Home Coffee Roasting for Beginners, Fully Explained

If you have never roasted coffee at home, you are in for a treat. Home DIY Coffee Roasting is affordable, delicious, and makes a great gift.

Some believe coffee was discovered by a herd of dancing goats and a boy who thought the animals were acting strange after eating coffee berries. This legend is still celebrated today in Ethiopia where it’s thought that coffee roasting began.

After the discovery of the plant, eventually the berries were peeled, the seeds (beans) dried, then heated in a skillet. A mortar was used to pulverize the roasted beans, then they were boiled. The drink we call coffee was born and it’s believed the first roast occurred in a skillet. Heat applied to green coffee beans is all that is needed to roast your first batch.

But if you want to optimize the flavor profile of the green beans you’ve purchased, there are many coffee-roasting devices to make the process more reliable than skillet and fire. We’ll explore roasters, green bean sources, and the roasting process next.

Coffee Roasters

Electric and gas roasters comprise most of the options available at this time of writing. While this article is not intended as a review of various roasters, we will categorize the basic types of equipment.

Flat surface conduction roasters
  • Skillet – on gas or electric burner
  • Popcorn popper with crank – on gas or electric burner
  • Electric skillet with stirrer
home DIY coffee roasting
Crank-style Popcorn Popper
Electric air convection roasters
  • Popcorn popper
  • Cylinder air roaster
home DIY coffee roasting
Electric Air Convection Roaster
Drum roasters
  • Horizontal rotating roasting chamber – gas or electric options available
home DIY coffee roasting
Commercial Drum Roaster
Flat surface conduction roasters

Flat surface roasters are some of the least expensive options available. But if you consider one, there are three additional issues to keep in mind. 

  1. If the roaster does not have a built-in stirrer, you will need to manually keep the beans moving while they roast. Just like cooking food, beans will burn if not continually stirred during the roasting process. 
  2. Choosing a well-ventilated area will be required as roasting beans give off a fair amount of smoke. 
  3. After the roasting cycle has been completed, the beans will need to be cooled as soon as possible, otherwise they will continue to cook and possibly over-roast. One method for quickly cooling beans is alternately pouring them into two metal colanders outdoors.

Flat surface roasting times will vary based on the green bean you have chosen and the ambient temperature.

Electric air convection roasters

Popcorn air poppers designed to be used for popcorn can be used to roast coffee. But we would recommend that you avoid using this method since the device was not intended to be used as a coffee roaster and will void the warranty. The good news is there are air roasters, also known as fluid bed roasters, specifically designed for roasting coffee. When roasted in micro-batches of 4 to 8 oz, forced air coffee roasters are typically fast and include a programmed cooling cycle. Some air roaster manufacturers indicate they have “low-smoke” designs that may be better suited for use indoors. Still, if using inside, you will want to roast in a room with an exhaust fan.

Drum roasters

While there are some low-capacity versions, most commercial roasters use a drum-style roasting machine that is designed with a spinning drum (cylinder) and heated with propane or natural gas. The batch capacity for these specialty machines is extremely large in the 75 lb (34kg) range. For many, a cooling tray is included where the freshly roasted coffee beans are stirred to cool them as quickly as possible. Ventilation tubes are attached to many commercial drum roasters to alleviate smoke indoors.

home DIY coffee roasting
Arabica Coffee Plants
Green Bean Sources

An online search for “green coffee beans” returned over 500 million results! The difficulty will not be finding green beans but deciding what origin to purchase and where to buy them.

Do you prefer fruity or earthy notes in your cup? Is coffee with a bright finish your favorite or is a rounded, smooth profile your preference? Answering questions like these will help direct you to make your green bean purchase. If budget is a factor, you could consider a green bean that ticks most of your tasting preferences but is also affordable. Before we explain coffee-growing regions and their typical tasting notes, a brief mention of bean type is mandatory.

Arabica vs Robusta

Even though the king of the coffee hill is Arabica, Robusta beans continue to be grown throughout the world because of their hearty composition that survives harsher growing conditions and disease.

  • Arabica: Approximately 85%-100% more sugar, less bitter, higher lipids (oil), more expensive
  • Robusta: Approximately 65%-100% more caffeine, more bitter, fewer lipids, less expensive

Which coffee has the most caffeine? Light-roasted Robusta.

Tasting notes from coffee single-origin regions

The general profiles from the following list vary from country to country and farm to farm. Elevation, soil, and other growing conditions can differ greatly, even with identical coffee plants. These three regional flavor profiles feature Arabica coffee beans.

  • Latin American – chocolate, nutty, balanced, mild acidity
  • African – fruity, floral, bright, acidic
  • Asian – Baker’s chocolate, earthy, smooth, low acidity
Transformation from Green Bean to Roasted

Thanks to Recent Beans in Castleford, England for their coffee bean display. Source

The Roasting Process

Before we dive into the details, if you and yours enjoy decaf as much, if not better, than caffeinated coffee, the roasting time (and even grinding for espresso machines) is usually different. From our experience, decaf green beans roast much faster than caffeinated ones. Depending on the decaf process, the roast time can be as much as 25% faster. A decaf grind for espresso usually requires a finer setting on the grinder.

With a broad brushstroke, there are four phases of transforming green to roasted coffee:

  1. Drying – the initial heating phase that removes moisture from green beans
  2. Browning – visible changes to the outer shell of the green beans from light brownish green to yellow to cinnamon to brown
  3. Roasting – when the temperature increases inside the bean to the point that the first crack occurs
  4. Cooling – a post-roast process to cool the beans as quickly as possible to avoid further roasting

Within each phase, time, temperature, and cooling are choices you can make to determine the final flavor profile. Roast profiles have names that are typically assigned based on a visual assessment of the final color. 

Cleanup

Although not considered a roasting phase, cleanup is one final step before starting the next batch. Chaff, also described as skin or membrane, is the outer layer of a green coffee bean. When heated, the chaff falls off the outer layer of the bean and requires a collector built into the roasting machine or manual winnowing where roasted bean and chaff are separated. 

Back to the roasting details, there are many variations of what may be perceived as white, light, medium, and dark roasted beans. Some of the descriptive names include:

  • White
    • White
    • Yellow
  • Light
    • Brown
    • Blonde
    • Cinnamon
  • Medium
    • City
    • City+
    • Full City
  • Dark
    • Viennese
    • French
    • Italian
    • Espresso

Typically, the lighter the roast, the higher the acidity. The darker the roast, the higher the bitterness. Also, light roasts have slightly more caffeine.

Coffee roasting and the five senses 

From our CJ staff’s experience, here is what you can expect in the coffee roasting transformation from green to roasted beans.

Sight

A quick online image search for “coffee roast profiles” will provide you with visual examples of what you can expect during the roasting color transformation from green to yellow, to cinnamon, and finally to shades of brown. Because you probably already know your favorite bean color, this will be one way to decide when your roast is finished. Keep in mind that once you take the beans off the heat, they will continue to roast until cool. So, you will want to anticipate what you want to accomplish for the final bean color before completing the roast.

Smell

Just as there are visual changes during the coffee roasting process, there are also changes to the smell as the beans go through a metamorphic transformation. Green coffee not only contains moisture but also lipids, an oil content that begins to react to heat. As you gain experience, roasting fragrance changes will give you additional clues as to what is happening inside the roasting chamber. Light to smoky variations is typical.

Your nose can also alert you to the danger of burning beans, especially if using a method like a popcorn popper over a gas grill where the excreted internal oils leach to the bean surface and begin to fry the beans. Hopefully, you will never experience a roast gone too far.

Hearing

If you have ever heard of first crack or second crack, this refers to the audio response of the coffee bean roasting transformation. This is similar but not exactly like the crack of popcorn while cooking. When beans reach beyond the visual stages of white, yellow, and cinnamon colors, the internal temperature will continue to become hotter and a size transformation begins to occur. In a few moments, the beans will become larger and lighter in weight. During this transformation, you will hear a crack.

The time of the crack is based on multiple variables, such as the bean origin, roasting temperature, and if the bean has been decaffeinated. Experienced roasters depend on the auditory response of coffee beans to determine where they are in the process. Some prefer to avoid the first crack altogether, which is also known as third-wave coffee roasting. Other roasters not only want beans to hit the first crack but also to hit the beginning or end of a second crack for dark roasts. Whatever your taste preference, listening for the crack will be another tool to achieve your perfect roast.

Touch

As it pertains to cooling post-roasted coffee beans, we include touch as an important method to confirm that the process has been completed. Beans removed from the heat continue to roast, which can be detrimental to hitting the flavor profile you intended. Whatever you decide to choose for roasting time and temperature, don’t forget the cooling process.

Taste

After finishing your DIY coffee roast, the next stage in your coffee journey is also the reward – taste. Is the final product of your efforts producing the cup you hoped for? Is the profile too acidic or too bitter, too bright or too dull? The way you roast coffee beans can massively impact the flavor, depending on roast time, temperature, and even cooling.

Another major factor impacting taste is the brewing or preparation of your freshly roasted beans. The identical bean will taste very different for a pour over vs. extruded as an espresso. Pairing your unique roast with a specific preparation method could also yield taste profiles that you can explore.

One thing is likely, in a short time you will undoubtedly be able to achieve and exceed the flavor profile of pre-roasted beans you have purchased in the past. This is because you now control the green bean origin used and the roasting process that appeals to your palate. Just be sure to allow time for your freshly roasted beans to de-gas for at least a day or two before preparation. Again, in our opinion, the peak flavor for freshly roasted coffee beans is on days 3 through 6 after roasting.

Conclusion

In an article like this, we just scratched the surface of all the possibilities that await you as you learn about coffee roasting. It’s our hope that you can take what you learned here and embark on the next step to give home roasting a try. We hope you are as excited about launching into your new coffee roasting adventure as we were writing about it!

Read more about this subject in the article, “Is Home Roasting Coffee Worth It?

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