Fermented Coffee Overview: Benefits, Brewing & More


Fermentation has given us some of the most delicious drinks that the world has ever known, like beer and wine. Both a delicacy and both rely heavily on fermentation. But what about coffee? Can it be fermented?

Coffee is actually fermented before it is roasted. Once the coffee fruit is picked, it can either be left to ferment under the sun or transferred to a water tank where all of the fruit is fermented together for a short period. Then, after the pulp is removed and we are left with the coffee bean, it is left to ferment for periods of 12 to 48 hours, depending on what kind of flavor you’re aiming for.

The key of fermentation is sugar, and coffee is full of it. The sugars in the coffee bean are left to ferment so that they break down; this gives the bean a richer taste. But if you ferment too long, there won’t be any actual sugar left, which is necessary for roasting.

But what about fermenting coffee that’s already been brewed? Yes, you can ferment brewed coffee. There are several different ways you can go about this, and each will provide your already delicious, nutritious coffee with a lot of extra flavor and extra healthy properties. First, we need to understand some of the most popular kinds of fermentation for beverages

Kinds of Fermentation


Kefir is a drink that is said to have originated in Europe. Farmers inoculated cow’s milk (or goat’s milk, or any other kind of milk they had on hand) with the kefir grains. This turned the milk into a completely new kind of beverage, more akin to yogurt and full of health benefits.

Nowadays, there’s more than one type of kefir: It used to work mostly with milk. Since fermentation needs sugar to happen, milk was a perfect match since it contains a sugar called lactose.

In time, other types of kefir have entered the mainstream. The most notable is water Kefir, a non-dairy alternative to milk Kefir. It is fermented using either naturally occurring sugars—fruit juice, coconut water—and with added sugar: tap water with sugar is enough for fermentation to take place.


Similarly to Kefir, Kombucha is a beverage that’s made by taking an already existing beverage (in this case, tea with sugar is the most common one) and adding a special mix of bacteria and yeast to ferment.

One word you’ll see often when talking about fermentation is SCOBY. This stands for Symbiotic Culture of Bacteria and Yeast. The SCOBY comes already fermented and grown to some extent, looking like a wet, floppy disk. This is what is added to your drink; you let it work on your beverage for a certain number of days, depending on what kind of result you want, and then you can consume your Kombucha.

Beer Yeast

Beer is also made with yeast. You steep the grain you want to make your beer from, and then add the yeast and let it work on it.

While the yeast used for beer is different from the previous ones, it works in the same way and can be applied to coffee just the same. Replace your water with brewed coffee, and add beer yeast and let it do the work just as if you were making homemade beer. Some adjustments for flavor must be made, though, and you’re going to want to add some sugar after it is fermented.

Now let’s apply this to coffee to make some fermented coffee drinks that will show how coffee can still very much surprise you.

Coffee + Kefir

Coffee and kefir seem like natural allies. Kefir is commonly associated with dairy flavors such as milk, yogurt… and we all know that coffee and dairy are a match made in heaven. Depending on what kind of coffee kefir beverage you want to make, you can also use water kefir.

Bacteria and fungi (yeast) thrive under warm climates. Therefore, you must avoid adding kefir SCOBYs right after brewing—let your coffee sit until it is at room temperature.

Now you can either add Kefir cultures to your coffee and let it ferment for a while, or you can add ready-to-drink Kefir to your coffee and mix well.

For the first method, you’ll need a glass container to put the coffee in and let the Kefir ferment in there. Keep in mind that the container must not be exposed to extreme temperatures so that the Kefir goodness is not affected. Like so:

  1. Fill two large glass jars with 1 liter of brewed coffee each. Must be already sweetened, or you can add sugar at this point: make sure it dissolves thoroughly. 
  2. Put ¼ cup of water kefir grains in each.
  3. Cover the lid with a thick cheesecloth and let ferment for 2 to 3 days.
  4. Get another two glass jars and strain the contents of your fermented coffee kefir into them. Add more sugars depending on taste (maple syrup, liquid caramel, vanilla, honey…) and then let it ferment a little more. It will also acquire some effervescence at this point. 
  5. After one day, you can move the coffee kefir to a different container and let it chill for a while. 

For the second method, it is recommended to brew strong coffee (think espresso) since it will be diluted when adding the Kefir. You only need to make either milk or water Kefir, and then mix it with your brewed coffee. The result will be a drink with a more mellow coffee flavor, but delicious nonetheless. Mix well, add sweetener of choice, and enjoy!

Health Benefits

  • High in protein
  • Full of vitamins
  • Promotes healthy gut bacteria
  • Protects your body against infection

Coffee + Kombucha

Homemade Kombucha is definitely good and fun to make. But what about Coffee Kombucha? Koffeembucha? No? Okay. 

Making Kombucha from coffee is very easy to do right at home, and it is a great drink for enjoying during summer when just the thought of hot coffee seems completely unbearable. We’ve made a quick how-to for those who haven’t dabbled with Kombucha before:

  1. Brew your coffee with your desired method. Add sugar, and let it sit until it is at room temperature.
  2. Transfer the coffee into a big (1-2 gallons) jar. 
  3. Add the SCOBY and cover the jar with cheesecloth. 
  4. Let ferment from 2 to 5 days: Taste it often to see when the taste is right for you. 
  5. Now add more sweetener (Honey or organic sugar) to cut the bitterness and let the SCOBY work on that for an extra day. 

And it is done! You could leave it to ferment a little more the second time. The longer you leave it, though, the more effervescent it will be, which is not desirable at a certain point. You can now enjoy a unique drink full of benefits. 

Health Benefits

  • Lowers Cholesterol 
  • Probiotic 
  • Full of B vitamins
  • Caffeine kick 
  • Good for digestion 
  • Low in sodium

Coffee Beer

Coffee beer is a type of beer where coffee is added: It can be added as brewed coffee or as grounds, depending at which point of the beer-making process you add the coffee. 

Since beer making is such a competitive field and people are quite protective of their methods, there is no real consensus as to how to make a “coffee beer”. There are plenty of coffee beers out there, each of them bringing a different kind of flavor to the table. 

For those who are feeling a little adventurous, we’ve prepared a very short guide to add coffee to your beer. Check it out:

  1. Steep grains in a large kettle. You’ll want to steep them for about 20 minutes. You can now remove the grains, leaving the water in the kettle.
  2. Boil water, let sit for five minutes, then add malt extract.
  3. You now have wort: Sugar water that is essential for beer making. Let cool.
  4. Pour the wort into a fermenter.
  5. Now you should pour about 4 gallons of water: For our coffee beer, we’re going to go with ⅔ brewed coffee (lighter roasts go better with beer) and ½ filtered water.
  6. Add your beer yeast, lock the fermenter tight and let it do its thing. Pretty soon, you’ll have a coffee beer!

Though short, this guide is to illustrate the most viable method of introducing coffee to beer: during the fermentation process. This is to avoid messing too much with the coffee flavor, so that in the end you get a beer that, instead of having a rich coffee flavor, tastes like it’s been artificially flavored.

Health Benefits

  • No more mixing red bull and alcohol. This is healthier and has a lot of caffeine!
  • Great for digestion.
  • Improves circulation.

As there is fermented coffee, there are also special types of fermented coffee beans. What this means is that, although it technically doesn’t fall under the category of “fermented coffee”, these types of coffee also involve a special type of fermentation.

Let’s see some types of coffee beans that have been fermented in a different way than regular coffee beans: 

Kopi Luwak

Bear with us here. Kopi Luwak is hailed as the best of all coffee because it undergoes a unique, special kind of fermentation. This fermentation occurs inside the belly of an animal.

That’s correct. The Civet, a sort of a cross between a raccoon and a cat, eats the coffee fruit and then the feces are collected and turned into the world’s best coffee. Some say it’s the best. 

What makes this coffee so special is that the civet has a keen sense of smell: It will only eat the best out of all the fruit, and will never pick bad fruit. This results in all the beans collected being, objectively, the best beans of the crop. After the beans are collected, they are washed thoroughly. Then they undergo roasting just like any other bean, effectively sanitizing them. 

It’s important to address the potential animal abuse of this coffee. Since it sells at a very high price, people resort to caging civets and force-feeding them coffee fruit. While this is profitable, the result will be far from real Kopi Luwak: the actual point of this coffee is that it happens naturally, and that is what makes it so good. A caged civet will not only eat whatever beans are available to them but will also produce lower quality Kopi Luwak regardless of what they are fed. So, whenever you’re buying a cup of this coffee, be sure you’re buying cruelty-free: It’s also your best chance at getting top-quality Kopi Luwak.

Health Benefits

  • Full of Amino Acids
  • Easier to digest
  • Diuretic
  • Less acidity

Cultured Coffee

Cultured coffee is a product that has been gaining interest in recent years. It is coffee beans that are subjected to a special kind of fermentation: Select microbes are added to the beans during the natural stages of fermentation. This process is engineered to make the beans, through fermentation, a whole new class of coffee– Cultured coffee. 

Cultured coffee has a very different taste, and is less bitter than regular coffee, regardless of the roast. The special microbes and bacteria eat away at the compounds found in coffee that would make it bitter while promoting the growth of other compounds that aid in aroma and richness of taste. 

To make cultured coffee, you only need the Cultured Coffee beans. Grind, and brew as you wish. We suggest trying it chilled first so you can really appreciate the difference. 

Health Benefits

  • Lower in caffeine
  • Easier on your stomach 
  • High in vitamin b3
  • Sweeter coffee, less need for sweeteners

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