1. Introduction

It is very important to maintain the quality of fresh agricultural products after harvesting. The control of post harvest food products by microorganisms has been extensively studied. The research and progress of post harvest technology is very fast. Previously, the political and economic significance of safe food supply was underestimated. Every year, there are 1.5 billion cases of food related diseases worldwide, which are the most common forms of illness worldwide. More than 3 million people die from food related illnesses every year. In the past 25 years, at least 30 new diseases caused by food or water have been recognized.

We need to ensure food safety during every post harvest processing, including the disposal and cleaning of raw materials, cleaning of utensils and pipelines, and packaging. Bacterial contamination on food processing surfaces, such as stainless steel, glass, cast iron, polypropylene, and bakelite, has been widely reported to cause food damage and disease transmission. On non food contact surfaces such as ceramic tiles, transparent porcelain, stainless steel, glassware (bathrooms and laundry shops, microbiology laboratories, swimming pools, and medical equipment), bacterial contamination can also occur if these surfaces are not completely clean. These contaminated surfaces can become reservoirs for pathogens, spreading diseases through contact with the surface.

Many commercial disinfectants and cleaning agents, such as potassium sulfate, isopropanol, hydrogen peroxide, sodium chloride, alcohol, phenol derivatives, tetramine mixtures, and chlorine, have been proven to effectively resist pathogens in food in suspension. However, because disinfectants cannot penetrate the protective layer of microbial polymer surfaces, microorganisms attached to the surface are less susceptible to influence compared to free bodies.

Chlorine bleaching is commonly used in processing (fruits, vegetables, meat, poultry, etc.) to reduce microbial pathogens. Some people also suggest using various other methods to eliminate or fully reduce bacterial populations. These methods include treatment with trisodium phosphate, hexadecyl chloride, hydrogen peroxide, photon radiation, microwave radiation, and rapid cooling. However, many of the discovered methods have not been fully accepted due to chemical residues, fading of chicken meat, high costs, or limited effectiveness. Therefore, research on reducing or eliminating bacterial populations in food, food processing surfaces, and non food contact surfaces is currently a hot topic.

Although there are currently several commercial products, new methods and technologies are still being researched. A recent discovery is the use of electrolyzed water as a disinfectant. This is the result of a new concept researched in Japan. There is evidence to suggest that electrolyzed water has a better effect as a disinfectant on meat, some fresh agricultural products, meat cutting boards, and utensils than water and chlorine solutions. Electrolyzed water can better contact the uneven surfaces of fruits and vegetables. This discovery is currently a hot topic in the United States, Canada, Japan, and other developed countries. Electrolyzed water has been introduced into the food industry as a new type of disinfectant.

The first report on the use of electrolyzed water was in the production of tofu; Alkaline electrolyzed water (BEW) is used for this purpose. Acidic electrolyzed water (AEW or AcEW) is a common disinfectant that has been confirmed to have strong bactericidal effects on many known pathogenic bacteria. Table 1 summarizes the research on the effects of AEW on many microorganisms. Although electrolyzed water does not work against bacteria, mycobacteria, fungi (and fungi), it has become a rapidly spreading disinfectant. According to reports, electrolyzed water can inhibit fungal decay in fruits. Research has shown that AEW has a good effect on reducing or eliminating pathogens caused by food and many food products on kitchen boards. For example. Electrolyzed water can reduce pathogens to undetectable levels in fish, poultry, and vegetables.

2. Electrolytic water

2.1 History

The water electrolysis technology was first used in the soda industry around 1900, including sodium hypochlorite (Japan Soda Industry Association, 1982). In 1980, this technology was introduced to the market as an automatic distributor for disinfectant supervision of stored water. With the improvement of technology and the miniaturization of machines, electrolysis technology has been applied to different fields and is regarded as a promising non heating method for hygiene control.

2.2 Terminology

Acidic electrolyzed water (AEW) is classified as functional water; Some scientists use the term electrolytic oxidized water (EO water). Similarly, alkaline electrolyzed water (AIEW) is referred to as electrolytic reduced (ER) water or alkaline electrolyzed water (BEW). Scientists have given various names to the water collected from the positive electrode, some of which are listed in Table 3. Some Japanese scientists believe that the oxidation-reduction potential (ORP) is not the principle of AEW disinfection, and they choose the terms AEW or EO water. But this article uses AEW and BEW.

2.3 Generation of electrolyzed water

Electrolyzed water is produced by a battery consisting of inert positively and negatively charged electrodes separated by a separator. The current through the electrolytic water generator and the voltage between the electrodes are set to 8-10 amperes and 9-10 volts, respectively. Saturated NaCl (or KCl/MgCl2) solution and tap water are simultaneously injected into the equipment through the laboratory water supply pipe. Continuously observe the indications on the monitor (ampere, volt, pH/ionizer) until the machine stabilizes. Batteries electrolyze water to produce two types of water, which have different properties and can be collected from different outlets.

(a) The electrolyte alkaline solution (BEW or ER water or AIEW) flowing out from the negative electrode (pH 11.4, ORP 795mV) has a strong reduction potential.

(b) The electrolyte acidic solution (AEW or EO water or AcEW) (pH 2.5, ORP>1100mV， Chlorine based reactants (10~90ppm) have strong bactericidal effects.

Record the pH value and ORP using a pH/ion analyzer. The pH, ORP, and free chlorine concentration of electrolyzed water made from tap water were found to be almost the same as those produced by electrolyzing distilled water. AEW and BEW were collected in different containers. Electrolyzed water is usually prepared before use, but the possibility of storing water in the dark and turning it into ice cubes for future use has also been studied. Some scientists also use electrolyzed neutral water (pH close to 7) for disinfection of food ingredients.

2.4 Types of Electrolysis Water Machines

There are many electrolytic water production machines on the market. Japan, as the country that introduced this technology, is the largest producer of this machine. Sumida mentioned four models: Type I, Type II, Type 1S, and Type 3, which produce AEW with pH values of 2.3-2.5, 2.5-3.5, 3.3-4.0, and 5.0-6.0, respectively.

Generally speaking, machines can be divided into two categories: one has a diaphragm and produces AEW with a pH value of 2 to 3; Another method is to produce neutral water with a pH value of 6.8 without a separator, as the HCl formed at the positive electrode neutralizes the NaOH on the negative electrode.

Al Haq and Sugiyama pointed out that the most commonly used in public reporting is ROX-20TA. ENW or Neutral Oxidized Water (NOW) is produced using a diaphragm free machine, typically with a pH of 5.0~5.5, an ORP of approximately 830mV, and a FAC of approximately 80ppm. There are over 20 companies in Japan that produce electrolyzers.

2.5 Use of AEW in Agriculture and Food Industry

AEW is used in medical, dental, food processing, agricultural, and dairy processing industries. It is widely used for disinfection purposes in Japanese hospitals and dental clinics. Tables 2 and 4 provide a brief summary of its use in the agricultural and food industries. AEW is mostly used for microbial control, but there are also some studies that use both AEW and BEW simultaneously.

2.6 Advantages of AEW

Disinfection with AEW is more convenient than traditional chlorine disinfection for the following reasons:

1) It can be manufactured on-site.

2) It can be produced by simple electrolysis with pure water, without the need for chemical agents other than diluting salt solutions (NaCl, KCl, or MgCl2); Therefore, it has less adverse impact on the environment.

3) Its use can reduce the costs and risks associated with the processing, transportation, and storage of concentrated chlorine solutions.

4) It is more environmentally friendly. Some machines may produce chlorine gas in addition to FAC substances (such as HOClH and OCl -) if the pH is set below 5.0. In this case, the operator must protect themselves from the harm of chlorine gas. In other cases, the machine is safe for both the environment and the operator.

5) To reduce the health problems caused by the use of chlorinated water, AEW can be adjusted to reduce the concentration of chlorine while maintaining its effectiveness against microorganisms.

6) After use, it can be restored to normal water without releasing a large amount of harmful gases (such as chlorine gas).

7) Some researchers claim that AEW can physically kill microorganisms, which do not have resistance.

8) After the initial payment for the electrolysis equipment, the usage cost is very low. Therefore, using electricity to generate chlorine is very cost-effective. Grech and Rijkenberg have calculated the cost of various chlorination methods, and the unit cost (in US dollars) for producing 100% free chlorine per kilogram is as follows: liquid chlorine is 1.6 US dollars, sodium hypochlorite solution (15%, w/v) is 2.70 US dollars, dry sodium hypochlorite (70%, w/v) is 2.87 US dollars, TCIA tablets are 3.64 US dollars, and electricity generated chlorine is 34 US cents.

9) As a non heating method, the use of AEW does not cause changes in composition, structure, odor, taste, and other aspects, which are all brought about by heat treatment.

10) AEW also has fewer cell toxins than traditional disinfectants.

2.7 Disadvantages of AEW

1) May cause some metal rusting.

2) The effect decreases when there is protein present, as chlorine reacts with the protein.

3) Some models of water electrolysis machines may produce irritating chlorine gas when operated at pH<5, which can cause discomfort to the operator.

4) The initial purchase cost of the equipment may be relatively expensive.

5) Over time, the bactericidal activity of AEW will decrease due to the loss of chlorine.

6) AEW contains free chlorine, which can have toxic effects on plants and damage plant tissues.

2.8 Principle of AEW antimicrobial activity

The antibacterial mechanism of AEW is currently not fully understood. AEW can contain chlorine gas (Cl2), HOCl, and OCl - ions, all of which are constituent factors of FAC, i.e. unbound chlorine atom groups (FAC is sometimes referred to as available chlorine concentration ACC). Some researchers believe that the antibacterial activity of AEW is due to the presence of chlorine components, while others attribute it to low pH. Several studies suggest that this activity is caused by high ORP. Some scientists claim that it is a mixture of all these reasons. But it cannot be denied that AEW has strong bactericidal, antiviral, and moderate fungicidal properties.

Chlorine is generated at the positive electrode (oxidation or acidic water), while hydrogen (H2) is generated at the negative electrode (reduction or alkaline water). Cl2 reacts with water to form HOCl and HCl. When the pH of AEW is low, HOCl is a very weak but effective disinfectant, which is actually not hydrolyzed and is called the much less effective hypochlorite ion (OCl -). Hotta and Kohno proposed that the bactericidal effect of AEW is generated by the non-equilibrium HOCl present at low pH during the electrolysis process. Research has also shown that hypochlorous acid (the undissociated form of chlorine) can invade microbial cell membranes and exert bactericidal effects through oxidation of key metabolic systems. Folkes et al. proposed that the reaction HOCl can provide species such as hydroxyl hydroxyl groups. White proposed that molecular Cl2 (in equilibrium with HOCl), HOCl, and FAC are the main reasons for the bactericidal effect of AEW. Park et al. proposed that the concentration of chlorine reactants in AEW is influenced by the amperage of the water generator, but other reports suggest that the amount of HOCl produced during electrolysis is directly proportional to the increase in NaCl. But to reduce the health problems of chlorinated water, adjustments can be made to the production of AEW to reduce the amount of HOCl produced while maintaining its bactericidal effect.

The pH value of AEW also plays a role in inhibiting bacterial growth. Iwasawa et al. discussed the effect of pH on the bactericidal properties of AEW; Len et al. discussed the effects of amperage and pH on these properties. In addition, Len also discussed the effects of storage conditions and pH on chlorine loss in AEW.

Scientists have reported that high ORP is the reason why AEW has bactericidal activity. The ORP of a solution is an indicator of its oxidation or reduction ability, and a high positive ORP value indicates strong oxidation ability. An ORP of+200 to+800mV is most ideal for the growth of aerobic bacteria, while+200 to+400mV is beneficial for the growth of anaerobic bacteria. One possible explanation for the high ORP of AEW is the release of oxygen from the unstable weak bond cleavage between hydroxyl and chlorine groups. Kim et al. proposed that the ORP of the treatment solution is the main factor affecting the bactericidal effect. They also agree with McPherson and Carlson's report on the application of water disinfection, that is, the ORP value of a solution is more indicative of disinfection characteristics than residual (free) or total chlorine concentration. McPherson also reported that ORP had become a world standard when the German Federal Health Office laboratory first confirmed in 1968 that E. coli was associated with ORP rather than residual chlorine. Carlson and Robbs also pointed out that the killing of bacteria is not based on chlorine reaction, and a higher ORP value is necessary to kill all E. coli in the sample. Therefore, having a certain chlorine measurement value alone cannot guarantee disinfection effectiveness. But ORP is the only measurement of total oxidation capacity, independent of pH and chlorine concentration. Al Haq et al. suggested that ORP, along with low pH and FAC, may have had an impact on the disinfection of berengeriana.

A series of oxidation-reduction reactions occur in electrolysis, producing many reactive and toxic compounds like ozone, as well as short-lived atomic groups such as O -, Cl -, and OH - in AEW. These compounds endow AEW with disinfectant properties.

Many scientists believe that all three factors (chlorine, pH, and high ORP) are the reasons why AEW has a disinfectant effect. But the presence of chlorine and high ORP seem to be the main factors for bactericidal activity. Some Japanese scientists believe that ORP is not the reason for AEW's bactericidal effect, and it should be called AEW instead of EO water.

2.9 Principle of BEW antibacterial activity

BEW (also known as AIEW or ER water) has a pH value greater than 11.3 and an ORP less than or equal to -800mV. Therefore, it has strong reducing ability, leading to the reduction of free radicals in biological systems. It can also be used for the treatment of organ dysfunction. BEW is considered to have surface activity due to the presence of diluted NaOH, dissolved hydrogen, and active hydrogen.

2.10 Factors affecting AEW activity

Storage conditions: One of the limitations of AEW is that it will lose its bactericidal activity over time, which is caused by the evaporation of dissolved chlorine gas and the decomposition of HOCl, resulting in the loss of chlorine.

The free chlorine content of AEW significantly decreased (up to 80%) after stirring for 120 minutes, while ORP remained unchanged, indicating the presence of other strong oxidants.

Len et al. reported that under open conditions, chlorine in AEW was completely lost after stirring for 30 hours, and without stirring, it was completely lost after 100 hours. Storing light has no significant effect on chlorine loss. The first-order kinetics based on chlorine evaporation is not suitable for closed conditions. The main mechanism of chlorine loss under closed conditions may be the automatic decomposition of chlorine in solution, as chlorine evaporation is limited at this time.

Light: Len et al. reported that regardless of the light, the chlorine loss rate remains almost unchanged, indicating that the effect of diffused light on chlorine loss is minimal under open conditions. Previously, El Din et al. demonstrated that the chlorine decomposition rate of chlorinated water exposed to light is 5 to 8 times higher than that of chlorinated water stored in the dark; But the light conditions used in this study are much stronger than the diffuse light conditions used in Len et al.'s research (373 lux). The study also found that lighting is a more important factor than agitation for chlorine loss under closed conditions. Under the given experimental conditions, approximately 60% of chlorine was lost after 1400 hours when diffused light was applied, while approximately 40% was lost in the dark. This indicates that diffused light can cause chlorine decomposition during storage.

Agitation: Park et al. reported that the therapeutic effect of AEW is worse without agitation than with agitation, perhaps because the ability of chlorine in AEW to invade the attached bacterial cell layer is limited. Washing the infected surface with AEW stirred at 50rpm can reduce the population of gas producing Escherichia coli and Staphylococcus aureus on different test surfaces to undetectable levels, while controlled treatment can reduce the two bacteria by approximately 3 log10 CFU/cm2. The observed reduction after this control treatment was caused by the removal of cells from the infected surface through stirring. After AEW treatment, no viable cells were found in both bacteria. However, the average amount of recovered cells in the control solution after treatment was 4.6-4.9 log10 CFU/ml, indicating that a large number of adherent cells were removed from the infected surface during stirring (approximately 2.5 log10 CFU/ml without stirring treatment). When not stirred, TSB medium can react with AEW to form combined chlorine, reducing the local active chlorine concentration on or near the test surface. The possible reasons for the complete inactivation of both types of bacteria on the test surface after stirring AEW treatment are: (1) cells removed from the surface during stirring immediately become inactive in AEW, (2) stirring promotes the penetration of AEW into the remaining cells on the test surface, and (3) stirring thoroughly mixes AEW, allowing chlorine to react more effectively with cells. In order to better understand the chlorine loss in the open state, Len et al. calculated the loss rate constant and pointed out that the chlorine loss rate increased by about 5 times under stirring conditions, which may be caused by the accelerated interfacial mass transfer of chlorine gas. Mixing can accelerate mass transfer; But it will not affect the decomposition of chlorine through single-phase reactions.

PH: The pH of AEW also affects the chlorine evaporation rate, as the ratio of dissolved chlorine gas to HOCl in solution depends on pH. The pH of AEW remains almost constant in all storage states, both in open and closed environments. But after increasing the pH, the chlorine loss of AEW and chlorinated water is greatly reduced. The researchers further explained that when the pH increased from 2.5 to 4.0, both solutions showed a significant decrease in k values (about 10 times). The decrease in H+concentration with increasing pH can alter the chemical equilibrium of equation 1 and lead to the formation of non-volatile HOCl. Therefore, the proportion of volatile dissolved Cl2 gas will decrease, resulting in a reduction in Cl2 evaporation. The higher k value of AEW compared to chlorinated water at the same pH may be due to the different chemical environments of the two solutions. The form of chlorine varies with environmental pH. In theory, at pH values of 6.0 and 9.0, the main chlorine species in the solution are not dissolved Cl2 gas, but HOCl and OCl -. Therefore, we found that there was no significant difference in the rate of Cl2 loss due to the evaporation of dissolved Cl2 gas at these pH values, but it was significantly lower than the observed values at acidic pH. When the pH is 9.0, there is almost no loss of Cl2. Len et al. stated that a lower loss rate of Cl2 was observed at pH 6.0 and 9.0, possibly due to the self decomposition of chlorine (similar to chlorine loss in a sealed state).

ORP: During the 120 minute AEW stirring process, ORP remained constant, indicating the presence of other strong oxidants. The study found that the ORP of AEW decreases during storage, which is consistent with the loss of oxidizing chlorine. The influence of stirring can also be clearly seen in the ORP profile. However, no significant effect of light on chlorine loss was observed in the ORP profile. The ORP profile obtained in a closed state is very similar to each other regardless of stirring and lighting, with only a slight decrease between 1100 and 1085mV.

The relationship between pH, ORP, and FAC: Most publicly available research in this field has been conducted using the machine shown in Figure 4, which can generate AEW with a pH of 2.6 ± 0.1. Al Haq et al. used a diaphragm free machine and proposed the relationship between AEW pH and ORP. They found that the ORP reached its maximum value of approximately 1200mV at pH 2.5 ± 0.1, and remained within the range of 1170 ± 20mV at pH 2.6 to 3.6.

3. The effects of AEW on microorganisms, food, and surfaces

3.1 Pre harvest use of AEW: impact on crops

Grech and Rijkenberg injected AEW into the micro irrigation system of citrus to control certain water containing pathogens, such as Aspergillus, Fusarium, algae, and skin forming bacteria. All bacteria have been killed. Nematodes can resist free chlorine levels in water up to 50 μ g/ml. No toxic side effects caused by chlorine have been found in plants grown in the wild. In greenhouse research, treatment levels between 200 and 500 μ g/ml can significantly reduce the proliferation of pathogenic fungi in soil, and in some cases even eliminate pathogens.

3.2 The effect of AEW on bacteria

Park et al. initially used 8.0 log10 CFU/ml of Clostridium perfringens and 8.04 log10 CFU/ml of Staphylococcus aureus, and exposed them to AEW containing approximately 25 or 50mg/l residual chlorine. Within 30 minutes, the Clostridium perfringens and Staphylococcus aureus were inactivated (reduction>91 log10 CFU/ml). Staphylococcus aureus has a stronger tolerance to diluted AEW containing approximately 10 mg/l residual chlorine than Escherichia coli. After 30 seconds of exposure to AEW containing approximately 10 mg/l residual chlorine, the population of gas producing Escherichia coli decreased to undetectable levels; The surviving population of Staphylococcus aureus is 3.9log10CFU/ml. Kim et al. reported that treatment with AEW containing 10mg/l residual chlorine for 60 seconds can effectively reduce the number of Escherichia coli O157: H7, Listeria monocytogenes, and Bacillus cereus vegetative cells to undetectable levels. Zhao et al. found that most strains of Escherichia coli O157: H7 are highly sensitive to chlorine, and a reduction of>7log10 CFU/ml can be achieved with 0.25mg/l of free chlorine.

3.3 The effect of AEW on the test surface

Park et al. initially used 6.1 log10 CFU/cm2 of gas producing Escherichia coli and Staphylococcus aureus populations on any surface type (glass, stainless steel, glazed tiles, unglazed tiles, transparent ceramics). After immersing the test surface in AEW for 5 minutes without stirring, the populations of gas producing Escherichia coli and Staphylococcus aureus decreased by 2.2 to 2.5 log10 CFU/cm2 and 1.7 to 1.9 log10 CFU/cm2, respectively. Rinsing the infected surface with a control solution has only a small effect (reducing 0.1 to 0.3 log10 CFU/cm2). The processed rinse solution was immediately tested and no viable cells of gas producing Escherichia coli and Staphylococcus aureus were found. But the treated control rinse solution can restore>2log10 CFU live cells/ml.

3.4 The effect of AEW on fungi

Effective disease management and the use of preventive fungicides after harvesting and in greenhouses are crucial. The increasing attention to pesticide issues, potential worker safety concerns, and fungicide tolerance in the environment indicates the need for other disease control measures. AEW is a potential alternative to fungicides in controlling leaf or post harvest diseases. The study conducted by Bonde et al. aimed to determine whether AEW could be used to stimulate the germination of Aspergillus niger spores. They found that treating wheat seeds with AEW for 20 minutes could eliminate contamination from fungi such as Aspergillus, Fusarium, and Penicillium.

AEW has a wide range of antifungal effects, which can promote its use as a contact fungicide on the surface of aerial plants and for general hygiene purposes in greenhouses. At present, some growers use spray or irrigation water to prevent the growth of fungi in horticultural crops. Yamaki used it to control powdery mildew on cucumbers and found that it significantly reduced powdery mildew within approximately two weeks starting from 18 days after planting. He also found that peaches treated with AEW delayed fungal decay by about two days, while those treated with BEW delayed it by one day, while the peaches in the control group began to rot on the day after harvest. He reported that the incidence of diseases in the control group was 70%, 22% in the BEW treated group, and 20% in the AEW treated group.

According to research conducted by Bonde et al., AEW can destroy fungi such as Aspergillus, Fusarium, and Penicillium in the short and medium term. This indicates that using AEW for treatment is a suitable alternative to using NaOCl for the treatment of Kanal black powder disease.

Buck et al. treated 22 fungal species with AEW in vitro and reported that the germination of all 22 fungal species was significantly reduced or prevented. All fungi with thinner walls, such as Botrytis cinerea and Alternaria, are killed in 30 seconds or less. Thicker walled colored fungi (such as Aspergillus and Colletotrichum) require 2 minutes or more to significantly reduce their germination. Diluted AEW with tap water in a ratio of 1:4 and 1:9 (AEW: tap water) will reduce its effectiveness against Botrytis cinerea. The presence of Triton X-100 (at any concentration) and Tween 20 (1 and 10%) will eliminate the anti Botrytis cinerea effect of AEW. AEW does not damage geranium leaf tissue, and can eliminate the damage caused by Botrytis cinerea within 24 hours after inoculation.

Al Haq et al. used AEW to control peach brown rot disease. Inject a spore suspension containing 5 × 105 conidia/ml of peach brown rot fungus into the fruit, and apply it in droplet form to both damaged and undamaged fruits, or apply it in uniform spray form to undamaged fruits. The fruits were soaked in tap water at 26 ℃ for 5 or 10 minutes (control group), or treated with AEW with various ORP, pH, and FAC values. After processing, the fruits are stored at 20 ℃ and 95% relative humidity for at least 10 days to simulate a retail environment. The incidence of disease is determined as the percentage of fruits exhibiting symptoms of disease, and the severity is expressed as the diameter of damage. AEW cannot control brown rot disease in fruits with damage, but it can reduce the incidence and severity of disease in undamaged peaches. Compared to non damaging peaches treated with droplets of bacteria, fruits treated with spray can delay the symptoms of brown rot disease more. Fruits treated with AEW did not develop brown rot after being stored at 2 ℃ and 50% RH for 8 days, until they were transferred to an environment of 20 ℃ and 95% RH. The incidence and severity of fruit diseases are lowest when immersed in AEW for 5 minutes. An AEW with a pH of 4.0, ORP of 1100mV, and FAC of 290mg/l can delay the onset of brown rot disease by 7 days, which is the approximate time it takes for fruits to reach consumers from the packaging site in the market. No toxic side effects caused by chlorine were found in the processed fruits. This study demonstrates that AEW is an effective surface disinfectant, but it delays the development of diseases rather than preventing their occurrence.

Al Haq et al. studied the effect of AEW soaking on controlling dry rot disease in European pears (Western pear varieties). The study conducted four independent experiments. Injury is a necessary condition for infection to occur. Apply 20 μ L spore suspension containing 5 × 105 conidia/ml of Botrytis cinerea to damaged fruits for 4 hours, then immerse them in AEW and store them at 20 ℃ and ≥ 90% RH (simulated retail environment) to mature and form diseases. No toxic side effects caused by chlorine were found in the processed fruits. AEW can suppress the incidence and severity of diseases. Soaking for 10 minutes resulted in the lowest incidence and severity of diseases. This study also demonstrates that AEW is an effective surface disinfectant.

Al Haq et al. also studied the effect of AEW on mango anthracnose caused by Colletotrichum gloeosporioides. The fruit was subjected to a spore suspension containing 5 × 105 conidia/ml of Colletotrichum gloeosporioides and immersed in AEW for varying durations. Research has shown that AEW is ineffective in controlling anthracnose in fruits with damage, but can reduce the incidence of the disease. The symptoms of fruit anthracnose treated with AEW appeared later than those in the control group. The incidence and severity of diseases with AEW soaking time of 30 minutes are the lowest. This study indicates that EO water has an impact on the fungus Colletotrichum gloeosporioides, which can inhibit the disease but cannot be controlled.

3.5 AEW Effect on Cut Vegetables

Izumi pointed out that AEW containing 15 to 50 ppm of effective chlorine can effectively reduce the microbial community in several fresh cut vegetables. Koseki et al. studied the preservation effect of frozen AEW (ice cubes, 2 to 3 ℃) on lettuce stored in styrene foam plastic boxes for 24 hours. They monitored the changes in chlorine during storage using tap water ice cubes, AEW ice cubes, and a mixture of AEW and BEW ice cubes. The concentration of Cl2 in the box filled with AEW ice cubes increased by 3.9 ppm/h, while the mixture of AEW and BEW ice cubes increased by 0.5 ppm/h. The mixture of tap water ice cubes did not increase.

3.6 Effects of AEW on Meat and Poultry

Park et al. reported that Campylobacter jejuni was completely inactivated within 10 seconds of exposure to AEW or chlorinated water (both containing 50mg/l residual chlorine) in pure culture. A strong bactericidal effect was also observed in diluted AEW (containing 25mg/l residual chlorine), and the average population of Campylobacter jejuni decreased to below 10 CFU/ml after 10 seconds of treatment (measured only by 48 hour concentration). They further evaluated the role of AEW in reducing Campylobacter jejuni during chicken cleaning process. Prove that both AEW and chlorinated water are equally effective: both reduce approximately 3 log10 CFU/g of Campylobacter jejuni on chickens, while the control group treated with deionized water only reduces 1 log10 CFU/g. There were no restored viable cells of Campylobacter jejuni in the AEW and chlorinated water after flushing treatment, but a high population of Campylobacter jejuni (4 log10 CFU/ml) was restored in the flushing solution treated with the control group. According to further reports, AEW can not only effectively reduce the population of curved bacteria in chicken jejunum, but also prevent cross contamination of the treatment environment.

4. Application of EW in food processing

Research has found that the use of BEW can increase the protein content of tofu. Research has found that tofu made with BEW and AEW has a softer texture than tofu made with tap water. There is no significant difference in free sugar content between tofu made with EW and tofu made with non EW, but from a sensory perspective, tofu made with BEW is sweeter than tofu made with tap water. Similarly, the total content of carbonyl groups related to the actual taste of tofu is higher in AEW and BEW tofu compared to tap water tofu. The study concluded that using EW can alter the nutritional value of tofu, especially BEW.

According to Hara et al.'s report, instrumental measurements and sensory tasting of cooked Japanese noodles (udon) showed that dough kneaded with AEW was harder and more elastic than dough kneaded with tap water. AEW can accelerate the breakdown of gluten and wheat gluten involved in the formation of gluten matrix, which is beneficial for the formation of better texture. However, the use of BEW produces less elasticity, indicating that it changes the gelling conditions of starch. When wheat starch is heated in EW, it also changes the gelation conditions. But when the noodles are heated in positive electrode water, the maximum and minimum viscosity will decrease, indicating that the sugar bonds of starch molecules will hydrolyze when heated at low pH. When wheat starch is heated in BEW, its maximum viscosity and decomposition increase, indicating that heating at high pH will release hydrogen bonds and promote the expansion and destruction of starch molecules. It is possible that when noodles are cooked in EW, the decomposition of starch molecules causes a large amount of water to diffuse into the noodles, reducing the difference in hardness between the inside and outside. Therefore, noodles cooked with EW are not as elastic as those cooked with tap water. Especially, using AEW can significantly reduce the elasticity of cooked noodles, and compared to noodles cooked with tap water, the viscosity is greatly increased. We can conclude from this that AEW is more effective than BEW in changing the conditions of flour gelatinization. The elasticity of cooked noodles is very important in Japanese cuisine. Therefore, it is not recommended to use EW to cook Japanese noodles (udon), as the elasticity of cooked noodles will decrease.

According to Kobayashi and Onishi et al., when aged rice is boiled with weak BEW, the rice becomes softer and stickier, which can improve its structure. Using BEW can improve the quality of freshly cooked rice; It can be found that it is not as hard and viscous as rice cooked with tap water, but rice cooked with BEW deteriorates faster. Further research has found that adding carbohydrates such as trehalose or surfactants such as polyoxyethylene polyoxypropylglycerol monoesters to water can slow down the degradation of rice cooked with weak BEW.

Hoshizaki Electric Company (Japan) has obtained a US patent for the method of making dough (such as bread). Using EW dough to improve the quality of processed food without any food additives. Bread crumbs made with weak AEW have higher elasticity than those made with tap water, while bread crumbs made with weak BEW are softer than those made with tap water.

Red bean rice (a Japanese food) is cooked with red beans and rice. Red beans can turn rice red and are often prepared as a festive food in Japan. In fact, if Japanese people say 'eat red bean rice', it means they are going to have a celebration. Kobayashi et al. investigated the effects of AEW and BEW on altering the color tone and astringency of red bean rice. They found that using AEW can greatly reduce astringency, but the color tone of the red beans becomes lighter. BEW can deepen the color, and the color of red bean rice also becomes darker.

5. Conclusion

AEW treatment can be used as an effective method to reduce microbial contamination on food processing surfaces and non food contact surfaces such as tiles, floors, stainless steel, laboratory glassware, or medical or dental facilities. The complete inactivation of Staphylococcus aureus and Escherichia coli in AEW after treatment indicates that AEW can also prevent cross contamination of the treatment solution. AEW exhibits a wide range of antifungal effects, which can promote it as a contact fungicide for aerial plants and can be used for general disinfection in greenhouses.

AEW can be generated on-site as needed and used directly. As it does not require the handling of concentrated chemicals, it can also reduce the health risks to workers. It can also be used as a food safety agent. AEW and BEW can both be used for food production and can be used according to the different types of food produced. The use of EW is an emerging technology that requires further research and development