The Art and Science of Roasting Part 1

Roasting coffee is both an art and a science. It’s one of those areas where both sides of the brain are used to create something very special. That something special starts with green beans. 

Green beans are what coffee looks like before it has been roasted. This the product of the coffee cherry, in which the seeds have been extracted from the fruit and dried. The result is a light greenish bean, which is sold to coffee companies to be roasted. 

There are three main kinds of roast: light, medium and dark. What determines which roast, depends on how long the beans are roasted. Seems simple, but it isn’t. This is where art and science come into play. 

Most coffee roasters are what are known as drum roasters. It usually looks like a huge circular contraption, much like the inside of a clothes dryer, with a hopper on the top. Beans are loaded into the hopper which go into the drum. 

Blue Bottle Coffee from San Francisco, has produced a wonderful book titled, “The Blue Bottle Craft of Coffee,” which details what the roasting process is like:

The beans roast through a combination of conductive heat(contacting the drum and each other) and convective heat)the flow of warm air through the drum). In the process, the beans gradually lose water content and begin to undergo chemical reactions, their precise nature determined by the amount of heat, air and moisture. You know where you want this coffee to go, so you set the timer and then take notes, recording batch size, varietal, and other crucial details.

Roasters constantly have to work with the temperature of the drum. Too hot, and you risk burning the beans. Too cool, and you may not have a successful roast. You also have to factor where the beans come from. Were they cultivated at higher or lower elevations? Why is this important? Where the beans come from determines how they handle the various temperatures. Different coffees will taste better when you factor where they came from, the roast and the temperatures of the roasting. 

The roaster is attempting to create a unique taste of the coffee. The problem is he/she doesn’t know at the point of roasting if all their figuring temperature, time, and beans will create what they want to accomplish. 

In the next posting, I will go into more detail about the roasting process.

Charlie