While origin, harvesting, and processing all play a significant role in the overall flavor and quality of coffee, how the coffee is roasted plays a significant part in the taste and profile of your brewed beverage. An understanding of how coffee flavor is affected by roast style will ultimately provide you with the tools to choose the right roast level for your taste preferences.
Exploring different roast levels can provide you with perspective that goes beyond your historical or regional roast levels. Not only can you expect certain flavor characteristics depending on the roast style, but coffees of different origins might be better suited to some roast styles over others.
The Roasting Process
Roasting takes the processed and dried cherry beans of the coffee plant and transforms them into a product that is eventually ground and brewed with water. Most roasting machines maintain a temperature of about 550°F while constantly moving or turning the beans throughout the entire process to keep them from burning.
First crack, is a brief reaction when the beans release heat (energy) in the form of steam, along with carbon dioxide. The beans will have doubled in size and shed the majority of their silver skin, but oils won’t yet be present.
When they reach an internal temperature of about 400° F, they begin to turn brown and the caffeol, a fragrant oil locked inside the beans, begins to emerge. This process called pyrolysis is at the heart of roasting, along with significant changes to the pH composition of the bean. These changes produce the flavor and aroma of coffee.
Water averages about 10-12% of the density of green, un-roasted coffee. Coffee will loose roughly 12-25% of its weight during roasting, depending on its moisture content prior to roasting, level of roast, and internal conductive environment of the bean during roasting. Typically the longer the bean is roasted, the more water weight is lost. Beans also increase in size, 150-190% in volume. Water weight loss and increased volume cut the density of the bean significantly, sometimes almost in half. Darker roasted beans are typically light in volume, but take up larger amount of space if measuring by scoop.
After roasting, the beans are immediately cooled then packaged, working quickly to maintain the flavor produced from the roasting process.
Common Roast Levels
Many roasters have unique titles for their specialized roast levels. This can cause some confusion when buying, but in general, roasts fall into one of four color categories — light, medium, medium-dark and dark. Using the four-color categories, you are likely to find common roasts as listed below:
Also called Light City, Cinnamon, New England, Half City
With a dry bean surface and light brown in color, this roast is more commonly used for balanced and approachable coffees. Acidity is usually high, while body and aromatics are not as pronounced. Because of shorter roast times oils do not break through to the surface of the beans.
Also called City, Breakfast, American
Medium brown in color with some evidence of oil on the surface of the bean, this is a preferred roast level in most of the United States. Acidity, body, and aroma are increased in this roast level compared to Light Roast. More oils from the center of the bean make their way to the surface of the bean.
Medium Dark Roast
Also called Full City, Light French roast
This roast produces rich, dark brown colored, shiny beans with significant signs of oil on the surface. While acidity in the bean starts to decrease at this point, body and aroma are typically at their highest level. Many single origin coffees for espresso are roasted to this level.
Also called Espresso, French, Italian, Viennese, High, New Orleans, European
This roast produces shiny black beans with an oily surface. The darker the roast, the less acidity will be found in the coffee resulting in an overly bitter taste. Aroma and body are still present.
Adapted from theperfectdailygrind.com