (3), the amount of curcumin / cyclodextrin inclusion complex added is adjusted to 2wt%, while other process parameters and operating steps are exactly the same as those of Example 1.

[0150] This embodiment also provides a method for using a nanocellulose-based edible preservative solution. Freshly harvested rapeseed and cucumbers are dipped in the preservative solution provided in this embodiment, and the treatment process is the same as in Example 1.

[0151] Example 13

[0152] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid. The difference between this method and that of Example 1 is that in step (3), the amount of curcumin / cyclodextrin inclusion complex added is adjusted to 12wt%, while other process parameters and operating steps are exactly the same as those of Example 1.

[0153] This embodiment also provides a method for using a nanocellulose-based edible preservative solution. Freshly harvested rapeseed and cucumbers are dipped in the preservative solution provided in this embodiment, and the treatment process is the same as in Example 1.

[0154] Comparative Example

[0155] This comparative example uses freshly picked rapeseed and cucumbers, without any preservation treatment.

[0156] The inclusion rates of the curcumin / cyclodextrin inclusion complexes provided in Examples 1-13 were tested, and the specific test steps are as follows:

[0157] Prepare curcumin-ethanol standard solutions (concentrations of 1 μg / mL, 5 μg / mL, 10 μg / mL, 25 μg / mL, and 50 μg / mL). Measure absorbance at 300-800 nm and plot a standard curve at the maximum absorbance (approximately 426 nm). Accurately weigh a certain mass of the inclusion complex, add anhydrous ethanol, and sonicate for 20 min. After dissolution, transfer to a 100 mL amber volumetric flask and dilute to the mark with anhydrous ethanol. Using anhydrous ethanol as a blank, measure the absorbance of the inclusion complex at 423 nm to calculate the inclusion rate of the curcumin / cyclodextrin inclusion complex.

[0158] The water vapor permeability and oxygen permeability of the preservation coatings provided in Examples 1-13 were tested. The specific test steps are as follows:

[0159] (1) Water vapor transmission coefficient of the preservation coating

[0160] The water vapor barrier properties of the food preservation coating were tested in accordance with the national standard GB / T 1037-2021 "Determination of Water Vapor Permeability of Plastic Films and Sheets - Cup Weight Gain and Weight Loss Method".

[0161] (2) Oxygen permeability coefficient of the preservation coating

[0162] The oxygen barrier performance was tested using an oxygen permeation meter. The specific method was as follows: one side of the coating film was filled with pure oxygen, and the other side was evacuated. Due to the osmotic pressure difference between the two sides of the film, oxygen permeated through the pure oxygen side of the film into the vacuum side. The oxygen barrier performance of the preservation coating could be obtained by monitoring the pressure change on the vacuum side.

[0163] The test results are shown in Table 1.

[0164] Table 1. Test results of the performance of the preservative liquid and preservative coating

[0165] Inclusion rate (%) of curcumin / cyclodextrin inclusion complex <![CDATA[Water vapor transmission coefficient kg·m / (s·m 2 ·Pa)]]> <![CDATA[Oxygen permeability coefficient cm 3 ·μm / (m 2 ·day·kPa)]]> Example 1 8.5 <![CDATA[10.5×10 -12 ]]> 148 Example 2 9.3 <![CDATA[9.8×10 -12 ]]> 142 Example 3 10.4 <![CDATA[9.3×10 -12 ]]> 135 Example 4 11.5 <![CDATA[8.4×10 -12 ]]> 114 Example 5 12.8 <![CDATA[8.7×10 -12 ]]> 127 Example 6 8.5 <![CDATA[14.6×10 -12 ]]> 166 Example 7 8.5 <![CDATA[10.1×10 -12 ]]> 145 Example 8 8.5 <![CDATA[13.3×10 -12 ]]> 162 Example 9 8.5 <![CDATA[12.5×10 -12 ]]> 147 Example 10 8.5 <![CDATA[13.0×10 -12 ]]> 158 Example 11 8.5 <![CDATA[12.8×10 -12 ]]> 152 Example 12 8.5 <![CDATA[10.3×10 -12 ]]> 145 Example 13 8.5 <![CDATA[10.7×10 -12 ]]> 150

[0166] The rapeseed provided in Example 1 and the comparative example of the present invention were stored in a low-temperature (0-1℃) environment. The appearance of the rapeseed provided in Example 1 after preservation treatment and the rapeseed provided in the comparative example without preservation treatment on the 60th day of storage is as follows: Figure 3 As shown, it can be seen that the rapeseed leaves provided in the comparative example that were not preserved showed extensive rot and even fell off, making them inedible; while the rapeseed provided in Example 1 that underwent preservation treatment remained intact and had edible and nutritional value.

[0167] The cucumbers provided in Example 1 and the comparative example of the present invention were stored in a medium-temperature (10°C) environment. The appearance of the cucumbers provided in Example 1 after preservation treatment and the cucumbers provided in the comparative example without preservation treatment on the 30th day of storage is as follows: Figure 4 As shown, the retention rate of the cucumbers provided in the comparative example without preservation treatment (the proportion of edible cucumbers to all cucumbers) was only 25%, while the retention rate of the cucumbers provided in Example 1 with preservation treatment was 100%.

[0168] The moisture content retention rate, chlorophyll content retention rate, and soluble solids content retention rate of the rapeseed provided in Examples 1-13 and the comparative examples were tested. The test conditions were: ambient temperature 0-1℃, relative humidity 80-90%, and storage time 60 days. The specific test steps are as follows:

[0169] (1) Moisture retention rate

[0170] The moisture content of rapeseed after preservation treatment was tested on day 0 and day 60 of storage, in accordance with the national standard GB 5009.3-201 "National Food Safety Standard - Determination of Moisture in Food". The moisture content of rapeseed before and after storage was obtained and the moisture retention rate was calculated.

[0171] (2) Chlorophyll content retention rate

[0172] Referring to the industry standard NY / T 3082-2017 "Determination of chlorophyll content in fruits, vegetables and their products by spectrophotometry", the chlorophyll content of rapeseed after preservation treatment was tested on day 0 and day 60 of storage to obtain the chlorophyll content of rapeseed before and after storage, and the chlorophyll content retention rate was calculated.

[0173] (3) Soluble solids content retention rate

[0174] Referring to the industry standard NY / T 2637-2014 "Determination of Soluble Solids Content in Fruits and Vegetables by Refractometer Method", the soluble solids content of rapeseed after preservation treatment was tested on day 0 and day 60 of storage. The soluble solids content of rapeseed before and after storage was obtained, and the soluble solids content retention rate was calculated.

[0175] The test results are shown in Table 2.

[0176] Table 2. Test results of rapeseed storage and preservation.

[0177] Moisture content retention rate % Chlorophyll content retention rate % Soluble solids retention rate (%) Example 1 95.1 50.3 80.3 Example 2 95.6 53.5 81.5 Example 3 96.5 57.6 86.6 Example 4 96.8 59.4 89.7 Example 5 96.2 58.2 85.4 Example 6 82.6 28.3 70.6 Example 7 93.2 43.5 75.5 Example 8 84.7 30.4 71.2 Example 9 87.3 35.8 74.3 Example 10 85.8 32.6 72.9 Example 11 86.4 33.4 73.5 Example 12 83.3 31.5 70.8 Example 13 90.5 39.2 74.8 Comparative Example 80.5 26.7 68.1

[0178] The same test method was used to test the moisture content retention rate, chlorophyll content retention rate and soluble solids content retention rate of cucumbers provided in Examples 1-13 and comparative examples. The test conditions were: ambient temperature 10℃, relative humidity 80-90%, and storage time 30 days.

[0179] The test results are shown in Table 3.

[0180] Table 3. Test results for cucumber storage and preservation.

[0181] Moisture content retention rate % Chlorophyll content retention rate % Soluble solids retention rate (%) Example 1 95.3 95.7 70.6 Example 2 95.8 96.2 72.3 Example 3 96.2 96.8 75.8 Example 4 96.7 97.3 77.7 Example 5 97.0 97.8 79.5 Example 6 82.5 90.5 61.3 Example 7 96.4 97.5 76.4 Example 8 88.7 92.2 63.5 Example 9 91.3 93.4 65.4 Example 10 84.3 91.0 61.8 Example 11 86.1 91.8 62.6 Example 12 81.2 90.3 60.5 Example 13 90.6 92.6 64.2 Comparative Example 76.2 86.5 56.1

[0182] As can be seen from the test data provided in Table 1, the water vapor transmission coefficient of the preservation coatings prepared in Examples 1-5 is 8 × 10⁻⁶. -12 -10×10 -12 kg·m / (s·m 2 (·Pa), oxygen permeability coefficient is 110-150cm 3 ·μm / (m 2The reading (·day·kPa) indicates that the preservation coating prepared by this invention has excellent oxygen barrier and water retention capabilities.

[0183] The test data provided in Tables 2 and 3 show that after 60 days of storage, rapeseed retains 95-97% of its moisture content, 40-60% of its chlorophyll content, and 80-90% of its soluble solids content. Cucumbers, after 30 days of storage, retain 95-97% of their moisture content, 95-98% of their chlorophyll content, and 70-80% of their soluble solids content.

[0184] The test data provided in Examples 1, 6, and 7 show that the mass fraction of the nanocellulose solution in Example 6 was too low, resulting in a low viscosity of the preservative solution, which affected its adhesion to the surface of fruits and vegetables. Therefore, it was not easy to form a complete preservative coating on the surface of fruits and vegetables by dip coating, ultimately affecting the preservation effect on rapeseed and cucumber. In Example 7, the mass fraction of the nanocellulose solution was too high, resulting in gelation of the fruit and vegetable preservative solution, which affected its processing performance. The preservative coating prepared by dip coating was uneven in thickness, affecting the actual preservation effect.

[0185] The test data provided in Examples 1, 8 and 9 show that the amount of beeswax added in Example 8 was too low, which could not enhance the moisture barrier and water resistance properties, and ultimately affected the preservation effect on rapeseed and cucumber. The amount of beeswax added in Example 9 was too high, which caused discontinuous crystallization of beeswax in the preservation coating, destroyed the three-dimensional network formed by nanocellulose, and resulted in poor oxygen barrier properties, which ultimately affected the preservation effect on rapeseed and cucumber.

[0186] The test data provided in Examples 1, 10, and 11 show that in Example 10, the amount of glycerol added was too low, causing the preservative coating to crack and failing to achieve the desired preservation effect. In Example 11, the amount of glycerol added was too high, reducing the density of the preservative coating and thus promoting the increase in oxygen permeability. This reduced the oxygen barrier capacity of the preservative coating, ultimately affecting the preservation effect on rapeseed and cucumber.

[0187] The test data provided in Examples 1, 12, and 13 show that the amount of curcumin / cyclodextrin inclusion complex added in Example 12 was too low. Due to the low effective content of the functional components, the antibacterial and antioxidant effects of the preservation coating were reduced, ultimately affecting the preservation effect on rapeseed and cucumber. In Example 13, the amount of curcumin / cyclodextrin inclusion complex added was too high. As the cyclodextrin molecules crystallized and precipitated during the formation of the preservation coating, the uniformity and integrity of the preservation coating were destroyed, affecting the barrier properties of the preservation coating and thus affecting the preservation effect of the preservation coating.

[0188] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. An edible compound preservative liquid for low-temperature refrigeration and preservation of fruits and vegetables, characterized in that, The edible composite preservative liquid includes a phosphorylated nanocellulose solution, a film-forming agent, a plasticizer, a biosurfactant, and a curcumin / cyclodextrin inclusion complex; The film-forming agent includes beeswax and / or coconut oil, the plasticizer includes glycerin and / or potassium sorbate, and the biosurfactant includes rhamnolipin and sophorolipid; The phosphorylated cellulose nanoparticle solution has a mass fraction of 0.2-0.4 wt%. The amount of film-forming agent added is 20-50 wt% based on the dry weight of phosphorylated nanocellulose in the phosphorylated nanocellulose solution. The amount of plasticizer added is 20-50 wt% based on the dry weight of phosphorylated nanocellulose in the phosphorylated nanocellulose solution. Based on the total mass of the phosphorylated nanocellulose solution, the amount of the biosurfactant added is 0.02-0.12 wt%, and the mass ratio of rhamnolipin to sophorolipid is 1:(0.2-0.3). The amount of curcumin / cyclodextrin inclusion complex added is 5-10 wt%, based on the dry weight of phosphorylated nanocellulose in the phosphorylated nanocellulose solution. The edible compound preservative liquid is prepared using the following method: (I) A modified solution is obtained by mixing phosphorylation reagent, urea and deionized water. The fiber raw material is immersed in the modified solution and taken out after a period of time. It is then subjected to heating and drying and high-temperature curing in sequence to obtain phosphorylated cellulose. Phosphorylated cellulose was dispersed in deionized water to form a mixture, and the mixture was homogenized under high pressure to obtain a phosphorylated nanocellulose solution. The mass fraction of the phosphorylation reagent in the modified solution is 10-20 wt%. The modified solution contains 25-40 wt% urea. (II) Prepare cyclodextrin solution and curcumin solution respectively. The mass fraction of cyclodextrin solution is 3-6 wt%, and the concentration of curcumin solution is 0.005-0.01 g / mL. Mix the cyclodextrin solution and curcumin solution evenly, then cool and crystallize. Collect the crystallized product, filter and dry the crystallized product in sequence to obtain curcumin / cyclodextrin inclusion complex. (III) The phosphorylated nanocellulose solution, film-forming agent, plasticizer, biosurfactant and curcumin / cyclodextrin inclusion complex are mixed in proportion and heated until the film-forming agent melts to obtain a precursor solution; then, the precursor solution is emulsified and defoamed in sequence to obtain the edible composite preservative liquid; The method of using the edible compound preservative liquid for low-temperature refrigeration and preservation of fruits and vegetables includes: Soak the fruits and vegetables to be preserved in an edible compound preservative solution, or spray the edible compound preservative solution onto the surface of the fruits and vegetables to be preserved. The fruits and vegetables are then air-dried naturally to form a preservative coating on their surface.

2. The edible compound preservative liquid according to claim 1, characterized in that, In step (I), the phosphorylation reagent includes any one or a combination of at least two of diammonium hydrogen phosphate, diammonium dihydrogen phosphate, disodium hydrogen phosphate, or sodium dihydrogen phosphate; The soaking time is 0.5-1.5 hours; The soaking temperature is 60-80℃; The high-temperature curing time is 20-30 minutes; The high-temperature curing temperature is 100-200℃; The solid content of the mixture is 0.5-0.7 wt%; Before high-pressure homogenization of the mixture, 10-30 wt% alkali solution is added to the mixture to adjust the pH value of the mixture to 9.3-9.6; The pressure of the high-pressure homogenizer is 600-1000 bar; The high-pressure homogenization is performed 3-6 times.

3. The edible compound preservative liquid according to claim 1, characterized in that, In step (II), the preparation process of the cyclodextrin solution includes: dissolving cyclodextrin in deionized water at an ambient temperature of 60-70℃ to obtain the cyclodextrin solution; The preparation process of the curcumin solution includes: dissolving curcumin in ethanol at an ambient temperature of 60-70℃ to obtain the curcumin solution; The mixing process of the cyclodextrin solution and curcumin solution includes: adding curcumin solution dropwise to the cyclodextrin solution at an ambient temperature of 60-70℃. After all the curcumin solution has been added, the ambient temperature is kept constant and stirring is continued for 2-4 hours.

4. The edible compound preservative liquid according to claim 1, characterized in that, In step (II), the temperature for cooling crystallization is 1-10℃; The cooling and crystallization time is 8-12 hours; The drying temperature is 40-60℃.

5. The edible compound preservative liquid according to claim 1, characterized in that, In step (III), the heating temperature is 80-90℃; The emulsification time is 1-10 minutes; The degassing time is 5-10 minutes.

6. The edible compound preservative liquid according to claim 1, characterized in that, The soaking time for a single soak is 5-60 seconds; The soaking is performed 2-5 times; The spraying flow rate is 5-20 mL / min.

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