As the coffee goes into the roaster’s drum, many people will say that Vietmay Coffee has already started roasting coffee! But the professional roaster doesn’t see it as the beginning of the natural coffee roasting process. Let’s learn about Drying when roasting coffee with Helena.
Drying when roasting coffee
Post-processing green coffee beans have 8 to 14% (ideally between 10 and 12%). Before we start developing new flavors, we need to dry them. Because the coffee beans contain water divided evenly in the grain structure, coffee beans cannot turn brown if they hold water.
During this period, the coffee – which is currently at room temperature (28 degrees, for example) – will absorb the heat of the roasting drum and hot-air airflow from the roaster burner. The coffee beans will absorb enough heat to evaporate the water after a given length of time. At this stage of heat collection, coffee begins to lose some of its properties but acquires others. During this period, the main metabolic changes are an increase in the volume of coffee beans and internal pressure (due to water turning into steam), loss of mass and physicality, and a change in color from green to yellow, then dark yellow. This color transition marks the end of the first phase, the “drying” phase.
The drying phase usually lasts 4 to 8 minutes. At the end of the period, the temperature is usually 140 – 160⁰C (Some explosives have just ended drying, it is not wrong, different concepts). Coffee beans will change little in color or taste in the first few minutes of this period.
How long should Drying last ideally? In general, no less than 30% and no more than 50% of the time of the entire roasting period. Too quickly, the drying phase will lead to an uneven distribution of heat inside the coffee beans, with a higher risk of external burning or burning. At the same time, the too slow drying phase will lead to undeveloped roasting leading to bitterness soil taste.
The drying process takes a relatively large amount of heat and time. This is the necessary preparation period before moving on to the following stages.