How Coffee Is Roasted

Roasting 101

The transformation of green beans to roasted coffee is truly magical
Posted on Novem​ber 6th 2014 by Maddie

The transformation of green beans to roasted coffee is truly magical. An art that has been perfected and developed over the course of hundreds of years. In some parts of the developing world, coffee is still roasted and prepared the same way it was at the beginning - in a pan, on an open flame. It’s a rich history of precise method and trust in taste.

Commercial roasting has been constantly evolving. The skill of roasting combines mathematics, chemistry and physics with the craft and nuance of creating a gourmet bouquet.

Kicking Horse Coffee samples, tests and develops specific profiles for each and every blend, in order to ensure we bring out the best characteristics with each roast.

During roasting a series of complex physical and chemical processes take place to transform green coffee into the roasted beans we love.

Physical Changes

Water Loss

As a result of the roasting process, the majority of moisture content in the green coffee evaporates. During the beginning of the roast, the beans begin to steam as their internal water content dissipates.

Expansion in Volume

The bean expands in volume. Due to the loss of water, the cellular tissue becomes dry and brittle. This eases the crushing of the coffee beans and increases the extraction capability.

Lower Density

Weight loss is associated with the water content of green coffee. The loss of mass and expansion in volume during roasting results in a reduction in the density of the coffee bean. Beans lose 12-25% of their weight.

Colour Changes

The green beans begin yellowing for the first few minutes emitting a grassy smell. Then through heating, some of the simple sugars present are caramelized into browning products.

The caramel products contribute, along with the melanoidins formed in the Maillard reaction, to the brown colour of the coffee beans.


If the coffee is roasted darkly, natural oils begin to migrate toward the bean surface.

Chemical Reactions

Roasting coffee changes the chemical makeup. Arising from a few initial chemical compounds during the roasting process are numerous volatile aromatic compounds. The transmission of heat to the surface of the coffee beans takes place by means of convection, radiation and contact.

Maillard Reaction

Known as the browning process in which reducing sugars react with amino acids. The Maillard reaction changes colours and flavours of certain food when they are cooked or processed. Not just coffee, this chemical process also occurs in toast, meat, beer and many other items. Most of the aromatic compounds are formed by the Maillard reaction.

First Crack

First crack is when structural changes occur. The beginning of the transformation to roasted coffee. This is when the endothermic reaction becomes exothermic as the beans begin releasing heat.

An exothermic reaction occurs as the heat is pushed out. And as the sugars begin to caramelize, you will hear the first crack. The first audible cracking is caused mainly by the escape of steam. The sound is much like the sound of popcorn popping.

Second Crack

Caramelization continues, oils migrate and the bean expands in size. During the second crack, the structure of the bean fractures from built up pressure.

Depending on each individual origin, we decide when we’d like to drop the roast. Once the beans are dropped they are immediately cooled.

Custom blends

Blending is the mixing of different varieties of beans prior to, or after roasting to capitalize on the best taste attributes of each varietal. Our blending processes remain a trade secret. Blends can be either pre-roast (first blended, then roasted) or post-roast (roasted separately then blended).

A great example of our post roast blends is our Three Sisters - a triple blend of light, medium, and dark roasts.