How do we determine the condition of our coffee beans when we roast them? Sound is an excellent indicator when roasting. Roasters listen for two temperature thresholds known as “cracks.” We call them “first crack” and “Second crack,” which are important markers that we use to determine the degree of roasting.
Temperature
The most critical factors in roasting are roasting temperature and roasting time. There is a danger that the beans can burn if your roaster has an excessively high temperature. You won’t obtain the desired outcome if it is too low either. Therefore, it is important to know the temperatures of the first and second cracks to achieve good roasting results.
Typically, the first crack occurs when the roasting temperature reaches about 196°C to 205°C ( 385°F to 401°F ). The second crack usually occurs when the roasting temperature reaches about 220°C to 225°C ( 428°F to 437°F ). The exact temperature range may vary slightly depending on the type of roasting equipment used, so it is essential to know the characteristics of your own roaster.
Different types of coffee roasters (e.g., electric vs. gas roasters) differ in their temperature control and heating methods. These differences have a direct impact on roasting time and final quality. Commercial coffee roasters are often equipped with more advanced control systems that precisely regulate temperature, time, and airflow for more consistent and repeatable roasting results. In a commercial environment, this precision is critical to improving coffee quality and meeting customer demands.
The Meaning Of First Crack
Approximately 196 °C (385 °F) will cause the coffee to start cracking. The coffee bean makes its cracking sound, which we call the “first crack.”
The first crack occurs when a significant portion of the moisture in the coffee has evaporated, causing the beans to enlarge. The chemical composition inside the coffee bean also begins to change. This temperature phase promotes the acceleration of biochemical reactions, including the Maillard and Caramelization Reactions.
The Maillard Reaction involves amino acids in the bean reacting with reducing sugars to produce complex flavor compounds, while caramelization consists of the conversion of sugars at high temperatures into compounds with a sweet taste and complex aroma. At this stage, the beans become brighter and more acidic in flavor, making them suitable for light to medium roasted coffees. If you wish to retain more acidity and sharp flavors, you may choose to stop roasting in a timely manner shortly after the first crack.
When reproducing a specific profile, the first crack is an excellent indicator. Some coffee roasters have a built-in sound sensor that can alert you when the first crack occurs.
Second crack
A second one, logically referred to as the “second crack,” will come after the first crack and a little more roasting time. At this point, the temperature inside the roaster is around 220°C to 225°C， and coffee beans begin to enter the deep roasting stage.
The cracking sound made by the beans at this stage is usually softer and more frequent than the first sound. This indicates further cracking of the beans, where the surface oils begin to melt. At this point, the beans will become darker in color, and the flavor will shift to a more intense, bittersweet character, such as chocolate or caramel notes. In addition, the acidity is reduced, and a deeper roast is achieved. This is due to the breakdown and conversion of acids at high temperatures, leading to a decrease in acidity, an increase in caramelization, and a further intensification of the Maillard reaction.
Compared to the first crack, the changes brought about by the second crack result in a coffee with significantly lower acidity and a Zdeeper roast, suitable for coffee lovers who prefer a full-bodied taste and complex flavors.
During the coffee roasting process, mastering changes in sound and temperature is critical to determining the condition of the beans. By watching and listening, roasters are able to accurately adjust the roasting process to achieve the desired flavor profile. Whether you’re looking for fresh acidity or craving a full-bodied flavor, correctly timing the first and second cracks is the key to a successful roast.
