Now is an exciting time to be a coffee lover. Quirky new coffee shops serving great coffee seem to be springing up everywhere and never before has it been easier to obtain premium-quality, specialist coffee beans.
Baristas everywhere are experimenting with new techniques while at the same time, trying out some older methods that have fallen out of favor.
One method undergoing a revival is the use of eggshells to brew coffee. But what are the benefits of eggshells in coffee? As it turns out, there are good scientific reasons why this might improve your brew. If you’re curious to find out how please read one.
Why is coffee bitter?
Coffee is naturally bitter. When we grind coffee beans and brew them into a drink, the resulting beverage is always, to a varying degree, bitter. People’s tastes vary, but for most people, if coffee is too bitter, it becomes unpleasant and undrinkable.
Coffee beans are packed with all kinds of flavor compounds. Some of these are the delicious, aromatic flavors that we want in our drink; some of them, on the other hand, are nasty flavors that spoil our brew and make it unpalatable.
When ground coffee comes into contact with water, the flavors begin to be released; this process is known as extraction. In general, the desirable flavors are the first to be extracted, followed by the undesirable ones (1, 2).
This means if we brew coffee correctly, ensuring that it is not over-extracted, the resulting drink will not be unpleasantly bitter. If we leave it to brew too long, the bitter compounds will be released, making the coffee more bitter and harder to drink.
Some coffee beans are naturally more bitter than others. There are several species of Coffea plants but only two are cultivated on a large scale for the production of coffee, Coffea arabica and Coffea canephora (commonly known as robusta) (3).
Of these two, robusta coffee beans contain roughly twice as much caffeine as arabica beans and also produce a much more bitter drink. Arabica beans are prized as the highest quality product and fetch a much higher price; robusta beans are reserved for more rustic coffees.
This all means that if you have high-quality arabica beans able to produce a coffee full of complex flavors with only mild bitterness and you use the correct brewing method, you will probably be able to enjoy the coffee without sweeteners.
If, however, you have lower grade arabica beans or robusta beans and you are using a less delicate brewing method, your coffee will turn out bitter and you will need to take steps to make the coffee taste better.
Fighting the bitterness
We are fortunate enough to be living in the age of the Third Wave of coffee and a specialist coffee shop with highly-trained baristas serving specialty coffees brewed to perfection is never far away. However, it has not always been so.
In years gone by, coffee was not always the luxury product it is today; when the coffee-drinking habit began to take off in the US in the early- to mid-twentieth century, much of the coffee being consumed was a far rougher product than we are used to today.
Brewing methods were often a lot cruder too, and much of the coffee being drunk would have been extremely bitter.
There are many ways of trying to combat this bitterness. One of the most common ways is by adding sugar or another sweetener. This is a simple way to mask the natural bitter flavor of coffee.
Another traditional way to do this was to add eggshells to the coffee grounds.
This may sound like the kind of thing your grandma might have done – some people perhaps even remember this from their childhood – but there is actually sound scientific reasoning behind this apparent craziness.
The scientific basis for adding eggshells to coffee
So how do eggshells make coffee less bitter?
The thing about coffee is it’s acidic, and it’s largely this acidity that makes it bitter. Eggshells, on the other hand, are made from calcium carbonate, an alkaline substance. So, in theory, if you add eggshells to coffee, you reduce the acidity of the drink and therefore the bitterness as well (4, 5).
This means due to eggshell calcium content, adding eggshells to coffee can help improve your brew.
As we said, in the old days, the coffee wasn’t necessarily of the highest quality and those drinking it weren’t looking for notes of berries and hints of chocolate. They wanted a hot drink with a kick that would just get them moving in the morning.
If you were drinking coffee like this, adding eggshells to reduce the acidity and make it more palatable would have made a lot of sense (6).
Eggshells were also commonly used to brew “cowboy coffee”, or campsite coffee. When people spent time away from the comforts of home, they didn’t always have very many tools for cooking and making drinks.
Coffee was often prepared in a large pot of boiling water over a campfire. Brewing coffee in this fashion is enough to make any modern Third Wave barista wince and cover their eyes; boiling coffee like this will lead to it being totally over-extracted and horribly bitter.
But back then, it was what they had. And to improve the flavor, they broke up some eggshells and threw them in too.
Eggshells also had another effect when making this kind of coffee. Since the ground coffee was boiled loose in the pot, when you came to drink it, you were likely to end up with a mouth full of powder along with the brew.
However, adding eggshells also caused the ground coffee to settle at the bottom of the pot, ensuring what you were drinking was free of sediment. This was another reason why the practice was so popular – they were a kind of natural cowboy coffee filter (7)!
Why would you want to try now?
Ok, so that was before, but now is now. Why would you want to revive this archaic practice when we have access to delicious beans sourced from specialist farms and all manner of precise brewing techniques that help fight bitterness without the need for eggshells?
Well, there are still plenty of reasons why you might want to try.
First, as we said, different people have different tastes. Some people like strong coffee so bitter it makes you screw up your face when you drink it. Others, however, prefer their coffee to be much milder, and some don’t even drink coffee because it is too acidic and bitter.
If this sounds like you, why not try brewing coffee with eggshells? The resulting drink will have a much smoother, mellower flavor – although if you are using high-quality beans, you may find they lose some of their complexity.
If you don’t like coffee, try making it with eggshells. You may find you enjoy the drink more like this.
Similarly, if you have made a batch of coffee that has turned out too strong, you may try throwing in some eggshells. As with using eggshells during brewing, you will find that the eggshells tame the acidity of the brew and make it easier to drink.
Another reason for using eggshells in coffee is if you find yourself with poor quality coffee. This may be because you bought cheap coffee in the first place or because you left it too long and it went stale.
Old coffee beans (or old ground coffee) make a poor drink, but you can take the edge off it by mixing in some eggshells.
If you’re a camper and you can relate to the problems of the old-fashioned way of boiling coffee on the campfire, you might also be interested in trying the old-fashioned solution (8).
For sure, nowadays there are lots of modern ways to make decent coffee while you’re out in the woods, but you might still be interested in trying the traditional remedy for this age-old problem.
Check out below video to see how to make cowboy coffee (this guy doesn’t use any eggshells – though maybe he should try!).
Finally, you may just be curious about the idea. At first, the thought of using eggshells to brew coffee seems strange and maybe even a little disgusting, but when you know what it’s supposed to do, it starts to sound intriguing.
Give it a go, even if it’s just to see what the result is like. The drink you produce will certainly be different to the one you usually sip – and who knows? You might even prefer it.
Why wouldn’t you want to try?
There are a couple of reasons why you wouldn’t want to use eggshells. First, obviously, if you have spent a lot of money on a bag of expensive specialty coffee, you want to brew the drink carefully and precisely to bring out all the subtle, complex flavors.
Using eggshells to brew high-quality coffee such as this would be an act of sacrilege – something akin to mixing a fine wine with lemonade.
If you use eggshells with good coffee, you will be removing or masking all the delicious flavors you are paying the extra money for. Eggshells are perfect for livening up poor coffee but are not suited for use with high-quality beans.
The other major reason why you wouldn’t want to use eggshells is another obvious one: if the coffee is for someone who suffers from an egg allergy, don’t do it!
How do you do it?
If you have been reading this and you’re convinced it’s something you want to try, here’s a brief description of how you can do it.
It doesn’t matter on your brewing method since eggshells are compatible with most ways of preparing coffee.
The first thing to remember is you should use the shells from raw eggs. If you boil the eggs first and then remove the shells and use them in your coffee, your drink will end up…tasting and smelling of boiled eggs!
Remove the white and the yolk from the shells and keep it for something else. Take the shells and wash them thoroughly. Is eggshell calcium safe? Well, yes, but remember, eggs come from chickens – and they haven’t been washed since they were laid!
A good way to wash and sterilize the eggshells so that they are clean and hygienic to use in your coffee is to make a solution of vinegar and hot water.
Once they are clean and ready to use, smash them up and simply mix them in with your ground coffee.
With the ground coffee and eggshell mixture, you can use whatever brewing method you usually prefer. Coffee with eggshells can be made with a French press, a drip coffee maker or most other kinds of coffee maker.
Brew as normal, and when brewing is complete, remove the coffee and eggshell mixture and discard as usual.
Next, simply serve the coffee and enjoy. You will find the coffee you have made is lighter in color and more mellow in flavor. After that, it’s up to you to adjust the recipe and experiment to come up with the perfect cup of coffee just the way you like it.
To begin with, as a general rule of thumb, the shell of one egg is roughly enough to make four cups of coffee. Any more than this and you will probably end up taking away too much of the coffee flavor and your brew will be insipid and tasteless.
Time to bring back an old tradition?
This is an old-fashioned way to make coffee, but in light of recent experimentation and innovation, maybe it’s time to revisit some of the practices that have fallen out of fashion to see if they can be brought up to date.
Perhaps making coffee with eggshells the way you remember your grandma doing it is ready to make a comeback!
Have you ever tried to make coffee with eggshells? Or perhaps you have other tricks for removing the bitterness and improving bad coffee. If you do, please leave us a comment since we love hearing from you – and if you enjoyed this article, please don’t forget to share!