TABLE 1.

Effects of various organic acids (at 0.2 to 1.6%) on nonadapted and acid-adapted E. coli O157:H7 cells treated at 22°C for 5 min

Organic acid and concn (% [wt/wt])	pH (mean ± SD)a	Effect of organic acid on indicated bacteria (log CFU/ml) (mean ± SD)b
		Nonadapted cells	Acid-adapted cells
Acetic acid
0.2	3.02 ± 0.01 A	−0.03 ± 0.06 Aa	−0.01 ± 0.05 Aa
0.4	2.86 ± 0.02 B	−0.02 ± 0.07 Aa	−0.01 ± 0.02 Aa
0.8	2.70 ± 0.01 C	−0.01 ± 0.08 Aa	−0.01 ± 0.03 Aa
1.6	2.53 ± 0.02 E	−0.04 ± 0.08 Aa	0.00 ± 0.09 Aa
Citric acid
0.2	2.49 ± 0.02 E	0.01 ± 0.01 Aa	−0.01 ± 0.02 Aa
0.4	2.31 ± 0.01 F	0.03 ± 0.01 Aa	0.00 ± 0.02 Aa
0.8	2.13 ± 0.01 GH	0.01 ± 0.01 Aa	−0.03 ± 0.01Ab
1.6	1.97 ± 0.01 J	0.60 ± 0.08 Ba	0.01 ± 0.07 Ab
Lactic acid
0.2	2.63 ± 0.01 D	0.01 ± 0.03 Aa	−0.02 ± 0.01 Aa
0.4	2.48 ± 0.02 E	0.01 ± 0.01 Aa	0.00 ± 0.02 Aa
0.8	2.29 ± 0.01 F	0.02 ± 0.01 Aa	0.00 ± 0.04 Aa
1.6	2.12 ± 0.01 H	0.64 ± 0.02 Ba	0.29 ± 0.12 ABb
Malic acid
0.2	2.53 ± 0.01 E	0.02 ± 0.01 Aa	0.00 ± 0.04 Aa
0.4	2.35 ± 0.01 F	0.03 ± 0.01 Aa	0.01 ± 0.03 Aa
0.8	2.19 ± 0.01 G	0.03 ± 0.03 Aa	0.02 ± 0.03 Aa
1.6	2.04 ± 0.02 I	0.03 ± 0.03 Aa	0.04 ± 0.04 Aa
Phytic acid
0.2	1.86 ± 0.01 K	0.46 ± 0.28 Ba	0.03 ± 0.20 Aa
0.4	1.64 ± 0.01 L	2.68 ± 0.39 Ca	0.41 ± 0.35 Bb
0.8	1.49 ± 0.04 M	5.77 ± 0.08 Da	4.01 ± 0.09 Cb
1.6	1.29 ± 0.08 N	>6.13 ± 0.02 Ea	4.54 ± 0.21 Db

^aThe initial pH value was 6.59 ± 0.02. Values in this column denoted by different capital letters (A through N) are significantly different (P < 0.05).

^bThe initial nonadapted and acid-adapted E. coli O157:H7 populations were 7.13 ± 0.02 log CFU/ml and 7.02 ± 0.06 log CFU/ml, respectively. Values in the same column (A to E) or row (a and b) but denoted by different letters are significantly different (P < 0.05).