The truth about ketchup

What you know-- or think you know-- about ketchup, you’ve known all along. It is made with tomatoes. It is not a vegetable. You put it on burgers, fries, meatloaf, hash browns, and hot dogs (except if you’re from Chicago, in which case NEVER). And it's as American as apple pie.

Or is it?

Actually, ketchup's surprising origins, as told by Stanford University professor Dan Jurafsky in his book "The Language of Food," go all the way back to 17th-century China. In short, ketchup started out as fish sauce, and it didn’t have tomatoes.

It has evolved since then, and its current popularity is undisputed. There is ketchup right this minute in 92 percent of U.S. households, according to the NPD Group, a research firm. Maybe (probably) it’s store-bought; maybe it’s homemade. Either way, we rarely go without it.

Here’s the rest of story on this sweet and tangy staple and how to get the most out of it.

A fishy start

Jurafsky says it was Vietnamese fishermen who introduced fermented fish sauce to Chinese traders traveling from their base in the southern Chinese province of Fujian.

The Chinese called it ke-tchup. (They also called it ge-tchup or kue-chiap; there was no one tidy English translation. Still, today, “tchup” means “sauce” in some dialects, according to Jurafsky.) And they brought the savory sauce further into Southeast Asia, where the seafaring British took a fancy to it, fiddled around with it, and eventually turned Americans on to it. Ketchup went 18th-century viral, basically.

Enter the tomato

Anchovies, mushrooms, walnuts, and oysters were common base ingredients for ketchup until the early 1800s, when tomatoes started showing up in recipes, Jurafsky says.

Ketchup turned sweeter in the mid-19th century with the addition of sugar to suit the American palate, according to Andrew F. Smith, author of Pure Ketchup: A History of America’s National Condiment, with Recipes.

In 1871, Heinz sold its first tomato ketchup. The brand, and flavor, remain synonymous with ketchup.

What’s in store-bought ketchup?

Ketchup, as the FDA now defines it, is tomato concentrate mixed with some combination of vinegar, sweeteners, and “spices, flavorings, onions, or garlic.” Those flavorings can run the gamut; Heinz’s line-up includes bacon, jalapeño, and Sriracha.

High-fructose corn syrup is the common sweetener, so check labels if you want to avoid it. Ketchup from small producers and “natural” and certified organic versions of commercial brands typically use cane sugar instead of corn syrup.

Reduced-sugar ketchup gets its sweetness from a sugar substitute, while no-salt ketchup contains a salt substitute.

A fruity option

Banana ketchup, a.k.a. banana sauce, is a popular Filipino condiment and yes, it’s made with bananas, not tomatoes, plus vinegar, sugar, salt, and spices. It's thicker and fruitier than regular ketchup. Food coloring gives it its bright red hue.

Find banana ketchup in Asian grocery stores and some well-stocked supermarkets. Jufran is the most popular brand.

To refrigerate or not to refrigerate?

“Refrigerate after opening.” It says it on pretty much every bottle of ketchup, and so you do it. But you don’t have to—not if you use ketchup regularly.

An opened bottle will stay fresh in your pantry for one month, and an unopened bottle for at least a year, according to USDA guidelines.

That’s because ketchup’s acidity, thanks to vinegar, makes it shelf-stable, says Jessica Ryan, director of brand building at Heinz.

But if you want your ketchup to last longer and taste its best, the consensus among experts is to keep it in the fridge. An opened bottle will last six months refrigerated. This goes for both classic ketchup and any flavored varieties.

If you lose track of how long that bottle’s been sitting around, trust your instincts. Check for mold or an off flavor or smell. Ketchup shouldn’t taste fishy—not any more.