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Molecules 2014, 19(12), 21310-21323; doi:10.3390/molecules191221310

Effects of High Hydrostatic Pressure on Escherichia coli Ultrastructure, Membrane Integrity and Molecular Composition as Assessed by FTIR Spectroscopy and Microscopic Imaging Techniques

1
Institute of Food Science and Technology, University of León, León 24071, Spain
2
Department of Food Hygiene and Technology, University of León, León 24071, Spain
3
Teagasc Food Research Centre, Moorepark, Fermoy, Co. Cork, Ireland
*
Author to whom correspondence should be addressed.
Received: 8 October 2014 / Revised: 27 November 2014 / Accepted: 9 December 2014 / Published: 18 December 2014
(This article belongs to the Special Issue Advances of Vibrational Spectroscopic Technologies in Life Sciences)
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Abstract

High hydrostatic pressure (HHP) is a novel food processing technology that is considered as an attractive alternative to conventional heat treatments for the preservation of foods, due to its lethal effects on pathogenic and spoilage microorganisms, while causing minor effects on food quality and sensorial attributes. This study is aimed at investigating how HHP treatments at varying intensities in the range 50–900 MPa affect the viability, membrane integrity, ultrastructure and molecular composition of Escherichia coli. Results of membrane integrity tests (measurement of cellular leakage and monitoring of propidium iodide uptake through fluorescence microscopy) and ultrastructural observations by transmission electron microscopy demonstrated that HHP gave rise to cellular enlargement, membrane damage or detachment, DNA and protein denaturation and loss of intracellular contents. Fourier-transform infrared (FTIR) spectroscopy analyses evidenced minor changes in molecular composition in response to high pressures, which were mostly observed on the spectral region w4 (1200–900 cm−1), mainly informative of carbohydrates and polysaccharides of the cell wall. These findings suggest that exposure of E. coli cells to HHP causes alterations in their physical integrity while producing minor modifications in biochemical cellular composition. The current study increases the knowledge on the mechanisms of E. coli inactivation by HHP and provides valuable information for the design of more effective food preservation regimes based on the integration of mild HHP in combination with other food preservation strategies into a multi-target hurdle technology approach. View Full-Text
Keywords: high hydrostatic pressure; Escherichia coli; FTIR spectroscopy; cell imaging; inactivation mechanism; food safety high hydrostatic pressure; Escherichia coli; FTIR spectroscopy; cell imaging; inactivation mechanism; food safety
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Prieto-Calvo, M.; Prieto, M.; López, M.; Alvarez-Ordóñez, A. Effects of High Hydrostatic Pressure on Escherichia coli Ultrastructure, Membrane Integrity and Molecular Composition as Assessed by FTIR Spectroscopy and Microscopic Imaging Techniques. Molecules 2014, 19, 21310-21323.

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