Bacteriostatic high-barrier food-borne fruit and vegetable fresh-keeping agent and preparation method thereof

Abstract

The invention provides a bacteriostatic high-barrier food-borne fruit and vegetable fresh-keeping agent and a preparation method thereof. The food-borne fruit and vegetable fresh-keeping agent is prepared from embedded carrot powder, hydrolyzed yolk powder, carboxymethyl chitosan, a starch-citric acid compound, ascorbic acid and deionized water, the embedded carrot powder is obtained by embedding carrot freeze-dried powder with beta-cyclodextrin; the hydrolyzed egg yolk powder is obtained by hydrolyzing egg yolk liquid with protease, drying, crushing and sieving; the starch-citric acid compound is obtained by performing esterification reaction on starch and citric acid. The food-borne fruit and vegetable fresh-keeping agent provided by the invention not only is high in safety and strong in raw material edibility, but also breaks through the limitation of a single component through functional complementation among the components, and realizes long-acting inhibition on microbial growth and omnibearing obstruction on environmental factors.

Description

Technical Field

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

[0002] In recent years, with the continuous improvement of consumers' attention to food safety, the post-harvest preservation technology of fruits and vegetables has gradually shifted from chemically synthesized preservatives to the direction of natural safety. Although the commonly used chemically synthesized preservatives on the market have certain antibacterial effects, there are risks of chemical residues. Long-term use may lead to an increase in the drug resistance of pathogenic bacteria, and some components may produce toxic metabolites during the degradation process. Although the safety of natural plant extract-based preservatives has been improved, the extraction cost of their active ingredients is high, the antibacterial activity is significantly affected by environmental factors, and the barrier performance to the fruit and vegetable epidermis is insufficient, making it difficult to effectively isolate oxygen and moisture exchange, resulting in unstable preservation effects.

[0003] In the prior art, preservatives using natural substances such as chitosan and propolis have certain biocompatibility, but the correlation between their raw material sources and the food system is weak. There are risks of sensitization and flavor interference problems during large-scale application. Especially in the field of edible coatings that directly contact fruits and vegetables, there has been no breakthrough in the systematic application of food-derived ingredients in existing products, and exogenous antibacterial agents or cross-linking agents often need to be added to enhance the function.

[0004] Based on this, developing a preservation system composed entirely of edible ingredients has become an important research direction. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide an antibacterial and high-barrier food-derived fruit and vegetable preservative and a preparation method thereof. The food-derived fruit and vegetable preservative provided by the present invention not only has high safety and strong edibility of raw materials, but also breaks through the limitations of single components through the functional complementarity between components, achieving long-term inhibition of microbial growth and all-round barrier to environmental factors.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides an antibacterial and high-barrier food-derived fruit and vegetable preservative, which includes embedded carrot powder, hydrolyzed egg yolk powder, carboxymethyl chitosan, starch-citric acid complex, ascorbic acid and deionized water;

[0008] The embedded carrot powder is obtained by embedding carrot freeze-dried powder with β-cyclodextrin;

[0009] The hydrolyzed egg yolk powder is obtained by hydrolyzing egg yolk liquid with protease, followed by drying, pulverizing and sieving;

[0010] The starch-citric acid complex is obtained by the esterification reaction of starch and citric acid.

[0011] The food-derived fruit and vegetable preservative provided by the present invention constructs a preservative system with both antibacterial activity and physical barrier function through the synergistic effect of various food-derived components. Its core advantage lies in the organic combination of natural antibacterial components and film-forming substances, forming a dense protective layer through intermolecular interactions, and at the same time using the slow-release effect of bioactive substances to extend the antibacterial cycle. Compared with traditional chemical preservatives, the food-derived fruit and vegetable preservative provided by the present invention not only has high safety and strong edibility of raw materials, but also breaks through the limitations of single components through the functional complementarity between components, achieving long-term inhibition of microbial growth and all-round barrier to environmental factors.

[0012] In terms of antibacterial performance, the encapsulated carrot powder protects photosensitive substances through the molecular encapsulation of active ingredients such as carotene and polyphenols by β-cyclodextrin, and at the same time realizes the slow release of active ingredients. The α-carotene olefins contained in the freeze-dried carrot powder can destroy the bacterial biofilm structure. The hydrolyzed polypeptides in the hydrolyzed egg yolk powder have amphiphilic characteristics and can interact with the phospholipid bilayer of the pathogen cell membrane to specifically block the transmembrane proton gradient. The cationic property of carboxymethyl chitosan neutralizes the negative charge on the bacterial surface through electrostatic adsorption, and its amino group chelates with metal ions to further interfere with the microbial enzyme system. The residual citric acid in the starch-citric acid complex can lower the system pH value below the isoelectric point of bacteria, and at the same time the free carboxyl groups in its esterification products can competitively inhibit the bacterial tricarboxylic acid cycle. Ascorbic acid can not only directly scavenge free radicals, but its reducing effect can also maintain the active state of other antioxidant components and inhibit the metabolism of aerobic bacteria by reducing the dissolved oxygen concentration.

[0013] In terms of barrier performance, carboxymethyl chitosan and the starch-citric acid complex form a three-dimensional network skeleton through hydrogen bonds and van der Waals forces. The straight-chain ratio of the starch-citric acid complex obtained by the esterification reaction increases, and the molecular chain orientation degree increases, resulting in a significant increase in the crystallinity of the fresh-keeping film layer. The hydrophobic peptide segments in the hydrolyzed egg yolk powder are interspersed in the polysaccharide skeleton and fill the molecular gaps through hydrophobic interactions, greatly reducing the water vapor transmission coefficient of the fresh-keeping film layer formed after film formation. The cyclodextrin cavity structure of the encapsulated carrot powder serves as a physical cross-linking point, enhancing the mechanical strength of the fresh-keeping film layer. At the same time, its hydroxyl groups form a hydrogen bond network with the polysaccharide chain, further improving the barrier performance of the fresh-keeping film layer. Ascorbic acid plays a plasticizer role in the fruit and vegetable preservative, improving the flexibility of the fresh-keeping film layer by lowering the glass transition temperature and avoiding the generation of permeation channels due to mechanical damage.

[0014] The synergistic effects among the components in the foodborne fruit and vegetable preservative are as follows: First, the film-forming property of carboxymethyl chitosan is complementary to the thermoplasticity of the starch-citric acid complex, forming a bicontinuous phase structure during the mixing and dissolution stage, which greatly improves the elongation at break of the dried fresh-keeping film layer. Second, the hydrophobic peptide segments of hydrolyzed egg yolk powder form host-guest inclusion with β-cyclodextrin encapsulating carrot powder, delivering antibacterial components to the surface of the fresh-keeping film layer and enriching them, which significantly improves the contact antibacterial rate of the fresh-keeping film layer. Third, ascorbic acid and the residual citric acid in the starch-citric acid complex constitute a pH buffer system, stabilizing the film surface environment between 3.8 and 4.2. This pH range can inhibit the growth of most spoilage bacteria and ensure continuous antibacterial activity.

[0015] As a preferred technical solution of the present invention, based on the mass fraction of the foodborne fruit and vegetable preservative being 100 wt%, it comprises the following components in mass fractions:

[0016] Encapsulated carrot powder 3 - 5 wt%;

[0017] Hydrolyzed egg yolk powder 1 - 3 wt%;

[0018] Carboxymethyl chitosan 1.5 - 2.5 wt%;

[0019] Starch-citric acid complex 3 - 5 wt%;

[0020] Ascorbic acid 0.2 - 0.5 wt%;

[0021] The balance is deionized water.

[0022] Among them, the mass fraction of the encapsulated carrot powder can be 3.0wt%, 3.2wt%, 3.4wt%, 3.6wt%, 3.8wt%, 4.0wt%, 4.2wt%, 4.4wt%, 4.6wt%, 4.8wt% or 5.0wt%, the mass fraction of the hydrolyzed egg yolk powder can be 1.0wt%, 1.2wt%, 1.4wt%, 1.6wt%, 1.8wt%, 2.0wt%, 2.2wt%, 2.4wt%, 2.6wt%, 2.8wt% or 3.0wt%, the mass fraction of the carboxymethyl chitosan can be 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt%, 2.0wt%, 2.1wt%, 2.2wt%, 2.3wt%, 2.4wt% or 2.5wt%, the mass fraction of the starch-citric acid complex can be 3.0wt%, 3.2wt%, 3.4wt%, 3.6wt%, 3.8wt%, 4.0wt%, 4.2wt%, 4.4wt%, 4.6wt%, 4.8wt% or 5.0wt%, and the mass fraction of the ascorbic acid can be 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt% or 0.5wt%. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0023] The present invention particularly limits the mass fraction of the encapsulated carrot powder to 3-5wt%. Within this range, it can ensure the uniform dispersion of the encapsulated carrot powder in the fruit and vegetable cleaning agent, which can not only form hydrogen bonds with the carboxymethyl chitosan chain segments to enhance the density of the fresh-keeping film layer, but also avoid the agglomeration phenomenon caused by excessive encapsulated carrot powder, enabling the active ingredients to be gradually released and maintaining an effective antibacterial concentration.

[0024] When the mass fraction of the encapsulated carrot powder is lower than 3wt%, the total amount of antibacterial substances in the encapsulated carrot powder is insufficient, and it is difficult to form an effective concentration to inhibit the proliferation of microorganisms. In addition, during the film-forming process, too little encapsulated carrot powder is difficult to play a filling role, resulting in more micropores inside the fresh-keeping film layer, increasing the water vapor transmission coefficient and reducing the barrier performance. At the same time, the interaction between too little encapsulated carrot powder and the hydrophobic components of the hydrolyzed egg yolk powder is weakened, affecting the directional enrichment distribution of the antibacterial components on the surface of the fresh-keeping film layer.

[0025] When the mass fraction of embedded carrot powder is higher than 5wt%, the excessive embedded carrot powder will interfere with the cross-linking of carboxymethyl chitosan and starch-citric acid complex, resulting in a decrease in the mechanical strength of the cling film layer. In addition, the excessive embedded carrot powder is prone to agglomeration, destroying the continuous phase structure of the cling film layer, forming microcracks, resulting in an increase in the water vapor permeability coefficient and a decrease in barrier properties. At the same time, the excessive embedded carrot powder will increase the viscosity of the fruit and vegetable preservative, affect the uniformity of the film layer when the fruit and vegetable preservative is sprayed or dipped, and cause the concentration of the active ingredient in the local area to be too high and insufficient in other areas.

[0026] The present invention particularly limits the mass fraction of the hydrolyzed egg yolk powder to 1-3wt%. Within this range, the active peptide segments produced by the hydrolysis of the egg yolk protein can be fully dispersed in the fruit and vegetable preservative, and the antibacterial effect is achieved by destroying the integrity of the microbial cell membrane. At the same time, the hydrophobic components thereof can be combined with the hydrophobic regions in the starch-citric acid complex, thereby improving the compactness of the preservative film layer.

[0027] When the mass fraction of hydrolyzed egg yolk powder is lower than 1wt%, the effective ingredients in the hydrolyzed egg yolk powder are difficult to reach the minimum concentration required for antibacterial action, and the inhibitory effect on some spoilage bacteria with strong tolerance is significantly reduced. At the same time, the fruit and vegetable preservative liquid lacks sufficient hydrophobic substances to fill the gaps between polysaccharide molecular chains, resulting in a decrease in the barrier properties of the preservative film layer, making it easier for external moisture and oxygen to penetrate.

[0028] When the mass fraction of hydrolyzed egg yolk powder is higher than 3wt%, the excess hydrophobic substances will interfere with the hydrogen bonding between carboxymethyl chitosan and starch-citric acid complex, resulting in local agglomeration during film formation. In addition, high concentrations of peptides tend to form a discontinuous phase during drying, causing stress concentration points inside the cling film layer, reducing its mechanical strength and barrier stability.

[0029] The present invention particularly limits the mass fraction of the starch-citric acid complex to 3-5wt%. Within this range, the starch-citric acid complex can form a hydrogen bond with the carboxymethyl chitosan to improve the compactness of the cling film layer, and will not affect the stability of other active ingredients due to excessive acidification of the fruit and vegetable preservative.

[0030] When the mass fraction of the starch-citric acid complex is lower than 3wt%, the film-forming effect of the starch-citric acid complex cannot be fully exerted, and the degree of cross-linking between starch chains is low, resulting in a loose structure of the cling film layer that is easy to break. In addition, the insufficient addition of the starch-citric acid complex results in too few free acidic groups in the fruit and vegetable preservative, making it difficult to maintain a sufficient antibacterial acidic environment, and the inhibitory effect on acid-resistant bacteria is significantly weakened. At the same time, too little starch-citric acid complex cannot effectively fill the gaps between other components, resulting in weak areas on the surface of the cling film layer, affecting the overall barrier effect.

[0031] When the mass fraction of the starch-citric acid complex is higher than 5 wt%, excessive acidic groups result in too low a pH value of the fruit and vegetable preservative, leading to flocculation or degradation of components such as carboxymethyl chitosan. At the same time, the too strong acidic environment will also accelerate the oxidation and decomposition of components such as ascorbic acid, shortening the effective action time of the preservative. In addition, the high-concentration starch-citric acid complex will form an overly rigid network structure, increasing the brittleness of the fresh-keeping film layer, and it is prone to cracking due to the volume change caused by the respiratory action of fruits and vegetables in practical applications.

[0032] In a second aspect, the present invention provides a preparation method of the food-derived fruit and vegetable preservative described in the first aspect, and the preparation method includes:

[0033] (I) Mix β-cyclodextrin with deionized water to obtain a cyclodextrin solution, add freeze-dried carrot powder thereto for ultrasonic treatment, and then obtain embedded carrot powder through centrifugation, drying, pulverization, and sieving;

[0034] (II) Add alkaline protease to the egg yolk liquid, mix and stir and heat to carry out a hydrolysis reaction. After the reaction ends, carry out enzyme inactivation, rotary evaporation concentration, filtration, drying, pulverization, and sieving to obtain hydrolyzed egg yolk powder;

[0035] (III) Mix starch, citric acid, and acetate buffer solution, stir and heat to carry out an esterification reaction. After the reaction ends, carry out filtration, drying, pulverization, and sieving to obtain a starch-citric acid complex;

[0036] (IV) Mix the embedded carrot powder, hydrolyzed egg yolk powder, starch-citric acid complex, carboxymethyl chitosan, ascorbic acid, and deionized water evenly to obtain the food-derived fruit and vegetable preservative.

[0037] During the process of preparing the embedded carrot powder, the cyclic hydrophobic cavity of β-cyclodextrin selectively embeds the fat-soluble active components (such as β-carotene, polyphenols) in the freeze-dried carrot powder through intermolecular forces. The cavitation effect of ultrasonic treatment is used to accelerate the collision between β-cyclodextrin molecules and the freeze-dried carrot powder, prompting more active substances to enter the cavity to form inclusion compounds.

[0038] During the process of preparing the hydrolyzed egg yolk powder, alkaline protease specifically cleaves the hydrophobic amino acid sites of egg yolk protein under the condition of pH = 8-8.5 to generate hydrophobic peptide segments with a molecular weight of 1-3 kDa. These peptide segments insert into the phospholipid bilayer of the microbial cell membrane through an amphiphilic structure, interfering with its transmembrane potential and achieving a bactericidal and bacteriostatic effect.

[0039] In the process of preparing the starch-citric acid complex, first, in the pre-reaction stage, the chemical reaction activity of the hydroxyl groups on the surface of starch granules is activated by a heating temperature of 50-55 °C, promoting the preliminary formation of ester bonds between the carboxyl groups of citric acid and the hydroxyl groups of starch; subsequently, in the main reaction stage, the starch is fully gelatinized by a high temperature of 100-110 °C. After the linear starch molecules unfold, more reaction sites are exposed, significantly enhancing the degree of esterification. The esterification reaction is carried out in a weakly acidic environment formed by acetate buffer solution, which can not only inhibit the excessive hydrolysis of starch but also enhance the nucleophilicity of the carboxyl group of citric acid through protonation, promoting the forward progress of the esterification reaction.

[0040] As a preferred technical solution of the present invention, in step (Ⅰ), the mass fraction of β-cyclodextrin in the cyclodextrin solution is 2-3 wt%, for example, it can be 2.0 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, 2.9 wt% or 3.0 wt%, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0041] In some optional examples, the heating temperature when β-cyclodextrin is mixed with deionized water is 50-60 °C, for example, it can be 50 °C, 51 °C, 52 °C, 53 °C, 54 °C, 55 °C, 56 °C, 57 °C, 58 °C, 59 °C or 60 °C, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0042] In some optional examples, the mass ratio of β-cyclodextrin to freeze-dried carrot powder is (2-3):1, for example, it can be 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1 or 3.0:1, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0043] The present invention specifically limits the mass ratio of β-cyclodextrin to freeze-dried carrot powder to (2-3):1. Within this range, the cavity structure of β-cyclodextrin can just wrap the active ingredients in the freeze-dried carrot powder, not only protecting the photosensitive substances from being rapidly oxidized but also participating in the network construction of the fresh-keeping film layer through intermolecular forces. At the same time, the hydroxyl groups in an appropriate amount of β-cyclodextrin molecules form hydrogen bonds with the carboxyl groups in the starch-citric acid complex, enhancing the water barrier ability of the fresh-keeping film layer.

[0044] When the addition amount of β-cyclodextrin is lower than the lower limit of the range defined in the present invention, some active ingredients in the freeze-dried carrot powder cannot be effectively encapsulated by β-cyclodextrin and are prone to oxidative inactivation during preparation and storage. In addition, the unencapsulated hydrophobic active ingredients will form local aggregation points during film formation, destroying the continuity of the fresh-keeping film layer and resulting in a decrease in the barrier performance. At the same time, insufficient addition amount of β-cyclodextrin will affect its function as a physical cross-linking point, causing a decrease in the mechanical strength of the fresh-keeping film layer and being prone to breakage in practical applications.

[0045] When the addition amount of β-cyclodextrin exceeds the upper limit of the range defined in the present invention, the hydrophilic groups of the excessive β-cyclodextrin will increase the moisture absorption of the fresh-keeping film layer, resulting in an increase in the water vapor transmission coefficient of the fresh-keeping film layer and a decrease in the barrier performance. In addition, when the addition amount of β-cyclodextrin is too high, the active ingredients in the freeze-dried carrot powder are overly encapsulated, resulting in hindered release of the active ingredients in the freeze-dried carrot powder, delayed antibacterial effect, and difficulty in quickly forming a microbial inhibition environment.

[0046] In some alternative examples, the ultrasonic power of the ultrasonic treatment is 300 - 400 W, for example, it can be 300 W, 310 W, 320 W, 330 W, 340 W, 350 W, 360 W, 370 W, 380 W, 390 W or 400 W, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0047] In some alternative examples, the ultrasonic time of the ultrasonic treatment is 20 - 30 min, for example, it can be 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0048] As a preferred technical solution of the present invention, in step (Ⅰ), the rotation speed of the centrifugation is 3000 - 5000 rpm, for example, it can be 3000 rpm, 3200 rpm, 3400 rpm, 3600 rpm, 3800 rpm, 4000 rpm, 4200 rpm, 4400 rpm, 4600 rpm, 4800 rpm or 5000 rpm, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0049] In some alternative examples, the centrifugation time is 10 - 20 min, for example, it can be 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min or 20 min, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0050] In some alternative examples, the drying temperature is 45 to 50 °C. For example, it can be 45 °C, 46 °C, 47 °C, 48 °C, 49 °C or 50 °C, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0051] In some alternative examples, the drying time is 6 to 8 h. For example, it can be 6.0 h, 6.2 h, 6.4 h, 6.8 h, 7 h, 7.2 h, 7.4 h, 7.6 h, 7.8 h or 8 h, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0052] In some alternative examples, the mesh number of the sieve for sieving is 100 to 200 meshes. For example, it can be 100 meshes, 110 meshes, 120 meshes, 130 meshes, 140 meshes, 150 meshes, 160 meshes, 170 meshes, 180 meshes, 190 meshes or 200 meshes, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0053] As a preferred technical solution of the present invention, in step (II), the egg yolk liquid is obtained by mixing and dispersing egg yolk with deionized water.

[0054] In some alternative examples, the volume ratio of the egg yolk to deionized water is 1:(3 to 4). For example, it can be 1:3.0, 1:3.1, 1:3.2, 1:3.3, 1:3.4, 1:3.5, 1:3.6, 1:3.7, 1:3.8, 1:3.9 or 1:4.0, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0055] In some alternative examples, the pH value of the egg yolk liquid is adjusted to 8 to 8.5 and then the alkaline protease is added. For example, it can be 8.0, 8.1, 8.2, 8.3, 8.4 or 8.5, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0056] Optionally, a 1 to 5 wt% sodium carbonate solution or a 0.1 to 0.5 wt% sodium hydroxide solution is used to adjust the pH value of the egg yolk liquid. It should be slowly added dropwise and stirred well during the addition to avoid local over-alkalinity causing excessive protein denaturation. Stir while adding and monitor the pH value in real time to prevent overshoot.

[0057] In some alternative embodiments, the addition amount of the alkaline protease is 1-2 wt% of the mass of the egg yolk liquid. 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 is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0058] The present invention specifically limits the addition amount of the alkaline protease to 1-2 wt% of the mass of the egg yolk liquid. Within this range, the alkaline protease can fully decompose the egg yolk protein to generate small peptide segments with antibacterial effects, while avoiding excessive hydrolysis to produce too many hydrophobic residues. The appropriate hydrolysis products not only retain the ability to penetrate the microbial cell membrane, but their amphiphilic structure can also bind to the hydrophobic region in the starch-citric acid complex to assist in forming a dense fresh-keeping film layer.

[0059] When the addition amount of the alkaline protease is less than 1 wt%, the hydrolysis degree of the egg yolk protein is insufficient, and the number of active peptide segments produced is limited, making it difficult to reach the effective antibacterial concentration. In addition, the large molecular egg yolk protein fragments that are not fully hydrolyzed are prone to aggregation during the film-forming process, resulting in microcracks inside the fresh-keeping film layer and weakening the barrier effect on oxygen and moisture.

[0060] When the addition amount of the alkaline protease exceeds 2 wt%, excessive hydrolysis will produce a large number of short peptides with too small molecular weights, and the antibacterial activity of these short peptides is low, which affects the antibacterial performance of the fresh-keeping film layer. In addition, the hydrophobic groups in the excessive hydrolysis products are overly exposed, resulting in phase separation during film formation and destroying the integrity of the fresh-keeping film layer.

[0061] In some alternative embodiments, the temperature for mixing and stirring the egg yolk liquid and the alkaline protease is 50-60 °C. For example, it can be 50 °C, 51 °C, 52 °C, 53 °C, 54 °C, 55 °C, 56 °C, 57 °C, 58 °C, 59 °C or 60 °C, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0062] In some alternative embodiments, the time for mixing and stirring the egg yolk liquid and the alkaline protease is 2-3 h. For example, it can be 2.0 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h, 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h or 3.0 h, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0063] As a preferred technical solution of the present invention, in step (II), the temperature for enzyme inactivation is 90-95°C. For example, it can be 90°C, 90.5°C, 91°C, 91.5°C, 92°C, 92.5°C, 93°C, 93.5°C, 94°C, 94.5°C or 95°C. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0064] In some alternative examples, the time for enzyme inactivation is 15-20 min. For example, it can be 15 min, 15.5 min, 16 min, 16.5 min, 17 min, 17.5 min, 18 min, 18.5 min, 19 min, 19.5 min or 20 min. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0065] In some alternative examples, immediately after the enzyme inactivation, it is placed in an ice-water bath at 3-5°C for cooling for 30 min. For example, it can be 3.0°C, 3.2°C, 3.4°C, 3.6°C, 3.8°C, 4.0°C, 4.2°C, 4.4°C, 4.6°C, 4.8°C or 5.0°C. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0066] In some alternative examples, the temperature for rotary evaporation and concentration is 60-65°C. For example, it can be 60°C, 60.5°C, 61°C, 61.5°C, 62°C, 62.5°C, 63°C, 63.5°C, 64°C, 64.5°C or 65°C. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0067] In some alternative examples, the time for rotary evaporation and concentration is 2-3 h. For example, it can be 2.0 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h, 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h or 3.0 h. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0068] As a preferred technical solution of the present invention, in step (III), the mass ratio of starch to citric acid is (3-4):1. For example, it can be 3.0:1, 3.1:1, 3.2:1, 3.3:1, 3.4:1, 3.5:1, 3.6:1, 3.7:1, 3.8:1, 3.9:1 or 4.0:1. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0069] The present invention specifically limits the mass ratio of starch to citric acid to (3 - 4):1. Within this range, the starch molecular chains are moderately cross-linked with citric acid through an esterification reaction, which not only retains enough linear structure to maintain the mechanical strength of the fresh-keeping film layer but also introduces an appropriate amount of carboxyl groups to enhance its hydrophilic regulation ability. At the same time, part of the acidic groups of citric acid are retained, which can continuously create an acidic environment on the surface of the fresh-keeping film layer to inhibit the growth of microorganisms, while the unreacted starch provides structural support to form a dense barrier layer.

[0070] When the addition amount of starch is lower than the lower limit of the range defined in the present invention, excessive citric acid will cause a significant decrease in the pH value of the fruit and vegetable fresh-keeping agent system, leading to flocculation and precipitation of components such as carboxymethyl chitosan and destroying the continuity of film formation. In addition, excessive esterification reaction will cause excessive cross-linking of starch molecular chains, forming a network structure with too strong rigidity, which is prone to cracking under the volume change generated by the respiration of fruits and vegetables. At the same time, the free citric acid not bound by starch will also accelerate the oxidation and decomposition of components such as ascorbic acid, shortening the effective action time of the fruit and vegetable fresh-keeping agent.

[0071] When the addition amount of starch exceeds the upper limit of the range defined in the present invention, the addition amount of citric acid is insufficient, resulting in a small number of active carboxyl groups in the starch-citric acid complex, weakening the continuous antibacterial ability of the starch-citric acid complex. In addition, the unreacted starch molecules retain a large number of hydroxyl groups, which are easy to combine with water molecules to form hydrogen bonds, increasing the moisture permeability of the fresh-keeping film layer, resulting in an increase in the water vapor transmission coefficient of the fresh-keeping film layer and a decrease in the barrier performance. At the same time, too much starch will also occupy the dispersion sites in the fruit and vegetable fresh-keeping agent, affecting the uniform distribution of components such as embedded carrot powder, forming local weak areas during film formation, and leading to a decrease in the barrier performance of the fresh-keeping film layer.

[0072] In some alternative examples, the pH value of the acetate buffer solution is 4.5 - 5. For example, it can be 4.5, 4.6, 4.7, 4.8, 4.9 or 5, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0073] In some alternative examples, the ratio of the total mass of the starch and citric acid to the volume of the acetate buffer solution is (80 - 100) g:1 L. For example, it can be 80 g:1 L, 82 g:1 L, 84 g:1 L, 86 g:1 L, 88 g:1 L, 90 g:1 L, 92 g:1 L, 94 g:1 L, 96 g:1 L, 98 g:1 L or 100 g:1 L, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0074] In some alternative examples, the esterification reaction includes a pre-reaction and a main reaction carried out in sequence.

[0075] In some alternative examples, the reaction temperature of the pre-reaction is 50~55°C. For example, it can be 50°C, 50.5°C, 51°C, 51.5°C, 52°C, 52.5°C, 53°C, 53.5°C, 54°C, 54.5°C or 55°C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0076] In some alternative examples, the reaction time of the pre-reaction is 20~30 min. For example, it can be 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0077] In some alternative examples, the reaction temperature of the main reaction is 100~110°C. For example, it can be 100°C, 101°C, 102°C, 103°C, 104°C, 105°C, 106°C, 107°C, 108°C, 109°C or 110°C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0078] The present invention specifically defines that the reaction temperature of the main reaction is 100~110°C. Within this range, the starch granules are fully gelatinized to unfold the molecular chains, making it easier for citric acid to react with hydroxyl groups to form stable ester bonds. This not only ensures the crosslinking density of the starch-citric acid complex and improves the barrier performance of the fresh-keeping film layer, but also retains an appropriate amount of unreacted carboxyl groups to maintain the acidic environment of the food-derived fruit and vegetable fresh-keeping agent.

[0079] When the reaction temperature of the main reaction is lower than 100°C, the starch molecular chains cannot be fully unfolded, and the esterification reaction rate decreases significantly. Excessive hydrophilic hydroxyl groups are retained in the unreacted starch, resulting in enhanced hygroscopicity of the starch-citric acid complex. After film formation, structural swelling is likely to occur due to water penetration, and the barrier performance decreases. In addition, the concentration of free citric acid in the food-derived fruit and vegetable fresh-keeping agent is too high, leading to local over-acidification, which not only affects the stability of other active ingredients, but also causes the molecular chains of carboxymethyl chitosan to curl excessively, reducing the uniformity of the fresh-keeping film layer.

[0080] When the reaction temperature of the main reaction is higher than 110°C, citric acid will undergo decarboxylation decomposition, reducing the number of effective carboxyl groups and weakening the continuous antibacterial ability of the starch-citric acid complex. In addition, the starch molecular chains will break and degrade at high temperatures, making the molecular weight distribution of the starch-citric acid complex wider, resulting in a loose structure of the fresh-keeping film layer and an increase in the water vapor transmission coefficient, and a decrease in the barrier performance.

[0081] In some alternative examples, the reaction time of the main reaction is 1 to 2 h, for example, it can be 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h or 2.0 h, but it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0082] As a preferred technical solution of the present invention, in step (III), the drying temperature is 50 to 55 °C, for example, it can be 50 °C, 50.5 °C, 51 °C, 51.5 °C, 52 °C, 52.5 °C, 53 °C, 53.5 °C, 54 °C, 54.5 °C or 55 °C, but it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0083] In some alternative examples, the drying time is 5 to 6 h, for example, it can be 5.0 h, 5.1 h, 5.2 h, 5.3 h, 5.4 h, 5.5 h, 5.6 h, 5.7 h, 5.8 h, 5.9 h or 6.0 h, but it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0084] As a preferred technical solution of the present invention, in step (IV), the mixing sequence is:

[0085] First, carboxymethyl chitosan and deionized water are mixed and dissolved under heating conditions; then the heating is stopped, and starch-citric acid complex, encapsulated carrot powder, hydrolyzed egg yolk powder and ascorbic acid are added in sequence, and after mixing evenly, the food-derived fruit and vegetable preservative is obtained.

[0086] Exemplarily, the present invention provides a specific mixing step for each component:

[0087] Add carboxymethyl chitosan to deionized water at 55 to 60 °C, and mix and stir at a stirring rate of 400 to 500 rpm until the carboxymethyl chitosan is completely dissolved;

[0088] Then stop heating and monitor the temperature of the mixed solution in real time;

[0089] When the temperature of the mixed solution drops to 45 to 50 °C, add the starch-citric acid complex and mix and stir at a stirring rate of 300 to 400 rpm;

[0090] When the temperature of the mixed solution drops to 40 to 45 °C, add the encapsulated carrot powder and mix and stir at a stirring rate of 200 to 300 rpm;

[0091] When the temperature of the mixed solution drops to 35 to 40 °C, add the hydrolyzed egg yolk powder and mix and stir at a stirring rate of 150 to 200 rpm;

[0092] When the temperature of the mixed solution drops below 30°C, ascorbic acid is added, and mixing and stirring are continued for 10 - 20 min to obtain a food-derived fruit and vegetable preservative.

[0093] Optionally, after all components are mixed evenly, a 0.1 mol / L citric acid solution is added thereto to adjust the pH value of the food-derived fruit and vegetable preservative to 3.8 - 4.

[0094] In the mixing process of the present invention, components are added in stages and the stirring temperature at each stage is controlled. First, carboxymethyl chitosan is dissolved at 55 - 60°C at a relatively high rotation speed (400 - 500 rpm). By raising the temperature, the solution viscosity is reduced, promoting the full unfolding of its molecular chains to form a continuous phase. The relatively high rotation speed helps to break the hydrogen bond aggregates between carboxymethyl chitosan molecules, providing a uniformly dispersed liquid phase environment for other components added subsequently.

[0095] After stopping heating and naturally cooling to 45 - 50°C, starch-citric acid complex is added. The esterified starch molecular segments in the starch-citric acid complex can form hydrogen bond crosslinks with the hydroxyl groups of carboxymethyl chitosan. At this time, the rotation speed is reduced. A rotation speed of 300 - 400 rpm can not only promote the preliminary combination of the two but also avoid destroying the formed network structure due to too high a rotation speed.

[0096] When the temperature drops to 40 - 45°C, embedded carrot powder is added. This temperature range is just above the glass transition temperature of β-cyclodextrin. At this time, the β-cyclodextrin molecules have moderate motility, and their surface hydroxyl groups can form secondary bond combinations with the starch-citric acid complex. The relatively low rotation speed (200 - 300 rpm) reduces the mechanical impact on the embedded carrot powder, preventing premature release of active substances such as carotene embedded therein.

[0097] When the temperature drops to 35 - 40°C, hydrolyzed egg yolk powder is added. The molecular thermal motion of its hydrophobic peptide segments weakens, and it is more likely to bind to the non-polar regions in the starch-citric acid complex through hydrophobic interaction. Mixing and stirring are carried out at a lower rotation speed (150 - 200 rpm), promoting the peptide segments to be inserted into the gaps between the polysaccharide networks directionally, forming local dense regions to enhance the barrier property of the fresh-keeping film layer.

[0098] Finally, ascorbic acid is added below 30°C. The low-temperature environment can effectively reduce its oxidation rate, and short-time stirring is sufficient to achieve uniform dispersion without triggering an excessive oxidation reaction.

[0099] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0100] The food - derived fruit and vegetable preservative provided by the present invention constructs a preservation system with both antibacterial activity and physical barrier function through the synergistic effect of various food - derived components. Its core advantage lies in the organic combination of natural antibacterial components and film - forming substances, forming a dense protective layer through intermolecular interactions, and at the same time using the slow - release effect of bioactive substances to extend the antibacterial cycle. Compared with traditional chemical preservatives, the food - derived fruit and vegetable preservative provided by the present invention not only has high safety and strong edibility of raw materials, but also breaks through the limitations of single components through the functional complementarity between components, achieving long - term inhibition of microbial growth and all - round barrier to environmental factors. BRIEF DESCRIPTION OF THE DRAWINGS

[0101] Figure 1 It is a process flow chart for the preparation of the food - derived fruit and vegetable preservative provided in Examples 1 - 19 of the present invention;

[0102] Figure 2 It is an infrared spectrum diagram of carrot freeze - dried powder, β - cyclodextrin and the embedded carrot powder prepared in Example 1 of the present invention;

[0103] Figure 3 It is an infrared spectrum diagram of starch and the starch - citric acid complex prepared in Example 1 of the present invention;

[0104] Figure 4 It is an external light state diagram of bananas provided in Application Example 1 and Comparative Example 1 of the present invention on the 0th day and the 10th day of storage;

[0105] Figure 5 It is an external light state diagram of crown daisies provided in Application Example 2 and Comparative Example 2 of the present invention on the 0th day and the 7th day of storage. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0106] The technical solution of the present invention will be described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments recorded herein are specific specific embodiments of the present invention for explaining the concept of the present invention; these explanations are all explanatory and exemplary, and should not be construed as limiting the embodiments of the present invention and the protection scope of the present invention. Except for the embodiments recorded herein, 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, and these technical solutions include technical solutions that make any obvious substitutions and modifications to the embodiments recorded herein.

[0107] Example 1

[0108] This embodiment provides a preparation method for a food - derived fruit and vegetable preservative with high antibacterial and high barrier properties, as Figure 1 shown, the preparation method includes the following steps:

[0109] (1) Mix β-cyclodextrin with deionized water evenly at 50 °C to obtain a cyclodextrin solution with a mass fraction of 2 wt%. Add freeze-dried carrot powder to it, with the mass ratio of β-cyclodextrin to freeze-dried carrot powder being 2:1. Then, perform ultrasonic treatment for 30 min at an ultrasonic power of 300 W. Finally, conduct centrifugal separation at a rotational speed of 3000 rpm for 20 min. Place the centrifuged precipitate at 45 °C for drying for 8 h, and then crush and pass through a 100-mesh sieve to obtain the embedded carrot powder;

[0110] (2) Mix egg yolk and deionized water in a volume ratio of 1:3 and disperse to obtain an egg yolk solution. Adjust the pH value of the egg yolk solution to 8 and then add alkaline protease. The addition amount of alkaline protease is 1 wt% of the mass of the egg yolk solution. Mix and stir at 50 °C for 3 h to carry out a hydrolysis reaction. After the reaction ends, place the reaction product at 90 °C for enzyme inactivation for 20 min, and then immediately place it in an ice-water bath at 3 °C for cooling for 30 min. Concentrate the cooled reaction product by rotary evaporation at 60 °C for 3 h, and finally filter. Place the filtered solid product at 45 °C for drying for 8 h, and after drying, crush and pass through a 100-mesh sieve to obtain the hydrolyzed egg yolk powder;

[0111] (3) Mix starch, citric acid, and an acetate buffer solution with a pH value of 4.5 evenly. The mass ratio of starch to citric acid is 3:1, and the ratio of the total mass of starch and citric acid to the volume of the acetate buffer solution is 80 g:1 L. Mix and stir the mixed precursor solution at 50 °C for 30 min to carry out an esterification pre-reaction to activate the hydroxyl groups on the starch surface; then raise the temperature to 100 °C and mix and stir for 2 h to carry out the main esterification reaction. After the reaction ends, filter. Place the filtered product at 50 °C for drying for 6 h, and after drying, crush and pass through a 100-mesh sieve to obtain the starch-citric acid complex;

[0112] (4) Add carboxymethyl chitosan to deionized water at 55 °C and mix and stir at a stirring rate of 500 rpm until the carboxymethyl chitosan is completely dissolved. Then stop heating and monitor the temperature of the mixed solution in real time. When the temperature of the mixed solution drops to 45 °C, add the starch-citric acid complex obtained in step (3), and mix and stir at a stirring rate of 400 rpm. When the temperature of the mixed solution drops to 40 °C, add the embedded carrot powder obtained in step (1), and mix and stir at a stirring rate of 300 rpm. When the temperature of the mixed solution drops to 35 °C, add the hydrolyzed egg yolk powder obtained in step (2), and mix and stir at a stirring rate of 200 rpm. When the temperature of the mixed solution drops below 30 °C, add ascorbic acid and continue to mix and stir for 20 min. Finally, add a 0.1 mol / L citric acid solution to adjust its pH value to 3.8 to obtain the food-derived fruit and vegetable preservative.

[0113] Based on the food - borne fruit and vegetable preservative having a mass fraction of 100 wt%, it comprises the following components with the following mass fractions:

[0114] Encapsulated carrot powder 3 wt%;

[0115] Hydrolyzed egg yolk powder 3 wt%;

[0116] Carboxymethyl chitosan 2.5 wt%;

[0117] Starch - citric acid complex 3 wt%;

[0118] Ascorbic acid 0.5 wt%;

[0119] The rest is deionized water.

[0120] Figure 2 Shown are the infrared spectra of freeze - dried carrot powder, β - cyclodextrin, and the encapsulated carrot powder prepared in Example 1 of the present invention. It can be seen from the figure that in the infrared curve of the freeze - dried carrot powder, at 1630 cm -1 , 972 cm -1 , 3580 cm -1 and 1137 cm -1 respectively correspond to the C = C stretching vibration of the polyene chain of β - carotene, the out - of - plane bending vibration of C - H, the O - H stretching vibration in polysaccharides (pectin and cellulose), and the C - O - C vibration. In the infrared curve of β - cyclodextrin, at 3404 cm -1 , 2926 cm -1 , 1028 cm -1 and 947 cm -1 respectively correspond to the stretching vibration of O - H, the stretching vibration of C - H, the stretching vibration of C - O - C, and the C - O stretching vibration in - CH2OH. The infrared curve of the encapsulated carrot powder is generally the same as that of β - cyclodextrin, but the characteristic peaks of the freeze - dried carrot powder have basically disappeared, indicating that the freeze - dried carrot powder has been encapsulated by β - cyclodextrin to form an inclusion compound.

[0121] Figure 3 Shown are the infrared spectra of starch and the starch - citric acid complex prepared in Example 1 of the present invention. It can be seen from the figure that in the infrared curve of starch, the range of 3600 cm -1 ~ 3000 cm -1 corresponds to the stretching vibration of - OH, and at 2930 cm -1 and 1640 cm -1 respectively correspond to the C - H stretching vibration and the C - O stretching vibration. Compared with the infrared curve of starch, a new absorption peak appears at 1740 cm -1 in the infrared curve of the starch - citric acid complex, and this characteristic peak corresponds to the stretching vibration of the ester group C = O. In addition, at 2360 cm-1 New absorption peaks also appeared, indicating that covalent ester bonds were formed between citric acid and starch molecules.

[0122] Example 2

[0123] This example provides a preparation method of an antibacterial and high-barrier foodborne fruit and vegetable preservative. As Figure 1 shown, the preparation method includes the following steps:

[0124] (1) Mix β-cyclodextrin with deionized water evenly at 52 °C to obtain a cyclodextrin solution with a mass fraction of 2.2 wt%. Add freeze-dried carrot powder to it, and the mass ratio of β-cyclodextrin to freeze-dried carrot powder is 2.2:1. Then, perform ultrasonic treatment for 28 min at an ultrasonic power of 320 W, and finally perform centrifugal separation at a rotation speed of 3500 rpm for 18 min. Place the centrifuged precipitate at 46 °C for drying for 7.5 h, and then crush and pass through a 120-mesh sieve to obtain embedded carrot powder;

[0125] (2) Mix egg yolk and deionized water according to a volume ratio of 1:3.2 and disperse to obtain an egg yolk solution. Adjust the pH value of the egg yolk solution to 8.2 and then add alkaline protease. Add alkaline protease to the egg yolk solution, and the addition amount of alkaline protease is 1.2 wt% of the mass of the egg yolk solution. Mix and stir at 52 °C for 2.8 h to carry out a hydrolysis reaction. After the reaction ends, place the reaction product at 92 °C for enzyme inactivation for 18 min, and then immediately place it in an ice-water bath at 3.5 °C for cooling for 30 min. Concentrate the cooled reaction product by rotary evaporation at 62 °C for 2.8 h, and finally filter. Place the filtered solid product at 46 °C for drying for 7.5 h, and after drying, crush and pass through a 120-mesh sieve to obtain hydrolyzed egg yolk powder;

[0126] (3) Mix starch, citric acid, and acetate buffer solution with a pH value of 4.6 evenly. The mass ratio of starch to citric acid is 3.2:1, and the ratio of the total mass of starch and citric acid to the volume of acetate buffer solution is 85 g:1 L. Mix and stir the mixed precursor solution at 52 °C for 28 min to carry out an esterification pre-reaction to activate the hydroxyl groups on the starch surface; then raise the temperature to 102 °C and mix and stir for 1.8 h to carry out an esterification main reaction. After the reaction ends, filter. Place the filtered product at 52 °C for drying for 5.8 h, and after drying, crush and pass through a 120-mesh sieve to obtain a starch-citric acid complex;

[0127] (4) Add carboxymethyl chitosan to deionized water at 56 °C and mix and stir at a stirring rate of 480 rpm until the carboxymethyl chitosan is completely dissolved. Then stop heating and monitor the temperature of the mixed solution in real time. When the temperature of the mixed solution drops to 46 °C, add the starch-citric acid complex obtained in step (3), and mix and stir at a stirring rate of 380 rpm. When the temperature of the mixed solution drops to 42 °C, add the embedded carrot powder obtained in step (1), and mix and stir at a stirring rate of 280 rpm. When the temperature of the mixed solution drops to 36 °C, add the hydrolyzed egg yolk powder obtained in step (2), and mix and stir at a stirring rate of 180 rpm. When the temperature of the mixed solution drops below 30 °C, add ascorbic acid and continue to mix and stir for 18 min. Finally, add 0.1 mol / L citric acid solution to adjust its pH value to 3.8 to obtain the food-derived fruit and vegetable preservative.

[0128] Taking the mass fraction of the food-derived fruit and vegetable preservative as 100 wt%, it comprises the following components with the following mass fractions:

[0129] Embedded carrot powder 3.5 wt%;

[0130] Hydrolyzed egg yolk powder 2 wt%;

[0131] Carboxymethyl chitosan 1.5 wt%;

[0132] Starch-citric acid complex 5 wt%;

[0133] Ascorbic acid 0.3 wt%;

[0134] The balance is deionized water.

[0135] Example 3

[0136] This example provides a preparation method of a food-derived fruit and vegetable preservative with antibacterial and high-barrier properties, as Figure 1 shown, the preparation method comprises the following steps:

[0137] (1) Mix β-cyclodextrin and deionized water evenly at 55 °C to obtain a cyclodextrin solution with a mass fraction of 2.5 wt%. Add freeze-dried carrot powder to it, and the mass ratio of β-cyclodextrin to freeze-dried carrot powder is 2.5:1. Then carry out ultrasonic treatment at an ultrasonic power of 350 W for 25 min, and finally carry out centrifugal separation at a rotation speed of 4000 rpm for 15 min. Place the centrifuged precipitate at 47 °C for drying for 7 h, and then pulverize and pass through a 150-mesh sieve to obtain embedded carrot powder;

[0138] (2) Mix and disperse egg yolk and deionized water according to a volume ratio of 1:3.5 to obtain an egg yolk solution. Adjust the pH value of the egg yolk solution to 8.3, then add alkaline protease. The addition amount of alkaline protease is 1.5 wt% of the mass of the egg yolk solution. Mix and stir at 55 °C for 2.5 h to carry out hydrolysis reaction. After the reaction ends, place the reaction product at 93 °C for 17 min for enzyme inactivation, and then immediately place it in an ice-water bath at 4 °C for 30 min. Concentrate the cooled reaction product by rotary evaporation at 63 °C for 2.5 h, and finally filter it. Place the solid product obtained by filtration at 47 °C for drying for 7 h. After drying, pulverize it and pass through a 150-mesh sieve to obtain hydrolyzed egg yolk powder;

[0139] (3) Mix starch, citric acid and acetate buffer solution with a pH value of 4.7 evenly. The mass ratio of starch to citric acid is 3.5:1, and the ratio of the total mass of starch and citric acid to the volume of acetate buffer solution is 90 g:1 L. Mix and stir the mixed precursor solution at 53 °C for 25 min to carry out pre-esterification reaction to activate the hydroxyl groups on the starch surface; then raise the temperature to 105 °C and mix and stir for 1.5 h to carry out main esterification reaction. After the reaction ends, filter it. Place the filtered product at 53 °C for drying for 5.5 h. After drying, pulverize it and pass through a 150-mesh sieve to obtain starch-citric acid complex;

[0140] (4) Add carboxymethyl chitosan to deionized water at 57 °C and mix and stir at a stirring rate of 450 rpm until the carboxymethyl chitosan is completely dissolved. Then stop heating and monitor the temperature of the mixed solution in real time; when the temperature of the mixed solution drops to 47 °C, add the starch-citric acid complex obtained in step (3), and mix and stir at a stirring rate of 350 rpm. When the temperature of the mixed solution drops to 43 °C, add the embedded carrot powder obtained in step (1), and mix and stir at a stirring rate of 250 rpm. When the temperature of the mixed solution drops to 37 °C, add the hydrolyzed egg yolk powder obtained in step (2), and mix and stir at a stirring rate of 170 rpm. When the temperature of the mixed solution drops below 30 °C, add ascorbic acid and continue to mix and stir for 15 min. Finally, add 0.1 mol / L citric acid solution to adjust its pH value to 3.9 to obtain the food-derived fruit and vegetable preservative.

[0141] Calculated 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:

[0142] Embedded carrot powder 4 wt%;

[0143] Hydrolyzed egg yolk powder 2.5 wt%;

[0144] Carboxymethyl chitosan 2 wt%;

[0145] Starch-citric acid complex 4 wt%;

[0146] Ascorbic acid 0.4 wt%;

[0147] The balance is deionized water.

[0148] Example 4

[0149] This example provides a preparation method of an antibacterial and high-barrier foodborne fruit and vegetable preservative, as Figure 1 shown, the preparation method includes the following steps:

[0150] (1) Mix β-cyclodextrin and deionized water evenly at 58 °C to obtain a cyclodextrin solution with a mass fraction of 2.8 wt%; add freeze-dried carrot powder to it, and the mass ratio of β-cyclodextrin to freeze-dried carrot powder is 2.8:1. Then, perform ultrasonic treatment for 22 min at an ultrasonic power of 380 W, and finally perform centrifugal separation at a rotation speed of 4500 rpm for 12 min. Place the centrifuged precipitate at 48 °C for drying for 6.5 h, and then pulverize and pass through a 180-mesh sieve to obtain encapsulated carrot powder;

[0151] (2) Mix egg yolk and deionized water according to a volume ratio of 1:3.8 and disperse to obtain an egg yolk solution. Adjust the pH value of the egg yolk solution to 8.4 and then add alkaline protease. Add alkaline protease to the egg yolk solution, and the addition amount of alkaline protease is 1.8 wt% of the mass of the egg yolk solution. Mix and stir at 58 °C for 2.2 h to carry out a hydrolysis reaction. After the reaction ends, place the reaction product at 94 °C for enzyme inactivation for 16 min, and then immediately place it in an ice-water bath at 4.5 °C for cooling for 30 min. Concentrate the cooled reaction product by rotary evaporation at 64 °C for 2.2 h, and finally perform filtration. Place the solid product obtained by filtration at 48 °C for drying for 6.5 h, pulverize after drying and pass through a 180-mesh sieve to obtain hydrolyzed egg yolk powder;

[0152] (3) Mix starch, citric acid and acetate buffer solution with a pH value of 4.8 evenly. The mass ratio of starch to citric acid is 3.8:1, and the ratio of the total mass of starch and citric acid to the volume of acetate buffer solution is 95 g:1 L. Mix and stir the mixed precursor solution at 54 °C for 22 min to carry out an esterification pre-reaction to activate the hydroxyl groups on the starch surface; then raise the temperature to 108 °C, mix and stir for 1.2 h to carry out an esterification main reaction. After the reaction ends, perform filtration. Place the filtered product at 54 °C for drying for 5.2 h, pulverize after drying and pass through a 180-mesh sieve to obtain a starch-citric acid complex;

[0153] (4) Add carboxymethyl chitosan into deionized water at 58 °C, and mix and stir at a stirring rate of 420 rpm until the carboxymethyl chitosan is completely dissolved. Then stop heating and monitor the temperature of the mixed solution in real time. When the temperature of the mixed solution drops to 48 °C, add the starch-citric acid complex obtained in step (3), and mix and stir at a stirring rate of 320 rpm. When the temperature of the mixed solution drops to 44 °C, add the embedded carrot powder obtained in step (1), and mix and stir at a stirring rate of 220 rpm. When the temperature of the mixed solution drops to 38 °C, add the hydrolyzed egg yolk powder obtained in step (2), and mix and stir at a stirring rate of 160 rpm. When the temperature of the mixed solution drops below 30 °C, add ascorbic acid and continue to mix and stir for 12 min. Finally, add 0.1 mol / L citric acid solution to adjust its pH value to 3.9 to obtain the food-derived fruit and vegetable preservative.

[0154] Taking the mass fraction of the food-derived fruit and vegetable preservative as 100 wt%, it comprises the following components with the following mass fractions:

[0155] Embedded carrot powder 4.5 wt%;

[0156] Hydrolyzed egg yolk powder 1 wt%;

[0157] Carboxymethyl chitosan 1.8 wt%;

[0158] Starch-citric acid complex 4.5 wt%;

[0159] Ascorbic acid 0.5 wt%;

[0160] The rest is deionized water.

[0161] Example 5

[0162] This example provides a preparation method of a food-derived fruit and vegetable preservative with antibacterial and high-barrier properties, as Figure 1 shown, the preparation method comprises the following steps:

[0163] (1) Mix β-cyclodextrin and deionized water evenly at 60 °C to obtain a cyclodextrin solution with a mass fraction of 3 wt%. Add freeze-dried carrot powder to it, and the mass ratio of β-cyclodextrin to freeze-dried carrot powder is 3:1. Then carry out ultrasonic treatment at an ultrasonic power of 400 W for 20 min, and finally carry out centrifugal separation at a rotation speed of 5000 rpm for 10 min. Place the centrifuged precipitate at 50 °C for drying for 6 h, and then pulverize and pass through a 200-mesh sieve to obtain embedded carrot powder;

[0164] (2) Mix and disperse egg yolk and deionized water according to a volume ratio of 1:4 to obtain an egg yolk solution. Adjust the pH value of the egg yolk solution to 8.5 and then add alkaline protease. The addition amount of alkaline protease is 2 wt% of the mass of the egg yolk solution. Mix and stir at 60 °C for 2 h to carry out hydrolysis reaction. After the reaction ends, place the reaction product at 95 °C for 15 min for enzyme inactivation, and then immediately place it in an ice-water bath at 5 °C for 30 min. Concentrate the cooled reaction product by rotary evaporation at 65 °C for 2 h, and finally filter it. Place the solid product obtained by filtration at 50 °C for drying for 6 h. After drying, pulverize and pass through a 200-mesh sieve to obtain hydrolyzed egg yolk powder;

[0165] (3) Mix starch, citric acid and acetate buffer solution with a pH value of 5 evenly. The mass ratio of starch to citric acid is 4:1, and the ratio of the total mass of starch and citric acid to the volume of acetate buffer solution is 100 g:1 L. Mix and stir the mixed precursor solution at 55 °C for 20 min to carry out esterification pre-reaction and activate the hydroxyl groups on the starch surface; then raise the temperature to 110 °C and mix and stir for 1 h to carry out the main esterification reaction. After the reaction ends, filter it. Place the filtered product at 55 °C for drying for 5 h. After drying, pulverize and pass through a 200-mesh sieve to obtain starch-citric acid complex;

[0166] (4) Add carboxymethyl chitosan to deionized water at 60 °C and mix and stir at a stirring rate of 400 rpm until the carboxymethyl chitosan is completely dissolved. Then stop heating and monitor the temperature of the mixed solution in real time; when the temperature of the mixed solution drops to 50 °C, add the starch-citric acid complex obtained in step (3), and mix and stir at a stirring rate of 300 rpm. When the temperature of the mixed solution drops to 45 °C, add the embedded carrot powder obtained in step (1), and mix and stir at a stirring rate of 200 rpm. When the temperature of the mixed solution drops to 40 °C, add the hydrolyzed egg yolk powder obtained in step (2), and mix and stir at a stirring rate of 150 rpm. When the temperature of the mixed solution drops below 30 °C, add ascorbic acid and continue to mix and stir for 10 min. Finally, add 0.1 mol / L citric acid solution to adjust its pH value to 4 to obtain the food-derived fruit and vegetable preservative.

[0167] Calculated 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:

[0168] Embedded carrot powder 5 wt%;

[0169] Hydrolyzed egg yolk powder 1.5 wt%;

[0170] Carboxymethyl chitosan 2.5 wt%;

[0171] Starch-citric acid complex 3.5 wt%;

[0172] Ascorbic acid 0.2 wt%;

[0173] The balance is deionized water.

[0174] Example 6

[0175] This example provides an antibacterial and high-barrier food-derived fruit and vegetable preservative. The difference from Example 1 is that the mass fraction of the embedded carrot powder is adjusted to 2 wt%. The mass fractions of the components in the adjusted food-derived fruit and vegetable preservative are as follows:

[0176] Embedded carrot powder 2 wt%;

[0177] Hydrolyzed egg yolk powder 3 wt%;

[0178] Carboxymethyl chitosan 2.5 wt%;

[0179] Starch-citric acid complex 3 wt%;

[0180] Ascorbic acid 0.5 wt%;

[0181] The balance is deionized water.

[0182] The preparation methods of the components in the food-derived fruit and vegetable preservative are exactly the same as those in Example 1.

[0183] Example 7

[0184] This example provides an antibacterial and high-barrier food-derived fruit and vegetable preservative. The difference from Example 1 is that the mass fraction of the embedded carrot powder is adjusted to 6 wt%. The mass fractions of the components in the adjusted food-derived fruit and vegetable preservative are as follows:

[0185] Embedded carrot powder 6 wt%;

[0186] Hydrolyzed egg yolk powder 3 wt%;

[0187] Carboxymethyl chitosan 2.5 wt%;

[0188] Starch-citric acid complex 3 wt%;

[0189] Ascorbic acid 0.5 wt%;

[0190] The balance is deionized water.

[0191] The preparation methods of the components in the food-derived fruit and vegetable preservative are exactly the same as those in Example 1.

[0192] Example 8

[0193] This example provides a bacteriostatic and high-barrier food-derived fruit and vegetable preservative. The difference from Example 1 is that the mass fraction of hydrolyzed egg yolk powder is adjusted to 0.5 wt%. The mass fractions of the components in the adjusted food-derived fruit and vegetable preservative are as follows:

[0194] Encapsulated carrot powder 3 wt%;

[0195] Hydrolyzed egg yolk powder 0.5 wt%;

[0196] Carboxymethyl chitosan 2.5 wt%;

[0197] Starch-citric acid complex 3 wt%;

[0198] Ascorbic acid 0.5 wt%;

[0199] The rest is deionized water.

[0200] The preparation methods of the components in the food-derived fruit and vegetable preservative are exactly the same as those in Example 1.

[0201] Example 9

[0202] This example provides a bacteriostatic and high-barrier food-derived fruit and vegetable preservative. The difference from Example 1 is that the mass fraction of hydrolyzed egg yolk powder is adjusted to 4 wt%. The mass fractions of the components in the adjusted food-derived fruit and vegetable preservative are as follows:

[0203] Encapsulated carrot powder 3 wt%;

[0204] Hydrolyzed egg yolk powder 4 wt%;

[0205] Carboxymethyl chitosan 2.5 wt%;

[0206] Starch-citric acid complex 3 wt%;

[0207] Ascorbic acid 0.5 wt%;

[0208] The rest is deionized water.

[0209] The preparation methods of the components in the food-derived fruit and vegetable preservative are exactly the same as those in Example 1.

[0210] Example 10

[0211] This example provides a bacteriostatic and high-barrier food-derived fruit and vegetable preservative. The difference from Example 1 is that the mass fraction of starch-citric acid complex is adjusted to 2 wt%. The mass fractions of the components in the adjusted food-derived fruit and vegetable preservative are as follows:

[0212] Encapsulated carrot powder 3 wt%;

[0213] Hydrolyzed egg yolk powder 3 wt%;

[0214] 2.5 wt% of carboxymethyl chitosan;

[0215] 2 wt% of starch-citric acid complex;

[0216] 0.5 wt% of ascorbic acid;

[0217] The balance is deionized water.

[0218] The preparation methods of the components in the food-derived fruit and vegetable preservative are exactly the same as those in Example 1.

[0219] Example 11

[0220] This example provides a food-derived fruit and vegetable preservative with antibacterial and high-barrier properties. The difference from Example 1 is that the mass fraction of the starch-citric acid complex is adjusted to 6 wt%. The mass fractions of the components in the adjusted food-derived fruit and vegetable preservative are as follows:

[0221] 3 wt% of embedded carrot powder;

[0222] 3 wt% of hydrolyzed egg yolk powder;

[0223] 2.5 wt% of carboxymethyl chitosan;

[0224] 6 wt% of starch-citric acid complex;

[0225] 0.5 wt% of ascorbic acid;

[0226] The balance is deionized water.

[0227] The preparation methods of the components in the food-derived fruit and vegetable preservative are exactly the same as those in Example 1.

[0228] Example 12

[0229] This example provides a food-derived fruit and vegetable preservative with antibacterial and high-barrier properties. The difference from Example 1 is that the mass ratio of β-cyclodextrin to freeze-dried carrot powder is adjusted to 1:1, and other operation steps and process parameters are exactly the same as those in Example 1.

[0230] Example 13

[0231] This example provides a food-derived fruit and vegetable preservative with antibacterial and high-barrier properties. The difference from Example 1 is that the mass ratio of β-cyclodextrin to freeze-dried carrot powder is adjusted to 4:1, and other operation steps and process parameters are exactly the same as those in Example 1.

[0232] Example 14

[0233] This embodiment provides a bacteriostatic and high-barrier food-derived fruit and vegetable preservative. The difference from Embodiment 1 is that the addition amount of alkaline protease is 0.5 wt% of the mass of the egg yolk liquid, and other operation steps and process parameters are exactly the same as those in Embodiment 1.

[0234] Example 15

[0235] This embodiment provides a bacteriostatic and high-barrier food-derived fruit and vegetable preservative. The difference from Embodiment 1 is that the addition amount of alkaline protease is 3 wt% of the mass of the egg yolk liquid, and other operation steps and process parameters are exactly the same as those in Embodiment 1.

[0236] Example 16

[0237] This embodiment provides a bacteriostatic and high-barrier food-derived fruit and vegetable preservative. The difference from Embodiment 1 is that the mass ratio of starch to citric acid is 2:1, and other operation steps and process parameters are exactly the same as those in Embodiment 1.

[0238] Example 17

[0239] This embodiment provides a bacteriostatic and high-barrier food-derived fruit and vegetable preservative. The difference from Embodiment 1 is that the mass ratio of starch to citric acid is 5:1, and other operation steps and process parameters are exactly the same as those in Embodiment 1.

[0240] Example 18

[0241] This embodiment provides a bacteriostatic and high-barrier food-derived fruit and vegetable preservative. The difference from Embodiment 1 is that the reaction temperature of the main reaction is 90 °C, and other operation steps and process parameters are exactly the same as those in Embodiment 1.

[0242] Example 19

[0243] This embodiment provides a bacteriostatic and high-barrier food-derived fruit and vegetable preservative. The difference from Embodiment 1 is that the reaction temperature of the main reaction is 120 °C, and other operation steps and process parameters are exactly the same as those in Embodiment 1.

[0244] Application Example 1

[0245] Soak the freshly picked bananas in the food-derived fruit and vegetable preservative provided in Embodiment 1, and take them out after 10 s and air-dry naturally.

[0246] Comparative Example 1

[0247] This comparative example is the freshly picked bananas without dip-coating treatment.

[0248] Application Example 2

[0249] The food-derived fruit and vegetable preservative provided in Example 1 is evenly sprayed on the surface of fresh chrysanthemum and allowed to air dry naturally.

[0250] Comparative Example 2

[0251] This comparative example is fresh chrysanthemum without spraying treatment.

[0252] The appearance of the bananas without dipping treatment provided in Comparative Example 1 and the bananas after dipping treatment provided in Application Example 1 were observed on the storage day 0 and after storage for 10 days (ambient temperature 25°C, relative humidity 50%). Figure 4 As shown, it can be seen that when stored for 10 days, the surface of the bananas provided in Comparative Example 1 without dip coating began to turn brown, and a large number of black patches appeared. However, the bananas provided in Application Example 1 after dip coating only had a small number of black spots, and still maintained a good appearance.

[0253] The appearance of the unsprayed chrysanthemum provided in Comparative Example 2 and the sprayed chrysanthemum provided in Application Example 2 was observed on the storage day 0 and after storage for 7 days (ambient temperature 25°C, relative humidity 50%). Figure 5 As shown, it can be seen that when stored for 7 days, the chrysanthemum without spraying treatment provided in Comparative Example 2 loses water and shrinks. However, the chrysanthemum with spraying treatment provided in Application Example 2 still maintains a good appearance.

[0254] Referring to Application Example 1, bananas were dipped and coated with the food-derived fruit and vegetable preservative provided in Examples 1-19, and the weight loss rate of the bananas after storage for 10 days was tested. The specific test steps are as follows:

[0255] The bananas on the 0th day of storage were weighed and the weight m0 was recorded. The bananas without dipping treatment and the bananas after dipping treatment were stored for 10 days in a constant temperature and humidity environment (ambient temperature 25°C, relative humidity 50%), and the weight m was recorded. n , the weight loss rate was calculated using the following formula:

[0256] Weight loss rate (%) = [(m0-m n ) / m0]×100%.

[0257] The antibacterial performance and barrier performance of the food-derived fruit and vegetable preservatives provided in Examples 1-19 were tested, and the specific testing steps are as follows:

[0258] (1) Water vapor transmission coefficient test

[0259] 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". The specific test steps are as follows:

[0260] 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 50% relative humidity 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%).

[0261] The fresh-keeping film layer was cut into a circular piece 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. The calculation formula is as follows:

[0262] Water vapor transmission rate (WVTR) = Δm / (A·t);

[0263] 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.

[0264] The water vapor transmission coefficient was calculated according to the water vapor transmission rate and the average thickness of the fresh-keeping film layer. The calculation formula is as follows:

[0265] Water vapor transmission coefficient (WVP) = (WVTR × d) / ΔP;

[0266] 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.

[0267] (2)Escherichia coli inhibition rate test

[0268] 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 50% relative humidity for 24 hours to form a uniform fresh-keeping film layer, and sterilized by ultraviolet irradiation for 30 minutes for standby.

[0269] Take the activated Escherichia coli (ATCC 25922), and adjust the concentration to 1×10 with normal saline 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.

[0270] 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.

[0271] 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:

[0272] 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%.

[0273] The test results are shown in Table 1.

[0274] Table 1

[0275] Water vapor transmission coefficient kg·m / (m²·s·Pa) Inhibitory rate against Escherichia coli (%) Weight loss rate (%) Example 1 <![CDATA[6.45×10 -12 > 93.7 5.8 Example 2 <![CDATA[6.82×10 -12 > 92.3 6.1 Example 3 <![CDATA[7.18×10 -12 > 94.5 5.5 Example 4 <![CDATA[5.93×10 -12 > 91.2 7.3 Example 5 <![CDATA[7.89×10 -12 > 90.8 6.9 Example 6 <![CDATA[10.72×10 -12 > 68.4 14.2 Example 7 <![CDATA[12.35×10 -12 > 78.9 13.8 Example 8 <![CDATA[11.24×10 -12 > 63.7 15.0 Example 9 <![CDATA[10.89×10 -12 > 82.6 12.5 Example 10 <![CDATA[12.83×10 -12 > 71.3 14.7 Example 11 <![CDATA[13.01×10 -12 > 59.8 15.3 Example 12 <![CDATA[9.57×10 -12 > 76.4 11.2 Example 13 <![CDATA[10.45×10 -12 > 84.3 10.8 Example 14 <![CDATA[11.12×10 -12 > 58.6 11.9 Example 15 <![CDATA[10.96×10 -12 > 87.1 10.5 Example 16 <![CDATA[9.34×10 -12 > 81.5 11.6 Example 17 <![CDATA[10.78×10 -12 > 73.2 12.3 Example 18 <![CDATA[9.89×10 -12 > 79.8 11.4 Example 19 <![CDATA[11.25×10 -12 > 68.9 12.8 Comparative Example 1 —— —— 18.7

[0276] It can be seen from the test data of Examples 1 - 19 that the water vapor transmission coefficient and weight loss rate of Examples 1 - 5 are much lower than those of Examples 6 - 19, and the antibacterial rate of Escherichia coli is much higher than that of Examples 6 - 19. This is because, in terms of barrier performance, the synergistic cross-linking of carboxymethyl chitosan and starch - citric acid complex forms a dense network, the β - cyclodextrin - entrapped carrot powder is evenly dispersed, and the hydrophobic peptide segments of hydrolyzed egg yolk powder fill the gaps, significantly blocking the penetration of water vapor. In terms of antibacterial performance, the slow - release antibacterial component (α - carotene) of the entrapped carrot powder and the antibacterial peptides of hydrolyzed egg yolk powder form a dual antibacterial mechanism, and the acidic environment of the starch - citric acid complex enhances the cationic antibacterial activity of carboxymethyl chitosan. The low water vapor transmission coefficient and high antibacterial rate jointly inhibit the respiratory action of fruits and vegetables and microbial metabolism, reduce water loss, and thus significantly reduce the weight loss rate of bananas during storage.

[0277] From the test data of Example 1, Example 6 and Example 7, it can be seen that the water vapor transmission coefficient and weight loss rate of Example 6 and Example 7 are lower than those of Example 1, and the antibacterial rate against Escherichia coli is higher than that of Example 1. This is because in Example 6 and Example 7, the addition amount of encapsulated carrot powder was adjusted. The β-cyclodextrin in the encapsulated carrot powder encapsulated active ingredients such as carotene and polyphenols. These ingredients have antibacterial effects and at the same time participate in the formation of the film network. In Example 6, the addition amount of encapsulated carrot powder was too low, resulting in a reduction of antibacterial components, leading to a decrease in the antibacterial rate. At the same time, the insufficient β-cyclodextrin led to a loose film structure and an increase in the water vapor transmission coefficient. In Example 7, the addition amount of encapsulated carrot powder was too high, and excessive encapsulated carrot powder agglomerated during the film-forming process, resulting in an uneven film structure and an increase in the water vapor transmission coefficient. At the same time, too much encapsulated carrot powder would slow down the release of active ingredients.

[0278] From the test data of Example 1, Example 8 and Example 9, it can be seen that the water vapor transmission coefficient and weight loss rate of Example 8 and Example 9 are lower than those of Example 1, and the antibacterial rate against Escherichia coli is higher than that of Example 1. This is because in Example 8 and Example 9, the addition amount of hydrolyzed egg yolk powder was adjusted. The hydrophobic peptide segments in the hydrolyzed egg yolk powder filled the voids in the film structure, enhancing the barrier property. At the same time, its antibacterial peptides damaged the cell membranes of microorganisms. In Example 8, the addition amount of hydrolyzed egg yolk powder was too low, resulting in insufficient hydrophobic peptide segments, a loose film structure, and an increase in the water vapor transmission coefficient. The reduction of antibacterial peptides led to a decrease in the antibacterial rate. In Example 9, the addition amount of hydrolyzed egg yolk powder was too high, and excessive hydrophobic peptide segments would phase-separate with other components, destroying the uniformity of the fresh-keeping film layer, resulting in an increase in the water vapor transmission coefficient and a decrease in the barrier performance.

[0279] From the test data of Example 1, Example 10 and Example 11, it can be seen that the water vapor transmission coefficient and weight loss rate of Example 10 and Example 11 are lower than those of Example 1, and the antibacterial rate against Escherichia coli is higher than that of Example 1. This is because in Example 10 and Example 11, the addition amount of starch-citric acid complex was adjusted. The starch-citric acid complex provided structural support and an acidic environment. In Example 10, the addition amount of starch-citric acid complex was too low, resulting in insufficient cross-linking, a loose film structure, and an increase in the water vapor transmission coefficient. At the same time, the acidic environment weakened, leading to a decrease in the antibacterial rate. In Example 11, the addition amount of starch-citric acid complex was too high, resulting in over-acidification, destroying the structures of other components (such as carboxymethyl chitosan). At the same time, too much starch would also hinder the dissolution of carboxymethyl chitosan, affecting film formation and resulting in a significant decrease in the antibacterial rate.

[0280] It can be seen from the test data of Example 1, Example 12, and Example 13 that the water vapor transmission coefficient and weight loss rate of Example 12 and Example 13 are lower than those of Example 1, and the antibacterial rate against Escherichia coli is higher than that of Example 1. This is because in Example 12 and Example 13, the mass ratio of β-cyclodextrin to freeze-dried carrot powder was adjusted. β-cyclodextrin protects carotene through cavity inclusion and serves as physical cross-linking points to enhance the film density. In Example 12, the proportion of β-cyclodextrin is too low, resulting in a decrease in the inclusion rate, oxidation and inactivation of carotene, leading to a decrease in the antibacterial rate. The un-included freeze-dried carrot powder forms holes in the fresh-keeping film layer, resulting in an increase in the water vapor transmission coefficient. In Example 13, the proportion of β-cyclodextrin is too high, resulting in a decrease in the cavity utilization rate. The unloaded β-cyclodextrin occupies the polysaccharide cross-linking sites, leading to an increase in the water vapor transmission coefficient of the fresh-keeping film layer.

[0281] It can be seen from the test data of Example 1, Example 14, and Example 15 that the water vapor transmission coefficient and weight loss rate of Example 14 and Example 15 are lower than those of Example 1, and the antibacterial rate against Escherichia coli is higher than that of Example 1. This is because in Example 14 and Example 15, the addition amount of alkaline protease was adjusted. The addition amount of alkaline protease affects the hydrolysis degree of egg yolk. In Example 14, the addition amount of alkaline protease is too low, resulting in insufficient hydrolysis of egg yolk, less antibacterial peptides generated, and a decrease in the antibacterial rate. In Example 15, the addition amount of alkaline protease is too high, resulting in excessive hydrolysis of egg yolk, generating too many small molecular peptides, interfering with the film formation of the fruit and vegetable preservative, and damaging the structure of the fresh-keeping film layer.

[0282] It can be seen from the test data of Example 1, Example 16, and Example 17 that the water vapor transmission coefficient and weight loss rate of Example 16 and Example 17 are lower than those of Example 1, and the antibacterial rate against Escherichia coli is higher than that of Example 1. This is because in Example 16 and Example 17, the mass ratio of starch to citric acid was adjusted. The mass ratio of starch to citric acid affects the esterification degree. In Example 16, the proportion of starch is too low, resulting in insufficient esterification reaction, reduced cross-linking density, and decreased barrier performance. In Example 17, the proportion of starch is too high. The unreacted starch has strong hygroscopicity, resulting in an increase in the water vapor transmission coefficient of the fresh-keeping film layer. At the same time, the effective carboxyl groups decrease, leading to a decrease in the antibacterial rate.

[0283] It can be seen from the test data of Example 1, Example 18, and Example 19 that the water vapor transmission coefficient and weight loss rate of Example 18 and Example 19 are lower than those of Example 1, and the antibacterial rate against Escherichia coli is higher than that of Example 1. This is because in Example 18 and Example 19, the reaction temperature of the main reaction of the esterification reaction was adjusted. The reaction temperature affects the esterification reaction efficiency. In Example 18, the reaction temperature of the main reaction is too low, resulting in incomplete esterification reaction, insufficient cross-linking, and decreased barrier performance. In Example 19, the reaction temperature of the main reaction is too high, resulting in the decomposition of citric acid and a decrease in the carboxyl group content, leading to a decrease in the antibacterial rate.

[0284] The applicant declares that the above is only a specific implementation manner 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 those 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 bacteriostatic and high-barrier food-borne fruit and vegetable preservative, characterized in that: The food-derived fruit and vegetable preservative comprises embedded carrot powder, hydrolyzed egg yolk powder, carboxymethyl chitosan, starch-citric acid complex, ascorbic acid and deionized water; The embedded carrot powder is obtained by embedding carrot freeze-dried powder with β-cyclodextrin; The hydrolyzed egg yolk powder is obtained by hydrolyzing egg yolk liquid with protease, followed by drying, crushing and sieving; The starch-citric acid complex is obtained by esterification reaction of starch and citric acid.

2. The food-derived fruit and vegetable preservative according to claim 1, characterized in that: Taking the mass fraction of the food-derived fruit and vegetable preservative as 100wt%, it includes the following components in mass fractions: Encapsulate carrot powder 3~5wt%; Hydrolyzed egg yolk powder 1~3wt%; Carboxymethyl chitosan 1.5~2.5wt%; Starch-citric acid complex 3~5wt%; Ascorbic acid 0.2~0.5wt%; The rest was deionized water.

3. A method for preparing the food-derived fruit and vegetable preservative according to claim 1 or 2, characterized in that: The preparation method comprises: (I) mixing β-cyclodextrin and deionized water to obtain a cyclodextrin solution, adding carrot freeze-dried powder to the cyclodextrin solution for ultrasonic treatment, and then centrifuging, drying, pulverizing and sieving to obtain embedded carrot powder; (II) adding alkaline protease to the egg yolk liquid, mixing, stirring and heating to cause a hydrolysis reaction, and after the reaction is completed, deactivating the enzyme, concentrating by rotary evaporation, filtering, drying, crushing and sieving to obtain a hydrolyzed egg yolk powder; (III) mixing starch, citric acid and acetate buffer, stirring and heating to cause an esterification reaction, and filtering, drying, crushing and sieving after the reaction to obtain a starch-citric acid complex; (IV) Evenly mixing the embedded carrot powder, the hydrolyzed egg yolk powder, the starch-citric acid complex, the carboxymethyl chitosan, ascorbic acid and deionized water to obtain the food-derived fruit and vegetable preservative.

4. The preparation method according to claim 3, characterized in that: In step (I), the mass fraction of β-cyclodextrin in the cyclodextrin solution is 2-3wt%; The heating temperature when the β-cyclodextrin is mixed with deionized water is 50-60°C; The mass ratio of the β-cyclodextrin to the carrot freeze-dried powder is (2-3):1; The ultrasonic power of the ultrasonic treatment is 300-400W; The ultrasonic treatment time is 20 to 30 minutes.

5. The preparation method according to claim 3, characterized in that: In step (I), the centrifugal speed is 3000-5000 rpm; The centrifugal time is 10 to 20 minutes; The drying temperature is 45-50°C; The drying time is 6 to 8 hours; The mesh number of the sieve is 100-200 meshes.

6. The preparation method according to claim 3, characterized in that: In step (II), the egg yolk liquid is obtained by mixing and beating egg yolk and deionized water; The volume ratio of the egg yolk to deionized water is 1:(3-4); The pH value of the egg yolk liquid is adjusted to 8-8.5 and then the alkaline protease is added; The amount of alkaline protease added is 1-2wt% of the mass of the egg yolk liquid; The temperature of mixing the egg yolk liquid and the alkaline protease is 50-60°C; The egg yolk liquid and alkaline protease are mixed and stirred for 2 to 3 hours.

7. The preparation method according to claim 3, characterized in that: In step (II), the temperature for inactivating the enzyme is 90-95°C; The enzyme inactivation time is 15 to 20 minutes; After the enzyme inactivation is completed, the enzyme is immediately placed in an ice water bath at 3-5°C for cooling for 30 minutes; The temperature of the rotary evaporation concentration is 60-65°C; The time of the rotary evaporation concentration is 2 to 3 hours.

8. The preparation method according to claim 3, characterized in that: In step (III), the mass ratio of starch to citric acid is (3-4):1; The pH value of the acetate buffer is 4.5-5; The ratio of the total mass of the starch and citric acid to the volume of the acetate buffer is (80-100) g:1 L; The esterification reaction includes a preliminary reaction and a main reaction which are carried out in sequence; The reaction temperature of the pre-reaction is 50-55°C; The reaction time of the pre-reaction is 20 to 30 minutes; The reaction temperature of the main reaction is 100-110°C; The reaction time of the main reaction is 1 to 2 hours.

9. The preparation method according to claim 3, characterized in that: In step (III), the drying temperature is 50-55°C; The drying time is 5 to 6 hours.

10. The preparation method according to claim 3, characterized in that: In step (IV), the order of mixing is: First, carboxymethyl chitosan and deionized water are mixed and dissolved under heating conditions; then the heating is stopped, starch-citric acid complex, embedded carrot powder, hydrolyzed egg yolk powder and ascorbic acid are added in sequence, and the mixture is evenly mixed to obtain the food-derived fruit and vegetable preservative.

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