What is development time in coffee roasting?

Development time is the window from first crack to the moment you drop the beans - the final phase of the roast where the sugar browning reactions that define a coffee's roasted character are most active. It's where many of the most consequential roasting decisions play out.

Too short and the coffee tastes underdeveloped - grassy, sharp, thin, lacking sweetness. Too long and origin character starts to disappear, replaced by generic roasty notes and increasing bitterness. Finding the right development time for a given coffee is one of the core challenges of roast profile work, and it varies between coffees, machines, and target styles.

Development time is often expressed as Development Time Ratio (DTR) - the percentage of total roast time spent in the development phase. A DTR of around 20–25% is a common working range for specialty profiles, though this varies considerably. What matters more than the number is what the coffee tastes like. DTR is a useful guide and a consistent reference point; the cup is still the final answer.