Evaluation of Liquid and Dry Chemical Treatments To Reduce Salmonella Typhimurium Contamination on Animal Food Manufacturing Surfaces

ABSTRACT

Salmonella can be isolated from animal food, ingredients, and animal food manufacturing surfaces. There are limited data regarding the sanitation of animal food manufacturing surfaces. This experiment evaluated the effects of nine chemical treatments on reduction of Salmonella Typhimurium contamination on various manufacturing surfaces. This experiment was a 9 × 5 factorial with nine chemical treatments and five surfaces. The nine chemical treatments included one with no inoculation or sanitation treatment (negative control). In the other eight treatments, inoculation with Salmonella Typhimurium was followed by either no sanitation treatment (positive control) or treatment with ground corn; liquid commercial formaldehyde; liquid food-grade sanitizer; liquid medium chain fatty acid blend of caprylic, caproic, and capric acids (MCFA); dry commercial calcium propionate; dry commercial acidulant; and dry commercial benzoic acid. The five surfaces included stainless steel, plastic, polypropylene tote bag, rubber belt, and rubber tire. Plastic had higher levels of Salmonella in the positive control than did the polypropylene tote bag; other surfaces had intermediate levels (P < 0.05). Surfaces treated with formaldehyde had no detectable Salmonella after treatment, and surfaces treated with MCFA had at least a 4-log reduction compared to the control (P < 0.05). The dry acidulant was the most effective dry sanitizer tested, but it had no impact on Salmonella concentration on rubber tires (P < 0.05). Whereas liquid sanitizers were the most effective in this experiment, they have limitations for use in dry bulk systems. In summary, formaldehyde, food-grade sanitizer, and MCFA were the most effective chemical treatments to reduce Salmonella surface contamination. Surface type can also influence Salmonella mitigation strategies; specifically, stainless steel and plastic can be more challenging to sanitize within animal food facilities.

HIGHLIGHTS

Research Note: 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 2 different dry 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. 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) a commercially available essential oil blend; or 3) rice hulls treated with a 10% concentration of a propriety blend of medium-chain fatty acids (MCFA). 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. 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 either feed (0.7 cfu/g for commercial essential oil blend) or surfaces (0.1 cfu/cm2 for MCFA) manufactured in sequence 1, but no residue was observed in sequence 2. These data suggest 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.