Working Temperature

Coffee Roasting Temperature and Coffee Profiles

The working temperature is the temperature set on the roasting machine. The source recommends a range of 140°C to 165°C, or roughly 300°F, in connection with Maillard reactions and the avoidance of excessive bitterness.

The machine temperature and the temperature of the coffee beans are not the same. According to the article, the beans’ roasting temperature can be measured as they leave the machine.

Temperature Gradients and Heat Transfer

During roasting, a changing temperature gradient allows heat to move from the exterior of each bean toward its center. Even if the roaster remains at approximately 160°C, the beans continue warming according to the rate of heat transfer and the time spent in the machine.

The fastest temperature change occurs after the beans are considered dry. During the drying phase, water contained in the beans becomes vapor, contributing to heat transfer through both contact and convection.

The Role of Bean Density

Heat transfer into the interior of a coffee bean depends partly on its density. The article describes density as resistance to physical and chemical change during roasting, including transformations involving chlorogenic and caffeic acids.

A high-density bean is identified in the source as having a density greater than 0.68 g/mL.