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Coffee Tips

Why are Coffee Beans Shiny?

What do you notice when you first open a fresh bag of coffee beans? Most people appreciate the aroma of coffee first.

Nothing beats the smell of quality roasted coffee beans. Depending on the beans you buy, you could smell fruity, floral, nutty, spicy, chocolatey, or mushroom flavor notes. These aromas always make us feel like brewing a cup of coffee.

But there are other characteristics of coffee beans that baffle us, one of which is a shiny film on their surface. Why does this happen?

coffee beans shiny

Here are several facts concerning why coffee beans are shiny.


1. Coffee Beans Shine Because They are Coated with Oils.

Coffee beans release their oils during intense roasting processes. These oils end up coating the surface of coffee beans even after they are packaged.

The darker a coffee roast, the more oils you can expect on them. You usually see this in French or Italian roasts.

The oily film on dark coffee beans comes from the lipids inside them. These compounds turn to oil during the roasting process.

The heat causes the coffee beans to crack open twice, allowing their oils to seep out. It also makes the sugars caramelize and intensifies their flavors


2. Coffee Beans Release Oils When Roasted at Extreme Temperatures

Coffee beans release their oils when roasted at temperatures between 370 – 540 degrees Fahrenheit. Dark roast coffees with an oily film on them are usually roasted at over 450 degrees Fahrenheit.

Once coffee beans are roasted at these temperatures, they continue releasing their oils for weeks after the roasting process. That occurs because their shell cracks open under the extreme heat, creating spaces for their lipids to flow out as oils.

That’s why light roast Coffee beans have a dry surface with a matte finish. They are not roasted under high temperatures allowing them to retain most of their oils.


3. Shiny Coffee Beans could be Fresh or Stale Coffee Beans

Shiny coffee beans could be a sign of freshness or staleness. The roast date on the coffee bag will give you an idea of which of these applies to your coffee beans. If they were produced within the last 2 weeks, the oils on the surface prove they are fresh.

But sometimes, the oil on coffee beans signifies they are old. They are stored for a long time, releasing their oils due to heat or light exposure. Coffee beans can also release their oils due to oxidation if they are poorly stored.

Always buy coffee beans that are closer to their roast date as possible. That will assure you that the oils on them are not a sign of staleness. You should also store coffee beans in air-tight containers to prevent their oils from getting rancid.


4. All Dark Coffee Roasts Are not Shiny

Although dark roasts are associated with oily surfaces, it doesn’t apply to all of them. Some freshly roasted dark roast coffees are not shiny because their oils have not yet had time to rise to the surface.

You may also notice the sheen on your dark roast disappear from their surfaces as they age. That occurs as the coffee oils on coffee beans evaporate with time. Any brew prepared using such coffee beans is usually flavorless.

The roasting process can also prevent coffee beans from developing an oily sheen. A good example is baking coffee beans which causes any oils they release to evaporate.

These coffee beans differ from those processed through roasting that are forced to release their oils during the intense roasting process.


5. Coffee Oils Create Flavorful Coffee Beverages

We’ve mentioned that the oils on shiny coffee beans give it a rich flavor, but what does that mean? It means the unique flavor of coffee beans comes out through their oils depending on their variety and roast type.

Arabica coffee beans may have a crisp floral or fruity flavor, while robusta coffee beans have chocolate, nutty, and smoky flavors.

These flavors reduce the more coffee beans are exposed to light, moisture, oxygen, and heat. It’s why stale coffee beans, which hardly have any oils on them, produce flat-tasting coffee.


6. Shiny Coffee Beans Can Destroy Your Coffee Machine and Coffee

The oils on shiny coffee beans clog automatic espresso machines and coffee makers with blade grinders. They also coat the hands and can stain your clothes.

Constantly clogging coffee-making equipment with coffee oils reduces their lifespan, so you should avoid using oily coffee beans for this reason.

Shiny coffee beans also lose most of their flavor during roasting. They end up brewing coffee with a charred, smoky, earthy, acidic flavors. That’s quite different from what you get when using light roasts to brew coffee.

Light roasts contain lots of oils that result in flavorful coffee characterized by authentic notes of the coffee beans. Some examples are sweet, floral, and fruity notes such as blueberry and citrus.

7. Immersion Coffee Making Methods Are Best for Shiny Coffee Beans

As we have pointed out, shiny coffee beans are usually dark roasts. They produce the best coffee when brewed using immersion coffee brewers such as French Presses or Aero Presses.

That’s because these machines do not require filters which usually remove some of the oils from coffee grounds.

You may also use an espresso coffee maker to extract all the oils from coffee grounds when using oily coffee beans. These oils are responsible for the rich crema you see on espresso coffee.


8. You Can Reduce the Bitterness Associated with Oily Coffee Beans

The oils that make coffee beans shiny result in a bitter brew. You can reduce these unpleasant flavors by grinding the coffee beans to a coarse grind.

It is the ideal grind to use if you want to extract the chocolate flavors in dark roast to reduce the bitterness produced by their oils.

Lowering the water temperature, you use to brew oily or shiny dark roast coffee beans can also reduce their bitterness. A suitable temperature to use is 195 degrees Fahrenheit.

You can also use shiny coffee beans to make cold brew because the cold water used to brew it won’t extract bitter flavors from them.

Using these tricks will help you to get the most from shiny coffee beans when they are fresh. Coffee brewed from them makes an excellent base for popular coffees such as Americanos and Long Blacks.



Now you know that shiny coffee beans are nothing to worry about. They are a sign of an intense roasting process.

These beans are safe for consumption and can make excellent brews such as Espresso coffee. But the flavor you get from them cannot compare to what you get from coffee beans without oils on them.

Shiny coffee beans produce bitter coffee with earthy, nutty flavors, while lightly roasted coffee beans with hardly any oils produce crisp, fruity, or floral brews.

The fewer coffee oils you lose from coffee beans through roasting or during storage, the more flavor you get in your coffee. Therefore, if you prefer light, crisp flavors, stick to light or medium roasts with little or no oils on their surfaces.


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