TABLE 1.

Tolerance of stationary phase L. monocytogenes to organic acids and/or ethanol at pH 3 and 4

Acid	% Survivala
	pH 3		pH 4
	Without ethanol	With ethanol (5% vol/vol)	Without ethanol	With ethanol (5% vol/vol)
None	72 ± 1.2	0.89 ± 0.20	85 ± 22	44 ± 30
Citrate (50 mM)b	93 ± 4.6	0.15 ± 0.10	11 ± 5	0.29 ± 0.20
l-Ascorbate (50 mM)	31 ± 8	0.14 ± 0.02	0.76 ± 0.80	6.2 ± 3.4
Propionate (50 mM)	7.7 ± 3.6	0.004 ± 0.004	57 ± 28	7.7 ± 3.7
Acetate (50 mM)	5.7 ± 3.7	0.045 ± 0.038	63 ± 26	13 ± 11
dl-Lactate (50 mM)	0.27 ± 0.25	NSc	9.3 ± 3.8	1.0 ± 0.3
dl-Malate (50 mM)	0.015 ± 0.012	NS	0.35 ± 0.11	0.042 ± 0.028
Formate (50 mM)	NS	NS	0.13 ± 0.05	0.002 ± 0.001
Sorbate (10 MM)	0.36 ± 0.12	NS	5.9 ± 2.1	0.056 ± 0.041
Benzoate (10 mM)	NS	NS	0.040 ± 0.015	NS

^aSurvival is expressed as a percentage of the colony counts obtained at time zero. Values were determined after 20 min of exposure at pH 3.0 or after 1 h of exposure at pH 4. The data are means ± standard deviations for experiments performed at least in triplicate. The limit of detection was 250 CFU ml⁻¹. 

^bThe values in parentheses are the concentrations of undissociated acids at pH 3 or 4. The total concentration of acid added was different for each pH. 

^cNS, no survivors detected.