Agtron Roast Value or How Do We Decide What is Light, Medium, or Dark
Roasters regularly give their customers clues to the type of coffee found in their bags. Flavor notes, origin, and altitude are some of these- but the roast degree, or how lightly or darkly a coffee is roasted, is probably the most valued piece of information.
We have a lot of customers who automatically say dark is their favorite when questioned, and in Seattle that is not surprising. Many palates were trained by Starbucks. My old café El Diablo Coffee (RIP) specialized in dark roast because it worked best for Cuban coffee, so we have a soft spot for it as well (and as such will always carry the El Diablo Blend).
However, people mostly buy the medium roast, the Cloud City Blend. Medium roasts are roasted right up the point where you can taste maximum sweetness and before the bitterness of a dark roast takes over.
Because we sell so much of this coffee, it is important to roast it exactly the same week after week. Consider that the blend changes throughout the year to reflect fresh crop coffees, and it becomes more complicated. To hit that roast degree consistently, we have one important tool in our arsenal: the Agtron spectrophotometer, which analyzes the roast value.
This unassuming but pricey little device measures how light or dark a coffee is by measuring the wavelengths of what is soluble in a cup of coffee. There are other methods of measuring the roast value of coffee, but we use this one because it has a long history of usage in the coffee community. These wavelength values are assigned numbers and we can aim for a specific number to ensure consistency between roasts.
For example, the Cloud City Blend measures a 63.9 Agtron and we aim to be within one number higher or lower to ensure we create the same product each time. And of course, this only applies to the current blend as the blend changes throughout the year and the Agtron goal changes with it. Agtron’s scale ranges between 25 and 95, with the darker coffees corresponding to the lower numbers.
You can either measure whole bean or ground coffee, and we opt for ground. We have steadily ground it a bit finer to present more surface area for the analyzer. Here is a photo of a the ground coffee prepared to be analyzed.
Photo depicts Light roast of Ethiopia Lecho Torka.
Higher numbers equate to lighter roasts.