To: Seafood Community
Fr: Pamela Tom
I asked Dr. Dee Graham (ozone expert) for information on the current
technology of mixing ozone gas in water. His reply is below:
"Modern ozone units inject ozone under pressure in a hyperconcentrator and
circulate it continuously, yielding as much as 10 PPM ozone in water. The
supersaturated water then is injected into the washing solutions or other
process environment. These systems use continuous, online measurement of
dissolved ozone concentration in the water and use a feedback loop to
control ozone at the target level. Ozone is a much stronger oxidant as
compared to free chlorine, which needs to be kept in mind when comparing
sanitizers. For example, 1 PPM ozone in water will provide microbial
lethality similar to 100 PPM chlorine. Contact time is critical for
determining appropriate treatment conditions. Normally ozone lethality in
water is stated as CT Value which is calculated as Ozone concentration in
PPM X Contact time in minutes. Thus 1 PPM ozone in water X 0.5
minutes equals CT 0.5, or 5 PPM ozone in water X 0.1 minute equals CT
0.5.
"The literature contains good data on CT values for killing many microbial
species. For most microorganisms of interest in food systems a CT value of
1 to 1.5 will yield about a 5-log count reduction. In practical
operations, assuring contact of ozone with the target surface is a
critical condition. Crevices, air bubbles, lumps of fat, etc. which impede
contact need to be considered.
"Regards, Dee"
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