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Råhlén, Ella, 2021. Survival of Campylobacter jejuni in frozen chicken breast fillet. Second cycle, A2E. Uppsala: SLU, Department of Molecular Sciences

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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.


Studiens syfte var att studera hur två olika sekvenstyper av Campylobacter jejuni, ST-257 och ST-918 överlever i frysen i kycklingkött. Campylobacterios är den mest rapporterade zoonosen i EU med över 200 000 fall årligen. Slaktkyckling anses vara den primära smittokällan. Nedfrysning reducerar antalet bakterier och kan användas som en förbyggande åtgärd efter slakt. Den här studien undersökte artificiellt kontaminerad kycklingfilé som frystes ned tillsammans med köttsaft och lagrades i frysen upp till 49 dagar. Under lagringstiden gjordes analys vid tio olika tillfällen. Kvantifieringen av C. jejuni i kycklingkött och köttsaft gjordes enligt ISO 10272 del 2. Medelvärdet av koncentrationerna innan nedfrysning var 5.3 och 4.2 log10 CFU/g i ST-257, och i ST-918 5.2 och 4.2 log10 CFU/g. I köttsaften var koncentrationerna i ST-257 5.1 log10 CFU/ml i båda koncentrationerna, medan i ST-918 var koncentrationerna 5.2 och 4.6 log10 CFU/ml. Störst minskning av antalet Campylobacter skedde under de första två till fyra dagarna i frysen och minskningen planade ut efter en vecka. Efter 49 dagar minskade ST-257 i genomsnitt med 1.6 och 2.0 log10 CFU/g i köttet och ST-918 minskade 0.7 och 1.0 log10 CFU/g i köttet. Reduceringen i köttsaften var likamed eller större än reduceringen i köttet. ST-918 överlevde frysningen bättre än ST-257, vilket tyder på olika förmåga att tåla nedfrysning.

Main title:Survival of Campylobacter jejuni in frozen chicken breast fillet
Authors:Råhlén, Ella
Supervisor:Hansson, Ingrid and Fernström, Lise-Lotte and Bergenkvist, Emma
Examiner:Jonsson, Hans
Series:Molecular Sciences
Volume/Sequential designation:2021:36
Year of Publication:2021
Level and depth descriptor:Second cycle, A2E
Student's programme affiliation:NY010 Agronomprogrammet - livsmedel, för antagna fr.o.m. 2016 300 HEC
Supervising department:(NL, NJ) > Department of Molecular Sciences
Keywords:Campylobacter jejuni, broiler meat, frozen, survival, ST-257, ST-918
Permanent URL:
Subjects:Food science and technology
Food contamination and toxicology
Deposited On:16 Sep 2021 12:39
Metadata Last Modified:17 Sep 2021 01:03

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