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Floor drains in processing environments harbor Listeria spp. due to continuous presence of humidity and organic substrates. Cleaning and washing activities in food-processing facilities can translocate the bacterial cells from the drain to the surrounding environment, thus contaminating food products still in production. This study evaluated the potential for translocation of Listeria monocytogenes from drains to food contact surfaces in the surrounding environment using Listeria innocua as a surrogate. A 7 × 7 × 8-foot polycarbonate flexi-glass chamber with a 10-inch-diameter drain mounted on an aluminum cabinet was used. Stainless steel coupons (6.4 × 1.9 × 0.1 cm, 12 per height) were hung at 1, 3, and 5 feet inside the chamber. Four treatment sets; non-inoculated, non-treated; non-inoculated, treated; inoculated, treated; inoculated non-treated; and two subtreatments of 8 h and 48 h were performed. For the inoculated sets, meat slurry (10 gof ground beef in 900 mL water) and a four-strain cocktail of Listeria innocua at 7 - 8 log CFU/mL were used. For the treated sets, in addition, a commercial cleaner and sanitizer was applied. The drain was cleaned using a pressure hose (40 - 50 psi) after 8 h and 48 h. Coupons were then removed and enriched in listeria enrichment broth to establish if any cell translocated from the drain onto the stainless steel coupons via aerosols generated during washing. Confirmation was done using VIP Listeria rapid test kits. Results indicated translocation at all three heights ranging from 2% - 25%. Significantly higher translocation (p < 0.05) was found at 1 foot (up to 25%), followed by 3 feet (up to 11%) and 5 feet (up to 2.7%). This research indicated that translocation of Listeria spp. from drains to food contact surfaces does occur and increases with increased proximity to the drain.
Commercially processed foods become contaminated with Listeria monocytogenes in
post-processing environments where favorable conditions help the bacteria
thrive. The US Food and Drug Administration has approved Lauric arginate
(LAE) as generally recognized as safe (GRAS) for certain food applications.
This study evaluated the efficacy of Mirenat-N (LAE dissolved in food-grade
propylene glycol) against L.
monocytogenes on food contact surfaces. A three-strain cocktail of L. monocytogenes was used to inoculate
24 polished stainless steel coupons with three treatments, 100 ppm and
200 ppm solutions of LAE and water (control); two sub-treatments of high (6 log
CFU/ml) and low (4 log CFU/ml) inoculum levels; and two contact times of 5 and
15 min. Attached bacteria were dislodged by vortexing coupons for 1 min with 20 g of 3-mm solid glass beads in 10 ml of
0.1% peptone diluent, and bacterial populations were calculated by plating onto
modified oxford medium (MOX) and thin agar layer MOX (TALMOX). The 100 ppm
treatment showed average reductions of 1.38 and 2.57 log CFU/coupon at the low
inoculum level and 0.37 and 0.62 log CFU/coupon
at high inoculum levels, after 5 and 15 min exposure, respectively. For 200 ppm
at the high inoculum level, 1.23 and 1.88 log CFU/coupon reductions were
seen for 5 and 15 min, respectively; the low inoculum level at 5 and 15 min
exposure showed reductions of ≤1.5 log CFU/coupon. The 100 ppm LAE
treatment was more effective at low inoculum levels for 5 and 15 min contact times
and may be used to control low levels of contamination of L. monocytogenes on food contact surfaces.
Principal component transformation is a standard technique for multi-dimensional data analysis. The purpose of the present article is to elucidate the procedure for interpreting PC images. The discussion focuses on logically explaining how the negative/positive PC eigenvectors (loadings) in combination with strong reflection/absorption spectral behavior at different pixels affect the DN values in the output PC images. It is an explanatory article so that fuller potential of the PCT applications can be realized.