8 Reasons For Bitter Coffee (and How to Fix)

Statistics say that 54% of Americans drink coffee (1) on a daily basis. My personal statistics would say that 99% of people cannot properly function without coffee (got one beside me right now in a mug that says “Don’t talk to me until I’ve had my coffee”).

No one is born a coffee lover. Like fine wine, it's an acquired taste. Coffee is naturally bitter, but there are times when your face may scrunch up after trying a new brew, because it is TOO bitter. What makes coffee bitter? We are about to look at 8 causes of that bitter taste + solutions to fix this.

1. Over-Steeping your Coffee

Steeping describes a method of brewing coffee where you directly mix your grinds with water (as opposed to passing it through a filter). It's common in most types of ‘press’ coffee makers, for example, the French Press or the AeroPress.

a coffee pot on top of an old steel stove

The danger, however, lies in knowing how long to steep for, because if you over-steep your coffee you’ll be left with a harsh, bitter flavor. This is because of over-extraction. Extract too much and the coffee tastes bitter. Extract too little and the coffee will be weak and taste sour. Get the extraction just right, and all the delicious flavors and oils inside the coffee grounds end up in your cup.

The solution: Reduce your steeping time. If you've been brewing French press coffee at six minutes, try knocking it down to four and see if that improves the flavor. There are other elements that can lead to over-extraction; we'll discuss them in a bit.

Steeping is really limited to a few specific coffee brewing methods. When you use an automatic espresso machine or a drip coffee maker, there is a low chance of over-steeping your brew - in fact, it's almost impossible. Use a French press or an AeroPress, however, and you’ll want to be on point when it comes time to plunge.

2. Dirty Equipment

This one’s obvious – keep your s**t clean! Rinsing your French press after every use is fine (as long as you back-flush the filter mesh thoroughly).

However, if you are using an automatic drip coffee maker, you should be running clean, fresh water through it at least once a week to make sure to get rid of the stinky “coffee-from-yesterday” taste. Don't be lazy. Give it a clean.

a rule that needs to be followed for cleaning coffee equipments

The solution: Neutralize acidity (a leading cause of bitterness) and keep your equipment clean by using a little baking soda to scrub it down, especially if your filter cone has grooves and ridges inside to help with the drawdown. A long-handled brush and a little baking soda will also make a glass carafe sparkle. This works whatever you use - a French press, a drip coffee maker or a pour over.

PRO TIP: Running hot water through your filter cone and coffee carafe immediately after brewing, while they're still hot and before the coffee dries on the surface, is the easiest way to keep everything clean. Once coffee dries, it takes more work to remove it.

The point is, when you brew coffee, you want to make sure you only savor the coffee from today. Wine might improve with age - coffee doesn't.

3. Your Grind and Brewing Methods Don’t Align

Brewing great coffee is a skill. With great power comes great responsibility - you’re going to need to know your ideal grind setting first. But a good burr grinder will give you fine control over grind size, and allow you the flexibility to try different sizes till you find one that works for you.

This way, your coffee tastes exactly like how it should - without extracting the bitter compounds that can spoil the flavor. Here’s a table to explain further:

Grind Size

Brewing method

Coarse

French Press

Percolator

Medium

Your regular household coffee maker with flat filters

Fine

Coffee Makers with Cone Shaped Filters

Extra Fine

Pump and Steam espresso machines

Rule of thumb: finer grinds extract more flavor but also contribute more bitterness, while a coarser grind makes a lighter but sweeter brew. There's a scientific explanation for this: more than 1800 compounds contribute to the flavor of a cup of coffee (2). Some are extracted fairly quickly, from the surface of the grinds, while others are extracted from the interior, which takes more time. By changing the grind, you change the relative extraction of the interior and surface compounds. Plus, a finer grind slows the process of water flowing through the grinds, which causes over-extraction, leading to more bitter flavors in the cup. 

The solution: If bitterness is your enemy, then grinding a little coarser just might be your best friend.

Here's a coffee grind chart. Print it off and use it.

4. Unreliable Water Clarity and Temperature

We all know that coffee should be prepared hot. But did you know that factors such as water type and temperature play a significant role in brewing the perfect cuppa? You need to be meticulous with the water you use!

It’s fairly easy to ruin a perfect cup of coffee using unfiltered water. Distilled water is not advisable either, because of its lack of mineral content. Bottled spring water is your best choice because it doesn’t have a discernable taste. Read more about the best water for coffee here.

Secondly, you need to pay close attention to your water temperature. Ideally, it should be between 195 F and 205 F. The closer it is to 205 F, the better, because bitterness is more prominent if the water is cooler. If you have a drip coffee maker, you may not have much control over temperature, but if you use a pour over, a French press or any other device where you add water from a kettle, a good rule of thumb is to let your water come to a full boil, then take it off the heat and wait 30 seconds before brewing.

The solution: Use a water filter or bottled spring water, and be careful about brewing temperature. You can still have your cake and eat it too, however, if you want cold coffee minus the bitterness. I’m sure you have heard of cold brew coffee - if not, this method has been proven to reduce bitterness.

5. Using Old, Stale Coffee Beans

Another factor might be the beans themselves. Most serious coffee drinkers are aware that coffee beans don’t stay fresh forever, but did you know that old beans can actually be adding to your bitter-tasting coffee?

There are a few different points at which beans begin to “go bad.” Once you get used to the flavor of really fresh coffee beans, you will become sensitive to the "off" or "stale" aroma that they have, even before you brew with them. While there are ways to prevent this, once your beans have gone stale, there's no turning back.

After being processed, unroasted or "green" beans are typically thought to stay good for months or even years, especially in cold storage.

However, our good friends over at Sweet Maria’s beg to differ. These green bean friends tend to put the limit on their green bean storage at 5-6 months (3) after receiving them in the U.S. Truth be told, though, other companies may not adhere to such strict standards.

 photo of green coffee beans

Green coffee beans aside, once a coffee bean has been roasted it’s usually a matter of hours to a few days before the beans get past their peak flavor. Once the beans have been roasted, and especially after they’ve been ground, things like oxidation, moisture, and CO2 depletion begin to factor in, bringing a “staleness” to their taste very quickly.

The solution: Buy only whole beans, buy only what you can use within a week or two, and grind only as many beans as you're planning to use in the coffee you're brewing right then.

PRO TIP: Just use  storage container made for coffee beans. They’ll help keep your coffee beans fresh and ready to brew for quite a bit longer than if you just leave them in the bag they came in.

6. Maybe You Just Haven’t Found the Right Roast...

As a general rule dark roasts taste more bitter than lighter roasts. That ebony French roast a friend raved about? If it tastes like chewing on a piece of charcoal right off the barbecue to you, try a lighter roast. The only definition that matters for "good coffee" is coffee you like. You shouldn't put it in your face if you don't like it.

Again, science comes to the rescue: it's not just the grind size that can contribute to a bitter cup - roasting is a key factor as well (4).

"Roasting is the key factor driving bitter taste in coffee beans. So the stronger you roast the coffee, the more harsh it tends to get." - Dr. Thomas Hoffman, Technical University of Munich

Look for light and medium roasts, instead of medium-dark and dark roasts. Some roasters print a scale on the bag to let you know how light or dark the coffee is. Aside from color, different roasts also differ in taste. The lighter the roast, the less bitter your coffee will be. Try a couple of different roasts until you find the... sweet spot.

The solution: If you want to try light-roast coffee to eliminate bitterness, go for roasts labeled Cinnamon or Half City; medium roasts are often called American or Breakfast. Dark roasts are the famous Italian, French, Espresso, Viennese and Continental varieties. Stay away from these last few if dark roasts give you the shivers.

7. The Source and Variety of Beans Make a Huge Difference

Two different species of plants are grown for coffee – Robusta and Arabica. Robusta is much more bitter than Arabica and has more caffeine, it also grows more quickly and is resistant to pests, so it tends to be less expensive. Arabica produces beans with more flavor, though the plants require more care, which drives up the cost.

roasted coffee in a stainless steel container

However, if you're sensitive to bitterness, look for Arabica beans. It shouldn't be too difficult; most premium coffee bean vendors specialize in Arabica and will say so on the label or on their website. 

The next aspect of selecting beans is learning what properties you can expect from beans grown in different parts of the world. Here are a few specific recommendations: Kona region, Brazilian or Costa Rican beans.

The solution: Look for Arabica beans, and read our guide to growing regions to find just what you're looking for (or start with beans from one of the three regions highlighted here).

8. The Ratio of Water to Coffee

When you were a kid, you probably learned that putting more sugar in your tea made it sweeter. Right? Well, the principle is exactly the same when brewing coffee, but in reverse: putting more coffee in your water can make it bitter.

an incorrect water to coffee ratio makes bitter coffee

The Specialty Coffee Association of America refers to what they call their "golden ratio," a balance of beans to water that makes for what they feel is the ideal brew: 55 grams of coffee per liter of water, for a ratio of 18:1 - that's 18 grams of water to 1 gram of coffee.

But just as with the laws of piracy, this rule is more of a guideline. Ask a number of baristas, and their preferred ratio at their coffee shop might range between 16:1 and 19:1. Why? Because they like the way it tastes.

As a very general rule, less coffee = less bitterness. So you might find that 50 grams of coffee is the perfect match to a liter of water for your palate. And note that the ratio may change depending on what kind of brewing equipment you use. A French press typically requires more coffee, while a pour over might be right on the "golden ratio."

The solution: Learn how much coffee to use for your perfect by weighing your coffee and your water. (As a reminder, 1 gram of water is 1 milliliter, so you can measure out a liter of water and know that it weighs 1000 grams, and therefore needs 55 grams of coffee to hit the golden ratio). Use a coffee scale.

And make notes, so when you find out your preferred ratio, you can the next time, and the time after that. Because it's not about making one perfect cup of coffee - it's about making it again and again.


The Verdict

Don’t forget that coffee is inherently bitter, which is what gives it It’s ‘kick.’ However, if your coffee is extra bitter (as in intolerably bitter) then remember everything that you have just learned:

  • Don’t over steep your coffee if you are using a ‘press’ maker
  • Use clean equipment
  • Use the right grind for your brewing method
  • Water – not too hot, not too cold, and definitely not dirty
  • Switch to a lighter roast
  • Try regions known for producing a lower-acid, smoother coffee
  • Experiment with the coffee-to-water ratio to find your ideal proportion

So now when someone asks you “why is my coffee so damn bitter?” you’ll be able to explain like the coffee hipster you were born to be! 

FAQs

Which coffee beans make less bitter coffee?

Arabica beans make coffee that is less bitter than Robusta beans. With Arabica beans, you can brew coffee with less bitterness and more flavor although they are a bit pricier. To make a less bitter cup, you can also try beans from Kona region, Brazil or Costa Rica.

Can salt make your coffee less bitter?

Yes, salt can make your coffee less bitter. In fact, one study found that salt is a better bitterness-neutralizer than sugar (5). Salt naturally suppresses the bitterness in coffee while also improving its flavor. Before you start cracking salt into your coffee however, here's a few tips.

Do light roast beans make less bitter coffee?

Yes, light roast  beans make less bitter coffee. Coffee drinks made from light roasts contain higher amounts of caffeine and taste generally brighter than the ones made with dark roasts.


References

  1. Statistic Brain. (2016, September 03). Coffee Drinking Statistics. Retrieved from https://www.statisticbrain.com/coffee-drinking-statistics/
  2. Rincon, P. (2016, November 15). Maths zeroes in on perfect cup of coffee. Retrieved from https://www.bbc.com/news/science-environment-37989169
  3. Sweet Maria's. Green Coffee Freshness: How Old is Too Old? (n.d.). Retrieved from https://legacy.sweetmarias.com/library/green.coffee.freshness
  4. American Chemical Society. (2007, August 22). Battling Bitter Coffee: Chemists Identify Roasting As The Main Culprit. ScienceDaily. Retrieved from www.sciencedaily.com/releases/2007/08/070821143629.htm
  5. Breslin, P. A. S. and Beauchamp, G. K. (1997, June 05). Salt enhances flavour by suppressing bitterness. Retrieved from https://www.nature.com/articles/42388
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Alex
 

Alex is the Founder and Editor of Homegrounds.co. He is passionate about brewing amazing coffee at home, and teaching others to do the same.