Espresso Grinding and Dosing
From Coffee Research.org
To extract espresso properly it is essential to use an espresso burr grinder and to grind per order. The two major types of burrs used are flat and conical. Conical burr coffee grinders are desirable because they increase the surface area of each particle and the amount of flavor that can be extracted from the coffee. Since a conical burr grinder has longer cutting edges, the burrs can rotate at lower speeds, which reduces the heat created. Flat burrs should be replaced after 600 pounds of coffee have been ground and conical burrs should be replaced after 2000 pounds of coffee have been ground.
Coffee Beans: Grinding Guide
Coffee is freshest immediately after it is ground. After grinding coffee beans, the volatile oils that were previously protected inside the bean are exposed to the air which oxidizes and stales the coffee. This effect occurs immediately after coffee grinding so it is important to tamp and extract the espresso as quickly as possible. The coffee grinder should be activated for 15-20 seconds every time a shot is desired so that only freshly ground coffee is used. Instead of two pulls on the doser, the barista should pull several times until the entire basket is filled with ground coffee. See the section on espresso tamping for additional instructions.
Espresso coffee should be ground to a size in which the extraction process takes 23-28 seconds. It is important to only adjust the grind and not the pressure one tamps with to control the flow rate. In addition to particle size, the humidity plays a dramatic role on extraction time. Since coffee is hydroscopic, it absorbs moisture from the air causing a tighter pack and longer extraction time. Thus, the grind setting must be changed slightly throughout the day as the barista perceives changes in extraction time.
Related Articles