Influence of physical variables on the transfer of Salmonella Typhimurium LT2 between potato (Solanum tuberosum) and stainless steel via static and dynamic contact

Bacterial cross-contamination between foods and contact surfaces can increase food safety risk; however, these processes are not well described in terms of fundamental variables. The objective was to determine the effect of sliding speed (3.75, 5.00, or 7.75 mm/s), contact time (5 or 40 s), normal pressure (~1217 to 8869 Pa), and number of sequential contacts on bacterial transfer to/from potato samples and stainless steel surfaces. Potato samples (~11 g, 3 × 3 × 1 cm) were either pulled across a stainless steel plate inoculated with Salmonella Typhimurium LT2 (~6.23 Log CFU/cm²) (dynamic contact) or placed on the inoculated plate for multiple sequential contacts on uninoculated squares (static contact). Salmonella on the potato and steel plate then were quantified by plating on modified trypticase soy agar. Bacterial transfer increased with increasing sliding speed (P = 0.0098) in dynamic tests and with contact time (P < 0.0001) in static tests. Salmonella on the inoculated potatoes decreased (P < 0.0001) from ~6.5 to ~5.5 Log CFU after 18 sequential static contacts with stainless steel. Reporting transfer results based on fundamental variables will improve the overall impact of bacterial transfer research on equipment design, cleaning/sanitation strategies, and overall food safety.

Keywords: Contact; Pathogen; Potato; Pressure; Speed; Stainless steel; Time; Transfer.