TABLE 5.
Survival of S. typhimurium SL1344(pACYC184) inoculated onto the surface of preacidified ground beef
| Ground beef acidificationa | pH on surface of beefb | % Survivalc |
|---|---|---|
| HCl | 1.0 | <0.01 |
| LB pH 2.5 (1 h) | 3.27 | 103.7 |
| LB pH 2.5 (16 h) | 2.61 | <0.01 |
a
Ground beef (0.1 g) was acidified by the direct addition of HCl or by being soaked in 10 ml of LB (pH 2.5) for the time indicated; it was then placed in 10 ml of fresh LB (pH 2.5) for 10 min.
b
The pH on the surface of the ground beef was determined immediately after the acidification treatment and before bacterial inoculation.
c
Acidified ground beef was inoculated with approximately 106 CFU of S. typhimurium and incubated for 2 h at room temperature. Surviving bacteria were enumerated by vigorous vortexing in 10 ml of PBS and are expressed as a percentage of the original inoculum exposed.