Degree or darkness of roast dramatically affects a coffee’s flavor profile, as does how the coffee has been brought to a given roast level: quickly with high temperatures, slowly with low temperatures, etc. Overly light roasts might taste bready, woody or grain-like; overly dark roasts often taste 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 pour-over or batch brewing is often roasted lighter than coffee intended for espresso or French press). Today, the best roasters seek to hit what, to their palates, is the “sweet spot” for each green coffee, the point at which the structure of the coffee is most balanced and the aromas and flavors most complete and complex. When Coffee Review first began reviewing coffees in 1997, darker roasts were more fashionable than they are today, and we often encountered coffees that tasted scorched, bitter and thin. Today, medium-to-light roasts are more the norm in specialty coffee, though we now occasionally cup a sample that is starchy or woody, indicating it is not fully developed in the roast.
A coffee’s degree of roast can be measured with some precision through the use of a specially modified spectrophotometer called an Agtron. We use the M-Basic or “Gourmet” Agtron scale, and for each coffee reviewed, we present readings of both 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 (SCA). 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. So, a coffee with a whole-bean reading of 55 and a ground reading of 66 would land at 60.5 (“medium”) in the chart below and consequently would be described as “medium” in our review.
| Roast | Agtron | Characteristics |
|---|---|---|
| Light | > 80 | Light brown to cinnamon color Lightish body, sometimes muted, sometimes delicately fresh in flavor No oil on surface of bean |
| Medium – Light | 70 – 80 | Moderately light brown color Bright, sweet acidity, green coffee distinctions clear Surface of bean remains dry |
| Medium | 60 – 70 | Medium brown color Balanced acidity, fuller body, green coffee distinctions still apparent Generally dry bean surface |
| Medium – Dark | 50 – 60 | Rich brown color Droplets of oil may appear on bean surface Fruit turns chocolaty, hints of roasty bittersweetness may emerge Muted acidity, sometimes heavier body |
| Dark | 40 – 50 | Deep brownish/black color Spots of oil to shiny surface Richly to sharply bittersweet, scorched-wood roast notes prominent Acidity muted |
| Very Dark | 25 – 40 | 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 |
