An Online Debate Rages: Should You Keep Ketchup in the Fridge or Not?

We asked ketchup makers and food safety experts, and we have a verdict. But you might not like it.

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Feb 8 2017, 8:00pm

In a cafe at Camden Lock.

Let us guess: Should you want to throw some ketchup on your burger, you'll find it right on the table (at room temperature) in many restaurants, but at home, you probably keep it in the fridge.

Or do you, too, leave it out? Which version of life are you living?

Recently, a debate's been going down online, with people divided over whether ketchup's rightful home is in the fridge or the cupboard.

The discussion seems to have started when a Twitter user asked the question, "Where does ketchup belong? In the fridge or not in the fridge?"

Seventy-seven percent of people said ketchup should call the cool confines of a refrigerator home, while 23 percent said to keep it at room temp. But long after the poll ended, the conversation continued.

If you check a bottle of, say, Heinz ketchup, you'll notice that the manufacturers would side with the fridge crowd, saying, "For best results, refrigerate after opening."

Reached for comment, a Heinz spokesperson referred to an FAQ on the Heinz website.

"Because of its natural acidity, Heinz® Ketchup is shelf-stable. However, its stability after opening can be affected by storage conditions. We recommend that this product be refrigerated after opening. Refrigeration will maintain the best product quality after opening."

Jeff Nelken, a food safety consultant based in Los Angeles, says that ketchup is indeed acidic enough to deter spoilage, but it will deteriorate in quality if left unrefrigerated.

"Let's assume that we're talking about ketchup that is the standard ketchup we see in the supermarket as opposed to homemade ketchup, because those are different animals," Nelken told MUNCHIES. "They all have some basic ingredients: sugar, salt, and vinegar."

Photo via Flickr user Bethany

Photo via Flickr user Bethany

Those three ingredients are stabilizing ingredients, Nelken says, and at a pH level around 3.7, ketchup is highly acidic and not conducive to bacteria growth. But still, leaving the ketchup on the counter isn't necessarily the greatest idea.

"When you open up a bottle of ketchup and you leave it unrefrigerated, every time you open up the cap you let air into it," Nelkin says. "Since there is bacteria and mold in the air, you're allowing some bacteria and mold into the bottle. In 30 days, you'll see separation and a little deterioration in quality.

"You'll also smell a little bit of rancidity. It's not spoiling, but there's mold growth and it stimulates some chemical reactions. If you put it in the refrigerator, you'll have six months of shelf life. If you leave it at room temp, when it hits 30 days, you'll smell and see a difference in the quality of the ketchup, [and] it will have a funky taste or funky smell."

Dr. Rick Holley, a researcher studying the microbial ecology of food spoilage at the University of Manitoba, said you'd be fine if you eat ketchup stored at room temp, but voted for storing ketchup in the fridge. "From a food safety perspective, because ketchup has a low (<4.6) pH, it is acidic [and] does not need refrigeration to keep it safe," Holley told MUNCHIES. "However, its color is more stable at lower temperature in the dark (fridge is better)."

READ MORE: This Is the Best Way to Get Ketchup Out of the Bottle According to Science

As for restaurants that leave ketchup on the counter at room temperature, perhaps they burn through enough ketchup before running into any deterioration in color or quality. Or perhaps in some cases there's something else going on…

"If you look at the inside of the cap of the ketchup, around the ridges where cap screws on the thread of the bottle, you'll see mold buildup," Nelken said.

That, Nelkin says, is often the result of restaurant employees marrying the bottles, combining the contents of multiple partially used bottles to create one bottle.

"From all this marrying of ketchup, you end up speeding up that 30-day process, so that when you put the ketchup on the food it's no longer as sweet or as enjoyable," Nelken said. For a restaurant, he says, "really what you're saving is pennies, and you're jeopardizing your reputation."

So those who are still on the no-refrigeration team may appreciate that funky taste that comes with room-temp ketchup, or maybe they're ripping through a whole bottle of ketchup in under 30 days. Suffice to say, though, people are passionate about the subject. In the wake of the online debate, the UK grocery store Asda began stocking unopened bottles of ketchup in the refrigerated aisle, something not even Heinz says is needed, and on normal unrefrigerated shelves.

We are truly a people divided over ketchup. But perhaps there's hope.

Keep us posted.