Submitted to: Journal of Food Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/20/2000
Publication Date: 9/1/2000
Citation: CASON JR, J.A., HINTON JR, A., INGRAM, K.D. COLIFORM, E.COLI, AND SALMONELLAE CONCENTRATIONS IN A MULTIPLE-TANK, COUNTERFLOW POULTRY SCALDER. JOURNAL OF FOOD PROTECTION. 2000. Interpretive Summary: During poultry processing, carcasses are passed through a hot water bath to make it easier to remove the feathers. This study sampled scald water and carcasses from a commercial processing plant to determine whether a relatively new scalder design reduces the chance for cross-contamination, or movement of bacteria from one carcass to another through the scald water. The study found that numbers of bacteria such as coliforms and E. coli, both associated with feces, are reduced in the last tank of a multiple-tank scalder to less than 1% of the numbers in the first tank. Incidence of salmonella bacteria in the last tank is also reduced. The results indicate that multiple-tank, counterflow scalders may reduce the chance of bacterial cross-contamination compared to older scalder designs.
Technical Abstract: Scald water from a broiler processing plant was tested for coliform, E. coli, and salmonellae to evaluate suspended bacteria in a multiple-tank, counterflow scalder. Water samples were taken from each of three tanks on eight different days. Numbers of coliforms, E. coli and salmonellae were determined both in water and in rinses of defeathered carcasses that were removed from the processing line immediately after taking the water samples. Mean coliform concentrations in Tanks 1, 2, and 3 (the last tank that carcasses pass through before being defeathered) were 3.4, 1.9, and 1.2 log10(cfu/ml), respectively. E. coli concentrations followed the same pattern with means of 3.2, 1.5, and 0.8 in Tanks 1, 2, and 3, respectively, with significant reductions in the concentrations of both coliforms and E. coli between the tanks. Counts of coliforms and E. coli in rinses of defeathered carcasses were positively correlated with bacteria in Tank 1, but there were no correlations for Tanks 2 and 3. Sixteen of 24 scald water samples were positive for salmonellae with a geometric mean of 10.9 MPN/100 ml in the positive samples. Five of the 16 positive samples had salmonellae concentrations over 7 MPN/100 ml, with a maximum of 251 MPN/100 ml. Salmonellae MPNs in carcass rinses were correlated with MPNs in scald water in Tanks 1 and 2, but only two of eight samples were positive in Tank 3. Most bacteria removed from carcasses during scalding are washed off during the early part of scalding. The main advantage of counterflow scalding is that it preserves that pattern so that scald water in the last part of scalding contains fewer suspended bacteria. Counterflow scalder designs should reduce the probability of cross-contamination.