Food-borne fruit and vegetable preservative as well as preparation method and use method thereof

Abstract

The invention provides a food-borne fruit and vegetable fresh-keeping agent as well as a preparation method and a use method thereof. The food-borne fruit and vegetable fresh-keeping agent comprises carrot powder, yolk powder, chitosan, citric acid and deionized water. All the components generate a synergistic effect through functional complementation, the antioxidant activity of the carrot powder delays oxidative browning of fruit and vegetable peels, the film forming characteristic of the chitosan is combined with the adhesion performance of the yolk powder, so that the preservative forms a uniformly-covered composite film layer on the surfaces of fruits and vegetables, and the existence of the citric acid maintains the stability of a system and improves the preservation effect of the fruits and vegetables. According to the fruit and vegetable fresh-keeping agent disclosed by the invention, the antibacterial efficiency of each component is synergistically enhanced, and the fruit and vegetable fresh-keeping agent has the comprehensive performance of inhibiting pathogenic bacterium proliferation and regulating and controlling microenvironment gas exchange while keeping high safety based on the functional synergy of the food-grade raw materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of fruit and vegetable preservation, and relates to a food-derived fruit and vegetable preservative, a preparation method thereof, and a usage method thereof. Background Art

[0002] Fruits and vegetables are prone to spoilage and deterioration during post-harvest storage and circulation due to respiration, microbial infection, and oxidative browning, resulting in huge economic losses. Although traditional preservation technologies such as refrigeration and controlled atmosphere storage can delay spoilage, they have problems such as high equipment costs and complex operations, and are difficult to apply to all scenarios. Chemical preservatives (such as benzoic acid and potassium sorbate) can significantly extend the shelf life, but there are risks of toxic side effects and chemical residues, and long-term use may pose potential hazards to human health and the environment. In recent years, natural preservatives have received attention due to their safety, but the existing technologies still have limitations: for example, although plant extracts (such as extracts from pomelo peel and apple peel) have antibacterial properties, the active ingredients are easily degraded rapidly and lack a slow-release mechanism, resulting in insufficient long-term preservation effects; some microbial-derived preservatives (such as lipopeptides and rhamnolipids) are green and safe, but have a narrow antibacterial spectrum and limited ability to synergistically inhibit complex spoilage flora. In addition, there are still deficiencies in the synergistic optimization of the film-forming property, water retention property, and antioxidant property of existing preservatives. For example, single components such as chitosan are difficult to simultaneously achieve multiple functions such as inhibiting respiration, regulating ethylene release, and physical barrier. Summary of the Invention

[0003] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a food-derived fruit and vegetable preservative, a preparation method thereof, and a usage method thereof. Based on the functional synergy of food-grade raw materials, the fruit and vegetable preservative of the present invention has comprehensive properties of inhibiting the proliferation of pathogenic bacteria and regulating microenvironmental gas exchange while maintaining high safety.

[0004] To achieve this purpose, the present invention adopts the following technical solutions:

[0005] In the first aspect, the present invention provides a food-derived fruit and vegetable preservative, which comprises carrot powder, egg yolk powder, chitosan, citric acid, and deionized water.

[0006] The food - derived fruit and vegetable preservative provided by the present invention achieves the dual effects of antibacterial and physical barrier through the synergistic effect of food - derived components such as carrot powder, egg yolk powder, chitosan, and citric acid. The β - carotene and polyphenolic substances contained in the carrot powder can interfere with the permeability of the microbial cell membrane. Its hydrophobic property acts together with the lecithin in the egg yolk powder to form a hydrophobic barrier on the surface of fruits and vegetables. Chitosan is protonated in the weak acidic environment provided by citric acid, adsorbs on the surface of microorganisms through positive charges to destroy the integrity of their cell walls, and at the same time forms a cross - linked network structure with the polysaccharide components in the carrot powder, significantly enhancing the compactness of the fresh - keeping film layer. In addition, citric acid not only enhances the solubility of chitosan as a pH regulator, but also blocks the enzymatic reactions of microorganisms by chelating metal ions. Combined with the lysozyme in the egg yolk powder, it further improves the antibacterial effect. The lipoprotein component of the egg yolk powder and the chitosan molecule form a composite matrix through hydrophobic interaction to construct a continuous barrier layer on the surface of fruits and vegetables, effectively slowing down the oxygen penetration and water loss.

[0007] Synergistic effects are generated through functional complementarity among the components. The antioxidant activity of the carrot powder delays the oxidative browning of the fruit and vegetable epidermis. The film - forming property of chitosan and the adhesion performance of the egg yolk powder are combined to form a composite film layer that evenly covers the surface of fruits and vegetables. The presence of citric acid not only maintains the stability of the system but also synergistically enhances the antibacterial efficiency of each component. Based on the functional synergy of food - grade raw materials, the fruit and vegetable preservative has the comprehensive performance of inhibiting the proliferation of pathogenic bacteria and regulating the micro - environmental gas exchange while maintaining high safety.

[0008] As a preferred technical solution of the present invention, the mass fraction of the carrot powder in the food - derived fruit and vegetable preservative is 0.8 - 1.2 wt%, for example, it can be 0.8 wt%, 0.85 wt%, 0.9 wt%, 0.95 wt%, 1 wt%, 1.05 wt%, 1.1 wt%, 1.15 wt% or 1.2 wt%, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0009] The present invention defines the mass fraction of the carrot powder as 0.8 - 1.2 wt%. Within this range, the β - carotene and polyphenolic substances in the carrot powder can be fully dissolved and dispersed. They can not only directly inhibit bacteria by destroying the microbial cell membrane but also form hydrogen bonds with the amino groups in the chitosan molecule to enhance the cross - linking density of the membrane structure. Appropriate addition of carrot powder makes the hydrophobic components in the carrot powder complement the lipids in the egg yolk powder, neither causing the preservative to be turbid and affecting the uniformity of film - forming due to excessive carrot powder nor ensuring the formation of a continuous protective layer on the surface of fruits and vegetables to effectively block the penetration of external water vapor.

[0010] When the mass fraction of carrot powder is lower than 0.8wt%, the concentration of active ingredients in carrot powder is insufficient to form an effective antibacterial barrier, and the hydrophobic components in carrot powder cannot fully fill the structural gaps in the chitosan-egg yolk powder matrix, resulting in defects in the formed preservative film layer and a significant increase in the water vapor permeability coefficient. At the same time, due to the insufficient concentration of polyphenols, the synergistic antibacterial effect of polyphenols and chitosan is weakened, and the inhibitory effect on Gram-negative bacteria such as Escherichia coli is significantly reduced. In addition, the antioxidant capacity of low-concentration carrot powder is limited, and it is difficult to effectively inhibit the enzymatic browning reaction of the fruit and vegetable epidermis, which shortens the maintenance time of the preservative on the appearance of fruits and vegetables.

[0011] When the mass fraction of carrot powder exceeds 1.2wt%, the excess solid particles of carrot powder will destroy the stability of the film-forming system. β-Carotene at high concentrations is prone to molecular aggregation, forming local crystallization areas. These microcrystals will produce stress concentration points inside the plastic wrap layer, reducing the flexibility and adhesion of the plastic wrap layer. At the same time, excessive polyphenols will also cross-link with chitosan, resulting in increased brittleness of the plastic wrap layer, which is prone to cracks in actual use. In addition, excessive carrot powder content will significantly increase the viscosity of the preservative, affect the spraying effect, cause uneven distribution of the preservative on the surface of fruits and vegetables, and form an overly thick plastic wrap layer in some areas, hindering the normal respiration of fruits and vegetables.

[0012] In some optional examples, the mass fraction of egg yolk powder in the food-derived fruit and vegetable preservative is 0.3~0.8wt%, for example, it can be 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, 0.5wt%, 0.55wt%, 0.6wt%, 0.65wt%, 0.7wt%, 0.75wt% or 0.8wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0013] The present invention specifically limits the mass fraction of egg yolk powder in the food-derived fruit and vegetable preservative to 0.3-0.8wt%. Within this range, the natural lysozyme and lipoprotein components in the egg yolk powder can be fully released, and the lysozyme achieves targeted antibacterial by hydrolyzing the peptidoglycan layer of the bacterial cell wall, while the amino groups in the lipoprotein and chitosan molecules form a stable composite structure through electrostatic attraction, thereby enhancing the mechanical strength of the cling film layer. In addition, the emulsifying properties of the egg yolk powder help the hydrophobic carotene component to be evenly dispersed, and the formed cling film layer has both flexibility and barrier ability on the surface of fruits and vegetables, and its lipid components can also form hydrophobic micro-regions on the surface of the cling film layer, reducing water loss without affecting the normal respiration of the fruit and vegetable epidermis.

[0014] When the mass fraction of egg yolk powder is lower than 0.3wt%, the concentration of lysozyme cannot achieve an effective antibacterial effect, and the inhibitory effect on Gram-positive bacteria is significantly weakened. At the same time, the low lipoprotein content leads to a loose structure of the cling film layer, insufficient binding sites with chitosan, a large number of nano-scale pores in the formed network structure, and an increase in the water vapor permeability coefficient, which accelerates the oxidation and corruption of fruits and vegetables. In addition, the low concentration of egg yolk powder has insufficient emulsification capacity, which can also cause local aggregation of β-carotene in carrot powder, reducing the uniform spreading of the preservative on the surface of fruits and vegetables.

[0015] When the mass fraction of egg yolk powder exceeds 0.8wt%, excessive lipoprotein will cross-link with chitosan excessively, resulting in increased rigidity and decreased elasticity of the cling film layer, which is prone to cracks due to surface deformation of fruits and vegetables in practical applications. In addition, high concentrations of lysozyme will self-aggregate in a weakly acidic environment, which will reduce its effective contact area with the bacterial cell wall. At the same time, excessive lipid components will destroy the colloidal stability of the chitosan-citric acid system, causing the preservative to stratify during storage. The thickness of the cling film layer formed after spraying is uneven, which hinders the normal escape of carbon dioxide in local overly thick areas, causing abnormal anaerobic respiration metabolism of fruits and vegetables.

[0016] In some optional examples, the mass fraction of chitosan in the food-derived fruit and vegetable preservative is 0.4-0.6wt%, for example, it can be 0.4wt%, 0.42wt%, 0.44wt%, 0.46wt%, 0.48wt%, 0.5wt%, 0.52wt%, 0.54wt%, 0.56wt%, 0.58wt% or 0.6wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] The present invention specifically limits the mass fraction of chitosan to 0.4-0.6wt%. Within this range, the chitosan molecular chain is fully stretched in the acidic fruit and vegetable preservative, and the positive charge formed by amino protonation can effectively adsorb the negative charge area on the surface of microorganisms and destroy the integrity of cell membranes. At the same time, the appropriate molecular chain length forms interlaced crosslinks with the polysaccharides in carrot powder to construct a preservative film layer with a three-dimensional network structure.

[0018] When the mass fraction of chitosan is lower than 0.4wt%, the polymer concentration in the preservative is insufficient to form a complete three-dimensional network. Discontinuous weak areas will appear inside the preservative film layer formed after coating, resulting in a significant decrease in barrier properties. Water vapor in the environment can more easily penetrate into the fruit and vegetable skin. In addition, the total amount of amino groups is reduced, and the electrostatic adsorption effect on microorganisms is weakened. At the same time, the interaction strength between low-concentration chitosan and egg yolk powder lipoprotein is insufficient, and the mechanical properties of the formed composite structure are poor, which is easy to fall off the surface of fruits and vegetables.

[0019] When the mass fraction of chitosan exceeds 0.6 wt%, the excessive entanglement of chitosan molecular chains will cause a sharp increase in the viscosity of the preservative. The high-viscosity preservative is difficult to form uniform droplets during the spraying process, resulting in uneven film thickness distribution. The locally over-thick areas will hinder the normal gas exchange of fruits and vegetables. In addition, excessive amino groups will agglomerate locally in a weak acid environment, affecting their contact with the surface of microorganisms. At the same time, the over-dense cross-linked network will reduce the flexibility of the fresh-keeping film layer. When shrinkage stress is generated due to water evaporation on the surface of fruits and vegetables, microcracks are likely to appear in the fresh-keeping film layer, becoming channels for microbial invasion and water loss.

[0020] In some alternative examples, the mass fraction of citric acid in the food-derived fruit and vegetable preservative is 1-2 wt%. For example, it can be 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt% or 2.0 wt%, but it is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0021] The present invention specifically limits the mass fraction of citric acid to 1-2 wt%. Within this range, the weak acid environment provided by citric acid not only ensures the full extension of chitosan molecular chains and amino protonation, enhancing its electrostatic adsorption ability with the microbial cell wall, but also avoids excessive acidity from damaging the emulsification stability of lipoproteins in egg yolk powder.

[0022] When the mass fraction of citric acid is lower than 1 wt%, the pH value of the preservative is relatively high, resulting in insufficient dissolution of chitosan. There are undissolved colloidal particles in the preservative, and these particles will destroy the film-forming continuity, forming a porous structure on the surface of fruits and vegetables, significantly increasing the water vapor transmission coefficient. In addition, the weaker acid environment reduces the degree of amino protonation of chitosan, and the positive charge density is not sufficient to effectively adsorb to the bacterial surface, significantly weakening the inhibitory effect on acid-resistant microorganisms such as yeasts.

[0023] When the mass fraction of citric acid exceeds 2 wt%, the overly strong acidity will cause the chitosan molecular chains to overstretch and undergo partial hydrolysis, resulting in weakened intermolecular forces after film formation and a decrease in the tear resistance of the fresh-keeping film layer. In addition, high-concentration citric acid will also cause irreversible denaturation of the lipoprotein structure in egg yolk powder, losing its original emulsification function and causing phase separation of hydrophobic components such as carotenoids. At the same time, excessive citric acid will also undergo a charge neutralization reaction with ε-polylysine, affecting its interaction with the bacterial cell membrane.

[0024] As a preferred technical solution of the present invention, the food-derived fruit and vegetable preservative further includes tea polyphenols.

[0025] In some optional examples, the food-derived fruit and vegetable preservative further includes ε-polylysine.

[0026] In some optional examples, the food-derived fruit and vegetable preservative further includes glycerol.

[0027] The food-derived fruit and vegetable preservative provided by the present invention also includes tea polyphenols, ε-polylysine and glycerol. Tea polyphenols mainly serve as antioxidants and broad-spectrum antibacterial agents, which delay the browning of fruits and vegetables by neutralizing free radicals through phenolic hydroxyl groups, and at the same time destroy the lipid structure of microbial cell membranes. ε-polylysine targets and binds to negatively charged sites on the surface of bacteria by virtue of its cationic properties, forming transmembrane ion channels, triggering cytoplasmic leakage, and has an inhibitory effect on acid-resistant pathogens in particular. Glycerol weakens the rigid structure of chitosan by inserting between polymer chains, improves the flexibility of the cling film layer, and at the same time adjusts the hydrophilic-hydrophobic balance to prevent the cling film layer from excessively absorbing moisture and swelling.

[0028] The synergistic effect between the components is reflected in:

[0029] Chitosan is fully protonated in a weak acid environment regulated by citric acid. Its linear molecular chain and egg yolk powder lipoprotein construct a three-dimensional network skeleton through hydrophobic interaction, and the β-carotene in carrot powder fills the network gap to form a hydrophobic barrier. At the same time, citric acid stabilizes metal ions through chelation, blocks the active sites of oxidases, and promotes the orderly arrangement of chitosan-lipoprotein complexes. In addition, the positive charge of ε-polylysine forms a gradient charge distribution with chitosan, enhancing the adsorption and interception efficiency of microorganisms with different charges. The phenolic hydroxyl groups of tea polyphenols form hydrogen bond cross-links with the amino groups of chitosan, which not only enhances the ultraviolet blocking ability of the cling film layer, but also the catechins released by them can penetrate into the microbial cells and form an antibacterial synergistic effect with ε-polylysine. The addition of glycerol gives the rigid network a moderate elastic deformation capacity, ensuring that the epidermal deformation caused by the respiration of fruits and vegetables will not destroy the continuity of the cling film layer.

[0030] In some optional examples, the mass fraction of tea polyphenols in the food-derived fruit and vegetable preservative is 0.5~1wt%, for example, it can be 0.5wt%, 0.55wt%, 0.6wt%, 0.65wt%, 0.7wt%, 0.75wt%, 0.8wt%, 0.85wt%, 0.9wt%, 0.95wt% or 1wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] The present invention specifically limits the mass fraction of tea polyphenols to 0.5 - 1 wt%. Within this range, catechins in tea polyphenols can fully exert their free radical scavenging effect, effectively inhibiting the browning reaction caused by oxidase on the surface of fruits and vegetables. At the same time, its phenolic hydroxyl groups form appropriate hydrogen bond crosslinks with the molecular chains of chitosan, enhancing the UV shielding ability of the fresh-keeping film layer. In addition, tea polyphenols at this concentration can also penetrate the cell membrane of microorganisms, complementing the antibacterial mechanism of chitosan, especially inhibiting the germination of fungal spores such as Botrytis cinerea.

[0032] When the mass fraction of tea polyphenols is lower than 0.5 wt%, the total amount of phenolic substances is not sufficient to cover the oxidation damage sites on the surface of fruits and vegetables, and its antioxidant ability cannot effectively block the browning chain reaction. Obvious spots appear on the treated fruits and vegetables in the middle stage of storage. In addition, the crosslinking density of low-concentration tea polyphenols and chitosan is insufficient, resulting in a decrease in the UV absorption ability of the fresh-keeping film layer. Environmental light will accelerate the aging and degradation of the fresh-keeping film layer, leading to a reduction in the barrier performance of the fresh-keeping film layer.

[0033] When the mass fraction of tea polyphenols exceeds 1 wt%, excessive phenolic hydroxyl groups cause excessive crosslinking, resulting in a significant increase in the rigidity of the fresh-keeping film layer. In addition, although the dense network formed by high-concentration tea polyphenols and chitosan can enhance the barrier property of the fresh-keeping film layer, excessive tea polyphenol molecules will self-polymerize in the preservative to form colloidal particles, and these colloidal particles become the attachment sites for microorganisms, resulting in an impact on the antibacterial effect of the fresh-keeping film layer.

[0034] In some optional examples, the mass fraction of ε-polylysine in the food-derived fruit and vegetable preservative is 0.05 - 0.1 wt%. For example, it can be 0.05 wt%, 0.055 wt%, 0.06 wt%, 0.065 wt%, 0.07 wt%, 0.075 wt%, 0.08 wt%, 0.085 wt%, 0.09 wt%, 0.095 wt% or 1 wt%, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0035] The present invention specifically limits the mass fraction of ε-polylysine to 0.05 - 0.1 wt%. Within this range, the positively charged amino groups of ε-polylysine specifically bind to the negatively charged regions of the phospholipid bilayer of the bacterial cell membrane, forming transmembrane ion channels, resulting in the outflow of potassium ions inside the cell to achieve the antibacterial effect. At the same time, its appropriate molecular size can be evenly distributed in the chitosan network structure, generating weak interactions with the phenolic hydroxyl groups of tea polyphenols, which not only enhances the antibacterial broad-spectrum property but also does not hinder the film-forming continuity of the chitosan and lipoprotein composite matrix.

[0036] When the mass fraction of ε-polylysine is less than 0.05 wt%, the molecular density of ε-polylysine cannot effectively cover the surface of microorganisms, resulting in a significant weakening of its ability to disrupt the cell membrane integrity and a substantial decline in the antibacterial performance. In addition, the charge synergistic effect between low-concentration ε-polylysine and chitosan is insufficient, leading to a reduction in the positive charge sites on the surface of the fresh-keeping film layer and a decrease in the adsorption and interception efficiency of mold spores settling in the air, indirectly affecting the barrier performance of the fresh-keeping film layer.

[0037] When the mass fraction of ε-polylysine exceeds 0.1 wt%, the excessive positive charge will affect the stability of the preservative. The high-concentration ε-polylysine will have a strong electrostatic interaction with negatively charged citric acid molecules, forming locally aggregated micelles. These micelles will disrupt the regularity of the chitosan network during the film-forming process, resulting in microcracks in the fresh-keeping film layer. In addition, the excessive ε-polylysine will also penetrate the epidermal wax layer of fruits and vegetables, change the ion balance of the cell protoplast membrane, trigger cell osmotic pressure disorders, and accelerate the softening of fruit and vegetable tissues.

[0038] In some alternative examples, the mass fraction of glycerol in the food-derived fruit and vegetable preservative is 1 - 2 wt%. For example, it can be 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt% or 2.0 wt%, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0039] The present invention specifically limits the mass fraction of glycerol to 1 - 2 wt%. Within this range, glycerol, as a plasticizer, can be inserted between the chitosan molecular chains, weakening the rigid structure of the polymer chains, enabling the formed fresh-keeping film layer to have appropriate ductility and not being easily brittle when the surface of fruits and vegetables deforms. At the same time, the hydrophilic groups of glycerol form hydrogen bond bindings with the phenolic hydroxyl groups of tea polyphenols, which can not only maintain the stable dispersion of antioxidant components but also prevent excessive swelling of the fresh-keeping film layer due to excessive moisture absorption.

[0040] When the mass fraction of glycerol is less than 1 wt%, too little glycerol results in insufficient plasticization, and the fresh-keeping film layer is too rigid. During the drying process, microcracks are likely to occur in the fresh-keeping film layer, and these cracks will become channels for microbial invasion and water loss. In addition, low-concentration glycerol is difficult to maintain the dispersion stability of hydrophobic components such as carotenoids, resulting in uneven distribution of active ingredients in the fresh-keeping film layer and insufficient concentration of antibacterial substances in local areas.

[0041] When the mass fraction of glycerol exceeds 2 wt%, the excessive glycerol will damage the integrity of the chitosan network structure. The excessive increase in the molecular chain spacing leads to a decrease in the density of the fresh-keeping film layer, a significant increase in the water vapor transmission coefficient, and a decline in the barrier performance. In addition, the high-concentration glycerol will also form a preferential path for the diffusion of water molecules, causing the fresh-keeping film layer to swell excessively after absorbing moisture, and reducing the durability of the water vapor barrier.

[0042] In a second aspect, the present invention provides a preparation method of the food-derived fruit and vegetable fresh-keeping agent described in the first aspect, and the preparation method includes:

[0043] Mixing carrot powder, egg yolk powder, chitosan, citric acid and deionized water evenly to obtain the food-derived fruit and vegetable fresh-keeping agent.

[0044] In some optional examples, the preparation method includes:

[0045] Mixing carrot powder, egg yolk powder, chitosan, citric acid, tea polyphenols, ε-polylysine, glycerol and deionized water evenly to obtain the food-derived fruit and vegetable fresh-keeping agent.

[0046] In a third aspect, the present invention provides a usage method of the food-derived fruit and vegetable fresh-keeping agent described in the first aspect, and the usage method includes:

[0047] Soaking the fruits and vegetables to be fresh-keeping treated in the food-derived fruit and vegetable fresh-keeping agent, and then taking them out and drying them naturally; or,

[0048] Spraying the food-derived fruit and vegetable fresh-keeping agent on the surface of the fruits and vegetables to be fresh-keeping treated, and then drying them naturally.

[0049] In some optional examples, the soaking time of the fruits and vegetables to be fresh-keeping treated in the food-derived fruit and vegetable fresh-keeping agent is 5 to 10 s, for example, it can be 5.0 s, 5.5 s, 6.0 s, 6.5 s, 7.0 s, 7.5 s, 8.0 s, 8.5 s, 9.0 s, 9.5 s or 10.0 s, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0050] Compared with the prior art, the beneficial effects of the present invention are:

[0051] The food - borne fruit and vegetable preservative provided by the present invention achieves the dual effects of antibacterial and physical barrier through the synergistic effect of food - borne components such as carrot powder, egg yolk powder, chitosan, and citric acid. The β - carotene and polyphenolic substances contained in carrot powder can interfere with the permeability of the microbial cell membrane. Its hydrophobic property and the lecithin in egg yolk powder act together to form a hydrophobic barrier on the surface of fruits and vegetables. Chitosan is protonated in the weakly acidic environment provided by citric acid, adsorbs on the surface of microorganisms through positive charges to destroy the integrity of their cell walls, and at the same time forms a cross - linked network structure with the polysaccharide components in carrot powder, significantly improving the compactness of the fresh - keeping film layer. In addition, citric acid not only enhances the solubility of chitosan as a pH regulator, but also blocks the enzymatic reactions of microorganisms by chelating metal ions. Combined with the lysozyme in egg yolk powder, it further improves the antibacterial effect. The lipoprotein component of egg yolk powder and chitosan molecules form a composite matrix through hydrophobic interaction to construct a continuous barrier layer on the epidermis of fruits and vegetables, effectively slowing down oxygen penetration and water loss.

[0052] Synergistic effects are generated through functional complementarity among the components. The antioxidant activity of carrot powder delays the oxidative browning of the epidermis of fruits and vegetables. The film - forming property of chitosan and the adhesion performance of egg yolk powder are combined to form a uniformly covered composite film layer on the surface of fruits and vegetables. The presence of citric acid not only maintains the stability of the system, but also synergistically enhances the antibacterial efficiency of each component. Due to the functional synergy of food - grade raw materials, the fruit and vegetable preservative has the comprehensive performance of inhibiting the proliferation of pathogenic bacteria and regulating the micro - environmental gas exchange while maintaining high safety. Brief Description of the Drawings

[0053] Figure 1 It is the external light state diagram of strawberries provided by Application Example 1 and Comparative Example 1 of the present invention on the 0th day and the 10th day of storage;

[0054] Figure 2 It is the external light state diagram of green peppers provided by Application Example 2 and Comparative Example 2 of the present invention on the 0th day and the 12th day of storage. Detailed Embodiments

[0055] The technical solutions of the present invention will be described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments recorded here are specific specific implementation manners of the present invention and are used to illustrate the concept of the present invention; these descriptions are all explanatory and exemplary, and should not be construed as limiting the implementation manner of the present invention and the protection scope of the present invention. Except for the embodiments recorded here, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of this application. These technical solutions include technical solutions that make any obvious substitutions and modifications to the embodiments recorded here.

[0056] Example 1

[0057] This embodiment provides a food-derived fruit and vegetable preservative. Based on the mass fraction of the food-derived fruit and vegetable preservative being 100 wt%, it comprises the following components with the following mass fractions:

[0058] Carrot powder 0.8 wt%;

[0059] Egg yolk powder 0.3 wt%;

[0060] Chitosan 0.6 wt%;

[0061] Citric acid 2 wt%;

[0062] The balance is deionized water.

[0063] Example 2

[0064] This embodiment provides a food-derived fruit and vegetable preservative. Based on the mass fraction of the food-derived fruit and vegetable preservative being 100 wt%, it comprises the following components with the following mass fractions:

[0065] Carrot powder 1 wt%;

[0066] Egg yolk powder 0.8 wt%;

[0067] Chitosan 0.5 wt%;

[0068] Citric acid 1 wt%;

[0069] The balance is deionized water.

[0070] Example 3

[0071] This embodiment provides a food-derived fruit and vegetable preservative. Based on the mass fraction of the food-derived fruit and vegetable preservative being 100 wt%, it comprises the following components with the following mass fractions:

[0072] Carrot powder 1.2 wt%;

[0073] Egg yolk powder 0.5 wt%;

[0074] Chitosan 0.4 wt%;

[0075] Citric acid 1.5 wt%;

[0076] The balance is deionized water.

[0077] Example 4

[0078] This embodiment provides a food-derived fruit and vegetable preservative. Based on the mass fraction of the food-derived fruit and vegetable preservative being 100 wt%, it comprises the following components with the following mass fractions:

[0079] Carrot powder 0.8 wt%;

[0080] Egg yolk powder 0.8 wt%;

[0081] Chitosan 0.5 wt%;

[0082] Citric acid 2 wt%;

[0083] Tea polyphenols 0.5 wt%;

[0084] ε-Polylysine 0.05 wt%;

[0085] Glycerol 1 wt%;

[0086] The balance is deionized water.

[0087] Example 5

[0088] This example provides a food-derived fruit and vegetable preservative. Based on the mass fraction of the food-derived fruit and vegetable preservative being 100 wt%, it includes the following components with the following mass fractions:

[0089] Carrot powder 1 wt%;

[0090] Egg yolk powder 0.6 wt%;

[0091] Chitosan 0.4 wt%;

[0092] Citric acid 1.8 wt%;

[0093] Tea polyphenols 0.7 wt%;

[0094] ε-Polylysine 0.06 wt%;

[0095] Glycerol 1.3 wt%;

[0096] The balance is deionized water.

[0097] Example 6

[0098] This example provides a food-derived fruit and vegetable preservative. Based on the mass fraction of the food-derived fruit and vegetable preservative being 100 wt%, it includes the following components with the following mass fractions:

[0099] Carrot powder 0.9 wt%;

[0100] Egg yolk powder 0.3 wt%;

[0101] Chitosan 0.4 wt%;

[0102] Citric acid 1.5 wt%;

[0103] Tea polyphenols 0.6 wt%;

[0104] ε-Polylysine 0.08 wt%;

[0105] Glycerol 2 wt%

[0106] The balance is deionized water.

[0107] Example 7

[0108] This example provides a food-derived fruit and vegetable preservative. Based on the mass fraction of the food-derived fruit and vegetable preservative being 100 wt%, it includes the following components with the following mass fractions:

[0109] Carrot powder 1.1 wt%

[0110] Egg yolk powder 0.7 wt%

[0111] Chitosan 0.6 wt%

[0112] Citric acid 1 wt%

[0113] Tea polyphenols 0.8 wt%

[0114] ε-Polylysine 0.1 wt%

[0115] Glycerol 1.5 wt%

[0116] The balance is deionized water.

[0117] Example 8

[0118] This example provides a food-derived fruit and vegetable preservative. Based on the mass fraction of the food-derived fruit and vegetable preservative being 100 wt%, it includes the following components with the following mass fractions:

[0119] Carrot powder 1.2 wt%

[0120] Egg yolk powder 0.5 wt%

[0121] Chitosan 0.5 wt%

[0122] Citric acid 1.2 wt%

[0123] Tea polyphenols 1 wt%

[0124] ε-Polylysine 0.07 wt%

[0125] Glycerol 1.4 wt%

[0126] The balance is deionized water.

[0127] Example 9

[0128] This embodiment provides a food-derived fruit and vegetable preservative, which is different from that of Example 4 in that the mass fraction of carrot powder is adjusted to 0.5 wt%, and the mass fractions of other components are exactly the same as those of Example 1.

[0129] Example 10

[0130] This embodiment provides a food-derived fruit and vegetable preservative, which is different from that of Example 4 in that the mass fraction of carrot powder is adjusted to 1.5 wt%, and the mass fractions of other components are exactly the same as those of Example 1.

[0131] Example 11

[0132] This embodiment provides a food-derived fruit and vegetable preservative, which is different from that of Example 4 in that the mass fraction of egg yolk powder is adjusted to 0.1 wt%, and the mass fractions of other components are exactly the same as those of Example 1.

[0133] Example 12

[0134] This embodiment provides a food-derived fruit and vegetable preservative, which is different from that of Example 4 in that the mass fraction of egg yolk powder is adjusted to 1 wt%, and the mass fractions of other components are exactly the same as those of Example 1.

[0135] Example 13

[0136] This embodiment provides a food-derived fruit and vegetable preservative, which is different from that of Example 4 in that the mass fraction of chitosan is adjusted to 0.2 wt%, and the mass fractions of other components are exactly the same as those of Example 1.

[0137] Example 14

[0138] This embodiment provides a food-derived fruit and vegetable preservative, which is different from that of Example 4 in that the mass fraction of chitosan is adjusted to 0.8 wt%, and the mass fractions of other components are exactly the same as those of Example 1.

[0139] Example 15

[0140] This embodiment provides a food-derived fruit and vegetable preservative, which is different from that of Example 4 in that the mass fraction of citric acid is adjusted to 0.5 wt%, and the mass fractions of other components are exactly the same as those of Example 1.

[0141] Example 16

[0142] This embodiment provides a food-derived fruit and vegetable preservative, which is different from that of Example 4 in that the mass fraction of citric acid is adjusted to 3 wt%, and the mass fractions of other components are exactly the same as those of Example 1.

[0143] Example 17

[0144] This embodiment provides a food - derived fruit and vegetable preservative. The difference from Embodiment 4 is that the mass fraction of tea polyphenols is adjusted to 0.1 wt%, and the mass fractions of other components are exactly the same as those in Embodiment 1.

[0145] Example 18

[0146] This embodiment provides a food - derived fruit and vegetable preservative. The difference from Embodiment 4 is that the mass fraction of tea polyphenols is adjusted to 1.5 wt%, and the mass fractions of other components are exactly the same as those in Embodiment 1.

[0147] Example 19

[0148] This embodiment provides a food - derived fruit and vegetable preservative. The difference from Embodiment 4 is that the mass fraction of ε - polylysine is adjusted to 0.01 wt%, and the mass fractions of other components are exactly the same as those in Embodiment 1.

[0149] Example 20

[0150] This embodiment provides a food - derived fruit and vegetable preservative. The difference from Embodiment 4 is that the mass fraction of ε - polylysine is adjusted to 0.5 wt%, and the mass fractions of other components are exactly the same as those in Embodiment 1.

[0151] Example 21

[0152] This embodiment provides a food - derived fruit and vegetable preservative. The difference from Embodiment 4 is that the mass fraction of glycerol is adjusted to 0.5 wt%, and the mass fractions of other components are exactly the same as those in Embodiment 1.

[0153] Example 22

[0154] This embodiment provides a food - derived fruit and vegetable preservative. The difference from Embodiment 4 is that the mass fraction of glycerol is adjusted to 3 wt%, and the mass fractions of other components are exactly the same as those in Embodiment 1.

[0155] Application Example 1

[0156] The food - derived fruit and vegetable preservative provided in Embodiment 4 is evenly sprayed on the surface of freshly picked strawberries and air - dried naturally.

[0157] Comparative Example 1

[0158] This comparative example is freshly picked strawberries without spraying treatment.

[0159] Application Example 2

[0160] The food - derived fruit and vegetable preservative provided in Example 4 was evenly sprayed on the surface of fresh green peppers and air - dried naturally.

[0161] Comparative Example 2

[0162] This comparative example is fresh green peppers without spraying treatment.

[0163] Observe the appearance states of the unsprayed strawberries provided in Comparative Example 1 and the sprayed strawberries provided in Application Example 1 on the 0th day and the 10th day of storage (environmental temperature 25 °C, relative humidity 50%), as Figure 1 shown. It can be seen that when stored until the 10th day, the surface of the unsprayed strawberries provided in Comparative Example 1 showed rot. While the sprayed strawberries provided in Application Example 1 still maintained a good appearance.

[0164] Observe the appearance states of the unsprayed green peppers provided in Comparative Example 2 and the sprayed green peppers provided in Application Example 2 on the 0th day and the 12th day of storage (environmental temperature 25 °C, relative humidity 50%), as Figure 2 shown. It can be seen that when stored until the 12th day, the unsprayed green peppers provided in Comparative Example 2 lost water and shrank, and showed rot. While the sprayed green peppers provided in Application Example 2 still maintained a good appearance.

[0165] Referring to Application Example 1, the strawberries were sprayed with the food - derived fruit and vegetable preservatives provided in Examples 1 - 22, and the weight loss rate of the strawberries after 10 - day storage was tested. The specific test steps are as follows:

[0166] Weigh the strawberries on the 0th day of storage and record the weight m0. Store the unsprayed strawberries and the sprayed strawberries for 10 days in a constant - temperature and constant - humidity environment (environmental temperature 25 °C, relative humidity 50%), then weigh and record the weight m n , and calculate the weight loss rate using the following formula:

[0167] Weight loss rate (%) = [(m0 - m n ) / m0] × 100%.

[0168] Test the antibacterial performance and barrier performance of the food - derived fruit and vegetable preservatives provided in Examples 1 - 22. The specific test steps are as follows:

[0169] (1) Test of water vapor transmission coefficient

[0170] The water vapor transmission coefficient of the fresh-keeping film layer formed by the foodborne fruit and vegetable fresh-keeping agent was tested with reference to the national standard GB / T 1037-2021 "Determination of water vapor transmission properties of plastic films and sheets - Cup method for weight gain and weight loss", and the specific test steps are as follows:

[0171] The foodborne fruit and vegetable fresh-keeping agent was evenly coated on a clean polytetrafluoroethylene plate, and the wet film thickness was controlled to be 0.5 - 1.0 mm. It was dried in a constant temperature and humidity chamber at 25°C and a relative humidity of 50% for 24 hours to form a uniform fresh-keeping film layer. The fresh-keeping film layer was peeled off from the polytetrafluoroethylene plate, and the thickness of the fresh-keeping film layer was measured with a micrometer (the average value of 5 points was taken, and the thickness difference ≤ 5%).

[0172] The fresh-keeping film layer was cut into circular pieces with a diameter of 70 mm, sealed and fixed at the mouth of the moisture permeation cup to ensure no gap. The moisture permeation cup was placed in a constant temperature and humidity chamber (38°C, 90%RH), and weighed every 24 hours. The test was ended when the weight change was less than 5% for 3 consecutive times. The water vapor transmission rate was calculated according to the test time, film area and weight gain, and the calculation formula is as follows:

[0173] Water vapor transmission rate (WVTR) = Δm / (A·t);

[0174] Where t is the test time, Δm is the weight gain of the moisture permeation cup during the test time, and A is the film area of the fresh-keeping film layer.

[0175] The water vapor transmission coefficient was calculated according to the water vapor transmission rate and the average thickness of the fresh-keeping film layer, and the calculation formula is as follows:

[0176] Water vapor transmission coefficient (WVP) = (WVTR × d) / ΔP;

[0177] Where WVTR is the water vapor transmission rate, d is the average thickness of the fresh-keeping film layer, and ΔP is the water vapor pressure difference on both sides of the fresh-keeping film layer under the test conditions, which is obtained by referring to the saturated water vapor pressure table.

[0178] (2)Escherichia coli inhibition rate test

[0179] The foodborne fruit and vegetable fresh-keeping agent was sprayed on the surface of a sterile glass slide (10 mm × 10 mm), dried in a constant temperature and humidity chamber at 25°C and a relative humidity of 50% for 24 hours to form a uniform fresh-keeping film layer, and sterilized by ultraviolet irradiation for 30 minutes for standby.

[0180] Take the activated Escherichia coli (ATCC 25922), and adjust the concentration to 1×10 6CFU / mL to obtain a bacterial suspension. Take 100 μL of the bacterial suspension and drop it onto the surface of the plastic wrap layer. Cover the surface of the plastic wrap layer with a sterile polyethylene plastic wrap layer (to prevent evaporation), and place it in an oscillating incubator at 37 °C for 24 h. Subsequently, rinse the surface of the plastic wrap layer with sterile PBS, collect the eluate for gradient dilution, and pour it onto a plate to count the number of surviving colonies, which is recorded as the number of colonies in the experimental group.

[0181] Meanwhile, set up a control group. Take 100 μL of the bacterial suspension and drop it onto the surface of a sterile glass slide. Cover the surface of the sterile glass slide with a sterile polyethylene plastic wrap layer (to prevent evaporation), and place it in an oscillating incubator at 37 °C for 24 h. Subsequently, rinse the surface of the glass slide with sterile PBS, collect the eluate for gradient dilution, and pour it onto a plate to count the number of surviving colonies, which is recorded as the number of colonies in the control group.

[0182] Calculate the antibacterial rate of Escherichia coli based on the number of colonies in the experimental group and the control group. The calculation formula is as follows:

[0183] Antibacterial rate of Escherichia coli (%) = [(Number of colonies in the control group - Number of colonies in the experimental group) / Number of colonies in the control group] × 100%.

[0184] The test results are shown in Table 1.

[0185] Table 1

[0186] Water vapor transmission coefficient kg·m / (m²·s·Pa) Inhibitory rate against Escherichia coli (%) Weight loss rate (%) Example 1 <![CDATA[13.45×10 -12 > 82.3 13.8 Example 2 <![CDATA[13.92×10 -12 > 81.6 14.5 Example 3 <![CDATA[13.67×10 -12 > 80.9 15.0 Example 4 <![CDATA[8.35×10 -12 > 91.3 7.5 Example 5 <![CDATA[9.12×10 -12 > 90.8 8.2 Example 6 <![CDATA[8.98×10 -12 > 92.0 6.9 Example 7 <![CDATA[9.67×10 -12 > 91.5 9.3 Example 8 <![CDATA[9.85×10 -12 > 90.7 7.8 Example 9 <![CDATA[11.24×10 -12 > 84.6 9.8 Example 10 <![CDATA[12.73×10 -12 > 86.9 11.2 Example 11 <![CDATA[10.85×10 -12 > 83.2 10.5 Example 12 <![CDATA[12.15×10 -12 > 88.4 12.7 Example 13 <![CDATA[10.32×10 -12 > 82.1 9.6 Example 14 <![CDATA[12.48×10 -12 > 89.7 11.9 Example 15 <![CDATA[11.93×10 -12 > 81.5 10.8 Example 16 <![CDATA[12.86×10 -12 > 85.3 12.3 Example 17 <![CDATA[10.67×10 -12 > 83.9 11.4 Example 18 <![CDATA[12.05×10 -12 > 89.1 10.1 Example 19 <![CDATA[10.54×10 -12 > 81.8 8.7 Example 20 <![CDATA[12.37×10 -12 > 87.6 11.5 Example 21 <![CDATA[11.82×10 -12 > 84.3 10.9 Example 22 <![CDATA[13.09×10 -12 > 86.2 12.6 Comparative Example —— —— 18.5

[0187] It can be seen from the test data of Examples 1 - 3 and Examples 4 - 8 that the water vapor transmission coefficient and weight loss rate of Examples 4 - 8 are significantly lower than those of Examples 1 - 3, and the antibacterial rate of Escherichia coli is significantly higher than that of Examples 1 - 3. This is because in Examples 4 - 8, tea polyphenols, ε - polylysine, and glycerol are added. Tea polyphenols cross - link with chitosan through phenolic hydroxyl groups, enhancing the compactness of the plastic wrap layer, reducing the water vapor transmission coefficient of the plastic wrap layer, and at the same time directly destroying the microbial cell membrane, improving the antibacterial rate of the plastic wrap layer; the positive charge of ε - polylysine enhances the electrostatic adsorption effect on bacteria, making up for the antibacterial limitations of single chitosan; glycerol can plasticize the three - dimensional network structure of chitosan, reduce the drying shrinkage cracks of the plastic wrap layer, and lower the weight loss rate during strawberry storage. Through the synergistic effect of tea polyphenols, ε - polylysine, and glycerol in Examples 4 - 8, the balance of film layer compactness, high - efficiency antibacterial property, and flexibility is achieved.

[0188] From the test data of Example 4, Example 9 and Example 10, it can be seen that the water vapor transmission coefficient and weight loss rate of Example 9 and Example 10 are higher than those of Example 4, and the antibacterial rate against Escherichia coli is lower than that of Example 4. This is because the mass fraction of carrot powder was adjusted in Example 9 and Example 10. In Example 9, the mass fraction of carrot powder was too low, resulting in insufficient β-carotene and polyphenol contents. The hydrophobic barrier formed by the fresh-keeping film layer was incomplete, the water vapor transmission coefficient was high, and the antioxidant capacity decreased, resulting in a reduction in the barrier performance and antibacterial performance of the fresh-keeping film layer. In Example 10, the mass fraction of carrot powder was too high, and β-carotene aggregated to form microcrystals in the preservative, resulting in stress concentration in the fresh-keeping film layer formed after drying and the formation of microcracks. In addition, the high addition amount of carrot powder made the viscosity of the preservative too high, affecting the spraying uniformity.

[0189] From the test data of Example 4, Example 11 and Example 12, it can be seen that the water vapor transmission coefficient and weight loss rate of Example 11 and Example 12 are higher than those of Example 4, and the antibacterial rate against Escherichia coli is lower than that of Example 4. This is because the mass fraction of egg yolk powder was adjusted in Example 11 and Example 12. In Example 11, the mass fraction of egg yolk powder was too low, resulting in insufficient lysozyme concentration and a decrease in the antibacterial rate of the fresh-keeping film layer. At the same time, the lipoprotein in the egg yolk powder could not effectively adhere to chitosan, resulting in an increase in the porosity of the fresh-keeping film layer and an increase in the water vapor transmission coefficient. In Example 12, the mass fraction of egg yolk powder was too high, and the lipoprotein was over-crosslinked with chitosan, resulting in an increase in the rigidity of the fresh-keeping film layer and the easy generation of microcracks during the drying process. In addition, the self-aggregation of lysozyme led to a decrease in the antibacterial rate.

[0190] From the test data of Example 4, Example 13 and Example 14, it can be seen that the water vapor transmission coefficient and weight loss rate of Example 13 and Example 14 are higher than those of Example 4, and the antibacterial rate against Escherichia coli is lower than that of Example 4. This is because the mass fraction of chitosan was adjusted in Example 13 and Example 14. In Example 13, the mass fraction of chitosan was too low to form a continuous three-dimensional network structure, resulting in a reduction in the mechanical strength of the fresh-keeping film layer. In Example 14, the mass fraction of chitosan was too high, and the molecular chain entanglement led to uneven spraying, resulting in a too thick local area of the fresh-keeping film layer. In addition, the aggregation of amino groups of chitosan led to a decrease in the antibacterial efficiency of the fresh-keeping film layer.

[0191] It can be seen from the test data of Example 4, Example 15 and Example 16 that the water vapor transmission coefficient and weight loss rate of Example 15 and Example 16 are higher than those of Example 4, and the antibacterial rate against Escherichia coli is lower than that of Example 4. This is because the mass fraction of citric acid was adjusted in Example 15 and Example 16. In Example 15, the mass fraction of citric acid was too low, and the chitosan was not completely dissolved, resulting in undissolved colloidal particles in the fresh-keeping film layer, which caused the water vapor transmission coefficient of the fresh-keeping film layer to increase. In Example 16, the mass fraction of citric acid was too high, resulting in the hydrolysis of chitosan, the decrease of the tear resistance of the fresh-keeping film layer. At the same time, too high acidity would also cause lipoprotein denaturation, resulting in the decrease of the antibacterial rate of the fresh-keeping film layer.

[0192] It can be seen from the test data of Example 4, Example 17 and Example 18 that the water vapor transmission coefficient and weight loss rate of Example 17 and Example 18 are higher than those of Example 4, and the antibacterial rate against Escherichia coli is lower than that of Example 4. This is because the mass fraction of tea polyphenols was adjusted in Example 17 and Example 18. In Example 17, the mass fraction of tea polyphenols was too low, the cross-linking of phenolic hydroxyl groups was insufficient, the ultraviolet shielding ability was weak, and the antioxidant effect was limited. In Example 18, the mass fraction of tea polyphenols was too high, resulting in excessive cross-linking of phenolic hydroxyl groups, the increase of the brittleness of the dried fresh-keeping film layer, the increase of the water vapor transmission coefficient, and the colloidal particles would also become the attachment sites of microorganisms, resulting in the decrease of the antibacterial rate of the fresh-keeping film layer.

[0193] It can be seen from the test data of Example 4, Example 19 and Example 20 that the water vapor transmission coefficient and weight loss rate of Example 19 and Example 20 are higher than those of Example 4, and the antibacterial rate against Escherichia coli is lower than that of Example 4. This is because the mass fraction of ε-polylysine was adjusted in Example 19 and Example 20. In Example 19, the mass fraction of ε-polylysine was too low to form a gradient charge distribution, resulting in the decrease of the antibacterial rate of the fresh-keeping film layer. In Example 20, the mass fraction of ε-polylysine was too high, electrostatically combined with citric acid to form micelles, and the number of microcracks in the dried fresh-keeping film layer increased, affecting the preservation effect.

[0194] It can be seen from the test data of Example 4, Example 21 and Example 22 that the water vapor transmission coefficient and weight loss rate of Example 21 and Example 22 are higher than those of Example 4, and the antibacterial rate against Escherichia coli is lower than that of Example 4. This is because the mass fraction of glycerol was adjusted in Example 21 and Example 22. In Example 21, the mass fraction of glycerol was too low, the rigidity of the three-dimensional network structure of chitosan was too high, and the drying stress caused microcracks to appear in the fresh-keeping film layer, affecting the preservation effect. In Example 22, the mass fraction of glycerol was too high, which destroyed the compactness of the three-dimensional network structure of chitosan, and the hygroscopic swelling accelerated the water loss, resulting in the increase of the water vapor transmission coefficient of the fresh-keeping film layer.

[0195] 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 thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A food-derived fruit and vegetable preservative, characterized in that: The food-derived fruit and vegetable preservative comprises carrot powder, egg yolk powder, chitosan, citric acid and deionized water.

2. The food-derived fruit and vegetable preservative according to claim 1, characterized in that: The mass fraction of carrot powder in the food-derived fruit and vegetable preservative is 0.8-1.2wt%; The mass fraction of the egg yolk powder in the food-derived fruit and vegetable preservative is 0.3-0.8wt%; The mass fraction of chitosan in the food-derived fruit and vegetable preservative is 0.4-0.6wt%; The mass fraction of citric acid in the food-derived fruit and vegetable preservative is 1-2 wt %.

3. The food-derived fruit and vegetable preservative according to claim 1, characterized in that: The food-derived fruit and vegetable preservative also includes tea polyphenols.

4. The food-derived fruit and vegetable preservative according to claim 1, characterized in that: The food-derived fruit and vegetable preservative further comprises ε-polylysine.

5. The food-derived fruit and vegetable preservative according to claim 1, characterized in that: The food-derived fruit and vegetable preservative also includes glycerol.

6. The food-derived fruit and vegetable preservative according to claim 1, characterized in that: The mass fraction of tea polyphenols in the food-derived fruit and vegetable preservative is 0.5-1wt%; The mass fraction of ε-polylysine in the food-derived fruit and vegetable preservative is 0.05-0.1wt%; The mass fraction of glycerol in the food-derived fruit and vegetable preservative is 1-2 wt %.

7. A method for preparing the food-derived fruit and vegetable preservative according to any one of claims 1 to 6, characterized in that: The preparation method comprises: Carrot powder, egg yolk powder, chitosan, citric acid and deionized water are uniformly mixed to obtain the food-derived fruit and vegetable preservative.

8. The preparation method according to claim 7, characterized in that: The preparation method comprises: Carrot powder, egg yolk powder, chitosan, citric acid, tea polyphenols, epsilon-polylysine, glycerol and deionized water are uniformly mixed to obtain the food-derived fruit and vegetable preservative.

9. A method for using the food-derived fruit and vegetable preservative according to any one of claims 1 to 6, characterized in that: The method of use includes: Soak the fruits and vegetables to be preserved in the food-derived fruit and vegetable preservative, then take them out and dry them naturally; or, The food-derived fruit and vegetable preservative is sprayed on the surface of the fruits and vegetables to be treated for freshness preservation, and then dried naturally.

10. The method of use according to claim 9, characterized in that: The fruits and vegetables to be preserved are immersed in the food-derived fruit and vegetable preservative for 5 to 10 seconds.

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