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Tea Though it has lent its name to many other infusions, tea tea - from the Chinese word - from the Chinese word cha cha - is a drink prepared from the green leaves of a kind of camellia. Young tea leaves turn out to be as packed with interesting defensive chemicals as any spice. Beginning in southwest China around 2,000 years ago, people learned how to use physical pressure, mild heat, and time to coax a number of different flavors and colors from the tea leaf. Tea became a staple of the Chinese diet around 1000 - is a drink prepared from the green leaves of a kind of camellia. Young tea leaves turn out to be as packed with interesting defensive chemicals as any spice. Beginning in southwest China around 2,000 years ago, people learned how to use physical pressure, mild heat, and time to coax a number of different flavors and colors from the tea leaf. Tea became a staple of the Chinese diet around 1000 CE CE. In 12th-century j.a.pan, Buddhist monks who valued tea as an aid to long hours of study found that tea itself was worthy of their contemplation. They developed the formal tea ceremony, which remains remarkable for the attention it pays to the simplest of preparations, an infusion of leaves in water.

The History of Tea Tea in China The tea tree, The tea tree, Camellia sinensis, Camellia sinensis, is native to Southeast Asia and southern China, and its caffeine-rich, tender young leaves were probably chewed raw long before recorded history. The preparation of tea leaves for infusion in water evolved slowly. There's evidence that by the 3rd century is native to Southeast Asia and southern China, and its caffeine-rich, tender young leaves were probably chewed raw long before recorded history. The preparation of tea leaves for infusion in water evolved slowly. There's evidence that by the 3rd century CE CE the leaves were boiled and then dried for later use, and that by the 8th century they were also stir-fried before drying. These techniques would give green or yellow-green leaves and infusions, and mild but bitter and astringent flavor. More strongly flavored and orange-red teas like modern oolongs were developed around the 17th century, probably beginning with the accidental observation that the leaves develop a distinctive aroma and color when they're allowed to wilt or are pressed before being dried. It was around this time that China began to trade extensively with Europe and Russia, and the new, more complex style of tea conquered England, where consumption rose from 20,000 pounds in 1700 to 20 million in1800. The strong "black" tea that's most familiar in the West today is a relatively recent invention, the result of intensive pressing; the Chinese developed it in the 1840s specifically for export to the West. the leaves were boiled and then dried for later use, and that by the 8th century they were also stir-fried before drying. These techniques would give green or yellow-green leaves and infusions, and mild but bitter and astringent flavor. More strongly flavored and orange-red teas like modern oolongs were developed around the 17th century, probably beginning with the accidental observation that the leaves develop a distinctive aroma and color when they're allowed to wilt or are pressed before being dried. It was around this time that China began to trade extensively with Europe and Russia, and the new, more complex style of tea conquered England, where consumption rose from 20,000 pounds in 1700 to 20 million in1800. The strong "black" tea that's most familiar in the West today is a relatively recent invention, the result of intensive pressing; the Chinese developed it in the 1840s specifically for export to the West.

The Spread of Tea Production Until the late 19th century, all tea in world trade was China tea. But when China began to resist Britain's practice of paying for its expensive tea habit with opium, the British intensified tea production in their own colonies, particularly India. For warm regions they cultivated an indigenous variety, Until the late 19th century, all tea in world trade was China tea. But when China began to resist Britain's practice of paying for its expensive tea habit with opium, the British intensified tea production in their own colonies, particularly India. For warm regions they cultivated an indigenous variety, Camellia sinensis Camellia sinensis var. var. a.s.samica, a.s.samica, or a.s.sam tea, which has more phenolic compounds and caffeine than China tea and produces a stronger, darker black tea. They planted the hardier China types in the Himalayan foothills of Darjeeling and at high elevations in the south. India is now the world's largest tea producer. or a.s.sam tea, which has more phenolic compounds and caffeine than China tea and produces a stronger, darker black tea. They planted the hardier China types in the Himalayan foothills of Darjeeling and at high elevations in the south. India is now the world's largest tea producer.

Today about three-quarters of the tea produced in the world is black tea. China and j.a.pan still produce and drink more green tea than black.

The Tea Leaf and Its Transformation A fresh tea leaf tastes bitter and astringent, and not much else. This is a reflection of the fact that its major chemical component, even more abundant than its structural materials, is a host of bitter and astringent phenolic substances whose purpose is to make the leaf unattractive to animals. And its aromatic molecules are locked up in nonvolatile combinations with sugar molecules. Green tea retains many of the qualities of the fresh leaf. But the key to making oolong and black teas is encouraging the leaf's own enzymes to transform these austere defensive materials into very different, delightful molecules. A fresh tea leaf tastes bitter and astringent, and not much else. This is a reflection of the fact that its major chemical component, even more abundant than its structural materials, is a host of bitter and astringent phenolic substances whose purpose is to make the leaf unattractive to animals. And its aromatic molecules are locked up in nonvolatile combinations with sugar molecules. Green tea retains many of the qualities of the fresh leaf. But the key to making oolong and black teas is encouraging the leaf's own enzymes to transform these austere defensive materials into very different, delightful molecules.

How Tea Enzymes Create Flavor, Color, and Body The period of enzyme activity during tea-making has traditionally been called "fermentation," but it doesn't involve any significant microbial activity. In tea-making, "fermentation" means enzymatic transformation. It occurs when the tea maker presses the leaves to break open their cells, and then allows the leaves to sit for some time while the enzymes do their work. The period of enzyme activity during tea-making has traditionally been called "fermentation," but it doesn't involve any significant microbial activity. In tea-making, "fermentation" means enzymatic transformation. It occurs when the tea maker presses the leaves to break open their cells, and then allows the leaves to sit for some time while the enzymes do their work.

There are two general kinds of enzymatic transformation in making tea. One is the liberation of a large range of aroma compounds, which in the intact leaf are bound up with sugars and so can't escape into the air. When the cells are crushed, enzymes break the aroma-sugar complex apart. This liberation makes the aroma of oolong and black teas fuller and richer than the aroma of green teas.

The second transformation builds large molecules from small ones, and thereby modifies flavor, color, and body. The small molecules are the tea leaf's abundant supply of three-ring phenolic compounds, which are astringent, bitter, and colorless. The leaf's browning enzyme, polyphenoloxidase, uses oxygen from the air to join the small phenolic molecules together into larger complexes (p. 269). A combination of two phenolics gives a kind of molecule (theaflavin) that's yellow to light copper in color, less bitter but still astringent. Complexes of from three to ten of the original phenolics are orange-red and less astringent (thearubigens). Even larger complexes are brown and not astringent at all. The more the tea leaves are pressed, and the longer they're allowed to sit before the enzymes are killed by heating, the less bitter and astringent and the more colored they become. In oolong teas, about half of the small phenolics have been transformed; in black teas, about 85%.

The red and brown phenolic complexes - and another complex, between double-ring molecules of caffeine and the theaflavins - lend body to brewed tea, because they're large enough to obstruct each other and slow the movement of the water.

The evolution of tea taste. The fresh tea leaf contains rich stores of simple phenolic compounds ( (catechin, left) left) that are colorless and bitter but not astringent. When the tea leaf is bruised or rolled, leaf enzymes and oxygen combine the simple compounds into larger ones with different colors and tastes. Brief enzyme action produces a yellowish compound that are colorless and bitter but not astringent. When the tea leaf is bruised or rolled, leaf enzymes and oxygen combine the simple compounds into larger ones with different colors and tastes. Brief enzyme action produces a yellowish compound(theaflavin, center) center) that is both very bitter and astringent. More extensive enzyme action produces a compound that is both very bitter and astringent. More extensive enzyme action produces a compound(theaflavin digallate, right) right)that is moderately bitter and astringent. As the phenolic molecules get larger, they get progressively darker and milder.

Making Tea The Tea Plant and Its Leaves The best tea is made from the plant's small young shoots and unopened leaf buds, which are the most tender and vulnerable and contain the highest concentrations of chemical defenses and related enzymes. The choice "pluck" is the terminal bud and two adjacent leaves. Most tea is now harvested by machine, and therefore contains a large proportion of older and less flavorful leaves. The best tea is made from the plant's small young shoots and unopened leaf buds, which are the most tender and vulnerable and contain the highest concentrations of chemical defenses and related enzymes. The choice "pluck" is the terminal bud and two adjacent leaves. Most tea is now harvested by machine, and therefore contains a large proportion of older and less flavorful leaves.

Tea Manufacturing The production of tea involves several different steps, some standard and some optional. The production of tea involves several different steps, some standard and some optional.

The newly harvested leaves may be allowed to "wither," or sit and wilt for minutes or hours. Withering causes them to shift their metabolism in ways that change their flavor, and to become physically more fragile. The longer the withering, the deeper the flavor and color of the leaves and the brew they make.

The leaves are almost always "rolled," or pressed to break down the tissue structure and release the cell fluids. If the leaves are rolled while they're still raw, this allows the leaf enzymes and oxygen to transform the cell fluids and generate additional flavor, color, and body.

The leaves may be heated to inactivate their enzymes and stop the enzymatic production of flavor and color. High dry heat will also generate flavor.

The leaves are heated to dry them out and preserve them for long keeping.

The dry leaves are sieved and graded by piece size, which ranges from whole leaves to "dust." The smaller the piece, the faster the extraction of color and flavor.

Major Tea Styles The Chinese developed a half-dozen different styles of tea. Three of them account for most of the tea consumed in the world. The Chinese developed a half-dozen different styles of tea. Three of them account for most of the tea consumed in the world.

Green Tea Green tea preserves some of the original qualities of the fresh leaf, while heightening them and rounding them out. It's made by cooking the fresh or briefly withered leaves to inactivate their enzymes, then pressing them to release their moisture, and drying them in hot air or on a hot pan. In China, the cooking is done on a hot pan, and this "pan-firing" produces aroma molecules characteristic of roasted foods (pyrazines, pyrroles) and a yellow-green infusion. In j.a.pan, the cooking is done with steam, which preserves more of the gra.s.sy flavor and green color in both leaf and tea. Green tea preserves some of the original qualities of the fresh leaf, while heightening them and rounding them out. It's made by cooking the fresh or briefly withered leaves to inactivate their enzymes, then pressing them to release their moisture, and drying them in hot air or on a hot pan. In China, the cooking is done on a hot pan, and this "pan-firing" produces aroma molecules characteristic of roasted foods (pyrazines, pyrroles) and a yellow-green infusion. In j.a.pan, the cooking is done with steam, which preserves more of the gra.s.sy flavor and green color in both leaf and tea.

Oolong Tea Oolong tea is made by allowing some modest enzyme transformation of leaf juices. The leaves are withered until they become significantly wilted and weakened. Then they are lightly agitated to bruise the leaf edges, allowed to rest for a few hours until enzyme action has turned the bruised edges red, pan-fired at a high temperature, rolled, and finally dried gently, at temperatures just below 212F/ 100C. Oolong tea brews to a light amber color with a distinctive fruity aroma. Oolong tea is made by allowing some modest enzyme transformation of leaf juices. The leaves are withered until they become significantly wilted and weakened. Then they are lightly agitated to bruise the leaf edges, allowed to rest for a few hours until enzyme action has turned the bruised edges red, pan-fired at a high temperature, rolled, and finally dried gently, at temperatures just below 212F/ 100C. Oolong tea brews to a light amber color with a distinctive fruity aroma.

Tea. The choicest pluck consists of the bud tip and two youngest leaves of each branch of the tea bush.

Making Green, Oolong, and Black Teas Black Tea Black tea is made by allowing a profound enzymatic transformation of the leaf fluids. The leaves are withered for hours, rolled repeatedly for as much as an hour, then are allowed to rest for between one and four hours, during which enzyme action turns them a coppery brown and causes them to emit the aroma of apples. Finally, the leaves are air-dried at temperatures around 100C, and become quite dark. Black tea is made by allowing a profound enzymatic transformation of the leaf fluids. The leaves are withered for hours, rolled repeatedly for as much as an hour, then are allowed to rest for between one and four hours, during which enzyme action turns them a coppery brown and causes them to emit the aroma of apples. Finally, the leaves are air-dried at temperatures around 100C, and become quite dark.

Tea Flavor The taste of tea, a lively, mouthfilling quality, comes from several different sources. Tea is mildly acid and bitter and contains traces of salt. It's also rich in a unique amino acid, theanine, which is itself sweet and savory, and partly breaks down during manufacturing to savory glutamic acid. Chinese green teas also contain synergizers of savoriness (GMP and IMP, p. 342). Finally, bitter caffeine and astringent phenolics bond to and take the edge off each other and produce the impression of a stimulating but not harsh body. This effect is especially important to the taste of black teas, in which it's called "briskness." The taste of tea, a lively, mouthfilling quality, comes from several different sources. Tea is mildly acid and bitter and contains traces of salt. It's also rich in a unique amino acid, theanine, which is itself sweet and savory, and partly breaks down during manufacturing to savory glutamic acid. Chinese green teas also contain synergizers of savoriness (GMP and IMP, p. 342). Finally, bitter caffeine and astringent phenolics bond to and take the edge off each other and produce the impression of a stimulating but not harsh body. This effect is especially important to the taste of black teas, in which it's called "briskness."

The aromas of different teas are strikingly different. In green teas, early application of heat prevents much enzyme activity in the leaves. Steam heat gives gra.s.sy and seaweed, sh.e.l.lfish notes to j.a.panese green teas (the sea notes from dimethyl sulfide), while pan-firing and drying produce moresavory, toasted notes in Chinese green teas. In oolong and black teas, enzyme activity liberates floral and fruity aroma molecules from their odorless storage forms, and produces a much richer, stronger aroma (more than 600 volatiles have been identified in black tea).

Some Prized and Unusual TeasHere are a number of teas made in unusual ways, with unusual qualities: White tea: a Chinese green tea made almost exclusively from buds whose hairs make them look white, withered for two to three days, sometimes steamed, then dried without rolling.

Pu-erh: a Chinese green tea that is made in the usual way, then moistened and fermented in heaps for some time by a variety of microbes. All of its phenolic contents are converted into nonastringent thearubigens and brown complexes, and it develops a complex, spicy, clove aroma.

Lapsang souchong: a Chinese black tea, dried over smoky pine fires.

Scented teas: Chinese teas of various types, scented by being held for 812 hours in the same container with flowers, including jasmine, ca.s.sia bud, rose, orchid, and gardenia. The packaged tea may include 12% flower petals.

Gyokura and kabesucha: j.a.panese green teas made from shoots that have been covered with bamboo boxes and almost completely shaded for the two weeks before harvest. They develop a higher content of carotenoid pigments that contribute violet notes to the unique "covered aroma."

Hoji-cha: j.a.panese green tea of standard grade that is roasted at high temperatures (360F/180C), which triples the volatile content and so boosts flavor.

OPPOSITE: Making green, oolong, and black teas. Variations in processing produce very different colors and flavors from the same fresh leaves. Making green, oolong, and black teas. Variations in processing produce very different colors and flavors from the same fresh leaves.

Cooks exploit tea flavor in a number of different preparations: marinades and cooking liquids, ices and ice creams, in steamed foods, and as a source of aromatic smoke (e.g., Chinese tea-smoked duck).

Keeping and Brewing Tea Well-made tea is fairly stable and can be stored for several months in an airtight container that is kept cool and dark. Tea quality does eventually deteriorate thanks to the effects of oxygen and some residual enzyme activity; aroma and briskness are lost, and the color of black tea infusions becomes less orange-red, more dull brown. Well-made tea is fairly stable and can be stored for several months in an airtight container that is kept cool and dark. Tea quality does eventually deteriorate thanks to the effects of oxygen and some residual enzyme activity; aroma and briskness are lost, and the color of black tea infusions becomes less orange-red, more dull brown.

Teas are brewed in various ways in different parts of the world. In the West, a relatively small quant.i.ty of black tea leaves - a teaspoon per 6-oz cup/25 gm per 180 ml - is brewed once, for several minutes, then discarded. In Asia, a larger quant.i.ty of leaves of any tea - as much as a third the volume of the pot - is first rinsed with hot water, then infused briefly several times, with the second and third infusions offering more delicate, subtle flavor balances. The infusion time ranges from 15 seconds to 5 minutes, and depends on two factors. One is leaf size; small particles and their great surface area require less time for their contents to be extracted. The other is water temperature, which in turn varies depending on the kind of tea being brewed. Both oolong and black teas are infused in water close to the boil, and relatively briefly. Green tea is infused longer in much cooler water, 160110F/7045C, which limits extraction of its still abundant bitter and astringent phenolics, and minimizes damage to its chlorophyll pigment.

In a typical 35 minute infusion of black tea, about 40% of the leaf solids are extracted into the water. Caffeine is rapidly extracted, more than three quarters of the total in the first 30 seconds, while the larger phenolic complexes come out much more slowly.

Serving Tea Once tea is properly brewed, the liquid should be separated from the leaves immediately; otherwise extraction continues and the tea gets harsh. All kinds of tea are best drunk fresh; as they stand, their aroma dissipates, and their phenolic components react with dissolved oxygen and each other, changing the color and taste. Once tea is properly brewed, the liquid should be separated from the leaves immediately; otherwise extraction continues and the tea gets harsh. All kinds of tea are best drunk fresh; as they stand, their aroma dissipates, and their phenolic components react with dissolved oxygen and each other, changing the color and taste.

Tea is sometimes mixed with milk. When it is, the phenolic compounds immediately bind to the milk proteins, become unavailable to bind to our mouth surfaces and salivary proteins, and the taste becomes much less astringent. It's best to add hot tea to warm milk, rather than vice versa; that way the milk is heated gradually and to a moderate temperature, so it's less likely to curdle.

Lemon juice is sometimes added to tea to bolster its tartness and add the fresh citrus note to its aroma. It also lightens the color of brewed black tea by altering the structure of the red phenolic complexes (the complexes are weak acids themselves, and take up hydrogen ions from the lemon juice). Alkaline brewing water, conversely, tends to produce blood-red infusions from black tea, and can even make green tea red.

Iced Tea Iced tea is the most popular form of tea in the United States; it first caught on at the 1904 World's Fair in steamy St. Louis. It's made by brewing tea with about half-again as much dry tea per cup, to compensate for the later dilution by melting ice. The addition of ice to normally brewed tea tends to make the tea cloudy, due to the formation of particles of a complex between caffeine and theaflavin. The way to avoid this is to brew the initial tea at room or refrigerator temperature, over several hours. This technique extracts less caffeine and theaflavin than brewing in hot water, so the caffeine-theaflavin complexes don't form in sufficient quant.i.ties to become visible in the chilled tea. Iced tea is the most popular form of tea in the United States; it first caught on at the 1904 World's Fair in steamy St. Louis. It's made by brewing tea with about half-again as much dry tea per cup, to compensate for the later dilution by melting ice. The addition of ice to normally brewed tea tends to make the tea cloudy, due to the formation of particles of a complex between caffeine and theaflavin. The way to avoid this is to brew the initial tea at room or refrigerator temperature, over several hours. This technique extracts less caffeine and theaflavin than brewing in hot water, so the caffeine-theaflavin complexes don't form in sufficient quant.i.ties to become visible in the chilled tea.

Coffee Coffee trees are native to east Africa, and were probably first valued for their sweet cherry-like fruits and for their leaves, which could be made into a kind of tea. Even today an infusion of the dried fruit pulp is enjoyed in Yemen, where the seeds or "beans" were apparently first roasted, ground, and infused in the 14th century. Our word coffee comes from the Arabic qahwah, qahwah, whose own origin is unclear. The coffee tree was taken to south India around 1600, from India to Java around 1700, and from Java (via Amsterdam and Paris) to the French Caribbean shortly thereafter. Today Brazil, Vietnam, and Colombia are the largest exporters of coffee; African countries contribute about a fifth of world production. whose own origin is unclear. The coffee tree was taken to south India around 1600, from India to Java around 1700, and from Java (via Amsterdam and Paris) to the French Caribbean shortly thereafter. Today Brazil, Vietnam, and Colombia are the largest exporters of coffee; African countries contribute about a fifth of world production.

The History of Coffee Brewing The original version of brewed roasted coffee beans is the Arab version, which still thrives in the Middle East, Turkey, and Greece. The finely powdered beans are combined with water and sugar in an open pot, the mixture boiled until the pot foams, then settled and boiled to a foam once or twice more, and finally decanted into small cups. This is the coffee that found its way to Europe around 1600; it's concentrated, includes some sediment, and has to be drunk right away or the sediment will increase the already considerable bitterness. The original version of brewed roasted coffee beans is the Arab version, which still thrives in the Middle East, Turkey, and Greece. The finely powdered beans are combined with water and sugar in an open pot, the mixture boiled until the pot foams, then settled and boiled to a foam once or twice more, and finally decanted into small cups. This is the coffee that found its way to Europe around 1600; it's concentrated, includes some sediment, and has to be drunk right away or the sediment will increase the already considerable bitterness.

French Refinements The first Western modifications of coffee brewing date from around 1700, when French cooks isolated the solid beans within the liquid by enclosing the grounds in a cloth bag, and thus produced a clearer, less gritty brew. Around 1750, the French came up with the most important advance before espresso: the drip pot, in which hot water was poured onto a bed of grounds and allowed to pa.s.s through into a separate chamber. This invention did three things: it kept the temperature of the extracting water below the boil, it limited the contact time between water and ground coffee to a matter of a few minutes, and it produced a sedimentless brew that would keep for a while without getting stronger. The limits on brewing temperature and time meant a less complete extraction of the coffee. This reduced the bitterness and astringency, and allowed the other elements of coffee flavor more prominence, the tartness and aroma that were more appealing to European tastes. The first Western modifications of coffee brewing date from around 1700, when French cooks isolated the solid beans within the liquid by enclosing the grounds in a cloth bag, and thus produced a clearer, less gritty brew. Around 1750, the French came up with the most important advance before espresso: the drip pot, in which hot water was poured onto a bed of grounds and allowed to pa.s.s through into a separate chamber. This invention did three things: it kept the temperature of the extracting water below the boil, it limited the contact time between water and ground coffee to a matter of a few minutes, and it produced a sedimentless brew that would keep for a while without getting stronger. The limits on brewing temperature and time meant a less complete extraction of the coffee. This reduced the bitterness and astringency, and allowed the other elements of coffee flavor more prominence, the tartness and aroma that were more appealing to European tastes.

Machine-Age Espresso The 19th century brought the invention of several new brewing methods. There was percolation, or allowing boiling water to rise in a central tube and irrigate a bed of ground coffee. There were plunger pots, which allowed the coffee brewer to steep the grounds, then push the grounds to the bottom with the plunger and pour the beverage off. But the biggest innovation in coffee brewing made its debut at the Paris Exhibition of 1855. That was Italian The 19th century brought the invention of several new brewing methods. There was percolation, or allowing boiling water to rise in a central tube and irrigate a bed of ground coffee. There were plunger pots, which allowed the coffee brewer to steep the grounds, then push the grounds to the bottom with the plunger and pour the beverage off. But the biggest innovation in coffee brewing made its debut at the Paris Exhibition of 1855. That was Italian espresso, espresso, a word which means something made at the moment it's ordered, rapidly, and for one customer. The way to make coffee fast is to force water through the grounds with high pressure. In the process, the pressure extracts a substantial amount of the coffee bean's oil, and emulsifies it into tiny droplets that create a velvety texture and lingering flavor in the drink. Espresso is an expression of the power of the machine to force the most and the best from a traditional ingredient and make it into something new. a word which means something made at the moment it's ordered, rapidly, and for one customer. The way to make coffee fast is to force water through the grounds with high pressure. In the process, the pressure extracts a substantial amount of the coffee bean's oil, and emulsifies it into tiny droplets that create a velvety texture and lingering flavor in the drink. Espresso is an expression of the power of the machine to force the most and the best from a traditional ingredient and make it into something new.

Coffee berries and seeds. Each red berry contains two seeds.

Coffee Beans Arabica and Robusta Coffees Coffee beans are the seeds of two species of a tropical relative of the gardenia. Coffee beans are the seeds of two species of a tropical relative of the gardenia. Coffea arabica, Coffea arabica, a 15 ft/5 m tree that is native to the cool highlands of Ethiopia and the Sudan, produces what are known as "arabica" beans; and a 15 ft/5 m tree that is native to the cool highlands of Ethiopia and the Sudan, produces what are known as "arabica" beans; and Coffea canephora, Coffea canephora, a larger tree native to hotter, more humid West Africa, produces "robusta" beans. About two-thirds of the beans in international trade are arabicas, which develop a more complex and balanced flavor than the robustas. They contain less caffeine (less than 1.5% by weight of the dry bean, vs. 2.5% for robustas), less phenolic material (6.5% vs. 10%), and more oil (16% vs. 10%) and sugar (7% vs. 3.5%). Robusta varieties didn't become prominent until the end of the 19th century, when their disease resistance became important in Indonesia and elsewhere. a larger tree native to hotter, more humid West Africa, produces "robusta" beans. About two-thirds of the beans in international trade are arabicas, which develop a more complex and balanced flavor than the robustas. They contain less caffeine (less than 1.5% by weight of the dry bean, vs. 2.5% for robustas), less phenolic material (6.5% vs. 10%), and more oil (16% vs. 10%) and sugar (7% vs. 3.5%). Robusta varieties didn't become prominent until the end of the 19th century, when their disease resistance became important in Indonesia and elsewhere.

Dry and Wet Processing To prepare coffee beans, the ripe coffee berries are picked from the trees, and the seeds cleaned of the fruit pulp by one of two basic methods. In the dry method, the berries are left in the sun to dry, or first piled to ferment for a few days, then spread out in the sun. The fruit is then removed by machine. In the wet method, most of the pulp is rubbed from the seeds by machine, then the remainder is liquefied by a day or two of fermentation by microbes. The seeds are then washed in copious water, dried to about 10% moisture, and the adherent inner "parchment sh.e.l.l" removed by machine. Some sugars and minerals are leached out of wet-processed beans, so they tend to produce coffee with less body and more acidity than dry-processed beans. However they often have more aroma, and tend to be of more uniform quality. To prepare coffee beans, the ripe coffee berries are picked from the trees, and the seeds cleaned of the fruit pulp by one of two basic methods. In the dry method, the berries are left in the sun to dry, or first piled to ferment for a few days, then spread out in the sun. The fruit is then removed by machine. In the wet method, most of the pulp is rubbed from the seeds by machine, then the remainder is liquefied by a day or two of fermentation by microbes. The seeds are then washed in copious water, dried to about 10% moisture, and the adherent inner "parchment sh.e.l.l" removed by machine. Some sugars and minerals are leached out of wet-processed beans, so they tend to produce coffee with less body and more acidity than dry-processed beans. However they often have more aroma, and tend to be of more uniform quality.

Roasting Raw green coffee beans are as hard as unpopped popcorn, and about as tasty. Roasting transforms them into fragile, easily opened packages of flavor. Most people let the professionals take care of roasting, but it's a fascinating (and smoky) experience to roast coffee at home, as cooks in many countries have long done and still do with equipment ranging from frying pans to popcorn poppers to special roasters. Raw green coffee beans are as hard as unpopped popcorn, and about as tasty. Roasting transforms them into fragile, easily opened packages of flavor. Most people let the professionals take care of roasting, but it's a fascinating (and smoky) experience to roast coffee at home, as cooks in many countries have long done and still do with equipment ranging from frying pans to popcorn poppers to special roasters.

Coffee beans are roasted to temperatures between 375 and 425F/190220C; the process usually takes between 90 seconds and 15 minutes. As the bean temperature approaches the boiling point of water, the small amounts of moisture inside the cells turn into steam and puff the bean up to half again its original volume. Then at progressively higher temperatures, the proteins, sugars, phenolic materials, and other const.i.tuents begin to break into molecular fragments and react with each other, and develop the brown pigments and roasted aromas typical of the Maillard reactions (p. 778). At around 320F/160C, these reactions become self-sustaining, like a candle flame, and extreme molecular breakdown generates more water vapor and carbon dioxide gas, whose production rises sharply at 400F/200C. If the roasting continues, oil begins to escape from the damaged cells to the bean surface, where it provides a visible gloss.

When the beans have reached the desired degree of roast, the roaster cools the beans immediately with cold air or a water spray to quench the molecular breakdown. The result is a brown, brittle, spongelike bean, with the holes in the sponge filled with carbon dioxide.

The Development of Coffee Flavor The hotter the bean is roasted, the darker it gets, and its color is a good indicator of flavor balance. In the early stages of roasting, sugars are broken down into various acids (formic, acetic, lactic), which together with their own organic acids (citric, malic) give light-brown beans a p.r.o.nounced tartness. As roasting proceeds, both the acids and astringent phenolic materials (chlorogenic acid) are destroyed, so acidity and astringency decline. However, bitterness increases because some of the browning-reaction products are bitter. And as the bean's color becomes darker than medium brown, the distinctive aromas characteristic of prized beans become overwhelmed by more generic roasted flavors - or, conversely, the flavor deficiencies of second-rate beans become less obvious. Finally, as acids and tannins and soluble carbohydrates decline with dark roasting, so does the brew's fullness of body: there's less there to stimulate our tongue. Medium roasts give the fullest body. The hotter the bean is roasted, the darker it gets, and its color is a good indicator of flavor balance. In the early stages of roasting, sugars are broken down into various acids (formic, acetic, lactic), which together with their own organic acids (citric, malic) give light-brown beans a p.r.o.nounced tartness. As roasting proceeds, both the acids and astringent phenolic materials (chlorogenic acid) are destroyed, so acidity and astringency decline. However, bitterness increases because some of the browning-reaction products are bitter. And as the bean's color becomes darker than medium brown, the distinctive aromas characteristic of prized beans become overwhelmed by more generic roasted flavors - or, conversely, the flavor deficiencies of second-rate beans become less obvious. Finally, as acids and tannins and soluble carbohydrates decline with dark roasting, so does the brew's fullness of body: there's less there to stimulate our tongue. Medium roasts give the fullest body.

Storing Coffee Once roasted, whole coffee beans keep reasonably well for a couple of weeks at room temperature, or a couple of months in the freezer, before becoming noticeably stale. One reason that whole beans keep as long as they do is that they're filled with carbon dioxide, which helps exclude oxygen from the porous interior. Once the beans have been ground, room-temperature shelf life is only a few days. Once roasted, whole coffee beans keep reasonably well for a couple of weeks at room temperature, or a couple of months in the freezer, before becoming noticeably stale. One reason that whole beans keep as long as they do is that they're filled with carbon dioxide, which helps exclude oxygen from the porous interior. Once the beans have been ground, room-temperature shelf life is only a few days.

Grinding Coffee The key to proper coffee grinding is obtaining a fairly consistent particle size that's appropriate to the brewing method. The smaller the particle size, the greater the surface area of bean exposed to the water, and the faster its contents are extracted. Too great a range of particle sizes makes it hard to control the extraction during brewing. Small particles may be overextracted and large ones underextracted, and the resulting brew can be both bitter and weak. The common propellor grinder smashes all the bean pieces until the machine is stopped, no matter how small the pieces get, so coa.r.s.e and medium grinds end up containing some fine powder. More expensive burr grinders allow small pieces to escape through grooves in the grinding surfaces, and give a more even particle size. The key to proper coffee grinding is obtaining a fairly consistent particle size that's appropriate to the brewing method. The smaller the particle size, the greater the surface area of bean exposed to the water, and the faster its contents are extracted. Too great a range of particle sizes makes it hard to control the extraction during brewing. Small particles may be overextracted and large ones underextracted, and the resulting brew can be both bitter and weak. The common propellor grinder smashes all the bean pieces until the machine is stopped, no matter how small the pieces get, so coa.r.s.e and medium grinds end up containing some fine powder. More expensive burr grinders allow small pieces to escape through grooves in the grinding surfaces, and give a more even particle size.

The Effects of Roasting on Coffee Beans Weight Loss of Roasted Coffee Beans

Degree of Roast

Weight Loss, % Weight Loss, %

Cinnamon (375F/190C)

12, mostly moisture 12, mostly moisture

Medium

13 13.

City

15 15.

Full city

16, half moisture and half bean solids 16, half moisture and half bean solids

French

17 17.

Italian (425F/220C)