Category Archives: Cold Atmospheric Plasma

Research – Cold Plasma and Pulsed Light Inactivates Escherichia coli O157: H7 in Romaine Lettuce and Preserves Produce Quality

Posted on November 17, 2024 by | Leave a comment

Wiley Online

ABSTRACT

Fresh produce safety is important for consumer health. Intervention technologies that can lessen the pathogen threat and produce contamination is needed. In this research, cold plasma (CP), pulsed light (PL) and their combinations were assessed for inactivating Escherichia coli O157:H7 on Romaine lettuce. The effects of treatment on native microflora and sensory attributes of lettuce was also determined. An inoculum of multiple E. coli O157:H7 strains was employed for this study. Lettuce leaves were spot inoculated and then treated with PL (1–60 s), CP (15–60 s) or their optimized treatment combinations. A 30 s treatment with PL (fluence dose of 31.5 J/cm2), was optimum which provided 2.7 log CFU/g reduction of the pathogen, while 45 s treatment of CP was optimum, that delivered 2.1 log CFU/g log reduction. Combinations of PL and CP treatments were investigated for enhanced inactivation. For PL-CP combination, inoculated lettuce was treated with PL for 30 s followed by 45 s of CP exposure. While for CP-PL combination, treatments sequences were 45 s of CP treatment followed by 30 s PL treatment. Both combination treatments, PL-CP and CP-PL, resulted in synergistic inactivation of E. coli cells with > 5 log reductions of the pathogen. These combination treatments significantly (p < 0.05) reduced native microbiota and slowed their growth during storage. Additionally, treatment effects on lettuce quality was not adversely impacted. PL and CP are both non-aqueous, sustainable technologies. This study demonstrated that integration of PL and CP technology can enhance microbial safety and preserve quality of Romaine lettuce.

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Posted in Cold Atmospheric Plasma, Cold Plasma, E.coli O157, E.coli O157:H7, Food Microbiology Research, Food Technology, Research, Technology

Research – Effects of Combined Cold Plasma and Organic Acid-Based Sanitizer Treatments Against Salmonella enterica on Tomato Surfaces

Posted on November 2, 2024 by | Leave a comment

Wiley Online

ABSTRACT

Incidence of foodborne illness due to bacterial contamination of fresh produce continue to exist despite continuous research on processing interventions to mitigate the problem. In this study, we combined atmospheric cold plasma treatments with an antimicrobial solution containing specific organic acids generally recognized as safe (GRAS) by the FDA and tested its antimicrobial efficacy against Salmonella enterica inoculated on tomato surfaces. Tomato surfaces were inoculated with at 5.6 log CFU/g of Salmonella by spotting 0.1 mL of 7 log CFU/ml Salmonella onto the tomato stem scars, and by dipping whole tomatoes into a solution of 7 log CFU/ml Salmonella for 3 min to achieve 4.1 log CFU/g. Antimicrobial efficacy of the organic acid-based sanitizer + cold plasma treatments for 30, 60, 120, 180, and 360 s, were investigated, and significant bacterial inactivation was achieved above 120 s treatments. At 120 s, surviving populations of aerobic mesophilic bacteria recovered on the tomatoes surfaces averaged < 2 logs/g while yeast and mold survival averaged < 1 CFU/g. Treatment combination with this organic acid-based sanitizer + cold plasma for 120 s resulted in a 4.9 log reduction of Salmonella on the stem scar area and a 3.9 log reduction on the smooth peel surface. Similarly, populations of aerobic mesophilic bacteria recovered on treated tomato surfaces averaged < 0.3 log CFU/g. The results of this study indicate that combining an organic acid-based sanitizer with cold plasma treatments for ≥ 120 s can inactivates significant populations of Salmonella to enhance the microbial safety of tomato surfaces designated for fresh-cut salad.

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Posted in Cold Atmospheric Plasma, Cold Plasma, Food Microbiology Research, Food Technology, Research, Salmonella, Technology

Research – Innovative Pathogen Reduction in Exported Sea Bass Through Atmospheric Cold Plasma Technology

Posted on October 21, 2024 by | Leave a comment

MDPI

Abstract

The safety of sea bass is critical for the global food trade. This study evaluated the effectiveness of atmospheric cold plasma in reducing food safety risks posed by Salmonella Enteritidis and Listeria monocytogenes, which can contaminate sea bass post harvest. Cold plasma was applied to inoculated sea bass for 2 to 18 min, achieving a maximum reduction of 1.43 log CFU/g for S. Enteritidis and 0.80 log CFU/g for L. monocytogenes at 18 min. Longer treatments resulted in greater reductions; however, odor and taste quality declined to a below average quality in samples treated for 12 min or longer. Plasma treatment did not significantly alter the color, texture, or water activity (aw) of the fish. Higher levels of thiobarbituric acid reactive substances (TBARSs) were observed with increased exposure times. Cold plasma was also tested in vitro on S. Enteritidis and L. monocytogenes on agar surfaces. A 4 min treatment eliminated the initial loads of S. Enteritidis (2.71 log CFU) and L. monocytogenes (2.98 log CFU). The findings highlight the potential of cold plasma in enhancing the safety of naturally contaminated fish. Cold plasma represents a promising technology for improving food safety in the global fish trade and continues to be a significant area of research in food science.

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Posted in Cold Atmospheric Plasma, Cold Plasma, Food Microbiology Research, Food Pathogen, Food Technology, Pathogen, pathogenic, Research, Technology

Research – Inactivation of Bacillus cereus Spores and Vegetative Cells in Inert Matrix and Rice Grains Using Low-Pressure Cold Plasma

Posted on July 21, 2024 by | Leave a comment

MDPI

Abstract

This study investigated the effects of low-pressure cold plasma on the inactivation of Bacillus cereus vegetative cells and spores in an inert matrix (borosilicate glass slide) and in rice grains, using oxygen as ionization gas. Greater reductions in B. cereus counts were observed in vegetative cells rather than spores. The experimental data obtained show that both the power of the plasma treatment and the matrix proved to be determining factors in the inactivation of both the spores and vegetative cells of B. cereus. To characterize the inactivation of B. cereus, experimental data were accurately fitted to the Weibull model. A significant decrease in parameter “a”, representing resistance to treatment, was confirmed with treatment intensification. Furthermore, significant differences in the “a” value were observed between spores in inert and food matrices, suggesting the additional protective role of the food matrix for B. cereus spores. These results demonstrate the importance of considering matrix effects in plasma treatment to ensure the effective inactivation of pathogenic microorganisms, particularly in foods with low water activity, such as rice. This approach contributes to mitigating the impact of foodborne illnesses caused by pathogenic microorganisms.

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Posted in Bacillus, Bacillus cereus, Bacterial Spores, Cold Atmospheric Plasma, Cold Plasma, Food Microbiology Research, Research, Spores

Research – Recent Advances in Non-Contact Food Decontamination Technologies for Removing Mycotoxins and Fungal Contaminants

Posted on July 20, 2024 by | Leave a comment

MDPI

Abstract

Agricultural food commodities are highly susceptible to contamination by fungi and mycotoxins, which cause great economic losses and threaten public health. New technologies such as gamma ray irradiation, ultraviolet radiation, electron beam irradiation, microwave irradiation, pulsed light, pulsed electric fields, plasma, ozone, etc. can solve the problem of fungal and mycotoxin contamination which cannot be effectively solved by traditional food processing methods. This paper summarizes recent advancements in emerging food decontamination technologies used to control various fungi and their associated toxin contamination in food. It discusses the problems and challenges faced by the various methods currently used to control mycotoxins, looks forward to the new trends in the development of mycotoxin degradation methods in the future food industry, and proposes new research directions.

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Posted in antifungal, Cold Atmospheric Plasma, Cold Plasma, Food Microbiology Research, Food Technology, fungi, mold, Mold Toxin, Mold/ MouldAscospores, Mould/Mold, Mycotoxin, Ozone, Research, Technology, UV Microbiology

Research – Cold plasma processing for food safety

Posted on June 8, 2024 by | Leave a comment

Food Safety News

 Cold plasma is an emerging food processing technology which has been shown to effectively inactivate pathogenic bacteria, viruses, parasites, and fungi. The process uses high-voltage electricity to ionize air and/or defined gas blends to create a mixture of ions, free electrons, ozone, radical species, and other reactive products. This energetic plasma, which operates near room temperature, has been tested with fruits, vegetables, nuts, meats, cheeses, poultry, seeds, powders, and other foods.

Once created at the high voltage electrodes, the cold plasma is applied to foods and food contact surfaces. Forced air can blow the cold plasma over products and surfaces, as with plasma jet systems. This allows for the varying treatment distances of irregularly shaped foods. The commodity may also be moved in and out of the plasma field, as with dielectric barrier (DBD) systems. In either case, reactive chemical species in the cold plasma break the cellular structures, DNA, and proteins of pathogens on foods, inactivating them. Efficacy is dependent on treatment intensity and duration. Combining cold plasma with chemical sanitizers, high intensity light, or other food safety interventions can provide enhanced, synergistic pathogen inactivation. Short treatments with cold plasma can induce sublethal injury in pathogens, rendering them more susceptible to another sanitizing processes.

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Posted in Cold Atmospheric Plasma, Cold Plasma, Food Microbiology Research, Food Pathogen, Food Technology, Hurdle Technology, Pathogen, pathogenic, Research, Technology

Research – Acid Adaptation Enhances Tolerance of Escherichia coli O157:H7 to High Voltage Atmospheric Cold Plasma in Raw Pineapple Juice

Posted on June 8, 2024 by | Leave a comment

MDPI

Abstract

Pathogens that adapt to environmental stress can develop an increased tolerance to some physical or chemical antimicrobial treatments. The main objective of this study was to determine if acid adaptation increased the tolerance of Escherichia coli O157:H7 to high voltage atmospheric cold plasma (HVACP) in raw pineapple juice. Samples (10 mL) of juice were inoculated with non-acid-adapted (NAA) or acid-adapted (AA) E. coli to obtain a viable count of ~7.00 log10 CFU/mL. The samples were exposed to HVACP (70 kV) for 1–7 min, with inoculated non-HVACP-treated juice serving as a control. Juice samples were analyzed for survivors at 0.1 h and after 24 h of refrigeration (4 °C). Samples analyzed after 24 h exhibited significant decreases in viable NAA cells with sub-lethal injury detected in both NAA and AA survivors (p < 0.05). No NAA survivor in juice exposed to HVACP for 5 or 7 min was detected after 24 h. However, the number of AA survivors was 3.33 and 3.09 log10 CFU/mL in juice treated for 5 and 7 min, respectively (p < 0.05). These results indicate that acid adaptation increases the tolerance of E. coli to HVACP in pineapple juice. The potentially higher tolerance of AA E. coli O157:H7 to HVACP should be considered in developing safe juice processing parameters for this novel non-thermal technology.

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Posted in Cold Atmospheric Plasma, Cold Plasma, E.coli, E.coli O157:H7, Enteropathogenic E. coli, ETEC E.coli, Food Microbiology Research, Food Pathogen, Food Technology, Hurdle Technology, Pathogen, pathogenic, Research

Research – Leveraging Plasma-Activated Seawater for the Control of Human Norovirus and Bacterial Pathogens in Shellfish Depuration

Posted on March 23, 2024 by | Leave a comment

MDPI

Abstract

Cold plasma is a promising alternative for water treatment owing to pathogen control and a plethora of issues in the agriculture and food sectors. Shellfish pose a serious risk to public health and are linked to large viral and bacterial outbreaks. Hence, current European regulations mandate a depuration step for shellfish on the basis of their geographical growth area. This study investigated the inactivation of relevant viral and bacterial pathogens of three plasma-activated seawaters (PASWs), and their reactive oxygen and nitrogen species (RONS) composition, as being primarily responsible for microbial inactivation. Specifically, F-specific (MS2) and somatic (φ174) bacteriophage, cultivable surrogate (murine norovirus, MNV, and Tulane virus, TV), and human norovirus (HuNoV GII.4) inactivation was determined using plaque counts and infectivity assays, including the novel human intestinal enteroid (HIE) model for HuNoV. Moreover, the kinetic decay of Escherichia coli, Salmonella spp., and Vibrio parahaemolyticus was characterized. The results showed the complete inactivation of phages (6–8 log), surrogates (5–6 log), HuNoV (6 log), and bacterial (6–7 log) pathogens within 24 h while preventing cytotoxicity effects and preserving mussel viability. Nitrites (NO2−) were found to be mostly correlated with microbial decay. This research shows that PASWs are a suitable option to depurate bivalve mollusks and control the biohazard risk linked to their microbiological contamination, either viral or bacterial.

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Posted in Cold Atmospheric Plasma, Cold Plasma, Decontamination Microbial, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, microbial contamination, Microbial growth, Microbial Spoilage, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Microbiology Risk

Research – In-Package Atmospheric Cold Plasma Treatment and Storage Effects on Membrane Integrity, Oxidative Stress, and Esterase Activity of Listeria monocytogenes

Posted on March 12, 2023 by | Leave a comment

MDPI

kswfoodworld

Abstract

Atmospheric cold plasma (ACP) treatment can reduce bacterial pathogens in foods. Additional reduction in bacterial cells during storage after ACP treatment was previously reported. The underlying mechanisms of bacterial inactivation during ACP treatment and post-treatment storage need to be understood. This study investigated the changes in the morpho-physiological status of Listeria monocytogenes on ham surfaces after post-ACP-treatment storage of 1 h, 24 h, and 7 days at 4 °C. The membrane integrity, intracellular oxidative stress, and esterase activity of L. monocytogenes were evaluated by flow cytometry. L. monocytogenes cells were under high oxidative stress conditions with slightly permeabilized membranes after 1 h of post-ACP-treatment storage according to the flow cytometry data. During the extended storage of 24 h, the percentage of cells with a slightly permeabilized membrane increased; subsequently, the percentage of cells with intact membranes decreased. The percentage of L. monocytogenes cells with intact membranes decreased to <5% with a treatment time of 10 min and after 7 days of post-treatment storage. In addition, the percentage of L. monocytogenes cells under oxidation stress decreased to <1%, whereas the percentage of cells with completely permeabilized membranes increased to more than 90% for samples treated with ACP for 10 min and 7 days of post-treatment storage. With increased ACP treatment time, for 1 h stored samples, the percentage of cells with active esterase and slightly permeabilized membranes increased. However, during the extended post-treatment storage of 7 days, the percentage of cells with active esterase and slightly permeabilized membranes decreased to below 1%. At the same time, the percentage of cells with permeabilized membrane increased to more than 92% with an increase in ACP treatment time of 10 min. In conclusion, the higher inactivation after 24 h and 7 days post-ACP-treatment storage compared to 1 h stored samples correlated with the loss of esterase activity and membrane integrity of L. monocytogenes cells.

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Posted in Cold Atmospheric Plasma, Cold Plasma, Decontamination Microbial, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Listeria, Listeria monocytogenes, microbial contamination, Microbial growth, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Microbiology Risk

Research – Treatment of Ready-To-Eat Cooked Meat Products with Cold Atmospheric Plasma to Inactivate Listeria and Escherichia coli

Posted on February 11, 2023 by | Leave a comment

MDPI

Abstract

Ready-to-eat meat products have been identified as a potential vehicle for Listeria monocytogenes. Postprocessing contamination (i.e., handling during portioning and packaging) can occur, and subsequent cold storage together with a demand for products with long shelf life can create a hazardous scenario. Good hygienic practice is augmented by intervention measures in controlling post-processing contamination. Among these interventions, the application of ‘cold atmospheric plasma’ (CAP) has gained interest. The reactive plasma species exert some antibacterial effect, but can also alter the food matrix. We studied the effect of CAP generated from air in a surface barrier discharge system (power densities 0.48 and 0.67 W/cm2) with an electrode-sample distance of 15 mm on sliced, cured, cooked ham and sausage (two brands each), veal pie, and calf liver pâté. Colour of samples was tested immediately before and after CAP exposure. CAP exposure for 5 min effectuated only minor colour changes (ΔE max. 2.7), due to a decrease in redness (a*), and in some cases, an increase in b*. A second set of samples was contaminated with Listeria (L.) monocytogenes, L. innocua and E. coli and then exposed to CAP for 5 min. In cooked cured meats, CAP was more effective in inactivating E. coli (1 to 3 log cycles) than Listeria (from 0.2 to max. 1.5 log cycles). In (non-cured) veal pie and calf liver pâté that had been stored 24 h after CAP exposure, numbers of E. coli were not significantly reduced. Levels of Listeria were significantly reduced in veal pie that had been stored for 24 h (at a level of ca. 0.5 log cycles), but not in calf liver pâté. Antibacterial activity differed between but also within sample types, which requires further studies.

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Posted in Cold Atmospheric Plasma, Decontamination Microbial, E.coli, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Listeria, Listeria monocytogenes, microbial contamination, Microbial growth, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Microbiology Risk