Which factors affect the rate of heat transfer during coffee roasting?

• A. Only the roasting machine size
• B. Bean density, batch size, and roasting machine design
• C. Air temperature alone
• D. The variety of coffee bean used

Answer: (B)

During coffee roasting, the rate of heat transfer is significantly influenced by several key factors. Bean density is important because it determines how quickly heat can penetrate the coffee beans; denser beans will generally absorb heat more slowly. Batch size also plays a critical role, as larger batches may restrict airflow and thus affect the overall heat distribution within the roaster. Lastly, the design of the roasting machine can impact heat transfer efficiency due to variations in airflow, drum material, and heating methods used. Each of these factors interact to influence how effectively heat is transferred to the coffee beans, subsequently affecting the roasting process and flavor development.

Other factors mentioned in the other options—such as the size of the roasting machine or the temperature of air alone—are less comprehensive in addressing the complexities of heat transfer during roasting. While they may have some impact, they do not encompass the multiple layers of interaction present in the roasting environment. Additionally, the variety of coffee bean does not fundamentally affect heat transfer rates directly but rather affects how the beans respond to the heat applied during roasting.