Coffee roasting

Roasting coffee transforms the chemical and physical properties of green coffee beans into roasted coffee products. The roasting process is what produces the characteristic flavor of coffee by causing the green coffee beans to change in taste. Unroasted beans contain similar if not higher levels of acids, protein, sugars, and caffeine as those that have been roasted, but lack the taste of roasted coffee beans due to the Maillard and other chemical reactions that occur during roasting.Green coffee as it arrives at the dock. The beans can be stored for approximately 12–18 months in a climate controlled environment before quality loss is noticeable. During the drying phase the beans are undergoing an endothermic process until their moisture content is evaporated, signifying first crack.A very light roast level which is immediately at first crack. Sweetness is underdeveloped, with prominent toasted grain, grassy flavors, and sharp acidity prominent. Moderate light brown, but still mottled in appearance. A preferred roast for some specialty roasters, highlights origin characteristics as well as complex acidity.Medium light brown, developed during first crack. Acidity is slightly muted, but origin character is still preserved. Medium brown, common for most specialty coffee. Good for tasting origin character, although roast character is noticeable. Medium-dark brown with dry to tiny droplets or faint patches of oil, roast character is prominent. At the beginning of second crack.Moderate dark brown with light surface oil, more bittersweet, caramel flavor, acidity muted. In the middle of second crack. Any origin characteristics have become eclipsed by roast at this level.Dark brown, shiny with oil, burnt undertones, acidity diminished. At the end of second crack. Roast character is dominant, none of the inherent aroma or flavors of the coffee remain.Nearly black and shiny, burnt tones become more distinct, acidity nearly eliminated, thin body.Diedrich IR Series Coffee Roaster.An old wood-fired coffee roaster.A two-barrel coffee roaster for roasting coffee samples prior to purchasing or roasting green coffee beans.An antique 'Mignon' five-barrel test roasting machine.The roasting room at a midsize coffee company. Roasting coffee transforms the chemical and physical properties of green coffee beans into roasted coffee products. The roasting process is what produces the characteristic flavor of coffee by causing the green coffee beans to change in taste. Unroasted beans contain similar if not higher levels of acids, protein, sugars, and caffeine as those that have been roasted, but lack the taste of roasted coffee beans due to the Maillard and other chemical reactions that occur during roasting. The vast majority of coffee is roasted commercially on a large scale, but small-scale commercial roasting has grown significantly with the trend toward 'single-origin' coffees served at specialty shops. Some coffee drinkers even roast coffee at home as a hobby in order to both experiment with the flavor profile of the beans and ensure the freshest possible roast. The first recorded implements for roasting coffee beans were thin pans made from metal or porcelain, used in the 15th century in the Ottoman Empire and Greater Persia. In the 19th century, various patents were awarded in the U.S. and Europe for commercial roasters, to allow for large batches of coffee. In the 1950s just as instant coffee was becoming a popular coffee drink, speciality coffee-houses began opening to cater to the connoisseur, offering a more traditionally brewed beverage. In the 1970s, more speciality coffee houses were founded, ones that offered a variety of roasts and beans from around the world. In the 1980s and 1990s, the gourmet coffee industry experienced great growth. This trend continued into the 21st Century. The first known implements for roasting coffee beans were thin, circular, often perforated pans made from metal or porcelain, used in the 15th century in the Ottoman Empire and Greater Persia. This type of shallow, dished pan was equipped with a long handle so that it could be held over a brazier (a container of hot coals) until the coffee was roasted. The beans were stirred with a slender spoon. Only a small amount of beans could be heated at one time. The first cylinder roaster with a crank to keep the beans in motion appeared in Cairo around 1650. It was made of metal, most commonly tinned copper or cast iron, and was held over a brazier or open fire. French, Dutch and Italian variations of this design quickly appeared. These proved popular over the next century in Europe, England and the American colonies. In the 19th century, various patents were awarded in the U.S. and Europe for commercial roasters, to allow for large batches of coffee. Nevertheless, home roasting continued to be popular. A man working at a commercial roasting plant beginning in the 1850s in St. Louis, Missouri, said that 'selling roasted coffee was up-hill work, as everyone roasted coffee in the kitchen oven.' Appliances catering to the home roaster were developed; in 1849 a spherical coffee roaster was invented in Cincinnati, Ohio, for use on the top of a wood-fired kitchen stove, fitted into a burner opening. Green beans were available at the local general store, or even through mail order. For roasting, many people used such simple methods as a layer of beans on a metal sheet in the oven, or beans stirred in a cast iron skillet over a fire. Despite the wide popularity of home roasting, Burns felt that it would soon disappear because of the great strides made in commercial roasting in the 1860s and 1870s, including the benefits of the economies of scale. The commercial roaster inventions patented by Burns revolutionized the U.S. roasting industry, much like the innovations of inventors in Emmerich am Rhein greatly advanced commercial coffee roasting in Germany. As well, the 1864 marketing breakthrough of the Arbuckle Brothers in Philadelphia, introducing the convenient one-pound (0.45 kg) paper bag of roasted coffee, brought success and imitators. From that time commercially roasted coffee grew in popularity until it gradually overtook home roasting during the 1900s in America. In 1903 and 1906 the first electric roasters were patented in the U.S. and Germany, respectively; these commercial devices eliminated the problem of smoke or fuel vapor imparting a bad taste to the coffee. In France, the home roaster did not yield to the commercial roaster until after the 1920s, especially in rural areas. Coffee was roasted to a dark color in small batches at home and by shopkeepers, using a variety of appliances including ones with a rotating cylinder of glass, sheet iron or wire mesh, and ones driven by hand, clockwork or electric motor. Because of the smoke and blowing chaff, country dwellers generally roasted outdoors. In the 1950s just as instant coffee was becoming a popular coffee drink, speciality coffee-houses began opening to cater to the connoisseur, offering a more traditionally brewed beverage. In the 1970s, more speciality coffee houses were founded, ones that offered a variety of roasts and beans from around the world. In the 1980s and 1990s, the gourmet coffee industry experienced great growth. Through the 1970s and 1980s, the Siemens Sirocco home roaster was made in West Germany and marketed globally. It was a small fluid-bed roaster made for the home enthusiast. The product was named after a commercial hot-air roasting process which itself was named after the hot Sahara winds called sirocco. In 1976, chemical engineer Michael Sivetz patented a competing hot air design for manufacture in the U.S.; this became popular as an economical alternative. Sivetz called for the home roaster to focus on the quality of the bean. From 1986 through 1999 there was a surge in the number of patents filed for home roasting appliances. In the 1990s, more electric home roasting equipment became available, including drum roasters, and variations on the fluid-bed roaster. By 2001, gourmet coffee aficionados were using the internet to purchase green estate-grown beans for delivery by mail. The coffee-roasting process follows coffee processing and precedes coffee brewing. It consists essentially of sorting, roasting, cooling, and packaging but can also include grinding in larger-scale roasting houses. In larger operations, bags of green coffee beans are hand- or machine-opened, dumped into a hopper, and screened to remove debris. The green beans are then weighed and transferred by belt or pneumatic conveyor to storage hoppers. From the storage hoppers, the green beans are conveyed to the roaster. Initially, the process is endothermic (absorbing heat), but at around 175 °C (347 °F) it becomes exothermic (giving off heat). For the roaster, this means that the beans are heating themselves and an adjustment of the roaster's heat source might be required. At the end of the roasting cycle, the roasted beans are dumped from the roasting chamber and air cooled with a draft inducer. During the roasting process, coffee beans tend to go through a weight loss of about 15 to 18% due to the loss of water and volatile compounds. Although the beans experience a weight loss, the size of the beans double after the roasting process due to the physical expansion of the cellulose structure which facilitates the release of carbon dioxide, volatile organic compounds, and water (in the form of steam). There are several traditional variations in bean roasting in different parts of the world. For example, in Vietnam coffee is often coated with oil (traditionally clarified butter) and a small amount of sugar prior to roasting to produce a 'butter roast'. The roasting process results in an additional caramelized coating on the beans.