Why Can My Espresso Taste Bitter, Sour, Or Burnt Sometimes?

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October 10, 2023

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Have you ever had an espresso and found it ridiculously sour? Maybe it was more bitter, maybe even burnt tasting. It shouldn’t taste like that at all. Espresso ideally tastes rich and smooth; like a regular non-bitter coffee, just with more intense flavor. It got me wondering. Why does an espresso taste sour sometimes?

The main cause of sour, bitter, and burnt flavors in espresso is over-extraction and under-extraction. With over-extraction the coffee becomes overcooked and releases unwanted flavors; it becomes harsh, bitter, and burnt. With under-extraction too few of the good flavors end up in the cup; it becomes weak and sour.

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Poorly Made Espresso

The sour taste in coffee comes from tannic acid in the coffee bean. Tannic acid builds up in the tougher outer exterior of the bean. It is a natural defense in the coffee plant against insects eating them.

Since tannic acid is in a tougher part of the bean, it takes higher temperatures and higher pressures to extract this compound. So when running a shot of espresso it will leak out toward the end of the pour.

An espresso brew should last 20-25 seconds at most. Allowing the extraction to run longer means that you are running a higher and higher risk of that bitter tannic acid leechine out into the cup.

How Do I Know If My Espresso Has Been Over Extracted?

Other than just tasting it; you can actually look at an espresso shot and know immediately if it has been over extracted.

A perfect non-bitter espresso should have a crema topping with a rich dark brown color.

When the tannic acid leaks through, it brings a blonding, as it’s called, to the crema color. So a bad espresso will have a much lighter brown color to its crema.

A good coffee shop barista will know the difference here. If they do pour an over-extracted espresso then they should just throw it away and brew a new one.

Try An Experiment

To really see for yourself just what a longer extraction time will do to your espresso you can run your own test.

Run an espresso pour into one cup for 15 seconds. Quickly switch a second cup under the pour to catch the final 15-30 second period. Have a sniff and a sip of both cups.

I promise the first cup will be lovely and the second cup will be full of bitter, sour, and burnt flavours.

Here’s our full guide for making espresso for those who are interested.

What Else Causes Bitter Coffee?

Grind,

There are a lot of factors that go into coffee, and bitterness doesn’t just show up in an espresso. While we know what compound is causing the nasty taste, there are lots of ways to end up with it in the cup.

Clean Equipment. Whether you’re using a French Press or making an Espresso; you need your coffee kit to be clean. Otherwise you will get a build up of old over-brewed residue tainting the taste.
The Grind. Different brewing methods need a different grind. If you’re making an espresso; you want a fine grind. If you’re making French Press coffee; you want a coarser grind. If you’re making drip coffee; you want a medium grind. The best kind of grinder is a burr grinder; it gives a very consistent grind and you can choose how coarse or fine it comes out. The alternative is a blade grinder; it gives a really inconsistent grind and you can easily end up grinding the beans too fine.
Quality. You absolutely want good quality beans. Unfortunately you sometimes only know they were poor quality after buying them. Brand awareness is often key. As a part of good quality beans; make sure they have not gone stale. You can actually buy coffee beans that have been chosen and processed specifically for espresso.
Ratio. Having too much water for the amount of beans, or vice versa, can lead to some strange flavours. The golden ratio of coffee is roughly 2 tablespoons of ground coffee for every 6 ounces of water. Coffee is both an art and a science; tweak it to your taste.
Time. If you brew your coffee for too long, you will absolutely begin to release those nasty flavours that just ruin your bean juice. Different brews take a different length of time. A French Press takes 4 minutes whereas an espresso shouldn’t be any longer than 25 seconds.
Temperature. Water that is too hot will be just as damaging as brewing for too long. The ideal coffee brewing temperature is 195°F to 205°F (90.5°C to 96.1°C).

Troubleshooting The Espresso

Why Does My Coffee Taste Bitter?

So your espresso crema looks very light. There are big patches of white and yellow on top. The puck in the espresso machine is saturated and sludgy. Most of all; it tastes particularly sour.

You have probably extracted your espresso for too long. The lighter colors really come out toward the end of the brew along with that nasty bitter taste.

Keep your brew time shorter. Keep it between 20 and 25 seconds.

But I Want More Espresso From My Brew

You need a larger portafilter basket, not a longer brew time. Either that or run a second espresso brew into your cup.

Why Does My Coffee Taste Sour?

Did your espresso pour out really fast? Is the crema looking thin, bubbly, pale, and yellow? I’m betting the still dry and powder-like.

This sounds like a case of under extraction. It can be caused by different things or a combination:

Tamping too lightly. You need to press the grounds down firmer.
There might not be enough coffee in the basket.
The coffee might be ground too coarse. You need a fine grind for espresso

Any one of these aspects could cause this problem. You essentially have a weak espresso from water being able to flow through the grounds too freely.

Make sure you are using a fine grind, put plenty of coffee in the basket, and tamp it down firmly. You will then create more resistance against the water and cause it to flow through the coffee more evenly.

Why Does My Coffee Taste Burnt?

Does your espresso pour look like a dripping muddy tap? Is it dripping out slowly? Does it look dark or even black? I’m betting you’ve only got a small volume of espresso after 30 seconds or even 45 seconds. I’m betting the puck has become a soggy sludge. Most of all, it has a definite burnt taste.

Your espresso has been over extracted. It sounds like there is a lot of resistance against the water. The coffee can’t pour out at the rate it is meant to and the grounds are becoming over cooked.

You might be tamping too firmly.
There might too much coffee in the basket.
The coffee might be ground too fine.

Try a slightly coarser grind, tamping lighter, and making sure you’re not overfilling the basket.

What Else Can Cause A Bad Espresso?

Beside over and under extraction there are some other ways that an espresso can be messed up.

The espresso machine could be running at too low, or even too high, a temperature.
The coffee beans might be stale.
The machine might need cleaned. A build-up of old over brewed coffee residue could throw the flavor right off.
Rubber seals in the machine could be worn and allowing the pressure to drop.