If you only bake occasionally, check your yeast's expiration date. It is only good for a year if it's sealed. If it's unsealed and in your pantry it's probably dead. Next time, refrigerate your yeast right after opening the jar.
Coffee beans have one of the shortest shelf lives of all pantry staples. They only stay fresh for one to two weeks. You can extend their lives by putting them in the fridge. Refrigeration gives them around a month's worth of good brews.
Unlike flour, which is good in your pantry for around a year, cornmeal shouldn't even be stored in the pantry. It should go in an air-tight container in the fridge or freezer. Even then, it only stays good for two to six months.
Olive oil can go rancid after just three to four months in the pantry if it has been opened before. If your bottle is sealed, it will stay good for up to a year. You can tell if olive oil is rancid by the smell. Rancid oil smells like rotten eggs.
Onions are not impenetrable to the effects of aging. They're only good for around two to four months. They don't have a label you can check for an expiration date, so look for soft spots or blackness. Both are signs that your onion is past its prime.
Like onions, garlic cloves are another pantry item that seems to stay fresh for an amazingly long time. Also like onions, they last around two to four months and show the same types of grossness when it's time to toss them.
I bet there's at least one potato in your pantry that is sprouting. Yep. It's OK. It seems like potatoes are a magical food that stays good forever, but they only have a shelf life of two to five weeks, depending on the type of potato. Any signs of shriveling or softness and it's time to compost.
Many canned foods are only good for one to two years, especially in humid parts of the world. It's probably hard to believe for those of you in dry climates, but seriously, I've had this problem. High acid foods can also cause can corrosion, according to the USDA. If it doesn't have an expiration date on the can, remember, if the can is deeply dented or is starting to bulge, leak or heavily rusting, tossing it is a must.
If your mustard, mayonnaise and ketchup are sealed, then keep them in the pantry for around a year. If not, toss them. These condiments need to be refrigerated to stay fresh. Don't believe me? Take a look at the fine print on the back label.
Unopened, maple syrup can stay in your pantry for around two years. After it's opened it needs to go into the fridge. If you have an opened bottle in the pantry, toss it or you may be pouring mold spores on your pancakes.