Coffee preparation
Coffee preparation is the making of liquid coffee using coffee beans. While the particular steps vary with the type of coffee and with the raw materials, the process includes four basic steps: raw coffee beans must be roasted, the roasted coffee beans must then be ground, and the ground coffee must then be mixed with hot or cold water for a specific time, the liquid coffee extraction must be separated from the used grounds, and finally, if desired, the extracted coffee is combined with other elements of the desired beverage, such as sweeteners, dairy products, dairy alternatives, or toppings.
Key variables in coffee preparation include grind size, water temperature, brew time, and the ratio of coffee to water, all of which influence extraction and flavour.
Coffee is usually brewed hot, at close to the boiling point of water, immediately before drinking, yielding a hot beverage capable of scalding if splashed or spilled; if not consumed promptly, coffee is often sealed into a vacuum flask or insulated bottle to maintain its temperature. In most areas, coffee may be purchased unprocessed, or already roasted, or already roasted and ground. Whole roast coffee or ground coffee is often vacuum-packed to prevent oxidation and lengthen its shelf life. Especially in hot climates, some find cold or iced coffee more refreshing. This can be prepared well in advance as it maintains its character when stored cold better than as a hot beverage.
Even with the same roast, the character of the extraction is highly dependent on distribution of particle sizes produced by the grinding process, temperature of the grounds after grinding, freshness of the roast and grind, brewing process and equipment, temperature of the water, character of the water itself, contact time with hot water, and the brew ratio employed. Preferred brew ratios of water to coffee often fall into the range of 15–18:1 by mass; even within this fairly small range, differences are easily perceived by an experienced coffee drinker. Processes can range from extremely manual to totally automated by a single appliance with a reservoir of roast beans which it automatically measures and grinds, and water, which it automatically heats and doses. Another common style of automated coffee maker is fed a single-serving "pod" of pre-measured coffee grounds for each beverage.
Characteristics which may be emphasized or deemphasized by different preparation methods include: acidity, aroma, mouthfeel, astringency, bitterness, and the duration and intensity of flavour perception in the mouth. The addition of sweeteners, dairy products, or dairy alternatives also changes the perceived character of the brewed coffee. Principally, dairy products mute delicate aromas and thicken mouthfeel, while sweeteners mask astringency and bitterness.
Roasting
Roasting coffee transforms the chemical and physical properties of green coffee beans. When roasted, the green coffee bean expands to nearly double its original size, changing in color and density. As the bean absorbs heat, its color shifts to yellow, then to a light "cinnamon" brown, and then to a rich dark brown color. During roasting, oils appear on the surface of the bean. The roast will continue to darken until it is removed from the heat source.Coffee can be roasted with ordinary kitchen equipment or by specialized appliances. A coffee roaster is a special pan or apparatus suitable to heat up and roast green coffee beans.
Grinding
The whole coffee beans are ground, also known as milling, to facilitate the brewing process.The fineness of the grind strongly affects brewing. Brewing methods that expose coffee grounds to heated water for longer require a coarser grind than faster brewing methods. Beans that are too finely ground for the brewing method in which they are used will expose too much surface area to the heated water and produce a bitter, harsh, "over-extracted" taste. At the other extreme, an overly coarse grind will produce weak coffee unless more is used. Due to the importance of a grind's fineness, a uniform grind is highly desirable.
If a brewing method is used in which the time of exposure of the ground coffee to the heated water is adjustable, then a short brewing time can be used for finely ground coffee. This produces coffee of equal flavor yet uses less ground coffee. A blade grinder does not cause frictional heat buildup in the ground coffee unless used to grind very large amounts as in a commercial operation. A fine grind allows the most efficient extraction but coffee ground too finely will slow down filtration or screening.
Ground coffee deteriorates faster than roasted beans because of the greater surface area exposed to oxygen. Many coffee drinkers grind the beans themselves immediately before brewing.
Used coffee grounds can be reused for hair care or skin care as well as in the garden. These can also be used as biodiesel fuel.
There are four methods of grinding coffee for brewing: burr-grinding, chopping, pounding, and roller grinding.
Burr-grinding
s use two revolving abrasive elements, such as wheels or conical grinding elements made of stainless steel or ceramic, between which the coffee beans are crushed or "torn" with little frictional heating. The process of squeezing and crushing of the beans releases the coffee's oils, which are then more easily extracted during the infusion process with hot water, making the coffee taste richer and smoother.Both manually and electrically powered mills are available. These mills grind the coffee to a fairly uniform size determined by the separation of the two abrasive surfaces between which the coffee is ground; the uniform grind produces a more even extraction when brewed, without excessively fine particles that clog filters.
These mills offer a wide range of grind settings, making them suitable to grind coffee for various brewing systems such as espresso, drip, percolators, French press, and others. Many burr grinders, including almost all domestic versions, are unable to achieve the extremely fine grind required for the preparation of Greek coffee; traditional Greek hand grinders are an exception.
Burr grinders are of two types - conical burrs and flat wheel burrs. Most manual coffee grinders use conical burrs, but there have been a number of exceptions recently using flat wheel burrs including ghost burrs and hybrid designs. Both of them grind coffee bean consistently and with uniform size. There are also burr grinders, including a few manual coffee grinders, utilizing two burr sets for prebreaking and fine-grinding in order to sieve out coffee chaff, potentially work as slow feeders, achieve more uniform coffee grinds, and, in the case of manual grinders, ease operation or improve through-put. Many electrical burr grinders offer larger hoppers for storing whole coffee beans and can be used with a portafilter for espresso grind.
Chopping
Coffee beans can be chopped by using blades rotating at high speed, either in a blade grinder designed specifically for coffee and spices, or in a general use home blender. Devices of this sort are cheaper than burr grinders, but the grind is not uniform and will produce particles of widely varying sizes, while ideally all particles should have the same size, appropriate for the method of brewing. Moreover, the particles get smaller and smaller during the grinding process, which makes it difficult to achieve a consistent grind from batch to batch.Blade grinders create "coffee dust" that can clog up sieves in espresso machines and French presses, and are best suited for drip coffee makers. They are not recommended for grinding coffee for use with pump espresso machines.
Pounding
and Greek coffee require that the grounds be almost powdery in fineness, finer than can be achieved by most burr grinders. Pounding the beans with a mortar and pestle can pulverise the coffee finely enough.Roller grinding
In a roller grinder, the beans are ground between pairs of corrugated rollers. A roller grinder produces a more even grind size distribution and heats the ground coffee less than other grinding methods. However, due to their size and cost, roller grinders are used exclusively by commercial and industrial scale coffee producers.Water-cooled roller grinders are used for high production rates as well as for fine grinds such as Greek and espresso.
Brewing
Coffee can be brewed in several different ways, but these methods fall into four main groups depending on how the water is introduced to the coffee grounds: decoction, infusion, gravitational feed, or pressurized percolation.Brewed coffee, if kept hot, will deteriorate rapidly in flavor, and reheating such coffee tends to give it a "muddy" flavor, as some compounds that impart flavor to coffee are destroyed if this is done. Even at room temperature, deterioration will occur; however, if kept in an oxygen-free environment it can last almost indefinitely at room temperature, and sealed containers of brewed coffee are sometimes commercially available in food stores in America or Europe, with refrigerated bottled coffee drinks being commonly available at convenience stores and grocery stores in the United States. Canned coffee is particularly popular in Japan and South Korea.
Electronic coffee makers boil the water and brew the infusion with little human assistance and sometimes according to a timer. Some such devices also grind the beans automatically before brewing.
The French press is considered one of the oldest and simplest methods to brew coffee. Despite its simplicity, it can be a little tricky. The most important part of the process is to not leave the coffee in the French press for too long after pressing.
Boiling
Boiling, decoction or maceration, was the main method used for brewing coffee until the 1930sand is still used in some European and Middle Eastern countries.
The aromatic oils in coffee are released at, which is just below boiling, while the bitter acids are released when the water has reached boiling point.
The simplest method is to put the ground coffee in a cup, pour hot water over it and let cool while the grounds sink to the bottom. This is a traditional method for making a cup of coffee that is still used in parts of Indonesia. This method, known as "mud coffee" in the Middle East owing to an extremely fine grind that results in a mud-like sludge at the bottom of the cup, allows for extremely simple preparation, but drinkers then have to be careful if they want to avoid drinking grounds either from this layer or floating at the surface of the coffee, which can be avoided by dribbling cold water onto the "floaters" from the back of a spoon. If the coffee beans are not ground finely enough, the grounds do not sink.
A modern variant of this method is utilized by the German Empot, a specially formed porcelain coffee pot with a reservoir at its bottom to hold back the sunken coffee grounds when pouring the finished coffee.
"Cowboy coffee" is made by heating coarse grounds with water in a pot, letting the grounds settle and pouring off the liquid to drink, sometimes filtering it to remove fine grounds. While the name suggests that this method was used by cowboys, presumably on the trail around a campfire, it is used by others.
The above methods are sometimes used with hot milk instead of water.
Turkish coffee, a very early method of making coffee, is used in the Middle East, North Africa, East Africa, Turkey, Greece, the Balkans, and Russia. Very finely ground coffee, optionally sugar, and water are placed in a narrow-topped pot, called a cezve, kanaka, briki, džezva or turka and brought to the boil then immediately removed from the heat. It may be very briefly brought to the boil two or three times. Turkish coffee is sometimes flavored with cardamom, particularly in Arab countries. The resulting strong coffee, with foam on the top and a thick layer of grounds at the bottom, is drunk from small cups.