ON FOOD AND COOKING The Science and Lore of the Kitchen PDF

ON FOOD AND COOKING The Science and Lore of the Kitchen COMPLETELY REVISED AND UPDATED Harold McGee Illustrations by Patricia Dorfman, Justin Greene, and Ann McGee SCRIBNER New York London Toronto Sydney ...

ON FOOD AND COOKING The Science and Lore of the Kitchen COMPLETELY REVISED AND UPDATED Harold McGee Illustrations by Patricia Dorfman, SCRIBNER New York London Toronto l ON FOOD AND COOKING The Science and Lore of the Kitchen COMPLETELY REVISED AND UPDATED Harold McGee Illustrations by Patricia Dorfman, SCRIBNER New York London Toronto l scribner 1230 Avenue New Copyright © Illustrations copyright Illustrations copyright Line drawings All rights reserved, including or scribner and design are trademarks used under license by Simon Set Library of Congress ISBN: Page 884 constitutes a Visit us http://www.Simon To Soyoung and to my family contents acknowledgments introduction: cooking Chapter 1 Milk and Dairy Products Chapter 2 Eggs Chapter 3 Meat Chapter 4 Fish and Shellﬁsh Chapter 5 Edible Plants: An Introduction Herbs and Spices Chapter 6 A Survey of Common Vegetables Chapter 7 A Survey of Common Fruits Chapter 8 Flavorings from Plants: Chapter 9 Seeds: Grains, Legumes, and Nuts Chapter 10 Cereal Doughs and Batters: Chapter 11 Sauces Chapter 12 Sugars, Chocolate, and Confectionery Chapter 13 Wine, Beer, and Distilled Spirits Chapter 14 Cooking Methods and Utensil Materials Chapter 15 The Four Basic Food Molecules appendix: a chemistry primer selected references index vii acknowledgments Along with many food writers today, I feel a great debt of gratitude to Alan Davidson for the way he brought new substance, scope, and playfulness to our subject. On top of that, it was Alan who informed me that I would have to revise On Food and Cooking—before I’d even held the first copy in my hands! At our ﬁrst meeting in 1984, over lunch, he asked me what the book had to say about ﬁsh. I told him that I mentioned ﬁsh in passing as one form of animal muscle and thus of meat. And so this great fish enthusiast and renowned authority on the creatures of several seas gently suggested that, in view of the fact that fish are diverse creatures and their ﬂesh very unlike meat, they really deserve special and extended attention. Well, yes, they really do. There are many reasons for wishing that this revision hadn’t taken as long as it did, and one of the biggest is the fact that I can’t show Alan the new chapter on ﬁsh. I’ll always be grateful to Alan and to Jane for their encouragement and advice, and for the years of friendship which began with that lunch. This book and my life would have been much poorer without them. I would also have liked to give this book to Nicholas Kurti—bracing myself for the discussion to come! Nicholas wrote a heartwarmingly positive review of the ﬁrst edition in Nature, then followed it up with a Sunday-afternoon visit and an extended interrogation based on the pages of ques- tions that he had accumulated as he wrote the review. Nicholas’s energy, curiosity, and x manuscript with her careful editing; Mia Crowley-Hald and her team produced the book under tough time constraints with meticulous care; and Erich Hobbing wel- comed my ideas about layout and designed pages that ﬂow well and read clearly. Jef- frey Wilson kept contractual and other legal matters smooth and peaceful, and Lucy Kenyon organized some wonderful early publicity. I appreciate the marvelous team effort that has launched this book into the world. I thank Patricia Dorfman and Justin Greene for preparing the illustrations with patience, skill, and speed, and Ann Hirsch, who produced the micrograph of a wheat kernel for this book. I’m happy to be able to include a few line drawings from the ﬁrst edition by my sister Ann, who has been prevented by illness from contributing to this revision. She was a wonderful collabo- rator, and I’ve missed her sharp eye and good humor very much. I’m grateful to sev- eral food scientists for permission to share their photographs of food structure and microstructure: they are H. Douglas Goff, R. Carl Hoseney, Donald D. Kasarda, William D. Powrie, and Alastair T. Pringle. Alexandra Nickerson expertly compiled some of the most important pages in this book, the index. Several chefs have been kind enough to invite me into their kitchens—or laborato- ries—to experience and talk about cooking at its most ambitious. My thanks to Fritz Blank, to Heston Blumenthal, and especially to Thomas Keller and his colleagues at The French Laundry, including Eric Ziebold, Devin Knell, Ryan Fancher, and Donald Gonzalez. I’ve learned a lot from them, and look forward to learning much more. Particular sections of this book have beneﬁted from the careful reading and com- ON FOOD AND COOKING The everyday alchemy of creating woodcut compares the alchemical form nature’s raw materials into tical chemists, drawing on the accumulated what the Earth offers us into more ﬁrst Latin caption reads “Thus things in books,” the library International Bee Research Association.) introduction Cooking and Science, This is the revised and expanded second edition of a book that I ﬁrst published in 1984, twenty long years ago. In 1984, canola oil and the computer mouse and compact discs were all novelties. So was the idea of inviting cooks to explore the bio- logical and chemical insides of foods. It was a time when a book like this really needed an introduction! Twenty years ago the worlds of science and cooking were neatly compartmental- ized. There were the basic sciences, physics and chemistry and biology, delving deep into the nature of matter and life. There was food science, an applied science mainly concerned with understanding the materials and processes of industrial manufacturing. And there was the world of small-scale home and restaurant cooking, traditional crafts that had never attracted much scien- tific attention. Nor did they really need any. Cooks had been developing their own body of practical knowledge for thousands of years, and had plenty of reliable recipes to work with. I had been fascinated by chemistry and physics when I was growing up, experi- mented with electroplating and Tesla coils and telescopes, and went to Caltech plan- ning to study astronomy. It wasn’t until after I’d changed directions and moved on to English literature—and had begun to cook—that I ﬁrst heard of food science. At dinner one evening in 1976 or 1977, a friend from New Orleans wondered aloud 2 authorities, Plato, Samuel Johnson, and Jean Anthelme Brillat-Savarin, all of whom suggested that cooking deserves detailed and serious study. I pointed out that a 19th- century German chemist still influences how many people think about cooking meat, and that around the turn of the 20th century, Fannie Farmer began her cook- book with what she called “condensed sci- entific knowledge” about ingredients. I noted a couple of errors in modern cook- books by Madeleine Kamman and Julia Child, who were ahead of their time in taking chemistry seriously. And I proposed that science can make cooking more inter- esting by connecting it with the basic work- ings of the natural world. A lot has changed in twenty years! It turned out that On Food and Cooking was riding a rising wave of general interest in food, a wave that grew and grew, and knocked down the barriers between science and cooking, especially in the last decade. Science has found its way into the kitchen, and cooking into laboratories and factories. In 2004 food lovers can ﬁnd the science of cooking just about everywhere. Maga- zines and newspaper food sections devote regular columns to it, and there are now a number of books that explore it, with Shirley Corriher’s 1997 CookWise remain- ing unmatched in the way it integrates explanation and recipes. Today many writ- ers go into the technical details of their subjects, especially such intricate things as pastry, chocolate, coffee, beer, and wine. Kitchen science has been the subject of tele- vision series aired in the United States, Canada, the United Kingdom, and France. And a number of food molecules and microbes have become familiar ﬁgures in the news, both good and bad. Anyone who follows the latest in health and nutrition knows about the beneﬁts of antioxidants and phytoestrogens, the hazards of trans fatty acids, acrylamide, E. coli bacteria, and mad cow disease. Professional cooks have also come to appreciate the value of the scientific approach to their craft. In the first few ered the quality and distinctiveness of food products: they taste much the same, and not very good. Improvements in quality can now mean a competitive advantage; and cooks have always been the world’s experts in the applied science of delicious- ness. Today, the French National Institute of Agricultural Research sponsors a group in Molecular Gastronomy at the Collège de France (its leader, Hervé This, directs the Erice workshop); chemist Thorvald Peder- sen is the inaugural Professor of Molecular Gastronomy at Denmark’s Royal Veteri- nary and Agricultural University; and in the United States, the rapidly growing membership of the Research Chefs Associ- ation specializes in bringing the chef’s skills and standards to the food industry. So in 2004 there’s no longer any need to explain the premise of this book. Instead, there’s more for the book itself to explain! Twenty years ago, there wasn’t much demand for information about extra-virgin olive oil or balsamic vinegar, farmed salmon or grass-fed beef, cappuccino or white tea, Sichuan pepper or Mexican mole, sake or well-tempered chocolate. Today there’s interest in all these and much more. And so this second edition of On Food and Cooking is substantially longer than the ﬁrst. I’ve expanded the text by two thirds in order to cover a broader range of ingredients and preparations, and to explore them in greater depth. To make room for new information about foods, I’ve dropped the separate chapters on human physiology, nutrition, and additives. Of the few sections that survive in similar form from the ﬁrst edition, practically all have been rewritten to reﬂect fresh infor- mation, or my own fresh understanding. This edition gives new emphasis to two particular aspects of food. The ﬁrst is the diversity of ingredients and the ways in which they’re prepared. These days the easy movement of products and people makes it possible for us to taste foods from the world. And traveling back in time through old cookbooks can turn up forgot- 4 us from the distraction of having to guess or experiment or analyze as we prepare a meal. On the other hand, the great virtue of thought and analysis is that they free us from the necessity of following recipes, and help us deal with the unexpected, including the inspiration to try something new. Thoughtful cooking means paying atten- tion to what our senses tell us as we pre- pare it, connecting that information with past experience and with an understanding of what’s happening to the food’s inner substance, and adjusting the preparation accordingly. To understand what’s happening within a food as we cook it, we need to be familiar with the world of invisibly small molecules and their reactions with each other. That idea may seem daunting. There are a hun- dred-plus chemical elements, many more combinations of those elements into mole- cules, and several different forces that rule their behavior. But scientists always sim- plify reality in order to understand it, and we can do the same. Foods are mostly built out of just four kinds of molecules—water, proteins, carbohydrates, and fats. And their behavior can be pretty well described with a few simple principles. If you know that heat is a manifestation of the movements of molecules, and that sufﬁciently energetic collisions disrupt the structures of mole- cules and eventually break them apart, then you’re very close to understanding why heat solidiﬁes eggs and makes foods tastier. Most readers today have at least a vague idea of proteins and fats, molecules and energy, and a vague idea is enough to fol- low most of the explanations in the ﬁrst 13 chapters, which cover common foods and ways of preparing them. Chapters 14 and 15 then describe in some detail the mole- introduction A Note About and About Throughout this book, temperatures dard units in the United States, by most other countries. The Fahrenheit converted to Celsius by using the 32) x 0.56. Volumes and weights are given in both U.S. kitchen units—teaspoons, milliliters, liters, grams, and (mm); 1 mm is about the diameter in microns ( ). One micron is 1 micrometer, or Single molecules are so small, abstract, hard to imagine. But they that determine how they—and the The better we can visualize what is to understand what happens in overall shape that matters, not drawings of molecules in this book, resented in different ways—as with some atoms indicated by letters—depending explained. Many food molecules are atoms, with a few other kinds of the backbone. The carbon backbone drawn with no indications of the between atoms. MILK AND DAIRY PRODUCTS Mammals and Milk 8 The Evolution of Milk 8 The Rise of the Ruminants 9 Dairy Animals of the World 9 The Origins of Dairying 10 Diverse Traditions 10 Milk and Health 12 Milk Nutrients 13 Milk in Infancy and Childhood: Nutrition and Allergies 14 Milk after Infancy: Dealing with Lactose 14 New Questions about Milk 15 Milk Biology and Chemistry 16 How the Cow Makes Milk 16 Milk Sugar: Lactose 17 Milk Fat 18 Milk Proteins: Coagulation by Acid and Enzymes 19 Milk Flavor 21 What better subject for the ﬁrst chapter than the food with which we all begin our lives? Humans are mammals, a word that means “creatures of the breast,” and the ﬁrst food that any mammal tastes is milk. Milk is food for the beginning eater, a gulpable essence distilled by the mother from her own more variable and challeng- ing diet. When our ancestors took up dairying, they adopted the cow, the ewe, and the goat as surrogate mothers. These 8 moved out from the Caucasian steppes to settle vast areas of Eurasia around 3000 BCE; and milk and butter are prominent in the creation myths of their descendents, from India to Scandinavia. Peoples of the Mediterranean and Middle East relied on the oil of their olive tree rather than butter, but milk and cheese still ﬁgure in the Old Testament as symbols of abundance and creation. The modern imagination holds a very different view of milk! Mass production turned it and its products from precious, marvelous resources into ordinary com- modities, and medical science stigmatized them for their fat content. Fortunately a more balanced view of dietary fat is devel- oping; and traditional versions of dairy foods survive. It’s still possible to savor the remarkable foods that millennia of human ingenuity have teased from milk. A sip of milk itself or a scoop of ice cream can be a Proustian draft of youth’s innocence and energy and possibility, while a morsel of ﬁne cheese is a rich meditation on maturity, the fulﬁllment of possibility, the way of all ﬂesh. Milk When the gods performed the the melted butter, summer the at the beginning, as a sacriﬁce the grains of butter, and made bring them up out of that land milk and honey.... Hast thou not poured me out THE RISE OF THE RUMINANTS All mammals produce milk for their young, but only a closely related handful have been exploited by humans. Cattle, water buf- falo, sheep, goats, camels, yaks: these sup- pliers of plenty were created by a scarcity of food. Around 30 million years ago, the earth’s warm, moist climate became sea- sonally arid. This shift favored plants that could grow quickly and produce seeds to survive the dry period, and caused a great expansion of grasslands, which in the dry seasons became a sea of desiccated, ﬁbrous stalks and leaves. So began the gradual decline of the horses and the expansion of the deer family, the ruminants, which evolved the ability to survive on dry grass. Cattle, sheep, goats, and their relatives are all ruminants. The key to the rise of the ruminants is their highly specialized, multichamber stomach, which accounts for a ﬁfth of their body weight and houses trillions of ﬁber- digesting microbes, most of them in the first chamber, or rumen. Their unique plumbing, together with the habit of regur- gitating and rechewing partly digested food, allows ruminants to extract nourish- ment from high-fiber, poor-quality plant material. Ruminants produce milk copi- ously on feed that is otherwise useless to humans and that can be stockpiled as straw or silage. Without them there would be no dairying. DAIRY ANIMALS OF THE WORLD Only a small handful of animal species contributes signiﬁcantly to the world’s milk supply. The Cow, European and Indian The immediate ancestor of Bos taurus, the common dairy cow, was Bos primigenius, the long-horned wild aurochs. This mas- sive animal, standing 6 ft/180 cm at the shoulder and with horns 6.5 in/17 cm in diameter, roamed Asia, Europe, and North Africa in the form of two overlapping 10 bushy-tailed cousin of the common cow is beautifully adapted to the thin, cold, dry air and sparse vegetation of the Tibetan plateau and mountains of central Asia. It was domesticated around the same time as lowland cattle. Yak milk is substantially richer in fat and protein than cow milk. Tibetans in particular make elaborate use of yak butter and various fermented products. The Goat The goat and sheep belong to the “ovicaprid” branch of the ruminant family, smaller animals that are especially at home in mountainous country. The goat, Capra hircus, comes from a denizen of the mountains and semidesert regions of cen- tral Asia, and was probably the ﬁrst animal after the dog to be domesticated, between 8000 and 9000 BCE in present-day Iran and Iraq. It is the hardiest of the Eurasian dairy animals, and will browse just about any sort of vegetation, including woody scrub. Its omnivorous nature, small size, and good yield of distinctively flavored milk—the highest of any dairy animal for its body weight—have made it a versatile milk and meat animal in marginal agricultural areas. The Sheep The sheep, Ovis aries, was domesticated in the same region and period as its close cousin the goat, and came to be valued and bred for meat, milk, wool, and fat. Sheep were originally grazers on grassy foothills and are somewhat more fastidious than goats, but less so than cattle. Sheep’s milk is as rich as the buffalo’s in fat, and even richer in protein; it has long been val- ued in the Eastern Mediterranean for mak- ing yogurt and feta cheese, and Europe for such cheeses as Roquefort and pecorino. The Camel The camel family is fairly far removed from both the bovids and ovi- caprids, and may have developed the habit of rumination independently during its early evolution in North America. Camels are well adapted to arid climates, and were domesticated around 2500 BCE in central Asia, primarily as pack animals. Their milk, long-keeping cheese. As dairyers became more adept and harvested greater quantities of milk, they found new ways to concen- trate and preserve its nourishment, and developed distinctive dairy products in the different climatic regions of the Old World. In arid southwest Asia, goat and sheep milk was lightly fermented into could be kept for several days, sun-dried, or kept under oil; or curdled into cheese that could be eaten fresh or preserved by drying or brining. Lacking the settled life that makes it possible to brew beer from grain or wine from grapes, the nomadic Tartars even fermented mare’s milk into lightly alcoholic koumiss, which Marco Polo described as having “the qualities and ﬂavor of white wine.” In the high country of Mongolia and Tibet, cow, camel, and yak milk was churned to butter for use as a high-energy staple food. In semitropical India, most zebu and buffalo milk was allowed to sour overnight into a yogurt, then churned to yield but- termilk and butter, which when clariﬁed into ghee (p. 37) would keep for months. Some milk was repeatedly boiled to keep it sweet, and then preserved not with salt, but by the combination of sugar and long, dehydrating cooking (see box, p. 26). The Mediterranean world of Greece and Rome used economical olive oil rather than butter, but esteemed cheese. The Roman Pliny praised cheeses from distant provinces that are now parts of France and Switzer- land. And indeed cheese making reached its zenith in continental and northern Europe, thanks to abundant pastureland ideal for cattle, and a temperate climate that allowed long, gradual fermentations. The one major region of the Old World not to embrace dairying was China, per- haps because Chinese agriculture began where the natural vegetation runs to often toxic relatives of wormwood and epazote rather than ruminant-friendly grasses. Even so, frequent contact with central Asian nomads introduced a variety of dairy prod- ucts to China, whose elite long enjoyed yogurt, koumiss, butter, acid-set curds, and, 12 milk dairying. The railroads made it possible to get fresh country milk to the cities, where rising urban populations and incomes fueled demand, and new laws regulated milk quality. Steam-powered farm machin- ery meant that cattle could be bred and raised for milk production alone, not for a compromise between milk and hauling, so milk production boomed, and more than ever was drunk fresh. With the invention of machines for milking, cream separation, and churning, dairying gradually moved out the hands of milkmaids and off the farms, which increasingly supplied milk to factories for mass production of cream, butter, and cheese. From the end of the 19th century, chem- ical and biological innovations have helped make dairy products at once more hygienic, more predictable, and more uniform. The great French chemist Louis Pasteur inspired two fundamental changes in dairy prac- tice: pasteurization, the pathogen-killing heat treatment that bears his name; and the use of standard, puriﬁed microbial tures to make cheeses and other fermented foods. Most traditional cattle breeds have been abandoned in favor of high-yielding black-and-white Friesian (Holstein) cows, which now account for 90% of all Ameri- can dairy cattle and 85% of British. The cows are farmed in ever larger herds and fed an optimized diet that seldom includes fresh pasturage, so most modern milk lacks Food In their roots, both milk and and transform it by hand. Milk “milk” and “to rub off,” squeeze milk from the teat. In room in which the dey, or woman turn came from a root meaning reﬂection not only of the servant’s squeeze buttermilk out of butter tial body-building nutrients, particularly protein, sugars and fat, vitamin A, the B vitamins, and calcium. Over the last few decades, however, the idealized portrait of milk has become more shaded. We’ve learned that the balance of nutrients in cow’s milk doesn’t meet the needs of human infants, that most adult humans on the planet can’t digest the milk sugar called lactose, that the best route to calcium balance may not be massive milk intake. These complications help remind us that milk was designed to be a food for the young and rapidly growing calf, not for the young or mature human. MILK NUTRIENTS Nearly all milks contain the same battery of nutrients, the relative proportions of which vary greatly from species to species. Generally, animals that grow rapidly are fed with milk high in protein and minerals. A calf doubles its weight at birth in 50 The Compositions The ﬁgures in the following its major components. Milk Fat Human 4.0 1.1 Cow 3.7 3.4 Holstein/Friesian 3.6 3.4 Brown Swiss 4.0 3.6 Jersey 5.2 3.9 Zebu 4.7 3.3 Buffalo 6.9 3.8 Yak 6.5 5.8 Goat 4.0 3.4 Sheep 7.5 6.0 Camel 2.9 3.9 Reindeer 17 11 Horse 1.2 2.0 Fin whale 42 12 14 milk MILK IN INFANCY AND CHILDHOOD: NUTRITION AND ALLERGIES In the middle of the 20th century, when nutrition was thought to be a simple mat- ter of protein, calories, vitamins, and min- erals, cow’s milk seemed a good substitute for mother’s milk: more than half of all six-month-olds in the United States drank it. Now that ﬁgure is down to less than 10%. Physicians now recommend that plain cow’s milk not be fed to children younger than one year. One reason is that it provides too much protein, and not enough iron and highly unsaturated fats, for the human infant’s needs. (Carefully prepared formula milks are better approx- imations of breast milk.) Another disad- vantage to the early use of cow’s milk is that it can trigger an allergy. The infant’s digestive system is not fully formed, and can allow some food protein and protein fragments to pass directly into the blood. These foreign molecules then provoke a defensive response from the immune sys- tem, and that response is strengthened each time the infant eats. Somewhere between 1% and 10% of American infants suffer from an allergy to the abundant protein in cow’s milk, whose symptoms may range from mild discomfort to intestinal damage to shock. Most children eventually grow out of milk allergy. MILK AFTER INFANCY: DEALING WITH LACTOSE In the animal world, humans are excep- tional for consuming milk of any kind after they have started eating solid food. And people who drink milk after infancy are the exception within the human species. The obstacle is the milk sugar lactose, which can’t be absorbed and used by the body as is: it must ﬁrst be broken down into its component sugars by digestive enzymes in the small intestine. The lactose-digesting enzyme, lactase, reaches its maximum lev- els in the human intestinal lining shortly after birth, and then slowly declines, with a tured from a fungus, Aspergillus), and add a few drops to any dairy product just before they consume it. NEW QUESTIONS ABOUT MILK Milk has been especially valued for two nutritional characteristics: its richness in cal- cium, and both the quantity and quality of its protein. Recent research has raised some fascinating questions about each of these. Perplexity about Calcium and Osteo- porosis Our bones are constructed from two primary materials: proteins, which form a kind of scaffolding, and calcium phosphate, which acts as a hard, mineral- ized, strengthening ﬁller. Bone tissue is con- stantly being deconstructed and rebuilt throughout our adult lives, so healthy bones require adequate protein and cal- cium supplies from our diet. Many women in industrialized countries lose so much The Many Good bone health results from bone deconstruction and reconstruction. levels in the body, but also and other controlling signals; sium, and zinc); and other as tea and in onions and parsley is essential for the efﬁcient bone building. It’s added to our own skin, where ultraviolet The amount of calcium we by how much we excrete in our from our foods. Various aspects boost our calcium requirement. intake of animal protein, the acidiﬁes our urine, and pulls The best insurance against bones that we want to keep strong, minerals, moderate in salt and foods. Milk is certainly a valuable tofu (both processed with calcium greens. 16 Japan, suffer much lower fracture rates than the United States and milk-loving Scandinavia, despite the fact that their peo- ple drink little or no milk. So it seems pru- dent to investigate the many other factors that influence bone strength, especially those that slow the deconstruction process (see box, p. 15). The best answer is likely to be not a single large white bullet, but the familiar balanced diet and regular exercise. Milk Proteins Become Something More We used to think that one of the major proteins in milk, casein (p. 19), was mainly a nutritional reservoir of amino acids with which the infant builds its own body. But this protein now appears to be a complex, subtle orchestrator of the infant’s metabo- lism. When it’s digested, its long amino- acid chains are first broken down into smaller fragments, or peptides. It turns out that many hormones and drugs are also peptides, and a number of casein peptides do affect the body in hormone-like ways. One reduces breathing and heart rates, another triggers insulin release into the blood, and a third stimulates the scavenging activity of white blood cells. Do the pep- tides from cow’s milk affect the metabolism of human children or adults in signiﬁcant ways? We don’t yet know. MILK BIOLOGY AND CHEMISTRY HOW THE COW MAKES MILK Milk is food for the newborn, and so dairy animals must give birth before they will produce signiﬁcant quantities of milk. The mammary glands are activated by changes in the balance of hormones toward the end of pregnancy, and are stimulated to con- tinue secreting milk by regular removal of milk from the gland. The optimum sequence for milk production is to breed the cow again 90 days after it calves, milk it for 10 months, and let it go dry for the two months before the next calving. In milk ble; it develops off-ﬂavors more slowly than raw milk. But the dynamism of raw milk is prized in traditional cheese making, where it contributes to the ripening process and deepens ﬂavor. Milk owes its milky opalescence to microscopic fat globules and protein bun- dles, which are just large enough light rays as they pass through the liquid. Dissolved salts and milk sugar, vitamins, other proteins, and traces of many other compounds also swim in the water that accounts for the bulk of the fluid. The sugar, fat, and proteins are by far the most important components, and we’ll look at them in detail in a moment. First a few words about the remaining components. Milk is slightly acidic, with a pH between 6.5 and 6.7, and both acidity and salt concentrations strongly affect the behavior of the proteins, as we’ll see. The fat globules carry colorless vitamin A and its yellow-orange precursors the carotenes, which are found in green feed and give milk and undyed butter whatever color they have. Breeds differ in the amount of carotene they convert into vitamin A; Guernsey and Jersey cows convert little and give especially golden milk, while at the other extreme sheep, goats, and water buffalo process nearly all of their carotene, 18 milk ready and can get a head start on all the others. The bacteria known as Lactobacilli and Lactococci not only grow on lactose immediately, they also convert it into lactic acid (“milk acid”). They thus acidify the milk, and in so doing, make it less habitable by other microbes, including many that would make the milk unpalatable or cause disease. Lactose and the lactic-acid bacteria therefore turn milk sour, but help prevent it from spoiling, or becoming undrinkable. Lactose is one-fifth as sweet as table sugar, and only one-tenth as soluble in water (200 vs. 2,000 gm/l), so lactose crys- tals readily form in such products as con- densed milk and ice cream and can give them a sandy texture. MILK FAT Milk fat accounts for much of the body, nutritional value, and economic value of milk. The milk-fat globules carry the fat- soluble vitamins (A, D, E, K), and about half the calories of whole milk. The higher the fat content of milk, the more cream or butter can be made from it, and so the higher the price it will bring. Most cows secrete more fat in winter, due mainly to concentrated winter feed and the approach- ing end of their lactation period. Certain breeds, notably Guernseys and Jerseys from the Channel Islands between Britain and France, produce especially rich milk and large fat globules. Sheep and buffalo milks contain up to twice the butterfat of whole cow’s milk (p. 13). The way the fat is packaged into glob- ules accounts for much of milk’s behavior in the kitchen. The membrane that sur- rounds each fat globule is made up of phos- pholipids (fatty acid emulsifiers, p. 802) and proteins, and plays two major roles. It separates the droplets of fat from each other and prevents them from pooling together into one large mass; and it protects the fat molecules from fat-digesting enzymes in the milk that would otherwise... attack them and break them down into rancid-smelling and bitter fatty acids. milk water both form large, solid, jagged crystals that pierce, crush, and rend the thin veil of phospholipids and proteins around the globule, just a few molecules thick. If you freeze milk or cream and then thaw it, much of the membrane material ends up ﬂoating free in the liquid, and many of the fat globules get stuck to each other in grains of butter. Make the mistake of heating thawed milk or cream, and the butter grains melt into puddles of oil. MILK PROTEINS: COAGULATION BY ACID AND ENZYMES Two Protein Classes: Curd and Whey There are dozens of different proteins ﬂoat- ing around in milk. When it comes to cook- ing behavior, fortunately, we can reduce the protein population to two basic groups: Little Miss Muffet’s curds and whey. The two groups are distinguished by their reac- tion to acids. The handful of curd proteins, the caseins, clump together in acid condi- tions and form a solid mass, or coagulate, while all the rest, the whey proteins, remain suspended in the liquid. It’s the clumping nature of the caseins that makes possible most thickened milk products, from yogurt to cheese. The whey proteins play a more minor role; they inﬂuence the casein curds, and stabilize the milk foams on specialty coffees. The caseins usually outweigh the whey proteins, as they do in cow’s milk by 4 to 1. casein proteins 20 certain size, prevents them from growing larger, and keeps them dispersed and sepa- rate. One end of the capping-casein mole- cule extends from the micelle out into the surrounding liquid, and forms a “hairy layer” with a negative electrical charge that repels other micelles. The intricate structure of casein micelles can be disturbed in several ways the micelles to ﬂock together and the milk to curdle. One way is souring. Milk’s nor- mal pH is about 6.5, or just slightly acidic. If it gets acid enough to approach pH 5.5, the capping-casein’s negative charge is neu- tralized, the micelles no longer repel each other, and they therefore gather in loose clusters. At the same acidity, the calcium glue that holds the micelles together dis- solves, the micelles begin to fall apart, and their individual proteins scatter. Beginning around pH 4.7, the scattered casein pro- teins lose their negative charge, bond to each other again and form a continuous, fine network: and the milk solidifies, or curdles. This is what happens when milk gets old and sour, or when it’s intentionally cultured with acid-producing bacteria to make yogurt or sour cream. Another way to cause the caseins to cur- A model of the milk protein casein, which occurs in micelles, or small bundles a fraction of the size of a fat globule. A single micelle consists of many indi- vidual protein molecules (lines) held together by particles of cal- cium phosphate (small spheres). unfermented on the casein micelles, which remain sepa- rate; so denatured lactoglobulin doesn’t coagulate. When denatured in acid condi- tions with relatively little casein around, as in cheese whey, lactoglobulin molecules do bind to each other and coagulate into little clots, which can be made into whey cheeses like true ricotta. Heat-denatured whey proteins are better than their native forms at stabilizing air bubbles in milk foams and ice crystals in ice creams; this is why milks and creams are usually cooked for these preparations (pp. 26, 43). MILK FLAVOR The ﬂavor of fresh milk is balanced and subtle. It’s distinctly sweet slightly salty from its complement of miner- als, and very slightly acid. Its mild, pleasant aroma is due in large measure to short- chain fatty acids (including butyric and capric acids), which help keep highly satu- rated milk fat ﬂuid at body temperature, and which are small enough that they can evaporate into the air and reach our nose. Normally, free fatty acids give an undesir- able, soapy ﬂavor to foods. But in sparing quantities, the 4- to 12-carbon rumen fatty acids, branched versions of these, and acid- alcohol combinations called esters, provide milk with its fundamental blend of animal and fruity notes. The distinctive smells of goat and sheep milks are due to two partic- ular branched 8-carbon fatty acids (4-ethyl- octanoic, 4-methyl-octanoic) that are absent in cow’s milk. Buffalo milk, from which tra- ditional mozzarella cheese is made, has a characteristic blend of modiﬁed reminiscent of mushrooms and freshly cut grass, together with a barnyardy nitrogen compound (indole). The basic ﬂavor of fresh milk is affected by the animals’ feed. Dry hay and silage are relatively poor in fat and protein and produce a less complicated, mildly cheesy aroma, while lush pasturage provides raw material for sweet, raspberry-like notes (derivatives of unsaturated long-chain acids), as well as barnyardy indoles. 22 milk MILKS Milk has become the most standardized of our basic foods. Once upon a time, people lucky enough to live near a farm could taste the pasture and the seasons in milk fresh from the cow. City life, mass produc- tion, and stricter notions of hygiene have now put that experience out of reach. Today nearly all of our milk comes from cows of one breed, the black-and-white Holstein, kept in sheds and fed year-round on a uniform diet. Large dairies pool the milk of hundreds, even thousands of cows, then pasteurize it to eliminate microbes and homogenize it to prevent the fat from separating. The result is processed milk of no particular animal or farm or season, and therefore of no particular character. Some small dairies persist in milking other breeds, allowing their herds out to pasture, pasteurizing mildly, and not homogeniz- ing. Their milk can have a more distinctive ﬂavor, a rare reminder of what milk used to taste like. Raw Milk Careful milking of healthy cows yields sound raw milk, which has its own fresh taste and physical behavior. But if it’s contaminated by a diseased cow or careless handling—the udder hangs right next to the tail—this nutritious ﬂuid soon teems with potentially dangerous microbes. The importance of strict hygiene in the dairy has been understood at least since the Middle Ages, but life far from the farms made contamination and even adulteration all too common in cities of the 18th and 19th centuries, where many children were killed by tuberculosis, undulant fever, and simple food poisoning contracted from tainted milk. In the 1820s, long before any- one knew about microbes, some books on domestic economy advocated boiling all milk before use. Early in the 20th century, national and local governments began to regulate the dairy industry and require that it heat milk to kill disease microbes. Today very few U.S. dairies sell raw milk. They must be certiﬁed by the state unfermented 130–150ºC either instantaneously or for 1 to 3 seconds, and produces milk that, if packaged under strictly sterile conditions, can be stored for months without refriger- ation. The longer UHT treatment imparts a cooked ﬂavor and slightly brown color to milk; cream contains less lactose and pro- tein, so its color and ﬂavor are less affected. Sterilized milk has been heated at 230–250ºF/110–121ºC for 8 to 30 minutes; it is even darker and stronger in ﬂavor, and keeps indeﬁnitely at room temperature. Homogenization Left to itself, fresh whole milk naturally separates into two phases: fat globules clump together and rise to form the cream layer, leaving a fat-depleted phase below (p. 18). The treatment called enization was developed in France around 1900 to prevent creaming and keep the milk fat evenly—homogeneously—dispersed. It involves pumping hot milk at high pressure through very small nozzles, where the tur- bulence tears the fat globules apart into smaller ones; their average diameter falls from 4 micrometers to about 1. The sudden increase in globule numbers causes a pro- portional increase in their surface area, which the original globule membranes are insufﬁcient to cover. The naked fat surface attracts casein particles, which stick and create an artiﬁcial coat (nearly a third of the milk’s casein ends up on the globules). The casein particles both weigh the fat glob- ules down and interfere with their usual Powdered [The Tartar armies] make provisions hard paste, which they prepare ming off the rich or creamy part butter; for so long as that remains exposed to the sun until it dries. as much water as is thought necessary. lently shaken, and a thin porridge 24 “Acidophilus” milk contains Lactobacil- lus acidophilus, a bacterium that metabo- lizes lactose to lactic acid and that can take up residence in the intestine (p. 47). More helpful to milk lovers who can’t digest lac- tose is milk treated with the puriﬁed diges- tive enzyme lactase, which breaks lactose down into simple, absorbable sugars. Storage Milk is a highly perishable food. Even Grade A pasteurized milk contains millions of bacteria in every glassful, and will sp Justin Greene, and Ann McGee Sydney Justin Greene, and Ann McGee Sydney of the Americas York, NY 10020 1984, 2004 by Harold McGee © 2004 by Patricia Dorfman © 2004 by Justin Greene by Ann B. McGee the right of reproduction in whole in part in any form. of Macmillan Library Reference USA, Inc., & Schuster, the publisher of this work. in Sabon Control Number: 2004058999 1-4165-5637-0 continuation of the copyright page. on the World Wide Web: Says.com ix and science, 1984 and 2004 1 7 68 118 179 to Fruits and Vegetables, 243 300 350 Herbs and Spices, Tea and Coffee 385 451 Bread, Cakes, Pastry, Pasta 515 580 645 713 777 792 811 819 835 enthusiasm for good food and the telling “little experiment” were infectious, and animated the early Erice workshops. They and he are much missed. Coming closer to home and the present, I thank my family for the affection and patient optimism that have kept me going day after day: son John and daughter Flo- rence, who have lived with this book and experimental dinners for more than half their years, and enlivened both with their gusto and strong opinions; my father, Chuck McGee, and mother, Louise Hammersmith; brother Michael and sisters Ann and Joan; and Chuck Hammersmith, Werner Kurz, Richard Thomas, and Florence Jean and Harold Long. Throughout these last few trying years, my wife Sharon Long has been constantly caring and supportive. I’m deeply grateful to her for that gift. Milly Marmur, my onetime publisher, longtime agent, and now great friend, has been a source of propulsive energy over the course of a marathon whose length nei- ther of us foresaw. I’ve been lucky to enjoy her warmth, patience, good sense, and her skill at nudging without noodging. I owe thanks to many people at Scribner and Simon & Schuster. Maria Guarna- schelli commissioned this revision with inspiring enthusiasm, and Scribner pub- lisher Susan Moldow and S&S president Carolyn Reidy have been its committed advocates ever since. Beth Wareham tire- lessly supervised all aspects of editing, pro- duction, and publication. Rica Buxbaum Allannic made many improvements in the ix on food and cooking ments of Anju and Hiten Bhaya, Devaki Bhaya and Arthur Grossman, Poornima and Arun Kumar, Sharon Long, Mark Pas- tore, Robert Steinberg, and Kathleen, Ed, and Aaron Weber. I’m very grateful for their help, and absolve them of any respon- sibility for what I’ve done with it. I’m glad for the chance to thank my friends and my colleagues in the worlds of writing and food, all sources of stimulating questions, answers, ideas, and encourage- ment over the years: Shirley and Arch Cor- riher, the best of company on the road, at the podium, and on the phone; Lubert Stryer, who gave me the chance to see the science of pleasure advanced and immedi- ately applied; and Kurt and Adrienne Alder, Peter Barham, Gary Beauchamp, Ed Behr, Paul Bertolli, Tony Blake, Glynn Christian, Jon Eldan, Anya Fernald, Len Fisher, Alain Harrus, Randolph Hodgson, Philip and Mary Hyman, John Paul Khoury, Kurt Koessel, Aglaia Kremezi, Anna Tasca Lanza, David Lockwood, Jean Matricon, Fritz Maytag, Jack McInerney, Alice Medrich, Marion Nestle, Ugo and Beatrice Palma, Alan Parker, Daniel Patterson, Thorvald Pedersen, Charles Perry, Maricel Presilla, P.N. Ravindran, Judy Rodgers, Nick Ruello, Helen Saberi, Mary Taylor Simeti, Melpo Skoula, Anna and Jim Spu- dich, Jeffrey Steingarten, Jim Tavares, Hervé This, Bob Togasaki, Rick Vargas, Despina Vokou, Ari Weinzweig, Jonathan White, Paula Wolfert, and Richard Zare. Finally, I thank Soyoung Scanlan for sharing her understanding of cheese and of traditional forms of food production, for reading many parts of the manuscript and helping me clarify both thought and expression, and above all for reminding me, when I had forgotten, what writing and life are all about. food for the body and the mind. This 17th-century (“chymick”) work of the bee and the scholar, who trans- honey and knowledge. Whenever we cook we become prac- knowledge of generations, and transforming concentrated forms of pleasure and nourishment. (The we bees make honey, not for ourselves”; the second, “All being the scholar’s hive. Woodcut from the collection of the 1984 and 2004 why dried beans were such a problematic food, why indulging in red beans and rice had to cost a few hours of sometimes embarrassing discomfort. Interesting ques- tion! A few days later, working in the library and needing a break from 19th- century poetry, I remembered it and the answer a biologist friend had dug up (indi- gestible sugars), thought I would browse in some food books, wandered over to that section, and found shelf after shelf of strange titles. Journal of Food Science. Poultry Sci- ence. Cereal Chemistry. I ﬂipped through a few volumes, and among the mostly bewil- dering pages found hints of answers to other questions that had never occurred to me. Why do eggs solidify when we cook them? Why do fruits turn brown when we cut them? Why is bread dough bouncily alive, and why does bounciness make good bread? Which kinds of dried beans are the worst offenders, and how can a cook tame them? It was great fun to make and share these lit- tle discoveries, and I began to think that many people interested in food might enjoy them. Eventually I found time to immerse myself in food science and history and write On Food and Cooking: The Science and Lore of the Kitchen. As I ﬁnished, I realized that cooks more serious than my friends and I might be skeptical about the relevance of cells and molecules to their craft. So I spent much of the introduction trying to bolster my case. I began by quoting an unlikely trio of 1 introduction years after On Food and Cooking appeared, many young cooks told me of their frustration in trying to ﬁnd out why dishes were prepared a certain way, or why ingredients behave as they do. To their tra- ditionally trained chefs and teachers, under- standing food was less important than mastering the tried and true techniques for preparing it. Today it’s clearer that curios- ity and understanding make their own con- tribution to mastery. A number of culinary schools now offer “experimental” courses that investigate the whys of cooking and encourage critical thinking. And several highly regarded chefs, most famously Fer- ran Adrià in Spain and Heston Blumen- thal in England, experiment with industrial and laboratory tools—gelling agents from seaweeds and bacteria, non-sweet sugars, aroma extracts, pressurized gases, liquid nitrogen—to bring new forms of pleasure to the table. As science has gradually percolated into the world of cooking, cooking has been drawn into academic and industrial sci- ence. One effective and charming force behind this movement was Nicholas Kurti, a physicist and food lover at the University of Oxford, who lamented in 1969: “I think it is a sad reﬂection on our civilization that while we can and do measure the tempera- ture in the atmosphere of Venus, we do not know what goes on inside our souf- ﬂés.” In 1992, at the age of 84, Nicholas nudged civilization along by organizing an International Workshop on Molecular and Physical Gastronomy at Erice, Sicily, where for the ﬁrst time professional cooks, basic scientists from universities, and food sci- entists from industry worked together to advance gastronomy, the making and appreciation of foods of the highest quality. The Erice meeting continues, renamed the “International Workshop on Molecular Gastronomy ‘N. Kurti’ ” in memory of its founder. And over the last decade its focus, the understanding of culinary excellence, has taken on new economic signiﬁcance. The modern industrial drive to maximize efﬁciency and minimize costs generally low- introduction 3 ten but intriguing ideas. I’ve tried through- out to give at least a brief indication of the range of possibilities offered by foods them- selves and by different national traditions. The other new emphasis is on the ﬂavors of foods, and sometimes on the particular molecules that create flavor. Flavors are something like chemical chords, composite sensations built up from notes provided by different molecules, some of which are found in many foods. I give the chemical names of flavor molecules when I think that being speciﬁc can help us notice ﬂavor relationships and echoes. The names may seem strange and intimidating at ﬁrst, but they’re just names and they’ll become more familiar. Of course people have made and enjoyed well seasoned dishes for thousands of years with no knowledge of molecules. But a dash of ﬂavor chemistry can help us make fuller use of our senses of taste and smell, and experience more—and ﬁnd more pleasure—in what we cook and eat. Now a few words about the scientific approach to food and cooking and the organization of this book. Like everything on earth, foods are mixtures of different chemicals, and the qualities that we aim to inﬂuence in the kitchen—taste, aroma, tex- ture, color, nutritiousness—are all manifes- tations of chemical properties. Nearly two hundred years ago, the eminent gastronome Jean Anthelme Brillat-Savarin lectured his cook on this point, tongue partly in cheek, in The Physiology of Taste: You are a little opinionated, and I have had some trouble in making you under- stand that the phenomena which take place in your laboratory are nothing other than the execution of the eternal laws of nature, and that certain things which you do without thinking, and only because you have seen others do them, derive nonetheless from the high- est scientiﬁc principles. all over The great virtue of the cook’s time- tested, thought-less recipes is that they free introduction cules and basic chemical processes involved in all cooking; and the Appendix gives a brief refresher course in the basic vocabu- lary of science. You can refer to these ﬁnal sections occasionally, to clarify the meaning of pH or protein coagulation as you’re reading about cheese or meat or bread, or else read through them on their own to get a general introduction to the science of cooking. Finally, a request. In this book I’ve sifted through and synthesized a great deal of information, and have tried hard to double- check both facts and my interpretations of them. I’m greatly indebted to the many sci- entists, historians, linguists, culinary pro- fessionals, and food lovers on whose learning I’ve been able to draw. I will also appreciate the help of readers who notice errors that I’ve made and missed, and who let me know so that I can correct them. My thanks in advance. As I ﬁnish this revision and think about the endless work of correcting and perfect- ing, my mind returns to the first Erice workshop and a saying shared by Jean- Pierre Philippe, a chef from Les Mesnuls, near Versailles. The subject of the moment was egg foams. Chef Philippe told us that he had thought he knew everything there was to know about meringues, until one day a phone call distracted him and he left his mixer running for half an hour. Thanks to the excellent result and to other sur- prises throughout his career, he said, Je sais, je sais que je sais jamais: “I know, I know that I never know.” Food is an inﬁ- nitely rich subject, and there’s always something about it to understand better, something new to discover, a fresh source of interest, ideas, and delight. 5 Units of Measurement, the Drawings of Molecules are given in both degrees Fahrenheit (ºF), the stan- and degrees Celsius or Centigrade (ºC), the units used temperatures shown in several charts can be formula ºC = (ºF quarts, pounds—and metric units— kilograms. Lengths are generally given in millimeters of the degree symbol º. Very small lengths are given 1 thousandth of a millimeter. a tiny fraction of a micron, that they can seem are real and concrete, and have particular structures foods made out of them—behave in the kitchen. they’re like and what happens to them, the easier it cooking. And in cooking it’s generally a molecule’s the precise placement of each atom. In most of the only the overall shapes are shown, and they’re rep- long thin lines, long thick lines, honeycomb-like rings on what behavior needs to be built from a backbone of interconnected carbon atoms (mainly hydrogen and oxygen) projecting from is what creates the overall structure, so often it is atoms themselves, just lines that show the bonds CHAPTER 1 Unfermented Dairy Products 21 Milks 22 Cream 27 Butter and Margarine 33 Ice Cream 39 Fresh Fermented Milks and Creams 44 Lactic Acid Bacteria 44 Families of Fresh Fermented Milks 45 Yogurt 47 Soured Creams and Buttermilk, Including Crème Fraîche 49 Cooking with Fermented Milks 51 Cheese 51 The Evolution of Cheese 51 The Ingredients of Cheese 55 Making Cheese 59 The Sources of Cheese Diversity 62 Choosing, Storing, and Serving Cheese 62 Cooking with Cheese 64 Process and Low-fat Cheeses 66 Cheese and Health 66 creatures accomplish the miracle of turning meadow and straw into buckets of human nourishment. And their milk turned out to be an elemental fluid rich in possibility, just a step or two away from luxurious cream, fragrant golden butter, and a multi- tude of flavorful foods concocted by friendly microbes. No wonder that milk captured the imaginations of many cultures. The ancient Indo-Europeans were cattle herders who 7 milk and dairy products MAMMALS AND MILK THE EVOLUTION OF MILK How and why did such a thing as milk ever come to be? It came along with warm- bloodedness, hair, and skin glands, all of which distinguish mammals from reptiles. Milk may have begun around 300 million years ago as a protective and nourishing skin secretion for hatchlings being incu- bated on their mother’s skin, as is true for the platypus today. Once it evolved, milk contributed to the success of the mam- malian family. It gives newborn animals the advantage of ideally formulated food from the mother even after birth, and there- fore the opportunity to continue their phys- ical development outside the womb. The human species has taken full advantage of this opportunity: we are completely helpless for months after birth, while our brains ﬁnish growing to a size that would be dif- ﬁcult to accommodate in the womb and birth canal. In this sense, milk helped make possible the evolution of our large brain, and so helped make us the unusual ani- mals we are. and Butter: Primal Fluids sacriﬁce, with the ﬁrst Man as the offering, spring was fuel, autumn the offering. They anointed that Man, born on the straw.... From that full sacriﬁce they gathered it into the creatures of the air, the forest, and the village... cattle were born from it, and sheep and goats were born from it. —The Rg Veda, Book 10, ca. 1200 BCE... I am come down to deliver [my people] out of the hands of the Egyptians, and to unto a good land and a large, unto a land ﬂowing with —God to Moses on Mount Horeb (Exodus 3:8) as milk, and curdled me like cheese? —Job to God (Job 10:10) mammals and milk 9 races: a humpless European-African form, and a humped central Asian form, the zebu. The European race was domesticated in the Middle East around 8000 BCE, the heat- and parasite-tolerant zebu in south- central Asia around the same time, and an African variant of the European race in the Sahara, probably somewhat later. In its principal homeland, central and south India, the zebu has been valued as much for its muscle power as its milk, and remains rangy and long-horned. The Euro- pean dairy cow has been highly selected for milk production at least since 3000 BCE, when conﬁnement to stalls in urban Mesopotamia and poor winter feed led to a reduction in body and horn size. To this day, the prized dairy breeds—Jerseys, Guernseys, Brown Swiss, Holsteins—are short-horned cattle that put their energy into making milk rather than muscle and bone. The modern zebu is not as copious a producer as the European breeds, but its milk is 25% richer in butterfat. The Buffalo The water buffalo is rela- tively unfamiliar in the West but the most important bovine in tropical Asia. Bubalus bubalis was domesticated as a draft animal in Mesopotamia around 3000 BCE, then taken to the Indus civilizations of present- day Pakistan, and eventually through India and China. This tropical animal is sensitive to heat (it wallows in water to cool down), so it proved adaptable to milder climates. The Arabs brought buffalo to the Middle East around 700 CE, and in the Middle Ages they were introduced throughout Europe. The most notable vestige of that introduction is a population approaching 100,000 in the Campagna region south of Rome, which supplies the milk for true mozzarella cheese, mozzarella di bufala. Buffalo milk is much richer than cow’s milk, so mozzarella and Indian milk dishes are very different when the traditional buf- falo milk is replaced with cow’s milk. The Yak The third important dairy bovine is the yak, Bos grunniens. This long-haired, milk and dairy products which is roughly comparable to cow’s milk, is collected in many countries, and in northeast Africa is a staple food. THE ORIGINS OF DAIRYING When and why did humans extend our biological heritage as milk drinkers to the cultural practice of drinking the milk of other animals? Archaeological evidence suggests that sheep and goats were domes- ticated in the grasslands and open forest of present-day Iran and Iraq between 8000 and 9000 BCE, a thousand years before the far larger, ﬁercer cattle. At ﬁrst these ani- mals would have been kept for meat and skins, but the discovery of milking was a signiﬁcant advance. Dairy animals could produce the nutritional equivalent of a slaughtered meat animal or more each year for several years, and in manageable daily increments. Dairying is the most efﬁcient means of obtaining nourishment from uncultivated land, and may have been especially important as farming communi- ties spread outward from Southwest Asia. Small ruminants and then cattle were almost surely ﬁrst milked into containers fashioned from skins or animal stomachs. The earliest hard evidence of dairying to date consists of clay sieves, which have been found in the settlements of the earliest northern European farmers, from around 5000 BCE. Rock drawings of milking scenes were made a thousand years later in the Sahara, and what appear to be the remains of cheese have been found in Egyptian tombs of 2300 BCE. elsewhere in DIVERSE TRADITIONS Early shepherds would have discovered the major transformations of milk in their ﬁrst containers. When milk is left to stand, fat- enriched cream naturally forms at the top, and if agitated, the cream becomes butter. The remaining milk naturally turns acid and curdles into thick yogurt, which draining separates into solid curd and liquid whey. Salting the fresh curd produces a simple, mammals and milk 11 around 1300 and thanks to the Mongols, even milk in their tea! Dairying was unknown in the New World. On his second voyage in 1493, Columbus brought sheep, goats, and the first of the Spanish longhorn cattle that would proliferate in Mexico and Texas. yogurt that Milk in Europe and America: From Farmhouse to Factory Preindustrial Europe In Europe, dairying took hold on land that supported abundant pasturage but was less suited to the cultiva- tion of wheat and other grains: wet Dutch lowlands, the heavy soils of western France and its high, rocky central massif, the cool, moist British Isles and Scandinavia, alpine valleys in Switzerland and Austria. With time, livestock were selected for the climate and needs of different regions, and diversi- ﬁed into hundreds of distinctive local breeds (the rugged Brown Swiss cow for cheese- making in the mountains, the diminutive Jersey and Guernsey for making butter in the Channel Islands). Summer milk was pre- served in equally distinctive local cheeses. By medieval times, fame had come to French Roquefort and Brie, Swiss Appenzeller, and Italian Parmesan. In the Renaissance, the Low Countries were renowned for their butter and exported their productive Friesian cattle throughout Europe. Until industrial times, dairying was done on the farm, and in many countries mainly by women, who milked the ani- mals in early morning and after noon and then worked for hours to churn butter or make cheese. Country people could enjoy good fresh milk, but in the cities, with con- fined cattle fed inadequately on spent brewers’ grain, most people saw only watered-down, adulterated, contaminated milk hauled in open containers through the streets. Tainted milk was a major cause of child mortality in early Victorian times. Industrial and Scientific Innovations Beginning around 1830, industrialization transformed European and American and dairy products the color, ﬂavor, and seasonal variation of preindustrial milk. Dairy Products Today Today dairying is split into several big businesses with noth- ing of the dairymaid left about them. Butter and cheese, once prized, delicate concen- trates of milk’s goodness, have become inexpensive, mass-produced, uninspiring commodities piling up in government ware- houses. Manufacturers now remove much of what makes milk, cheese, ice cream, and butter distinctive and pleasurable: they remove milk fat, which suddenly became undesirable when medical scientists found that saturated milk fat tends to raise blood cholesterol levels and can contribute to heart disease. Happily the last few years have brought a correction in the view of saturated fat, a reaction to the juggernaut of mass production, and a resurgent inter- est in full-ﬂavored dairy products crafted on a small scale from traditional breeds that graze seasonally on green pastures. cul- MILK AND HEALTH Milk has long been synonymous with wholesome, fundamental nutrition, and for good reason: unlike most of our foods, it is actually designed to be a food. As the sole sustaining food of the calf at the beginning of its life, it’s a rich source of many essen- Words: Milk and Dairy dairy recall the physical effort it once took to obtain milk comes from an Indo-European root that meant both the connection perhaps being the stroking necessary to medieval times, dairy was originally dey-ery, meaning the servant, made milk into butter and cheese. Dey in “to knead bread” (lady shares this root)—perhaps a several duties, but also of the kneading required to (p. 34) and sometimes the whey out of cheese. milk and health 13 days, a human infant in 100; sure enough, cow’s milk contains more than double the protein and minerals of mother’s milk. Of the major nutrients, ruminant milk is seri- ously lacking only in iron and in vitamin C. Thanks to the rumen microbes, which convert the unsaturated fatty acids of grass and grain into saturated fatty acids, the milk fat of ruminant animals is the most highly saturated of our common foods. Only coconut oil beats it. Saturated fat does raise blood cholesterol levels, and high blood cholesterol is associated with an increased risk of heart disease; but the other foods in a balanced diet can com- pensate for this disadvantage (p. 253). The box below shows the nutrient con- tents of both familiar and unfamiliar milks. These ﬁgures are only a rough guide, as the breakdown by breed indicates; there’s also much variation from animal to ani- mal, and in a given animal’s milk as its lac- tation period progresses. of Various Milks table are the percent of the milk’s weight accounted for by Protein Lactose Minerals Water 6.8 0.2 88 4.8 0.7 87 4.9 0.7 87 4.7 0.7 87 4.9 0.7 85 4.9 0.7 86 5.1 0.8 83 4.6 0.8 82 4.5 0.8 88 4.8 1.0 80 5.4 0.8 87 2.8 1.5 68 6.3 0.3 90 1.3 1.4 43 and dairy products steady minimum level commencing at between two and ﬁve years of age and con- tinuing through adulthood. The logic of this trend is obvious: it’s a waste of its resources for the body to pro- duce an enzyme when it’s no longer needed; and once most mammals are weaned, they never encounter lactose in their food again. But if an adult without much lactase activ- ity does ingest a substantial amount of milk, then the lactose passes through the small intestine and reaches the large intes- tine, where bacteria metabolize it, and in the process produce carbon dioxide, hydro- gen, and methane: all discomforting gases. Sugar also draws water from the intestinal walls, and this causes a bloated feeling or diarrhea. Low lactase activity and its symptoms are called lactose intolerance. It turns out that adult lactose intolerance is the rule rather than the exception: lactose-tolerant adults are a distinct minority on the planet. Several thousand years ago, peoples in northern Europe and a few other regions underwent a genetic change that allowed them to produce lactase throughout life, probably because milk was an exception- ally important resource in colder climates. About 98% of Scandinavians are lactose- tolerant, 90% of French and Germans, but only 40% of southern Europeans and North Africans, and 30% of African Amer- icans. Coping with Lactose Intolerance For- tunately, lactose intolerance is not the same as milk intolerance. Lactase-less adults can consume about a cup/250 ml of milk per day without severe symptoms, and even more of other dairy products. Cheese con- tains little or no lactose (most of it is drawn off in the whey, and what little remains in the curd is fermented by bacteria and molds). The bacteria in yogurt generate lactose-digesting enzymes that remain active in the human small intestine and work for us there. And lactose-intolerant milk fans can now buy the lactose-digesting enzyme itself in liquid form (it’s manufac- milk and health 15 bone mass after menopause that they’re at high risk for serious fractures. Dietary cal- cium clearly helps prevent this potentially dangerous loss, or osteoporosis. Milk and dairy products are the major source of cal- cium in dairying countries, and U.S. gov- ernment panels have recommended that adults consume the equivalent of a quart (liter) of milk daily to prevent osteoporosis. This recommendation represents an extraordinary concentration of a single food, and an unnatural one—remember that the ability to drink milk in adulthood, and the habit of doing so, is an aberration limited to people of northern European descent. A quart of milk supplies two-thirds of a day’s recommended protein, and would displace from the diet other foods— vegetables, fruits, grains, meats, and ﬁsh —that provide their own important nutri- tional beneﬁts. And there clearly must be other ways of maintaining healthy bones. Other countries, including China and Inﬂuences on Bone Health a proper balance between the two ongoing processes of These processes depend not only on calcium on physical activity that stimulates bone-building; hormones trace nutrients (including vitamin C, magnesium, potas- yet unidentiﬁed substances. There appear to be factors in that slow bone deconstruction signiﬁcantly. Vitamin D absorption of calcium from our foods, and also inﬂuences milk, and other sources include eggs, ﬁsh and shellﬁsh, and light from the sun activates a precursor molecule. have available for bone building is importantly affected urine. The more we lose, the more we have to take in of modern eating increase calcium excretion and so A high intake of salt is one, and another is a high metabolism of whose sulfur-containing amino acids neutralizing calcium salts from bone. osteoporosis appears to be frequent exercise of the and a well-rounded diet that is rich in vitamins and meat, and includes a variety of calcium-containing one, but so are dried beans, nuts, corn tortillas and salts), and several greens—kale, collards, mustard milk and dairy products intensive operations, cows aren’t allowed to waste energy on grazing in variable pas- tures; they’re given hay or silage (whole corn or other plants, partly dried and then preserved by fermentation in airtight silos) in conﬁned lots, and are milked only during their two or three most productive years. The combination of breeding and optimal feed formulation has led to per-animal yields of a hundred pounds or 15 gallons/58 liters per day, though the American average is about half that. Dairy breeds of sheep and goats give about one gallon per day. The ﬁrst ﬂuid secreted by the mammary gland is colostrum, a creamy, yellow solu- tion of concentrated fat, vitamins, and pro- teins, especially immunoglobulins and antibodies. After a few days, when the colostrum ﬂow has ceased and the milk is saleable, the calf is put on a diet of recon- stituted and soy milks, and the cow is milked two or three times daily to keep the secretory cells working at full capacity. The Milk Factory The mammary gland is an astonishing biological factory, with many different cells and structures working together to create, store, and dispense milk. Some components of milk come directly from the cow’s blood and collect in the udder. The principal nutrients, however— fats, sugar, and proteins—are assembled by the gland’s secretory cells, and then released into the udder. A Living Fluid Milk’s blank appearance belies its tremendous complexity and vital- ity. It’s alive in the sense that, fresh from the udder, it contains living white blood cells, some mammary-gland cells, and various bacteria; and it teems with active enzymes, some ﬂoating free, some embedded in the membranes of the fat globules. Pasteuriza- tion (p. 22) greatly reduces this vitality; in fact residual enzyme activity is taken as a sign that the heat treatment was insufﬁ- cient. Pasteurized milk contains very few living cells or active enzyme molecules, so it is more predictably free of bacteria that could cause food poisoning, and more sta- biology and chemistry 17 fat globules casein proteins The making of milk. Cells in the cow’s mammary gland synthesize the components of milk, including proteins and globules of milk fat, and release them into many thou- sands of small compartments that drain toward the teat. The fat globules pass through the cells’ outer membranes, and carry parts of the cell membrane on their surface. so their milk and butter are nutritious but white. Riboflavin, which has a greenish color, can sometimes be seen in skim milk or in the watery translucent whey that drains from the curdled proteins of yogurt. MILK SUGAR: LACTOSE to deﬂect The only carbohydrate found in any quan- tity in milk is also peculiar to milk (and a handful of plants), and so was named lac- tose, or “milk sugar.” (Lac- is a prefix based on the Greek word for “milk”; we’ll encounter it again in the names of milk proteins, acids, and bacteria.) Lactose is a composite of the two simple sugars glu- cose and galactose, which are joined together in the secretory cell of the mam- mary gland, and nowhere else in the animal body. It provides nearly half of the calories in human milk, and 40% in cow’s milk, and gives milk its sweet taste. The uniqueness of lactose has two major practical consequences. First, we need a special enzyme to digest lactose; and many adults lack that enzyme and have to be careful about what dairy products they consume (p. 14). Second, most microbes take some time to make their own lactose- digesting enzyme before they can grow well in milk, but one group has enzymes at the and dairy products Creaming When milk fresh from the udder is allowed to stand and cool for some hours, many of its fat globules rise and form a fat-rich layer at the top of the con- tainer. This phenomenon is called creaming, and for millennia it was the natural ﬁrst step toward obtaining fat-enriched cream and butter from milk. In the 19th century, centrifuges were developed to concentrate the fat globules more rapidly and thor- oughly, and homogenization was invented to prevent whole milk from separating in this way (p. 23). The globules rise because their fat is lighter than water, but they rise much faster than their buoyancy alone can account for. It turns out that a number of minor milk proteins attach themselves loosely to the fat globules and knit together clusters of about a million globules that have a stronger lift than single globules do. Heat denatures these proteins and prevents the globule clustering, so that the fat glob- ules in unhomogenized but pasteurized milk rise more slowly into a shallower, less distinct layer. Because of their small glob- ules and low clustering activity, the milks of goats, sheep, and water buffalo are very slow to separate. Milk Fat Globules Tolerate Heat... Interactions between fat globules and milk proteins are also responsible for the remarkable tolerance of milk and cream to heat. Milk and cream can be boiled and reduced for hours, until they’re nearly dry, without breaching the globule membranes enough to release their fat. The globule membranes are robust to begin with, and it turns out that heating unfolds many of the milk proteins and makes them more prone to stick to the globule surface and to each other—so the globule armor actually gets progressively thicker as heating proceeds. Without this stability to heat, it would be impossible to make many cream-enriched sauces and reduced-milk sauces and sweets. But Are Sensitive to Cold Freezing is a different story. It is fatal to the fat globule membrane. Cold milk fat and freezing biology and chemistry 19 Both caseins and whey proteins are unusual among food proteins in being largely tolerant of heat. Where cooking coagulates the proteins in eggs and meat into solid masses, it does not coagulate the proteins in milk and cream—unless the milk or cream has become acidic. Fresh milk and cream can be boiled down to a fraction of their volume without curdling. The Caseins The casein family includes four different kinds of proteins that gather together into microscopic family units called micelles. Each casein micelle con- tains a few thousand individual protein molecules, and measures about a ten- thousandth of a millimeter across, about one-ﬁftieth the size of a fat globule. Around a tenth of the volume of milk is taken up by casein micelles. Much of the calcium in milk is in the micelles, where it acts as a kind of glue holding the protein molecules together. One portion of calcium binds individual protein molecules together into small clusters of 15 to 25. Another portion then helps pull several hundred of the clus- ters together to form the micelle (which is also held together by the water-avoiding hydrophobic portions of the proteins bond- ing to each other). texture of Keeping Micelles Separate... One member of the casein family is especially inﬂuential in these gatherings. That is kappa-casein, which caps the micelles once they reach a whey proteins A close-up view of milk. Fat globules are suspended in a ﬂuid made up of water, indi- vidual molecules of whey pro- tein, bundles of casein protein molecules, and dissolved sug- ars and minerals. milk and dairy products dle is the basis of cheese making. Chy- mosin, a digestive enzyme from the stom- ach of a milk-fed calf, is exquisitely designed to give the casein micelles a hair- cut (p. 57). It clips off just the part of the capping-casein that extends into the sur- rounding liquid and shields the micelles from each other. Shorn of their hairy layer,... And Knitting Them Together in Curds the micelles all clump together—without the milk being noticeably sour. that cause The Whey Proteins Subtract the four caseins from the milk proteins, and the remainder, numbering in the dozens, are the whey proteins. Where the caseins are mainly nutritive, supplying amino acids and cal- cium for the calf, the whey proteins include defensive proteins, molecules that bind to and transport other nutrients, and enzymes. The most abundant one by far is lactoglob- ulin, whose biological function remains a mystery. It’s a highly structured protein that is readily denatured by cooking. It unfolds at 172ºF/78ºC, when its sulfur atoms are exposed to the surrounding liquid and react with hydrogen ions to form hydrogen sul- ﬁde gas, whose powerful aroma contributes to the characteristic ﬂavor of cooked milk (and many other animal foods). In boiling milk, unfolded lactoglobulin binds not to itself but to the capping-casein dairy products 21 Flavors from Cooking Low-temperature pasteurization (p. 22) slightly modiﬁes milk ﬂavor by driving off some of the more del- icate aromas, but stabilizes it by inactivat- ing enzymes and bacteria, and adds slightly sulfury and green-leaf notes (dimethyl sul- ﬁde, hexanal). High-temperature pasteur- ization or brief cooking—heating milk above 170ºF/76ºC—generates traces of many ﬂavorful substances, including those characteristic of vanilla, almonds, and cultured butter, as well as eggy hydrogen sulfide. Prolonged boiling encourages browning or Maillard reactions between lactose and milk proteins, and generates molecules that combine to give the ﬂavor of butterscotch. from the lactose, The Development of Off-Flavors The ﬂavor of good fresh milk can deteriorate in several different ways. Simple contact with oxygen or exposure to strong light will cause the oxidation of phospholipids in the globule membrane and a chain of reactions that slowly generate stale cardboard, metal- lic, ﬁshy, paint-like aromas. If milk is kept long enough to sour, it also typically devel- ops fruity, vinegary, malty, and more unpleasant notes. Exposure to sunlight or fluorescent lights also generates a distinctive cabbage- like, burnt odor, which appears to result from a reaction between the vitamin riboﬂavin and the sulfur-containing amino acid methionine. Clear glass and plastic containers and supermarket lighting cause this problem; opaque cartons prevent it. fatty acids UNFERMENTED DAIRY PRODUCTS Fresh milk, cream, and butter may not be as prominent in European and American cooking as they once were, but they are still essential ingredients. Milk has bub- bled up to new prominence atop the coffee craze of the 1980s and ’90s. fatty and dairy products and inspected frequently, and the milk car- ries a warning label. Raw milk is also rare in Europe. Pasteurization and UHT Treatments In the 1860s, the French chemist Louis Pasteur studied the spoilage of wine and beer and developed a moderate heat treatment that preserved them while minimizing changes in their ﬂavor. It took several decades for pas- teurization to catch on in the dairy. Nowa- days, in industrial-scale production, it’s a practical necessity. Collecting and pooling milk from many different farms increases the risk that a given batch will be contaminated; and the plumbing and machinery required for the various stages of processing afford many more opportunities for contamina- tion. Pasteurization extends the shelf life of milk by killing pathogenic and spoilage microbes and by inactivating milk enzymes, especially the fat splitters, whose slow but steady activity can make it unpalatable. Pas- teurized milk stored below 40ºF/5ºC should remain drinkable for 10 to 18 days. There are three basic methods for pasteurizing milk. The simplest is batch pasteurization, in which a ﬁxed volume of milk, perhaps a few hundred gallons, is slowly agitated in a heated vat at a mini- mum of 145ºF/62ºC for 30 to 35 minutes. Industrial-scale operations use the high- temperature, short-time (HTST) method, in which milk is pumped continuously through a heat exchanger and held at a minimum of 162ºF/72ºC for 15 seconds. The batch process has a relatively mild effect on ﬂavor, while the HTST method is hot enough to denature around 10% of the whey proteins and generate the strongly aromatic gas hydrogen sulfide (p. 87). Though this “cooked” ﬂavor was consid- ered a defect in the early days, U.S. con- sumers have come to expect it, and dairies now often intensify it by pasteurizing at well above the minimum temperature; 171ºF/77ºC is commonly used. The third method of pasteurizing milk is the ultra-high temperature (UHT) method, which involves heating milk at 265–300ºF/ dairy products 23 clumping: and so the fat remains evenly dis- persed in the milk. Milk is always pasteur- ized just before or simultaneously with homogenization to prevent its enzymes from attacking the momentarily unprotected fat globules and producing rancid ﬂavors. Homogenization affects milk’s flavor and appearance. Though it makes milk taste blander—probably because flavor molecules get stuck to the new fat-globule surfaces—it also makes it more resistant to developing most off-ﬂavors. Homogenized milk feels creamier in the mouth thanks to its increased population (around sixty-fold) of fat globules, and it’s whiter, because the carotenoid pigments in the fat are scattered into smaller and more numerous particles. homog- Nutritional Alteration; Low-Fat Milks One nutritional alteration of milk is as old as dairying itself: skimming off the cream layer substantially reduces the fat content of the remaining milk. Today, low-fat milks are made more efﬁciently by centrifuging off some of the globules before homoge- nization. Whole milk is about 3.5% fat, low-fat milks usually 2% or 1%, and skim milks can range between 0.1 and 0.5%. More recent is the practice of supple- menting milk with various substances. Nearly all milks are fortiﬁed with the fat- soluble vitamins A and D. Low-fat milks have a thin body and appearance and are usually ﬁlled out with dried milk proteins, which can lend them a slightly stale ﬂavor. Milk in 13th-Century Asia also of milk, thickened or dried to the state of a in the following manner. They boil the milk, and skim- as it rises to the top, put it into a separate vessel as in the milk, it will not become hard. The milk is then [When it is to be used] some is put into a bottle with By their motion in riding, the contents are vio- is produced, upon which they make their dinner. —Marco Polo, Travels milk and dairy products ply milk’s characteristic contribution to the texture and ﬂavor of baked goods and con- fectionery, but without milk’s water. Condensed or evaporated milk is made by heating raw milk under reduced pressure (a partial vacuum), so that it boils between 110 and 140ºF/43–60ºC, until it has lost about half its water. The resulting creamy, mild-ﬂavored liquid is homogenized, then canned and sterilized. The cooking and concentration of lactose and protein cause some browning, and this gives evaporated

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