Effect of polyphosphate and sodium chloride on the growth of Listeria monocytogenes and Staphylococcus aureus in ultra-high temperature milk.

With UHT-sterilized milk as a model system, combinations of polyphosphate (.5 and 1.0%) and NaCl (.5 and 4.5%) were studied to determine their effects on the growth kinetics of Listeria monocytogenes Scott A and Staphylococcus aureus 196E. The milk was inoculated with 10(3) to 10(4) cfu/ml of either L. monocytogenes or S. aureus and incubated under aerobic conditions at 12, 19, 28, or 37 degrees C. The addition of polyphosphate did not significantly inhibit the growth of either microbe at the temperatures studied, but the addition of NaCl or a combination of salts significantly inhibited growth. The addition of .5 or 1.0% polyphosphate alone to dairy products is not likely to affect substantially the growth of S. aureus or L. monocytogenes.