Food Protection Trends - September/October 2023 - 379

TABLE 1. Number of recovered cells on wood, nylon, and polycarbonate after exposure to
treatments lactic acid, SDC, UV-C light, and the simultaneous use of UV-C light
and a chemical sanitizer
Material
Interventiona
PAA control
Lactic acid
Thymol
SDC
Wood
UV-C
UV + lactic acid
UV + thymol
UV + SDC
PAA control
Lactic acid
Thymol
SDC
Nylon
UV-C
UV + lactic acid
UV + thymol
UV + SDC
PAA control
Lactic acid
Thymol
SDC
Polycarbonate
UV-C
UV + lactic acid
UV + thymol
UV + SDC
A
on wood, nylon, and polycarbonate, respectively.
Log CFU/cm2
after 2-min exposure
7.31 ± 0.64AB
8.09 ± 0.09A
7.87 ± 0.10A
7.86 ± 0.16A
8.70 ± 0.14A
7.94 ± 0.12A
8.18 ± 0.51A
7.91 ± 0.05A
4.83 ± 0.28A
7.05 ± 0.90B
7.84 ± 0.32B
6.83 ± 0.21B
9.45 ± 0.30C
6.94 ± 0.57B
6.89 ± 0.14B
6.83 ± 0.54D
3.98 ± 0.60A
5.62 ± 0.22B
4.10 ± 0.4A
4.55 ± 0.52A
6.75 ± 0.28C
5.64 ± 0.33B
4.57 ± 0.47A
3.81 ± 1.72A
Log CFU/cm2
after 5-min exposure
7.20 ± 0.52A
7.84 ± 0.18A
7.94 ± 0.06A
7.61 ± 0.18A
8.52 ± 0.13A
7.49 ± 0.41A
7.65 ± 0.10A
7.31 ± 0.58A
4.51 ± 0.22A
6.96 ± 0.55B
5.85 ± 1.56B
6.80 ± 1.25B
8.85 ± 1.03C
6.71 ± 0.44B
7.12 ± 0.77B
5.60 ± 0.53D
3.27 ± 0.87A
5.20 ± 0.35B
4.06 ± 1.08A
4.04 ± 0.42A
6.35 ± 0.77C
4.43 ± 0.40B
3.64 ± 0.24A
3.35 ± 1.53A
Two controls were included in this experiment: controls with untreated biofilms and PAA controls (see text for details). The
following counts were recovered on untreated coupons with mature biofilms after 96 h: 8.87 ± 0.13, 9.60 ± 0.32, and 7.68 ± 0.06 log
CFU/cm2
BUppercase letters compare individual and simultaneous treatments within the same material.
of wood, nylon, and polycarbonate were enumerated after 96
h, resulting in counts of 8.87 ± 0.13, 9.60 ± 0.32, and 7.68 ±
0.06 log CFU/cm2
, respectively. Table 1 shows the effects of
single and simultaneous sanitizer applications of lactic acid,
SDC, thymol, and UV-C light on experimentally inoculated
wood, nylon, and polycarbonate coupons.
Materials and sanitizers were the only interaction found
to be significant (P < 0.05; Table 2). This highlights that the
effectiveness of the sanitizer on mature biofilms is influenced
by the substrate material. Biofilms developed on wood were
found to be the most resistant to treatments compared with
those on nylon and polycarbonate, resulting in ≤ 1-log CFU/
cm2
reduction for all selected sanitizers at each application
time. As expected, the use of PAA was the most effective
among the single-treatment applications. Nevertheless, a
significant difference was only observed for nylon coupons
(P < 0.05). Even if in wood and polycarbonate the highest log
reduction was achieved with PAA, no statistical difference
was observed compared with the other treatments.
The sanitizers applied were highly effective on biofilms
grown on polycarbonate coupons, with reductions nearing
3.6 log CFU/cm2
. In Bang et al. (6), similar results were observed
wherein Escherichia coli O157:H7 biofilms were most
persistent on wood surfaces after treatments with NaOCl and
September/October Food Protection Trends 379
Food Protection Trends - September/October 2023

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