eCite Digital Repository

Differentiation of the effects of lethal pH and water activity: food safety implications


Shadbolt, CT and Ross, T and McMeekin, TA, Differentiation of the effects of lethal pH and water activity: food safety implications, Letters in Applied Microbiology, 32, (2) pp. 99-102. ISSN 0266-8254 (2001) [Refereed Article]

DOI: doi:10.1046/j.1472-765x.2001.00862.x


The influence of a second lethal stress (SLS) was investigated when populations of Escherichia coli M23 OR.H-were exposed to either a low water activity (aw) of 0.90 or a pH of 3.50 after 24 h at 25°C. Regardless of the initial stress, E. coli M23 OR.H- populations initially demonstrated biphasic inactivation kinetics consisting of a rapid first phase of death followed by a slower second phase. When cultures initially exposed to aw 0.90 experienced an SLS of pH 3.50, a second rapid inactivation period was observed before a subpopulation of more resistant cells emerged. This subpopulation was able to persist for approximately 50 h after imposition of the SLS. In contrast, E. coli M23 OR.H- cells first exposed to a pH of 3.50 were inactivated rapidly to levels below the limits of detection upon imposition of an SLS of aw 0.90. It is hypothesized that pH stress constitutes a large energy drain on the cell and subsequently sensitizes it to other environmental constraints requiring expenditure of metabolic energy.

Item Details

Item Type:Refereed Article
Research Division:Biological Sciences
Research Group:Microbiology
Research Field:Bacteriology
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the environmental sciences
UTAS Author:Shadbolt, CT (Mr Craig Shadbolt)
UTAS Author:Ross, T (Professor Tom Ross)
UTAS Author:McMeekin, TA (Professor Thomas McMeekin)
ID Code:21048
Year Published:2001
Web of Science® Times Cited:55
Deposited By:Agricultural Science
Deposited On:2001-08-01
Last Modified:2011-08-02

Repository Staff Only: item control page