Impact of storage time and temperature on thermal inactivation of Salmonella enteritidis PT 30 on oil-roasted almonds
Whole Nonpareil variety almonds were inoculated with Salmonella Enteritidis PT 30 and stored at 4 or 23 °C for up to 48 wk. At 1, 12, 24, 37, and 48 wk of storage, almonds were heated by immersion in 121 °C oil. After heating for 0.5 to 2.5 min, almonds were drained, transferred to tryptic soy broth, and mixed with a stomacher prior to plating onto tryptic soy and bismuth sulfite agars. Over the 48 wk of storage, Salmonella declined by 0.5 and 2.1 log CFU/g at 4 and 23 °C, respectively. The survivor inactivation curves were upwardly concave with rapid initial reductions in the levels of Salmonella. For up to 24 wk of storage, the mean counts of the survivors after treatment were not significantly different. The Weibull model predicted 4- and 5-log reductions of Salmonella in 0.85 ± 0.16 and 1.8 ± 0.43 min, respectively, for almonds stored at 4 °C, and in 1.6 ± 0.53 and 3.2 ± 1.0 min, respectively, for almonds stored at 23 °C. Refrigerated storage had little impact on heat resistance of Salmonella that were inoculated on almonds.