8 Rules for Avoiding Food Poisoning on the Trail

On the fourth day of a Grand Canyon backpacking trip, I watched one of my companions eat his sixth room-temp hot dog and blurted out, “I really don’t think that’s safe.”

“Haven’t died yet,” he replied in a tone so flippant it was almost as if he was personally challenging the Grim Reaper to a duel.

But on the trail, what doesn’t kill you may not necessarily make you stronger. Hiking out with a serious case of food poisoning is one of the most unpleasant experiences you can have. Who wants to get out their Leave No Trace poop shovel every 17 feet? This is apparently a common concern: When I took to Facebook to ask my community about their most-pressing backcountry food safety worries, more than 100 people commented. So I had a food safety expert respond to eight of the most common queries.

Q: If I bring a frozen steak in my pack and let it defrost while I hike, can I safely cook it for dinner?

A: It depends. “Temperature matters. You need to make sure the steak is not above 41 degrees for more than four hours,” says Benjamin Chapman, an associate professor and food safety specialist at North Carolina State University. Once the meat is above 41 degrees, heat-stable toxins—the byproducts of bacteria found in meat—begin to enter the equation. As the name implies, high temperatures may kill microbes, but they won’t destroy heat-stable toxins that begin to form at these temperatures. Plus, there’s the potential for cross-contamination from steak juice leaking in your pack. “That’s even more problematic than the temperature aspect, in my mind,” says Chapman.

If you really want to bring a steak (or other raw meat) in your pack, here’s how to do it safely:

1. Make sure the meat is solidly frozen, well wrapped, and in a sealed, leakproof container.
2. Check the forecast. If the temperature will be in the fifties or above, you’re tempting fate, because your meat will pass that magical 41-degree threshold within a couple hours.
3. Pack the meat as far away from your body as possible to keep your body heat from accelerating the thawing process.
4. Bring a meat thermometer and test the center of your choice cut a few hours into your hike and before you cook. Anything above 41 degrees is risky, but the real question is how long has it been warmer than that? Heat-stable toxins take time to develop, so if the meat is 50 degrees, it’s probably been above 41 degrees for more than four hours, which puts it in the danger zone.

Q: How long will hard-boiled eggs keep in my pack?

A: If you’ve peeled your egg, the window for safe eating is pretty slim: Consume it within two hours. In the shell, though, hard-boiled eggs can last significantly longer, says Chapman. The only thing is that one tiny crack in the shell—even one you can’t see—can let in all kinds of bacteria. So, if the egg is in your pack and jostled enough to possibly form a crack, try to eat it within four hours, even if you stored it in an egg holder. And don’t even think about packing soft-boiled eggs. For safety, eggs should cook for ten minutes at a full boil.

Q: I didn’t finish my freeze-dried dinner. Can I eat the leftovers for breakfast?

A: Here’s what bacteria need to go nuts: food, water, and time. Chapman says that by adding water to a freeze-dried meal and leaving it overnight, you’re basically creating the perfect conditions for pathogens to multiply. The only time eating leftovers might be okay is if the air temperature gets into the thirties at night (that is, refrigerator temps), or if you’re eating something highly acidic, like tomato soup, since bacteria can’t thrive in a highly acidic environment.

Q: On a trip, I ate yogurt that had been out of the fridge for days, and it tasted fine. Was that safe to eat?

A: Surprisingly, yes. “Yogurt is highly acidic,” says Chapman, meaning bacteria can’t efficiently reproduce. “It may start to spoil and may smell and taste bad after a few days, but from a food safety perspective, it’s probably pretty safe to eat.” One caveat: This is not the case for raw-milk yogurts. Those are not safe to pack in.

Q: My dog got into my pack and ate half a granola bar. Can I eat the other half?

A: You probably will, no matter what we tell you, but you shouldn’t. “While dogs are not typically a source for foodborne pathogens, they can move pathogens to humans,” says Chapman. In fact, the CDC just put out a warning after puppies sold at a pet store chain made humans in seven states sick from Campylobacter, a bacteria that is one of the most common causes of diarrheal diseases in the world. And if your pooch has been drinking from giardia-laced streams, it’s possible he could pass that to you, too.

Q: I like to bring cheese along, but sometimes it gets spots of mold on it. Can I just cut those off?

A: Absolutely, says Chapman. But only if it’s a hard cheese, like Parmesan or cheddar. “It’s unlikely that you’d get a pathogen from that,” he says, adding that you do need to cut the mold off cleanly and make sure not to get the mold on your knife, which could result in cross-contamination. If there’s mold on your brie, goat, or other soft cheese, chuck it. In soft cheeses, the environment is perfect for pathogen growth, so a single spot of mold could indicate that there’s even more that your eye can’t see.

Q: I ate something questionable, but it’s okay because I drank whiskey with it, and alcohol kills germs, right?

A: “There are reports of people on cruise ships who drank wine not getting the food poisoning that the other passengers got, but that’s just anecdotal. There isn’t any data to back it up,” says Chapman. You can’t reliably use whiskey to clean your hands or a knife, either. Yes, hospitals sterilize implements with alcohol, “but they’re using like 90 percent alcohol. Your whisky is 40 to 50 percent.” If you need to sterilize a knife, a better way to do it is to stick it (carefully) into your campfire. Technically, Chapman says it needs to be above 171 degrees Fahrenheit for 30 seconds. That’s a hard thing to gauge with a campfire, so do your best (and then congratulate yourself for even thinking to sterilize your knife).

Q: What about my friend’s hot dog habit? Was that safe?

A: Yes and no. Hot dogs are precooked and require no heating, so, at least in that regard, my companion was okay. However, they don’t keep well. “Listeria is what I would worry about,” Chapman says. “It takes a lot of listeria to make you sick, but listeria also grows really, really fast.” An open pack of hot dogs will keep for seven days at 41 degrees and four days at 45 degrees, but at the bottom of Grand Canyon, where temps were often in the eighties? “You really only have about four hours at 60 or 70 degrees,” says Chapman.