Proper Grinding is essential to ensure a high quality cup of brewed coffee. Insufficient grinding produces a weak and flavorless coffee, while excessive grinding causes staling (oxidation). For most home-brewers, buying a coffee grinder is one of the best investments they can make. While whole bean coffees stay fresh for weeks after roasting if properly stored, pre-ground coffee goes stale within days and provides a lackluster, sub-par drinking experience. Coffee grinders range in price from under $100 to several hundred dollars.
Coffee Grind Sizes
Coffee grind sizes vary from fine to coarse, and this is generally controlled by how long you continue to run the coffee grinder. The coffee grind size for a particular beverage depends upon several factors including the type of coffee brewer or espresso maker being used. Coffee grinds are given a number that correlates across some of the top manufacturers such as Bunn. Note that these are not rankings, they're an arbitrary numbering system.
#1 Coffee Grind - Turkish
Turkish coffee makers brew the coffee right into the water and allow it to settle before pouring - the finest grind possible here increases absorption by exposing more surface area
#4 Coffee Grind - Espresso
This grind is used in most manual and semi-automatic and super-automatic espresso machines, including commercial espresso makers.
#6 Coffee Grind - Cone Filter Drip Coffee
This is most prominently used in drip coffee makers and pour-over coffee makers that make use of a cone filter.
#7 Coffee Grind - Stove Top Espresso Maker
Stove top espresso makers from companies such as Bialetti and Grosche use this grind.
#9 Coffee Grind - Flat Bottom Drip Coffee
Equipment that uses a flat-bottom filter such as drip coffee makers work best with this grind.
#11 Coffee Grind - Percolator
Coffee percolators operate by running water continuously through coffee grinds over an extended period, requiring the that the coffee doesn't seep into brew, which requires a coarse grind
#13 Coffee Grind - French Press
Generally a course grind size is used in the French Press coffee brewing method. Coffee grinds are relatively coarse because of the time spent immersed in water while brewing, and the fact that they need to be stopped from passing through the filter on the plunger. A french press grind is also typically used to make cold brewed coffee.
Burr Coffee Grinders
Gourmet coffee lovers generally prefer burr grinders because they produce a more consistent coffee grind size. Burr grinders work by crushing the coffee beans between a moving grinding wheel and a stationary surface.
Generally, a burr grinder will be preferably for finer grinds like grinding for a moka pot / stove top espresso maker, because of a higher consistency, and avoids overheating (e.g., re-roasting) the coffee beans creating an off-taste.
A burr coffee grinder uses a burr to crush the whole coffee beans between a stationary surface and a moving grinding wheel. Wheel burr grinders use a high speed rotation while conical burr grinders use a slower rotation and are more expensive.
Blade Coffee Grinders
Blade Coffee Grinders use propeller-like metal blades to chop up (smash) the whole coffee beans. The grind size varies from fine to coarse, and this is controlled by how long you continue to run the coffee grinder. Blade Coffee Grinders usually run at very high speeds (typically 20,000 rpm to 30,000 rpm to) which may cause the coffee beans to become so hot that the beans are essentially re-roasted.
This overheating caused by the propeller-like metal blades of a blade coffee grinder can create an off-taste that taints the fine flavors and aromas of the premium coffee. Some higher end blade grinders therefore have a counter internally that limits how long it can be run for continuously before shutting down to cool off.
One of the problems with blade grinders is that they produce an uneven grind size (e.g., larger and smaller particles), which leads to inconsistency in brewing. The blades also produce coffee dust that may clog the sieve in an espresso machine or a French Press.
Coffee Brewing Systems
Grinding coffee is the process of physically breaking down coffee by crushing or cutting the roasted coffee beans into small particles to facilitate an optimal extraction of the coffee's flavor components including both the inorganic as well as the organic materials that, when the coffee is brewing, create the coffee's overall flavor and aroma characteristics.
Determining Grind Size Based On Espresso Machine Type
The grind size for a steam-driven espresso machine should be finer than for a pump-driven espresso machine because the steam-driven machine doesn't have as much pressure to push the water through the coffee grinds.
Finer Points of Choosing Coffee Grind Size
More subtle factors in determining a grind size to produce a high quality espresso include the current temperature and humidity, which might cause a variation requiring adjustments. Ultimately the barista must choose the optimal grind size for the particular brewing coffee or espresso in order to achieve the desired flavor.
Master Barista Guide For Creating Perfect Espresso Drinks
Perfect espresso brewing is described along with tips on Pulling A Perfect Espresso Shot and Steaming and Frothing Milk. You can take a shortcut on becoming a master barista by buying an espresso machine that comes with a built-in coffee grinder and performs most of the labor-intensive steps for you automatically.
Gourmet Coffee Terminology and a History Coffee!
It should be noted that you never want to try grinding green coffee beans in a grinder designed for roasted coffee. While roasted coffee is large and brittle, unroasted coffee beans are dehydrated and dense - essentially little rocks. Green coffee will likely damaged blade grinders or break burr grinders.
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