What does retention refer to in the grinding of coffee?

Retention in the context of coffee grinding refers specifically to the amount of ground coffee that remains in the grinder between doses. This is an important consideration for baristas and coffee enthusiasts alike, as it directly affects the freshness and flavor profile of the coffee being brewed. If coffee grounds are retained in the grinder, they can become stale over time, leading to undesirable flavors in subsequent brews. Managing retention is crucial for achieving consistent taste and quality in coffee preparation, as it ensures that each dose is as fresh as possible.

In contrast, the other options touch on different aspects of coffee brewing and grinding but do not capture the essence of retention. For example, over-extraction relates to the brewing process and extraction time, while grind size consistency pertains to the uniformity of the particles produced by the grinder. The presence of old grounds highlights the issue of coffee staleness but does not focus specifically on the measurement of what remains in the grinder between uses, which is what retention signifies.