Nonthermal Plasma Inactivation of Food-Borne Pathogens

Cold plasma: Unveiling its impact on hydration, rheology, nutritional, and anti-nutritional properties in food materials - An overview

Non-thermal technologies, primarily employed for microbial inactivation and quality preservation in foods, have seen a surge in interest, with non-thermal plasma garnering particular attention. Cold plasma exhibits promising outcomes, including enhanced germination, improved functional and rheological properties, and microorganism destruction. This has sparked increased exploration across various domains, notably in hydration and rheological properties for creating new products. This review underscores the manifold benefits of applying cold plasma to diverse food materials, such as cereal and millet flours, and gums. Notable improvements encompass enhanced functionality, modified color parameters, altered rheological properties, and reduced anti-nutritional factors. The review delves into mechanisms like starch granule fragmentation, elucidating how these processes enhance the physical and structural properties of food materials. While promising for high-quality food development, overcoming challenges in scaling up production and addressing legal issues is essential for the technology's commercialization.

Degradation of Toxins Derived from Foodborne Pathogens by Atmospheric-Pressure Dielectric-Barrier Discharge

Foodborne diseases can be attributed not only to contamination with bacterial or fungal pathogens but also their associated toxins. Thus, to maintain food safety, innovative decontamination techniques for toxins are required. We previously demonstrated that an atmospheric-pressure dielectric-barrier discharge (APDBD) plasma generated by a roller conveyer plasma device is effective at inactivating bacteria and fungi in foods. Here, we have further examined whether the roller conveyer plasma device can be used to degrade toxins produced by foodborne bacterial pathogens, including aflatoxin, Shiga toxins (Stx1 and Stx2), enterotoxin B and cereulide. Each toxin was spotted onto an aluminum plate, allowed to dry, and then treated with APDBD plasma applied by the roller conveyer plasma device for different time periods. Assessments were conducted using a competitive enzyme-linked immunosorbent assay (ELISA) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results demonstrate a significant time-dependent decrease in the levels of these toxins. ELISA showed that aflatoxin B1 concentrations were reduced from 308.6 µg/mL to 74.4 µg/mL within 1 min. For Shiga toxins, Stx1 decreased from 913.8 µg/mL to 65.1 µg/mL, and Stx2 from 2309.0 µg/mL to 187.6 µg/mL within the same time frame (1 min). Enterotoxin B levels dropped from 62.67 µg/mL to 1.74 µg/mL at 15 min, and 1.43 µg/mL at 30 min, but did not display a significant decrease within 5 min. LC-MS/MS analysis verified that cereulide was reduced to below the detection limit following 30 min of APDBD plasma treatment. Taken together, these findings highlight that a range of foodborne toxins can be degraded by a relatively short exposure to plasma generated by an APDBD using a roller conveyer device. This technology offers promising advancements in food safety, providing a novel method to alleviate toxin contamination in the food processing industry.

Surface air gas discharge plasma: An ecofriendly virus inactivation approach to enhance CPRRs mediated antiviral genes expression against airborne bio-contaminant (human Coronavirus-229E)

Emerging bio-contaminants (airborne viruses) exploits and manipulate host (human) metabolism to produce new viral particles, evading the host's immune defences and leading to infections. Non-thermal plasma, operating at atmospheric pressure and ambient temperature, is explored for virus inactivation, generating RONS that interact and denatures viral proteins. However, various factors affecting virus survival influence the efficacy of non-thermal plasma. Glucose analogue 2-DG, a metabolic modifier used in this study, disrupts the glycolysis pathway viruses rely on, creating an unfavourable environment for replication. Here, airborne HCoV-229E bio-contaminant was treated with plasma for inactivation, and the presence of RONS was analysed. Metabolically altered lung cells were subsequently exposed to the treated airborne viruses. Cytopathic effect, spike protein, and cell death were evaluated via flow cytometry and confocal microscopy, and CPRRs mediated antiviral gene expression was evaluated using PCR. Gas plasma-treated viruses led to reduced virus proliferation in unaltered lung cells, although few virus particles survived the exposure, as confirmed by biological assessment (cytopathic effects and live/dead staining). A combination approach of gas plasma-treated viruses and altered lung cells displayed drastic virus reduction compared to the control group, established through confocal microscopy and flow cytometry. Furthermore, altered lung cell enhances gene transcription responsible for innate immunity when exposed to the gas plasma-treated virus, thereby impeding airborne virus propagation. This study demonstrates the significance of a surface air gas plasma and metabolic alteration approach in enhancing genes targeted towards antiviral innate immunity and tackling outbreaks of emerging bio-contaminants of concerns (airborne viruses).

Shade of Innovative Food Processing Techniques: Potential Inducing Factors of Lipid Oxidation

With increasing environmental awareness and consumer demand for high-quality food products, industries are strongly required for technical innovations. The use of various emerging techniques in food processing indeed brings many economic and environmental benefits compared to conventional processes. However, lipid oxidation induced by some "innovative" processes is often "an inconvenient truth", which is scarcely mentioned in most studies but should not be ignored for the further improvement and optimization of existing processes. Lipid oxidation poses a risk to consumer health, as a result of the possible ingestion of secondary oxidation products. From this point of view, this review summarizes the advance of lipid oxidation mechanism studies and mainly discloses the shade of innovative food processing concerning lipid degradation. Sections involving a revisit of classic three-stage chain reaction, the advances of polar paradox and cut-off theories, and potential lipid oxidation factors from emerging techniques are described, which might help in developing more robust guidelines to ensure a good practice of these innovative food processing techniques in future.

Effect of plasma-activated water on the biofilm-forming ability of Salmonella enterica serovar Enteritidis and expression of the related genes

In recent years, microbial decontamination with plasma-activated water (PAW) has attracted a lot of research attention in the field of food industry. Despite several studies showing that PAW effectively inactivates planktonic bacteria, few studies have been conducted on biofilms. The present study was, therefore, designed to evaluate the effect of PAW on the biofilm formation characteristics of Salmonella Enteritidis. Comparing the expression patterns of biofilm-related genes in PAW-treated and non-treated planktonic and biofilm cells provided insight into how PAW regulates this process. The results showed that a 30-minute exposure to PAW at room temperature significantly reduced S. enteritidis planktonic cells. This exposure resulted in a decreased expression of the genes involved in the early stages of biofilm formation (csgD, agfA, fimA, lpfE, and rpoS), and an increased expression of the csrA gene in S. enteritidis planktonic cells. These results indicated the inhibitory effect of PAW on the biofilm formation process in S. enteritidis. Results of the initial attachment assay confirmed these findings, where, after 6 h, the number of PAW-treated cells attached to the stainless steel surfaces were significantly lower than non-treated ones. Furthermore, biofilm development assay revealed that the number of PAW-treated biofilm cells were significantly lower than non-treated ones after 24 h incubation at 37 °C. These findings were confirmed by measurements of the major components of biofilm i.e., extracellular DNA (eDNA), protein and carbohydrate. The amount of these components in 24-hour biofilms produced by PAW-treated S. enteritidis cells was significantly lower than that of non-treated cells. PAW's treatment on preformed 24-hour biofilms for 30 min led to a decrease in the expression of genes involved in quorum sensing and cellulose synthesis (csgD, bapA, adrA, luxS and sdiA) and an increase in the expression of the csrA gene. This treatment also reduced the number and metabolic activity of biofilm cells compared to non-treated biofilm cells. In total, the present study demonstrated that PAW has an inhibitory effect on the process of biofilm formation in S. enteritidis and hence, the food industry should pay special attention to PAW as a promising treatment to eliminate bacterial biofilms.

Bactericidal efficacy difference between air and nitrogen cold atmospheric plasma on Bacillus cereus: Inactivation mechanism of Gram-positive bacteria at the cellular and molecular level

As an emerging food processing technology, cold atmospheric plasma (CAP) has attracted great attention in the field of microbial inactivation. Although CAP has been proven to effectively inactivate a variety of foodborne pathogens, there is less research on the inactivation of Bacillus cereus, and the exact inactivation mechanism is still unclear. Elucidating the inactivation mechanism will help to develop and optimize this sterilization method, with the prospective application in industrialized food production. This study aims to explore the bactericidal efficacy difference between air and nitrogen CAP on B. cereus, a typical Gram-positive bacterium, and reveals the inactivation mechanism of CAP at the cellular and molecular level, by observing the change of the cell membrane, cell morphological damage, intracellular antioxidant enzyme activity and cellular biomacromolecules changes. The results showed that both air CAP and nitrogen CAP could effectively inactivate B. cereus, which was due to the reactive oxygen and nitrogen species (RONS) generated by the plasma causing bacterial death. The damage pathways of CAP on Gram-positive bacteria could be explained by disrupting the bacterial cell membrane and cell morphology, disturbing the intracellular redox homeostasis, and destroying biomacromolecules in the cells. The differences in active species generated by the plasma were the main reason for the different bactericidal efficiencies of air CAP and nitrogen CAP, where air CAP producing RONS with stronger oxidative capacity in a shorter time. This study indicates that air CAP is an effective, inexpensive and green technology for B. cereus inactivation, providing a basis for industrial application in food processing.

Innovative Application of Cold Plasma Technology in Meat and Its Products

The growing demand for sustainable food production and the rising consumer preference for fresh, healthy, and safe food products have been driving the need for innovative methods for processing and preserving food. In the meat industry, this demand has led to the development of new interventions aimed at extending the shelf life of meats and its products while maintaining their quality and nutritional value. Cold plasma has recently emerged as a subject of great interest in the meat industry due to its potential to enhance the microbiological safety of meat and its products. This review discusses the latest research on the possible application of cold plasma in the meat processing industry, considering its effects on various quality attributes and its potential for meat preservation and enhancement. In this regard, many studies have reported substantial antimicrobial efficacy of cold plasma technology in beef, pork, lamb and chicken, and their products with negligible changes in their physicochemical attributes. Further, the application of cold plasma in meat processing has shown promising results as a potential novel curing agent for cured meat products. Understanding the mechanisms of action and the interactions between cold plasma and food ingredients is crucial for further exploring the potential of this technology in the meat industry, ultimately leading to the development of safe and high-quality meat products using cold plasma technology.

Insights into application progress of seafood processing technologies and their implications on flavor: a review

Seafood tends to be highly vulnerable to spoilage and deterioration due to biochemical reactions and microbial contaminations, which requires appropriate processing technologies to improve or maintain its quality. Flavor, as an indispensable aspect reflecting the quality profile of seafood and influencing the final choice of consumers, is closely related to the processing technologies adopted. This review gives updated information on traditional and emerging processing technologies used in seafood processing and their implications on flavor. Traditional processing technologies, especially thermal treatment, effectively deactivate microorganisms to enhance seafood safety and prolong its shelf life. Nonetheless, these methods come with limitations, including reduced processing efficiency, increased energy consumption, and alterations in flavor, color, and texture due to overheating. Emerging processing technologies like microwave heating, infrared heating, high pressure processing, cold plasma, pulsed electric field, and ultrasound show alternative effects to traditional technologies. In addition to deactivating microorganisms and extending shelf life, these technologies can also safeguard the sensory quality of seafood. This review discusses emerging processing technologies in seafood and covers their principles, applications, developments, advantages, and limitations. In addition, this review examines the potential synergies that can arise from combining certain processing technologies in seafood processing.

Comparison of the efficacy of physical and chemical strategies for the inactivation of biofilm cells of foodborne pathogens

Biofilm formation is a strategy in which microorganisms generate a matrix of extracellular polymeric substances to increase survival under harsh conditions. The efficacy of sanitization processes is lowered when biofilms form, in particular on industrial devices. While various traditional and emerging technologies have been explored for the eradication of biofilms, cell resistance under a range of environmental conditions renders evaluation of the efficacy of control challenging. This review aimed to: (1) classify biofilm control measures into chemical, physical, and combination methods, (2) discuss mechanisms underlying inactivation by each method, and (3) summarize the reduction of biofilm cells after each treatment. The review is expected to be useful for future experimental studies and help to guide the establishment of biofilm control strategies in the food industry.

Efficacy of cold plasma-activated water as an environmentally friendly sanitizer in egg washing

Eggs in the United States are typically washed using chemical sanitizers such as quaternary ammonia (QA) or chlorine. Such treatments generate wash water, which could be potentially hazardous to the environment. A novel, nonthermal sanitization technique for washing shell eggs using cold plasma-activated water (PAW) was investigated in this study. The inactivation efficacy of PAW on Klebsiella michiganensis and the impact of PAW on the cuticle of the eggshell and shell strength were tested in comparison to QA. Washing inoculated eggs with PAW and QA achieved a similar microbial reduction (>5.28 log CFU/egg). Colorimetric analysis showed that ∆E-value for PAW-treated eggs was significantly lower than QA-treated eggs, suggesting higher cuticle coverage in eggs treated with PAW. The texture analysis to test for shell egg strength indicated that washing eggs with PAW did not affect the structural integrity of the eggshell when compared to eggs washed with QA. According to this study, PAW has the potential as an alternative to commercial sanitizers like QA in the egg-washing industry. PAW does not detrimentally impact shell strength or cuticle coverage and provides similar microbial reduction efficacy.

The combined effects of ultrasound and plasma-activated water on microbial inactivation and quality attributes of crayfish during refrigerated storage

In this study, a decontamination technology combining ultrasound (US) and plasma-activated water (PAW) was developed to better preserve crayfish. First, the decontamination efficacy of US, PAW and their combinations (UP) on crayfish was quantified after 0, 20, 40, or 60 min of treatments. The total viable count (TVC) was reduced by 0.27-0.77 Log CFU/g after individual US or PAW treatments, while a TVC reduction of 1.17 Log CFU/g was achieved after 40 min of UP treatment. Besides, the changes in psychrotrophic bacteria, lactic acid bacteria, yeasts and molds followed a similar trend to TVC. UP treatments normally resulted in more significant reductions in the natural microbiota of crayfish than US or PAW treatments. Furthermore, the microbial quality, physicochemical properties and sensory properties of crayfish after different treatments were assessed during storage at 4 °C for 12 days. According to TVC and total volatile basic nitrogen (TVB-N) values, the control group became unacceptable from 4 days, US or PAW groups became unacceptable from 6 days, while UP group extended the storage time to 8-10 days. During storage, thiobarbituric acid reactive substances (TBARS) values of all the groups were maintained below 0.5 mg/kg, among which the control group exhibited the highest value (0.39 mg/kg). Moreover, UP treatment effectively retarded the deterioration in color and texture properties of crayfish. Fourier transform infrared (FTIR) spectroscopy analysis indicated that UP treatment decreased the α-helix contents and increased the β-sheet contents of crayfish proteins, while the structural changes were not evident at the end of storage. Low-field nuclear magnetic resonance (LF-NMR) analysis revealed that UP treatment reduced the water migration and enhanced the stability of bond water in crayfish. In addition, E-nose analysis revealed the protection of UP treatment on the sensory properties of crayfish during storage. This study demonstrated that the combinations of US and PAW treatments effectively accelerated the decontamination of crayfish and contributed to better storage quality.

Partial hydrogenation of oils using cold plasma technology and its effect on lipid oxidation

The formation of trans-fatty acids during the hydrogenation of oils using traditional methods is a known fact. Hydrogenation involves the conversion of unsaturation to saturation to enhance the keeping quality of oils. These trans-fatty acids are considered harmful leading to several cardiovascular diseases. Methods like the use of novel catalysts, interesterification, supercritical CO2 hydrogenation and electrocatalytic hydrogenation have been employed to reduce the trans-fatty acid formation. Recently, the application of cold plasma for hydrogenation was employed as an eco-friendly technology. The use of hydrogen as a feed gas will be the source of atomic hydrogen required for the conversion of unsaturated to saturated bonds. The hydrogenation using cold plasma did not result in the formation of trans-fatty acids. However, some reports have shown insignificant levels of trans-fatty acids and secondary lipid oxidation compounds after the plasma treatment. Therefore, it is necessary to optimize the plasma parameters, feed gas type and composition, processing condition to avoid practical implications. It can be concluded that after the detailed investigation of role of reactive species in the partial hydrogenation of oils cold plasma can be considered as an alternative technology.

EFFECTS OF COLD PLASMA ON CHLOROPHYLLS, CAROTENOIDS, ANTHOCYANINS, AND BETALAINS

Plasma is considered by several researchers to be the fourth state of matter. Cold plasma has been highlighted as an alternative to thermal treatments because heat induces less degradation of thermolabile bioactive compounds, such as natural pigments. In this review, we provide a compilation of the current information about the effects of cold plasma on natural pigments, such as the changes caused by plasma to the molecules of chlorophylls, carotenoids, anthocyanins, and betalains. As a result of the literature review, it is noted that can degrade cell membrane and promote damage to pigment storage sites; thereby releasing pigments and increasing their content in the extracellular space. However, the reactive species contained in the cold plasma can cause degradation of the pigments. Cold plasma is a promising technology for extracting pigments; however, case-by-case optimization of the extraction process is required.

Role of Non-Thermal Plasma in Fusarium Inactivation and Mycotoxin Decontamination

Fusarium spp. is a well-studied pathogen with the potential to infect cereals and reduce the yield to maximum if left unchecked. For decades, different control treatments have been tested against different Fusarium spp. and for reducing the mycotoxins they produce and are well documented. Some treatments also involved integrated pest management (IPM) strategies against Fusarium spp. control and mycotoxin degradation produced by them. In this review article, we compiled different control strategies against different Fusarium spp. In addition, special focus is given to the non-thermal plasma (NTP) technique used against Fusarium spp. inactivation. In a separate group, we compiled the literature about the use of NTP in the decontamination of mycotoxins produced by Fusarium spp., and highlighted the possible mechanisms of mycotoxin degradation by NTP. In this review, we concluded that although NTP is an effective treatment, it is a nice area and needs further research. The possibility of a prospective novel IPM strategy against Fusarium spp. is also proposed.

Practice and Progress: Updates on Outbreaks, Advances in Research, and Processing Technologies for Low-moisture Food Safety

Large, renowned outbreaks associated with low-moisture foods (LMFs) bring to light some of the potential, inherent risks that accompany foods with long shelf lives if pathogen contamination occurs. Subsequently, in 2013, Beuchat et al. (2013) noted the increased concern regarding these foods, specifically noting examples of persistence and resistance of pathogens in low-water activity foods (LWAFs), prevalence of pathogens in LWAF processing environments, and sources of and preventive measures for contamination of LWAFs. For the last decade, the body of knowledge related to LMF safety has exponentially expanded. This growing field and interest in LMF safety have led researchers to delve into survival and persistence studies, revealing that some foodborne pathogens can survive in LWAFs for months to years. Research has also uncovered many complications of working with foodborne pathogens in desiccated states, such as inoculation methods and molecular mechanisms that can impact pathogen survival and persistence. Moreover, outbreaks, recalls, and developments in LMF safety research have created a cascading feedback loop of pushing the field forward, which has also led to increased attention on how industry can improve LMF safety and raise safety standards. Scientists across academia, government agencies, and industry have partnered to develop and evaluate innovate thermal and nonthermal technologies to use on LMFs, which are described in the presented review. The objective of this review was to describe aspects of the extensive progress made by researchers and industry members in LMF safety, including lessons-learned about outbreaks and recalls, expansion of knowledge base about pathogens that contaminate LMFs, and mitigation strategies currently employed or in development to reduce food safety risks associated with LMFs.

Biofilms: Formation, Research Models, Potential Targets, and Methods for Prevention and Treatment

Due to the continuous rise in biofilm-related infections, biofilms seriously threaten human health. The formation of biofilms makes conventional antibiotics ineffective and dampens immune clearance. Therefore, it is important to understand the mechanisms of biofilm formation and develop novel strategies to treat biofilms more effectively. This review article begins with an introduction to biofilm formation in various clinical scenarios and their corresponding therapy. Established biofilm models used in research are then summarized. The potential targets which may assist in the development of new strategies for combating biofilms are further discussed. The novel technologies developed recently for the prevention and treatment of biofilms including antimicrobial surface coatings, physical removal of biofilms, development of new antimicrobial molecules, and delivery of antimicrobial agents are subsequently presented. Finally, directions for future studies are pointed out.

Oxidative lesions and post-treatment viability attenuation of listeria monocytogenes triggered by atmospheric non-thermal plasma

AIMS

The aim of the current study was to investigate the effect of plasma-mediated oxidative stress on the post-treatment viability of Listeria monocytogenes at the physiological and molecular levels.

METHODS AND RESULTS

10⁷  CFU/ml L. monocytogenes in 10 ml phosphate-buffered saline (PBS) was treated with atmospheric non-thermal plasma for 0, 30, 60, 90 and 120 s respectively. Optical diagnostics using optical emission spectroscopy (OES) confirmed that dielectric barrier discharge (DBD) plasma was a significant source of ample exogenous reactive oxygen and nitrogen species (RONS). The development of extracellular main long-lived species was associated with plasma exposure time, accompanied by a massive accumulation of intracellular ROS in L. monocytogenes (p < 0.01). With the exception of virulence genes (hly), most oxidation resistance genes (e.g. sigB, perR, lmo2344, lmo2770 and trxA) and DNA repair gene (recA) were upregulated significantly (p < 0.05). A visible fragmentation in genomic DNA and a decline in the secretion of extracellular proteins and haemolytic activity (p < 0.01) were noticed. The quantitate oxygen consumption rates (OCRs) and extracellular acidification rates (ECARs) confirmed the viability attenuation from the aspect of energy metabolism. Survival assay in a real food system (raw milk) further suggested not only the viability attenuation, but also the resuscitation potential and safety risk of mild plasma-treated cells during post-treatment storage.

CONCLUSION

DBD plasma had the potential to inactivate and attenuate the virulence of L. monocytogenes, and it was recommended that plasma exposure time longer than 120 s was more suitable for attenuating viability and avoiding the recovery possibility of L. monocytogenes in raw milk within 7 days.

SIGNIFICANCE AND IMPACT OF THE STUDY

The current results presented a strategy to inactivate and attenuate the viability of L. monocytogenes, which could serve as a theoretical basis for better application of non-thermal plasma in food in an effort to effectively combat foodborne pathogens.

Nonthermal Plasma Effects on Fungi: Applications, Fungal Responses, and Future Perspectives

The kingdom of Fungi is rich in species that live in various environments and exhibit different lifestyles. Many are beneficial and indispensable for the environment and industries, but some can threaten plants, animals, and humans as pathogens. Various strategies have been applied to eliminate fungal pathogens by relying on chemical and nonchemical antifungal agents and tools. Nonthermal plasma (NTP) is a potential tool to inactivate pathogenic and food-contaminating fungi and genetically improve fungal strains used in industry as enzyme and metabolite producers. The NTP mode of action is due to many highly reactive species and their interactions with biological molecules. The interaction of the NTP with living cells is believed to be synergistic yet not well understood. This review aims to summarize the current NTP designs, applications, and challenges that involve fungi, as well as provide brief descriptions of underlying mechanisms employed by fungi in interactions with the NTP components.

Study on Active Particles in Air Plasma and Their Effect on α-Amylase

As a new technology for food processing, plasma has good prospects for protein modification. This study investigated the effect of plasma on the activity of the α-amylase. The composition of the active particles in air plasma generated by spark discharge was analyzed and determined. Furthermore, the quantitative analysis of the active particles such as H₂O₂, O₃, and -OH was made by the chemical detection method. Powdered α-amylase was treated with plasma in various conditions, in which α-amylase and the variation of α-amylase activity under the action of air plasma were quantitatively analyzed. The results showed that the concentration of active particles in the system was positively correlated with the action time for air plasma. After 5 min of plasma action, the concentration of O₃ and H₂O₂ was large enough for food disinfection, but the concentration of -OH was smaller and its lifetime was extremely short. Moreover, it was determined that the optimum action time for the activation of solid powdered α-amylase by air plasma was 120 s. With higher energy, the air plasma acts directly on solid powdered α-amylase to destroy its spatial structure, resulting in enzyme inactivation, sterilization, and disinfection.

Impacts of Cold Plasma Technology on Sensory, Nutritional and Safety Quality of Food: A Review

As an emerging non-thermal food processing technology, cold plasma (CP) technology has been widely applied in food preservation due to its high efficiency, greenness and lack of chemical residues. Recent studies have indicated that CP technology also has an impressing effect on improving food quality. This review summarized the impact of CP on the functional composition and quality characteristics of various food products. CP technology can prevent the growth of spoilage microorganisms while maintaining the physical and chemical properties of the food. It can maintain the color, flavor and texture of food. CP can cause changes in protein structure and function, lipid oxidation, vitamin and monosaccharide degradation, starch modification and the retention of phenolic substances. Additionally, it also degrades allergens and toxins in food. In this review, the effects of CP on organoleptic properties, nutrient content, safety performance for food and the factors that cause these changes were concluded. This review also highlights the current application limitations and future development directions of CP technology in the food industry. This review enables us to more comprehensively understand the impacts of CP technology on food quality and promotes the healthy application of CP technology in the food industry.

A Plasma-Based Decontamination Process Reveals Potential for an in-Process Surface-Sanitation Method

Methods, which use an indirect plasma treatment for the inactivation of microorganisms in foods, claim a vastly growing field of research. This paper presents a method that uses plasma-processed air (PPA) as a sanitizer. In addition to a sanitation concept for the decontamination of produce in the value chain, the presented method offers a possible application as an “in-process” surface sanitation. PPA provides antimicrobial-potent species, which are predominantly reactive nitrogen species (RNS); this has an outstanding groove penetration property. In an experimental approach, surfaces, made from materials, which are frequently used for the construction of food-processing plants, were inoculated with different microorganisms. Listeria monocytogenes (ATCC 15313), Staphylococcus aureus (ATCC 6538), Escherichia coli (ATCC 10538), Salmonella enterica subsp. enterica serovar Typhimurium (ATCC 43971), and Salmonella enterica subsp. enterica serovar Enteritidis (ATCC 13076) are all microorganisms that frequently appear in foods and possess the risk for cross-contamination from the plant to the produce or vice versa. The contaminated samples were treated for various treatment times (1–5 min) with PPA of different antimicrobial potencies. Subsequently, the microbial load on the specimens was determined and compared with the load of untreated samples. As a result, reduction factors (RF) up to several log10-steps were obtained. Although surface and the bacterial strain showed an influence on the RF, the major influence was seen by a prolongation of the treatment time and an increase in the potency of the PPA.

Inactivation of Escherichia coli in apple cider using atmospheric cold plasma

Atmospheric cold plasma (ACP) is a promising non-thermal technology that has the potential to inactivate microorganisms in foods. In this work, the inactivation of E. coli K12, acid-adapted E. coli K12, and E. coli O157:H7 in apple cider by ACP was investigated using feed gases as simulated air (SA) (80 % N₂ + 20 % O₂) and a mixture of 90 % N₂ + 10 % O₂ with various processing times (0 to 180 s). We obtained the reduced the populations of both acid-adapted and non-adapted E. coli K12 by 5 log CFU/mL within 120 s, and E. coli O157:H7 within 90 s. Additionally, no significant changes in the °Brix, pH, temperature, or titratable acidity (TA) of apple cider were observed after exposure to ACP. However, processing times longer than 120 s resulted in significant changes in the pH values. The highest concentration of ozone and hydrogen peroxide reached to 0.22 ± 0.1 mg/L for CG in 180 s and 0.07 ± 0.01 mg/L for SA in 150 s, respectively. Both acid-adapted and non-acid adapted E. coli K12 was found to be more resistant to ACP processing than E. coli O157:H7 after the 90 s, so it could serve as a surrogate for E. coli O157:H7. When we compared the effect of the gas type on inactivation, non-selective media, the results showed no significant differences between the gas types, while selective media demonstrated significant differences. In optical absorption spectroscopy measurements of plasma species, primarily ozone peaks were observed. Furthermore, the optical absorption spectroscopy also revealed that the inactivation of the bacteria could be attributed to some plasma species with wavelengths between 190 and 308 nm. The findings provided a perspective on the use of ACP as a method for decontaminating fruit juices as a non-thermal processing.

Control of aflatoxin M1 in skim milk by high voltage atmospheric cold plasma

Cold plasma has potential for the degradation of aflatoxins in corn and hazelnuts; however, this has not been demonstrated for aflatoxin in milk. In this study, the efficacy of high voltage atmospheric cold plasma (HVACP) on the reduction of aflatoxin M1 (AFM1) in skim milk improved with increasing treatment times (1-20 min), using gas containing 65% oxygen (MA65) rather than air, increasing voltage (60-80 kV) and reducing sample volume (30 mL-10 mL). Direct treatment was more effective than indirect treatment. AFM1 in milk was degraded by 65.0 % and 78.9 % by air and MA65 respectively in 20 min with no change in milk colour. The toxicity of AFM1 after treatment was assessed using a brine shrimp model. A five-minute HVACP treatment reduced the toxicity of AFM1 by 83.9 % based on the increase in brine shrimp survival. HVACP is a promising method to reduce AFM1 in milk.

A comprehensive study on decontamination of food-borne microorganisms by cold plasma

Food-borne microorganisms are one of the biggest concern in food industry. Food-borne microorganisms such as Listeria monocytogenes, Escherichia coli, Salmonella spp., Vibrio spp., Campylobacter jejuni, Hepatitis A are commonly found in food products and can cause severe ailments in human beings. Hence, disinfection of food is performed before packaging is performed to sterilize food. Traditional methods for disinfection of microorganisms are based on chemical, thermal, radiological and physical principles. They are highly successful, but they are complex and require more time and energy to accomplish the procedure. Cold plasma is a new technique in the field of food processing. CP treatments has no or very low effect on physical, chemical and nutritional properties of food products. This paper reviews the effect of plasma processing on food products such as change in colour, texture, pH level, protein, carbohydrate, and vitamins. Cold plasma by being a versatile, effective, economical and environmentally friendly method provides unique advantages over commercial food processing technologies for disinfection of food.

Low Temperature Plasma Strategies for Xylella fastidiosa Inactivation

The quarantine bacterium Xylella fastidiosa was first detected in Salento (Apulia, Italy) in 2013 and caused severe symptoms in olives, leading to plant death. The disease, named Olive Quick Decline Syndrome (OQDS), is caused by the strain “De Donno” ST53 of the subspecies pauca of this bacterium (XfDD), which is spread by the insect Philaenus spumarius. The epidemic poses a serious threat to the agricultural economy and the landscape, as X. fastidiosa infects several plant species and there is yet no recognized solution. Research on OQDS is focused on finding strategies to control its spread or mitigate its symptoms. As a perspective solution, we investigated the efficacy of the low-temperature plasma and plasma-activated water to kill bacterial cells. Experiments were conducted in vitro to test the biocidal effect of the direct application of a Surface Dielectric Barrier Discharge (SDBD) plasma on bacteria cells and Plasma Activated Water (PAW). PAW activity was tested as a possible biocidal agent that can move freely in the xylem network paving the way to test the strategy on infected plants. The results showed a high decontamination rate even for cells of XfDD embedded in biofilms grown on solid media and complete inactivation in liquid culture medium.

Disinfection of an ambulance using a compact atmospheric plasma device

AIMS

The worldwide spread of the coronavirus SARS-CoV-2 has highlighted the need for fast and simple disinfection processes, amongst others for ambulance cars on site. To overcome current drawbacks regarding room disinfection, the use of cold atmospheric plasma in remote operation represents a promising alternative for the disinfection of larger volumes. In this study, a compact plasma system was evaluated regarding its disinfection efficiency inside an ambulance car.

METHODS AND RESULTS

The developed plasma device is based on a dielectric barrier discharge (DBD) and operates with ambient air as process gas. The humidified afterglow from the plasma nozzle was introduced into an ambulance car with a volume of approximately 10 m³ while B. atrophaeus endospores, S. aureus or Phi 6 bacteriophages dried on different surfaces (PET-films, glass slides or aluminum foil) were exposed to the reactive gas inside the ambulance vehicle at eight different positions. Reductions of spores by more than 4 orders of magnitude were found on all surfaces and positions within 2 hours. Due to their higher susceptibility, Phi 6 bacteriophages and S. aureus counts were reduced by at least 4 orders of magnitude within 30 min on all surfaces.

CONCLUSION

The results show that different microorganisms dried on variable surfaces can be inactivated by several orders of magnitude inside an ambulance by plasma gas from of a compact DBD plasma nozzle.

SIGNIFICANCE AND IMPACT OF STUDY

Plasma gas generated on site by a DBD plasma nozzle proved to be highly efficient for the disinfection of the interior of an ambulance car. Compact plasma systems could be a viable alternative for the disinfection of vehicles or rooms.

Recent trends and technological development in plasma as an emerging and promising technology for food biosystems

The rising need for wholesome, fresh, safe and “minimally-processed” foods has led to pioneering research activities in the emerging non-thermal technology of food processing. Cold plasma is such an innovative and promising technology that offers several potential applications in the food industry. It uses the highly reactive, energetic and charged gas molecules and species to decontaminate the food and package surfaces and preserve the foods without causing thermal damage to the nutritional and quality attributes of food. Cold plasma technology showed promising results about the inactivation of pathogens in the food industry without affecting the food quality. It is highly effective for surface decontamination of fruits and vegetables, but extensive research is required before its commercial utilization. Recent patents are focused on the applications of cold plasma in food processing and preservation. However, further studies are strongly needed to scale up this technology for future commercialization and understand plasma physics for getting better results and expand the applications and benefits. This review summarizes the emerging trends of cold plasma along with its recent applications in the food industry to extend shelf life and improve the quality of food. It also gives an overview of plasma generation and principles including mechanism of action. Further, the patents based on cold plasma technology have also been highlighted comprehensively for the first time.

Cold plasma technology: An insight on its disinfection efficiency of various food systems

Cold plasma technology is considered as one of the novel potential non-thermal techniques for food disinfection. The acceptability of any food product depends upon its physicochemical properties and shelf life. Recent studies have confirmed that plasma can effectively reduce the pathogenic microbes in various food systems. Further, there are reports that cold plasma showed minimal or no effect on the physicochemical and sensory properties of the foods owing to its low-temperature operation. The present review explores the recent reports on cold plasma technology emphasizing its disinfection efficacy on different food categories. Various researchers have demonstrated that plasma successfully reduced the microorganisms on cereals, milk, meat, fish and spices. Therefore, based on the current research, it can be suggested that cold plasma is an effective disinfectant technology for the inactivation of pathogenic microorganisms, and its non-thermal and environmentally friendly nature is an added advantage over traditional processing technologies.

Behavior of the Surviving Population of Listeria monocytogenes and Salmonella Typhimurium Biofilms Following a Direct Helium-Based Cold Atmospheric Plasma Treatment

Although the Cold Atmospheric Plasma (CAP) technology proved promising for inactivation of biofilms present on abiotic food contact surfaces, more research is required to examine the behavior of the CAP surviving biofilm-associated cells. It was therefore examined whether (i) CAP treated (Listeria monocytogenes and Salmonella Typhimurium) biofilm-associated cells were able to further colonize the already established biofilms during a subsequent incubation period and (ii) isolates of the surviving population became less susceptible toward CAP when the number of biofilm development—CAP treatment cycles increased. For this purpose, a direct treatment was applied using a helium-based Dielectric Barrier Discharge electrode configuration. Results indicated that the surviving population was able to further colonize the already established biofilms, since the cell density of the CAP treated + incubated biofilms equaled the initial density of the untreated biofilms. For the L. monocytogenes biofilms, also the total biomass proved to further increase, which might result in an even further increased resistance. The susceptibility of the biofilm-associated cells proved to be influenced by the specific number of CAP treatment cycles, which might potentially result in an overestimation of the CAP treatment efficacy and, consequently, an increased risk of food contamination.

Nonthermal physical modification of starch: An overview of recent research into structure and property alterations

To tailor the properties and enhance the applicability of starch, various ways of starch modification have been practiced. Among them, physical modification methods (micronization, nonthermal plasma, high-pressure, ultrasonication, pulsed electric field, and γ-irradiation) are highly potential for starch modification considering its safety, environmentally friendliness, and cost-effectiveness, without generating chemical wastes. Thus, this article provides an overview of the recent advances in nonthermal physical modification of starch and summarizes the resulting changes in the multi-level structures and physicochemical properties. While the effect of these techniques highly depends on starch type and treatment condition, they generally lead to the destruction of starch granules, the degradation of molecules, decreases in crystallinity, gelatinization temperatures, and viscosity, increases in solubility and swelling power, and an increase or decrease in digestibility, to different extents. The advantages and shortcomings of these techniques in starch processing are compared, and the knowledge gap in this area is commented on.

Inactivation of isolated fungi on Erythrina velutina Willd. seeds through atmospheric plasma

This study aimed to evaluate the effect of atmospheric plasma application on the inactivation of fungi on the surface of Erythrina velutina seeds and on isolated fungal colonies. Two experiments were conducted using a completely randomized design. First, plasma was applied to the surface of the seeds using helium gas and atmospheric plasma for 3, 6, and 9 min in addition to the control (untreated seeds), constituting seven treatments with five repetitions each. In the second experiment, Petri dishes containing the inoculum of different fungi were treated with atmospheric air plasma for 3, 6, and 9 min (Air-3, Air-6, and Air-9) and were compared with untreated fungi in Petri dishes without treatment (control), totaling four treatments and five repetitions each. We found that the application of atmospheric air plasma to E. velutina seeds for 9 min had an antimicrobial effect on the fungi Aspergillus niger, Aspergillus flavus, Fusarium sp., Brachysporium sp., and Rhizopus sp. The formation of fungal colonies isolated from E. velutina seeds was also inhibited by 3 min of exposure to atmospheric air plasma, except for A. niger, whose inhibition occurred after 6 min of exposure to atmospheric plasma.

Mild processing of seafood-A review

Recent years have shown a tremendous increase in consumer demands for healthy, natural, high-quality convenience foods, especially within the fish and seafood sector. Traditional processing technologies such as drying or extensive heating can cause deterioration of nutrients and sensory quality uncompilable with these demands. This has led to development of many novel processing technologies, which include several mild technologies. The present review highlights the potential of mild thermal, and nonthermal physical, and chemical technologies, either used alone or in combination, to obtain safe seafood products with good shelf life and preference among consumers. Moreover, applications and limitations are discussed to provide a clear view of the potential for future development and applications. Some of the reviewed technologies, or combinations thereof, have shown great potential for non-seafood products, yet data are missing for fish and seafood in general. The present paper visualizes these knowledge gaps and the potential for new technology developments in the seafood sector. Among identified gaps, the combination of mild heating (e.g., sous vide or microwave) with more novel technologies such as pulsed electric field, pulsed light, soluble gas stabilization, cold plasma, or Ohmic heat must be highlighted. However, before industrial applications are available, more research is needed.

A Review of Microbial Decontamination of Cereals by Non-Thermal Plasma

Cereals, an important food for humans and animals, may carry microbial contamination undesirable to the consumer or to the next generation of plants. Currently, non-thermal plasma (NTP) is often considered a new and safe microbicidal agent without or with very low adverse side effects. NTP is a partially or fully ionized gas at room temperature, typically generated by various electric discharges and rich in reactive particles. This review summarizes the effects of NTP on various types of cereals and products. NTP has undisputed beneficial effects with high potential for future practical use in decontamination and disinfection.

Cold Plasma Processing on Fruits and Fruit Juices: A Review on the Effects of Plasma on Nutritional Quality

This review aims to present the effects of cold plasma technology on the nutritional quality of fruits and fruit juices. This review focuses on the chemical changes induced by plasma on several bioactive compounds, such as sugars, starch, lipids, vitamins, phenolic compounds, carotenoids, and anthocyanins. The main plasma-reacting species that reacts with fruit compounds are presented and discussed. The review presents the mechanisms that lead to the improvement and degradation of the main compounds, showing both the advantages and disadvantages of cold plasma technology.

A modified quick, easy, cheap, effective, rugged, and safe method for determination of by-products originating from ozonation of chlorpyrifos and diazinon spiked in cherry tomato and perilla leaf

In this study, sample pretreatment methods have been developed for the determination of chlorpyrifos, diazinon, and their by-products present in cherry tomato and perilla leaf using liquid chromatography-tandem mass spectrometry. To optimize a quick, easy, cheap, effective, rugged, and safe method, the recoveries at each step were evaluated. The steps improved the recoveries of chlorpyrifos, chlorpyrifos oxon, diazinon, diazoxon, and 2-isopropyl-6-methyl-4-pyrimidinol up to 80% or more by removing interferents, but diethyl phosphate was almost lost during the partition procedure, and the 3,5,6-trichloro-2-pyridinol recovery was below 65%. Therefore, the compounds were evaluated using different solvent compositions based on a quick polar pesticides method; note that 100% methanol showed acceptable extraction results. The optimized method provided method detection limits ranging from 0.03 to 1.22 ng/g and good linearities (R²  > 0.996). The recovery values were between 82.1 and 113.3%. The intra- and interday reproducibility was evaluated to be within 8.6 and 9.9%, respectively. The method was applied to determine the degradation efficiency of chlorpyrifos and diazinon and their by-products formed during plasma treatment.

Preservatives from food-For food: Pea protein hydrolysate as a novel bio-preservative against Escherichia coli O157:H7 on a lettuce leaf

Fresh-cut fruits and vegetables are becoming particularly popular as healthy fast-food options; however, they present challenges such as accelerated rates of decay and increased risk for contamination when compared to whole produce. Given that food safety must remain paramount for producers and manufacturers, research into novel, natural food preservation solutions which can help to ensure food safety and protect against spoilage is on the rise. In this work, we investigated the potential of using a novel protein hydrolysate, produced by the enzymatic hydrolysis of Pisum sativum (PSH), as a novel bio-preservative and its abilities to reduce populations of Escherichia coli O157:H7 after inoculation on a lettuce leaf. While unhydrolyzed P. sativum proteins show no antimicrobial activity, once digested, and purified, the enzymatically released peptides induced in vitro bactericidal effects on the foodborne pathogen at 8 mg/ml. When applied on an infected lettuce leaf, the PSH significantly reduced the number of bacteria recovered after 2 hr of treatment. PSH may be preferred over other preservation strategies based on its natural, inexpensive, sustainable source, environmentally friendly process, nontoxic nature, good batch to batch consistency, and ability to significantly reduce counts of E. coli both in vitro and in a lettuce leaf.