Agriculture Reference
In-Depth Information
it creates conditions diffi cult for microorganisms to survive. Furthermore, the
disinfecting effect of AEW can be strengthened by the residual chlorine in it,
which may function to decompose fat and protein of the cell membrane. The syner-
gistic effect of low pH, high ORP, and free chlorine was found to inactivate cytoplas-
mic enzymes (Kiura and others 2002), make the membrane potential of organelles
exceed its stabilizing limit, and inhibit energy metabolism and respiration (Anonymous
2004 ).
AEW has been examined for its effi cacy in food safety and agricultural applica-
tions. Venkitanarayanan and others (1999) used AEW to treat cell suspensions of
E.
coli
O157:H7,
S. enteritidis
, and
L. monocytogenes
, and reported a reduction of
>
7.0 log CFU/ml for all three organisms in a few minutes. AEW was also used to treat
surfaces of fresh vegetables (Kolseki and others 2004). Koseki and others (2001) used
AEW to wash lettuce in comparison with ozone and sodium hypochlorite. They found
that AEW failed to inactivate microbes inside the cellular tissue. Park and others
(2001) conducted inactivation tests with lettuce inoculated with
E. coli
O157:H7 and
L. monocytogenes
and examined the quality of treated lettuce during 2 weeks of
storage. The effectiveness of AEW for inactivating
L. monocytogenes
biofi lms was
studied by Kim and others (2001). They reported that the adherent cell population on
stainless steel coupons was reduced by about 9 log CFU/ml after 300 sec of treatment.
The fungicidal effect of AEW on pear fruit was demonstrated by Al-Haq and others
(2002). The effect of frozen AEW on lettuce during storage was examined by Koseki
and others (2002) and a 1.5 log CFU/g reduction of aerobic bacteria was achieved. In
the tests using AEW to inactivate
Salmonella
on alfalfa seeds and sprouts, Kim and
others (2003) reported that 10 min of treatment with AEW can reduce the population
of
Salmonella
by 1.66 log CFU/g for alfalfa seeds. When combining AEW with sonica-
tion, they were able to achieve 2.3 log CFU/g greater reduction than with treatments
of AEW alone. AEW was found to be very effective in inactivating
E. coli
O157:H7,
Salmonella
and
L. monocytogenes
spot-inoculated on tomato surfaces, with reductions
of 7.85, 7.46, and 7.54 log CFU/g after 40 sec of treatment (Bari and others 2003),
respectively. AEW wash effectively inhibited natural fl ora growth on fresh-cut cilantro
during a 14-day storage (Wang and others 2004).
Other types of electrolysis equipment do not contain the separating membrane and
therefore produce electrolyzed neutral water (ENW) with pH close to neutral. ENW
was effective for decontaminating fresh-cut vegetables, such as spinach (Izumi and
others 2000), and carrots and cucumbers (Izumi 1999). The bactericidal effect of ENW
was 2-3 times higher than that of the sodium hypochlorite solution with the same
active chlorine concentration (Izumi 1999).
The advantages of AEW and ENW include their lack of production of chlorinated
by-products and their nontoxicity in humans. The pH, ORP, and chlorine ion concen-
tration of ENW do not change much during storage in a closed dark-brown glass bottle
at room temperature for 21 days; the total free available chlorine and dissolved oxygen
concentration in ENW signifi cantly decrease in storage (Hsu and Kao 2004). Similar
to chlorinated water, the effi cacy of electrolyzed water can decrease in the presence
of organic matter that contributes to diminishing the amount of freely available chlo-
rine (Oomori and others 2000).
