Eggshells Are The Ultimate Fix For Overly Bitter Coffee

Say you have an over-bitter cup of coffee, what's your go-to way of fixing it? Some opt for a generous amount of sugar, while others prefer a splash of creamer. There are dozens of tricks to turn a bitter cup of coffee around, but it's probably a safe bet to assume that you haven't heard of anyone crumbling and dropping eggshells into their coffee as a fix for bitterness before.

Believe it or not, it was the go-to method to take out the acridness in bitter coffee back in the days of the Wild West. Cowboys and travelers obviously didn't have access to high-quality grounds, which they would brew over a campfire (they had to make do without a coffee maker in the 19th century!) They would compensate for the bitterness by crushing eggshells and sprinkling them into the coffee, letting the bits soak up the bitterness for a few minutes, then straining out the eggshells for a more balanced cuppa. This might sound like a campsite myth, but this trick not only works, it's also supported by science!

First, it's important to look at why a cup of coffee — campfire-brewed or otherwise — tastes bitter in the first place. A range of acids called chlorogenic acid lactones are responsible for the bitterness and harsh tastes in coffee. To counter the acidity, you'll need to add a basic chemical, which can "soak up" the acidity and lower the overall pH of the coffee.

Luckily, eggshells, composed primarily of calcium carbonate, fit the bill perfectly! Calcium carbonate is alkaline and can absorb all the bitter, acidic compounds, resulting in a smoother, more mellow flavor.

America's Test Kitchen did a quick test of this method by mixing crumbled eggshells into a cup of coffee that had been intentionally over-brewed so that it was extra bitter. They found that the coffee tasted significantly more palatable, but they also noted that removing the acids led to a loss of complexity in the flavor. As such, you should only try this trick when you're dealing with cheap coffee grounds — you probably don't want to sacrifice the complexity of a specialty coffee in this manner!

The easiest way to get eggshells is by boiling the egg first (you can use the soft-boiled egg inside to make a quick dish like a high protein egg salad). This helps eliminate most of the dirt and bacteria on the outer shell, making it safe to add directly to your coffee. But if you crack open a fresh egg, it's best to soak the shells in vinegar and water to sanitize them.

You can crush the eggshells by using the rolling technique, or using a pestle and mortar if you have a lot to process. Each egg usually yields enough shell bits for about four cups (a pot), so adjust accordingly based on how many people you're serving.

Once you've added the eggshells to the coffee, it's best not to drink it straight from the pot away unless you like the crunch of eggshells in your mouth. Instead, use a ladle to pour the mellowed coffee from the pot into a cup. Alternatively, strain it through a mesh screen to remove all the bits before kicking it back!