What is the function of a knock box in coffee preparation?

A knock box is a specific piece of equipment used in coffee preparation primarily to dispose of used coffee grounds. When brewing espresso, the spent coffee puck needs to be removed from the portafilter after extraction. The knock box serves as an efficient means to do this. Baristas can simply "knock" the portafilter against a padded edge of the knock box, causing the used grounds to fall out into the container.

This process is important for maintaining a clean workspace, as it prevents grounds from accumulating on the counter, and ensures that the barista can quickly and easily prepare the next espresso shot without delay. The design of the knock box allows for easy disposal of the grounds, facilitating a more efficient workflow in a busy coffee environment.

The other options do not accurately describe the primary function of a knock box. It does not store coffee beans, measure coffee portions, or keep coffee warm, which distinguishes its role clearly in the coffee preparation process.