What effect does roasting have on coffee beans?

Roasting coffee beans plays a pivotal role in developing their flavor and aroma, primarily through the caramelization of sugars present in the beans. During the roasting process, the temperature increases, causing the sugars to undergo a transformation that enhances the overall sensory experience of the coffee. This Maillard reaction and caramelization impart various flavors ranging from fruity and nutty to chocolaty and spicy, depending on the roast level and the beans used. The complex interplay of heat plus the natural compounds in the beans results in the rich, aromatic characteristics that coffee drinkers enjoy.

The other options do not accurately reflect the primary effects of roasting. While some roasting can introduce a degree of bitterness, it does so in the context of enhancing flavor rather than merely increasing bitterness. Freshness is a factor before roasting; once roasted, beans begin to lose freshness over time, and roasting can actually increase acidity in some cases rather than minimizing it. Lastly, roasting does not eliminate caffeine content; in fact, most roasting methods preserve most of the original caffeine, although slight variations may occur depending on the duration and intensity of the roasting process.