Resistance of Staphylococcus aureus to UV-C light and combined UV-heat treatments at mild temperatures

Author: Gayan, E.; Garcia-Gonzalo, D.; Alvarez, I.; Condon, S.

Description: 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 sigma(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 degrees 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 Log(1)(0) cycles of S. aureus by applying UV-C treatments of 27.1 mJ/L for 3.6 min at 52.5 degrees C or 13.6 mJ/L for 1.8 min at 55.0 degrees C.

Subject headings: Cell Membrane/radiation effects; Food Handling/methods; Food Microbiology; Hot Temperature; Microbial Viability/radiation effects; Oxidation-Reduction/radiation effects; Staphylococcus aureus/growth & development/radiation effects; Temperature; Ultraviolet Rays; Combined treatments; Liquid foods; S. aureus; Sub-lethal damages; UV-C light; Food contamination

Publication year: 2014

Journal or book title: International Journal of Food Microbiology

Volume: 172

Pages: 30-39

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Type: Journal Article

Serial number: 3045