Coffee beans are best fresh. They must be roasted in order to be used, a process that typically takes place before the beans are sold. Roasting at home is less common, yet is quite feasible. This roasting starts a degradation process, whereby the oils and flavor compounds break down and generally become bitter and less flavorful. Surface area is a large part of the degradation, so ground coffee degrades considerably faster than whole-bean coffee. The degradation process is accelerated by oxidation, ergo roasted coffee should be stored in airtight containers to minimize potential for oxidation to occur.
The flavors in coffee are extracted by water, forming a solution that is the coffee beverage; and there are a number of ways by which to extract these flavors. In all extraction methods, Coffee beans and water are combined, with water acting as a solvent to the volatile, aromatic compounds in the roasted coffee. The coffee must be ground specifically for each of these methods -- just as the increased surface area contributes to faster degradation, it also allows the rapid extraction of flavor by water. Grind particle sizes specific to each brewing method optimize the final results, creating more ideally extracted coffee beverages.
There are two basic methods by which this is done, either by allowing the grounds to sit in hot water and steep like tea, or by forcing hot water through the grounds. Generally some combination of these two processes is done. Another process is cold brewing, which replaces the heat component that makes the volatile components of coffee soluble in typical brewing with time. This generally entails steeping ground coffee at room temperature for 8-12 hours (easily done overnight) and then removing the grounds from the prepared beverage by pouring through a strainer.
On the one extreme is the French press (Figures 1 and 2). The grounds are placed into the bottom of a vessel and hot water is poured onto them. The mixture sits for a few minutes (A), then a mesh strainer is pushed down onto the mass (B) and the coffee (C) is poured off to drink. French presses are also suitable for use in cold brewing, by using the same process with unheated water and steeping the proper amount of time.
The other extreme is espresso. A fine grind of strong coffee is packed into a small metal container with a hole in the bottom. Pressurized water is forced through the grounds, where it extracts a "strong flavor," then falls into the pot below. A higher percentage of coffee solids are dissolved and extracted under pressure, creating an end product with less water by volume. Although some sources say that espresso is made with pressurized steam, no modern espresso machine actually works this way. The pressure is usually driven by some type of electric pump, but older-style hand-operated pistons are also available. Steam pressure systems predate the modern espresso machine.
In America, the most common brewing method is the drip method, which is halfway between these two. The grounds are placed in a basket with a non-reactive liner of paper or sometimes gold, with a small hole in the bottom. Hot water is poured over the grounds, where it soaks the grounds and steeps for a short time while being slowly forced by gravity through the hole into the container below where it is kept warm (or at least insulated) while the brewing process finishes.
In Italy, the most common method of brewing coffee is in a moka-style percolator (Figure 3), which emulates the function of the aforementioned steam pressure brewing systems. Water is placed in the lower section (A) and the raw coffee grounds in the mid-section (B) with the spout reaching below the water level. After the top section, initially empty, is affixed, the pot is placed on a heat source. As the water reaches boiling point it turns to steam and eventually creates sufficient pressure to force all the water from the lower section up the tube at once, through the grounds — which are held in place by a metal filter above and below — and through a second tube until it hits the lid of the pot and is collected in the upper section (C), producing a strong, concentrated coffee. Gaskets and safety valves to ensure a tightly closed unit allow for pressure to safely build up in the lower section and provide a necessary security release if this pressure gets too high.
There are many factors which contribute to the final result of any brewing process. First is the roast and quality of the coffee beans. Freshly ground, newly roasted beans will always give a better cup of coffee than pre-ground, older beans. Clean fresh water is necessary, and the temperature of the water will have some bearing on the result. Cooler water will not extract flavors as efficiently as hot water, but boiling water can be a little too good with a very dark roast. Lastly, the coarseness of the grind and the ratio of grounds to water are also important, and vary according to the brewing method used.
A good rule of thumb for beginning brewers is to use the simple drip method. Use 2 tablespoons of finely ground coffee for every 6-7 oz of fresh water. Bring the water just to a boil, then pour slowly over the grounds, stirring gently. Stirring will result in the grounds retaining some extra water, but do not try to squeeze the water out. When it stops dripping, the coffee is ready to drink.
Coffee is most commonly known simply as a beverage. The standard ways to drink coffee are with some combination of milk, cream and/or sugar, or with none of these. Many variations of coffee and milk (or cream) make up the standard fare of espresso bars.
Coffee is sometimes used in recipes, especially desserts, such as the Swedish Chokladboll. The flavour of chocolate or cocoa is known to be enhanced by the addition of a small amount of coffee. For recipes using coffee as an ingredient, see Category:Coffee recipes.