12 pantry staples that don't last as long as you think they do

• Whether dealing with pantry staples or leftovers that we put in the back of the freezer and totally forget about, it's easy to think that certain foods will last forever — or at least for a very long time.
• But some foods expire much more quickly than you'd think, potentially leading to illness or an overall unpleasant taste.
• INSIDER spoke with two chefs and a registered dietitian, and they told us about many foods don't last nearly as long as you think they do.

Few of us are able to reasonably consume all of our food before it expires — after all, expiration dates aren't always the best guideline to work from, because plenty of foods last much longer than we might believe, leading many of us to throw out food that is still safe to eat.

But then life gets in the way and we end up with a stocked pantry or freezer filled with food that sits for days, weeks, months … or even years, and we're left wondering if those pantry staples like canned tomatoes or frozen leftovers are safe to eat, especially when they look and smell totally fine.

INSIDER spoke with two chefs and a registered dietitian, and they told us about many of the foods that don't last nearly as long as you think they do and some of them will definitely surprise you.

Check your condiments — opened ketchup and mayonnaise can go bad within weeks.

Ketchup and mayo aren't refrigerated in stores and often have listed expiration dates years in the future, but that doesn't mean your jumbo jar of mayo will last into the next presidency.

According to Isabel Maples, MEd, RDN, a Virginia-based registered dietitian nutritionist and volunteer spokesperson for the Academy of Nutrition and Dietetics, you should consume your favorite condiments within weeks, even if they're refrigerated.

She says that ketchup and chili sauce are safe for up to 12 months if unopened, but should be consumed within one month if opened. Mayo will last 10 to 12 weeks in the fridge once opened.

The trouble with condiments is that "the texture and flavor will be compromised," according to Alisa Rosa, an executive chef.

Mustard, however, will last up to two years if unopened, around six to eight months if opened and un-refrigerated, but longer if kept sealed in the fridge.

Tea and coffee can go bad much more quickly than you'd think.

We tend to think that "nonperishable" means it will last forever, but this is rarely the case, according to our experts.

In fact, tea, including tea bags, loose teas, and instant tea, should be consumed within one year. "The oils in tea will go rancid," explained Rosa.

As for coffee, Rosa told INSIDER that the beans or grounds will go rancid "after time … especially if the packaging has been opened." Maples recommends consuming within two to four weeks if opened and a year if unopened. For instant coffee, java drinkers can eke out a bit more time: two months if opened and six months if unopened. She adds, "For longer shelf life, store in the freezer, not the refrigerator."

Some canned goods can last up to five years — others expire much more quickly.

Stocking up on canned goods might seem like a good way to save money on pantry essentials so that you'll always have them on hand. But the safety of these items typically depends on how acidic the canned good is … meaning tomato-based cans and canned fruits like pineapple will lose their quality much faster.

Maples recommends consuming highly acidic canned goods within 18 months, adding, "canned goods like green beans are probably good for five years even they aren't stored in a crawl space or attic where they're exposed to heat."

"Use a first-in, first-out rotation to use up older pantry items first. Inspect cans before using them; avoid bulging, cracked or leaking cans," she told INSIDER. "Don't use cans that squirt liquid when opened. And don't taste the contents to see if they are safe — just throw them away. Look at ‘best by' and ‘expiration dates' when cleaning out your pantry."

"For most pantry items, the issue in storing foods too long is food quality, not food safety," she said, adding, "Never taste foods to see if they are safe. Pathogens are usually not detected like that but still can make you sick." The ideal storage temps for pantry items range between 50 and 70 degrees, according to Maples.

All three experts agree that canned goods will begin to taste less like what they should and more like a metallic "can," thanks to broken down texture over time.