Campylobacter jejuni reductions on poultry due to domestic and commercial freezing practices

Experiments to quantify the effects of freezing prior to domestic frozen storage on the reduction of Campylobacter jejuni on chicken portions.

Year of Publication2008

Introduction: Campylobacteriosis is the most frequently reported gastrointestinal illness in New Zealand, with more than 50% of cases attributed to chicken consumption. Given the pathogen’s sensitivity to freezing, it has been argued that all fresh poultry should be temporarily withdrawn and replaced with frozen/processed alternatives. However, domestic freezing of fresh poultry is a relatively common practice among New Zealand consumers. Experiments were therefore initiated to quantify the effects of both domestic and commercial freezing prior to domestic frozen storage on the reduction of C. jejuni on chicken portion surfaces. Methods: Irradiated skin-on chicken breasts were surface inoculated with ~5 log cfu of either C. jejuni STu48 or ST474, then frozen and stored for up to 70 days. Domestic freezing was simulated using a fridge-freezer with bottom-loading freezer compartment, while blast freezing was conducted by a commercial poultry processor. Data loggers monitored air and sample temperatures. At intervals during frozen storage, samples were removed, thawed at either 4 or 20°C and enumerated for C. jejuni using a rinse method and plating on mCCDA. Selected colonies were confirmed as C. jejuni by PCR. Counts were converted to log cfu reductions (versus day 0 counts) prior to statistical analysis. Results: Individual C. jejuni reductions ranged from 0.08 to >4.49 and 0.93 to 4.22 log cfu per portion following domestic and commercial freezing respectively. Mean reductions after blast freezing were up to 0.8 log cfu greater than those achieved by domestic freezing for up to 28 days of frozen storage, but differences in reductions beyond this storage period were not statistically significant. The largest reductions were typically associated with longer storage times in both cases, but neither freezing regime completely eliminated C. jejuni. Differences in isolate behaviour and the potential impact of thawing temperature on pathogen reduction could not be ascertained due to the variability of obtained data. Discussion: Regardless of freezing regime, the largest reductions in C. jejuni occurred after at least 28 days suggesting that domestic freezing could be an effective alternative to commercial freezing. Our data also indicate that freezing is an inconsistent process subject to significant variability. Given reports of the pathogen’s lesser survival on poultry skin (vs. skinned/ cut muscle) the results presented here should be considered best case scenario.

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