A astaxanthin-based leaf color promoting foliar fertilizer and application thereof

Abstract

The application provides a astaxanthin-based color promoting foliar fertilizer and application thereof. The foliar fertilizer comprises the following raw materials: astaxanthin, hydroxypropyl-beta-cyclodextrin, reduced glutathione, L-ascorbic acid, L-phenylalanine, soybean lecithin, organic silicon surfactant, sea buckthorn seed meal extract, radix sanguisorbae extract, sodium iminodisuccinate, and a citric acid-sodium citrate buffer pair. The application breaks through the technical limitation of traditional color promoting agents, which sacrifice quality in exchange for appearance color. Through the directional supply of L-phenylalanine as a direct precursor of anthocyanin synthesis, combined with the up-regulation of chalcone isomerase activity by sea buckthorn seed meal extract, the metabolic flow is effectively pulled into the phenylpropanoid secondary metabolic pathway, so that the photosynthetic products are preferentially used for the synergistic accumulation of anthocyanins and soluble sugars, so that the sugar and flavor substances are synchronously enriched while the fruit color is deepened, and the perfect ripe quality of color, aroma and sweetness is realized.

Description

Technical Field

[0001] This invention relates to the field of foliar fertilizer and its application technology, specifically to a color-changing foliar fertilizer based on astaxanthin and its application. Background Technology

[0002] Fruit color is not only the most direct sensory indicator of ripeness, but also a core element determining the economic value and market competitiveness of agricultural products. Excellent color change signifies a large accumulation of secondary metabolites such as anthocyanins and carotenoids within the fruit, directly related to the harmonious proportions of soluble sugars, organic acids, and aromatic substances, thus laying the foundation for the fruit's rich flavor and abundant nutritional quality. Furthermore, fully color-changed fruits have a more developed cuticle layer, effectively reducing post-harvest respiration and water transpiration, significantly improving their storage and transport resistance. Therefore, promoting uniform, safe, and efficient color change is a crucial management step in ensuring high yields and quality in both greenhouse and open-field cultivation, achieving staggered market entry, and extending shelf life.

[0003] However, current mainstream ripening techniques have many shortcomings and safety hazards that urgently need to be addressed. While widely used chemical ripening agents (such as ethephon and exogenous abscisic acid) can force coloring in the short term, they are essentially stress signals that disrupt the balance of endogenous hormones, causing "false ripening"—that is, bright red color but insufficient accumulation of dry matter and sugar, resulting in a sour and bland taste. They also often induce abnormal respiratory climacteric changes, leading to significant pre-harvest fruit drop and abnormal softening, severely shortening shelf life. Furthermore, their effectiveness is highly dependent on temperature and humidity; high temperatures can easily cause sunburn or rust spots on the fruit peel, and even slight deviations in concentration control can cause irreversible phytotoxicity.

[0004] It is worth noting that while there are currently products on the market containing novel antioxidants such as astaxanthin, their technological bottlenecks are significant. Astaxanthin molecules contain long polyolefin chains, are chemically reactive, and sensitive to ultraviolet light, high temperatures, and metal ions. After conventional dilution and spraying, they quickly oxidize and degrade, failing to maintain an effective active concentration to scavenge reactive oxygen species and induce anthocyanin synthase gene expression during the critical fruit coloring period. Furthermore, existing formulations lack synergistic targeted regulation of the reactive oxygen species scavenging system and the phenylpropanoid metabolic pathway, leading to disordered coloring gradients and poor uniformity. Summary of the Invention

[0005] In view of this, the present invention proposes a foliar fertilizer based on astaxanthin to promote color change and its application to solve the above problems.

[0006] The technical solution of this invention is implemented as follows:

[0007] A foliar fertilizer for promoting color change based on astaxanthin includes the following raw materials: astaxanthin, hydroxypropyl-β-cyclodextrin, reduced glutathione, L-antioxidant, L-phenylalanine, soybean lecithin, organosilicon surfactant, sea buckthorn seed meal extract, Sanguisorba officinalis root extract, and sodium iminodisuccinate.

[0008] Furthermore, this also includes pH buffer pairs.

[0009] Furthermore, the pH buffer pair is a citrate-sodium citrate buffer pair.

[0010] Furthermore, the contents of each component are as follows: astaxanthin 30-80g / L, hydroxypropyl-β-cyclodextrin 100-250g / L, reduced glutathione 2-5g / L, L-antiseptic acid 8-25g / L, L-phenylalanine 15-40g / L, soybean lecithin 2-15g / L, organosilicon surfactant 1-4g / L, sea buckthorn seed meal extract 0.5-2.0g / L, Sanguisorba officinalis root extract 2-5g / L, sodium iminodisuccinate 1-5g / L, citric acid-sodium citrate buffer to adjust pH to 5.0-5.5, and deionized water to a final volume of 1000L.

[0011] Furthermore, the sea buckthorn seed meal extract is prepared by the following method: The dried sea buckthorn seed meal after low-temperature pressing is pulverized and passed through an 80-100 mesh sieve to obtain sea buckthorn seed meal powder; the sea buckthorn seed meal powder is placed in a 60% ethanol aqueous solution at a material-to-liquid ratio of 1:10-12 (material-to-liquid ratio unit: kg / L), and extracted at 73-77℃ for 80-100 min. The extract is filtered, and the filter residue is extracted under the same conditions for 50-70 min. The two extracts are combined, and the combined extract is concentrated under reduced pressure at ≤45℃ to 30-35% of its original volume. Then, a 95% ethanol aqueous solution is added to bring the ethanol concentration in the system to 80%. The mixture is allowed to stand at 3-5℃ for 10-15 h for alcohol precipitation, followed by centrifugation at 10000-15000 rpm for 8-15 seconds. After 1 minute, collect the supernatant; add citric acid to adjust the pH to 4.0-4.5, use D101 macroporous adsorption resin, and load the sample at a flow rate of 1.5 BV / h. First, wash with 20% ethanol aqueous solution for 3 BV, then elute with 40% ethanol aqueous solution for 4 BV. Collect this eluent, pass it through a ceramic ultrafiltration membrane with a molecular weight cutoff of 1000 Da, collect the permeate, and then pass it through a nanofiltration membrane with a molecular weight cutoff of 300 Da, collect the retentate. Add 2-3% by volume of β-cyclodextrin to the retentate, concentrate under reduced pressure at ≤50℃ and vacuum degree of -0.08~-0.09Mpa to a solid content of 18-22%, and then spray dry at an inlet air temperature of 160-170℃ and an outlet air temperature of 70-80℃ to obtain sea buckthorn seed meal extract.

[0012] Furthermore, the Sanguisorba officinalis root extract is prepared by the following method: Fresh Sanguisorba officinalis roots are washed, sliced, and dried at ≤50℃ until the moisture content is ≤10%. The dried roots are then pulverized and passed through a 40-60 mesh sieve to obtain Sanguisorba officinalis root powder. The Sanguisorba officinalis root powder is added to deionized water at a material-to-liquid ratio of 1:7-9 (unit: kg / L). The mixture is heated to 45-50℃, and a heat-resistant α-amylase is added at a concentration of 0.2-0.3% of the Sanguisorba officinalis root powder mass. The mixture is kept at this temperature for 50-70 minutes for enzymatic hydrolysis, followed by heating to 90-95℃ to inactivate the enzyme for 8-10 minutes. n, to obtain enzymatically hydrolyzed Sanguisorba officinalis root; add the enzymatically hydrolyzed Sanguisorba officinalis root to a 50% ethanol aqueous solution at a volume ratio of 1:9-11, extract at 63-67℃ for 80-100 min, filter and collect the filtrate, extract the residue again under the same conditions for 55-65 min, combine the two extracts after extraction, then concentrate the extract under reduced pressure at ≤45℃ to 20-30% of the original volume, cool the concentrate to 9-11℃, adjust the pH to 4.5-5.0 with citric acid, and dropwise add a 1% gelatin aqueous solution while stirring. Add the gelatin aqueous solution to the concentrate, the amount of which is 8-12% of the concentrate volume. Let it stand for 2.0-2.5 hours, then centrifuge at 10000-12000 rpm for 10-15 minutes and collect the supernatant. Use AB-8 macroporous adsorption resin, adjust the pH of the supernatant to 4.0-4.5 with citric acid, and load the sample at a flow rate of 1.5 BV / h. First, wash with deionized water for 3 BV and discard it, then elute with 35% ethanol for 4 BV. Collect this eluent and concentrate it under reduced pressure at ≤45℃ to remove ethanol. The alcohol was saturated until no alcohol odor remained, and water was added to the original volume. The permeate was first passed through a ceramic ultrafiltration membrane with a molecular weight cutoff of 2000 Da and collected. The permeate was then passed through a nanofiltration membrane with a molecular weight cutoff of 300 Da and the retentate was collected. 2% sodium thiosulfate by volume was added to the retentate, and the mixture was stirred evenly. Nitrogen gas was introduced, and the mixture was concentrated under reduced pressure at ≤50℃ and a vacuum degree of -0.08 to -0.09 MPa to a solid content of 20-25%. Subsequently, the mixture was spray-dried at an inlet air temperature of 150-160℃ and an outlet air temperature of 65-72℃ to obtain the Sanguisorba officinalis root extract.

[0013] Furthermore, the above-mentioned method for preparing a color-promoting foliar fertilizer based on astaxanthin includes the following steps:

[0014] S1. Heat 60% of the total water volume of deionized water to 55-65℃, add hydroxypropyl-β-cyclodextrin and stir at 200-300 rpm until completely dissolved to obtain a hydroxypropyl-β-cyclodextrin solution. Purge dissolved oxygen with nitrogen gas. Disperse astaxanthin in anhydrous ethanol at a mass-to-volume ratio of 1:5-8 (g / mL) and shear at 8000-12000 rpm for 5-10 min to obtain an astaxanthin ethanol dispersion. Add the astaxanthin ethanol dispersion dropwise to the hydroxypropyl-β-cyclodextrin solution at a speed of ≥10000 rpm and shear for 90-150 min. The entire process, from the start of addition to the end of shearing and inclusion, is carried out in a dark environment to obtain the astaxanthin active component treated with hydroxypropyl-β-cyclodextrin inclusion. Then cool to 35-40℃.

[0015] S2. Under the condition of keeping warm at 35-40℃, add reduced glutathione, L-ascorbic acid and L-phenylalanine to the astaxanthin active component of shrimp treated with hydroxypropyl-β-cyclodextrin in sequence, stir until completely dissolved, cool to ≤30℃, add sea buckthorn seed meal extract and Sanguisorba officinalis root extract, stir until completely dissolved, and obtain a mixture.

[0016] S3. Take 5-10% of the total water volume as deionized water, heat it to 40-45℃, add soybean lecithin to it, and disperse it at 3000-5000 rpm for 10-15 min to obtain a lecithin pre-hydrated emulsion; add the lecithin pre-hydrated emulsion to the mixture, add sodium iminodisuccinate and citrate-sodium citrate buffer pair, stir evenly, add the remaining deionized water, and continue stirring at 100-150 rpm for 20-30 min to obtain the crude product solution;

[0017] S4. The crude product liquid is pressurized and circulated at 25-35℃ using a plate and frame filter. The first stage is filtered through a 200-mesh filter screen, and the second stage filtrate is filtered through a 5-10μm melt-blown filter element. The filtrate is then collected.

[0018] S5. Cool the filtrate to 20-25℃, and slowly add the organosilicon surfactant below the liquid surface while stirring at 80-120 rpm. After the addition is complete, continue stirring for 15-20 minutes. After stirring, let it stand for 30-60 minutes to defoam, and then fill it into a container to obtain a color-promoting foliar fertilizer based on astaxanthin.

[0019] Furthermore, the aforementioned astaxanthin-based foliar fertilizer for promoting fruit color change is applied to promote fruit color change. When using this foliar fertilizer, it should be diluted 800-1200 times and sprayed in the evening of a sunny day from 16:00 to 17:00 or on a cloudy day. The first spray should be carried out after the fruit enters the pit hardening stage until it begins to turn from green to white. The second spray should be carried out at an interval of 7-15 days. The fertilizer should be sprayed on the surface of the crop fruit and the adjacent functional leaves.

[0020] Furthermore, crops include grapes, tomatoes, citrus fruits, apples, and peppers.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1. This invention utilizes the synergistic combination of sea buckthorn seed meal extract and Sanguisorba officinalis root extract. The sea buckthorn seed meal extract, rich in proanthocyanidin B-type dimers, acts as an allosteric activator of chalcone isomerase, significantly increasing the metabolic flux of phenylpropane and accelerating the uniform synthesis of anthocyanins. Meanwhile, the gallotannins in the Sanguisorba officinalis root extract effectively inhibit anthocyanin-degrading enzymes, preventing the local degradation of synthesized pigments. The synergistic effect of these two ingredients, simultaneously promoting synthesis and inhibiting degradation, combined with the redox buffer of reduced glutathione / L-antioxidant to eliminate oxidative interference in metabolic pathways caused by reactive oxygen species bursts during the color-changing period, achieves a simultaneous improvement in minimizing color differences between the light and dark sides of the fruit surface and enhancing the uniformity of coloring across the entire fruit population, significantly increasing the marketable fruit yield.

[0023] 2. This invention overcomes the technical limitations of traditional color-changing agents that sacrifice quality for color appearance. By using L-phenylalanine as a direct precursor for anthocyanin synthesis and combining it with the upregulation of chalcone isomerase activity by sea buckthorn seed meal extract, metabolic flux is effectively directed to phenylpropane secondary metabolic pathways. This allows photosynthetic products to be preferentially used for the synergistic accumulation of anthocyanins and soluble sugars, resulting in deeper fruit coloring while simultaneously enriching sugars and flavor compounds. This fundamentally solves the industry problem of traditional chemical ripening agents causing rapid coloring but poor quality, achieving a fully ripe quality with harmonious color, aroma, and sweetness.

[0024] 3. This invention addresses the core technological bottleneck of astaxanthin molecules' high sensitivity to light, heat, and metal ions by constructing a triple stabilization and protection system consisting of an outer optical filter, a middle molecular inclusion layer, and an inner chemical removal layer. Hydroxypropyl-β-cyclodextrin forms a cage-like structure through molecular inclusion, significantly enhancing the water solubility of astaxanthin and physically isolating it from ultraviolet light quanta and oxygen; sodium iminodisuccinate chelates Fe in the water and leaf surface environment. 3+ Cu 2+ Mn 2+ The presence of transition metal ions greatly reduces the generation of hydroxyl radicals that attack astaxanthin in the metal-catalyzed Fenton reaction. Reduced glutathione, due to its low redox potential, preferentially reacts with free radicals before astaxanthin and is oxidized. At this time, L-antioxidant in the formula acts as a reducing agent to reduce it back to its original state, thereby significantly prolonging the effective action time of astaxanthin. Detailed Implementation

[0025] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention.

[0026] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0027] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0028] Example 1

[0029] A foliar fertilizer for promoting color change based on astaxanthin comprises the following raw materials: astaxanthin, hydroxypropyl-β-cyclodextrin, reduced glutathione, L-antiseptic acid, L-phenylalanine, soybean lecithin, organosilicon surfactant, sea buckthorn seed meal extract, Sanguisorba officinalis root extract, sodium iminodisuccinate, and a pH buffer pair. The organosilicon surfactant is a polyether-modified trisiloxane, and the pH buffer pair is a citrate-sodium citrate buffer pair.

[0030] The contents of each component are as follows: astaxanthin 30g / L, hydroxypropyl-β-cyclodextrin 100g / L, reduced glutathione 2g / L, L-antiseptic acid 8g / L, L-phenylalanine 15g / L, soybean lecithin 2g / L, organosilicon surfactant 1g / L, sea buckthorn seed meal extract 0.5g / L, Sanguisorba officinalis root extract 2g / L, sodium iminodisuccinate 1g / L, pH adjusted to 5.0 by citrate-sodium citrate buffer pair, and deionized water brought to a final volume of 1000L.

[0031] The sea buckthorn seed meal extract was prepared by the following method: The dried sea buckthorn seed meal after low-temperature pressing was pulverized and passed through an 80-mesh sieve to obtain sea buckthorn seed meal powder; the sea buckthorn seed meal powder was placed in a 60% ethanol aqueous solution at a material-to-liquid ratio of 1:10 (material-to-liquid ratio unit: kg / L), and extracted at 73℃ for 100 min. The extract was filtered, and the filter residue was extracted under the same conditions for 70 min. The two extracts were combined, and the combined extract was concentrated under reduced pressure at 45℃ to 35% of its original volume. Then, a 95% ethanol aqueous solution was added to bring the ethanol concentration in the system to 80%. The mixture was allowed to stand at 3℃ for 10 h for alcohol precipitation, followed by centrifugation at 10000 rpm for 15 min. The supernatant was prepared by adding citric acid to adjust the pH to 4.0. A D101 macroporous adsorption resin was used, and the sample was loaded at a flow rate of 1.5 BV / h. The eluent was first washed with 20% ethanol aqueous solution for 3 BV, then eluted with 40% ethanol aqueous solution for 4 BV. This eluent was collected and passed through a ceramic ultrafiltration membrane with a molecular weight cutoff of 1000 Da to collect the permeate. Then, it was passed through a nanofiltration membrane with a molecular weight cutoff of 300 Da to collect the retentate. 2% (by volume) of β-cyclodextrin was added to the retentate, and the mixture was concentrated under reduced pressure at 50℃ and a vacuum of -0.08 MPa to a solid content of 22%. Subsequently, it was spray-dried at an inlet air temperature of 160℃ and an outlet air temperature of 70℃ to obtain the sea buckthorn seed meal extract.

[0032] The Sanguisorba officinalis root extract was prepared by the following method: Fresh Sanguisorba officinalis roots were washed, sliced, and dried at 50℃ to a moisture content of 10%. The dried roots were then pulverized and passed through a 40-mesh sieve to obtain Sanguisorba officinalis root powder. The powder was added to deionized water at a ratio of 1:7 (unit: kg / L), heated to 45℃, and thermoresistant α-amylase (0.2% of the powder's mass) was added. The mixture was kept at this temperature for 70 minutes for enzymatic hydrolysis, followed by inactivation at 90℃ for 10 minutes to obtain enzymatically hydrolyzed Sanguisorba officinalis root. The hydrolyzed root was added to a 50% ethanol aqueous solution at a volume ratio of 1:9, and extracted at 63℃ for 100 minutes. The filtrate was collected, and the residue was extracted again under the same conditions for 65 minutes. After extraction, the two extracts were combined, and the extract was concentrated under reduced pressure at 45℃ to 30% of its original volume. The concentrate was cooled to 9℃, and the pH was adjusted to 4.5 with citric acid. A 1% gelatin aqueous solution was added dropwise to the concentrate with stirring. In this process, the amount of gelatin aqueous solution added is 8% of the volume of the concentrated solution. After standing for 2.5 hours, it is centrifuged at 10,000 rpm for 15 minutes, and the supernatant is collected. AB-8 macroporous adsorption resin is used, and the pH of the supernatant is adjusted to 4.0 with citric acid. The sample is loaded at a flow rate of 1.5 BV / h. First, it is washed with deionized water for 3 BV and discarded. Then, it is eluted with 35% ethanol for 4 BV. This eluent is collected, and the eluent is concentrated under reduced pressure at 45°C to remove ethanol until no alcohol is present. The sample was diluted with water to its original volume, and then passed through a ceramic ultrafiltration membrane with a molecular weight cutoff of 2000 Da to collect the permeate. The permeate was then passed through a nanofiltration membrane with a molecular weight cutoff of 300 Da to collect the retentate. 2% sodium thiosulfate was added to the retentate and stirred until homogeneous. Nitrogen gas was introduced, and the sample was concentrated under reduced pressure at 50°C and a vacuum of -0.08 MPa to a solid content of 25%. Subsequently, the sample was spray-dried at an inlet air temperature of 150°C and an outlet air temperature of 65°C to obtain the Sanguisorba officinalis root extract.

[0033] The above-mentioned method for preparing a color-promoting foliar fertilizer based on astaxanthin includes the following steps:

[0034] S1. Heat 60% of the total water volume of deionized water to 55°C, add hydroxypropyl-β-cyclodextrin and stir at 200 rpm until completely dissolved to obtain a hydroxypropyl-β-cyclodextrin solution. Purge dissolved oxygen with nitrogen gas. Disperse astaxanthin in anhydrous ethanol at a mass-to-volume ratio of 1:5 (g / mL) and shear at 8000 rpm for 10 min to obtain an astaxanthin ethanol dispersion. Add the astaxanthin ethanol dispersion dropwise to the hydroxypropyl-β-cyclodextrin solution at 10000 rpm and shear for 150 min. The entire process, from the start of addition to the end of shearing and inclusion, is carried out in a dark environment to obtain the astaxanthin active component treated with hydroxypropyl-β-cyclodextrin inclusion. Then cool to 35°C.

[0035] S2. Under the condition of keeping warm at 35℃, reduced glutathione, L-ascorbic acid and L-phenylalanine are added sequentially to the astaxanthin active component of shrimp treated with hydroxypropyl-β-cyclodextrin. The mixture is stirred until completely dissolved, cooled to 30℃, and sea buckthorn seed meal extract and Sanguisorba officinalis root extract are added. The mixture is stirred until completely dissolved to obtain a mixture.

[0036] S3. Take 5% of the total water volume as deionized water, heat it to 40℃, add soybean lecithin to it, and disperse it at 3000 rpm for 15 min to obtain lecithin pre-hydrated emulsion; add the lecithin pre-hydrated emulsion to the mixture, add sodium iminodisuccinate and citrate-sodium citrate buffer pair, stir evenly, add the remaining deionized water, and continue stirring at 100 rpm for 30 min to obtain crude product solution;

[0037] S4. The crude product liquid is pressurized and circulated at 25°C using a plate and frame filter. The first stage is filtered through a 200-mesh filter screen, and the second stage filtrate is filtered through a 5μm melt-blown filter element. The filtrate is then collected.

[0038] S5. Cool the filtrate to 20°C, and slowly add the organosilicon surfactant below the liquid surface while stirring at 800 rpm. After the addition is complete, continue stirring for 20 minutes. After stirring, let it stand for 30 minutes to defoam, and then fill it into a container to obtain a color-promoting foliar fertilizer based on astaxanthin.

[0039] The above-mentioned astaxanthin-based foliar fertilizer for promoting fruit color change is used to promote fruit color change. The foliar fertilizer is diluted 800 times and sprayed at 16:00 on a sunny evening. The first spray is carried out after the fruit enters the hardening stage until it begins to turn from green to white. The second spray is carried out after 7 days. The fertilizer is sprayed on the surface of the fruit and the adjacent functional leaves. Citrus is selected as the crop.

[0040] Example 2

[0041] A foliar fertilizer for promoting color change based on astaxanthin comprises the following raw materials: astaxanthin, hydroxypropyl-β-cyclodextrin, reduced glutathione, L-antiseptic acid, L-phenylalanine, soybean lecithin, organosilicon surfactant, sea buckthorn seed meal extract, Sanguisorba officinalis root extract, sodium iminodisuccinate, and a pH buffer pair. The organosilicon surfactant is a polyether-modified trisiloxane, and the pH buffer pair is a citrate-sodium citrate buffer pair.

[0042] The contents of each component are as follows: astaxanthin 55g / L, hydroxypropyl-β-cyclodextrin 175g / L, reduced glutathione 3.5g / L, L-antiseptic acid 18.5g / L, L-phenylalanine 27.5g / L, soybean lecithin 8.5g / L, organosilicon surfactant 2.5g / L, sea buckthorn seed meal extract 1.2g / L, Sanguisorba officinalis root extract 3.5g / L, sodium iminodisuccinate 3g / L, pH adjusted to 5.2 by citrate-sodium citrate buffer pair, and volume brought to 1000L with deionized water.

[0043] The sea buckthorn seed meal extract was prepared by the following method: The dried sea buckthorn seed meal after low-temperature pressing was pulverized and passed through a 90-mesh sieve to obtain sea buckthorn seed meal powder; the sea buckthorn seed meal powder was placed in a 60% ethanol aqueous solution at a material-to-liquid ratio of 1:11 (material-to-liquid ratio unit: kg / L), and extracted at 75℃ for 90 min. The extract was filtered, and the filter residue was extracted under the same conditions for 60 min. The two extracts were combined, and the combined extract was concentrated under reduced pressure at 40℃ to 33% of its original volume. Then, a 95% ethanol aqueous solution was added to bring the ethanol concentration in the system to 80%. The mixture was allowed to stand at 4℃ for 12.5 h for alcohol precipitation, followed by centrifugation at 12500 rpm for 12 min. The supernatant was collected. The solution was prepared by adding citric acid to adjust the pH to 4.0-4.5, using D101 macroporous adsorption resin, and loading the sample at a flow rate of 1.5 BV / h. The sample was first washed with 20% ethanol aqueous solution for 3 BV, then eluted with 40% ethanol aqueous solution for 4 BV. This eluent was collected and passed through a ceramic ultrafiltration membrane with a molecular weight cutoff of 1000 Da to collect the permeate. Then, it was passed through a nanofiltration membrane with a molecular weight cutoff of 300 Da to collect the retentate. 2.5% by volume of β-cyclodextrin was added to the retentate, and the solution was concentrated under reduced pressure at 45℃ and a vacuum of -0.08 MPa to a solid content of 20%. Subsequently, it was spray-dried at an inlet air temperature of 165℃ and an outlet air temperature of 75℃ to obtain the sea buckthorn seed meal extract.

[0044] The Sanguisorba officinalis root extract was prepared by the following method: Fresh Sanguisorba officinalis roots were washed, sliced, and dried at 45℃ to a moisture content of 10%. The dried roots were then pulverized through a 50-mesh sieve to obtain Sanguisorba officinalis root powder. The powder was added to deionized water at a ratio of 1:8 (unit: kg / L), heated to 48℃, and thermoresistant α-amylase (0.2% of the powder's mass) was added. The mixture was kept at this temperature for 60 minutes for enzymatic hydrolysis, followed by inactivation at 93℃ for 9 minutes to obtain enzymatically hydrolyzed Sanguisorba officinalis root. The hydrolyzed root was added to a 50% ethanol aqueous solution at a volume ratio of 1:10, and extracted at 65℃ for 90 minutes. The filtrate was collected, and the residue was extracted again under the same conditions for 60 minutes. After extraction, the two extracts were combined, and the extract was concentrated under reduced pressure at 40℃ to 25% of its original volume. The concentrate was cooled to 10℃, and the pH was adjusted to 4.8 with citric acid. A 1% gelatin aqueous solution was added dropwise to the concentrate with stirring. In this process, the amount of gelatin aqueous solution added is 10% of the volume of the concentrated solution. After standing for 2.2 hours, it is centrifuged at 11,000 rpm for 12 minutes, and the supernatant is collected. AB-8 macroporous adsorption resin is used, and the pH of the supernatant is adjusted to 4.2 with citric acid. The sample is loaded at a flow rate of 1.5 BV / h. First, it is washed with deionized water for 3 BV and discarded. Then, it is eluted with 35% ethanol for 4 BV. This eluent is collected, and the eluent is concentrated under reduced pressure at 40°C to remove ethanol until no alcohol is present. The sample was diluted with water to its original volume, and then passed through a ceramic ultrafiltration membrane with a molecular weight cutoff of 2000 Da to collect the permeate. The permeate was then passed through a nanofiltration membrane with a molecular weight cutoff of 300 Da to collect the retentate. 2% sodium thiosulfate was added to the retentate and stirred until homogeneous. Nitrogen gas was introduced, and the sample was concentrated under reduced pressure at 45°C and a vacuum of -0.08 MPa to a solid content of 22%. Subsequently, the sample was spray-dried at an inlet air temperature of 155°C and an outlet air temperature of 68°C to obtain the Sanguisorba officinalis root extract.

[0045] The above-mentioned method for preparing a color-promoting foliar fertilizer based on astaxanthin includes the following steps:

[0046] S1. Deionized water (60% of the total water volume) was heated to 60°C, and hydroxypropyl-β-cyclodextrin was added and stirred at 250 rpm until completely dissolved to obtain a hydroxypropyl-β-cyclodextrin solution. Nitrogen gas was then introduced to replace dissolved oxygen. Astaxanthin was dispersed in anhydrous ethanol at a mass-to-volume ratio of 1:7 (g / mL), and sheared at 10,000 rpm for 8 min to obtain an astaxanthin ethanol dispersion. The astaxanthin ethanol dispersion was then added dropwise to the hydroxypropyl-β-cyclodextrin solution at 11,000 rpm and sheared for 120 min. The entire process, from the start of the addition to the end of the shearing inclusion, was carried out under light-protected conditions to obtain the astaxanthin active component treated with hydroxypropyl-β-cyclodextrin inclusion. The solution was then cooled to 38°C.

[0047] S2. Under the condition of keeping warm at 38℃, reduced glutathione, L-ascorbic acid and L-phenylalanine are added sequentially to the astaxanthin active component of shrimp treated with hydroxypropyl-β-cyclodextrin. The mixture is stirred until completely dissolved, cooled to 30℃, and sea buckthorn seed meal extract and Sanguisorba officinalis root extract are added. The mixture is stirred until completely dissolved to obtain a mixed solution.

[0048] S3. Take 8% of the total water volume as deionized water, heat it to 42℃, add soybean lecithin to it, and disperse it at 4000 rpm for 12 min to obtain lecithin pre-hydrated emulsion; add the lecithin pre-hydrated emulsion to the mixture, add sodium iminodisuccinate and citrate-sodium citrate buffer pair, stir evenly, add the remaining deionized water, and continue stirring at 120 rpm for 25 min to obtain crude product solution;

[0049] S4. The crude product liquid is pressurized and circulated at 30°C using a plate and frame filter. The first stage is filtered through a 200-mesh filter screen, and the second stage filtrate is filtered through an 8μm melt-blown filter element. The filtrate is then collected.

[0050] S5. Cool the filtrate to 22℃, and slowly add the organosilicon surfactant below the liquid surface while stirring at 100 rpm. After the addition is complete, continue stirring for 18 minutes. After stirring, let it stand for 45 minutes to defoam, and then fill it to obtain a color-promoting foliar fertilizer based on astaxanthin.

[0051] The above-mentioned astaxanthin-based foliar fertilizer for promoting fruit color change is used to promote fruit color change. The foliar fertilizer is diluted 1000 times and sprayed at 17:00 on a sunny evening. The first spray is carried out after the fruit enters the hardening stage until it begins to turn from green to white. The second spray is carried out after 10 days. The fertilizer is sprayed on the surface of the fruit and the adjacent functional leaves. Citrus is one of the selected crops.

[0052] Example 3

[0053] A foliar fertilizer for promoting color change based on astaxanthin comprises the following raw materials: astaxanthin, hydroxypropyl-β-cyclodextrin, reduced glutathione, L-antiseptic acid, L-phenylalanine, soybean lecithin, organosilicon surfactant, sea buckthorn seed meal extract, Sanguisorba officinalis root extract, sodium iminodisuccinate, and a pH buffer pair. The organosilicon surfactant is a polyether-modified trisiloxane, and the pH buffer pair is a citrate-sodium citrate buffer pair.

[0054] The contents of each component are as follows: astaxanthin 80g / L, hydroxypropyl-β-cyclodextrin 250g / L, reduced glutathione 5g / L, L-antiseptic acid 25g / L, L-phenylalanine 40g / L, soybean lecithin 15g / L, organosilicon surfactant 4g / L, sea buckthorn seed meal extract 2.0g / L, Sanguisorba officinalis root extract 5g / L, sodium iminodisuccinate 5g / L, pH adjusted to 5.5 by citrate-sodium citrate buffer pair, and volume brought to 1000L with deionized water.

[0055] The sea buckthorn seed meal extract was prepared by the following method: The dried sea buckthorn seed meal after low-temperature pressing was pulverized and passed through a 100-mesh sieve to obtain sea buckthorn seed meal powder; the sea buckthorn seed meal powder was placed in a 60% ethanol aqueous solution at a material-to-liquid ratio of 1:12 (material-to-liquid ratio unit: kg / L), and extracted at 77℃ for 80 min. The extract was filtered, and the filter residue was extracted under the same conditions for 60 min. The two extracts were combined, and the combined extract was concentrated under reduced pressure at 40℃ to 33% of its original volume. Then, a 95% ethanol aqueous solution was added to bring the ethanol concentration in the system to 80%. The mixture was allowed to stand at 4℃ for 12 h for alcohol precipitation, followed by centrifugation at 12000 rpm for 12 min. The supernatant was prepared by adding citric acid to adjust the pH to 4.2. A D101 macroporous adsorption resin was used, and the sample was loaded at a flow rate of 1.5 BV / h. The eluent was first washed with 20% ethanol aqueous solution for 3 BV, then eluted with 40% ethanol aqueous solution for 4 BV. This eluent was collected and passed through a ceramic ultrafiltration membrane with a molecular weight cutoff of 1000 Da to collect the permeate. Then, it was passed through a nanofiltration membrane with a molecular weight cutoff of 300 Da to collect the retentate. 3% (by volume) of β-cyclodextrin was added to the retentate, and the mixture was concentrated under reduced pressure at 45℃ and a vacuum of -0.09 MPa to a solid content of 18%. Subsequently, it was spray-dried at an inlet air temperature of 170℃ and an outlet air temperature of 80℃ to obtain the sea buckthorn seed meal extract.

[0056] The Sanguisorba officinalis root extract was prepared by the following method: Fresh Sanguisorba officinalis roots were washed, sliced, and dried at 45℃ to a moisture content of 10%. The dried roots were then pulverized through a 60-mesh sieve to obtain Sanguisorba officinalis root powder. The powder was added to deionized water at a ratio of 1:9 (unit: kg / L), heated to 50℃, and 0.3% (by weight) of thermoresistant α-amylase was added. The mixture was kept at this temperature for 50 min for enzymatic hydrolysis, followed by inactivation at 95℃ for 8 min to obtain enzymatically hydrolyzed Sanguisorba officinalis root. The hydrolyzed root was added to a 50% ethanol aqueous solution at a volume ratio of 1:11, and extracted at 67℃ for 80 min. The filtrate was collected, and the residue was extracted again under the same conditions for 55 min. After extraction, the two extracts were combined, and the extract was concentrated under reduced pressure at 40℃ to 25% of its original volume. The concentrate was cooled to 11℃, and the pH was adjusted to 5.0 with citric acid. A 1% gelatin aqueous solution was added dropwise to the concentrate with stirring. In this process, the amount of gelatin aqueous solution added was 12% of the volume of the concentrate. After standing for 2.0 h, it was centrifuged at 12000 rpm for 10 min, and the supernatant was collected. AB-8 macroporous adsorption resin was used, and the pH of the supernatant was adjusted to 4.5 with citric acid. The sample was loaded at a flow rate of 1.5 BV / h. First, it was washed with deionized water for 3 BV and discarded. Then, it was eluted with 35% ethanol for 4 BV. This eluent was collected, and the eluent was concentrated under reduced pressure at 40℃ to remove ethanol until no alcohol was present. The sample was diluted with water to its original volume, and then passed through a ceramic ultrafiltration membrane with a molecular weight cutoff of 2000 Da to collect the permeate. The permeate was then passed through a nanofiltration membrane with a molecular weight cutoff of 300 Da to collect the retentate. 2% sodium thiosulfate was added to the retentate and stirred until homogeneous. Nitrogen gas was introduced, and the sample was concentrated under reduced pressure at 45°C and a vacuum of -0.09 MPa to a solid content of 20%. Subsequently, the sample was spray-dried at an inlet air temperature of 160°C and an outlet air temperature of 72°C to obtain the Sanguisorba officinalis root extract.

[0057] The above-mentioned method for preparing a color-promoting foliar fertilizer based on astaxanthin includes the following steps:

[0058] S1. Heat 60% of the total water volume of deionized water to 65°C, add hydroxypropyl-β-cyclodextrin and stir at 300 rpm until completely dissolved to obtain a hydroxypropyl-β-cyclodextrin solution. Purge dissolved oxygen with nitrogen gas. Disperse astaxanthin in anhydrous ethanol at a mass-to-volume ratio of 1:8 (g / mL) and shear at 12000 rpm for 5 min to obtain an astaxanthin ethanol dispersion. Drop the astaxanthin ethanol dispersion into the hydroxypropyl-β-cyclodextrin solution at 12000 rpm and shear for 90 min. The entire process, from the start of dropwise addition to the end of shearing and inclusion, is carried out in a light-protected environment to obtain the astaxanthin active component treated with hydroxypropyl-β-cyclodextrin inclusion. Then, cool to 40°C.

[0059] S2. Under the condition of keeping warm at 40℃, reduced glutathione, L-ascorbic acid and L-phenylalanine are added sequentially to the astaxanthin active component of shrimp treated with hydroxypropyl-β-cyclodextrin. The mixture is stirred until completely dissolved, cooled to 30℃, and sea buckthorn seed meal extract and Sanguisorba officinalis root extract are added. The mixture is stirred until completely dissolved to obtain a mixture.

[0060] S3. Take 10% of the total water volume as deionized water, heat it to 45℃, add soybean lecithin to it, and disperse it at 5000 rpm for 10 min to obtain lecithin pre-hydrated emulsion; add the lecithin pre-hydrated emulsion to the mixture, add sodium iminodisuccinate and citrate-sodium citrate buffer pair, stir evenly, add the remaining deionized water, and continue stirring at 150 rpm for 20 min to obtain crude product solution;

[0061] S4. The crude product liquid is pressurized and circulated at 35°C using a plate and frame filter. The first stage is filtered through a 200-mesh filter screen, and the second stage filtrate is filtered through a 10μm melt-blown filter element. The filtrate is then collected.

[0062] S5. Cool the filtrate to 25°C, and slowly add the organosilicon surfactant below the liquid surface while stirring at 120 rpm. After the addition is complete, continue stirring for 15 minutes. After stirring, let it stand for 60 minutes to defoam, and then fill it to obtain a color-promoting foliar fertilizer based on astaxanthin.

[0063] The above-mentioned astaxanthin-based foliar fertilizer for promoting fruit color change is used to promote fruit color change. The fertilizer is diluted 1200 times and sprayed on a cloudy day. The first spray is carried out after the fruit enters the hardening stage until it begins to turn from green to white. The second spray is carried out 15 days later. The fertilizer is sprayed on the surface of the fruit and the adjacent functional leaves. Citrus is one of the selected crops.

[0064] Comparative Example 1

[0065] The difference between this comparative example and Example 2 is that the raw materials do not contain sea buckthorn seed meal extract.

[0066] Comparative Example 2

[0067] The difference between this comparative example and Example 2 is that the raw materials do not contain Sanguisorba officinalis root extract.

[0068] Comparative Example 3

[0069] The difference between this comparative example and Example 2 is that the raw materials do not contain sodium iminodisuccinate.

[0070] Comparative Example 4

[0071] The difference between this comparative example and Example 2 is that the raw materials do not contain reduced glutathione.

[0072] Comparative Example 5

[0073] The difference between this comparative example and Example 2 is that the raw materials do not contain L-antioxidant.

[0074] Comparative Example 6

[0075] The difference between this comparative example and Example 2 is that a commercially available ethephon-based color-changing agent was used instead.

[0076] field trials

[0077] The experiment selected 10-year-old Newhall navel orange trees in their prime fruiting period and conducted in orchards with flat terrain and uniform soil fertility in the main citrus-producing area of ​​southern Jiangxi. Ten treatment groups were established: Examples 1-3, Comparative Examples 1-6, and a blank control. The blank control group was sprayed with an equal volume of purified water. Each treatment group had three replicates, resulting in 30 plots, with three trees in each plot, using a randomized block design. Foliar fertilizers prepared according to Examples 1-3 and Comparative Examples 1-5 were sprayed. Samples were collected one day before spraying, 10 days after the second spraying, and at fruit harvest. Two fruits were collected from each tree in each of the four cardinal directions (east, south, west, and north). Measurements were completed on the same day after sampling. Color uniformity and fruit quality were determined. Color uniformity was tested as follows: Samples were harvested 10 days after the second spray. The a* value was measured at four equally spaced points on the equatorial plane of the fruit using a handheld colorimeter. The coefficient of variation (CV) of the a* value within a single fruit was calculated to evaluate the uniformity of color difference between the shading and shading sides of the fruit. The average CV of each group was taken. The results are shown in Table 1. The CV of a* value was calculated using the following formula: CV per fruit = Standard deviation of a* value per fruit ÷ Average a* value per fruit × 100%. Fruit quality was tested as follows: At harvest, soluble solids were measured using a handheld refractometer, titratable acid was determined using NaOH titration, and total sugar content was determined using the DNS colorimetric method. The average values ​​were taken. The results are shown in Table 1.

[0078] Table 1

[0079]

[0080] A smaller coefficient of variation (a*) indicates more uniform coloring on both the light and dark sides of the fruit. The a* coefficient of variation in Example 2 was only 8.2%, significantly better than Comparative Examples 1-5 and the blank control group. The a* coefficient of variation in Comparative Example 1 increased to 18.7%, because the B-type proanthocyanidin dimer in the sea buckthorn seed meal extract activates chalcone isomerase through allosteric transformation, which is a key rate-limiting enzyme regulator ensuring uniform anthocyanin synthesis. The a* coefficient of variation in Comparative Example 2 was 15.6%, significantly higher than Example 2, because the Sanguisorba officinalis root extract effectively prevented mottled coloring caused by local anthocyanin degradation by inhibiting anthocyanin-β-glucosidase activity. The a* coefficient of variation in Comparative Example 3 was 13.2%, because the lack of a metal ion chelating agent led to aggravated local oxidative degradation of astaxanthin after spraying due to the Fenton reaction. The coefficients of variation (a*) for Comparative Examples 4 and 5 were as high as 14.8% and 16.3%, respectively. This is because the lack of L-aminophenol and the absence of reduced glutathione (a redox buffer) led to the gradual deactivation of astaxanthin in the light and heat environment, resulting in a significant decrease in uniformity. The coefficient of variation for the a* value in Comparative Example 6 was as high as 22.4%, because forced ripening with chemical hormones easily caused significant color differences and severe mottled appearance in the fruit. The coefficient of variation for the a* value in the blank control group was as high as 31.5%, indicating extremely uneven natural color change.

[0081] The sugar-to-acid ratio is a core indicator for measuring the intensity of fruit flavor; a higher ratio indicates a more harmonious taste and a balanced sweet and sour flavor. Example 2 achieved a sugar-to-acid ratio of 20.3, significantly better than Comparative Example 6 (11.5) and the blank control (9.0). The total sugar content of Example 2 reached 12.4%, a 36.3% increase compared to the ethephon group (9.1%). This is because the present invention achieves a true color-changing effect by simultaneously increasing color and sugar content through multiple mechanisms, including scavenging reactive oxygen species, activating the phenylpropanoid metabolic pathway, and inhibiting anthocyanin-degrading enzymes, rather than the short-term coloring effect of the false ripening seen in ethephon-based products. Comparative Examples 1 and 2 had sugar-to-acid ratios of 14.2 and 15.5, respectively. This is because the absence of sea buckthorn and Sanguisorba officinalis extracts not only affected the uniformity of color change but also interfered with the normal diversion of carbon to secondary metabolism, resulting in insufficient accumulation of dry matter and sugar.

[0082] 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 foliar fertilizer for promoting color change based on astaxanthin, characterized in that, The ingredients include: astaxanthin, hydroxypropyl-β-cyclodextrin, reduced glutathione, L-antioxidant, L-phenylalanine, soybean lecithin, organosilicon surfactant, sea buckthorn seed meal extract, Sanguisorba officinalis root extract, and sodium iminodisuccinate.

2. The astaxanthin-based foliar fertilizer for promoting color change as described in claim 1, characterized in that, It also includes a pH buffer pair, which is a citrate-sodium citrate buffer pair.

3. The astaxanthin-based foliar fertilizer for promoting color change as described in claim 2, characterized in that, The contents of each component are as follows: astaxanthin 30-80g / L, hydroxypropyl-β-cyclodextrin 100-250g / L, reduced glutathione 2-5g / L, L-antiseptic acid 8-25g / L, L-phenylalanine 15-40g / L, soybean lecithin 2-15g / L, organosilicon surfactant 1-4g / L, sea buckthorn seed meal extract 0.5-2.0g / L, Sanguisorba officinalis root extract 2-5g / L, sodium iminodisuccinate 1-5g / L, citric acid-sodium citrate buffer to adjust pH to 5.0-5.5, and deionized water to a final volume of 1000L.

4. The astaxanthin-based foliar fertilizer for promoting color change as described in claim 3, characterized in that, The sea buckthorn seed meal extract is prepared by the following method: dried sea buckthorn seed meal after low-temperature pressing is pulverized and passed through an 80-100 mesh sieve to obtain sea buckthorn seed meal powder; the sea buckthorn seed meal powder is placed in a 60% ethanol aqueous solution at a material-to-liquid ratio of 1:10-12 (material-to-liquid ratio unit: kg / L), and extracted at 73-77℃ for 80-100 min; the extract is filtered, and the filter residue is extracted under the same conditions for 50-70 min; the two extracts are combined, and the combined extract is concentrated under reduced pressure at ≤45℃ to 30-35% of its original volume; then a 95% ethanol aqueous solution is added to bring the ethanol concentration in the system to 80%; the mixture is allowed to stand at 3-5℃ for 10-15 h for alcohol precipitation, followed by centrifugation at 10000-15000 rpm for 8-15 min. Take the supernatant; adjust the pH to 4.0-4.5 with citric acid; use D101 macroporous adsorption resin and load the sample at a flow rate of 1.5 BV / h; first wash with 20% ethanol aqueous solution for 3 BV, then elute with 40% ethanol aqueous solution for 4 BV, collect this eluent; first pass it through a ceramic ultrafiltration membrane with a molecular weight cutoff of 1000 Da, collect the permeate, then pass it through a nanofiltration membrane with a molecular weight cutoff of 300 Da, collect the retentate; add 2-3% by volume of β-cyclodextrin to the retentate, concentrate under reduced pressure at ≤50℃ and vacuum degree -0.08~-0.09Mpa to a solid content of 18-22%, then spray dry at an inlet air temperature of 160-170℃ and an outlet air temperature of 70-80℃ to obtain sea buckthorn seed meal extract.

5. A foliar fertilizer for promoting color change based on astaxanthin as described in claim 3, characterized in that, The *Sanguisorba officinalis* root extract is prepared by the following method: Fresh *Sanguisorba officinalis* roots are washed, sliced, and dried at ≤50℃ until the moisture content is ≤10%. The dried roots are then pulverized and passed through a 40-60 mesh sieve to obtain *Sanguisorba officinalis* root powder. The powder is added to deionized water at a ratio of 1:7-9 (unit: kg / L), heated to 45-50℃, and then heat-resistant α-amylase is added at a concentration of 0.2-0.3% of the *Sanguisorba officinalis* root powder mass. The mixture is kept at this temperature for 50-70 minutes for enzymatic hydrolysis, followed by inactivation at 90-95℃ for 8-10 minutes to obtain the final product. Enzymatically hydrolyze the roots of Sanguisorba officinalis; add the enzymatically hydrolyzed Sanguisorba officinalis root to a 50% ethanol aqueous solution at a volume ratio of 1:9-11, and extract at 63-67℃ for 80-100 min. Filter and collect the filtrate. Extract the residue again under the same conditions for 55-65 min. Combine the two extracts after extraction, and then concentrate the extract under reduced pressure at ≤45℃ to 20-30% of the original volume. Cool the concentrate to 9-11℃, adjust the pH to 4.5-5.0 with citric acid, and add a 1% gelatin aqueous solution dropwise with stirring. In the concentrate, the amount of gelatin aqueous solution added is 8-12% of the concentrate volume. After standing for 2.0-2.5 hours, centrifuge at 10000-12000 rpm for 10-15 minutes and collect the supernatant. Using AB-8 macroporous adsorption resin, adjust the pH of the supernatant to 4.0-4.5 with citric acid. Load the sample at a flow rate of 1.5 BV / h. First, wash with deionized water for 3 BV and discard the water. Then, elute with 35% ethanol for 4 BV, collecting this eluent. Concentrate the eluent under reduced pressure at ≤45℃ to remove the ethanol. The solution is brought to a complete boil until no alcohol odor is detected. Water is added to the original volume. The solution is first passed through a ceramic ultrafiltration membrane with a molecular weight cutoff of 2000 Da to collect the permeate. The permeate is then passed through a nanofiltration membrane with a molecular weight cutoff of 300 Da to collect the retentate. 2% sodium thiosulfate by volume is added to the retentate and stirred until homogeneous. Nitrogen gas is introduced and the solution is concentrated under reduced pressure at ≤50℃ and a vacuum degree of -0.08 to -0.09 MPa to a solid content of 20-25%. Subsequently, the solution is spray-dried at an inlet air temperature of 150-160℃ and an outlet air temperature of 65-72℃ to obtain the Sanguisorba officinalis root extract.

6. A method for preparing a foliar fertilizer based on astaxanthin to promote color change, as described in any one of claims 3-5, characterized in that, Includes the following steps: S1. Heat 60% of the total water volume of deionized water to 55-65℃, add hydroxypropyl-β-cyclodextrin and stir at 200-300 rpm until completely dissolved to obtain a hydroxypropyl-β-cyclodextrin solution. Purge dissolved oxygen with nitrogen gas. Disperse astaxanthin in anhydrous ethanol at a mass-to-volume ratio of 1:5-8 (g / mL) and shear at 8000-12000 rpm for 5-10 min to obtain an astaxanthin ethanol dispersion. Add the astaxanthin ethanol dispersion dropwise to the hydroxypropyl-β-cyclodextrin solution at a speed of ≥10000 rpm and shear for 90-150 min. The entire process, from the start of addition to the end of shearing and inclusion, is carried out in a dark environment to obtain the astaxanthin active component treated with hydroxypropyl-β-cyclodextrin inclusion. Then cool to 35-40℃. S2. Under the condition of keeping warm at 35-40℃, add reduced glutathione, L-ascorbic acid and L-phenylalanine to the astaxanthin active component of shrimp treated with hydroxypropyl-β-cyclodextrin in sequence, stir until completely dissolved, cool to ≤30℃, add sea buckthorn seed meal extract and Sanguisorba officinalis root extract, stir until completely dissolved, and obtain a mixture. S3. Take 5-10% of the total water volume as deionized water, heat it to 40-45℃, add soybean lecithin to it, and disperse it at 3000-5000 rpm for 10-15 min to obtain a lecithin pre-hydrated emulsion; add the lecithin pre-hydrated emulsion to the mixture, add sodium iminodisuccinate and citrate-sodium citrate buffer pair, stir evenly, add the remaining deionized water, and continue stirring at 100-150 rpm for 20-30 min to obtain the crude product solution; S4. The crude product liquid is pressurized and circulated at 25-35℃ using a plate and frame filter. The first stage is filtered through a 200-mesh filter screen, and the second stage filtrate is filtered through a 5-10μm melt-blown filter element. The filtrate is then collected. S5. Cool the filtrate to 20-25℃, and slowly add the organosilicon surfactant below the liquid surface while stirring at 80-120 rpm. After the addition is complete, continue stirring for 15-20 minutes. After stirring, let it stand for 30-60 minutes to defoam, and then fill it into a container to obtain a color-promoting foliar fertilizer based on astaxanthin.

7. The application of a foliar fertilizer based on astaxanthin to promote color change as described in any one of claims 1-5, characterized in that, The aforementioned foliar fertilizer for promoting color change should be diluted 800-1200 times and sprayed on sunny evenings between 16:00 and 17:00 or on cloudy days. The first spray should be applied after the fruit enters the hardening stage until it begins to turn from green to white. The second spray should be applied 7-15 days later, spraying the surface of the crop fruit and adjacent functional leaves.

8. The method for preparing a color-promoting foliar fertilizer based on astaxanthin as described in claim 7, characterized in that, The crops mentioned include grapes, tomatoes, citrus fruits, apples, and peppers.

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