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Why Are Some Coffee Beans Oily?

Coffee made from a fresh batch of beans is all that every coffee drinker desires. And if you love coffee, you know how exciting it is to find a new type of bean that you haven’t tried before, especially when brewing at home.

oil in coffee beans.

But what happens when you find certain coffee beans with a greasy, oily sheen on them? Is this something normal? Let me give you some information about that.

I enjoy discovering different types of coffee beans. On one of my excursions in my hometown, I happened to find coffee bags containing dark coffee beans I have never seen before.

I was surprised by the shiny coating of oil on these beans, and it got me wondering. So, I did some research, and this is what I discovered in this article.


What are some beans made of?

For starters, if you want to know what is contained in coffee beans, you have to find out what they are made of.

Knowing what coffee beans contain will help you understand their flavors and characteristics. So let’s learn about coffee beans.

A coffee bean (although referred to as a bean) is actually a little bean/seed. It contains an endosperm similar to what you find in maize seeds.

The endosperm of a bean coffee is packed with several compounds including amino acids, carbohydrates, antioxidants, lipids, caffeine, fiber, and water.

Each of these substances reacts differently during the drying, heating, and processing of the beans. For example, caffeine extract is easy to get from coffee beans because it is water-soluble.

Apart from the coffee extract and the compounds mentioned above, coffee beans also contain oils. It’s where the coffee’s oil comes from that many people are unaware of.


Where does the oil in coffee beans come from?

So why are some beans oily? Well, apart from caffeine molecule, proteins, and sugars, coffee beans also contain lipids. These lipids come to the surface when you store the beans in a coffee bag or packaging for a long time. Also, the lipid content varies depending on the roasting level. If you roast the beans longer, a thicker layer of oil will coat their entire surface area.

If your coffee beans are oily, it’s because they have been exposed to heat during the roasting process or air while in storage, causing their natural oils to leak out.

Although some people believe oily coffee beans are old, it’s not always the case. It is just a myth. The coffee bean’s roasting process can also result in oily beans and a strong flavor. Thus, oily beans still have their freshness intact, especially when using single-origin beans rather than a roast blend.


How coffee roasting brings out natural coffee oils

When coffee beans are still in the cherry stage during harvest, they are bright green and filled with juices, sugar, and other nutrients.

As the beans start to dry in a roaster, their outer cellulose structure starts to break in what is referred to as the “first crack.” You’ll hear a cracking sound as the shell cracks due to the rising temperature.

Once the “first crack” occurs, the beans darken further in the heat, turning brown through the Maillard reaction process.

During the Maillard reaction, gases and oils within the coffee bean are released. Also, heating sugars in coffee makes them caramelized. The first crack is an indicator that the coffee is at a light to medium roast level.

Some roasters prefer to stop heating their beans at this point. Others go further to the second crack, which is experienced as the temperatures rise.

The “second crack” is a sign that the internal shell of the coffee beans is breaking down under the heat.

The cracking of the internal shell makes the coffee beans more porous, leading to the release of oils at various roasting changes. Also, roasting changes the chemicals and structures of the beans. Thus, coffee changes in appearance at different roasting stages.

Once the oils are exposed to oxygen, they oxidize, leaving the roasted coffee beans with a shiny, oily coating.

Coffee beans that are roasted up to the second crack stage are referred to as medium to dark roasts. They often have an oily sheen on them due to the lengthy roasting process they undergo. Heating beans beyond a dark roast may turn them into charcoal and release a lot of smoke.

However, light to medium roast coffee beans don’t get to the second crack stage. Therefore, their oils don’t come out onto the surface. It’s the reason why they rarely have the appearance of an oily film on them unless they’ve been stored for too long.

Once I understood these facts concerning different types of coffee, I realized that if I come across a bag of oily dark roast beans, it doesn’t mean they are old. It’s a result of the roasting process.


Is the oil in coffee beans bad?

So, after all is said and done, does it means the oils from coffee beans are bad for you? No!

The lipids in coffee beans that eventually come out as oils contain most of the caffeine, aromas, and flavor profile you enjoy when sipping on your favorite cup of coffee.

The only difference is that you’ll find some oils on dark roast beans, while in light to medium roasts, they are left inside the coffee beans.

And, if your wondering which coffee beans contain more oils, it’s the heavier and darker ones that are also known to produce more robust flavors when brewed.

What determines the taste of coffee and the color of the beans that make it is how long they are roasted and their color at harvest.

An important point to note is that light to medium roasts should not have oiliness on the surface. If you find an oily coating on light to medium roast coffee beans, they are probably stale and will have no flavor.

On the other hand, dark roast beans are likely to have an oily coating on them, intense flavor notes, and more complexity because they have undergone a lengthy coffee roasting process.

Therefore, when brewing coffee from dark roast beans, expect bold flavors with a hint of smokiness due to the longer roasting time.

When brewed, their resulting flavor compounds are less sweet than light to medium roast coffee, which has fruity, floral, or sweet undertones such as citrus, blueberry, or caramel.

Since dark coffee roasts are strong, it is common for people to use flavored creamer when drinking coffee from dark roasted beans. Dark roasts are also used in espresso machines to make espresso coffee, especially for people who love strong cups of coffee. Using a lighter roast in an espresso machine won’t offer a great coffee experience.

Unfortunately, some coffee connoisseurs considered dark roast coffee inferior because it does not emphasize the original flavor of the coffee bean.

People who love coffee would rather taste light to medium roasts which have not been over-roasted and retain the flavor of the coffee bean.

That’s why medium-to-light roasts taste fruity, sweet, or floral. They are often classified as high-quality coffee in shops and among coffee drinkers.


How to get the best flavour from coffee beans

There’s more to making an excellent cup of joe than just adding scoops of coffee grounds into a coffee pot, filling it with water to extract flavors, and taking the beverage that comes out of it.

If you’re looking to create a flavourful cup of coffee, the oxidization of coffee beans is beyond your control.

However, you have control over how you brew your coffee and the type of beans you use. These two things can make all the difference in your brews for a rich coffee tasting and drinking experience.

For example, if you like bold coffee flavours, pick a darker roast from specialty roasters as it contains more coffee bean oils. Grind the beans into a fine grind size. Use a substantial amount of grounds to brew your coffee.

You can use grinders such as a burr grinder or blade grinder to grind the beans at home. Make a point of brewing the coffee for some time to ensure the grounds release all their oils and rich flavor.

If you like lightly flavored coffees, pick drier coffee beans that are unlikely to contain a lot of oil. Grind the light, dry coffee beans coarsely instead of finely, which may release more flavour compounds than you want.

Use a small amount of grounds and brew them for a short time to give the resulting cup of coffee a subtle flavor.

When you have these factors in your head, you can customize a cup of coffee to taste sweet and mild or strong with a rich flavor, depending on your preference.


How to store your coffee and keep it fresh

However, no matter how careful you are when brewing coffee, if the beans you use are of low quality, you’ll end up with horrible coffee.

Therefore, when purchasing a bag of coffee beans, pick the best kind.

Keep in mind that when coffee beans are left on the shelves for more than a month, their oils and moisture evaporate, resulting in a loss of aroma and flavor.

When such beans are brewed, you can expect the coffee to taste bitter, dry, and bland.

Therefore, ask how old coffee beans are before buying them to ensure you are purchasing a fresh bag.

And to avoid destroying your fresh batch of coffee beans after purchase, store them in an airtight container after opening the package.

If you want to get the best flavor from a bag of fresh coffee beans, it’s best to use them within a month of purchase. Thus, buy coffee beans from coffee roasters in small batches.

If, by any chance, you happened to leave your beans on the shelf for longer than a month, there are some things you can use to determine their quality.

For example, the drier the beans look, the older they probably are, and the less aromatic or flavorful you can expect them to be.

Also, if you find the color of your beans is reducing, they are most likely going stale. Even decaf beans go stale.

Most times, when they don’t have any other beans around, some people choose to drink stale coffee. Is it dangerous? It’s not!

But if you choose to brew a cup of coffee from stale coffee beans, expect the resulting cup of coffee to taste unpleasant or, at the very least, not what you are used to.


Dealing with coffee oil stains

Brewing bad coffee is not the only problem you can expect as a coffee lover. Sometimes, you also have to deal with more problems like coffee stains on your clothes and coffee brewing apparatus.

After days of using your favorite cup for drinking coffee, it can also get stained.

Coffee stains are not hard to remove. The best way to do it is by using vinegar, laundry detergent, and baking soda.

If the coffee stain is on a cloth, scrub it off using a toothbrush with warm water and detergent.

If the stain is persistent, sprinkle baking soda and vinegar on the cloth, leave it for a while, and then scrub it off with warm water and laundry detergent using a toothbrush. Then watch the results.

If you are cleaning coffee stains off your coffee machine, french press, or cup, use some vinegar and baking soda to loosen the stain. Then, you can wash it as you usually do with some warm water and dishwashing detergent.

With such tips, you can enjoy lots of coffee without worrying about keeping your brewing equipment clean or getting rid of an occasional coffee stain.


Last word 

In summary, here is what we have learnt about coffee in this guide.

  • Dark roast coffee beans with an oily film on them are not necessarily stale. Thus, presence of oil shouldn’t be used as a determinant of their age.
  • Light to medium roast coffee beans with an oily film on them are most likely old. They make coffee with less strength than darker roasts.
  • The roasting process determines how oily coffee beans get. Light to medium roasts don’t undergo a lengthy roast process. In addition, they are less likely to have oil on their surface when fresh.
  • Dark coffee beans are roasted for a long time, during which the lipids inside them come to the surface, creating an oily film coating around them. So, even when they are fresh, expect them to have some oil on the surface.
  • You control the flavor of coffee by how finely you grind the coffee beans and the amount of grounds you use to make it. However, choosing the best quality beans from the start is most important.
  • Regardless of the recipe guidelines or brewing methods you use, it’s best to use a bag of good quality, fresh coffee beans within the first month of purchase.
  • And, if you want your coffee beans or ground coffee to stay fresh for longer, store them in airtight containers or vacuum sealed packet immediately after purchase.

Hopefully, since you now have all these facts in mind, you’ll have a much better time shopping for and brewing different types of coffee.




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