Dataset Information

Increased water activity reduces the thermal resistance of Salmonella enterica in peanut butter.

ABSTRACT: Increased water activity in peanut butter significantly (P < 0.05) reduced the heat resistance of desiccation-stressed Salmonella enterica serotypes treated at 90 °C. The difference in thermal resistance was less notable when strains were treated at 126 °C. Using scanning electron microscopy, we observed minor morphological changes of S. enterica cells resulting from desiccation and rehydration processes in peanut oil.

SUBMITTER: He Y

PROVIDER: S-EPMC3719514 | biostudies-literature | 2013 Aug

REPOSITORIES: biostudies-literature

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Increased water activity reduces the thermal resistance of Salmonella enterica in peanut butter.

He Yingshu Y Li Ye Y Salazar Joelle K JK Yang Jingyun J Tortorello Mary Lou ML Zhang Wei W

Applied and environmental microbiology 20130531 15

Increased water activity in peanut butter significantly (P < 0.05) reduced the heat resistance of desiccation-stressed Salmonella enterica serotypes treated at 90 °C. The difference in thermal resistance was less notable when strains were treated at 126 °C. Using scanning electron microscopy, we observed minor morphological changes of S. enterica cells resulting from desiccation and rehydration processes in peanut oil. ...[more]

PMID: 23728806

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Project description: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 (aw, 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 aw,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 (R2, 0.83 to 0.97). Reductions in the aw,80°C values of bacterial cells exponentially increased the D80°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 D80°C values for each strain in silicon dioxide and its aw,80°C values was also verified for organic wheat flour. E. faecium showed consistently higher D80°C values than S Enteritidis over the aw,80°C range tested. The estimated zaw (the change in aw,80°C needed to change D80°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 D80°C values of each strain in silicon dioxide and its aw,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.

Project description:Establishing an association between possible food sources and clinical isolates requires discriminating the suspected pathogen from an environmental background, and distinguishing it from other closely-related foodborne pathogens. We used whole genome sequencing (WGS) to Salmonella subspecies enterica serotype Tennessee (S. Tennessee) to describe genomic diversity across the serovar as well as among and within outbreak clades of strains associated with contaminated peanut butter. We analyzed 71 isolates of S. Tennessee from disparate food, environmental, and clinical sources and 2 other closely-related Salmonella serovars as outgroups (S. Kentucky and S. Cubana), which were also shot-gun sequenced. A whole genome single nucleotide polymorphism (SNP) analysis was performed using a maximum likelihood approach to infer phylogenetic relationships. Several monophyletic lineages of S. Tennessee with limited SNP variability were identified that recapitulated several food contamination events. S. Tennessee clades were separated from outgroup salmonellae by more than sixteen thousand SNPs. Intra-serovar diversity of S. Tennessee was small compared to the chosen outgroups (1,153 SNPs), suggesting recent divergence of some S. Tennessee clades. Analysis of all 1,153 SNPs structuring an S. Tennessee peanut butter outbreak cluster revealed that isolates from several food, plant, and clinical isolates were very closely related, as they had only a few SNP differences between them. SNP-based cluster analyses linked specific food sources to several clinical S. Tennessee strains isolated in separate contamination events. Environmental and clinical isolates had very similar whole genome sequences; no markers were found that could be used to discriminate between these sources. Finally, we identified SNPs within variable S. Tennessee genes that may be useful markers for the development of rapid surveillance and typing methods, potentially aiding in traceback efforts during future outbreaks. Using WGS can delimit contamination sources for foodborne illnesses across multiple outbreaks and reveal otherwise undetected DNA sequence differences essential to the tracing of bacterial pathogens as they emerge.

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Increased water activity reduces the thermal resistance of Salmonella enterica in peanut butter.

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Increased water activity reduces the thermal resistance of Salmonella enterica in peanut butter.

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