Defining the colour profile of coffee – with the help of spectral colorimeters
Before roasting, coffee beans are green, beige and yellow. It is roasting that gives them their brown colour, which is standardized in a roast coffee set by the SCAA (Specialty Coffee Association of America) in eight shades from light to dark.
The colour of coffee can reflect its flavor profile. Different colours result from different roasting times. During the roasting process, differences in the minute range can have excessive effects on the aroma, acidity, body and aftertaste of the coffee. Therefore, determining the exact colour of a coffee bean after roasting can provide a producer with a lot of information about how the coffee will taste.
Lighting conditions, the gender and age of the observer as well as the sample preparation influence the colour perception.
For an objective, reproducible and communicable evaluation of roasting degrees, producers and coffee roasters need clear and reliable numerical values. Does the colour of ground coffee tend more towards blue or gray or rather brown, or is the coffee bean still bluish or already grayish during the roasting process? Judging this is an almost impossible task for the human eye. Hue, intensity and brightness make the identification of colour complex and extremely difficult.
The SCAA scale is used to classify the colour of coffee
For this reason, coffee roasters rely on the SCAA scale to evaluate the colour of their beans during the production process. By comparing the colour of a bean to a printed sample, it can be determined with a reasonable margin of error whether each batch has been properly roasted. However, this method has disadvantages. First of all, exact colour matching is difficult with textured materials. The differences in the surface texture of coffee beans and vinyl prints affect human colour perception. People are also subjective by nature when it comes to evaluating colour. Colour perception differs between different observers or even for the same observer at different times of day. Sample preparation and measurement can cost producers valuable time if not done properly. Storing data from a test takes even more time, as an initial recording must be made, the data from which must then be entered into one or more data storage systems.
Spectrophotometers determine colour and degree of roast precisely and reliably
ColorFlex EZ for all coffee samples
To counteract errors in subjective colour perception, numerous coffee roasters have opted to use the HunterLab ColorFlex EZ Coffee spectrophotometer. These devices measure colour with extreme precision and can be supplied programmed to display their results according to the SCAA scale. HunterLab even developed the HCCI (Hunter Color Coffee Index), which incorporates input from coffee roasters worldwide to improve the SCAA scale.
Aeros spectrophotometer for coffee
Aeros for large batches
Whether coffee powder or whole beans, the integrated software of the Aeros® allows you to determine the exact colour.
With its large measuring surface, the Aeros® creates a reference value with which comparative measurements can be made, even with irregular samples. The easy-to-change sample plate is also an advantage in terms of handling. The Aeros® measures the still raw, green coffee beans, whole roasted beans and ground coffee.
