1820, mostly bean solids 1820, mostly bean solids

Composition of Raw and Roasted Coffee Beans, Percent by Weight

Raw Roasted Roasted

Water 12 12.

4 4.

Protein 10 10.

7 7.

Carbohydrate 47 47.

34 34.

Oil 14 14.

16 16.

Phenolics 6 6.

3 3.

Large complex aggregates that provide color, body 0 0.

25 25.

Coffee Flavor, from the Bean into the Cup Coffee Flavor, from the Bean into the CupThis chart shows the relationships between coffee flavor and the fraction of the coffee bean extracted into the water by various brewing methods. Balanced flavor corresponds to an extraction of around 20% of the coffee solids. The strength of the flavor depends on the relative proportions of coffee and water: espresso is made with a much higher proportion of coffee than other brews.

Brewing Coffee Brewing is the extraction into water of desirable substances from the coffee bean, in amounts that produce a balanced, pleasing drink. These substances include many aroma and taste compounds, as well as browning pigments that provide color (almost a third of the total extract) and cell-wall carbohydrates that provide body (also almost a third). The flavor, color, and body of the finished drink are determined by how much ground coffee is used for a given volume of water, and by what proportion of that coffee is extracted into the water. Inadequate extraction and a watery, acid brew are caused by grinding the beans too coa.r.s.ely, so that flavor is left inside the particles, by too brief a contact time between coffee and water, or by too low a brewing temperature. Overextraction and a harsh, bitter brew result from an excessively fine grind, or long contact time, or high brewing temperature. Brewing is the extraction into water of desirable substances from the coffee bean, in amounts that produce a balanced, pleasing drink. These substances include many aroma and taste compounds, as well as browning pigments that provide color (almost a third of the total extract) and cell-wall carbohydrates that provide body (also almost a third). The flavor, color, and body of the finished drink are determined by how much ground coffee is used for a given volume of water, and by what proportion of that coffee is extracted into the water. Inadequate extraction and a watery, acid brew are caused by grinding the beans too coa.r.s.ely, so that flavor is left inside the particles, by too brief a contact time between coffee and water, or by too low a brewing temperature. Overextraction and a harsh, bitter brew result from an excessively fine grind, or long contact time, or high brewing temperature.

The ideal brewing temperature for any style of coffee is 190200F/8593C; anything higher extracts bitter compounds too quickly. For a standard cup of American coffee, the usual brewing time ranges from 1 to 3 minutes for a fine grind, to 6 to 8 minutes for a coa.r.s.e grind.

Brewing Methods There are a number of different methods for brewing coffee. Most of them extract between 20 and 25% of the bean's substance, and produce a cup containing somewhere between 1.3% and5.5% bean solids by weight. The facing chart places some of the major styles in relation to each other. Standard American filter-drip coffee is the lightest, and Italian espresso the strongest. The initial proportion of coffee to water is 1:15 for American, 1:5 for espresso. One clear lesson from the chart is that it's always best to use too much coffee rather than too little: a strong but balanced cup can be diluted with hot water and remain balanced, but a weak cup can't be improved. This principle can help avoid problems caused by the fact that cup and coffee scoop measures vary, and that scoops themselves are a very approximate measure (one 2-tablespoon/30-ml scoop may deliver anywhere from 8 to 12 gm coffee, depending on grind and packing). There are a number of different methods for brewing coffee. Most of them extract between 20 and 25% of the bean's substance, and produce a cup containing somewhere between 1.3% and5.5% bean solids by weight. The facing chart places some of the major styles in relation to each other. Standard American filter-drip coffee is the lightest, and Italian espresso the strongest. The initial proportion of coffee to water is 1:15 for American, 1:5 for espresso. One clear lesson from the chart is that it's always best to use too much coffee rather than too little: a strong but balanced cup can be diluted with hot water and remain balanced, but a weak cup can't be improved. This principle can help avoid problems caused by the fact that cup and coffee scoop measures vary, and that scoops themselves are a very approximate measure (one 2-tablespoon/30-ml scoop may deliver anywhere from 8 to 12 gm coffee, depending on grind and packing).

Each brewing method has its drawbacks. Percolators operate at the boil and tend to overextract. Many automatic drip brewers aren't able to deliver near-boiling water, so they brew for a long time to compensate, lose aroma, and extract some bitterness. Manual drip cones give little control over extraction time. The plunger pot leaves tiny suspended particles in the brew that keep releasing bitterness. The Italian stovetop moka pot operates above the boil, at around 230F/110C (and 1.5 atmospheres of pressure), and produces a somewhat harsh brew. Overnight extraction in cold water doesn't obtain as many aromatic compounds from the ground coffee as the hot-water methods.

Espresso True espresso is made very quickly, in about 30 seconds. A piston or spring or electrical pump drives 200F/93C water through finely ground coffee at 9 atmospheres of pressure. (Inexpensive household machines rely on excessively hot steam, develop far less pressure, and take longer to brew, so the result is relatively thin and harsh.) The proportion of ground coffee is three to four times the amount used in unpressurized brewing, and deposits three to four times the concentration of coffee materials in the brew, creating a substantial, velvety body and intense flavor. These extracted materials include a relatively large amount of coffee oils, which the high pressure forces from the bean particles to form a creamy emulsion of tiny droplets, and which contribute to the slow, prolonged release of coffee flavor in the mouth, long after the last sip. Another unique feature of espresso is the True espresso is made very quickly, in about 30 seconds. A piston or spring or electrical pump drives 200F/93C water through finely ground coffee at 9 atmospheres of pressure. (Inexpensive household machines rely on excessively hot steam, develop far less pressure, and take longer to brew, so the result is relatively thin and harsh.) The proportion of ground coffee is three to four times the amount used in unpressurized brewing, and deposits three to four times the concentration of coffee materials in the brew, creating a substantial, velvety body and intense flavor. These extracted materials include a relatively large amount of coffee oils, which the high pressure forces from the bean particles to form a creamy emulsion of tiny droplets, and which contribute to the slow, prolonged release of coffee flavor in the mouth, long after the last sip. Another unique feature of espresso is the crema, crema, the remarkably stable, creamy foam that develops from the brew and covers its surface. It's the product of carbon dioxide gas still trapped in the ground coffee, and the mixture of dissolved and suspended carbohydrates, proteins, phenolic materials, and large pigment aggregates, all of which bond in one way or another to each other and hold the bubble walls together. (For the milk foams often served with coffee, seep. 26.) the remarkably stable, creamy foam that develops from the brew and covers its surface. It's the product of carbon dioxide gas still trapped in the ground coffee, and the mixture of dissolved and suspended carbohydrates, proteins, phenolic materials, and large pigment aggregates, all of which bond in one way or another to each other and hold the bubble walls together. (For the milk foams often served with coffee, seep. 26.) This chart summarizes the important features of some common ways of brewing coffee, and the kinds of brew they produce. The sta bility of a brew is determined by how many coffee particles remain in it; the more particles, the more bitterness and astringency continue to be extracted in the cup or pet Methods of Brewing Coffee Serving and Holding Coffee Freshly brewed coffee is best enjoyed immediately - its flavor is evanescent. The ideal drinking temperature is around 140F/ 60C, where a sip won't scald the mouth, and the coffee's full aroma comes out. Because it cools in the cup, coffee is usually held in the pot just below the brewing temperature. High heat accelerates chemical reactions and the escape of volatile molecules, so coffee flavor changes noticeably after less than an hour in the pot; it becomes more acid and less aromatic. Coffee is best kept hot by retaining its original heat in a preheated, insulated, closed container, not on a hot plate that constantly supplies excessive heat from below while heat and aroma escape above. Freshly brewed coffee is best enjoyed immediately - its flavor is evanescent. The ideal drinking temperature is around 140F/ 60C, where a sip won't scald the mouth, and the coffee's full aroma comes out. Because it cools in the cup, coffee is usually held in the pot just below the brewing temperature. High heat accelerates chemical reactions and the escape of volatile molecules, so coffee flavor changes noticeably after less than an hour in the pot; it becomes more acid and less aromatic. Coffee is best kept hot by retaining its original heat in a preheated, insulated, closed container, not on a hot plate that constantly supplies excessive heat from below while heat and aroma escape above.

Coffee Flavor Coffee has one of the most complex flavors of all our foods. At its base is a mouth-filling balance of acidity, bitterness, and astringency. A third or less of the bitterness is due to easily extracted caffeine, the rest to more slowly extracted phenolic compounds and browning pigments. More than 800 aroma compounds have been identified, and they supply notes that are described as nutty, earthy, flowery, fruity, b.u.t.tery, chocolate-like, cinnamon, tea, honeyed, caramel, bready, roasty, spicy, even winey and gamy. Robusta coffees, with their substantially higher content of phenolic substances than arabicas, develop a characteristic smoky, tarry aroma that is valued in dark roasts (they are also distinctly less acidic than arabicas). Milk and cream reduce the astringency of coffee by providing proteins that bind to the tannic phenolic compounds, but these liquids also bind aroma molecules and weaken the overall coffee flavor. Coffee has one of the most complex flavors of all our foods. At its base is a mouth-filling balance of acidity, bitterness, and astringency. A third or less of the bitterness is due to easily extracted caffeine, the rest to more slowly extracted phenolic compounds and browning pigments. More than 800 aroma compounds have been identified, and they supply notes that are described as nutty, earthy, flowery, fruity, b.u.t.tery, chocolate-like, cinnamon, tea, honeyed, caramel, bready, roasty, spicy, even winey and gamy. Robusta coffees, with their substantially higher content of phenolic substances than arabicas, develop a characteristic smoky, tarry aroma that is valued in dark roasts (they are also distinctly less acidic than arabicas). Milk and cream reduce the astringency of coffee by providing proteins that bind to the tannic phenolic compounds, but these liquids also bind aroma molecules and weaken the overall coffee flavor.

Decaffeinated Coffee Decaffeinated coffee was invented in Germany around 1908. It's made by soaking green coffee beans with water to dissolve the caffeine, extracting the caffeine from the beans with a solvent (methylene chloride, ethyl acetate), and steaming the beans to evaporate off any remaining solvent. In the "Swiss" or "water" process, water is the only solvent used, the caffeine removed from the water by charcoal filters, and the other water-solubles are then added back to the beans. Some of the organic solvents used in other processes have been suspected of being health hazards even in the tiny traces left in the beans (around 1 part per million). The commonest, methylene chloride, is now thought to be safe. More recently, highly pressurized ("supercritical") and nontoxic carbon dioxide has been used. Where ordinary brewed coffee may contain 60180 milligrams caffeine per cup, decaffeinated coffee will contain 25 mg. Decaffeinated coffee was invented in Germany around 1908. It's made by soaking green coffee beans with water to dissolve the caffeine, extracting the caffeine from the beans with a solvent (methylene chloride, ethyl acetate), and steaming the beans to evaporate off any remaining solvent. In the "Swiss" or "water" process, water is the only solvent used, the caffeine removed from the water by charcoal filters, and the other water-solubles are then added back to the beans. Some of the organic solvents used in other processes have been suspected of being health hazards even in the tiny traces left in the beans (around 1 part per million). The commonest, methylene chloride, is now thought to be safe. More recently, highly pressurized ("supercritical") and nontoxic carbon dioxide has been used. Where ordinary brewed coffee may contain 60180 milligrams caffeine per cup, decaffeinated coffee will contain 25 mg.

Instant Coffee Instant coffee became commercially practical in Switzerland just before World War II. It's made by brewing ground coffee near the boil to obtain aroma, then a second time at 340F/170C and high pressure to maximize the extraction of pigments and body-producing carbohydrates. Water is removed from the two extracts by hot spray-drying or by freeze-drying, which retains more of the volatile aroma compounds and produces a fuller flavor. The two are then blended together and supplemented with aromas captured during the drying stage. Instant coffee crystals contain about 5% moisture, 20% brown pigments, 10% minerals, 7% complex carbohydrate, 8% sugars, 6% acids, and 4% caffeine. As an essentially dry concentrate, instant coffee is a valuable flavoring for baked goods, confections, and ice creams. Instant coffee became commercially practical in Switzerland just before World War II. It's made by brewing ground coffee near the boil to obtain aroma, then a second time at 340F/170C and high pressure to maximize the extraction of pigments and body-producing carbohydrates. Water is removed from the two extracts by hot spray-drying or by freeze-drying, which retains more of the volatile aroma compounds and produces a fuller flavor. The two are then blended together and supplemented with aromas captured during the drying stage. Instant coffee crystals contain about 5% moisture, 20% brown pigments, 10% minerals, 7% complex carbohydrate, 8% sugars, 6% acids, and 4% caffeine. As an essentially dry concentrate, instant coffee is a valuable flavoring for baked goods, confections, and ice creams.

Wood Smoke and Charred Wood Neither wood nor the smoke it gives off is an herb or a spice, strictly speaking. Yet cooks and makers of alcoholic liquids often use burned or burning wood as flavoring agents - in barbecuing meats, in barrel-aging wines and spirits - and some of the flavors they supply are identical to spice flavors: vanilla's vanillin, for example, and clove's eugenol. That's because wood is strengthened with ma.s.ses of interlinked phenolic units, and high heat breaks these ma.s.ses apart into smaller volatile phenolics (p. 390).

The Chemistry of Burning Wood Charred wood and smoke are products of the incomplete combustion of organic materials in the presence of limited oxygen and at the relatively low temperatures of ordinary burning (below 1,800F/1,000C). Complete combustion would produce only odorless water and carbon dioxide.

The Nature of Wood Wood consists of three primary materials: cellulose and hemicellulose, which form the framework and the filler of all plant cell walls, and lignin, a reinforcing material that binds neighboring cell walls together and gives wood its strength. Cellulose and hemicellulose are both aggregates of sugar molecules (pp. 265,266). Lignin is made of intricately inter-locked phenolic molecules - essentially rings of carbon atoms with various additional chemical groups attached - and is one of the most complex natural substances known. The higher the lignin content of a wood, the harder it is and the hotter it burns; its combustion releases 50% more heat than cellulose. Mesquite wood is well-known for its high-temperature fire, which it owes to its 64% lignin content (hickory, a common hardwood, is 18% lignin). Most wood also contains a small amount of protein, enough to support the browning reactions that generate typical roasted flavors (p. 778) at moderately hot temperatures. Evergreens such as pine, fir, and spruce also contain significant amounts of resin, a mixture of compounds related to fats that produce a harsh soot when burned. Wood consists of three primary materials: cellulose and hemicellulose, which form the framework and the filler of all plant cell walls, and lignin, a reinforcing material that binds neighboring cell walls together and gives wood its strength. Cellulose and hemicellulose are both aggregates of sugar molecules (pp. 265,266). Lignin is made of intricately inter-locked phenolic molecules - essentially rings of carbon atoms with various additional chemical groups attached - and is one of the most complex natural substances known. The higher the lignin content of a wood, the harder it is and the hotter it burns; its combustion releases 50% more heat than cellulose. Mesquite wood is well-known for its high-temperature fire, which it owes to its 64% lignin content (hickory, a common hardwood, is 18% lignin). Most wood also contains a small amount of protein, enough to support the browning reactions that generate typical roasted flavors (p. 778) at moderately hot temperatures. Evergreens such as pine, fir, and spruce also contain significant amounts of resin, a mixture of compounds related to fats that produce a harsh soot when burned.

How Burning Transforms Wood into Flavor Burning temperatures transform each of the wood components into a characteristic group of compounds (see box, p.449). The sugars in cellulose and hemicellulose break apart into many of the same molecules found in caramel, with sweet, fruity, flowery, bready aromas. And the interlocked phenolic rings of lignin break apart from each other into a host of smaller, volatile phenolics and other fragments, which have the specific aromas of vanilla and clove as well as a generic spiciness, sweetness, and pungency. Cooks get these volatiles into solid foods, usually meats and fish, by exposing the foods to the smoky vapors emitted by burning wood. Makers of wine and spirits store them in wood barrels whose interiors have been charred; the volatiles are trapped in and just below the barrels' inner surface, and are slowly extracted by the liquid (p. 721). Burning temperatures transform each of the wood components into a characteristic group of compounds (see box, p.449). The sugars in cellulose and hemicellulose break apart into many of the same molecules found in caramel, with sweet, fruity, flowery, bready aromas. And the interlocked phenolic rings of lignin break apart from each other into a host of smaller, volatile phenolics and other fragments, which have the specific aromas of vanilla and clove as well as a generic spiciness, sweetness, and pungency. Cooks get these volatiles into solid foods, usually meats and fish, by exposing the foods to the smoky vapors emitted by burning wood. Makers of wine and spirits store them in wood barrels whose interiors have been charred; the volatiles are trapped in and just below the barrels' inner surface, and are slowly extracted by the liquid (p. 721).

The flavor that wood smoke imparts to food is determined by several factors. Above all there's the wood. Oak, hickory, and the fruit-tree woods (cherry, apple, pear) produce characteristic and pleasing flavors thanks to their moderate, balanced quant.i.ties of the wood components. A second important factor is the combustion temperature, which is partly determined by the wood and its moisture content. Maximum flavor production takes place at relatively low, smoldering temperatures, between 570 and 750F/300400C; at higher temperatures, the flavor molecules are themselves broken down into simpler harsh or flavorless molecules. High-lignin woods burn too hot unless their combustion is slowed by restricted airflow or a high moisture content. When smoking is done by throwing wood chips onto glowing charcoal, the wood chips should be pre-soaked in water so that they'll cool the coals. Because it's largely pure carbon, charcoal burns mostly smokelessly at temperatures approaching 1,800F/1,000C.

Though smoke helps stabilize the flavors of meats and fish, smoke flavor itself is unstable. The desirable phenolic compounds are especially reactive, and largely dissipate in a few weeks or months.

The Toxins in Wood Smoke: Preservatives and Carcinogens In the beginning, smoking was not just a way of giving foods an interesting flavor: it was a way of delaying their spoilage. Wood smoke contains many chemicals that slow the growth of microbes. Among them are formaldehyde, and acetic acid (vinegar) and other organic acids, thanks to which the pH of smoke is a very microbe-unfriendly 2.5. Many of the phenolic compounds in wood smoke are also antimicrobials, and phenol itself is a strong disinfectant. The phenolic compounds are also effective antioxidants, and slow the development of rancid flavors in smoked meats and fish. In the beginning, smoking was not just a way of giving foods an interesting flavor: it was a way of delaying their spoilage. Wood smoke contains many chemicals that slow the growth of microbes. Among them are formaldehyde, and acetic acid (vinegar) and other organic acids, thanks to which the pH of smoke is a very microbe-unfriendly 2.5. Many of the phenolic compounds in wood smoke are also antimicrobials, and phenol itself is a strong disinfectant. The phenolic compounds are also effective antioxidants, and slow the development of rancid flavors in smoked meats and fish.

In addition to antimicrobial compounds, smoke also contains antihuman compounds, substances that are harmful to our long-term health. Prominent among these are the polycyclic aromatic hydrocarbons, or PAHs, which are proven carcinogens and are formed from all of the wood components in increasing amounts as the temperature is raised. Hot-burning mesquite wood generates double the quant.i.ty that hickory wood does. The deposition of PAHs on meat can be minimized by limiting the fire temperature, keeping the meat as far as possible from the fire, and allowing free air circulation to carry soot and other PAH-containing particles away. Commercial smokers use air filters and temperature control for these purposes.

Liquid Smoke Liquid smoke is essentially smoke-flavored water. Smoke consists of two phases: microscopic droplets that make it visible as a haze, and an invisible vapor. It turns out that much of the flavor and preservative materials are in the vapor, while the droplets are largely aggregates of tars, resins, and heavier phenolic materials, including the PAHs. PAHs are largely insoluble in water, while most of the flavor and preservative compounds do dissolve to some extent. This difference makes it possible to separate most of the PAHs from the vapors and dissolve the vapors in water. Cooks then use this liquid extract of smoke to flavor foods. Toxicological studies of liquid smoke have found that though it is full of biologically active compounds, the quant.i.ties normally used in foods are harmless. Those PAHs that do make it into liquid smoke tend to aggregate and sink over time, so it's best not to shake bottles of liquid smoke before use. Leave the sediment at the bottom.

Wood Components and Smoke Flavors

Wood Component % of dry weight

Combustion Temperature Combustion Temperature

Combustion By-Products and Their Aromas Combustion By-Products and Their Aromas

Cellulose (cell-wall frame, from glucose) 4045% 540610F 280320C 540610F 280320C Furans: sweet, bready, floral Lactones: coconut, peach Acetaldehyde: green apple Furans: sweet, bready, floral Lactones: coconut, peach Acetaldehyde: green apple

Hemicellulose (cell-wall filler, from mixed sugars) 2035% 390480F 390480F Acetic acid: vinegar 200250C Diacetyl: b.u.t.tery Acetic acid: vinegar 200250C Diacetyl: b.u.t.tery

Lignin (cell-wall strengthener, from phenolic compounds) 2040% 750F 400C 750F 400C.

Guaiacol: smoky, spicy Vanillin: vanilla Phenol: pungent, smoky Isoeugenol: sweet, cloves Syringol: spicy, sausage-like Guaiacol: smoky, spicy Vanillin: vanilla Phenol: pungent, smoky Isoeugenol: sweet, cloves Syringol: spicy, sausage-like

Chapter 9.

Seeds Grains, Legumes, and Nuts

Seeds as Food Some Definitions Seeds and Health Valuable Phytochemicals from SeedsProblems Caused by SeedsSeeds Are Common Food AllergensSeeds and Food Poisoning The Composition and Qualities of Seeds Parts of the SeedSeed Proteins: Soluble and InsolubleSeed Starches: Orderly and DisorderlySeed OilsSeed Flavors Handling and Preparing Seeds Storing SeedsSproutsCooking Seeds The Grains, or Cereals Grain Structure and CompositionMilling and RefiningBreakfast CerealsWheatBarleyRyeOatsRiceMaize, or CornMinor CerealsPseudocereals Legumes: Beans and Peas Legume Structure and CompositionLegumes and Health: The Intriguing SoybeanThe Problem of Legumes and FlatulenceBean FlavorBean SproutsCooking LegumesCharacteristics of Some Common Legumes...o...b..ans and Their Transformations Nuts and Other Oil-Rich Seeds Nut Structures and QualitiesThe Nutritional Value of NutsNut FlavorHandling and Storing NutsCooking NutsCharacteristics of Some Common NutsCharacteristics of Other Oil-Rich Seeds Seeds as Food Seeds are our most durable and concentrated foods. They're rugged lifeboats, designed to carry a plant's offspring to the sh.o.r.e of an uncertain future. Tease apart a whole grain, or bean, or nut, and inside you find a tiny embryonic shoot. At harvest time that shoot had entered suspended animation, ready to survive months of drought or cold while waiting for the right moment to come back to life. The bulk of the tissue that surrounds it is a food supply to nourish this rebirth. It's the distillation of the parent plant's lifework, its gathering of water and nitrogen and minerals from the soil, carbon from the air, and energy from the sun. And as such it's an invaluable resource for us and other creatures of the animal kingdom who are unable to live on soil and sunlight and air. In fact, seeds gave early humans both the nourishment and the inspiration to begin to shape the natural world to their own needs. Ten thousand turbulent years of civilization have unfolded from the seed's pale repose.

The story began when inhabitants of the Middle East, Asia, and Central and South America learned to save some large, easily harvested seeds from wild plants, and sow them in clearings to produce more seeds of a similar kind. It appears that agriculture first arose in the highlands of southeastern Turkey, around the upper reaches of the Tigris and Euphrates rivers, and in the Jordan River valley. The first plants to be brought under human selection there were einkorn and emmer wheat, barley, lentil, pea, bitter vetch, and chickpea: a mixture of seed-bearing cereals and legumes. Gradually the nomadic life of the hunter-gatherer gave way to growing settlements alongside the large grainfields that fed them. The need arose for planning the sowing and the distribution of the harvests, for antic.i.p.ating seasonal changes before they occurred, for organizing the work, and for keeping records. Some of the earliest known writing and arithmetical systems, dating from at least 5,000 years ago, are devoted to the accounting of grain and livestock. So the culture of the fields encouraged the culture of the mind. At the same time it brought problems, among them a drastic simplification of the hunter-gatherer's varied diet and consequent damage to human health, and the development of a social hierarchy in which a few benefit from the labor of many.

Seeds of ThoughtThe development of agriculture had a deep influence on human feeling and thought, on mythology and religion and science, that is hard to capture in a few quotations. The religious historian Mircea Eliade summarized it this way:We are used to thinking that the discovery of agriculture made a radical change in the course of human history by ensuring adequate nourishment and thus allowing a tremendous increase in the population. But the discovery of agriculture had decisive results for a quite different reason.... Agriculture taught man the fundamental oneness of organic life; and from that revelation sprang the simpler a.n.a.logies between women and field, between the s.e.xual act and sowing, as well as the most advanced intellectual syntheses: life as rhythmic, death as a return, and so on. These syntheses were essential to man's development, and were possible only after the discovery of agriculture.- Patterns in Comparative Religion Patterns in Comparative Religion, 1958 In the Odyssey, Odyssey, Homer called wheat and barley "the marrow of men's bones." It's less obvious to us in the modern industrialized world than it has been through much of human history, but seeds remain the essential food of our species. Grains directly provide the bulk of the caloric intake for much of the world's population, especially in Asia and Africa. The grains and legumes together provide more than two-thirds of the world's dietary protein. Even the industrial countries are fed indirectly by the shiploads of corn, wheat, and soybeans on which their cattle, hogs, and chickens are raised. The fact that the grains come from the gra.s.s family adds a layer of significance to the Old Testament prophet Isaiah's admonishment that "All flesh is gra.s.s." Homer called wheat and barley "the marrow of men's bones." It's less obvious to us in the modern industrialized world than it has been through much of human history, but seeds remain the essential food of our species. Grains directly provide the bulk of the caloric intake for much of the world's population, especially in Asia and Africa. The grains and legumes together provide more than two-thirds of the world's dietary protein. Even the industrial countries are fed indirectly by the shiploads of corn, wheat, and soybeans on which their cattle, hogs, and chickens are raised. The fact that the grains come from the gra.s.s family adds a layer of significance to the Old Testament prophet Isaiah's admonishment that "All flesh is gra.s.s."

As ingredients, seeds have much in common with milk and eggs. All consist of basic nutrients created to nourish the next generation of living things; all are relatively simple and bland in themselves, but have inspired cooks to transform them into some of the most complex and delightful foods we have.

Some Definitions Seeds Seeds are structures by which plants create a new generation of their kind. They contain an embryonic plant together with a food supply to fuel its germination and early growth. And they include an outer layer that insulates the embryo from the soil and protects it from physical damage and from attack by microbes or animals. Seeds are structures by which plants create a new generation of their kind. They contain an embryonic plant together with a food supply to fuel its germination and early growth. And they include an outer layer that insulates the embryo from the soil and protects it from physical damage and from attack by microbes or animals.

The most important seeds in the kitchen fall into three groups.

Grains, or Cereals These words are near synonyms. The These words are near synonyms. The cereals cereals (from (from Ceres, Ceres, the Roman G.o.ddess of agriculture) are plants in the gra.s.s family, the Gramineae, whose members produce edible and nutritious seeds, the the Roman G.o.ddess of agriculture) are plants in the gra.s.s family, the Gramineae, whose members produce edible and nutritious seeds, the grains. grains. But But cereal cereal is also used to mean their seeds and products made from them - as in "breakfast cereals" - and the plants are sometimes called is also used to mean their seeds and products made from them - as in "breakfast cereals" - and the plants are sometimes called grains. grains. The cereals and other gra.s.ses are creatures of the open plain or high-alt.i.tude steppe, areas too dry for trees. They live and die in a season or two, and are easily gathered and handled. They grow in densely packed stands that crowd out compet.i.tion, and produce many small seeds, relying on numbers rather than chemical defenses to ensure that some offspring will survive. These characteristics made the gra.s.ses ideal for agriculture. With our help, they have come to cover vast areas of the globe. The cereals and other gra.s.ses are creatures of the open plain or high-alt.i.tude steppe, areas too dry for trees. They live and die in a season or two, and are easily gathered and handled. They grow in densely packed stands that crowd out compet.i.tion, and produce many small seeds, relying on numbers rather than chemical defenses to ensure that some offspring will survive. These characteristics made the gra.s.ses ideal for agriculture. With our help, they have come to cover vast areas of the globe.

Wheat, barley, oats, and rye have been the most important grains in the Middle East and Europe; in Asia, rice; in the New World, maize, or corn; in Africa sorghum and millets. The grains are of special culinary significance because they make possible beer and bread, both staples in the human diet for at least 5,000 years.

An oat kernel, lentils in their pod, and a hazelnut. All are seeds, and consist of a living embryonic plant together with a food supply to fuel its early growth. In the cereal grains, the food supply is a separate tissue, the endosperm. In the beans and their relatives, and in most nuts, the food supply fills the first two leaves of the embryo, the cotyledons, which are unusually ma.s.sive and thick.

Legumes The The legumes legumes (from the Latin (from the Latin legere, legere, "to gather") are plants in the bean family, the Leguminosae, whose members bear pods that contain several seeds. The term "to gather") are plants in the bean family, the Leguminosae, whose members bear pods that contain several seeds. The term legume legume is also used to name their seeds. Many legumes are vines that climb on tall gra.s.ses and other plants to reach full sunlight, and like the gra.s.ses grow, go to seed, and die over a few months. The legumes produce seeds that are especially rich in protein, thanks to their symbiosis with bacteria that live in their roots and feed them with nitrogen from the air. The same symbiosis means that legumes actually enrich the soil they grow in with nitrogen compounds, which is why various legumes have been grown as rotation crops at least since Roman times. Their relatively large seeds are attractive to animals, and it's thought that much of the remarkable diversity in the beans and peas is the result of survival pressures exerted by insects. Legume seeds are camouflaged by colored coats, and protected with an array of several biochemical defenses. is also used to name their seeds. Many legumes are vines that climb on tall gra.s.ses and other plants to reach full sunlight, and like the gra.s.ses grow, go to seed, and die over a few months. The legumes produce seeds that are especially rich in protein, thanks to their symbiosis with bacteria that live in their roots and feed them with nitrogen from the air. The same symbiosis means that legumes actually enrich the soil they grow in with nitrogen compounds, which is why various legumes have been grown as rotation crops at least since Roman times. Their relatively large seeds are attractive to animals, and it's thought that much of the remarkable diversity in the beans and peas is the result of survival pressures exerted by insects. Legume seeds are camouflaged by colored coats, and protected with an array of several biochemical defenses.

Lentils, broad beans, peas, and chick peas are all native to the Fertile Crescent of the Near East. They were adapted for sprouting and quickly reproducing in the cool, wet season before the summer drought, and were the first substantial foods to ripen in the spring. The soy and mung beans were indigenous to Asia, and peanuts, lima beans, and common beans to the Americas.

Nuts The The nuts nuts (from an Indo-European root meaning "compressed") come from several different plant families, not just one. They are generally large seeds enclosed in hard sh.e.l.ls, and borne on long-lived trees. The seeds are large both to make them attractive to animal dispersers (which bury some for later use and effectively plant the ones they forget), and to give the seedling an adequate food supply for slow, prolonged growth in the partial shade. Most of them store their energy not in starch but in oil, a more compact, concentrated chemical form (p. 121). (from an Indo-European root meaning "compressed") come from several different plant families, not just one. They are generally large seeds enclosed in hard sh.e.l.ls, and borne on long-lived trees. The seeds are large both to make them attractive to animal dispersers (which bury some for later use and effectively plant the ones they forget), and to give the seedling an adequate food supply for slow, prolonged growth in the partial shade. Most of them store their energy not in starch but in oil, a more compact, concentrated chemical form (p. 121).

Nuts are much less important in the human diet than grains or legumes because nut trees don't begin to bear until years after they're planted, and can't produce as much per acre as the quick-growing grains and legumes. The biggest exception to this rule is the coconut, a staple food in many tropical countries. Another is the peanut, which is a legume with an uncharacteristically oily, tender seed, and which can be grown quickly in ma.s.sive numbers.

Seeds and Health Our seed foods provide us with many nutritional benefits. To begin with, they're our most important staple sources of energy and protein, and carry the B vitamins that are required for the chemical work of generating energy and building tissue. In fact, they're such a good source of these essential nutrients that cultures have occasionally relied on the grains too heavily, and suffered from dietary deficiencies as a result. The debilitating disease called beriberi plagued rice-eating Asia in the 19th century when milling machines made it easier to remove the inconvenient, unattractive outer bran layer from rice grains - and along with it their thiamin, which the rest of the largely vegetarian diet couldn't make up (meats and fish are rich in thiamin). A different deficiency disease called pellagra struck the rural poor in Europe and the southern United States in the 18th and 19th centuries, when they adopted corn from Central and South America as a staple food, but without the processing method (cooking in alkaline water) that makes its stores of niacin available to the human body.

Beriberi and pellagra led early in the 20th century to the discovery of the vitamins whose deficiencies cause them. Today, even though most people in Asia eat refined rice, and polenta and grits are still not cooked in alkaline water, more balanced diets have made these deficiency diseases far less common.

Valuable Phytochemicals From Seeds Toward the end of the 20th century, we came to realize that seeds have more to offer us than the basic machinery of life. Epidemiological studies have found a general a.s.sociation between the consumption of whole grains, legumes, and nuts and a reduced risk of various cancers, heart disease, and diabetes. What do these foods provide that refined grains do not? Hundreds or even thousands of chemicals that are concentrated in the outer protective and active layers of the seeds, and that are not found in inner storage tissues, which are mainly depots of starch and protein. Among the chemicals that have been identified and seem likely to be helpful are a variety of vitamins, including antioxidant vitamin E and its chemical relatives the tocotrienols soluble fiber: soluble but undigestible carbohydrates that slow digestion, moderate blood insulin and blood sugar levels, and reduce cholesterol levels, and provide energy for beneficial intestinal bacteria, which alter their chemical environment, suppress the growth of harmful bacteria, and influence the health of intestinal cells insoluble fiber, which speeds pa.s.sage of food through the digestive system and reduces our absorption of carcinogens and other undesirable molecules a variety of phenolic and other defensive compounds, some of which are effective antioxidants, some of which resemble human hormones and may restrain cell growth and thereby the development of cancer Medical scientists are still in the early stages of identifying and evaluating these substances, but in general it looks as though regular consumption of whole grains, legumes, and nuts can indeed make a real contribution to our long-term health.

Problems Caused by Seeds Seeds are not perfect foods. Legumes in particular contain defensive chemicals - lectins and protease inhibitors - that can cause malnourishment and other problems. Fortunately, simple cooking disarms these defenses (p. 259). The fava bean contains amino-acid relatives that cause serious anemia in susceptible people (p. 490), but both the bean and the susceptibility are relatively rare. Two other problems are more common.

Seeds are Common Food Allergens True food allergies are overreactions of the body's immune system, which mistakes a food component as a sign of invasion by a bacterium or virus and initiates a defense that damages the body. The damage may be mild and manifest itself as discomfort, itchiness, or a rash, or it may be a life-threatening asthma or change in blood pressure or heart rhythm. It's estimated that about 2% of adults in the United States have one or more food allergies, and up to 8% of young children. Allergic reactions to food cause around 200 deaths per year in the United States. Peanuts, soybeans, and tree nuts are among the most common food allergens. The offending components are usually seed proteins, and cooking does not render them less allergenic. Tiny quant.i.ties of nut proteins are sufficient to cause reactions, including the levels sometimes found in mechanically extracted nut oils.

Gluten Sensitivity A special form of food allergy is the disease called gluten-sensitive enteropathy, celiac disease, or sprue, in which the body forms defensive antibodies against a portion of the harmless gliadin proteins in wheat, barley, rye, and possibly oats. These defenses end up attacking the nutrient-absorbing cells in the intestine, and therefore cause serious malnourishment. Celiac disease can develop in early childhood or later, and is a lifelong condition. The standard remedy is strict avoidance of all gluten-containing foods. Several grains don't contain gliadin proteins and therefore don't aggravate celiac disease; they are corn, rice, amaranth, buckwheat, millet, quinoa, sorghum, and teff. A special form of food allergy is the disease called gluten-sensitive enteropathy, celiac disease, or sprue, in which the body forms defensive antibodies against a portion of the harmless gliadin proteins in wheat, barley, rye, and possibly oats. These defenses end up attacking the nutrient-absorbing cells in the intestine, and therefore cause serious malnourishment. Celiac disease can develop in early childhood or later, and is a lifelong condition. The standard remedy is strict avoidance of all gluten-containing foods. Several grains don't contain gliadin proteins and therefore don't aggravate celiac disease; they are corn, rice, amaranth, buckwheat, millet, quinoa, sorghum, and teff.

Seeds and Food Poisoning Seeds are generally dry, with only about 10% of their weight coming from water. As a result, they keep well without special treatment; and because we prepare them by thoroughly boiling or roasting them, freshly cooked grains, beans, and nuts generally don't carry bacteria that cause food poisoning. However, moist grain and bean dishes become very hospitable to bacteria as they cool down. Leftovers should be refrigerated promptly and reheated to the boil before serving. Rice dishes are particularly vulnerable to contamination by Bacillus cereus Bacillus cereus and require special care (p. 475). and require special care (p. 475).

Even dry seeds aren't entirely immune to contamination and spoilage. Molds, or fungi, are able to grow with relatively little moisture, and can contaminate seed crops both in the field and in storage. Some synthesize deadly toxins that can cause cancer and other diseases (for example, species of Aspergillus Aspergillus produce a carcinogen called aflatoxin, and produce a carcinogen called aflatoxin, and Fusarium moniliforme Fusarium moniliforme produces another called fumonisin). The presence of fungal toxins in our foods is generally invisible to the consumer, and is monitored by producers and government agencies. They're not now considered a major health risk. But the least sign of mold or other spoilage on grains and nuts means that the food should be discarded. produces another called fumonisin). The presence of fungal toxins in our foods is generally invisible to the consumer, and is monitored by producers and government agencies. They're not now considered a major health risk. But the least sign of mold or other spoilage on grains and nuts means that the food should be discarded.

The Composition and Qualities of Seeds Parts of the Seed All of our food seeds consist of three basic parts: an outer protective coat, a small embryonic portion capable of growing into the mature plant, and a large ma.s.s of storage tissue that contains proteins, carbohydrates, and oils to feed the embryo. Each part influences the texture and flavor of the cooked seeds.

The outer protective coat, called the bran bran in grains and the in grains and the seed coat seed coat in legumes and nuts, is a dense sheet of tough, fibrous tissue. It's rich in defensive or camouflaging phenolic compounds, including anthocyanin pigments and astringent tannins. And it slows the pa.s.sage of water into grains and legumes during cooking. It's often removed from grains (especially rice and barley), legumes (notably in Indian dals), and nuts (almonds, chestnuts) to speed the cooking and obtain a more refined appearance, texture, and flavor. in legumes and nuts, is a dense sheet of tough, fibrous tissue. It's rich in defensive or camouflaging phenolic compounds, including anthocyanin pigments and astringent tannins. And it slows the pa.s.sage of water into grains and legumes during cooking. It's often removed from grains (especially rice and barley), legumes (notably in Indian dals), and nuts (almonds, chestnuts) to speed the cooking and obtain a more refined appearance, texture, and flavor.

The embryonic portion of legumes and nuts is not of much practical significance, but the germ of the grains is: it contains much of the oil and enzymes in these seeds, and thus is the source of potential flavor, both desirable cooked aromas and undesirable stale ones.

The bulk of the seed is a ma.s.s of storage tissue, and its makeup determines the seed's basic texture. The storage cells are filled with particles of concentrated protein, granules of starch, and sometimes with droplets of oil. In some grains, notably barley, oats, and rye, the cell walls are also filled with storage carbohydrates - not starch, but other long sugar chains that like starch can absorb water during cooking. The strength of the cement that holds the storage cells together, and the nature and proportions of the materials they contain, determine the seed's texture. Bean cells and grain cells are filled with solid, hard starch granules and protein bodies; most nut cells are filled with liquid oil, and so are more fragile. Grains retain their shape and some firmness even when we mill away their protective bran envelope and boil them in plenty of water. Beans remain intact as long as we cook them in their seed coats; otherwise they rapidly disintegrate into a puree.

The particular contents of the seed storage cells influence texture and culinary usefulness in a number of ways. So it's worth knowing about the proteins, starches, and oils in some detail.

Seed Proteins: Soluble and Insoluble Seed proteins are cla.s.sified by a particular aspect of their chemical behavior, which also determines their behavior during cooking: the kind of liquid in which they dissolve. This may be pure water, water and some salt, water and dilute acid, or alcohol (these types are called "alb.u.mins," "globulins," "glutelins," and "prolamins"). Most of the proteins in legumes and nuts are soluble in a salt solution or water alone, so during ordinary cooking in salted water, bean and pea proteins become dispersed in the moisture within the seeds and the cooking liquid surrounding them. By contrast, the main storage proteins in wheat, rice, and other grains are acid-soluble and alcohol-soluble types. In ordinary water, these proteins don't dissolve; instead they bond to each other and clump up into a compact ma.s.s. Wheat, rice, corn, and barley kernels develop a chewy consistency in part because their insoluble proteins clump together in the grain during cooking and form a sticky complex with the starch granules.

Seed Starches: Orderly and Disorderly All the grains and legumes contain a substantial amount of starch, enough that it plays a significant role in the texture of the cooked seeds and their products. It can make one grain variety behave very differently from another variety of the same grain.

Two Kinds of Starch Molecules The parent plant lays down starch molecules in microscopic, solid granules that fill the cells of the seed storage tissue. All starch consists of chains of individual molecules of the sugar called glucose (p. 804). But there are two different kinds of starch molecules in starch granules, and they behave very differently. The parent plant lays down starch molecules in microscopic, solid granules that fill the cells of the seed storage tissue. All starch consists of chains of individual molecules of the sugar called glucose (p. 804). But there are two different kinds of starch molecules in starch granules, and they behave very differently. Amylose Amylose molecules are made from around 1,000 glucose sugars, and are mainly one extended chain, with just a few long branches. molecules are made from around 1,000 glucose sugars, and are mainly one extended chain, with just a few long branches. Amylopectin Amylopectin molecules are made from 5,000 to 20,000 sugars and have hundreds of short branches. Amylose is thus a relatively small, simple molecule that can easily settle into compact, orderly, tightly bonded cl.u.s.ters, while amylopectin is a large, bushy, bulky molecule that doesn't cl.u.s.ter easily or tightly. Both amylose and amylopectin are packed together in the raw starch granule, in proportions that depend on the kind and variety of seed. Legume starch granules are 30% or more amylose, and wheat, barley, maize, and long-grain rice granules are around 20%. Short-grain rice granules contain about 15% amylose, while "sticky" rice starch granules are almost pure amylopectin. molecules are made from 5,000 to 20,000 sugars and have hundreds of short branches. Amylose is thus a relatively small, simple molecule that can easily settle into compact, orderly, tightly bonded cl.u.s.ters, while amylopectin is a large, bushy, bulky molecule that doesn't cl.u.s.ter easily or tightly. Both amylose and amylopectin are packed together in the raw starch granule, in proportions that depend on the kind and variety of seed. Legume starch granules are 30% or more amylose, and wheat, barley, maize, and long-grain rice granules are around 20%. Short-grain rice granules contain about 15% amylose, while "sticky" rice starch granules are almost pure amylopectin.

The Proportions of Proteins in Seeds Cooking Separates Starch Molecules and Softens Granules When a seed is cooked in water, the starch granules absorb water molecules, and swell and soften as the water molecules intrude and separate the starch molecules from each other. This granule softening, or When a seed is cooked in water, the starch granules absorb water molecules, and swell and soften as the water molecules intrude and separate the starch molecules from each other. This granule softening, or gelation, gelation, takes place in a temperature range that depends on the seed and starch, but is in the region of 140160F/6070C. (The conversion of solid starch into a starch-water gel is often referred to as "gelatinization," but this is unnecessarily confusing; starch has nothing to do with gelatin.) The tightly ordered cl.u.s.ters of amylose molecules require higher temperatures, more water, and more cooking time to be pulled and kept apart than do the looser cl.u.s.ters of amylopectin molecules. This is why long-grain Chinese rices are made with more water than short-grain j.a.panese rices. takes place in a temperature range that depends on the seed and starch, but is in the region of 140160F/6070C. (The conversion of solid starch into a starch-water gel is often referred to as "gelatinization," but this is unnecessarily confusing; starch has nothing to do with gelatin.) The tightly ordered cl.u.s.ters of amylose molecules require higher temperatures, more water, and more cooking time to be pulled and kept apart than do the looser cl.u.s.ters of amylopectin molecules. This is why long-grain Chinese rices are made with more water than short-grain j.a.panese rices.

Cooling Reorganizes Starch Molecules and Firms Granules Once the cooking is finished and the seeds cool down below the gelation temperature, the starch molecules begin to re-form some cl.u.s.ters with pockets of water in between, and the soft, gelated starch granules begin to firm up again. This process is called Once the cooking is finished and the seeds cool down below the gelation temperature, the starch molecules begin to re-form some cl.u.s.ters with pockets of water in between, and the soft, gelated starch granules begin to firm up again. This process is called retrogradation. retrogradation. The simpler amylose molecules start bonding to each other again almost immediately, and finish within a few hours at room or refrigerator temperatures. Sprawling, bushy amylopectin molecules take a day or more to rea.s.sociate, and form relatively loose, weak cl.u.s.ters. This difference explains why long-grain rices high in amylose have a firm, springy texture when served right after cooking and get inedibly hard when refrigerated overnight, while short-grain rices low in amylose have a softer, sticky texture and harden much less during overnight refrigeration. The hardness of all leftover grains can be largely remedied simply by reheating and so regelating their starch. The simpler amylose molecules start bonding to each other again almost immediately, and finish within a few hours at room or refrigerator temperatures. Sprawling, bushy amylopectin molecules take a day or more to rea.s.sociate, and form relatively loose, weak cl.u.s.ters. This difference explains why long-grain rices high in amylose have a firm, springy texture when served right after cooking and get inedibly hard when refrigerated overnight, while short-grain rices low in amylose have a softer, sticky texture and harden much less during overnight refrigeration. The hardness of all leftover grains can be largely remedied simply by reheating and so regelating their starch.

Starch gelation and retrogradation. Starch granules are compact, organized ma.s.ses of long starch chains (left) (left) . When a starchy cereal is cooked, water penetrates the granule and separates the chains from each other, thus swelling and softening the granule in the process called gelation . When a starchy cereal is cooked, water penetrates the granule and separates the chains from each other, thus swelling and softening the granule in the process called gelation (center) (center) . When the cooked cereal cools down, the starch chains slowly rebond to each other in tighter, more organized a.s.sociations, and the granule becomes firmer and harder, a process called retrogradation . When the cooked cereal cools down, the starch chains slowly rebond to each other in tighter, more organized a.s.sociations, and the granule becomes firmer and harder, a process called retrogradation (right). (right).

Starch Firming Can Be Useful Reheated grains never get quite as soft as they were when first cooked. This is because during the process of retrogradation, amylose molecules manage to form some cl.u.s.ters that are even more highly organized than the cl.u.s.ters in the original starch granule, crystalline regions that resist breaking even at boiling temperatures. These regions act as reinforcing junctions in the overall network of amylose and amylopectin molecules, and give the granules greater strength and integrity. Cooks take advantage of this strengthening to make bread puddings and starch noodles; parboiled (converted) rice and American breakfast cereals keep their shape because much of their starch has been allowed to retrograde during manufacturing. And it turns out that retrograded starch is good for our bodies! It resists our digestive enzymes and therefore slows the rise in blood sugar following a meal, and feeds desirable bacteria in the large intestine (p. 258). Reheated grains never get quite as soft as they were when first cooked. This is because during the process of retrogradation, amylose molecules manage to form some cl.u.s.ters that are even more highly organized than the cl.u.s.ters in the original starch granule, crystalline regions that resist breaking even at boiling temperatures. These regions act as reinforcing junctions in the overall network of amylose and amylopectin molecules, and give the granules greater strength and integrity. Cooks take advantage of this strengthening to make bread puddings and starch noodles; parboiled (converted) rice and American breakfast cereals keep their shape because much of their starch has been allowed to retrograde during manufacturing. And it turns out that retrograded starch is good for our bodies! It resists our digestive enzymes and therefore slows the rise in blood sugar following a meal, and feeds desirable bacteria in the large intestine (p. 258).