Roasting is where green, grassy-smelling coffee seeds transform into the aromatic brown beans we all recognize. It's the step that creates nearly all of the flavors and aromas we associate with coffee — and it's the heart of what we do at Olivenhain Coffee Roasters Here's a look at what actually happens inside a roaster.
The Stages of a Roast
Drying Phase (0–4 minutes)
Green coffee beans contain around 10-12% moisture. The first stage of roasting is driving off this moisture. The beans are absorbing heat, and their temperature climbs. They'll turn from green to a pale yellowish color and start to smell a bit like baking bread or toasted grain. Not much visible action happens yet, but the beans are getting ready for the big changes ahead.
Browning / Maillard Phase (4–8 minutes)
As the temperature continues to rise, the Maillard reaction kicks in — the same chemical reaction that browns bread crust, sears steak, and creates caramel from sugar. This is where the beans start developing their complex flavor compounds. The color shifts from yellow to light brown, and the aromas become more recognizably "coffee-like." Hundreds of volatile aromatic compounds are forming during this phase.
First Crack (~385–400°F)
This is the moment every roaster listens for. As the internal temperature of the beans reaches around 385-400°F, moisture inside the bean turns to steam and pressure builds up until — crack! The beans physically pop, expanding in size and releasing steam and carbon dioxide. It sounds a bit like popcorn popping. First crack marks the beginning of what's considered "light roast" territory. The beans are now drinkable coffee, though on the lighter end.
Development Phase (after First Crack)
After first crack is where the roaster's decisions really shape the coffee. The longer you develop the roast past first crack, the darker and more caramelized the flavors become. Stop quickly after first crack and you have a bright, acidic, origin-forward light roast. Keep going and you get into medium territory, where sweetness, body, and balance increase. The origin characteristics start to blend with roast-derived flavors like chocolate and caramel.
Second Crack (~435–450°F)
If you continue roasting further, the beans will eventually reach a second crack — a quieter, more rapid crackling sound. This happens as the cellular structure of the bean begins to fracture and oils start migrating to the surface (which is why dark-roasted beans look shiny and oily). Second crack territory is dark roast: French roast, Italian roast, and the like. The coffee's origin characteristics are mostly replaced by bold, smoky, bittersweet roast flavors.
Roast Levels Explained
The specialty coffee world uses some common terms for roast levels, roughly mapped to temperature and development:
City (Light): Stopped shortly after the start of first crack. Bright acidity, light body, most origin character. Good for showcasing exceptional single-origin beans.
City+ (Medium-Light): Developed a bit further past first crack. Still bright but with more sweetness and body developing.
Full City (Medium-Dark): Approaching but not reaching second crack. Balanced sweetness and acidity with good body. A versatile roast level — this is roughly where William's Classic lives.
Full City+ (Dark): Just touching second crack. Bittersweet flavors dominate, fruit fades, chocolate and caramel notes are prominent. This is Graham's Bold territory — excellent for espresso.
French / Italian (Very Dark): Well into or past second crack. Smoky, bold, with oils on the surface. The bean's origin is almost entirely masked by roast character.
Why Small-Batch Matters
Roasting in small batches — which is what we do at Olivenhain Coffee Roasters — has real advantages. Small batches heat more evenly, which means less variation between the beans in a single roast. The roaster (or in our case, William or Graham) can monitor the entire batch closely, making adjustments to heat in real time. And because each batch is small, we can give it individual attention rather than relying on automated programs.
The downside? It's slower. We can only roast a small amount at a time, which means each bag represents a meaningful chunk of our production. But that's kind of the point — every bag of Olivenhain Coffee has been personally watched over.
The Learning Curve
Roasting coffee well is harder than it looks. The difference between a good roast and a bad one can be a matter of 15-30 seconds. Roast too fast and the outside of the bean chars while the inside stays underdeveloped ("tipping" or "scorching"). Roast too slow and you end up with flat, baked flavors. Getting the rate of rise, the timing of first crack, and the development time just right takes practice — lots of it.
William and Graham are learning this firsthand. Some batches have been great. Some have been... educational. That's how you learn.