Why are coffee beans oily? And is that a bad thing?

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Do you like your coffee with a little bit of oil? No, not that kind of oil. We’re talking about the kind that comes from roasted coffee beans.

Yep, those little guys. The ones that are so shiny and oily that they almost look like they’ve been deep-fried. Well, there’s a good reason for that. You see, when those beans are roasted too long, they start to release carbon dioxide gas. And when that gas comes into contact with oxygen, it creates this thick, oily substance that coats the beans.

Don’t worry, though. It’s not always a bad thing. In fact, the oil in the beans is what gives coffee its distinctive flavor and aroma. But if you don’t like the idea of drinking oily coffee, you might want to start with a lighter roast.

So, let’s find out why are coffee beans oily sometimes.


Why are coffee beans oily

What makes coffee beans oily

Well, it all has to do with a chemical reaction that happens when the beans are roasted. If they’re roasted too long and the internal shell cracks, that’s when carbon dioxide gas is released and reacts with oxygen. This creates the oil that makes coffee beans so shiny and… oily.

Now, this isn’t always a bad thing. In fact, it’s what gives coffee beans their distinctive flavor and aroma. But it can also make them a little bit harder to digest. So if you’re not used to drinking coffee with all that oil, you might want to start with a lighter roast.


Why are coffee beans oily

What causes coffee to be covered in oil

The three main causes of coffee being covered in oil are the beans being full of oil, being roasted for a long time, or the beans having been allowed to sit. The oily coating on coffee beans can also be caused by a combination of these three factors.

Naturally oily coffee beans: Certain coffee bean strains are just more oily than others. Some of these include the Arabica variety from Ethiopia and some beans from Central and South America.

Over-roasting: If coffee beans are roasted for too long, it can cause them to release an excess of oil. This usually happens with darker roasts and is not necessarily a sign of bad beans.

Allowing the coffee to sit: If your coffee beans have been sitting on a shelf at the store for a long time, the beans’ oils will start seeping out. This is why buying beans with a known roast date is always best.


Why are coffee beans oily

The benefits of oily coffee beans

Oily coffee beans are rich in antioxidants and caffeine, providing various health benefits. Caffeine is known for its ability to increase energy levels and help with weight loss, while antioxidants protect the body from free radicals that can cause damage.

Coffee bean oil is also anti-inflammatory, meaning it can help to soothe inflammation and puffy eyes. It can also be used to treat acne and bee stings. Additionally, coffee bean oil is beneficial for the skin and can decrease wrinkles, ease sore muscles, and treat cellulite and signs of aging.

Finally, coffee bean oil is known to improve cognitive function and protect the brain from damage. Studies have shown that it can help to improve memory, reaction time, and vigilance. It has also been shown to reduce the risk of Alzheimer’s disease and other forms of dementia.


Why are coffee beans oily

What are coffee essential oils?

The coffee essential oil is a potent and fragrant oil that is derived from the cold-pressed distillation of coffee beans. This oil is packed with antioxidants and other active ingredients that provide various potential health benefits.

The oil has a deep, rich coffee scent that is sure to invigorate the senses. It can be used in a diffuser to promote alertness and wakefulness, or it can be added to massage oil for an invigorating treatment.

Coffee essential oils can be ingested by adding a drop or two to water, tea, or juice. However, there may be side effects, including allergic reactions, skin irritation, and gastrointestinal distress if consumed.


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The drawbacks of oily coffee beans

Of course, there are also some drawbacks to having oily coffee beans. One is that the oil can go rancid more quickly than other types of coffee beans. This means that you’ll need to drink it sooner after roasting to get the best flavor.

Additionally, oily beans can clog automatic espresso machines. Clogged machines can be a real pain to clean, so you might want to stick to manual brewing methods if you’re using oily beans.


Why are coffee beans oily

How to store oily coffee beans

Oily coffee beans should be stored in an airtight container in a cool, dark place. This will help them stay fresh for longer and prevent the oil from going rancid.

If you don’t use the beans immediately, you can freeze them. Just make sure to vacuum seal them. Any air or moisture that gets in can cause the beans to go bad.


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Some science behind carbon dioxide gas and oxygen reaction in coffee beans

When coffee beans are roasted, the heat causes the release of carbon dioxide gas. This gas then reacts with oxygen to create carbonic acid. This acid is what gives coffee its distinctive flavor and aroma.

Interestingly, this same reaction also happens when you roast meat. That’s why your steak tastes different when it’s cooked rare, medium, or well-done. The longer you cook it, the more carbonic acid is produced, and the more intense the flavor becomes.

In the human body, carbon dioxide combines with water to form carbonic acid. That acid then dissociates into a hydrogen ion and bicarbonate. The hydrogen ion is what makes your blood acidic, and the bicarbonate is what helps to buffer that acidity.

So when you drink coffee with all that oil in it, you’re basically getting a dose of carbonic acid. That’s why it can be hard on your stomach if you’re not used to it.

If you’ve ever wondered why your barista told you to wait a few days before brewing newly roasted coffee, it’s not just because they wanted to procrastinate making your drink. Coffee needs time to off-gas or release carbon dioxide gas. If the coffee is not able to off-gas, then the excessive CO2 in the coffee beans will bind with H20 during extraction and create H2CO3 which is carbonic acid.

This has a sharp, bitter taste. So when you’re waiting for your coffee to rest, you’re really allowing the Carbon dioxide to escape so it won’t make your coffee taste like battery acid.


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Tips for brewing oily coffee beans

Dark, oily coffee beans can be challenging to brew, but the results are worth it. Those who love their dark roasts do so because they have a strong and intense flavor. Others find it off-putting. If you’re in the latter camp, don’t worry—there are still plenty of ways to enjoy dark roast coffee without having to deal with the oil and tone down the intensity.

This type of bean is best used for espresso or French press coffee. But if you don’t have either of those methods available, you can still make a delicious cup of coffee with your dark roast beans.

Lower the Water Temperature – One trick people use to get more out of oily dark roasts is to lower the water temperature. I tend to brew specialty coffee around 205°F, but for oily beans, I drop the temperature as low as 195°F for the darkest, oiliest beans.

Grind Coarsely – Finely ground coffee can be challenging to brew and easy to overextract. For this reason, try to grind your beans more coarsely when brewing with oily beans. I like to use a burr grinder at home, but if you don’t have one, you can always ask your local barista to grind the beans for you. Just be sure to tell them that you’re brewing with a French press so they know to grind accordingly.

Use a Paper Filter – If you’re using an AeroPress to brew your coffee, use a paper filter. Oily coffee beans can clog up a metal filter, making it difficult to get a good cup of coffee. Paper filters will help ensure that your coffee comes out tasting great.


Final Thoughts

Coffee beans are oily because they are full of natural oils that give them their flavor and aroma. These oils can go rancid quickly, so it’s essential to store oily coffee beans in an airtight container in a cool, dark place. Additionally, the oils can clog automatic espresso machines, so you might want to stick to manual brewing methods if you’re using oily beans. Finally, the oil is full of carbonic acid, which can be hard on your stomach if you’re not used to it.

No matter what, it’s important that a coffee lover find a coffee that they love and can enjoy. Different coffees have different properties, so it’s up to the drinker to find the perfect bean for them. For some, that might mean a light, airy coffee with no oil. For others, it might mean a rich, flavorful cup of coffee with plenty of oil. Ultimately, it’s up to the coffee drinker to decide what they like best. Happy brewing!

Kris Silvey

I've been drinking coffee my entire life, from a little boy stealing coffee off the counter to an adult (who still steals his wife's coffee occasionally). I'm passionate about exploring the world of coffee and finding another great roast to experience.

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