Influence of Milk Components on the Injury, Repair of Injury, and Death of Salmonella anatum Cells Subjected to Freezing and Thawing

Abstract

Fast freezing and slow thawing Salmonella anatum cells in various milk components inactivated from 20 to 98% of the cells and damaged 40 to 90% of the cells surviving the treatments. Injured cells failed to form colonies on a selective medium (xylose-lysine-peptone agar with 0.2% sodium deoxycholate) but did form colonies on a nonselective plating medium (xylose-lysine-peptone agar). The major milk components—lactose, milk salts, casein, and whey proteins—influenced the extent of injury, repair of injury, and death. The percentages of cells injured and inactivated were decreased by the presence of any milk components except whey proteins. Also, repair of injury was promoted by the presence of each milk component except whey proteins, which in contrast inhibited repair. Phosphate was the most influential milk salts component that protected the cells and promoted repair of injury. These individual milk components may have decreased the extent of freezing-induced death and cellular damage by stabilizing the S. anatum cell envelope.

Repair of Heat-Injured Staphylococcus aureus 196 E on Food Substrates and Additives and at Different Temperatures

“…Wilson and Davis (12) observed repair of heat-injured Salmonella senftenberg in a broth system containing materials (at the 10% level) such as bone meal, whole egg and fresh egg albumen. Janssen and Busta (5) found that repair of freeze-injured Salmonella anatum was promoted by milk components. With freeze-injured Escherichia coli, Ray and Speck (7) observed some repair in egg and crab meat broth.…”