A postharvest preservation method of mango

Abstract

The application provides a postharvest preservation method of mango, which comprises the following steps: S1. picking and pretreatment, S2. short-wave ultraviolet mild irradiation treatment, S3. preservative solution immersion and storage. The preservative solution is composed of phyllium extract solution, mango leaf extract solution, arginine grafted modified chitosan, glacial acetic acid and sterile water. Through the synergistic process of the short-wave ultraviolet mild irradiation and the preservative solution immersion, combined with the multiple effects of the modified chitosan coating and the plant extract, the mango can be stored for 30 days under the condition of 13-15 DEG C and 85-90% relative humidity, the good fruit rate is still kept to be more than 90%, and the weight loss rate is less than 5%, so that the industry problems that the mango is prone to rot and fast water loss after harvesting are effectively solved. The components of the preservative solution used in the application are all safe natural sources, no chemical synthetic fungicides are used in the whole process, there is no pesticide residue risk, and the green preservation and food safety requirements are met.

Description

Technical Field

[0001] This invention relates to the field of fruit preservation technology, specifically to a method for post-harvest preservation of mangoes. Background Technology

[0002] Mangoes are typical tropical climacteric fruits, maintaining vigorous metabolic activity even after harvest. They release large amounts of ethylene and have high respiration rates. Combined with their thin, easily damaged skin, they are highly susceptible to premature ripening, dehydration and shriveling, softening of the flesh, and fungal infections such as anthracnose and stem rot at room temperature. This results in post-harvest losses of 20-40%, severely restricting long-distance transportation and processing. Currently, post-harvest preservation of mangoes mainly employs methods such as low-temperature refrigeration, controlled atmosphere storage, chemical fungicide soaking, and edible coatings. While low-temperature refrigeration can inhibit respiration, mangoes are sensitive to chilling injury; temperatures below 10℃ easily lead to dull skin and spots, and uneven coloring after long-term refrigeration. Controlled atmosphere storage equipment requires large investments and has high operating costs, making it difficult to widely adopt in production areas. Chemical fungicides (such as imazalil and prochloraz) are highly effective, but pose a risk of pesticide residues, have low consumer acceptance, and some pathogens have developed resistance. Edible coatings (such as chitosan and sodium alginate) can delay water loss and aging to some extent, but the ability of a single coating to regulate ethylene is limited, and there is a lack of synergistic disease resistance mechanisms. Therefore, developing efficient, safe, and environmentally friendly post-harvest preservation methods for mangoes has significant economic value. Summary of the Invention

[0003] In view of this, the present invention proposes a method for post-harvest preservation of mangoes to solve the above problems.

[0004] The technical solution of this invention is implemented as follows:

[0005] A method for post-harvest preservation of mangoes includes the following steps:

[0006] S1. Harvesting and Pre-treatment: Harvest fresh fruit at 80% ripeness, remove diseased or damaged fruit, wash with clean water, and place in a ventilated place to air dry naturally.

[0007] S2. Short-wave ultraviolet light and irradiation treatment: The dried mangoes are laid flat on a wire rack and irradiated with short-wave ultraviolet light so that the surface of the fruit is evenly exposed to light.

[0008] S3. Preservative solution soaking and storage: After irradiation treatment, the mangoes are soaked in the preservative solution, and after soaking, they are naturally dried and then transferred to the storage room for storage.

[0009] Furthermore, the preservation solution is composed of amla extract, mango leaf extract, arginine-grafted modified chitosan, glacial acetic acid, and sterile water.

[0010] Furthermore, in step S2, the wavelength of the short-wave ultraviolet light is 254 nm, the distance between the light source and the mango is 30-40 cm, and the irradiation dose is 0.5-1.0 kJ / m². 2 Irradiate for 5-10 minutes.

[0011] Furthermore, in step S3, soak in the preservation solution for 3-5 minutes. Based on 100mL of preservation solution: 0.20-0.50mL of amla extract, 0.40-0.60mL of mango leaf extract, 0.80-1.20g of arginine-grafted modified chitosan, 0.80-1.50mL of glacial acetic acid, and sterile water to make up the remaining amount to 100mL.

[0012] Furthermore, the preservative solution is prepared by the following method: Take half of the sterile water, add glacial acetic acid, stir evenly, heat in a water bath to 38-42℃, add arginine-grafted modified chitosan while stirring, stir until completely dissolved, add amla extract, mango leaf extract, and the remaining sterile water, stir evenly, and store at 3-5℃ in the dark to obtain the preservative solution.

[0013] Furthermore, the amla extract is prepared by the following method: Fresh, ripe amla fruits are taken, washed, drained, pitted, and pulp is removed. The pulp is placed in a crushing device, and an equal mass of pre-cooled purified water at 3-5℃ is added. Citric acid is added to the purified water to adjust the pH to 3.5-4.0. The pulp is crushed to obtain amla pulp. The amla pulp is transferred to an ultrasonic extraction container, and 1-2 times the volume of purified water is added. The mixture is extracted for 25-35 minutes at 250-350W, 30-50kHz, and 38-42℃, with stirring every 5 minutes during the extraction. After ultrasonic extraction, the filtrate is collected by filtration. The residue is extracted again once with 2-3 times its volume of purified water, and the two filtrates are combined. The combined filtrate is first coarsely filtered through double-layer gauze, then vacuum filtered, and then concentrated to 15-25% of the original volume at 48-52℃ and -0.07 to -0.09MPa to obtain the amla extract.

[0014] Furthermore, the mango leaf extract was prepared by the following method: Fresh mature mango leaves were taken, cut into 1-2 cm pieces, and then dried at 38-42℃ to constant weight. After drying, the leaves were pulverized and passed through a 30-60 mesh sieve to obtain mango leaf powder. A 60 wt% ethanol solution was added to the mango leaf powder at a material-to-liquid ratio of 1:6-10 (material-to-liquid ratio unit is Kg / L). Citric acid was added to adjust the pH to 4.0-5.0. The mixture was heated to 78-80℃ and refluxed for 1.8-2.2 h. The filtrate was collected after filtration. The residue was extracted again, and the two filtrates were combined. The combined filtrate was first filtered through double-layer gauze, then vacuum filtered, and then concentrated to 20-30% of the original volume at 48-52℃ and -0.07 to -0.09 MPa to obtain the mango leaf extract.

[0015] Furthermore, the arginine-grafted modified chitosan was prepared by the following method: Chitosan was dissolved in a 1% glacial acetic acid aqueous solution at a mass-to-volume ratio of 1:40-60 (g / mL), and the solution was magnetically stirred until completely dissolved to obtain a chitosan solution. The solution was filtered through a 0.45 μm filter membrane, and the filtrate was collected for later use. Arginine was dissolved in a 0.1M 2-morpholine ethanesulfonic acid buffer solution at a mass-to-volume ratio of 1:18-22 (g / mL), and the solution was stirred until completely dissolved. 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide were added in a molar ratio of 1:1:1 with arginine. The solution was stirred and activated at 25-30℃ for 25-35 min to obtain an activated arginine solution. The activated arginine solution was added dropwise to the chitosan solution at a mass ratio of chitosan to arginine of 1:0.8-1.2, with the dropping speed increasing. The reaction rate is 4-6 mL / min, added dropwise while stirring to obtain a reaction solution. The pH of the reaction solution is adjusted to 5.5-6.0, and the reaction is carried out at 25-30℃ with stirring for 24 h. After the reaction is completed, 2-3 times the volume of anhydrous ethanol is added, stirred to precipitate, and allowed to stand for 25-35 min. The supernatant is removed, and the precipitate is washed 3 times with 70wt% ethanol. The washed precipitate is redissolved in 0.5wt% glacial acetic acid aqueous solution at a mass-to-volume ratio of 1:40-60 and stirred until completely dissolved. The solution is transferred to a dialysis bag with a molecular weight cutoff of 3000-4000 Da and dialyzed in deionized water for 48 h, with the water changed every 6 h. The dialyzed solution is centrifuged at 7000-9000 rpm for 12-18 min, and the supernatant is collected. Then, it is vacuum dried at 48-52℃ and pulverized through a 60-100 mesh sieve to obtain arginine-grafted modified chitosan.

[0016] Furthermore, in step S3, the storage temperature is 13-15℃ and the storage humidity is 85-90%.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] 1. This invention utilizes a synergistic process of first applying gentle short-wave ultraviolet light irradiation followed by soaking in a preservative solution, combined with the multiple effects of modified chitosan coating and plant extracts. This allows mangoes to be stored at 13-15℃ and 85-90% relative humidity for 30 days while maintaining a good fruit rate of over 90% and a weight loss rate of less than 5%. This effectively solves the industry problem of mangoes being prone to rotting and losing water quickly after harvest.

[0019] 2. The guanidino group of arginine-grafted chitosan of the present invention can efficiently adsorb ethylene. The active ingredients such as polyphenols and mangiferin in the extracts of Phyllanthus emblica and mango leaves can inhibit the activity of the key enzyme in ethylene synthesis (ACC oxidase). Combined with the resistance response induced by short-wave ultraviolet light, the respiration intensity and ethylene release of mangoes remain at extremely low levels for 30 days, thereby delaying fruit softening, color change and nutrient consumption, and maintaining good commercial quality.

[0020] 3. All components of the preservative solution used in this invention are from safe natural sources, and no chemically synthesized fungicides (such as imazalil) are used throughout the process, eliminating the risk of pesticide residues and meeting the requirements for green preservation and food safety. Furthermore, the pits of Phyllanthus emblica and mango leaf residues can be further composted or biotransformed, embodying the concept of recycling agricultural by-products and demonstrating significant ecological benefits and industrial promotion value. Detailed Implementation

[0021] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention.

[0022] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0023] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0024] Example 1

[0025] A method for post-harvest preservation of mangoes includes the following steps:

[0026] S1. Harvesting and Pre-treatment: Harvest fresh fruit at 80% ripeness, remove diseased or damaged fruit, wash with clean water, and place in a ventilated place to air dry naturally.

[0027] S2. Short-wave ultraviolet warming and irradiation treatment: The dried mangoes were laid flat on a wire rack and irradiated with short-wave ultraviolet light with a wavelength of 254nm. The light source was 30cm away from the mangoes, and the irradiation dose was 0.5kJ / m². 2 Irradiation treatment for 10 minutes ensures that the fruit surface is evenly exposed to light.

[0028] S3. Preservative Solution Immersion and Storage: After irradiation treatment, the mangoes are immersed in the preservative solution for 3 minutes. After immersion, they are air-dried naturally and then transferred to a storage room for storage at 13℃ and 85% humidity. The preservative solution consists of amla extract, mango leaf extract, arginine-grafted modified chitosan, glacial acetic acid, and sterile water. Based on 100mL of preservative solution: 0.20mL amla extract, 0.40mL mango leaf extract, 0.80g arginine-grafted modified chitosan, 0.80mL glacial acetic acid, and sterile water to bring the total volume to 100mL.

[0029] The preservative solution is prepared by the following method: Take half of the sterile water, add glacial acetic acid, stir evenly at 200 rpm, heat in a water bath to 38°C, add arginine-grafted modified chitosan, and stir at 300 rpm until completely dissolved while adding. Add amla extract, mango leaf extract, and the remaining sterile water, stir evenly at 200 rpm, and store at 3°C ​​in the dark to obtain the preservative solution.

[0030] The amla extract was prepared by the following method: Fresh, ripe amla fruits were taken, washed, drained, pitted, and pulp was removed. The pulp was placed in a crushing device, and an equal mass of pre-cooled purified water at 3°C ​​was added. Citric acid was added to the purified water to adjust the pH to 3.5. The pulp was crushed to obtain amla pulp. The amla pulp was transferred to an ultrasonic extraction container, and purified water with a volume equal to that of the amla pulp was added. The mixture was extracted at 250W, 30kHz, and 38°C for 35 minutes. During the extraction, the mixture was stirred at 100rpm for 2 minutes every 5 minutes. After ultrasonic extraction, the filtrate was collected by filtration. The residue was extracted again with purified water with a volume equal to that of the residue. The two filtrates were combined. The combined filtrate was first coarsely filtered through double-layer gauze, and then vacuum filtered at -0.06MPa using a 0.45μm filter membrane. The filtrate was then concentrated to 25% of its original volume at 48°C and -0.07MPa to obtain the amla extract.

[0031] The mango leaf extract was prepared by the following method: Fresh mature mango leaves were taken, cut into 1cm pieces, dried at 38℃ to constant weight, then pulverized and passed through a 30-mesh sieve to obtain mango leaf powder; 60wt% ethanol solution was added to the mango leaf powder at a material-to-liquid ratio of 1:6 (material-to-liquid ratio unit is Kg / L), citric acid was added to adjust the pH to 4.0, the mixture was heated to 78℃ and refluxed for 2.2h, and the filtrate was collected after filtration; the residue was extracted again, and the two filtrates were combined; the combined filtrate was first filtered through double-layer gauze, then vacuum filtered at -0.06MPa using a 0.45μm filter membrane, and then concentrated to 30% of the original volume at 48℃ and -0.07MPa to obtain the mango leaf extract.

[0032] The arginine-grafted modified chitosan was prepared by the following method: Chitosan was dissolved in a 1% glacial acetic acid aqueous solution at a mass-to-volume ratio of 1:40 (g / mL), and the solution was magnetically stirred at 200 rpm until completely dissolved to obtain a chitosan solution. The solution was filtered through a 0.45 μm filter membrane, and the filtrate was collected for later use. Arginine was dissolved in a 0.1 M 2-morpholine ethanesulfonic acid buffer solution at a mass-to-volume ratio of 1:18 (g / mL), and the solution was stirred at 200 rpm until completely dissolved. 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide were added in a molar ratio of 1:1:1 with arginine. The solution was activated by stirring at 200 rpm for 35 min at 25 °C to obtain an activated arginine solution. The activated arginine solution was added dropwise to the chitosan solution at a mass ratio of 1:0.8 (chitosan to arginine) at a dropping rate of 4 mL / min. While adding n, stir at 300 rpm to obtain a reaction solution. Adjust the pH of the reaction solution to 5.5 and react at 25℃ with stirring at 300 rpm for 24 h. After the reaction is complete, add 2 times the volume of anhydrous ethanol to the reaction solution and stir at 100 rpm to precipitate. Let stand for 25 min, remove the supernatant, and wash the precipitate three times with 70 wt% ethanol. After each addition of ethanol, stir at 100 rpm for 10 min. Redissolve the washed precipitate in 0.5 wt% glacial acetic acid aqueous solution at a mass-to-volume ratio of 1:40 and stir at 200 rpm until completely dissolved. Transfer to a dialysis bag with a molecular weight cutoff of 3000 Da and dialyze in deionized water for 48 h, changing the water every 6 h. Centrifuge the dialyzed solution at 7000 rpm for 18 min, collect the supernatant, and then vacuum dry at 48℃. After drying, pulverize and pass through a 60-mesh sieve to obtain arginine-grafted modified chitosan.

[0033] Example 2

[0034] A method for post-harvest preservation of mangoes includes the following steps:

[0035] S1. Harvesting and Pre-treatment: Harvest fresh fruit at 80% ripeness, remove diseased or damaged fruit, wash with clean water, and place in a ventilated place to air dry naturally.

[0036] S2. Short-wave ultraviolet warming and irradiation treatment: The dried mangoes were laid flat on a wire rack and irradiated with short-wave ultraviolet light with a wavelength of 254nm. The light source was 35cm away from the mangoes, and the irradiation dose was 0.8kJ / m². 2 Irradiation treatment for 8 minutes resulted in uniform light exposure on the fruit surface.

[0037] S3. Preservative Solution Immersion and Storage: After irradiation treatment, the mangoes are immersed in the preservative solution for 4 minutes. After immersion, they are naturally air-dried and then transferred to a storage room for storage at 14℃ and 88% humidity. The preservative solution consists of amla extract, mango leaf extract, arginine-grafted modified chitosan, glacial acetic acid, and sterile water. Based on 100mL of preservative solution: 0.35mL amla extract, 0.50mL mango leaf extract, 1.00g arginine-grafted modified chitosan, 1.15mL glacial acetic acid, and sterile water to bring the total volume to 100mL.

[0038] The preservative solution is prepared by the following method: Take half of the sterile water, add glacial acetic acid, stir evenly at 300 rpm, heat in a water bath to 40°C, add arginine-grafted modified chitosan, and stir at 400 rpm until completely dissolved while adding. Add amla extract, mango leaf extract, and the remaining sterile water, stir evenly at 300 rpm, and store at 4°C in the dark to obtain the preservative solution.

[0039] The amla extract was prepared by the following method: Fresh, ripe amla fruits were taken, washed, drained, pitted, and pulp was removed. The pulp was placed in a crushing device, and an equal mass of pre-cooled purified water at 4°C was added. Citric acid was added to the purified water to adjust the pH to 3.8. The pulp was crushed to obtain amla pulp. The amla pulp was transferred to an ultrasonic extraction container, and 1.5 times the volume of purified water was added. The mixture was extracted at 300W, 40kHz, and 40°C for 30 minutes. During the extraction, the mixture was stirred at 150rpm for 1.5 minutes every 5 minutes. After ultrasonic extraction, the filtrate was collected by filtration. The residue was extracted again with 2.5 times its volume of purified water. The two filtrates were combined. The combined filtrate was first coarsely filtered through double-layer gauze, and then vacuum filtered at -0.07MPa using a 0.45μm filter membrane. The filtrate was then concentrated to 20% of its original volume at 50°C and -0.08MPa to obtain the amla extract.

[0040] The mango leaf extract was prepared by the following method: Fresh mango leaves were taken, cut into 2cm pieces, dried at 40℃ to constant weight, then pulverized and passed through a 50-mesh sieve to obtain mango leaf powder; 60wt% ethanol solution was added to the mango leaf powder at a material-to-liquid ratio of 1:8 (material-to-liquid ratio unit is Kg / L), citric acid was added to adjust the pH to 4.5, the mixture was heated to 79℃ and refluxed for 2.0h, and the filtrate was collected after filtration; the residue was extracted again, and the two filtrates were combined; the combined filtrate was first filtered through double-layer gauze, then vacuum filtered at -0.07MPa using a 0.45μm filter membrane, and then concentrated to 25% of the original volume at 50℃ and -0.08MPa to obtain the mango leaf extract.

[0041] The arginine-grafted modified chitosan was prepared by the following method: Chitosan was dissolved in a 1% glacial acetic acid aqueous solution at a mass-to-volume ratio of 1:40-60 (g / mL), and the solution was magnetically stirred at 300 rpm until completely dissolved to obtain a chitosan solution. The solution was filtered through a 0.45 μm filter membrane, and the filtrate was collected for later use. Arginine was dissolved in a 0.1 M 2-morpholine ethanesulfonic acid buffer solution at a mass-to-volume ratio of 1:20 (pH 5.5). The volume ratio is in g / mL. Stir at 300 rpm until completely dissolved. Add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide in a molar ratio of 1:1:1 with arginine. Activate by stirring at 300 rpm for 30 min at 28°C to obtain an activated arginine solution. Add the activated arginine solution dropwise to the chitosan solution at a mass ratio of 1:1.0 (chitosan to arginine), at a dropping rate of 5 mL / min. Add the solution dropwise while stirring at 400 rpm to obtain the reaction solution. Adjust the pH of the reaction solution to 5.8 and react at 28℃ with stirring at 400 rpm for 24 h. After the reaction is complete, add 2.5 times the volume of anhydrous ethanol to the reaction solution and stir at 150 rpm to precipitate the precipitate. Let it stand for 30 min, remove the supernatant, and wash the precipitate three times with 70 wt% ethanol. After each addition of ethanol, stir at 150 rpm for 8 min. Redissolve the washed precipitate in 0.5 wt% glacial acetic acid aqueous solution at a mass-to-volume ratio of 1:50 and stir at 300 rpm until completely dissolved. Transfer the solution to a dialysis bag with a molecular weight cutoff of 3500 Da and dialyze it in deionized water for 48 h, changing the water every 6 h. Centrifuge the dialyzed solution at 8000 rpm for 15 min, collect the supernatant, and then vacuum dry it at 50℃. After drying, pulverize it through an 80-mesh sieve to obtain arginine-grafted modified chitosan.

[0042] Example 3

[0043] A method for post-harvest preservation of mangoes includes the following steps:

[0044] S1. Harvesting and Pre-treatment: Harvest fresh fruit at 80% ripeness, remove diseased or damaged fruit, wash with clean water, and place in a ventilated place to air dry naturally.

[0045] S2. Short-wave ultraviolet warming and irradiation treatment: The dried mangoes were laid flat on a wire rack and irradiated with short-wave ultraviolet light with a wavelength of 254nm. The light source was 40cm away from the mangoes, and the irradiation dose was 1.0kJ / m². 2 Irradiation treatment for 5 minutes ensures that the fruit surface is evenly exposed to light.

[0046] S3. Preservative Solution Immersion and Storage: After irradiation treatment, the mangoes are immersed in the preservative solution for 5 minutes. After immersion, they are air-dried naturally and then transferred to a storage room for storage at 15℃ and 90% humidity. The preservative solution consists of amla extract, mango leaf extract, arginine-grafted modified chitosan, glacial acetic acid, and sterile water. Based on 100mL of preservative solution: 0.50mL amla extract, 0.60mL mango leaf extract, 1.20g arginine-grafted modified chitosan, 1.50mL glacial acetic acid, and sterile water to bring the total volume to 100mL.

[0047] The preservative solution is prepared by the following method: Take half of the sterile water, add glacial acetic acid, stir evenly at 400 rpm, heat in a water bath to 42°C, add arginine-grafted modified chitosan, stir while adding at 500 rpm until completely dissolved, add amla extract, mango leaf extract, and the remaining sterile water, stir evenly at 400 rpm, and store at 5°C in the dark to obtain the preservative solution.

[0048] The amla extract was prepared by the following method: Fresh, ripe amla fruits were taken, washed, drained, pitted, and pulp was removed. The pulp was placed in a crushing device, and an equal mass of pre-cooled purified water at 5°C was added. Citric acid was added to the purified water to adjust the pH to 4.0. The pulp was crushed to obtain amla pulp. The amla pulp was transferred to an ultrasonic extraction container, and twice the volume of purified water was added. The mixture was extracted at 350W, 50kHz, and 42°C for 25 minutes. During the extraction, the mixture was stirred at 200rpm for 1 minute every 5 minutes. After ultrasonic extraction, the filtrate was collected by filtration. The residue was extracted again with three times its volume of purified water, and the two filtrates were combined. The combined filtrate was first coarsely filtered through double-layer gauze, and then vacuum filtered at -0.08MPa using a 0.45μm filter membrane. The filtrate was then concentrated to 15% of its original volume at 52°C and -0.09MPa to obtain the amla extract.

[0049] The mango leaf extract was prepared by the following method: Fresh mature mango leaves were taken, cut into 2cm pieces, dried at 42℃ to constant weight, then pulverized and passed through a 60-mesh sieve to obtain mango leaf powder; 60wt% ethanol solution was added to the mango leaf powder at a material-to-liquid ratio of 1:10 (material-to-liquid ratio unit is Kg / L), citric acid was added to adjust the pH to 5.0, the mixture was heated to 80℃ and refluxed for 1.8h, and the filtrate was collected after filtration; the residue was extracted again, and the two filtrates were combined; the combined filtrate was first filtered through double-layer gauze, then vacuum filtered at -0.08MPa using a 0.45μm filter membrane, and then concentrated to 20% of the original volume at 52℃ and -0.09MPa to obtain the mango leaf extract.

[0050] The arginine-grafted modified chitosan was prepared by the following method: Chitosan was dissolved in a 1% glacial acetic acid aqueous solution at a mass-to-volume ratio of 1:60 (g / mL), and the solution was magnetically stirred at 400 rpm until completely dissolved to obtain a chitosan solution. The solution was filtered through a 0.45 μm filter membrane, and the filtrate was collected for later use. Arginine was dissolved in a 0.1 M 2-morpholine ethanesulfonic acid buffer solution at a mass-to-volume ratio of 1:22 (g / mL), and the solution was stirred at 400 rpm until completely dissolved. 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide were added in a molar ratio of 1:1:1 to arginine, and the mixture was stirred at 400 rpm at 30°C. Activate the chitosan solution by stirring at rpm for 25 min to obtain an activated arginine solution. Add the activated arginine solution dropwise to the chitosan solution at a chitosan to arginine mass ratio of 1:1.2, at a dropping rate of 6 mL / min, while stirring at 500 rpm to obtain a reaction solution. Adjust the pH of the reaction solution to 6.0 and react at 30℃ with stirring at 500 rpm for 24 h. After the reaction is complete, add three times the volume of anhydrous ethanol to the reaction solution and stir at 200 rpm to precipitate the precipitate. Let stand for 35 min, remove the supernatant, and precipitate with 70 wt% ethanol. Wash three times, adding ethanol each time and stirring at 200 rpm for 5 min. The washed precipitate was then redissolved in a 0.5 wt% glacial acetic acid aqueous solution at a mass-to-volume ratio of 1:60 and stirred at 400 rpm until completely dissolved. The solution was then transferred to a dialysis bag with a molecular weight cutoff of 4000 Da and dialyzed in deionized water for 48 h, with the water changed every 6 h. The dialyzed solution was centrifuged at 9000 rpm for 12 min, and the supernatant was collected. Subsequently, the solution was vacuum dried at 52 °C and then pulverized through a 100-mesh sieve to obtain arginine-grafted modified chitosan.

[0051] Comparative Example 1

[0052] The difference between this comparative example and Example 2 is that no short-wave ultraviolet temperature or irradiation treatment was performed.

[0053] Comparative Example 2

[0054] The difference between this comparative example and Example 2 is that no preservative solution was used for soaking.

[0055] Comparative Example 3

[0056] The difference between this comparative example and Example 2 is that the preservation solution does not contain the preservative extract of Phyllanthus emblica.

[0057] Comparative Example 4

[0058] The difference between this comparative example and Example 2 is that the preservation solution does not contain mango leaf extract.

[0059] Comparative Example 5

[0060] The difference between this comparative example and Example 2 is that the arginine-grafted modified chitosan in the preservation liquid was replaced by an equal mass of unmodified chitosan.

[0061] Experiment 1: Surface disease incidence, disease index, and weight loss rate

[0062] Nine hundred Tainong No. 1 mangoes, uniform in size, free from mechanical damage and pests / diseases, were selected. They were randomly divided into three groups: Examples 1-3, Comparative Examples 1-5, and a blank control group, with 100 mangoes in each group. The blank control group was not treated with short-wave ultraviolet light or gentle irradiation and was soaked in purified water. At the beginning of the experiment, the total weight of the mangoes in each group was recorded as W0. Subsequently, the mangoes from the nine groups were placed at 13℃ and 88% humidity, ventilated for 10 minutes every two days. After 30 days, the total weight of the mangoes in each group was recorded as W1. The weight loss rate was calculated, and the incidence of surface diseases and the disease index were measured. The results are shown in Table 1.

[0063] Weightlessness rate = (W0 - W1) ÷ W0

[0064] Disease incidence rate = Number of fruits with diseased spots ÷ 100 × 100%

[0065] Disease index = [Σ(Disease grade value × Number of fruits at that grade) ÷ (Highest disease grade × Total number of fruits)] × 100%

[0066] The disease severity index is divided into 0-5 levels, and is classified according to the following standards, with level 5 being the highest:

[0067] Grade 0: No lesions

[0068] Grade 1: Lesion area 0.1-4.9%

[0069] Grade 2: Lesion area 5.0–14.9%

[0070] Grade 3: Lesion area 15.0–24.9%

[0071] Grade 4: Lesion area 25.0–49.9%

[0072] Grade 5: Lesion area ≥ 50.0%

[0073] Taking Example 1 as an example, there are a total of 100 mangoes, of which 83 are grade 0, 14 are grade 1, 3 are grade 2, 0 are grade 3, 0 are grade 4, and 0 are grade 5. The numerator is calculated as: Σ(disease grade value × number of fruits of that grade) = 0 × 83 + 1 × 14 + 2 × 3 + 3 × 0 + 4 × 0 + 5 × 0 = 0 + 3 + 4 + 6 + 4 + 0 = 20. The denominator is: highest disease grade (5) × total number of fruits (100) = 5 × 100 = 500. The disease index is (20 ÷ 500) × 100% = 4.0%. In addition, the area of ​​lesions in this experiment was measured using a ruler.

[0074] Table 1

[0075]

[0076] Experiment 2: Measurement of Respiratory Intensity and Ethylene Release

[0077] 135 Tainong No. 1 mangoes of uniform size, free from mechanical damage and pests / diseases, were selected. They were randomly divided into three groups: Examples 1-3, Comparative Examples 1-5, and a blank control group, with 15 mangoes in each group and three replicates per group. The mangoes from Examples 1-3, Comparative Examples 1-5, and the blank control group were placed at 13℃ and 88% humidity, ventilated every two days for 10 minutes each time, for 30 days. Respiration intensity and ethylene release were measured on days 0, 15, and 30 of storage. Respiration intensity was measured as follows: Each replicate of mango was placed in a 10L sealed container and sealed at 25℃ for 1 hour. 10mL of gas was extracted from the sealed container using a syringe and injected into a CO2 analyzer. The CO2 concentration (μL / L) was recorded, and the respiration intensity was calculated using the following formula:

[0078] Breathing intensity = (C × V) ÷ (W × t);

[0079] C: CO2 concentration difference, C=C 终 -C 初 ;

[0080] V: Volume of the sealed container (L);

[0081] W: Fruit weight (kg);

[0082] t: time (h)

[0083] Ethylene release was determined as follows: Each replicate mango was placed in a sealed container of volume X and kept at 25°C for 2 hours. 1 mL of gas was extracted from the container using a syringe and injected into the chromatograph (column temperature 70°C, detector 150°C, carrier gas N2, flow rate 30 mL / min). The ethylene concentration (μL / L) was recorded, and the ethylene release was calculated using the following formula:

[0084] Ethylene release = (C2H4 concentration × V) ÷ (W × t)

[0085] For each replicate, the total mass (W, kg) of the mangoes must be weighed before each measurement. The actual mass before the measurement should be used in the formula. There are 3 replicates per group, and each replicate is measured independently. The average value is taken. The results are shown in Table 2.

[0086] Table 2

[0087]

[0088] The post-harvest preservation method for mangoes of this invention uses short-wave ultraviolet light and irradiation to not only directly kill pathogens on the surface of the fruit peel, but more importantly, induces the mango itself to produce resistance substances such as phytoalexins and lignin, activating the system to acquire resistance. Subsequently, a preservative solution is applied for immersion and coating, which avoids the film layer blocking ultraviolet light and seals the induced resistance substances on the fruit peel surface. The arginine-grafted modified chitosan in the preservative solution can form a dense, edible film, effectively reducing water evaporation. Simultaneously, its guanidine groups efficiently adsorb ethylene through electrostatic interaction, delaying the catalytic process. The amla extract is rich in ellagic acid, gallic acid, and natural vitamin C, which can effectively resist oxidation, inhibit polyphenol oxidase, destroy fungal cell membranes, and chelate iron ions required for ethylene synthesis. The mangiferin and quercetin in the mango leaf extract further inhibit anthracnose and stem-rot fungi and induce resistance to chilling injury. The combined effect of these three factors keeps ethylene release and respiration intensity at extremely low levels for 30 days, while reducing the incidence of disease to 5.6%, thereby extending the shelf life of mangoes to more than 30 days and achieving a good fruit rate of over 90%.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for post-harvest preservation of mangoes, characterized in that, Includes the following steps: S1. Harvesting and Pre-treatment: Harvest fresh fruit that is 80% ripe, remove diseased or damaged fruit, wash with clean water, and place in a ventilated place to air dry the surface moisture. S2. Short-wave ultraviolet gentle irradiation treatment: The dried mangoes are laid flat on a wire rack and irradiated with short-wave ultraviolet light, so that the surface of the fruit is evenly illuminated. S3. Preservative solution soaking and storage: After irradiation treatment, the mangoes are soaked in the preservative solution, and after soaking, they are air-dried naturally and then transferred to the storage room for storage. The preservation solution is composed of amla extract, mango leaf extract, arginine-grafted modified chitosan, glacial acetic acid, and sterile water.

2. The method for post-harvest preservation of mangoes as described in claim 1, characterized in that, In step S2, the wavelength of the short-wave ultraviolet light is 254 nm, the distance between the light source and the mango is 30-40 cm, and the irradiation dose is 0.5-1.0 kJ / m². 2 Irradiate for 5-10 minutes.

3. The method for post-harvest preservation of mangoes as described in claim 1, characterized in that, In step S3, soak in the preservation solution for 3-5 minutes. Based on 100mL of preservation solution: 0.20-0.50mL of amla extract, 0.40-0.60mL of mango leaf extract, 0.80-1.20g of arginine-grafted modified chitosan, 0.80-1.50mL of glacial acetic acid, and sterile water to make up the remaining amount to 100mL.

4. A method for post-harvest preservation of mangoes as described in claim 3, characterized in that, The preservative solution is prepared by the following method: take half of sterile water and add glacial acetic acid to it. Stir well, heat in a water bath to 38-42℃, add arginine-grafted modified chitosan while stirring until completely dissolved, add amla extract, mango leaf extract, and the remaining sterile water, stir well, and store in the dark at 3-5℃ to obtain the preservation solution.

5. A method for post-harvest preservation of mangoes as described in claim 4, characterized in that, The amla extract is prepared by the following method: Fresh, ripe amla fruits are taken, washed, drained, pitted, and pulp is removed. The pulp is placed in a crushing device, and an equal mass of pre-cooled purified water at 3-5℃ is added. Citric acid is added to the purified water to adjust the pH to 3.5-4.

0. The pulp is crushed to obtain amla pulp. The amla pulp is transferred to an ultrasonic extraction container, and 1-2 times the volume of purified water is added. The mixture is extracted for 25-35 minutes at 250-350W, 30-50kHz, and 38-42℃, with stirring every 5 minutes during the extraction. After ultrasonic extraction, the filtrate is collected by filtration. The residue is extracted again with 2-3 times its volume of purified water, and the two filtrates are combined. The combined filtrate is first coarsely filtered through double-layer gauze, then vacuum filtered, and then concentrated to 15-25% of the original volume at 48-52℃ and -0.07 to -0.09MPa to obtain the amla extract.

6. A method for post-harvest preservation of mangoes as described in claim 4, characterized in that, The mango leaf extract was prepared by the following method: Fresh mature mango leaves were taken, cut into 1-2 cm pieces, dried at 38-42℃ to constant weight, then pulverized and passed through a 30-60 mesh sieve to obtain mango leaf powder; a 60 wt% ethanol solution was added to the mango leaf powder at a material-to-liquid ratio of 1:6-10 (material-to-liquid ratio unit is Kg / L), citric acid was added to adjust the pH to 4.0-5.0, the mixture was heated to 78-80℃ and refluxed for 1.8-2.2 h, and the filtrate was collected after filtration; the residue was extracted again, and the two filtrates were combined; The combined filtrate was first filtered through double-layer gauze, then vacuum filtered, and then concentrated to 20-30% of the original volume at 48-52℃ and -0.07 to -0.09 MPa to obtain mango leaf extract.

7. A method for post-harvest preservation of mangoes as described in claim 4, characterized in that, The arginine-grafted modified chitosan was prepared by the following method: Chitosan was dissolved in a 1 wt% glacial acetic acid aqueous solution at a mass-to-volume ratio of 1:40-60 (g / mL), and the solution was magnetically stirred until completely dissolved to obtain a chitosan solution. The solution was filtered through a 0.45 μm filter membrane, and the filtrate was collected for later use. Arginine was dissolved in a 0.1 M 2-morpholine ethanesulfonic acid buffer solution at a mass-to-volume ratio of 1:18-22 (g / mL), and the solution was stirred until completely dissolved. 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide were added in a molar ratio of 1:1:1 with arginine. The solution was stirred and activated at 25-30 °C for 25-35 min to obtain an activated arginine solution. The activated arginine solution was added dropwise to the chitosan solution at a mass ratio of chitosan to arginine of 1:0.8-1.2, with a dropping rate of [missing information]. Add the solution dropwise at a rate of 4-6 mL / min while stirring to obtain a reaction solution. Adjust the pH of the reaction solution to 5.5-6.0 and stir at 25-30℃ for 24 h. After the reaction is complete, add 2-3 times the volume of anhydrous ethanol to the reaction solution and stir to precipitate. Let it stand for 25-35 min, remove the supernatant, and wash the precipitate three times with 70wt% ethanol. Redissolve the washed precipitate in 0.5wt% glacial acetic acid aqueous solution at a mass-to-volume ratio of 1:40-60 and stir until completely dissolved. Transfer the solution to a dialysis bag with a molecular weight cutoff of 3000-4000 Da and dialyze it in deionized water for 48 h, changing the water every 6 h. Centrifuge the dialyzed solution at 7000-9000 rpm for 12-18 min, collect the supernatant, and then vacuum dry it at 48-52℃. After drying, pulverize it through a 60-100 mesh sieve to obtain arginine-grafted modified chitosan.

8. A method for post-harvest preservation of mangoes as described in claim 1, characterized in that, In step S3, the storage temperature is 13-15℃ and the storage humidity is 85-90%.

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