Coffee bean roasting: the transformation from green beans to aromatic coffee

1. Origin and classification of coffee beans

Coffee beans are seeds from coffee trees and are mainly divided into two varieties: Arabica and Robusta. Arabica coffee beans have lower yields but higher quality, with aroma, higher acidity, and smooth taste, while Robusta has higher yields but relatively poor quality, bitter taste and contains more caffeine.

2. Coffee Bean Processing

Before roasting, green coffee beans need to go through a series of processing steps. The first is to remove the skin and pulp, which can improve the taste through fermentation. The peeled and pulped green beans are then dried and screened to remove impurities that do not meet the standards.

3. Green beans and roasting degree

Green beans refer to coffee seeds that have been harvested in their original state without any processing or roasting. They usually have a dark green appearance and contain moisture and caffeine. The roasting degree refers to the time and temperature control of the coffee beans during the roasting process, which determines the color, aroma and taste of the final coffee beans.

4. Baking process

Roasting is the process of heating green beans to high temperatures to cause chemical changes and transform them into edible coffee beans. The whole process can be divided into three stages: drying stage, brown stage and first crack (first bloom).

During the drying phase, water begins to evaporate from the beans and starch fermentation begins. This phase usually lasts from a few minutes to more than ten minutes.

Next is the yellow-brown stage, during which the internal temperature gradually rises and the surface begins to turn yellow-brown. At this time, the starch inside is converted into soluble substances and more gas is produced.

When the temperature reaches a certain level, the first burst will occur. The coffee beans will rapidly increase in size and make a "bursting" sound. At this point, the internal temperature of the coffee beans reaches about 200°C.

5. Roasting degree and coffee taste

The degree of roasting refers to the time and temperature control of coffee beans during the roasting process. Different roasting degrees will produce different taste characteristics.

Light Roast: This roasting method retains more of the original flavor, has a higher acidity and a light aroma. It is suitable for people who like a fresh taste and floral and fruity aroma.

Medium Roast: This roast is one of the most common and popular choices. It retains some acidity and has more dark cocoa, nutty or chocolate flavors.

Dark Roast: This method of ripening makes the surface of the coffee beans shiny and produces a bitter and strong flavor. It is suitable for people who like strong taste and bitter flavor.

6. Coking and special treatment

In some cases, the roasting process can cause the coffee beans to burn. In this case, the surface of the coffee beans will become very black and have a burnt taste. In order to avoid this, some special treatment methods are used.

For example, a "City+" roast is a darker roast that is roasted slightly longer after the first crack, while a "Full City" roast is a roast that is steeped in water to slow down the cracking.

7. Storage and Use

To preserve the freshness and taste of coffee beans, try to avoid exposure to air, sunlight or moisture after purchase. It is best to store them in a sealed container in a cool and dry place.

When you need to use it, you can choose the appropriate grinding coarseness according to your personal taste, and use the appropriate proportion of water to brew it to make a mellow and delicious coffee.

8. Conclusion

From raw beans to fragrant and delicious coffee, each step has an important impact on the final taste. Choosing the roasting degree and processing method that suits your taste will bring you a pleasant cup of coffee experience.