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The effect of ultrasound treatment in combination with nisin on the inactivation of Listeria innocua and Escherichia coli

Costello, KM; Velliou, E; Gutierrez-Merino, J; Smet, C; El Kadri, H; Van Impe, JF; Bussemaker, M; (2021) The effect of ultrasound treatment in combination with nisin on the inactivation of Listeria innocua and Escherichia coli. Ultrasonics Sonochemistry , 79 , Article 105776. 10.1016/j.ultsonch.2021.105776. Green open access

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Abstract

Ultrasound, alone or in combination with natural antimicrobials, is a novel food processing technology of interest to replace traditional food decontamination methods, as it is milder than classical sterilisation (heat treatment) and maintains desirable sensory characteristics. However, ultrasound efficacy can be affected by food structure/composition, as well as the order in which combined treatments are applied. More specifically, treatments which target different cell components could result in enhanced inactivation if applied in the appropriate order. The microbial properties i.e. Gram positive/Gram negative can also impact the treatment efficacy. This work presents a systematic study of the combined effect of ultrasound and nisin on the inactivation of the bacteria Listeria innocua (Gram positive) and Escherichia coli (Gram negative), at a range of cavitation conditions (44, 500, 1000 kHz). The order of treatment application was varied, and the impact of system structure was also investigated by varying the concentration of Xanthan gum used to create the food model systems (0 – 0.5% w/v). Microbial inactivation kinetics were monitored, and advanced microscopy and flow cytometry techniques were utilised to quantify the impact of treatment on a cellular level. Ultrasound was shown to be effective against E. coli at 500 kHz only, with L. innocua demonstrating resistance to all frequencies studied. Enhanced inactivation of E. coli was observed for the combination of nisin and ultrasound at 500 kHz, but only when nisin was applied before ultrasound treatment. The system structure negatively impacted the inactivation efficacy. The combined effect of ultrasound and nisin on E. coli was attributed to short-lived destabilisation of the outer membrane as a result of sonication, allowing nisin to penetrate the cytoplasmic membrane and facilitate cell inactivation.

Type: Article
Title: The effect of ultrasound treatment in combination with nisin on the inactivation of Listeria innocua and Escherichia coli
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.ultsonch.2021.105776
Publisher version: https://doi.org/10.1016/j.ultsonch.2021.105776
Language: English
Additional information: © 2021 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Keywords: Ultrasound, Nisin, L. innocua, E. coli, Inactivation, Hurdle technology
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Div of Surgery and Interventional Sci
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Div of Surgery and Interventional Sci > Department of Targeted Intervention
URI: https://discovery.ucl.ac.uk/id/eprint/10135463
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