The degree of roasting, a simple description of this concept, is the degree to which green coffee beans are roasted to mature beans. Generally, it is more intuitive to distinguish by the color of coffee beans. Light-colored coffee beans are roasted lightly, and dark-colored coffee beans are roasted darkly. Compared with observing with the naked eye, it is more accurate to measure through instruments and provide data feedback. Currently, on the market, the color value (Agtron) is mostly used to indicate the degree of roasting. According to the principle that white objects reflect light and black objects absorb light, the value of light reflected by cooked beans is read through the instrument, which is the color value. The lighter the roasted beans, the lighter the color (closer to the color of green beans), reflect more light, and the higher the reading value; the darker the roasted beans, the darker the color, absorb more light, and the reading value will be higher. The lower the value. The color value is, theoretically, from 100 to 0, which corresponds to light-to-dark roasting.
When many people first come into contact with coffee, they learn about the eight stages of roasting, some of which are named after different regions that have different preferences for coffee roasting, but there is no uniform standard for the overall corresponding color value range. The American Coffee Association (SCA) divides the color from light to dark into eight standard color blocks to represent different degrees of roasting.
The degree of roasting is used as a reference factor for classifying and identifying cooked coffee beans, and not only the color value can be measured and expressed. Through comparison with the color spectrum, cupping and tasting, and even gravity measurement, etc., there are also some ways to identify the degree of roasting, of course, the standards are different. For people in the industry such as roasters and coffee bean traders, in addition to keeping records, they also hope to communicate as accurately and conveniently as possible. Consumers and enthusiasts can have a general grasp of shallow, medium, and deep roasting.
Here is the process of coffee beans roasting and changing their color of them: https://youtu.be/Nu_TVVCCHeQ, from our coffee roaster machine.