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In this study, Listeria monocytogenes from minced pork was evaluated for changes in resistance to thermal treatment and gastric fluid following environmental stresses during food processing. Bacteria were exposed to cold stress, followed by successive exposures to different stressors (lactic acid (LA), NaCl, or Nisin), followed by thermal treatments, and finally, their gastrointestinal tolerance was determined. Adaptation to NaCl stress reduced the tolerance of L. monocytogenes to subsequent LA and Nisin stress. Adaptation to LA stress increased bacterial survival in NaCl and Nisin-stressed environments. Bacteria adapted to Nisin stress showed no change in tolerance to subsequent stress conditions. In addition, treatment with NaCl and LA enhanced the thermal tolerance of L. monocytogenes, but treatment with Nisin decreased the thermal tolerance of the bacteria. Almost all of the sequential stresses reduced the effect of a single stress on bacterial thermal tolerance. The addition of LA and Nisin as a second step of stress reduced the tolerance of L. monocytogenes to gastric fluid, whereas the addition of NaCl enhanced its tolerance. The results of this study are expected to inform processing conditions and sequences for meat preservation and processing and reduce uncertainty in risk assessment of foodborne pathogens due to stress adaptation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Listeria monocytogenes (L. monocytogenes) is a foodborne pathogen often found in ready-to-eat (RTE) foods, posing significant threats to human health. In this study, an active film based on cross-linking via Schiff base and electrostatic interaction to inactivate L. monocytogenes on RTE foods was constructed. Zinc-casein hydrolysate chelates (Zn-HCas) was prepared and blended with cationic starch (CSt) to form the substrates of the film. Then, Citral (CI) with excellent antibacterial properties was added to enhance the biological and packaging properties of the film through covalent cross-linking (Schiff base). Based on the zinc ion-activated metalloproteinases produced by L. monocytogenes, the cross-linked film could be disrupted and the release of CI was accelerated. The variation in color, FTIR, and amino group content proved that Schiff base reaction had taken place. Enhanced mechanical properties, barrier properties, thermal stability and antimicrobial activity against L. monocytogenes (exceed 99.99 %) were obtained from the CI/Zn-HCas/CSt film. The application on RTE cheese results demonstrated that the cross-linked film could be employed in active packaging field with the ability in maintaining the original chroma and texture properties of RTE cheese. In summary, the prepared cross-linked film could be used as an active packaging against L. monocytogenes contamination with great potential., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Fruits and vegetables are susceptible to Listeria monocytogenes. In this study, the nano emulsion of oregano essential oil (OEO) prepared by ultrasonic (US) nanoemulsion method combined with US has a promising synergistic bactericidal effect on L. monocytogenes , with 255 W/cm2+0.06 μL/mL origano essential oil nanoemulsion (OEONE) completely kill the initial number of bacteria (8.67 ± 0.17 log CFU/mL) after 15 min of treatment. Compared to control, reactive oxygen species (ROS), malondialdehyde (MDA) detection, nucleic acid and protein release tests showed that US + OEONE intensified cell membrane lipid peroxidation and increased cell membrane permeability. Flow cytometry (FCM) once again demonstrated the damage to cell membrane integrity caused by US + OEONE treatment. The results of field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) indicate that US + OEONE treatment alter cell morphology. Also, this study provides evidence to support the use of US + OEONE as a practical preservation method to minimize the presence of L. monocytogenes on the surface of blueberries, and sensory evaluations indicate that US + OEONE-treated blueberries are acceptable. In addition, this method demonstrated the ability to retard microbial proliferation without affecting the color, texture, and antioxidant properties of blueberries during storage. These results indicate that the implementation of US + OEONE is expected to improve the microbial safety of fresh produce. [Display omitted] • Ultrasound (US) and oregano essential oil (OEONE) had a synergistic antibacterial efficacy. • US + OEONE significantly disrupted the permeability and integrity of cell membranes. • US + OEONE obviously altered the morphology and internal microstructure of cells. • US + OEONE caused bacterial oxidative stress and lipid peroxidation. • The treatment method of US + OEONE has promising application effect on blueberry preservation. [ABSTRACT FROM AUTHOR]