Here’s the situation: A couple you don’t know very well invites you over for a Saturday afternoon get-together. One of your hosts is grilling his famous Yucatan chicken, and in the kitchen, you spot it, smeared with achiote paste, covered in plastic, but sitting out on the counter. It looks like it’s been marinating there for a while. It stays unrefrigerated for the couple of hours you drink margaritas and talk, and sits around a while longer after it comes off the grill. You wonder if you should say something to your hosts, but end up keeping quiet. Lecturing people you barely know about the dangers of salmonella poisoning? Nobody wants to be that guy.

Except that, next day, you feel a little achy, and the day after that, you feel full-blown awful. You can’t be positive, but it seems pretty clear that your hosts’ unrefrigerated Yucatan chicken has given you salmonella poisoning, with symptoms that feel like Montezuma’s revenge. You totally should have said something. You totally should have been that guy.

The problem is, not everyone will believe you when you tell them about the dangers of unrefrigerated food. Me, I cooked in restaurants, and had to get my sanitation certification in a couple of states. Those courses scare the crap out of you—it’s so easy to make people sick via food-borne illnesses it’s kind of amazing that more people aren’t smacked down by salmonella.

Unless they are, and just don’t recognize the symptoms.

I asked Richard Lee of the San Francisco Department of Public Health about the etiquette of alerting your host at a dinner party about perceived health risks. It’s both simpler and more complicated than I thought.

As a public health official, Lee felt obliged to be firm about the safe temperature zone. All foods, he says, must be kept below 41 degrees Fahrenheit or above 135 degrees Fahrenheit at all times. But realistically, Lee says, you’ve got a four-hour window to leave foods in the unsafe temperature zone. That meant my host, the one with the Yucatan chicken (OK, the theoretical situation I started with actually happened to me last weekend), did have four hours to marinate at room temperature before risking salmonella growth. But Lee wasn’t willing to give his blessing to that, not for restaurants, not for anybody.

The more complicated part is that not everybody will get sick from foods left in the unsafe temperature zone for more than four hours. “Some people might be more resistant to it,” Lee says. “You might actually serve something contaminated to people who might have no reaction to it.”

That probably explains why my parents-in-law—who both grew up in the Philippines—routinely leave certain foods out overnight, covered but unrefrigerated, and don’t get sick (I think they believe that things taste better if they stay at room temperature).

And it depends on the type of food you leave out. Highly vinegary things—chicken adobo, say—might be perfectly fine left out, even for people who haven’t built up resistance. “If you change the pH level to below 4.5,” Lee says, “you can leave it out,” though he’s careful not to recommend the practice. Still, he says, his department gives an exemption to certain foods to stay unrefrigerated longer than four hours—the Peking ducks that hang in shop windows, for instance. Those can stay out for eight hours.

Is that because they have a low pH, I ask? “Supposedly they did a study on it,” Lee says. “They can be safe.”

As for the situation involving the Yucatan chicken, Lee is clear: Always be the guy who tells your host to pop something into the fridge, to keep from making everybody sick come Monday morning. Then again, he’s a public health official, so people are likely to listen—and actually invite him back again.

Photo by Flickr member micsten under Creative Commons

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