Heat-resistant bacteria in pasteurized whole egg.

Samples of egg melange taken from an egg packing station contained an average of 7·3 x 104 organisms/ml which survived laboratory pasteurization at 65°C for 3 min. Many of the organisms surviving pasteurization were found to be coryneform bacteria related to Microbacterium lacticum which could be differentiated into several groups. The remainder were a miscellaneous collection of unidentified cocci and coccobacilli and some Bacillus spp. The coryneform bacteria were shown to be the most heat-resistant isolates with negligible loss of viability after 60 min at 65°C, At least two of the representative strains were very heat-resistant, 0·01% surviving 20 and 38 min at 80°C in phosphate buffer at pH 7·1. Growth tests showed that none of the isolates grew at 5°C after 10 d incubation but those capable of growing most rapidly at 10° and 15°C were also the most heat-resistant. Such strains had a doubling time at 15°C of between 6 and 8 h in whole egg. Freezing the coryneform bacteria in liquid whole egg at –18°C had negligible effect on viability or heat-resistance at 65°C.