The first step in preparation is sorting of beans by color and size. In many less developed countries, hand sorting is still done because of the low cost of labor. Elsewhere, beans are sorted automatically by sophisticated machines that employ CCD cameras and can determine both size and color. Automatic sorting is cost-effective for large producers where quantity and throughput are important factors in production.
Although it is still widely debated, certain types of green coffee are believed to improve with age; especially those that are valued for their low acidity, such as coffees from Indonesia or India. Several of these coffee producers sell coffee beans that have been aged for as long as 3 years, with some as long as 8 years.
However, most coffee experts agree that a green coffee peaks in flavor and freshness within one year of harvest.
The roasting process is integral to producing a savory cup of coffee. When roasted, the green coffee bean expands to nearly double its original size, changing in color and density. As the bean absorbs heat, the color shifts to yellow and then to a light "cinnamon" brown. During this stage the moisture in the beans is expelled. When the inside of the bean reaches about 400 degrees Fahrenheit, it begins to turn brown and the oil is released from the interior of the bean. This oil contains the distinctive compounds which give coffee its flavor; the more oil released, the stronger the flavor. Coffee beans will crack during the roasting process, not unlike popping popcorn. "First crack" and "second crack" are benchmarks that a roaster will use to gauge how the roast progresses. The beans will continue to darken and the oils will begin to be expelled to the surface until the beans are removed from the heat source.
Unroasted coffee beans at various stages Râ€“L: fresh picked, after drying, one year after drying. Photos taken at Toko Aroma in Bandung, Indonesia.
Unroasted coffee beans at later stages. The beans are 7 and 8 years old. Photos taken at Toko Aroma in Bandung, Indonesia.
An old large-capacity coffee roaster made from cast iron. It is wood fired, and is located at Toko Aroma, Bandung, Indonesia
Roasted coffee beans
At lighter roasts, the bean will exhibit more of its "origin flavor"â€”the flavors created in the bean by the soil and weather conditions in the location where it was grown. Coffee beans from famous regions like Java and Kenya are usually roasted lightly so their signature characteristics dominate the flavor. A roasting method native to the Ipoh town in Malaysia involves the inclusion of butter and sugar during the roasting process, producing a variety of roast known as the Ipoh "white" coffee.
As the beans darken to a deep brown, the origin flavors of the bean are eclipsed by the flavors created by the roasting process itself. At darker roasts, the "roast flavor" is so dominant that it can be difficult to distinguish the origin of the beans used in the roast. These roasts are sold by the degree of roast, ranging from "Vienna Roast" to "French Roast" and beyond. The dividing line between extremely dark roast and "burnt" is a matter of some debate. Contrary to popular belief, the darker roasts and more strongly flavored coffees do not deliver any more caffeine than lighter roasts. In the United States, major national coffee suppliers tailor their product to tastes in particular regions of the country; for instance, a can of ground coffee purchased in the northeast or northwest will contain a darker roast than an identically appearing can purchased in the central United States.
In the 19th century coffee was usually bought in the form of green beans and roasted in a frying pan. This form of roasting requires much skill to do well, and fell out of favor when vacuum sealing of pre-roasted coffee became possible. Today home roasting is becoming popular again. Computerized drum roasters are available which simplify home roasting, and some home roasters will simply roast in an oven or in air popcorn makers.
Because coffee emits CO2 for days after it is roasted, one must allow the coffee to degas before it can be packaged in sealed containers. For this reason, many roasters who package whole beans immediately after roasting do so in bags with one-way valves, allowing the CO2 to escape but nothing in. This CO2 also affects the flavor of the brewed coffee, and most experts recommend a two- to five-day "resting" period post-roast for the CO2 to sufficiently escape.
Once roasted, the volatile compounds that give coffee its complex flavors dissipate quickly. Despite the varying claims of "what is fresh" when it comes to coffee, the industry leaders in specialty coffee generally agree that roasted coffee should be ground and brewed no more than about 14 days off-the-roast. Some companies have tried to extend the freshness using a nitrogen-infusion system that flushes the inert gas into the roasted coffee, replacing the oxygen, ostensibly reducing oxidation. However, as is said in the coffee industry, "the proof is in the cup."
The fineness of the grounds has a major impact on the brewing process, and matching the consistency of the grind with the brewing method is critical to extracting the optimal amount of flavor from the roasted beans. Brewing methods which expose coffee grounds to heated water for a longer duration of time require a coarser grind than faster brewing methods. Beans which 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 a weak, watery, under-flavored result.
The rate of deterioration increases when the coffee is ground, as a result of the greater surface area exposed to oxygen. With the rise of coffee as a gourmet beverage, it has become much more popular to grind the beans at home before brewing, and there are many home appliances available which are dedicated to the process.
There are two methods of producing coffee grounds ready for brewing.
Coffee can be brewed in several different ways, but these methods fall into four main groups depending upon how the water is introduced to the coffee grounds. If the method allows the water to pass only once through the grounds, the resulting brew will contain mainly the more soluble components (including caffeine), whereas if the water is repeatedly cycled through the beans (as with the common percolator), the brew will contain more of the relatively less soluble compounds found in the bean; as these tend to be more bitter; that type of process is less favored by coffee aficionados.
Coffee in all these forms is made with coffee grounds (coffee beans that have been roasted and ground) and hot water, the grounds either remaining behind or being filtered out of the cup or jug after the main soluble compounds have been removed. The fineness of the grind required differs by the method of extraction.
Water temperature is crucial to the proper extraction of flavor from the ground coffee. The recommended brewing temperature of coffee is 93 ÂşC (204 ÂşF). Any cooler and some of the solubles that make up the flavor will not be extracted. If the water is too hot, some undesirable elements will be extracted, adversely affecting the taste, especially in bitterness.
The usual ratio of coffee to water for the style of coffee most prevalent in Europe, America, and other Westernized nations is between one and two tablespoons of ground coffee per six ounces of water; the full two tablespoons per six ounces tends to be recommended by experienced coffee lovers.
Brewed coffee continually heated will deteriorate rapidly in flavor; even at room temperature, deterioration will occur. For this reason aficianados frown upon the hotplate which is sometimes used to keep brewed coffee warm prior to serving. However, if it is 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.
Electronic coffee makers boil the water and brew the infusion with little human assistance and sometimes according to a timer. Some even grind the beans automatically before brewing. Connoisseurs shun such conveniences as compromising the flavor of the coffee; they prefer freshly ground beans and traditional brewing techniques.