Before there was an entire social media culture dedicated to meal prep hacks, there were sandwiches. With just two pieces of bread and some filling, you’ve got a quick and easy meal that’s easy to take on the go or make ahead of time. It’s never a good idea to let a good sandwich hang around for too long, however. If you’ve ever eyeballed a turkey and cheese that’s been sitting out on a plate for hours and wondered if it’s still okay, or pondered when to eat that Italian sub in your lunchbox, the answer is simple: Most sandwiches with perishable ingredients will stay fresh for two hours at room temperature. So, if you’ve got a spread of tea sandwiches laid out on a girls’ night, or you’ve stashed an egg salad sandwich in your handbag for the plane, the clock is ticking.
Food safety is nothing to mess around with. Foodborne pathogens like E. coli and Salmonella, which are always lurking in our food supply, can make you pretty sick, and science has mapped out some straightforward rules to keep you safe. According to the United States Department of Agriculture (USDA), bacteria can rapidly grow in sandwich-friendly foods like deli meat, cheese, and mayonnaise anywhere in the temperature range of 40 and 140 degrees Fahrenheit, which is often called the temperature danger zone.
Sandwiches deteriorate over time
If you’re wondering what defines room temperature, it’s not an exact science, but it’s mostly agreed upon as around 70 degrees Fahrenheit. This is the temperature that most people find comfortable while dressed in a normal layer of clothing. Warmer temperatures will speed up the growth of pathogens, so if a platter of pinwheels is sitting out in the sun at a barbecue at 90 degrees Fahrenheit, you actually only have about an hour before they’re not safe to eat according to the Centers for Disease Control and Prevention (CDC). Colder temperatures will slow the process down, but only an environment that’s colder than 40 degrees is truly safe, which is the temperature sweet spot for refrigerators is typically set at around 35 to 38 degrees Fahrenheit.
Of course, food safety isn’t the only deterrent to the life cycle of a sandwich. Many ingredients simply degrade over time and become unappetizing if they’re left out at room temperature. Bread gets soggy or stale, cheese will crack and look greasy, and meats dry out in just an hour or two. So, always eat your sandwiches within two hours, and if you’re packing them up for later, store them in a cooler or insulated lunch bag with a cold pack, which will keep your food cold for three to four hours — plenty of time for a school lunch.
