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Effects of dry acidulant coating of commercial pet food on Salmonella contamination
Salmonella is currently a concern in the pet food industry. One potential method of Salmonella mitigation is through the use of acidifiers to reduce pH to inhibit growth of bacteria. The objective of this experiment was to determine if coating pet food with a dry acidulant, sodium bisulfate (SBS, Jones-Hamilton, Co.,Waldridge, OH ), would reduce Salmonella growth over time in pet food of varying surface area, bulk density and piece density. A total of 10 commercial extruded pet foods were utilized in nested design with two food types: cat vs. dog, and three SBS concentrations within food type: 0, 0.6, or 0.8% SBS for cat and 0, 0.2, and 0.4% for dog foods. Samples were analyzed for surface area, bulk density, and piece density. Samples were dry inoculated with Salmonella cocktail on d 0 and analyzed for Salmonella counts on d 0, 1, 2, 7, and 14 by direct plating to Xylose Lysine Deoxycholate (XLD) agar. Piece density was correlated with Salmonella counts (P = 0.001, correlation coefficient = 0.47), but not bulk density or surface area (P = 0.16 and 0.68, respectively). Food type, SBS concentration, and time, as well as their interactions, all significantly impacted Salmonella counts (P < 0.05). Salmonella in the non-coated control decreased in both cat and dog food over the 14-d period (P < 0.05; 1.0 log reduction and 1.5 log reduction in cat and dog food, respectively). Coating pet foods with SBS further decreased (P < 0.05) Salmonella by d 1 through d 14, but the lowest tested concentration offered adequate reduction at most time points. In conclusion, piece density and time can influence Salmonellaquantity in extruded pet foods, and a moderate inclusion of a dry acidulant may further reduce contamination.
Table 1. |
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|
Cat food |
|
Dog food |
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SBS Concentration, %: |
0.0 |
0.6 |
0.8 |
|
0.0 |
0.2 |
0.4 |
Salmonella, log10 cfu/g |
|
|
|
|
|
|
|
d 0 |
4.43 |
4.41 |
4.29 |
|
4.84 |
4.93 |
4.95 |
d 1 |
3.73 |
3.22 |
3.16 |
|
3.56 |
3.64 |
3.61 |
d 2 |
3.01 |
2.56 |
2.63 |
|
3.64 |
2.67 |
2.51 |
d 7 |
3.21 |
1.88 |
1.38 |
|
3.20 |
2.22 |
2.05 |
d 14 |
3.47 |
1.31 |
1.01 |
|
3.36 |
2.09 |
1.92 |
Food type: P = 0.04, SEM = 0.125; Time: P < 0.0001, SEM = 0.115; SBS concentration (food type) P < 0.0001; SEM = 1.146. |
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Keywords: Salmonella, commercial pet food, sodium bisulfate