Moka pots can produce a rich, tasty and full-bodied coffee experience that most coffee enthusiasts will enjoy. Unfortunately, many people have trouble brewing and end up with an unpleasantly bitter cup of moka pot coffee. Why does this happen and how can you fix it?
Why your moka pot coffee tastes bitter
Moka pot coffee tastes bitter when the bean has been over-extracted. This is caused by the grind size being too fine, brew temperature being too high or coffee-to-water ratio being too low. Bitter coffee may also be caused by stale beans, pre-ground beans or certain bean varieties.
Moka pot bitterness is often caused by coffee bean over-extraction
Coffee beans go through phases of extraction when submerged in water. These phases occur one after another because some organic coffee bean compounds take longer to dissolve than others.
Fats and acids dissolve in the first phase, which adds an acidic and sour taste to moka pot coffee. If you stop the brewing process here then the coffee will taste sour and unpleasant. This is called under extraction.
The second phase is where many of the sweet and pleasant-tasting sugar compounds dissolve.
The third phase is where the most chemically complex organic compounds start dissolving. These compounds are what add bitter tastes and astringent textures to our moka pot coffee. We consider a coffee over-extracted when these compounds are dissolved.
Our goal is to stop the brewing process before this happens.
Causes of moka pot over-extraction
These over extracted and unpleasant bitter flavors are most often caused by the grind size being too fine, the temperature being too hot or the coffee-to-water ratio being too small.
Moka pot bitterness is also caused by roast type and bean variety
There are a few other factors that may cause a moka pot coffee to taste bitter.
An over-roasted or very dark roast coffee may extract more quickly than a lighter roast. One reason for this is that the more sweet and subtle flavor profiles of a coffee bean are removed the longer it is roasted.
Therefore, some of the coffee’s naturally bitter flavors may not be balanced out by the contrasting sweetness that is no longer there.
The bean variety may be a possible cause of bitter moka pot coffee as well.
Robusta coffee tends to have a more bitter and rubbery taste because it contains more caffeine than Arabica coffee. Arabica beans also contain about 60% more fat and almost twice as much sugar as Robusta, which makes it taste less naturally bitter.
How to reduce moka pot bitterness
Use a coarser grind size
A coarse grind will cause the coffee beans to have a smaller surface area and extract mroe slowly. This will prevent your beans from reaching the third stage of extraction where the bitter compounds start dissolving.
Start with boiling water in the bottom chamber
Adding boiling water to the bottom moka pot chamber will decrease the total brew time. This will reduce the probability of bitter flavors being extracted due to a prolonged brew.
Increase your heat source temperature
The longer your moka pot sits on its heat source, the more likely the unpleasant bitter flavors will start to dissolve into your coffee. By increasing the temperature of the heat source, the moka pot will complete its brew more quickly.
Try a lighter coffee bean roast
Light roast coffee beans contain more of the sweet characteristics that may help to balance out bitter flavors. You can even try a medium roast if you’re currently using a dark roast.
Try Arabica or Robusta beans
Consider trying Arabica beans if you’re currently brewing with Robusta. Arabica tends to be less naturally bitter.
Use beans that have been roasted within 4 weeks
Old or stale beans lose many of the pleasant flavors due to oxidation. It’s possible that your stale beans are contributing to your bitter tasting coffee. It’s best to brew freshly roasted beans anyways because they simply taste better!
Most coffee beans you purchase at the grocery store will have been sitting there for weeks. As a rule of thumb, do not buy coffee that does not advertise its roast date.
To buy freshly roasted beans you may have to go to your local cafe, visit a nearby coffee roaster or search online for companies that sell freshly roasted beans.
Grind your beans immediately before brewing
Coffee begins going stale as soon as it is roasted. This happens because of a process called oxidation.
Whole beans stale more slowly because they have a smaller surface area. In other words, there is less contact area for oxygen to reduce the tasty coffee bean flavors.
Ground coffee beans have a substantially larger surface area, which allows the oxidation process to happen more quickly. As a result, we recommend using freshly ground coffee beans in your moka pot coffee to minimize the chance of it tasting bitter.
Increase your coffee-to-water ratio
A small amount of coffee in a large volume of water will extract more quickly, causing bitterness. Therefore, increasing the ratio of coffee will allow more of the sweet and pleasant notes to come through before the bitterness.