Survival of Campylobacter jejuni in frozen chicken breast fillet

Sammanfattning: This thesis aimed to study how two sequence types of Campylobacter jejuni, ST-257 and ST-918, survive freezing in broiler fillets. Campylobacteriosis is the most reported zoonosis in the EU, with over 200,000 reported cases annually. Broilers are considered the primary source of human exposure. Freezing reduces the concentration of bacteria and can be used as a post-harvest preventive measure. In this thesis, broiler meat was artificially contaminated and frozen together with meat juice, thereafter stored for 49 days. During the time, analysis was performed at ten different occasions. The quantification of C. jejuni in broiler meat and meat juice was made according to ISO 10272 part 2. Mean concentrations in the meat before freezing were 5.3 and 4.2 log10 CFU/g in ST-257, and in ST-918 5.2 and 4.2 log10 CFU/g. In the meat juice, the mean concentrations in ST-257 were 5.1 log10 CFU/ml for both concentrations, while for ST-918 concentrations were 5.2 and 4.6 log10 CFU/ml. The largest rate of decrease occurred the first two or four days after freezing, and the rate of decrease flattened after approximately one week. After 49 days, ST-257 decreased by a mean 1.6 and 2.0 log10 CFU/g in the meat and ST-918 decreased by 0.7 and 1.0 log10 CFU/g in the meat. The reduction in the meat juice was equal to or larger than the reduction in the meat. ST-918 survived freezing to a greater extent than ST-257, indicating different abilities to stand the stress from low temperatures.