The green bean needs to be roasted to make the coffee brown and flavourful.
Decaffeinated coffee is produced out of green coffee beans before they are roasted.
ROASTING:
Roasting is a process of converting green coffee beans to brown beans in order to brew aromatic and flavourful coffee. It gives the green coffee beans its unique flavour and aroma.
Before being roasted, the green beans have the look of jade and smell of freshly- cut grass. To develop and extract the depth of flavours and a distinct aroma, there is a range of different coffee-roasting techniques, styles, and approaches applied.
First, when the beans are heated, they change from green to a slightly yellow colour. The beans would now emit a grassy aroma. Soon the water inside the beans starts to evaporate as steam.
Next, the real roasting begins. Depending on the temperature and airflow, the beans will produce an audible crack after 6 to 8 minutes. The cracking is similar to the sound of popcorn popping. This is called a ‘Light Roast’ where the coffee is mild in flavour with bright acidity.
Then, as the coffee bean’s sugar further caramelises, the beans swell in size for a roast that is both popular and aromatic. The beans are medium-brown in colour with a balanced flavour and acidity.
After this, the bean’s flavours further intensify. Medium-dark roasts are rich and dark in colour.
Finally, the beans will reach the verge of a second cracking. Any roast beyond the second crack gives the dark-brown to almost black in colour.