Reading roast curves

Every bag you buy already survived a ten-minute drama, and its plot is drawn as a roast curve: bean temperature against time. Reading one tells you why the coffee tastes the way it does — and how to brew it.

Act one, drying: the green bean sheds free moisture and slides from grass-green to pale yellow. Little flavor is made here, but rushing it sets up unevenness later. Act two, Maillard: from yellow through cinnamon-brown, amino acids and sugars weave themselves into hundreds of aroma compounds and the melanoidins that give coffee its color and body — the same browning chemistry as bread crust and seared steak. Act three arrives with a sound: first crack, near 196 °C, when steam pressure finally fractures the bean from the inside with an audible pop, like faint popcorn.