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From green bean to aromatic coffee bean
Roasting is a fascinating chemical and physical process where hundreds of reactions transform raw, green coffee beans into the fragrant, brown beans we love. Here, you get a clear overview of what actually happens inside the bean – and why it matters so much for the final flavor.
Roasting takes place at 180–250 °C and typically lasts 10–20 minutes. Three main reactions drive the process:
The Maillard reaction The most important flavor creator. Sugars and amino acids react to form hundreds of aroma compounds – caramel, nuts, chocolate, bread, and the classic coffee aroma. It starts already at 140–165 °C and is responsible for the brown color.
Caramelization Sugars break down at higher temperatures (>170 °C). This provides sweetness, but also bitterness and complex notes like toast and syrup.
Pyrolysis Thermal decomposition at high temperatures (from about 220 °C). Here CO₂, water, and volatile compounds are released – this causes the second crack and the smoky, dark notes in dark roast.
The water evaporates. The beans change from green to yellowish. This phase is critical for an even roast.
The first aromas develop. The beans turn light brown.
An audible “pop” like popcorn. The beans expand, and most of the flavor compounds are released. This marks the end of a light roast.
The flavor continues to develop. The longer this phase lasts, the more caramelized and darker the coffee becomes.
Finer crackling. Oils seep to the surface – the beginning of dark roasting.
RoR is the rate of temperature increase per minute in the bean. A smooth, decreasing RoR curve provides the best flavor. Too high RoR results in burnt notes, too low gives a flat taste.
Light roast – Stopped just after the first crack. High acidity, fruity and floral notes. Best preserves the bean's original character.
Medium roast – Developed further after the first crack. Balanced sweetness, caramel, and nuts with some acidity. Most versatile.
Dark roast – Into or after the second crack. Low acidity, full body, smoky and chocolatey notes.
When you roast yourself, you gain full control over the entire process. You can experiment with time, temperature, and RoR to create exactly the flavor profile you want.
At BloomVik, we have all the equipment to get started – from compact Santoker roasters to professional solutions with precise temperature control and app monitoring.
Do you have questions about roasting profiles or need help choosing the right roaster?
Write to us in the chat or email kontakt@bloomvik.dk – we’re happy to help you get started.
Happy roasting! ☕
