Coffee roasting is not just cooking; it is chemistry happening at 200°C. It is the volatile dance of transforming a hard, green, tasteless seed into a brittle, brown, aromatic bean. At Decimal, we believe understanding this process is key to appreciating your cup.
Phase 1: The Drying (Ambient to 160°C)
Fresh green coffee contains 10-12% moisture. The first few minutes are all about energy absorption (endothermic). You'll recall the smell of wet grass changing to hay. We are ensuring the bean dries evenly from the inside out. Rush this, and you get "tipping" (burnt edges) while the center remains raw.
Phase 2: The Maillard Reaction (160°C to 195°C)
This is where the magic happens. Reducing sugars interact with amino acids to create hundreds of new flavor compounds and the distinct brown color. It smells like baking bread. We carefully control the "Rate of Rise" (RoR) here to develop body and sweetness without baking the coffee flat.
Phase 3: First Crack (Approx. 196°C)
Usually around 9-10 minutes in, you hear an audible "pop", sounding like popcorn. This is the First Crack. Steam pressure inside the bean breaks the cellular structure. The bean expands effectively doubling in size.
Light Roasts (City Roast) are dropped right after this point (approx 205°C). They retain high enzymatic acidity, floral notes, and the distinct character of the origin.
Phase 4: Development & The Second Crack (205°C to 225°C+)
Between the first and second crack is the "Development Time". This determines the balance.
As we approach 224°C, the Second Crack begins. It sounds like milk poured on Rice Krispies—a rapid snapping. This is the cellulose fracturing. Oils migrate to the surface.
We rarely venture deep into Second Crack unless crafting a specific Vienna or French Roast profile, where the flavor becomes dominated by the roast process itself—smoky, bittersweet, and heavy-bodied, masking the origin nuances.