Survival of cold-stressed Campylobacter jejuni on ground chicken and chicken skin during frozen storage

Abstract

Campylobacter jejuni is prevalent in poultry, but the effect of combined refrigerated and frozen storage on its survival, conditions relevant to poultry processing and storage, has not been evaluated. Therefore, the effects of refrigeration at 4 degrees C, freezing at -20 degrees C, and a combination of refrigeration and freezing on the survival of C. jejuni in ground chicken and on chicken skin were examined. Samples were enumerated using tryptic soy agar containing sheep's blood and modified cefoperazone charcoal deoxycholate agar. Refrigerated storage alone for 3 to 7 days produced a reduction in cell counts of 0.34 to 0.81 log10 CFU/g in ground chicken and a reduction in cell counts of 0.31 to 0.63 log10 CFU/g on chicken skin. Declines were comparable for each sample type using either plating medium. Frozen storage, alone and with prerefrigeration, produced a reduction in cell counts of 0.56 to 1.57 log10 CFU/g in ground chicken and a reduction in cell counts of 1.38 to 3.39 log10 CFU/g on chicken skin over a 2-week period. The recovery of C. jejuni following freezing was similar on both plating media. The survival following frozen storage was greater in ground chicken than on chicken skin with or without prerefrigeration. Cell counts after freezing were lower on chicken skin samples that had been prerefrigerated for 7 days than in those that had been prerefrigerated for 0, 1, or 3 days. This was not observed for ground chicken samples, possibly due to their composition. C. jejuni survived storage at 4 and -20 degrees C with either sample type. This study indicates that, individually or in combination, refrigeration and freezing are not a substitute for safe handling and proper cooking of poultry.

FIG. 1.

Survival of C. jejuni with refrigeration only (4°C). Series 1, ground chicken plated on TSAB; series 2, ground chicken plated on mCCDA; series 3, chicken skin plated on TSAB; series 4, chicken skin plated on mCCDA. The values plotted are means ± SD (n = 3).

FIG. 2.

Survival of C. jejuni with freezing only (−20°C). Series 1, ground chicken plated on TSAB; series 2, ground chicken plated on mCCDA; series 3, chicken skin plated on TSAB; series 4, chicken skin plated on mCCDA. The values plotted are means ± SD (n = 3).

FIG. 3.

Survival of C. jejuni with freezing (−20°C) after 1 day of refrigeration (4°C). Series 1, ground chicken plated on TSAB; series 2, ground chicken plated on mCCDA; series 3, chicken skin plated on TSAB; series 4, chicken skin plated on mCCDA. The values plotted are means ± SD (n = 3).

FIG. 4.

Survival of C. jejuni with freezing (−20°C) after 3 days of refrigeration (4°C). Series 1, ground chicken plated on TSAB; series 2, ground chicken plated on mCCDA; series 3, chicken skin plated on TSAB; series 4, chicken skin plated on mCCDA. The values plotted are means ± SD (n = 3).

FIG. 5.

Survival of C. jejuni with freezing (−20°C) after 7 days of refrigeration (4°C). Series 1, ground chicken plated on TSAB; series 2, ground chicken plated on mCCDA; series 3, chicken skin plated on TSAB; series 4, chicken skin plated on mCCDA. The values plotted are means ± SD (n = 3).