Purpose: This study was conducted to identify the maximum synergistic effect points of UV irradiation and chlorine treatment for inactivating feline calicivirus strain-9 (FCV-9) and murine norovirus type 1 (MNV-1) on stainless steel surfaces and to develop predictive reduction models using response surface methodology (RSM).
Methods: As surrogate models of norovirus, FCV-9 and MNV-1 were used in this study. The reduction levels of FCV-9 and MNV-1 on stainless steel surfaces were investigated by UV irradiation (0- 120m W·s/µ²) and chlorine concentrations (0-5,000 ppm). The Polynomial models were developed for predicting reduction models of FCV and MNV by UV irradiation and chlorine disinfection.
Results: The reduction levels of FCV were steadily increased in the 0-80 mW·s/µ² of UV irradiation at the higher chlorine concentration. However, chlorine disinfection did not affect reduction of FCV in the 80-100 mW·s/µ² of UV irradiation. The reduction levels of MNV at the treatment of 3,000-4,000 ppm chlorine were much more significantly affected at 60-120 mW·s/µ² of UV irradiation than at 0-60 mW·s/µ² of UV irradiation. The polynomial equations predicting the inactivation of FCV and MNV were as follows: FCV (log TCID50/coupon) = 1.294+0.007 x1a + 0.0003 x2b + 0.0002 x12 (x1: UV and x2: chlorine); and MNV (log TCID50/coupon) = 1.638-0.026 x1 + 0.0008 x2 + 0.0003 x12 (x1: UV and x2: chlorine). The predictive reduction models by RSM were fit well (R2 = 0.9939 and 0.9332) and expressed as adequate models by Prob > F-value (P< 0.0001).
Significance: Combined treatment of UV irradiation and chlorine disinfection provides effective reduction of norovirus on stainless steel surfaces and the predictive reduction models of FCV and MNV could be used in food manufacturing facilities.