Coffee

Coffee is a brewed beverage with a bitter, acidic flavor prepared from the roasted seeds of the coffee plant. The beans are found in coffee cherries, which grow on trees cultivated in over 70 countries, primarily in equatorial Latin America, Southeast Asia, South Asia and Africa. Green (unroasted) coffee is one of the most traded agricultural commodities in the world. Coffee can have a stimulating effect on humans due to its caffeine content. It is one of the most-consumed beverages in the world.

Coffee has played a crucial role in many societies. The energizing effect of the coffee bean plant is thought to have been discovered in the northeast region of Ethiopia, and the cultivation of coffee first expanded in the Arab world. The earliest credible evidence of coffee drinking appears in the middle of the 15th century, in the Sufi shrines of Yemen in southern Arabia. From the Muslim world, coffee spread to India, Italy, then to the rest of Europe, to Indonesia, and to the Americas. In East Africa and Yemen, it was used in religious ceremonies. As a result, the Ethiopian Church banned its secular consumption, a ban in effect until the reign of Emperor Menelik II of Ethiopia. It was banned in Ottoman Turkey during the 17th century for political reasons, and was associated with rebellious political activities in Europe.

Coffee berries, which contain the coffee seeds or "beans", are produced by several species of small evergreen bush of the genus Coffea. The two most commonly grown are the highly regarded Coffea arabica, and the "robusta" form of the hardier Coffea canephora. The latter is resistant to the devastating coffee leaf rust (Hemileia vastatrix). Once ripe, coffee berries are picked, processed, and dried. The seeds are then roasted to varying degrees, depending on the desired flavor. They are then ground and brewed to create coffee. Coffee can be prepared and presented in a variety of ways.

An important export commodity, coffee was the top agricultural export for twelve countries in 2004, and it was the world's seventh-largest legal agricultural export by value in 2005. Some controversy is associated with coffee cultivation and its impact on the environment. Many studies have examined the relationship between coffee consumption and certain health conditions; whether the overall effects of coffee are ultimately positive or negative has been widely disputed. The method of brewing coffee has been found to be important to its health effects.

Etymology
The first reference to "coffee" in the English language is in the form chaoua and dates to 1598. In English and other European languages, coffee derives from the Ottoman Turkish kahve, via the Italian caffè. The Turkish word in turn was borrowed from the قهوة, qahwah. Arab lexicographers maintain that qahwah originally referred to a type of wine, and gave its etymology, in turn, to the verb qaha, signifying "to have no appetite", since this beverage was thought to dull one's hunger.

Several alternative etymologies exist that hold that the Arab form may disguise a loanword from an Ethiopian or African source, suggesting Kaffa, the highland in southwestern Ethiopia as one, since the plant is indigenous to that area. However, the term used in that region for the berry and plant is bunn, the native name in Shoa being būn.'

Biology
Several species of shrub of the genus Coffea produce the berries from which coffee is extracted. The two main species commercially cultivated are Coffea canephora (predominantly a form known as 'robusta') and C. arabica. C. arabica, the most highly regarded species, is native to the southwestern highlands of Ethiopia and the Boma Plateau in southeastern Sudan and possibly Mount Marsabit in northern Kenya. C. canephora is native to western and central subsaharan Africa, from Guinea to the Uganda and southern Sudan. Less popular species are C. liberica, excelsa, stenophylla, mauritiana, and racemosa.

All coffee plants are classified in the large family Rubiaceae. They are evergreen shrubs or small trees that may grow 5 m (15 ft) tall when unpruned. The leaves are dark green and glossy, usually 10–15 cm (4–6 in) long and 6 cm (2.4 in) wide. The flowers are axillary, and clusters of fragrant white flowers bloom simultaneously and are followed by oval berries of about 1.5 cm (0.6 in). Green when immature, they ripen to yellow, then crimson, before turning black on drying. Each berry usually contains two seeds, but 5–10% of the berries have only one; these are called peaberries. Berries ripen in seven to nine months.

Coffea arabica is predominantly self-pollinating, and as a result the seedlings are generally uniform and vary little from their parents. In contrast, Coffea canephora, C. excelsa, and C. liberica are self-incompatible and require outcrossing. This means that useful forms and hybrids must be propagated vegetatively. Cuttings, grafting, and budding are the usual methods of vegetative propagation. On the other hand, there is great scope for experimentation in search of potential new strains.

Cultivation
The traditional method of planting coffee is to put 20 seeds in each hole at the beginning of the rainy season; half are eliminated naturally. A more effective method of growing coffee, used in Brazil, is to raise seedlings in nurseries that are then planted outside at six to twelve months. Coffee is often intercropped with food crops, such as corn, beans, or rice during the first few years of cultivation.

Of the two main species grown, arabica coffee (from C. arabica) is generally more highly regarded than robusta coffee (from C. canephora); robusta tends to be bitter and have less flavor but better body than arabica. For these reasons, about three-quarters of coffee cultivated worldwide is C. arabica. Robusta strains also contain about 40–50% more caffeine than arabica. For this reason, it is used as an inexpensive substitute for arabica in many commercial coffee blends. Good quality robusta beans are used in some espresso blends to provide a full-bodied taste, a better foam head (known as crema), and to lower the ingredient cost.

However, Coffea canephora is less susceptible to disease than C. arabica and can be cultivated in lower altitudes and warmer climates where C. arabica will not thrive. The robusta strain was first collected in 1890 from the Lomani River, a tributary of the Congo River, and was conveyed from Zaire to Brussels to Java around 1900. From Java, further breeding resulted in the establishment of robusta plantations in many countries. In particular, the spread of the devastating coffee leaf rust (Hemileia vastatrix), to which C. arabica is vulnerable, hastened the uptake of the resistant robusta. Coffee leaf rust is found in virtually all countries that produce coffee.

Over 900 species of insect have been recorded as pests of coffee crops worldwide. Of these, over a third are beetles, and over a quarter are bugs. Some 20 species of nematodes, 9 species of mites, several snails and slugs also attack the crop. Birds and rodents sometimes eat coffee berries but their impact is minor compared to invertebrates. In general, arabica is the more sensitive species to invertebrate predation overall. Each part of the coffee plant is assailed by different animals. Nematodes attack the roots, and borer beetles burrow into stems and woody material, the foliage is attacked by over 100 species of larvae (caterpillars) of butterflies and moths.

Mass spraying of insecticides has often proven disastrous, as the predators of the pests are more sensitive than the pests themselves. Instead, integrated pest management has developed, using techniques such as targeted treatment of pest outbreaks, and managing crop environment away from conditions favouring pests. Branches infested with scale are often cut and left on the ground, which promotes scale parasites to not only attack the scale on the fallen branches but in the plant as well.

World production
In 2009 Brazil was the world leader in production of green coffee, followed by Vietnam, Indonesia and Colombia. Arabica coffee beans are cultivated in Latin America, eastern Africa, Arabia, or Asia. Robusta coffee beans are grown in western and central Africa, throughout southeast Asia, and to some extent in Brazil.

Beans from different countries or regions can usually be distinguished by differences in flavor, aroma, body, and acidity. These taste characteristics are dependent not only on the coffee's growing region, but also on genetic subspecies (varietals) and processing. Varietals are generally known by the region in which they are grown, such as Colombian, Java and Kona.

Ecological effects


Originally, coffee farming was done in the shade of trees that provided a habitat for many animals and insects. Remnant forest trees were used for this purpose, but many species have been planted as well. These include leguminous trees of the genera Acacia, Albizia, Cassia, Erythrina, Gliricidia, Inga, and Leucaena, as well as the nitrogen-fixing non-legume sheoaks of the genus Casuarina, and the silky oak Grevillea robusta.

This method is commonly referred to as the traditional shaded method, or "shade-grown". Starting in the 1970s, many farmers switched their production method to sun cultivation, in which coffee is grown in rows under full sun with little or no forest canopy. This causes berries to ripen more rapidly and bushes to produce higher yields, but requires the clearing of trees and increased use of fertilizer and pesticides, which damage the environment and cause health problems.

Unshaded coffee plants grown with fertilizer yield the most coffee, although unfertilized shaded crops generally yield more than unfertilized unshaded crops: the response to fertilizer is much greater in full sun. Although traditional coffee production causes berries to ripen more slowly and produce lower yields, the quality of the coffee is allegedly superior. In addition, the traditional shaded method provides living space for many wildlife species. Proponents of shade cultivation say environmental problems such as deforestation, pesticide pollution, habitat destruction, and soil and water degradation are the side effects of the practices employed in sun cultivation.

The American Birding Association, Smithsonian Migratory Bird Center, National Arbor Day Foundation, and the Rainforest Alliance have led a campaign for "shade-grown" and organic coffees, which can be sustainably harvested. Shaded coffee cultivation systems show greater biodiversity than full-sun systems, and those more distant from continuous forest compare rather poorly to undisturbed native forest in terms of habitat value for some bird species.

Another issue concerning coffee is its use of water. According to New Scientist, using industrial farming practices, it takes about 140 l of water to grow the coffee beans needed to produce one cup of coffee, and the coffee is often grown in countries where there is a water shortage, such as Ethiopia.

By using sustainable agriculture methods, the amount of water usage can be dramatically reduced, while retaining comparable yields. For comparison, the United States Geological Survey reports that one egg requires an input of 454 l of water; one serving of milk requires an input of 246 l of water; one serving of rice requires an input of 132 l of water; and one glass of wine requires an input of 120 l of water.

Coffee grounds may be used for composting or as a mulch. They are especially appreciated by worms and acid-loving plants such as blueberries. Some commercial coffee shops run initiatives to make better use of these grounds, including Starbucks' "Grounds for your Garden" project, and community sponsored initiatives such as "Ground to Ground".

Starbucks sustainability chief Jim Hanna has warned that Climate change may eliminate coffee production within a few decades.

Processing
Coffee berries and their seeds undergo several processes before they become the familiar roasted coffee. Berries have been traditionally selectively picked by hand; a labor intensive method, it involves the selection of only the berries at the peak of ripeness. More commonly, crops are strip picked, where all berries are harvested simultaneously regardless of ripeness by person or machine. After picking, green coffee is processed by one of two methods—the dry process method, simpler and less labor intensive as the berries can be strip picked, and the wet process method, which incorporates fermentation into the process and yields a mild coffee.

Then they are sorted by ripeness and color and most often the flesh of the berry is removed, usually by machine, and the seeds—usually called beans—are fermented to remove the slimy layer of mucilage still present on the bean. When the fermentation is finished, the beans are washed with large quantities of fresh water to remove the fermentation residue, which generates massive amounts of coffee wastewater. Finally, the seeds are dried.

The best (but least used) method of drying coffee is using drying tables. In this method, the pulped and fermented coffee is spread thinly on raised beds, which allows the air to pass on all sides of the coffee, and then the coffee is mixed by hand. In this method the drying that takes place is more uniform, and fermentation is less likely. Most African coffee is dried in this manner and certain coffee farms around the world are starting to use this traditional method.

Next, the coffee is sorted, and labeled as green coffee. Another way to let the coffee beans dry is to let them sit on a concrete patio and rake over them in the sunlight. Some companies use cylinders to pump in heated air to dry the coffee beans, though this is generally in places where the humidity is very high.

Some coffee undergoes a peculiar process, such as kopi luwak. It is made from the beans of coffee berries which have been eaten by the Asian Palm Civet and other related civets, passing through its digestive tract. This process resulted in coffee beans with much less bitterness, widely noted as the most expensive coffee in the world with prices reaching $160 per pound.

Roasting
The next step in the process is the roasting of the green coffee. Coffee is usually sold in a roasted state, and with rare exceptions all coffee is roasted before it is consumed. It can be sold roasted by the supplier, or it can be home roasted. The roasting process influences the taste of the beverage by changing the coffee bean both physically and chemically. The bean decreases in weight as moisture is lost and increases in volume, causing it to become less dense. The density of the bean also influences the strength of the coffee and requirements for packaging.

The actual roasting begins when the temperature inside the bean reaches approximately 200 °C, though different varieties of beans differ in moisture and density and therefore roast at different rates. During roasting, caramelization occurs as intense heat breaks down starches in the bean, changing them to simple sugars that begin to brown, changing the color of the bean.

Sucrose is rapidly lost during the roasting process and may disappear entirely in darker roasts. During roasting, aromatic oils and acids weaken, changing the flavor; at 205 °C, other oils start to develop. One of these oils is caffeol, created at about 200 °C, which is largely responsible for coffee's aroma and flavor.

Degree of roasting
Many coffee companies have specialized terminology for their different roasts and there is not much industry standardization. The different names for flavored roasts can cause confusion, but in general, the types of roasts fall into one of four color categories: light, medium, medium-dark, dark.

Grading the roasted beans
Depending on the color of the roasted beans as perceived by the human eye, they will be labeled as light, medium light, medium, medium dark, dark, or very dark. A more accurate method of discerning the degree of roast involves measuring the reflected light from roasted beans illuminated with a light source in the near infrared spectrum. This elaborate light meter uses a process known as spectroscopy to return a number that consistently indicates the roasted coffee's relative degree of roast or flavor development.

Roast characteristics
The degree of roast has an effect upon coffee flavor and body. Darker roasts are generally bolder because they have less fiber content and a more sugary flavor. Lighter roasts have a more complex and therefore perceived stronger flavor from aromatic oils and acids otherwise destroyed by longer roasting times. A small amount of chaff is produced during roasting from the skin left on the bean after processing. Chaff is usually removed from the beans by air movement, though a small amount is added to dark roast coffees to soak up oils on the beans.

Decaffeination
Decaffeination may also be part of the processing that coffee seeds undergo. Seeds are decaffeinated when they are still green. Many methods can remove caffeine from coffee, but all involve either soaking the green beans in hot water (often called the "Swiss water" process) or steaming them, then using a solvent to dissolve caffeine-containing oils. Decaffeination is often done by processing companies, and the extracted caffeine is usually sold to the pharmaceutical industry.

Storage
Once roasted, coffee beans must be stored properly to preserve the fresh taste of the bean. Ideally, the container must be airtight and kept in a cool, dry and dark place. In order of importance: air, moisture, heat, and light are the environmental factors responsible for deteriorating flavor in coffee beans.

Folded-over bags, a common way consumers often purchase coffee, are generally not ideal for long-term storage because they allow air to enter. A better package contains a one-way valve, which prevents air from entering.

In 1931, a method of vacuum packed cans of coffee was introduced, in which the roasted coffee was packed, ninety-nine percent of the air was removed and the coffee in the can could be stored indefinitely until the can was opened. Today this method is in mass use for coffee in a large part of the world.

Brewing
Coffee beans must be ground and brewed to create a beverage. The criteria for choosing a method include flavor and economy. Almost all methods of preparing coffee require the beans to be ground and mixed with hot water long enough to extract the flavor, but without overextraction that draws out unnecessary bitter compounds. The spent grounds are removed and the liquid is consumed. There are many variations in the fineness of grind, the ways in which the water extracts the flavor, additional flavorings (sugar, milk, spices), and spent ground separation techniques. The ideal holding temperature is 79 to 85 C and the ideal serving temperature is 68 to 79 C.

The roasted coffee beans may be ground at a roastery, in a grocery store, or in the home. Most coffee is roasted and ground at a roastery and sold in packaged form, though roasted coffee beans can be ground at home immediately before consumption. It is also possible, though uncommon, to roast raw beans at home.

Coffee beans may be ground in several ways. A burr grinder uses revolving elements to shear the bean; a blade grinder cuts the beans with blades moving at high speed; and a mortar and pestle crushes the beans. For most brewing methods, a burr grinder is deemed superior because the grind is more even and the grind size can be adjusted.

The type of grind is often named after the brewing method for which it is generally used. Turkish grind is the finest grind, while coffee percolator or French press are the coarsest grinds. The most common grinds are between the extremes; a medium grind is used in most common home coffee-brewing machines.

Coffee may be brewed by several methods: boiled, steeped, or pressurized.

Brewing coffee by boiling was the earliest method, and Turkish coffee is an example of this method. It is prepared by grinding or pounding the beans to a fine powder, then adding it to water and bringing it to the boil for no more than an instant in a pot called a cezve or, in Greek, a bríki. This produces a strong coffee with a layer of foam on the surface and sediment (which is not meant for drinking) settling on the bottom of the cup.

Coffee percolators and automatic coffeemakers brew coffee using gravity. In an automatic coffeemaker hot water drips onto coffee grounds held in a coffee filter made of paper, plastic, or perforated metal, allowing the water to seep through the ground coffee while extracting its oils and essences. The liquid drips through the coffee and the filter into a carafe or pot, and the spent grounds are retained in the filter.

In a percolator, boiling water is forced into a chamber above a filter by steam pressure created by boiling. The water then seeps through the grounds, and the process is repeated until terminated by removing from the heat, by an internal timer, or by a thermostat that turns off the heater when the entire pot reaches a certain temperature.

Coffee may be brewed by steeping in a device such as a French press (also known as a cafetière or coffee press). . Ground coffee and hot water are combined in a cylindrical vessel and left to brew for a few minutes. A circular filter which fits tightly in the cylinder fixed to a plunger is then pushed down from the top to force the grounds to the bottom. Because the coffee grounds are in direct contact with the water, all the coffee oils remain in the beverage, making it stronger and leaving more sediment than in coffee made by an automatic coffee machine. The coffee is poured from the container; the filter retains the grounds at the bottom. 95% of the caffeine is released from the coffee beans within the first minute of brewing.

The espresso method forces hot pressurized and vaporized water through ground coffee. As a result of brewing under high pressure (ideally between 9–10 atm), the espresso beverage is more concentrated (as much as 10 to 15 times the quantity of coffee to water as gravity-brewing methods can produce) and has a more complex physical and chemical constitution. A well-prepared espresso has a reddish-brown foam called crema that floats on the surface. Other pressurized water methods include the moka pot and vacuum coffee maker.

Cold brew coffee is made by steeping coarsely ground beans in cold water for several hours, then filtering them. This results in a brew lower in acidity than most hot-brewing methods.

Serving
Once brewed, coffee may be served in a variety of ways. Drip-brewed, percolated, or French-pressed/cafetière coffee may be served as white coffee with a dairy product such as milk or cream, or dairy substitute, or as black coffee with no such addition. It may be sweetened with sugar or artificial sweetener. When served cold, it is called iced coffee.

Espresso-based coffee has a wide variety of possible presentations. In its most basic form, espresso is served alone as a shot or with hot water added, known as Caffè Americano. Reversely, long black is made by pouring espresso in water, which retains the crema compared to Caffè Americano. Milk is added in various forms to espresso: steamed milk makes a caffè latte, equal parts steamed milk and milk froth make a cappuccino, and a dollop of hot foamed milk on top creates a caffè macchiato. The use of steamed milk to form patterns such as hearts or maple leaves is referred to as latte art.

Coffee can also be incorporated with alcohol in beverages—it is combined with whiskey in Irish coffee, and forms the base of alcoholic coffee liqueurs such as Kahlúa, and Tia Maria.

Instant coffee
A number of products are sold for the convenience of consumers who do not want to prepare their own coffee.

Instant coffee is dried into soluble powder or freeze-dried into granules that can be quickly dissolved in hot water. Originally invented in 1907, it rapidly gained in popularity in many countries in the post-war period, with Nescafé being the most popular product. Many consumers determined that the convenience in preparing a cup of instant coffee more than made up for a perceived inferior taste. Paralleling (and complementing) the rapid rise of instant coffee was the coffee vending machine, invented in 1947 and multiplying rapidly through the 1950s.

Canned coffee has been popular in Asian countries for many years, particularly in China, Japan, South Korea, and Taiwan. Vending machines typically sell varieties of flavored canned coffee, much like brewed or percolated coffee, available both hot and cold. Japanese convenience stores and groceries also have a wide availability of bottled coffee drinks, which are typically lightly sweetened and pre-blended with milk. Bottled coffee drinks are also consumed in the United States.

Liquid coffee concentrates are sometimes used in large institutional situations where coffee needs to be produced for thousands of people at the same time. It is described as having a flavor about as good as low-grade robusta coffee, and costs about 10¢ a cup to produce. The machines  can process up to 500 cups an hour, or 1,000 if the water is preheated.

Sale and distribution
Coffee ingestion on average is about a third of that of tap water in North America and Europe. Behind petroleum, coffee is the second most traded product in the world. Worldwide, 6.7 million metric tons of coffee were produced annually in 1998–2000, and the forecast is a rise to seven million metric tons annually by 2010. C

Brazil remains the largest coffee exporting nation, but Vietnam tripled its exports between 1995 and 1999, and became a major producer of robusta beans. Indonesia is the third-largest exporter and the largest producer of washed arabica coffee.

Commodity
Coffee is bought and sold by roasters, investors and price speculators as a tradable commodity in commodity markets. Coffee futures contracts for Grade 3 washed arabicas are traded on the New York Mercantile Exchange under ticker symbol KC, with contract deliveries occurring every year in March, May, July, September, and December. Coffee is an example of a product that has been susceptible to significant commmodity futures price variations.

Higher and lower grade arabica coffees are sold through other channels. Futures contracts for robusta coffee are traded on the London International Financial Futures and Options Exchange and, since 2007, on the New York IntercontinentalExchange. Coffee has been described by many, including historian Mark Pendergrast, as the world's "second most legally traded commodity." However, this claim has been recently refuted by Pendergrast among others after further research.

Fair trade
The concept of fair trade labeling, which guarantees coffee growers a negotiated preharvest price, began with the Max Havelaar Foundation's labeling program in the Netherlands. In 2004, 24,222 metric tons (of 7,050,000 produced worldwide) were fair trade; in 2005, 33,991 metric tons out of 6,685,000 were fair trade, an increase from 0.34% to 0.51%. A number of fair trade impact studies have shown that fair trade coffee has a positive impact on the communities that grow it. Coffee was incorporated into the fair-trade movement in 1988, when the Max Havelaar mark was introduced in the Netherlands. The very first fair-trade coffee was an effort to import a Guatemalan coffee into Europe as "Indio Solidarity Coffee".

Since the founding of organisations such as the European Fair Trade Association (1987), the production and consumption of fair trade coffee has grown as some local and national coffee chains started to offer fair trade alternatives. For example, in April 2000, after a year-long campaign by the human rights organization Global Exchange, Starbucks decided to carry fair-trade coffee in its stores. Since September 2009 all Starbucks Espresso beverages in UK and Ireland are made with Fairtrade and Shared Planet certified coffee.

A 2005 study done in Belgium concluded that consumers' buying behavior is not consistent with their positive attitude toward ethical products. On average 46% of European consumers claimed to be willing to pay substantially more for ethical products, including fair-trade products such as coffee. The study found that the majority of respondents were unwilling to pay the actual price premium of 27% for fair trade coffee.

Health and pharmacology
Scientific studies have examined the relationship between coffee consumption and an array of medical conditions. Findings have been contradictory as to whether coffee has any specific health benefits, and results are similarly conflicting regarding the potentially harmful effects of coffee consumption. Variations in findings can be at least partially resolved by considering the method of preparation. Coffee prepared using paper filters removes oily components called diterpenes that are present in unfiltered coffee. Two types of diterpenes are present in coffee: kahweol and cafestol, both of which have been associated with increased risk of coronary heart disease via elevation of low-density lipoprotein (LDL) levels in blood. Metal filters, on the other hand, do not remove the oily components of coffee.

In addition to differences in methods of preparation, conflicting data regarding serving size could partially explain differences between beneficial/harmful effects of coffee consumption. Coffee consumption has been shown to have minimal or no impact, positive or negative, on cancer development; researchers involved in an ongoing 22-year study by the Harvard School of Public Health state that "the overall balance of risks and benefits [of coffee consumption] are on the side of benefits." For example, men who drank six or more cups of coffee per day were found to have a 20% reduction in developing prostate cancer.

Other studies suggest coffee consumption reduces the risk of being affected by Alzheimer's disease, Parkinson's disease, heart disease, diabetes mellitus type 2, cirrhosis of the liver, and gout. A longitudinal study in 2009 showed that those who consumed a moderate amount of coffee or tea (3–5 cups per day) at midlife were less likely to develop dementia and Alzheimer's disease in late-life compared with those who drank little coffee or avoided it altogether. It increases the risk of acid reflux and associated diseases.

Most of coffee's beneficial effects against type 2 diabetes are not due to its caffeine content, as the positive effects of consumption are greater in those who drink decaffeinated coffee. A study from the Republic of China (Taiwan) offered an answer as to why coffee may reduce the risk of type 2 diabetes. The authors reported that two major components of coffee—caffeic acid and chlorogenic acid--significantly suppressed the formation of human islet amyloid polypeptide (hlAPP) in their laboratory.

The presence of antioxidants in coffee has been shown to prevent free radicals from causing cell damage. A recent study showed that roast coffee, high in lipophilic antioxidants and chlorogenic acid lactones, protected primary neuronal cell cultures against hydrogen peroxide-induced cell death.

In a healthy liver, caffeine is mostly broken down by the hepatic microsomal enzymatic system. The resulting metabolites are mostly paraxanthines—theobromine and theophylline—and a small amount of unchanged caffeine is excreted by urine. Therefore, the metabolism of caffeine depends on the state of this enzymatic system of the liver.

Elderly individuals with a depleted enzymatic system do not tolerate coffee with caffeine. They are recommended to take decaffeinated coffee, and this only if their stomach is healthy, because both decaffeinated coffee and coffee with caffeine cause heartburn. Moderate amounts of coffee (50–100 mg of caffeine or 5–10 g of coffee powder a day) are well tolerated by most elderly people.

In many individuals, excessive amounts of coffee can cause very unpleasant, even life-threatening adverse effects. The benefits of coffee on abnormal liver biochemistry, cirrhosis and hepatocellular carcinoma have been reported, but there is a lack of satisfactory explanation. A possible opposite, if not antagonistic, role of coffee and Mediterranean diet with regard to weight and insulin resistance is envisaged in the natural history of non-alcoholic fatty liver disease.

Coffee consumption can lead to iron deficiency anemia in mothers and infants. Coffee also interferes with the absorption of supplemental iron. Interference with iron absorption is due to the polyphenols present in coffee. Four major classes were identified: flavan-3-ols (monomers and procyanidins), hydroxycinnamic acids, flavonols and anthocyanidins. Although the inhibition of iron absorption can cause an iron deficiency, iron is considered a carcinogen in relation to the liver. Polyphenols contained in coffee are therefore associated with decreasing the risk of liver cancer development.

American scientist Yaser Dorri has suggested that the smell of coffee can restore appetite and refresh olfactory receptors. He suggests that people can regain their appetite after cooking by smelling coffee beans, and that this method can also be used for research animals.

Over 1,000 chemicals have been reported in roasted coffee; more than half of those tested (19/28) are rodent carcinogens at maximum tolerated dose, but due to the fact that animal cancer tests build in enormous safety factors, these chemicals should not be considered true risks. Coffee's negative health effects are often blamed on its caffeine content. Instant coffee has a much greater amount of acrylamide than brewed coffee. Research suggests that drinking caffeinated coffee can cause a temporary increase in the stiffening of arterial walls. Caffeinated coffee is not recommended for everybody. It may aggravate pre-existing conditions such as gastroesophageal reflux disease, migraines, arrhythmias, and cause sleep disturbances.

Coffee is no longer thought to be a risk factor for coronary heart disease. One study suggests that it may have a mixed effect on short-term memory, by improving it when the information to be recalled is related to the current train of thought but making it more difficult to recall unrelated information. Caffeine has been associated with its ability to act as an antidepressant. A review by de Paulis and Martin indicated a link between a decrease in suicide rates and coffee consumption, and suggested that the action of caffeine in blocking the inhibitory effects of adenosine on dopamine nerves in the brain reduced feelings of depression.

A 1992 study concluded that about 10% of people with a moderate daily intake (235 mg per day) experienced increased depression and anxiety when caffeine was withdrawn, but a 2002 review of the literature criticised its methodology and concluded that "[t]he effects of caffeine withdrawal are still controversial." About 15% of the U.S. general population report having stopped drinking coffee altogether, citing concern about health and unpleasant side effects of caffeine.

Caffeine and headaches
There is some controversy as to whether the caffeine in coffee causes headaches or, on the contrary, helps to relieve headaches. A controlled study by the Diamond Headache Clinic in Chicago, Illinois, undertaken in 2000, revealed that adults who took ibuprofen, an over-the-counter pain killer, combined with caffeine or who drank one cup of coffee found it alleviated their tension headaches. The study did not recommend that the caffeine and ibuprofen combination was effective against migraine headaches. A Johns Hopkins controlled study has linked drinking coffee with addictive withdrawal headaches, even for those who drink coffee in moderation. A 2009 Norwegian University of Science and Technology controlled study claims that heavy coffee drinkers, those who drank four or more cups a day, are more likely to suffer occasional headaches than persons who have low coffee or caffeine consumption.

Caffeine content
The stimulant effect of coffee is due to its caffeine content. The caffeine content of a cup of coffee varies depending mainly on the brewing method, and also on the variety of bean.

According to an article in the Journal of the American Dietetic Association, coffee has the following caffeine content, depending on how it is prepared:


 * brewed: 1 cup (7 oz, 207 ml) = 80–135 mg.
 * drip: 1 cup (7 oz, 207 ml) = 115–175 mg.
 * espresso: 1 shot (1.5–2 oz, 45–60 ml) = 100 mg

While the percent of caffeine content in coffee beans themselves diminishes with increased roast level, this does not hold true for the same coffee brewed from different grinds and brewing methods using the same proportion of coffee to water volume. The coffee sack (similar to the French press and other steeping methods) extracts more caffeine from dark roasted beans, while the percolator and espresso methods extracts more caffeine from light roasted beans.

History


Ethiopian ancestors of today's Oromo people were believed to have been the first to recognize the energizing effect of the coffee bean plant, though no direct evidence has been found indicating where in Africa coffee grew or who among the natives might have used it as a stimulant or even known about it, earlier than the 17th century. The story of Kaldi, the 9th-century Ethiopian goatherder who discovered coffee, did not appear in writing until 1671 and is probably apocryphal.

Other accounts attribute the discovery of coffee to Sheik Omar. According to the ancient chronicle (preserved in the Abd-Al-Kadir manuscript), Omar, who was known for his ability to cure the sick through prayer, was once exiled from Mocha to a desert cave near Ousab. Starving, Omar chewed berries from nearby shrubbery, but found them to be bitter. He tried roasting the beans to improve the flavor, but they became hard. He then tried boiling them to soften the bean, which resulted in a fragrant brown liquid. Upon drinking the liquid Omar was revitalized and sustained for days. As stories of this "miracle drug" reached Mocha, Omar was asked to return and was made a saint. From Ethiopia, the beverage was introduced into the Arab world through Egypt and Yemen.

The earliest credible evidence of either coffee drinking or knowledge of the coffee tree appears in the middle of the fifteenth century, in the Sufi monasteries around Mokha in Yemen. It was here in Arabia that coffee beans were first roasted and brewed, in a similar way to how it is now prepared. By the 16th century, it had reached the rest of the Middle East, Persia, Turkey, and northern Africa. Coffee beans were first exported from Ethiopia to Yemen. Yemeni traders brought coffee back to their homeland and began to cultivate the bean. The first coffee smuggled out of the Middle East was by Sufi Baba Budan from Yemen to India in 1670. Before then, all exported coffee was boiled or otherwise sterilised. Portraits of Baba Budan depict him as having smuggled seven coffee beans by strapping them to his chest. The first plants grown from these smuggled seeds were planted in Mysore. Coffee then spread to Italy, and to the rest of Europe, to Indonesia, and to the Americas.

In 1583, Leonhard Rauwolf, a German physician, gave this description of coffee after returning from a ten-year trip to the Near East: "A beverage as black as ink, useful against numerous illnesses, particularly those of the stomach. Its consumers take it in the morning, quite frankly, in a porcelain cup that is passed around and from which each one drinks a cupful. It is composed of water and the fruit from a bush called bunnu."

From the Muslim world, coffee spread to Italy. The thriving trade between Venice and North Africa, Egypt, and the Middle East brought many goods, including coffee, to the Venetian port. From Venice, it was introduced to the rest of Europe. Coffee became more widely accepted after it was deemed a Christian beverage by Pope Clement VIII in 1600, despite appeals to ban the "Muslim drink." The first European coffee house opened in Italy in 1645.

The Dutch East India Company was the first to import coffee on a large scale. The Dutch later grew the crop in Java and Ceylon. The first exports of Indonesian coffee from Java to the Netherlands occurred in 1711.

Through the efforts of the British East India Company, coffee became popular in England as well. Oxford's Queen's Lane Coffee House, established in 1654, is still in existence today. Coffee was introduced in France in 1657, and in Austria and Poland after the 1683 Battle of Vienna, when coffee was captured from supplies of the defeated Turks.

When coffee reached North America during the Colonial period, it was initially not as successful as it had been in Europe as alcoholic beverages remained more popular. During the Revolutionary War, the demand for coffee increased so much that dealers had to hoard their scarce supplies and raise prices dramatically; this was also due to the reduced availability of tea from British merchants.

After the War of 1812, during which Britain temporarily cut off access to tea imports, the Americans' taste for coffee grew, and high demand during the American Civil War together with advances in brewing technology secured the position of coffee as an everyday commodity in the United States. Coffee consumption declined in England, giving way to tea during the 18th century. The latter beverage was simpler to make, and had become cheaper with the British conquest of India and the tea industry there. During the Age of Sail, seamen aboard ships of the British Royal Navy made substitute coffee by dissolving burnt bread in hot water.

The Frenchman Gabriel de Clieu brought a coffee plant to the French territory of Martinique in the Caribbean, from which much of the world's cultivated arabica coffee is descended. Coffee thrived in the climate and was conveyed across the Americas. The territory of San Domingo (now Haiti) saw coffee cultivated from 1734, and by 1788 it supplied half the world's coffee. The conditions that the slaves worked in on coffee plantations were a factor in the soon to follow Haitian Revolution. The coffee industry never fully recovered there.

Meanwhile, coffee had been introduced to Brazil in 1727, although its cultivation did not gather momentum until independence in 1822. After this time, massive tracts of rainforest were cleared first from the vicinity of Rio and later São Paulo for coffee plantations. Cultivation was taken up by many countries in Central America in the latter half of the 19th century, and almost all involved the large-scale displacement and exploitation of the indigenous people. Harsh conditions led to many uprisings, coups and bloody suppression of peasants. The notable exception was Costa Rica, where lack of ready labor prevented the formation of large farms. Smaller farms and more egalitarian conditions ameliorated unrest over the 19th and 20th centuries.

Coffee has become a vital cash crop for many Third World countries. Over one hundred million people in developing countries have become dependent on coffee as their primary source of income. It has become the primary export and backbone for African countries like Uganda, Burundi, Rwanda, and Ethiopia, as well as many Central American countries.

Social and culture
Coffee is often consumed alongside (or instead of) breakfast by many at home. It is often served at the end of a meal, normally with a dessert, and at times with an after-dinner mint especially when consumed at a restaurant or dinner party.

Aggressively promoted by the Pan-American Coffee Bureau, the "coffee break" was first promoted in 1952. Hitherto unknown in the workplace, its uptake was facilitated by the recent popularity of both instant coffee and vending machines, and has become an institution of the American workplace.

Coffeehouses
Most widely known as coffeehouses or cafés, establishments serving prepared coffee or other hot beverages have existed for over five hundred years.

Various legends involving the introduction of coffee to Constantinople at a "Kiva Han" in the late 15th century circulate in culinary tradition, but with no documentation.

Coffeehouses in Mecca soon became a concern as places for political gatherings to the imams who banned them, and the drink, for Muslims between 1512 and 1524. In 1530 the first coffee house was opened in Damascus,. First coffee houses in Constantinople was opened in 1555 by traders arriving from Damascus and Aleppo. Soon after, coffee houses became part of the Ottoman Culture, spreading rapidly to all regions of the Ottoman Empire.

In the 17th century, coffee appeared for the first time in Europe outside the Ottoman Empire, and coffeehouses were established and quickly became popular. The first coffeehouses in Western Europe appeared in Venice, a result of the traffic between La Serenissima and the Ottomans; the very first one is recorded in 1645. The first coffeehouse in England was set up in Oxford in 1650 by a Jewish man named Jacob in the building now known as "The Grand Cafe". A plaque on the wall still commemorates this and the Cafe is now a trendy cocktail bar. By 1675, there were more than 3,000 coffeehouses in England.

In 1672 an Armenian named Pascal established a coffee stall in Paris that was ultimately unsuccessful and the city had to wait until 1689 for its first coffeehouse when Procopio Cutò opened the Café Procope. This coffeehouse still exists today and was a major meeting place of the French Enlightenment; Voltaire, Rousseau, and Denis Diderot frequented it, and it is arguably the birthplace of the Encyclopédie, the first modern encyclopedia. America had its first coffeehouse in Boston, in 1676. Coffee, tea and beer were often served together in establishments which functioned both as coffeehouses and taverns; one such was the Green Dragon in Boston, where John Adams, James Otis and Paul Revere planned rebellion.

The modern espresso machine was born in Milan in 1945 by Achille Gaggia, and from there spread across coffeehouses and restaurants across Italy and the rest of Europe and North America in the early 1950s. An Italian named Pino Riservato opened the first espresso bar, the Moka Bar, in Soho in 1952, and there were 400 such bars in London alone by 1956. Cappucino was particularly popular among English drinkers. Similarly in the United States, the espresso craze spread. North Beach in San Francisco saw the opening of the Caffe Trieste in 1957, which saw Beat Generation poets such as Allen Ginsberg and Bob Kaufman alongside bemused Italian immigrants. Similar such cafes existed in Greenwich Village and elsewhere.

The first Peet's Coffee & Tea store opened in 1966 in Berkeley, California by Dutch native Alfred Peet. He chose to focus on roasting batches with fresher, higher quality beans than was the norm at the time. He was a trainer and supplier to the founders of Starbuck’s.

The international coffeehouse chain Starbucks began as a modest business roasting and selling quality coffee beans in 1971, by three college students Jerry Baldwin, Gordon Bowker and Zev Siegl. The first store opened on March 30, 1971 at the Pike Place Market in Seattle, followed by a second and third over the next two years. Entrepreneur Howard Schultz joined the company in 1982 as Director of Retail Operations and Marketing, and pushed to sell premade espresso coffee. The others were reluctant, but Schultz opened Il Giornale in Seattle in April 1986. He bought the other owners out in March 1987 and pushed on with plans to expand—from 1987 to the end of 1991, the chain (rebranded from Il Giornale to Starbucks) expanded to over 100 outlets. The company has 16,600 stores in over 40 countries worldwide.

Prohibition


Coffee was initially used for spiritual reasons. At least 1,100 years ago, traders brought coffee across the Red Sea into Arabia (modern-day Yemen), where Muslim dervishes began cultivating the shrub in their gardens. At first, the Arabians made wine from the pulp of the fermented coffee berries. This beverage was known as qishr (kisher in modern usage) and was used during religious ceremonies.

Coffee drinking was prohibited by jurists and scholars (ulema) meeting in Mecca in 1511 as haraam, but the subject of whether it was intoxicating was hotly debated over the next 30 years until the ban was finally overturned in the mid 16th century. Use in religious rites among the Sufi branch of Islam led to coffee's being put on trial in Mecca: it was accused of being a heretical substance, and its production and consumption were briefly repressed. It was later prohibited in Ottoman Turkey under an edict by the Sultan Murad IV.

Coffee, regarded as a Muslim drink, was prohibited by Ethiopian Orthodox Christians until as late as 1889; it is now considered a national drink of Ethiopia for people of all faiths. Its early association in Europe with rebellious political activities led to Charles II outlawing coffeehouses from January 1676 (although the uproar created forced the monarch to back down two days before the ban was due to come into force). Frederick the Great banned it in Germany in 1777 for nationalistic and economic reasons; concerned about the price of import, he sought to force the public back to consuming beer. Lacking coffee-producing colonies, Germany had to import all its coffee at a great cost.

A contemporary example of religious prohibition of coffee can be found in The Church of Jesus Christ of Latter-day Saints. The organization holds that it is both physically and spiritually unhealthy to consume coffee. This comes from the Mormon doctrine of health, given in 1833 by founder Joseph Smith in a revelation called the Word of Wisdom. It does not identify coffee by name, but includes the statement that "hot drinks are not for the belly," which has been interpreted to forbid both coffee and tea.

Quite a number of members of the Seventh-day Adventist Church also avoid caffeinated drinks. In its teachings, the Church encourages members to avoid tea and coffee and other stimulants. Abstinence from coffee, tobacco and alcohol by many Adventists has afforded a near unique opportunity for studies to be conducted within that population group on the health effects of coffee drinking, free from confounding factors. One study was able to show a weak but statistically significant association between coffee consumption and mortality from ischemic heart disease, other cardiovascular disease, all cardiovascular diseases combined, and all causes of death.

For a time, there had been controversy in the Jewish community over whether the coffee bean was a legume and therefore prohibited for Passover. Upon petition from coffeemaker Maxwell House, the coffee bean was classified in 1923 as a berry rather than a bean by orthodox Jewish rabbi Hersch Kohn, and therefore kosher for Passover.

Folklore and culture
The Oromo people would customarily plant a coffee tree on the graves of powerful sorcerers. They believed that the first coffee bush sprang up from the tears that the god of heaven shed over the corpse of a dead sorcerer.

Johann Sebastian Bach was inspired to pen the Coffee Cantata, about dependence on the beverage.

Coffee Day
In the United States, September 29 is celebrated as "National Coffee Day."