An edible preservative solution with sustained-release antibacterial components, its preparation method and usage method

Abstract

This invention provides an edible preservative solution with sustained-release antibacterial components, its preparation method, and its usage method, comprising a nanocellulose solution, beeswax, glycerin, and a curcumin / cyclodextrin inclusion complex. The preparation method includes: (I) mixing a cyclodextrin solution and a curcumin solution uniformly, cooling to crystallize, filtering and drying to obtain the curcumin / cyclodextrin inclusion complex; (II) mixing a nanocellulose solution, beeswax, and glycerin in a specific ratio and heating until the beeswax melts to obtain a mixture, which is then emulsified to obtain a nanocellulose emulsion; (III) mixing the curcumin / cyclodextrin inclusion complex obtained in step (I) and the nanocellulose emulsion obtained in step (II) in a specific ratio to obtain a precursor solution, which is then degassed under vacuum to obtain the edible preservative solution. This invention utilizes cyclodextrin to encapsulate curcumin, which enhances the solubility of curcumin in the preservative solution. The curcumin is contained within the hydrophobic cavity of the cyclodextrin molecule and released gradually, resulting in a long-lasting antibacterial effect.

Description

Technical Field

[0001] This invention belongs to the field of fruit and vegetable preservation technology, and relates to an edible preservation liquid with antibacterial component slow-release function, its preparation method and usage method. Background Technology

[0002] Fresh agricultural products such as fruits and vegetables suffer particularly severe losses in the post-harvest supply chain due to factors such as dehydration and respiration metabolism. my country is a major consumer of fruit and a major importer of tropical fruits; 20-30% of its fruit is wasted annually in the post-harvest supply chain, causing significant economic losses. To extend shelf life, various fruit preservation technologies have been developed, such as refrigeration, modified atmosphere packaging (MAP), and preservation coatings. Preservation coatings are transparent, uniform, inert barrier substances applied directly to the fruit's surface. They extend shelf life by blocking gases, inhibiting respiration, reducing moisture loss, and minimizing fruit shrinkage. Simultaneously, preservation coatings also delay fruit color changes, preserve fruit aroma, and inhibit microbial growth. Edible preservation coatings are typically composed of polysaccharides, proteins, lipids, or combinations of these substances and can be consumed with food.

[0003] Nanocellulose exhibits significant application potential in the field of edible preservation coatings due to its high strength, excellent gas barrier properties and film-forming performance, safety, non-toxicity, and good biocompatibility. However, single nanocellulose materials often fail to meet the simultaneous needs of fruit and vegetable preservation due to their limited functionality; therefore, the development of multifunctional nanocellulose-based composite coatings with combined functional components has become a research hotspot in recent years.

[0004] Currently, curcumin, used as an antibacterial component for food preservation, suffers from problems such as low solubility, high volatility, and strong odor. Direct physical blending with the coating matrix leads to low bioavailability, short duration of action, and poor consumer acceptance. Therefore, there is an urgent need to develop suitable encapsulation technologies to improve the solubility and stability of functional components, control their release, and enhance the performance of food preservation coatings. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide an edible preservative liquid with antibacterial component slow-release function, its preparation method and usage method.

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

[0007] In a first aspect, the present invention provides an edible preservative liquid with a sustained-release function of antibacterial components, the edible preservative liquid comprising a nanocellulose solution, beeswax, glycerin and curcumin / cyclodextrin inclusion complex.

[0008] This invention develops an edible and easy-to-wash preservative liquid based on nanocellulose. A dip-coating method is used to coat fruits and vegetables, forming a micro-nano-scale preservative coating on their surface. The three-dimensional network structure formed by the cross-entanglement of nanocellulose extends the diffusion path of gases within the preservative coating, thereby reducing its gas permeability and minimizing the loss of moisture and nutrients from the surface and interior of the fruits and vegetables. It also significantly enhances the mechanical strength of the preservative coating. Simultaneously, curcumin in the curcumin / cyclodextrin inclusion complex is contained within the hydrophobic cavity of the cyclodextrin molecule and is gradually released, providing sustained drug release and long-lasting antibacterial effects, further extending the shelf life of fruits and vegetables.

[0009] The nutrient content of fruits and vegetables gradually decreases during respiration. Therefore, reducing respiration can achieve a certain preservation effect and effectively prevent nutrient loss. Lowering the oxygen content of the storage environment while increasing the CO2 content can slow down the respiration intensity of fruits and vegetables, thus achieving a preservation effect. This invention adds nanocellulose to the preservation liquid. After impregnation and coating, the nanocellulose is arranged in an interlaced pattern within the preservation coating, making the diffusion paths of water vapor and other small molecules more tortuous and lengthy, reducing the loss of moisture and nutrients from the surface and interior of the fruits and vegetables, and lowering the gas permeability of the preservation coating. Furthermore, after coating and drying, beeswax forms a strong film layer with a certain gas barrier capacity on the surface of fruits and vegetables. Simultaneously, due to the excellent hydrophobic properties of beeswax, it can reduce the sensitivity of the preservation coating to moisture and improve its water retention capacity. Glycerin, acting as a plasticizer, penetrates into the nanocellulose matrix, improving the fluidity of the nanocellulose molecular chains, thus enhancing the toughness and elasticity of the preservation coating.

[0010] 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, a higher CO2 concentration is 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 inedible. The preservative liquid provided by this invention can prevent external oxygen from penetrating the preservative coating and entering the interior of fruits and vegetables, while also dissipating excess CO2 accumulated by respiration to a certain extent. This is because CO2 has high inductive polarity, generating strong intermolecular forces with nanocellulose molecules containing numerous polar groups. This results in high solubility of CO2 within the preservative coating, exhibiting a high CO2 permeability and effectively preventing the accumulation of toxins caused by anaerobic respiration in fruits and vegetables.

[0011] The preservative solution provided by this invention can regulate O2 and CO2 permeability while also achieving water retention for fruits and vegetables. This is because nanocellulose molecules have a microscopic network structure, exhibiting 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 weight loss and effectively adjusting the air humidity on the surface of fruits and vegetables. By adding nanocellulose to the preservative solution, this invention can effectively inhibit water loss and respiration activity of fruits and vegetables during storage, reducing respiration consumption and achieving long-lasting preservation at room temperature.

[0012] Because cyclodextrin has a special three-dimensional cyclic structure that is hydrophobic inside and hydrophilic outside, this invention uses food-grade, safe, and non-toxic bio-derived cyclodextrin molecules to encapsulate curcumin. This allows curcumin and cyclodextrin to interact through non-covalent bonds, encapsulating the poorly soluble curcumin into its hydrophobic cavity to form a curcumin / cyclodextrin inclusion complex. This not only improves the water solubility of curcumin but also mitigates its light-induced decomposition, resulting in a significant enhancement of curcumin's water solubility, bioavailability, and antioxidant capacity.

[0013] This invention utilizes nanocellulose, which possesses excellent renewability and biocompatibility, to construct a preservative coating that controls and sustainably releases functional components. The nanocellulose, with its high aspect ratio and rod-like structure, has a large specific surface area, facilitating deposition and retention on fruit and vegetable surfaces. 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 nanocellulose and cyclodextrin molecules, allowing for uniform dispersion 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.

[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 by rinsing with water, eliminating consumers' concerns about the safety of preservative coatings.

[0016] As a preferred embodiment of the present invention, the mass fraction of the nanocellulose solution is 0.5-1.5 wt%, for example, it can be 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, or 1.5 wt%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0017] The ultimate goal of this invention, which involves coating fruits and vegetables with a preservative solution, is to provide them with an ideal gaseous environment. By regulating the gaseous atmosphere on the surface of the fruits and vegetables, the storage and shelf life of these products can be extended. This invention incorporates nanocellulose into the preservative solution, enabling the coated film to act as a barrier against moisture transport, reducing water loss from the fruit surface. It also serves as a barrier to protect fruits and vegetables from microbial infection, thereby reducing post-harvest diseases and slowing down respiration rates. Furthermore, the addition of cellulose nanofibers makes the structure of the coated preservative film softer and denser. This preservative coating can delay yellowing of fruits and vegetables such as bananas, mangoes, and strawberries during room temperature storage and significantly inhibit respiration and quality loss, thus maintaining the quality of the fruits and vegetables.

[0018] This invention specifically limits the mass fraction of the nanocellulose solution to 0.5-1.5 wt%. When the mass fraction of the nanocellulose solution is less than 0.5 wt%, the viscosity of the preservative solution is too low due to the low concentration of 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 nanocellulose solution is higher than 1.5 wt%, the viscosity of the preservative solution is too high due to the high concentration of 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 will have uneven thickness, affecting the actual preservation effect.

[0019] As a preferred embodiment of the present invention, the amount of beeswax added is 20-50 wt% based on the dry weight of nanocellulose in the 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.

[0020] This invention uses beeswax as a film-forming agent. The amount of beeswax added directly affects the internal structure of the preservation coating, thereby influencing its comprehensive properties such as water vapor transmission rate, oxygen transmission rate, elongation at break, and tensile strength. Because beeswax contains fatty acids, the hydroxyl groups in the nanocellulose molecular chains interact with the carboxylic acids in the fatty acids through hydrogen bonding and electrostatic interactions. This allows the nanocellulose in the preservation coating to be arranged in a tight and orderly manner, giving the coating a dense network structure and improving its oxygen barrier and water retention capabilities.

[0021] This invention specifically limits the amount of beeswax added to 20-50 wt%. When the amount of beeswax added is less than 20 wt%, it cannot enhance the water barrier and water resistance properties. When the amount of beeswax added exceeds 50 wt%, the hydrophobic and emulsifying effects of beeswax weaken the bonding between nanocellulose molecules, leading to a significant decrease in the tensile strength and elongation at break of the preservation coating. Furthermore, excessive beeswax addition causes discontinuous crystallization in the preservation coating, disrupting the three-dimensional network formed by nanocellulose and resulting in poor oxygen barrier properties. It also leads to uneven stress distribution within the preservation coating, deteriorating mechanical properties. Simultaneously, some lipids precipitate, reducing the smoothness of the preservation coating surface, ultimately resulting in a significant decrease in the tensile strength and elongation at break of the preservation coating. This invention comprehensively considers the impact of the amount of beeswax added on various properties of the preservation coating and particularly optimizes the beeswax addition amount to 20-50 wt%.

[0022] In some preferred embodiments, the amount of glycerol added is 20-50 wt% based on the dry weight of the nanocellulose in the 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.

[0023] This invention uses glycerol as a plasticizer, and the amount of glycerol added significantly affects the performance of the preservation coating. First, since glycerol is a small organic molecule, adding an appropriate amount can increase the interaction between nanocellulose molecules and beeswax molecules, and also fill the gaps in the 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 can penetrate into the nanocellulose matrix, reducing the intermolecular forces between nanocellulose molecular chains, activating the chains and making them easier to slide, increasing the fluidity of the nanocellulose molecular chains and improving the toughness and elasticity of the preservation coating. Third, the hydroxyl groups in the glycerol molecules form hydrogen bonds with the carboxyl groups on the nanocellulose molecular chains, enhancing the intermolecular interactions of the preservation coating and increasing its tensile strength and elongation at break.

[0024] This invention specifically limits the amount of glycerol added to 20-50 wt%. When the amount of glycerol added is less than 20 wt%, the brittleness of the nanocellulose leads to cracking of the preservative coating, rendering it ineffective for preservation. When the amount of glycerol added exceeds 50 wt%, the fluidity of the nanocellulose molecular chains is further enhanced, leading to increased porosity between the nanocellulose molecular chains, reducing the density of the preservative coating, and thus promoting oxygen permeability, resulting in a decrease in the oxygen barrier capacity of the preservative coating. Furthermore, excessive glycerol addition enhances the softening effect of glycerol on the preservative coating, thereby weakening its rigidity and reducing its tensile strength. This invention comprehensively considers the impact of the amount of glycerol added on various properties of the preservative coating and particularly optimizes the amount of glycerol added to 20-50 wt%.

[0025] In some preferred embodiments, the amount of curcumin / cyclodextrin inclusion complex added is 5-10 wt% based on the dry weight of nanocellulose in the 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] As a preferred embodiment of the present invention, the nanocellulose solution is composed of nanocellulose and water.

[0030] In some preferred embodiments, the nanocellulose comprises cellulose nanofibers and / or cellulose nanocrystals.

[0031] As a preferred technical solution of the present invention, the nanocellulose is cellulose nanofiber and cellulose nanocrystal.

[0032] Nanocellulose includes cellulose nanofibers and cellulose nanocrystals. This invention uses a specific ratio of cellulose nanofibers and cellulose nanocrystals to effectively improve the gas barrier properties of the preservation coating and the stability of the preservation liquid.

[0033] In improving the gas barrier properties of food preservation coatings, cellulose nanocrystals are extracted from the crystalline regions of microfibers through strong acid hydrolysis of disordered cellulose. They are highly crystalline rod-shaped structures with lengths of several hundred nanometers and diameters of less than one hundred nanometers. Cellulose nanofibers, on the other hand, are fibrous structures with high aspect ratios, ranging in length from several micrometers to tens of micrometers and diameters of less than 100 nanometers. They can form a three-dimensional network structure through physical entanglement. The porous structure within the food preservation coating is the main channel for oxygen permeation. This invention combines cellulose nanofibers and cellulose nanocrystals in a specific ratio. Through the physical entanglement of the cellulose nanofibers, a three-dimensional network structure with a certain degree of porosity is formed. The highly crystalline rod-shaped cellulose nanocrystals can be embedded within this three-dimensional network structure, thereby increasing the density of the food preservation coating. This dense network structure increases the tortuosity of gas passage within the coating, thus reducing oxygen permeability.

[0034] In improving the storage stability of preservative solutions, the stabilizing performance of nanocellulose emulsions is mainly related to their morphology and hydrophilic / hydrophobic properties. Shorter cellulose nanocrystals are more rigid and can be tightly adsorbed onto the surface of emulsion droplets during emulsion stabilization, but they are prone to emulsion flocculation. Longer cellulose nanofibers, on the other hand, are more flexible and mainly distributed in the aqueous phase in a three-dimensional network structure, which can inhibit emulsion flocculation. This invention combines cellulose nanofibers and cellulose nanocrystals to achieve a synergistic effect. The shorter cellulose nanocrystals are tightly adsorbed at the oil / water interface, while the longer cellulose nanofibers form bridging structures between adjacent emulsion droplets and a three-dimensional network structure in the continuous phase, thereby improving the storage stability of the preservative solution.

[0035] In some preferred embodiments, the mass ratio of the cellulose nanofibers to the cellulose nanocrystals is (1-3):1, for example, it can be 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1 or 3:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0036] This invention further specifies that the mass ratio of cellulose nanofibers to cellulose nanocrystals is (1-3):1. When the proportion of cellulose nanocrystals added is low, the cellulose nanocrystals cannot completely coat the emulsion droplets. At this time, the emulsion droplets will aggregate, resulting in a gradual increase in particle size. Emulsion instability leads to the precipitation and stratification of the oil phase in the preservative liquid, resulting in poor stability of the preservative liquid. In addition, due to the reduced proportion of cellulose nanocrystals, the free volume of the coating increases, and the gas barrier performance deteriorates. As the proportion of cellulose nanocrystals added increases, a sufficient number of cellulose nanocrystals adsorb onto the surface of the emulsion droplets and form a dense monolayer interfacial film, thereby preventing the emulsion droplets from contacting each other. At this time, the size of the emulsion droplets will be reduced to a minimum and remain basically unchanged. As the proportion of cellulose nanocrystals added continues to increase, the cellulose nanocrystals will form a multilayer dense interfacial film on the surface of the emulsion droplets or form a gel network structure in the continuous phase, which can effectively prevent the aggregation between emulsion droplets, making the emulsion system of the preservative liquid more stable. However, when the proportion of cellulose nanocrystals added to the preservative liquid is too high, the cellulose nanocrystals in the dispersed phase of the preservative liquid are prone to agglomeration and emulsion flocculation, which leads to instability of the preservative liquid. In addition, the proportion of cellulose nanofibers decreases accordingly, resulting in a reduction of the three-dimensional network structure in the preservative coating matrix, which ultimately affects the gas barrier performance of the preservative coating.

[0037] Secondly, the present invention provides a method for preparing the edible preservative liquid described in the first aspect, the preparation method comprising:

[0038] (I) Mix the cyclodextrin solution and curcumin solution evenly, then cool and crystallize, filter and dry to obtain curcumin / cyclodextrin inclusion complex;

[0039] (II) Mix nanocellulose solution, beeswax and glycerin in a certain proportion and heat until the beeswax melts to obtain a mixture; then emulsify the mixture to obtain a nanocellulose emulsion;

[0040] (III) The curcumin / cyclodextrin inclusion complex obtained in step (I) is mixed with the nanocellulose emulsion obtained in step (II) in a certain proportion to obtain a precursor solution. The precursor solution is then degassed under vacuum to obtain the edible preservative liquid.

[0041] This invention uses safe, non-toxic, and low-cost agricultural waste beeswax and nanocellulose to prepare a Pickering emulsion (preservative liquid) with preservation function through high-temperature emulsification. The preservative liquid is applied to the surface of fruits and vegetables by coating, impregnation, coating or spraying, and a film is formed on the surface to form a preservative coating, which can effectively extend the storage period and freshness period of fruits and vegetables.

[0042] Compared with other physical or chemical preservation materials, the biomass material preservation liquid provided by this invention has excellent biodegradability. The preparation process does not require the addition of toxic or harmful chemical reagents, making it environmentally friendly and in line with the development concept of green chemistry.

[0043] The preservation coating formed by the edible preservation liquid provided by this invention has selective air permeability and anti-permeability, which can prevent the migration of moisture and nutrients on the surface and inside of fruits and vegetables, thus preventing food spoilage. This extends the storage and freshness period of fruits and vegetables, and improves their oxygen-barrier and water-retention capacity. Fruits and vegetables coated with the preservation liquid provided by this invention can still retain an intact preservation coating after being soaked in water for 24 hours. Therefore, the preservation liquid provided by this invention can be used in fruit and vegetable preservation application scenarios under extreme conditions of high relative humidity.

[0044] 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.

[0045] As a preferred technical solution of the present invention, in step (I), 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] In some preferred embodiments, 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°C. After all the curcumin solution has been added, the ambient temperature is maintained and stirring is continued for 2-4 hours. 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. Other unlisted values ​​within this range are also applicable.

[0050] In some preferred embodiments, the cooling crystallization temperature is 1-10°C, for example, it can be 1°C, 2°C, 3°C, 4°C, 5°C, 6°C, 7°C, 8°C, 9°C or 10°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0051] 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.

[0052] 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.

[0053] As a preferred technical solution of the present invention, in step (II), 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.

[0054] 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.

[0055] This invention does not impose specific requirements or limitations on the emulsification method, such as ultrasonic emulsification, homogenization, ultra-high pressure homogenization, or grinding.

[0056] 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.

[0057] In some preferred embodiments, in step (III), the mixing method is mechanical stirring.

[0058] In some preferred embodiments, the mechanical stirring speed is 200-1000 rpm, for example, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm, 800 rpm, 850 rpm, 900 rpm, 950 rpm, or 1000 rpm, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0059] In some preferred embodiments, the mechanical stirring time is 1-5 min, for example, it can be 1.0 min, 1.5 min, 2.0 min, 2.5 min, 3.0 min, 3.5 min, 4.0 min, 4.5 min or 5.0 min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0060] In some preferred embodiments, the vacuum degassing time is 5-10 min, for example, it can be 5.0 min, 5.5 min, 6.0 min, 6.5 min, 7.0 min, 7.5 min, 8.0 min, 8.5 min, 9.0 min, 9.5 min or 10.0 min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0061] Thirdly, the present invention provides a method for using the edible preservative liquid described in the first aspect, the method comprising:

[0062] Soak the fruits and vegetables to be preserved in an edible preservative solution at least once. After soaking, remove the fruits and vegetables and let them air dry naturally to form a preservative coating on the surface of the fruits and vegetables.

[0063] 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.

[0064] 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.

[0065] For example, the present invention provides a method for preparing an edible preservative liquid with a sustained-release function of antibacterial components, specifically including the following steps:

[0066] (1) 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 1-10℃ for 8-12 h. The crystallized product was filtered and dried at 40-60℃ to obtain the curcumin / cyclodextrin inclusion complex.

[0067] (2) Mix 0.5-1.5 wt% of nanocellulose solution (including cellulose nanofibers and cellulose nanocrystals in a mass ratio of (1-3):1), beeswax and glycerin; wherein, based on the dry weight of nanocellulose in the nanocellulose solution, the amount of beeswax added is 20-50 wt% and the amount of glycerin added is 20-50 wt%; after mixing, heat to 80-90℃ until the beeswax melts to obtain a mixture; emulsify the mixture for 1-10 min to obtain a nanocellulose emulsion;

[0068] (3) Mix the curcumin / cyclodextrin inclusion complex obtained in step (1) with the nanocellulose emulsion obtained in step (2). The amount of curcumin / cyclodextrin inclusion complex added is 5-10 wt% based on the dry weight of nanocellulose in the nanocellulose solution. Stir at 200-1000 rpm for 1-5 min to obtain a precursor solution. Degas the precursor solution under vacuum for 5-10 min to obtain the edible preservative liquid.

[0069] For example, the present invention also provides a method for using an edible preservative liquid, which specifically includes the following steps:

[0070] Soak freshly picked fruits and vegetables in an edible preservative solution 2-5 times, each time for 5-60 seconds. After soaking, remove the fruits and vegetables and let them air dry naturally to form a preservative coating on the surface.

[0071] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0072] This invention develops an edible and easy-to-wash preservative liquid based on nanocellulose. A dip-coating method is used to coat fruits and vegetables, forming a micro-nano-scale preservative coating on their surface. The three-dimensional network structure formed by the cross-entanglement of nanocellulose extends the diffusion path of gases within the preservative coating, thereby reducing its gas permeability and minimizing the loss of moisture and nutrients from the surface and interior of the fruits and vegetables. It also significantly enhances the mechanical strength of the preservative coating. Simultaneously, curcumin in the curcumin / cyclodextrin inclusion complex is contained within the hydrophobic cavity of the cyclodextrin molecule and is gradually released, providing sustained drug release and long-lasting antibacterial effects, further extending the shelf life of fruits and vegetables.

[0073] The nutrient content of fruits and vegetables gradually decreases during respiration. Therefore, reducing respiration can achieve a certain preservation effect and effectively prevent nutrient loss. Lowering the oxygen content of the storage environment while increasing the CO2 content can slow down the respiration intensity of fruits and vegetables, thus achieving a preservation effect. This invention adds nanocellulose to the preservation liquid. After impregnation and coating, the nanocellulose is arranged in an interlaced pattern within the preservation coating, making the diffusion paths of water vapor and other small molecules more tortuous and lengthy, reducing the loss of moisture and nutrients from the surface and interior of the fruits and vegetables, and lowering the gas permeability of the preservation coating. Furthermore, after coating and drying, beeswax forms a strong film layer with a certain gas barrier capacity on the surface of fruits and vegetables. Simultaneously, due to the excellent hydrophobic properties of beeswax, it can reduce the sensitivity of the preservation coating to moisture and improve its water retention capacity. Glycerin, acting as a plasticizer, penetrates into the nanocellulose matrix, improving the fluidity of the nanocellulose molecular chains, thus enhancing the toughness and elasticity of the preservation coating.

[0074] 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, a higher CO2 concentration is 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 inedible. The preservative liquid provided by this invention can prevent external oxygen from penetrating the preservative coating and entering the interior of fruits and vegetables, while also dissipating excess CO2 accumulated by respiration to a certain extent. This is because CO2 has high inductive polarity, generating strong intermolecular forces with nanocellulose molecules containing numerous polar groups. This results in high solubility of CO2 within the preservative coating, exhibiting a high CO2 permeability and effectively preventing the accumulation of toxins caused by anaerobic respiration in fruits and vegetables.

[0075] The preservative solution provided by this invention can regulate O2 and CO2 permeability while also achieving water retention for fruits and vegetables. This is because nanocellulose molecules have a microscopic network structure, exhibiting 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 weight loss and effectively adjusting the air humidity on the surface of fruits and vegetables. By adding nanocellulose to the preservative solution, this invention can effectively inhibit water loss and respiration activity of fruits and vegetables during storage, reducing respiration consumption and achieving long-lasting preservation at room temperature.

[0076] Because cyclodextrin has a special three-dimensional cyclic structure that is hydrophobic inside and hydrophilic outside, this invention uses food-grade, safe, and non-toxic bio-derived cyclodextrin molecules to encapsulate curcumin. This allows curcumin and cyclodextrin to interact through non-covalent bonds, encapsulating the poorly soluble curcumin into its hydrophobic cavity to form a curcumin / cyclodextrin inclusion complex. This not only improves the water solubility of curcumin but also mitigates its light-induced decomposition, resulting in a significant enhancement of curcumin's water solubility, bioavailability, and antioxidant capacity.

[0077] This invention utilizes nanocellulose, which possesses excellent renewability and biocompatibility, to construct a preservative coating that controls and sustainably releases functional components. The nanocellulose, with its high aspect ratio and rod-like structure, has a large specific surface area, facilitating deposition and retention on fruit and vegetable surfaces. 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 nanocellulose and cyclodextrin molecules, allowing for uniform dispersion 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.

[0078] 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.

[0079] 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 by rinsing with water, eliminating consumers' concerns about the safety of preservative coatings. Attached Figure Description

[0080] Figure 1 The infrared spectrum of the curcumin / cyclodextrin inclusion complex prepared in Example 1 of this invention;

[0081] Figure 2 Here is a photograph of the curcumin / cyclodextrin inclusion complex prepared in Example 1 of this invention;

[0082] Figure 3 These are photographs showing the appearance of bananas during storage and preservation tests conducted in Example 1 and the comparative example of the present invention.

[0083] Figure 4 These are photographs showing the appearance of strawberries during storage and preservation tests conducted in Example 1 and the comparative example of this invention. Detailed Implementation

[0084] 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.

[0085] Example 1

[0086] This embodiment provides a method for preparing an edible preservative liquid with antibacterial component slow-release function, specifically including the following steps:

[0087] (1) At an ambient temperature of 60℃, β-cyclodextrin was dissolved in 100g of deionized water to obtain a 3wt% β-cyclodextrin solution; at an ambient temperature of 60℃, curcumin was dissolved in 210mL of ethanol to obtain a 0.005g / mL curcumin solution; at an ambient temperature of 60℃, 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 and crystallized at 1℃ for 8h. The crystallized product was filtered and dried at 40℃ to obtain a curcumin / cyclodextrin inclusion complex.

[0088] (2) Mix 0.5 wt% nanocellulose solution (including cellulose nanofibers and cellulose nanocrystals in a mass ratio of 1:1), beeswax and glycerin; wherein, based on the dry weight of nanocellulose in the nanocellulose solution, the amount of beeswax added is 20 wt% and the amount of glycerin added is 20 wt%; after mixing, heat to 80°C until the beeswax melts to obtain a mixture; emulsify the mixture for 1 min to obtain a nanocellulose emulsion;

[0089] (3) The curcumin / cyclodextrin inclusion complex obtained in step (1) is mixed with the nanocellulose emulsion obtained in step (2). The amount of curcumin / cyclodextrin inclusion complex added is 5 wt% based on the dry weight of nanocellulose in the nanocellulose solution. The mixture is stirred at 200 rpm for 1 min to obtain the precursor solution. The precursor solution is then degassed under vacuum for 5 min to obtain the edible preservative liquid.

[0090] This embodiment also provides a method for using an edible preservative liquid, which specifically includes the following steps:

[0091] Freshly picked bananas and strawberries are soaked in an edible preservative solution twice, for 60 seconds each time. After soaking, the bananas and strawberries are removed and air-dried to form a preservative coating on their surface.

[0092] Figure 2 Photographs of β-cyclodextrin, curcumin, a blend of β-cyclodextrin and curcumin, and the curcumin / cyclodextrin inclusion complex prepared in step (1) are shown. Infrared spectral analysis was performed on the β-cyclodextrin, curcumin, the blend of β-cyclodextrin and curcumin, and the curcumin / cyclodextrin inclusion complex prepared in step (1), yielding the following results: Figure 1 The infrared spectrum shown.

[0093] exist Figure 1 Middle, 3510cm -1 The characteristic absorption peak that appears is caused by the stretching vibration of the phenolic hydroxyl group, at 1627 cm⁻¹. -1 and 1505cm -1 The characteristic peak at 3402 cm⁻¹ corresponds to the stretching vibrations (C=O and C=C) of the benzene ring. In the infrared spectrum of β-cyclodextrin, the peak at 3402 cm⁻¹... -1 The characteristic absorption peak that appears is caused by the stretching vibration of the hydroxyl group, at 2927 cm⁻¹. -1 1167cm -1 and 1032cm -1 The characteristic absorption peaks at [values ​​missing] correspond to the stretching vibrations of CH, COC, and CO, respectively. In the infrared spectrum of the physical blend of β-cyclodextrin and curcumin, it is clearly a simple superposition of the infrared spectra of curcumin and β-cyclodextrin, indicating that no other interactions occurred during the physical mixing process. The infrared spectrum of the curcumin / cyclodextrin inclusion complex [values ​​missing] at 1281 cm⁻¹ [values ​​missing]. -1 The peak is 1278cm high. -1 -1361cm -1 The three weak peaks between [a specific value] indicate that β-cyclodextrin reacts with the benzene ring on the enol side of the curcumin molecule. (1627 cm⁻¹) -1 The peak at that location shifted to 1635 cm. -1The infrared spectrum of the β-cyclodextrin and curcumin blend did not show any peak shift, indicating a change in the benzene ring of the curcumin / cyclodextrin inclusion complex. Furthermore, almost all characteristic peaks of curcumin disappeared, while the infrared spectrum of the curcumin / cyclodextrin inclusion complex was similar to that of β-cyclodextrin. This is because the amount of curcumin in the curcumin / cyclodextrin inclusion complex is very small. These changes indicate that the present invention prepared a curcumin / cyclodextrin inclusion complex, rather than a simple physical blend.

[0094] Example 2

[0095] This embodiment provides a method for preparing an edible preservative liquid with antibacterial component slow-release function, specifically including the following steps:

[0096] (1) 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.

[0097] (2) Mix 0.7wt% nanocellulose solution (including cellulose nanofibers and cellulose nanocrystals in a mass ratio of 1.5:1), beeswax and glycerin; wherein, based on the dry weight of nanocellulose in the nanocellulose solution, the amount of beeswax added is 30wt% and the amount of glycerin added is 30wt%; after mixing, heat to 82℃ until the beeswax melts to obtain a mixture; emulsify the mixture for 3min to obtain a nanocellulose emulsion;

[0098] (3) The curcumin / cyclodextrin inclusion complex obtained in step (1) is mixed with the nanocellulose emulsion obtained in step (2). The amount of curcumin / cyclodextrin inclusion complex added is 6 wt% based on the dry weight of nanocellulose in the nanocellulose solution. The mixture is stirred at 400 rpm for 2 min to obtain a precursor solution. The precursor solution is then degassed under vacuum for 6 min to obtain the edible preservative liquid.

[0099] This embodiment also provides a method for using an edible preservative liquid, which specifically includes the following steps:

[0100] Freshly picked bananas and strawberries are soaked in an edible preservative solution three times, for 40 seconds each time. After soaking, the bananas and strawberries are removed and air-dried to form a preservative coating on their surface.

[0101] Example 3

[0102] This embodiment provides a method for preparing an edible preservative liquid with antibacterial component slow-release function, specifically including the following steps:

[0103] (1) 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 a curcumin / cyclodextrin inclusion complex.

[0104] (2) Mix 1 wt% nanocellulose solution (including cellulose nanofibers and cellulose nanocrystals in a mass ratio of 2:1), beeswax and glycerin; wherein, based on the dry weight of nanocellulose in the nanocellulose solution, the amount of beeswax added is 40 wt% and the amount of glycerin added is 40 wt%; after mixing, heat to 85°C until the beeswax melts to obtain a mixture; emulsify the mixture for 5 min to obtain a nanocellulose emulsion;

[0105] (3) The curcumin / cyclodextrin inclusion complex obtained in step (1) is mixed with the nanocellulose emulsion obtained in step (2). The amount of curcumin / cyclodextrin inclusion complex added is 7wt% based on the dry weight of nanocellulose in the nanocellulose solution. The mixture is stirred at 600 rpm for 3 min to obtain the precursor solution. The precursor solution is then degassed under vacuum for 7 min to obtain the edible preservative liquid.

[0106] This embodiment also provides a method for using an edible preservative liquid, which specifically includes the following steps:

[0107] Freshly picked bananas and strawberries are soaked in an edible preservative solution four times, for 30 seconds each time. After soaking, the bananas and strawberries are removed and air-dried to form a preservative coating on their surface.

[0108] Example 4

[0109] This embodiment provides a method for preparing an edible preservative liquid with antibacterial component slow-release function, specifically including the following steps:

[0110] (1) At an ambient temperature of 68℃, β-cyclodextrin was dissolved in 100g of deionized water to obtain a 5wt% β-cyclodextrin solution; at an ambient temperature of 68℃, curcumin was dissolved in 210mL of ethanol to obtain a 0.008g / mL curcumin solution; at an ambient temperature of 68℃, 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℃ for 11h. The crystallized product was filtered and dried at 55℃ to obtain a curcumin / cyclodextrin inclusion complex.

[0111] (2) Mix 1.2 wt% nanocellulose solution (including cellulose nanofibers and cellulose nanocrystals in a mass ratio of 2.5:1), beeswax and glycerin; wherein, based on the dry weight of nanocellulose in the nanocellulose solution, the amount of beeswax added is 40 wt% and the amount of glycerin added is 40 wt%; after mixing, heat to 88°C until the beeswax melts to obtain a mixture; emulsify the mixture for 7 min to obtain a nanocellulose emulsion;

[0112] (3) The curcumin / cyclodextrin inclusion complex obtained in step (1) is mixed with the nanocellulose emulsion obtained in step (2). The amount of curcumin / cyclodextrin inclusion complex added is 8 wt% based on the dry weight of nanocellulose in the nanocellulose solution. The mixture is stirred at 800 rpm for 4 min to obtain the precursor solution. The precursor solution is then degassed under vacuum for 8 min to obtain the edible preservative liquid.

[0113] This embodiment also provides a method for using an edible preservative liquid, which specifically includes the following steps:

[0114] Freshly picked bananas and strawberries are soaked in an edible preservative solution four times, for 10 seconds each time. After soaking, the bananas and strawberries are removed and air-dried to form a preservative coating on their surface.

[0115] Example 5

[0116] This embodiment provides a method for preparing an edible preservative liquid with antibacterial component slow-release function, specifically including the following steps:

[0117] (1) 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 to crystallize at 10°C for 12h. The crystallized product was filtered and dried at 60°C to obtain a curcumin / cyclodextrin inclusion complex.

[0118] (2) Mix 1.5wt% nanocellulose solution (including cellulose nanofibers and cellulose nanocrystals in a mass ratio of 3:1), beeswax and glycerin; wherein, based on the dry weight of nanocellulose in the nanocellulose solution, the amount of beeswax added is 50wt% and the amount of glycerin added is 50wt%; after mixing, heat to 90℃ until the beeswax melts to obtain a mixture; emulsify the mixture for 10min to obtain a nanocellulose emulsion;

[0119] (3) The curcumin / cyclodextrin inclusion complex obtained in step (1) is mixed with the nanocellulose emulsion obtained in step (2). The amount of curcumin / cyclodextrin inclusion complex added is 10 wt% based on the dry weight of nanocellulose in the nanocellulose solution. The precursor solution is stirred at 1000 rpm for 5 min to obtain the precursor solution. The precursor solution is then degassed under vacuum for 10 min to obtain the edible preservative liquid.

[0120] This embodiment also provides a method for using an edible preservative liquid, which specifically includes the following steps:

[0121] Freshly picked bananas and strawberries are soaked in an edible preservative solution five times, for five seconds each time. After soaking, the bananas and strawberries are removed and air-dried to form a preservative coating on their surface.

[0122] Example 6

[0123] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid. The difference between the preparation method and that in Example 1 is that in step (2), the mass fraction of the nanocellulose solution is adjusted to 0.3 wt% (wherein the ratio of cellulose nanofibers to cellulose nanocrystals remains unchanged), and other process parameters and operating steps are exactly the same as in Example 1.

[0124] This embodiment also provides a method for using a nanocellulose-based edible preservative liquid. Freshly picked bananas and strawberries are dipped in the preservative liquid provided in this embodiment, and the treatment process is the same as in Example 1.

[0125] Example 7

[0126] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid. The difference between the preparation method and that in Example 1 is that in step (2), the mass fraction of the nanocellulose solution is adjusted to 1.8 wt% (wherein the ratio of cellulose nanofibers to cellulose nanocrystals remains unchanged), and other process parameters and operating steps are exactly the same as in Example 1.

[0127] This embodiment also provides a method for using a nanocellulose-based edible preservative liquid. Freshly picked bananas and strawberries are dipped in the preservative liquid provided in this embodiment, and the treatment process is the same as in Example 1.

[0128] Example 8

[0129] 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 (2), the mass ratio of cellulose nanofibers to cellulose nanocrystals is adjusted to 0.5:1 (the mass fraction of the nanocellulose solution remains unchanged), while other process parameters and operating steps are exactly the same as those of Embodiment 1.

[0130] This embodiment also provides a method for using a nanocellulose-based edible preservative liquid. Freshly picked bananas and strawberries are dipped in the preservative liquid provided in this embodiment, and the treatment process is the same as in Example 1.

[0131] Example 9

[0132] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid. The difference between this preparation method and that of Embodiment 1 is that in step (2), the mass ratio of cellulose nanofibers to cellulose nanocrystals is adjusted to 5:1 (the mass fraction of the nanocellulose solution remains unchanged), while other process parameters and operating steps are exactly the same as those of Embodiment 1.

[0133] Example 10

[0134] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid. The difference between this preparation method and that of Embodiment 1 is that in step (2), 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.

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

[0136] Example 11

[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 (2), 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.

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

[0139] Example 12

[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 (2), the amount of glycerol added is adjusted to 15wt%, 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 liquid. Freshly picked bananas and strawberries are dipped in the preservative liquid provided in this embodiment, and the treatment process is the same as in Example 1.

[0142] Example 13

[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 (2), 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.

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

[0145] Example 14

[0146] 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.

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

[0148] Example 15

[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 12wt%, 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 liquid. Freshly picked bananas and strawberries are dipped in the preservative liquid provided in this embodiment, and the treatment process is the same as in Example 1.

[0151] Comparative Example

[0152] This comparison uses freshly picked bananas and strawberries, without any preservation treatment.

[0153] The inclusion rates of the curcumin / cyclodextrin inclusion complexes provided in Examples 1-15 were tested, and the specific test steps are as follows:

[0154] 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.

[0155] The water vapor permeability and oxygen permeability of the preservation coatings provided in Examples 1-15 were tested. The specific test steps are as follows:

[0156] (1) Water vapor transmission coefficient of the preservation coating

[0157] 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".

[0158] (2) Oxygen permeability coefficient of the preservation coating

[0159] 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.

[0160] The test results are shown in Table 1.

[0161] Table 1. Test results of the performance of the preservative liquid and preservative coating

[0162] 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[9.6×10 -12 ]]> 132 Example 2 9.3 <![CDATA[8.2×10 -12 ]]> 128 Example 3 10.4 <![CDATA[7.4×10 -12 ]]> 114 Example 4 11.5 <![CDATA[5.3×10 -12 ]]> 106 Example 5 12.8 <![CDATA[6.8×10 -12 ]]> 110 Example 6 8.5 <![CDATA[13.8×10 -12 ]]> 154 Example 7 8.5 <![CDATA[9.0×10 -12 ]]> 128 Example 8 8.5 <![CDATA[12.2×10 -12 ]]> 144 Example 9 8.5 <![CDATA[12.5×10 -12 ]]> 147 Example 10 8.5 <![CDATA[13.0×10 -12 ]]> 150 Example 11 8.5 <![CDATA[11.8×10 -12 ]]> 138 Example 12 8.5 <![CDATA[12.1×10 -12 ]]> 141 Example 13 8.5 <![CDATA[12.6×10 -12 ]]> 147 Example 14 8.5 <![CDATA[9.5×10 -12 ]]> 133 Example 15 8.5 <![CDATA[9.8×10 -12 ]]> 135

[0163] Freshly picked bananas and strawberries were coated with the preservative solution provided in Example 1. The coated bananas and strawberries, as well as the untreated bananas and strawberries, were stored for 11 days and 7 days respectively under constant temperature and humidity conditions (ambient temperature 25°C, relative humidity 50%). The appearance of the bananas and strawberries was observed and photographed every one day. The appearance of the bananas is shown in the figure below. Figure 3 As shown, the appearance of strawberries is as follows Figure 4 As shown, when bananas and strawberries are dipped in the preservative solution provided by this invention, the shelf life of bananas can be extended by 3-7 days, and the shelf life of strawberries can be extended by 2-4 days.

[0164] The weight loss rate, vitamin C content, and firmness of the bananas after preservation treatment provided in Examples 1-15 and the comparative examples were tested. The specific test steps are as follows:

[0165] (1) Weight loss rate

[0166] The weight of the bananas was measured during storage. On day 0 of storage, the bananas were weighed and the weight m0 was recorded. After 11 days of storage under constant temperature and humidity conditions (ambient temperature 25℃, relative humidity 50%), the bananas were weighed and the weight m was recorded. n The weight loss rate w (%) of the bananas is calculated using the following formula:

[0167]

[0168] (2) Vitamin C content

[0169] The vitamin C content in bananas was determined according to the third method of the national standard GB 5009.86-2016 "National Food Safety Standard - Determination of Ascorbic Acid in Food" - 2,6-dichlorophenolindophenol titration method.

[0170] (3) Hardness

[0171] The hardness of bananas after preservation treatment during storage was measured using a GY-4 digital fruit hardness tester. A 5mm diameter planar probe was inserted into 5 circumferential positions at the largest longitudinal section of the banana to obtain 5 sets of hardness values, and the average value was taken.

[0172] The test results are shown in Table 2.

[0173] Table 2. Test results for banana storage and preservation.

[0174] Banana weight loss rate % Banana Vitamin C content (mg / 100g) Banana hardness N Example 1 13.5 10.3 10.4 Example 2 11.6 11.5 12.6 Example 3 10.3 13.4 14.5 Example 4 8.2 14.6 14.8 Example 5 9.7 12.7 13.3 Example 6 16.4 7.6 7.8 Example 7 15.3 8.1 8.6 Example 8 15.8 7.9 8.0 Example 9 14.2 8.5 9.2 Example 10 16.8 7.2 7.5 Example 11 14.7 8.3 8.8 Example 12 15.0 8.0 8.6 Example 13 13.8 9.8 10.2 Example 14 18.1 6.6 6.8 Example 15 13.2 10.1 10.3 Comparative Example 20.4 5.2 5.6

[0175] The weight loss rate, VC content, and soluble solids content of strawberries after preservation treatment provided in Examples 1-15 and the comparative examples were tested using the same testing method as for bananas. The test conditions were: ambient temperature 25°C, relative humidity 50%, and storage time 11 days.

[0176] Table 3. Test results for strawberry storage and preservation.

[0177] Strawberry weight loss rate % Strawberry Vitamin C content (mg / 100g) Strawberry hardness N Example 1 38.6 70.3 2.5 Example 2 36.2 78.4 2.6 Example 3 32.8 82.4 2.8 Example 4 30.3 90.2 3.0 Example 5 34.5 85.5 2.7 Example 6 43.3 65.2 1.8 Example 7 42.5 68.1 2.0 Example 8 41.6 66.9 1.9 Example 9 39.4 68.8 2.2 Example 10 42.3 64.3 1.6 Example 11 40.7 69.0 2.1 Example 12 41.3 67.7 1.9 Example 13 38.8 69.8 2.2 Example 14 43.2 62.1 1.5 Example 15 38.5 70.2 2.4 Comparative Example 45.5 60.5 1.3

[0178] 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 5 × 10⁻⁶. -12 -10×10 -12 kg·m / (s·m 2 (·Pa), oxygen permeability coefficient is 100-150cm 3 ·μm / (m 2 The reading (·day·kPa) indicates that the preservation coating prepared by this invention has excellent oxygen barrier and water retention capabilities.

[0179] The test data provided in Tables 2 and 3 show that the weight loss rate of bananas after 11 days of storage was 8-14%, and that of strawberries after 7 days of storage was 30-40%, both significantly lower than that of untreated bananas and strawberries. Furthermore, the vitamin C content of bananas after 11 days of storage was 10-15 mg / 100g, and their firmness was 10-15 N; the vitamin C content of strawberries after 7 days of storage was 70-90 mg / 100g, and their firmness was 2.5-3.0 N, both significantly higher than that of untreated bananas and strawberries.

[0180] The test data provided in Examples 1, 6, and 7 show that in Example 6, the mass fraction of the nanocellulose solution was too low, resulting in a low viscosity of the preservative solution, which affected the adhesion of the preservative solution to the surfaces of bananas and strawberries. Therefore, it was not easy to form a complete preservative coating on the surfaces of bananas and strawberries by dip coating, ultimately affecting the preservation effect on bananas and strawberries. 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.

[0181] The test data provided in Examples 1, 8, and 9 show that the proportion of cellulose nanofibers in Example 8 is relatively low, which leads to a reduction in the three-dimensional network structure composed of cellulose nanofibers in the preservation coating, resulting in poorer barrier performance of the preservation coating and ultimately affecting the preservation effect on bananas and strawberries. In Example 9, the proportion of cellulose nanocrystals is relatively low, which leads to a larger free volume of the coating, resulting in poorer gas barrier performance and ultimately affecting the preservation effect on bananas and strawberries.

[0182] The test data provided in Examples 1, 10, and 11 show that the amount of beeswax added in Example 10 was too low, which failed to enhance the moisture barrier and water resistance properties, ultimately affecting the preservation effect on bananas and strawberries. In Example 11, the amount of beeswax added 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, ultimately affecting the preservation effect on bananas and strawberries.

[0183] The test data provided in Examples 1, 12, and 13 show that in Example 12, the amount of glycerol added was too low, causing the preservative coating to crack and failing to achieve the desired preservation effect. In Example 13, the amount of glycerol added was too high, reducing the density of the preservative coating and thus promoting oxygen permeability, which in turn reduced the oxygen barrier capacity of the preservative coating and ultimately affected the preservation effect on bananas and strawberries.

[0184] The test data provided in Examples 1, 14, and 15 show that the amount of curcumin / cyclodextrin inclusion complex added in Example 6 was too low. Due to the low effective content of functional components, the antibacterial and antioxidant effects and preservation effect of the preservation coating were reduced. In Example 7, the amount of curcumin / cyclodextrin inclusion complex added was too high. As 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.

[0185] 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 preservative solution with a sustained-release function of antibacterial components, characterized in that, The edible preservative solution includes a nanocellulose solution, beeswax, glycerin, and curcumin / cyclodextrin inclusion complex; The mass fraction of the nanocellulose solution is 0.5-1.5 wt%. The amount of beeswax added is 20-50 wt% based on the dry weight of the nanocellulose in the nanocellulose solution. The amount of glycerol added is 20-50 wt% based on the dry weight of the nanocellulose in the nanocellulose solution. The amount of curcumin / cyclodextrin inclusion complex added is 5-10 wt% based on the dry weight of nanocellulose in the nanocellulose solution. The nanocellulose solution is composed of nanocellulose and water, wherein the nanocellulose is cellulose nanofibers and cellulose nanocrystals, and the mass ratio of the cellulose nanofibers to the cellulose nanocrystals is (1-3):

1. The preparation method of the edible preservative liquid with antibacterial component slow-release function includes: (I) A cyclodextrin solution and a curcumin solution are mixed evenly, then cooled to crystallize, filtered and dried to obtain a curcumin / cyclodextrin inclusion complex; the mass fraction of the cyclodextrin solution is 3-6 wt%, and the concentration of the curcumin solution is 0.005-0.01 g / mL; (II) A nanocellulose solution, beeswax and glycerin are mixed in proportion and heated until the beeswax melts to obtain a mixture; then, the mixture is emulsified to obtain a nanocellulose emulsion; (III) The curcumin / cyclodextrin inclusion complex obtained in step (I) and the nanocellulose emulsion obtained in step (II) are mixed evenly in proportion to obtain a precursor solution. The precursor solution is then degassed under vacuum to obtain the edible preservative liquid. The method of using the edible preservative liquid with antibacterial component slow-release function includes: Soak the fruits and vegetables to be preserved in an edible preservative solution at least once. After soaking, remove the fruits and vegetables and let them air dry naturally to form a preservative coating on the surface of the fruits and vegetables.

2. The edible preservative liquid with antibacterial component slow-release function according to claim 1, characterized in that, In step (I), 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 addition is completed, the ambient temperature is kept constant and stirring is continued for 2-4 hours. The temperature for cooling and crystallization is 1-10℃; The cooling and crystallization time is 8-12 hours; The drying temperature is 40-60℃.

3. The edible preservative liquid with antibacterial component slow-release function according to claim 1, characterized in that, In step (II), the heating temperature is 80-90℃; The emulsification time is 1-10 minutes; In step (III), the mixing method is mechanical stirring; The mechanical stirring speed is 200-1000 rpm; The mechanical stirring time is 1-5 minutes; The vacuum degassing time is 5-10 minutes.

4. The edible preservative liquid with antibacterial component slow-release function 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.

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