Preparation of a fresh-keeping composition for precooked dishes and a fresh-keeping method

Abstract

This application relates to the field of pre-prepared food preservation technology, specifically disclosing a pre-preservation and freshness-locking composition for pre-prepared foods. The composition mainly consists of hydrogel, ferrite magnetic powder, and iron powder. The hydrogel comprises a solvent and a solute; the solvent is a water-glycerol mixture; the solute mainly includes the following raw materials: surfactant, acrylamide, dodecyl 2-acrylate, hydroxyethyl methacrylate, polyvinyl alcohol aqueous solution, synergist, ammonium persulfate, and boric acid. This pre-preservation and freshness-locking composition disperses ferrite magnetic powder and iron powder in the hydrogel. Utilizing the electromagnetic effect generated by the ferrite magnetic powder and the oxygen absorption effect of the iron powder, it significantly inhibits pre-prepared food metabolism and bacterial growth, exhibiting excellent preservation effect and high freshness-locking degree.

Description

Technical Field

[0001] This application relates to the field of pre-prepared food preservation technology, and more specifically, it relates to a pre-preserved food preservation composition and preservation method. Background Technology

[0002] Pre-cooked meals are semi-finished dishes prepared in advance. Some manufacturers wash, cut, wash again, and drain fresh fruits and vegetables to obtain pre-cooked meals, which are then packaged. Fresh fruits and vegetables include spinach, carrots, cucumbers, grapes, and apples. However, pre-cooked meals are prone to spoilage as their storage time increases. Current technology often involves low-temperature storage. If pre-cooked meals are frozen at temperatures below 0°C, ice crystals inevitably form. These ice crystals may affect the cell microstructure, thus impacting the taste. Therefore, most consumers store pre-cooked meals in an environment of 0-10°C, but this has a relatively short shelf life. Summary of the Invention

[0003] In order to extend the shelf life of pre-cooked dishes, this application provides a preservative and freshness-locking composition and method for pre-cooked dishes.

[0004] In a first aspect, this application provides a preservative and freshness-locking composition for prepared vegetables, employing the following technical solution:

[0005] The preservative and freshness-locking composition for prepared dishes is mainly made of hydrogel, ferrite magnetic powder, and iron powder; the hydrogel is composed of a solvent and a solute, and the solvent is a water-glycerol mixture.

[0006] Based on 1000 mL of solvent, the solute mainly includes the following raw materials: 9-11 g of surfactant, 55-65 g of acrylamide, 10-20 g of dodecyl 2-acrylate, 6-8 g of hydroxyethyl methacrylate, 65-75 g of polyvinyl alcohol aqueous solution, 1-3 g of synergist, 9-11 g of ammonium persulfate, and 4-6 g of boric acid; the mass concentration of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 10-20%; based on 1000 mL of solvent, the amount of ferrite magnetic powder added is 50-60 g, and the amount of iron powder added is 20-30 g.

[0007] By employing the above technical solution, ferrite magnetic powder and iron powder are dispersed in a hydrogel. The ferrite magnetic powder can generate an electromagnetic effect, which can influence the metabolism of pre-cooked food, delay cell aging and death, inhibit physiological activities, reduce respiration, and decrease water evaporation. Simultaneously, it can effectively inhibit bacterial growth and extend shelf life. The iron powder mainly acts as an oxygen absorber, reacting with oxygen in the air in an oxidation-reduction reaction to reduce oxygen content, thereby reducing respiration and extending shelf life. In this application, through the synergistic effect of ferrite magnetic powder and iron powder, the metabolism of pre-cooked food is significantly inhibited, as well as bacterial growth. After 7 days of storage, the vitamin C retention rate of spinach is >72%, and the total bacterial count is <3 cfu / g, demonstrating good preservation effect and high freshness retention, extending shelf life and meeting market demand.

[0008] In the preparation of the hydrogel in this application, acrylamide, dodecyl 2-acrylate, and hydroxyethyl methacrylate can undergo a polymerization reaction under the action of ammonium persulfate to form a high molecular weight polymer, which then forms a hydrogel in the presence of water and glycerol. The synergistic effect between these polymers increases the strength and stability of the hydrogel. Furthermore, the high molecular weight polymer contains terminal primary amine groups and terminal hydroxyl groups, while polyvinyl alcohol contains a large number of terminal hydroxyl groups. Combined with boric acid, the boric acid can undergo a cross-linking reaction with the terminal hydroxyl groups, forming a tight three-dimensional network structure between the high molecular weight polymer and polyvinyl alcohol, increasing the cross-linking density and improving the hydrogel strength. Moreover, the resulting hydrogel is permeable to oxygen and does not affect the effectiveness of the iron powder. Further, the addition of ferrite magnetic powder and iron powder during the hydrogel preparation process ensures that the ferrite magnetic powder and iron powder are uniformly dispersed in the hydrogel, guaranteeing the effectiveness of the preservative and freshness-locking composition.

[0009] Optionally, the ferrite magnetic powder is one or more of barium ferrite, manganese-zinc ferrite, and nickel-zinc ferrite. Preferably, the ferrite magnetic powder is barium ferrite.

[0010] By adopting the above technical solution, the ferrite magnetic powder is optimized, facilitating the selection of ferrite magnetic powder. Moreover, barium ferrite not only generates a magnetic field, but also has the characteristics of high remanence, high coercivity, and good chemical stability, while also having low magnetic loss, resulting in superior magnetic properties and stability.

[0011] Optionally, the average particle size of the ferrite magnetic powder is 0.5-3 μm, and the average particle size of the iron powder is 0.5-3 μm. Preferably, the average particle size of the ferrite magnetic powder is 1-3 μm, and the average particle size of the iron powder is 1-3 μm. More preferably, the average particle size of the ferrite magnetic powder is 1-2 μm, and the average particle size of the iron powder is 1-2 μm.

[0012] By adopting the above technical solution, the average particle size of the ferrite magnetic powder and iron powder is limited, which not only facilitates the selection of ferrite magnetic powder and iron powder, but also facilitates their dispersion in the hydrogel. In several embodiments, the average particle size of the ferrite magnetic powder is 2 μm, but it can also be set to 0.5 μm, 1 μm, 1.5 μm, 2.5 μm, 3 μm, etc., as needed. In several embodiments, the average particle size of the iron powder is 2 μm, but it can also be set to 0.5 μm, 1 μm, 1.5 μm, 2.5 μm, 3 μm, etc., as needed.

[0013] Optionally, the weight ratio of water to glycerol in the water-glycerol mixture is 1:(0.1-0.3).

[0014] By adopting the above technical solution, the weight ratio of water and glycerin is optimized, which not only increases the compatibility of raw materials but also facilitates the formation of hydrogels. In several embodiments, the weight ratio of water to glycerin is 1:0.2, but it can also be set to 1:0.1, 1:0.15, 1:0.25, 1:0.3, etc., as needed.

[0015] Optionally, the synergistic agent is one or more of carboxymethyl chitosan, carboxymethyl cellulose, and hydroxyethyl cellulose.

[0016] By adopting the above technical solution, the synergistic additives are optimized, facilitating their selection. Furthermore, carboxymethyl chitosan, carboxymethyl cellulose, and hydroxyethyl cellulose can all increase the intermolecular forces between hydrogel raw materials, increase cross-linking density, enhance the strength of the preservative-locking composition, and improve its stability during use.

[0017] Optionally, the surfactant is one or more of Tween 80, Tween 60, Tween 40, and Tween 20.

[0018] By adopting the above technical solutions, the surfactants are optimized, which facilitates the selection of surfactants. Moreover, Tween 80, Tween 60, Tween 40, and Tween 20 can increase the compatibility between hydrogel raw materials, which facilitates the preparation of hydrogels and also facilitates the preparation of preservative and freshness-locking compositions.

[0019] Optionally, the polyvinyl alcohol aqueous solution is prepared by the following method: heating water to 90-98°C, then adding polyvinyl alcohol, stirring to dissolve it, cooling, and obtaining a polyvinyl alcohol solution.

[0020] By adopting the above technical solution, polyvinyl alcohol is dissolved in hot water and then cooled, which facilitates the dissolution of polyvinyl alcohol and the preparation of polyvinyl alcohol aqueous solution.

[0021] Optionally, the polyvinyl alcohol is one or more of PVA-0388, PVA-0588, PVA-1788, and PVA-2488.

[0022] By adopting the above technical solution, polyvinyl alcohol is optimized, which not only facilitates the selection of polyvinyl alcohol, but also maintains good viscosity of polyvinyl alcohol and ensures the stability of the preservative and freshness-locking composition.

[0023] Optionally, the preservative and freshness-locking composition for prepared vegetables is prepared using the following method:

[0024] Add surfactant, acrylamide, dodecyl 2-acrylate, hydroxyethyl methacrylate, polyvinyl alcohol aqueous solution, and synergist to a water-glycerol mixture and stir for 20-40 minutes. Then add ferrite magnetic powder and iron powder and stir for 20-40 minutes. After that, add ammonium persulfate and boric acid and stir for 20-40 minutes. Pour the mixture into a mold, let it stand for 40-50 hours, and then magnetize it to obtain the preservative and freshness-locking composition.

[0025] By employing the above technical solution, acrylamide, dodecyl 2-acrylate, hydroxyethyl methacrylate, and polyvinyl alcohol aqueous solution are mixed in a water-glycerol mixture, with the aid of ammonium persulfate and boric acid to form a hydrogel. Ammonium persulfate initiates a polymerization reaction, causing acrylamide, dodecyl 2-acrylate, and hydroxyethyl methacrylate to form a high-molecular-weight polymer containing terminal primary amine groups and terminal hydroxyl groups. Polyvinyl alcohol contains a large number of terminal hydroxyl groups; combined with boric acid, the boric acid reacts with the terminal hydroxyl groups to form a cross-linked structure, achieving cross-linking between the high-molecular-weight polymer and polyvinyl alcohol, forming a three-dimensional network structure, increasing the cross-linking density, and obtaining a high-strength hydrogel. Adding ferrite magnetic powder and iron powder during the hydrogel preparation process not only ensures the uniform dispersion of the ferrite magnetic powder and iron powder in the hydrogel, obtaining an antiseptic and fresh-locking composition, but also because the surfaces of the ferrite magnetic powder and iron powder contain certain terminal carboxyl groups, which can also react with boric acid to achieve cross-linking, increasing the stability of the antiseptic and fresh-locking composition.

[0026] Secondly, this application provides a method for locking in the freshness of pre-cooked dishes, employing the following technical solution:

[0027] Methods for pre-cooked dishes to preserve freshness include the following steps:

[0028] S1. Wash, cut, wash again, and drain the water from the fresh fruits and vegetables to be processed to obtain pre-cooked vegetables.

[0029] S2. Microwave sterilization of pre-prepared dishes;

[0030] S3. Place the preservative and freshness-locking composition into the built-in antibacterial bag and seal it;

[0031] S4. Attach an inner antibacterial bag containing the preservative and freshness-locking composition to the bottom of the food storage container or bag, then add the microwave-sterilized pre-cooked food, seal the container or bag, and store it in an environment with a temperature of 0-10℃ and a static voltage of 200-400mV to complete the freshness-locking of the pre-cooked food.

[0032] By adopting the above technical solution, pre-prepared dishes are first prepared, and then microwave-sterilized to reduce the impact of bacteria on their preservation. Next, the preservative-locking composition is placed in an internal antibacterial bag. This bag not only allows oxygen to pass through but also separates the preservative-locking composition from the pre-prepared dish, increasing safety. Finally, the internal antibacterial bag and the pre-prepared dish are placed in a sealed food storage container or bag and stored in an environment of 0-10℃ and 200-400mV static voltage. This low-temperature, low-static-voltage storage reduces cell and bacterial activity in the pre-prepared dish, minimizes nutrient loss, enhances preservation, and extends shelf life.

[0033] Furthermore, in step S2, the microwave sterilization radiation power is 5-30W, the radiation temperature is 40-60℃, and the microwave sterilization treatment time is 10-90s. In many embodiments, the microwave sterilization radiation power is 10W, but it can also be set to 5W, 15W, 20W, 25W, 30W, etc., as needed. In many embodiments, the microwave sterilization radiation temperature is 48℃, but it can also be set to 40℃, 45℃, 50℃, 55℃, 60℃, etc., as needed. In many embodiments, the microwave sterilization treatment time is 30s, but it can also be set to 10s, 20s, 40s, 50s, 60s, 70s, 80s, 90s, etc., as needed.

[0034] In summary, this application has at least the following beneficial effects:

[0035] 1. The pre-preservative and fresh-locking composition for prepared vegetables of this application disperses ferrite magnetic powder and iron powder in a hydrogel. Utilizing the electromagnetic effect generated by the ferrite magnetic powder and the oxygen-absorbing effect of the iron powder, it significantly inhibits the metabolism and bacterial growth of the prepared food, thus extending the shelf life. After 7 days of storage, the vitamin C content retention rate of spinach is >72%, and the total bacterial count is <3 cfu / g, demonstrating good preservation effect and high degree of freshness locking.

[0036] 2. In the hydrogel preparation of this application, acrylamide, dodecyl 2-acrylate, hydroxyethyl methacrylate, and polyvinyl alcohol form a three-dimensional network structure hydrogel under the action of a water-glycerol mixture, ammonium persulfate, and boric acid. This increases the crosslinking density, improves the strength of the preservative composition, and enhances its stability. Furthermore, it allows oxygen to permeate without affecting the effectiveness of the iron powder. Simultaneously, the addition of ferrite magnetic powder and iron powder during hydrogel preparation not only ensures their uniform dispersion within the hydrogel but also, given the presence of terminal carboxyl groups on their surfaces, allows them to react with boric acid and achieve crosslinking, further enhancing the stability and effectiveness of the preservative composition. Detailed Implementation

[0037] To make this application easier to understand, the following detailed description will be provided with reference to embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of application of this application. Unless otherwise specified, the raw materials or components used in this application can be obtained commercially or by conventional methods.

[0038] Example

[0039] Table 1. Raw materials and dosage of the preservative and freshness-locking composition

[0040]

[0041] Example 1

[0042] A pre-preservative and fresh-locking composition for prepared dishes is mainly made of hydrogel, ferrite magnetic powder, and iron powder; the raw materials and their proportions are shown in Table 1.

[0043] The hydrogel consists of a solvent and a solute. The solvent is a water-glycerol mixture with a weight ratio of water to glycerol of 1:0.2. The surfactant is Tween 80. The synergist is carboxymethyl chitosan, selected from Hebei Hongtao Bioengineering Co., Ltd. The ferrite magnetic powder is barium ferrite with an average particle size of 2 μm, selected from Hubei Shineng Chemical Technology Co., Ltd. The iron powder has an average particle size of 2 μm.

[0044] The polyvinyl alcohol aqueous solution has a polyvinyl alcohol mass concentration of 15%, the polyvinyl alcohol is PVA-1788, and the polyvinyl alcohol aqueous solution is prepared by the following method: water is heated to 95°C, then polyvinyl alcohol is added, stirred for 20 min, and cooled to 23°C to obtain a polyvinyl alcohol solution.

[0045] A method for preparing a preservative and freshness-locking composition for pre-cooked vegetables includes the following steps:

[0046] A surfactant, acrylamide, dodecyl 2-acrylate, hydroxyethyl methacrylate, polyvinyl alcohol aqueous solution, and synergist were added to a water-glycerol mixture, and the mixture was stirred for 30 minutes. Then, ferrite magnetic powder and iron powder were added, and the mixture was stirred for 30 minutes. Next, ammonium persulfate and boric acid were added, and the mixture was stirred for 30 minutes. The mixture was then poured into a mold, allowed to stand for 45 hours, and then magnetized to obtain the preservative and freshness-locking composition.

[0047] Example 2

[0048] A pre-preservative and fresh-locking composition for prepared dishes differs from Example 1 in that the raw material ratios of the preservative and fresh-locking composition are different, as shown in Table 1.

[0049] Example 3

[0050] A pre-preservative and fresh-locking composition for prepared dishes differs from Example 1 in that the raw material ratios of the preservative and fresh-locking composition are different, as shown in Table 1.

[0051] Comparative Example

[0052] Comparative Example 1

[0053] A pre-preservative and fresh-locking composition for prepared dishes differs from Example 1 in that an equal amount of ferrite magnetic powder replaces iron powder in the raw materials of the preservative and fresh-locking composition.

[0054] Comparative Example 2

[0055] A pre-preservative and fresh-locking composition for prepared dishes differs from Example 1 in that an equal amount of iron powder replaces the ferrite magnetic powder in the raw materials of the preservative and fresh-locking composition.

[0056] Comparative Example 3

[0057] A pre-preservative and fresh-locking composition for prepared dishes differs from Example 1 in that, in the raw materials of the hydrogel of the preservative and fresh-locking composition, an equal amount of acrylamide is used to replace dodecyl 2-acrylate and hydroxyethyl methacrylate.

[0058] Comparative Example 4

[0059] A pre-preservative and fresh-locking composition for prepared dishes differs from Example 1 in that, in the raw materials of the hydrogel of the preservative and fresh-locking composition, an equal amount of dodecyl 2-acrylate is used to replace acrylamide and hydroxyethyl methacrylate.

[0060] Comparative Example 5

[0061] A preservative and fresh-locking composition for prepared dishes differs from Example 1 in that, in the raw materials of the hydrogel of the preservative and fresh-locking composition, an equal amount of hydroxyethyl methacrylate is used to replace acrylamide and dodecyl 2-acrylate.

[0062] Application examples

[0063] Application Example 1

[0064] A method for pre-cooked food to lock in freshness includes the following steps:

[0065] S1. Wash, cut, wash again, and drain the water from the fresh fruits and vegetables to be processed to obtain pre-cooked dishes.

[0066] Among them, the fresh fruit and vegetable is spinach.

[0067] S2. Microwave sterilization of pre-cooked dishes.

[0068] The microwave sterilization process involves a radiation power of 10W, a radiation temperature of 48℃, and a sterilization time of 30s.

[0069] S3. Place the preservative and freshness-locking composition in the built-in antibacterial bag and seal it.

[0070] The preservative-preserving composition was prepared using the method described in Example 1; and the built-in antibacterial bag not only allows oxygen to pass through, but also enables the separation of the preservative-preserving composition from the prepared food.

[0071] S4. Attach an inner antibacterial bag containing the preservative and freshness-locking composition to the bottom of the food storage container or bag. Then add the microwave-sterilized pre-cooked food. Seal the container or bag afterward. Store in an environment with a temperature of 5℃ and a static voltage of 300mV to complete the freshness-locking process for the pre-cooked food.

[0072] The weight ratio of the preservative-preserving composition to the pre-cooked vegetables is 1:20.

[0073] Application Example 2-3

[0074] A method for pre-prepared dishes to lock in freshness, which differs from Application Example 1 in that the source of the preservative and freshness-locking composition in step S3 is different, and the preservative and freshness-locking compositions of Application Examples 2-3 are prepared sequentially using the methods of Examples 2-3 respectively.

[0075] Comparative application examples

[0076] Compare and contrast examples 1-5

[0077] A method for pre-prepared food to lock in freshness, which differs from Application Example 1 in that the source of the preservative and freshness-locking composition in step S3 is different, and the preservative and freshness-locking compositions of Comparative Application Examples 1-5 are prepared sequentially using the methods of Comparative Examples 1-5 respectively.

[0078] Performance testing

[0079] (1) The preservative and freshness-locking compositions obtained in Examples 1-3 and Comparative Examples 1-5 were taken as samples. The toxicological properties and human safety of the samples were tested according to GB / T16886. After testing, the preservative and freshness-locking compositions obtained in Examples 1-3 and Comparative Examples 1-5 all had skin sensitization ≤ Grade I, intradermal irritation ≤ 1.0, and cytotoxicity ≤ Grade I, which showed good safety.

[0080] (2) The preservative and freshness-locking compositions obtained in Examples 1-3 and Comparative Examples 1-5 were taken as samples, and the puncture force of the samples was tested. The greater the puncture force, the better the strength of the preservative and freshness-locking composition. The test results are shown in Table 2.

[0081] (3) The freshness-locking methods of Application Examples 1-3 and Comparative Application Examples 1-5 were used to store pre-cooked dishes for 7 days. The vitamin C content and total bacterial count in the pre-cooked dishes were tested, and the vitamin C retention rate was calculated. The higher the vitamin C retention rate and the lower the total bacterial count, the better the freshness-locking effect. The test results are shown in Table 2.

[0082] Table 2 Detection Results

[0083]

[0084]

[0085] As shown in Table 2, the preservative and freshness-locking composition of this application has high puncture force, ranging from 3.28 to 3.36 N / 10 mm, demonstrating high strength, increasing stability in use, and reducing the likelihood of breakage. Furthermore, when applied to the freshness-locking treatment of prepared dishes, after 7 days of storage, the vitamin C content retention rate of spinach was 72.6-73.8%, and the total bacterial count was 2.67-2.81 cfu / g, exhibiting good preservation effect and high degree of freshness locking.

[0086] Comparing Example 1 and Comparative Examples 1-2, it can be seen that adding ferrite magnetic powder or iron powder to the raw materials of the preservative and freshness-locking composition has virtually no effect on the puncture force. Furthermore, combining Application Example 1 and Comparative Application Examples 1-2, it can be seen that simultaneously adding ferrite magnetic powder and iron powder to the preservative and freshness-locking composition, and utilizing their synergistic effect, can significantly increase the retention rate of vitamin C in spinach and significantly reduce the total bacterial count, thereby improving the preservation effect.

[0087] Comparing Example 1 and Comparative Examples 3-5, it can be seen that the simultaneous addition of acrylamide, dodecyl 2-acrylate, and hydroxyethyl methacrylate to the hydrogel raw materials of the preservative and freshness-locking composition, and the synergistic effect between them, can increase the strength of the preservative and freshness-locking composition. Furthermore, combining Application Example 1 and Comparative Application Examples 3-5, it can be seen that the synergistic effect between acrylamide, dodecyl 2-acrylate, and hydroxyethyl methacrylate can also improve the retention rate of vitamin C in spinach and reduce the total bacterial count, resulting in a superior performance of the preservative and freshness-locking composition. This may be because the hydrogels formed by acrylamide, dodecyl 2-acrylate, hydroxyethyl methacrylate, and polyvinyl alcohol respectively affect oxygen permeability, thereby affecting the effectiveness of iron powder, and consequently affecting the retention rate of vitamin C in spinach and the total bacterial count.

[0088] It should be noted that the embodiments described above are only for explaining this application and do not constitute any limitation on this application. This application has been described with reference to typical embodiments, but it should be understood that the terms used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to this application within the scope of the claims, and revisions can be made to the invention without departing from the scope and spirit of this application. Although the application described herein relates to specific methods, materials, and embodiments, it does not mean that this application is limited to the specific examples disclosed herein; on the contrary, this application can be extended to all other methods and applications with the same function.

Claims

1. A preservative and freshness-locking composition for prepared vegetables, characterized in that: It is mainly made of hydrogel, ferrite magnetic powder, and iron powder; the hydrogel is composed of solvent and solute, and the solvent is a water-glycerol mixture; Based on 1000 mL of solvent, the solute mainly comprises the following raw materials: 9-11 g of surfactant, 55-65 g of acrylamide, 10-20 g of dodecyl 2-acrylate, 6-8 g of hydroxyethyl methacrylate, 65-75 g of polyvinyl alcohol aqueous solution, 1-3 g of synergist, 9-11 g of ammonium persulfate, and 4-6 g of boric acid; the mass concentration of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 10-20%. Based on 1000mL of solvent, the amount of ferrite magnetic powder added is 50-60g, and the amount of iron powder added is 20-30g; The ferrite magnetic powder has an average particle size of 0.5-3 μm, and the iron powder has an average particle size of 0.5-3 μm; the synergist is one or more of carboxymethyl chitosan, carboxymethyl cellulose, and hydroxyethyl cellulose. The preservative and freshness-locking composition for prepared vegetables is prepared by the following method: Add surfactant, acrylamide, dodecyl 2-acrylate, hydroxyethyl methacrylate, polyvinyl alcohol aqueous solution, and synergist to a water-glycerol mixture and stir for 20-40 minutes. Then add ferrite magnetic powder and iron powder and stir for 20-40 minutes. After that, add ammonium persulfate and boric acid and stir for 20-40 minutes. Pour the mixture into a mold, let it stand for 40-50 hours, and then magnetize it to obtain the preservative and freshness-locking composition.

2. The pre-prepared food preservation and lock-in freshness composition according to claim 1, characterized in that: The ferrite magnetic powder is one or more of barium ferrite, manganese zinc ferrite, and nickel zinc ferrite.

3. The preservative and freshness-locking composition for prepared vegetables according to claim 1, characterized in that: The weight ratio of water to glycerol in the water-glycerol mixture is 1:(0.1-0.3).

4. The pre-prepared food preservation and lock-in freshness composition according to claim 1, characterized in that: The surfactant is one or more of Tween 80, Tween 60, Tween 40, and Tween 20.

5. The pre-prepared food preservation and lock-in freshness composition according to claim 1, characterized in that: The polyvinyl alcohol aqueous solution is prepared by the following method: heating water to 90-98℃, then adding polyvinyl alcohol, stirring to dissolve it, cooling, and obtaining a polyvinyl alcohol solution.

6. The pre-prepared food preservation and lock-in freshness composition according to claim 1, characterized in that: The polyvinyl alcohol is one or more of PVA-0388, PVA-0588, PVA-1788, and PVA-2488.

7. A method for preserving the freshness of pre-prepared foodstuffs, characterized in that: Includes the following steps: S1. Wash, cut, wash again, and drain the water from the fresh fruits and vegetables to be processed to obtain pre-cooked vegetables. S2. Microwave sterilization of pre-prepared dishes; S3. Place the preservative and freshness-locking composition into the built-in antibacterial bag and seal it; S4. Attach an inner antibacterial bag containing the preservative and freshness-locking composition to the bottom of the food storage container or bag, then add the microwave-sterilized pre-cooked food, seal the food storage container or bag, and store it in an environment with a temperature of 0-10℃ and a static voltage of 200-400mV to complete the freshness-locking of the pre-cooked food. The preservative and freshness-locking composition is the preservative and freshness-locking composition for prepared dishes as described in any one of claims 1-6.

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