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Evaluation of thermal inactivation of Escherichia coli using microelectrode ion flux measurements with osmotic stress


Koseki, S and Tamplin, ML and Bowman, JP and Ross, T and McMeekin, TA, Evaluation of thermal inactivation of Escherichia coli using microelectrode ion flux measurements with osmotic stress, Letters in Applied Microbiology, 54, (3) pp. 203-208. ISSN 0266-8254 (2012) [Refereed Article]

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DOI: doi:10.1111/j.1472-765X.2011.03194.x


Aims: To elucidate the potential use of microelectrode ion flux measurements to evaluate bacterial responses to heat treatment.

Methods and Results: Escherichia coli K12 was used as a test bacterium to determine if various heat treatments (55C to 70C for 15 min) affected net ion flux across E. coli cell membranes using the MIFE system to measure net K+ fluxes. No difference in K+ fluxes was observed before and after heat treatments regardless of the magnitude of the treatment. Applying hyperosmotic stress (3% NaCl w/v) during flux measurement led to a net K+ loss from the heat-treated E. coli cells below 65C as well as from non-heated cells. In contrast, with E. coli cells treated at and above 65C, hyperosmotic stress disrupted the pattern of K+ flux observed at lower temperatures and resulted in large flux noise with random scatter. This phenomenon was particularly apparent above 70C. Although E. coli cells lost the potential to recover and grow at and above 62C, K+ flux disruption was not clearly observed until 68C was reached.

Conclusions: No changes in net K+ flux from heat-stressed E. coli cells were observed directly as a result of thermal treatments. However, regardless of the magnitude of heat treatment above 55C, loss of viability indicated by enrichment culture, correlated with disrupted K+ fluxes when previously heated cells were further challenged by imposing hyperosmotic stress during flux measurement. This two-stage process enabled evaluation of the lethality of heat treated bacterial cells within 2 h and may be an alternative and more rapid method to confirm the lethality of heat treatment.

Significance and Impact of the Study: The ability to confirm the lethality of thermal treatments and to specify minimal time/temperature combinations by a non-culture dependent test offers an alternative system to culture-based methods.

Item Details

Item Type:Refereed Article
Keywords:cell membranes, E. coli viability, K + flux, lethal thermal stress, microelectrode ion flux measurement, moderate osmotic stress
Research Division:Agricultural, Veterinary and Food Sciences
Research Group:Food sciences
Research Field:Food packaging, preservation and processing
Objective Division:Manufacturing
Objective Group:Processed food products and beverages (excl. dairy products)
Objective Field:Non-dairy milk
UTAS Author:Koseki, S (Dr Shigenobu Koseki)
UTAS Author:Tamplin, ML (Professor Mark Tamplin)
UTAS Author:Bowman, JP (Associate Professor John Bowman)
UTAS Author:Ross, T (Professor Tom Ross)
UTAS Author:McMeekin, TA (Professor Thomas McMeekin)
ID Code:75048
Year Published:2012
Web of Science® Times Cited:3
Deposited By:Agricultural Science
Deposited On:2012-01-05
Last Modified:2018-06-25

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