The influence of scald water pH on the death rates of Salmonella typhimurium and other bacteria attached to chicken skin

Release of Escherichia coli from Feathered and Featherless Broiler Carcasses in Warm Wate

Release of bacteria from individual broiler carcasses in warm water was measured as a model of bacterial contamination of scald water. Immediately after shackling and electrocution, feathered and genetically featherless broiler carcasses (n = 24 of each) were immersed individually in 42 degrees C, air-agitated tap water for 150 s. Although any visible fecal material expelled as a result of electrocution was removed before sampling, carcass condition was typical for market-age broilers subjected to 12 h of feed withdrawal. Duplicate water samples were taken at 10, 30, 70, 110, and 150 s, and Escherichia coli counts were determined. Samples of initial tap water and contaminated water approximately 2 min after removal of carcasses indicated that E. coli could not be detected in the original water source and that mortality of E. coli in the warm water was negligible. Mean numbers of E. coli released were 6.2 and 5.5 log(10) (cfu/carcass) at 150 s for feathered and featherless carcasses, respectively. For both feathered and featherless carcasses, the rate of release of E. coli was highest in the first 10 s, and the rate declined steadily during the remaining sampling period. This result is compatible with published reports of sampling of operating multiple-tank scalders, indicating that a high proportion of total bacteria in a multiple-tank scalder are in the first scald tank that carcasses enter. Higher numbers of E. coli released from feathered carcasses are probably due to the much greater surface area of contaminated feathers compared with the skin of featherless carcasses.

Salmonella and Campylobacter contamination of broiler chicken carcasses and scald tank water: the influence of water pH

Scalding at 50 degrees +/- 0.5 degrees C, in water maintained at pH 9.0 +/- 0.2 by the addition of sodium hydroxide, had no effect on the incidence of salmonella or campylobacter contamination of chicken carcasses. There were significant reductions, however, in the numbers of these organisms in the water itself.

Use of egg washwater pH to prevent survival of Salmonella at moderate temperatures

The survival and thermal resistance of Salmonella typhimurium N+L141083 was examined in egg washwater at moderate temperatures over a range of pH values. Salmonella were able to grow at 38 and 42 C when washwater pH was less than or equal to 9.5, but substantial lethality was noted at greater than or equal to pH 10. At pH 10.5 and 11, Salmonella were eliminated within 5 hr. At 6 C, Salmonella levels were maintained for 18 hr without lethality up to pH 11. At pH 11, some lethality was noted after 5 hr. A D42 value at pH 7.0 could not be calculated, but at pH 10, a value of 40.8 sec was determined. Narrow range pH paper (pH 8 to 10) responded to egg washwater contact at or above pH 10 with a clear color reaction. Below pH 10, the paper signalled the need for addition of alkaline detergent to prevent the growth of Salmonella.