Low-temperature survival and through-ice UV disinfection on surfaces: A factorial study across pathogens, surfaces and light sources

Cold-chain sanitation often occurs on nonporous food-contact surfaces where low temperature and ice can affect both survival and UV delivery. We compared low-pressure mercury lamps (LPM) and pulsed xenon lamps (PX) under a factorial design crossing temperature (−15, 4, 20 °C), surface (glass, stainless steel, high-density polyethylene), and ice thickness (0−40 mm), using four test organisms ( Escherichia coli , Staphylococcus aureus , Listeria monocytogenes and Salmonella Typhimurium). Without radiation, temperature was dominated 7-day survival, with smaller surface and strains effects. On bare surfaces, log reduction increased approximately linearly with fluence. LPM reached 3-log at 30−250 mJ/cm 2 , while PX typically required 150−600 mJ/cm 2 . A thermal sleeve restored LPM irradiance at low temperature, and similar time-matched reductions for LPM and PX. Through clear, bubble-free ice at −15 °C, inactivation decreased with thickness, while the time-matched contrast remained near zero under the specific geometry and clear ice tested, and two-way ANOVA showed no significant effects of thickness or time. However, complex field geometries and shadowing could alter these operational outcomes. For implementation, prioritize how quickly the target fluence can be delivered and verify irradiance at worst-case locations. For the clear, bubble-free ice and fixed geometry, adjusting exposure based on transmittance is effective.