How to grade coffee by roast color?

Grading coffee by roast color is a vital practice for roasters who prioritize consistency and quality control. While sensory evaluation—tasting the coffee—is the ultimate test, color measurement provides an objective, repeatable metric that helps roasters dial in their profiles. By using a colorimeter, a device that measures the light reflected off ground coffee, roasters can assign a numerical value to their roast degree, ensuring that the coffee they produce today matches the coffee they produced yesterday.

This process typically relies on the Agtron scale, an industry-standard system that uses a series of standardized tiles to represent different roast levels. A lower number on the Agtron scale indicates a darker roast, while a higher number indicates a lighter roast. By measuring the color of both the whole bean and the ground coffee, roasters can gain insights into the roast bean structure and ensure that the heat application was uniform throughout the batch.

Maintaining color consistency is not just about aesthetics; it is about flavor. A roast that is too light may taste underdeveloped or grassy, while a roast that is too dark may lose its origin characteristics to the taste of carbon or smoke. By tracking the color of every batch, roasters can identify trends in their production, adjust their roast profiles, and ensure that the coffee reaching the consumer is exactly as intended. This is especially important for specialty coffee, where the goal is to highlight the unique terroir of the beans.

In practice, color grading is a key component of a professional roastery's workflow. It allows for data-driven decision-making, reducing the reliance on guesswork and subjective visual inspection. For the reader, this means that when you buy a bag of coffee from a reputable roaster, you can expect a consistent experience from the first cup to the last. It is a testament to the precision and care that goes into modern coffee roasting, turning a craft into a science.