UV-C inactivation of Escherichia coli at different temperatures

Gayán,E. (Universidad de Zaragoza) ; Monfort,S. (Universidad de Zaragoza) ; Álvarez,I. (Universidad de Zaragoza) ; Condón,S. (Universidad de Zaragoza)

Resumen: The influence of treatment parameters (dose and temperature), treatment medium characteristics (absorption coefficient, pH and water activity) and microbiological factors (strain, growth phase and UV damage and repair capacity) on Escherichia coli UV-C resistance has been investigated. UV-C doses to inactivate at 25 °C 99.99% of the initial population (4D) of five strains of E. coli in McIlvaine buffer of pH 7.0 with tartrazine added (absorption coefficient of 10.77 cm−1) were 16.60, 14.36, 14.36, 13.22, 11.18 J/mL for strains E. coli STCC 4201, STCC 471, STCC 27325, O157:H7 and ATCC 25922, respectively. The entrance in the stationary growth phase increased the 4D value of the most resistant strain, E. coli STCC 4201, from 13.09 to 17.23 J/mL. Survivors to UV treatments showed neither oxidative damages nor injuries in cell envelopes. On the contrary, the photoreactivation by the incubation of plates for 60 min below visible light (11.15 klx) increased the dose to 18.97 J/mL. The pH and the water activity of the treatment medium did not affect the UV tolerance of E. coli STCC 4201, but the lethal effect of the treatments decreased exponentially (Log10 4D = − 0.0628α + 0.624) by increasing the absorption coefficient (α). A treatment of 16.94 J/mL reached 6.35, 4.35, 2.64, 1.93, 1.63, 1.20, 1.02 and 0.74 Log10 cycles of inactivation with absorption coefficients of 8.56, 10.77, 12.88, 14.80, 17.12, 18.51, 20.81 and 22.28 cm−1. The temperature barely changed the UV resistance up to 50.0 °C. Above this threshold, inactivation rates due to the combined process synergistically increased with the temperature. The magnitude of the synergism decreased over 57.5 °C. An UV treatment of 16.94 J/mL in media with an absorption coefficient of 22.28 cm−1 reached 1.23, 1.64, 2.36, 4.01 and 6.22 Log10 cycles of inactivation of E. coli STCC 4201 at 50.0, 52.5, 55.5, 57.5 and 60.0 °C, respectively.

Idioma: Inglés

DOI: 10.1016/j.ifset.2011.07.008

Año: 2011

Publicado en: INNOVATIVE FOOD SCIENCE & EMERGING TECHNOLOGIES 12, 4 (2011), 531-541
ISSN: 1466-8564

Factor impacto JCR: 3.03 (2011)

Categ. JCR: FOOD SCIENCE & TECHNOLOGY rank: 12 / 127 = 0.094 (2011) - Q1 - T1

Financiación: info:eu-repo/grantAgreement/ES/CICYT-FEDER/CIT-020000-2009-40

Tipo y forma: Article (Published version)

Área (Departamento): Área Tecnología de Alimentos (Dpto. Produc.Animal Cienc.Ali.)