Prevalence and amounts of salmonella found on Raw California inshell pistachios

Linda J. Harris, Vanessa Lieberman, Rupinder P. Mashiana, Edward R Atwill, Mai Yang, Jeffrey C. Chandler, Bledar Bisha, Thomas Jones

Research output: Contribution to journalArticle

12 Citations (Scopus)

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.

Original languageEnglish (US)
Pages (from-to)1304-1315
Number of pages12
JournalJournal of Food Protection
Volume79
Issue number8
DOIs
StatePublished - Aug 1 2016

Fingerprint

Pistacia
pistachios
Salmonella
serotypes
Nuts
sampling
confidence interval
Confidence Intervals
Pulsed Field Gel Electrophoresis
Dermatoglyphics
pulsed-field gel electrophoresis
nuts
Serogroup
Water

Keywords

  • Nuts
  • Pistachios
  • Salmonella concentration
  • Salmonella levels
  • Salmonella prevalence
  • Salmonella survey

ASJC Scopus subject areas

  • Food Science
  • Microbiology
  • Medicine(all)

Cite this

Harris, L. J., Lieberman, V., Mashiana, R. P., Atwill, E. R., Yang, M., Chandler, J. C., ... Jones, T. (2016). Prevalence and amounts of salmonella found on Raw California inshell pistachios. Journal of Food Protection, 79(8), 1304-1315. https://doi.org/10.4315/0362-028X.JFP-16-054

Prevalence and amounts of salmonella found on Raw California inshell pistachios. / Harris, Linda J.; Lieberman, Vanessa; Mashiana, Rupinder P.; Atwill, Edward R; Yang, Mai; Chandler, Jeffrey C.; Bisha, Bledar; Jones, Thomas.

In: Journal of Food Protection, Vol. 79, No. 8, 01.08.2016, p. 1304-1315.

Research output: Contribution to journalArticle

Harris, LJ, Lieberman, V, Mashiana, RP, Atwill, ER, Yang, M, Chandler, JC, Bisha, B & Jones, T 2016, 'Prevalence and amounts of salmonella found on Raw California inshell pistachios', Journal of Food Protection, vol. 79, no. 8, pp. 1304-1315. https://doi.org/10.4315/0362-028X.JFP-16-054
Harris, Linda J. ; Lieberman, Vanessa ; Mashiana, Rupinder P. ; Atwill, Edward R ; Yang, Mai ; Chandler, Jeffrey C. ; Bisha, Bledar ; Jones, Thomas. / Prevalence and amounts of salmonella found on Raw California inshell pistachios. In: Journal of Food Protection. 2016 ; Vol. 79, No. 8. pp. 1304-1315.
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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.",
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