Rate of Rise Curve

The Rate of Rise (RoR) curve is perhaps the most important visual tool for a modern coffee roaster. It represents the change in bean temperature per unit of time, usually measured in degrees per minute. By monitoring this curve on roasting software, a roaster can see exactly how much energy is being applied to the beans at any given moment during the roast.

What is the RoR curve telling the roaster? It shows the momentum of the roast. A healthy RoR curve typically starts high during the drying phase, gradually declines as the beans absorb heat and undergo endothermic reactions, and continues to taper off as the roast approaches the first crack. If the RoR drops too sharply, the roast may 'stall' or 'bake,' resulting in flat, dull flavors. If it spikes, the roaster risks 'tipping' or 'scorching' the beans, which introduces harsh, burnt notes.

For the consumer, the RoR curve is the difference between a balanced, sweet roast and one that is underdeveloped or over-roasted. Roasters use this curve to ensure consistency from batch to batch. By replicating a successful RoR curve, they can ensure that the coffee you buy today tastes as good as the bag you bought last month, regardless of changes in ambient temperature or humidity in the roastery.

In practice, the RoR curve is about control. It allows the roaster to make micro-adjustments to airflow and gas pressure to guide the coffee through the Maillard reaction and caramelization phases. When you enjoy a coffee with a clean, sweet finish, it is often the result of a roaster who has successfully managed the RoR curve to develop the bean's potential without introducing the defects associated with poor heat management.