Deactivation of Salmonella Typhimurium, Bacillus cereus vegetative cells and spores by a non-thermal indirect plasma for food industry applications

Bacillus cereus and Salmonella enterica are among the most common species known for causing foodborne outbreaks in the United States. An alternative sterilization method, the cold plasma, is introduced to prevent these outbreaks. This study investigates the effectiveness of cold plasma in sterilizations of B. cereus vegetative cells and spores, S. Typhimurium on agar, and eggs shells. The plasma was applied to B. cereus ATCC 14579 vegetative cells on  tryptic soy agar plates (TSA) for various exposure times (0 s, to 90 s) after incubation percentage of inactivation was recorded. B. cereus was incubated for 10 days at 30^oC for sporulation. A spore suspension with ~ 2 x 10³ spores was dispersed on glass petri plates and treated for 360 s. Treated spores were suspended in water and plated to determine spores inactivation. Plasma was also applied to Salmonella enterica subesp. enterica serovar Thyphimurium ATCC 14028  inoculum with ~ 1x10⁵ cells on TSA plates, and eggs shells for various times (0 s to 360 s). Treated agar and eggshells were vortexed in 10ml water to suspend cells. Suspensions were diluted and plated to record inactivation. Results confirmed 99% of B. cereus vegetative cells inactivation after 90s and 0.84 log reduction of spores after 360 s. Results show Salmonella on agar after 180 s of treatment have inactivation with viable cells below detection limits and on eggshells ~0.9 log reduction after 360 s. Preliminary results show that cold plasma can be an alternative sterilization method with applications in food industry.