Annona squamosa fruit fresh-keeping agent, fresh-keeping paper, fresh-keeping sheet and fresh-keeping method thereof

Abstract

The invention discloses an annona squamosa fruit fresh-keeping agent, fresh-keeping paper, a fresh-keeping sheet and a fresh-keeping method thereof, and belongs to the technical field of fruit and vegetable fresh-keeping. According to the preservative, a sodium carboxymethyl cellulose solution is used as a film-forming substrate and is compounded with 1-methylcyclopropene, salicylic acid, spermine, gallic acid, peppermint essential oil, eleocharis tuberosa peel extract and other bacteriostatic preservative components, and long-acting preservation of annona squamosa is achieved through a multi-target synergistic effect. Preservative paper is prepared by using the preservative and is used for wrapping fruits. The liquid fresh-keeping agent, soluble starch and diatomite are blended and pressed into a solid fresh-keeping sheet to be used in a fruit box. Through a triple fresh-keeping mode of post-harvest dipping, fresh-keeping paper wrapping and fresh-keeping piece releasing, after-ripening and aging of the annona squamosa are delayed from multiple dimensions of ethylene inhibition, antibiosis, corrosion prevention, oxidation resistance and the like, rapid browning of epidermis and softening of pulp are inhibited, the shelf life of the annona squamosa at normal temperature is prolonged to 15-20 days from conventional 5-6 days, the fruit hardness, color and flavor are kept good, and the fresh-keeping effect is good. And the requirements of long-distance transportation and terminal sales of fruits are met.

Description

Technical Field

[0001] This invention relates to the field of postharvest preservation technology for fruits and vegetables, specifically to a preservative for custard apple fruit, preservation paper, preservation sheet, and preservation method thereof. Background Technology

[0002] Custard apple (Annona squamosa L.), also known as sugar apple, is a tropical fruit tree belonging to the genus Annonaceae in the family Annonaceae. Its fruit has a unique flavor and is rich in nutrients, making it popular with consumers. In my country, custard apple production areas are mainly concentrated in Guangxi, Guangdong, Hainan, Yunnan, and Taiwan, with the harvest season primarily from November to March of the following year.

[0003] Custard apples are typical climacteric fruits, exhibiting extremely vigorous respiration and metabolism after harvest. Their peels are thin, delicate, and easily damaged due to prominent scales, making them highly susceptible to browning, softening, and pathogen infection during ripening, leading to rot and mold. Under normal temperature conditions, conventionally harvested custard apples have a shelf life of only 5-6 days: the fruit appears bright from day 1 to 5 after harvest; noticeable browning and softening begin on day 6; and by day 8, widespread rot occurs, severely limiting long-distance transportation and market reach, resulting in significant post-harvest economic losses. Therefore, to extend the fruit's shelf life, producers are forced to harvest fruits at 60-70% maturity prematurely, leading to a severe decline in fruit quality and yield; or they must rely on expensive air freight to complete transportation and sales in a very short time, significantly increasing logistics costs.

[0004] Currently, post-harvest preservation of custard apples mainly employs methods such as low-temperature storage, chemical preservative treatment (e.g., 1-methylcyclopropene, salicylic acid), or physical wrapping. However, improper low-temperature storage can easily lead to chilling injury, causing abnormal fruit firmness, internal browning, and flavor degradation. Single chemical treatments have extremely limited effectiveness in preserving climacteric fruits and pose risks of residue and resistance. Ordinary plastic wrapping is insufficient to effectively inhibit microbial growth, fruit respiration, and water transpiration. Existing technologies generally suffer from short preservation periods and poor adaptability to long-distance transportation, failing to meet the needs of sustainable industry development.

[0005] Therefore, the urgent need to develop a preservation technology that has good preservation effect, can delay fruit browning, extend shelf life, reduce the use of chemical agents, meet the needs of long-distance transportation, and is highly safe has become the key to solving the pain points of the custard apple industry. Summary of the Invention

[0006] This invention aims to overcome the shortcomings of existing technologies, such as short shelf life, easy browning and softening, limited preservation techniques, and insufficient safety of custard apples. It provides a custard apple fruit preservative, preservation paper, preservation sheets, and preservation method that offer significant preservation effects, are easy to operate, and have high safety. This technology utilizes a liquid preservative, preservation paper for direct fruit wrapping, and solid preservation sheets for easy transport. Employing multiple slow-release and synergistic effects, it achieves end-to-end preservation from post-harvest processing and long-distance transportation to the final shelf, effectively inhibiting the growth of pathogens on the fruit surface, slowing down browning and decay, and meeting the needs of long-distance transportation.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A preservative for custard apple fruit uses sodium carboxymethyl cellulose (CMC-Na) aqueous solution as a film-forming matrix and is compounded with a variety of antibacterial and preservative ingredients. Based on 100% by weight of the sodium carboxymethyl cellulose aqueous solution, the antibacterial and preservative ingredients include the following raw materials in weight percentages: 0.5–1.0% 1-methylcyclopropene (1-MCP), 0.5–1.0% salicylic acid, 0.08–0.12% spermine, 0.05–0.20% gallic acid, 0.01% peppermint oil, and 0.1–0.2% water chestnut peel extract.

[0009] Furthermore, based on an aqueous solution of sodium carboxymethyl cellulose as 100% by weight, the antibacterial and preservative ingredients contain the following raw materials in weight percentages: 0.5% 1-methylcyclopropene, 0.5% salicylic acid, 0.12% spermine, 0.05% gallic acid, 0.01% peppermint oil, and 0.1% water chestnut peel extract.

[0010] Furthermore, the sodium carboxymethyl cellulose aqueous solution has a mass concentration of 2-3%.

[0011] Furthermore, the water chestnut peel extract is obtained by vacuum drying and pulverizing fresh water chestnut peel; then adding water at a material-to-liquid ratio of 1:8~10 (g / ml), and extracting by ultrasonic vibration in a water bath at 45~55℃ for 3-4 hours; centrifuging to collect the supernatant, drying and pulverizing to obtain the water chestnut peel extract.

[0012] The present invention relates to a preservative paper loaded with custard apple fruit preservative. The preservative paper uses biodegradable non-woven fabric as the base material, is fully immersed in the preservative of the present invention for 30-40 minutes, and is then removed and dried to obtain the preservative paper loaded with custard apple fruit preservative.

[0013] Furthermore, the loading of the preservative active ingredient in the preservation paper is controlled at 5-20 g / m².

[0014] The preparation process of the preservative containing custard apple fruit preservative is as follows: the preservative of the present invention, soluble starch and diatomaceous earth are mixed evenly in a mass ratio of 3:4-5:2 to form a paste or slurry, vacuum dried at 50-60°C, pulverized and pressed into preservative sheets.

[0015] Furthermore, the preservation sheet has a thickness of 2-3 mm and a weight of 1-5 g per sheet.

[0016] The method for preserving custard apple fruit of the present invention includes the following steps:

[0017] (1) Post-harvest soaking treatment: Immerse custard apples that are about 80-90% mature and have no obvious mechanical damage in the surface into the pre-prepared preservative for 10-15 minutes to ensure that the surface of the fruit is completely soaked. After taking them out, let them drain naturally to avoid residual moisture that could lead to the growth of microorganisms.

[0018] (2) Wrapping with preservative paper: After the custard apples have been drained, they are wrapped individually with the preservative paper of the present invention loaded with preservative. The preservative paper can ensure the breathability required for the fruit to breathe and slow down the rapid loss of moisture.

[0019] (3) Assisted slow-release preservation: Pack the wrapped custard apples into boxes, and place the preservation tablets evenly in the fruit boxes at a ratio of 5-10g of the preservation tablets per 10kg of custard apples. After sealing, store or transport them.

[0020] The preservation sheet of this invention uses soluble starch and diatomaceous earth as carriers, and adds the active ingredients of a preservative. The soluble starch and diatomaceous earth can slowly release the preservative ingredients, providing a long-lasting preservation effect.

[0021] The preservation principle of the preservative of this invention is as follows: using sodium carboxymethyl cellulose aqueous solution as a base, it is safe and non-toxic, and can form a uniform edible microporous membrane on the surface of the fruit, which can moderately block gas exchange, reduce water evaporation and external microbial invasion; 1-methylcyclopropene, as an ethylene receptor inhibitor, can effectively inhibit the production of ethylene in custard apple fruit, delay ripening and senescence, and better maintain the firmness, crispness, color and flavor of the fruit. Salicylic acid can inhibit the biosynthesis and action of ethylene, indirectly reducing the respiration rate of custard apples after harvest, reducing nutrient consumption, delaying ripening and softening, and enhancing the fruit's resistance to adverse conditions. Spermine, as a polyamine, has the effect of antagonizing ethylene, delaying senescence, and inhibiting ethylene biosynthesis. Adding trace amounts of gallic acid can play a strong antioxidant and antibacterial role, effectively inhibiting microbial growth and reducing fruit decay. By binding or reducing quinones and the copper cofactor that may chelate polyphenol oxidase, it can effectively inhibit browning after cutting or damaging the fruit, maintaining its appearance quality. Peppermint oil can not only enhance the antibacterial effect but also maintain the fruit's fresh flavor. The flavonoids and polyphenols contained in water chestnut peel extract also have synergistic antioxidant and antibacterial effects, further improving the preservation effect.

[0022] Beneficial effects:

[0023] 1. The custard apple fruit preservative of the present invention is a scientific compound of 1-MCP, salicylic acid, spermine, gallic acid, peppermint oil and water chestnut peel extract. The effects of each component are complementary and synergistic, overcoming the limitations of single component effects. Its preservation effect is significantly better than single component preservatives and commercially available common preservatives.

[0024] 2. This invention employs a synergistic triple preservation method: soaking in a preservative solution, wrapping in preservative paper, and using preservative sheets. The preservative forms a protective film on the fruit surface, and the specially made preservative paper maintains its concentration for a longer period, effectively reducing moisture loss and enhancing antioxidant effects. The preservative sheets are made by mixing liquid preservative with soluble starch and diatomaceous earth to create solid preservative sheets that slowly release preservative components, providing continuous preservation. The combination of these three methods effectively extends the shelf life of custard apples to approximately 20 days, meeting the requirements for long-distance transportation and shelf life.

[0025] 3. The main film-forming agent and carrier of this invention are all food-grade or biodegradable materials. The amount of functional ingredients used is low, there are no toxic or harmful substance residues, which meet food safety requirements and can maintain the original flavor and nutrition of the fruit.

[0026] 4. The preservation method of the present invention is simple, easy to operate, and low in cost, making it suitable for large-scale promotion and application. It can effectively reduce post-harvest losses of custard apples and improve the economic benefits for fruit farmers and sellers. Attached Figure Description

[0027] Figure 1Comparative images of the appearance of custard apple fruits from different treatment groups on days 5, 10, 15, and 20 of storage, from top to bottom: Comparative Example 1, Comparative Example 2, and Example 1.

[0028] Figure 2 This is a diagram showing the ripening process of custard apples. From left to right, it represents day 0 of storage, early stage of soft ripening, and soft ripening and rotting. Detailed Implementation

[0029] The present invention will be further illustrated below with specific embodiments to make the advantages and features of the present invention easier to understand. It should be understood that the following embodiments are merely preferred embodiments of the present invention and not limitations thereof.

[0030] Example 1

[0031] 1. A preservative for custard apple fruit, using a 2% sodium carboxymethyl cellulose solution as a film-forming agent (based on 100% by weight of the sodium carboxymethyl cellulose aqueous solution), followed by the addition of antibacterial and preservative components. These antibacterial and preservative components comprise the following raw materials by weight percentage: 0.5% 1-methylcyclopropene, 0.5% salicylic acid, 0.12% spermine, 0.05% gallic acid, 0.01% peppermint oil, and 0.1% water chestnut peel extract. The specific preparation involves first preparing the sodium carboxymethyl cellulose solution according to the formulated concentration, then weighing the other components and adding them sequentially, stirring for 25-30 minutes until thoroughly mixed.

[0032] The water chestnut peel extract of the present invention is obtained by vacuum drying fresh water chestnut peel, followed by pulverizing to obtain water chestnut peel powder; water is then added to the water chestnut peel powder at a material-to-liquid ratio of 1:10 (g / ml), and ultrasonic extraction is performed for 4 hours at a temperature controlled at 45~50℃. After extraction, the mixture is centrifuged, the supernatant is collected, dried, and pulverized to obtain the water chestnut peel extract.

[0033] 2. Preservative paper loaded with custard apple fruit preservative. This preservative paper uses biodegradable nonwoven fabric as the base material, which is then fully impregnated in the prepared preservative for 30 minutes. After removal, excess liquid is drained, and the impregnated biodegradable nonwoven fabric is dried at 50℃ to constant weight to obtain the preservative paper loaded with custard apple fruit preservative. The loading of the active ingredient in the preservative is controlled at 5-20 g / m².

[0034] 3. Preparation of Preservative Sheets Containing Custard Apple Fruit Preservative: The pre-prepared preservative, soluble starch, and diatomaceous earth are mixed evenly at a mass ratio of 3:5:2 to form a paste. The paste is spread on a tray and dried in a vacuum drying oven at 50-60℃ until the moisture content is below 8%. The dried solid is then crushed and passed through an 80-mesh sieve. 3.0g of powder is taken each time and pressed into round sheets with a diameter of approximately 2cm using a tablet press under appropriate pressure to obtain the preservative sheets. The thickness of each preservative sheet is 2-3mm, and the weight is approximately 3g.

[0035] 4. The method for preserving custard apple fruit according to the present invention includes the following steps:

[0036] (1) Post-harvest soaking treatment: Immerse custard apples that are about 80-90% mature and have no obvious mechanical damage in the surface into the pre-prepared preservative for 10 minutes to ensure that the surface of the fruit is completely soaked. After taking them out, let them drain naturally to avoid residual moisture that could lead to the growth of microorganisms.

[0037] (2) Wrapping with preservative paper: After the custard apples have been drained, they are wrapped individually with the preservative paper of the present invention loaded with preservative. The preservative paper can ensure the breathability required for the fruit to breathe and slow down the rapid loss of moisture.

[0038] (3) Assisted slow-release preservation: Pack the wrapped custard apples into boxes, and place the preservation tablets evenly in the fruit boxes at a ratio of 9g of the preservation tablets per 10kg of custard apples. After sealing, store or transport the fruit.

[0039] (1) Soak the harvested custard apples with no obvious damage to the skin and a maturity of 8-9 in the pre-prepared custard apple fruit preservative for 10 minutes to ensure that the fruit surface is evenly in contact with the preservative. Take them out and let them drain naturally to avoid moisture residue leading to the growth of microorganisms.

[0040] (2) Each dried custard apple is wrapped with the custard apple fruit preservative of the present invention. The preservative paper can ensure the breathability required for the fruit to breathe and reduce the rate of moisture loss.

[0041] (3) Then put the wrapped custard apples into the fruit box, and evenly place the preservation film of the present invention in the fruit box. Place 9g of preservation film for every 10kg of custard apples, seal the fruit box and store or transport it.

[0042] Example 2

[0043] 1. A preservative for custard apple fruit, using a 3% sodium carboxymethyl cellulose solution as a film-forming agent (based on 100% by weight of the sodium carboxymethyl cellulose aqueous solution), followed by the addition of antibacterial and preservative components. These antibacterial and preservative components comprise the following raw materials by weight percentage: 1.0% 1-methylcyclopropene, 1.0% salicylic acid, 0.08% spermine, 0.2% gallic acid, 0.01% peppermint oil, and 0.15% water chestnut peel extract. The specific preparation involves first preparing the sodium carboxymethyl cellulose solution according to the formulated concentration, then weighing the other components and adding them sequentially, stirring for 25-30 minutes until thoroughly mixed.

[0044] The water chestnut peel extract of the present invention is obtained by vacuum drying fresh water chestnut peel, followed by pulverizing to obtain water chestnut peel powder; water is then added to the water chestnut peel powder at a material-to-liquid ratio of 1:8 (g / ml), and ultrasonic extraction is performed for 4 hours at a temperature controlled at 50~55℃. After extraction, the mixture is centrifuged, the supernatant is collected, dried, and pulverized to obtain the water chestnut peel extract.

[0045] 2. Preservative paper loaded with custard apple fruit preservative. This preservative paper uses biodegradable nonwoven fabric as the base material, which is then fully impregnated in the prepared preservative for 40 minutes. After removal, excess liquid droplets are drained, and the impregnated biodegradable nonwoven fabric is dried at 50℃ to constant weight to obtain the preservative paper loaded with custard apple fruit preservative. The loading of the active ingredient in the preservative is controlled at 5-20 g / m².

[0046] 3. Preparation of Preservative Sheets Containing Custard Apple Fruit Preservative: The pre-prepared preservative, soluble starch, and diatomaceous earth are mixed evenly in a mass ratio of 3:4:2 to form a paste. The paste is spread on a tray and dried in a vacuum drying oven at 50-60℃ until the moisture content is below 8%. The dried solid is then crushed and passed through an 80-mesh sieve. 5.0g of powder is taken and pressed into round sheets with a diameter of approximately 2cm using a tablet press under appropriate pressure to obtain the preservative sheets. The thickness of each preservative sheet is 2-3mm, and the weight is approximately 5g.

[0047] 4. Methods for preserving custard apple fruit, including the following steps:

[0048] (1) Post-harvest soaking treatment: Immerse custard apples that are about 80-90% mature and have no obvious mechanical damage in the surface into the pre-prepared preservative for 10 minutes to ensure that the surface of the fruit is completely soaked. After taking them out, let them drain naturally to avoid residual moisture that could lead to the growth of microorganisms.

[0049] (2) Wrapping with preservative paper: After the custard apples have been drained, they are wrapped individually with the preservative paper of the present invention loaded with preservative. The preservative paper can ensure the breathability required for the fruit to breathe and slow down the rapid loss of moisture.

[0050] (3) Assisted slow-release preservation: Pack the wrapped custard apples into boxes, and place the preservation tablets evenly in the fruit boxes at a ratio of 10g of the preservation tablets per 10kg of custard apples. After sealing, store or transport them.

[0051] Example 3

[0052] 1. A preservative for custard apple fruit, using a 2% sodium carboxymethyl cellulose solution as a film-forming agent (based on 100% by weight of the sodium carboxymethyl cellulose aqueous solution), followed by the addition of antibacterial and preservative components. These antibacterial and preservative components comprise the following raw materials by weight percentage: 0.8% 1-methylcyclopropene, 0.8% salicylic acid, 0.1% spermine, 0.1% gallic acid, 0.01% peppermint oil, and 0.2% water chestnut peel extract. The specific preparation involves first preparing the sodium carboxymethyl cellulose solution according to the formulated concentration, then weighing the other components and adding them sequentially, stirring for 20-25 minutes until thoroughly mixed.

[0053] The water chestnut peel extract of the present invention is obtained by vacuum drying fresh water chestnut peel, followed by pulverizing to obtain water chestnut peel powder; water is then added to the water chestnut peel powder at a material-to-liquid ratio of 1:9 (g / ml), and ultrasonic extraction is performed for 3.5 h at a temperature controlled at 50~55℃. After extraction, the mixture is centrifuged, the supernatant is collected, dried, and pulverized to obtain the water chestnut peel extract.

[0054] 2. Preservative paper loaded with custard apple fruit preservative. This preservative paper uses biodegradable nonwoven fabric as the base material, which is then fully impregnated in the prepared preservative for 35 minutes. After removal, excess liquid is drained, and the impregnated biodegradable nonwoven fabric is dried at 50℃ to constant weight to obtain the preservative paper loaded with custard apple fruit preservative. The loading of the active ingredient in the preservative is controlled at 5-20 g / m².

[0055] 3. Preparation of preservative sheets containing custard apple fruit preservative: The pre-prepared preservative, soluble starch, and diatomaceous earth are mixed evenly in a mass ratio of 3:5:2 to form a paste. The paste is spread on a tray and dried in a vacuum drying oven at 50-60℃ until the moisture content is below 8%. The dried solid is then crushed and passed through an 80-mesh sieve. 4.0g of powder is taken and pressed into round sheets with a diameter of approximately 2cm using a tablet press under appropriate pressure to obtain the preservative sheets. The thickness of the preservative sheets is 2-3mm, and each sheet weighs approximately 4g.

[0056] 4. Methods for preserving custard apple fruit, including the following steps:

[0057] (1) Post-harvest soaking treatment: Immerse custard apples that are about 80-90% mature and have no obvious mechanical damage in the surface into the pre-prepared preservative for 15 minutes to ensure that the surface of the fruit is completely soaked. After taking them out, let them drain naturally to avoid residual moisture that could lead to the growth of microorganisms.

[0058] (2) Wrapping with preservative paper: After the custard apples have been drained, they are wrapped individually with the preservative paper of the present invention loaded with preservative. The preservative paper can ensure the breathability required for the fruit to breathe and slow down the rapid loss of moisture.

[0059] (3) Assisted slow-release preservation: Pack the wrapped custard apples into boxes, and place the preservation tablets evenly in the fruit boxes at a ratio of 8g of the preservation tablets per 10kg of custard apples. After sealing, store or transport them.

[0060] Comparative Example 1

[0061] Freshly picked custard apples with no obvious damage to the skin and a maturity of 8-90% are wrapped directly in ordinary plastic wrap, then placed in fruit boxes, sealed, and stored.

[0062] Comparative Example 2

[0063] Picked custard apples with no obvious skin damage and a maturity of 8-90% are soaked in a 1.0% 1-methylcyclopropene preservative solution for 10-15 minutes to ensure that the surface of the fruit is evenly in contact with the preservative solution. After soaking, the fruit is removed and allowed to drain naturally. Then, it is wrapped directly with ordinary plastic wrap and placed in a fruit box. The fruit box is then sealed for storage.

[0064] Comparison of preservation effects

[0065] Preservation treatments were performed using the methods described in Example 1, Comparative Example 1, and Comparative Example 2, with 50 custard apples treated in each group. All fruits were harvested at the same time, were about 70% ripe, and had undamaged, bright green surfaces. After treatment, the fruits were stored at room temperature (25±2℃) and relative humidity of 85-90%. The degree of browning of the peel, the firmness of the flesh, and changes in flavor were observed periodically and recorded in Table 1.

[0066] Table 1. Fruit condition of custard apples under different preservation treatments.

[0067]

[0068] As shown in Table 1, the fruit condition of Example 1 (the method of the present invention) was significantly better than that of Comparative Example 1 and Comparative Example 2 on the 5th, 10th, 15th, and 20th days of preservation. In particular, Comparative Example 1, without special preservation measures, had a shelf life of approximately 5 days, while Comparative Example 2 (treated with traditional preservative solution) had a shelf life of approximately 10 days. The present invention, through a triple preservation method of soaking in preservative solution, wrapping in preservative paper, and using preservative sheets, can extend the shelf life to approximately 15-20 days, effectively reducing post-harvest losses of custard apples, meeting the needs of long-distance transportation and shelf life, and improving the economic benefits for fruit growers and distributors.

[0069] The above description is merely a preferred embodiment of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A preservative for custard apple fruit, characterized in that, The preservative is a film-forming agent sodium carboxymethyl cellulose with added antibacterial and preservative components. Based on 100% by weight of an aqueous solution of sodium carboxymethyl cellulose, the antibacterial and preservative components contain the following raw materials in weight percentages: 0.5-1.0% 1-methylcyclopropene, 0.5-1.0% salicylic acid, 0.08-0.12% spermine, 0.05-0.20% gallic acid, 0.01% peppermint oil, and 0.1-0.2% water chestnut peel extract.

2. The custard apple fruit preservative according to claim 1, characterized in that, Based on an aqueous solution of sodium carboxymethyl cellulose as 100% by weight, the antibacterial and preservative ingredients contain the following raw materials in weight percentages: 0.5% 1-methylcyclopropene, 0.5% salicylic acid, 0.12% spermine, 0.05% gallic acid, 0.01% peppermint oil, and 0.1% water chestnut peel extract.

3. The custard apple fruit preservative according to claim 1, characterized in that, The sodium carboxymethyl cellulose aqueous solution has a mass concentration of 2-3%.

4. The custard apple fruit preservative according to claim 1, characterized in that, The water chestnut peel extract is obtained by vacuum drying fresh water chestnut peels, followed by pulverizing them to obtain water chestnut peel powder; water is then added to the water chestnut peel powder at a material-to-liquid ratio of 1:8~10, and ultrasonic extraction is performed for 3-4 hours at a temperature controlled at 45~55℃. After extraction, the extract is centrifuged, and the supernatant is collected, dried, and pulverized to obtain the water chestnut peel extract.

5. A preservative paper loaded with the custard apple fruit preservative according to any one of claims 1-5, characterized in that, The preservation paper uses biodegradable non-woven fabric as the base fabric, is fully immersed in the preservation agent described in claim 1 for 30-40 minutes, lifted out, and dried to obtain the preservation paper loaded with custard apple fruit preservation agent.

6. The preservative paper loaded with custard apple fruit preservative according to claim 5, characterized in that, The loading of the preservative active ingredients in the preservation paper is controlled at 5-20 g / m².

7. A preservative sheet containing the custard apple fruit preservative according to any one of claims 1-5, characterized in that, The preservation sheet is prepared by mixing the preservative described in claim 1, soluble starch and diatomaceous earth in a mass ratio of 3:4-5:2 to form a paste or slurry, drying it under vacuum at 50-60°C, pulverizing it, and pressing it into a preservation sheet.

8. The preservative paper loaded with custard apple fruit preservative according to claim 7, characterized in that, The preservation sheet has a thickness of 2-3mm and a weight of 1-5g per sheet.

9. A method for preserving custard apple fruit using the preservative of custard apple fruit according to claim 1, the preservative paper according to claim 5, and the preservative sheet according to claim 7, characterized in that, Includes the following steps: (1) Post-harvest soaking treatment: The harvested custard apples with a maturity of 8-9 ripeness and no obvious mechanical damage on the surface are soaked in the pre-prepared custard apple fruit preservative as described in claim 1 for 10-15 minutes, then taken out and allowed to drain the surface moisture naturally. (2) Wrapping with preservative paper: After the water has been drained, the custard apples are wrapped individually with the preservative paper loaded with custard apple fruit preservative as described in claim 5. (3) Assisted slow-release preservation: Pack the wrapped custard apples into boxes, and evenly place the preservation sheet described in claim 7 in the fruit boxes. After sealing the fruit boxes, store or transport them.

10. The method for preserving custard apple fruit according to claim 9, characterized in that, Place 5-10g of preservation tablets on every 10kg of custard apple fruit.

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