Ohio State University Extension Bulletin

Research and Reviews: Meat 2001

Special Circular 183-02

Lactic acid and Chlorine Solutions Inhibition of Staphylococcus aureus and Salmonella derby

Results and Discussion

The results indicate that the number of Salmonella derby decrease as the concentration of lactic acid increased and the maximum decrease was at 3% (v/v) (Table 1). Staphylococcus aureus was significantly inhibited by lactic acid solution but no significance differences were found for concentration of 1, 2, and 3% (v/v). The effect of contact time for lactic acid decreased the number of Salmonella derby and Staphylococcus aureus with longer contact time significant at 24 and 48 hours (Table 2). These results are supported by Syed-Ziauddin et al. (1993), and they reported that lactic acid at 1 and 2% completely inhibited growth of S. faecalis, S. aureus, P. fragi, S. newport, E.coli, and B. cereus.

Table 1. Efficiency of lactic acid in Experiment 1 and sodium hypochlorite in Experiment 2 in reducing the level of Salmonella derby or Staphylococcus aureus.

Solution Concentration Bacterial count (log CFU/ml.)
(Average of storage times)

Salmonella derby Staphylococcus aureus

Exp.1 Lactic acid
%(v/v) 0 8.00^a 8.45^a

1 6.96^b 8.16^b

2 4.91^c 8.10^b

3 ND^d 8.01^b

Exp.2 Sodium Hypochlorite (ppm) 0 8.12^a 8.50^a

20 8.03^b 8.56^a

40 7.88^b 8.57^a

60 7.89^b 8.58^a

^abcMeans with different superscripts within the same column, in different experiments, are significantly different (P < 0.01).
^dND = non-detected (too low to count).

Table 2. Effect of contact time of lactic acid solution mixed with a culture of Salmonella derby or Staphylococcus aureus.

Contact time (hours) Bacterial count (log CFU/ml.)
(Average for all concentrations)

(After mixing) Salmonella derby Staphylococcus aureus

0 5.88^a 8.42^a

1 5.68^a 8.27^a

2 5.69^a 8.23^a

3 5.58^a 8.30^a

4 5.67^a 8.17^a

5 5.36^a 8.26^a

24 3.69^b 7.94^b

48 1.96^b 7.85^b

^ab Means with different superscripts with in the same column are significantly different (P < 0.01).

Sodium hypochlorite solution showed a significant decrease only on the number of Salmonella derby (Table 1). No significant different was found with Staphylococcus aureus (Table 3). Time of application had no effect on the number of Salmonella derby or Staphylococcus aureus. This study show the same trend as Bailey et al. (1986) who reported when 100 cells of salmonella/cm²were inoculated in a thin layer on chicken, the Salmonella count was reduced about 90% with 20 ppm chlorine and 96% with 40 ppm of sodium hypochlorite.

Table 3. Effect of contact time of sodium hypochlorite solution mixed with a culture of Salmonella derby and Staphylococcus aureus.

Contact time (hours) Bacterial count (log CFU/ml.)
(Average for all concentrations)

(After mixing) Salmonella derby Staphylococcus aureus

0 8.14^a 8.51^a

1 8.12^a 8.53^a

2 8.03^a 8.61^a

3 8.08^a 8.55^a

4 8.05^a 8.46^a

5 7.96^a 8.60^a

24 7.80^b 7.50^a

48 7.46^c 7.61^a

^abcMeans with different superscripts within the same column are significantly different (P < 0.01).

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*Table 1. Efficiency of lactic acid in Experiment 1 and sodium hypochlorite in Experiment 2 in reducing the level of Salmonella derby* or Staphylococcus aureus.**
	Solution	Concentration	Bacterial count (log CFU/ml.) (Average of storage times)
	Solution	Concentration	*Salmonella derby*	*Staphylococcus aureus*
Exp.1	Lactic acid %(v/v)	0	8.00^a	8.45^a
		1	6.96^b	8.16^b
		2	4.91^c	8.10^b
		3	ND^d	8.01^b
Exp.2	Sodium Hypochlorite (ppm)	0	8.12^a	8.50^a
		20	8.03^b	8.56^a
		40	7.88^b	8.57^a
		60	7.89^b	8.58^a
^abcMeans with different superscripts within the same column, in different experiments, are significantly different (P < 0.01). ^dND = non-detected (too low to count).

*Table 2. Effect of contact time of lactic acid solution mixed with a culture of Salmonella derby* or Staphylococcus aureus.**
Contact time (hours)	Bacterial count (log CFU/ml.) (Average for all concentrations)
(After mixing)	*Salmonella derby*	Staphylococcus aureus
0	5.88^a	8.42^a
1	5.68^a	8.27^a
2	5.69^a	8.23^a
3	5.58^a	8.30^a
4	5.67^a	8.17^a
5	5.36^a	8.26^a
24	3.69^b	7.94^b
48	1.96^b	7.85^b
^ab Means with different superscripts with in the same column are significantly different (P < 0.01).