Why your coffee tastes bitter (and how to fix it)

Have you ever had a cup of coffee that tasted too bitter? Perhaps you made it at home, or perhaps you got it at a coffee shop or in the break room at work, but it was a struggle for you to drink it without adding some milk or sugar to alleviate the bitter taste.

Coffee, like many other plants, naturally contains bitter tasting components as a protection mechanism. Some bitterness in your coffee is not a bad thing. However, if the bitter taste is intense and dominates the flavor profile of your coffee, it can be unpleasant.

Woman reacting to bitter coffee
© Henry Soderlund | Creative Commons

What is bitter taste?

Bitterness is one of the five basic tastes; the others are salty, sweet, sour, and umami. We are born disliking bitter taste, an innate aversion passed down from our ancestors, because bitter taste signaled poison. Of course, this bitterness aversion can be overcome, and many people find themselves enjoying a variety of bitter foods and beverages as they get older: coffee, dark chocolate, vegetables, beer, etc.

The ability to overcome bitter taste aversion and develop a tolerance for bitterness is influenced by many factors:

  • genetics of taste perception
  • increased exposure and familiarity of the food or beverage
  • pharmacological feedback (e.g., the desirable effects of caffeine and alcohol associated with the bitter beverage)
  • changing taste preferences over time

Genetics plays a large role in an individual’s sensitivity to bitter taste. A brew that is perceived to be extremely bitter and unpleasant by a highly sensitive bitter taster may be perceived to be only slightly bitter and more pleasant to an individual with lower bitterness sensitivity.

How to fix bitter coffee

There could be a number of reasons why coffee tastes bitter, and there are several possible fixes.

Decrease your coffee-to-water ratio

It is possible that your coffee-to-water ratio is too high, meaning the amount of coffee is too high compared to the amount of water you are using for your brew. This leads to an increase in total dissolved solids (TDS) in the coffee; essentially, there is too much “coffee” in your coffee!

The TDS is the amount of the coffee components that are dissolved in the hot water and it is measured with an instrument called a refractometer. The refractometer tells you how translucent or opaque your coffee is. If the TDS is high, your coffee will be more opaque (more difficult to see through). When TDS increases, bitterness increases and sweetness decreases. Thus, if your coffee is too bitter, a lower TDS may decrease the bitterness and increase the sweetness in your cup.

Dark coffee in a clear glass cup
Everything in the cup that isn’t water contributes to the total dissolved solids percentage.

Since you probably do not have a refractometer lying around, it is likely easier to reduce your coffee-to-water ratio. The recommended ratio typically falls into the range of 1:15 to 1:18; that is, 1 gram of coffee for every 15-18 grams of water. If you do not have a kitchen scale, it is typically recommended to use 1-2 tablespoons for every 6 ounces of water. The ideal ratio for you will vary depending on the grind size and brew method.  

Decrease your extraction time

A long brew time causes over-extraction of the coffee, which makes it taste more bitter. This may be more difficult to control if you are using a brew method like a pour-over or other drip coffee, but if you are using AeroPress or French Press, you can control the brew time. The National Coffee Association and Specialty Coffee Association recommend brew times of 4-5 minutes for a pour-over, 2-4 minutes for a French Press, and 2-2.5 minutes for an AeroPress.

Try a coarser grind size

If the grind size is too fine, there is more surface area for the coffee components to dissolve into the water, leading to over-extraction, which can increase the bitterness in your cup. Try an intermediate or coarse grind size, depending on your brewing method.

Try a new roast type

Darker roasts tend to have more burnt and acrid flavor notes from the browning reactions during roasting, which are associated with bitterness. A medium or light roast will typically contain less of these flavors.

Make sure your coffee is fresh

Buy your coffee in small amounts to maintain freshness longer. Older coffee loses some of its aromatic compounds that contribute to a balanced, fuller flavor. The absence of these desirable, fragrant flavors can make the bitterness and other unpleasant flavor notes more noticeable.

Making one or more of these changes could reduce the bitterness in your coffee. Enjoy!

Dr. Molly Spencer worked closely with the Specialty Coffee Association to redesign the Coffee Taster’s Flavor Wheel as part of her Ph.D. studies in Food Science at UC Davis.

References

  1. “Effects of brew strength, brew yield, and roast on the sensory quality of drip brewed coffee,” Journal of Food Science: https://onlinelibrary.wiley.com/doi/abs/10.1111/1750-3841.15326
  2. “Towards a new brewing chart,” Specialty Coffee Association: https://sca.coffee/sca-news/25/issue-13/towards-a-new-brewing-chart
  3. “Protocols and best practices,” Specialty Coffee Association: https://sca.coffee/research/protocols-best-practices
  4. “How to brew coffee,” National Coffee Association USA: https://www.ncausa.org/About-Coffee/How-to-Brew-Coffee
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