Why Does My Coffee Taste Bitter and How Do I Fix It?

To a coffee lover, the practice of starting the day with a strong brew is ingrained into our morning routine. Imagine the joy and anticipation of taking that first sip out of an aromatic cup…only for it to be ruined by a wave of lingering bitterness.

Contrary to popular belief, bitterness isn’t caused by the strength of the coffee. To put it into perspective, a Kopi-Gao shouldn’t be tasting any more bitter than a standard Kopi. Neither is it true that darker coffee is more bitter.

No one can afford to start their mornings on a bitter note (figuratively and literally), so go through this list to find out what’s causing the bitterness in your coffee and how to fix it the next time you prepare a cup for yourself.

Grind Size

a white scoop placed into a jar of coffee granules
If the grind is too fine, your coffee will be over-extracted and bitter. Photo from Andrea Tummons

In coffee making, one size doesn’t fit all. If your cup is bitter-tasting, the most likely reason is that your coffee grounds are too fine. The finer the grind, the slower the rate water seeps through the grounds. This results in an over-extracted brew that is bitter, hollow, and tasteless.

The solution is to use coarser coffee ground for your next cup. Still too bitter? Adjust the grind size accordingly to find that sweet spot that suits your taste buds.

Did you know that there’s a recommended grind size for every coffee maker? Here’s a handy guide.

The Golden Ratio of Coffee to Water

pouring water into a coffee filter cup
Using too little coffee grounds or too much water results in over-extracted coffee. Photo from Patrick Fore

Is your cup bitter yet weak and diluted? An incorrect ratio of water to coffee might be the cause.

To put it into perspective, using a gallon of water and two teaspoons of coffee powder just won’t make the cut. When too much water is poured over those grounds, the additional water extracts the “remnant” compounds that make a brew bitter.

The solution is to follow the golden ratio of 1:17. For every gram of coffee, use 17 grams of water to make that ideal cup. Using a digital scale will ensure that the proportions are perfect every time.

Here are our top 6 useful coffee accessories to help you brew better.

Water Temperature

pouring hot water into a coffee filter of a chemex
Using freshly boiled water will destroy the flavours and oils in the coffee bean. Photo from Eiliv-Sonas Aceron

If you are one of those who only drink coffee when it’s boiling hot, you are breaking the rules of brewing. Many of us are accustomed to pouring freshly boiled water over the grounds; however, the ideal temperature for optimal extraction is slightly below boiling point, between 90°C to 96°C.

Water beyond that temperature destroys the oils and flavours in the beans. The compounds and aroma of the beans will be released too quickly, causing an unpleasantly low-quality taste. On the other hand, underheated water slows down the extraction process. As a result, the beans can’t reach the full expression of its flavour.

Ensuring a consistent and accurate water temperature is one of the most important qualities of coffee-making. The simplest solution is to use a barista milk frothing thermometer, or allow freshly boiled water to sit for a minute before pouring over the grounds.

Brewing Time

A french press placed on a stovetop
Bitterness can be caused by infusing the coffee grounds in water for too long. Photo from Izzy Rivi

Leave a teabag in water for too long and all you get is an over-infused mug of bitter-tasting tea. Same goes for coffee; if the brew time is too long, over-extraction occurs.

This issue is more common with the French Press as people have a tendency of not removing the grounds even after pushing down the plunger. This allows the continuous release of bitter chemicals that spoil a good cup.

Refer to the recommended brewing time at the back of your coffee bean package or talk to your barista if you are buying it over the counter. If you prefer sipping on your coffee over an extended period of time, transfer it to a thermal flask before risking a bitter brew.

Don’t have the patience and time to attend to your brew? This bean-to-cup machine does it all for you.

Caffeine Content

coffee cherries on a coffee plant
The origin and growing conditions of the coffee bean can affect the amount of caffeine present in your brew which ultimately affects its bitterness. Photo from Rodrigo Flores

The quality and flavour of your beans aren’t just fully determined by the brewing method, but also the caffeine content which affects the bitterness of the brew.

Based on your coffee brewing method, find out how much caffeine is in your cup of coffee.

The bean’s origin, as well as its variety and how its grown can affect the taste of the final product. Coffee is grown in more than 50 regions around the world which means that the altitude, temperature, and growing conditions vary.

For example, beans such as the Robusta are grown in lower regions that have warmer climates which promote the growth of not only the coffee plant but pesticides. These beans then tend to have a higher caffeine content t at acts as a natural insecticide.

Whereas, beans like the Arabica are grown in regions with high altitudes such as Colombia and Kenya. The elevation provides a cooler climate that allows the beans to mature progressively, producing an acidic and aromatic coffee of lower-caffeine content.

Learn the difference between Arabica, Robusta, and Liberica beans.

Make sure to check on the origin, caffeine content, and taste notes of the coffee before you purchase your next bag of beans.

Dirty Equipment

When was the last time you washed the water reservoir of your coffee machine? If you can’t remember exactly when, then it is time for some spring cleaning.

Over time, the build-up of minerals from the water will accumulate along the interior of the machine’s heating element. That build-up is known as limescale; a hard, off-white chalky deposit that causes issues in heating and the extraction of flavours from the beans.

Even if your coffee equipment looks shiny on the outside, remember to give it a little scrub or use a descaler as there are pesky residues that might be overlooked. If you prefer to use a homemade descaler, here’s how.