How does roasting affect caffeine content in coffee?

The relationship between roasting and caffeine content in coffee is indeed influenced by the roasting process, which alters the coffee beans' chemical structure. When coffee beans are roasted, they undergo significant physical and chemical transformations, culminating in changes to the caffeine content.

Darker roasts, which are roasted for a longer period and at higher temperatures, generally have slightly less caffeine than lighter roasts. This reduction occurs because, during the roasting process, some caffeine can be lost as the beans expand and contract due to heat. The roasting duration affects the final weight of the coffee bean; as beans lose moisture and some of their mass, darker roasts may appear to have less caffeine when measured by volume, though the actual concentration might not dramatically differ.

In contrast, lighter roasts retain more moisture and often maintain a denser structure, which can lead to a slightly higher caffeine concentration per volume. However, when measuring caffeine content in brewed coffee, factors like the grind size, brewing method, and extraction time also play significant roles.

Thus, the initial correct answer highlights the nuanced relationship between roasting levels and caffeine content, reflecting a general understanding that darker roasts typically contain slightly less caffeine than their lighter counterparts due to the extensive changes they undergo during the roasting process.