Development time (DTR)
also: DTR, development time ratio, post-crack development
The stretch of a roast from first crack to the end, often given as a percentage of total roast time; shapes sweetness and body.
Development time is the portion of a roast that runs from first crack to the moment the beans are dropped. Roasters often express it as a ratio, the development time ratio (DTR): the post-crack time divided by the total roast time, frequently landing somewhere around 15 to 25 percent, though there is no single correct figure.
Why it matters: this final stretch is where much of a coffee’s flavor is decided. Too little development and the inside of the bean stays underdeveloped even if the outside looks done, giving grassy, sour, sharp cups. Push development longer and you build sweetness, body, and roasty notes, eventually trending toward bitterness if taken too far.
It is a balancing act, not a number to chase. Development interacts with how hot and how fast the roast ran, since the Maillard and caramelization chemistry continues throughout. Two coffees can hit the same roast level color yet taste very different depending on how that time was spent, which is why roasters watch it closely alongside the cracks.