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 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 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.
Rich, dark color with some oil on the surface and with a slight bittersweet aftertaste
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!
- New Orleans
Degree or darkness of roast dramatically affects a coffee’s flavor profile, as does how the coffee has been brought to a given roast: quickly with high temperatures, slowly with low, and so on. Overly light roasts may taste bready, woody or grain-like; overly dark roasts charred and thin. But aside from these extremes, no single degree of roast is necessarily better than another. Preferences in roast vary widely, influenced by tradition, brewing style (coffee intended for drip brewing is often roasted lighter than coffee intended for espresso or French-press brewing) and drinking style (people who take their coffee with milk often prefer darker roasts to lighter.) Today, the best roasters seek to hit what to their palates is the “sweet spot” for a given green coffee, the point at which the structure of the coffee is most balanced and the aroma/flavor most complete and complex. When Coffee Review first began reviewing coffees darker roasts were fashionable, and we very often encountered coffees that tasted scorched, bitterish and thin. Today medium-to-light roasts are fashionable, much to our relief, although we now occasionally cup a sample that is starchy or woody, indicating it is not fully developed in the roast.
Degree of roast can be measured with some precision through the use of a specially modified spectrophotometer popularly called an Agtron. We use the M-Basic or “Gourmet” Agtron scale, and for each coffee reviewed we present readings both of the whole beans before grinding (the number preceding the slash) and the same beans after grinding (the number after the slash). For example, a reading of 55/68 would describe a coffee with an external, whole-bean M-Basic reading of 55, and a ground reading of 68. Agtron readings range from the lightest, around 70 whole bean and 95 ground, to 25 whole-bean and 30 ground (very dark; essentially burned, although some coffee drinkers like the style). Most coffees we review at Coffee Review come in near the middle of the scale, with the darkest whole-bean around 45 and the lightest around 60. Based on the Agtron readings, we also insert general descriptive terms for roast color – light, medium, medium-dark, dark, etc. – for each coffee reviewed based on terminology developed by the Specialty Coffee Association of America. These deliberately simple terms avoid the glamour of more popular roast terms like French, Viennese, Espresso, Italian and the like, which can be confusing because their use varies so widely. A Starbucks regular roast may be considerably darker than many espresso roasts, for example, while a Viennese roast can mean almost anything depending on who is doing the roasting and labeling.
The following chart can be used as a general guide to describe different roast levels. The number we use in assigning names for roast levels reflects an average of the two values indicated for each coffee, whole-bean and ground. Thus a coffee with a whole-bean reading of 53 and a ground reading of 70 would land at 57 (“Medium”) in the chart below and consequently would be described as “Medium” in our review.
|Light||> 70||Light brown to cinnamon color
Lightish body, sometimes muted aroma, tea-like flavor
No oil on surface of bean
|Medium – Light||61 – 70||Moderately light brown color
Bright, sweet acidity, green coffee distinctions clear
Surface of bean remains dry
|Medium||51 – 60||Medium brown color
Balanced acidity, fuller body, green coffee distinctions still apparent
Generally dry bean surface
|Medium – Dark||41 – 50||Rich brown color
Droplets of oil appear on bean surface
Fruit turns chocolaty, hints of roasty bittersweetness emerge
Muted acidity, sometimes heavier body
|Dark||35 – 40||Deep brownish/black color
Spots of oil to shiny surface
Bittersweet, scorched-wood roast notes are prominent
|Very Dark||25 – 34||Black surface covered brightly with oil
Bitter/bittersweet tones dominate
Body thins, green coffee distinctions are fully muted
|Extreme – Dark||< 25||Black, shiny surface
Burned bitter tones dominate