Coffee preparation is, by definition, a way of turning coffee beans into a tasty drink. Although there are many types of coffee drinks all steps can be classified in four basic steps. Raw coffee beans are roasted, then ground, then are mixed with hot water (brewed) and then the liquid coffee must be separated from the used grounds.
Roasting green coffee beans removes its chlorogenic acid and changes the taste of the coffee and caffeine content depending on the temperature of roasting. Levels of roasting depending on the temperature on which beans are roasted are: Green Beans (on the room temperature, not considered roasting :) ), Drying Phase (165 °C), Cinnamon Roast (196 °C), New England Roast (205 °C), American Roast (210 °C), City Roast (219 °C), Full City Roast (225 °C), Vienna Roast (230 °C), French Roast (240 °C), Italian Roast (245 °C), and Spanish Roast (250 °C). As the roasting level increases caffeine level decreases.
Whole roasted coffee beans are ground which makes brewing easier. The way of grounding affects brewing. If the coffee grounds are exposed to heated water for longer can be ground coarser while faster brewing methods require finer grind. If the finer ground coffee is exposed to heated water for longer times, it will give more bitter taste. Because of that, a method of grinding must be matched to the brewing method for best results.
Burr-grinding is done in burr mills which have two revolving abrasive elements, wheels or cones, between which the coffee beans are crushed. This kind of grinding gives coffee that tastes richer and smoother.
Chopping is done in a blade grinders or home blenders. Coffee grinded like this is used in drip coffee makers. Arabic coffee and Turkish coffee require very fine, powdery coffee. This kind of grind is done in mortar and pestle. In a roller grinder, which is used exclusively by commercial and industrial scale coffee producers, the beans are ground between pairs of corrugated rollers which gives more even grind size distribution.
Four types of brewing of coffee are: decoction (through boiling), infusion (through steeping), gravitational feed (used with percolators and in drip brewing), and pressurized percolation (as with espresso).
Boiling is done by putting the ground coffee in a cup, pouring hot water over it and letting the mix cool while the grounds sink to the bottom. Steeping is done in a few ways. With French press, grounds are placed in the cylinder and covered with boiling water. After left in the cylinder for a few minutes, a plunger that includes a metal or nylon mesh filter is pushed down the cylinder which holds the ground at the bottom of the cylinder and allows for liquid to be poured out. Other methods of steeping are coffee bags (filter bags with coffee) and vacuum coffee maker which brews coffee using two chambers where vapor pressure and vacuum produce coffee. Pressure method of brewing is done when boiling water is forced through coffee.
At the end, separation of ground from liquid is done with filters.