Death rates of L. monocytogenes at pH 3.5 after exposure to different types of stressing treatments for 90 min

TreatmentInitial shockDeath rate (h−1)aSDr2 (minimum-maximum)c
1No shock (control)1.810.140.976-0.980
2pH 4.0 at 30°C1.930.090.978-0.986
3pH 4.5 at 30°C1.750.160.988-0.990
4pH 5.0 at 30°C0.92*0.010.941-0.987
5pH 5.5 at 30°C0.81*0.080.938-0.978
6pH 6.0 at 30°C1.32*0.080.972-0.994
7pH 7.0 at 30°C1.790.180.982-0.986
8pH 5.5 at 15°C1.20*0.010.974-0.983
9pH 5.5 at 4°C1.510.160.992-0.996
10pH 5.5 + 10.5% NaCl at 30°C1.24*0.040.969-0.977
11Gradual decrease of pHb0.34*0.030.908-0.944
1210.5% NaCl at 30°C1.830.140.951-0.961
1320.5% NaCl at 30°C2.06*0.020.982-0.985
  • a Each number is a mean of four values. Values without an asterisk are not statistically different (P> 0.05) from values for nonshocked (control) cultures. An asterisk indicates that the value is statistically different (P < 0.05) from that for the nonshocked (control) culture.

  • b Cultures grown in TSB with 1% glucose at 30°C for 24 h.

  • c Correlation coefficient of data fit to the exponential model.