COMPARATIVE GROWTH OF SALMONELLAE, COLIFORMS, AND OTHER MEMBERS OF THE MICROFLORA OF RAW AND RADURIZED GROUND BEEF1

Abstract

The population of salmonellae in raw ground beef at 5 C was stable during 6 days while that of the total microflora increased markedly. Radurization reduced the numbers of salmonellae and of the total population. The buildup of numbers also was retarded by radurization so that the total count was < 106 per gram after 6 days while the number of salmonellae remained constant. Ground beef incubated at 25 C showed a rapid increase in numbers of salmonellae, coliforms, and in the total microflora. While radurization reduced the numbers of these microorganisms, it did change the general pattern of competitive growth. Highly contaminated samples contained some coliforms able to grow at 5 C. Unirradiated samples as well as samples immediately following irradiation showed the coliforms to consist predominately of Escherichia coli, but during storage there was an increase in the proportion of intermediate types and of Aerobacter.