Quantitative detection and contamination analysis of Salmonella in broiler slaughter and processing chain in Shaanxi

Objective To investigate the contamination situation of Salmonella at different times, slaughtering and processing sites in a broiler slaughter factory to acquire the key contamination point. Methods Chicken anal swabs, carcasses and broiler samples in different slaughtering stages were timely collected in a broiler slaughterhouse in Shaanxi Province from November 2016 to November 2017, Salmonella concentration was quantitatively detected by most probable number (MPN) method, Salmonella isolate recovered from positive samples were identified by polymerase chain reaction (PCR) combined with serum agglutination techniques. Results Among the 284 samples, 67 (23.6%) were positive to Salmonella, the average MPN value was 0.051 6 MPN/g. During sampling period, samples in July was the most frequently contaminated with the positive rate of 37.8% (14/37) and average MPN value of 0.064 7 MPN/g. the lowest Salmonella contamination rate was detected in November 2016 (13.9%, 5/36) with average MPN value of 0.043 6 MPN/g. Among different processing stages, the highest positive rate was detected after scalding and fading (43.3%, 26/60), the average MPN value of which was 0.060 5 MPN/g. The positive rate of chicken breast before freezing was the lowest (18.3%, 11/60), and the average MPN value was 0.036 8 MPN/g, which was slightly higher than that of the whole chicken carcass/chicken breast collected from distribution and storage processes (0.035 8 MPN/g). Conclusion The result showed detection rate and MPN values of Salmonella positive samples in broiler slaughtering process had a strong seasonality, detection of Salmonella in different slaughtering stages indicated that vertical and cross-contamination might happen during the whole process. It was necessary to strengthen the regulation of broilers processing as well as the critical control points.