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J Food Prot. 2016 Aug;79(8):1304-15. doi: 10.4315/0362-028X.JFP-16-054.

Prevalence and Amounts of Salmonella Found on Raw California Inshell Pistachios.

Author information

1
Department of Food Science and Technology, University of California, Davis, One Shields Avenue, Davis, California 95616, USA; Western Center for Food Safety, University of California, Davis, One Shields Avenue, Davis, California 95616, USA. ljharris@ucdavis.edu.
2
Department of Food Science and Technology, University of California, Davis, One Shields Avenue, Davis, California 95616, USA.
3
Western Center for Food Safety, University of California, Davis, One Shields Avenue, Davis, California 95616, USA; Department of Population, Health, and Reproductive Medicine, University of California, Davis, One Shields Avenue, Davis, California 95616, USA.
4
DFA of California, 1855 South Van Ness Avenue, Fresno, California 93721, USA.
5
Department of Animal Science, University of Wyoming, 1000 East University Avenue, Laramie, Wyoming 82071, USA; Department of Agriculture, National Wildlife Research Center, 4101 LaPorte Avenue, Fort Collins, CO 80521, USA.
6
Department of Animal Science, University of Wyoming, 1000 East University Avenue, Laramie, Wyoming 82071, USA.

Abstract

After harvest, pistachios are hulled with mechanical abrasion and then separated in a float tank containing water; the nuts that float (∼15%; floaters) and those that sink (∼85%; sinkers) are dried and stored separately. To determine the prevalence of Salmonella in pistachios, a total of 3,966 samples (1,032 floaters and 2,934 sinkers) were collected within 4 months of the 2010, 2011, and 2012 harvests from storage silos (12 samples from each silo, in most cases) and were stored at 4°C; 100-g subsamples were enriched for the presence of Salmonella. Twenty-one of the floater samples and 11 of the sinker samples were positive for Salmonella: 2.0% prevalence (95% confidence interval [CI], 1.3 to 3.1%) and 0.37% prevalence (95% CI, 0.21 to 0.67%), respectively, for a weighted average prevalence of 0.61%. Levels of Salmonella were determined for positive samples using a most-probable-number (MPN) method with multiple 50-g, three 5.6-g, and three 0.56-g subsamples. Geometric mean levels of Salmonella in floaters and sinkers were 0.66 MPN/100 g (0.14 to 5.3 MPN/100 g) and 0.18 MPN/100 g (0.10 to 0.62 MPN/100 g), respectively. Seven different serovars were identified among the isolates, with nine pulsed-field gel electrophoresis fingerprints; as many as four serovars were isolated from some samples. Salmonella serovars Montevideo (44%), Enteritidis (19%), Senftenberg (16%), Worthington (12%), and Liverpool (9.4%) were most commonly isolated from the initial 100-g samples. The prevalence and levels of Salmonella in pistachios are within those observed for other tree nuts, but the limited number of serovars isolated suggests a narrow and persistent contamination source.

PMID:
27497117
DOI:
10.4315/0362-028X.JFP-16-054
[Indexed for MEDLINE]

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