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What Causes Oily Coffee Beans?

French roast coffee beans

When you open a brand-new bag of coffee beans and see a brilliant sheen of oil, you may wonder: why do some coffee beans have oil while others don’t? There is a simple reason — and it’s probably not what you think.

Today, we’re unpacking the mysteries of oily coffee beans. What does that layer of oil tell you, and is it something you should seek out or avoid? Let’s get started!

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Why are coffee beans oily?

Contrary to a common myth, oil on your coffee beans doesn’t always indicate freshness. Oily beans aren’t just fresh beans, and non-oily beans aren’t necessarily stale. The oils you find on some coffee beans appear during the roasting process.

coffee beans roasting

When you roast coffee beans, you start with raw green beans. At around 400 Fahrenheit, your beans will hit the first crack, where they begin to expand and caramelize. If you stop roasting here, you’ll have a light roast bean that holds onto its grassy, raw flavors. Beans that are darkly roasted, past the second crack at around 450 Fahrenheit, are typically oily. The oil emerges from inside the beans as the chemical structure starts to break down.

For that reason, light roast and medium roast coffee beans aren’t oily — whether or not they’re fresh. They simply haven’t been roasted long enough to draw the oils out.

What’s the problem with oily coffee beans?

The biggest potential problem with oily coffee beans involves your grinder. If you buy whole coffee beans — the only way to see oil on the bean surface — you have to grind them before brewing, and this is where things can get a little hairy.

electric coffee grinder
Image credit: Unsplash

The oil in coffee beans can clog your grinder, especially if you have a burr grinder or a coffee machine with a built-in grinder. No one wants a clogged, unusable coffee grinder in the morning!

Another problem is that oily beans are very, very darkly roasted. You may love the burnt, caramelized flavor of French roast coffee, but if you prefer more complexity, you won’t find it in oily beans.

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The Bottom Line

The short answer is that oily coffee beans are dark roast beans roasted beyond the second crack. Despite common belief, oily coffee beans aren’t necessarily more fresh than non-oily beans — they’re just more intensely roasted. Oily beans can clog your grinder and generally indicate a very dark roast that is likely to have a burnt flavor. If your grinder can handle it and you like the taste, go ahead and buy French roast beans! If not, you may want to stick to light roast, medium roast, or medium-dark roast coffee beans.

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Kate MacDonnell

Kate is a lifelong coffee enthusiast and homebrewer who enjoys writing for coffee websites and sampling every kind of coffee known to man. She’s tried unusual coffees from all over the world and owns an unhealthy amount of coffee gear.

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