There were warning signs. After stirring a quintuple batch of roux for a full hour, hacking apart dozens of alliums and a 5-pound kielbasa, and sluicing in 10 quarts of chicken stock, a strange scum appeared. It was gray, bubbly, and slightly fetid. But there was salad to toss, bread to cut, a table to set, toys to hide, and a husband to berate about mopping the floor. By the time I returned to the stove—ready to add the finishing touch, $100 worth of rock shrimp—the pot was a foamy, churning mass, reminiscent of an underwater sewage break. I paused for a moment, then did what any desperate hostess would do under the circumstances: I bailed ladleful after ladleful of stinky froth, pitched in the crustaceans, and clapped down the lid.
The going-away party for Hilary went off without a hitch. I greeted each guest with a steaming bowl of shrimp and sausage gumbo—the perfect antidote to a cold January night—and a glass of wine, then directed her to the dining room. We told stories about our friendship with Hilary, presented her with a scrapbook, and promised to visit her in Querétaro, a university city in central Mexico. I did notice, with an odd feeling of relief, that quite a few people had left their gumbo half-eaten or untouched. Except for Amita, Hilary's workmate. "Oh, this is sooo good," she'd said, refilling her bowl for the third time, as I quashed the impulse to wrest it from her hands. After the last person had left, I served myself and finally sat down. Completely putrid. I poured the evidence down the disposal and went to bed, trying very hard not to think the words food poisoning.
The CDC estimates that 48 million people get sick from foodborne viruses, bacteria, or parasites every year. I've been one of them. Here in the United States, my most frequent complaint has been post-restaurant stomachache, undoubtedly from norovirus, which is both extremely common— 58 percent of the 9 million cases from known pathogens are attributed to it—and quite mild—fewer than .00003 percent of them die. It's Latin America, where I've lived and often travel, that has been my undoing, digestively speaking. In Honduras after a bus ride, I paid for a stack of banana-leaf-wrapped tortillas first with lempiras and then with three straight days of toilet-perching. In Ecuador, after snacking on a bola verde (plantain and meat ball) from a restaurant display case, I had to sprint to my apartment—luckily nearby—to spend an hour vomiting and going cheek-to-tile with the bathroom floor.
Fully versed with the icky effects of enteric diseases, I've always—well, except under the duress of entertaining—given spoiled food a wide berth. After all, why would nature have bothered with the poison labels (nasty smell, gross appearance, foul taste) if ingesting it didn't make you sick? Ergo, my relentless crusade against senescent foodstuffs. Not a day goes by that I don't discover in the hinterlands of my refrigerator sour milk, yellowing broccoli, mushy lettuce, powder-covered lemons, slimy lunch meat, moldy cheese, or the venerable remains of takeout and home-cooked meals. Out! In this policy I have plenty of company: Americans chuck an estimated 16 percent of their food uneaten, either because it goes bad, they prepare too much, or they're spooked by expired use-by/open dates. A sensible precaution, except for one thing: In my experience, every gastrointestinal illness has been preceded by consuming something that seemed perfectly fresh.
Could it be that eating spoiled food doesn't actually make you sick? To find out, I dusted off my high-school biology and spent weeks devouring peer-reviewed studies by food microbiologists. Here's what I learned.
To spoil, something must be dead, which, unless you're a fan of mollusks on the half-shell or maggot-infested Sardinian casu marzu, is generally how we prefer our food. Once this unfortunate event has occurred, the plant or animal tissue is fair game for invasion by decomposers—the omnipresent yeasts, molds, and bacteria. We'll gloss over the first two, as they are almost always innocuous. (Some molds produce dangerous mycotoxins on crops and stored fruits and grains, but this is an agricultural hazard, not a household one.) When it comes to bacteria, however, things get complicated. The reason: There are two distinct types that invade edibles. Once you understand their different ecological niches, you'll never confuse them again.
Spoilage bacteria turn last week's roast chicken into a scene from Zombie Flesh Eaters. Like the undead, they're everywhere (air, soil, water, plants, and animals), so the invasion of your groceries is pretty much inevitable. Evolved to consume corpses and dead plants, which are customarily served cool, they're the dominant bacteria in your 35-40-degree fridge. (Conversely, temperatures above 85 degrees enervate them.) The stench is from the breakdown of amino acids into amines, which include the evocatively named cadaverine, putrescine, and spermidine. As repulsive as they are, only one, histamine, has been linked to negative health effects, and that's just for people who have allergies to it or who eat certain kinds of improperly stored fish. Spoilage bacteria are harmless.
Pathogenic bacteria make you wish you could exchange your Caribbean bungalow for a hospital room with an IV drip and a bedpan. The preferred habitat of salmonella, E. coli, and campylobacter—three moderately serious foodborne illnesses—is the nutrient-packed guts of warm-blooded animals, but these also do well at room temperature. The journey to your plate usually starts at the slaughterhouse or meat processing facility, where a minute amount of animal poop gets on your future burger. So long as the meat's under refrigeration, that's no big deal, since cold inhibits the proliferation of pathogens (most people can fight off low doses). But then—maybe at home, more likely at a food-service establishment—the ground beef sits out for several hours, allowing the bacteria to multiply. As a finishing touch, you order your patty medium rare, so the center doesn't get hot enough to kill its microscopic passengers. It smells good, looks good, tastes good. (Pathogenic bacteria provide no sensory clues as to their presence in food.) But hours to days later: stomach cramps, nausea, diarrhea, or worse.
Need more persuasion before you tuck into the green-streaked, two-week-old steak buried in your meat compartment? Consider this: We're lethal—at least to the decomposers. If the 98.6-degree heat doesn't get them ( an adaptation by warm-blooded animals to elude the fungal infections endemic to the rest of the animal and plant kingdoms), a dousing in stomach acid—pH 1-2, also good for tanning leather and sterilizing pools—will. And should a few spoilage bacteria survive to venture further downstream, they face almost certain death by a squad of intestinal immune cells. Pathogens, by contrast, are as well-prepared for this treacherous terrain as a USAF special op. They strike without warning. In the stomach, they may become temporarily acid-tolerant. In the small intestine, some can bind to and disrupt immunological command centers. And then there's their clever strategy for meeting new hosts. Excreted poisons or the infection itself make you feel very, very sick, triggering a release of bodily effluvia. Greetings, family and friends!
The morning after the dinner party, I called Hilary to see how she thought it had gone. Subtext: Were there any sudden deaths, ER visits, or irate phone calls from gastrointestinally afflicted guests? "It was just lovely," she said in her Irish lilt. "Amita even called to say what a good time she'd had—and to ask me to get her your gumbo recipe!"