Caramelization
also: sugar browning
The browning of sugars under roasting heat that builds sweetness, color, and bittersweet depth in the cup.
Caramelization is the breakdown and browning of sugars when they are heated, the same process that turns table sugar into caramel. During roasting it contributes to the color change and to the sweetness, bittersweet, and toffee-like notes in coffee. It generally needs higher heat than the Maillard reaction, with pure sugar caramelization beginning around 160 to 170 C (320 to 338 F).
Why it matters: caramelization is one of the main sources of perceived sweetness and rounded depth in roasted coffee, working alongside Maillard browning. As the roast progresses, more sugar caramelizes, which is part of why lighter roasts can taste brighter and more acidic while medium roasts often read as sweeter and more balanced.
Pushed too far, caramelization tips toward burnt, ashy, and bitter, which is one reason very dark roasts lose sweetness and origin character. Roasters balance it against Maillard development through how they manage heat and development time, aiming for the sweet spot before the sugars char. It is a key lever in shaping any roast level.