title: Effect of culture age, pre-incubation at low temperature and pH on the thermal resistance of Aeromonas hydrophila.
abstract: The thermal resistance of Aeromonas hydrophila strain NCTC 8049 was determined within the range 48 degrees-65 degrees C with a thermoresistometer TR-SC and McIlvaine buffer. The effects of culture age, pre-incubation at 7 degrees C and the pH of the heating menstruum were evaluated. The pattern of thermal death was dependent on culture age. Cells heated in the late logarithmic growth phase (15 h at 30 degrees C) were twice as resistant as those in the early stage (5 h at 30 degrees C), and the maximum D-value was obtained after 72 h incubation (5.5 total increase). The age of the cells did not affect z-values significantly. The heat resistance of cells incubated for 48 h at 30 degrees C increased (twice) after holding at 7 degrees C for 72 h. Pre-incubation at low temperature of older cultures (72 h, 30 degrees C) did not influence their D-values. Maximum heat resistance was found at pH 6.0 and minimal at pH 4.0. Decreasing the pH from 6.0 to 4.0 reduced D-values by a factor of 5. Although the strain studied was heat-sensitive (D55 degrees C = 0.17 min; z = 5.11 degrees C), survivor curves of cultures older than 50 h showed a significant tailing. Organisms surviving in the tails were only slightly more resistant than were the original population.
authors.affiliation: Department of Food Hygiene and Food Technology, Veterinary Faculty, University of León, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Condón
authors.forename: M L
authors.initials: ML
authors.lastname: García
authors.forename: A
authors.initials: A
authors.lastname: Otero
authors.forename: F J
authors.initials: FJ
authors.lastname: Sala
mesh_terms: D016980:Aeromonas hydrophila / Q000254:growth & development*; D015169:Colony Count, Microbial; D003470:Culture Media; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D013696:Temperature; D013997:Time Factors
chemical_list: D003470:Culture Media