Purpose: This study was conducted to assess a poultry rinse limits test application in real-world production while comparing qualitative detection methods.
Methods: Poultry rinse samples (N=240) were collected over 5 weeks from two plants in the eastern United States. Within each week, sampling was conducted over 4 days, 2 shifts and 3 processing locations including re-hang, pre-chill and parts. One carcass or 4 lbs of parts were rinsed in 400 ml of BPW and shipped at 4°C overnight to a 3rd party laboratory. Rinses were evaluated via 4 diagnostic pathways including the Limits Test (3.5 h enrichment), Undiluted Rinse Qualitative Test (20-24 h), and the USDA MLG 4.08 with paired analyses (20-24 h). The limits test was optimized to detect Salmonella loads of ~ 1.30 CFU/ml of rinsate while minimizing detection of loads below. Method results were evaluated for prevalence across sampling variables and McNemar Chi-square for method comparison.
Results: For 213 complete samples, qualitative prevalence by the MLG 4.08 method across re-hang, pre-chill and parts ranged from 35.29-86.84%, 30.30-80.56% and 14.71-26.32% for plants A and B, respectively. In contrast, direct rinse enrichment qualitative prevalence ranged from 55.88-94.74%, 39.39-91.67% and 23.53-44.74%, respectively. Prevalence of samples above the application limit of ~1.30 CFU/ml ranged from 26.47-57.89%, 15.15-55.56% and 5.88-7.89%, respectively across locations for Plant A and B. Salmonella load as observed through limits positive samples trended with prevalence. Finally, no significant differences were observed between the Roka and BAX qualitative tests following MLG 4.08, however, a significant difference was observed between direct rinse enrichment and MLG 4.08.
Significance: Limits testing may provide an alternative means of monitoring process control and intervention efficacy. Qualitative testing may be impacted by sample preparation.