Kinetic modeling of dairy phages inactivation under UV-C irradiation

The inactivation of sixteen dairy phages was tested as a function of time in a laboratory scale reactor, under near UV-C radiation (λ = 254 nm). Unlike previous studies focusing on liquid suspensions, this work specifically examines phage inactivation on dry surfaces, mimicking industrial environments where bioaerosols and contaminated surfaces contribute to phage dissemination. Moreover, most of the tested phages were isolated in our country and have not been studied using this technology yet. Phage suspensions (10⁶-10⁷ PFU/mL) were deposited on borosilicate glass plates, dried and exposed to increasing UV-C doses. No infective phage particles were detected for six phages when treated with a dose of 0.13 J/cm², while the remaining ten exhibited titer reductions between 3.16 and 4.45 log orders when treated with doses of 0.13 or 0.32 J/cm². These dose values are feasible to apply in the industry, since short treatment times and few lamps are required, which implies a low investment and maintenance cost. For higher doses, a tailing effect was evidenced for the 10 phages. This behavior was also demonstrated in a second cycle of treatment under UV-C radiation for phages MLC-A and LDG. To quantify and predict phage inactivation, eight kinetic models were applied, with the Geeraerd and Baranyi and Roberts models providing the best fit (RMSE: 6.86 × 10^-6 - 3.54 %). These findings offer valuable insights into phage control strategies for the dairy industry, improving current sanitation protocols and contributing to the development of effective UV-C disinfection guidelines for food processing environments.