Interaction of Salt, p H, and Temperature on the Growth and Survival of Salmonellae in Ground Pork

Abstract

The interaction of temperature, p H, and NaCl concentration on the growth and survival of several strains of salmonellae has been determined in broth and ground pork. Growth of 23 strains occurred in broth at 30 C over a wide range of p H-NaCl combinations; at 10 C, growth was limited to only a few combinations. Cultures which would not grow at 10 C because of the p H-NaCl effect survived for long periods, however. In contrast, cultures which would not grow at 30 C remained viable for only a short time. Results in fresh ground pork were in close agreement with the broth studies. Salmonellae would not grow in ground pork stored at 4 C but would grow in pork containing 3.5% salt stored at 10 C. Salmonellae grew competitively with the natural background flora at 10 C even when the salmonellae constituted less than 5% of the initial flora, and the background flora would grow at a lower temperature than the salmonellae. The data show that, whereas decreasing temperatures increase the inhibitory effects of p H and NaCl, they decrease the lethal effects.