The effect of sampling time on the levels of micro-organisms recovered from broiler carcasses in a commercial slaughter plant

Abstract

Changes in the levels of indicator micro-organisms and Listeria on broiler carcasses were determined at various stages of commercial broiler slaughter and processing. In addition, the effect of time of day that sampling was carried out within the plant on the microbial profile of samples was evaluated. Counts of total aerobic organisms (37°C and 22°C), Enterobacteriaceae, E. coli and Staphylococcus aureus on broiler skin samples were consistently lower on samples obtained during evening visits to the co-operating broiler slaughter plant when compared with corresponding morning samples. Counts of S. aureus were significantly lower for both morning and evening samples taken following final carcass rinsing when compared to pre-evisceration equivalents ( P<0.05). The number of total viable aerobic bacteria, Enterobacteriaceae and E. coli in scald tank water samples taken early each morning prior to processing start-up were significantly lower than corresponding samples obtained after flocks had been processed where an average of 3912 and 42 475 birds had been processed on morning and evening visits, respectively ( P<0.05). The prevalence of Listeria on broiler skin samples consistently increased for both morning and evening samples through the various stages of processing. For example, the prevalence on samples taken in the morning following defeathering, final carcass rinsing, in-line chilling and final carcass chilling was 10%, 40%, 56% and 72%, respectively. The most frequently recovered species of Listeria from these samples were L. innocua (86%), L. monocytogenes (6%), L. grayi (6%) and L. seeligeri (2%).