Roast Development

Roast Development

1 November 2016

Coffee beyond the visible spectrum

By Caleb Holstein

I often hear people in the coffee industry referring to the visible colour of a roast as a gauge or measurement of the roast’s development. And sure, you can see basic colours with the human eye i.e. light and dark, but as an industry we should strive for a more measurable and consistently accurate method in the analysis of roast development. We are lucky to be a part of the coffee industry in an era where we have access to high quality roast development analytics such as abridged spectrophotometers.

Using an abridged spectrophotometer provides roasters with the most accurate and consistent data to track roast/profile progression and development. Using this equipment gives us the ability to measure beyond the humanly visible spectrum and gives an insight into the effect roasting has on the organic material at energy wavelengths in the near infrared spectrum.

I appreciate the use of a spectrophotometer may sound excessive. But the emphasis the specialty industry is instilling on quantifying the variables of our beloved coffee should be scientifically based. And it should be based on the most current and accurate equipment available to us, rather than mere unverifiable approximations like this coffee is light, medium or dark.

The accepted global specialty coffee standard for roast development is based on a spectrophotometer scale.  This is certainly helpful in improving common agreement about how a specific coffee roast profile tastes. The difference between the external development of the coffee bean and the internal development is called the delta.  This delta further empowers coffee roasters with more sophisticated knowledge about different roast profiles and the effects they have on desired flavour profiles.  This is similar to different taste outcomes chefs have in mind for a steak that has been cooked rare, medium-rare or well done.  The outside can look the same on all three of these steaks, but it will clearly taste completely different based on how the inside is cooked.

For a roaster to rely on only the humanly visible spectrum for roasted coffee would be like a barista relying on their ability to feel the weight of coffee in their hand rather than using a set of digital scales when brewing a coffee. I believe the answer is to use the equipment available and improve our collective understanding and heighten the conversation away from visible approximations such as light and dark.