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In our homebrewing life, we’ve all had our bad coffee experiences like espresso that tastes sour, a burnt or bitter taste. This should not be the case as a well-brewed espresso should taste very smooth and intense. So, why is it possible that espresso can get sour?

The answer is clear, extraction. Plain and simple.

It needs to be extracted evenly and gradually over time. Espresso can get too extracted (over-extraction) and less extracted (under-extraction).

When espresso is over-extracted, it will taste sour. The coffee grounds have given all their good flavors to the water and what’s left behind is sour, bitter, or burnt, simply bad. Under-extraction also tastes sour, but for a different reason.

When the coffee grounds are under-extracted, it means that not all the flavors have been extracted from the coffee grounds. The water hasn’t had enough time to draw out all the flavors, so what you taste is sour.

What is sour espresso?

We’ve all been there before and have tasted a sour espresso. It is not a great experience and the first thing that comes to mind is throwing it away.

How can you identify a sour espresso? There are 3 big signs you can test:


After you make your espresso, remove the portafilter and check the used coffee grounds (puck).

If you see that the mass is saturated and very thick and wet, that’s not a good sign. That water should be elsewhere, along with the good flavors.


When your espresso is extracted in the right way, it should have a crema, coming from the oils in the coffee. It tops your espresso with a beautiful brown layer.

If the color is lighter, less brown, and not very thick, you’ll likely have a sour espresso before you. This is called blonding.


This is the last sign you’ll tell it directly after your first sip. There are different degrees of sourness but it dominates every other taste in your espresso.

Some add milk to consume it or others simply throw it away, which is always a pity but part of our journey.

Why can espresso taste sour?

You might have already spotted a few of the signs after pulling your espresso shot.

The crema is not brown but lighter, the puck was very wet or the espresso just tastes sour.

There are 3 possibilities when it comes to extraction:

  • under-extraction
  • extraction
  • over-extraction

Of course, extraction, which we see as a good possibility which we won’t discuss in detail. We all know that you have good, better, or perfect, we’ll save that topic for another day.

We will dive deeper into the topics of under-extraction and over-extraction.


Under-extraction simply means that the coffee grounds were not in contact long enough with water to extract all the good flavors into your cup. Simply too fast!


Over-extraction is the opposite of under-extraction and it happens when the coffee grounds were in contact with water for too long. The water has extracted all the good flavors, but also the bad ones. The latter can dominate the other flavors and give you a bad experience.

The problem with over-extraction is that you can’t go back, you can only hope to make it a bit less bad by adding milk, sugar, or other sweeteners.

7 ways to prevent your espresso from going sour

Luckily, we can prepare ourselves by brewing sour espresso. There are a few things we can do:

Equipment cleaning

Respect for your coffee gear and equipment is key for increasing its lifespan and your ROI on the coffee and coffee experience.

The most important part is to descale your espresso machine regularly. Depending on the water hardness in your area and how much you use your espresso machine, this can be every few months or once a year.

If you don’t descale your machine, the calcium and magnesium will start to build up in the boiler and heating element. This will eventually lead to a decrease in heating efficiency and, as a result, irregular temperatures during extraction.

And we all know that temperature is key for a good espresso!


The brew temperature is the temperature at which water and coffee come in contact. The ideal range is between 195°F (90.5°C) – 204°F (96°C).

If the water is too cold, it will not be able to extract all the flavors from your coffee grounds. This will lead to an under-extracted espresso and reward you with a sour espresso.

On the other hand, if the brew temperature is too high, it will extract all the flavors from your coffee grounds, including the bad ones. The outcome will be an over-extracted espresso and a sour taste.

So, how do you make sure you have the right brew temperature? One is way is to invest in top gear and equipment, like a quality espresso machine that comes with a built-in water boiler with a thermostat. This is part of controlling the brewing process.

If your gear doesn’t have a built-in water boiler, you can go with a separate kettle with a temperature to heat the water to the desired heat.

Coffee bean quality

You can have the best equipment in the world, but if you don’t start with good coffee beans, you’ll never make a great espresso.

The quality of the coffee beans is determined by many factors, such as the country of origin, variety, altitude, and processing method.

Are you buying beans or grounds?

How long are they already on the shelves in the store? Are you storing them in the right way at home and so on.


A great grinder is important when it comes to brewing coffee. As we’ve said before here, not all the grinders are the same, avoid grinders with blades and aim for at least burr grinders.

This gets us to the grind size.

Grind size

The grind size is very important for a good espresso. Here, we’ll need the grind size to be fine and grounded evenly.

The grind should be uniform and consistent, meaning all the coffee grounds should be of the same size.

Doing this can provide a challenge with manual grinders, depending on the one you have. Generally, with a burr grinder, you’re fine. Blade grinders are a synonym for inconsistency.

(Golden) Ratio

Another important factor is the coffee-to-water ratio. This is the number of coffee grounds you use for brewing your espresso and the amount of water.

Brewing coffee is about control and the golden ratio can give you general guidance on this but can be tweaked rather, needs to be tweaked, for a better result depending on the beans you’ve chosen.

A good start is a 1:2 ratio (coffee to water) and goes from there.

The general rule we use is: the lighter the roast, the less coffee you’ll need, the opposite is true for darker roasts.

When preparing for extraction, make sure the coffee is tamped evenly, this is needed to avoid channeling (water in specific areas, not everywhere) and thus under-extraction.

Timing: pulling the shot

The timing of your espresso shot is vital and gets better over time when done more (experience). You learn by doing.

While you’re pulling the shot, you can look for the brown crema as a tell.

You can pull out of the range or in the range. Out of the range is of course too long or too short:

  • too short: In the beginning, the brighter and sour tastes will be extracted and make it to your cup. The heat needs time to go deeper and get the sweeter oily tastes out of it.
  • too long: you’ll have gone too far, meaning you’ll have heated things too far and this will cause over-extraction and a burnt, bitter taste. The bad flavors will overrule the good flavors and get the upper hand.

Generally, keep the shot time at around 25 to 30 seconds and tweak your coffee-to-water ratio to get it right or the length of your shot time.

Wrapping up

No need to get frustrated. You learn by doing and nothing is perfect from the first time, this is the same for brewing a great espresso. We will have a sour espresso from time to time.

As with everything on our coffee journey, learn, and tweak the coffee-to-water ratio, grind size, and length of your shot. You can track these things easily in a spreadsheet.

Only by following up on your own experiences, you can perfect your espresso-brewing skills and impress your guests or family on their next visit.


Should espresso be slightly sour?

No, an espresso should not taste sour at all. This means you’ve done something wrong. If your crema doesn’t have a brown color but a more blonde color, chances are high that it will be sour.

Why is my espresso sour and bitter?

One word: extraction. It’s all about extraction. If you have a sour or bitter taste, this means that your coffee is under-extracted or over-extracted.

By under-extraction, we mean that not all parts are used and thus not all the good flavors find their way to your cup.

Over-extraction means that they’ve been heated too long and opens the door for bad flavors. This will result in a more bitter or burnt taste.

Do espresso shots go sour?

Unfortunately yes. The Key is the duration of your espresso shot, keep it within the range of 25-30 seconds. If the duration is lower, chances are that it can get sour. Other factors contribute to a certain degree of sourness like grind size, water temperature, ratio, maintenance of your equipment, and so on.

Enjoy your coffee!