On Food And Cooking Part 32

Haddock, gutted, split, cold-smoked (peat) Haddock, gutted, split, cold-smoked (peat)

Norwegian/Scotch smoked salmon; "Nova"

Salmon fillets, cold-smoked Salmon fillets, cold-smoked

Marinated Fish In chemical terms, an acid is a substance that readily releases free protons, the small reactive nuclei of hydrogen atoms. Water is a weak acid, and living cells are designed to operate while bathed in it. But strong acids flood living cells with more protons than they can handle, and cripple their chemical machinery. This is why acids are good at preserving foods: they cripple microbes. In the case of acidifying fish, a happy side benefit is that it leaves the fish with a distinctive, almost fresh aroma. Acid conditions cause heavy-smelling aldehydes, which accentuate the fis.h.i.+ness of TMA, to react with water molecules and become nonvolatile, so that lighter alcohols dominate the aroma. Pickled herring and other fish can be surprisingly delicate.

As the recipe from Apicius shows (see box below), inhabitants of the Mediterranean region have been marinating fish for thousands of years. The common modern term, escabeche escabeche and variants on it, derives from the Arabic and variants on it, derives from the Arabic sikbaj, sikbaj, which in the 13th century named meat and fish dishes with vinegar (acetic acid, p. 772) added toward the end of the preparation. Other acidic liquids were also used, including wine and verjuice, the juice of unripe grapes. which in the 13th century named meat and fish dishes with vinegar (acetic acid, p. 772) added toward the end of the preparation. Other acidic liquids were also used, including wine and verjuice, the juice of unripe grapes.

Fish and sh.e.l.lfish can be marinated in acid either raw or after an initial salting or cooking. In northern Europe, for example, raw herring are immersed in marinade (3 parts fish to 2 parts of a 10% salt, 6% acetic acid mixture) for up to a week, at a temperature around 50F/10C; while for marinated j.a.panese mackerel (s.h.i.+mesaba) the fillets are first dry-salted for a day, then immersed in vinegar for a day. In the case of precooked fish, the initial heat treatment kills bacteria and firms texture, so the subsequent marination is a milder one, and there is less development of texture and flavor.

Canned Fish Because canned fish keep indefinitely without refrigeration and in a handy package, this is the preserved fish that most of us eat most often. In the United States, it is the most popular of all fish products: we consume more than a billion cans of tuna every year. Fish and sh.e.l.lfish were first heated in a hermetically sealed container around 1810 by Nicholas Appert, princ.i.p.al inventor of the process. Fellow Frenchman Joseph Colin started canning sardines a little over a decade later; American fishermen canned oysters in Delaware around 1840 and Pacific salmon around 1865, and Italian immigrants founded the canned tuna industry around San Diego in 1903. Today, salmon, tuna, and sardines are the most popular canned seafoods worldwide.

Most canned fish are heated twice: once before the cans are sealed, to cause the inevitable cooking losses and allow the moisture (as well as flavor and healthful oils) to be drained away, so that the can contents won't be watery; and once after the cans are sealed to sterilize the contents, usually under pressurized steam at about 240F/115C. This second treatment is sufficient to soften fish bones, so fish canned with its bones is an excellent source of calcium (fresh fish contains about 5 milligrams of calcium per 4 oz/100 g; canned salmon contains 200 to 250). A number of additives are permitted in canned fish, particularly tuna, to improve flavor and appearance. These include monosodium glutamate and various forms of hydrolyzed protein, which are proteins broken down into savory amino acids (including glutamate). Premium canned fish is cooked only once, in the container, retaining its juices, and needs no improvement by additives.

Ancient EscabecheTo make fried fish keep longer. The moment that they are fried and lifted from the pan, pour hot vinegar over them.- Apicius, first few centuries CE CE Fish Eggs Of all foods from the waters, the most expensive and luxurious are fish eggs. Caviar, the salted roe of the sturgeon, is the animal kingdom's truffle: a remarkable food that has become increasingly rare as civilization has encroached on its wild source. Happily, sturgeon farms are now producing good caviar, and a variety of other fish eggs are available as affordable and interesting alternatives.

The ovaries or "roes" of fish acc.u.mulate vast numbers of eggs in preparation for sp.a.w.ning: as many as 20,000 in a single salmon, and several million in a sturgeon, carp, or shad. Because fish eggs contain all the nutrients that one cell will need to grow into a hatchling, they're often a more concentrated form of nourishment than the fish itself, with more fat (between 10 and 20% in sturgeon and salmon caviars) and large quant.i.ties of savory building-block amino acids and nucleic acids. They often contain attractive pigments, sometimes bright pink or yellow carotenoids, sometimes camouflaging brown-black melanins.

The best roes for both cooking and salting are neither very immature nor fully ripe: immature eggs are small and hard and have little flavor; eggs ready for sp.a.w.ning are soft, easily crushed, and quick to develop off-flavors. Roes consist of separate eggs barely held together in a dilute protein solution and enclosed in a thin, fragile membrane. They can be easier to handle in the kitchen if they're first briefly poached to coagulate the protein solution and give them a firmer consistency.

Male fish acc.u.mulate sperm to release into the water when the females release their eggs. The sperm ma.s.s is called white roe, milt, or laitance, laitance, and is creamy rather than granular (the sperm cells suspended in the proteinaceous fluid are microscopic). Sea bream and cod milts are prized in j.a.pan, where they're cooked gently to a delicate custard-like consistency. and is creamy rather than granular (the sperm cells suspended in the proteinaceous fluid are microscopic). Sea bream and cod milts are prized in j.a.pan, where they're cooked gently to a delicate custard-like consistency.

A salmon egg. Like the chicken egg, the inner yolk is surrounded by a protein-rich fluid, and contains fatty materials, including fat-soluble carotenoid pigments, and the living egg cell.

Salt Transforms Egg Flavor and Texture Heavy Salting: Bottarga Bottarga Fish eggs are more frequently consumed salted than they are fresh. Originally, salting was simply a means of preserving the eggs. For millennia in the Mediterranean, whole mullet and tuna ovaries have been dry-salted, pressed, and dried to make what's now best known as Fish eggs are more frequently consumed salted than they are fresh. Originally, salting was simply a means of preserving the eggs. For millennia in the Mediterranean, whole mullet and tuna ovaries have been dry-salted, pressed, and dried to make what's now best known as bottarga bottarga (there are almost identical Asian versions). The salting and drying cause a concentration of amino acids, fatty materials, and sugars, which react with each other in the complex browning reactions to darken the color to a deep red-brown and generate rich, fascinating flavors reminiscent of parmesan cheese and even tropical fruits! Bottarga is now a delicacy, sliced paper-thin and served as an antipasto, or grated onto plain hot pasta. (there are almost identical Asian versions). The salting and drying cause a concentration of amino acids, fatty materials, and sugars, which react with each other in the complex browning reactions to darken the color to a deep red-brown and generate rich, fascinating flavors reminiscent of parmesan cheese and even tropical fruits! Bottarga is now a delicacy, sliced paper-thin and served as an antipasto, or grated onto plain hot pasta.

Light Salting: Caviar It turned out that salting has even more to offer when applied sparingly to loose, moist fish eggs. A small dose of salt triggers the action of protein-digesting enzymes in the egg, which boost the levels of taste-stimulating free amino acids. It also triggers another enzyme (transglutaminase) that cross-links proteins in the outer egg membrane and helps toughen it, thus giving the egg more texture. By generating a brine that gets drawn into the s.p.a.ce between the outer and yolk membranes, salt plumps the egg, making it rounder and firmer. And by changing the distribution of electrical charges on the proteins within, it causes the proteins to bond to each other and thicken the watery egg fluids to a honey-like luxuriousness. It turned out that salting has even more to offer when applied sparingly to loose, moist fish eggs. A small dose of salt triggers the action of protein-digesting enzymes in the egg, which boost the levels of taste-stimulating free amino acids. It also triggers another enzyme (transglutaminase) that cross-links proteins in the outer egg membrane and helps toughen it, thus giving the egg more texture. By generating a brine that gets drawn into the s.p.a.ce between the outer and yolk membranes, salt plumps the egg, making it rounder and firmer. And by changing the distribution of electrical charges on the proteins within, it causes the proteins to bond to each other and thicken the watery egg fluids to a honey-like luxuriousness.

In sum, a light salting transforms fish eggs from a mere pleasant mouthful into the remarkable food known as caviar: a fleeting taste of the primordial brine and the savory molecules from which all life springs.

Caviar Caviar appears to have arisen in Russia sometime around 1200 CE CE as a more palatable alternative to the traditional preserved sturgeon ovaries. Though the term as a more palatable alternative to the traditional preserved sturgeon ovaries. Though the term caviar caviar is now widely used to describe any sort of lightly salted loose fish eggs, for many centuries it referred only to loose sturgeon eggs. The most sought-after caviar still comes from a handful of sturgeon species mainly harvested by Russian and Iranian fishermen as the fish enter the rivers that drain into the Caspian Sea. is now widely used to describe any sort of lightly salted loose fish eggs, for many centuries it referred only to loose sturgeon eggs. The most sought-after caviar still comes from a handful of sturgeon species mainly harvested by Russian and Iranian fishermen as the fish enter the rivers that drain into the Caspian Sea.

Just 150 years ago, sturgeon were common in many large rivers the northern hemisphere, and caviar was plentiful enough in Russia that Elena Molokhovets suggested using it to clarify bouillons and to decorate sauerkraut "so that it appears as if it were strewn with poppy seeds"! But overfis.h.i.+ng, dams and hydroelectric plants, and industrial pollution have since put many sturgeon species in danger of extinction. Around 1900, sturgeon roe became rare, expensive, and therefore a sought-after luxury - and so even more expensive. The trend has continued, with Caspian sturgeon populations plummeting and U.N. organizations considering an export ban on caviar from the region. In recent decades, caviar production has been growing further east, along the Amur River in both Russia and China, and on sturgeon farms in the United States and elsewhere.

Making Caviar In traditional caviar-making, sturgeon are captured alive in nets, stunned, and their roe sacs removed before they are killed and butchered. The caviar maker pa.s.ses the roe through screens to loosen the eggs and separate them from the ovary membrane, sorts and grades the eggs, and then dry-salts and mixes them by hand for two to four minutes to obtain a final salt concentration between 3 and 10%. (Small amounts of alkaline borax [sodium borate] have been used since the 1870s to replace part of the salt, making the caviar taste sweeter and improving its shelf life, but the United States and some other countries forbid borax in their imports.) The eggs are allowed to drain for 5 to 15 minutes, filled into large cans, and chilled to 26F/3C (the salt prevents freezing at this temperature). In traditional caviar-making, sturgeon are captured alive in nets, stunned, and their roe sacs removed before they are killed and butchered. The caviar maker pa.s.ses the roe through screens to loosen the eggs and separate them from the ovary membrane, sorts and grades the eggs, and then dry-salts and mixes them by hand for two to four minutes to obtain a final salt concentration between 3 and 10%. (Small amounts of alkaline borax [sodium borate] have been used since the 1870s to replace part of the salt, making the caviar taste sweeter and improving its shelf life, but the United States and some other countries forbid borax in their imports.) The eggs are allowed to drain for 5 to 15 minutes, filled into large cans, and chilled to 26F/3C (the salt prevents freezing at this temperature).

The most highly prized caviar is the most perishable. It goes by the Russian term malossol, malossol, which means "little salt," and ranges from 2.53.5% salt. The cla.s.sicCaspian caviars have distinctive sizes, colors, and flavors. Beluga is the rarest, largest, and most expensive. Osetra, the most common wild caviar, comes mainly from the Black and Azov seas, is tinged with brown, and has a flavor reminiscent of oysters. Sevruga caviar is dark and has a less complicated flavor. "Pressed caviar" is a relatively inexpensive, saltier (to 7%), strong-tasting paste made from overmature eggs, and can be frozen. which means "little salt," and ranges from 2.53.5% salt. The cla.s.sicCaspian caviars have distinctive sizes, colors, and flavors. Beluga is the rarest, largest, and most expensive. Osetra, the most common wild caviar, comes mainly from the Black and Azov seas, is tinged with brown, and has a flavor reminiscent of oysters. Sevruga caviar is dark and has a less complicated flavor. "Pressed caviar" is a relatively inexpensive, saltier (to 7%), strong-tasting paste made from overmature eggs, and can be frozen.

Salmon and Other Caviars Russia pioneered the development of salmon caviar in the 1830s, and it's a delicious and affordable alternative, with its striking red-pink translucence and large grains. The separated eggs of chum and pink salmons are soaked in saturated brine for 2 to 20 minutes to achieve a final salt level of 3.54%, then drained and dried for up to 12 hours. Lumpfish caviar dates from the 1930s, when the sevruga-sized eggs of this otherwise little-used fish were salted and dyed to imitate the real thing. Whitefish eggs are similar in size and left undyed to retain their golden color. In recent years, the roe of herring, anchovy, and even lobster have been used to make caviars. Caviars may be pasteurized (120160F/5070C for 12 hours) to prolong their shelf life, but this can produce a rubbery off-aroma and chewy texture. Russia pioneered the development of salmon caviar in the 1830s, and it's a delicious and affordable alternative, with its striking red-pink translucence and large grains. The separated eggs of chum and pink salmons are soaked in saturated brine for 2 to 20 minutes to achieve a final salt level of 3.54%, then drained and dried for up to 12 hours. Lumpfish caviar dates from the 1930s, when the sevruga-sized eggs of this otherwise little-used fish were salted and dyed to imitate the real thing. Whitefish eggs are similar in size and left undyed to retain their golden color. In recent years, the roe of herring, anchovy, and even lobster have been used to make caviars. Caviars may be pasteurized (120160F/5070C for 12 hours) to prolong their shelf life, but this can produce a rubbery off-aroma and chewy texture.

Commonly Eaten Fish Eggs

Source

Qualities, Names Qualities, Names

Carp

1Very small, light pink; sometimes salted Greece: 1Very small, light pink; sometimes salted Greece: tarama tarama

Cod, pollack

Very small, pink, sometimes salted, pressed, dried, smoked j.a.pan: Very small, pink, sometimes salted, pressed, dried, smoked j.a.pan: ajitsuki, tarako, momijiko ajitsuki, tarako, momijiko

Flying fish

Small, yellow, often dyed orange or black, crunchy j.a.pan: Small, yellow, often dyed orange or black, crunchy j.a.pan: tobiko tobiko

Grey mullet

Small; often salted; pressed and dried for Small; often salted; pressed and dried for bottarga bottarga Italy: Italy: bottarga, bottarga, Greece: Greece: tarama tarama; j.a.pan: karasumi karasumi

Herring

Medium, yellow-gold, sometimes salt-cured; prized in j.a.pan when attached to kelp j.a.pan: Medium, yellow-gold, sometimes salt-cured; prized in j.a.pan when attached to kelp j.a.pan: kazunoko kazunoko

Lumpfish

Small, fish common in North Atlantic and Baltic; greenish eggs often dyed red or black, heavily salted, pasteurized, bottled Small, fish common in North Atlantic and Baltic; greenish eggs often dyed red or black, heavily salted, pasteurized, bottled

Salmon

Large (45 mm) red-orange eggs mainly from chum salmon ( Large (45 mm) red-orange eggs mainly from chum salmon (Oncorhynchus keta), usually lightly brined and sold fresh j.a.pan: whole ovary sujiko, sujiko, separated eggs separated eggs ikura ikura

Shad

Small, from herring relative Small, from herring relative

Sturgeon

Medium-sized; lightly salted to make caviar Medium-sized; lightly salted to make caviar

Trout

Large yellow eggs from Great Lakes trout Large yellow eggs from Great Lakes trout

Tuna

Small; often salted; pressed and dried for Small; often salted; pressed and dried for bottarga bottarga Italy: Italy: bottarga bottarga

Whitefish

Small, golden, crunchy, from freshwater cousins of salmon in Northern Hemisphere; often flavored or smoked Small, golden, crunchy, from freshwater cousins of salmon in Northern Hemisphere; often flavored or smoked

Chapter 5.

Edible Plants An Introduction to Fruits and Vegetables, Herbs and Spices

Plants as Food The Nature of PlantsDefinitionsPlant Foods Through History Plant Foods and Health Essential Nutrients in Fruits and Vegetables: VitaminsPhytochemicalsFiberToxins in Some Fruits and VegetablesFresh Produce and Food Poisoning The Composition and Qualities of Fruits and Vegetables Plant Structure: Cells, Tissues, and OrgansTextureColorFlavor Handling and Storing Fruits and Vegetables Post-Harvest DeteriorationHandling Fresh ProduceThe Storage AtmosphereTemperature Control: RefrigerationTemperature Control: Freezing Cooking Fresh Fruits and Vegetables How Heat Affects the Qualities of Fruits and VegetablesHot Water: Boiling, Steaming, Pressure-CookingHot Air, Oil, and Radiation: Baking, Frying, and GrillingMicrowave CookingPulverizing and Extracting Preserving Fruits and Vegetables Drying and Freeze-DryingFermentation and Pickling: Sauerkraut and Kimchi, Cuc.u.mber Pickles, OlivesSugar PreservesCanning We turn now from milk, eggs, meats, and fish, all expressions of animating protein and energizing fat, and enter the very different world that sustains them and us alike. The plant world encompa.s.ses earthy roots, bitter and pungent and refres.h.i.+ng leaves, perfumed flowers, mouth-filling fruits, nutty seeds, sweetness and tartness and astringency and pleasing pain, and aromas by the thousands! It turns out that this exuberantly diverse world was born of simple, harsh necessity. Plants can't move as animals do. In order to survive their immobile, exposed condition, they became virtuosic chemists. They construct themselves from the simplest materials of the earth itself, water and rock and air and light, and thus transform the earth into food on which all animal life depends. Plants deter enemies and attract friends with colors, tastes, and scents, all chemical inventions that have shaped our ideas of beauty and deliciousness. And they protect themselves from the common chemical stresses of living with substances that protect us as well. So when we eat vegetables and fruits and grains and spices, we eat the foods that made us possible, and that opened our life to a kaleidoscopic world of sensation and delight.

Human beings have always been plant eaters. For a million years and more, our omnivorous ancestors foraged and lived on a wide range of wild fruits, leaves, and seeds. Beginning around 10,000 years ago they domesticated a few grains, seed legumes, and tubers, which are among the richest sources of energy and protein in the plant world, and can be grown and stored in large quant.i.ties. This control over the food supply made it possible for many people to be fed reliably from a small patch of land: so cultivation of the fields led to settlement, the first cities, and cultivation of the human mind. On the other hand, agriculture drastically reduced the variety of plant foods in the human diet. Millennia later, industrialization reduced it even further. Fruits and vegetables became accessory, even marginal foods in the modern Western diet. Only recently have we begun to understand how the human body still depends for its long-term health on a various diet rich in fruits and vegetables, herbs and spices. Happily, modern technologies now give us unprecedented access to the world's cornucopia of edible plants. The time is ripe to explore this fascinating - and still evolving - legacy of natural and human inventiveness.

This chapter is a general introduction to the foods that we obtain from plants. Because there are so many of them, particular fruits and vegetables, herbs and spices are described in subsequent chapters. Foods derived from seeds - grains, legumes, nuts - have special properties, and are described separately in chapter 9.

The Original FoodThe idea that plants are our original and therefore only proper food has deep cultural roots. In the Golden Age described by Greek and Roman mythology, the earth gave of itself freely, without cultivation, and humans ate only nuts and fruit. And in Genesis, Adam and Eve spend their brief innocence as gardeners:And the Lord G.o.d planted a garden eastward in Eden; and there he put the man whom he had formed. And out of the ground made the Lord G.o.d to grow every tree that is pleasant to the sight, and good for food...And the Lord G.o.d took the man, and put him into the Garden of Eden to dress it and to keep it.The Bible doesn't mention meat as food until after it records the first killing, Cain's murder of his brother Abel. Many individuals and groups from Pythagoras to the present have chosen to eat only plant foods to avoid taking the life of another creature capable of feeling pain. And most people throughout history have had no choice, because meat is far more costly to produce than grains and tubers.

Plants as Food The Nature of Plants Plants and animals are very different kinds of living things, and this is because they have evolved different solutions to a single basic challenge: how to obtain the energy and substance necessary to grow and reproduce. Plants essentially nourish themselves. They build their tissues out of water, minerals, and air, and run them on the energy in sunlight. Animals, on the other hand, can't extract energy and construct complex molecules from such primitive materials. They must obtain them premade, and they do so by consuming other living things. Plants are independent autotrophs, autotrophs, while animals are parasitic while animals are parasitic heterotrophs. heterotrophs. (Parasitism may not sound especially admirable, but without it there would be no need to eat and so none of the pleasures of eating and cooking!) (Parasitism may not sound especially admirable, but without it there would be no need to eat and so none of the pleasures of eating and cooking!) There are various ways of being an autotroph. Some archaic bacteria, which are microbes consisting of a single cell, manipulate sulfur, nitrogen, and iron compounds to produce energy. The most important development for the future of eating came more than 3 billion years ago with the evolution of a bacterium that could tap the energy in sunlight and store it in carbohydrate molecules (molecules built from carbon, hydrogen, and oxygen). Chlorophyll, the green pigment we see in vegetation all around us, is a molecule that captures sunlight and initiates this process of photosynthesis, photosynthesis, which culminates in the creation of the simple sugar glucose. which culminates in the creation of the simple sugar glucose.

6CO2 + 6H + 6H2O + light energy[image] C C6H12O6 + 6O + 6O2carbon dioxide + water + light energy[image] glucose + oxygen glucose + oxygen The bacteria that managed to "invent" chlorophyll gave rise to algae and all green land plants - and indirectly to land animals as well. Before photosynthesis, the earth's atmosphere contained little oxygen, and the sun's killing ultraviolet rays penetrated all the way to the ground and several feet into the oceans. Living organisms could therefore survive only in deeper waters. When photosynthetic bacteria and early algae burgeoned, they liberated vast quant.i.ties of oxygen (O2), which radiation in the upper atmosphere converted to ozone (O3), which in turn absorbed ultraviolet light and prevented much of it from reaching the earth's surface. Land life was now possible.

The challenging life of the plant. Plants are rooted to one spot in the earth, where they absorb water and minerals from the soil, carbon dioxide and oxygen from the air, and light energy from the sun, and transform these inorganic materials into plant tissues - and into nourishment for insects and other animals. Plants defend themselves against predators with a variety of chemical weapons, some of which also make them flavorful, healthful, or both. In order to spread their offspring far and wide, some plants surround their seeds with tasty and nouris.h.i.+ng fruits that animals carry away and eat, often spilling some seeds in the process.

So we owe our very existence as oxygen-breathing, land-dwelling animals to the greenery we walk through and cultivate and consume every day of our lives.

Why Plants Aren't Meaty Land-dwelling plants that can nourish themselves still need access to the soil for minerals and trapped water, to the atmosphere for carbon dioxide and oxygen, and to the sun for energy. All of these sources are pretty reliable, and plants have developed an economical structure that takes advantage of this reliability. Roots penetrate the soil to reach stable supplies of water and minerals; leaves maximize their surface area to capture sunlight and exchange gases with the air; and stalks support leaves and connect them with roots. Plants are essentially stationary chemical factories, made up of chambers for carbohydrate synthesis and carbohydrate storage, and tubes to transfer chemicals from one part of the factory to another, with structural reinforcement - also mainly carbohydrates - to provide mechanical rigidity and strength. Parasitic animals, by contrast, must find and feed on other organisms, so they are constructed mainly of muscle proteins that transform chemical energy into physical motion (p. 121). Land-dwelling plants that can nourish themselves still need access to the soil for minerals and trapped water, to the atmosphere for carbon dioxide and oxygen, and to the sun for energy. All of these sources are pretty reliable, and plants have developed an economical structure that takes advantage of this reliability. Roots penetrate the soil to reach stable supplies of water and minerals; leaves maximize their surface area to capture sunlight and exchange gases with the air; and stalks support leaves and connect them with roots. Plants are essentially stationary chemical factories, made up of chambers for carbohydrate synthesis and carbohydrate storage, and tubes to transfer chemicals from one part of the factory to another, with structural reinforcement - also mainly carbohydrates - to provide mechanical rigidity and strength. Parasitic animals, by contrast, must find and feed on other organisms, so they are constructed mainly of muscle proteins that transform chemical energy into physical motion (p. 121).

Why Plants Have Strong Flavors and Effects Animals can also use their mobility to avoid becoming another creature's meal, by fleeing or fighting. But stationary plants? They compensate for their immobility with a remarkable ability for chemical synthesis. These master alchemists produce thousands of strong-tasting, sometimes poisonous warning signals that discourage bacteria, fungi, insects, and us from attacking them. A partial list of their chemical warfare agents would include irritating compounds like mustard oil, hot-chilli capsaicin, and the tear-inducing factor in onions; bitter and toxic alkaloids like caffeine in coffee and solanine in potatoes; the cyanide compounds found in lima beans and many fruit seeds; and substances that interfere with the digestive process, including astringent tannins and inhibitors of digestive enzymes. Animals can also use their mobility to avoid becoming another creature's meal, by fleeing or fighting. But stationary plants? They compensate for their immobility with a remarkable ability for chemical synthesis. These master alchemists produce thousands of strong-tasting, sometimes poisonous warning signals that discourage bacteria, fungi, insects, and us from attacking them. A partial list of their chemical warfare agents would include irritating compounds like mustard oil, hot-chilli capsaicin, and the tear-inducing factor in onions; bitter and toxic alkaloids like caffeine in coffee and solanine in potatoes; the cyanide compounds found in lima beans and many fruit seeds; and substances that interfere with the digestive process, including astringent tannins and inhibitors of digestive enzymes.

If plants are so well endowed with their own natural pesticides, then why isn't the world littered with the corpses of their victims? Because animals have learned to recognize and avoid potentially harmful plants with the help of their senses of smell and taste, which can detect chemical compounds in very small concentrations. Animals have developed appropriate innate responses to significant tastes - aversion to the bitterness typical of alkaloids and cyanide, attraction to the sweetness of nutritionally important sugars. And some animals have developed specific detoxifying enzymes that enable them to exploit an otherwise toxic plant. The koala bear can eat eucalyptus leaves, and monarch b.u.t.terfly caterpillars milkweed. Humans invented their own ingenious detoxifying methods, including plant selection and breeding and cooking. Cultivated varieties of such vegetables as cabbage, lima beans, potatoes, and lettuce are less toxic than their wild ancestors. And many toxins can be destroyed by heat or leached away in boiling water.

A fascinating wrinkle in this story is that humans actually prize and seek out certain plant toxins! We've managed to learn which irritating warning signals are relatively harmless, and have come to enjoy sensations whose actual purpose is to repel us. Hence our seemingly perverse love of mustard and pepper and onions. This is the essential appeal of herbs and spices, as we'll see in chapter 8.

Why Ripe Fruits Are Especially Delicious The higher plants and animals reproduce by fusing genetic material from male and female s.e.x organs, usually from different individuals. Animals have the advantage of being mobile: male and female can sense each other's presence and move toward each other. Plants can't move, and instead have to depend on mobile go-betweens. The male pollen of most land plants is carried to the female ovule by the wind or by animals. To encourage animals to help out, advanced plants evolved the flower, an organ whose shape, color, and scent are designed to attract a particular a.s.sistant, usually an insect. As it flies around and collects nutritious nectar or pollen for food, the insect spreads the pollen from one plant to another. The higher plants and animals reproduce by fusing genetic material from male and female s.e.x organs, usually from different individuals. Animals have the advantage of being mobile: male and female can sense each other's presence and move toward each other. Plants can't move, and instead have to depend on mobile go-betweens. The male pollen of most land plants is carried to the female ovule by the wind or by animals. To encourage animals to help out, advanced plants evolved the flower, an organ whose shape, color, and scent are designed to attract a particular a.s.sistant, usually an insect. As it flies around and collects nutritious nectar or pollen for food, the insect spreads the pollen from one plant to another.

Once male and female cells have come together and developed into offspring, they must be given a good start. The animal mother can search out a promising location and deposit her young there. But plants need help. If the seeds simply dropped from the plant to the ground, they would have to compete with each other and with their overshadowing parent for sunlight and soil minerals. So successful plant families have developed mechanisms for dispersing their seeds far and wide. These mechanisms include seed containers that pop open and propel their contents in all directions, seed appendages that catch the wind or the fur of a pa.s.sing animal - and structures that hitch a ride inside inside pa.s.sersby. Fruits are plant organs that actually invite animals to eat them, so that the animals will carry their seeds away, and often pa.s.s them through their digestive system and deposit them in a nouris.h.i.+ng pile of manure. (The seeds escape destruction in various ways, among them by being large and armored, or tiny and easily spilled, or poisonous.) pa.s.sersby. Fruits are plant organs that actually invite animals to eat them, so that the animals will carry their seeds away, and often pa.s.s them through their digestive system and deposit them in a nouris.h.i.+ng pile of manure. (The seeds escape destruction in various ways, among them by being large and armored, or tiny and easily spilled, or poisonous.) So, unlike the rest of the plant, fruit is meant meant to be eaten. This is why its taste, odor, and texture are so appealing to our animal senses. But the invitation to eat must be delayed until the seeds are mature and viable. This is the purpose of the changes in color, texture, and flavor that we call ripening. Leaves, roots, stalks can be eaten at any time, generally the earlier the tenderer. But we must wait for fruit to signal that it is ready to be eaten. The details of ripening are described in chapter 7 (p. 350). to be eaten. This is why its taste, odor, and texture are so appealing to our animal senses. But the invitation to eat must be delayed until the seeds are mature and viable. This is the purpose of the changes in color, texture, and flavor that we call ripening. Leaves, roots, stalks can be eaten at any time, generally the earlier the tenderer. But we must wait for fruit to signal that it is ready to be eaten. The details of ripening are described in chapter 7 (p. 350).