Survival and Thermal Resistance of Salmonella Enteritidis PT 30 on Almonds after Long-Term Storage

Abstract

Salmonella survival and thermal resistance on the surface of almond kernels were evaluated after periods of storage. Almond kernels were inoculated with Salmonella Enteritidis PT 30 and equilibrated to 0.45 water activity. Samples were separated into two groups (I and II) and stored in sealed metal cans at room temperature. Group I samples (stored 7, 15, 27, and 68 weeks) were re-equilibrated in controlled humidity chambers to 0.45 water activity before performing the thermal treatments after each storage period, but group II samples (stored 70 and 103 weeks) were thermally treated immediately after the cans were opened. For thermal treatments, individual almond kernels were vacuum sealed in thin plastic bags, heated isothermally in a water bath (80°C) for nine intervals, immediately cooled in an ice bath, and assayed for surviving Salmonella. Log-linear and Weibull models were fit to the inactivation data. Salmonella population decreased (P < 0.05) more than 2 log CFU/g during the long-term storage. Salmonella survival in group II at 70 weeks (7.3 log CFU/g) was higher (P < 0.05) than in group I (which had been re-equilibrated multiple times) at 68 weeks (6.2 log CFU/g). However, the thermal resistance of Salmonella Enteritidis PT 30 did not decrease (P > 0.05) for up to 68 weeks of storage, and the log-linear model best described the thermal inactivation data. Overall, the results suggest that re-equilibrating almonds (group I) multiple times may have increased the rate of reduction of Salmonella populations during long-term storage. However, Salmonella thermal resistance on almonds appears to be essentially unaffected by long-term storage, which is important information for designing and conducting validation studies for pathogen control processes.

Evaluation of Enterococcus faecium NRRL B-2354 as a surrogate for Salmonella enterica in milk powders at different storage times and temperatures

“…These results suggest that the thermal resistance of Salmonella is not affected by storage time. Abd et al (2012) and Limcharoenchat et al (2019) also reported that the storage time had no effect on the heat resistance of Salmonella in almonds, which is in agreement with this study. Similarly, the thermal resistance of L. monocytogenes adapted to NFDM (Ballom et al, 2020), chicken meat powder, and pet food (Rachon et al, 2016) was shown to remain constant during prolonged storage.…”

Listeria monocytogenes in Almond Meal: Desiccation Stability and Isothermal Inactivation

“…The microbial safety risks of almond and almond products was highlighted by Salmonella outbreaks implicated in raw almonds in Canada and the United States ( CDC, 2004 ; Isaacs et al, 2005 ), as well as recent almond product recalls associated with potential L. monocytogenes contamination ( FDA, 2017b FDA, 2017c ; FDA, 2018 FDA, 2019 ). However, the current thermal intervention studies in almond/almond meal have been focused on Salmonella ( Du et al, 2010 ; Villa-Rojas et al, 2013 ; Limcharoenchat et al, 2019 ; Xu et al, 2019 ). As an important foodborne pathogen with high mortality, it is important to evaluate the factors that impact desiccation and thermal stability of L. monocytogenes in almond meal.…”

Consumer Knowledge and Behaviors Regarding Food Safety Risks Associated with Wheat Flour

“…Myoda et al (57) surveyed U.S. wheat at harvest and found Salmonella and E. coli in 1.23 and 0.44% of the samples, respectively. Once these pathogens are present, they are difficult to eliminate due to increased persistence (27,31,50,51,72), significantly enhanced thermal resistance (43,66,67,70), and limitations of existing sanitation solutions (32,39,41). Despite these dangers, many consumers in this study did not consider flour to be a food product that poses a food safety risk.…”