Recent Advances in Cold Atmospheric Pressure Plasma for E. coli Decontamination in Food: A Review

Abstract

Cold atmospheric plasma (CAP) acts as a powerful antibacterial tool in the food industry, effectively eliminating E. coli and a wide range of pathogens, including bacteria, viruses, fungi, spores, and biofilms in meat and vegetables. Unlike traditional bactericidal methods, CAP leverages an arsenal of reactive species, including reactive oxygen species (ROS) such as ozone (O3) and hydroxyl radicals (OH•), and reactive nitrogen species (RNS) like nitric oxide (NO•), alongside UV radiation and charged particles. These agents synergistically dismantle E. coli’s cell membranes, proteins, and DNA, achieving high degradation rates without thermal or chemical damage to processed food. This non-thermal, eco-friendly technology preserves food’s nutritional and sensory integrity, offering a transformative edge over conventional approaches. It emphasizes the critical need to optimize treatment parameters (exposure time, gas composition, power) to unlock CAP’s full potential. This review explores CAP’s effectiveness in degrading E. coli, emphasizing the optimization of treatment parameters for practical food industry applications and its potential as a scalable food safety solution. It is crucial to conduct further studies to enhance its implementation, establishing CAP as a fundamental element of advanced food processing technologies and a key measure for protecting public health.

1. Introduction

The hazardous effects of foodborne pathogens have been a consistent threat to living beings around the world. Such effects not only affect human beings but also billions of dollars in losses in the food industry. Recent studies have shown a remarkable percentage increase in losses due to such pathogens. Researchers have listed many hazardous pathogens in the past few decades; among them is Escherichia coli (E. coli), which causes gastrointestinal infections and is a significant threat to living beings. It can cause severe diseases like diarrhea and abdominal cramps [1,2,3,4,5]. The strong sources of its spread include raw meat, dairy products, poultry foods, and uncooked liquids. E. coli can also be transmitted through various sources, including contaminated drinking water, recreational water bodies such as swimming pools and lakes, and the consumption of tainted food. High-risk foods include undercooked meat, improperly washed leafy greens and fruits, and unpasteurized beverages like apple juice. Additionally, direct exposure to infected animals at petting farms poses a transmission risk. Fresh produce contamination often results from fecal contamination in irrigation water or agricultural runoff [6,7,8,9].

Table 1. Types of E. coli existing in various foods, food sources, and in human consuming elements and their retardation potential against antibiotics.

No	E. coli Type	Antibiotic-Resistant Profile	Ref.
1	Enterohemorrhagic E. coli (EHEC)	Notably, strains like O157:H7 have resisted multiple antibiotics, including ampicillin and tetracycline. Multidrug resistance (resistance to ≥3 antimicrobial classes) in E. coli has increased from 7.2% in the 1950s to 63.6% in the 2000s. Commonly found in foods like undercooked ground beef, unpasteurized milk and dairy, raw vegetables, fruits, and unpasteurized juices.	[15]
2	Enterotoxigenic E. coli (ETEC)	ETEC strains have resisted antibiotics such as ampicillin, trimethoprim–sulfamethoxazole, and ciprofloxacin. Commonly found in contaminated water, raw vegetables, unpasteurized milk, and undercooked seafood.	[16]
3	Enteropathogenic E. coli (EPEC)	EPEC strains have demonstrated resistance to multiple antibiotics, including ampicillin, tetracycline, and co-trimoxazole. The presence of multidrug-resistant EPEC strains has been reported in various studies. It exists in Contaminated water, raw or undercooked meats, unpasteurized milk, and dairy.	[16]
4	Enteroaggregative E. coli (EAEC)	EAEC strains have shown resistance to a range of antibiotics, including ampicillin, tetracycline, and ciprofloxacin. Multidrug-resistant EAEC strains have been identified, complicating treatment options. It is found in Contaminated water, fresh produce, unpasteurized juices, and raw meats.	[16]
5	Enteroinvasive E. coli (EIEC)	EIEC strains have been found to be resistant to antibiotics such as ampicillin and trimethoprim–sulfamethoxazole. The occurrence of multidrug-resistant EIEC strains has been documented in various regions. This type of E. coli is commonly found in Contaminated water, raw vegetables, soft cheeses, and undercooked meats.	[16]
6	Shiga toxin-producing E. coli (STEC)	STEC strains, including O157:H7, have exhibited resistance to multiple antibiotics, such as ampicillin and tetracycline. The rise in multidrug-resistant STEC strains is a growing public health concern. This type of E. coli exists in Undercooked beef, raw milk, unpasteurized juices, raw sprouts, contaminated water, and soft cheeses.	[15]
7	Uropathogenic E. coli (UPEC)	UPEC strains have shown resistance to various antibiotics, including ampicillin, ciprofloxacin, and trimethoprim–sulfamethoxazole. The prevalence of multidrug-resistant UPEC strains has increased, leading to challenges in treating urinary tract infections. This type is not commonly linked to food but may be transmitted through contaminated water or poor hygiene.	[16]
8	Avian Pathogenic E. coli (APEC)	APEC strains have demonstrated resistance to antibiotics such as tetracycline, streptomycin, and sulfonamides. The emergence of multidrug-resistant APEC strains affects both animal health and poses potential risks to human health. It exists mainly in Poultry products.	[17]
9	Neonatal Meningitis-causing E. coli (NMEC)	NMEC strains have been found to be resistant to antibiotics, including ampicillin and gentamicin. The presence of multidrug-resistant NMEC strains complicates the management of neonatal meningitis. This type of E. coli primarily infects newborns, possibly transmitted through contaminated water, dairy products, or maternal transmission.	[16]
10	Adherent-Invasive E. coli (AIEC)	AIEC strains have shown resistance to multiple antibiotics, including ampicillin and ciprofloxacin. Detecting multidrug-resistant AIEC strains is concerning, especially given their association with inflammatory bowel diseases. This type of E. coli is not directly foodborne; rather, it is possibly linked to contaminated water, dairy products, and poor hygiene.	[16]

indicates the types of E. coli existing in various foods, food sources, and in human consuming elements and their retardation potential against antibiotics. Instead of various food safety techniques, advanced sanitary facilities, and advanced preservation methods, there is a great need to control microbial effects in foods and water by adopting effective, economical, and controlled methods of degrading such pathogens [10,11,12,13,14].

Several traditional methods for sterilizing E. coli in food processing are emphasized in the research literature to reduce contamination risks. Thermal processing techniques, like boiling or heating, generally require temperatures between 70 and 100 °C for 1–5 min to reduce E. coli levels effectively. For example, pasteurization at 72 °C for 15 s is widely employed for milk, whereas ground beef must reach an internal temperature of 71 °C for safety [18]. Chemical methods utilize sanitizers such as chlorine (50–200 ppm for 1–2 min) to wash fresh produce like lettuce or peracetic acid (80–200 ppm) for processing poultry [19]. Irradiation employs doses of 1–7 kGy to decontaminate spices or ground meat, effectively reducing E. coli without applying heat [20,21]. Antibiotics, although less common in food processing due to concerns about resistance, are sometimes used in animal feed (e.g., tetracycline at 100–200 mg/kg) to reduce E. coli in livestock, thus affecting meat safety [19]. These methods, while effective, can alter food quality or introduce residues, prompting an exploration of alternatives like CAP [22,23,24,25,26,27,28].

These methods have disadvantages, as they can affect food nutrition, flavor, the generation of organic acids in foods, toxicity generation in foods, and antimicrobial effects [29,30,31]. Although radiation treatment could be helpful in this matter, a large amount of food and the long processing time can affect radiation performance and reduce sterilization efficiency [32,33,34,35]. Due to these limitations, there is an increasing demand for alternative and practical approaches to E. coli sterilization in foods. Such a method must be environmentally friendly, cost-effective, time-saving, capable of large-scale treatment, and ensure food safety without any side effects. The cold atmospheric pressure plasma (CAP) sterilization technique has attracted researchers for the last few decades as a practical and alternative approach to E. coli sterilization in foods and liquids. CAP has proven a cost-effective, non-thermal approach capable of large-scale food sterilization in the industry, using various CAP sources, depending upon the requirements [36,37,38,39,40,41]. CAP is a dynamic, non-equilibrium system of free electrons, ions, and neutral particles exhibiting macroscopic variations over time and space. It is produced at ambient atmospheric pressure through various discharge mechanisms, including dielectric barrier, glow, corona, and arc discharge. Moreover, having the ability to generate ROS, RNS, intense electric fields, energetic electrons, heavy energetic ions, UV radiations, and high-pressure plasma waves, it can exhibit strong antimicrobial properties. It can effectively sterilize pathogens at maximum rates [29,30,42,43,44,45]. Because CAP functions close to ambient temperatures, it is particularly effective for heat-sensitive food products. It can sterilize these foods while preserving their nutritional value [10]. Research has proven CAP’s strong, practical effects on E. coli sterilization from foods like vegetables, meat, poultry, seafood, and even beverages [2,46,47,48,49,50,51,52,53]. Depending upon the plasma generating systems, especially the electrode assembly, input power, type of gas used, and plasma processing time, plasma can rupture the DNA structure of E. coli, making it ineffective so that it can regenerate itself. Also, plasma treatment causes oxidative stress in E. coli and its protein oxidation, leading to E. coli cell death [22,54,55,56,57]. The research reported the formation of biofilms on the surfaces of various materials, especially in foods like meat and vegetables, which show resistance to antibiotics and are essential to treat before use [58,59,60,61,62,63]. CAP has proven to be an up-and-coming source for such biofilm degradation. The CAP treatment of E. coli depends upon various factors, as reported by different researchers, summarized below:

(I)

Plasma Treatment Time: Prolonged exposure enhances microbial inactivation but may affect food quality [64].

(II)

Gas Composition: Different gas mixtures (e.g., helium, argon, oxygen, and nitrogen) generate varying reactive species, which influence antimicrobial activity [65,66].

(III)

Food Surface Characteristics: The porosity, moisture content, and organic matter on food surfaces can impact plasma penetration and effectiveness [67].

(IV)

Plasma Device Configuration: Variations in electrode design, voltage, and plasma jet type affect microbial inactivation efficiency [68,69,70,71].

Recent comparative studies have evaluated the efficiency of CAP against conventional decontamination methods. The endogenous reactive species generated from other sources also have similar biomedical applications [72,73,74,75]. Findings suggest that CAP achieves comparable or superior microbial reductions while maintaining food quality attributes [76,77,78]. Unlike chemical sanitizers, plasma does not leave harmful residues, making it a safer alternative [79,80,81]. Moreover, the ability of CAP to target a broad spectrum of microorganisms, including antibiotic-resistant strains, highlights its potential as a sustainable food safety solution [82,83]. Despite its promising applications, several challenges must be addressed before the widespread industrial adoption of CAP, as listed below:

(I)

Scalability and Cost: Translating laboratory-scale plasma treatments to large-scale food processing requires cost-effective and efficient plasma generation systems [38,84,85].

(II)

Regulatory Approval: The regulatory status of plasma-treated foods varies globally, necessitating further safety assessments and standardization [86,87].

(III)

Consumer Perception: Educating consumers about the safety and benefits of plasma technology is crucial for market acceptance [86,88,89].

This review provides an extensive analysis of recent advancements in CAP for E. coli degradation in food systems. It explores the underlying antimicrobial mechanisms, compares different plasma treatment approaches, discusses industrial feasibility, and identifies key research gaps that must be addressed for future implementation.

2. Mechanism of CAP in Microbial Inactivation

2.1. Basic Principles of Plasma Science

Plasma is considered the fourth state of matter, characterized as a partially ionized or sometimes fully ionized gas. In this state of matter (plasma state), the ionized gas is comprised of electrons, ions (both positive and negative), and neutral species (atoms, molecules, radicals, and excited and de-excited species). Thermal plasma operates at high temperatures (5000–10,000 K) where electrons, ions, and neutral species exist in thermal equilibrium [90]. The formation of plasma depends upon the gas ionization process, either by heating or by any electric and magnetic fields, or using radiations and waves, which turn ordinary gas into an ionized state, known as plasma. Plasma can be categorized as thermal and non-thermal plasma depending upon the temperature and densities of species (Figure 1). Figure 1 summarizes the plasma classifications, depending upon various parameters, while

Table 2. Characteristics of Plasma [94].

Low-Temperature Plasma	High-Temperature Plasma
$T_i\approx T\approx 300 \mathrm{K}$ $T_i \ll T_e\ll {10}^5 \mathrm{K}$ e.g., Low-pressure plasma (glow discharge)	$T_i\approx T_e\ge {10}^7 \mathrm{K}$ (e. g., Fusion plasmas)

represents the characteristics of low-temperature plasma (LTP) and high-temperature plasma (HTP) [91,92].

CAP can be generated by various plasma sources operating at atmospheric pressure, such as dielectric barrier discharges (DBDs), plasma jets, corona, and arc-type discharges. These sources can generate reactive species like ROS and RNS, such as hydroxyl radicals (OH•), superoxide anions (O₂⁻), and nitric oxide (NO•), which are responsible for microbial inactivation and material modification [65]. The characteristics of CAP, which are useful for biomedical applications, are shown in Figure 2.

Due to its low-temperature characteristics, CAP has demonstrated significant utility in various applications. It is particularly beneficial for procedures involving heat-sensitive tissues in the medical and therapeutic fields. Similarly, in agriculture, CAP has been effectively employed to enhance seed germination and control plant diseases, where maintaining a low temperature is crucial. In food processing, CAP is vital in preserving nutritional quality and taste by minimizing thermal degradation. These low-temperature operating conditions make CAP particularly advantageous for biomedical and food applications, where high temperatures could cause damage [66,67,96].

2.2. Reactive Species Generated in CAP

Several factors, including electrode configuration, reactor design, working gas pressure, gas composition, and the type of input power, influence CAP generation. CAP generation starts with the ionization of neutral gas, initiated by electron impact processes from applied electric fields. Noble gases, including argon or helium, are generally chosen as carrier gases because of their inert properties and low breakdown voltage, which stabilize the plasma discharge. Although these gases do not produce specific RONS directly, they do affect the distribution of electron energy, thus influencing subsequent reactions when combined with molecular gases such as oxygen or nitrogen. The plasma chemistry that results, especially in mixed-gas settings, is intricate and governs the type and amount of RONS generated. Consequently, noble gases primarily contribute to the formation of plasma and energy transfer rather than directing the formation of specific compounds. These plasmas can produce a wide range of highly reactive species [97,98,99,100]. When oxygen is utilized for CAP generation, it can make both ROS and RNS [101].

Notable species include singlet oxygen (¹O₂), superoxide anion (O₂⁻), hydroxyl radicals (OH•), atomic oxygen (O), and ozone (O₃), mainly when mixed with oxygen or water vapor. These reactive species play a crucial role in various environmental, biological, and agricultural applications, contributing to desired outcomes in microbial inactivation, plant growth promotion, and other beneficial processes [68]. Air is comprised of 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon monoxide, 0.0018% neon, 0.0005% Helium, 0.0002% methane, 0.0001% krypton, and 0.00005% hydrogen. Due to this composition, when air plasma is generated at atmospheric pressure, it generates nitric oxide (NO•), nitrogen dioxide (NO₂), and peroxynitrite (ONOO⁻), along with ROS and RNS [69]. Oxygen plasma has the ability to generate high amounts of reactive oxygen-based species, including OH• radicals, ozone (O₃), and superoxide anions, which are beneficial in sterilization, wound healing, microbial inactivation, and food preservation [102,103,104,105]. Although researchers have made significant advancements in the last few decades in the field of oxygen-based CAP, many avenues remain unexplored and need to be explored for both scientific and industrial applications [13,76]. Helium plasma is eco-friendly and nontoxic; when it interacts with ambient air, it not only produces ROS and RNS but also generates peroxynitrite, and it causes the breaking of pesticides and contaminants in foods to increase food shelf life [106,107,108]. Similarly, nitrogen plasma, being rich in RNS, is highly applicable in biological applications [26,80,109,110,111,112,113]. All these plasmas are beneficial in different fields. The primary applications encompass bacterial inactivation, wound healing, and cancer treatment via oxidative stress mechanisms, seed germination, enhancing plant resistance to pathogens, and aiding in growth regulation within agriculture. Additionally, they are used for microbial decontamination, pesticide breakdown, and food preservation, all while maintaining nutritional quality and taste. As a result, these plasmas play a critical role in advancing various applications.

2.3. Mode of Action Against E. coli

Escherichia coli (E. coli) is a gram-negative foodborne pathogen in water, meat, food, and poultry. Several diagnostics and degradation mechanisms have been developed to degrade E. coli from water and solid foods. Some conventional approaches have been adopted for sterilizing food and water from E. coli, like heating or boiling, radiation treatment, the membrane method, washing, or the use of antibiotics. However, all traditional approaches have proven to have some disadvantages. Sometimes, these conventional methods affect the nutritional value of food, sometimes taste; mainly, these methods cause the generation of harmful ingredients in food and water, which makes such approaches less popular. These limitations were overcome by introducing the CAP technique of E. coli sterilization. It has proven to be a nontoxic, environment-friendly, and quick processing approach for E. coli sterilization. Research has proven that CAP is a non-thermal and advanced sterilization technique. CAP generates highly reactive species capable of interacting with food and water in various forms to achieve sterilization. The most prominent include ROS, RNS, charged particles, UV radiation, and transient electric fields [82]. The primary mechanisms through which these reactive species contribute to the degradation of E. coli are outlined below and graphically illustrated in Figure 3 [38].

(i). Oxidative stress and reactive species effect: The CAP-generated ROS and RNS, like ozone (O₃), superoxide anion (O₂⁻), hydroxyl radicals (OH•), hydrogen peroxide (H₂O₂), nitric oxide (NO), and peroxynitrite (ONOO⁻), induce oxidative stress, which causes lipid peroxidation, protein oxidation, and DNA damage in E. coli cells [86,90]. Oxidative damage causes the cell death of E. coli due to disruption in cell membrane integrity.

(ii). Disintegration of Cell Membrane Integrity: CAP exposure has proven to cause significant morphological changes through oxidative damage and membrane lipid peroxidation. Plasma-generated radicals, UV radiations, electric fields, electrons, ions, ROS, and RNS react with E. coli and cause an increase in permeability and subsequent cytoplasmic leakage. Such plasma exposure causes the loss of essential intercellular components of E. coli, resulting in its deactivation [91].

(iii). DNA and Protein Damage: A study on the effectiveness of underwater capillary discharge plasma in eliminating Escherichia coli (E. coli) from water demonstrated the effect of arc plasma generated by oxygen injection in water, resulting in DNA damage to E. coli through strong electric fields and an arc-type discharge. The plasma-generated species in water, like ozone (O₃), hydrogen peroxide (H₂O₂), UV radiation, plasma-generated shock waves, RNS, and ROS, were found to be responsible for E. coli cell destruction. Bactericidal tests, colony-forming unit (CFU) counting, and DNA and protein leakage have proven effective in degrading E. coli and rendering it ineffective for potential regeneration. Research has demonstrated that the waterborne E. coli capillary discharge method can be highly effective for E. coli degradation [92]. In solid food materials, CAP-generated ROS causes the splitting of C-O, C-N, and C-C bonds, disrupting E. coli’s molecular structure and eliminating it from the process.

(iv). Induction of apoptosis-like pathways: The CAP-generated reactive species depend upon the type of plasma, the gas used for plasma generation, the ratios of a mixture of gases, and the discharge power. These species have the potential to generate oxidative stress in E. coli and cause cell damage following a cell death process, which resembles a process known as apoptosis in eukaryotic cells. This oxidative process in E. coli cells causes significant membrane leakage and surface changes. The biochemical and cell tests revealed the cellular-damaging effect of reactive oxygen and nitrogen species (RONS). The process of cell disruption by CAP through oxidative stress resembles apoptosis-like pathways. The research has proven that CAP treatment effects on E. coli cause oxidative damage and damage to key cellular components like lipids, proteins, and nucleic acids. The CAP effect and all mentioned damages of E. coli by CAP depend upon important plasma parameters, like exposure time, type of gas used, and other plasma dynamics. Therefore, research revealed that CAP’s effects on E. coli cell damage resemble the process of apoptosis, like the cell death process, and can cause the complete sterilization of materials under plasma exposure. This CAP treatment has proven to be a promising antibacterial technique, especially for E. coli [114,115].

(v). Electrical and UV effects of CAP on E. coli: The bacterial cells, especially E. coli cells, are polarized in a normal state, are very stable, and offer resistance against antibiotics. E. coli cells can turn into a sleeping mode if treated with antibiotics and regenerate after a specific time. In comparison with antibiotic treatment, CAP generates intense electric fields. When CAP treats E. coli-affected material like food or water, transient electric fields cause depolarization of E. coli, resulting in the electrochemical instability of E. coli, and not only cause cell death but also permanently damage its DNA structure, making it ineffective for regeneration. Along with intense electric fields, CAP generates intense UV radiations, which can affect E. coli transcription processes and cause thymine dimer formation in bacterial DNA, producing another cause of the degradation of E. coli by CAP [53]. Studies have proven that the CAP treatment of food surfaces containing E. coli has bactericidal effects: up to a 5-log reduction of E. coli can be achieved after plasma treatment, depending upon plasma parameters like gas type, exposure time, proximity of food, and quantity of food to be treated [116,117]. The advantage of the CAP treatment of food against E. coli is that it eliminates the microbial effects from food and water while preserving texture and flavor and maintaining food pH, moisture level, sensory attributes, and nutritional values. Since CAP operates at room temperature and is categorized as low-temperature plasma, it is beneficial for treating heat-sensitive food products. The CAP generates intense electric fields and high voltages that not only ionize gas but also can yield RONS and electron-driven chemical reactions, causing the acceleration of free electrons and heavy ions, which collectively play a vital role in E. coli inactivation from foods. In summary, plasma sources such as dielectric barrier discharge (DBD) effectively treat foods by inducing oxidative stress, damaging the DNA of E. coli, destabilizing the E. coli membrane, and causing electrical disruption, which leads to microbial destabilization [118,119,120,121]. Still, further investigations are required to establish standard industrial protocols for developing novel plasma reactors for food treatment that are cost-effective and easy to handle.

3. E. coli Decontamination Using CAP in Different Food Systems

Several factors influence the effectiveness of CAP in E. coli decontamination, including plasma parameters, food surface properties, and environmental conditions [122,123]. Although the presence of moisture can enhance plasma-induced reactions, including the potential formation of nitric acid, CAP treatments are typically optimized to prevent such adverse effects [124]. By carefully controlling parameters such as treatment time, gas composition, and discharge power, the reactivity of generated species can be confined to microbial inactivation without significantly altering the physicochemical properties of the food [125]. Moreover, the highly transient nature of ROS and RNS ensures minimal residual impact, preserving the pH, moisture content, and overall quality of the treated food [125,126]. The choice of carrier gases, such as air, argon, or helium, significantly affects the formation of reactive species, with oxygen-based plasmas enhancing oxidative stress on bacteria for higher inactivation rates. Higher voltage and power densities generate more reactive species, improving bacterial inactivation but potentially affecting food quality, while longer exposure times increase microbial reduction but may cause undesirable surface modifications. The texture and porosity of food surfaces, such as those of lettuce or meat, can shield E. coli from direct plasma exposure, reducing treatment effectiveness. In contrast, moisture content enhances plasma-induced chemical reactions, increasing bacterial inactivation. Additionally, organic loads like proteins, fats, and carbohydrates can scavenge reactive species, diminishing CAP efficacy [127]. Components like proteins, lipids, and carbohydrates can function as physical and chemical barriers by scavenging ROS/RNS or by protecting microorganisms from direct CAP exposure. For instance, lipids and proteins might create protective layers, which hinder the diffusion of ROS/RNS, while compounds like polyphenols and organic acids can interact with and neutralize ROS/RNS, thus reducing their antimicrobial effectiveness. Moreover, high moisture levels can change the plasma chemistry through the generation of secondary species, such as nitric acid, which might influence food quality. Biofilms, plant fibers, or leftover blood in meat can restrict the effectiveness of CAP [128]. Thus, it is essential to optimize plasma parameters—like gas type, power input, treatment duration, and distance from the food surface—to achieve adequate microbial inactivation. This optimization also helps reduce unwanted chemical changes while maintaining the food’s nutritional and sensory qualities [129].

Environmental factors, including temperature and humidity, influence plasma reactivity and microbial susceptibility, while post-treatment residual antimicrobial effects may provide extended protection against recontamination. Overall, CAP is a versatile and practical non-thermal decontamination technology for E. coli in various food systems, with its efficacy depending on food composition, plasma parameters, and environmental conditions. Figure 3 illustrates CAP action against E. coli in multiple food systems. Future research should optimize treatment conditions, improve plasma penetration, and assess large-scale industrial applications [23,130,131,132,133,134,135].

3.1. Fresh Fruits and Vegetables

CAP has proven a promising food processing technique for decontaminating foods from E. coli. Since it works at low temperatures and the plasma processing of foods does not influence their taste, nutrition, flavor, and sensitiveness, the research revealed that the CAP treatment of foods ranging from 1 to 5 min could reduce E. coli from fresh foods up to 3–5 log CFU/g. Among fresh foods like spinach and lettuce, the effects of E. coli can be reduced enormously due to CAP-generated RONS and oxidative stress [9,12,36,136].

3.2. Meat and Poultry

Past research demonstrated a high prevalence of E. coli in meat and poultry. Some of the E. coli strains existing in meat are capable of causing severe diseases like urinary tract infections (UTIs). The consumption of contaminated or undercooked meat can cause serious infections in humans if such meat is consumed without sterilization; it includes diarrhea or even hemolytic uremic syndrome, which occurs in more severe cases. There are several types of E. coli that are reported to exist in meat and poultry, like E. coli O157:H7, Enterotoxigenic E. coli (ETEC), Enteropathogenic E. coli (EPEC), Enteroaggregative E. coli (EAEC), and Extraintestinal Pathogenic E. coli (ExPEC) [36]. All these types of E. coli in meat and poultry are seriously harmful. E. coli O157:H7 mainly exists in raw beef and poultry products and can cause severe diarrhea, hemolytic uremic syndrome (HUS), and kidney failure [137,138,139,140,141,142,143]. Similarly, ETEC exists in meat and flourishes, mostly in unhygienic processing environments. It can cause watery diarrhea in travelers, especially abdominal cramps and dehydration. Similarly, if consumed with EPEC in raw meat and poultry, it can cause infection in young children and lead to gastrointestinal infections. In contrast, EAEC thrives in unsanitary conditions, causing infections that are often harder to treat with antibiotics. Another strain, ExPEC, is being found in meat and other foods, including its variant Uropathogenic E. coli (UPEC), which is associated with urinary tract infections and bloodstream infections in humans [144,145,146,147,148,149]. All these types of E. coli exist in meat and poultry and pose enormous risks for humans consuming nonsterilized meat. Many conventional techniques and antibiotics have been reported for meat and poultry sterilization from E. coli; however, they have limitations. CAP has been proven to be a dominant technique in degrading E. coli from meat and poultry products, up to a 4–6 log CFU/g reduction, especially on beef and chicken. Although research has proven CAP a dominant source of E. coli degradation, due to the existence of organic matter in meat, the CAP-generated RONS can neutralize, thereby reducing the sterilization efficiency of CAP. This requires further advanced research on optimized treatment conditions, plasma parameters, advanced plasma sterilization techniques, and more in-depth research [107,108,118,150].

Figure 4 illustrates how CAP is used to decontaminate various foods contaminated with E. coli. The CAP treatment effectively lowers bacterial counts by damaging bacterial cells, which is vital for ensuring food safety. The figure also addresses the potential impacts of CAP on food components, such as protein damage, which is an essential factor in maintaining food quality. Key aspects highlighted include the action against microbes, the reduction in bacterial counts, and the broader applications of CAP in food decontamination. While CAP effectively decreases microbial load, balancing its decontamination effectiveness with its potential effects on food quality, such as protein integrity, is crucial. This figure underscores the potential of CAP as a promising technology for food safety while also pointing out areas that require careful consideration to optimize its use in the food industry.

3.3. Dairy Products

The research revealed the existence of many types of E. coli in dairy products, like Shiga Toxin-Producing E. coli (STEC) and Enteropathogenic E. coli (EPEC). It can cause severe foodborne diseases like diarrhea, gastrointestinal illness, and hemolytic uremic syndrome (HUS), which can cause kidney failure [151,152,153]. The primary sources of such types of E. coli in dairy are unpasteurized (raw) milk, contaminated cheese, and an improper hygiene environment of food processing and preservation [154,155,156,157,158]. Although many traditional methods like good manufacturing techniques, milk pasteurization before use, and proper preservation are practiced to degrade E. coli from dairy products, challenges still exist [92,159,160,161,162,163]. Research has proven that CAP applications in sterilizing E. coli from dairy products are limited but effective. A 5–10 min CAP cheese treatment has shown E. coli degradation up to 2–4 log CFU/mL [164]. The existence of E. coli-formed biofilms on dairy products requires prolonged CAP treatment for effective sterilization [165].

3.4. Seafood

In the sea, the most commonly human-consumed species are fish of different types, shrimp, and shellfish, which are mostly affected by waterborne E. coli [166,167,168]. The common types of waterborne E. coli are Enterotoxigenic Escherichia coli (ETEC) and Shiga Toxin-Producing Escherichia coli (STEC), which produce illness and gastroenteritis in humans consuming such seafood [169,170,171,172,173,174,175,176,177]. Other than conventional methods like proper cooking and hygiene methods, CAP treatments of proven shrimp, salmon, and oysters have achieved bacterial reductions of 3–5 log CFU/g. Further, advanced research is required to increase sterilization efficiency [178,179,180,181].

3.5. Processed and Ready-to-Eat Foods

Research has shown that some ready-to-eat foods contain different types of E. coli. In raw vegetables, salads, and unpasteurized dairy products, some severe types of E. coli, like Shiga toxins (Stx1 and Stx2), Enteroaggregative E. coli (EAEC), Enteropathogenic E. coli (EPEC), and Enteroinvasive E. coli (EIEC) exist, which cause hemorrhagic colitis and hemolytic uremic syndrome (HUS), leading to severe diarrhea, vomiting, and dehydration for consumers. Despite low infectious doses of <100 CFU, these are harmful to consumers. In ready-to-eat (RTE) foods like sandwiches, prepackaged meals, and seafood, there exist heat-labile toxins (LTs) and heat-stable toxins (HTs), resulting in diarrhea and severe dehydration. All these types of E. coli in ready-to-eat foods result in common problems like severe gastrointestinal infections and hemolytic uremic syndrome (HUS), which can result in kidney damage, antibiotic resistance, and foodborne outbreaks [108,182,183,184,185].

The major causes of such E. coli involve cross-contamination, inadequate temperature control during food processing, the use of contaminated water and other infectious ingredients, poor hygiene practices by handlers, and the formation of biofilms in food processing methods. However, many sterilization methods exist but have limitations, like requirements of sterilization effectiveness for the long-term, post-process needs of large-volume processing, as well as the requirements of nontoxic mechanisms and environment-friendly methods. Research has revealed that CAP has proven and fulfilled all the above requirements of food processing and packaging. The existence of moisture in meat causes enhanced chemical reactions over the surface of meat and food, improving the effectiveness of CAP against E. coli degradation. Although CAP treatment against fats and carbohydrates can reduce its efficiency, some environmental factors like temperature, humidity, plasma reactivity, microbial stability, and post-treatment of foods can enhance the sterilization factors and extend protection against recontamination. All these factors strictly depend upon the CAP generating condition, plasma properties, used gas characteristics, plasma treatment time, intensity of plasma-induced electric fields, and UV radiations. Overall, CAP has proven to be a practical and versatile non-thermal decontamination technology against E. coli. Further, more detailed investigations are required to develop optimized conditions and plasma parameters for large-scale applications in the food industry [186,187,188]. Table 3 presents previous research data on the effectiveness of various CAP sources in the inactivation of E. coli.

Figure 5 presents a comprehensive schematic of plasma jet and DBD systems frequently employed in CAP treatment, highlighting their bactericidal effects on E. coli. Figure 5A displays the setups for the plasma jet and DBD, which include a gas inlet and key components such as a high-voltage electrode, dielectric material, and a ground electrode, directing plasma toward the bacterial target. Additionally, an inset illustrates the DBD configuration, featuring the layout of power and ground electrodes divided by a dielectric layer to produce plasma. Figure 5B illustrates how CAP inactivates bacteria by generating reactive species, including electrons, both positive and negative ions, radicals, and UV photons (hv) [189]. These species engage with E. coli in both active and distant areas, leading to protein oxidation, lipid peroxidation, DNA damage, and harm to intracellular structures [190]. Moreover, the plasma causes cell wall damage via etching, lipid peroxidation, and bond disruption, resulting in leakage and bacterial cell death. This schematic underscores the multifaceted impact of CAP on bacterial cells, demonstrating its efficacy in sterilization applications [189,190,191].

4. Comparison of CAP with Conventional E. coli Decontamination Methods

Several traditional food sterilization methods exist, but have different disadvantages and limitations, especially when E. coli is degraded in foods. This includes the development of unwanted biofilms on food surfaces, which are harmful to consumers, affect the nutrition of foods shelf life of foods, and are less cost-effective, less environment-friendly, and less efficient from a technical point of view. Compared to them, CAP has proven to be an eco-friendly, cost-effective, and very smart approach to food processing against E. coli. In evaluating CAP as a food sterilization method, it is essential to distinguish its mechanisms from those of conventional chemical treatments, despite some overlap in the reactive species involved, such as ozone and RNS. Unlike traditional approaches that may utilize liquid chemicals, vapors, or externally produced gases (e.g., ozone from generators), CAP generates a plasma state from gases using strong electric fields, producing a unique blend of RONS, UV radiation, energetic electrons, and shock waves [192]. This combination enables precise, localized microbial inactivation—effective against pathogens like E. coli—while preserving the nutritional and sensory qualities of food. In contrast, conventional chemical treatments often rely on less dynamic applications of reactive species, which may leave residues or require more invasive conditions [193]. CAP’s transient and synergistic effects thus offer a safer, more sustainable alternative, minimizing environmental concerns, such as those associated with persistent RNS, and highlighting its potential as an advanced sterilization technology.

Table 3. Summary of major findings from the most effective CAP treatment of E. coli in foods.

No	Food Product	CAP Sources and Parameters	E. coli Inactivation	Ref.
1	Apple Cider	Atmospheric Cold Plasma (ACP) using simulated air (80% N2 + 20% O2) for 180 s	Significant reduction	[194]
2	Sour Cherry Juice	Dielectric Barrier Discharge (DBD) plasma with 1% oxygen in argon, 50 kV/cm field intensity, 9-min exposure	6-log reduction	[195]
3	Orange Juice	Atmospheric Pressure Plasma Jet (APPJ) treatment	Significant reduction	[46]
4	Golden Delicious Apples	Atmospheric Cold Plasma using purified air as carrier gas, treatment time not specified	Significant reduction	[196]
5	Fresh Produce	High-Voltage Atmospheric Cold Plasma (HVACP) treatment	Significant reduction	[197]
6	Liquid Media	Dielectric Barrier Discharge Atmospheric Cold Plasma (DBD-ACP) generated inside a sealed package; 20 s direct exposure	Complete inactivation (7-log reduction)	[10]
7	Cherry Tomatoes, strawberries	Dielectric Barrier Discharge Atmospheric Cold Plasma (DBD-ACP) at 70 kV RMS for 120–300 s	Reduction to undetectable levels from initial 6.3 log10 CFU/sample	[198]
8	Chicken Fillets	Dielectric Barrier Discharge Atmospheric Cold Plasma (DBD-ACP) treatment voltage and time varied	Significant reduction	[199]
9	Fresh Produce	Atmospheric Cold Plasma (ACP) treatment parameters varied	Significant reduction	[200]
10	Meat and Meat Products	Dielectric Barrier Discharge Cold Atmospheric Plasma (DBD-CAP); parameters varied	Significant reduction	[201]
11	Grape Tomato, Spinach, and Cantaloupe	Cold Plasma-Activated Hydrogen Peroxide Aerosol; parameters varied	Significant reduction	[202]
12	Roma Tomatoes	X-Ray Radiation; parameters varied	Significant reduction	[203]
13	Fresh Produce	Atmospheric Cold Plasma (ACP) treatment parameters varied	Significant reduction	[204]
14	FFP3 Face Masks	Surface Micro-Discharge (SMD) plasma device; nitrogen mode at 12 kVpp, 5 kHz; 1-min exposure	5-log reduction	[205]
15	Liquid Media	Dielectric Barrier Discharge Atmospheric Cold Plasma (DBD-ACP) inside a sealed package; 20 s direct exposure	Complete inactivation (7-log reduction)	[10]
16	Cherry Tomatoes	Dielectric Barrier Discharge Atmospheric Cold Plasma (DBD-ACP) at 70 kV RMS for 120 s	Reduction to undetectable levels from initial 6.3 log10 CFU/sample	[198]

Table 3. Summary of major findings from the most effective CAP treatment of E. coli in foods.

No	Food Product	CAP Sources and Parameters	E. coli Inactivation	Ref.
1	Apple Cider	Atmospheric Cold Plasma (ACP) using simulated air (80% N2 + 20% O2) for 180 s	Significant reduction	[194]
2	Sour Cherry Juice	Dielectric Barrier Discharge (DBD) plasma with 1% oxygen in argon, 50 kV/cm field intensity, 9-min exposure	6-log reduction	[195]
3	Orange Juice	Atmospheric Pressure Plasma Jet (APPJ) treatment	Significant reduction	[46]
4	Golden Delicious Apples	Atmospheric Cold Plasma using purified air as carrier gas, treatment time not specified	Significant reduction	[196]
5	Fresh Produce	High-Voltage Atmospheric Cold Plasma (HVACP) treatment	Significant reduction	[197]
6	Liquid Media	Dielectric Barrier Discharge Atmospheric Cold Plasma (DBD-ACP) generated inside a sealed package; 20 s direct exposure	Complete inactivation (7-log reduction)	[10]
7	Cherry Tomatoes, strawberries	Dielectric Barrier Discharge Atmospheric Cold Plasma (DBD-ACP) at 70 kV RMS for 120–300 s	Reduction to undetectable levels from initial 6.3 log10 CFU/sample	[198]
8	Chicken Fillets	Dielectric Barrier Discharge Atmospheric Cold Plasma (DBD-ACP) treatment voltage and time varied	Significant reduction	[199]
9	Fresh Produce	Atmospheric Cold Plasma (ACP) treatment parameters varied	Significant reduction	[200]
10	Meat and Meat Products	Dielectric Barrier Discharge Cold Atmospheric Plasma (DBD-CAP); parameters varied	Significant reduction	[201]
11	Grape Tomato, Spinach, and Cantaloupe	Cold Plasma-Activated Hydrogen Peroxide Aerosol; parameters varied	Significant reduction	[202]
12	Roma Tomatoes	X-Ray Radiation; parameters varied	Significant reduction	[203]
13	Fresh Produce	Atmospheric Cold Plasma (ACP) treatment parameters varied	Significant reduction	[204]
14	FFP3 Face Masks	Surface Micro-Discharge (SMD) plasma device; nitrogen mode at 12 kVpp, 5 kHz; 1-min exposure	5-log reduction	[205]
15	Liquid Media	Dielectric Barrier Discharge Atmospheric Cold Plasma (DBD-ACP) inside a sealed package; 20 s direct exposure	Complete inactivation (7-log reduction)	[10]
16	Cherry Tomatoes	Dielectric Barrier Discharge Atmospheric Cold Plasma (DBD-ACP) at 70 kV RMS for 120 s	Reduction to undetectable levels from initial 6.3 log10 CFU/sample	[198]

This review section involves a comparative analysis of CAP with conventional E. coli decontamination methods. Figure 6 summarizes the traditional techniques for E. coli decontamination, including chemical treatment, thermal processing, irradiation, and UV sterilization. Each technique comes with its own set of advantages and disadvantages. For example, while chemical treatments are cost-effective and easy to handle, they can negatively impact food quality and harm the environment. Thermal processing is commonly used and delivers quick results; however, it may change the surface and composition of foods, making it unsuitable for heat-sensitive items. In contrast, CAP is highlighted as an environmentally friendly alternative that preserves food quality, taste, and nutrients. It is cost-effective, user-friendly, and applicable to various foods. However, challenges remain regarding device stability, optimization, and large-scale implementation. This comparison emphasizes the importance of balancing effectiveness, food safety, and environmental impact when selecting decontamination methods. CAP is a promising alternative, though further research and development are necessary to address its current limitations.

4.1. Chemical Treatments

Several chemical disinfectants are used in practice for sterilizing foods. Among them, chlorine-based disinfectants (sodium hypochlorite), peracetic acid, ethylene oxide, supercritical carbon dioxide, beta-propiolactone, glutaraldehyde, and hydrogen peroxide are being widely used in the industry against E. coli degradation. However, such chemical baths have the potential for E. coli cell death by disrupting microbial membranes and several metabolic functions. However, such chemical disinfectants also have negative aspects. The following are some limitations [1,206,207]:

(i)

After chemical treatment, some chemical residues remain in foods longer, causing serious health risks for consumers.

(ii)

Such chemical treatments are not long-lasting and have antibacterial effects for a limited time.

(iii)

Some food products, including raw food, ready-to-eat foods, and fruits, have limited penetration ability; therefore, these chemicals can only treat upper surfaces, leaving bactericidal effects inside foods.

In contrast, CAP technology offers a promising non-thermal alternative with several key advantages [208]. CAP operates through a complex combination of physicochemical mechanisms, including the generation of RONS, energetic electrons, intense electric fields, UV photons, and shock waves. These components act synergistically to inactivate pathogens like E. coli not only on the surface but potentially within the micro-environments of the food matrix, depending on the food’s structure and the plasma parameters applied. Importantly, when applied at optimized conditions, CAP has been shown to selectively inactivate microbial contaminants while preserving key food properties such as taste, texture, color, and nutritional value [209]. Unlike chemical disinfectants, CAP leaves no harmful chemical residues, as the reactive species involved tend to decay rapidly into benign byproducts such as oxygen, nitrogen, and water vapor. Nevertheless, challenges remain. The precise control of CAP parameters (e.g., treatment time, gas composition, voltage, and distance from the sample) is critical to avoid unintended oxidation or quality degradation. Further research is warranted to tailor CAP treatments to specific food types and ensure safety and efficacy on an industrial scale [210].

4.2. Thermal Processing

The heating, boiling, and wave-heating treatment of foods at high temperatures to reduce microbial effects is a conventional method that has been used for a long time. Although the heat treatment of foods against microbial, especially against foodborne and waterborne E. coli, is a highly effective sterilization technique, it has significant drawbacks, as mentioned below [211,212]:

(i)

Some foods are temperature-sensitive and can lose their nutritional quality, taste, effects of ingredients, and necessary vitamins at high temperatures. For example, boiling water can disturb water hardness, green vegetables may lose iron, and the taste of fruits may also change.

(ii)

Depending on the mass volume of foods, the heating process can not completely and permanently eliminate biofilms.

Compared to these methods, CAP has proven an effective alternative since it operates at room temperature. Therefore, it is suitable for heat-sensitive foods and is not harmful at all, providing safe and long-lasting, effective microbial treatment. CAP-generated RONS can kill E. coli at low energy, preserving food taste and ensuring long-term microbial safety, especially against E. coli [213,214,215].

4.3. Irradiation and UV Treatment

The irradiation and UV treatment of foods is a reliable sterilization method where foods are exposed to different radiations like gamma rays, X-rays, electron beams, and UV radiation to sterilize them from foodborne and water pathogens, especially against E. coli. In the case of E. coli, such radiations, although showing potential in destroying the DNA structure of bacteria, still have some challenging limitations, as given below [1,216,217,218,219]:

(i)

Irradiations can alter food taste and biological composition, altering food flavor and producing undesirable effects, especially when preserved for a long time.

(ii)

Some radiations are restricted to use, like nuclear radiations, and even many radiations have consumers’ perceptions of radiated foods, limiting widespread adoption.

(iii)

Due to its lower penetration depth and intensity challenges than foods’ penetration depth, it is less effective against embedded bacteria in food matrices and multilayer biofilms.

Compared to this, CAP generates intense and strong electric fields and more powerful UV radiation, which can penetrate deep inside food matrices and permanently deactivate E. coli biofilms. CAP has been proven to be more consumer-friendly and environment-friendly.

4.4. Potential Synergies with CAP

CAP presents a significant advantage as a hybrid decontamination technique, integrating multiple microbial inactivation mechanisms simultaneously. One of its key features is the generation of RONS, which plays a crucial role in disrupting microbial cell structures and metabolic functions. Additionally, CAP operates at a low temperature, enabling mild thermal treatment that prevents heat-induced damage to sensitive materials while still contributing to microbial deactivation. Furthermore, CAP emits intense UV radiation, which directly damages microbial DNA and inhibits replication. The process also involves the emission of electron beams and energetic ions, both of which contribute to cellular membrane disruption. Moreover, the presence of strong electric fields enhances permeability effects, further compromising microbial integrity. Additionally, CAP produces pressure waves that create mechanical stress on microbial cells, leading to their structural breakdown. The synergistic action of these diverse physical and chemical effects makes CAP an exceptionally efficient and versatile tool for microbial decontamination across various applications, including healthcare, food safety, and environmental sterilization. Potential synergies include CAP + chemical sanitizers, in which hydrogen peroxide can generate more intense and reactive species in large amounts, which becomes an effective tool against E. coli. Similarly, CAP+ mild heat treatment has proven to be another improved non-thermal technique. While CAP + UV radiations have proven very effective against E. coli DNA structure damage. These three combinations provide baseline ideas for developing novel machines for plasma-based food preservation from microbial effects, especially against E. coli [44,220,221]. Hence, integrating the CAP method with existing conventional sterilization techniques can enhance degradation efficiency, especially against E. coli. Figure 6 represents a summary of traditional E. coli treatment methods, where further improvement can enhance E. coli inactivation efficiency.

5. Challenges and Future Prospects of CAP in Food Decontamination

Although CAP has demonstrated remarkable success in degrading microbial biofilms, particularly E. coli biofilms in food, and has significantly contributed to the sterilization of E. coli in drinking water, several challenges remain that must be addressed for its widespread and practical implementation in the food processing industry and for ensuring clean water access for consumers. This section of the review will discuss the current limitations of CAP in food processing, recent advancements, and the challenges CAP users face in this field. Additionally, it will provide recommendations for further advancements in CAP technology to address future challenges and applications in the food industry.

5.1. Current Limitations of CAP

CAP is typically generated between two electrodes at atmospheric pressure by applying a high voltage in the presence of a working gas such as air, argon, oxygen, helium, or other gases. In some cases, a mist of chemicals like hydrogen peroxide is also introduced between the electrodes to enhance the plasma process. Although this configuration effectively generates plasma between the electrodes, it remains two-dimensional, oriented vertically or horizontally. Consequently, only the surface directly exposed to the plasma undergoes processing, while the sides and hidden portions of food or other materials remain untreated. This non-uniform plasma exposure poses a significant challenge in CAP-based food processing, often resulting in inconsistent microbial inactivation [222].

(i)

The transition of CAP research from laboratory studies to large-scale industrial applications faces significant challenges, particularly in optimizing key parameters such as inactivation efficiency, power consumption, processing costs, and reactor installation expenses. To facilitate this transition, further research is needed on the design, development, scalability, and throughput of optimized processing conditions, ensuring the successful implementation of CAP technology at an industrial level [39].

(ii)

CAP encompasses various types, including arc plasma, spark discharge, and corona discharge, each generating RONS, electric fields, UV radiation, electron energies, ion energies, and electron and ion densities at different intensities. These variations can influence food surfaces differently, sometimes altering color, texture, composition, and sensory attributes. Developing and optimizing CAP sources tailored to specific food categories based on properties such as heat sensitivity, texture stability, and nutritional constraints is essential to address these challenges. In summary, selecting an appropriate CAP source for a given application is crucial to ensuring effective and controlled food processing [223].

(iii)

In many cases, it is reported that CAP-generated RONS are short-lived, and there is a chance of biofilm regrowth if processed food is not adequately protected from environment-borne pathogens. Therefore, innovative multidisciplinary approaches and advanced control mechanisms are essential for effectively generating high-potency plasma species capable of permanently eliminating E. coli biofilms [224].

(iv)

The most challenging issue in the CAP treatment of foods is operational cost. Since CAP requires gases, reactor development, typical electrode assembly, and input energy, it is less economically friendly. Profound innovation and optimization of the reactors that consume low energy while processing foods using CAP are required [116].

5.2. Emerging Innovations

This review presents some ideas to overcome the challenging issues that the industry faces while adopting CAP technology for food processing against microbial films, especially E. coli-based biofilms.

(i)

A hybrid plasma system could be the best approach for completely sterilizing biofilms. Combining CAP with ozone treatments and using the mists of chemicals like hydrogen peroxide can be more effective [225].

(ii)

CAP-induced nanoparticles can act as medical probes for sterilizing foods from biofilms by transferring CAP effects deep inside the foods. Such nanoparticles should be extracted from foods, plants, and other human consumer items to avoid harmful side effects [225].

(iii)

The challenging issue can be solved by developing automated and adaptive plasma devices, in which advanced robotics and artificial intelligence should be used to develop smart and portable plasma systems. Such techniques are convenient for transforming laboratory-scale work to the industrial level [226].

(iv)

Washing foods to overcome microbial effects like E. coli can be useful, and plasma-activated waters (PALs) can play a vital role in this purpose, especially for sterilizing ready-to-eat foods [227].

(v)

The design and development of continuous plasma-generating reactors capable of large-scale food processing are essential for enhancing the feasibility of CAP treatments in the food processing industry. These advancements would enable efficient and uninterrupted plasma-based food treatment, ensuring greater practicality and scalability in industrial applications [1,228].

5.3. Regulatory and Consumer Acceptance Issues

Several regulatory and consumer acceptance challenges must be addressed to implement CAP technology in food processing successfully. This includes obtaining approvals from relevant authorities such as the U.S. Food and Drug Administration (FDA), the European Food Safety Authority (EFSA), and other regional regulatory bodies. Standardized protocols for CAP-based food processing should also be established to ensure clear guidelines for different food products. Consumer awareness is also crucial; CAP-processed foods should be clearly labeled, and comprehensive information about the process should be communicated through electronic media and online educational content, highlighting its benefits. Furthermore, risk assessment studies are essential, particularly concerning the formation of nitrates and peroxides during plasma treatment of microbial biofilms on food surfaces. A key consideration, especially for developing countries, is the cost-effectiveness and processing of CAP systems. To facilitate its widespread adoption in the food sector, the cost–benefit ratio of CAP technology must be optimized and effectively communicated to industries [204,229,230,231,232].

6. Future Recommendations

Future advancements in CAP applications for food processing and microbial sterilization should optimize plasma parameters such as voltage, frequency, and gas composition to enhance microbial inactivation efficiency. Developing advanced plasma devices and integrating synergistic antimicrobial techniques like UV and ozone can further improve effectiveness. Ensuring food safety and quality requires studies on nutritional and sensory impacts, shelf-life extension, and regulatory validation. For effective pathogen control, CAPP can be applied across various food categories, including fresh produce, dairy, meat, seafood, and packaged foods. Industrial-scale implementation demands cost-effective, energy-efficient systems with optimized plasma exposure for mass production, supported by large-scale validation studies. Figure 7 represents a flowchart of future recommendations and industrial applications of CAP in food processing. Regulatory approvals and consumer acceptance are essential, necessitating compliance with FDA and EFSA standards, public awareness campaigns, and alignment with sustainable food processing practices.

7. Conclusions

CAP is a practical, environmentally friendly, novel non-thermal plasma technique for microbial inactivation, especially against E. coli-based biofilms. The CAP-generated RONS, UV radiations, electric fields, electrons, and ions are highly useful against microbial effects. CAP can disrupt the DNA structure of foodborne pathogens, particularly E. coli, rendering it permanently inactive for regeneration and capable of producing long-lasting antibacterial effects. The CAP food processing method does not change food ingredients, nutrition, taste, and composition in optimized conditions. CAP food processing can be equally valid for all types of foods, like grains, vegetables, fruits, ready-to-eat food, seafood, and frozen foods.

CAP treatment depends upon plasma parameters (e.g., gas composition, power density, and exposure time), biofilm compositions and their antimicrobial potential (e.g., texture, moisture content), and environmental conditions (e.g., temperature, humidity). The future of CAP-based food processing requires integration into existing technologies, hybrid-mode plasma sources, and cost-effective CAP sources. CAP offers a groundbreaking advancement in food processing to protect foods from microbial effects without compromising food quality, and has proven advantageous compared to conventional methods. Further advanced research and innovation in CAP can further unlock its potential, providing a better way for safer and healthier food production and preservation practices.