Why You Should Add a Whole Raw Egg (Shell Included) To Your Coffee | America's Test Kitchen (2024)

Eggs and coffee are typical breakfast fare. But have you ever had eggs in coffee?

It sounds like something a bodybuilder would drink for extra protein. But it’s far more delicious—and purposeful—than it sounds. In fact, brewing what’s known as Swedish egg coffee will result in a spectacularly smooth and mellow cup of joe. Here’s why.

Swedish egg coffee is a method of using eggs to brew a large batch of deliciously smooth coffee. It’s also referred to as Norwegian egg coffee, Scandinavian egg coffee, or just egg coffee.

According to Danish coffee expert Asser Christensen, “Swedish egg coffee was brought to the U.S. by Scandinavian settlers, and it’s still popular in certain states today.” It’s also known as “church basem*nt coffee” because it is often served at church gatherings for Scandinavian Americans in the Midwest.

To make it, all you need to do is crack an entire egg (yolk, white, and shell) into your coffee grounds, creating a potting soil–like texture, before adding it to boiling water, simmering the mixture, and pouring off your coffee. You don’t need to strain the resulting coffee—the egg binds the grounds so completely that you can simply scoop off the mixture that floats to the top.

The staying power of this technique in the fringes of American coffee culture is surprising to Christensen. “It’s an interesting trend to observe,” he says. “This type of coffee has been out of fashion for almost a century in Denmark, Sweden, and Norway.”

So how did it come about, then? “Modern coffee makers had not yet been invented [in the late 1800s], so people attempted many different things to get a delicious and clean cup,” Christensen said. “In Norway, where there is a robust tradition for cowboy coffee, dried fish skin was used instead of egg.”

But given just how smooth Swedish egg coffee is, it may be ready for a comeback.

Much like assessing the value of a brilliant diamond, clarity is important for good coffee. By combining the grounds with raw egg, the mixture separates more easily from the boiling water, ensuring that no bitter coffee grounds are left floating in the end product.

But the reasons behind the egg making a better cup of coffee extend even further than that, and for this part, we’re going to have put on our science goggles.

Due to their chemical composition, eggshells are an important component to a delicious final result (despite some recipes saying that they’re optional). Eggshells are composed mostly of calcium carbonate: an alkaline material, which, when mixed with acidic coffee grounds, has the ability to soak up some of that acidity and remove it from the coffee’s final taste.

The result? A considerably more mellow brew.

Cook’s Illustrated’s test cooks, knowing the power of an egg combined with coffee, conducted an experiment to determine if eggshells could also be used to extract bitter compounds from coffee that accidentally turns out too strong.

“We purposely brewed a batch for too long, lightly crushed an eggshell (rinsed in vinegar and then water to kill any bacteria), stirred it into the potent coffee, and strained out the shell. Indeed, this quick treatment produced a milder cup,” the team said.

“The same effect can also be seen nowadays when people use gelatin to clarify homemade wine,” Christensen said of the practice.

So the next time you’re looking for a smooth cup of coffee, don’t be afraid to mix in a whole egg (shell included!) for a mellow cup. We promise that the resulting drink won’t be an eggy mess.