Coliforms, Escherichia coli, Campylobacter, and Salmonella in a Counterflow Poultry Scalder with a Dip Tank

Abstract

Suspended bacteria were enumerated in scald water and carcass rinse samples from a commercial broiler chicken processing plant with a multiple-tank, counterflow scalder. Coliforms, Escherichia coli, and Campylobacter were enumerated and the Most Probable Number (MPN) of salmonellae was determined in water samples from each of three scald tanks, from a dip tank located between defeathering machines, and in rinses of carcasses removed from the processing line immediately after defeathering. Mean coliform concentrations in Tanks 1, 2, and 3 were 4.6, 2.5, and 1.6 log₁₀(cfu/ml), respectively. E. coli concentrations followed the same pattern with means of 4.4, 2.1, and 1.4 in Tanks 1, 2, and 3, respectively, with significant differences (P< 0.05) in the concentrations of both coliforms and E. coli between tanks. Mean Campylobacter concentration in four positive samples from Tank 1 was 4.0 log₁₀ (cfu/ml), but only one water sample from Tank 2 and none from Tank 3 were Campylobacter positive. Coliforms and E. coli were found in dip tank samples in only two instances, with no isolations of Campylobacter or salmonellae. Mean numbers of coliforms, E. coli, and Campylobacter in carcass rinses were 3.1, 2.7, and 3.3 log₁₀(cfu/ml). Salmonellae were isolated from five of six water samples from Tank 1 with a mean MPN of 13.3/100mL, but were isolated from only three of six water samples from Tank 2 and two of six from Tank 3. Salmonellae were isolated from half (18/36) of all carcass rinses. Most bacteria suspended in scald water were found in the first tank, with no Campylobacter or salmonellae found in the dip tank. Counterflow, multiple-tank scalders appear to reduce the opportunity for cross-contamination during scalding.