Ketchup is a popular condiment—and for good reason. Its tangy-sweet flavor goes just as well with french fries as it does in barbecue sauces, on top of meatloaf, with scrambled eggs and on a hamburger. While there may be some debate about its true origins (it’s believed you can trace the tomato condiment’s roots to China), ketchup is as American as apple pie.  

But where is the best place to store an open bottle of ketchup? That’s a question I thought was pretty simple. Of course you should refrigerate an open bottle of ketchup just as you would other common condiments like mustard, mayonnaise or relish. Right? But then I was at a burger joint with my family a couple weeks ago, and when my kids asked for ketchup, I went up to the counter, grabbed a little white paper cup and filled it with ketchup from a giant plastic jug. I have to assume that big jug gets refilled with new ketchup every so often, but it’s likely never stored in the refrigerator. So was it safe to eat?

I put this question up to the folks at Conagra Brands, makers of Hunt’s Tomato Ketchup, along with some other industry experts, and it turns out they all agree that ketchup should be stored in the refrigerator. 

Why You Should Store Ketchup in the Refrigerator

“Once opened, ketchup should be stored in the refrigerator for best results,” said Jennifer Sargent, culinary specialist at Conagra Brands. “Due to the acidity of tomatoes, ketchup is naturally shelf-stable, but refrigeration ensures a better flavor and texture experience over a longer period of time.”

While every company has their own take on ketchup, they all have a very similar ingredient list. It all starts with tomato concentrate (essentially this is ripe tomatoes with much of the natural water removed). Tomatoes alone are fairly acidic, but cooking them with distilled vinegar makes for an inhospitable place for bacteria to grow.

However, that doesn’t mean ketchup is completely immune to picking up little bugs from the air. Bryan Quoc Le, Ph.D., a food scientist, author of 150 Food Science Questions Answered and founder of Mendocino Food Consulting, explained that it’s best to store ketchup in the refrigerator but not for food safety reasons. “Technically you could keep ketchup in the pantry, but certain yeasts that are acid-resistant can proliferate at room temperature,” said Le. “These are not dangerous but can greatly impact the taste and flavor of the ketchup. Some ketchup bottles that have been improperly manufactured or stored have been known to explode due to the growth of yeasts in the bottles.” 

How to Keep Ketchup Tasting Great

While there may be little risk in storing ketchup at room temperature (potentially exploding bottles aside), it is best to refrigerate a bottle once opened to preserve taste. A bottle of opened ketchup stored in the refrigerator can last for quite a long time. Simply follow the dates on the bottle. “Always check the ‘best by’ or ‘use by’ date on your ketchup bottle to ensure freshness,” said Sargent.

‘’Refrigeration keeps ketchup fresh for longer by slowing down oxidation and bacterial growth,” said food industry veteran Dennis Littley, chef and recipe expert at Ask Chef Dennis. “While an unopened bottle can sit in the pantry for months, an opened one should be refrigerated to maintain its best quality. If left out at room temperature, ketchup can develop off flavors, darken in color and even separate over time.” 

How to Tell If Your Ketchup Is No Longer Good

Storing ketchup in a cool dark place, like the pantry, is completely safe if you go through it quickly, say a few weeks or so. That is why restaurants often keep ketchup at room temperature, like that big jug at the burger joint I went to. But there are other factors that can cause ketchup to spoil or affect its quality. 

“If it’s kept out, it’s best to keep the bottle in a cool place away from sunlight, as ultraviolet light and heat can damage the flavor,” Le explained. “Ketchup rarely suffers from pathogens, as the pH is quite low due to the acidity of the product. If there is the rare instance that mold is growing in the ketchup, then it is no longer safe to eat, as mold can release mycotoxins that affect your health.”

Aside from storing a bottle of opened ketchup in the refrigerator, it’s also best practice to wipe the cap clean after use, as leftover residue can dry out, get crusty and lead to spoilage, Littley explained. If using a glass bottle, be sure the cap is on tight to prevent moisture from getting inside, and squeeze out excess air before closing plastic bottles to help slow oxidation, he suggested. 

“If you’re wondering when ketchup has gone bad, the easiest way to tell is changes in color, texture or smell,” Littley said. ”If the ketchup looks significantly darker, smells off, has mold or has separated into a watery liquid and thick paste, it’s time to toss it. While small amounts of natural separation are normal, excessive wateriness or clumps are signs that the emulsion has broken down, and it won’t taste as good.” 

The Bottom Line

It’s best to store an opened bottle of ketchup in the refrigerator. According to a culinary specialist at Conagra Brands, refrigeration will preserve the flavor and texture better over a longer period of time. Be sure to check your ketchup’s “use by” date to ensure freshness. If your ketchup has changed color significantly, smells off or has signs of mold, you should toss it.