Survival of Salmonellae in Refrigerated, Agitated Water and Water/Glycol Mixtures

Abstract

Survival of Salmonella typhimurium in refrigerated water and a 30:70 mixture of ethylene glycol and water was studied. Survival was determined with an MPN procedure using 333 ml of the cooling medium. Initial populations were determined by spread plating 1 ml of sample on 3 plates of XLD. With water as the suspending medium, the temperature of the circulating water was 1°C. When the cooling medium was the glycol/water mixture, the temperature was −1°C. Low numbers of S. typhimurium were recovered from the cold water for 9 d and from the glycol/water mixture for 14 d. The initial population in the water was 310 CFU/ml and 630 CFU/ml in the glycol/water system. A preliminary survey of the pressure relationships in the cooling sections of HTST pasteurizers in 8 fluid milk plants showed that 3 had higher pressures on the coolant side than on the pasteurized side. Such a pressure relationship could result in the contamination of pasteurized milk with the cooling medium.