Samantha Nestel

Foodborne pathogens such as E. coli, B. cereus, L. monocytogenes, and S. aureus cause many illnesses in Europe each year due to traits like biofilm formation, spore production, and high resistance to harsh conditions. This study investigated plasma-treated water (PTW) as an eco-friendly antimicrobial approach and examined its effect on bacterial growth curves to improve food safety. PTW was generated using a microwave plasma source, then applied to bacterial cultures that were monitored by optical density and colony counts. The bacterial growth was described by application of a logistic growth model to the optical density and colony count data. Results show that PTW mainly prolonged the lag phase of growth, with a stronger effect on Gram-positive bacteria than on Gram-negative bacteria. Although PTW initially reduced viable cell numbers, most bacteria eventually recovered and reached the stationary phase after a delay of about 2 to 11 h depending on the species. These effects may be due to cell damage, cell death, viable but nonculturable state induction, or stress responses such as spore formation. Further studies are needed to confirm how PTW performs in real food systems and biofilm settings.

Non-thermal decontamination methods offer energy-efficient, lower-temperature alternatives to conventional heat treatments with potentially milder effects on nutritional and sensory quality. This critical review synthesizes evidence for ultraviolet (UV), electron-beam irradiation (EBI), atmospheric-pressure plasma (APP), ultrasound (US), high-pressure processing (HPP), supercritical fluids (SCF), pulsed electric fields (PEF), protective cultures (PC), and membrane filtration (MF). It evaluates technical requirements and the impacts on food quality of liquid, semi-solid, and solid food matrices. No single method is universally applicable, but complement the toolbox of non-thermal decontamination methods. Key contrasts include deep penetration by EBI versus surface/clarity limitations of UV. HPP’s uniform bulk inactivation but limited sporicidal activity and potential off-flavor formation. APP and US generating reactive species or cavitation that can alter texture and color. SCF’s microbial inactivation coupled with extraction of desirable components. PEF’s suitability for flowing liquids and potential electrophoretic effects on proteins. MF’s efficacy for microbial removal in liquids but inapplicability to solids and PCs’ targeted biological control that may modify sensory profiles. Broader commercial adoption will require matrix-specific validation (microbial log-reductions and quality metrics), quantitative mechanistic studies (e.g. reactive oxygen/nitrogen species, extraction yields, molecular changes), and pilot-scale, interdisciplinary scale-up with economic assessment to produce standardized, product-tailored protocols.

There was an error in the original publication

Foodborne illness caused by bacterial pathogens is a global health concern and results in millions of infections annually. Therefore, food products typically undergo several processing stages, including sanitation steps, before being distributed in an attempt to remove pathogens. However, many sanitation methods have compounding effects on the color, texture, flavor, and nutritional quality of the product or do not effectively reduce the pathogens that food can be exposed to. Some bacterial pathogens particularly possess traits and tactics that make them even more difficult to mitigate such as biofilm formation. Non-thermal plasma sanitation techniques, including plasma-treated water (PTW), have proven to be promising methods that significantly reduce pathogenic bacteria that food is exposed to. Published work reveals that PTW can effectively mitigate both gram-positive and gram-negative bacterial biofilms. This study presents a novel analysis of the differences in antimicrobial effects of PTW treatment between biofilm-forming gram-positive bacteria, commonly associated with foodborne illness, that are sporulating (Bacillus cereus) and non-sporulating (Listeria monocytogenes). After treatment with PTW, the results suggest the following hypotheses: (1) that the non-sporulating species experiences less membrane damage but a greater reduction in metabolic activity, leading to a possible viable but non-culturable (VBNC) state, and (2) that the sporulating species undergoes spore formation, which may subsequently convert into vegetative cells over time. PTW treatment on gram-positive bacterial biofilms that persist in food processing environments proves to be effective in reducing the proliferating abilities of the bacteria. However, the variance in PTW’s effects on metabolic activity and cell vitality between sporulating and non-sporulating species suggest that other survival tactics might be induced. This analysis further informs the application of PTW in food processing as an effective sanitation method.