Food Protection Trends - November/December 2023 - 474

rate was set to 3 liters/min per equipment design and
delivered from a hose with a 3/8-in. (9.525 mm) diameter.
Three concentrations of ozone were used: 2.5, 5.0, and
10 ppm. The ozone levels were monitored and displayed
by a Q46H-64 Dissolved Ozone Monitor (Analytical
Technologies Industries, Collegeville, PA), which was
integrated into the aqueous ozone system. In addition,
ozone concentration was corroborated with a CHEMets
ozone measuring kit (K-7404; CHEMetrics, Midlands,
VA). Two treatment configurations were tested. For the
first set of experiments, or immersion treatment, ozonated
water was used to fill a covered stainless steel container
(4.5 qt [4.25 liters]; Syscoware, Houston, TX). Chicken
wing sections were immersed in the ozonated water for 15,
30, or 45 s. These times were chosen based on industry
input to simulate realistic product postchill interventions.
The container was kept covered to decrease the loss of
ozone into the atmosphere, and the flow of ozonated water
was kept constant to avoid depleting the ozone inside
the container. Three wing sections (51.3 ± 12.4 g each)
were individually treated for each of the time and ozone
concentration combinations. The used ozonated water
was discarded and the container was refilled with fresh
ozonated water for each wing section. The experiment was
repeated using tap water as a control.
For the second set of experiments, or direct application
treatment, chicken wing sections were held with sterile
tongs under the opening of a hose with the ozonated
water for 15, 30, or 45 s and turned halfway through the
treatment time so that both sides were exposed to the
ozone treatment. The wing sections were placed 1 cm
below the hose opening. The flow of ozonated water was
kept at 3 liters/min. The direct application treatment was
repeated with tap water as a control, using the same flow
rate and a hose of the same diameter (9.525 mm). Three
wing sections (51.3 ± 12.4 g each) were individually
treated for each of the times and ozone concentration
combinations described earlier. After treatment, wing
sections were placed individually in sterile Whirl-Pak bags
for microbial analysis.
Microbiological analysis
Buffered peptone water (BPW, 100 ml; Sigma-Aldrich,
St. Louis, MO) was added to each bag containing one
chicken wing section, and the samples were manually
massaged for 30 s to detach bacteria, as previously
described (18, 25). Appropriate serial decimal dilutions
were prepared in 0.1% BPW. For samples artificially
inoculated with Salmonella, dilutions were plated onto
XLD agar and then incubated at 37°C for 18-24 h before
counting colonies. For noninoculated samples, dilutions
were spread onto Petrifilm APC plates (3M, Saint Paul,
MN) and incubated at 35°C for 48 h. The experiments
were repeated in triplicate, and results were recorded
474 Food Protection Trends November/December
as log10 CFU/ml rinsate to reflect changes in surface
contamination because of the treatments.
Statistical analysis
Each microbiological response (Salmonella or APC) and
treatment combination application (immersion or direct
application) was analyzed separately. Data were analyzed
as a randomized complete trial with two factors (exposure
time and ozone concentration) at three levels each for a
total of nine treatments. Mean log10
CFU/ml rinsate was
compared through double-factor analysis of variance on
Excel (P < 0.05; Microsoft, Redmond, WA), and means
were separated using the Tukey post hoc method. The
experiments were performed in triplicate.
RESULTS AND DISCUSSION
The initial mean Salmonella counts were 6.3 ± 0.3
log10 CFU/ml rinsate, whereas the average starting
concentration of indigenous microflora (APC values)
in noninoculated samples was 4.3 ± 0.7 log10
CFU/ml
rinsate. Chicken wings inoculated with Salmonella were
stored at 4°C for 18-24 h to simulate the worst-case
scenario for microbial contamination, where the bacteria
have attached to the matrix and adapted to the cold
temperatures.
Salmonella counts for chicken wings treated with
ozonated and tap water are presented in Table 1. When
treating chicken wing sections with tap water, counts
ranged from 6.0 ± 0.1 to 6.2 ± 0.1 log10
which corresponds to reductions of 0.1 ± 0.1 to 0.3 ±
0.1 log10
CFU/ml rinsate. From initial counts of 6.3 ±
0.3 log10 CFU/ml rinsate, ozonated water treatment
CFU/ml rinsate. There was a significant effect of
achieved reductions that ranged from 0.3 ± 0.2 to 0.6 ±
0.1 log10
concentration (P = 0.003) but no significant effect of time
of application (P = 0.635) on the observed reductions.
The reductions with higher ozone concentrations (5 and
10 ppm) were significantly greater than those with tap
water and the lower (2.5 ppm) ozone treatment. However,
the differences between reductions were less than 0.5 log10
CFU/ml rinsate, and reductions in all treatments were
lower than 1.0 log10
CFU/ml rinsate. Reductions lower
than 1 log may not be considered of practical application
for industry (2). Salmonella reductions of 0.74 log10
ml rinsate were observed in carcasses treated with 10ppm
ozonated water for 45 min (11). Megahed et al. (19)
found Salmonella reductions of 1.2 log10
CFU/cm2
on
chicken drumsticks soaked in 8-ppm ozonated water for
4 min. Agirdemir et al. (1) immersed chicken carcasses
inoculated with Salmonella in 1.5-ppm ozonated water for
5, 10, and 15 min and achieved reductions of 1.21, 1.43,
and 1.13 log10
CFU/ml rinsate, respectively. Based on our
results and other findings, it seems that longer ozonated
water treatments are required to observe practical
CFU/
CFU/ml rinsate,
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