Mixed terpinene microemulsion and application thereof

Abstract

The invention provides a mixed terpinene microemulsion and application thereof, and the mixed terpinene microemulsion is obtained by dispersing and diluting a mixed terpinene preparation in pure water and self-emulsifying; wherein the volume ratio of the mixed terpinene preparation to the pure water is 1: (99-600); the mixed terpinene preparation is formed by mixing mixed terpinene and a compound emulsifier, and the compound emulsifier is formed by compounding a rosin emulsifier and calcium alkyl benzene sulfonate. The mixed terpinene microemulsion has good stability, can be used for preservation and fresh-keeping of fruits and vegetables, prolongs the shelf life, and has the advantages of high efficiency, environmental protection, no residue and the like. The preparation method is simple and convenient, the mixed terpinene preparation only needs to be diluted, dispersed and self-emulsified in pure water, the requirement for equipment is low, industrial large-scale production is easy, and the production threshold and the cost input are greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of preservation, and particularly relates to a mixed terpinene microemulsion and its application in the preservation of fruits and vegetables. Background Art

[0002] Fruits and vegetables are rich in various nutrients and are an indispensable part of people's diet. However, after being harvested, due to their own physiological metabolism and microbial infection, the problem of rotting and deterioration is serious, and the global post-harvest loss rate is as high as 20%-40%. This not only causes waste of resources, but also affects the stability of fruit and vegetable supply and economic benefits. Therefore, it is urgent to develop efficient and safe preservation technologies.

[0003] Traditional preservation methods have many defects. Refrigeration preservation inhibits the respiration of fruits and vegetables and the reproduction of microorganisms by lowering the temperature, but it has high energy consumption. Some tropical and subtropical fruits and vegetables are also prone to chilling injury and the quality deteriorates. Controlled atmosphere preservation requires professional equipment to accurately control the gas composition. The equipment is expensive and the operation is complex. If there is a slight problem with the gas seal, the preservation effect will be affected. Although chemical preservatives can inhibit bacteria, chemical residues are harmful to health and will also affect the flavor and appearance of fruits and vegetables. With the increasing concern of consumers about food safety, their application is limited. Natural preservatives have emerged as the times require. Chitosan, tea polyphenols, plant essential oils, etc. have been used in the research of fruit and vegetable preservation. However, plant essential oils have strong volatility and poor solubility, and it is difficult to form a stable and uniform protective film on the surface of fruits and vegetables, resulting in poor preservation effects.

[0004] Mixed terpinene is a renewable natural resource that can be extracted from plants such as pine trees. Its main component is terpinene, which has biological activities such as antibacterial and anti-inflammatory effects. However, due to the strong volatility and poor stability of terpinene, the application of mixed terpinene is limited. Summary of the Invention

[0005] The present invention provides a preservation method that is efficient, environmentally friendly and can effectively extend the preservation period of fruits and vegetables. The rosin emulsifier involved therein is derived from the natural product rosin resin and is used in combination with calcium alkylbenzene sulfonate. It has excellent emulsifying effects and is suitable for the preparation of mixed terpinene microemulsions. The obtained mixed terpinene microemulsions have the characteristics of high stability, good biocompatibility, high efficiency without residues, and environmental friendliness. Moreover, the preparation of mixed terpinene preparations and microemulsions is simple, the raw materials are easy to obtain, and the requirements for equipment are low.

[0006] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0007] A mixed terpinene microemulsion is obtained by self-emulsifying a mixed terpinene preparation dispersed and diluted in pure water; wherein, the volume ratio of the mixed terpinene preparation to pure water is 1:(99-600); the mixed terpinene preparation is formed by mixing mixed terpinene and a composite emulsifier, and the composite emulsifier is formed by compounding a rosin emulsifier and calcium alkylbenzene sulfonate.

[0008] The mixed terpinene microemulsion of the present invention is simple to prepare, has good stability, and has a particle size in the range of 50 to 230 nm. It can be used for the anti-corrosion and fresh-keeping of fruits and vegetables and extend the shelf life.

[0009] Dilute the mixed terpinene preparation 100 times, 300 times, 500 times, 600 times, etc. with pure water respectively to obtain a uniformly dispersed and stable mixed terpinene microemulsion.

[0010] The preparation of the above composite emulsifier is to mix the rosin emulsifier and calcium alkylbenzene sulfonate evenly.

[0011] The preparation of the above mixed terpinene preparation is to mix the composite emulsifier and the mixed terpinene evenly.

[0012] The raw material components of the mixed terpinene preparation and microemulsion of the present invention are simple, and the obtained products have excellent performance.

[0013] To balance the cost and the fresh-keeping effect, in the above mixed terpinene microemulsion, the volume ratio of the mixed terpinene preparation to pure water is 1:(450 - 550). In this application, under the condition of extremely low dosages of the mixed terpinene and the emulsifier, the stability and fresh-keeping effect of the microemulsion can be ensured, and the cost is significantly reduced.

[0014] To obtain a mixed terpinene preparation with high stability and good dispersibility, the mass ratio of the above composite emulsifier to the mixed terpinene is 1:(3 - 0.3), such as 3:7, 4:6, 5:5, 6:4, 7:3 or other ratios; further preferably, 3:7 or 4:6, that is, in the mixed terpinene preparation, the mass content of the mixed terpinene is 60 - 70%, and the mass content of the composite emulsifier is 30 - 40%. Further preferably, the mass content of the mixed terpinene is 70%, and the mass content of the composite emulsifier is 30%.

[0015] The above compounding of the composite emulsifier and the mixed terpinene in a specific mass ratio can not only maximize the performance of the emulsifier, but also have good compatibility and stability with the mixed terpinene, so as to prepare a microemulsion for fruit and vegetable fresh-keeping.

[0016] The inventor found through experiments that the above mixed terpinene preparation has a significant antibacterial effect on Escherichia coli and Staphylococcus aureus, and there is an obvious improvement compared with the mixed terpinene. That is, the composite emulsifier of this application can not only promote the improvement of the dispersibility and stability of the mixed terpinene, but also has an obvious promotion effect on the antibacterial effect.

[0017] The above mixed terpinene preparation has two rapid decomposition temperatures of 154°C and 294°C, and has good thermal stability; the mixed terpinene preparation has good compatibility and high stability, and the closed-cup flash point is not lower than 25°C.

[0018] To ensure the stability of the composite emulsifier and its compatibility with terpeneol mixture, the mass ratio of the above-mentioned rosin emulsifier to calcium alkylbenzene sulfonate is (0.5 - 5):1, such as 0.5:1, 1:1, 2:1, 5:1, etc., and more preferably (0.8 - 1.2):1.

[0019] The above-mentioned rosin emulsifier is prepared by the esterification reaction of maleic rosin and polyethylene glycol, and the calcium alkylbenzene sulfonate is calcium dodecylbenzene sulfonate.

[0020] The inventors found through experiments that the effect of preparing the microemulsion of terpeneol mixture by compounding the rosin emulsifier prepared by the esterification of maleic rosin and polyethylene glycol with calcium alkylbenzene sulfonate is the best. The polyethylene glycol is preferably polyethylene glycol 200, polyethylene glycol 400, and polyethylene glycol 600, and more preferably polyethylene glycol 600.

[0021] The above-mentioned microemulsion of terpeneol mixture has good stability, and the particle size is in the range of 50 - 230 nm. It can be used for the anti-corrosion and fresh-keeping of fruits and vegetables, and extend the shelf life.

[0022] During use, by spraying, soaking or coating the fruits and vegetables, fresh-keeping can be achieved, and the fresh-keeping period of fruits and vegetables can be effectively extended.

[0023] The above-mentioned fruits and vegetables include strawberries, citrus fruits, bananas, sweet oranges, etc.

[0024] The above-mentioned microemulsion of terpeneol mixture can also be used alone to inhibit Escherichia coli and Staphylococcus aureus, and there is a significant improvement compared with the inhibition effect of terpeneol mixture.

[0025] The method for preparing the microemulsion of terpeneol mixture of the present invention is simple, has good stability, and a high essential oil retention rate, and can be used for the fresh-keeping of fruits and vegetables.

[0026] Unless otherwise specified, all percentages in the present invention are mass percentages.

[0027] For the technologies not mentioned in the present invention, reference is made to the prior art.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The raw materials for preparing the microemulsion of terpeneol mixture are easily available, have a wide source and controllable cost. The preparation method is simple. It only needs to dilute and disperse the terpeneol mixture preparation in pure water for self-emulsification, has low requirements for equipment, is easy for large-scale industrial production, greatly reduces the production threshold and cost investment, and the terpeneol mixture preparation still maintains excellent fresh-keeping performance and stability after being diluted more than 500 times.

[0030] (2) In the preparation, the compound emulsifier and mixed terpinene are optimized in proportion, having good compatibility and stability, which can ensure the stability of the microemulsion system. The closed flash point of the mixed terpinene preparation is not lower than 25°C, and there is a specific rapid decomposition temperature, and it can maintain stable performance under different environmental conditions, ensuring its long-term effect during the fruit and vegetable preservation process and reducing the risk of failure of the preservative.

[0031] (3) The mixed terpinene preparation has a significant antibacterial effect on common pathogenic bacteria such as Escherichia coli and Staphylococcus aureus.

[0032] (4) The mixed terpinene microemulsion can significantly reduce the possibility of fruits and vegetables rotting and deteriorating due to bacterial infection, extend the shelf life of fruits and vegetables, and has the advantages of high efficiency, environmental protection, and no residue, providing a new effective method for fruit and vegetable preservation. The microemulsion can be used to treat fruits and vegetables in various ways such as spraying, soaking, or coating, and the application methods are flexible and convenient, capable of adapting to the preservation needs and treatment scenarios of different fruits and vegetables, providing diversified solutions for fruit and vegetable preservation.

[0033] (5) It meets the needs of consumers for high-quality and safe fruits and vegetables, promotes the green and efficient development of the fruit and vegetable preservation industry, reduces resource waste, improves economic and social benefits, and shows broad application prospects in the field of fruit and vegetable preservation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is the appearance diagram of the mixed terpinene preparation and microemulsion in the embodiment of the present invention;

[0035] Figure 2 It is the thermal analysis diagram of the mixed terpinene preparation in the embodiment of the present invention;

[0036] Figure 3 It is the antibacterial effect diagram of the mixed terpinene preparation in the embodiment of the present invention;

[0037] Figure 4 It is the particle size distribution diagram of the mixed terpinene microemulsion in the embodiment of the present invention (abscissa Diameter(nm), ordinate Intensity);

[0038] Figure 5 It is the strawberry preservation effect diagram of the mixed terpinene microemulsion diluted 500 times in the present invention and the control group. DETAILED DESCRIPTION OF THE INVENTION

[0039] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0040] In each example, if the temperature is not specifically stated, the operation is carried out at room temperature (20 - 25 °C). If the stirring speed is not specifically stated, the operation is carried out at 150 r / min.

[0041] Example 1

[0042] Preparation of rosin emulsifier:

[0043] Weigh 302 g of rosin (natural wetland rosin, model: AX01, product grade: first grade, origin: Jiangxi Jiajing, cas: 8050 - 09 - 7) and add it to a four - necked flask. Pass in nitrogen for protection and heat it to 120 °C on an electric heating mantle until it is completely melted. Then add 98 g of maleic anhydride, stir and raise the temperature to 190 °C, and react for 4 hours. Then add 900 g of polyethylene glycol 600, stir evenly, and raise the temperature to 270 °C for heat - preservation reaction for 6 hours. When the acid value is less than 20 mgKOH / g, cool it to below 120 °C, add 3 g of antioxidant 1010, stir evenly and then discharge to obtain rosin emulsifier 1.

[0044] Weigh 302 g of rosin (natural wetland rosin, model: AX01, product grade: first grade, origin: Jiangxi Jiajing, cas: 8050 - 09 - 7) and add it to a four - necked flask. Pass in nitrogen for protection and heat it to 120 °C on an electric heating mantle until it is completely melted. Then add 98 g of maleic anhydride, stir and raise the temperature to 190 °C, and react for 4 hours. Then add 600 g of polyethylene glycol 400, stir evenly, and raise the temperature to 270 °C for heat - preservation reaction for 6 hours. When the acid value is less than 20 mgKOH / g, cool it to below 120 °C, add 3 g of antioxidant 1010, stir evenly and then discharge to obtain rosin emulsifier 2.

[0045] Preparation of composite emulsifier:

[0046] Accurately weigh 20 g of rosin emulsifier (rosin emulsifier 1 or 2) and 20 g of calcium dodecylbenzenesulfonate, place them in a clean and dry 100 - ml beaker, install a stirring device, turn on the stirring device, set the stirring speed to 400 rpm, stir at room temperature for 5 minutes to preliminarily mix the mixed emulsifier evenly in the beaker. Observe that the mixed liquid of the emulsifier gradually becomes uniform and clear, without obvious stratification or precipitation phenomenon. Continue to stir for 5 minutes, then turn off the stirring device to obtain a composite emulsifier with a mass - fraction ratio of 1:1. The composite emulsifier prepared with rosin emulsifier 1 is defined as composite emulsifier 1, and the composite emulsifier prepared with rosin emulsifier 2 is defined as composite emulsifier 2.

[0047] Example 2

[0048] Preparation of mixed terpinene:

[0049] Accurately weigh 70 g of mixed terpinene (purchased from: Fujian Senmeida Biotechnology Co., Ltd., α-terpinene ≥ 20%, γ-terpinene ≥ 30%, terpinolene ≥ 30%), and pour it into a 250 mL three-necked flask. Weigh 30 g of the composite emulsifier (composite emulsifier 1 or composite emulsifier 2 prepared in Example 1), and add it to the three-necked flask. Turn on the stirrer and stir at a speed of 600 rpm for 5 minutes to fully mix the composite emulsifier and mixed terpinene evenly, obtaining a mixed terpinene preparation with a mass ratio of 3:7, which is yellow and transparent, as Figure 1 shown in (a), where 3.1 is the mixed terpinene preparation obtained using composite emulsifier 1, and 3.2 is the mixed terpinene preparation obtained using composite emulsifier 2.

[0050] Accurately weigh 20 g of the newly prepared mixed terpinene preparation, and separately fill it into 30 mL transparent glass bottles (that is, each glass bottle contains 20 g of the mixed terpinene preparation). After sealing, place them in environments at 55 °C, 25 °C, and -4 °C for 6 months respectively, and set 2 samples in each group. After observation, no stratification, precipitation, or turbidity occurred in each group regardless of whether rosin emulsifier 1 or rosin emulsifier 2 was used as the composite emulsifier, and the original particle size was basically maintained (particle size change rate ≤ 3%), indicating that the mixed terpinene preparation has good compatibility and stability.

[0051] Use a closed-cup flash point tester to measure the closed-cup flash point of the mixed terpinene preparation. The closed-cup flash points of the mixed terpinene preparations 3.1 and 3.2 are not lower than 25 °C, meeting the requirements for safe storage and use.

[0052] Use a thermogravimetric analyzer to conduct thermal analysis tests on the mixed terpinene preparation. As Figure 2 shown, there are two rapid decomposition temperatures for the mixed terpinene preparation 3.1, which are about 154 °C and 294 °C respectively, providing an important basis for temperature control during the processing and application of the preparation.

[0053] Comparative Example 1

[0054] Replace calcium dodecylbenzenesulfonate with agricultural emulsion 600, and the rest refer to Example 2. That is, in this example, the composite emulsifier is composed of 20 g each of rosin emulsifier 1 and agricultural emulsion 600. Then weigh 70 g of mixed terpinene and 30 g of the composite emulsifier to prepare a mixed terpinene preparation. Stratification occurred after 1 week at room temperature, after 8 h at 55 °C, and after 30 min at -4 °C.

[0055] Example 3

[0056] Antibacterial effect test:

[0057] Name the prepared mixed terpinene preparations as 3.1 (using rosin emulsifier 1) and 3.2 (using rosin emulsifier 2), as Figure 1As shown in (a). Using LB medium, after activating the strain, it was diluted to 10 7 CFU / mL with sterile normal saline at a mass concentration of 0.9% to obtain a bacterial suspension. Take 150 μL of the bacterial suspension and evenly coat it on the LB medium plate, which were respectively labeled as the control group, group 3.1, and group 3.2. On the plates of group 3.1 and group 3.2, a mixed terpinene preparation with a mass concentration of 2% was dropped respectively (the mixed terpinene preparation was diluted to a mass concentration of 2% with sterile water. The mixed terpinene preparation corresponding to rosin emulsifier 1 was used on the plate of group 3.1, and the mixed terpinene preparation corresponding to rosin emulsifier 2 was used on the plate of group 3.2), and an equal amount of sterile water was dropped in the control group. After culturing the plates at 37°C for 24 h, the colony growth situation was observed and recorded. As Figure 3 shown, compared with the control group, the mixed terpinene preparations of 3.1 and 3.2 both had obvious inhibitory effects on the growth of Staphylococcus aureus and Escherichia coli, and the number of colonies decreased significantly. The antibacterial rates of the mixed terpinene preparation 3.1 against Escherichia coli and Staphylococcus aureus were 92% and 96% respectively under the current experimental conditions, and the antibacterial rates of the mixed terpinene preparation 3.2 against Escherichia coli and Staphylococcus aureus were 91% and 94% respectively under the current experimental conditions. While the antibacterial rates of directly using mixed terpinene against Escherichia coli and Staphylococcus aureus were 75% and 78% respectively under the same experimental conditions, indicating that the mixed terpinene preparation has better antibacterial performance.

[0058] Antibacterial rate (%) = [(average number of colonies in the control group - average number of colonies in the experimental group) / average number of colonies in the control group] * 100%.

[0059] Example 4

[0060] Prepare a mixed terpinene microemulsion:

[0061] Mixed terpinene microemulsion diluted 100 times: Accurately measure 10 mL of the mixed terpinene 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 thorough mixing. A mixed terpinene microemulsion diluted 100 times was obtained, which was evenly dispersed, without floating oil, and could be stored stably.

[0062] Mixed terpinene microemulsion diluted 300 times: Accurately measure 3.33 mL of the mixed terpinene preparation (prepared in Example 2) and add it to 996.67 mL of pure water. Use a magnetic stirrer to stir at a speed of 800 rpm at room temperature for 5 minutes to prepare a mixed terpinene microemulsion diluted 300 times, which was evenly dispersed, without floating oil, and could be stored stably.

[0063] Mixed terpinene microemulsion diluted 500 times: Accurately measure 2 mL of the mixed terpinene preparation (prepared in Example 2) and mix it with 998 mL of pure water. Use a magnetic stirrer to stir at a speed of 800 rpm at room temperature for 5 minutes to obtain a mixed terpinene microemulsion diluted 500 times, as Figure 1 (b) shown (3.1 corresponds to rosin emulsifier 1, 3.2 corresponds to rosin emulsifier 2), evenly dispersed, without floating oil, and can be stored stably.

[0064] Use a laser particle size analyzer to measure the particle size of the above three different dilution multiples of the mixed terpinene microemulsion, as Figure 4 shown. The results show that the average particle sizes and PDI of 3.1-100, 3.1-300, 3.1-500, 3.2-100, 3.2-300, and 3.2-500 are 141.99, 209.58, 163.76 nm, 228.48, 218.14, 146.89 and 0.327, 0.237, 0.311, 0.340, 0.258, 0.318 respectively, indicating that the particle size of the microemulsion is evenly dispersed and has good stability, meeting the requirements of preservation applications. As mentioned above, 3.1 corresponds to rosin emulsifier 1, 3.2 corresponds to rosin emulsifier 2, and 100 / 300 / 500 are the dilution multiples respectively.

[0065] Use the specific gravity method to measure the retention rate of mixed terpinene in the mixed terpinene microemulsion. Place the newly prepared mixed terpinene microemulsion and pure mixed terpinene under the same experimental conditions and leave them open at room temperature for 7 days. The experimental results show that the retention rates of mixed terpinene in the mixed terpinene microemulsions 3.1-500 and 3.2-500 reach 78.93% and 76.58% respectively, while the retention rate of the pure mixed terpinene preparation is only 52.85%. This indicates that the mixed terpinene microemulsion has good stability, there is a synergistic protection effect among its internal components, effectively inhibiting the volatilization loss of mixed terpinene, thereby increasing the retention rate of mixed terpinene and achieving the effect of extending its effective action time, providing guarantee for the long-term effectiveness of mixed terpinene in practical applications.

[0066] Comparative Example 2

[0067] Replace the composite emulsifier with a mixture of polyoxyethylene castor oil, clove oil and ethanol in a mass ratio of 8:1:6. Refer to the method and data of Example 2 to prepare mixed terpinene. According to the method of Example 3, the inhibition rates against Escherichia coli and Staphylococcus aureus are measured to be 74% and 78% respectively, which are equivalent to the test effects of mixed terpinene under the same conditions and do not show better antibacterial performance. The retention rate of the mixed terpinene diluted 500 times according to the method of Example 4 is 62.36%.

[0068] Example 5

[0069] In this example, strawberry fruits were treated with a mixed terpinene microemulsion diluted 500 times with pure water (3.1-500 and 3.2-500). The appearance changes of the treated strawberry fruits were evaluated and photographed, and the weight loss rate, chromaticity, and hardness were measured.

[0070] The method described in this example specifically includes the following steps:

[0071] (1) Select strawberry fruits with consistent maturity, uniform size, no pests, diseases, and mechanical damage (experimental time: October, experimental site: Xiamen Campus of Huaqiao University);

[0072] (2) Randomly divide the strawberries into an experimental group and a control group. Each group is set with three parallel samples, and each parallel sample contains three strawberries to reduce the influence of accidental errors on the experimental results. Control group (KB): The strawberries were treated by spraying, soaking, or coating with pure water. During spraying treatment, a sprayer was used to evenly spray pure water on the surface of the strawberries until there was a thin water film on the surface; during soaking treatment, the strawberries were completely immersed in pure water for 5 minutes and then taken out, and the surface moisture was blotted dry with filter paper; during coating treatment, a soft brush was dipped in pure water and gently applied on the surface of the strawberries to form a uniform water film. Experimental group: The strawberries were treated with the above-prepared microemulsion diluted 500 times in the same spraying, soaking, or coating manner as the control group. Storage conditions: The treated strawberries were placed in a room temperature environment for storage, and relevant indicators were regularly detected.

[0073] Perception of the appearance state: The appearance changes of the strawberries were observed with the naked eye, including color, gloss, whether there were mildew and rot spots, and the fullness of the fruits, etc. The state of the strawberries was observed every 12 hours and photographed. As Figure 5 shown, in the early stage of storage, the appearances of the strawberries in both the control group and the experimental group remained good. However, as time passed, the color of the strawberries in the control group gradually darkened, the surface lost its luster, and slight mildew appeared on the second day, and they were basically completely mildewed in more than 3 days. While the appearance state of the strawberries in the experimental group was significantly better than that of the control group, the color vividness and fruit fullness were maintained well. Until the 5th day, there was still no mildew and rot, only the appearance became worse.

[0074] Measurement of the weight loss rate: An electronic balance was used to weigh the initial weight (W0) of the strawberries in each parallel sample before storage and the weight (W t ) at each measurement. According to the formula: weight loss rate (%) = (W0 - W t ) / W0 × 100, the weight loss rate was calculated. The weight of the strawberries was measured every 24 hours, and the results are shown in Table 1. The results show that the weight loss rate of the strawberries in the control group increased relatively fast with the extension of storage time, while after the strawberries in the experimental group were treated with the microemulsion, the weight loss rate increased relatively slowly, indicating that the microemulsion can better inhibit the water loss of strawberries during storage and maintain the freshness of the fruits.

[0075] Table 1

[0076] Weight loss rate (%) 1 day 2 days 3 days 4 days 5 days Sample 3.1 5.9 10.0 14.5 17.3 22.2 Sample 3.2 6.9 11.8 16.8 21.5 27.2 Sample KB 5.9 14.1 21.9 29.3 37.1

[0077] For colorimetric determination, a color difference meter was used to measure the color of the strawberry surface, and three parameters, namely L (luminance value), a (red / green chromaticity value), and b (yellow / blue chromaticity value), were recorded. The calculation formula for the total color difference ΔE is as follows:

[0078] Among them, ΔE is the total color difference, the lightness difference ΔL* = L1* - L2*

[0079] (lightness difference), the red / green chromaticity difference Δa* = a1* - a2* (red / green difference), and the yellow / blue chromaticity difference Δb* = b1* - b2* (yellow / blue difference). The color changes of strawberries were statistically detected before and after 5 days, and the chromaticity differences were calculated. The results are shown in Table 2. As the storage time increased, the L value of the control group strawberries gradually decreased, and the a and b values also changed significantly, indicating serious color deterioration; while for the experimental group strawberries treated with the fresh-keeping microemulsion, the changes in chromaticity parameters were relatively small. Especially in the initial stage of storage, the color of strawberries in each experimental group was closer to that at the time of fresh picking, indicating that the microemulsion helps to maintain the color stability of strawberries and improve their appearance quality.

[0080] Table 2

[0081] Sample number 3.1 3.2 KB Total color difference 6.96 17.67 35.86

[0082] For hardness determination, a hardness tester was used to measure the hardness at the equatorial part of the strawberry fruit, and the initial hardness and the hardness value after 5 days were measured. The results are shown in Table 3. During storage, the hardness of strawberries gradually decreased. The hardness of the control group strawberries decreased at a relatively fast rate, while for the experimental group strawberries treated with the fresh-keeping microemulsion, the hardness decreased relatively gently, showing better performance in maintaining the hardness of strawberries, indicating that the microemulsion can, to a certain extent, delay the softening process of strawberries and maintain the taste and texture of the fruit.

[0083] Table 3

[0084] Sample number 3.1 3.2 KB Initial hardness (kgf) 0.875 0.897 0.912 Hardness after 5d (kgf) 0.699 0.668 0.185

Claims

1. A mixed terpinene microemulsion, characterized in that: The mixed pinene preparation is dispersed and diluted in pure water for self-emulsification; wherein the volume ratio of the mixed pinene preparation to pure water is 1:(99-600); the mixed pinene preparation is mixed with mixed pinene and a composite emulsifier, and the composite emulsifier is formed by compounding a rosin emulsifier and calcium alkylbenzene sulfonate.

2. The mixed terpinene microemulsion according to claim 1, characterized in that: The volume ratio of the mixed terpinene preparation to pure water is 1:(450-550).

3. The mixed terpinene microemulsion according to claim 1 or 2, characterized in that: In the mixed terpinene preparation, the mass content of the mixed terpinene is 60-70%, and the mass content of the composite emulsifier is 30-40%.

4. The mixed terpinene microemulsion according to claim 1 or 2, characterized in that: The mixed terpinene preparation has two rapid decomposition temperatures of 154°C and 294°C; the closed cup flash point of the mixed terpinene preparation is not less than 25°C.

5. The mixed terpinene microemulsion according to claim 1 or 2, characterized in that: The mass ratio of rosin emulsifier to calcium alkylbenzene sulfonate is (0.5-5):

1.

6. The mixed terpinene 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 calcium alkylbenzene sulfonate is calcium dodecylbenzene sulfonate.

7. A use of the mixed terpinene microemulsion according to claim 1, characterized in that: Used to keep fruits and vegetables fresh.

8. The use of the mixed terpinene microemulsion according to claim 7, characterized in that: Spray, soak or coat fruits and vegetables to preserve freshness.

9. The use of the mixed terpinene microemulsion according to claim 7 or 8, characterized in that: Fruits and vegetables include strawberries, tangerines, bananas or oranges.

10. The use of the mixed terpinene microemulsion according to claim 7 or 8, characterized in that: Used for the inhibition of Escherichia coli and Staphylococcus aureus.

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