Biology subjects

Slaughter, C.

Publications and source records attributed to Slaughter, C..

3 recordsLinked to original sources

bioRxiv2026

Variable fluid mechanics explain why static efficacy tests overestimate sanitizer performance against Listeria

Pathogen cross-contamination during food production is primarily controlled through environmental sanitation. However, sanitizer efficacy is often studied in bench-scale experiments that poorly approximate the fluid dynamics of sanitization and limits our understanding of commercial sanitization efficacy. This study paired computational fluid dynamics (CFD) estimates of shear stress with experimental measurements of Listeria innocua reduction on stainless steel following treatment with 100 ppm hypochlorite sanitizer. At the pilot-scale, sanitizer spray manually applied by researchers achieved a 2.6 {+/-} 0.4 log CFU/surface reduction; however, microbial reduction from manual operation of sanitizer spray equipment differed significantly between researchers (p < 0.05). Microbial reduction varied by location following stationary, bench-scale spray application of sanitizer for 3 s. The greatest reduction was at the point of sanitizer spray impingement (7.5 {+/-} 0.5 log CFU/surface) and directly adjacent to the impingement point (6.4 {+/-} 0.7 log CFU/surface) where shear stress was the highest. Significantly less microbial reduction (0.4 {+/-} 0.1 log CFU/surface) occurred where shear stress was lowest in the fluid-film of sanitizer running down from the impingement point (p < 0.05). Static submersion of inoculated coupons in sanitizer for 3 s resulted in a log reduction of 2.3 {+/-} 0.1 log CFU/surface. Discrepancies between bench-scale spraying, pilot-scale spraying, and submerged coupons demonstrate the need for sanitizer efficacy testing under realistic conditions to better estimate the risk reduction achieved through sanitation programs. IMPORTANCESanitation is critical for controlling pathogen cross-contamination during food production. These findings highlight the limitations of traditional approaches to sanitizer efficacy testing, not because they are invalid, but because they do not reflect the level of microbial reduction typically achieved in application. We demonstrate that these differences in outcomes are attributable to fluid dynamics and exposure, which are not well approximated in submerged coupon experiments. Accurate estimation of microbial reduction from sanitizer application is needed to guide food safety policy decisions. For example, overestimation of the risk reduction conferred by sanitizer treatment may result in food safety policies that neglect other sources of microbial reduction within sanitation programs.

microbiology↗

bioRxiv2025

Moisture Matters: Unintended Consequences of Performing Wet Sanitation in Dry Environments.

Cross-contamination of low-moisture foods (LMFs) with pathogens from equipment and environmental surfaces during production is a food safety concern. Wet sanitation is sometimes employed to mitigate cross-contamination in LMF facilities, but the introduction of moisture to otherwise dry environments can inadvertently promote pathogen growth. This study evaluated the risks associated with wet sanitation in LMF facilities by characterizing evaporation kinetics on powdered infant formula (PIF)-soiled surfaces, monitoring relative humidity (RH) in a LMF facility during and after wet sanitation, and assessing growth of Salmonella, Listeria monocytogenes, Cronobacter sakazakii, and Enterococcus faecium spot inoculated on PIF-soiled stainless steel coupons under dynamic RH conditions. As expected, higher RH slowed drying of PIF-soiled surfaces, prolonging periods when the soils water activity (aw) was high enough to support microbial growth. Correspondingly, all four organisms grew significantly at 81 and 97% RH over 120 h (p<0.05), while only E. faecium grew significantly below 81% RH (p<0.05). Monitoring of RH during and after wet sanitation in a commercial facility revealed spikes up to 100% RH during sanitation and sustained RH above 75% for more than 7 h in poorly ventilated areas. When those facility RH conditions were simulated in the laboratory, Salmonella populations on PIF-soiled coupons increased by more than 3.5 Log CFU/coupon within 66 h. These findings demonstrate the potential for wet sanitation to unintentionally enable environmental pathogen growth and highlight the importance of moisture and RH control in LMF facilities. ImportanceWet sanitation is commonly employed by LMF manufacturers for allergen changeovers and to prevent cross-contamination from surfaces, but regulators, manufacturers, and researchers have all expressed concerns that wet sanitation may promote the growth of pathogens in otherwise dry production environments. Despite these concerns, research on the impact of wet sanitation on facility RH and its influence on microbial proliferation in low moisture production environments remains limited. This study provides evidence that wet sanitation substantially increases facility RH, leading to persistent hydration of soiled surfaces, creating conditions that enable microbial growth. These findings reinforce concerns over the use of wet sanitation in LMF production. This also demonstrates the need for reducing water use in LMF production facilities, implementing RH control strategies, as well as the adoption of alternative or supplemental dry sanitation strategies to mitigate microbial risks.

microbiology↗

bioRxiv2025

Reduction of Listeria on stainless steel surfaces is impacted by sanitizer application method

Pathogen cross-contamination during food production is controlled through sanitation. However, sanitizer efficacy is often studied in bench-scale experiments (e.g., submerged coupons in static or stirred sanitizer) which poorly approximate fluid dynamics. This limits our understanding of how effective sanitization is in commercial application. This study paired computational fluid dynamic (CFD) estimates of shear stress during spray application of sanitizer with measurements of Listeria innocua reduction on stainless steel by 100 ppm hypochlorite sanitizer under various application methods. Static submersion of inoculated coupons for 3 s resulted in a log reduction of 2.3 {+/-} 0.1 log CFU. Bench-scale spray application for 3 s had the largest microbial reduction at the point of sanitizer spray impingement (7.5 {+/-} 0.5 log CFU) and directly adjacent to the impingement point (6.4 {+/-} 0.7 log CFU) where shear stress was the highest. Surface locations below the impingement point that only received fluid film sanitizer run-off had a significantly lower microbial reduction of 0.4 {+/-} 0.1 log CFU (p < 0.05). At the pilot scale, sanitizer spray manually applied by operators achieved a 2.5 {+/-} 0.4 log CFU reduction, which was significantly lower than what was achieved during bench-scale spray application (p < 0.05). Microbial reduction from manual operation of spray equipment was also significantly different among operators (p < 0.05). Discrepancies between bench-scale spraying, pilot-scale spraying, and submerged coupons underscores the need for sanitizer validation under realistic conditions to better understand the risk reduction achieved through sanitation programs during food processing.

microbiology↗