The Manufacturing Process
Drying and husking the cherries
1. First, the coffee cherries must be harvested, a process that is still done manually. Next, the cherries are dried and husked using one of the two methods. The dry method is an older, primitive, and labor-intensive process of distributing the cherries in the sun, raking them several times a day, and allowing them to dry. When they have dried to the point at which they contain only 12 percent water, the beans’ husks become shriveled. At this stage, they are hulled, either by hand or by a machine.
2. In employing the wet method, the hulls are removed before the beans have dried. Although the fruit is initially processed in a pulping machine that removes most of the material surrounding the beans, some of this glutinous covering remains after pulping. This residue is removed by letting the beans ferment in tanks where their natural enzymes digest the gluey substance over a period of 18 to 36 hours. Upon removal from the fermenting tank, the beans are washed, dried by exposure to hot air, and put into large mechanical stirrers called hullers. There, the beans’ last parchment covering, the pergamino, crumbles and falls away easily. The huller then polishes the bean to a clean, glossy finish.
Cleaning and grading the beans
3. The beans are then placed on a conveyor belt that carries them past workers who remove sticks and other debris. Next, they are graded according to the size, the location and the altitude of the plantation where they were grown, drying and husking methods, and the taste. All these factors contribute to certain flavors that consumers will be able to select thanks in part to the grade. To make instant coffee, manufacturers grind the beans and brew the mixture in percolators. During this process, an extract forms and is sprayed into a cylinder. As it travels down the cylinder, the extract passes through warm air that converts it into a dry powder.
4. Once these processes are completed, workers select and pack particular types and grades of beans to fill orders from the various roasting companies that will finish preparing the beans. When beans (usually robusta) are harvested under the undesirable conditions of hot, humid countries or coastal regions, they must be shipped as quickly as possible, because such climates encourage insects and fungi that can severely damage a shipment.
5. When the coffee beans arrive at a roasting plant, they are again cleaned and sorted by mechanical screening devices to remove leaves, bark, and other remaining debris. If the beans are not to be decaffeinated, they are ready for roasting.
6. If the coffee is to be decaffeinated, it is now processed using either a solvent or a water method. In the first process, the coffee beans are treated with a solvent (usually methylene chloride) that leaches out the caffeine. If this decaffeination method is used, the beans must be thoroughly washed to remove traces of the solvent before roasting. The other method entails steaming the beans to bring the caffeine to the surface and then scraping off this caffeine-rich layer.
7. The beans are roasted in huge commercial roasters according to procedures and specifications which vary among manufacturers (specialty shops usually purchase beans directly from the growers and roast them on-site). The most common process entails placing the beans in a large metal cylinder and blowing hot air into it. An older method, called singeing, calls for placing the beans in a metal cylinder that is then rotated over an electric, gas, or charcoal heater.
Regardless of the particular method used, roasting gradually raises the temperature of the beans to between 431 and 449 degrees Fahrenheit (220-230 degrees Celsius). This triggers the release of steam, carbon monoxide, carbon dioxide, and other volatiles, reducing the weight of the beans by 14 to 23 percent. The pressure of these escaping internal gases causes the beans to swell, and they increase their volume by 30 to 100 percent. Roasting also darkens the color of the beans, gives them a crumbly texture, and triggers the chemical reactions that imbue the coffee with its familiar aroma (which it has not heretofore possessed).
8. After leaving the roaster, the beans are placed in a cooling vat, wherein they are stirred while cold air is blown over them. If the coffee being prepared is high-quality, the cooled beans will now be sent through an electronic sorter equipped to detect and eliminate beans that emerged from the roasting process too light or too dark.
9. If the coffee is to be pre-ground, the manufacturer mills it immediately after roasting. Special types of grinding have been developed for each of the different types of coffee makers, as each functions best with the coffee ground to a specific fineness.
10. If the coffee is to be instant, it is brewed with water in huge percolators after the grinding stage. An extract is clarified from the brewed coffee and sprayed into a large cylinder. As it falls downward through this cylinder, it enters a warm air stream that converts it into a dry powder.
11. Because it is less vulnerable to flavor and aroma loss than other types of coffee, the whole bean coffee is usually packaged in foil-lined bags. If it is to retain its aromatic qualities, pre-ground coffee must be hermetically sealed: it is usually packaged in impermeable plastic film, aluminum foil, or cans. Instant coffee picks up moisture easily, so it is vacuum-packed in tin cans or glass jars before being shipped to retail stores.