Food Protection Trends - November/December 2024 - 425

tion relative to the negative control used for reference (5.75
log CFU/cm2
; 95% CI: 5.61, 5.90). Compared with the
negative control, reductions of Salmonella were observed
for every treatment combination (P < 0.0001) except when
cleaning was used without a sanitizing method. No significant
difference (P > 0.05) was observed between cleaning by
wiping followed by bleach for 5 min and no cleaning followed
by bleach for 5 min.
Salmonella counts and reductions on bamboo basket
surfaces
No interaction between cleaning and sanitizing methods
was found for Salmonella counts on bamboo basket surfaces
(P = 0.9691); however, regardless of cleaning method,
sanitizing methods had different effects (P < 0.0001).
Table 3 presents estimates for log reductions in Salmonella
counts on bamboo basket surfaces by treatment relative
to the negative control (i.e., no sanitizing averaged across
cleaning methods; 5.37 log CFU/cm2
; 95% CI: 5.29, 5.45).
Compared with the control, a significant reduction in
Salmonella counts was observed for every sanitizing method
regardless of the cleaning method it was combined with.
The use of PAA for 5 min resulted in the largest reduction
(2.26 log CFU/cm2
for 5 min (1.46 log CFU/cm2
and bleach applied for 3 min also yielded a reduction in
Salmonella counts on bamboo basket surfaces, although the
reduction was less at 1.36 log CFU/cm2
and 1.14 log CFU/cm2 (95% CI: 0.83, 1.45), respectively.
Attachment of Salmonella on bamboo basket and banana
leaf surfaces determined by SEM
The attachment of Salmonella on banana leaf and bamboo
basket surfaces was visualized by SEM. Fig. 1A shows a typical
surface structure of a banana leaf, with stomata and wax
platelets distributed over the leaf surface. Wax platelets were
abundant and formed peaks and valleys, thereby creating air
pockets and increasing surface roughness. These structures
made it difficult to clearly observe the attachment of Salmonella
cells on banana leaf surfaces (Fig. 1B). Nevertheless, Salmonella
cells were observed with higher magnification (Fig. 1C).
Fig. 2A shows a typical bamboo basket surface under SEM,
revealing the roughness of the surface. Salmonella cells attached
strongly to the surface and formed lumps on the grooves
of bamboo epidermal cells (arrow in Fig. 2B and Fig. 2C),
although no Salmonella cells were observed around trichomes
or stomata.
DISCUSSION
In the present study, we investigated the attachment of
Salmonella cells to banana leaf and bamboo basket surfaces
and evaluated the efficacy of cleaning and sanitizing methods
for reducing Salmonella counts on these food-contact
surfaces commonly used in Cambodian fresh food markets.
On banana leaf surfaces, findings indicate that sanitizing
with PAA reduced Salmonella counts to below the detection
limit within 3 min of application. Beyond PAA, reduction of
Salmonella counts on banana leaf surfaces was dependent on
the combination of cleaning and sanitizing method used; the
most effective combination was wiping plus the use of bleach
for 5 min. Although applying bleach for at least 3 min was less
effective than the 5-min application, a 3-min application was
more effective than use of no sanitizing method, regardless of
cleaning method.
Wiping or scrubbing with cloths or a kitchen sponge are
common household practices used to physically remove food
residues from surfaces. In this study, traditional cleaning
methods alone (without sanitizing), such as wiping with
a dry paper towel or scrubbing with a dry kitchen sponge,
had no significant effect on Salmonella counts on banana
leaves or bamboo baskets. In contrast, Kusumaningrum et
al. (14) reported that wiping with a kitchen sponge reduced
Salmonella Enteritidis from initial levels of 5.8 ± 0.6 log
CFU/100 cm2
to <1.2 log CFU/100 cm2
on stainless steel,
; 95% CI: 1.98, 2.54), followed by bleach
; 95% CI: 1.15, 1.76). PAA
(95% CI: 1.08, 1.64)
achieving a ca. 4.5-log reduction. Sun-Young et al. (34)
found that wiping with a dry paper towel reduced E. coli
O157:H7 cells attached to wood cutting boards to 2.16 ±
1.09 log CFU/100 cm2
± 0.32 log CFU/100 cm2). Kim et al. (13) observed that
Vibrio parahaemolyticus counts were reduced to below
the detection limit (1 log CFU per unit area) from 3.58 ±
0.27 log CFU per unit area when the wood cutting boards
were wiped with a dry paper towel. Although these studies
indicated that cleaning may reduce pathogen presence, we
reconcile the apparent conflict with our results by noting that
our study used different, previously untested food-contact
surfaces. This inconsistency also may be explained by the
variation in the amount of pressure applied to dry paper
towels or kitchen sponges during cleaning, which was not
monitored in our study.
Our results indicate that a combination of cleaning
and sanitizing may be necessary to reduce microbial
contamination, particularly for banana leaves. In several
studies conducted on other food-contact surfaces such as
low-density polyethylene, Formica dining tables, and apple
packing equipment surfaces, the results were consistent
with ours; sanitizing efficacy was enhanced by the cleaning
method applied (17, 24, 25). Røssvoll et al. (24) found that
the efficacy of chlorine-based disinfection was improved to
a ca. 1- to 2-log reduction when combined with cleaning by
wiping with a water-moist cloth or brushing with running
water. Similarly, Masuku et al. (17) found that the effect
of sanitizing was significantly improved by the use of wipe
clothes combined with silver hydrogen citrate compared with
wiping with a cloth by itself. In another study of the efficacy
of cleaning and sanitizing methods against Listeria innocua
on apple packing equipment surfaces, the use of a degreaser
or detergent to clean rollers and conveyor belt followed by
November/December Food Protection Trends 425
, much lower than the control (3.31
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