Why Are Coffee Beans Roasted? Read This First!

Why are coffee beans roasted before they are brewed? Read on to find out the reasons and how they are roasted to give you the perfect flavors.

Coffee beans in a sack - why are coffee beans roasted
Coffee beans are roasted to get the aroma and flavor

From being picked as coffee cherries in the country of origin to getting processed, and shipped worldwide for roasting, coffee beans go through a lot before they reach your mug. I feel surprised at people who think coffee beans are picked as-is from the trees! If you love your cup of Joe, you must at least know your bean’s fateful journey!

So, why are coffee beans roasted in the first place?

Unroasted beans have no aroma, no flavor. They are seeds contained within the coffee cherries. Although raw green beans contain all the complex makeup and chemicals, they exude irresistible coffee flavors and aromas only when roasted on intense heat.

When raw coffee beans are exposed to varying degrees of heat in a roaster, the complex structure disintegrates and releases carbohydrates, minerals, amino acids, water, proteins, lipids, and caffeine. The roasting process gives coffee beans the flavors of caramels, chocolates, flowers, and fruits.

Green beans are hard, tasteless, and insoluble. Intense heat during the roasting process breaks down the external cellulose structure and makes the outer shell porous. This allows water to have better access to the coffee solubles when dissolved. This is called extraction during the brewing method.

Unfortunately, roasted coffee beans are susceptible to aging and they start losing flavor soon after they are roasted and exposed to air. As a result, you must always buy freshly roasted beans and store them in an airtight container away from air, moisture, and direct sunlight.

How Are Coffee Beans Roasted?

If you ever get a chance to visit the inside of a coffee roasting unit, you can see how the green seeds stacked inside large sacks are transformed into aromatic beans. Here’s a breakdown of the steps that bring about that delightful change.


The raw green beans are first dropped into huge loaders that are the roaster’s charge system. As the internal air temperature hits the 500F mark, the beans are unloaded into a rotating hot drum to kickstart the roasting process.

Inside the drum, numerous paddles toss the beans through the air to foster uniform heating throughout the process. It works in a similar fashion as a house clothing dryer.


The green beans are treated with high heat for the first five minutes to bring them to perfect roasting temperatures. This stage is carefully done to ensure there’s enough moisture inside the beans without letting the external skin get scorched.

During this stage, the color of the beans changes from green to light yellow and the aroma also shifts from the smell of fresh grass to something like hay.


For the next 5 minutes, the beans roast slowly at roasting temperatures that usually varies between 300F and 350F. This stage develops the precursors to the flavors and aromas that follow subsequently when the roasting temperature reaches a high.

During this step, the internal pressure, temperature, and moisture have to be regulated with caution and care. In this phase, beans turn from yellow to light brown, and aroma changes from hay to that of freshly baked bread.


The full flavor of coffee beans is developed in the final 2-5 minutes. The first crack often referred to as popping happens at about 360°F when the beans expand under the pressure of water vapor and carbon dioxide produced as a result of chemical reactions.

During this stage, the internal pressure drops drastically and the resulting gasses within the beans are allowed to escape. This creates the ideal internal pressure, temperature, and moisture conducive for optimum flavor development.


When the temperature reaches the range of 360°F and 395°F, the amino acids and sugars contained within the coffee beans react at a rapid pace. It helps in developing final and fuller flavors of coffee. The caramelization of natural sugars during the Maillard reaction gives a distinct flavor to the medium roast.

When the temperature reaches the range of 360°F and 395°F, the amino acids and sugars contained within the coffee beans react at a rapid pace. It helps in developing final and fuller flavors of coffee. The caramelization of natural sugars during the Maillard reaction gives a distinct flavor to the medium roast.

In this stage, the coffee beans turn slightly darker in shade and develop a malty character and nutty taste like that of cocoa. It looks visually pleasing and almost like the coffee beans you see in the stores.


Different types of coffee beans are treated to distinct temperatures and roasting periods. These intricacies are decided by the roasting team. For example, the Honduran Espresso coffee beans are roasted to 389°F a temperature while the Yirgacheffe coffee beans are roasted to a 380 °F temperature.


When beans are roasted above the 395 mark, their shade darkens further and they are known as dark roasts. At the extreme temperature, the flavor and aromas developed during the initial stage undergo a complete overhaul and the beans develop new aromas that are smoky, spicy, and toasty.

The acidic and sweet taste is replaced by a dash of bitterness. Most of the pure dark roasts are treated to a temperature between 410°F and 420°F to develop fuller and deeper characteristics.

What Are The Different Coffee Roast Profiles

Light Roasts

The light roasts are often referred to as Half City, Light City, Cinnamon Roast, or New England Roast in the world of coffee. They are light brown in appearance with no oil on the outer surface. They are gently toasted to a grain taste and are acidic in nature.

The original flavors are retained in a light roast and they have a higher content of caffeine present in a coffee bean. Light roasts are created when the temperature inside the roaster reaches 356 – 401°F. At about 401°F, the beans pop or crack indicating the first crack.

Light roast means that the coffee beans have not been roasted after the first pop. This type of roast is popular in the northeastern United States.

Medium Roasts

roasted coffee beans
Medium roast don’t have an oily surface

The medium roasts are often referred to as American Roast, Regular Roast, City Roast, or Breakfast Roast. They sport a medium brown and have a fuller body than the light roasts. Similar to the light roasts, they also do not have an oily surface but they are not grainy.

Medium roasts are developed when the roaster reaches an internal temperature of 410 to 428. The phase starts from the first crack and ends just before the second crack.

They exhibit a more balanced flavor, aroma, and acid level. This profile has reduced caffeine content and it again peaks up in the darker roasts

Medium-Dark Roasts

Medium-dark roasts are also known as Full-City Roast, Vienna Roast, and After Dinner Roast. They look richer and darker in appearance with the external surface starting to get oily. These beans have a fuller and heavier body compared to the versions of lighter or medium roasts.

The medium-dark beans are developed when the roaster reaches a temperature between 437- 446°F. They are roasted to the beginning of the second crack and some variations are roasted to the middle of the second popping sound. The aromas and flavors are more pronounced and the taste of brew made from medium roasts may be slightly spicy.

Dark Roasts

Dark roasts are often known as Italian Roast, French Roast, Continental Roast, Espresso Roast, New Orleans Roast, and Spanish Roast. They have a dark brown color, close to black shade. You can see a thin film of oil on the surface that lends them a glossy appearance.

Dark roasts are achieved when the roaster’s internal temperature reaches 464°F and above. The original flavors of dark roasts are overpowered by the flavors emitted due to the roasting process. If you use dark roasts for brewing, your coffee will have a smoky, bitter, or even sour taste.

These distinct flavors are developed when the second crack comes to an end or beyond that. They are rarely roasted to a temperature exceeding 482°F and this often gives beans the flavors of charcoal and tar.

How To Tell If Your Beans Are Freshly Roasted

When buying coffee bags or loose coffee beans from the store, you may often wonder whether they have been recently roasted or have been lying on the shelves for days. Although roasted beans can stay good for about a month, they must be stored carefully to avoid the loss of distinct flavors and aromas.

My friends often ask me how to tell if the beans are freshly roasted as they look at awe at my judging skills! I realized many people out there have the same problem so I decided to share some tips to help you find out how fresh your roasted beans are.

1. Check for an oily or glossy skin

Coffee grounds are brimming with acids, oils, and other essential compounds that give your morning cuppa its mesmerizing aroma and lip-smacking taste. These chemical compounds are often referred to as coffee solubles that are released during the extraction process.

When green beans are treated to high heat, the internal moisture gets evaporated and the heat extracts an oil-like substance that gets coated on the external surface. This is not real oil and evaporates pretty fast when the beans are exposed to air.

If the beans have been sitting for a long time after being roasted, the surface will not be oily. However, please note that all bean varieties do not emit the same amount of oil so be careful when using oil as an indication of freshness. Also, the lighter roasts will not have a very shiny surface.

2. Keep an eye for the residue

If the beans are roasted using the Swiss water process (caffeine is extracted with water instead of chemicals), you will get comparatively duller-looking roasts. Pick some beans in your hands and you will see that they leave a residue behind. You may even notice a residue inside the bag of beans you got from the store.

The residue implies that the beans are freshly roasted, hence oily. The lighter roasts may not be as oily as the darker ones, so do not expect a lot of residue in that case.

3. Pop some beans in a resealable plastic bag and see what happens

coffee beans in a vacuum-sealed bags
Carbon dioxide is evident inside the vacuum-sealed bags if the coffee beans are freshly roasted

Many people prefer buying beans in bulk instead of picking vacuum-sealed bags from the store shelves. So, if you bought them in bulk quantity, but a few beans inside a plastic bag, press out all air inside the bag, and then seal. Let the bag sit like that overnight.

Examine the plastic bag the next morning to see any difference. If the beans have been freshly roasted in a week or even the last ten days, the plastic bag will blow up like a balloon due to the carbon dioxide gas releasing from them.

4. Check for a gas outlet in the coffee bag

Coffee beans release a lot of gas (primarily carbon dioxide) after they are roasted in high heat and then cooled. The gas continues to release for a few days to many weeks after being roasted, and this period is often referred to as degassing’ or outgassing’.

In the first few days of roasting, the beans release rapidly and the intensity decreases gradually. When the freshly roasted degassing beans are packed in vacuum-sealed bags, they need an outlet or else the bag will blow up like a balloon.

So, the manufacturers include one-way valves in the tightly sealed bags to let the gas escape without letting air in. If the vacuum-sealed bag has an air valve then it indicates that your beans are freshly roasted.

Why Are Coffee Beans Roasted: The Final Words

I sometimes feel the process of roasting beans is just like true friendship. There is nothing in the beginning, neutral just like the raw green beans. As you get to know each other, the flavors start cooking slowly like the light roasts and once a lifetime bond is established, it releases the deepest aromas and strongest flavors!

You may choose from the light roast, medium roast, or dark roast beans, depending on the type of coffee you prefer. When you buy whole beans next time, look out for the signs that tell whether or not they have been freshly roasted.

Beans that are roasted within a week have a distinct smell that will overwhelm your senses as you grind them, and your morning Joe will taste heavenly! If you are new to coffee brewing, you will soon be able to tell the fresh beans from the stale ones by simply looking at them.