Coffee roasting is an important process in determining flavor, and even the same beans can taste different depending on how they're roasted.
When roasting begins in a roaster, the beans first enter the drying stage at 100-160°, which removes the green smell of the raw beans.
The temperature then rises to around 150°, causing sugars and amino acids to combine and release an aroma. This change in state is called the Maillard reaction, and a fragrant aroma is released. The Maillard reaction brings out sweetness and aroma.
At around 160°, only the sugars begin to react, bringing out the coffee's bitter-sweet flavor. This state is called caramelization.
Then, at 200°, the beans begin to make a popping sound like popcorn.
This state is called the first crack, and the beans develop a sour and fruity flavor.
As the roasting continues, a fine popping sound will begin to emerge. This stage is called the second crack, and the surface oils are released, bringing out a rich, bitter flavor.
In other words, if you stop roasting a little after the first crack, the taste will be sour and fruity, but the further you roast from the second crack onwards, the stronger the bitterness and richness will become.
In this way, you can change the taste by roasting, taking advantage of the chemical reactions that occur during roasting.
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