Agriculture Reference
In-Depth Information
Chlorine wash is the most widely used industrial washing method in the produce
industry, mainly because of its effi cacy, availability, relatively low cost, and ease of
operation. However, current chlorine-based sanitizers used to wash fresh produce do
not provide satisfactory microbial reduction in industrial scale sanitizing treatments.
Within the FDA approved concentration, a chlorine wash can only achieve a
1 - 2 log CFU/g reduction in microbial populations (Hegenbart 2002 ). The use of
chlorine also brings up health and environmental concerns due to the generation of
chlorinated by-products with some carcinogenic properties such as chloroform and
trihalomethane (THM) during a washing treatment when precursor organic com-
pounds, such as humic and fulvic acids are present (Richardson and others 1998;
Menzer and Nelson 2001). Additional limitations of chlorine include its rapid deple-
tion under high organic loading, the requirement for pH adjustment and off-gassing
during processing. Therefore, the fresh produce industry constantly seeks alternative
sanitizers—which are safe, environmentally friendly, and more effective—to replace
chlorine.
Electrolyzed Water
Electrolyzed water is a technique developed in Japan. It is produced by electrolysis
of water containing a low concentration of sodium chloride (0.1%) in an electrolysis
chamber where anode and cathode are separated by a bipolar membrane. The water
from the anode normally has a pH of
<
2.6, and an oxidation-reduction potential (ORP)
of
1,100 mV, and hypochlorous acid is present. The water produced from the cathode
has a pH of
>
795 mV. The chemical reactions that occur at the
anode and cathode are listed in Table 9.2. The strong bactericidal ability of AEW was
fi rst reported in 1982 in Japan, which led to the development of a variety of applica-
tions in food, medicine, and agriculture. AEW was approved in Japan as a bactericidal
agent for food products in 2000. In the U.S., AEW has been used for sanitation of
fertile hatching eggs (Yoshida 2004; Russell 2004) and in the brewing industry
(Hopkins and Kindred 2006 ).
AEW has shown a strong bactericidal effect against a wide spectrum of microor-
ganisms, including pathogens such as E. coli , Salmonella , L. monocytogenes , Shigella ,
Bacillus cereus , and Campylobacter jejuni (Bari and others 2003; Park and others
2002; Kim and others 2000) and spoilage microorganisms such as Penicilium expan-
sum and Aspergillus parasiticus (Okull and Laborde 2004). The biosphere of micro-
organisms (bacteria and viruses) is defi ned by a region with pH from 3 to 10 and ORP
from +900 to
>
11.4 and ORP of
<
400 mV. Because the AEW has a pH of
<
2.6 and an ORP of
>
1100 mV,
Table 9.2. Chemical reactions at the anode and cathode of an electrolyzing unit
Anode
Cathode
2H 2 O → O 2 + 4H + + 4e
2OH − 2 e → 2OH ·
2OH . → (O) + H 2 O (O) + O 2 → O 3
2Cl → C l 2 + 2e
Cl 2 + H 2 O → HOCl + HCl
2H 2 O + 4e → H 2 + 2OH
Na + + OH → NaOH
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