Coffee common sense Coffee roasting process after picking

Generally speaking, coffee roasting is a "time-temperature" interdependent process, in which physical changes and chemical reactions occur in raw coffee.

Roasting is the last and most important step in the processing of coffee beans after they have been picked. Green coffee beans cannot be used directly to make drinking coffee. All coffee beans must be roasted before grinding and brewing.

Unroasted coffee is often referred to as "green coffee" and has a shelf life of up to a year compared to roasted coffee. Green coffee beans are small, dense and very hard, and people who are not in the coffee industry may not recognize them. Green coffee has a grassy taste, almost unlike the coffee beans we normally imagine, in appearance and flavor. It is the roasting process that produces coffee's unique flavor and wonderful aroma.

Generally speaking, coffee roasting is a "time-temperature" interdependent process, in which physical changes and chemical reactions occur in raw coffee. During the initial stages of roasting, green beans gradually turn yellow and water is gradually expelled. When the temperature rises to a certain threshold, the first burst occurs and the coffee beans become larger. In the second stage of roasting, as the temperature of the beans increases, a series of complex chemical transformations begin to occur, and the coffee beans continue to increase in size and color. As the temperature continues to rise, aromatic oils form on the surface of the beans, resulting in a second burst. Many of the ingredients extracted from brewed coffee do not exist in green coffee at all, but are produced during the roasting process.

Finally, deciding when to end roasting: the beans move from the roasting bin to a cooling bin where they cool and stop reacting chemically.

The following pictures show how the color of the coffee bean table changes during roasting: