Affiliation:
1. Department of Biological Systems Engineering, Washington State University, Pullman, Washington, USA
2. School of Food Science, Washington State University, Pullman, Washington, USA
Abstract
ABSTRACT
Salmonella
spp. exhibit prolonged survivability and high tolerance to heat in low-moisture foods. The reported thermal resistance parameters of
Salmonella
spp. in low-moisture foods appear to be unpredictable due to various unknown factors. We report here that temperature-dependent water activity (a
w, treatment temperature
) plays an important role in the sharply increased thermal resistance of
Salmonella enterica
serovar Enteritidis PT 30 and its potential surrogate
Enterococcus faecium
NRRL B-2354. In our study, silicon dioxide granules, as carriers, were separately inoculated with these two microorganisms and were heated at 80°C with controlled relative humidity between 18 and 72% (resulting in corresponding a
w,80°C
values for bacteria between 0.18 and 0.72) in custom-designed test cells. The inactivation kinetics of both microorganisms fitted a log-linear model (
R
2
, 0.83 to 0.97). Reductions in the a
w,80°C
values of bacterial cells exponentially increased the
D
80°C
(the time needed to achieve a 1-log reduction in a bacterial population at 80°C) values for
S
. Enteritidis and
E. faecium
on silicon dioxide. The log-linear relationship between the
D
80°C
values for each strain in silicon dioxide and its a
w,80°C
values was also verified for organic wheat flour.
E. faecium
showed consistently higher
D
80°C
values than
S
. Enteritidis over the a
w,80°C
range tested. The estimated z
aw
(the change in a
w,80°C
needed to change
D
80°C
by 1 log) values of
S
. Enteritidis and
E. faecium
were 0.31 and 0.28, respectively. This study provides insight into the interpretation of
Salmonella
thermal resistance that could guide the development and validation of thermal processing of low-moisture foods.
IMPORTANCE
In this paper, we established that the thermal resistance of the pathogen
S
. Enteritidis and its surrogate
Enterococcus faecium
, as reflected by
D
values at 80°C, increases sharply with decreasing relative humidity in the environment. The log-linear relationship between the
D
80°C
values of each strain in silicon dioxide and its a
w,80°C
values was also verified for organic wheat flour. The results provide new quantitative insight into the way in which the thermal resistance of microorganisms changes in low-moisture systems, and they should aid in the development of effective thermal treatment strategies for pathogen control in low-moisture foods.
Funder
U.S. Department of Agriculture
China Scholarship Council
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Reference47 articles.
1. FDA. 15 January 2016. FDA investigated multistate outbreak of Salmonella infections linked to raw nut butter products. FDA, Silver Spring, MD. https://www.fda.gov/food/recallsoutbreaksemergencies/outbreaks/ucm475416.htm.
2. An International Outbreak of Salmonellosis Associated with Raw Almonds Contaminated with a Rare Phage Type of Salmonella Enteritidis†
3. CDC. 15 January 2016. Multistate outbreak of Salmonella Paratyphi B variant L(+) tartrate(+) infections linked to JEM raw brand sprouted nut butter spreads (final update). CDC, Atlanta, GA. https://www.cdc.gov/salmonella/paratyphi-b-12-15/index.html.
4. CDC. 20 May 2016. Multistate outbreak of Salmonella Montevideo and Salmonella Senftenberg infections linked to Wonderful pistachios (final update). CDC, Atlanta, GA. https://www.cdc.gov/salmonella/montevideo-03-16/index.html.
5. FDA. 2015. FSMA final rule for preventive controls for human food. FDA, Silver Spring, MD. https://www.fda.gov/food/guidanceregulation/fsma/ucm334115.htm.
Cited by
75 articles.
订阅此论文施引文献
订阅此论文施引文献，注册后可以免费订阅5篇论文的施引文献，订阅后可以查看论文全部施引文献