Heat Resistance and Growth of Listeria monocytogenes in Liquid Whole Egg .

Listeria monocytogenes F5069, ATCC 19111, Scott A, and two L. monocytogenes strains isolated from egg were evaluated for growth and thermal resistance in liquid whole egg. Each strain grew in liquid whole egg at temperatures between 4 and 30°C, except Scott A which did not grow at 4 or 10°C. Generation times ranged from 24 h for F5069 to 51 h for ATCC 19111 at 4°C and from 7.8 h for one of the egg isolates to 31 h for ATCC 19111 at 10°C. Maximum populations for each strain increased with increasing growth temperature and were between 10 and 3 × 10 CFU/g. Decimal reduction times (D-values) of each L. monocytogenes strain in raw liquid whole egg were similar to D-values reported in milk. The heat resistance of all strains was similar. For L. monocytogenes F5069, D-values ranged from 22.6 min at 51°C to 0.20 min at 66°C. The z-value for F5069 was 7.2°C. Minimal pasteurization parameters (60°C, 3.5 min) for liquid whole egg would result in 99 to 99.9% inactivation (populations reduced 2 to 3 log cycles) of the L. monocytogenes strains tested.