The Story of a Cup of Coffee

From Bean to Cup - How coffee is grown, harvested, and roasted

A hot cup of coffee is not as simple as it may appear. Most people know that coffee comes from the coffee bean and are quite likely to have bought coffee beans in bulk. But what was the humble coffee bean before it was roasted and bagged? It must come from some type of plant. What kind of plant is the coffee bush? Or is it a tree? Do coffee beans grow like peas in a pod? Or are they more like peanuts in a shell? What eventually becomes coffee has to go though a lot of different processes before it becomes the world's favourite beverage. Most people are not even aware of the number of steps for the cultivation, harvesting, roasting, grinding and brewing of coffee.

Growing Coffee

This short plant with smooth oval leaves, in the genus coffea, blossoms with small white flowers that become a cherry-like fruit that starts out green, becomes yellow, ripens to red and can over-ripen to black. Each mature coffee cherry is about one and a quarter centimetres or about half an inch long and contains two seed kernels that end up as the coffee beans that are ground to make coffee, The coffee plant grows best in a moist cool, but frost-free, climate that occurs at higher altitudes of the tropics and subtropics.

Coffee Plant

The coffee plant grows best in organic topsoil mixed with pulverised volcanic debris in a locale with an average temperature of 24 C (75 F). The region should have a rainy season with about 127 cm (50 inches) of rainfall annually alternating with a dry season. Though the coffee plant can grow an any altitude from sea level to a max of 1830 m (6000 feet), of the two types, the Robusta bean grows best at low altitudes, while the higher-quality Arabica bean grows best above 460 m (1500 feet). Because strong winds tend to dehydrate the fruit, a coffee plant grows best when sheltered from the wind by other trees.

The coffee plant will not bear fruit for the first two years of its life; it may bear fruit in its third year; it will definitely bear fruit in its fourth year. The coffee plant will produce fruit at a maximum rate from its fifth through tenth year of life and may continue to bear some fruit right through its thirtieth year.

Harvesting the Coffee

The harvesting of coffee cherries is very labour intensive. There are two methods, the first being the picking of only ripe cherries from each branch and the second being a wholesale stripping of all berries from a branch onto a tarp below. The first method takes more time, but produces a better quality harvest -- also, the unripe cherries are left on the plant for picking later when they ripen. The second method must be timed to match the ripening of most of the coffee cherries on the plant. Some coffee plantations do use mechanical harvesters to remove all the cherries from the branches at one time.

The next step is to produce two green coffee beans from each cherry by removing the skin, the pulpy fruit and the mucilaginous parchment that surrounds the kernel and seeds. Either the wet or dry method can be used. The dry method works by the power of the sun upon layers of washed coffee cherries laid out on drying tables, cement slabs or plastic sheets. The cherries are raked periodically to turn them and are covered when it rains. After four weeks in the sun, the fruit dehydrates into a brittle shell. Some coffee processors use mechanical dryers that accomplish the same result in three to four days. A hulling machine removes the outer layers of the dried coffee cherries to reveal the green coffee bean.

The wet method begins by running the coffee cherries through a pulping machine within twenty-four hours after harvest. The machine removes the skin and most of the fruit pulp. The kernels are washed and are allowed to ferment in water. The pulp completely dissolves away from the kernel, leaving a parchment-covered green bean. The fermentation step can be skipped by using a machine called the demucilaginer that removes the mucilage layer mechanically. The beans then go through the drying process described above.

In a third unique method called kopi luwak in Indonesia and kape alamid or motit coffee in the Philippines, civet cats are fed ripe coffee cherries. The green coffee beans are retrieved from the animal's excrement, washed, dried and moved on to the roasting process.

Both of the last two methods produce the highest-quality coffee and make use of coffee cherries harvested by selective hand-picking of ripe cherries. The dry method, however, is the least expensive.

Roasting the Coffee Beans

Roasting the coffee beans is the next step toward your cup of hot coffee. The green coffee bean, though it contains all the elements of flavour, has no flavour itself. Roasting produces from those elements in the coffee bean the aromatic oils that we recognise as the aroma and taste of coffee.

Roasted Coffee Beans

You must not roast the bean too soon, though. A roasted coffee bean will retain its flavour for only two weeks after roasting, whereas a green coffee bean can be kept for two years and still be good for roasting. You want to roast the bean as closely to the time the bean will be ground and the coffee brewed as is possible. So, today, green beans are transported to the region where the coffee is to be sold and the roasting is done just before the bags of roasted coffee beans appear on the grocery shelves.

Coffee grown in different parts of the world in different ways require different patterns of roasting. Basically, though, the temperature must be monitored during the roast so that the bean is neither under-roasted, resulting in little flavour, nor over-roasted, where all the oils are burnt off. The interior of the bean must reach at least 204C (400F) and will achieve its own particular peak of flavour at some stage of time and temperature beyond that initial threshold.

Before the twentieth century, a coffee drinker would buy green coffee beans that were then roasted at home in cast iron pans or iron drums before grinding and brewing. Commercial roasting and the sale of roasted coffee beans became common in Europe and North America after World War One. The development of instant coffee also reduced the need for home roasting. In recent years, however, with the renewed interest in culinary arts, home roasting of coffee beans has returned as a kitchen hobby.

The majority of the coffee in the world today is roasted by commercial processors who produce tons of roasted coffee beans annually via automated machines. Green coffee beans are dumped, screened and weighed before riding conveyor belts to one of two types of roasters: hot-air and drum. Drums rotate over a heat source; hot-air roasters pump extremely hot air into layers of coffee beans. Both types operate at temperatures between 188C (370F) and 282C (540F). The beans stay in the roaster between three minutes and half an hour. When done, the roasted beans are cooled by air or a fine water mist.

The most common way for a roastmaster to determine whether a batch of coffee beans is sufficiently roasted is by sound. The popping sound of the "first crack" occurs around 204-207C (400-405F) and marks the beginning of the range for light roasts. A "second crack" designating the boundary between medium and dark roast occurs at 224-227c (435-440F). Another way to distinguish the level of roasting is by the colour of the bean, shifting from green to yellow to brown, with an oily sheen appearing at the highest temperatures. The smell of the roast is another measure, albeit more subjective.

Levels of Roasted Coffee Beans

The levels of roast and the resulting brew of coffee are well-defined:

  • Light, also known as Half-City, Cinnamon or New England Roast, is the American commercial standard for a light-bodied acidic coffee with little roast flavour.
  • Medium, also known as Full-City, Brown, American or Breakfast Roast, is the American specialty standard for a coffee that is less acidic and more balanced in aroma and roast flavour.
  • Full, also known as Continental, Viennese or High Roast, produces a coffee that is spicier and that has a heavier body than medium, with more of a roast flavour.
  • Dark Roast produces a coffee with an intense flavour and a heavy body.
  • Double French, done when the beans begin to smoke and lose some of their oils, produces a light-bodied coffee that has a strong roast flavour dominating the coffee flavour.

The flavour of roast coffee stays at its peak for one to seven days, though a good roast can keep for two weeks. Ground coffee, however, loses its flavour in two hours or less. The reason, of course, is the reason why you grind coffee - you're exposing more of the surface area to release the aromatic oils that mix with hot water. However, a side-effect of grinding is that those aromatic oils immediately begin to dissipate into the air.

The grind you pick for your roasted coffee beans will depend entirely on the brewing method you will be using. Selecting the perfect grinder is a whole other matter discussed at length elsewhere. For our purposes here, it's sufficient to say you'll want a grind varying from very fine to coarse. In ascending order of coarseness, you'll want a very fine almost-pulverised grind for Turkish coffee, a very fine grind for a filter coffee machine, a fine grind for an espresso or mocha machine, a medium grind for your percolator or cafetiere and a medium grind with some coarseness for a vacuum method brewer.

Compared to all the steps described here, brewing is simplicity itself: mix hot water and coffee grounds. Every brew method has a way to separate the grounds from the beverage. Add sugar, milk or cream, or drink it black.

Instant Coffee

A grind far more coarse than any you'd use to brew coffee is part of the process to make instant coffee. Roast beans are coarsely ground and placed into a series of extractor cells through which hot water is passed. The cells are constructed so that a thick coffee syrup eventually emerges. this syrup is converted into powder by one of two methods, either spray-drying, where the coffee syrup is sprayed into a cylinder with a continual stream of hot air and the residue collected at the bottom, or freeze-drying, where the syrup is frozen to about forty degrees below zero Centigrade, shattered and placed in a vacuum to evaporate the water. The result of both of these methods is a mixture of water-soluble coffee particles which is wetted and sieved to enforce a uniform size upon the powder particles. These soluble granules are then vacuum sealed inside glass or plastic containers along with some of the captured aroma and sold as instant coffee.

Decaffeinated coffee

Decaffeinated coffee is another choice for coffee drinkers. Caffeine, technically known as the chemical 1,3,7-trimethylxanthine, is a mild stimulant that is a natural component of cocoa, tea leaves, coffee beans and over sixty other plants. Scientific studies have proven that the total caffeine taken in by an individual drinking up to five cups of coffee per day is not harmful. Caffeine is added to carbonated soft drinks and is an ingredient in many pharmacological compounds and medications, including diet aids, cold and flu remedies and pain relievers. Some people would rather not include caffeine in their daily diet or it may be late at night and, from experience, people know that caffeine will keep them up all night when they would rather be sleeping. The answer then for these people who still like the taste of coffee is a decaffeinated blend.

The definition of decaffeinated coffee is instant coffee with no more than 0.3% caffeine and roast and ground coffee with no more than 0.1% caffeine. There are four similar methods to remove caffeine from green coffee beans, all of which use a liquid or gas to swell the bean, a solvent to extract the caffeine, a solvent remover to cleanse the bean of the solvent and a method of drying to return the bean to a moisture content suitable for roasting. One problem is that the solvent may also remove many of the aromatic oils needed for flavour and aroma - all four methods use some variation of a procedure by which the liquid or gas is cleansed of caffeine and allowed to return the other substances back into the beans.

Water, at high temperatures and pressures, is the most common solvent used to remove caffeine from coffee beans. Ethyl acetate, a naturally-occurring substance in fruits, and methylene chloride, also known as dichloromethane, are two chemicals used because of their low boiling points. Carbon dioxide gas will also act as a caffeine solvent, but only in its supercritical state between gas and liquid at the extraordinarily high pressure of 250 atmospheres, meaning that complex pressure containment is necessary for its use.

Coffee Farmers and Fair Trade

Whether regular or decaffeinated, your cup of coffee comes from the efforts of one of the twenty-five million farmers in one of the fifty developing countries where it's possible to grow the coffee plant. Over 70% of the world's coffee is grown on farms of only a few acres in size and most farmers sell their total annual harvest of a few bags of coffee beans locally to traders, cooperatives, processors and exporters. Farmers find they make more money cultivating and harvesting a high-yield low-quality crop rather than a low-yield high-quality one.

In the past, coffee manufacturers in the UK would purchase most of their green coffee beans from international exporters and only a small proportion directly from farmers and farmers' cooperatives. However, the purchase of coffee directly from the people who grow it helps farmers produce sustainable crops and ensures a long-term income for them and their families. The production of high-quality coffee can be encouraged by a willingness to pay a bit more to the farmer rather than parcel out the same amount among all the middlemen.

Environmental, social and economic issues are all addressed by FairTrade programmes that support coffee farmers directly with training, technical assistance and information about the possible markets for their coffee harvests. These activities all ensure a steady market for the coffee grower and a good supply of high-quality coffee for the consumer. In addition, manufacturers who address any health issues about coffee in addition to developing new products will further help the growth of a healthy market demand for coffee.

Specifically, FairTrade certification is done to help bring up standards for coffee farms. Direct-buying improves the farmer's income and promotes the cultivation of high-quality coffee. Any push to increase coffee consumption in the coffee-producing countries themselves is a direct benefit for those local and national economies. Farmers improve their social standing and become pillars of their local community. And all of that can come about because of you sipping your daily cup of coffee.

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