Abstract
The effects of pH, the major food ingredients sodium chloride, sucrose, protein and organic acids on Escherichia coli inactivation by hydrostatic pressure treatment with the addition of allyl isothiocyanate (AIT) were investigated. E. coli JCM 1649 and CR-3, the latter of which was O157:H7, were increasingly inactivated by pressurization at pHs lower or higher than neutral. That is, both strains were completely inactivated by pressure treatment: JCM 1649 at 200 MPa and CR-3 at 300 MPa, at pH 4.5 or 8 when %80 μg/ml of AIT was added, although at other pHs they survived under the same pressure and AIT condition. Sucrose or protein decreased inactivation of E. coli JCM 1649 in pressure treatment combined with AIT, and the presence of 1% or more did not change the number of bacterial cells inactivated, regardless of the AIT concentration. The presence of 3% or more of sodium chloride also decreased inactivation but a lower concentration, i.e., 1% or so, enhanced the inactivation of the bacterium. Lowering pH by adding 0.01% of the organic acids succinic or malic acid was effective in combined treatment-induced inactivation. These findings suggested that some food ingredients, for example, a small amount of sodium chloride and organic acids, might enhance inactivation in pressure treatment combined with AIT, and that this combination was effective in practical application.
