Evaluating the Roles of Surface Sanitation and Feed Sequencing on Mitigating Salmonella Enteritidis Contamination on Animal Food Manufacturing Equipment

The objective of this study was to evaluate the efficacy of flushing surfaces with untreated feed vs. the use of two different chemical sanitizers on residual surface and feed Salmonella Enteritidis contamination. First, a Salmonella-negative batch of poultry feed was mixed in 9 laboratory-scale paddle mixers. A feed sample was collected, and targeted locations on surfaces within the mixer were swabbed to confirm Salmonella-negative status. Next, a Salmonella-positive batch of poultry feed was mixed, sampled, and mixer surfaces swabbed. Mean Salmonella Enteritidis contamination across all 9 mixers were 3.63 CFU/g for sampled feed and 1.27 CFU/cm² for surface contamination. Next, the mixers manufactured one of the following treatments (3 mixers/treatment): 1) none (control); 2) concentrated commercial product containing a eubiotic blend of essential oils (benzoic acid and blend of essential oils: thymol, eugenol, piperine and other essential oil compounds); or 3) rice hulls treated with a 10% wt/wt addition of a medium chain fatty acid (MCFA; 1:1:1 blend of caprylic, caproic, and capric acids). Each treatment was previously weighed and manufactured prior to inoculation of Salmonella. After each treatment, each mixer manufactured another 2 batches of Salmonella-free feed (Sequence 1 and Sequence 2). Feed samples were collected, and surfaces were swabbed between each batch of feed. Mixers were not physically cleaned after each sequence, only feed discharged from the mixers. Manufacturing sequence (P < 0.0001), but not treatment (P > 0.05) impacted feed or surface contamination of Salmonella Enteritidis. There was Salmonella-positive residue in the batch of feed manufactured immediately after the positive control batch. However, no Salmonella residue was detected in batches of feed treated with either the commercial essential oil blend or MCFA. Low levels of Salmonella residue were observed from feed (0.7 cfu/g for commercial essential oil blend) and surfaces (0.1 cfu/cm² for MCFA) manufactured in Sequence 1, but no residue was observed by Sequence 2. This data suggests that sequencing of feed during manufacturing reduces Salmonella-positive contamination within animal food and on manufacturing surfaces, particularly after the second batch or with the use of chemical treatments.