Destruction of Enteric Bacteria in Liquid Egg with β-Propiolactone

Abstract

Liquid whole egg or egg white, inoculated with Escherichia coli 1485, Salmonella senftenberg ATCC 8400, or Salmonella typhimurium 84-I, was treated with concentrations of beta-propiolactone ranging from 0.05 to 0.3%. Egg white containing 1 x 10(3) to 1 x 10(6) cells of E. coli 1485 per ml was sterilized in 1 hr at 27 C by lactone concentrations of 0.2 and 0.3%. Egg white containing 1 x 10(5) cells of S. senftenberg ATCC 8400 per ml was sterilized in 12 hr at 10 C by 0.1% lactone and in 2 to 3 hr by 0.3% lactone at the same temperature. Liquid whole egg inoculated with 1 x 10(5) cells of either species of Salmonella was sterilized in 4 to 5 hr at 10 C with 0.2% lactone or in 2 to 3 hr by 0.3% lactone at this temperature. A mild heat treatment of either 15 min at 37 C or 1 min at 55 C markedly shortened the exposure times required for sterilization by beta-propiolactone at 10 C. After disinfection was complete, the lactone-treated liquid whole egg was reinoculated with low cell numbers of either species of Salmonella to determine the presence of residual lactone or toxic products. Liquid whole egg treated with 0.2% lactone would support the growth of salmonellae after 13 to 14 hr at 10 C. A heat treatment of 45 min at 37 C or 10 min at 55 C immediately after addition of 0.2% lactone allowed growth of the salmonellae in the lactone-treated liquid whole egg. No evidence of residual toxicity from the lactone treatment was found. The amount of lactone needed to prevent the outgrowth of low cell numbers of either strain of Salmonella in liquid whole egg was quantitated. Liquid whole egg containing 0.06 to 0.07% lactone would not support salmonellae growth from inocula of 1 to 10 cells per ml of egg. Lactone concentrations above 0.08% prevented outgrowth of salmonellae inocula of 10 to 200 cells per ml of liquid whole egg.