Thermal inactivation of Campylobacter jejuni in broth.
New Zealand has a high rate of reported campylobacteriosis compared with other developed countries. One possible reason is that local strains have greater heat tolerance and thus are better able to survive undercooking; this hypothesis is supported by the remarkably high D-values  reported for Campylobacter jejuni in The Netherlands. The objective of this study was to investigate the thermal inactivation of isolates from New Zealand in broth, using strains that are commonly found in human cases and food samples in New Zealand. Typed Campylobacter strains  were heated to a predetermined temperature using a submerged-coil heating apparatus. The first-order kinetic model has been used extensively in the calculation of the thermal inactivation parameters, D and z; however, nonlinear survival curves have been reported, and a number  of models have been proposed to describe the patterns observed. Therefore, this study compared the conventional first-order model with eight nonlinear models for survival curves. Kinetic parameters were estimated using both one- and two-step regression techniques. In general, nonlinear models  fit the individual inactivation data sets better than the log-linear model. However, the log-linear and the (nonlinear) Weibull models were the only models that could be successfully fitted to all data sets. For seven relevant New Zealand C. jejuni strains, at temperatures from 51.5  to 60°C, D- and z-values were obtained, ranging from 1.5 to 228 s and 4 to 5.2°C, respectively. These values are in broad agreement with published international data and do not indicate that the studied New Zealand C. jejuni strains are more heat resistant than  other strains, in contrast with some reports from The Netherlands.
Institute of Food, Nutrition and Human Health, Massey University, Palmerston North 4442, New Zealand. alsakkafali@gmail.com
Ali
A
Al Sakkaf
Geoff
G
Jones
D000818:Animals; D002169:Campylobacter Infections / Q000453:epidemiology / Q000382:microbiology; D016123:Campylobacter jejuni / Q000254:growth & development*; D015169:Colony Count, Microbial; D003470:Culture Media; D005511:Food Handling / Q000379:methods*; D006358:Hot Temperature; D006801:Humans; D007700:Kinetics; D050296:Microbial Viability; D008954:Models, Biological; D009426:Netherlands; D009520:New Zealand
D003470:Culture Media