Effect of ionizing dose rate on the radioresistance of some food pathogenic bacteria

Abstract

Food pathogenic bacteria including Listeria monocytogenes (1A1 and ATCC 19111), Staphylococcus aureus (GD13 and ATCC 13565), Escherichia coli O157:H7 (ATCC 35150), Salmonella typhimurium, Yersinia enterocolitica, Vibrio parahaemolyticus, and Campylobacter jejuni were exposed to various rates of ionizing radiation (0.78, 2.6, and 22 kGy/h) emitted by three different 60Co irradiators. D10 values (D10 is the radiation dose required to eliminate 90% of a bacterial population (one logarithmic cycle reduction)) were calculated for the various strains and growth conditions tested. A covariance analysis of these results revealed that the dose rates studied had no significant influence on the radiosensitivity of these bacteria. At all dose rates, the bacteria were more radiosensitive when irradiated in a saline solution (0.85% NaCl) than in a chicken breast meat suspension. The growth phase of the bacterial population had a variable influence on its radioresistance. For L. monocytogenes 1A1, Staphylococcus aureus ATCC 13565, E. coli O157:H7, Y. enterocolitica, and V. parahaemolyticus, radioresistance was not significantly different in the exponential and stationary phases. Populations of L. monocytogenes ATCC 19111 and Staphylococcus aureus GD13 were significantly more resistant in the stationary phase (D10 = 0.23 and 0.12 kGy, respectively) than in the exponential phase (D10 = 0.17 and 0.09 kGy, respectively). Among the pathogenic bacteria investigated in this study, the most radioresistant was L. monocytogenes (D10 = 0.16-0.38 kGy, Gram-positive bacilli) and the most radiosensitive was V. parahaemolyticus (D10 = 0.03-0.04 kGy, halophilic Gram-negative bacilli).

Optimization of E-beam irradiation treatment to eliminate Listeria monocytogenes from ready-to-eat (RTE) cooked ham

“…(Augustin, 1996;Mahapatra, Muthukumarappan, & Julson, 2005;Tarte, Murano, & Olson, 1996;Zhu et al, 2005), the irradiation decimal reduction here obtained may be considered as usual values since they are in the range reported by several authors in a variety of conditions. So, from the data of Mendonca, Romero, Lihono, Nannapaneni and Johnson (2004) D-values of 0.41 and 0.65 kGy may be deduced for normal and starved cells of the strain Scott A suspended in physiological saline solution and 0.301-0.648 kGy (Grant & Patterson, 1992) and 0.16-0.38 kGy (Dion, Charbonneau, & Thibault, 1994) for several strains of L. monocytogenes. In meat products, D-values of 0.49 kGy in broiler at 12°C (Patterson, 1989) and 0.56 kGy in inoculated bologna (Sommers, Fan, Niemira, & Sokorai, 2003) have been reported.…”

Inactivation of Escherichia coli O157:H7 in hamburgers by gamma irradiation

“…Thayer and Boyd (17) found a D value of 0.28 kGy for E. coli O157:H7 inoculated in finely ground lean beef when irradiated in vacuum at 5ºC and a value of 0.27 kGy on either lean ground beef or mechanically deboned chicken meat. Dion et al (4) (2) probably due to differences in the temperature during irradiation treatment, presence or absence of oxygen and substrate. Besides, different species or strains of the same species may require different doses to achieve the same degree of inactivation (3).…”

Modeling and optimization of sensory changes and shelf-life in vacuum-packaged cooked ham treated by E-beam irradiation

“…The strain of L. monocytogenes used here presented the lowest D-value (0.36 kGy), compared with other listeria strains (Cabeza et al, 2007). This means that, to avoid the risk that comes from the routine use of L. monocytogenes Scott A in experiments, it is possible to work normally with more resistant strains (Dion et al, 1994;Grant and Patterson, 1992;Mendonca et al, 2004). Other authors have used non-linear models (Gompertz) to describe the inactivation kinetics of L. monocytogenes (Linton et al, 1995).…”