On Food And Cooking Part 43

Undaria Undaria species species

Miso soup, salads (j.a.pan) Miso soup, salads (j.a.pan)

Hiziki

Hizikia fusiformis Hizikia fusiformis

Vegetable, soups, "tea" (j.a.pan, China) Vegetable, soups, "tea" (j.a.pan, China)

Seaweed and the Original MSG Seaweed and the Original MSGIt was a seaweed that provoked a breakthrough in the understanding of human taste - and also brought the world the controversial food additive known as MSG. For better than a thousand years, the j.a.panese have been using the brown alga kombu as the base for soup stocks. In 1908 a j.a.panese chemist, Kikunae Ikeda, found that kombu is an especially rich source of monosodium glutamate - in fact it forms crystals on the surface of dried kombu. He also found that MSG provides a unique, savory taste sensation, different from the standard sweet, sour, salty, and bitter. He named this sensation umami umami (a rough translation is "delicious"), and pointed out that other foods, including meats and cheese, also provide it. For decades, Western scientists were skeptical that umami was a genuine taste sensation of its own, and not just a general taste enhancer. Finally, in 2001, biologist Charles Zuker at the University of California, San Diego, and colleagues demonstrated conclusively that humans and other animals do have a specific taste receptor for MSG. (a rough translation is "delicious"), and pointed out that other foods, including meats and cheese, also provide it. For decades, Western scientists were skeptical that umami was a genuine taste sensation of its own, and not just a general taste enhancer. Finally, in 2001, biologist Charles Zuker at the University of California, San Diego, and colleagues demonstrated conclusively that humans and other animals do have a specific taste receptor for MSG.A few years after Ikeda's observations, a colleague of his discovered a different umami substance (inosine monophosphate, or IMP) in cured skipjack tuna, another soup-base ingredient (p. 237). Then in 1960, Akira Kuninaka reported an umami substance in s.h.i.+take mushrooms (guanosine monophosphate, or GMP). Kuninaka also discovered that these different substances were synergistic with each other and with MSG: a very small amount of each strengthens the other's taste. Sensory scientists are still working to understand the nature of these effects.A year after Ikeda's discovery, the j.a.panese company Ajinomoto began selling pure MSG as a seasoning, extracting it from the wheat gluten proteins that are a rich source of glutamate and in fact gave it its name. It caught on quickly, first with cooks in j.a.pan and China and then with food manufacturers throughout the world. Ajinomoto is now a large multinational corporation; it and other companies produce MSG by the ton using bacteria that synthesize large amounts and excrete it into the liquid they grow in.Beginning in the late 1960s, MSG was blamed for the "Chinese restaurant syndrome," in which distressing sensations of burning, pressure, and chest pain suddenly strike susceptible people who begin a Chinese meal with MSG-laden soup. Many studies later, toxicologists have concluded that MSG is a harmless ingredient for most people, even in large amounts. The most unfortunate aspect of the MSG saga is how it has been exploited to provide a cheap, one-dimensional subst.i.tute for real and remarkable foods. As Fuchsia Dunlop writes in her book on Sichuan cooking, Land of Plenty Land of Plenty,It is a bitter irony that in China of all places, where chefs have spent centuries developing the most sophisticated culinary techniques, this ma.s.s-produced white powder should have been given the name wei jing, wei jing, "the essence of flavor." "the essence of flavor."

The watery home of the seaweeds has shaped their nature in several ways that matter to the cook: Their buoyancy in water has allowed free-floating algae to minimize tough structural supports and maximize photosynthetic tissue. Some algae (e.g., nori, sea lettuce) are essentially all leaf, just one or two cells thick, very tender and delicate.

Their immersion in salt waters of varying concentration has led algae to acc.u.mulate various molecules to keep their cells in osmotic balance. Some of these molecules contribute to their characteristic flavor. Mannitol, a sugar alcohol, is sweet (and, since our bodies can't metabolize it, low-calorie; see p. 662); glutamic acid is savory; and certain complex sulfur compounds give rise to aromatic, oceany dimethyl sulfide.

Because water selectively absorbs red wavelengths from sunlight, some algae supplement their chlorophyll with special pigments for capturing the remaining wavelengths. Many seaweeds are either brown or reddish-purple, and change color when cooked.

The many physical stresses of ocean life have encouraged some seaweeds to fill their cell walls with large quant.i.ties of jelly-like material that gives their tissues strength and flexibility, can be sloughed from their surface, and can help keep coastal species moist when they're exposed to the air at low tide. These special carbohydrates turn out to be useful for making jellies (agar) and for thickening various foods (algin, carrageenan). (More on thickeners in chapter 11.) Green, Red, and Brown Algae Nearly all edible seaweeds belong to one of three broad groups: the green algae, the red algae, and the brown algae.

Green algae - sea lettuce, awonori - are the most like the land plants to which they gave rise. Their primary photosynthetic pigments are chlorophylls, with smaller amounts of carotenoids, and they store energy in the form of starch.

Red algae - nori, dulse - are most common in tropical and subtropical waters. They owe their color to special pigment-protein complexes that are soluble in water and sensitive to heat: so during cooking their color can change quite strikingly from red to green. Red algae store their energy in a distinctive form of starch, and also produce large quant.i.ties of the sugar galactose and chains made up from it, which give us the gelling agents agar-agar and carrageenan.

Brown algae - kelp, wakame - dominate temperate waters and supplement their chlorophyll with a group of carotenoid pigments, notably brownish fuc.o.xanthin. They store some of their energy in the sweet sugar alcohol mannitol, which can amount to a quarter of the dry weight of fall-harvested kelp, and their typical mucilaginous material is algin.

Some freshwater algae are also collected from rivers and ponds: for example, species of Cladophora, Cladophora, which in Southeast Asia are pressed into nori-like sheets and used similarly (Laotian kaipen). Two alga-like creatures that are actually blue-green bacteria sometimes figure in the kitchen: the nutritional supplement spirulina and the Chinese "hair vegetable" or "hair moss," species of which in Southeast Asia are pressed into nori-like sheets and used similarly (Laotian kaipen). Two alga-like creatures that are actually blue-green bacteria sometimes figure in the kitchen: the nutritional supplement spirulina and the Chinese "hair vegetable" or "hair moss," species of Nostoc, Nostoc, which grows in mountain springs in the Mongolian desert. which grows in mountain springs in the Mongolian desert.

Seaweed Flavors When it comes to flavor, the three seaweed families share a basic salty-savory taste from concentrated minerals and amino acids, especially glutamic acid, which is one of the molecules used to transport energy from one part of the seaweed to another. Seaweeds also share the aroma of dimethyl sulfide, which is found in cooked milk, corn, and sh.e.l.lfish as well as in seacoast air. There are also fragments of highly unsaturated fatty acids (mainly aldehydes) that contribute green-tea-like and fishy overtones. Against this common background, the three families do have distinctive characters. Dried, the red seaweeds tend to develop a deeper sulfury aroma from hydrogen sulfide and methanethiol, as well as flowery, black-tea-like notes from breakdown of their carotene pigments. When fried, dulse develops a distinct aroma of bacon. Some red algae, including the limu kohu of Hawaii (Asparagopsis), acc.u.mulate compounds of bromine and iodine, and can have a strong iodine flavor. The generally mild brown seaweeds have a characteristic iodine note (iodooctane) as well as a hay-like one (from the terpene cubenol). A few, notably species of Dictyopteris Dictyopteris used as flavorings in Hawaii, have spicy aroma compounds that are apparently reproductive signals. Some browns are noticeably astringent thanks to the presence of tannin-like phenolic compounds, which in the dried seaweed form brown-black complexes (phycophaeins). used as flavorings in Hawaii, have spicy aroma compounds that are apparently reproductive signals. Some browns are noticeably astringent thanks to the presence of tannin-like phenolic compounds, which in the dried seaweed form brown-black complexes (phycophaeins).

Prolonged cooking in liquid tends to accentuate fishy aromas, so often seaweeds are cooked only briefly. The first step in making the j.a.panese soup base das.h.i.+, for example, is to start dried brown kelp kombu in cold water, bring it just to the boil, then remove the kombu, leaving behind mainly its savory soluble minerals and amino acids. Because flavorsome minerals and amino acids crystallize on and in dried seaweeds, they contribute more when they're left unwashed, and if thick, when scored with a knife to release substances from within.

Mushrooms, Truffles, and Relatives Mushrooms and their relatives are not true plants. They belong to a separate biological kingdom, the Fungi (the plural form of fungus fungus), which they share with molds and yeasts.

Creatures of Symbiosis and Decay Unlike plants, the fungi have no chlorophyll and cannot harvest energy from sunlight. They therefore live off the substance of other living things, including plants and plant remains. Different mushrooms do this in different ways. Some mushrooms, including boletes and truffles, form a symbiosis with living trees, a relations.h.i.+p in which both partners benefit: the mushrooms gather soil minerals and share them with the tree roots, which in turn share the tree's sugars with the mushrooms. Some fungi are parasites on living plants and cause disease; we eat the plant parasite that infects corncobs (corn s.m.u.t, or huitlacoche). And some, including the world's most popular mushrooms, live off the decaying remains of dead plants. White and brown mushrooms apparently evolved along with plant-eating mammals to take advantage of the animals' partly digested but nutrient-rich dung! They now thrive in artificial piles of compost and manure.

Mushrooms that live on decaying plants have been relatively easy to cultivate. The Chinese were raising s.h.i.+take mushrooms on oak logs in the 13th century. The cultivation of the common white mushroom began in 17th-century France and boomed during the Napoleonic era in quarry tunnels near Paris. Today, Agaricus bisporus Agaricus bisporus (or (or A. brunnescens A. brunnescens) is grown on a mixture of manure, straw, and soil in dark buildings with carefully controlled humidity and temperature. The tropical zone's version of the b.u.t.ton mushroom is the (paddy-) straw mushroom, which grows on composted rice straw. On the other hand, cultivation of symbiotic species is difficult, because the mushrooms need living trees, and intensive production requires a forest. This is why boletes, chanterelles, and truffles are relatively rare and expensive: they're still largely gathered from the wild. Of an estimated 1,000 edible mushroom species, only a few dozen have been successfully cultivated.

The Structure and Qualities of Mushrooms Mushrooms differ from plants in several important ways. The part we eat is only one small portion of the organism, most of which lives invisibly underground as a fine, cottony network of fibers, or hyphae, which ramify through the soil to gather nutrients. A single cubic centimeter of soil - a small fraction of a cubic inch - can contain as much as 2,000 meters/yards of hyphae! When the underground ma.s.s of fibers has acc.u.mulated enough material and energy, it organizes a new, dense growth of interwoven hyphae into a fruiting body, which it pumps up with water to break above the soil surface and release its offspring spores into the air. The mushrooms that we eat are these fruiting bodies. (Morels form unusual hollow fruiting bodies with a distinctive honeycombed cap; the depressions bear the spores.) Because the fruiting body is critical to the mushroom's reproduction and survival, it's often protected from animal attack by defensive poisons. Some mushroom poisons are deadly. This is why wild mushrooms should be gathered only by experts in mushroom identification. One mushroom traditionally gathered and eaten in Europe is now thought to present an unpredictable but real risk of potentially fatal hydrazine poisoning; this is the gyromitre or false morel (species of Gyromitra Gyromitra).

Inflated by water as they are, mushrooms are 8090% water, with a thin outer cuticle that allows rapid moisture loss and gain. Their cell walls are reinforced not by plant cellulose, but by chitin, chitin, the carbohydrate-amine complex that also makes up the outer skeleton of insects and crustaceans. Mushrooms are notable for containing much more protein and vitamin B the carbohydrate-amine complex that also makes up the outer skeleton of insects and crustaceans. Mushrooms are notable for containing much more protein and vitamin B12than other fresh produce. A number of mushrooms have been used in traditional medicines, and there is scientific evidence that some of the unusual cell-wall carbohydrates in s.h.i.+takes, matsutakes, and the interestingly crunchy-gelatinous ear mushrooms contain substances that inhibit tumor growth. Another factor in s.h.i.+takes may limit the production of mutagenic nitrosamines in our digestive systems.

The anatomy of a mushroom. The hyphae are nutrient-gathering threads that grow through the soil. The main body of the mushroom is a fruiting body that the hyphae push up through the soil surface, which disperses spores from its gills.

The Distinctive Flavors of Mushrooms We prize fungi for their rich, almost meaty flavor and their ability to intensify the flavor of many dishes. These qualities are largely due to a high content of free amino acids, including glutamic acid, which makes mushrooms - like seaweeds - a concentrated natural source of monosodium glutamate. Another taste enhancer that's synergistic with glutamate, GMP (guanosine monophosphate), was first discovered in s.h.i.+take mushrooms, and contributes to the rich taste.

The characteristic aroma of fresh common mushrooms is mainly due to octenol (an 8-carbon alcohol), which is produced by enzymes from polyunsaturated fats when the tissue is damaged, and which helps deter attack by some snails and insects. More octenol is generated from the gill tissues than from other parts, and this is one reason that common mushrooms with immature, unopened caps are less flavorful than the mature version with prominent gills. Brown and field mushrooms have more flavor than the white mushroom, and the "portobello," a brown mushroom allowed to mature for an additional five or six days until it's about 6 in/15 cm across, is especially intense.

Other mushrooms offer a wide range of aromas. A close relative of the common mushroom produces the essence of almond extract, while more exotic species are valued for such flavor notes as cinnamon, pepper, garlic, pine needles, b.u.t.terscotch, and sh.e.l.lfish. s.h.i.+take mushrooms owe their distinctive aroma to an unusual molecule called lenthionine, a ring of carbon and sulfur atoms, which is created by enzymes when the tissue is damaged. Lenthionine production is maximized by the common practice of drying and then rehydrating s.h.i.+takes in warm water (it's minimized by rapid cooking of the fresh or dried mushroom, which destroys enzymes before they have a chance to act). With a few exceptions (chanterelles, oysters, matsutakes), drying intensifies mushroom flavor by a combination of heightened enzyme activities and browning reactions between amino acids and sugars. s.h.i.+takes and boletes, or porcini, are familiar examples, and especially flavorful because they're endowed with sulfur compounds that generate meaty aromas. Even home-dried b.u.t.ton mushrooms are far more flavorful than the fresh originals, though they lose their fresh-mushroom octenol.

Storing and Handling Mushrooms Mushrooms remain very active after harvest compared to most produce, and may even continue to grow. During four days' storage at room temperature, they lose about half of their energy reserves to the formation of cell-wall chitin. At the same time, they lose some of the enzyme activities that generate their fresh flavor, while protein-digesting enzymes become active in the stalk and turn the stalk proteins into amino acids for the cap and gills; so these parts become slightly more savory. Refrigeration at 4045F/46C will slow mushroom metabolism, but they should be loosely wrapped in moisture-absorbing packaging to avoid having the moisture they exhale wet their surfaces and encourage spoilage. Mushrooms should be used as quickly as possible after purchase.

Cookbooks often advise against was.h.i.+ng mushrooms so as not to make them soggy or dilute their flavor. However, they're already mostly water, and lose little if any flavor from a brief rinse. They should be cooked immediately, however, since was.h.i.+ng can damage the surface cells and cause general discoloration.

Cooking Mushrooms Mushrooms can be cooked in many different ways. Their flavor is generally most developed and intense when they are cooked slowly with dry heat to allow enzymes some time to work before being inactivated, and to cook out some of their abundant water and concentrate the amino acids, sugars, and aromas. Heat also collapses air pockets and consolidates the texture. (The combination of water and air loss means that mushrooms shrink considerably when cooked.) Like cellulose, chitin and some other cell-wall materials are not soluble in water, so mushrooms don't get mushy with prolonged cooking. The jelly and ear fungi, which are popular in Asian cuisines, contain an unusual amount of soluble carbohydrates, and this is why they develop a gelatinous texture.

Many mushrooms, and especially their gills, are rich in browning enzymes and blacken rapidly when cut or crushed. The dark pigments are water-soluble and can stain other ingredients in a dish, which may or may not be desirable.

Truffles Truffles are the fruiting bodies of species in the genus Tuber, Tuber, of which there are a handful of commercially important ones. They're typically a dense, k.n.o.bby ma.s.s, ranging from walnut-to fist-sized or larger. Unlike mushrooms, truffles remain hidden underground. They spread their spores by emitting a scent to attract animals - including beetles, squirrels, rabbits, and deer - which find and eat them and spread the spores in their dung. This is why truffles have a musky, persistent aroma - to attract their spore spreaders - and why they're still gathered with the help of trained dogs or pigs or by spotting truffle "flies," insects that hover over truffled ground and lay their eggs there so that the larvae can burrow down and feed on the fungus. of which there are a handful of commercially important ones. They're typically a dense, k.n.o.bby ma.s.s, ranging from walnut-to fist-sized or larger. Unlike mushrooms, truffles remain hidden underground. They spread their spores by emitting a scent to attract animals - including beetles, squirrels, rabbits, and deer - which find and eat them and spread the spores in their dung. This is why truffles have a musky, persistent aroma - to attract their spore spreaders - and why they're still gathered with the help of trained dogs or pigs or by spotting truffle "flies," insects that hover over truffled ground and lay their eggs there so that the larvae can burrow down and feed on the fungus.

Truffles grow only in symbiosis with trees, usually oaks, hazels, or lindens, so cultivation means finding or planting a forest, with significant harvests coming only after a decade or more. The Perigord region in France remains renowned for its black winter truffles, Tuber melanosporum, Tuber melanosporum, and northern and central Italy for its white truffle, and northern and central Italy for its white truffle, Tuber magnatum Pico. Tuber magnatum Pico. Both are in great demand, in limited supply, and so quite expensive. Their flavor can be bought more reasonably in the form of cooked whole truffles or truffle paste, or truffle-infused oils, b.u.t.ter, and flours, though some of these may be flavored artificially. There are a number of other truffle species harvested in Europe, Asia, and North America, but they're not as flavorful. Unripe truffles of any species will have little flavor. Both are in great demand, in limited supply, and so quite expensive. Their flavor can be bought more reasonably in the form of cooked whole truffles or truffle paste, or truffle-infused oils, b.u.t.ter, and flours, though some of these may be flavored artificially. There are a number of other truffle species harvested in Europe, Asia, and North America, but they're not as flavorful. Unripe truffles of any species will have little flavor.

The flavors of black and white truffles are quite distinct. Black truffles are relatively subtle and earthy, with a mix of a dozen or so alcohols and aldehydes, and some dimethyl sulfide. (They also contain small amounts of androstenone, a steroid compound also found in men's underarm sweat and secreted in the saliva of the male pig, where it prompts mating behavior in the sow. Some people are unable to smell androstenone, while others can and may find it unappetizing.) White truffles have a stronger, pungent, somewhat garlicky aroma thanks to a number of unusual sulfur compounds. The flavor of black truffles is generally thought to be enhanced by gentle cooking, while the flavor of white truffles, though strong, is fragile, and best enjoyed by shaving paper-thin slices onto a dish just before serving. Such cross sections of truffle reveal its inner structure: a network of fine veins running between ma.s.ses of spore-bearing cells.

Truffle anatomy. Like mushrooms, the truffle is the fruiting body of a fungus; unlike mushrooms, it remains underground. The spores are contained in the thick ma.s.ses of tissue between the vein-like folds.

Mushroom Types and QualitiesMushrooms are grouped by broad family relations.h.i.+ps. Most edible mushrooms bear their spores on gills.

Mushrooms with Gills

Common mushrooms White, b.u.t.ton Brown, cremini, portobello Champignon, field Almond

Cultivated leaf and dung decomposers Almond flavor Cultivated leaf and dung decomposers Almond flavor

Agaricus Agaricus species species A. bisporus A. bisporus var. var. alba alba A. bisporus A. bisporus var. var. avellanea avellanea Agaricus campestris Agaricus subrufescens Agaricus campestris Agaricus subrufescens

Oyster, tree oyster

Cultivated wood decomposers Cultivated wood decomposers

Pleurotus Pleurotus species species

s.h.i.+take

Cultivated oak decomposers Cultivated oak decomposers

Lentinus edodes Lentinus edodes

Matsutake

Wild red pine decomposers; pine, cinnamon flavors Wild red pine decomposers; pine, cinnamon flavors

Tricholoma Tricholoma species species

Honey

Wild wood decomposers Wild wood decomposers

Armillariella Armillariella species species

Mousseron, fairy ring

Wild leaf decomposers Wild leaf decomposers

Marasmius Marasmius species species

Winter, enokitake

Cultivated wood decomposers;grows at 32F/0C Cultivated wood decomposers;grows at 32F/0C

Flammulina velutipes Flammulina velutipes

Blewit

Wild leaf decomposers;purple, blue colors Wild leaf decomposers;purple, blue colors

c.l.i.tocybe nuda c.l.i.tocybe nuda

Straw mushroom

Rice straw decomposers Rice straw decomposers

Volvariella volvacea Volvariella volvacea

Parasol

Wild, cultivated leaf decomposers Wild, cultivated leaf decomposers