Open AccessSterilization by Cooling in Isochoric Conditions: The Case of Escherichia coli
Author(s) -
Samuel Salinas-Almaguer,
Abril Angulo-Sherman,
Francisco J. Sierra-Valdez,
Hilda Mercado-Uribe
Publication year - 2015
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0140882
Subject(s) - isochoric process , escherichia coli , hydrostatic pressure , sterilization (economics) , population , chemistry , bacteria , metastability , materials science , microbiology and biotechnology , biology , biochemistry , thermodynamics , physics , genetics , organic chemistry , demography , sociology , foreign exchange , monetary economics , economics , foreign exchange market , gene
High hydrostatic pressure (HHP) affects the structure, metabolism and survival of micro-organisms including bacteria. For this reason HHP is a promising treatment in the food industry. The aim of this work is to evaluate the effect of high pressure, under isochoric cooling conditions, on Escherichia coli , where such high pressure develops due to the fact water cannot expand. We combine survival curves obtained by spectrophotometry and images of atomic force microscopy in this study. Our results show that cooling at -20 and -30°C leads to a partial destruction of a Escherichia coli population. However, cooling at -15°C causes a total extermination of bacteria. This intriguing result is explained by the phase diagram of water. In the first case, the simultaneous formation of ice III and ice Ih crystals provides a safe environment for bacteria. In the second case (-15°C) Escherichia coli remains in a metastable and amorphous free-of-crystals liquid subjected to high pressure. Our work is the first experimental study carried out to inactivate Escherichia coli under isochoric cooling conditions. Unlike HHP, which is based on the application of an external load to augment the pressure, this technique only requires cooling. The method could be used for annihilation of other Escherichia coli strains and perhaps other micro-organisms.