Nothing ruins a good day more than a bitter cup of coffee.
While coffee typically has a 10 to 15 percent bitterness due to caffeine content, coffee should evoke different flavors depending on the roast and variety.
Your coffee can be nutty, fruity, chocolaty, or citrus-like.
If your coffee has overpowering bitterness or moves from mild to unpleasant, don’t worry.
In this post, we will help you learn why coffee comes with some bitterness and the common reasons your coffee is too bitter, so you know how to make a perfect brew every time.
The Science Behind Bitterness in Coffee
Studies have proven that coffee contains caffeine, which adds some low level of bitterness.
The main purpose of this bitterness is to tame acidity.
However, decaffeinated coffee is also bitter, which raises the question, “what exactly makes coffee bitter?”
Researchers studied every compound found in coffee to determine which ones cause bitterness.
The chemical composition in raw coffee, such as Chlorogenic acids, produces a lingering bitterness in coffee and makes up 60 to 70 percent of the bitterness.
A 2018 research also found that “bitterness” in coffee is simply a perception.
The chlorogenic acid and caffeine content in the coffee are the primary causes of bitterness in any cup of coffee.
However, the more you drink your cup of joe, the more your brain and body system adjust to this flavor.
Caffeine also plays a role in positive reinforcement ( stimulation).
New coffee drinkers may need more time to adjust to the bitterness than heavy coffee drinkers.
Humans have an inborn aversion to bitterness, which is a solid defensive mechanism that prevents them from ingesting poisonous foods.
The concept applies to alcohol and tea drinkers.
What is the Difference Between Good and Bad Bitterness?
The chlorogenic acids we discussed above generally have a sour taste.
However, during roasting, chlorogenic acids are converted into lactones.
This critical step turns the acidic chlorogenic acids into bitter-tasting chlorogenic acid lactones.
Fortunately, the lactones cause a mild, balanced bitterness.
For companies that roast beans above 210 degrees, chlorogenic acid lactones undergo further degradation to form the metallic, lingering bitter phenylindanes.
That’s why the decaffeinated coffee still tastes bitter.
While these compounds contribute to the harsh, bitter taste in coffee, they have multiple health benefits, including reducing blood pressure and anti-inflammatory properties.
Top Reasons Why Your Coffee is Bitter
Roasting is not the only process that contributes to bitterness in your coffee.
How you prepare your cup also determines the level of bitterness.
If you’re a coffee enthusiast or purist, you already have an idea of what your perfect cup of joe should taste like.
If it’s nothing close to what you expected, you should check your brewing process, the grounds, water temperature, brewing equipment, and overall method to know what went wrong.
Here are a few reasons your coffee might taste bitter.
You Let Your Coffee Steep for Too Long
Overextraction is the main reason for a highly bitter coffee.
It happens when you directly mix your grounds with water (not passing it through a filter).
Some coffee makers, such as the aero press and French press, are designed to mix water and grounds.
For an inexperienced coffee brewer, it’s not easy to know how long to steep, as over-extraction leads to bitterness, and under extraction leads to a weak sour taste.
To avoid over-extraction, avoid leaving the coffee in the French press for too long.
Your Measurements are Not Correct
Coffee brewing is a skill that you perfect with time.
You’ll need to master your measurements to get the same great-tasting cup every time.
That means your water to coffee ratio should align every time for a balanced flavor.
Generally, the more coffee you add to the same amount of water, the stronger it becomes.
A stronger brew means more caffeine and more bitterness.
It’s also wise to keep in mind that different types of coffee have been roasted at different levels and require different measurements to retain their original flavor.
Your Brewing Equipment is Dirty or Too Old
Using the wrong, dirty, or old brewer might be the reason your coffee has some extra bitterness.
If you don’t remember the year you bought your coffee equipment, maybe it’s time to replace it.
Oil builds up in old or dirty coffee machines, and if you don’t remove it, it gets rancid and produces that bitter, metallic taste.
The blocked areas also restrict water flow, which leads to a challenging and uneven extraction.
It might not feel like you need to clean your machine every time you use it.
Well, skipping this critical step is what is costing you a great cup of coffee.
Your Water Temperature is Too High or Too Low
The right temperature for brewing any cup of coffee is 195 to 205 F.
That means your water is hot but not boiling.
If it’s too hot, you could be destroying the essential oils in the coffee grounds that give it subtle flavors.
If too cool, your coffee will be under-extracted.
Distilled water is not advisable as it lacks some minerals. Bottled spring water may be a perfect choice.
Your Coffee Grounds are Too Big or Too Small
Grinding coffee also plays a significant role in the outcome of your coffee.
The process affects how the flavor compounds dissolve.
That means if too coarse, you risk over-extraction or underexcretion.
Finely ground coffee beans also have similar effects.
As a coffee drinker, you need to understand that different brewing methods require different grind levels.
Sometimes you need to experiment to get the right size.
More than 28 percent of the mass of a coffee bean dissolves in the water.
The rest is fiber and cellulose.
Different flavors are extracted from the coffee bean at different stages in the brewing process.
Your Beans are Not Fresh
Using old stale coffee beans can be the primary source of bitterness in your coffee.
Like any other consumer product, coffee grounds don’t stay fresh forever.
When coffee beans roasted, they undergo so many processes like oxidation that often lead to staleness.
To avoid using less fresh grounds, buy whole beans and grind them when brewing your coffee.
Final Thoughts on Why Your Coffee Tastes Bitter
By now, you already know what caused your coffee to taste so bitter.
That means you know how to correct the problem, so you have a great cup of coffee in your next brew.
It’s also prudent to explore different types of coffee and brewers until you find what works for you.
Finally, coffee brewing is more of an art.
Every brew takes you closer to the perfect cup, so keep learning and exploring.
It takes hard work to become an expert home barista, but with a little patience, practice and tenacity, you’ll get there.