Coffee: From an Ethiopian Shrub to the World's Favorite Morning Drink

What Coffee Really Is

Coffee is a drink made by brewing roasted, ground coffee beans in hot water. It is usually dark brown, slightly bitter and full of aroma, and many people drink it because it makes them feel more awake. That effect comes from caffeine, a natural substance found in the beans. For people who love the taste but not the stimulation, there is also decaffeinated coffee, and for those who want something similar without any coffee at all, there are substitutes made from roasted roots and grains.

The word "bean" is a little misleading. A coffee bean is not a bean like a lentil or a pea. It is the seed of a small fruit, often called a coffee cherry, that grows on shrubs and small trees of the genus Coffea. These plants belong to the same botanical family as gardenias, the Rubiaceae. Each cherry usually holds two seeds pressed flat against each other, which is why most coffee beans have one flat side. Sometimes only one rounded seed develops inside the fruit; coffee growers call this a peaberry and often sort it out and sell it separately.

The Coffee Plant and Where It Grows

Scientists have described more than 120 species of Coffea, but almost all the coffee people drink comes from just two of them.

Arabica and robusta

• Arabica (Coffea arabica) originally comes from the highlands of Ethiopia. It grows best at higher altitudes, in cool, frost-free climates, and is prized for its sweeter, more complex and often fruity flavors. It makes up the larger share of the world's coffee.
• Robusta (Coffea canephora) grows at lower altitudes and in hotter conditions. As its name suggests, it is a tougher plant that resists many diseases better. Its beans contain roughly twice as much caffeine as arabica beans and taste stronger and more bitter. Robusta is widely used in instant coffee and in many espresso blends.

A curious fact links the two: arabica itself is a natural hybrid. Its ancestors are robusta and another wild species, Coffea eugenioides, which crossed long ago in East Africa. Other species, such as Coffea liberica, are grown on a small scale in some countries.

The coffee belt

Coffee plants need warmth, regular rain and no frost, so they are grown in a band around the Earth between the Tropic of Cancer and the Tropic of Capricorn, often called the coffee belt. A young plant takes about three to four years before it produces its first real harvest. Its white flowers smell sweet, a bit like jasmine, and they last only a few days. After flowering, the green cherries slowly ripen, usually turning bright red. Because cherries on the same branch ripen at different times, the finest coffees are picked by hand, cherry by cherry, over several rounds.

From Ethiopia to Yemen: The Origins of Coffee

A famous legend says that an Ethiopian goatherd named Kaldi noticed his goats becoming unusually lively after nibbling the red berries of a certain shrub. He tried the berries himself, and the discovery of coffee began. It is a charming story, but it appears in writing only in the 17th century, long after coffee had become popular, so historians treat it as folklore rather than fact.

What historians can document is that by the 15th century coffee was being prepared as a drink in Yemen, on the southern tip of the Arabian Peninsula. Members of Sufi religious orders drank it to stay alert during long night-time prayers. The coffee plants themselves almost certainly came from across the Red Sea in Ethiopia. Yemen's port of Mocha became so closely tied to the coffee trade that its name is still used for coffee drinks today.

The English word "coffee" has traveled almost as far as the drink. It came into English through the Dutch word koffie, which was borrowed from the Ottoman Turkish kahve, which in turn came from the Arabic qahwa.

How Coffee Conquered the World

Coffeehouses of the Middle East

During the 16th century coffee spread to Mecca, Cairo and other cities of the Islamic world. In Istanbul, the capital of the Ottoman Empire, coffeehouses became popular meeting places where people talked, played games, listened to stories and discussed the news. Some rulers and officials worried that these lively gatherings encouraged rebellious ideas, and at various times coffeehouses were restricted or banned, but the bans never lasted for long.

Europe's "penny universities"

Coffee reached Europe in the 17th century, first through trading cities such as Venice. Coffeehouses soon opened in Oxford, London, Paris, Vienna and many other cities. In England they were nicknamed "penny universities", because for the price of a cup anyone could sit and listen to conversations about science, politics and business. Some famous institutions grew out of them: the insurance market Lloyd's of London began in a coffeehouse run by Edward Lloyd in the late 17th century, where merchants and ship owners met to share news about ships and cargo.

Coffee even found its way into music. Around the 1730s the German composer Johann Sebastian Bach wrote a humorous piece now known as the Coffee Cantata, in which a father tries, without success, to stop his daughter from drinking coffee.

Plantations across the tropics

For a long time Yemen controlled most of the world's coffee supply. That changed when European powers began growing coffee in their colonies. The Dutch established plantations on the island of Java, in today's Indonesia, which is why "java" became a nickname for coffee. In the 18th century coffee plants were carried to the Caribbean and to South America. Coffee came to Brazil in 1727, and by the 19th century Brazil had become the largest coffee producer in the world, a position it still holds.

This expansion has a dark side that is important to remember. On many plantations in the Americas and the Caribbean, coffee was grown and harvested by enslaved people, and the wealth of the coffee trade was built in part on their forced labor.

From Cherry to Cup: How Coffee Is Made

Turning a coffee cherry into a drink takes several careful steps, and each one shapes the final flavor.

1. Harvesting. Ripe cherries are picked by hand or, on large flat farms, by machines that shake the branches.
2. Processing. The seeds must be separated from the fruit. In the washed (wet) method, the skin and most of the pulp are removed, the beans are fermented briefly in water and then washed, which tends to give a clean, bright taste. In the natural (dry) method, whole cherries are dried in the sun before the dried fruit is removed, which often gives fruitier, heavier flavors. A middle path, often called the honey process, leaves some of the sticky fruit on the bean while it dries.
3. Drying and hulling. The beans are dried and their thin papery layers removed. The result is green coffee: pale, hard beans that smell grassy and can be stored and shipped around the world.
4. Roasting. Green beans are heated to temperatures of around 200 °C or more. They lose most of their water, swell, turn brown and make a cracking sound, much like popcorn. Chemical changes, including the Maillard reaction (the same kind of browning that happens on toast) and caramelization of sugars, create hundreds of aroma compounds that were not present in the green bean.
5. Grinding and brewing. Roasted beans are ground and mixed with hot water, which dissolves flavors, oils and caffeine to make the drink.

A common belief is that a dark roast contains more caffeine than a light roast. In fact, caffeine is quite stable during roasting. Dark roasts taste stronger and more bitter because of roasting flavors, not because they contain much more caffeine.

Many Ways to Brew a Cup

Over the centuries people have invented a remarkable variety of ways to brew coffee:

• Turkish coffee is made by simmering very finely ground coffee with water, often with sugar, in a small pot, and serving it unfiltered so the grounds settle in the cup. Turkish coffee culture and tradition is included on UNESCO's list of the Intangible Cultural Heritage of Humanity.
• Espresso, developed in Italy in the early 20th century, forces hot water through tightly packed, finely ground coffee under high pressure. The result is a small, concentrated shot topped with a golden foam called crema. Cappuccino and latte are espresso mixed with steamed milk.
• Filter coffee lets hot water drip through ground coffee held in a filter. In 1908 a German housewife, Melitta Bentz, patented a coffee filter system using paper, which led to a company that still bears her name.
• The moka pot, an Italian stovetop pot popularized by the Bialetti company, pushes boiling water up through the coffee using steam pressure.
• The French press soaks coarse grounds in hot water and then separates them with a metal mesh plunger.
• Cold brew steeps coffee in cold water for many hours, producing a smooth, less acidic drink.
• Instant coffee is brewed coffee that has been dried into powder or granules, so it dissolves in water in seconds.

Coffee is also at the heart of many traditions. In Ethiopia, the coffee ceremony is an important act of hospitality: green beans are roasted in a pan in front of the guests, ground by hand and brewed in a clay pot called a jebena, and the coffee is served in several rounds.

Why Coffee Wakes You Up

The science of caffeine

Throughout the day, a substance called adenosine builds up in the brain. When adenosine attaches to special receptors on nerve cells, it slows them down and makes us feel sleepy. Caffeine molecules have a shape similar to adenosine, so they can sit in those receptors and block them without triggering the sleepy signal. The result is that we feel more alert and less tired. Caffeine does not create energy; it mainly hides tiredness for a while. Its effects in adults usually last for several hours, which is why coffee late in the day can make it harder to fall asleep.

For the coffee plant, caffeine has a very different job. It is bitter and toxic to many insects, so it helps protect the plant's leaves and seeds from being eaten.

Coffee and health

A typical cup of brewed coffee contains very roughly 80 to 100 milligrams of caffeine, though the amount varies a lot with the beans and the brewing method. Health authorities in the United States and Europe consider up to about 400 milligrams of caffeine a day generally safe for healthy adults. Large studies have linked moderate coffee drinking in adults with a lower risk of some illnesses, such as type 2 diabetes, but researchers are still working out exactly why. Too much caffeine can cause a racing heart, nervousness, stomach trouble and poor sleep. Children are more sensitive to caffeine, and health experts advise that they avoid it or keep it to small amounts, which is one reason coffee is usually considered a grown-up drink.

Decaf and Coffee Substitutes

The first commercial method for removing caffeine from coffee was developed in Germany in the early 20th century by the merchant Ludwig Roselius. Today, decaffeination is done while the beans are still green, using one of several methods: soaking them in water and filtering out the caffeine with activated charcoal (as in the Swiss Water Process), using carbon dioxide under high pressure, or using special solvents that bind to caffeine. Decaf is not completely caffeine-free, but the process removes the great majority of the caffeine, typically about 97 percent or more.

People have also made coffee-like drinks without any coffee at all, often when real coffee was too expensive or hard to get. The best known substitute is roasted chicory root, which became popular in France in the early 19th century, when trade blockades during the Napoleonic Wars made coffee scarce. Chicory coffee remains a tradition in New Orleans to this day. Other substitutes are made from roasted barley, rye, dandelion roots and even acorns. None of them contain caffeine, but they can give a similar dark, roasted taste.

Coffee and the Modern World

Coffee is one of the most widely traded agricultural products on the planet. Each year, farmers grow well over 150 million sacks of 60 kilograms each. Brazil is by far the biggest producer, followed by Vietnam, which grows mostly robusta. Colombia, Indonesia and Ethiopia are also among the major producers. Most of the world's coffee comes from millions of small family farms, and the price farmers receive can rise and fall sharply with the weather and world markets. Certification schemes such as Fairtrade were created partly to help growers earn a more stable income.

Coffee plants are also vulnerable. In the 19th century a fungal disease called coffee leaf rust destroyed the coffee plantations of Ceylon, today's Sri Lanka. Planters there switched to growing tea, which is why Sri Lanka is famous for its tea rather than its coffee. Today, climate change is a major worry. Arabica needs a narrow range of temperatures, and rising heat could shrink the land where it grows well. A 2019 study led by the Royal Botanic Gardens, Kew, found that around 60 percent of wild coffee species are threatened with extinction. These wild relatives matter because their genes could help breeders develop coffee plants that resist disease and heat.

Lesser-Known Coffee Facts

• Coffee leaves can also be brewed into a tea-like drink, which is traditional in parts of Ethiopia.
• Fresh coffee cherries are edible. The dried fruit skins, called cascara, are used to make a fruity infusion.
• Roasted coffee loses its freshness fairly quickly, because aroma compounds escape and react with oxygen. That is why many coffee lovers grind their beans just before brewing.
• Nordic countries such as Finland are regularly found near the top of the world's rankings for coffee drunk per person.
• Since 2015, the International Coffee Organization has promoted 1 October as International Coffee Day.

From a shrub in the Ethiopian highlands to plantations on several continents, from Sufi prayers in Yemen to busy cafés in every major city, coffee has shaped trade, conversation, art and daily routines for more than five centuries. Every cup carries the work of farmers, the chemistry of roasting and a long and sometimes surprising history.