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Roasting Coffee - From Green Bean to Your Cup

Article by Andréanne Hamel

For the coffee connoisseur knowledge of the different roasts of coffee beans is important. Having this information will allow them to choose the right roast. It isn’t always enough just to know what Vienna coffee is, or what makes a full French roast. A general understanding of the entire commercial roasting process is also important.

Commercial Roasting
The coffee roasting process includes all of the steps required to take a bean from green to the desired darkness. Green coffee arrives at the factory in large bags. Most operations then dump these bags into large hoppers and conveyers take them up the line for cleaning, and then onto another conveyer for roasting.

The typical commercial machine is a drum style roaster. These machines may be fired by gas, wood, or heated by electricity. They operate at temperatures between 370°F and 540°F. Large horizontal drums tumble the green beans over the heat source until roasting is complete. There are both direct fired roasters, in which the flame contacts the beans, and indirect fired, where the drum is heated instead.

There are several factors that may be taken into consideration when choosing a temperature, and length of time to roast. Coffee origin, desired flavor, variety, and other factors may all be considered. Some factories even go as far as using temperature probes and data loggers, which compare the process to premade graphs, to manage the whole roasting process. From beginning to end it, usually takes anywhere from a few minutes to a half hour to finish.

The Stages of Roasting
The coffee develops cracks twice during the process (depending on the desired darkness). The first pop is due to the expansion of the coffee, and the second comes from physical fracturing due to heat. Here are the stages that the beans go through, and the roasts that they compare to:
1. Light (Cinnamon, New England) – As the beans begin to turn into a usable darkness they pop, and the first crack appears. At this point it has doubled in size, and a light roast is achieved. With a temperature of around 425°F a light roast is usually achieved in about 10 minutes. Lightly roasted coffee is best for showing through the flavors of its origin.  

2. Medium (Full City, American, Breakfast) – After a couple more minutes the second crack is about to appear. At this point a medium roast is achieved.

3. Dark (Viennese, Italian Espresso, Continental) – As the second crack develops in the beans the oil in the coffee rises to the surface. At this point a dark roast is achieved. Most coffees aren’t roasted beyond this level.  Darker coffees tend to get their flavor more from the roasting process than from the coffee bean itself.

4. Darkest (French Roast) – The darkest roasts of coffee come after the third step. A full French roast develops as the sugars in the coffee begin to caramelize. At this point the coffee bean is on the verge of burning.

When it comes to coffee, it isn’t just about finding the latest reviews of super automatic espresso machines to learn how to choose the best espresso machines.  It’s about bean selection, knowing your preferences, and having knowledge of roasting and the different roasts you can buy.  The next time you use that stovetop espresso maker you now have the knowledge you’ll need to fully understand how that dark bean got there.