What does the "first crack" signify in coffee roasting?

The "first crack" in coffee roasting is an important auditory and visual cue that indicates the stage when the coffee beans start to expand and release moisture. As the beans are heated, they undergo a series of physical and chemical changes. The first crack occurs as the pressure inside the beans builds due to steam and gases released during the roasting process, culminating in the breaking of the outer shell.

This moment is crucial for roasters because it marks the transition from the drying phase of roasting to the development phase. It helps roastmasters determine the degree to which the beans have been roasted, influencing flavor and overall characteristics of the coffee. Recognizing the first crack allows roasters to manage the roast profile effectively, enabling them to achieve desired flavors in the final brew.

In contrast, the other options represent different aspects of coffee roasting that do not align with the specific significance of the first crack. For instance, the first crack does not signify that beans are fully roasted or that they are cooling down, nor does it directly correspond to the visual change of turning brown; those events occur either before or after the first crack.