Degassing

During roasting, green coffee undergoes a transformation: it changes colour, loses weight, becomes more brittle, and at the same time increases in volume.

This increase in volume is mainly due to the formation of gases, such as water vapour and CO₂, inside the bean, which makes its outer surface more porous.

Most of these gases are released in the first few days after roasting, but in some cases, it can take several weeks for complete degassing.

This phase is essential for an espresso to fully express its qualities in the cup, for at least two reasons:

1. The presence of carbon dioxide in the coffee limits the flow of water inside the extraction chamber of the espresso machine, resulting in excessively long extraction times. This can ruin the crema of the coffee, turning it into foam.

2. The oils contained within the bean are released through its porous surface, creating the ideal conditions for the espresso to reveal its best aromas and maintain a rich, persistent crema.