Coffee berries are picked by hand by labourers who receive payment by the basketful. As of 2003, payment per basket is between US$2.00 to $0.10 with the overwhelming majority of the labourers receiving payment at the lower end. An experienced coffee picker can collect up to 6-7 baskets a day. Depending on the grower, coffee pickers are sometimes specifically instructed to not pick green coffee berries since the seeds in the berries are not fully formed or mature. This discernment typically only occurs with growers who harvest for higher end specialty coffee where picker are paid better for their labour.
Mixes of green and red berries, or just green berries, are used to produce cheaper mass consumer coffee beans, which are characterized by a displeasurable bitter/astringent flavour and a sharp greenish odour. Red berries, with its higher aromatic oil and lower organic acid content are more fragrant, smooth, and mellow. As such coffee picking is one of the most important stages in coffee production, and is the chief determinant for the quality of the end product. Picked coffee berries are collected and defruited within hours of picking.
The coffee berries are a type of drupe, with fruit flesh directly covering the coffee bean. After harvesting, the flesh of the coffee berry must be is quickly removed by soaking, scouring and mechanical rubbing. This stage is critical in preserving the coffee flavours since the fruit is quick to ferment in coffee growing climates, and will give the resulting coffee a disagreeable odour. The defruited coffee bean is flushed with water to remove clinging fruit and additional sugars before drying.
Traditional coffee-drying in Boquete, Panama
Coffee beans are spread over a large concrete or rock surface where they are dried by air and sunlight. The beans are repeatedly raked into rows and spread out over the course of several days until they are largely dry. At this stage, the beans are referred to as "green coffee".
Hand sorting of coffee beans in Salento, Colombia
The first step in preparation is sorting of beans by color and size. Discoloured, rotten, and damaged beans are also removed at this point. 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, because over-aged coffee beans will lose much of its essential oil content.
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.
At lighter roasts, the bean will exhibit more of its "origin flavor"-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."