Behaviour of foodborne pathogens in cooked liver sausage containing lactates

Abstract

Previous reports from our laboratory showed sensitivity of Listeria monocytogenes to lactates in cooked pork liver sausage. Further studies were undertaken to explain the antilisterial effects and to examine the sensitivity of Escherichia coli O157:H7 and Salmonella typhimurium strains to lactates. To determine the effect of heat treatment on the antilisterial activity during storage at 5 and 20°C, 3% sodium or calcium lactate (NaL or CaL) were added to sausage emulsion, followed by (1) sterilization (121°C, 15 min); (2) processing in a water bath to internal temperature of 70°C; or (3) added to ready-to-eat sausage (no additional heat treatment). Inhibition of L. monocytogenes strain Scott A was highest after heat sterilization and storage at 5°C. Growth of S. typhimurium and E. coli O157:H7 was abated in sterilized sausage by 3% NaL and CaL. Changes in log cfu g−1 after 4 days at 20°C were (1) L. monocytogenes: control, 5·96; 3% NaL, −0·17; 3% CaL, −0·77; (2) E. coli: control, 4·01; NaL, 0·34; CaL, −0·06; (3) S. typhimurium: control, 3·92; NaL, 1·14; CaL, 0·92. While CaL was consistently more effective than NaL, examination of other calcium salts (carbonate, chloride, citrate and phosphate, dibasic) confirmed that lactate is the principal antibacterial factor.