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Y.-R. Huang et al. / Food Control 19 (2008) 329–345 331

Fig. 1. Schematics of electrolyzed water generator and produced compounds.

hydroxide in the diluted salt solution move to the anode to water generators, made by the Hoshizaki Ò Company,
give up electrons and become oxygen gas, chlorine gas, allows the users to select amperages and/or voltages, while
hypochlorite ion, hypochlorous acid and hydrochloric acid, the machines change brine flow rate accordingly. The third
Ò
while positively charged ions such as hydrogen and sodium type of EO water generators, made by the Toyo and the
Ò
move to the cathode to take up electrons and become Nippon Intek companies, allows the users to select a pre-
hydrogen gas and sodium hydroxide (Hsu, 2005). Two set chlorine concentration level of EO water from a display
types of water are produced simultaneously. EO water, panel and the machines change brine flow rate and amper-
with low pH (2.3–2.7), high oxidation–reduction potential ages and/or voltages automatically (Hsu, 2003).
(ORP, >1000 mV), high dissolved oxygen and contains free Hsu (2003) investigated relationship among water flow
chlorine (concentration depends on the EO water machine rate, water temperature and salt concentration on electrol-
setting), is produced from anode side. However, electro- ysis efficiency, and separation efficiency of an EO water
lyzed reduced (ER) water, with high pH (10.0–11.5), high generator. He made following conclusions: (1) electric
dissolved hydrogen, and low ORP ( 800 to 900 mV), is potential (7.9–15.7 V) and power consumption (16–
produced from the cathode side. ER water with strong 120 W) of electrolysis cell were not affected by water flow
reducing potential can be used to remove dirt and grease rate, water temperature or salt concentration in the feed
from items such as cutting boards and other kitchen uten- solution; (2) electric current changed with water tempera-
sils (Hsu, 2005). ture and water flow rate; and (3) electrolysis efficiency of
The principle of producing electrolyzed water is shown the electrolysis cell and separation efficiency of the ion
in the Fig. 1 with the following: exchange membrane were significantly decreased by the
increases in water flow rate and salt concentration in the
þ

Positivepole : 2H 2 O ! 4H þ O 2 "þ4e
feed solution. Later, Hsu (2005) also reported that ORP

2NaCl ! Cl 2 "þ2e þ 2Na þ decreased with increases in water follow rate and free chlo-
Cl 2 þ H 2 O ! HCl þ HOCl rine increased with increases of salt concentration and

Negativepole : 2H 2 O þ 2e ! 2OH þ H 2 " decrease of water flow rate.

2NaCl þ 2OH ! 2NaOH þ Cl
4. The advantages and disadvantages of EO water
3. Systems for generation of electrolyzed water The main advantage of EO water is its safety. EO water
which is also a strong acid, is different to hydrochloric acid
Commercial EO water generators can be divided into or sulfuric acid in that it is not corrosive to skin, mucous
three major types based on their automatic control sys- membrane, or organic material. On the other hand, sodium
tems. The first type of EO water generators, made by the hypochlorite was proved to have a strong toxicity, such as
ARV Ò and the Amano Ò companies, allows the users to skin irritation, membrane irritation, acute toxicity, and so
select brine flow rate while the machines adjust voltages on (Mori et al., 1997; Sekiya, Ohmori, & Harii, 1997;
and/or amperages automatically. The second type of EO Shigeto et al., 2000). Currently used hatchery sanitizers