Survival and death of Salmonella typhimurium and Campylobacter jejuni in processing water and on chicken skin during poultry scalding and chilling

Salmonella Typhimurium and Campylobacter jejuni were inoculated in scalding water, in chilled water, and on chicken skins to examine the effects of scalding temperature (50, 55, and 60 degrees C) and the chlorine level in chilled water (0, 10, 30, and 50 ppm), associated with the ages of scalding water (0 and 10 h) and chilled water (0 and 8 h), on bacterial survival or death. After scalding at 50 and 60 degrees C, the reductions of C. jejuni were 1.5 and 6.2 log CFU/ml in water and <1 and >2 log CFU/cm2 on chicken skins; the reductions of Salmonella Typhimurium were <0.5 and >5.5 log CFU/ml in water and <0.5 and >2 log CFU/cm2 on skins, respectively. The age of scalding water did not significantly (P > 0.05) affect bacterial heat sensitivity. However, the increase in the age of chilled water significantly (P < 0.05) reduced the chlorine effect. In 0-h chilled water. C. jejuni and Salmonella Typhimurium were reduced by 3.3 and 0.7 log CFU/ml, respectively, after treatment with 10 ppm of chlorine and became nondetectable with 30 and 50 ppm of chlorine. In 8-h chilled water, the reduction of C. jejuni and Salmonella Typhimurium was <0.5 log CFU/ml with 10 ppm of chlorine and ranged from 4 to 5.5 log CFU/ml with 50 ppm of chlorine. Chlorination of chilled water did not effectively reduce the bacteria attached on chicken skins. The D-values of Salmonella Typhimurium and C. jejuni were calculated for the prediction of their survival or death in the poultry scalding and chilling.