Inhibition of Salmonella spp. in Raw Pet Food Using Log10® Pre-LiminateTM Probiotic Blends


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Commercially available raw ground turkey pet food was inoculated with Salmonella spp. and treated with wet Pre-Liminate™ Formula W41 containing probiotic organisms selected for competitive inhibition and analyzed for Salmonella using BAM Chapter 5 methodology. All products were stored in their original packaging at refrigerated temperature (4°C) for the duration of the study. This study is an initial step in demonstrating the ability of probiotics in reducing and eliminating Salmonella in raw and minimally processed pet food held under refrigerated conditions. Results show probiotics can be an effective control of pathogens in raw pet foods at refrigerated temperatures; for maximum effectiveness, probiotics should be incorporated into the process as early as possible.


The study consisted of two sets of raw ground turkey pet food. Both sets were inoculated with a Salmonella cocktail at a level of 9.5 x 102 CFU/g. One set was treated with Pre-Liminate™ pro-biotics at a level of 2.3 x 107 CFU/g and one set was left untreated. All samples were held at refrigerated temperatures (4oC) and plated on agar for enumeration of Salmonella (BAM Chapter 5: Salmonella methodology) and on MRSA agar for enumeration of pro-biotics (Internal Log10® method; TEM-LB-06 Enumeration of Probiotics). Plates were analyzed every 3 days over a 30 day period. Upon initial analysis, re-duction in Salmonella levels was observed as early as day 3. Salmonella levels continued to decrease with each subsequent analysis, until day 21 when a complete elimination of Salmonella spp. was noted (see Figure 1). In comparison, Salmonella levels in the untreated samples remained constant (see Table 1). These results demonstrate that probiotics can reduce and eliminate Salmonella in raw pet food even when held at refrigerated temperatures, but for maximum effectiveness would need to be incorporated into the product process as early as possible.


Table 1.  Raw Ground Turkey Pet Food Inoculated With Salmonella spp. & With and Without Probiotics, stored at 4°C
Gr. Pet Food + Salmonella Day 0 9.5E+02 9.8E+02
Gr. Pet Food + Salmonella Day 3 7.0E+02 9.6E+02
Gr. Pet Food + Salmonella Day 6 6.2E+02 9.5E+02
Gr. Pet Food + Salmonella Day 9 4.5E+02 9.1E+02
Gr. Pet Food + Salmonella Day 12 1.6E+02 9.6E+02
Gr. Pet Food + Salmonella Day 15 2.8E+01 1.0E+02
Gr. Pet Food + Salmonella Day 18 3.0E+00 9.4E+02
Gr. Pet Food + Salmonella Day 21 <10 1.0E+03
Gr. Pet Food + Salmonella Day 24 <10 8.9E+02
Gr. Pet Food + Salmonella Day 27 <10 1.0E+03
Gr. Pet Food + Salmonella Day 30 <10 9.0E+02


Probiotic Stability

Storage data for probiotic inoculated raw ground turkey pet food, held at refrigerated temperature (4oC), indicated that the probiotic levels remained relatively stable (107 CFU/g) over the entire 30-day study. Further research is ongoing to determine the length of time probiotic viability can be maintained. Additionally, it is important to note other studies conducted by Log10® show these probiotic strains have maintained levels at or near inoculated concentrations in dry pet food, dry meal and other matrices stored at room temperature for greater than 120 days.

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