Science Fair Project Encyclopedia
Coffee as a drink, usually served hot, is prepared from the roasted seeds (beans) of the coffee plant.
Coffee bean types
There are two main species of the coffee plant; Coffea arabica is the traditional coffee, and considered superior in flavor. Robusta, which is higher in caffeine, can be cultivated in environments where Arabica will not thrive, leading to its use as an inexpensive substitute for Arabica in many commercial coffee products. Robusta is not usually consumed by itself, due to its bitter and acidic flavor. Higher quality Robustas are used as ingredients in some espresso blends.
Coffee is the world's second most widely traded product . Arabica coffees were traditionally named by the port they were exported from, the two oldest being Mocha and Java. The modern coffee trade is much more specific about origin, labeling coffees by country, region, and sometimes even the producing estate. Coffee aficionados may even distinguish auctioned coffees by lot number. The largest coffee exporting nation is Brazil, but in recent years, as the demand for coffee beans has risen, the coffee bean market has been flooded by large quantities of inexpensive but very low grade robusta beans from Vietnam , mostly destined for large industrial clients (instant coffee producers, etc.) where unappetizing appearance or aroma, or the presence of contaminating debris and so forth are less serious problems.
One unusual and very expensive variety of robusta is the Indonesian Kopi Luwak. The beans are collected from the droppings of the Common Palm Civet, whose digestive processes give it a distinctive flavour.
Although not well-known, certain types of coffee improve with age; they obtain a less acidic, more well-balanced flavor. Several coffee producers sell coffee beans that have been aged to 3 years, and there are several specialty stores (such as Toko Aroma in Bandung, Indonesia) which age their unroasted beans to 8 years.
The roasting process is integral to producing a savory cup of coffee. When roasted, the green coffee bean expands to nearly double its original size, changing in color and density. As the bean absorbs heat, the color shifts to yellow and then to a light "cinnamon" brown. During roasting oils appear on the surface of the bean. The roast will continue to darken until it is removed from the heat source.
At lighter roasts, the bean will exhibit more of its "origin flavor" - the flavors created in the bean by the soil and weather conditions in the location where it was grown. Coffee beans from famous regions like Java and Kenya are usually roasted lightly so their signature characteristics dominate the flavor. A roasting method native to the Ipoh town in Malaysia involves the inclusion of butter during the roasting process, producing a variety of roast known as the Ipoh "white" coffee.
As the beans darken to a deep brown, the origin flavors of the bean are eclipsed by the flavors created by the roasting process itself. At darker roasts, the "roast flavor" is so dominant that it can be difficult to distinguish the origin of the beans used in the roast. These roasts are sold by the degree of roast, ranging from "Light Cinnamon Roast" through "Vienna Roast" to "French Roast" and beyond. The dividing line between extremely dark roast and "burnt" is a matter of some debate. Contrary to popular belief, the darker roasts and more stronger flavored coffees do not deliver any more caffeine than lighter roasts. Major national coffee suppliers tailor their product to tastes in particular regions of the country; for instance, a can of ground coffee purchased in the Northeast or Northwest of the United States will contain a darker roast than an identically appearing can purchased in the central United States.
In the 19th century coffee was usually bought in the form of green beans and roasted in a frying pan. This form of roasting requires much skill to do well, and fell out of favor when vacuum sealing of pre-roasted coffee became possible. Unfortunately, because coffee emits CO2 for days after it is roasted, one must allow the coffee to get slightly stale before it can be vacuum sealed. For this reason two technologies have recently been employed: Illy has begun to use pressurized cans and many roasters bag whole beans immediately after roasting in bags with pressure release valves. Today home roasting is becoming popular again. Computerized drum roasters are available which simplify home roasting, and some home roasters will simply roast in an oven or in air popcorn poppers. Once roasted, coffee loses its flavor quickly, although being kept in the absence of oxygen can greatly delay the process. Although some prefer to wait 24 hours after roasting to brew the first cup, all agree that it begins to get off-flavors and bitterness about a week after roasting, even under ideal conditions.
The fineness of the grounds has a major impact on flavour, with finer grinding leading to a more intense and full flavour. The main reason to use coarser grounds is simply to prevent the grounds from being pushed through coarser filter types (such as the cafetière), or to allow the grounds to settle rapidly where there is no filter. The rate of deterioration increases when the coffee is ground, as a result of the greater surface area exposed. Until relatively recently, it was almost impossible to find whole beans in American stores, with ground coffee being the only variety available; with the rise of coffee as a gourment beverage, however, it has become much more popular to grind the beans at home before brewing, and there are many home appliances available which are dedicated to the process.
There are two methods of producing coffee grounds ready for brewing.
- Grinding: burr based with two revolving elements crushing or "tearing" the bean and with less risk of burning. Burr grinders can be either wheel or conical with the latter being quieter and having less chance of clogging. The grinding burrs in these machines wear rapidly, however, which makes them less popular in the home.
- Conical Burr Grinders preserve the most aroma and can grind very fine and very consistent. The intricate design of the steel burrs allow a high gear reduction to slow down the grinding speed. The slower the speed the less heat is imparted to the ground coffee thus preserving maximum amount of aroma. Because of the wide range of grind settings these grinders are ideal for all kinds of coffee equipment, Espresso, Drip, Percolators, French Press. The better Conical Burr Grinders can also grind extra fine for the preparation of Turkish coffee. Grinding speed is generally below 500 rpm.
- Burr Grinders with disk type burrs grind at a faster speed than conical burr grinders and create a bit more warmth in the coffee (10,000 to 20,000 rpm). They are the most economical way of getting a consistent grind in a wide range of applications. They are well suited for most home pump espresso machines. However they do not grind as fine as Conical Burr Grinders.
- Chopping: Most modern 'grinders' actually chop the bean into pieces (and some coffee drinkers merely use a home blender to do the job). Although giving a similar result to proper grinding and enjoying a much longer life before wearing out the blades, purists suggest that the result is less effective in producing a homogenously ground result.
- Blade Grinders “smash” the beans with a blade at very high speed (20,000 to 30,000 rpm). The ground coffee has larger and smaller particles and is warmer than ground coffee from burr grinders. Blade grinders create “coffee dust” which can clog up sieves in espresso machines and French presses. These type of grinders are suitable for drip coffee makers. They also can do a great job for grinding spices and herbs. They are not recommended for use with pump espresso machines.
- Pounding: Turkish coffee is produced from an infusion where the beans are pounded nearly to dust in a mortar and pestle. It produces grounds which are too fine for other preparation methods.
Coffee can be brewed in several different ways, but these methods fall into four main groups depending upon how the water is introduced to the coffee grounds. If the method allows the water to pass only once through the grounds, the resulting brew will contain mainly the more soluble components (including caffeine), whereas if the water is repeatedly cycled through the beans (as with the common percolator), the brew will contain more of the relatively less soluble compounds found in the bean; as these tend to be more bitter, that type of process is less favored by coffee afficianados.
Coffee in all these forms is made with coffee grounds (coffee beans that have been roasted and ground) and hot water, the grounds either remaining behind or being filtered out of the cup or jug after the main soluble compounds have been removed. The fineness of the grinding required differs by the method of intended drink production.
- Turkish coffee. A very early method of making coffee, still used in the Middle East, North Africa, Turkey and Greece, is to put the water together with very finely ground coffee in a narrow-topped pot, called an ibrik (Arabic), cezve (Turkish) or dzezva (Serbo-Croatian), and allow it to briefly come to the boil. It is sometimes drunk sweet, in which case sugar is added to the pot and boiled with the coffee; it also often flavoured with cardamom. The result is small cups of very strong coffee with a foam on the top and thick layer of sludgy grounds at the bottom of the cup.
- "Cowboy coffee" is made by simply boiling coarse grounds with water in a pot, letting the grounds settle and pouring off the liquid to drink. While the name suggests that this method was derived or used by cowboys, presumably on the trail around a campfire, it is also frequently seen among others who do not drink coffee frequently and lack any specialized equipment for otherwise brewing.
- Espresso is made with pressurised hot water which converts to steam within a tightly packed container of very finely ground extremely darkly roasted grounds, during the brewing process. It can be served alone (often after an evening meal), and is the basis for many coffee drinks. It is one of the strongest tasting forms of coffee regularly consumed, with a distinctive flavour and crema, the stiff foam standing over the liquid. Classically, in Europe, the crema was the point of the exercise, rather than the liquid below it in the cup.
- A Percolator (or mocha pot) is a three-chamber design which boils water in the lower section and forces the boiling water through the separated coffee grounds in the middle section. The resultant, almost espresso strength, coffee (although without the crema) is collected in the upper section. It usually sits directly on a heater or stove. Some models feature a glass or plastic top to view the coffee as it is forced up.
- Drip brew (or filter coffee) is made by letting hot water drip onto coffee grounds held in a filter (paper or perforated metal). Strength varies according to the ratio of water to coffee, but is typically weaker than espresso.
- The common electric percolator which was almost universal prior to the 1970s and is still popular today differs from the pressure percolator described above, in that it uses the pressure of the boiling water to force it to a chamber above the grounds, but relies on gravity to pass the water down through the grounds, where it then repeats the process until shut off by an internal timer. The coffee produced is held in low esteem by coffee afficianados because of this multiple pass process.
- A French press (or cafetière) is a tall narrow glass cylinder with a plunger that includes a filter. The coffee and hot water are mixed in the cylinder (normally for a few minutes) before the plunger, in the form of a metal foil, is depressed, leaving the coffee at the top ready to be poured.
- Coffee bags (akin to tea bags) are much rarer than their tea equivalents, as they are much bulkier (more coffee is required in a coffee bag than tea in a tea bag).
Electronic coffee makers boil the water and brew the infusion with little human assistance and sometimes according to a timer. Some even grind the beans automatically before brewing. Connoisseurs shun such conveniences as compromising the flavor of the coffee; they prefer freshly ground beans and traditional brewing techniques.
- Black coffee is drip brew, percolated or French press style coffee served without milk; sugar may be added.
- White coffee is coffee with milk added after preparation, perhaps with sugar.
- Cappuccino comprises equal parts espresso, steamed milk, and frothed milk in 4.5 oz. (served in a 5 oz. cup), is occasionally garnished with powdered cinnamon, other spices, or cocoa.
- Caffè e latte (or caffelatte or in America plainly latte, which is Italian for "milk" ) is espresso with steamed milk, traditionally topped with frothed milk. It is not as strong as a Cappuccino because of a greater quantity of milk.
- A Café au lait is like a Latte except that drip-brewed coffee is used instead of espresso, with an equal amount of milk. Sugar is added to taste.
- Americano style coffee is made with espresso (normally several shots) and hot water to give a similar strength (but different flavour) from drip brewed coffee.
- Iced coffee is normally served with milk and sugar.
- Flavoured coffee: In some cultures, flavored coffees are common. Chocolate is a common additive that is either sprinkled on top or added to the coffee to imitate the taste of Mocha. Other flavourings include spices such as cinnamon, nutmeg, cardamom or Italian syrups.
- Irish coffee is hot brewed coffee spiked with whiskey and with a layer of cream on the top.
- Indian (Madras) filter coffee, particularly common in the south of the country, is prepared off rough ground dark roasted coffee beans (Arabica, PeaBerry). The coffee is drip brewed for a few hours in a traditional metal Coffee filter before being served with milk and sugar. The ratio is usually (1/4 - decoction, 3/4 - milk).
- Vietnamese style coffee is another form of drip brew. In this form, hot water is allowed to drip though a metal mesh into a cup with the resulting strong brew being poured over ice into a glass containing sweetened condensed milk. Due to the high volume of coffee grounds required to make strong coffee in this fashion the brewing process is quite slow.
- Greek coffee or Turkish coffee is made by boiling finely ground coffee and water together in an ibrik, which is a long-handled, open, brass or copper pot. When done, it is poured directly into tiny demitasse cups, along with the fine grounds. The coffee is then allowed to settle before consumption. Spice and sugar are often added into the mix.
- Kopi tubruk is an Indonesian-style coffee similar in presentation to the Greek coffee. However, kopi tubruk is made from coarse coffee grounds, and is boiled together with a solid lump of sugar. It is popular on the islands of Java and Bali and their surroundings.
- A demitasse is, somewhat similar to an espresso without the crema, a small cup of strong black coffee, often served after a meal.
- Coffee Pots come in many shapes and sizes. Traditional coloring uses brown or black colored pots for regular caffeinated coffee, and orange is used for decaffeinated coffee.
- Brewed coffee left on the warmer will deteriorate rapidly in flavor; even at room temperature deterioration will occur. However, if kept in an oxygen free environment, it can last almost indefinitely at room temperature; sealed containers of brewed coffee are sometimes commercially available in food stores in America or Europe.
- Chocolate covered roasted coffee beans are available as a confection; unless the beans have been decaffeinated, these will deliver the same caffeine content as brewed coffee and have the same physiological effects.
Instant and soluble coffee has been dried into soluble powder or granules, which can be quickly dissoved in hot water for consumption. It is distinct from fresh coffee and is commercially prepared differently, by vigorous extraction of almost all soluble material from the ground roasted beans. This process naturally produces a different mix of components than home brewing; in particular, the percentage of caffeine in instant coffee is less, and less desirable bitter flavor components are more present. Sometimes lower grade beans are used. Opinions on instant coffee range from "intolerable imposter" to "reasonable alternative" to "better than the real thing", and in some areas of the world it is seen as a sophisticated beverage popular in America. Some varieties are freeze dried in an effort to maintain a flavor more similar to brewed coffee. In countries where it is popular it is often referred to as "Café Puro" to the horror of coffee aficionados. Instant coffee is also convenient for preparing iced coffee, which is popular in warmer climates and/or hot seasons.
Liquid coffee concentrate
Another type of pre-made coffee is liquid coffee concentrate. It is described as having a flavor about as good as low-grade robusta coffee. It costs about 10 cents a cup to produce. It's primary use is in large institutional situations where coffee needs to be produced for thousands of people at the same time. The machines used to process it can handle up to 500 cups an hour, or 1,000 if the water is pre-heated.
Social aspects of coffee
The United States is the largest market for coffee, followed by Germany. Finland consumes the most coffee per capita. Coffee is so popular in The Americas, the Middle East, and Europe that many restaurants specialize in coffee; these are called "coffeehouses" or "cafés". Most cafés also serve tea, sandwiches, pastries, and other light refreshments. Some cafés are miniature shacks that specialize in coffee to go for hurried travelers. Some travelers transport their coffee in vacuum bottles, which can keep a beverage hot for hours.
In some countries, notably in northern Europe, coffee parties are a popular form of entertaining. Besides coffee, the host or hostess at the coffee party also serves cake and pastries, hopefully homemade.
The stimulant properties of coffee and the fact that coffee does not adversely impact higher mental functions causes coffee to be associated with white collar jobs. Social habits involving coffee include the morning coffee and coffee breaks.
See also dunk (biscuit) for the habit of dipping one's biscuit or cake into one's coffee.
Coffee as a stimulant
Coffee contains caffeine, which acts as a stimulant. For this reason, it is often consumed in the morning, and during working hours. Students preparing for examinations with late-night "cram sessions" use coffee to maintain their concentration. Office workers take a "coffee break" whenever their energy is diminished.
Recent research has uncovered additional stimulating effects of coffee which are not related to the caffeine. Coffee contains an as yet unknown chemical agent which stimulates the production of cortisone and adrenaline, two stimulating hormones.
For occasions when one wants to enjoy the flavor of coffee with less stimulation, decaffeinated coffee, also called decaf, is available. This is coffee from which most of the caffeine has been removed by water or a chemical solvent such as trichloroethylene ("tri"). There are also tisanes that resemble coffee in taste but contain no caffeine (see below).
Coffee dependence is widespread and withdrawal symptoms are real. See the caffeine article for more on the pharmacological effects of caffeine.
Coffee increases the effectiveness of pain killers -- especially migraine medications -- and can rid some people of asthma. Some of the beneficial effects may be restricted to one sex, for instance it has been shown to reduce suicide for women, and prevent gallstones and gallbladder disease in men. It also reduces the incidence of diabetes in both sexes, but reduces the risk by about 30% in women and over 50% in men. Coffee can also reduce the incidence of liver cirrhosis and prevent colon and bladder cancers. Coffee can reduce the risk of hepatocellular carcinoma, a variety of liver cancer (Inoue, 2005). Finally, coffee reduces the incidence of heart disease, though whether this is simply because it rids your blood of excess fat or because of its stimulant effect is unknown.
There are of course the reasons most people drink coffee such as its ability to increase short term recall and increase IQ. It also changes the metabolism of a person so that their body burns a higher proportion of lipids to carbohydrates, which can help athletes avoid muscle fatigue.
Some of these health effects are realized by as little as 4 cups a day (24 oz), but others kick in at 6 or more cups a day (32 oz or more).
NOTE: Health benefits of decaffeinated coffee have not been found.
Many coffee drinkers are familiar with "coffee jitters", a nervous condition that occurs when one has had too much caffeine. Coffee can also increase blood pressure among those with high blood pressure, but follow-up studies showed that coffee still decreased the chance of dying from heart disease in the aggregate. Coffee can also cause insomnia in some, while paradoxically it helps a few sleep more soundly. It can also cause anxiety and irritability, in some with excessive coffee consumption, and some as a withdrawal symptom. There are also sex specific effects, in some PMS sufferers it increases the symptoms, and it can reduce fertility in women, also it may increase the risk of osteoporosis in postmenopausal women, and there may be risks to a fetus if a pregnant woman drinks 8 or more cups a day (48 oz or more).
A February 2003 Danish study of 18,478 women linked heavy coffee consumption during pregnancy to significantly increased risk of stillbirths (but no significantly increased risk of infant death in the first year). "The results seem to indicate a threshold effect around four to seven cups per day," the study reported. Those who drank eight or more cups a day (48 oz or more) were at 220% increased risk compared to non-drinkers. This study has not yet been repeated but has caused some doctors to caution against excessive coffee consumption during pregnancy.
A study published in 2004 in the American Journal of Clinical Nutrition (abstract available online at ) tried to discover why the beneficial and detrimental effects of coffee are conflicting and found that consumption of coffee is associated with significant elevations in biochemical markers of inflammation. This is a detrimental effect of coffee on the cardiovascular system which may explain why coffee has so far only been shown to help the heart at levels of 4 or less cups a day (20oz or less).
Caffeine is toxic in high enough doses. It is unlikely though, that a toxic dose will be ingested in the form of common drinks. In concentrated forms such as pills or powders it can be taken in sufficient quantities to cause vomiting, unconsciousness, and even death. A single box of caffeine pills can be fatal if taken at one time.
The health risks of decaffeinated coffee have been studied, with varying results. One variable is the type of decaffeination process used; while some involve the use of organic solvents which may leave residual traces, others rely on steam.
Coffee as a fertilizer
Spent coffee grounds are a good fertilizer in gardens because of their high nitrogen content. Coffee grounds also contain potassium, phosphorus and many other trace elements that aid plant development. Many gardeners report that roses love coffee grounds and when furnished with the same become big and colorful. When added to a compost pile, spent coffee grounds compost very rapidly.
Coffee grounds can be obtained inexpensively (usually free) from local coffee shops. Large coffee shop chains may have a policy of composting coffee grounds or giving them away to those who ask.
- Just About Coffee - Detailed information website about coffee
- CoffeeFaq.com: Information about the various major methods of coffee preparation
- The Coffee FAQ: Guide to coffee, coffee preparation coffee roasting, and coffee paraphernalia
- about.com: Blade vs Burr grinders
- TooMuchCoffee: The European Coffee and Espresso Resource Offers non-commercial articles and discussion about coffee, coffee preparations and homeroasting.
- Coffeekid.com: Information about coffee making, and essays on various aspects of coffee presentation.
- The Open Coffee Library: An encyclopedia about coffee with links and quotations from other coffee-related websites.
- Wisborg, Kirsten et al. Maternal consumption of coffee during pregnancy and stillbirth and infant death in first year of life: prospective study. British Medical Journal 2003 (326): 420 (22 February). Online copy.
- Inoue, Manami et al. (2005). Influence of Coffee Drinking on Subsequent Risk of Hepatocellular Carcinoma: A Prospective Study in Japan. Journal of the National Cancer Institute, Vol. 97, No. 4, 293-300.
- regarding liquid coffee concentrate: Wall St. Journal, March 21st, 2005, page C4, Commodities Report
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