7 Foods That Can Survive Outside the Fridge

NEW YORK ( MainStreet) -- When Hurricane Irene barreled up the East Coast in late August, many people in the storm's path rushed out to the grocery store to get canned food and other nonperishable items. After all, in the event power did get knocked out, all the food in their fridges would have spoiled and needed to be thrown out -- right?

Actually, it's a bit more complicated. While milk, for instance, will spoil after a few hours at room temperature, some cheeses are safe to eat after the same amount of time. In fact, the U.S. Department of Agriculture's Food Safety Inspection Service put out a special bulletin informing hurricane-stricken residents what they do and do not need to throw out in the event of a prolonged power outage. Apparently, not everything you normally put in the fridge will quickly go bad if it gets warm.
Left food on the counter? Storm knocked out the fridge's power? You don't need to throw out everything.

To find out more, we spoke to Jeff Potter, a food science expert and author of Cooking for Geeks.

"The important thing to understand about refrigeration is that it slows down how quickly the bacteria multiplies," he says. "It changes the temperature of the environment so the bacteria don't multiply fast enough." And the slower the bacteria multiply, the slower it will take for your food to go bad.

That's not the end of the story, though. Temperature is just one of many factors that determine how hospitable the environment is for the bacteria to make your food go bad.

Bacteria need water to survive, for instance, which is why dry foods such as crackers are OK at room temperature. Maintaining a proper pH level is also crucial, which is why something such as hot sauce (which tends to be vinegar-based and thus acidic) doesn't need to be refrigerated. It also needs to have oxygen, as well as the right kind of food to munch on (which is why Crisco and other oils, lacking sugars and water, can be stored on the shelf without going bad for a long time).

The result is that some refrigerated foods are simply less prone to spoilage than others, even when they warm up. Here are a few foods that won't turn rancid on you if they spend more than a few hours outside the fridge.

Salted butter
It may seem odd that butter would be OK at room temperature, while milk quickly goes bad. But the two dairy products are different in crucial ways.

"Milk is mostly water, while butter is mostly fat," Potter says. That alone means bacteria won't multiply as quickly in warm temperatures.

But that's not the whole story. Butter comes in salted and unsalted varieties (the latter used mainly for baking or for people on low-fat diets), and he says the salted kind should be fine indefinitely at room temperature.

"Butter is right on the threshold as for whether it's safe unrefrigerated, and salt lowers the water available to the bacteria ," he says. "Unsalted butter should be refrigerated, but salted butter should be OK out on the counter."

Up to this point we've been referring to "bacteria" as if it were a single species. But the bacteria responsible for spoiling food, for instance, are totally different from food-borne illnesses such as listeria. In fact, food spoilage bacteria won't even make you sick -- although, since they tend to reproduce under similar conditions as food-borne illnesses, the fact a food item has spoiled makes it more likely the nastier bacteria are also present.

And as most of us learn in high school science class, some bacteria are actually good for us.

Case in point: Yogurt is actually made with bacteria, and some of it is even "probiotic," meaning it contains microbes thought to be beneficial to humans. Obviously, leaving this stuff at a temperature where the bacteria become more plentiful isn't a bad thing.

"The bacteria that are in that container are actually a strain that's beneficial to us, so if you accidentally leave yogurt out for eight hours, it's going to be OK," Potter says.

Of course, it will also be warm, and you might not be into warm yogurt.

Hard cheese
Cheese comes in many varieties, almost all of which are delightful. There are soft cheeses including mozzarella and Brie, and there are hard cheeses such as Parmesan and Romano.

Surprisingly, these different cheeses spoil at much different rates. According to the U.S. Department of Agriculture, soft cheeses should be discarded if they spend more than two hours over 40 degrees Fahrenheit. By contrast, hard cheeses (which also include cheddar, Swiss and provolone) should be fine if they get a little warm. Processed cheese is also OK if the fridge loses power.

"The difference between Parmesan and soft cheeses is water availability -- is there sufficient moisture to reproduce?" Potter says.

Eggs (Sort of)
We're wary of saying this after last year's massive salmonella outbreak, but eggs are probably OK to leave at room temperature for a little while, according to our expert.

The main concern here is not spoilage but salmonella, and as such it's a matter of playing your odds. Potter points out that in parts of Europe salmonella is virtually nonexistent, and even in the U.S. only 1 in 10,000 eggs actually has the disease. And even if it does, cooking it properly will kill the bacteria.

Whether you decide to take your chances should depend on who you are. Salmonella can be more serious for certain groups.

"If you're a healthy male adult, you'll have a couple of uncomfortable days," Potter says. "If you're really young or old, or you're pregnant or sick, it could lead to secondary complications."

Eggs won't spoil if you leave them out for more than a few hours, and even if there's salmonella present there's a low chance of it causing serious health problems. But that doesn't mean we can recommend taking the chance.

Most people know they can store bread for long periods by freezing it, and therefore logically conclude that keeping it cool in the fridge will extend its shelf life over the short term.

Unfortunately, that's not true. Putting bread in the fridge actually makes your bread go stale more quickly than simply leaving it at room temperature.

As Potter explains, freshly baked bread (and other baked goods) should be moist on the inside and dry on the outside when first baked. When bread goes stale, it's because the water has migrated around and become more uniformly moist. Keeping bread at a cool temperature actually accelerates this process, though actually freezing it obviously keeps the water in place.

In other words, you're not doing your bread any favors by sticking it in the fridge, but it's OK to put it in the freezer or leave it at room temperature.

Ketchup, mustard and other vinegar-based condiments are able to survive warm environments for the same reason hot sauce doesn't need to be in the fridge: The high acidity of these foods makes them poor breeding grounds for bacteria. The USDA also lists pickles as being OK at room temperature for much the same reason.

"The pH of ketchup is around 3.6, which is acidic enough to avoid needing to refrigerate it," Potter says. "Likewise, as long as the mustard is of low enough pH (less than 4, according to the FDA), then there's no need to refrigerate it, although a number of mustard manufacturers recommend keeping their product refrigerated to help maintain flavor."

Basically, if you're having a barbecue, it's OK if the burger toppings sit outside all afternoon. The exception is mayonnaise (if you're a mayo-on-your-burger type). The USDA says mayonnaise, tartar sauce and horseradish should be discarded if they spend more than eight hours above 50 degrees Fahrenheit.

Beef jerky is created by removing all the moisture from a piece of meat, thereby making it inhospitable to bacteria and able to last a long time. Jam is a similar situation: While there is water present, the high levels of sugar means the water is not "bioavailable," which means the bacteria can't access it.

"There's a lot of water in jam, but it's locked up in sugar so the bacteria can't get to it," Potter explains. "Keep in mind that there has to be sufficient sugar in the jam for this to be true, so heed the advice on the label."

Basically, think of the bacteria as floating in a lifeboat in the middle of the ocean: There's water, water everywhere, but not a drop to drink. That's why jam is sometimes referred to as "fruit preserves."

Health department guidelines generally say refrigerated foods shouldn't be held between 40 and 140 degrees Fahrenheit for either two or four hours, depending on which state you live in. The foods listed here are the ones that can survive longer than that at room temperature.

Still, food safety is full of gray areas, for reasons that should be clear: There are numerous variables determining whether bacteria can reproduce, and it's not always obvious which foods do or don't fall in the danger zone. Is this cheese soft or hard? Is this butter sufficiently salted? Are these pickles acidic enough?

For this reason, it's always better to err on the side of caution and stick it in the fridge (with the exception of bread, obviously). Chances are you have enough room in the fridge for that carton of eggs, so there's no reason to tempt fate and leave it out.

"It's always safer to refrigerate," Potter says. "When in doubt, put it in the fridge."

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