Food Protection Trends - July/August 2022 - 286

TABLE 1. pH and aw
of treatments of ethanol-fruit cocktail mixtures prepared with 10,
20, 30, 40, and 50% ethanol concentrations
Ethanol % (vol/vol)
10
Treatments
pH
Control
Banana
Pear
Orange
Apple
6.68
4.95
4.84
4.12
3.82
aw
0.976
0.965
0.970
0.972
0.969
pH
6.76
5.03
4.87
4.17
3.89
aw
0.967
0.956
0.963
0.963
0.962
Data analysis
The bacterial populations were enumerated as the log
CFU values per milliliter of product. For each pathogen,
three replications of the experiment were conducted. In each
replication, the samples were inoculated and analyzed in
duplicate for E. coli O157, Salmonella, and L. monocytogenes
counts at different data points. Data points were expressed as
mean ± standard deviation of the three replications.
RESULTS
pH and aw
The pH levels of the different juice mixes and control ranged
from 3.82 to 6.94 (Table 1). The highest pH among the cocktails
was in control, and apple juice cocktail had the lowest pH. The
pH of the mixtures increased with increasing concentrations of
ethanol. Most treatments, fruit juices, and ethanol mixtures were
pH ≥ 4.2 and would require refrigeration as TCS foods under
the FDA Food Code (13). The aw
. The aw
ranged from 0.938 to 0.969
of the mixtures decreased with
for all mixtures, where control had the highest and banana puree
cocktail had the lowest aw
increasing concentrations of ethanol, supporting that ethanol
acts as a hydrogen-bonding, polar humectant (5).
Control (ethanol plus distilled water)
The initial inocula of E. coli O157 in control were 6.98, 7.11,
6.80, 6.79, and 6.37 log CFU/ml in 10, 20, 30, 40, and 50%
ethanol concentrations, respectively. There was a reduction in E.
coli O157 counts for all concentrations (Figure 1). E. coli O157
survived for 48 h of incubation in the lower three concentrations
evaluated. The total reductions were 0.41, 1.36, and 1.72 log
CFU/ml for 10, 20, and 30% ethanol concentrations after
48 h of incubation. In the cocktails with 40 and 50% ethanol
concentrations, E. coli O157 was not detected (<1 CFU/ml)
after 48 and 24 h of incubation. In control inoculated with
Salmonella, the mean inoculum levels were 6.84, 6.55, 6.12,
6.16, and 6.13 log CFU/ml in 10, 20, 30, 40, and 50% ethanol
concentrations, respectively. The counts reached <1 CFU/ml
286 Food Protection Trends July/August
pH
6.84
5.04
4.99
4.23
3.96
aw
0.959
0.947
0.955
0.955
0.953
pH
6.87
5.17
5.04
4.28
4.01
aw
0.951
0.936
0.948
0.947
0.945
pH
6.94
5.21
5.11
4.32
4.07
aw
0.944
0.927
0.941
0.938
0.938
in 30, 40, and 50% concentrations after 24, 12, and 6 h, and no
Salmonella was detected for up to 48 h, whereas survival was
observed for 48 h with a decrease of 0.67 log CFU/ml in a 10%
concentration and 2.9 log CFU/ml in a 20% concentration
(Figure 1). In L. monocytogenes-inoculated control, mean
inoculum levels were 7.89, 7.08, 7.22, 6.94, and 6.97 log
CFU/ml in 10, 20, 30, 40, and 50% ethanol concentrations,
respectively. At a 10% concentration, L. monocytogenes survived
the 48 h of incubation with a total reduction of 2.13 log CFU/
ml. In 20, 30, and 40% concentrations, L. monocytogenes was
not detected after 6 h, and it was not detected after 3 h in a 50%
concentration for up to 48 h of incubation (Figure 1).
Banana puree cocktail
The banana puree cocktails with 10, 20, 30, 40, and 50%
ethanol had initial inocula of 8.94, 7.97, 7.86, 7.59, and 7.45
log CFU/ml of E. coli O157, respectively. In the two lower
concentrations evaluated, E. coli O157 survived for 48 h with a
total reduction of 2.05 log CFU/ml in 10% ethanol and 3.72 log
CFU/ml in 20% ethanol. The counts for E. coli O157 reached
an undetectable level after 12, 9, and 3 h in 30, 40, and 50%
concentrations, respectively, and were undetected for up to 48
h of incubation (Figure 2). For Salmonella, the mean inoculum
levels were 7.63, 6.79, 6.49, 6.36, and 6.35 log CFU/ml in 10, 20,
30, 40, and 50% ethanol concentrations, respectively. Salmonella
survived for 48 h in the 10 and 20% concentrations, with
reductions of 1.04 and 1.49 log CFU/ml. The counts reached
an undetectable level after 9, 3, and 3 h for 30, 40, and 50%
concentrations and remained the same until 48 h of incubation
(Figure 2). In the cocktails with 10, 20, 30, 40, and 50% ethanol
inoculated with L. monocytogenes, the levels of inoculum were
8.62, 7.87, 5.56, 5.49, and 5.65 log CFU/ml, respectively. L.
monocytogenes survived for 48 h in 10 and 20% concentrations,
with reductions of 1.58 and 3.73 log CFU/ml, respectively,
whereas in 30, 40, and 50% concentrations, the pathogen was
undetectable after 9, 6, and 3 h, respectively (Figure 2).
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30
40
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