Why Is My Espresso So Bitter? How to Fix Bitter Espresso?


Why Is My Espresso So Bitter header image

Ever drank an espresso that was just so bitter it’s hard to finish even though it’s just a little bit of liquid? Here you can find why that happens and what you can do about it.

Espresso is often quite bitter because it’s brewed with dark roasted beans. Dark roasted coffees have more bitterness. Using a medium roast will produce a more balanced espresso but grinding slightly coarser, using more grounds, using cooler water and reducing fines also helps.

Those are the most important things you can change to make your espresso less bitter. There are quite a few other things you can try. I’ll go into them in detail below.

Why Is My Espresso Bitter?

There is a lot going on when brewing espresso. I’ll go into depth about what’s going on below in the lower chapters. However, to help you quickly, here is a summary of what follows below:

  • Use lighter roasted beans: Try medium or medium-dark roasted beans if you’re using dark beans now.
  • Use more grounds: Using more grounds for the same amount of water lowers the overall extraction, preventing the extraction of the most bitter compounds.
  • Grind slightly coarser: A coarser grind provides less surface area for the water to act on and extract. However, too coarse will result in a weak, sour espresso.
  • Reduce fines: Fines are coffee dust created during grinding. These fines extract very quickly so they contribute quite a bit to the bitterness.
  • Reduce coffee puck resistance. If the espresso flows too slow (around 25-30 seconds for a single shot of 28 ml is considered normal), there is probably too much resistance in the coffee puck.
  • Grinding slightly coarser can help.
  • Make sure the pick isn’t channeling:  Check the coffee  puck after brewing. If there are tiny holes in the puck, the coffee is ground too finely. This causes channeling which results in simultaneously sour and bitter espresso.

Suggested: Why is espresso so strong?

Espresso is a concentrated form of coffee. That means that any taste in the coffee beans is stronger as well. So if a certain coffee would be bitter when brewed with a pour over method, those same beans are going to be even more bitter when used for espresso. Beans used for espresso are often darkly roasted. Darkly roasted beans have more bitter tastes in them. So an easy way to reduce bitterness is to use a medium roasted bean to make espresso instead.

However, there are also some things you can do during the brewing process to make less bitter coffee with a dark roast.

1. Strength

Espresso is a very concentrated coffee. TO brew a single shot of espresso of 28 ml, you’ll use about 14 grams of coffee grounds. That is much more ground coffee for the final amount of liquid than any other type of coffee. For example: a pour over uses about 20 grams of grounds to brew 300 ml of coffee.

So you can understand that if you put all the taste of so much coffee grounds into a tiny bit of liquid, it becomes super strong. So all the taste notes that are in normal coffee will be present even stronger in espresso.

However, not all coffees have the same type of bitterness. There are a few things you can do in your brewing and bean choice that make certain brews much less bitter than others. Since espresso is a really concentrated version of coffee, changes in taste will be quite noticeable in espresso, maybe even more than in another type of coffee. Especially the big tastes like bitterness and sourness can be adjusted quite dramatically in espresso.

Two shots of espresso flowing into two cups.

2. Dark roast

Many espressos have quite a bitter taste because it’s brewed with a dark roast. Darker roasted beans have a more bitter taste than lighter roasts. That’s because of a few reasons:

  1. The chemical makeup of a coffee bean changes when roasting. The darker you roast a bean, the more it changes. It’s the same reaction that makes bread and meat brown when you bake/fry it. And just like with other foods, a little brown crust tastes great, black tastes disgustingly bitter. Coffee beans are usually not roasted until they’re charcoal but still, the darker the more bitterness.
  2. There are a lot of different compounds and oils in coffee beans. These react differently with different roast levels. They don’t all ‘roast’ at the same rate and temperatures. Some of the compounds are volatile which basically means they can evaporate. With roasting, there is a tremendous pressure within the bean. That pressure can rupture the cell walls and let out some of the compounds before they ever get to your cup of coffee. The compounds that are released first are the ones that give light roasted coffee its fruity, acidic taste. With darker roasted coffee those tastes are gone which would otherwise balance out the bitterness.
  3. A dark roasted bean is also easier to extract. The heat and internal pressure that happen during roasting break down the cell walls. That means the dark beans are more porous. Water can get into the grounds easier and extract them. The bitter compounds are the last ones to dissolve into the water. Because it’s easier for the water to get in, it can dissolve the bitter compounds easier than with lighter roasted beans.
Dark and light roasted coffee beans mixed
A mix of light and dark roasted beans.

Read more about dark roasted beans in this article.

For many people espresso has to be made with dark roasted beans because that’s the taste they expect from an espresso. However, if it’s too bitter for your taste, there are some things you can try:

  • Increase the amount of grounds slightly: Add an extra gram of coffee grounds to the basket (yes, weigh it). This might seem counterintuitive; wouldn’t adding more grounds just make it stronger? Yes and no. The overall strength might increase a little but the extraction will be a little lower. Because you’re still using the same amount of water that does a certain amount of extraction, every piece of coffee is a little less extracted. Since the most bitter compounds are extracted last, this way you’ll avoid them altogether.
  • Use cooler water: Most espresso machines don’t have this option but if it does, try lowering the water temperature a few degrees. Since dark roasted coffee extracts easier and hotter water extracts more, using cooler water reduces extraction avoiding some bitterness.
  • Grind slightly larger: Since you want to reduce extraction, grinding slightly larger means there is less surface area for the water to act on. More on this below.
  • Use a lighter roast: The tips above will reduce the bitterness to a level that’s good for most people. However, there is only so much you can do to change the taste of a bean that has a certain taste. If you want to try to reduce the bitterness in your espresso, try a lighter roasted bean than you’re currently using. Go one level lighter and see if that’s what you like better. If you buy your coffee in the supermarket, it probably won’t say a roast level on the bag. It will probably say a strength instead. That strength usually relates to the roast. Going to a good local coffee shop that sells beans and asking for advice is also a good idea.

3. Grind size

I already touched a little on this above. The grind size is very important for any type of brewing but espresso is especially sensitive to it. Tiny changes in grind size can impact the taste of your espresso quite a lot.

If you buy pre-ground supermarket coffee, there isn’t much you can do here. I would suggest upgrading to grinding your own coffee. Getting fresh beans ground at your local roaster is also going to be an upgrade and you can tell them what you want.

For people that grind their coffee fresh, here’s what you should understand: The smaller you grind, the more surface area there is on the grounds. This results in more extraction because the water has more surface area to interact with the grounds. Grinding coarser will reduce the surface area and reduce extraction.

As you can read above, the most harsh, bitter compounds are extracted last. So if you’re getting that taste, grind slightly coarser to reduce extraction. Make very small adjustments if possible. Not all simple grinders are actually capable of adjusting the grind size finely enough and one step is already too much. But grinders are easy to adjust. Just try it and see if it works.

Espresso grounds being ground.

4. Fines

If you’re using your own grinder and it’s not the highest quality, consider the amount of fines. Fines are basically coffee dust that’s created when grinding. They are super tiny particles that are very easily extracted. That means you also extract all the bitterness.

Take a look at the grounds after grinding. How even are they? Are there a lot of particles that are smaller than wanted? An easy way to see this is to spread a little bit of grounds out over a sheet of white paper.

If you’ve got a lot of fines, those will contribute quite a bit to the bitterness of your espresso as well as slow down the shot by increasing resistance and so also increasing the extraction of the rest of the coffee compounding the problem.

It’s not easy to solve this problem. Upgrading to a better grinder is the best option but that’s expensive. Expect to pay $300 and up for a grinder that grinds well for espresso with not too much fines.

Another option is to use a sieve. There are special coffee sieves that allow you to filter for certain sizes. Those filters aren’t cheap either although cheaper than a high end grinder. However, filtering your ground coffee by hand takes some time and effort and it means you are throwing away some of the coffee. So over time, the better grinder is probably worth it.

If you dive into what it takes to grow a coffee bean and all the time, effort and resources it takes to get you enough beans for your cup of coffee, you don’t really want to waste any.

5. Pressure

Espresso machines work by forcing hot water through a coffee puck under pressure. The pressure helps extract the coffee grounds faster so you need only a little bit of water.

Not all machines are the same. It’s generally accepted that the best espresso is brewed with around 8 bar of pressure. However, some machines crank up the pressure way higher. There are reasons for this but it doesn’t result in the best espresso.

Better machines have an overpressure valve that prevents the pressure from rising too high but especially the entry level machines don’t always have one. That leads to much higher pressures and therefore higher extraction which results in higher bitterness.

However, it’s not always easy to solve this problem. Few machines give you direct control over the pressure. So the only thing you can do is to reduce the resistance of the coffee puck by grinding a little bit larger.

6. Channeling

Finally there is one more important concept to understand and that is channeling. Channeling is when the water digs a little hole in the bed of coffee. The water will choose the path of least resistance so it’ll all flow through the little tunnel. That has as a result that most of the grounds are not extracted but the grounds around the channel it’s really over extracted. That has as a result that your espresso is both weak and bitter at the same time.

Channeling happens because there is too much resistance in the coffee bed. The water can’t get through at the right rate so it starts looking for an emergency escape. If there is none, it has a way of finding the weakest spot in the coffee bed and flowing through there. Then more water starts flowing through there and it takes more and more of the coffee soluble with it and it starts eroding like a river in a canyon.

Channeling happens because of two main reasons:

  • The grind size is too fine: the finer the grounds, the less space there is between the particles. This means the water has more flow resistance. Grinding coffee for espresso is a difficult balance in a small sweet spot between too fine and too coarse.
  • The machine pressure is too high: I’ve already talked about this above. Some machines let the pressure ramp up way too high. In some cases this can help force the water through the coffee puck (probably resulting in too high extraction). But in other cases it can compress the puck so much there is no way the water can get through at all, leading to channeling.

Read more here: 5 Reasons why your espresso puck is channeling

Espresso puck in hand
A good espresso puck

Espresso Essentials

Recommended Espresso Equipment

Besides an espresso machine, there are a few other tools that can make your espresso better. Here are my favorites:

  • Espresso Machine: The Breville Barista Express (Amazon) is the sweet spot in price and quality for most casual home baristas. It comes with a built in grinder and most tools you need to brew espresso.
  • Tamper: A nice tamper helps you tamp your grounds in the filter for the best result. Any correctly sized tamper can do the job but a nice heavy one just feels so much better in your hand than a plastic model. This Luxhaus one (Amazon) has a nice trick up it’s sleeve to make tamping very consistent.
  • Beans: Good espresso starts with good beans. Using fresh beans is a big improvement over pre-ground coffee.
  • Scales: Getting consistently good espresso means you have to know how much grounds is going into the machine and how much is coming out and how long this takes. A coffee scale is going to make your espresso much more consistent and also makes adjustments a lot easier. The Apexstone coffee scale (Amazon) is cheap and doesn’t look too sleek but is just as accurate as more expensive scales. The TimeMore scales (Amazon) look and feel a lot nicer but cost a bit more.
  • Distribution tool: After grinding you can get some clumps in the coffee grounds. Those clumps should be broken up so the water can extract all the coffee grounds equally. Distribution tools are very simple things but this one (Amazon) is beautifully made and will look good in your kitchen.

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