Retention of Viability of Salmonella in Sucrose as Affected by Type of Inoculum, Water Activity, and Storage Temperature

Introduction: Outbreaks of salmonellosis have been associated with consumption of high sugar, low water activity (a_w) foods stored for several months after manufacture. Factors affecting survival of Salmonella in sucrose in the absence of other food components have not been described.

Purpose: The objective of this study was to determine the effect of a_w and storage temperature on survival of Salmonellain dry- and wet-inoculated sucrose.

Methods: Sucrose (a_w 0.24 to 0.26 and a_w 0.44 to 0.54) was dry- and wet-inoculated with low (2.3 to 2.9 log CFU/g) and high (5.2 to 5.8 log CFU/g) populations of a five-serotype mixture of Salmonella and stored at 5°C and 25°C for up to 36 weeks. Duplicate samples representing all combinations of test parameters, in two independent trials, were analyzed for the presence (by enrichment) and number of Salmonella surviving for 0, 1, 3, 12, 18, 26, 28, and 36 weeks.

Results: Initial high counts in dry-inoculated sucrose stored at 5°C for 36 weeks decreased by 0.7 log CFU/g. Counts decreased (>3.7 log CFU/g) significantly (P≤0.05) in sucrose stored at 25°C. Inactivation rates in wet-inoculated sucrose were similar to those in dry-inoculated sucrose. Survival of Salmonella was not markedly affected by a_w.  Salmonella survived in low-inoculum sucrose stored at 5°C for 36 weeks, regardless of a_w or type of inoculum. In dry-inoculated sucrose (a_w 0.54) and wet-inoculated sucrose (a_w 0.24) stored at 25°C, Salmonellasurvived for up to 12 and 26 weeks, respectively.

Significance: The ability of Salmonella to survive in sucrose for extended periods of time highlights the need to prevent postprocessing contamination. Consideration should be given to routinely monitoring sucrose for the presence of Salmonella, particularly if it is intended for use as an ingredient in foods not receiving a treatment that would be lethal to the pathogen.