Ultraviolet (UV-C) Light Systems for the Inactivation of Feline Calicivirus and Tulane Virus in Model Fluid Foods

Conventional UV-C (254 nm) inactivation technologies have limitations and potential operator-safety risk. To overcome these disadvantages, novel UV-C light-emitting diodes (LED) are developed and investigated for their performance. This study aimed to determine the inactivation of human norovirus (HuNoV) surrogates, Tulane virus (TV), and feline calicivirus (FCV-F9), by UV-C (254 nm) in comparison to UV-C LED (279 nm) in phosphate-buffered saline (PBS) and coconut water (CW). Five-hundred microliters of FCV-F9 (~ 5 log plaque forming units (PFU)/mL) or TV (~ 6 log PFU/mL) were added to 4.5 mL PBS or CW in continuously stirred glass beakers and exposed to 254 nm UV-C for 0 up to 15 min (maximum dosage of 33.89 mJ/cm²) or 279 nm UV-C LED for 0 up to 2.5 min (maximum dosage of 7.03 mJ/cm²). Recovered viruses were assayed in duplicate from each treatment replicated thrice. Mixed model analysis of variance was used for data analysis. Significantly lower D₁₀ values were obtained in PBS and CW (p ≤ 0.05) for both tested viruses using UV-C LED (279 nm) where FCV-F9 showed D₁₀ values of 7.08 ± 1.75 mJ/cm² and 3.75 ± 0.11 mJ/cm², while using UV-C (254 nm) showed D₁₀ values of 13.81 ± 0.40 mJ/cm² and 6.43 ± 0.44 mJ/cm² in PBS and CW, respectively. Similarly, lower D₁₀ values were obtained for TV of 3.91 ± 1.03 mJ/cm² and 4.26 ± 1.02 mJ/cm² with 279 nm UV-C LED and were 18.76 ± 3.16 mJ/cm² and 10.21 ± 1.48 mJ/cm² with 254 nm UV-C in PBS and CW, respectively. Viral resistance to these treatments was fluid-matrix dependent. These findings indicate that use of 279 nm UV-C LED is more effective in inactivating HuNoV surrogates than conventional 254 nm UV-C in the tested fluids.