January 6, 2009
Q & A
Microwaves and Leaks

Q. Is it healthy to store foods near a microwave oven? I worry that cooking oil, spices or canned foods may be receiving unhealthy doses of microwave emissions.
A. If the foods you are storing near your microwave oven are not somehow visibly changed, as if cooked, then they are not being affected by your microwave, which is shielded against leaks of microwave energy while operating and is designed to shut off when the door opens.

“Microwaves cause water molecules in food to vibrate, producing heat that cooks the food,” according to a fact sheet from the United States Food and Drug Administration Center for Devices and Radiological Health. “The microwave energy is changed to heat as it is absorbed by food, and does not make food ‘radioactive’ or ‘contaminated.’ ”

A microwave with a leaky seal or door may conceivably cook adjacent foods, but that would be rare.

“There is little cause for concern about excess microwaves leaking from ovens unless the door hinges, latch or seals are damaged,” the fact sheet says. “In F.D.A.’s experience, most ovens tested show little or no detectable microwave leakage.”

A federal standard limits the amount of microwaves that can leak from an oven throughout its lifetime to five milliwatts of microwave radiation per square centimeter at approximately two inches from the oven’s surface, far below the level known to harm people.

Some early worries about microwaves, like possible damage to pacemakers, have largely been resolved, the agency says; modern pacemakers are shielded against electrical interference.

Did Your Microwave Nuke the Bacteria?

I’VE gotten used to the idea that hamburgers can make you sick. But frozen dinners?

Consider Amy Reinert’s recent nightmare.

On Aug. 18, Ms. Reinert’s daughter Isabelle, then 19 months old, became so violently ill that she passed out and had a seizure, a 104-degree fever and nearly constant diarrhea.

Panicked, Ms. Reinert rushed her to the emergency room, where she was given an IV and eventually sent home. But the severe diarrhea continued for 48 hours, requiring six to eight diaper changes an hour.

“I was a basket case,” said Ms. Reinert, a 26-year-old mother of three from Sauk Rapids. Minn. “It was scary to see her lying there completely out of it.”

On Aug. 22, the Reinerts learned that their daughter had become infected with the potentially deadly pathogen salmonella. Investigators questioned the family for weeks about what they had eaten but did not zero in on the likely cause until this week: Banquet-brand chicken and turkey pot pies.

Isabelle wasn’t the only one doubled over with cramps and violent diarrhea after eating pot pies. The Centers for Disease Control and Prevention now says at least 165 people in 31 states have become ill with the same strain of salmonella, with the Banquet pot pies being the likely source.

At least 30 people have been hospitalized. No deaths have been reported.

The salmonella outbreak came amid a banner year for food-borne illnesses, with one recent example requiring the recall of 21.7 million pounds of frozen hamburger by a New Jersey business, the Topps Meat Company.

But what makes the pot-pie case remarkable is the likely reason people became sick — and the company’s initial response.

It turns out that at least some of the victims of salmonella probably didn’t zap the pot pies long enough in the microwave. And ConAgra Foods, which owns Banquet, initially suggested that consumers should have known better.

“The company believes the issue is likely related to consumer undercooking of the product,” ConAgra said. “The cooking instructions for these products are specifically designed to eliminate the presence of common pathogens found in many uncooked products.”

It is relatively easy to figure out when a hamburger is well done by checking to see that it is no longer pink. But it’s preposterous to expect consumers to know how the cooking power of their microwave compares with others.

Some have more watts than others, and the makers of ready-to-cook products expect you to know the difference.

For instance, the Banquet pot-pie instructions tell consumers to microwave the pie on high for four minutes if they have medium- or high-wattage microwaves, and six minutes if they have low-wattage microwaves. It says ovens vary, so cooking time “may need to be adjusted.”

“Even if I have a 1,000-watt microwave, how do I know if it’s high, medium or low?” said Douglas Powell, an associate professor and scientific director of the International Food Safety Network at Kansas State University.

Professor Powell bought one of the pot pies and cooked it, following the instructions, then checked the temperature with a thermometer.

After four minutes, the pie was 48 degrees, leading him to conclude his microwave was low wattage. After six minutes, it was 204 degrees near the top but 127 degrees farther into the pie.

He finally ate it after zapping it for another two minutes, when the pie temperature was 194 degrees. (An account of the experiment is at barfblog.foodsafety.ksu.edu)

I bought a handful of ready-to-cook dinners. The instructions all noted in the fine print that microwave ovens varied, so cooking times might have to be adjusted. They also recommended vastly different cooking times.

For instance, Amy’s brand vegetable frozen pot pies are supposed to be cooked on high for four to five minutes in a microwave. A Boston Market frozen chicken pot pie advises consumers to cook it on high for eight minutes. Marie Callender’s Creamy Parmesan Chicken Pot Pie suggests nine and a half minutes for a medium- or high-wattage microwave, 14 minutes for low wattage.

The front of the Stouffer’s frozen meat loaf package warns to “cook thoroughly.” It tells consumers to cook it on high for four minutes, then on 50 percent power for five and a half or six.

With the proliferation of ready-to-cook foods in the frozen foods aisle, the variation in the cooking times is a little scary. Is it long enough to kill the bugs, even if my microwave is 15 years old?

ConAgra Foods finally came to its senses on Thursday night and recalled all of its pot pies. It also acknowledged problems with its cooking instructions.

In addition to the Banquet brand, the company recalled several private label brand pot pies, including Kroger, Food Lion and Great Value, which is sold at Wal-Mart.

“What we’ve learned is that there is some consumer confusion about the microwave instructions,” said Stephanie Childs, a spokeswoman for ConAgra. “It says cook thoroughly. How do you best explain that to consumers?”

She said the products would not be back on the shelf until ConAgra officials were satisfied the instructions were clear. Perhaps they should throw a food thermometer in with the new packages.

Carlota Medus, an epidemiologist for the Minnesota Department of Health, said the outbreak wasn’t the first time frozen products were linked to salmonella poisoning. There have been four other outbreaks in the state from frozen breaded, prebrowned chicken since 1998, caused in part by confusion over microwave instructions.

“The issue is that people think it’s cooked and it just needs to be heated up, she said. “Microwave cooking for something that has to be cooked isn’t always a good idea.”

Ms. Reinert said she called ConAgra soon after she learned that pot pies had likely made her daughter sick. Isabelle had diarrhea for six weeks before she fully recovered, her mother said.

“I said, ‘What are you doing to prevent more people from eating them?’” she recalled. She said they replied, “‘You have to cook our products more thoroughly.’ I was very upset by that.”

Ms. Reinert said the cooking instructions made no sense, so she ended up cooking the pies in her microwave for seven and a half minutes. Apparently her microwave is ultralow-wattage.

Told Thursday night that ConAgra had acknowledged that the instructions were unclear and that the company was recalling the products and rewriting the instructions, she said, “Duh!”

“I’m relieved to know that there is not a possibility out there that more people can get sick,” she added.

So what should you do with frozen dinners piled up in the back of your freezer? If you still have an appetite, you might consider nuking the heck out of them in your microwave. Or better yet, stick them in the oven and buy a food thermometer.