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Article

Ozone in the Kitchen

Do You Really Need an Ozone Sanitizer to Disinfect Your Food?

Fine Cooking Issue 90

Perhaps you know that the upper atmosphere’s ozone layer protects us from the sun’s harmful ultraviolet radiation. But did you know that ozone can also protect you by killing any pathogenic bacteria, viruses, and molds that might lurk on the surface of your foods? It’s true. And for anywhere from $50 to $200 you can buy a machine that will generate ozone right in your own kitchen.
Given the spate of reports about contaminated produce in recent years, it’s hard not to worry about what hazards we might bring home in our grocery bags. But do you really need to disinfect your food with ozone? Here are a few things to consider before you decide:

  • Most produce is not contaminated and traditional washing techniques are sufficient for cleaning it.
  • Sanitizing food that you intend to cook (which the literature accompanying one of the devices recommends) is just plain silly because the heat of cooking will kill most pathogenic microbes. But if you’re concerned about food that you plan to eat raw, ozone sanitization may make sense.
  • The literature that accompanies these machines says that they can keep your foods “fresh” and “more healthful,” and maybe “even save your life.” Those are grand claims, but without enlisting the services of a sophisticated laboratory to put them to the test, I can’t say for certain whether these products really do accomplish these objectives.
  • The machines are also supposedly able to eliminate carcinogens, hormones, antibiotics, and pesticides. But as a chemist, I’m very skeptical about these claims. Even if hormones and antibiotics are present in factory-farmed meat, ozone can’t reach them; it’s just a surface treatment. And even if traces of pesticides and other chemicals are on foods’ surfaces, there are hundreds of such substances, and while some can be broken down by ozone, many cannot. But, anyway, it’s harmful microbes that we’re most worried about—and ozone does indeed kill those. That much is indisputable.

How does ozone sanitize food?

Ozone is a form of oxygen that contains three atoms of oxygen per molecule (O3) instead of the normal two (O2). It isn’t happy with that extra, three’s-a-crowd atom, so it gets rid of it as soon as it can by foisting it upon any receptive molecule it comes in contact with, thereby oxidizing it.
Oxidation changes substances chemically, often in drastic ways, and the odds are pretty good that a colored or smelly molecule will be turned into one that is neither colored nor smelly. Thus, oxidation can bleach some colors and destroy some flavor- and odor-causing compounds. It can also kill bacteria and viruses by attacking and rupturing their cell walls or protective coatings. (If you’re thinking that ozone does precisely what household chlorine bleach does, you’re right, except that ozone is a much stronger oxidizer, and it leaves no lingering odor or toxic residue.)
Ozone is a gas, so you can’t just keep a bottle of it around and pour yourself a glass whenever you need it. Moreover, ozone is unstable. When mixed with air, half of it disappears in three days by reverting to regular oxygen, O2. But ozone dissolves in water—about 13 times more readily than regular oxygen—so you can make “ozonated” water and use it as you would a liquid disinfectant. The thing is, in water, ozone decomposes even faster than in air; half of it disappears in just 15 to 20 minutes. So if you want ozonated water, you have to make it fresh and use it fast.

Did you know?

Ozone generators also have been sold to “purify the air” in homes. But ozone is quite toxic to breathe. The United States Environmental Protection Agency has concluded that “the concentration of ozone would have to greatly exceed health standards to be effective in removing most indoor air contaminants.” The ozone-generating devices we’re discussing here don’t put ozone into the air, except perhaps inside the refrigerator, where it’s not apt to be a problem.

An overview of ozone sanitizers

I’ve seen three kinds of ozone generators designed expressly for home food disinfection, and I tried one of each type.
1. Machines that make batches of ozonated water, either in a plastic bowl containing the food to be washed or in a removable spray bottle. Ozonated water looks perfectly normal, so it may be hard to believe that it’s capable of sanitizing anything. But I have seen the results of tests performed by an independent laboratory on one such machine, the Lotus Sanitizing System. The results show that the ozonated water reduced the amounts of E. coli, Salmonella, and Listeria bacteria on a variety of vegetables by an average of 99.9%. So it really does work. With a spray bottle, I spritzed ozonated water on an iodine stain, a cat stain on the carpet, a veritable Jackson Pollack of splatters on a kitchen towel, and on stains from barbecue sauce, Worcestershire sauce, and grape jelly on my shirt (deliberately applied, I hasten to add). In every case, the stain was almost completely gone after three or four spray-and-wipe treatments.
2.Machines that are essentially washing machines for produce. These vigorously whirl and slosh your fruits and vegetables around in ozonated water—so vigorously, in fact, that in one of my tests it abraded the skin off a ripe peach. I have no doubt that such machines do an effective washing job, though I haven’t seen actual before-and-after microbe counts. The models I’ve seen are big and heavy and claim a prime plot of countertop real estate right next to the sink, where the machine needs to be kept for filling and draining.
3. Machines that release ozone gas into your refrigerator. On the upside, these devices are small and relatively inexpensive. On the downside, I can’t help but wonder if they work. They sit in your fridge and generate ozone gas that reputedly deodorizes and disinfects everything inside. Sounds great, but if it is your habit occasionally to open the refrigerator door, it would seem to me that most of the heavier-than-air ozone would spill out. To test the effectiveness of these machines, one would have to compare the numbers of bacteria and viruses, both with and without the gadget, inside many refrigerators with many kinds of contents. To my knowledge, this has never been done.

The bottom line

Ozone sanitizers are what I call “feel-good appliances.” If you believe that food is crawling with dangerous bacteria, molds, and viruses—which is far from a foregone conclusion—then using one of these machines routinely on all your fresh produce could make you feel a lot better. But for most people, they’re not necessary.
As for me, I’ll welcome an occasional spray bottle of ozonated water into my house for bleaching stains and sanitizing cutting boards and countertops. But I’ll continue to trust that a plain cold-water wash will keep my fruits and vegetables from killing me.

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