The heat resistance of Salmonella inoculated onto almonds was determined after immersion in hot oil. Whole almonds were inoculated with Salmonella Enteritidis PT 30 or Salmonella Senftenberg 775W and heated in oil. After heating, almonds were drained, transferred to cold tryptic soy broth, and mixed with a stomacher, and samples were plated onto tryptic soy and bismuth sulfite agars. Salmonella survivor inactivation curves were upwardly concave. Rapid reductions of 2.9, 3.0, or 3.6 log CFU/g for Salmonella Enteritidis were observed after 30 s of exposure to oil at 116, 121, or 127°C, respectively. Thereafter, reduction occurred at a much slower rate. Similar reductions were observed at 127°C for Salmonella Senftenberg. The Weibull model was used to predict 4- and 5-log reductions of Salmonella Enteritidis after 0.74 and 1.3 min at 127°C, respectively. Neither Salmonella serovar could be recovered by enrichment of 1-g samples after almonds inoculated at 5 log CFU/g were exposed to oil at 127°C for 1.5 min. Standard oil roasting times and temperatures that achieve acceptable kernel color and texture should result in much greater than 5-log reductions of Salmonella in almonds.

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Author notes

Present address: U.S. Department of Agriculture, Agricultural Research Service, Western Regional Research Center, Processed Foods Research Unit, 800 Buchanan Street, Albany, CA 94710, USA.

Present address: National Food Laboratory, 365 North Canyon Parkway, Livermore, CA 94551-7703, USA.