Combined water activity and solute effects on growth and survival of Listeria monocytogenes Scott A

Abstract

Water activity and solute effects were determined on the growth and survival of Listeria monocytogenes Scott A in bacteriological media. Media were adjusted to water activity (aw) levels of 0.99-0.80 with NaCl, glycerol (GLY), or propylene glycol (PG). Minimum aw levels for growth occurred at 0.90, 0.92, and 0.97 for GLY, NaCl, and PG, respectively. Survival was related to the aw level, as well as the solute employed. Cells survived the longest in GLY and died earliest in PG; NaCl was intermediate. These results provide quantitative isothermal criteria for estimating the aw level necessary to prevent growth of L. monocytogenes in food.