What is the primary roasting factor that contributes to bitterness?

The primary roasting factor that contributes to bitterness is indeed related to the products of Maillard reactions. These complex chemical reactions occur between amino acids and reducing sugars when coffee beans are roasted, leading to the development of a wide range of flavors and aromas, but also to the creation of bitter compounds.

As the roasting process progresses, the Maillard reaction generates pyrazines and other nitrogen-containing compounds which can impart a bitter taste. These reactions are crucial as they not only influence flavor but also the color of the coffee. The more intense and extended the roasting process, the more pronounced these bitter compounds become, especially if the beans are roasted to a dark profile.

While caramelization and the formation of new sugars play significant roles in developing sweetness and complexity in flavor, they do not primarily contribute to bitterness in the same way that the products of the Maillard reaction do. Similarly, while the oxidation of acids can impact the flavor profile, it is not the primary factor leading to bitterness in roasted coffee. Thus, the relationship between the Maillard reaction and bitterness highlights its critical role in the overall sensory experience of coffee.