Batdorf & Bronson Coffee Roasters


What causes oily coffee beans? - Debunking oily coffee myths

What causes oily coffee beans?

A common misconception is that oily beans=bad.

And truthfully, if you own a super-automatic coffee machine, oily beans are definitely a problem you need to watch out for.

However, visible oils on coffee beans don’t necessarily mean the beans are stale or of a lesser quality. Oils on the beans are the result of a natural oxidation reaction that occurs both during roasting, and over time in already roasted beans.

A Breville Super-automatic espresso machine sits on a counter alongside a plethora of espresso drinks and supplies.

We will discuss why oily beans are not necessarily a bad thing, address the common misconception that oily beans are necessary for good espresso, & offer tips for choosing the right beans for your application (oily or not).

One of the more prevalent misunderstandings about coffee is that oil on the coffee beans represents cheap, old, beans.

This is not always the case. All coffee beans, quality or not, have the potential to become oily.

Finding a roaster you trust is key to getting excellent beans.

A good artisan roaster uses quality beans to craft light, medium, and dark roasted single origin and blended coffee.

A female coffee roaster monitors the progress of her roast by smelling a small sample of the beans.

Roasting coffee is a bit of science, and, a bit of art.

Roasters test out roast profiles on the beans, with trial-and-error, until they find the perfect flavor that highlights the nuances within each bean.

After numerous attempts, they settle on the roast that showcases the beans’ best qualities, which may be dark, medium, or light. The roasting process is also where the oil comes into play.

But why?

When beans are heated in the roaster, oxygen reacts with compounds within the bean producing oil.

The longer the bean is in the roaster, the longer it is heated up, and the more oil that is produced.

Therefore, lighter roasted coffee beans tend to be less oily than their darker roasted counterparts because they have been heated for a shorter amount of time.

So decaf and dark roasted beans not only start oilier than lightly roasted beans, but all coffee beans continue to increase their oily appearance as they sit in your kitchen.

A photo gradient of roasted coffee beans from light to very dark roast.

In fact, the more a coffee bean is processed in any way, the faster the coffee will oxidize, and the oilier it will be.

That is why decaf coffee also tends to become oily quickly. Additionally, as coffee sits, oxygen will continue reacting with the compounds in the bean and increase the appearance of oil on the outside of the bean.

This is why oily appearance has widely become a marker for old or poor quality beans, leading to the misconception that all oily beans are bad.

The 2nd most significant misconception about oily beans is that you need oily beans to make a good espresso shot.

Why does this misconception exist? Why is it wrong?

When coffee shops first hit the scene, many of them bought over-roasted, oily coffee. The misconception grew from here. Many consumers thought that espresso beans were always a bit oily by requirement.

cup spilling over with dark roasted coffee beans

Oily beans can be a big problem if you are using a super-automatic or semi-automatic coffee machine (The coffee machines that grind the whole beans for you, before making coffee).

At-home, modern, super-automatic, and semi-automatic coffee machines can produce delicious coffee--consistently, without the need to learn barista skills.

(Though, of course, we love for you to come in and visit with our baristas.) However, these machines are susceptible to clogging and output issues if they are used with oily coffee beans.

Large buckets of roasted coffee beans on a coffee roastery floor

So, how can you be sure you are not getting oily coffee beans that will clog your appliances?

The short answer is, go fresh, and avoid the dark.

Because the light roasts are less oily, to begin with, they will last longer in your pantry before becoming overly oily.

Artisan roasters have a variety of lighter roasts that they will happily recommend for your daily espresso or coffee needs.

That doesn’t mean that you can’t use dark roasts in your machine.

What it means is that if you love drinking dark roasted or decaf coffee, you might need to buy your coffee in smaller batches, so your coffee beans have less time sitting on the shelf off-gassing.

A miniature statue of Elvis Presley stands in the middle of a coffee bean mixer.

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