# The Application of Ozone Micro-nano Bubble Treatment Vegetable Fresh-Keeping Technology in Air Logistics Transportation

Authors: Yang Yang; Qiang Chen
Journal: Advances in Materials Science and Engineering
 (2022)

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## Abstract

In recent years, fresh fruits and vegetables have been sought after by Chinese people. The fresh-keeping technology, storage, and transportation of fruits and vegetables have also attracted a large number of people’s attention. Various methods of preservation, storage, and transportation of fruits and vegetables have begun to appear in the society. Micro and nanobubbles have the characteristics of long stay time, larger than the surface, high surface negative electricity, strong reliability, high efficiency of heat transfer, can cause oxygen free radicals, can greatly improve the actual effect of ozone and ozone utilization rate, and reduce the operation cost. This article aims to study the application of ozone micro-nano bubble processing vegetable fresh-keeping technology in air logistics and transportation, and put forward the idea of applying ozone micro-nano bubble processing fresh-keeping technology to fruits and vegetables fresh-keeping and transportation more widely. This article focuses on the introduction of ozone micro-nano bubbles, fresh-keeping technology, air transportation, and experiments on some fresh-keeping technologies in the article. The experimental results show that the vegetable preservation technology based on ozone micro-nano bubbles can better maintain the moisture and nutrients in the vegetables. The preservation technology of ozone micro-nano bubble treatment has improved the preservation of fruits and vegetables by 12%.


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## Body

## 1. Introduction

In recent years, fresh fruits and vegetables have emerged in various large and medium-sized supermarkets and online fresh food malls. They are loved by consumers because of their health, freshness, and convenient eating. This is a fast-developing new field in the food industry. However, after being picked, fruits and vegetables are susceptible to decay and deterioration due to the influence of the external environment. Efficient and convenient fruit and vegetable preservation technology is favored by more and more fruit and vegetable manufacturers and fruit and vegetable transportation enterprises.Fruits and vegetables are still alive after harvest. They are rich in water and nutrients, but the fruit has poor protective tissue, is vulnerable to mechanical damage and microbial invasion, and is a perishable commodity. In order to better preserve fresh fruits and vegetables, in addition to necessary commercial processing after harvest, it is also necessary to provide appropriate fresh preservation facilities and create an appropriate preservation environment based on the physiological characteristics of the fruits. The physiological properties of fruits include respiration, evapotranspiration, and dormancy. Under the premise of maintaining the normal metabolism of vegetables after harvest and not causing physiological obstacles, the abnormal metabolism of fruits and vegetables is hindered to the greatest extent, thereby reducing the material consumption of fruits and vegetables, and extending the life and storage life after harvest. At the same time, it can effectively prevent the reproduction of microorganisms and prevent the corruption and deterioration of fruits and vegetables due to the penetration of microorganisms.In recent years, people have paid more and more attention to food safety, and many scientific researchers have increased their research on the preservation of fruits and vegetables and logistics and transportation. Rida’s research indicates that most research related to food-borne human pathogens is conducted on the transmission of pathogens from animal-derived foods [1]. Through research on food preservation, B A J indicated that the modified atmosphere packaging can be used to extend the shelf life and maintain the quality of fresh fruits and vegetables by changing the required gas concentration and relative humidity in the fresh produce packaging [2]. In research on fruits and vegetables, Amrutha B said that food-borne epidemics related to fresh fruits and vegetables are on the rise globally. Biofilm formation is one of the important characteristics of pathogens, making them firmly attached to the substrate and showing a virulent phenotype [3]. In the same research on fruits and vegetables as Amrutha et al. said that fresh fruits, vegetables, mushrooms, and other fresh produce are considered to be important carriers of several food-borne parasitic infections, especially those with fecal-oral transmission and parasites in the stage of strong environmental transmission [4]. Researchers have also drawn many conclusions in the research on the logistics and transportation of fruits and vegetables. In his research, Kim et al. proposed a logistics transportation robot design method based on modular conveyor rack and path planning considering the logistics center environment. The driving part of the logistics transportation robot is designed, and the working method of the lift with the lifting and transportation function is explained [5]. Researcher MHumayun research direction is different from Kim Y. MHumayun M’s research aims to contribute to the field of logistics and transportation by exploring the potential of IoT and blockchain technology in smart logistics and transportation. And MHumayun proposed a layered framework for intelligent logistics and transportation, integrating the Internet of Things and blockchain to provide intelligent logistics and transportation systems [6]. In order to facilitate logistics transportation, Cho proposed a logistics transportation robot based on automatic guided vehicles, with fork-type manipulators, which can effectively transport various small commodities on the shelves. The proposed robot system can be divided into a main server part, a drive control part and a forklift motion control part [7]. In the research of these researchers, most of them did not put forward some feasible solutions for the preservation of fruits and vegetables.The innovation of this paper is to study the existing fresh-keeping technology of fruits and vegetables, air transportation, and the fresh-keeping technology based on ozone micro-nano bubble treatment, and conduct comparative experiments on the fresh-keeping technology based on ozone micro-nano bubble treatment to verify that it is based on ozone micro-nano bubble treatment. The effectiveness of bubble treatment preservation technology provides a theoretical basis for better promoting the development of preservation technology based on ozone micro-nano bubble treatment.


## 2. Fresh-Keeping Technology and Air Logistics Transportation

### 2.1. Ozone Micro-nano Bubbles

Although ozone has strong oxidizing properties, it cannot oxidize and decompose all organic matter by itself. However, research has found that using ozone as a carrier gas for micro-nano foams can effectively decompose organic substances that are difficult to decompose. For example: PAH hydrocarbons, phenols and crephenols, heterocyclic compounds and surfactant organic compounds. More importantly, ozone may promote the generation of more hydroxyl groups from micro-nano bubbles. The hydroxyl group can play a great role in the decomposition of organic pollutants. Hydroxyl is a typical polar group that can form hydrogen bonds with water and exist in aqueous solutions of inorganic compounds, which can be used to improve the molecular structure of insoluble drugs and facilitate drug synthesis [8].


#### 2.1.1. Micro and Nano Bubbles

People usually call bubbles existing in water with a size of 10 to tens of microns as microbubbles. Bubbles with a size smaller than a few hundred nanometers are called nanobubbles [9]. In order to generate micro-nano bubbles, the existing technologies include a dissolved gas release method, an ultrasonic method, a chemical reaction method, and a shear air method. The gas release method reduces the gas solubility through the gas. The principle of shear air method is similar to that of nitrogen, which relies on the energy of laser to melt objects and uses high pressure to blow away molten objects. During which part of the material will oxidize or burn, forming oxide on the cut surface. More suitable are the shear air method and the dissolved gas release method. Table 1 shows the definitionof different bubbles.Table 1
Definition of bubbles of different sizes.
DiameterNameYears＜50μmMicro-nano bubbles20121～50μmMicrobubbles20121nm～1μmNanobubbles2012＜3μmUltrafine bubbles20081～10μmSubmicron bubbles2017Figure 1
The change of bubbles of various diameters in the water.


### 2.2. The Basic Characteristics of Micro-nano Bubbles

(1)
Micro-nano bubbles can stay in the water for a long time. After ordinary bubbles are generated in the water, they will rise rapidly to the water surface and burst and disappear. In other words, they exist for a short time. However, it takes tens of seconds for the microbubbles to disappear in the water after rupture, and in some cases several minutes [10]. Figure 1 shows a graph showing the change of bubbles of various diameters in the water(2)
Generate free radical ions. Generally speaking, when the microbubbles are smaller than 10μm and shrink continuously, the charge density of the electric double layer will increase sharply. In addition, there are many free radical ions such as oxygen ions, hydrogen ions, and hydroxide ions. Among them, the oxidation of hydroxyl groups is strong, and the organic pollutants that are difficult to be decomposed by oxidative decomposition have a great effect on the purification of water quality [11].(3)
Chargeability. The surface of the microbubbles is negatively charged, which is higher than that of ordinary bubbles. Generally speaking, the surface charge of bubbles below 30μ is about -40mv, so the microbubbles will not be damaged if they gather together. Utilizing the negative charge of microbubbles, it can adsorb positively charged substances in water, and has a good effect on the adsorption and separation of floating substances and pollutants in water.


### 2.3. The Use of Micro-nano Bubbles

#### 2.3.1. Water Treatment

Micro-nano bubble technology is a high-end water environment treatment technology that integrates water environment treatment, air flotation, filtration, disinfection, and dissolved oxygen. Especially through appropriate horizontal stirring, it can accelerate the oxidation and decomposition of organic pollutants in the water. The horizontal distribution range of microbubbles and nanobubbles can be expanded, and they can be completely mixed with the surrounding water body as much as possible, and oxidation reaction can be performed, which plays an important role in the effect of water purification [12]. This is a fundamental change in the water environment, which can maximize the biochemical efficiency of microbes with good oxygen.


#### 2.3.2. Disposal of Agricultural and Sideline Products

Functional micro-nano bubbles can achieve harmless physical sterilization, not only can maintain the species and original quality of plants but also achieve the purpose of sterilization. It has a greater effect on removing pesticide residues attached to fresh fruits and vegetables and can better solve the pollution problems of food, vegetables, and fruits [13].


#### 2.3.3. Water Saving Irrigation

Adding dry water to the irrigation water can directly supply oxygen to the roots of crops, optimize the root gas environment, promote crop growth, and achieve a very good new high-efficiency water-saving irrigation technology. In addition, water saving, energy saving, and environmental protection can also increase crop yields and increase crop income.Micro-nano bubbles are used in many aspects. Figure2 shows a schematic diagram of the more widely used fields of micro-nano bubbles.Figure 2
Application areas of micro-nano bubbles.


### 2.4. Ozone

Ozone is a powerful oxidant. When S and N atoms are present, it can convert organic compounds into smaller compounds orCO2, H2O, sulfate and nitrate anions. It is characterized by short life and low solubility in water media. In order to overcome low solubility, some technologies have been explored, such as porous glass or metal fixed bed, solid catalyst, stirring, linear mixer, contact tower, and increasing retention time by large bubble tower or diffuser. Linear mixer are strong, the overall aluminum alloy casting, work will not produce movement, and easy to use, a touch can be, a single speed mixing to reduce the operation error. O3 is usually generated in situ by an electric discharge in a stream of oxygen or air, leaving neither odor nor residual taste. When O3 is used in alkaline medium, it is used in combination with ultraviolet light/sunlight or the addition of transition metal cations, and it is characterized by AOP. In an acidic medium, the proton H +  reacts with O3 to generate O2 and H2O, preventing aa from directly reacting with pollutants, as shown in formula fd1:(1)O3+2H++2e−⟶O2+H2OAt alkaline pH, the effect ofO3 is beneficial. O3 reacts with OH- to form HO-, as described in Equation fd2.(2)O3+H2O⟶O3−+HO.Free radicals (H2O), which react with O3 again to generate (3)and (4)(3)O3.−⟶O3.−+O2(4)OH.−+H+⟶HO..


### 2.5. Ozone Calculation

The effect of dissolved ozone concentration on the inactivation of water parameters is determined by the ozone dose in the reactor, that is, the ozone concentration in the ozone generator is measured with iodine. Ozone is a strong oxidant. Potassium iodide solution reacts with free iodine. Using starch as an indicator, titration and acidification with 0.100 mol/L sodium thiosulfate standard solution are used to calculate ozone consumption.(5)O3+2KI+H2O⟶O2+I2+2KOHI2+2Na2S2O3⟶2NaI+Na2S4O6


### 2.6. Experimental Steps

In the first step, measure 20 ml of potassium iodide solution, pour it into a 500 ml Erlenmeyer flask, and add 350 ml of distilled water.The second step is to sample the ozone gas from the ozone generator and record the sampling time t (for example, 4 min). In the third step, immediately add 5 ml (1 + 5) sulfuric acid solution (pH value lower than (2) after sampling, shake well, and leave for 5 minutes; in the fourth step, after 5 minutes, use 0.1 mol/L sodium thiosulfate standard solution, drop the solution into the back flask, the solution in the flask is light yellow, add a few drops of starch solution, and quickly drop until the color disappears. The fifth step is to record the amount of sodium thiosulfate standard solution.


### 2.7. Calculation of Dissolved Ozone Concentration

#### 2.7.1. Preparation Procedure

(6)DO3mg/min=L1−P1∗Z2m=2.4∗P1m.In the formula, L1 represents the molar concentration of sodium thiosulfate standard solution, and P1 represents the volume of sodium thiosulfate standard solution.The measuring method of dissolved ozone concentration is as follows:(7)NO3mg/l=QO−QIε∗M∗TOTa∗Y∗103=62544∗QO−QI.


### 2.8. Fresh-Keeping Technology

Vegetables have the characteristics of seasonality, regionality, instability, prone to spoilage, and corruption. In addition to selecting suitable varieties, mastering cultivation and management techniques, and obtaining excellent products, they must also have good post-harvest processing and preservation techniques to ensure that the vegetables are exhausted. It may keep fresh and excellent texture, flavor and nutritional value for a long time [14]. Figure 3 shows the most commonly used vegetable preservation technology in the world.Figure 3
Commonly used preservation technology.


### 2.9. Vacuum Precooling

The boiling point of water under normal pressure is 100 °C, and the latent heat of evaporation is 2256 KJ/kg. If the pressure is lowered, the boiling point of water will also drop. When the air pressure is 621 Pa, the boiling point of water is 0 °C, and the latent heat of evaporation is 2400 KJ/kg. Vacuum precooling is a cooling method that uses reduced pressure to reduce the boiling point of water and takes away the heat of vegetable products through water vaporization [15]. Therefore, as long as a certain degree of vacuum is maintained, the moisture of vegetables will evaporate at low temperatures, consuming more heat. Most of the required latent heat is generated from the sensible heat emitted by the article itself, and it can be cooled quickly. Most of the water during cooling evaporates on the surface of the vegetables, and there is also the possibility of part of the water evaporating between the cells [16].


### 2.10. Refrigerate and Keep Fresh

Ice storage is a storage method that uses natural ice to maintain a low storage temperature. There are two methods of direct cooling and indirect cooling. The so-called direct refrigeration refers to placing ice directly in the storage warehouse and cooling the products in the ice storage after absorbing heat and melting. It has the characteristics of high refrigeration efficiency and low storage cost, but it is not easy to control the humidity of the storage environment. The indirect cooling method uses brine as the intermediate cooling medium, which is convenient for temperature adjustment. However, the thermal efficiency is low, the investment is high, and the maintenance cost is also high. Because the freezing point temperature of salt water is lower than that of water, the water temperature will drop rapidly, so the salt water will absorb more heat from the boiling water, so the water will be cold faster. This is the reason why salt is sprinkled on ice roads in winter. Reference [17].


### 2.11. PVC Cling Film to Keep Fresh

Modified atmosphere storage and preservation of plastic film tents, this method is to place vegetables in a sealed environment created by plastic film tents to achieve modified atmosphere preservation [18]. Atmosphere adjustment methods are divided into two categories. One is natural oxygen method. Through the respiration of fruits and vegetables, the required low oxygen and high carbon dioxide gas concentration is gradually formed in the tent. Because the plastic film has a certain degree of air permeability, it can realize simple air adjustment; it is also possible to use the cassia rubber film with selective air permeability to open a certain area of the window on the tent to automatically adjust the gas. In order to prevent excessive accumulation of carbon dioxide, the lime can be used in the tent to absorb carbon dioxide. The main components of lime contain alkaline substances such as calcium oxide and sodium hydroxide, which can react with CO₂. Reference [19].The PVC fresh-keeping storage method is to realize gas regulation, placing vegetables in a closed environment made of PVC plastic film. There are two types of gas adjustment methods. One is the natural oxygen method. Through the respiration of fruits and vegetables, the required concentration of low oxygen and high carbon dioxide in the film is gradually formed. The plastic film has certain air permeability, so it can easily realize the gas exchange; you can also use the cassia rubber film with selective ventilation to open a specific area of the film to automatically adjust the gas. To prevent excessive accumulation of carbon dioxide, lime can be used to absorb carbon dioxide in the film.


#### 2.11.1. Ozone Micro-nano Bubble Treatment and Preservation Technology

As a powerful oxidant, ozone can oxidize gases such as ethylene and ethanol released through respiration and metabolism. It has bactericidal properties and is widely used in the preservation of fruits and vegetables after harvesting [20]. Because ozone is unstable and easily decomposes in water, combined with micro-nano bubbles, the amount of dissolved water increases, and a certain concentration can be maintained through continuous bleaching.


### 2.12. Air Transportation

Air transportation refers to the use of airplanes to transport goods from one place to another. This transportation includes land transportation within the airport, as well as the origin of the goods, the destination of the goods and the land transportation between the corresponding airports [21].


### 2.13. Classification of Air Transportation

According to the transportation boundary, air cargo can be divided into domestic air cargo and international air cargo. Domestic air cargo means that the origin and destination of cargo transportation are within the same country. International air cargo means that the origin and destination of cargo transportation are in two different countries [22]. Figure 4 shows the common types of air transport.Figure 4
Common types of air cargo transportation.


### 2.14. Characteristics of Air Transportation

The main characteristics of air cargo are high speed, safety, high cost, and high mobility. Fast is the main feature of air cargo. Nowadays, the flying speed of aircraft is basically about 900 kilometers per hour. Compared with other transportation methods, especially long-distance transportation, it has obvious advantages in transit time [23]. The safety characteristics of air cargo are embodied in the high safety of the aircraft itself, the high driving height, and the relatively simple transportation environment. Moreover, air transportation is carried out in the air during the entire transportation process. The flight environment is relatively stable, and its protective effect on cargo is also strong [24]. The high mobility of air cargo is mainly because it is less restricted by geographical conditions. As long as there is a civil airport that can carry out aircraft take-off and landing, it can be transported [25].


## 2.1. Ozone Micro-nano Bubbles

Although ozone has strong oxidizing properties, it cannot oxidize and decompose all organic matter by itself. However, research has found that using ozone as a carrier gas for micro-nano foams can effectively decompose organic substances that are difficult to decompose. For example: PAH hydrocarbons, phenols and crephenols, heterocyclic compounds and surfactant organic compounds. More importantly, ozone may promote the generation of more hydroxyl groups from micro-nano bubbles. The hydroxyl group can play a great role in the decomposition of organic pollutants. Hydroxyl is a typical polar group that can form hydrogen bonds with water and exist in aqueous solutions of inorganic compounds, which can be used to improve the molecular structure of insoluble drugs and facilitate drug synthesis [8].


### 2.1.1. Micro and Nano Bubbles

People usually call bubbles existing in water with a size of 10 to tens of microns as microbubbles. Bubbles with a size smaller than a few hundred nanometers are called nanobubbles [9]. In order to generate micro-nano bubbles, the existing technologies include a dissolved gas release method, an ultrasonic method, a chemical reaction method, and a shear air method. The gas release method reduces the gas solubility through the gas. The principle of shear air method is similar to that of nitrogen, which relies on the energy of laser to melt objects and uses high pressure to blow away molten objects. During which part of the material will oxidize or burn, forming oxide on the cut surface. More suitable are the shear air method and the dissolved gas release method. Table 1 shows the definitionof different bubbles.Table 1
Definition of bubbles of different sizes.
DiameterNameYears＜50μmMicro-nano bubbles20121～50μmMicrobubbles20121nm～1μmNanobubbles2012＜3μmUltrafine bubbles20081～10μmSubmicron bubbles2017Figure 1
The change of bubbles of various diameters in the water.


## 2.1.1. Micro and Nano Bubbles

People usually call bubbles existing in water with a size of 10 to tens of microns as microbubbles. Bubbles with a size smaller than a few hundred nanometers are called nanobubbles [9]. In order to generate micro-nano bubbles, the existing technologies include a dissolved gas release method, an ultrasonic method, a chemical reaction method, and a shear air method. The gas release method reduces the gas solubility through the gas. The principle of shear air method is similar to that of nitrogen, which relies on the energy of laser to melt objects and uses high pressure to blow away molten objects. During which part of the material will oxidize or burn, forming oxide on the cut surface. More suitable are the shear air method and the dissolved gas release method. Table 1 shows the definitionof different bubbles.Table 1
Definition of bubbles of different sizes.
DiameterNameYears＜50μmMicro-nano bubbles20121～50μmMicrobubbles20121nm～1μmNanobubbles2012＜3μmUltrafine bubbles20081～10μmSubmicron bubbles2017Figure 1
The change of bubbles of various diameters in the water.


## 2.2. The Basic Characteristics of Micro-nano Bubbles

(1)
Micro-nano bubbles can stay in the water for a long time. After ordinary bubbles are generated in the water, they will rise rapidly to the water surface and burst and disappear. In other words, they exist for a short time. However, it takes tens of seconds for the microbubbles to disappear in the water after rupture, and in some cases several minutes [10]. Figure 1 shows a graph showing the change of bubbles of various diameters in the water(2)
Generate free radical ions. Generally speaking, when the microbubbles are smaller than 10μm and shrink continuously, the charge density of the electric double layer will increase sharply. In addition, there are many free radical ions such as oxygen ions, hydrogen ions, and hydroxide ions. Among them, the oxidation of hydroxyl groups is strong, and the organic pollutants that are difficult to be decomposed by oxidative decomposition have a great effect on the purification of water quality [11].(3)
Chargeability. The surface of the microbubbles is negatively charged, which is higher than that of ordinary bubbles. Generally speaking, the surface charge of bubbles below 30μ is about -40mv, so the microbubbles will not be damaged if they gather together. Utilizing the negative charge of microbubbles, it can adsorb positively charged substances in water, and has a good effect on the adsorption and separation of floating substances and pollutants in water.


## 2.3. The Use of Micro-nano Bubbles

### 2.3.1. Water Treatment

Micro-nano bubble technology is a high-end water environment treatment technology that integrates water environment treatment, air flotation, filtration, disinfection, and dissolved oxygen. Especially through appropriate horizontal stirring, it can accelerate the oxidation and decomposition of organic pollutants in the water. The horizontal distribution range of microbubbles and nanobubbles can be expanded, and they can be completely mixed with the surrounding water body as much as possible, and oxidation reaction can be performed, which plays an important role in the effect of water purification [12]. This is a fundamental change in the water environment, which can maximize the biochemical efficiency of microbes with good oxygen.


### 2.3.2. Disposal of Agricultural and Sideline Products

Functional micro-nano bubbles can achieve harmless physical sterilization, not only can maintain the species and original quality of plants but also achieve the purpose of sterilization. It has a greater effect on removing pesticide residues attached to fresh fruits and vegetables and can better solve the pollution problems of food, vegetables, and fruits [13].


### 2.3.3. Water Saving Irrigation

Adding dry water to the irrigation water can directly supply oxygen to the roots of crops, optimize the root gas environment, promote crop growth, and achieve a very good new high-efficiency water-saving irrigation technology. In addition, water saving, energy saving, and environmental protection can also increase crop yields and increase crop income.Micro-nano bubbles are used in many aspects. Figure2 shows a schematic diagram of the more widely used fields of micro-nano bubbles.Figure 2
Application areas of micro-nano bubbles.


## 2.3.1. Water Treatment

Micro-nano bubble technology is a high-end water environment treatment technology that integrates water environment treatment, air flotation, filtration, disinfection, and dissolved oxygen. Especially through appropriate horizontal stirring, it can accelerate the oxidation and decomposition of organic pollutants in the water. The horizontal distribution range of microbubbles and nanobubbles can be expanded, and they can be completely mixed with the surrounding water body as much as possible, and oxidation reaction can be performed, which plays an important role in the effect of water purification [12]. This is a fundamental change in the water environment, which can maximize the biochemical efficiency of microbes with good oxygen.


## 2.3.2. Disposal of Agricultural and Sideline Products

Functional micro-nano bubbles can achieve harmless physical sterilization, not only can maintain the species and original quality of plants but also achieve the purpose of sterilization. It has a greater effect on removing pesticide residues attached to fresh fruits and vegetables and can better solve the pollution problems of food, vegetables, and fruits [13].


## 2.3.3. Water Saving Irrigation

Adding dry water to the irrigation water can directly supply oxygen to the roots of crops, optimize the root gas environment, promote crop growth, and achieve a very good new high-efficiency water-saving irrigation technology. In addition, water saving, energy saving, and environmental protection can also increase crop yields and increase crop income.Micro-nano bubbles are used in many aspects. Figure2 shows a schematic diagram of the more widely used fields of micro-nano bubbles.Figure 2
Application areas of micro-nano bubbles.


## 2.4. Ozone

Ozone is a powerful oxidant. When S and N atoms are present, it can convert organic compounds into smaller compounds orCO2, H2O, sulfate and nitrate anions. It is characterized by short life and low solubility in water media. In order to overcome low solubility, some technologies have been explored, such as porous glass or metal fixed bed, solid catalyst, stirring, linear mixer, contact tower, and increasing retention time by large bubble tower or diffuser. Linear mixer are strong, the overall aluminum alloy casting, work will not produce movement, and easy to use, a touch can be, a single speed mixing to reduce the operation error. O3 is usually generated in situ by an electric discharge in a stream of oxygen or air, leaving neither odor nor residual taste. When O3 is used in alkaline medium, it is used in combination with ultraviolet light/sunlight or the addition of transition metal cations, and it is characterized by AOP. In an acidic medium, the proton H +  reacts with O3 to generate O2 and H2O, preventing aa from directly reacting with pollutants, as shown in formula fd1:(1)O3+2H++2e−⟶O2+H2OAt alkaline pH, the effect ofO3 is beneficial. O3 reacts with OH- to form HO-, as described in Equation fd2.(2)O3+H2O⟶O3−+HO.Free radicals (H2O), which react with O3 again to generate (3)and (4)(3)O3.−⟶O3.−+O2(4)OH.−+H+⟶HO..


## 2.5. Ozone Calculation

The effect of dissolved ozone concentration on the inactivation of water parameters is determined by the ozone dose in the reactor, that is, the ozone concentration in the ozone generator is measured with iodine. Ozone is a strong oxidant. Potassium iodide solution reacts with free iodine. Using starch as an indicator, titration and acidification with 0.100 mol/L sodium thiosulfate standard solution are used to calculate ozone consumption.(5)O3+2KI+H2O⟶O2+I2+2KOHI2+2Na2S2O3⟶2NaI+Na2S4O6


## 2.6. Experimental Steps

In the first step, measure 20 ml of potassium iodide solution, pour it into a 500 ml Erlenmeyer flask, and add 350 ml of distilled water.The second step is to sample the ozone gas from the ozone generator and record the sampling time t (for example, 4 min). In the third step, immediately add 5 ml (1 + 5) sulfuric acid solution (pH value lower than (2) after sampling, shake well, and leave for 5 minutes; in the fourth step, after 5 minutes, use 0.1 mol/L sodium thiosulfate standard solution, drop the solution into the back flask, the solution in the flask is light yellow, add a few drops of starch solution, and quickly drop until the color disappears. The fifth step is to record the amount of sodium thiosulfate standard solution.


## 2.7. Calculation of Dissolved Ozone Concentration

### 2.7.1. Preparation Procedure

(6)DO3mg/min=L1−P1∗Z2m=2.4∗P1m.In the formula, L1 represents the molar concentration of sodium thiosulfate standard solution, and P1 represents the volume of sodium thiosulfate standard solution.The measuring method of dissolved ozone concentration is as follows:(7)NO3mg/l=QO−QIε∗M∗TOTa∗Y∗103=62544∗QO−QI.


## 2.7.1. Preparation Procedure

(6)DO3mg/min=L1−P1∗Z2m=2.4∗P1m.In the formula, L1 represents the molar concentration of sodium thiosulfate standard solution, and P1 represents the volume of sodium thiosulfate standard solution.The measuring method of dissolved ozone concentration is as follows:(7)NO3mg/l=QO−QIε∗M∗TOTa∗Y∗103=62544∗QO−QI.


## 2.8. Fresh-Keeping Technology

Vegetables have the characteristics of seasonality, regionality, instability, prone to spoilage, and corruption. In addition to selecting suitable varieties, mastering cultivation and management techniques, and obtaining excellent products, they must also have good post-harvest processing and preservation techniques to ensure that the vegetables are exhausted. It may keep fresh and excellent texture, flavor and nutritional value for a long time [14]. Figure 3 shows the most commonly used vegetable preservation technology in the world.Figure 3
Commonly used preservation technology.


## 2.9. Vacuum Precooling

The boiling point of water under normal pressure is 100 °C, and the latent heat of evaporation is 2256 KJ/kg. If the pressure is lowered, the boiling point of water will also drop. When the air pressure is 621 Pa, the boiling point of water is 0 °C, and the latent heat of evaporation is 2400 KJ/kg. Vacuum precooling is a cooling method that uses reduced pressure to reduce the boiling point of water and takes away the heat of vegetable products through water vaporization [15]. Therefore, as long as a certain degree of vacuum is maintained, the moisture of vegetables will evaporate at low temperatures, consuming more heat. Most of the required latent heat is generated from the sensible heat emitted by the article itself, and it can be cooled quickly. Most of the water during cooling evaporates on the surface of the vegetables, and there is also the possibility of part of the water evaporating between the cells [16].


## 2.10. Refrigerate and Keep Fresh

Ice storage is a storage method that uses natural ice to maintain a low storage temperature. There are two methods of direct cooling and indirect cooling. The so-called direct refrigeration refers to placing ice directly in the storage warehouse and cooling the products in the ice storage after absorbing heat and melting. It has the characteristics of high refrigeration efficiency and low storage cost, but it is not easy to control the humidity of the storage environment. The indirect cooling method uses brine as the intermediate cooling medium, which is convenient for temperature adjustment. However, the thermal efficiency is low, the investment is high, and the maintenance cost is also high. Because the freezing point temperature of salt water is lower than that of water, the water temperature will drop rapidly, so the salt water will absorb more heat from the boiling water, so the water will be cold faster. This is the reason why salt is sprinkled on ice roads in winter. Reference [17].


## 2.11. PVC Cling Film to Keep Fresh

Modified atmosphere storage and preservation of plastic film tents, this method is to place vegetables in a sealed environment created by plastic film tents to achieve modified atmosphere preservation [18]. Atmosphere adjustment methods are divided into two categories. One is natural oxygen method. Through the respiration of fruits and vegetables, the required low oxygen and high carbon dioxide gas concentration is gradually formed in the tent. Because the plastic film has a certain degree of air permeability, it can realize simple air adjustment; it is also possible to use the cassia rubber film with selective air permeability to open a certain area of the window on the tent to automatically adjust the gas. In order to prevent excessive accumulation of carbon dioxide, the lime can be used in the tent to absorb carbon dioxide. The main components of lime contain alkaline substances such as calcium oxide and sodium hydroxide, which can react with CO₂. Reference [19].The PVC fresh-keeping storage method is to realize gas regulation, placing vegetables in a closed environment made of PVC plastic film. There are two types of gas adjustment methods. One is the natural oxygen method. Through the respiration of fruits and vegetables, the required concentration of low oxygen and high carbon dioxide in the film is gradually formed. The plastic film has certain air permeability, so it can easily realize the gas exchange; you can also use the cassia rubber film with selective ventilation to open a specific area of the film to automatically adjust the gas. To prevent excessive accumulation of carbon dioxide, lime can be used to absorb carbon dioxide in the film.


### 2.11.1. Ozone Micro-nano Bubble Treatment and Preservation Technology

As a powerful oxidant, ozone can oxidize gases such as ethylene and ethanol released through respiration and metabolism. It has bactericidal properties and is widely used in the preservation of fruits and vegetables after harvesting [20]. Because ozone is unstable and easily decomposes in water, combined with micro-nano bubbles, the amount of dissolved water increases, and a certain concentration can be maintained through continuous bleaching.


## 2.11.1. Ozone Micro-nano Bubble Treatment and Preservation Technology

As a powerful oxidant, ozone can oxidize gases such as ethylene and ethanol released through respiration and metabolism. It has bactericidal properties and is widely used in the preservation of fruits and vegetables after harvesting [20]. Because ozone is unstable and easily decomposes in water, combined with micro-nano bubbles, the amount of dissolved water increases, and a certain concentration can be maintained through continuous bleaching.


## 2.12. Air Transportation

Air transportation refers to the use of airplanes to transport goods from one place to another. This transportation includes land transportation within the airport, as well as the origin of the goods, the destination of the goods and the land transportation between the corresponding airports [21].


## 2.13. Classification of Air Transportation

According to the transportation boundary, air cargo can be divided into domestic air cargo and international air cargo. Domestic air cargo means that the origin and destination of cargo transportation are within the same country. International air cargo means that the origin and destination of cargo transportation are in two different countries [22]. Figure 4 shows the common types of air transport.Figure 4
Common types of air cargo transportation.


## 2.14. Characteristics of Air Transportation

The main characteristics of air cargo are high speed, safety, high cost, and high mobility. Fast is the main feature of air cargo. Nowadays, the flying speed of aircraft is basically about 900 kilometers per hour. Compared with other transportation methods, especially long-distance transportation, it has obvious advantages in transit time [23]. The safety characteristics of air cargo are embodied in the high safety of the aircraft itself, the high driving height, and the relatively simple transportation environment. Moreover, air transportation is carried out in the air during the entire transportation process. The flight environment is relatively stable, and its protective effect on cargo is also strong [24]. The high mobility of air cargo is mainly because it is less restricted by geographical conditions. As long as there is a civil airport that can carry out aircraft take-off and landing, it can be transported [25].


## 3. Fruit and Vegetable Storage Experiment Based on Different Fruit and Vegetable Preservation Technologies

In the experiments in this article, the vacuum precooling preservation technology, PVC plastic wrap preservation technology, and ozone micro-nano treatment preservation technology were carried out as control experiments. These three preservation technologies can compare which preservation effect is better and make use of real applications [26]. During the experiment, the experiment data were recorded on the same fresh vegetable (lettuce).


### 3.1. Vegetable Fresh-Keeping Experiment Based on Vacuum Precooling Fresh-Keeping Technology

In this experiment, the water loss rate, chlorophyll content, and ascorbic acid content of lettuce in the vacuum precooling fresh-keeping machine were recorded. The water loss rate, chlorophyll content, and ascorbate content of lettuce can obviously reflect the freshness of the fruit. Table2 shows the experimental data in this experiment.Table 2
Experimental data table of vegetable preservation based on vacuum precooling preservation technology.
Day 1Day 4Day 5Day 7Day 9Day 11Day 13Water loss rate0%7%12%19%30%36%42%Ascorbic acid content13976.554.63.7Chlorophyll content90%86%80%75%69%60%59%


### 3.2. Vegetable Fresh-Keeping Experiment Based on PVC Cling Film Fresh-Keeping Technology

In this experiment, lettuce was covered with a film, and the material used was PVC cling film. The characteristics of PVC protective film are that it is firm and not firm and it sticks firmly to the surface of various sheets. When the processing process is completed and it is uncovered, it is not easy to have collagen fibers remaining, and it will not cause corrosion. The whole experiment was carried out under normal temperature environment. Table3 shows the experimental data in this experiment.Table 3
Experimental data table of vegetable preservation based on PVC plastic film preservation technology.
Day 1Day 2Day 3Day 4Day 5Day 6Water loss rate1%3%5%18%24%30%Ascorbic acid content12864.8542.8Chlorophyll content91%78%62%54%41%35%


### 3.3. Vegetable Fresh-Keeping Experiment Based on Ozone Micro-nano Bubble Fresh-Keeping Technology

In this experiment, the experiment was carried out under the storage condition of (20 ± 1) °C. Table4 shows the experimental data in this experiment.Table 4
Experimental data table of vegetable preservation based on ozone micro-nano bubble preservation technology.
Day 1Day 2Day 3Day 4Day 5Water loss rate (Na)0%2%3%5%6%Ascorbic acid content1413.612.111.510Chlorophyll content (Na)92%91%90%88.2%87.1%Yellowing index0%5%7%12%14%Sensory score98764


## 3.1. Vegetable Fresh-Keeping Experiment Based on Vacuum Precooling Fresh-Keeping Technology

In this experiment, the water loss rate, chlorophyll content, and ascorbic acid content of lettuce in the vacuum precooling fresh-keeping machine were recorded. The water loss rate, chlorophyll content, and ascorbate content of lettuce can obviously reflect the freshness of the fruit. Table2 shows the experimental data in this experiment.Table 2
Experimental data table of vegetable preservation based on vacuum precooling preservation technology.
Day 1Day 4Day 5Day 7Day 9Day 11Day 13Water loss rate0%7%12%19%30%36%42%Ascorbic acid content13976.554.63.7Chlorophyll content90%86%80%75%69%60%59%


## 3.2. Vegetable Fresh-Keeping Experiment Based on PVC Cling Film Fresh-Keeping Technology

In this experiment, lettuce was covered with a film, and the material used was PVC cling film. The characteristics of PVC protective film are that it is firm and not firm and it sticks firmly to the surface of various sheets. When the processing process is completed and it is uncovered, it is not easy to have collagen fibers remaining, and it will not cause corrosion. The whole experiment was carried out under normal temperature environment. Table3 shows the experimental data in this experiment.Table 3
Experimental data table of vegetable preservation based on PVC plastic film preservation technology.
Day 1Day 2Day 3Day 4Day 5Day 6Water loss rate1%3%5%18%24%30%Ascorbic acid content12864.8542.8Chlorophyll content91%78%62%54%41%35%


## 3.3. Vegetable Fresh-Keeping Experiment Based on Ozone Micro-nano Bubble Fresh-Keeping Technology

In this experiment, the experiment was carried out under the storage condition of (20 ± 1) °C. Table4 shows the experimental data in this experiment.Table 4
Experimental data table of vegetable preservation based on ozone micro-nano bubble preservation technology.
Day 1Day 2Day 3Day 4Day 5Water loss rate (Na)0%2%3%5%6%Ascorbic acid content1413.612.111.510Chlorophyll content (Na)92%91%90%88.2%87.1%Yellowing index0%5%7%12%14%Sensory score98764


## 4. Experimental Analysis of Vegetable Preservation Technology

### 4.1. Experimental Analysis of Vegetable Preservation Based on Vacuum Precooling and PVC Plastic Film Preservation Technology

According to Table2 and 3, the changes of various indexes in vegetables under different preservation techniques during the experiment period can be obtained, as shown in Figure 5:Figure 5
The results of the fresh-keeping experiment based on vacuum precooling and PVC cling film.According to Figure5, it can be concluded that the preservation technology based on vacuum precooling is superior to the PVC preservation film technology in terms of water loss rate and chlorophyll content. In this experiment, the lettuce based on vacuum precooling technology had a water loss rate of only 12% on the fifth day of the experiment, while the lettuce based on the PVC cling film preservation technology had a water loss rate of 24% on the fifth day of the experiment.


### 4.2. Experimental Results of Vegetable Preservation Based on Ozone Micro-nano Bubble Preservation Technology

According to Table4, this experiment obtained a schematic diagram of the experimental results of vegetable preservation based on ozone micro-nano bubble preservation technology, as shown in Figure 6:Figure 6
Schematic diagram of the experimental results of vegetable preservation based on the ozone micro-nano bubble preservation technology.According to Figure6, it can be concluded that the water loss rate, chlorophyll content, and ascorbic acid content of lettuce based on ozone micro-nano bubble fresh-keeping technology are better than vacuum precooling and PVC cling film fresh-keeping technology. In the experiment based on ozone micro-nano bubble fresh-keeping technology, the water loss rate of lettuce in five days was only 6%, which is much better than the other two fresh-keeping technologies in the effect of keeping vegetable moisture. In addition, the ozone-based micro-nano bubble preservation technology can effectively maintain the VC content in vegetables, which is 12% higher than the original preservation technology [27, 28].


## 4.1. Experimental Analysis of Vegetable Preservation Based on Vacuum Precooling and PVC Plastic Film Preservation Technology

According to Table2 and 3, the changes of various indexes in vegetables under different preservation techniques during the experiment period can be obtained, as shown in Figure 5:Figure 5
The results of the fresh-keeping experiment based on vacuum precooling and PVC cling film.According to Figure5, it can be concluded that the preservation technology based on vacuum precooling is superior to the PVC preservation film technology in terms of water loss rate and chlorophyll content. In this experiment, the lettuce based on vacuum precooling technology had a water loss rate of only 12% on the fifth day of the experiment, while the lettuce based on the PVC cling film preservation technology had a water loss rate of 24% on the fifth day of the experiment.


## 4.2. Experimental Results of Vegetable Preservation Based on Ozone Micro-nano Bubble Preservation Technology

According to Table4, this experiment obtained a schematic diagram of the experimental results of vegetable preservation based on ozone micro-nano bubble preservation technology, as shown in Figure 6:Figure 6
Schematic diagram of the experimental results of vegetable preservation based on the ozone micro-nano bubble preservation technology.According to Figure6, it can be concluded that the water loss rate, chlorophyll content, and ascorbic acid content of lettuce based on ozone micro-nano bubble fresh-keeping technology are better than vacuum precooling and PVC cling film fresh-keeping technology. In the experiment based on ozone micro-nano bubble fresh-keeping technology, the water loss rate of lettuce in five days was only 6%, which is much better than the other two fresh-keeping technologies in the effect of keeping vegetable moisture. In addition, the ozone-based micro-nano bubble preservation technology can effectively maintain the VC content in vegetables, which is 12% higher than the original preservation technology [27, 28].


## 5. Conclusions

This paper first introduces the preservation technology and aviation logistics transportation, including ozone micro-nano bubbles, ozone, then introduces the preservation technology, air transportation, and then based on different fruit and vegetable storage test, and finally, the experimental analysis of vegetable preservation technology. Through the experiments in this article, the following conclusions can be drawn: the fresh-keeping technology based on ozone micro-nano bubble treatment is better than other fresh-keeping technologies. The fresh-keeping technology based on ozone micro-nano bubble treatment can effectively inhibit the growth and reproduction of microorganisms in vegetables. At the same time, it can also maintain the moisture and VC content in vegetables and minimize the loss of moisture and nutrients in vegetables. The experiment in this paper shows that the fresh-keeping technology based on ozone micro-nano bubbles has made great progress compared with the original fresh-keeping technology, and the effectiveness has been increased by 12%.



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*Source: 4981444-2022-07-21.xml*