Method for prolonging fresh-keeping period of peony and shrub althea flowers

Abstract

The invention provides a method for prolonging the fresh-keeping period of peony and shrub althea flowers, which comprises the following steps: disinfecting stem bases of fresh-cut peony and shrub althea flowers with dimethyl dicarbonate, spraying a film coating liquid for fresh keeping, and putting the stem bases and modified fresh-keeping paper into a low-density polyethylene functional modified atmosphere bag for storage and fresh keeping. According to the invention, silk fibroin, pullulan and the like are adopted to prepare the fresh-keeping liquid, and laccase enables ellagic acid to form o-quinone which is combined with silk fibroin and the like to form a film, so that moisture diffusion and primary bacteriostasis are slowed down; in addition, lignin microspheres are prepared from composite modified lignin loaded with 1-methylcyclopropene microcapsules and limonene, preservative paper base coating liquid is formed, the modified preservative paper is obtained, release of 1-methylcyclopropene and limonene is controlled, and loss of edible quality of the peony hibiscus flowers is inhibited. According to the invention, through the cooperation of coating preservation, preservative paper and modified atmosphere preservation, the storage period of the peony shrub althea flowers is obviously prolonged, good quality characteristics of the peony shrub althea flowers are retained, and the preservation stability and practical value are improved.

Description

Technical Field

[0001] This invention belongs to the field of flower preservation technology, specifically relating to a method for extending the shelf life of peony and hibiscus flowers. Background Technology

[0002] The hibiscus peony, belonging to the genus Hibiscus in the Malvaceae family, is one of the main varieties of Hibiscus. It is native to provinces such as Zhejiang, Jiangxi, Shaanxi, and Guizhou in my country, and is now cultivated throughout the country. Hibiscus has a long history of cultivation in my country, with records dating back to the Book of Songs (Shijing) 3000 years ago and ancient poems from the Tang Dynasty. Both the buds and flowers of the hibiscus peony are edible, highly nutritious, and can be prepared in various ways. Traditional Chinese medicine considers it to have the effects of clearing heat and dampness, cooling blood, and detoxifying, making it a popular green food. Currently, in some counties and cities in Fujian and Jiangxi provinces, hibiscus peony has begun large-scale cultivation as an edible flower, yielding considerable economic benefits.

[0003] To ensure optimal taste and nutritional value, prevent premature spoilage during transportation, meet the needs of different populations, and extend the shelf life of high-quality food, food preservation technology plays a crucial role. Currently, existing preservation technologies for peony and hibiscus flowers mainly include refrigeration, chemical preservation, and vacuum packaging. However, each of these methods has its own problems. For example, while refrigeration can inhibit physiological activity and microbial growth in flowers, and is low-cost and easy to operate, it is only suitable for short-term preservation (1-3 days) and is not suitable for low-temperature sensitive varieties. Vacuum packaging, while able to seal air in vacuum bags and combine with refrigeration for 3-5 days of preservation, is suitable for long-distance transportation, but pressure changes can easily cause sensory damage to the flowers. Chemical preservation often uses preservatives prepared as solutions or coated onto paper-based materials to form preservation paper. Both low and high concentrations of preservatives can affect the quality of peony and hibiscus flowers. Furthermore, the rapid release of active ingredients from the preservation paper leads to a shorter preservation period and less than ideal preservation results. Therefore, how to extend the shelf life of peony and hibiscus flowers and ensure the quality of fresh food is one of the key challenges that urgently needs to be addressed in the field of peony and hibiscus flower preservation. Summary of the Invention

[0004] Technical Problem to be Solved: To address the aforementioned technical problems, the purpose of this invention is to provide a method for extending the shelf life of peony and hibiscus flowers. This method involves disinfecting the base of freshly cut peony and hibiscus stems with dimethyl dicarbonate, then spraying a preservative coating, and finally storing the flowers and modified preservative paper in a low-density polyethylene functional modified atmosphere bag. This invention uses silk fibroin, pullulan, and other ingredients to formulate a preservative solution. Laccase causes ellagic acid to form ortho-quinones, which bind to silk fibroin and other ingredients to form a film, slowing moisture diffusion and providing preliminary antibacterial effects. Additionally, lignin microspheres are prepared by loading 1-methylcyclopropene microcapsules and limonene onto a composite modified lignin base coating solution to obtain modified preservative paper. This controls the release of 1-methylcyclopropene and limonene, inhibiting the loss of the edible quality of the peony and hibiscus flowers. This invention, through the synergistic effect of coating preservation, preservative paper, and modified atmosphere packaging, significantly extends the storage period of peony and hibiscus flowers, retains their good quality characteristics, and improves preservation stability and practical value.

[0005] Technical solution: A method for extending the shelf life of peony and hibiscus flowers, comprising the following steps: S1. Pick peony and hibiscus flowers that are free from pests and diseases and have all the flower buds open. Apply a 0.05-0.1% dimethyl dicarbonate solution to the base of the stem for disinfection and pre-cool at 0-4℃ for 25-35 minutes. S2. Apply the preservative solution to the surface of the peony and hibiscus flowers using a light spraying method, and let it stand for 15-20 minutes to obtain pretreated peony and hibiscus flowers; S3. Place the pretreated peony and hibiscus flowers on composite modified preservation paper, package them in low-density polyethylene functional modified atmosphere bags, and store them at 0-4℃ and 70-75% relative humidity.

[0006] Furthermore, the preparation method of the preservation liquid in S2 is as follows: silk fibroin and pullulan polysaccharide are mixed and dissolved evenly at a mass ratio of (1.5-4):(1-3), 2-4wt% of o-quinone crosslinking agent is added, and the mixture is reacted at 45-60℃ and 150-250rpm for 1.0-1.5h; 0.5-2.0wt% sorbitol, 0.2-0.5wt% tea polyphenols and 0.2-1.0wt% proline are added and ultrasonically treated to dissolve evenly to obtain the preservation liquid.

[0007] Furthermore, the preparation method of the o-quinone crosslinking agent is as follows: ellagic acid is dissolved in ethanol to prepare an ellagic acid solution with a concentration of 0.1-0.5%, 2-7 U / mL laccase is added to the ellagic acid solution and the pH of the solution is adjusted to 4.0-6.0, the reaction is carried out at 25-40℃ and 150-200 rpm for 1.0-3.0 h, and then the enzyme is inactivated by heating at 85-90℃ for 1-2 min. The o-quinone crosslinking agent is obtained by dialysis and freeze drying.

[0008] Furthermore, the preparation method of the composite modified preservation paper in S3 includes the following steps: Step 1. Dissolve lignin in buffer solution, sonicate for 5-10 min to obtain lignin suspension, add 2-5 U / mL laccase to lignin suspension and stir to activate for 30 min, then adjust pH to 4.5-6.0, add L-histidine and react at 30-40℃ and 200-300 rpm for 1-2.5 h, inactivate enzyme, centrifuge, wash and dry to obtain modified lignin; Step 2. Dissolve the modified lignin and phytic acid in ethanol at a mass ratio of 1:(4-5.5), adjust the pH to 4.0-6.0 with citric acid solution, react at 60-70℃ and 150-300rpm for 2-4h, centrifuge, wash, vacuum dry, pulverize and sieve to obtain composite modified lignin; Step 3. Dissolve the composite modified lignin in water to obtain an aqueous solution with a concentration of 3-6 wt%. Then dissolve 1-methylcyclopropene microcapsules and limonene in water and oil to prepare an oil solution. Mix the oil solution and the aqueous solution and then perform high-speed shearing to obtain an emulsion system. Slowly add anhydrous ethanol to the emulsion system, let it stand for 2-3 hours and centrifuge to obtain the precipitate. Vacuum dry to obtain lignin microspheres. Step 4. Immerse kraft paper in a lignin microsphere solution with a mass fraction of 10-20 wt%, and dry it at 60-70℃ for 1-4 hours to obtain modified preservation paper.

[0009] Furthermore, in step 1, the mass ratio of lignin to L-histidine is 1:(1-2).

[0010] Furthermore, in step 3, the concentration of 1-methylcyclopropene microcapsules is 0.5-2.0 wt%; and the concentration of limonene is 1.0-3.5 wt%.

[0011] Furthermore, in step 3, the volume ratio of the oil phase solution to the aqueous phase solution is (3-6):(15-20); the conditions for high-speed shearing are a shearing speed of 7500-9000 rpm and a processing time of 5-10 min.

[0012] Furthermore, in step 3, the volume of anhydrous ethanol is 15-25 times the total volume of the oil phase solution and the aqueous phase solution.

[0013] Furthermore, the density of the low-density polyethylene functional modified atmosphere bag in S3 is 0.91-0.93 g / cm³. 3 The oxygen permeability of low-density polyethylene functional modified atmosphere bags is 10,000-12,000 cm³. 3 / m 2 • 24h • 0.1Mpa; The carbon dioxide permeability of the low-density polyethylene functional modified atmosphere bag is 5000-6000 cm³. 3 / m 2• 24h • 0.1Mpa; The water vapor transmission rate of the low-density polyethylene functional modified atmosphere bag is 60-70cm. 3 / m 2 24h 0.1Mpa; Furthermore, the oxygen permeability of the low-density polyethylene functional modified atmosphere bag is 11643 cm³. 3 / m 2 • 24h • 0.1Mpa; The carbon dioxide permeability of the low-density polyethylene functional modified atmosphere bag is 5821.5cm². 3 / m 2 • 24h • 0.1Mpa; The water vapor transmission rate of the low-density polyethylene functional modified atmosphere bag is 62.586cm. 3 / m 2 ·24h·0.1Mpa. Beneficial effects

[0014] 1. This invention uses ortho-quinones generated by laccase oxidation of ellagic acid as a cross-linking agent, combined with silk fibroin, pullulan, sorbitol, tea polyphenols, and proline to form a preservative solution, which is then lightly sprayed onto the surface of peony and hibiscus flowers. Laccase oxidizes the phenolic hydroxyl groups of ellagic acid to form ortho-quinone structures. The quinone groups covalently bind to the amino and hydroxyl groups of silk fibroin and the hydroxyl groups of pullulan, forming a three-dimensional network that forms a film on the flower surface, slowing water diffusion, maintaining petal plumpness, reducing friction and microbial invasion, and ensuring freshness. Sorbitol, on the one hand, forms hydrogen bonds with macromolecules in the film through its hydroxyl groups, improving the network's flexibility and extensibility, thus aiding film formation; on the other hand, it creates a slightly moist environment on the film surface through its hygroscopic properties, replenishing water lost from the petals. Tea polyphenols can scavenge reactive oxygen free radicals, protect cells and proteins, delay browning and wilting; they can also disrupt microbial cell membranes, inhibit respiratory enzymes, reduce harmful bacteria, and lower the risk of decay.

[0015] 2. This invention uses phytic acid-modified lignin as the wall material, introduces L-histidine (CO2-responsive unit), and loads 1-methylcyclopropene microcapsules and limonene to prepare modified lignin microspheres, which are then used to form a coating liquid for preservation paper, resulting in a composite modified preservation paper. Phytic acid and lignin phenolic hydroxyl groups form a balanced structure through hydrogen bonding and electrostatic interactions, improving the compatibility of lignin with microspheres and the mechanical stability of the microspheres. Phosphate groups endow the microspheres with antibacterial and antioxidant properties, providing primary protection. The phenolic hydroxyl groups of lignin are oxidized to phenolic free radicals under the action of laccase, which couple with the amino groups of L-histidine to form stable CN bonds, endowing the microspheres with CO2 responsiveness. The modified lignin microspheres encapsulate the active ingredients through a porous cross-linked network. The hydroxyl groups on the lignin surface and the hydroxyl groups of the α-cyclodextrin on the outer layer of the 1-MCP microcapsule restrict the diffusion of the active ingredients through hydrogen bonding. The phytic acid cross-linked network reduces the loss due to storage volatilization. Limonene and the modified lignin phenylpropane units are embedded into the hydrophobic structure through hydrophobic interactions and van der Waals forces. The cross-linked network confines them to the hydrophobic region of the microspheres, achieving uniform and stable encapsulation.

[0016] 3. The composite modified preservation paper in this invention is CO2 responsive. During storage, the respiration of peony and hibiscus flowers releases CO2, increasing its concentration within the packaging. CO2 reacts with the imidazole group in L-histidine to form an imidazole salt structure, disrupting the hydrogen bonds and hydrophobic interactions of the preservation paper coating network, creating micropores that release 1-MCP and limonene. 1-MCP competitively binds to ethylene receptors in petal cells, blocking ethylene signal transduction and inhibiting petal shedding and fading. The hydrophobic structure of limonene penetrates the cell membrane of pathogens, disrupting membrane integrity, inhibiting microbial growth, and reducing spoilage. Its natural citrus aroma masks fermentation odors, making it suitable for consumption. Both reduce damage from harmful microorganisms, prolong the effect of 1-MCP, maintain the color and fullness of the petals, and extend the storage and preservation period.

[0017] 4. This invention utilizes a combination of coating preservation, preservation paper, and modified atmosphere packaging to preserve peony and hibiscus flowers. The coating preservation forms a protective film on the flower surface, isolating oxygen and water, reducing oxidation and water loss; the preservation paper slowly releases active ingredients, inhibiting microbial growth and flower senescence; modified atmosphere packaging precisely controls the oxygen and carbon dioxide ratio within the packaging, slowing down respiration, thereby significantly extending the storage time of peony and hibiscus flowers while preserving their excellent shape, color, and natural characteristics, greatly improving the stability and practical value of preservation. Attached Figure Description

[0018] Figure 1 The POD activity, SOD activity, and CAT activity of Examples 12, 13, and Comparative Examples 6-11 are shown, where A represents POD activity, B represents CAT activity, and C represents SOD activity. Figure 2 The changes in the content of cellulose, hemicellulose, and pectin in Examples 12, 13, and Comparative Examples 6-11 are shown. Figure 3 The superoxide anion content, MDA content, anthocyanin content, and total phenol content are for Examples 12, 13, and Comparative Examples 6-11, where A represents superoxide anion content, B represents anthocyanin content, C represents MDA content, and D represents total phenol content. Detailed Implementation

[0019] The present invention will be further described below with reference to embodiments. These embodiments are illustrative of the present invention, but the present invention is not limited to these embodiments: The 1-methylcyclopropene microcapsules (a 1-methylcyclopropene / α-cyclodextrin inclusion complex) described in this invention were purchased from Beijing Coolplay Technology Co., Ltd.

[0020] Example 1 A method for preparing a preservative solution includes the following steps: Step 1. Dissolve ellagic acid in ethanol to prepare a 0.3% ellagic acid solution. Add 4 U / mL laccase to the ellagic acid solution and adjust the pH of the solution to 6.0. React at 30℃ and 150 rpm for 2 h, then heat at 85℃ for 1 min to inactivate the enzyme. Obtain the o-quinone crosslinking agent by dialysis and freeze drying. Step 2. Mix 20g silk fibroin with 10g pullulan polysaccharide and dissolve evenly in 500mL of water. Add 0.9g of o-quinone crosslinking agent and react at 60℃ and 200rpm for 1.5h. Add 5g sorbitol, 2.5g tea polyphenols and 2.5g proline and sonicate to dissolve evenly to obtain the preservation solution. Example 2

[0021] A method for preparing a preservative solution includes the following steps: Step 1. Ellagic acid was dissolved in ethanol to prepare a 0.5% ellagic acid solution. 4 U / mL laccase was added to the ellagic acid solution and the pH of the solution was adjusted to 5.5. The reaction was carried out at 30℃ and 200 rpm for 2 h, and then heated at 85℃ for 1 min to inactivate the enzyme. The o-quinone crosslinking agent was obtained by dialysis and freeze drying. Step 2. Mix 20g silk fibroin with 10g pullulan polysaccharide and dissolve evenly in 500mL of water. Add 0.9g of o-quinone crosslinking agent and react at 60℃ and 200rpm for 1.5h. Add 5g sorbitol, 2.5g tea polyphenols and 2.5g proline and sonicate to dissolve evenly to obtain the preservation solution. Example 3

[0022] A method for preparing a preservative solution includes the following steps: Step 1. Dissolve ellagic acid in ethanol to prepare an ellagic acid solution with a mass fraction of 0.3%. Add 2.5 U / mL laccase to the ellagic acid solution and adjust the pH of the solution to 6.0. React at 30℃ and 150 rpm for 2 h, then heat at 85℃ for 1 min to inactivate the enzyme. Obtain the o-quinone crosslinking agent by dialysis and freeze drying. Step 2. Mix 20g silk fibroin with 10g pullulan polysaccharide and dissolve evenly in 500mL of water. Add 0.9g of o-quinone crosslinking agent and react at 60℃ and 200rpm for 1.5h. Add 5g sorbitol, 2.5g tea polyphenols and 2.5g proline and sonicate to dissolve evenly to obtain the preservation solution. Example 4

[0023] A method for preparing a preservative solution includes the following steps: Step 1. Ellagic acid was dissolved in ethanol to prepare a 0.5% ellagic acid solution. 4 U / mL laccase was added to the ellagic acid solution and the pH of the solution was adjusted to 5.5. The reaction was carried out at 30℃ and 200 rpm for 2 h, and then heated at 85℃ for 1 min to inactivate the enzyme. The o-quinone crosslinking agent was obtained by dialysis and freeze drying. Step 2. Mix 20g silk fibroin with 20g pullulan polysaccharide and dissolve evenly in 500mL of water. Add 1.2g of o-quinone crosslinking agent and react at 60℃ and 200rpm for 1.5h. Add 5g sorbitol, 2.5g tea polyphenols and 2.5g proline and sonicate to dissolve evenly to obtain the preservation solution. Example 5

[0024] A method for preparing a preservative solution includes the following steps: Step 1. Dissolve ellagic acid in ethanol to prepare a 0.3% ellagic acid solution. Add 4 U / mL laccase to the ellagic acid solution and adjust the pH of the solution to 6.0. React at 30℃ and 150 rpm for 2 h, then heat at 85℃ for 1 min to inactivate the enzyme. Obtain the o-quinone crosslinking agent by dialysis and freeze drying. Step 2. Mix 20g silk fibroin with 10g pullulan polysaccharide and dissolve evenly in 500mL of water. Add 0.9g of o-quinone crosslinking agent and react at 60℃ and 200rpm for 1.5h. Add 10g sorbitol, 1.5g tea polyphenols and 5g proline and sonicate to dissolve evenly to obtain the preservation solution. Comparative Example 1

[0025] The difference between this comparative example and Example 1 is that no ortho-quinone crosslinking agent is added; the remaining operations are the same as in Example 1. Comparative Example 2

[0026] The difference between this comparative example and Example 1 is that the ortho-quinone crosslinking agent is replaced with genipin, and the remaining operations are the same as in Example 1. Performance testing

[0027] (1) Antibacterial activity Activated Staphylococcus aureus and Pseudomonas aeruginosa were transferred to LB nutrient broth and cultured at 37°C for 12 h. The bacterial cells were then obtained by centrifugation at 5000 r / min for 10 min. The bacterial cells were appropriately diluted with nutrient broth to obtain a bacterial concentration of 10. 4 The bacterial culture of CFU / mL was added to 20mL of preservation solution and incubated at room temperature for 60min. 50μL was taken out and plated and incubated upside down at 37℃ for 24h. The colony growth was observed. Sterile water was used instead of tea polyphenols as a blank control. The inhibition rate was calculated as (total number of control colonies - total number of treated colonies) / total number of control colonies × 100%.

[0028] Table 1. Antibacterial activity of Examples 1-5, Comparative Examples 1 and 2

[0029] As shown in Table 1, compared with Comparative Example 1 and Comparative Example 2, the preservation solutions prepared in Examples 1-5 have better antibacterial activity, especially Example 1, which has the best antibacterial effect against Staphylococcus aureus and Pseudomonas aeruginosa. Example 6

[0030] A method for preparing composite modified lignin microspheres includes the following steps: Step ①. Dissolve 20g of lignin in 480mL of water, sonicate at 800W for 10min to obtain a lignin suspension, add 3.5U / mL of laccase to the lignin suspension and stir to activate for 30min, then adjust the pH to 5.5, add 20g of L-histidine and react at 40℃ and 200rpm for 1.5h, inactivate the enzyme at 85℃ for 1min, centrifuge at 4000rpm for 10min, wash and dry to obtain modified lignin; Step ②. Dissolve 30g of modified lignin and 120g of phytic acid in ethanol, adjust the pH to 5.0 with citric acid solution, react at 65℃ and 300rpm for 3h, centrifuge at 4000rpm for 10min, wash with water 3 times, vacuum dry at 65℃, and pulverize and sieve using a wall-breaking machine to obtain composite modified lignin. Step ③. Dissolve 10g of composite modified lignin in water to obtain an aqueous solution with a concentration of 4wt%. Then, dissolve 5g of 1-methylcyclopropene microcapsules and 10g of limonene in rapeseed oil to prepare an oil solution (the concentration of 1-methylcyclopropene microcapsules is 1wt% and the concentration of limonene is 2wt%). Mix 40mL of oil solution and 200mL of aqueous solution and shear at 9000rpm for 10min to obtain an emulsion system. Slowly add 4.8L of anhydrous ethanol to the emulsion system, let it stand for 2-3h, and centrifuge at 4000rpm for 10min to obtain a precipitate. Vacuum dry at 65℃ to obtain lignin microspheres. Example 7

[0031] A method for preparing composite modified lignin microspheres includes the following steps: Step ①. Dissolve 20g of lignin in 480mL of water, sonicate at 800W for 15min to obtain a lignin suspension, add 3.5U / mL of laccase to the lignin suspension and stir to activate for 30min, then adjust the pH to 6.0, add 40g of L-histidine and react at 40℃ and 200rpm for 1.5h, inactivate the enzyme at 85℃ for 1min, centrifuge at 4000rpm for 10min, wash and dry to obtain modified lignin; Step ②. Dissolve 30g of modified lignin and 120g of phytic acid in ethanol, adjust the pH to 5.0 with citric acid solution, react at 65℃ and 300rpm for 3h, centrifuge at 4000rpm for 10min, wash with water 3 times, vacuum dry at 65℃, and pulverize and sieve using a wall-breaking machine to obtain composite modified lignin. Step ③. Dissolve 10g of composite modified lignin in water to obtain an aqueous solution with a concentration of 4wt%. Then, dissolve 5g of 1-methylcyclopropene microcapsules and 10g of limonene in rapeseed oil to prepare an oil solution (the concentration of 1-methylcyclopropene microcapsules is 1wt% and the concentration of limonene is 2wt%). Mix 40mL of oil solution and 200mL of aqueous solution and shear at 9000rpm for 10min to obtain an emulsion system. Slowly add 3.6L of anhydrous ethanol to the emulsion system, let it stand for 2-3h, and centrifuge at 4000rpm for 10min to obtain a precipitate. Vacuum dry at 65℃ to obtain lignin microspheres. Example 8

[0032] A method for preparing composite modified lignin microspheres includes the following steps: Step ①. Dissolve 20g of lignin in 480mL of water, sonicate at 800W for 10min to obtain a lignin suspension, add 5U / mL of laccase to the lignin suspension and stir to activate for 35min, then adjust the pH to 5.5, add 20g of L-histidine and react at 40℃ and 200rpm for 2h, inactivate the enzyme at 85℃ for 1min, centrifuge at 4000rpm for 5min, wash and dry to obtain modified lignin; Step ②. Dissolve 30g of modified lignin and 120g of phytic acid in ethanol, adjust the pH to 5.0 with citric acid solution, react at 65℃ and 300rpm for 3h, centrifuge at 4000rpm for 10min, wash with water 3 times, vacuum dry at 65℃, and pulverize and sieve using a wall-breaking machine to obtain composite modified lignin. Step ③. Dissolve 10g of composite modified lignin in water to obtain an aqueous solution with a concentration of 4wt%. Then, dissolve 5g of 1-methylcyclopropene microcapsules and 10g of limonene in rapeseed oil to prepare an oil solution (the concentration of 1-methylcyclopropene microcapsules is 1wt% and the concentration of limonene is 2wt%). Mix 40mL of oil solution and 200mL of aqueous solution and shear at 9000rpm for 10min to obtain an emulsion system. Slowly add 4.8L of anhydrous ethanol to the emulsion system, let it stand for 2-3h, and centrifuge at 4000rpm for 10min to obtain a precipitate. Vacuum dry at 65℃ to obtain lignin microspheres. Example 9

[0033] A method for preparing composite modified lignin microspheres includes the following steps: Step ①. Dissolve 20g of lignin in 480mL of water, sonicate at 800W for 10min to obtain a lignin suspension, add 3.5U / mL of laccase to the lignin suspension and stir to activate for 30min, then adjust the pH to 5.5, add 20g of L-histidine and react at 40℃ and 200rpm for 1.5h, inactivate the enzyme at 85℃ for 1min, centrifuge at 4000rpm for 10min, wash and dry to obtain modified lignin; Step ②. Dissolve 25g of modified lignin and 125g of phytic acid in ethanol, adjust the pH to 5.0 with citric acid solution, react at 65℃ and 300rpm for 3h, centrifuge at 4000rpm for 10min, wash with water 3 times, vacuum dry at 65℃, and pulverize and sieve using a wall-breaking machine to obtain composite modified lignin. Step ③. Dissolve 10g of composite modified lignin in water to obtain an aqueous solution with a concentration of 4wt%. Then, dissolve 5g of 1-methylcyclopropene microcapsules and 10g of limonene in rapeseed oil to prepare an oil solution (the concentration of 1-methylcyclopropene microcapsules is 1wt% and the concentration of limonene is 2wt%). Mix 40mL of oil solution and 200mL of aqueous solution and shear at 9000rpm for 10min to obtain an emulsion system. Slowly add 4.8L of anhydrous ethanol to the emulsion system, let it stand for 2-3h, and centrifuge at 4000rpm for 10min to obtain a precipitate. Vacuum dry at 65℃ to obtain lignin microspheres. Example 10

[0034] A method for preparing composite modified lignin microspheres includes the following steps: Step ①. Dissolve 20g of lignin in 480mL of water, sonicate at 800W for 10min to obtain a lignin suspension, add 5U / mL of laccase to the lignin suspension and stir to activate for 35min, then adjust the pH to 5.5, add 20g of L-histidine and react at 40℃ and 200rpm for 2h, inactivate the enzyme at 85℃ for 1min, centrifuge at 4000rpm for 5min, wash and dry to obtain modified lignin; Step ②. Dissolve 30g of modified lignin and 120g of phytic acid in ethanol, adjust the pH to 5.0 with citric acid solution, react at 65℃ and 300rpm for 3h, centrifuge at 4000rpm for 10min, wash with water 3 times, vacuum dry at 65℃, and pulverize and sieve using a wall-breaking machine to obtain composite modified lignin. Step ③. Dissolve 10g of composite modified lignin in water to obtain an aqueous solution with a concentration of 6wt%. Then, dissolve 5g of 1-methylcyclopropene microcapsules and 10g of limonene in rapeseed oil to prepare an oil solution (the concentration of 1-methylcyclopropene microcapsules is 0.5wt% and the concentration of limonene is 1wt%). Mix 40mL of oil solution and 200mL of aqueous solution and shear at 9000rpm for 10min to obtain an emulsion system. Slowly add 6.0L of anhydrous ethanol to the emulsion system, let it stand for 2-3h, and centrifuge at 4000rpm for 10min to obtain a precipitate. Vacuum dry at 65℃ to obtain lignin microspheres. Example 11

[0035] A method for preparing composite modified lignin microspheres includes the following steps: Step ①. Dissolve 20g of lignin in 480mL of water, sonicate at 800W for 10min to obtain a lignin suspension, add 3.5U / mL of laccase to the lignin suspension and stir to activate for 30min, then adjust the pH to 5.5, add 20g of L-histidine and react at 40℃ and 200rpm for 1.5h, inactivate the enzyme at 85℃ for 1min, centrifuge at 4000rpm for 10min, wash and dry to obtain modified lignin; Step ②. Dissolve 30g of modified lignin and 120g of phytic acid in ethanol, adjust the pH to 5.0 with citric acid solution, react at 65℃ and 300rpm for 3h, centrifuge at 4000rpm for 10min, wash with water 3 times, vacuum dry at 65℃, and pulverize and sieve using a wall-breaking machine to obtain composite modified lignin. Step ③. Dissolve 10g of composite modified lignin in water to obtain an aqueous solution with a concentration of 4wt%. Then, dissolve 5g of 1-methylcyclopropene microcapsules and 10g of limonene in rapeseed oil to prepare an oil solution (the concentration of 1-methylcyclopropene microcapsules is 1wt% and the concentration of limonene is 2wt%). Mix 60mL of oil solution and 180mL of aqueous solution and shear at 9000rpm for 10min to obtain an emulsion system. Slowly add 4.8L of anhydrous ethanol to the emulsion system, let it stand for 2-3h, and centrifuge at 4000rpm for 10min to obtain a precipitate. Vacuum dry at 65℃ to obtain lignin microspheres. Comparative Example 3

[0036] The difference between this comparative example and Example 7 is that L-histidine-modified lignin is not used; the remaining operations are the same as in Example 7. Comparative Example 4

[0037] The difference between this comparative example and Example 7 is that phytic acid-modified lignin is not used; the remaining operations are the same as in Example 7. Comparative Example 5

[0038] The difference between this comparative example and Example 7 is that L-histidine and phytic acid-modified lignin are not used; the remaining operations are the same as in Example 7. Performance testing

[0039] (1) Average particle size The average particle size of the lignin microspheres prepared in Examples 6-11 and Comparative Examples 3-5 was determined using a laser particle size analyzer.

[0040] (2) Embedding efficiency Weigh 2g of lignin microspheres and add them to 200mL of distilled water. Then, sonicate at 300W for 15min and centrifuge at 10000rpm for 5min. Collect the supernatant for later use. Determine the 1-methylcyclopropene encapsulation rate by gas chromatography and the limonene encapsulation rate by high performance liquid chromatography.

[0041] Table 2. Average particle size and encapsulation efficiency of Examples 6-11 and Comparative Examples 3-5

[0042] As shown in Table 2, the average particle size of Examples 6-11 is smaller than that of Comparative Examples 3-5, while the encapsulation efficiency of 1-MCP and limonene is higher than that of Comparative Examples 3-5. This indicates that the lignin microspheres prepared in this example can bind more tightly and encapsulate 1-MCP and limonene more efficiently.

[0043] Example 12 A method for extending the shelf life of peony and hibiscus flowers includes the following steps: S1. Pick peony and hibiscus flowers that are free from pests and diseases and have all the flower buds open, apply a 10% dimethyl dicarbonate solution to the base of the stem for disinfection, and pre-cool at 4℃ for 30 minutes. S2. The preservative solution prepared in Example 5 was lightly sprayed onto the surface of the peony hibiscus flowers and left to stand for 20 minutes to obtain pretreated peony hibiscus flowers; S3. Food-grade kraft paper is immersed in a lignin microsphere solution prepared in Example 7 with a mass fraction of 15 wt%, and dried at 65°C for 3 hours to obtain modified preservation paper; S4. Place the pretreated peony and hibiscus flowers on modified preservation paper, and then use a low-density polyethylene functional modified atmosphere bag (with an oxygen permeability of 11643 cm⁻¹). 3 / m 2 • 24h • 0.1 MPa, carbon dioxide transmission rate 5821.5 cm³ 3 / m 2 • 24h • 0.1 MPa, water vapor transmission rate is 62.586 cm³ 3 / m 2Peony and hibiscus flowers were packaged at 0.1 MPa for 24 hours and stored at 4°C and 70% relative humidity. Example 13

[0044] A method for extending the shelf life of peony and hibiscus flowers includes the following steps: S1. Pick peony and hibiscus flowers that are free from pests and diseases and have all the flower buds open, apply a 10% dimethyl dicarbonate solution to the base of the stem for disinfection, and pre-cool at 4℃ for 30 minutes. S2. The preservative solution prepared in Example 5 was lightly sprayed onto the surface of the peony hibiscus flowers and left to stand for 20 minutes to obtain pretreated peony hibiscus flowers; S3. Food-grade kraft paper was immersed in a lignin microsphere solution prepared in Example 7 with a mass fraction of 20 wt%, and dried at 65°C for 3 h to obtain modified preservation paper; S4. Place the pretreated peony and hibiscus flowers on modified preservation paper, and then use a low-density polyethylene functional modified atmosphere bag (with an oxygen permeability of 11643 cm⁻¹). 3 / m 2 • 24h • 0.1 MPa, carbon dioxide transmission rate 5821.5 cm³ 3 / m 2 • 24h • 0.1 MPa, water vapor transmission rate is 62.586 cm³ 3 / m 2 Peony and hibiscus flowers were packaged at 0.1 MPa for 24 hours and stored at 4°C and 70% relative humidity. Comparative Example 6

[0045] The difference between this comparative example and Example 13 is that the preservative liquid prepared in Example 5 is replaced with the preservative liquid prepared in Comparative Example 1, and the remaining operations are the same as in Example 13. Comparative Example 7

[0046] The difference between this comparative example and Example 13 is that the preservative solution prepared in Example 5 is replaced with the preservative solution prepared in Comparative Example 2, and the remaining operations are the same as in Example 13. Comparative Example 8

[0047] The difference between this comparative example and Example 13 is that the lignin microspheres prepared in Example 7 are replaced with the lignin microspheres prepared in Comparative Example 3, and the remaining operations are the same as in Example 13. Comparative Example 9

[0048] The difference between this comparative example and Example 13 is that the lignin microspheres prepared in Example 7 are replaced with the lignin microspheres prepared in Comparative Example 4, and the remaining operations are the same as in Example 13. Comparative Example 10

[0049] The difference between this comparative example and Example 13 is that the lignin microspheres prepared in Example 7 are replaced with the lignin microspheres prepared in Comparative Example 5, and the remaining operations are the same as in Example 13. Comparative Example 11

[0050] The difference between this comparative example and Example 13 is that the low-density polyethylene functional modified atmosphere bag is replaced with a commercially available PE bag; the remaining operations are the same as in Example 13. Performance testing

[0051] The hibiscus flowers treated in Examples 12-13 and Comparative Examples 6-11 were stored at 4°C and 70% relative humidity for 8 days. The physicochemical indicators were measured on day 0, day 4, and day 8, with untreated hibiscus flowers as a blank control. The hydroxylamine method was used to determine the superoxide anion content, the kit method was used to determine the malondialdehyde (MDA) content, the visible spectrophotometry method was used to determine the peroxidase (POD) activity, the micro-method was used to determine the superoxide dismutase (SOD) activity, the ultraviolet spectrophotometry method was used to determine the catalase (CAT) activity, the anthrone method was used to determine the cellulose content, the DNS colorimetric method was used to determine the hemicellulose content, the carbazole colorimetric method was used to determine the pectin content, the differential method was used to determine the total anthocyanin content, and the Folin-phenol method was used to determine the total phenol content.

[0052] Depend on Figure 1 It can be seen that the POD, SOD, and CAT activities of Examples 12 and 13 are all higher than those of Comparative Examples 6-11 and the blank control. This indicates that the treatment method described in the examples can better activate the activities of POD, SOD, and CAT in the hibiscus flower, resist the toxic effects of reactive oxygen species during the preservation and storage of the hibiscus flower, and further enhance the hibiscus flower's adaptability to adversity, so as to maintain the balance between various internal metabolisms. Figure 2 It can be seen that with the extension of storage time, the cellulose, hemicellulose, and pectin content of peony and hibiscus flowers all showed a decreasing trend. However, the rate of decrease of cellulose, hemicellulose, and pectin in Examples 12 and 13 was lower than that in Comparative Examples 6-11, and the retention of cellulose, hemicellulose, and pectin was higher than that in the blank control. This indicates that the treatment method described in the examples can better preserve the morphological characteristics of peony and hibiscus petals, preventing premature wilting and withering, and effectively maintaining the freshness and quality of peony and hibiscus flowers. Figure 3It was found that during the storage of peony and hibiscus flowers, the superoxide anion and MDA contents of Examples 12 and 13 were significantly lower than those of Comparative Examples 6-11 and the blank control, while the anthocyanin and total phenol contents increased to some extent. This indicates that the peony and hibiscus flowers described in the examples can maintain better cell membrane structural integrity, slow down oxidative damage, delay the aging process, and promote the accumulation of secondary metabolites, thereby enhancing their ornamental value and physiological activity. The above results show that this preservation treatment technology can effectively extend the storage period of peony and hibiscus flowers and maintain their quality stability by synergistically regulating the antioxidant enzyme system and cell wall component metabolism.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the technical solutions of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A method for extending the shelf life of peony and hibiscus flowers, characterized in that, Includes the following steps: S1. Pick peony and hibiscus flowers that are free from pests and diseases and have all the flower buds open. Apply a 0.05-0.1% dimethyl dicarbonate solution to the base of the stem for disinfection and pre-cool at 0-4℃ for 25-35 minutes. S2. Apply the preservative solution to the surface of the peony and hibiscus flowers using a light spraying method, and let it stand for 15-20 minutes to obtain pretreated peony and hibiscus flowers; S3. Place the pretreated peony and hibiscus flowers on composite modified preservation paper, package them in low-density polyethylene functional modified atmosphere bags, and store them at 0-4℃ and 70-75% relative humidity.

2. The method for extending the shelf life of peony and hibiscus flowers according to claim 1, characterized in that, The preparation method of the preservation solution in S2 is as follows: Silk fibroin and pullulan polysaccharide are mixed and dissolved evenly at a mass ratio of (1.5-4):(1-3), 2-4wt% of o-quinone crosslinking agent is added, and the mixture is reacted at 45-60℃ and 150-250rpm for 1.0-1.5h; 0.5-2.0wt% sorbitol, 0.2-0.5wt% tea polyphenols and 0.2-1.0wt% proline are added and ultrasonically treated to dissolve evenly to obtain the preservation solution.

3. The method for extending the shelf life of peony and hibiscus flowers according to claim 2, characterized in that: The preparation method of the o-quinone crosslinking agent is as follows: ellagic acid is dissolved in ethanol to prepare an ellagic acid solution with a concentration of 0.1-0.5%. 2-7 U / mL laccase is added to the ellagic acid solution and the pH of the solution is adjusted to 4.0-6.

0. The reaction is carried out at 25-40℃ and 150-200 rpm for 1.0-3.0 h. The enzyme is then inactivated by heating at 85-90℃ for 1-2 min. The o-quinone crosslinking agent is obtained by dialysis and freeze drying.

4. The method for extending the shelf life of peony and hibiscus flowers according to claim 1, characterized in that, The preparation method of the composite modified preservation paper in S3 includes the following steps: Step 1. Dissolve lignin in buffer solution, sonicate for 5-10 min to obtain lignin suspension, add 2-5 U / mL laccase to lignin suspension and stir to activate for 30 min, then adjust pH to 4.5-6.0, add L-histidine and react at 30-40℃ and 200-300 rpm for 1-2.5 h, inactivate enzyme, centrifuge, wash and dry to obtain modified lignin; Step 2. Dissolve the modified lignin and phytic acid in ethanol at a mass ratio of 1:(4-5.5), adjust the pH to 4.0-6.0 with citric acid solution, react at 60-70℃ and 150-300rpm for 2-4h, centrifuge, wash, vacuum dry, pulverize and sieve to obtain composite modified lignin; Step 3. Dissolve the composite modified lignin in water to obtain an aqueous solution with a concentration of 3-6 wt%. Then dissolve 1-methylcyclopropene microcapsules and limonene in oil to prepare an oil solution. Mix the oil solution and the aqueous solution and shear at high speed to obtain an emulsion system. Slowly add anhydrous ethanol to the emulsion system, let it stand for 2-3 hours and centrifuge to obtain the precipitate. Vacuum dry to obtain lignin microspheres. Step 4. Immerse kraft paper in a lignin microsphere solution with a mass fraction of 10-20 wt%, and dry it at 60-70℃ for 1-4 hours to obtain modified preservation paper.

5. The method for extending the shelf life of peony and hibiscus flowers according to claim 4, characterized in that: In step 1, the mass ratio of lignin to L-histidine is 1:(1-2).

6. The method for extending the shelf life of peony and hibiscus flowers according to claim 4, characterized in that: In step 3, the concentration of 1-methylcyclopropene microcapsules is 0.5-2.0 wt%; the concentration of limonene is 1.0-3.5 wt%.

7. The method for extending the shelf life of peony and hibiscus flowers according to claim 4, characterized in that: In step 3, the volume ratio of the oil phase solution to the aqueous phase solution is (3-6):(15-20); the conditions for high-speed shearing are a shearing speed of 7500-9000 rpm and a processing time of 5-10 min.

8. A method for extending the shelf life of peony and hibiscus flowers according to claim 4, characterized in that: In step 3, the volume of anhydrous ethanol is 15-25 times the total volume of the oil phase solution and the aqueous phase solution.

9. A method for extending the shelf life of peony and hibiscus flowers according to claim 1, characterized in that: The density of the low-density polyethylene functional modified atmosphere bag in S3 is 0.91-0.93 g / cm³. 3 The oxygen permeability of low-density polyethylene functional modified atmosphere bags is 10,000-12,000 cm³. 3 / m 2 • 24h • 0.1Mpa; The carbon dioxide permeability of the low-density polyethylene functional modified atmosphere bag is 5000-6000 cm³. 3 / m 2 • 24h • 0.1Mpa; The water vapor transmission rate of the low-density polyethylene functional modified atmosphere bag is 60-70cm. 3 / m 2 ·24h·0.1Mpa.

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