Challenges of Dry Sanitization to Control Salmonella Dry Surface Biofilms
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Salmonella is a pathogen linked to foodborne outbreaks, including low-moisture foods. Its ability to resist desiccation can contribute to the formation of dry surface biofilms (DSB). This study evaluated the impact of 3 DSB formation protocols (P1=48-h hydrated phase/48-h dry phase, P2=24-h/120-h and P3=8-h/48-h) on the resistance of Salmonella DSB to 70% alcohol, a commercial product (based on 0.015% quaternary ammonium and 25% isopropyl alcohol), gaseous ozone (45 ppm), hot air (90 °C) and UV-C light (254 nm). The type of DSB protocol impacted the efficacy of the sanitizers (p < 0.05). The biofilm with the shortest hydration phase showed the greatest susceptibility; three out of the five sanitizers evaluated (70% alcohol, commercial product, and UV-C) promoted significant reductions in P3, with counts below the detection limit (0.8 log CFU/cm²) after 5 to 15 min exposure. Regarding protocols P1 and P2, in general, the best performance was from UV-C, especially against DSB on polypropylene, where it achieved reductions of 1.3 log CFU/cm² for P1 and 2.9 log CFU/cm² for P2 after 15 to 30 min of exposure. In contrast, hot air and ozone showed less effectiveness, with reductions ≤1.2 log CFU/cm². In most scenarios, confocal microscopy images corroborated the plate count results (log CFU/cm²). In summary, our data indicates limited action of dry sanitizers on Salmonella DSB, requiring validation and optimization of sanitization processes to ensure the microbiological safety of low-moisture products.
