Food Protection Trends - July/August 2022 - 290

Apple juice cocktail
The initial mean inocula for E. coli O157 in apple juice
cocktails with 10, 20, 30, 40, and 50% ethanol were 7.73,
7.12, 6.11, 5.96, and 5.66 log CFU/ml, respectively. In a 10%
concentration, E. coli O157 survived for 48 h with a reduction of
1.08 log CFU/ml, whereas in a 20% concentration, the pathogen
was not detected after 36 h. In the higher three concentrations,
the E. coli O157 counts reached an undetectable level after
6 h of incubation (Figure 5). Salmonella-inoculated cocktails
had initial inocula of 6.81, 6.15, 6.12, 6.09, and 6.07 log CFU/
ml in 10, 20, 30, 40, and 50% concentrations, respectively.
In a 10% concentration, Salmonella survived for 48 h with a
decrease of 1.15 log CFU/ml. In a 20% concentration, the
Salmonella counts were undetectable after 36 h. For the higher
three concentrations, the pathogen was undetectable after 6 h
in 30% and 3 h in 40 and 50% concentrations (Figure 5). For L.
monocytogenes, the inoculum levels were 5.65, 5.82, 5.63, 5.57,
and 5.53 log CFU/ml of the cocktails with 10, 20, 30, 40, and
50% ethanol. L. monocytogenes was not detected after 9 h for a
10% concentration, whereas for the higher four concentrations,
the pathogen was not detected after 3 h of incubation (Figure 5).
DISCUSSION
There were reductions in pathogen counts for all cocktail
drinks and control with concentrations of ethanol from 10
to 50%. This supports statements by Kalathenos and Russell
that bacterial growth could be inhibited with ethanol starting
at 8-11% (vol/vol) (5). Inoculated pathogens were detected
for all 10% ethanol cocktail mixtures after 48 h except for L.
monocytogenes in apple juice cocktail, where the counts were
undetectable after 9 h. For fruit juice mixtures with a 20%
ethanol concentration, L. monocytogenes reached an undetectable
level in control after 6 h but was detected for 48 h in Asian
pear puree, banana puree, and orange juice. E. coli O157 and
Salmonella were detected after 48 h in control, Asian pear puree,
banana puree, and orange juice.
For the fruit juices with a 30% ethanol concentration,
significant reductions of all pathogens were observed after
3 h. The counts for all three pathogens in banana puree and
apple juice cocktails reached an undetectable level within 48 h.
However, at the same time, E. coli O157 and Salmonella were
detected after 48 h in Asian pear puree cocktail. In addition,
for control and orange juice cocktail, E. coli O157 and L.
monocytogenes, respectively, were detected after 48 h. Waite and
Daeschel also observed increased log reductions of S. aureus and
E. coli O157:H7 when the ethanol concentration in wine was
increased from 12.1 to 14.7% (14).
REFERENCES
1. Barker, C., and S. F. Park. 2001. Sensitization
of Listeria monocytogenes to low pH, organic
acids, and osmotic stress by ethanol. Appl.
Environ. Microbiol. 67:1594-1600.
2. Brewer, R., M. R. Adams, and S. F. Park.
2002. Enhanced inactivation of Listeria
monocytogenes by nisin in the presence of
ethanol. Lett. Appl. Microbiol. 34:18-21.
3. Centers for Disease Control and Prevention.
2021. Alcohol use basics: Frequently asked
questions. Available at: https://www.cdc.
gov/alcohol/faqs.htm. Accessed 10 October
2021.
For the fruit juices with 40 and 50% ethanol concentrations,
there was a significant decrease in the pathogen counts after
3 h of incubation in all cocktail mixtures, and the counts of
all three pathogens evaluated reached an undetectable level
within 48 h. These data agree with statements by Kalathenos
and Russell that solutions containing >30% (vol/vol) ethanol
could be biocidal (5).
Among the three pathogens evaluated, L. monocytogenes was
found to be the most sensitive to ethanol, and the counts decreased
rapidly in almost all treatments and more prominently in
the lower three concentrations. However, E. coli O157 survived
longer in the presence of ethanol and had the least log reduction
compared with L. monocytogenes and Salmonella. For all treatments
tested, increasing ethanol concentration with lower pH
demonstrated increased pathogen reduction. At higher ethanol
concentrations, the effect of pH was somewhat masked because
the rate of decrease in the pathogens counts was similar, but the
reduction for lower pH was still comparatively quicker than that
for higher pH. This aligns with the concept that pH and ethanol
act as hurdles for pathogens and together can exert synergistic
action and that the effect is increased with increasing concentration
of alcohol and decreasing pH (1, 9).
CONCLUSION
Based on the pH and aw
of the cocktail mixtures evaluated
and ethanol increasing the pH value of the juices, many
cocktail drinks prepared in bars and restaurants are likely to
be categorized as TCS (pH > 4.2). This study indicates that
a cocktail made with 10-50% ethanol and fruit juice would
likely show no growth of selected pathogens, suggesting these
beverages are low risk. From a pathogen reduction standpoint,
ethanol at a 40-50% concentration mixed with fruit juice
resulted in significant lethality of all three pathogens studied
(>6 log) within 48 h at 25°C.
Operators who are under the FDA Food Code and who wish
to prepare and display these types of ethanol and fruit juice
mixtures at room temperature need to ensure that the pH of
the beverage is <4.2 or have a combination of pH and aw
values
based on Table B of the FDA Food Code. If the beverage cannot
be modified into the non-TCS category, then the beverage
should only be displayed and dispensed for 4 h and then
discarded afterward or kept under refrigeration at a temperature
≤ 41°F until served. In addition, operators should use caution
when adding low-acid foods (whole, pieces, purees, or juices)
to the cocktail mixture such that the equilibrium pH increases
above pH 4.6.
290 Food Protection Trends July/August
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