A method for promoting color change and sweetness increase of citrus

Abstract

The application discloses a method for promoting color change and sweetness increase of citrus, and belongs to the field of physiological regulation of citrus cultivation. The application provides application of spearmint oil in the field of promoting color change and sweetness increase of citrus. In view of the problems of slow color change and insufficient sugar accumulation of citrus fruits, the application provides a method for improving quality of citrus based on plant secondary metabolites. The plant source preparation containing the spearmint oil is applied to the citrus, and good effects of promoting color change and sweetness increase can be achieved, the fruit quality is improved, and the commodity value is improved. The application adopts pure plant source medicinal ingredients as the medicinal ingredients for promoting color change and sweetness increase of citrus, so that the green food production standard can be met while the commodity value is improved.

Description

Technical Field

[0001] This invention relates to the field of physiological regulation in citrus cultivation, and in particular to a method for promoting color change and sweetening of citrus fruits. Background Technology

[0002] Citrus fruits are the world's largest category of fruits and one of the most important economic crops globally. In recent years, the global citrus planting area and yield have steadily increased, and the total industry output value has also risen significantly. However, due to various factors, the actual profit of the citrus industry has not been effectively improved. The citrus industry suffers from seasonal oversupply, intense market competition, rising production costs, and inconsistent fruit quality, resulting in a phenomenon of "increased production without increased efficiency and income." If citrus fruits have problems such as low average sugar content and uneven fruit color, which affect their quality, their commercial value will be severely impacted, leading to a decline in market competitiveness. Therefore, how to better solve the problems of slow fruit coloring and insufficient sugar accumulation is a key research focus for those skilled in the art.

[0003] Among the factors determining the quality of citrus fruits, carotenoids are the main pigments present during fruit ripening. Their composition and content directly affect the appearance and color of the fruit, serving as crucial indicators of its internal and external quality. Traditionally used ethephon, a chemical ripening agent, works by promoting the synthesis of anthocyanins and carotenoids through ethylene, thus accelerating fruit color change. However, excessive concentrations or improper use can easily lead to significant fruit drop, premature softening, low sugar-acid ratio, shortened shelf life, and a substantial reduction in commercial value, demonstrating highly unstable efficacy. Furthermore, commonly used agents such as gibberellins and cytokinins, at low concentrations, can delay chlorophyll loss and inhibit the accumulation of other pigments, extending fruit shelf life and preventing concentrated market entry. However, their effects are short-lived, and dosage requires careful control. Excessive use results in persistently green fruit, inhibits sugar accumulation, and diminishes flavor, negatively impacting taste. While exogenous plant growth regulators can promote fruit coloring, they cannot simultaneously achieve sugar accumulation and flavor enhancement. Their practical application is limited by various factors, and they also lead to fruit drop and flavor degradation in citrus fruits. Chinese invention patent application CN116621641A discloses an amino acid-based calcium-magnesium liquid fertilizer for promoting tomato coloring and its preparation method. This invention, by adding compound amino acids, addresses the problem of low tomato coloring rates in existing technologies to some extent. However, this patented technology has significant limitations: firstly, it requires high concentrations to be effective, increasing application costs; secondly, its effect is short-lived and easily washed away by rain, leading to unstable results; and thirdly, its coloring mechanism is singular, only activating the ethylene signaling pathway, easily causing uneven tomato coloring. Chinese invention patent application CN114793734B discloses a method for increasing the soluble solids content and color intensity of citrus fruits. This patent uses a mixed aqueous solution of sodium molybdate, soybean protein peptides, and Mg at a certain mass concentration as a synergistic mixture, spraying the entire citrus tree with the solution when the citrus fruit begins to color. This method can effectively promote the increase of soluble solids content and color enhancement in citrus fruits, but it suffers from poor stability and high cost. Chinese invention patent application CN105859444A discloses a method for preparing a color-enhancing and sugar-increasing fertilizer containing polypeptides, amino acids, glycosidases, and compound phosphorus and potassium. By formulating specific mass concentrations of polypeptides, amino acids, glycosidases, and compound phosphorus and potassium, it effectively solves problems related to nutrient absorption, color enhancement, and sugar enhancement in crops, thereby improving fruit quality. However, this patented technology has significant limitations: firstly, the polypeptides have poor stability and are easily inactivated in environments with pH > 7.0; secondly, it relies on chelating trace elements to enhance the effect, leading to a complex formulation process; and thirdly, it is costly, with an average cost exceeding 80 yuan per mu. Chinese invention patent application CN120040219A discloses a foliar fertilizer that promotes sugar enhancement and color enhancement in citrus fruits and inhibits peel flaking, and its application.This micronutrient fertilizer contains sugar alcohol calcium, magnesium sulfate, boric acid, selenomethionine, and sodium molybdate. It can supplement the tree with deficient nutrients, inhibit skin flaking during late fruit ripening, promote chlorophyll synthesis and enhance photosynthesis, thereby promoting fruit sugar accumulation and activating the jasmonic acid signaling pathway to promote early fruit coloring. However, excessive use may lead to heavy metal accumulation. Chinese invention patent application CN118908766A discloses a foliar fertilizer and its preparation process that promotes grape fruit coloring. Through a scientifically formulated ratio of nutrients and micronutrients, this foliar fertilizer can directly provide necessary nutrients to grape leaves, promoting anthocyanin synthesis and accumulation, thus significantly improving the coloring effect of grape fruit. It has high safety and excellent coloring effect; although the coloring is relatively slow, it has no side effects and does not affect the taste. The micronutrients in the foliar fertilizer help prevent soft or rotten fruit during the ripening period, improving the overall quality of the fruit. However, this patented technology has significant limitations: firstly, it suffers from soil fixation effects (molybdenum / boron utilization rate <20%); secondly, excessive use may lead to heavy metal accumulation. Therefore, developing safe and efficient plant-derived color-changing and sweetening technologies to achieve green and organic agricultural production has become a key requirement for the sustainable development of the citrus industry. Summary of the Invention

[0004] The purpose of this invention is to provide a method for promoting color change and sweetening of citrus fruits, thereby solving the aforementioned problems in the background art. Addressing the issues of slow color change and insufficient sugar accumulation in citrus fruits, this invention proposes a method for improving citrus quality based on plant secondary metabolites. Applying the plant-derived preparation containing spearmint oil designed in this invention to citrus fruits can effectively promote color change and sweeten the fruit, thereby improving fruit quality and increasing commercial value.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] One of the technical solutions of this invention is to provide an application of spearmint oil in promoting the color change and sweetening of citrus fruits.

[0007] The second technical solution of the present invention provides a plant-derived preparation that promotes color change and sweetness enhancement in citrus fruits, the raw materials of which include spearmint oil.

[0008] Preferably, the dosage form of the plant-derived preparation that promotes color change and sweetness enhancement in citrus is a microcapsule suspension.

[0009] Preferably, the spearmint oil contains 45-70 wt% carvacrol, 12-30 wt% limonene, and 2-10 wt% eucalyptol.

[0010] Preferably, the plant-derived preparation comprises a core material and a wall material, wherein the core material contains the spearmint oil.

[0011] Preferably, the mass ratio of the core material to the wall material is 1:5 to 5:1, more preferably 1:1 to 3:1.

[0012] Preferably, the wall material is composed of polybutylene succinate and polyhydroxybutyrate in a mass ratio of 1:4 to 4:1, more preferably 1:1 to 1:1.5.

[0013] The third technical solution of the present invention provides a method for preparing the above-mentioned plant-derived preparation for promoting color change and sweetening of citrus, comprising the following steps:

[0014] Spearmint oil and raw materials used to prepare wall materials are mixed in an organic solvent to obtain an oil phase containing drug components and a carrier;

[0015] The emulsifying dispersant is dissolved in water to obtain an aqueous phase;

[0016] The oil phase containing the drug component and carrier is added to the aqueous phase, sheared to obtain a microemulsion, the organic solvent is removed, and then solid-liquid separation is performed to obtain drug-loaded microcapsules; the drug-loaded microcapsules are suspended to obtain the plant-derived preparation that promotes color change and sweetness enhancement of citrus.

[0017] More preferably, the preparation method includes the following steps:

[0018] (1) Preparation of oil phase: Spearmint oil, polyhydroxybutyrate and polybutylene succinate are dissolved in a low-boiling-point organic solvent to obtain an oil phase containing drug components and carrier;

[0019] (2) Preparation of the aqueous phase: The emulsifying dispersant is dissolved in water to obtain the aqueous phase;

[0020] (3) Preparation of microcapsules: The oil phase containing the drug component and carrier in step (1) is added to the aqueous phase in step (2), and high-speed shearing is performed at room temperature. After shearing, a microemulsion is obtained. The microemulsion is stirred at a temperature of 10-30°C until the organic solvent is completely evaporated. After centrifugation and drying, drug-loaded microcapsules are obtained.

[0021] (4) Preparation of microcapsule suspension: Microcapsules and functional adjuvants are added and combined in a container and dispersed by shearing to form a formulation; more preferably, the drug-loaded microcapsules are added to water and stirred to disperse, then a pre-dissolved xanthan gum aqueous solution is added, then magnesium aluminum silicate, wetting and dispersing agent SK-34SC and chitosan are added, and dispersed by shearing to form the microcapsule suspension.

[0022] More preferably, the raw materials in the microcapsule suspension are, by mass percentage: 10% spearmint oil microcapsules, 0.12% xanthan gum, 0.24% magnesium aluminum silicate, 4% wetting and dispersing agent SK-34SC, 2% chitosan, and the remainder is water (all indicators meet the relevant standards for suspensions).

[0023] More preferably, the functional additives include one or more of surfactants, fillers, solvents, carriers, emulsifiers, dispersants, wetting agents, foaming agents, defoamers, thickeners, penetrants, stabilizers, antifreeze agents, film-forming agents, color pastes, and fragrances.

[0024] The third technical solution of the present invention provides a method for promoting color change and sweetening of citrus fruits by applying the above-mentioned plant-derived preparation.

[0025] Preferably, the plant-derived preparation is applied during the fruit expansion and / or color-changing stages of citrus trees.

[0026] Fruit expansion period regulation: Spraying the plant-derived preparation during the fruit cell expansion period can effectively promote the establishment of channels for the transport of photosynthetic products to the fruit, laying the material basis for subsequent sugar accumulation.

[0027] Enhanced color change period: Spraying the plant-derived preparation at the stage when the chloroplasts in the peel begin to disintegrate can specifically accelerate the color change of citrus and simultaneously enhance sugar conversion.

[0028] Preferably, the organic solvent is dichloromethane; and the emulsifying dispersant is polyvinyl alcohol.

[0029] The concentration of the plant-derived preparation is 10-1000 mg / L.

[0030] The core of this invention lies in establishing a synergistic promotion mechanism between color change efficiency and sugar accumulation by targeting and regulating the physiological process of citrus fruit ripening.

[0031] The spearmint oil, a medicinal ingredient in this invention, is a plant extract that is highly susceptible to oxidation and volatility under natural conditions. Direct exposure to air during field application can lead to degradation or loss of the medicinal ingredient, reducing its effective utilization on the plant. However, preparing the medicinal ingredient into a microcapsule suspension effectively encapsulates the active ingredient, preventing volatilization and degradation caused by ultraviolet radiation, thus improving the utilization rate and significantly enhancing its field application efficacy. The choice of microcapsule wall material is highly correlated with the encapsulated medicinal ingredient, directly affecting whether it is adequately encapsulated. The ratio in this invention represents the optimal ratio of spearmint oil to wall material; ratios that are too high or too low will negatively impact the encapsulation effect.

[0032] The wall materials used in this invention are polyhydroxybutyrate (PHB) and polybutylene succinate (PBS). Testing showed that PHB has advantages over other wall materials in terms of morphology, particle size, and drug loading capacity. The prepared microcapsules have regular morphology without aggregation, smaller particle size, higher encapsulation efficiency and drug loading, and better sustained-release properties, exhibiting superior color-changing and sweetening effects in the field. Regarding the spearmint oil core material of this invention, when polylactic acid (PLA) and polybutylene succinate (PBS) are used as wall materials for encapsulation, the resulting microcapsules have irregular morphology, are prone to pores, have low encapsulation efficiency, and exhibit rapid drug release and short duration of effect. This may be because PLA and PBS are typical incompatible blend systems with significant differences in their molecular chain structures (PLA is a rigid chain, while PBS is a flexible aliphatic polyester), resulting in weak interfacial bonding. During solvent evaporation, phase separation easily occurs, forming a heterogeneous wall material structure, and the surface of the blended film often shows obvious pores and rough areas. Microcapsules prepared using polyhydroxybutyrate (PHB) and polybutylene succinate (PBS) of this invention exhibit better encapsulation, with regular spherical morphology, no aggregation, higher encapsulation efficiency and drug loading, and better efficacy. This may be because both are aliphatic polyesters with matching chain segment polarities (Δδ<0.5), inhibiting phase separation and forming a dense, non-porous wall layer (porosity <5%). Furthermore, their crystallization temperatures overlap and form a eutectic structure, eliminating shrinkage stress and improving toughness (elongation at break 200-300%). In addition, the hydrophobic synergy between the two (contact angle >95°) ensures a high encapsulation efficiency (≥60%), and the difference in degradation rate (PBS fast / PHB slow) enables controllable sustained release. Overall performance is significantly better than traditional PLA and other systems. Spearmint oil microcapsules prepared using polyhydroxybutyrate (PHB) and polybutylene succinate (PBS) were characterized by scanning electron microscopy, laser particle size analysis, and controlled-release performance. The microcapsules were spherical with a regular and uniform morphology, an average particle size of 3.4 μm, a drug loading of 68.67%, and an encapsulation efficiency of 86.25%. The sustained-release test results showed that the spearmint oil in the microcapsules was continuously released for 32 days, and the cumulative release rate of spearmint oil was 94.68%.

[0033] The beneficial technical effects of the present invention are as follows:

[0034] To address the problems of slow color change and insufficient sugar accumulation in citrus fruits, this invention proposes a method for improving citrus quality based on plant secondary metabolites. Applying the plant-derived preparation containing spearmint oil designed in this invention to citrus fruits can effectively promote color change, increase sweetness, improve fruit quality, and enhance commercial value.

[0035] This invention, through research, has found that foliar spraying of spearmint oil microcapsule formulations during the critical developmental stages of citrus fruits (fruit expansion / color change stage) can significantly accelerate carotenoid biosynthesis, advance the peel color change process by 10-21 days, increase the color value (a*) of mature fruits by 36.8-75.75%, and simultaneously promote an increase in soluble solids content by 2.6-3.8%. This invention provides an innovative solution for improving the quality of citrus fruits, and is particularly suitable for improving the quality of citrus varieties such as navel oranges, sugar oranges, and Wogan tangerines.

[0036] Compared to conventional technologies, this invention represents a triple breakthrough:

[0037] (1) Physiological synergy: This invention breaks through the traditional mode of separating and regulating color change and sweetening, and realizes the simultaneous optimization of appearance quality and internal flavor;

[0038] (2) Timing precision: Determine the optimal treatment window based on the fruit development to ensure that technical measures are highly compatible with physiological processes;

[0039] (3) Ecological compatibility: The regulatory system is constructed using pure plant-derived drug components, which can meet the green food production standards while enhancing the value of the product. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 The images show a comparison of the skin coloring effect of 10% spearmint oil microcapsule suspension on sugar oranges treated with it, as in Example 1. The left image represents the experimental group, and the right image represents the control group.

[0042] Figure 2 The images show a comparison of the skin coloring effects of 10% spearmint oil microcapsule suspension on navel oranges in Example 2. The left image represents the experimental group, and the right image represents the control group.

[0043] Figure 3 The images show a comparison of the skin coloring effect of 10% spearmint oil microcapsule suspension on sugar oranges in Example 3. The left image represents the experimental group, and the right image represents the control group. Detailed Implementation

[0044] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0045] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0046] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. It should be noted that any aspects of this invention not described in detail are conventional practices in the art and are not the focus of this invention.

[0047] The terms “comprising,” “including,” “having,” “containing,” etc., used in this invention are all open-ended terms, meaning that they include but are not limited to.

[0048] This invention can significantly accelerate and enhance the speed and extent of color change and sweetness enhancement in citrus fruits during fruit development. In actual citrus production, growers often harvest and market citrus early to gain a competitive edge and maximize profits. However, premature harvesting can negatively impact the quality of the fruit and the consumer experience. The technical solution provided by this invention promotes color change and increases sugar content in citrus fruits, thereby improving their quality and commercial value. This is of great significance for enhancing the economic benefits of citrus cultivation and promoting the healthy development of the industry.

[0049] Spearmint oil is a plant secondary metabolite, with carvone accounting for 45-70 wt%, limonene for 12-30 wt%, and eucalyptol for 2-10 wt% of its main components.

[0050] This invention addresses the problems of asynchronous color change and sugar accumulation, and the potential for chemical residues, in existing citrus ripening technologies. It provides a synergistic solution for color change and sweetening based on plant physiological regulation. By precisely controlling the key stages of fruit development, a specific concentration of spearmint oil is used to achieve dual activation of pigment metabolism and sugar transport systems.

[0051] The color change of citrus fruits is mainly related to the accumulation of pigments such as carotenoids and anthocyanins. Unlike commonly used sweeteners on the market, such as gibberellin inhibitors (paclobutrazol, etc.), which work by inhibiting gibberellin synthesis to reduce shoot growth and thus promote fruit sweetness by diverting more nutrients to the fruit in a way that is unhealthy for tree development, and whose sweetening effect is not significant, the spearmint oil of this invention promotes the activity of key enzymes in the related pigment synthesis pathways, affecting the metabolism of sucrose, a precursor to anthocyanin synthesis, and thus accelerating the fruit color change process. This is mainly because carvone increases SnRK1 kinase activity, relieves the inhibition of sucrose decomposition, and increases the sucrose concentration in the peel by 40%. Sucrose is decomposed into UDP-glucose (anthocyanin precursor), which is then efficiently converted into anthocyanins by the ANS enzyme under the regulation of the MYB transcription factor. Carvone induces the expression of SGR protein (hysteresis protein), which, by activating PAO enzyme, increases the chlorophyll degradation rate by 2.5 times. Following rapid chlorophyll degradation, previously obscured β-carotene / lycopene becomes visible, resulting in an orange-red fruit peel. Simultaneously, the increased chlorophyll degradation rate in the fruit indirectly promotes the increase of carotenoids, thus contributing to the orange-red fruit color.

[0052] Spearmint oil promotes sugar accumulation primarily by enhancing photosynthesis in fruits and leaves, thus facilitating the transport of photosynthetic products. Carvone activates the PsbS protein (photosystem II protective protein), expanding the light-harvesting cross-section of chloroplasts and increasing the electron transport rate (ETR) by 35%, leading to increased ATP / NADPH synthesis. It upregulates Rubisco activator (RCA) expression, increasing Rubisco carboxylation efficiency by 40% and doubling the rate of CO2 fixation to 3-phosphoglycerate (3-PGA). Carvone induces a 200% increase in the expression of the SWEET15 sucrose transporter gene, promoting efficient sucrose transport from leaves (source) to fruits (sink). It also regulates sucrose-H... +Increased SUT1 cotransporter activity led to a 30% increase in fruit sugar input. Photosynthesis is a crucial process for synthesizing sugars and other organic matter. Enhanced photosynthesis produces more photosynthetic products, such as glucose, fructose, and sucrose, providing more raw materials for fruit sugar accumulation. Furthermore, a sufficient sugar supply provides energy and a material basis for pigment synthesis, indirectly promoting fruit coloring. Studies have shown that plant hormones such as abscisic acid (ABA) and gibberellin (GA) play important regulatory roles in fruit coloring and sugar accumulation. Spearmint oil can also participate in regulating the hormonal balance within plants, promoting an increase in ABA content, facilitating the breakdown of starch in the fruit into soluble sugars, and increasing sugar content. Simultaneously, ABA can also promote pigment synthesis to some extent, thereby accelerating fruit coloring. Finally, spearmint oil also affects the transport and distribution of nutrients in the fruit, prompting more photosynthetic products to be transported from leaves and other parts to the fruit, increasing the amount of sugar accumulated. One reason is that its main component, carvone, induces the production of ethylene in the fruit, triggering a "sinking" signal (increased fruit demand), attracting photosynthetic products to be preferentially allocated to the fruit. Secondly, the expression of the SWEET15 sucrose transporter protein in leaves is enhanced, accelerating sucrose loading into the vascular bundles; the activity of the SUT1 transporter in the vascular bundles of the fruit is increased, improving sucrose unloading efficiency. Carvone enhances the carboxylation efficiency of Rubisco enzyme, leading to a 40% increase in CO2 fixation rate; thirdly, its light energy conversion rate is improved, generating more sucrose raw material (triose phosphate). Spearmint oil achieves efficient and targeted transport of photosynthetic products from source to sink through hormone signaling (ethylene) driving sink demand + dual-terminal activation of transporters (SWEET / SUT) + increased photosynthetic raw material production, resulting in rapid accumulation of sugar in the fruit. Sufficient nutrient supply is beneficial for maintaining normal physiological metabolism in the fruit, a necessary condition for pigment synthesis, and contributes to fruit color change. While improving the appearance and marketability of the fruit, spearmint oil also optimizes its internal quality, effectively promoting fruit color change and sweetening, breaking through the industry bottleneck of difficulty in balancing quality and safety caused by traditional chemical ripening techniques.

[0053] This invention provides a method for regulating the color change and sweetness enhancement of citrus fruits based on microcapsule sustained-release technology. Its core lies in achieving simultaneous improvement of the fruit's appearance quality and internal sugar content through precise intervention at specific developmental stages and synergistic optimization of formulation processes.

[0054] This invention further discloses a method for promoting color change and sweetening of citrus fruits, comprising the following application steps:

[0055] Fruit expansion stage treatment: After full bloom, use a backpack sprayer to spray the whole plant with the plant-derived preparation of this invention, focusing on covering the surface of new shoots and fruits;

[0056] Color-changing period treatment: When the area of ​​fruit surface turning green is ≥15%, spray the fruit bunch area directly onto the fruit surface to form a continuous liquid film.

[0057] Practical experience has shown that spraying this agent can significantly change the color of the fruit peel and increase the accumulation of sugar in the pulp, without causing the peel floating and sugar loss phenomena commonly seen in chemical ripening agents.

[0058] The spearmint oil used in this invention was purchased from Hubei Maidehao Biotechnology Co., Ltd., and contained 60 wt% carvone, 35 wt% limonene, and 5 wt% eucalyptol.

[0059] Unless otherwise specified, "room temperature" in this invention refers to 20-30°C.

[0060] All raw materials used in the following embodiments of the present invention are commercially available products.

[0061] Example 1

[0062] A plant-derived preparation that promotes color change and sweetness enhancement in citrus fruits is made from the following raw materials in parts by weight:

[0063] 98 parts deionized water, 2 parts polyvinyl alcohol, 10 parts spearmint oil, 2.25 parts polybutylene succinate (PBS), 2.75 parts polyhydroxybutyrate (PHB), and 30 parts dichloromethane.

[0064] The specific preparation process is as follows: 98g of deionized water was measured into an Erlenmeyer flask, and 2g of polyvinyl alcohol was slowly added. The mixture was heated to 60℃ using a digital display magnetic stirrer and stirred at high speed until completely dissolved. After cooling to room temperature, the aqueous phase was obtained. 2.25g of polybutylene succinate (PBS) and 2.75g of polyhydroxybutyrate (PHB) were dissolved in 30mL of dichloromethane and stirred thoroughly on a magnetic stirrer. Then, 10g of the active ingredient, spearmint oil, was added and stirred until dissolved (core-to-wall ratio 2:1), yielding the oil phase. The oil phase was poured into the aqueous phase and emulsified and sheared at 6000r / min for 5min using a T25 digital display disperser to prepare a stable oil-in-water emulsion. The emulsion was stirred at 600r / min for 6–7h on a magnetic stirrer until the dichloromethane solvent completely evaporated. After the microcapsules solidified, they were centrifuged, dried, and the drug loading of the active ingredient was determined. The formulation of the spearmint oil microcapsule suspension is as follows: 10% spearmint oil microcapsules, 0.12% xanthan gum, 0.24% magnesium aluminum silicate, 4% wetting and dispersing agent SK-34SC, 2% chitosan, and the remainder water. All indicators meet the relevant standards for suspensions. Based on this, the prepared microcapsules were added to water and stirred to disperse them. Then, a pre-dissolved xanthan gum solution was added, followed by magnesium aluminum silicate, wetting and dispersing agent SK-34SC, and chitosan. The mixture was then sheared and dispersed to prepare the microcapsule suspension.

[0065] When using this plant-derived preparation, dilute it with water at a ratio of 1:200 by mass, and then spray it onto the citrus plants.

[0066] Example 1

[0067] A method to promote color change and sweetness enhancement in citrus fruits was tested at a rock sugar orange plantation.

[0068] 1.1 Experimental Orchard

[0069] The experimental orchard is located at the Institute of Horticulture, Hunan Academy of Agricultural Sciences; the variety is Bing Tang Orange, with 5-year-old fruit-bearing trees; the area is 2 hectares. 2 Planting dimensions: 3m x 2m, per 667m² 2 110 trees were planted, with a height of 1.8-2m and a crown height of 1.6-1.8m. The soil in the experimental site was red soil with a pH of 5.2 and moderate fertility and management level.

[0070] 1.2 Test reagents

[0071] 10% spearmint oil microcapsule suspension; water CK.

[0072] 1.3 Experimental Design and Implementation

[0073] The experiment consisted of two treatments: Treatment 1: a 10 wt% spearmint oil microcapsule suspension prepared in Example 1 was diluted with water at a ratio of 1:200, serving as the experimental group; Treatment 2: water, serving as the control group (CK). Each treatment was replicated three times, with 30 trees per replicate, for a total of 60 trees. Before spraying, five fruits (of similar color) were randomly labeled on each tree.

[0074] On July 28, 2024, the weather was sunny with a high of 38°C. The first spraying was carried out, with a spray volume of 1500mL per tree, focusing on covering the surface of new shoots and young fruits. On August 26, 2024, the weather was cloudy turning partly cloudy with a high of 39°C. The second spraying was carried out, with a spray volume of 1500mL per tree. Care was taken to spray the fruit clusters directly onto the fruit surface to form a continuous liquid film. Both sprayings were carried out using a backpack electric sprayer.

[0075] 2. Trial Follow-up and Data Recording

[0076] 2.1 Experimental investigation on the effects on fruit growth and coloring

[0077] After the fruit has fully ripened and colored, all marked fruits were harvested and brought indoors on November 4, 2024. The orange color of the fruit was tested using a portable colorimeter, and the average value of the CCI (Citrus Color Index, the higher the value, the more complete the color change) was used for evaluation.

[0078] 2.2 Impact on fruit quality

[0079] The collected marked fruits were subjected to quality analysis. The soluble solids content (%) of the fruit was analyzed and determined using conventional methods, and the fruit flavor was evaluated.

[0080] 3. Comparison of coloring and sweetness of citrus peel treated with different methods

[0081] 3.1 Effects on fruit coloring

[0082] Figure 1 The images show a comparison of the skin coloring effect of 10% spearmint oil microcapsule suspension on sugar oranges treated with it, as in Example 1. The left image represents the experimental group, and the right image represents the control group.

[0083] Each replicate of the experimental treatment was compared with its corresponding control. The orange color of the rock sugar was detected by using a portable colorimeter. The fruit coloring of the 10% spearmint oil microcapsule suspension was significantly different from that of the control. The results showed that the application of spearmint oil microcapsule suspension about 90 days before harvest had a significant effect on the coloring of the fruit.

[0084] 3.2 Analysis of Sweetness Data Processed by Different Schemes

[0085] 3.2.1 Impact on fruit quality

[0086] After color comparison, the harvested tagged fruits were sent to the laboratory for quality analysis, and the results are shown in Table 1. As can be seen from Table 1, the color value CCI, soluble solids content, solid-acid ratio, and vitamin C (VC) of the spearmint oil microcapsule suspension treatment group were significantly higher than those of the control group, and the titratable acid was 0.24 lower, with significant differences.

[0087] Table 1 Comparison of various indicators of citrus

[0088]

[0089] Example 2

[0090] A method to promote color change and sweetness enhancement in citrus fruits was tested in a navel orange plantation.

[0091] 1.1 Experimental Orchard

[0092] The experimental orchard is located in Zhangjiajie Navel Orange Orchard, Hunan Province; the variety is Newhall Navel Orange, with 5-year-old fruit-bearing trees; the area is 150 hectares. 2 The planting dimensions are 3m x 1.5m, per 667m². 2 Sixty-five trees were planted, with a height of 1.8–2 m and a crown height of 1.2–1.6 m. The soil in the experimental site was red soil with a pH of 6.5 and moderate fertility and management level.

[0093] 1.2 Test reagents

[0094] 10% spearmint oil microcapsule suspension; water CK.

[0095] 1.3 Experimental Design and Implementation

[0096] The experiment consisted of two treatments: Treatment 1: the 10% spearmint oil microcapsule suspension prepared in Example 1 was diluted with water at a mass ratio of 1:200, serving as the experimental group; Treatment 2: water, serving as the control group (CK). Each treatment was replicated three times, with 30 trees per replicate, for a total of 60 trees. Before spraying, five fruits (of similar color) were randomly labeled on each tree.

[0097] On May 12, 2024, the weather was sunny with a high of 28°C. The first spraying was conducted with a dosage of 1500 mL per tree. On June 15, 2024, the second spraying was conducted with a dosage of 1500 mL per tree. The weather was cloudy turning partly cloudy with a high of 39°C. On July 24, 2024, the third spraying was conducted with a dosage of 1500 mL per tree. The weather was sunny with a high of 37°C. On October 23, 2024, the fourth spraying was conducted with a dosage of 1500 mL per tree. The weather was partly cloudy with a high of 28°C. All four sprayings were suitable for experimental operations. At this time, the fruit in the experimental orchard had already begun to show some color. All four sprayings were conducted using a backpack electric sprayer.

[0098] 2. Trial Follow-up and Data Recording

[0099] 2.1 Experimental Investigation

[0100] After the fruit had fully ripened and colored, all marked fruits were harvested and brought indoors on November 10, 2024. The orange color intensity was measured using a portable colorimeter, and the average value of the CCI (Citrus Color Index, the higher the value, the more complete the color change) was used for evaluation. The effects of each treatment on fruit coloring were compared and analyzed.

[0101] 2.2 Impact on fruit quality

[0102] The harvested tagged fruits were subjected to quality analysis. The main indicators reflecting fruit quality were analyzed and determined using conventional methods: soluble solids content (%), titratable acid (citric acid %), and vitamin C content (%). The solids-acid ratio was calculated, and the fruit flavor was evaluated.

[0103] 3. Comparison of coloring and sweetness of citrus peel treated with different methods

[0104] 3.1 Effects on fruit coloring

[0105] Each replicate of the experimental treatment was compared with its corresponding control. The color of the navel orange was detected by using a portable colorimeter. The color change of the fruit treated with 10% spearmint oil microcapsule suspension was significantly different from that of the control, indicating that the spearmint oil microcapsule suspension has a significant effect on the coloring of the fruit.

[0106] 3.2 Effect on fruit sweetness

[0107] After color comparison, the harvested tagged fruits were sent to the laboratory for quality analysis, and the results are shown in Table 2. Table 2 shows that the spearmint oil microcapsule suspension treatment group had significantly higher CCI, soluble solids content, solid-acid ratio, and vitamin C than the control group, and a significantly lower titratable acidity of 0.16.

[0108] Table 2 Comparison of various indicators of citrus

[0109]

[0110] Example 3

[0111] A method to promote color change and sweetness enhancement in citrus fruits was tested at a rock sugar orange plantation.

[0112] 1.1 Experimental Orchard

[0113] The experimental orchard is located in Bing Tang Orange Orchard, Mayang Miao Autonomous County, Hunan Province; the variety is Jinmi, and the trees are 5-year-old fruit trees; the area is 16 hectares. 2 The planting dimensions are 2m x 1.5m, per 667m². 2 Eighty-two trees were planted, with a height of 1.2–1.8 m and a crown height of 1.2–1.6 m. The soil in the experimental site was red soil with a pH of 6.8 and moderate fertility and management level.

[0114] 1.2 Test reagents

[0115] 10% spearmint oil microcapsule suspension; water CK.

[0116] 1.3 Experimental Design and Implementation

[0117] The experiment consisted of two treatments: Treatment 1: the 10% spearmint oil microcapsule suspension prepared in Example 1 was diluted with water at a mass ratio of 1:200, serving as the experimental group; Treatment 2: water, serving as the control group (CK). Each treatment was replicated three times, with 30 trees per replicate, for a total of 60 trees. Before spraying, five fruits (of similar color) were randomly labeled on each tree.

[0118] The first spraying was carried out on September 6, 2024, with sunny weather and a high of 36°C. The second spraying was carried out on October 15, 2024, with cloudy weather and a high of 35°C. Both were suitable for trial operations. Both sprayings were carried out using backpack electric sprayers.

[0119] Trial follow-up and data recording

[0120] 2. Experimental Investigation

[0121] 2.1 Effects on fruit growth and coloring

[0122] After the fruit had colored, all marked fruits were collected and brought indoors on November 25, 2024. The orange color intensity of the fruit was measured using a portable colorimeter. The average value of the measured CCI (Citrus Color Index, the higher the value, the more complete the color change) was used for evaluation. The effects of each treatment on fruit coloring were observed, compared and analyzed.

[0123] 2.2 Impact on fruit quality

[0124] The harvested tagged fruits were subjected to quality analysis. The main indicators reflecting fruit quality were analyzed and determined using conventional methods: soluble solids content (%), titratable acid (citric acid %), sugar-acid ratio, and fruit flavor were evaluated.

[0125] 3. Comparison of coloring and sweetness of citrus peel treated with different methods

[0126] 3.1 Effects on fruit coloring

[0127] Each replicate of the experimental treatment was compared with its corresponding control. The orange color of the rock sugar was detected by using a portable colorimeter. The color change of the fruit treated with 10% spearmint oil microcapsule suspension was significantly different from that of the control, indicating that spearmint oil microcapsule suspension has a significant effect on the coloring of the fruit.

[0128] 3.2 Effect on fruit sweetness

[0129] After color comparison, the harvested tagged fruits were sent to the laboratory for quality analysis, and the results are shown in Table 3. As can be seen from Table 3, the color value CCI, soluble solids content, solid-acid ratio, and vitamin C of the spearmint oil microcapsule suspension treatment group were significantly higher than those of the control group, while the titratable acid was 0.16 lower, showing significant differences.

[0130] Table 3 Comparison of various indicators of citrus

[0131]

[0132] In summary, spraying spearmint oil during the fruit enlargement and color-changing stages significantly affects the color and sugar content of citrus fruits at maturity. The flavor of citrus fruits mainly depends on the soluble solids (TSS) and sugar-acid ratio. Citrus fruits with a sugar-acid ratio higher than 12:1 exhibit a pleasantly sweet and sour taste and a richer flavor. In the experiment, spearmint oil microcapsule suspension affected various indicators of fruit quality; however, the sugar-acid ratio in all treatments was above 24, indicating a highly significant impact on fruit flavor.

[0133] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. An application of spearmint oil in promoting color change and sweetening of citrus fruits.

2. A method for preparing a plant-derived preparation that promotes color change and sweetness enhancement in citrus fruits, characterized in that, Includes the following steps: Spearmint oil and raw materials used to prepare wall materials are mixed in an organic solvent to obtain an oil phase containing drug components and a carrier; The emulsifying dispersant is dissolved in water to obtain an aqueous phase; The oil phase containing the drug component and carrier is added to the aqueous phase, sheared to obtain a microemulsion, the organic solvent is removed, and then solid-liquid separation is performed to obtain drug-loaded microcapsules; the drug-loaded microcapsules are suspended to obtain the plant-derived preparation that promotes color change and sweetness enhancement of citrus. The plant-derived preparation includes a core material and a wall material, wherein the core material contains the spearmint oil; The mass ratio of the core material to the wall material is 1:5 to 5:1; The wall material is composed of polybutylene succinate and polyhydroxybutyrate in a mass ratio of 1:4 to 4:

1.

3. A method for promoting color change and sweetening of citrus fruits, characterized in that, Apply the plant-derived preparation prepared by the method described in claim 2.

4. The method according to claim 3, characterized in that, The plant-derived preparation is applied during the fruit expansion and / or color-changing stages of citrus trees.

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