Survival of multidrug-resistant Salmonella typhimurium DT104 in egg powders as affected by water activity and temperature

A study was done to determine if a four-strain mixture of multidrug-resista nt Salmonella typhimurium definitive type 104 (DT104) cells and a four-stra in mixture of S. typhimurium non-DT104 cells differed in ability to survive in whole egg powder, whole egg powder supplemented with corn syrup solids (38%) and salt (1.9%), egg yolk powder, and egg white powder as affected by a(w) (0.29-0.37 and 0.51-0.61) during storage at 13 or 37 degrees C for 8 weeks. Rates of inactivation of S. typhimurium DT104 and non-DT104 cells we re similar within each set of test parameters. With the exception of whole egg powder supplemented with corn syrup solids and salt, death was enhanced at a(w) 0.29-0.37 compared to a(w) 0.51-0.61 when powders were stored at 1 3 degrees C. Survival of cells in whole egg powder supplemented with corn s yrup solids and salt was significantly (P less than or equal to 0.05) highe r compared to survival in other egg powders stored at 13 degrees C. The opp osite trend occurred in powders at a(w) 0.51-0.61 stored at 37 degrees C. S urvival of S. typhimurium DT104 and non-DT104 cells at initial populations of 5.01-5.39 log(10) cfu/g of egg white powder containing 4.9, 6.1, or 8.2% moisture at 54 or 82 degrees C for 7 days or 8 h: respectively, was determ ined. Rates of inactivation of DT104 and non-DT104 cells did not differ. Bo th cell types were detected in egg white powder containing 4.9% moisture bu t not in powder containing 8.2% moisture when held at 54 degrees C for 7 da ys. Heating at 82 degrees C for 8 h failed to eliminate 5 log(10) S. typhim urium per g of egg white powder, regardless of the moisture content. (C) 19 99 Elsevier Science B.V. All rights reserved.