FIGURE 4.
Effect of pressure and RTE meat microbiota on survival and post-pressure growth of L. monocytogenes and RTE meat microbiota on ham treated with 0.02 N HCl (solvent control) or an equivalent volume of a nisin preparation in 0.02 N HCl to achieve a concentration of 2 μg/cm2, corresponding to 0.05 μg/cm2 pure nisin. Shown are total cell counts (A) on non-selective agar and cell counts of L. monocytogenes (B) enumerated on selective PALCAM (B) agar. Samples were treated at 500 MPa for 1 or 3 min without (white) or with (gray) nisin. Cell counts ere enumerated immediately after pressure treatment (solid columns) and after storage for 4 weeks at 4°C (hatched columns). Data are shown as means ± standard deviations of triplicate independent experiments. Treatment means (solid columns) within each panel with different letters are significantly different (P < 0.05). The interception point of abscissa and ordinate represents the highest detection limit.