These results from Experiment 1 revealed that total bacterial count at 5 hours and 48 hours after spraying with lactic acid was significantly decreased (P < 0.05) when compared with initial bacterial count (Tables 1 and 2). As the concentration of lactic acid increased, the number of total bacterial count significantly decreased (P < 0.05). This result is the same trend observed in research by Prasai et al. (1992) which showed that mean aerobic plate count (log 10/cm2 ) of 1% lactic acid spray on surface of pork carcasses was lower than control. However, in most cases these reductions were not statistically significant.
| Table 1. Average bacterial count on the surface of pork carcasses sprayed with lactic acid or sodium hypochlorite solution. | |||
| Solution | Concentration | Total bacterial count (colony/g)
(Average of before, after spray with solution 5 or 48 hours) |
|
| Exp. 1 | Lactic acid (%v/v) | 1 | 3.92a |
| 2 | 3.72ab | ||
| 3 | 3.47b | ||
| Exp. 2 | Sodium hypochlorite (ppm) | 20 | 3.91a |
| 40 | 3.89a | ||
| 60 | 3.93a | ||
| abMeans with different superscripts, in different experiments, are significantly different (P < 0.05). | |||
| Table 2. Average bacterial count on the surface of hygienic and unhygienic pork carcasses sprayed with lactic acid or sodium hypochlorite solutions and stored. | ||||
| Exp. | Solution | Total bacterial count (colony/g) | ||
| Before spray | After spray 5 hours | After spray 48 hours | ||
| 1 | Lactic acid (Average of 1, 2 and 3 % v/v) |
4.10a | 3.52b | 3.47b |
| 2 | Sodium hypochlorite (Average of 20, 40, and 60 ppm) |
4.12a | 3.68b | 3.92ab |
| abMeans with different superscripts
within the same row, in different experiments are significantly
different (P < 0.05). |
||||
Experiment 2 results show that total bacterial count 5 hours after spraying with sodium hypochlorite was significantly decreased (P < 0.05) but not significantly different at the three different concentrations. Wei et al. (1985) reported that chlorine kills bacteria by reaction with membrane proteins, resulting in N-Chloro compound that interferes with cell metabolism. Furthermore, Marshall et al. (1977) reported that hypochlorite sprays (the rate of application of hypocholite was 200 to 250 mg/liter) reduce microbial counts significantly more than did water applied under the same conditions. However, the result from both experiments showed that pork carcasses slaughtered under unhygienic conditions had a significantly higher number of total bacterial count than hygienic conditions (Tables 3 and 4) (P < 0.01).
| Table 3. Average of means of bacterial count before spray, and after spray 5 and 48 hours from hygienic and unhygienic carcass surface. | ||
| Exp. | Average of total bacterial count (colony/g) for before and after spray 5 and 48 hours | |
| Hygienic | Unhygienic | |
| Exp. 1 Lactic acid | 3.37a | 4.03b |
| Exp. 2 Sodium hypochlorite | 3.42a | 4.40b |
| abMeans with different superscripts with in the same row, in different experiments, are significantly different (P < 0.01). | ||
| Table 4. Interaction between slaughtering processes and contact time on bacterial count of pork carcass surface in Experiments 1 and 2. | |||||
| Exp. | Slaughterhouse | Solution Concentration |
Total bacterial count (colony/g) | ||
| Before spray |
After spray 5 hours |
After spray 48 hours |
|||
| 1 | Lactic acid | ||||
| Hygienic | 1% (v/v) | 3.66 | 3.30 | 3.48 | |
| 2% (v/v) | 3.79 | 3.02 | 3.30 | ||
| 3% (v/v) | 2.58 | 2.80 | 2.99 | ||
| Unhygienic | 1% (v/v) | 4.41 | 4.50 | 3.72 | |
| 2% (v/v) | 4.65a | 3.83b | 3.71b | ||
| 3% (v/v) | 4.53a | 3.68b | 3.24b | ||
| 2 | Sodium hypochlorite | ||||
| Hygienic | 20 ppm | 3.50 | 3.48 | 3.47 | |
| 40 ppm | 4.04a | 2.91b | 3.16b | ||
| 60 ppm | 3.67 | 3.21 | 3.38 | ||
| Unhygienic | 20 ppm | 4.82a | 3.73b | 4.44a | |
| 40 ppm | 4.92 | 4.27 | 4.52 | ||
| 60 ppm | 4.30 | 4.48 | 4.57 | ||
| abMeans with different superscripts within the
same row, in different experiments, are significantly different
(P < 0.05). |
|||||