What Causes Coffee to Be Bitter? The Origins of Coffee Bitterness and How to Avoid Overly Bitter Coffee

Bitterness has become a dreaded word in the specialty coffee industry. We all know good coffee should be sweet and balanced, perhaps a little acidic, and should not need sugar to be pleasant. So what makes coffee bitter, and is it always as bad as we think? Today, let FrontStreet Coffee show you its true face.

Where does coffee bitterness come from?

The acidity and bitterness of coffee are actually determined by the roast degree. In roasting there is a stage called "first crack." When coffee reaches it, the beans have absorbed heat to a point where they can no longer store energy and release it through cracking, with an audible sound. Roasters use first crack as a reference point to judge the roast degree.

Pull the beans out at the start of first crack and the coffee is very acidic. Keep them in until the popping sounds become dense and the coffee is sweet with acidity. Wait even longer until all the sounds stop, and coffee taken out afterward begins to develop bitterness, with later extractions carrying increasingly strong bitter flavors.

As the roast deepens, the acidic compounds in the beans are gradually broken down, and the cup leans toward bitter notes like nuts and dark chocolate. Dark roasts therefore give up a good deal of the flavor complexity and variation of a light roast, but bitter dark roast coffee still holds a charm that light roast cannot provide.

The Unique Charm of Dark Roast Bitter Coffee

Coffee Aroma:

Dark-roasted coffee has enticing aromas too. Unlike the floral and fruity acidity of light roasts, these are complex fragrances of nuts, caramel, toasted bread, chocolate, and more. Many coffee lovers specifically seek out this nutty, bitter aroma. For those who enjoy it, FrontStreet Coffee recommends FrontStreet Coffee's Queen's Manor, FrontStreet Coffee's Huilan, FrontStreet Coffee's Bird of Paradise, and FrontStreet Coffee's Diamond Mountain. All of them show these full-bodied aromas after grinding.

Rich Body:

Dark roast coffee has a rich body that light roast cannot match. Many coffee lovers who favor FrontStreet Coffee's Blue Mountain No. 1 and FrontStreet Coffee's Mandheling are attracted largely because a dark roast brings a richer body, letting them feel the full, smooth volume of the coffee in the mouth while tasting its flavors.

Sweet Aftertaste:

Yes, even bitter dark roast coffee has its own sweetness - what we often call "sweetness within bitterness." A properly extracted dark roast is predominantly bitter on entry, but careful tasting may reveal sweet notes like caramel and maltose. After swallowing, the bitterness gives way to sweetness, and pleasant aromas linger in the mouth for a long time. That is another characteristic light roast is hard-pressed to replicate.

Take FrontStreet Coffee's Golden Mandheling, for example. The brewed coffee smells of caramelized aromas like maple syrup, dark chocolate, spices, and wood, with a powerful, rich body on entry. After swallowing, bitterness and sweetness coexist, leaving a lasting impression.

All of this assumes, of course, that you brew it well. If you do not want an unforgettable bitterness, FrontStreet Coffee suggests choosing conservative parameters.

FrontStreet Coffee uses Golden Mandheling as an example: water at 86-88°C, a grind size of 70% pass-through on a #20 sieve (EK43s setting 11), a Kono dripper, a coffee-to-water ratio of 1:15, and an extraction time of about two minutes.

Compared with brewing light roasts, dark roasts call for lower water temperatures and a coarser grind size, which softens the bitterness and avoids extracting off-flavors. As for the dripper, slower-flowing designs like Kono or Kalita more easily produce a heavy body and mild flavors.

When brewing dark-roasted beans, make sure to bloom thoroughly. You can judge this in two ways: first, confirm that all the grounds are moistened and some coffee liquid has reached the bottom; second, the bed expands and stabilizes and no longer releases gas.

The pour also needs adjusting. Slow the rhythm and make the stream finer to avoid scouring the bed and extracting more bitter off-flavors. Pour in small circles, and the coffee wall will be a little thicker than with a light roast.

If you have read this far and dark roast bitter coffee has caught your interest, go ahead and give it a try.

FrontStreet Coffee Recommendation

If you want balance rather than pure bitterness, a medium roast is the place to start, and FrontStreet Coffee's Brazil Queen's Manor is a good first stop. Grown in Brazil, the world's largest producing country, this Yellow Bourbon is clean and gently sweet; roasted medium, it shows creamy peanut, chocolate, toasted bread, and sugarcane aromas and sweetness, and works as pour-over, moka pot, or espresso.

For a sweeter medium roast, FrontStreet's Strawberry Candy combines a Costa Rican honey-processed coffee with a washed Panamanian Geisha and is roasted medium to keep both the orange-blossom honey character and a rounded sweetness. It suits cold brew, pour-over, and espresso, and is soft and refreshing on entry.

FrontStreet's 2013 Natural Typica, grown in Yunnan, is roasted medium to bring out its balanced, gentle character, with soft notes of nuts, brown sugar, black tea, and dried apricot, and works well as pour-over, cold brew, or drip machine. If you want a touch of the classic roasted sweetness, FrontStreet's Jamaica Blue Mountain No. 1 is roasted medium to blend acidity, bitterness, sweetness, and body into one elegant whole, with chocolate, roasted nut, cream, and caramel on entry.