Roasting coffee is a refined and painstaking craft, a family-guarded trade. A true professional will never simply “give away the secret”—it is like giving someone the fishing rod instead of the fish.
Below is a classic, fundamental method of coffee roasting that we would like to share:
1. Green Coffee Beans
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Unroasted Moka coffee beans have a beautiful jade-green color at normal room temperature (around 22–25 °C). Even in their raw state (known as green beans), they possess a distinct fragrance—especially Moka beans, which give off a pleasant scent reminiscent of medicinal herbs, dried flowers, and traditional herbal remedies.
2. Starting the Roast – Above 100 °C
The first stage is about transferring heat into the bean. As the beans slowly heat up, internal moisture begins to evaporate; the beans shrink slightly but show little visual change.
Key secret: avoid hardening the beans. Ensure maximum hot-air convection inside the drum so heat transfers evenly to every bean.
3. Pale Yellow Stage – Above 150 °C
The beans continue absorbing heat and releasing moisture. They begin to change slightly in volume and emit a distinctive aroma of fresh grass and dry hay—an earthy scent that evokes quiet fields and shaded gardens.
4. Deep Yellow Stage – Around 180 °C
Beans turn a deeper yellow, volume expands 20–30%, and faint ridges appear on their surfaces. The aroma shifts to notes of toasted bread, charred wood, rain-damp earth, and even the sweet smell of roasted sweet potato.
5. Light Brown Stage – Around 200 °C
The beans swell rapidly in preparation for the first crack. Sweet, honey-like notes emerge, similar to ripe fruit and malt. The beans are not yet fully developed; if ground and brewed now, the coffee tastes sharp and slightly raw.
6. Brown Stage – 210 °C
The first sharp pops begin inside the roasting drum. Heat triggers the Maillard reaction, browning the sugars and deepening aroma—malt and caramel tones grow stronger.
7. First Crack – Around 210 °C
A chorus of crisp cracks signals the start of dramatic chemical changes. Smoke increases, and a rich fragrance fills the air. From here, the roast becomes vibrant—the roaster must use every sense and passion to guide the batch.
8. After First Crack – Around 215 °C
The first crack is exothermic: beans expand suddenly (up to 150% of original size) while losing 10–17% of their weight. Then the beans immediately begin absorbing heat again. Caramelization accelerates; smoke thickens; fine wrinkles appear on the bean surface.
9. Post-First Crack – Around 220 °C
Beans release carbon dioxide, producing more smoke and a warm, baked-nut aroma. Weight continues to drop.
10. Approaching Second Crack – Around 225 °C
Beans keep expanding, especially Moka beans, sometimes reaching over 150% of their original size. Internal chemical reactions intensify.
11. Beginning of Second Crack – Around 225 °C
Natural oils migrate to the bean surface, giving a glossy sheen. The fragrance becomes even more refined and captivating.
12. Second Crack – Around 235 °C
The second series of cracks is drier and more brittle than the first—like snapping dry twigs. These pops mark the physical fracturing of cellulose structures and signal deeper roast development.
Experienced roasters use sight, sound, and smell—observing the smoke color, bean hue, and crackling sounds—to judge when to stop for the desired flavor profile.
13. After Second Crack – Around 240 °C
Beans turn a rich dark brown, volume nearly doubles, and weight drops 20–30%. The air fills with intense aromas—sometimes, when roasting cà phê chồn (civet coffee), a subtle animalic note is present.
At this moment, all key flavor-developing reactions are complete. The beans have finished their transformation and are ready for cooling.
14. Cooling and Optional Finishing
Beans are quickly released from the drum and cooled to preserve their captivating aroma. Some Vietnamese artisans skillfully mist the hot beans with fine spirits, butter, or caramel. The heat allows these flavors to bind through slight esterification, adding unique fragrance and moisture without masking the coffee’s inherent character.
15. A Living Art
Whether roasted in modern automated machines or traditional wood-fired drums, many connoisseurs believe that hand-roasted coffee carries the soul and passion of the roaster. Roasting coffee is not just a process; it is the creation of a work of art.