Leaving soup out is risky business


November 08, 2006|By Erica Marcus | Erica Marcus,Newsday

A friend of mine makes chicken soup at night, turns off the heat before he goes to bed, leaves the pot covered overnight and in the morning puts it in the refrigerator. I shudder at the thought of leaving food for more than a couple of hours at anything but a cooking temperature or refrigerator temperature. What do you think?

I think it sounds fishy. And Kathryn Boor, professor of food microbiology at Cornell University, thinks it sounds downright dangerous.

Your friend may well have killed a lot of garden-variety microbes as his soup bubbles away, but he has not eliminated the risk of botulism, "a rare but serious paralytic illness caused by a nerve toxin that is produced by the bacterium Clostridium botulinum," according to the Centers for Disease Control and Prevention.

Boor said that Clostridium botulinum is found in soil and thus can turn up on virtually any agricultural product. The bacteria form spores that are not killed by boiling.

As the hot soup cools, she said, "the temperature is perfect for the bacteria to produce the toxin." She noted that the incidence of botulism is rare (according to the CDC, there are about 27 cases of food-borne botulism reported each year in the United States) but the disease is serious and, in about 8 percent of cases, fatal.

Botulism aside, Boor said that "the critical zone for food is from 40 degrees to 140 degrees. The longer you let it linger in that range, the more potential there is for hazard." The goal when dealing with hot food is to cool it down as soon as possible, and Boor advised a strategy of divide and conquer.

"If you just put the pot in the refrigerator," she said, "it can be hours before it drops out of the danger zone." Instead, she advised dividing the contents of the pot into two (if not three or four) individual containers and refrigerating them.

Erica Marcus writes for Newsday. E-mail your queries to burningquestions@newsday.com, or send them to Erica Marcus, Food/Part 2, Newsday, 235 Pinelawn Road, Melville, NY 11747-4250.

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