Should Espresso Beans Be Oily? Bad For Your Machine?


Should Espresso Beans Be Oily header image

You might have noticed that the beans you’ve been buying to make your morning espresso with are oily. It that a good or a bad thing and why does that happen?

In general, espresso is made with dark roasted beans which can be oily on the outside. Dark roasted beans are what create the typical espresso taste but can be problematic for some grinders and automatic espresso machines. It’s possible to use lighter roasted beans and brew good espresso.

What makes coffee beans oily and how can you keep your machine in best shape? Find out below.

Should Espresso Beans Be Oily?

You’ve heard beans that are good for espresso are oily. Is that actually true?

Just having an oily exterior is not what makes beans good for espresso. The oily exterior is an indicator of a dark roast which is often used for espresso and is largely responsible for the typical intensely bitter espresso taste. However, it’s possible to make great espresso without the beans being oily.

Oily beans are roasted dark and darkly roasted beans are often used for espresso. That’s for a few reasons:

  • Darker roasted beans are easier to extract: To make espresso, you have to extract the grounds with little water and in a short amount of time. Because with a dark roast the cell walls are broken down already, it’s much easier for the water to extract the grounds than with lighter roasts.
  • Dark roasts create the typical espresso taste: The darker the roast, the more bitter notes you get in your coffee. This creates the intensely bitter taste of espresso most people know and expect. However, darker roasts tend to have a little less caffeine.

The traditional Italian espresso is made with dark roasted beans. In the last years, many espresso aficionados have actually moved towards using lighter roasts. This is because lighter roasts can produce a more balanced espresso with less harsh bitterness and more sweet notes. This brings its own set of challenges though, more on that below.

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Note: On darkly roasted oily coffee beans the oil is exposed to oxygen. The oil is where a lot of the taste of espresso actually comes from. Exposed oils can oxidize and go rancid much faster than when they are contained. That means dark roasted beans actually deteriorated much faster than lighter roasted beans.  

Why Are Some Coffee Beans Oily?

You might have noticed that some beans are oily and others aren’t. Before we get into espresso, it’s good to know why some beans are oily in the first place.

The reason coffee beans are sometimes oily on the outside is because they are roasted dark. Every coffee bean has oil inside of it. It’s usually contained within the cells. Coffee beans have cellulose cells that contain all the oils and other compounds. What happens when you roast the beans is that the cell walls of the cellulose break down and the oils escape. That shows up as a shiny oily surface on the outside of the beans.

If this happens depends on how darkly the beans are roasted. There is a very wide range of roast levels and not all roasts are oily. Since it happens because of the breakdown of the cellulose, the darker the roast, the more oil you tend to have. But, there are some differences in how quickly those oils are released and evaporate.

The oils will evaporate over time so if you have beans that were oily and aren’t anymore, they’ve probably gone stale. Also, on some beans the oil appears a few days after roasting and not immediately since it takes a while for the oils to make its way to the surface of the bean.

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Oily, dark roasted, coffee beans

Are Oily Beans Bad For An Espresso Machine?

Oily beans are dark roasted beans and that’s what brews the espresso you know and love. But is that oil going to be a problem for your espresso machine?

Using oily beans in an espresso machine is not going to break it but it does raise the cleaning requirements quite a bit. You’ll have to clean the grinder and all the places the grounds go often. Some machines will be much more sensitive than others. This is largely because of the design which you can’t do much about.

Oily beans are dark roasted beans and that’s what brews the espresso you know and love. But is that oil going to be a problem for your espresso machine?

If oily (dark roasted) beans are good for the taste you want is one thing. However, oily beans can potentially be a problem with your espresso machine. The oils on the outside of the beans can combine with the fine coffee grounds and make a kind of sticky, muddy substance. This can clog up the teeth of a grinder and preventing other beans from being ground properly.

The beans can also stick together in some cases which can sometimes lead to the beans not being fed into the grinder properly. Can you grind your own espresso?

With other brewing methods where you need a coarser grind, this is less of an issue but for espresso the beans have to be ground fine. The finer you grind the more likely your grinder is to get clogged because it creates that clay like substance quicker. If you use oily beans, you’ll have to clean your grinder much more often.

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In an automatic espresso machine that fills the filter basket for you, oily beans can cause problems because the pathways the coffee grounds have to travel through can get sticky and clogged up by the muddy results of the oily beans. Often on automatic machines the whole unit with all the pathways can be taken out so it’s easy to wash but it’ll have to be done more often than with non-oily beans.

Manual machines don’t have a problem with oily beans because you have to fill the basket yourself. So while your grinder might have a little trouble, a separate, manual espresso machine will work fine.

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Coffee grinder hopper with beans.

Can You Use Light Roasted Beans To Make Espresso?

If your machine is having trouble with the oily beans, can you use a lighter roast to make espresso? Using lighter roasts to make espresso is not only possible but has become quite popular over the last years. The traditional Italian espresso is made with dark roasted beans, however many of the third wave coffee shops actually use lighter roasts.

So it’s absolutely possible to do and actually has good results. You might get slightly different tasting espresso than with the traditional dark roast. If that’s to your liking is up to you. There will be slightly less bitterness and more balance in the espresso. Lighter roasts are known for having more aroma and a more floral character and when brewed often have a bit more depth of flavor.

There are some things to know about using a lighter roast to make espresso:

  • Lighter roasts are harder to extract: Because the cells walls are more intact on lighter roasts, what’s inside those cells is harder to get out. You’ll have to grind a little bit finer than you would dark roasts. Hotter water will also help but this is hard to control on many domestic espresso makers.
  • You don’t have to go all the way to light. If you just want to avoid machine troubles, a medium roast will work well. Medium to medium-dark will usually not have an oily surface but will still have much of the bitterness you like in espresso although it’ll be a little more subdued and balanced.
  • Use slightly less grounds: Because it takes more work to extract lighter roasts, it could mean you under extract the grounds if you use the same amount of coffee grounds. If your espresso is coming out too sour and already adjusted the grind size, try using slightly less grounds (adjust by +- gram at a time) can help. Because you use less coffee but the same amount of water, that water has to extract less grounds leading to a higher extraction of the used grounds.

Favorite Espresso Tools

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

  • 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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