Roast Level Identification and Sample Roasting
What you must know
Roast progression has three phases: drying (moisture loss), Maillard (browning and aroma development, roughly 150–196 °C bean temperature), and development (first crack at about 196–205 °C through drop). First crack is the audible fracture of cell walls releasing steam and CO2; second crack at roughly 225–230 °C marks structural breakdown and rising oil. As roast darkens, acidity falls, body and bitterness rise, and surface oils appear.
Cupping requires a consistent light-to-medium sample roast, typically completed in about 8–12 minutes, with colour checked on ground coffee for repeatability. Consistent roast is essential: darker samples taste sweeter and heavier and will inflate scores.
Learn the defect vocabulary: scorching (dark patches from excessive charge temperature), tipping (charred bean tips), facing (flat-side burn from too much heat late in the roast), baked (flat, papery, thin, from a stalled or extended roast), underdeveloped (grassy, hay, sour), and quakers (pale, unripe beans that never brown, tasting papery or peanutty).
Traps
- Mixing baked and underdeveloped. Baked is dull and flat; underdeveloped is sharp and green.
- Confusing scorching (patches on the surface) with tipping (burned extremities).
- Judging roast level by whole-bean colour only; ground colour is the standard reference.
- Cupping a sample roasted the same day, when rest is required.
Rule of thumb
A few pale beans in an otherwise even batch are quakers, not a roast fault - sort and note them.