Coffee Roasting Introduction

How to Roast Coffee Beans

Your Guide to Roasting and Blending Coffee

Both very important phases of gourmet coffee production, roasting and blending, start with high quality coffee beans.

It may seem obvious, but without a quality bean, it is unlikely you’ll create a quality coffee beverage. Both single origin roasts and blends can be delicious in their own way, and understanding what goes into both is vital for coffee professionals and hobbyists.

An Introduction to Coffee Roasting

Coffee roasting is part science, part art, and part harmonizing in order to achieve the best quality and consistency possible. During roasting, elements within the bean such as starches, sugars, and fats go through the process of blending, caramelization, and release in order to create coffee oil substance. This “oil” is water-soluble and is responsible for coffee’s flavor and aroma. 

Roasting Machines and Techniques

coffee beans in roaster

Cylindrical / Drum Roaster 
These mechanical machines are where green coffee is roasted at a temperature of approximately 400 degrees. The rotating, heated drum tumbles the beans until the desired roast is achieved. 

Hot-Air / Fluid-Bed Roaster This machine is an alternative to the cylindrical / drum roaster where a current of hot air roasts the beans as they tumble.

Cooling Hopper The beans are then transferred into the rounded cooling hopper in order to prevent over-cooking.
A rotating arm mechanism with paddles keeps the beans moving, as the arm sprays cold water over them to further cool them.

Air Cooling The beans are cooled by blowing air over them while the beans are lightly agitated. This method is considered superior and most specialty coffee beans are cooled this way instead.

This process of roasting coffee induces a swelling in the bean with a 50% increase in size. 

Post-Roasting Storage

Once the beans are roasted, they release hundreds of chemical vapors which take around one to three days to vent. It is not until these have vented that you should use the beans. 

One-Way Valves Many roasters have begun to use airtight bags with an incorporated one-way valve system to allow for the gasses to exit the bag, but prevent outside air from entering. This lessens the deterioration time for the beans as the oils are not vulnerable to deterioration by outside air. 

Airtight, dry containers This storage method keeps the beans fresh for around one to two weeks post-roast.

The Difference Between Light and Dark Roast

If a bean ranges in color from a cinnamon tone to light brown/tan, it is considered a light roast. These roasts are usually not traditionally utilized in the making of espresso beverages as they can have a very sharp and acidic taste. Single-origin coffees are frequently roasted lighter, as this style preserves more of the natural and unique characteristics of the coffee.

In comparison, a dark roast has a more full, bittersweet and tangy flavor. The longer the beans spend roasting, the more oil is drawn to the surface of the bean, giving it a darker color. The color of this bean ranges from a shiny medium-chocolate, to a nearly black and, somewhat, oily coloration. In some of the darker roasts, one may taste more char with a smokier flavor. These roasts are best for brewed coffee, rather than espresso.

Many people don’t realize that the darker the roast, the less caffeine the coffee is likely to have. A lighter roast will almost always give you a better buzz.

Cinnamon; New England; LightLight cinnamon brown with a dry surfaceToasted grain taste; distinct acid overtones
Regular; American; Medium-high; Medium; BrownMedium milk-chocolate brown with a dry surfaceNo grain taste; sharpness of acid is rich and rounded
Full City; City; High; Viennese*Darker brown with a slight sheen of oil on the surfaceSlight bittersweet tang; less acid with a more rounded flavor
Italian; Espresso; European; French; After-dinner; Continental; DarkDark chocolate-brown with patches of visible oilDefinite bittersweet tang; very little acidity
Heavy; Dark Italian; Dark FrenchDarker brown to black; oily appearanceDefinite bittersweet tang; virtually no acid overtones

*Viennese is sometimes referred to as a blend of ⅓ dark roasted beans and ⅔ medium roasted beans

Many of these terms have no defined standards in specialty coffee, and are merely used as general descriptors for how long the coffee has been roasted. 

The term, “French Roast,” is often used on the U.S. West Coast to describe the darkest roast. These descriptive terms have no relationship to the bean’s origin or roastery.

man roasting coffee


There are more than one hundred different types of coffee beans with their own unique characteristics. When creating a blend for coffee and espresso, it becomes necessary for the roaster to properly balance each flavor and characteristic of beans from all over the world. 

To this day, roasters continue to argue as to whether roasting should occur before blending and vice versa. Before modern roasting techniques were developed, the Old World tradition was to do individual bean-type roasting and then follow with the blending process. Many techniques have been employed and there are many ways to make great blends.

Espresso Blends 

One single bean type is challenging to process and roast to possess complex properties for superior espresso. For this reason, espresso blends tend to contain three to seven different bean types. 

As found in the United States, 100% Arabica beans are often utilized to create gourmet espresso blends. For an increased amount of crema, Robusta beans are added to the blends. They also enhance the complexity of the blend with a higher level of caffeine.


Whether about to open a shop, a barista, or a hobbyist, it is useful and (hopefully) fun to know a bit about what goes into roasting coffee. Especially as a coffee shop owner, being informed about roasting means having a better idea of what you’ll be buying and serving, and ultimately makes your shop better. Although these processes may seem tedious, this knowledge of roasting and blending can be beneficial in more ways than one. The success of a specialty coffee shop lies in the quality of drip coffee and espresso beverages they are servings.

Our Roasting Workshop teaches you everything you need to know from one of the top roasters in Portland, the heart of coffee. We’ll take you through the equipment, techniques, how Water Avenue has become a successful roaster, and how you can too. 


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