Roasting Special | Coffee Roasting Basics for Beginners | Best Coffee Official Site Updated Oct 12, 2026

Roasting Special | Coffee Roasting Basics for Beginners

Source:Best Coffee > News Author:Best Coffee Published:2019-08-10 18:45:06

[What Is Coffee Roasting]

In fact, so-called coffee roasting refers to the process of heating green coffee beans to trigger a series of physical and chemical reactions inside and outside the beans. During this process, various flavors such as acidity, bitterness, and sweetness are generated, along with body and color tone, ultimately transforming the green beans into dark brown roasted beans.

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[Charge Temperature]

Before loading the beans, the boiler temperature is kept at a stable value. Generally, the charge temperature is between 180℃-200° (this drop temperature varies depending on the roaster model, the amount of beans loaded, the variety of green beans, and other conditions). It mainly affects the degree of caramelization and pyrolysis reactions of sugars in the coffee— ( primarily sucrose. ) These caramelization and pyrolysis reactions require heat absorption to occur, so they need a continuous supply of heat to proceed. Therefore, in coffee roasting, the extent of these two reactions is directly proportional to the drop temperature—the higher the drop temperature, the deeper the reaction. [Turning Point]

Once the beans are loaded into the boiler, they immediately absorb heat, causing the boiler temperature to drop sharply. Then, at a certain point, the temperature begins to rise again, and this equilibrium point is the turning point. The dehydration process of green beans also occurs at the turning point, and the duration of this turning point is related to the drop temperature. 】

[Yellowing Point] The green beans enter the heat absorption phase. To transfer heat to the interior of the beans, the conductivity of water is utilized. If the beans have low moisture content, the time to reach the yellowing point will be shorter. Conversely, if the beans have high moisture content, it will take longer to reach the yellowing point.

Water evaporates and turns into steam, increasing the internal vapor pressure and temperature of the beans. At this point, the bean structure begins to expand, breaking down chlorophyll and entering the yellowing point. The yellowing point is also the moment when the grassy flavor of green beans transitions into sweetness.

[First Crack] "First crack" refers to the distinct and intense popping sound emitted by coffee beans inside the roaster during roasting—

somewhat similar to the sound of popcorn popping or wood burning.

When the coffee beans absorb enough heat that the pressure from evaporated internal moisture exceeds the structural strength of the beans, the cell walls can no longer withstand the expansion pressure from the bean core, causing them to burst. This produces the first crack sound, releasing thermal and acoustic energy. This is how the first crack occurs. It releases various flavor compounds and initiates browning. The duration of first crack development determines the evolution of coffee flavors, making it a key point in defining coffee taste. “[Cooling After Roasting] ” After roasting, coffee must be cooled immediately upon exiting the roaster to rapidly halt high-temperature pyrolysis, locking in the flavors. Otherwise, if the high temperature inside the beans continues to act, it will burn off aromatic compounds and impart smoky or burnt notes to the coffee.

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Roasting Special | Coffee Roasting Basics for Beginners

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