Sweet Marias Coffee Roasting Basics – Color Changes
As the bean absorbs heat, the color shifts to yellow and then to varying shades of brown. During the later stages of roasting, oils appear on the surface of the bean, making it shiny. The roast will continue to darken until it is removed from the heat source. At lighter roasts, the bean will exhibit more of its “origin flavor” – the flavors created in the bean by the soil and weather conditions in the location where it was grown.
Coffee beans from famous regions like Java, Kenya, Hawaiian Kona, and Jamaican Blue Mountain are usually roasted lightly so their signature characteristics dominate the flavor. As the beans darken to a deep brown, the origin flavors of the bean are eclipsed by the flavors created by the roasting process itself. At darker roasts, the “roast flavor” is so dominant that it can be difficult to distinguish the origin of the beans used in the roast.
Below, roast levels and their respective flavors are described. These are qualitative descriptions, and thus subjective. As a rule of thumb, the “shinier” the bean is, the more dominant the roasting flavors are.
|Light||Cinnamon roast, half city, New England||After several minutes the beans “pop” or “crack” and visibly expand in size. This stage is called first crack. American mass-market roasters typically stop here.||Dry||Lighter-bodied, higher acidity, no obvious roast flavor|
|Medium||Full city, American, regular, breakfast, brown||After a few short minutes the beans reach this roast, which U.S. specialty sellers tend to prefer.||Dry||Sweeter than light roast; more body exhibiting more balance in acid, aroma, and complexity. Smoother than the traditional American “medium” roast, but may display fewer of the distinctive taste characteristics of the original coffee.|
|Full Roast||High, Viennese, Italian Espresso, Continental||After a few more minutes the beans begin popping again, and oils rise to the surface. This is called second crack.||Slightly shiny||Somewhat spicy; complexity is traded for heavier body/mouth-feel. Aromas and flavors of roast become clearly evident.|
|Double Roast||French||After a few more minutes or so the beans begin to smoke. The bean sugars begin to carbonize.||Very oily||Smokey-sweet; light bodied, but quite intense. None of the inherent flavors of the bean are recognisable.|
Roasting is a heat process that turns coffee into the fragrant, dark brown beans with which we are most familiar. Before being roasted, the beans were stored green, a state in which they can be kept without loss of quality or taste. Once roasted, however, they should be used as quickly as possible before the fresh roast flavor begins to diminish.
Roasting is a technical skill which approaches an art form. It takes years of training to become an expert roaster with the ability to ‘read’ the beans and make decisions with split second timing. The difference between perfectly roasted coffee and a ruined batch can be a matter of seconds.
Roasting brings out the aroma and flavor that is locked inside the green coffee beans. A green bean has none of the characteristics of a roasted bean. It is soft and spongy to the bite and smells green, almost ‘grassy.’ Roasting causes numerous chemical changes to take place as the beans are rapidly brought to very high temperatures. When they reach the peak of perfection, they are quickly cooled to stop the process. Roasted beans smell like coffee, and weigh less because the moisture has been roasted out. They are crunchy to the bite, ready to be ground and brewed.
Most roasters have specialized names for their favored roasts and there is very little industry standardization. This can cause a great deal of confusion for the buyer. But in general, roasts fall into one of four color categories — light, medium, medium-dark or dark. The perfect roast is a subjective choice that is sometimes determined by national preference or geographic location
Within the four color categories, you are likely to find common roasts as listed below. But it is a good idea to ask before you buy. There can be a world of difference between roasts!
Light Roasts — light brown in color. This roast is generally preferred for milder coffee varieties. There will be no oil on the surface of these beans, because they are not roasted long enough for the oils to break through to the surface
- Light City
- Half City
- New England
Medium Roasts — medium brown in color with a stronger flavor, and a non-oily surface. This roast is often referred to as the American roast because it is generally preferred in the United States.
Medium – Dark Roasts — rich, dark color with some oil on the surface and with a slight bittersweet aftertaste
Dark Roasts — shiny black beans with a oily surface and a pronounced bitterness. The darker the roast, the less acidity will be found in the coffee beverage. Dark roast coffees run from slightly dark to charred and the names are often used interchangeably which can be very confusing. Be sure to check your beans before you buy them!
This movie clip taken by COFFEE ANALYSIS CENTER in korea is being attempted worldwidely for the first time to show coffee bean’s physical changes during roastings. By laboratory’s micro-transparent roaster developed by COFFEE ANALYSIS CENTER, it became possible to demonstrate all process of coffee roastings which had been veiled before.