What is the primary purpose of the tamper in espresso preparation?

The primary purpose of the tamper in espresso preparation is to compress ground coffee in the portafilter. This action is crucial because it creates a uniform and dense bed of coffee grounds, which allows for even extraction of flavors during the brewing process. When the coffee is tamped correctly, the water flows through the grounds under pressure evenly, producing a consistent and high-quality espresso shot.

Tamping also affects the resistance the water encounters as it passes through the coffee. If the coffee is not tamped with the right force and uniformity, it can lead to channeling, where water finds an easier path through the grounds rather than flowing evenly, ultimately resulting in a poorly extracted shot.

In contrast, while measuring the coffee dose and brewing the coffee are important parts of espresso preparation, they are distinct actions that do not involve the physical compression of the coffee itself. Frothing milk is a process used for creating textures and temperatures in milk but is unrelated to the function of a tamper. Thus, the tamper's role is specifically tied to achieving the proper density of coffee in the portafilter for optimal extraction.