Predictive model for the survival, death, and growth of Salmonella typhimurium in broiler hatchery

Contamination and penetration of salmonellae into hatching eggs may comprise an important link in the transmission of these bacteria to growing birds, processed carcasses, and eventually to the consumer. In this study, a predictive model for Salmonella typhimurium as a function of initial cell number and storage or incubation time at a nearly constant temperature and humidity was developed and evaluated to compute the bacterial load after 1 d (holding), 10 d (candling), 17 d (incubation), and 21 d (chick processing). Experiments were conducted for S. typhimurium with both high initial bacterial load (HIBL) and low initial bacterial load (LIBL) of 6.0 and 3.5 log cfu/egg, respectively. Eggs with HIBL experienced 2.0 log reduction in the bacterial load after holding at 4 degrees C for 24 h and 3.0 log increase in the bacterial load during incubation and hatch at approximately 37 degrees C between 17 d and 21 d. Experimental data showed that bacterial load of S. typhimurium from holding to chick processing changed from 3.7 to 6.6 log cfu/egg and from 3.7 to 2.7 log cfu/egg in HIBL and LIBL eggs, respectively. The developed model was able to predict bacterial load of S. typhimurium from 3.6 to 6.6 log cfu/egg in HIBL eggs and from 3.4 to 2.7 log cfu/egg in LIBL eggs from holding to chick processing. Root mean square errors and plot of predicted compared with observed bacterial load of S. typhimurium in contaminated eggs yielded a good fit and prediction. The predicted and experimental results indicated that incubated broiler eggs have an increase in internal bacterial loads between incubation and hatch. This model can be used as a tool to predict bacterial load of S. typhimurium in contaminated eggs as well as help predict the behavior of S. typhimurium during hatch.

Effect of high-temperature inside-outside spray on survival of campylobacter jejuni attached to prechill chicken carcasses

Prechill chicken carcasses, inoculated with Campylobacter jejuni, were sprayed in an inside-outside birdwasher at 20, 55, or 60 C, with or without 50 ppm chlorine, in a poultry processing pilot plant. Carcasses were sprayed for 12 s at 80 pounds per square inch (psi). Next, carcasses were placed in a chiller filled with 50 ppm chlorinated ice water at 4 C for 50 min. Most probable numbers of C. jejuni were determined based on chicken carcass wash water before and after the spray treatment. The skin color of chicken carcasses was measured. The results of this study showed that the 55 and 60 C water spray treatments significantly reduced C. jejuni by more than 0.78 log cfu/carcass compared with the 20 C water spray treatment. However, all of the 50 ppm chlorine spray treatments at three different temperatures were not significantly different. The skin color of chicken carcasses did not change significantly after the spray treatments at temperatures less than 60 C. The chilling process with 50 ppm chlorinated ice water at 4 C further reduced more C. jejuni (approximately 1 log cfu/carcass) among the water spray treatments but did not result in greater reduction of C. jejuni among the chlorine spray treatments.