title: Resistance of Staphylococcus aureus to UV-C light and combined UV-heat treatments at mild temperatures.
abstract: In this investigation, the resistance of enterotoxigenic Staphylococcus aureus to short-wave ultraviolet light (UV-C) and to combined UV C-heat (UV-H) treatments in buffers and in liquid foods with different physicochemical characteristics was studied. Microbial resistance to UV-C varied slightly among the S. aureus strains tested. The UV-C resistance of S. aureus increased in the entry of stationary growth phase, which in part was due to the expression of the alternative sigma factor σ(B). The UV-C resistance of S. aureus was independent of the treatment medium's pH and water activity, but it decreased exponentially as the absorption coefficient increased. UV-C bactericidal efficacy in liquids of high absorption coefficients was improved synergistically when combined with a mild heat treatment at temperatures ranging from 50.0 to 57.5 °C. pH of the treatment medium modified the lethality of UV-H treatments and therefore the temperature of maximum synergy. The advantage of combined UV-H treatments was demonstrated in fruit juices and vegetable and chicken broths, inactivating 5 Log₁₀ cycles of S. aureus by applying UV-C treatments of 27.1 mJ/L for 3.6 min at 52.5 °C or 13.6 mJ/L for 1.8 min at 55.0 °C.
authors.affiliation: Tecnología de los Alimentos, Universidad de Zaragoza, C/Miguel Servet 177, CP 50013, Zaragoza, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Gayán
authors.affiliation: Tecnología de los Alimentos, Universidad de Zaragoza, C/Miguel Servet 177, CP 50013, Zaragoza, Spain.
authors.forename: D
authors.initials: D
authors.lastname: García-Gonzalo
authors.affiliation: Tecnología de los Alimentos, Universidad de Zaragoza, C/Miguel Servet 177, CP 50013, Zaragoza, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Alvarez
authors.affiliation: Tecnología de los Alimentos, Universidad de Zaragoza, C/Miguel Servet 177, CP 50013, Zaragoza, Spain. Electronic address: scondon@unizar.es.
authors.forename: S
authors.initials: S
authors.lastname: Condón
mesh_terms: D002462:Cell Membrane / Q000528:radiation effects; D005511:Food Handling / Q000379:methods*; D005516:Food Microbiology; D006358:Hot Temperature; D050296:Microbial Viability / Q000528:radiation effects; D010084:Oxidation-Reduction / Q000528:radiation effects; D013211:Staphylococcus aureus / Q000254:growth & development / Q000528:radiation effects*; D013696:Temperature; D014466:Ultraviolet Rays
keywords: Combined treatments; Liquid foods; S. aureus; Sub-lethal damages; UV-C light