After countless hours fussing over a holiday feast, you may see leftovers as liberation from the kitchen. But before you re-heat and eat that once-hot turkey, ham, sweet potato casserole or custard pie, you should know that they can make you so sick you might wish you were dead.
Food safety specialists explain that when cooked foods linger more than two hours at room temperature, they can become mess halls for colorless, odorless, tasteless bacteria.
You might suspect such dangers in meat or turkey, and you've probably heard that it's important to separate turkey from the stuffing when storing them. But what might surprise you is that even simple, starchy dishes like mashed potatoes enter a bacterial "danger zone" at temperatures between 40 degrees and 140 degrees Fahrenheit. At those temperatures, toxic bacteria can quickly multiply, stealing your holiday spirit -- and squashing your appetite.
Given enough warmth, nutrients and moisture, a single bacterium dividing every half-hour can produce 17 million offspring in 12 hours, according to figures cited by the Center for Science in the Public Interest.
Three particularly nasty microbes can hitch a ride on hands and steam tables, turning a Christmas or New Year's party into anything but a celebration, according to the U.S. Department of Agriculture's Food Safety and Inspection Service:
Staphylococcus aureus, which lives harmlessly on the skin and inside the nose and throat, frequently spreads through improper food handling. Cooking kills staph bacteria, but the toxin the bacteria produce are like action movie villains, withstanding heat, refrigeration and freezing temperatures to wreak havoc inside the intestines. The toxin attacks cells lining the gut, producing cramps and bloody diarrhea that may begin hours to days after you've swallowed the offending food.
Clostridium perfringens, sometimes called the cafeteria germ, is frequently found on cafeteria steam tables holding meat and gravy.
Listeria monocytogenes, often found in soft unpasteurized cheeses, thrives on cold buffet foods and continues multiplying inside refrigerators. Many people can be exposed without any health consequences, but this microbe poses peril to pregnant women, in whom it can trigger miscarriages, and to the elderly, who could land in the hospital after exposure.
In general, food safety experts recommend chilling leftover foods at 40 degrees or less, and re-heating them to at least 165 degrees to eliminate dangerous bacteria.
Soups should be heated to a rolling boil and stirred to heat throughout, advises Caroline Smith DeWaal, food safety director for CSPI, a consumer advocacy organization in Washington, D.C.
Food safety experts try to encourage good food-handling practices. DeWaal likes to invoke the following rule of thumb for holiday foods: 2 hours -- 2 inches -- 4 days.
2 hours is the maximum time a food can go from oven to refrigerator. "You take it out of the oven, you have your nice meal, but within two hours, you really need to be putting that food away and in the refrigerator," she said in a pre-holiday interview.
2 inches is the depth of containers you should use to quickly cool warm foods. That means dividing up big pots of soup, taking turkey meat off the bones and putting these into multiple, small containers.
4 days is how long leftovers can stay in the fridge, unless you freeze them. However, stuffing and gravy go bad more quickly and should stay in the fridge no more than 2 days before you must eat them or toss them.
DeWaal said turkey took the No. 1 spot in a CSPI analysis of foods at highest risk of triggering food-borne illness during November and December in the years 2004 through 2008, the most recent available.
CSPI based its list on data reported to the federal Centers for Disease Control and Prevention in Atlanta, which defined an outbreak as an episode in which at least two people became sickened by the same food, were seen by a doctor and had the illness confirmed by tests.
CSPI tracked food-linked infections during the months that include Thanksgiving and Christmas celebrations; people who became sick after eating contaminated turkey were infected with clostridium, norovirus, salmonella and staph aureus.
Food poisoning has undergone shifts over the years, DeWaal said. "Traditional cuisine back 40 to 50 years ago was really overcooked by today's standards, but that's protective. Your green beans would be wilted. Now they're cooked al dente, or sometimes not cooked at all. We're eating a lot more fresh food, which is really good for us, as long as it doesn't carry a lot of harmful bacteria."
She said canning has become much safer because of strict regulatory controls, but at the same time, raw shellfish is more likely to be contaminated with dangerous microbes like Vibrio cholerae.
Today, food safety specialists worry about potentially fatal E. coli 0157:H7, first identified in the early 1980s, which has been traced to meat and some fresh vegetables.
It can shut down the kidneys and destroy red blood cells. They're also seeing newer strains of an antibiotic-resistant bacterium called shiga toxin-producing E. coli, (STEC) first identified in the 1990s and at the beginning of this decade.
To learn how long a food can stay in the refrigerator or freezer before bacteria make it unhealthful, you can check StillTasty.com, a website co-founded by Janice Revell, a New York-based journalist, and her mother Jeannie Revell, a former food safety specialist for the Canadian government, who lives on Prince Edward Island.
Their site provides information from several U.S. agencies about how long foods can be safely stored and consumed.
Revell says many people mistakenly assume that main courses pose the biggest food poisoning dangers. "You have to actually start thinking about the appetizers," she said. "The pre-meal in many cases is more dangerous than the main meal." Hosts and hostesses typically leave pates, soft cheeses like Brie, and dairy-based dips out for hours, even though they're particularly susceptible to bacterial growth. Many guests pay scant or no attention to side dishes, which "can be absolutely just as harmful to you."
Big offenders include rice salads, pasta salads and "that bowl of mashed potatoes, if it's not put into the fridge a couple of hours after serving it."
These starchy dishes are breeding grounds for Bacillus cereus, a microbe that can cause severe vomiting or disabling diarrhea.
And don't forget gravy.
If it's been left on the countertop for hours on end, even boiling may not guarantee it's safe to serve, she said. "You can't take that kind of chance."
Revell advised against the old-fashioned sniff test, especially with cooked food. "There are all kinds of harmful bacteria and toxins you can't smell. You can't rely on your nose to tell you."
Once foods have been sitting around more than 2 hours, "it's not worth trying to eat them again. Throw them out; they're dangerous," Revell said. "It's painful to throw out food, but it's even more painful to have food illness or food poisoning over the holidays."
You can take it from my mother, Doris J. Allen, whose simple rule in our family's New Jersey home applies equally well to clearing a cluttered room or a refrigerator chock full of carefully wrapped leftovers: "When in doubt, throw it out."
The USDA Meat and Poultry Hotline, 1-888-674-6854, fields 80,000 calls a year with questions about the storage, handling and preparation of meats, poultry and eggs.
StillTasty.com provides specifics for thousands of foods about how long they're edible before they should be tossed out.
The Partnership for Food Safety Education,including representatives of the USDA, FDA and CDC created a joint campaign with advice on how to safely handle and cook many types of food.
FoodSafety.gov is a gateway site for federal food safety information.