Taos Roasters - Roasting

Coffee roasting is the art and science of roasting green coffees at approximately 400 degrees. Although it sounds simple, roasting and blending are two of the most important parts of creating a great cup of coffee. The roasting process caramelizes the sugars and carbohydrates in coffee beans creating an oil-like substance which gives the coffee its flavor and aroma. The longer the coffee is roasted, the darker and more oily it becomes.

ROASTING EQUIPMENT
The average specialty roaster uses a batch roaster, which is any machine that roasts a batch of coffee at a time rather than the same coffee for most of the day. The most common design of batch roaster consists of a rotating drum above a heat source, usually a gas flame. Operating like a clothes drier, the rotating drum tumbles the beans, ensuring an even roast, while convection currents of heated air move through the drum. Drum roasters may be as large as five or six feet in diameter, or as small as a small waste can set on its side. More sophisticated batch roasters retain the basic structure of but use a stronger current of hot air to heat the beans, so that the metal drum itself remains relatively cool. These are sometimes called convection roasters.

Another kind of recently developed batch roaster uses radiant heat panels on either side of the drum. Some contemporary roasters, called fluidized-bed roasters, carry the hot air principle of convection roasters even further by dispensing with the drum entirely and agitating the beans with a column of hot air, much as an electric popcorn popper does with corn kernels.

THE ROASTING PROCESS

The way in which coffee is roasted can have a profound effect its taste. Roast too quickly at too high a temperature, and you'll scorch the exterior of the bean. Roast too slowly at too low a temperature, and you'll sap the bean of its of flavor. Over the years, numerous roasting methods have been developed to address these challenges, all with the same objective: To transfer heat to the coffee bean, initiating a series of chemical reactions that prepare it for consumption.

Drying Cycle: The first phase of the roasting process, when the temperature of the beans rises to 100 degrees centigrade.

The First Nine Minutes: Once the coffee roasting begins, at just 3 minutes, the beans emanate a grassy fragrance. At about 4-5 minutes, the beans begin to swell and change colors from green to a pale yellow. It is now that the smell changes to that of toasted wheat. After 6 minutes, the bean turns a brownish color, smelling similar to bread. In 8 minutes, a cinnamon color appears and the smell of coffee begins.

The First Crack: Around 10 minutes, gasses build up in the beans causing them to swell to about double their original size and then rupture. This rupture releases the gas and can be heard in the roaster kind of like popcorn. The swelling smoothes out the surface of the bean and then it begins to even out in color to a very light brown. This is the lightest roast and is referred to as cinnamon roast.

Pause
In this phase, the audible cracking ceases, but the reactions continue. The time of this silence will depend on the amount of heat applied by the roaster.

The Second Crack: After about 11 minutes, the color changes to a darker brown known as full city. At around 12 minutes the color and aroma of the coffee begin to change very rapidly. Just as in the first pop, the gasses build up and burst creating a second pop. The progressive dehydration of the beans has made them brittle. As a result, more cracking can be heard. It is at this stage that elements in the bean begin to carbonize, producing the burnt characteristics of extremely dark roasts.

The Dark Roasts: At around 15 minutes the coffee beans now look very dark. A little bit more and we finally come to the darkest roast, the French roast. It is important to note that this has nothing to do with where the beans come from, just how much the beans are roasted. In the 1st place, this is sometimes known as the Italian or Espresso roast. The beans are then poured out onto a cooling vat which stirs the beans to quickly cool them in order to halt the cooking. It is important to note that the freshness of coffee has to do with when it was roasted not when it was harvested.

Stopping the Roast
Once the optimal amount of roasting time has elapsed, the beans must be cooled quickly. This is usually accomplished by introducing large amounts of cool air or water.