Coffee Bean Roasting: The Secret of Expansion Variation

The roasting process of coffee beans is to treat the raw beans with high temperature to change their internal structure, thus producing a specific flavor and aroma. During the roasting process, the coffee beans will expand, which is called "expansion change". This change not only affects the taste and aroma of coffee, but is also an important reference indicator for roasters.

First, when coffee beans are roasted, the moisture gradually evaporates due to the high temperature, and the moisture content becomes lower and lower over time. When the moisture is completely evaporated, gas begins to be produced inside the coffee beans. These gases are mainly composed of carbon dioxide, which is formed and accumulated inside the beans at high temperatures.

Secondly, under the action of high temperature, as time goes by and the amount of carbon dioxide generated increases, the pressure will gradually increase. When the pressure exceeds the limit that the surface of the beans can withstand, the shell will crack, releasing the cavities that have accumulated a lot of carbon dioxide inside, thus forming a swelling degree. This change in swelling degree will not only affect the appearance of the coffee beans, but also affect the internal structure of the coffee beans, further changing the flavor and aroma of the coffee.

Finally, during the roasting process, the roaster can adjust the expansion of the coffee beans by controlling the temperature and time. Higher temperatures and longer times will result in a greater degree of expansion, while lower temperatures and shorter times will produce a relatively small degree of dehydration and slight shelling of the beans. Therefore, it is very important to precisely control these parameters in order to obtain a coffee with the ideal taste and rich aroma.