title: Effect of citral on the thermal inactivation of Escherichia coli O157:H7 in citrate phosphate buffer and apple juice.
abstract: Inactivation and sublethal injury of Escherichia coli O157:H7 cells induced by heat in citrate phosphate buffer and apple juice (both at pH 3.8) were studied, and the effect of a combined preservation treatment using citral and heat treatments was determined. Heat resistance of E. coli O157:H7 was similar in both treatment media; after 27 min at 54°C, 3 log units of the initial cell population was inactivated in both treatment media. However, under less harsh conditions a protective effect of apple juice was found. Whereas inactivation followed linear kinetics in the citrate phosphate buffer, when cells were treated in apple juice the survival curves were concave downward. Heat treatment caused a great degree of sublethal injury; 4 min at 54°C inactivated less than 0.5 log CFU/ml but sublethally injured more than 3 log CFU/ml. The addition of 18 and 200 ppm of citral to the treatment medium acted synergistically with heat at 54°C to inactivate 3 × 10(4) and 3 × 10(7) CFU/ml, respectively. Addition of citral thus reduced the time needed to inactivate 1 log unit of the initial E. coli O157:H7 population from 8.9 to 1.7 min. These results indicate that a combined process of heat and citral can inactivate E. coli O157:H7 cells and reduce their potential negative effects.
authors.affiliation: Tecnología de los Alimentos, Universidad de Zaragoza, C/ Miguel Servet, 177, 50013, Zaragoza, Spain.
authors.forename: L
authors.initials: L
authors.lastname: Espina
authors.forename: M
authors.initials: M
authors.lastname: Somolinos
authors.forename: R
authors.initials: R
authors.lastname: Pagán
authors.forename: D
authors.initials: D
authors.lastname: García-Gonzalo
mesh_terms: D000080462:Acyclic Monoterpenes; D001628:Beverages / Q000382:microbiology; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004305:Dose-Response Relationship, Drug; D019453:Escherichia coli O157 / Q000187:drug effects / Q000254:growth & development*; D005511:Food Handling / Q000379:methods; D005516:Food Microbiology; D005519:Food Preservation / Q000379:methods*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D027845:Malus / Q000382:microbiology*; D039821:Monoterpenes / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D000080462:Acyclic Monoterpenes; D039821:Monoterpenes; C007076:citral