Tea tree essential oil microemulsion as well as preparation method and application thereof

Abstract

The invention provides a tea tree essential oil microemulsion as well as a preparation method and application thereof, and the tea tree essential oil microemulsion is prepared by mixing water and a tea tree essential oil preparation, the tea tree essential oil preparation is composed of a compound emulsifier and tea tree essential oil, and the mass ratio of the compound emulsifier to the tea tree essential oil is (3-7): (7-3). The compound emulsifier is prepared by compounding a rosin emulsifier and phosphate. When the tea tree essential oil microemulsion is prepared, all the components are uniformly mixed in sequence. The preparation method is simple and convenient, and the obtained tea tree essential oil microemulsion can be used for preservation and fresh-keeping of fruits and vegetables, has the advantages of lasting fresh-keeping and good stability, has the advantages of high efficiency, environmental protection, no residue and the like, and has a good application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of preservation, and particularly relates to the application of tea tree essential oil preparation in the preparation of microemulsion for fruit and vegetable preservation. Background Art

[0002] In the technical field of preservation, fruit and vegetable preservation has always been an important research topic. With the improvement of people's living standards, the demand for fresh and safe fruits and vegetables is increasing day by day. However, after being picked, fruits and vegetables are extremely prone to decay and deterioration due to their own physiological metabolism activities and microbial infection, resulting in a decline in their quality, a shortening of the shelf life, and causing huge economic losses and resource waste.

[0003] Traditional fruit and vegetable preservation methods include refrigeration, controlled atmosphere preservation, chemical preservative treatment, etc. Although refrigeration can slow down the respiration of fruits and vegetables and the growth of microorganisms to a certain extent, the cost is relatively high and it is not applicable to some fruits and vegetables prone to chilling injury; controlled atmosphere preservation inhibits the respiratory metabolism of fruits and vegetables by adjusting the environmental gas composition, but the equipment is complex and the operation requirements are high. Chemical preservatives such as sulfur dioxide and potassium sorbate, although having a certain preservation effect, may pose a potential threat to human health if used for a long time, and are prone to chemical residue pollution of the environment, causing consumers' concerns about food safety.

[0004] In recent years, natural plant extract preservatives have received extensive attention due to their green, safe, and environmentally friendly characteristics. As a natural volatile essential oil extracted from tea trees, tea tree essential oil has a variety of biological activities such as broad-spectrum antibacterial and antioxidant properties. Its unique chemical components such as terpene compounds and phenolic compounds can inhibit the growth and reproduction of various post-harvest pathogenic microorganisms of fruits and vegetables, and at the same time regulate the physiological metabolism process of fruits and vegetables, reduce water loss and degradation of nutrients, thereby extending the shelf life of fruits and vegetables and maintaining their quality. However, due to the volatility of tea tree essential oil, its application is limited.

[0005] In this application, tea tree essential oil is made into a microemulsion form for application in fruit and vegetable preservation. The prepared microemulsion has good stability, dispersibility, and permeability, which can make tea tree essential oil more evenly distributed on the surface of fruits and vegetables, increase its contact area and action efficiency with fruits and vegetables, and thus better exert its preservation effect, realizing a more extensive and effective application of tea tree essential oil in the field of fruit and vegetable preservation, meeting the increasing demand for fruit and vegetable preservation, and promoting the development of preservation technology towards a more green, efficient, and safe direction. Summary of the Invention

[0006] The present invention aims to provide a fresh-keeping method which is efficient, environmentally friendly and can effectively extend the shelf life of fruits and vegetables. The rosin emulsifier involved is derived from the natural product rosin resin and is used in combination with isomeric alcohol polyoxyethylene ether phosphate to prepare a highly stable tea tree essential oil microemulsion, which has the characteristics of high stability, good biocompatibility, high efficiency, no residue, and environmental friendliness. The preparation is extremely simple, the raw materials are easily available, and the equipment requirements are low.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A tea tree essential oil microemulsion is prepared by mixing water and a tea tree essential oil preparation; the tea tree essential oil preparation consists of a composite emulsifier and tea tree essential oil, and the mass ratio of the composite emulsifier to the tea tree essential oil is (3-7):(7-3); the composite emulsifier is prepared by compounding a rosin emulsifier and a phosphate ester.

[0009] In order to further improve the stability and dispersibility of tea tree essential oil, the phosphate ester is isomeric alcohol polyoxyethylene ether phosphate ester, and more preferably isomeric alcohol polyoxyethylene ether phosphate ester E1310P.

[0010] In order to ensure the stability of the composite emulsifier and its compatibility with tea tree essential oil, the composite emulsifier is prepared by compounding rosin emulsifier and isomeric alcohol polyoxyethylene ether phosphate in a mass ratio of (0.5-5):1. For example, the mass ratio of rosin emulsifier and isomeric alcohol polyoxyethylene ether phosphate can be 1:1, 2:1 or other ratios. It is further preferred that in the composite emulsifier, the mass ratio of nonionic rosin emulsifier and nonionic isomeric alcohol polyoxyethylene ether phosphate is (0.8-1.2):1.

[0011] The composite emulsifier has excellent emulsification and dispersion effect on n-hexane.

[0012] The preparation of the composite emulsifier is very simple, and the preparation method only needs to uniformly mix the rosin emulsifier and the isomeric alcohol polyoxyethylene ether phosphate.

[0013] The rosin emulsifier is prepared by esterification reaction of maleic rosin and polyethylene glycol, and the polyethylene glycol is polyethylene glycol 200, polyethylene glycol 400 and polyethylene glycol 600.

[0014] In order to further improve the antiseptic and fresh-keeping effects, the polyethylene glycol is polyethylene glycol 400.

[0015] The inventors have found through experiments that the compounding effect of the rosin emulsifier prepared by esterification of maleic rosin and polyethylene glycol and isomeric alcohol polyoxyethylene ether phosphate E1310P is the best. The polyethylene glycol is preferably polyethylene glycol 200, polyethylene glycol 400 and polyethylene glycol 600, and more preferably polyethylene glycol 400.

[0016] When preparing microemulsions, different substances require different emulsifiers. The stability and antiseptic effect of polyethylene glycol 400 and isomeric alcohol polyoxyethylene ether phosphate are the best. The present application not only effectively promotes the stable dispersion of tea tree essential oil by selecting a rosin emulsifier with a specific ratio, but also has a significant promoting effect on antibacterial and antiseptic properties.

[0017] The mass ratio of the composite emulsifier to the tea tree essential oil in the tea tree essential oil preparation can be 3:7, 4:6, 5:5, 6:4, 7:3, etc. In order to obtain a tea tree essential oil preparation with high stability and good dispersibility, preferably, the mass ratio of the composite emulsifier to the tea tree essential oil in the tea tree essential oil preparation is (3-4): (7-6), more preferably 3:7. By selecting a specific mass ratio of the composite emulsifier and the tea tree essential oil, not only can the performance of the emulsifier be maximized, but also good compatibility and stability can be achieved with the tea tree essential oil, thereby laying a foundation for the preparation of a microemulsion for preserving fruits and vegetables.

[0018] The raw material components used in the tea tree essential oil preparation of the invention are simple, and the obtained product has excellent performance.

[0019] The tea tree essential oil preparation has two rapid decomposition temperatures, 160°C and 296°C; the tea tree essential oil preparation has good compatibility and high stability, and the closed cup flash point is not less than 25°C.

[0020] In order to take into account both the preservation effect and the cost, the volume ratio of water to tea tree essential oil preparation is (99-600): 1. The tea tree essential oil preparation is diluted 100 times, 300 times, 500 times, etc. with pure water to obtain a fruit and vegetable preservation microemulsion.

[0021] More preferably, the volume ratio of water to the tea tree essential oil preparation is (450-550):1.

[0022] A method for preparing the tea tree essential oil microemulsion according to any one of claims 1 to 7, comprising mixing a rosin emulsifier and isomeric alcohol polyoxyethylene ether phosphate to obtain a composite emulsifier, mixing the composite emulsifier and tea tree essential oil to obtain a tea tree essential oil preparation, and diluting the tea tree essential oil preparation with water to a desired multiple and mixing to obtain the tea tree essential oil microemulsion.

[0023] The tea tree essential oil microemulsion of the present application has good stability, a particle size in the range of 100 to 330 nm, and can be used for the preservation of fruits and vegetables to extend the shelf life.

[0024] The tea tree essential oil preparation of the present application has a significant antibacterial effect on Escherichia coli and Staphylococcus aureus, and can be used to inhibit Escherichia coli and Staphylococcus aureus. The inventors have found through experiments that the tea tree essential oil preparation has a significantly better antibacterial effect than tea tree essential oil.

[0025] The tea tree essential oil microemulsion of the invention has good stability and a simple preparation method.

[0026] The tea tree essential oil microemulsion of the present application is used for preserving fruits and vegetables after picking, or for preparing preservative preparations.

[0027] The above-mentioned fruits and vegetables include strawberries, citrus, tomatoes, small apples, blueberries, kiwis, grapes or dates, etc.

[0028] When using, just spray, soak or coat the fruits and vegetables directly.

[0029] The above tea tree essential oil is Australian tea tree essential oil.

[0030] % in this application, unless otherwise specified, are all mass percentages.

[0031] The technologies not mentioned in the present invention are all referred to the prior art.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) With tea tree essential oil as the core active ingredient, the appropriate proportion range in the preparation and microemulsion is determined through screening and optimization. A suitable surfactant is selected, such as a composite emulsifier containing a rosin emulsifier, which has good compatibility with tea tree essential oil and can effectively reduce the oil-water interfacial tension, so that the tea tree essential oil is evenly dispersed in the microemulsion system, ensuring the stability and dispersibility of the microemulsion, which helps the tea tree essential oil to better play its antiseptic and fresh-keeping role.

[0034] (2) The preparation process is simple. The composite emulsifier and tea tree essential oil can be evenly mixed by a simple stirring method to obtain a stable tea tree essential oil preparation. The tea tree essential oil preparation is then added to water and stirred for self-emulsification to obtain a fruit and vegetable fresh-keeping microemulsion.

[0035] (3) The application method is simple and diverse. The prepared tea tree essential oil preservative microemulsion is applied to the surface of fruits and vegetables by spraying, soaking or coating. For fruits and vegetables that are susceptible to mechanical damage, the coating method is preferred to form a uniform, thin and breathable protective film on the surface of fruits and vegetables, which can prevent microbial invasion and reduce water loss; for fruits and vegetables with regular shapes and relatively smooth skin, the spray method can be used to ensure that the microemulsion evenly covers the surface of fruits and vegetables; the soaking method is suitable for batch processing of small fruits and vegetables, so that the fruits and vegetables are fully exposed to the microemulsion to achieve the best preservation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is an appearance diagram of the tea tree essential oil preparation and the fruit and vegetable fresh-keeping microemulsion in the embodiments of the present invention;

[0037] Figure 2 This is an antibacterial test diagram of the tea tree essential oil preparation in the embodiment of the present invention;

[0038] Figure 3This is a particle size distribution diagram of the tea tree essential oil fruit and vegetable fresh-keeping microemulsion in an embodiment of the present invention;

[0039] Figure 4 This is a graph showing the strawberry preservation effect of the microemulsion diluted 500 times of the present invention and the control group (abscissa: Diameter (nm), ordinate: Intensity). DETAILED DESCRIPTION

[0040] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with examples. It should be understood by those skilled in the art that the examples are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0041] In each case, if the temperature is not particularly specified, the reaction was carried out at room temperature (20-25° C.) and if the stirring speed is not particularly specified, the reaction was carried out at 150 r / min.

[0042] Example 1

[0043] Preparation of rosin emulsifier:

[0044] Weigh 302g of rosin (natural wetland fragrance, model: AX01, product grade: first level, origin: Jiangxi Jiajin, cas: 8050-09-7) and add it to a four-necked flask, introduce nitrogen protection, heat to 120°C on an electric heating mantle to make it completely melted, then add 98g of maleic anhydride, stir and heat to 190°C, react for 4 hours, then add 900g of polyethylene glycol 600, stir evenly, and heat to 270°C for insulation reaction for 6 hours, the acid value is less than 20mgKOH / g, cool to below 120°C, add 3g of antioxidant 1010, stir evenly and discharge to obtain rosin emulsifier 1.

[0045] Weigh 302g of rosin (natural wetland fragrance, model: AX01, product grade: first level, origin: Jiangxi Jiajin, cas: 8050-09-7) and add it to a four-necked flask, introduce nitrogen protection, heat to 120°C on an electric heating mantle to make it completely melted, then add 98g of maleic anhydride, stir and heat to 190°C, react for 4 hours, then add 600g of polyethylene glycol 400, stir evenly, and heat to 270°C and keep warm for 6 hours, the acid value is less than 20mgKOH / g, cool to below 120°C, add 3g of antioxidant 1010, stir evenly and discharge to obtain rosin emulsifier 2.

[0046] Preparation of composite emulsifier:

[0047] Accurately weigh 30g of rosin emulsifier (rosin emulsifier 1 or 2) and 30g of isomeric alcohol polyoxyethylene ether phosphate (manufacturer: Linyi Lusen Chemical Co., Ltd., model: E1310P), place in a clean, dry 100ml beaker, install a stirring device, turn on the stirring device, set the stirring speed to 500rpm, stir at room temperature for 5 minutes, make the emulsifier preliminarily mixed at the bottom of the beaker, observe that the mixed liquid of the emulsifier gradually becomes uniform and clear, without obvious stratification or precipitation, continue stirring for 5 minutes, then turn off the stirring device to obtain a composite emulsifier. The composite emulsifier prepared using rosin emulsifier 1 is defined as composite emulsifier 1, and the composite emulsifier prepared using rosin emulsifier 2 is defined as composite emulsifier 2.

[0048] 5 ml of the composite emulsifier was added to 45 ml of a mixture of n-hexane and water (volume ratio 1:1), stirred at 1000 rpm for 5 minutes, and then the mixture was transferred to a separatory funnel and allowed to stand for 30 minutes to observe the stratification and stability of the emulsion. The results showed that whether the composite emulsifier was rosin emulsifier 1 or rosin emulsifier 2, the resulting emulsion was stable and did not stratify after standing, indicating that the composite emulsifier had good emulsification properties.

[0049] Example 2

[0050] To prepare tea tree essential oil preparations:

[0051] Accurately weigh 70g of Australian tea tree oil (purchased from Fujian Senmeida Biotechnology Co., Ltd., colorless to light yellow liquid, with fragrance, 4-pinene alcohol ≥ 40%), pour into a 250mL three-necked flask, and then add 30g of composite emulsifier (compound emulsifier 1 or composite emulsifier 2 prepared in Example 1). Place the three-necked flask in a constant temperature water bath, set the temperature to 40°C, turn on the stirrer, and stir at 600rpm for 5 minutes to fully mix the composite emulsifier and tea tree oil to obtain a tea tree essential oil preparation with a mass ratio of 3:7. Figure 1 As shown in (a), 1.1 is a tea tree essential oil preparation prepared by using composite emulsifier 1, and 1.2 is a tea tree essential oil preparation prepared by using composite emulsifier 2.

[0052] 20g of tea tree essential oil preparation was put into a 30mL transparent glass bottle, sealed and placed in an environment of 55℃, 25℃ and -4℃ (55℃, 25℃ and -4℃ for 60 days respectively), and 2 samples were set in each group. It was observed that no matter whether the composite emulsifier was rosin emulsifier 1 or rosin emulsifier 2, the tea tree essential oil preparation did not show stratification, precipitation or turbidity, and basically maintained the original particle size (particle size change rate ≤1%), and had good compatibility and stability.

[0053] The closed cup flash point tester was used to test the closed cup flash point of each tea tree essential oil preparation according to the standard operating procedures. The closed cup flash point of the tea tree essential oil preparation was not less than 25°C, which met the requirements for safe storage and use.

[0054] Thermogravimetric analyzer was used to test the thermal decomposition temperature of each tea tree essential oil preparation. Tea tree essential oil preparation 1.1 has two rapid decomposition temperatures, which are about 160°C and 296°C, respectively. It has good thermal stability and can avoid the loss of active ingredients. This provides an important basis for temperature control during the processing and application of the preparation.

[0055] Comparative Example 1

[0056] The isomeric alcohol polyoxyethylene ether phosphate E1310P was replaced with Peregal, and the rest was referred to Example 2, that is, in this example, the composite emulsifier was prepared by mixing 30g of rosin emulsifier 2 and Peregal, and then weighing 70g of Australian tea tree oil and 30g of the composite emulsifier to prepare a tea tree essential oil preparation. The tea tree essential oil preparation obtained in this example was diluted 100 times, 300 times and 500 times with pure water, respectively, and floating oil appeared, and no stable microemulsion could be obtained.

[0057] Example 3

[0058] The prepared tea tree essential oil preparations are named 1.1 (using rosin emulsifier 1) and 1.2 (using rosin emulsifier 2). Figure 1 As shown in (a). Select LB culture medium, activate the bacteria, and then dilute it with 0.9% sterile saline to obtain a bacterial suspension of 10^7CFU / mL. Take 150 microliters of the bacterial suspension and evenly spread it on the LB culture medium plate, marked as the control group, group 1.1, and group 1.2. On the plates of group 1.1 and group 1.2, add 1% concentration of tea tree essential oil preparation (the tea tree essential oil preparation is diluted with sterile water to a mass concentration of 1%, the tea tree essential oil preparation prepared with rosin emulsifier 1 on the plate of group 1.1 corresponds to the tea tree essential oil preparation prepared with rosin emulsifier 2 on the plate of group 1.2), and add an equal amount of sterile water to the control group. Incubate the plates at 37°C for 24 hours, and observe and record the growth of the colonies. As shown Figure 2 As shown, compared with the control group, the preparations 1.1 and 1.2 had a significant inhibitory effect on the growth of Staphylococcus aureus and Escherichia coli, and the number of colonies was significantly reduced. The antibacterial rates of tea tree essential oil preparation 1.1 against Escherichia coli and Staphylococcus aureus were 93% and 98% respectively under the current experimental conditions, and the antibacterial rates of tea tree essential oil preparation 1.2 against Escherichia coli and Staphylococcus aureus were 95% and 99% respectively under the current experimental conditions, while the antibacterial rates of direct use of Australian tea tree oil against the two were 82% and 86% respectively under the same experimental conditions, indicating that tea tree essential oil preparations have stronger antibacterial effects on Escherichia coli and Staphylococcus aureus than direct use of Australian tea tree oil.

[0059] Bacterial inhibition rate (%) = [(average colony count of the control group - average colony count of the experimental group) / average colony count of the control group] * 100%.

[0060] Example 4

[0061] Preparation of microemulsion for preserving fruits and vegetables:

[0062] 100-fold diluted fruit and vegetable fresh-keeping microemulsion: Accurately measure 10 mL of the tea tree essential oil preparation (prepared in Example 2), add it to 990 mL of pure water, and use a magnetic stirrer to stir at a speed of 800 rpm at room temperature for 5 minutes to ensure full mixing to obtain a 100-fold diluted fruit and vegetable fresh-keeping microemulsion, which is evenly dispersed, has no floating oil, and can be stably stored.

[0063] 300-fold diluted fruit and vegetable fresh-keeping microemulsion: 3.33 mL of the tea tree essential oil preparation (prepared in Example 2) was added to 996.67 mL of pure water, and stirred at 800 rpm for 5 minutes using a magnetic stirrer at room temperature to prepare a 300-fold diluted fruit and vegetable fresh-keeping microemulsion, which was evenly dispersed, free of floating oil, and could be stably stored.

[0064] 500-fold diluted fruit and vegetable fresh-keeping microemulsion: 2 mL of tea tree essential oil preparation (prepared in Example 2) was mixed with 998 mL of pure water, and stirred at 800 rpm for 5 minutes using a magnetic stirrer at room temperature to prepare a 500-fold diluted fruit and vegetable fresh-keeping microemulsion. Figure 1 As shown in (b) (1.1 corresponds to rosin emulsifier 1, 1.2 corresponds to rosin emulsifier 2), it is evenly dispersed without floating oil and can be stored stably.

[0065] The particle size of the three different dilution multiples of the above-mentioned fruit and vegetable preservation microemulsions was measured using a laser particle size analyzer. The results showed that the particle size was between 100 and 400 nm. The average particle size and PDI of samples 1.1-100, 1.1-300, 1.1-500, 1.2-100, 1.2-300, and 1.2-500 were 328.05, 203.79, 116.60, 241.49, 175.77, and 127.88 nm and 0.368, 0.280, 0.285, 0.226, 0.290, and 0.260, respectively, indicating that the microemulsion has good stability and meets the requirements of preservation applications. As mentioned above, 1.1 corresponds to rosin emulsifier 1, 1.2 corresponds to rosin emulsifier 2, and 100 / 300 / 500 are dilution multiples.

[0066] The retention rate of tea tree essential oil in microemulsion was determined by specific gravity method. The newly prepared microemulsion and pure tea tree essential oil were placed under the same experimental conditions at the same time and left exposed in a dark environment at room temperature for 7 days. The experimental results showed that the retention rate of tea tree essential oil 1.1-500 in microemulsion reached 82.6%, the retention rate of tea tree essential oil 1.2-500 in microemulsion reached 83.9%, and the retention rate of pure Australian tea tree oil was 68.3%. This shows that microemulsion effectively inhibits the volatilization loss of tea tree essential oil, improves the retention rate, and prolongs the effective action time.

[0067] Example 5

[0068] In this embodiment, the fruit and vegetable fresh-keeping microemulsion (1.1-500 and 1.2-500) diluted 500 times with pure water was used to treat strawberry fruits. The appearance changes of the treated strawberry fruits, including color, glossiness, whether there was mildew, rotten spots, and the fullness of the fruit, were evaluated and photographed, and the weight loss rate, chroma, and hardness were tested.

[0069] The method described in this example specifically comprises the following steps:

[0070] (1) Select strawberry fruits with uniform maturity, size, and no pests or mechanical damage (experimental time: October, experimental location: Xiamen Campus of Huaqiao University);

[0071] (2) The strawberries were randomly divided into an experimental group and a control group. Three parallel samples were set up in each group, and each parallel sample contained three strawberries to reduce the impact of accidental errors on the experimental results. Control group (KB): The strawberries were sprayed, soaked or coated with pure water. During the spray treatment, pure water was evenly sprayed on the surface of the strawberries using a sprayer until a thin layer of water film formed on the surface; the soaking treatment was to completely immerse the strawberries in pure water for 5 minutes and then take them out, and use filter paper to absorb the surface moisture; the coating treatment was to use a soft brush to dip pure water and gently apply it on the surface of the strawberries to form a uniform water film. Experimental group: The above-prepared 500-fold diluted fruit and vegetable fresh-keeping microemulsion was used to treat the strawberries in the same spraying, soaking or coating manner as the control group. Storage conditions: The treated strawberries were stored at room temperature and relevant indicators were tested regularly.

[0072] Appearance status perception: observe the appearance changes of strawberries with the naked eye, including color, glossiness, whether there is mildew, rot spots, and the fullness of the fruit. Observe the state of the strawberries every 12 hours and take photos to record. Figure 4As shown in the figure, in the early stage of storage, the appearance of the strawberries in the control group and the experimental group remained good, but as time went on, the strawberries in the control group gradually darkened in color and lost their luster on the surface. On the second day, they began to slightly mold, and they were basically completely moldy in more than 3 days. The appearance of the strawberries in the experimental group was significantly better than that of the control group, and the color brightness and fruit fullness remained good. Until the 5th day, there was still no mold or rot, but the appearance deteriorated.

[0073] For weight loss determination, the initial weight of strawberries in each parallel sample before storage (W 0 ) and the weight at each measurement (W t ), according to the formula: weight loss rate (%) = (W 0 -W t ) / W 0 ×100, calculate the weight loss rate. The weight of strawberries was tested every 24 hours, and the results are shown in Table 1. The weight loss rate of strawberries in the control group increased rapidly with the extension of storage time, while the weight loss rate of strawberries in the experimental group increased relatively slowly after being treated with microemulsions of different concentrations, indicating that the microemulsion can effectively inhibit the water loss of strawberries during storage and maintain the freshness of the fruit.

[0074] Table 1

[0075] Weight loss rate (%) 1 day 2 days 3 days 4 days 5 days Sample 1.1 5.2 9.9 14.2 17.5 24.9 Sample 1.2 4.0 8.9 12.3 16.0 22.3 Sample KB 5.9 14.1 21.9 29.3 37.1

[0076] Chromaticity measurement: The color of the strawberry surface was measured using a colorimeter, and the three parameters of L (brightness value), a (red-green value) and b (yellow-blue value) were recorded. The calculation formula for the total color difference ΔE was: Among them, ΔE is the total color difference, lightness difference ΔL*=L1*-L2*(lightness difference), red / green color difference Δa*=al*-a2*(red / green difference), yellow / blue color difference Δb*=bl*-b2*(yellow / blue difference), the color change of strawberry before and after 5 days was statistically detected and the color difference was calculated, and the results are shown in Table 2. With the increase of storage time, the L value of strawberry in the control group gradually decreased, and the a value and b value also changed significantly, indicating that the color deteriorated seriously; while the color parameters of the experimental group strawberry after being treated with fresh-keeping microemulsion were relatively small, especially in the early stage of storage, the color of the strawberry in each experimental group was closer to that when freshly picked, indicating that the fresh-keeping microemulsion helps to maintain the color stability of strawberry and improve its appearance quality.

[0077] Table 2

[0078] Sample No. 1.1 1.2 KB ΔE 15.27 7.07 35.86

[0079] Hardness test: The hardness of the strawberry fruit was measured at the equator using a hardness tester, and the initial hardness of the strawberry and the hardness value after 5 days were measured. The results are shown in Table 3. During storage, the hardness of the strawberry gradually decreased. The hardness of the strawberry in the control group decreased at a faster rate, while the hardness of the strawberry in the experimental group decreased relatively slowly after being treated with the fresh-keeping microemulsion, and the performance of maintaining the hardness of the strawberry was better, indicating that the microemulsion can delay the softening process of the strawberry to a certain extent and maintain the taste and texture of the fruit.

[0080] Sample No. 1.1 1.2 KB Initial hardness (kgf) 0.930 0.985 0.912 Hardness after 5d (kgf) 0.527 0.581 0.185

Claims

1. A tea tree essential oil microemulsion, characterized in that: The invention is prepared by mixing water and tea tree essential oil preparation; the tea tree essential oil preparation is composed of a composite emulsifier and tea tree essential oil, and the mass ratio of the composite emulsifier to the tea tree essential oil is (3-7):(7-3); the composite emulsifier is prepared by compounding a rosin emulsifier and a phosphate ester.

2. The tea tree essential oil microemulsion according to claim 1, characterized in that: The phosphate ester is isomeric alcohol polyoxyethylene ether phosphate ester; the composite emulsifier is prepared by compounding the rosin emulsifier and the isomeric alcohol polyoxyethylene ether phosphate ester in a mass ratio of (0.5-5):

1.

3. The tea tree essential oil microemulsion according to claim 1 or 2, characterized in that: The rosin emulsifier is prepared by esterification reaction of maleic rosin and polyethylene glycol, and the polyethylene glycol is polyethylene glycol 200, polyethylene glycol 400 and polyethylene glycol 600.

4. The tea tree essential oil microemulsion according to claim 1 or 2, characterized in that: The mass ratio of the composite emulsifier to the tea tree essential oil in the tea tree essential oil preparation is (3-4):(7-6).

5. The tea tree essential oil microemulsion according to claim 1 or 2, characterized in that: Tea tree essential oil preparations have two rapid decomposition temperatures, 160°C and 296°C; the closed cup flash point of tea tree essential oil preparations is not less than 25°C.

6. The tea tree essential oil microemulsion according to claim 1 or 2, characterized in that: The volume ratio of water to tea tree essential oil preparation is (99-600):

1.

7. The tea tree essential oil microemulsion according to claim 6, characterized in that: The volume ratio of water to tea tree essential oil preparation is (450-550):

1.

8. A method for preparing the tea tree essential oil microemulsion according to any one of claims 1 to 7, characterized in that: The rosin emulsifier and isomeric alcohol polyoxyethylene ether phosphate are mixed to obtain a composite emulsifier, the composite emulsifier and tea tree essential oil are mixed to obtain a tea tree essential oil preparation, the tea tree essential oil preparation is diluted with water to a desired multiple and mixed to obtain a tea tree essential oil microemulsion.

9. Use of the tea tree essential oil microemulsion according to any one of claims 1 to 7, characterized in that: Used for preserving fruits and vegetables after picking, or for the preparation of preservatives.

10. The use of the tea tree essential oil microemulsion according to claim 9, characterized in that: Fruits and vegetables include strawberries, citrus fruits, tomatoes, small apples, blueberries, kiwis, grapes or dates.

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