Introduction:Understanding the roast level of coffee beans is key to mastering a great cup of coffee. This article delves into the roast profiles of light, medium, and medium-dark roasts, covering the entire process from bean loading and drying to first and second crack, and uses the scientific Agtron color standard to assist in evaluation. Through actual cupping data and parameters such as the yellowing point and development time, it helps readers clearly identify how different roast levels affect flavor, and provides roast references for classic beans such as Blue Mountain No.1 — making it a practical guide for both coffee beginners and enthusiasts looking to refine their skills.
Roasting is not just about heating coffee beans, but rather the core technique that shapes their final flavor. The same green coffee bean can transform from bright acidity to rich roasted notes simply by altering the roast level. This article will break down each stage of the roasting process from bean loading to the finished product, explain the characteristics of the three main roast levels — light, medium, and medium-dark — and use scientific color values and real test data to help you grasp the roasting logic behind the flavors.
Coffee roasting can be roughly divided into stages such as bean loading, drying, yellowing, first crack, and second crack. First, before loading the beans, the roaster must be preheated, typically to a temperature between 180 and 200°C, and beans should only be added once the drum has stabilized. After the beans are dropped in, they begin to absorb heat, causing the drum temperature to briefly drop to around 100°C. This turning point is the starting point of the roast. About five minutes later, the bean surface gradually turns yellow, and the grassy aroma transitions into a scent similar to toasted bread — this yellowing point is an important indicator of the bean’s initial development.
As heat penetrates deeper, internal moisture in the beans begins to evaporate, and pressure builds up until it breaks through the cell walls, creating the first "crack" sound — marking the beginning of first crack. First crack usually lasts several minutes and can be divided into an initial phase and a more intense, dense phase. During this time, a large amount of aromatic compounds are released, greatly influencing the final flavor. After first crack ends, the beans enter a transitional period from exothermic to endothermic, followed by the second crack stage. At this point, the woody fibers begin to break, oils seep out, and the bean surface gradually takes on a shiny, oily appearance. The second crack sounds softer than the first but signifies a deeper transformation in the roast.
The timing of dropping the beans can be chosen at any point between first and second crack, determining the final roast level. Immediately after roasting, the beans must be cooled to prevent residual heat from continuing to act, which could lead to over-extraction and burnt, bitter flavors. The general dropping temperature is above 180°C, but the exact temperature may be fine-tuned based on the bean variety and target flavor profile.
How can you distinguish between different roast levels? Take natural Yirgacheffe as an example: for a light roast, the yellowing point is around 5 minutes, first crack begins at 8 minutes 30 seconds at 185.8°C, with a development time of 1 minute 30 seconds, and the drop temperature is 196.3°C; for a medium roast, first crack begins at 8 minutes 32 seconds at 186.9°C, with the development time extended to 2 minutes 30 seconds, and the drop temperature is 197°C; for a medium-dark roast, the yellowing point is slightly later at 5 minutes 20 seconds, first crack begins at 8 minutes 42 seconds at 185.4°C, the development time is further extended to 3 minutes 30 seconds, and the drop temperature reaches 198°C. These subtle differences in time and temperature result in distinctly different cup profiles.
Cupping results show that lightly roasted coffee has a wet aroma featuring berry, cream, and citrus notes, and when sipped, reveals layers of blueberry, citrus, berries, tropical fruits, and cream. Medium roasts present spicy, berry, and fermented aromas, with balanced flavors of peach, plum, lemon, cream, almond, and floral notes. Medium-dark roasts have a wet aroma leaning toward spices, smoke, and cocoa, and when sipped, showcase a rich profile of nuts, dark chocolate, cream, and herbs. It's clear that the lighter the roast, the more pronounced the acidity and fruity character; as the roast deepens, sweetness and caramelization reactions gradually dominate, ultimately leading to bold nutty and chocolatey flavors.
To define roast levels more scientifically, the industry often uses the Agtron color value system. Light roasts such as Agtron #95 (light roast) are typically dropped at the end of the dense first crack phase; Agtron #85 (cinnamon roast) is dropped around the time first crack ends. Medium roasts include Agtron #75 (medium roast) and #65 (dark medium roast), corresponding respectively to the period after first crack and the quiet phase between first and second crack. Medium-dark roasts such as Agtron #55 (city roast) are dropped at the start of second crack, while Agtron #45 (full city roast) is dropped just before the dense second crack. Further dark roasts like Agtron #35 (French roast) are dropped during the dense second crack, and Agtron #25 (Italian roast) completes the roast when oils begin to emerge.
With an understanding of these roast parameters, readers can more specifically choose coffee that suits their taste preferences. For example, light roasts are ideal for those who enjoy bright acidity and floral notes, and commonly include beans from Africa and the Americas. Medium roasts are known for their balance, such as classic beans like Blue Mountain No.1. Medium-dark roasts emphasize richness and depth, such as the Indonesian Mandheling series, delivering profound flavors of nuts, cocoa, and herbs. Mastering these basics will help you make more precise judgments when selecting and brewing coffee.
The above content is compiled by CoffeeHunters, a coffee news website.
