Inactivation of E. coli by high hydrostatic pressure (250 to 400 MPa) with salts was investigated based on kinetic analysis. At concentrations from 0.074 to 0.145 M and from 0.240 to 0.290 M, both the absolute activation volumes and the preexponential factors were similar in KCl, NaCl, and LiCl solutions, suggesting that pressure inactivation is not salt-specific. On the other hand, in the intermediate salt-concentration range of 0.145 to 0.240 M, inactivation kinetics in the presence of the Na(+) and K(+) differed significantly from those in the presence of Li(+) (P < 0.05). In this concentration range, effect of salt stress and osmotic stress differed significantly from those in concentrations below 0.145 M or above 0.240 M. The cellular response to pressure varies with salt type and salt concentration. These novel findings provide important clues to distinguish between salt stress and osmotic stress in the inactivation of E. coli.

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