Survival at refrigeration and freezing temperatures of Campylobacter coli and Campylobacter jejuni on chicken skin applied as axenic and mixed inoculums

Campylobacter is considered to be the most common cause of bacterial diarrhoeal illness in the developed world. Many cases are thought to be acquired from consumption of undercooked poultry. The aim of this study was to compare the effect of the rate of cooling on the survival, at 4 °C and − 20 °C, of Campylobacter coli and Campylobacter jejuni strains, inoculated on chicken skin from axenic culture or as mixed inoculums. Strains chilled in a domestic refrigerator varied in their tolerance to storage at 4 °C. Statistically significant differences between strains applied as axenic or mixed inoculums were observed for specific strain combinations using two-way ANOVA, including the enhanced survival of antibiotic resistant C. coli 99/367 at 4 °C. The use of rapid cooling (at − 20 °C/min) enhanced the survival of all the Campylobacter strains chilled to 4 °C compared to standard refrigeration. Freezing to − 20 °C reduced viable counts by 2.2–2.6 log10 CFU/cm2 in 24 h. Rapid cooling to − 20 °C (at − 30 °C/min) enhanced the survival of C. coli 99/367 compared to freezing in a domestic freezer. Statistically significant interaction terms between specific strains were observed in mixed inoculums chilled to − 20 °C by freezing in a domestic freezer and by rapid chilling to − 20 °C. Rapid chilling of poultry, particularly for 4 °C storage may enhance survival of Campylobacter and although this is an issue that affects meat quality, it should be considered by poultry processors.