7 Items You Should Toss From Your Refrigerator ASAP, According to Food Scientists

Your fridge’s oldest residents—those jars and condiments—may be past their prime.

Key Points

• Once opened, even salty, sugary, or fermented foods start to spoil because exposure to air, light, and microbes breaks them down.

• Subtle changes—like mushy pickles, bubbly jam, or spongy olives—mean spoilage has started, even if mold isn’t visible yet.

• To make jars last longer, refrigerate promptly, use clean utensils, tighten lids, and trust your senses if anything seems off.

It's pretty obvious that those leftovers that have been in the fridge for over a week need to go. Ditto that dried-out, once-tasty pizza. But there are plenty of foods that need to be tossed that are not so obvious.

We spoke to food scientists to find out which items lurking in your refrigerator might be overstaying their welcome. If your fridge door looks like a museum of half-empty jars—pickles from last summer’s barbecue, miso from your last soup phase, jam from who-knows-when—you’re not alone.

MEET the Experts

• Kantha Shelke, PhD, is an Institute of Food Technologists Fellow, principal at food science and research firm Corvus Blue LLC, and senior lecturer, food safety regulations, Johns Hopkins University.

• Abbey Thiel, PhD, writes about food science at AbbeyTheFoodScientist.com and shares videos on her YouTube channel.

Watch the Jars

Which are the foods we tend to overlook and hold onto too long? The main culprits, our experts say, are those salty, sugary, or fermented foods that seem like they last forever. Many of us operate under the assumption that foods high in salt, sugar, or acid can keep almost indefinitely. “That’s true only until you open them,” explains food scientist Abbey Thiel. The truth is, even the most preserved foods eventually go bad—and often sooner than you think. 

The Shelf Life Myth

When these foods are sealed, Thiel says, they’re “commercially sterile”—processed with heat or pressure so no dangerous microorganisms can grow inside. But once opened, everything changes. “Now the food is again exposed to outside microorganisms, oxygen, humidity, and light,” she says. “That’s when the quality can quickly start to decrease due to microbial growth, enzymatic reactions, and chemical reactions.”

In other words, your opened pickle jar is now fair game for spoilage.

Kantha Shelke, PhD, a food scientist and Institute of Food Technologists Fellow, agrees: “Salt and sugar slow down microbial activity, but some molds and yeasts can still grow in high-salt or high-sugar environments that inhibit most bacteria.” Over time, those tiny organisms do their work. “Food is always slowly changing,” says Shelke. “Fats oxidize and become rancid, colors fade, flavors change, and nutrients degrade.” In other words: nothing lasts forever.

Foods to Toss

Mold is usually the first culprit to appear in these foods, says Thiel, since it can grow even when there’s very little moisture available. You might see it on the surface of jam or around the edge of a pickle jar. But even subtler changes can signal trouble.

Shelke points out clues home cooks often miss with seven common foods.

Mushy Pickles and Sauerkraut

If pickles and sauerkraut have lost their crunch and turned mushy, they are “telling you that unwanted microbes are also at work.” And if you see a thin white film floating on pickle brine, it “should not be skimmed off—it’s a sign of spoilage microbes.”

Spongy Olives

Olives that become spongy or develop pink or red tinges are spoiled.

Separated Mayonnaise

Mayonnaise that separates or develops watery pools is breaking down due to bacterial enzymes.

Unpleasant Miso Paste

Miso should smell deep and earthy—“not sharp, alcoholic, or bitter,” says Shelke.

Bubbling Jam

Jam that’s bubbling or weeping liquid could be fermenting. “Tiny bubbles indicate yeast fermentation despite the high sugar content,” she says.

Thiel’s rule of thumb: “Use your nose and eyes. If a food looks questionable, give it a good sniff. You’d be surprised how good we humans are at determining if food is bad.”

How to Help Food in Jars Last Longer

Once you’ve opened a jar, care and handling make all the difference. Always make sure to put the food back into the refrigerator promptly, Thiel says. “I hate to see food sitting out on the counter!” Keep lids tight, squeeze out air from flexible containers, and always use a clean utensil—never your fingers. “Digging for that pickle with your fingers is actually a great way to add more microorganisms,” she says.

Shelke offers a few more guidelines:

• Keep it cold: Refrigeration slows down microbes and helps maintain flavor. Even shelf-stable miso should be refrigerated after opening.

• Keep it clean: “Do not double dip or introduce moisture, crumbs, or particles,” she warns.

• Keep it sealed: Wipe rims and tighten lids to limit oxygen exposure.

• Keep track of time: Once opened, she recommends roughly two months for mayo, one to three months for pickles and olives, four to six months for sauerkraut and miso, and six to twelve months for jam.

And finally, Shelke’s golden rule: “Trust your instincts. If texture, smell, or appearance has drifted from what you know is right—even slightly—it’s time to let it go.”

Because in the end, even the best-preserved foods have a shelf life—and no condiment, no matter how delicious, is worth a brush with spoilage.