Coffee roasting defects

Roasting defects are the result of errors in the roasting process that negatively impact the quality of the final cup. Even the highest-quality green coffee can be ruined by poor roasting technique. Understanding these defects is essential for any roaster who wants to produce consistent, high-quality coffee.

Common roasting defects include 'scorching' and 'tipping.' Scorching occurs when the drum temperature is too high at the start of the roast, causing the edges of the beans to burn while the center remains underdeveloped. Tipping is similar, where the tips of the bean are burnt, often due to excessive heat during the later stages of the roast. Another common defect is 'baking,' which happens when the roast takes too long or the heat is applied too slowly, resulting in a flat, dull, and papery flavor profile. This is often caused by a lack of airflow or an incorrect roast development time.

These defects are not just sensory; they are often visible to the trained eye. A roaster can inspect the roasted beans for signs of uneven color, charred edges, or a lack of expansion. However, the most definitive way to identify roasting defects is through cupping. A 'baked' coffee, for example, will lack the vibrant acidity and sweetness that the coffee should possess, instead tasting muted and uninteresting. A 'burnt' or 'scorched' coffee will have harsh, bitter, or ashy notes that mask the coffee's origin character.

In practice, identifying and correcting roasting defects is a continuous process of learning and calibration. Roasters use roast profile software to track their curves and identify where things might have gone wrong. By comparing their roast logs with the results on the cupping table, they can adjust their heat, airflow, and batch size to avoid these defects in future batches. Ultimately, the goal of a professional roaster is to minimize these defects, ensuring that the coffee's true potential is expressed in every cup.