Cooked - A Natural History of Transformat Part 13

Clearly Robertson's loose, novelistic approach to the whole notion of baking was driving a certain kind of person absolutely crazy. And then all at once, I was buoyed by this thought: I am not that kind of person! This was the moment when I decided I was ready to jump in. It was time to start my starter.

Considering what it is (a living thing) and what it does (leaven and flavor a bread), the instructions for starting a sourdough culture could not be much simpler. Take some flour, preferably a fifty-fifty mixture of white and whole grain, and mix it by hand in a gla.s.s bowl with some warm water until you have something that feels like a smooth pancake batter. Cover the bowl with a cloth and leave it in a cool spot for two or three days. If by then nothing has happened, wait a few more days and check it again.

Simple maybe, but not foolproof: My first attempt at starting a starter didn't start. After a week of inactivity, the batter separated into a layer of cement beneath a layer of perfectly clear water. It remained absolutely inert and odorless. I did some reading to figure out what was supposed to be happening but wasn't. Wild yeasts and bacteria were supposed to find their way into the batter, take up residence, and eventually organize themselves into a more or less stable microbial community. Curiously, none of the authorities I consulted could say with certainty just where these yeasts and bacteria came from or how they got here, if and when they did. They might already be in the flour, or on my hands (which is why Robertson suggests mixing by hand), or in the air. Indeed, one of the many mysteries of sourdough culture is the origin of its resident microbes, some of which-like the all-important Lactobacillus sanfranciscensis-have never been found anywhere on earth except in a sourdough bread culture.* This suggests these "wild" microbes are actually in some sense domesticated-dependent upon us (and our love of bread) to create and maintain their highly specialized ecological niche. But either I had failed to create a niche to their liking or the bugs had failed to find it, because even after two weeks my starter was as lifeless as plaster.

I started a new culture, but this time after mixing it I gave the bowl an hour or two outside in the sun, hoping to snag some airborne microbes. I also gave it some vigorous stirs whenever I remembered to, in order to work some oxygen into the mixture. Within a week, my batter was showing tentative signs of life in what seemed very much like an instance of spontaneous generation: proposing the occasional bubble and giving off a faint, not-unpleasant scent reminiscent of rotten apples. But a couple of days later, the odor had taken an unpleasant turn, veering toward strong cheese or worn sock. Something bacterial was definitely afoot. So, following Robertson's directions, I discarded 80 percent of the starter, more or less, and fed what remained a couple tablespoons of fresh flour and warm water. Within a day, the bowl was burbling contentedly. I had a starter! Whether it was lively enough to leaven a dough, I wasn't yet sure, but it was definitely alive.

A couple weeks later, when my starter seemed to be settling into a predictable daily rhythm, rising in the hours after its morning feeding and then subsiding again overnight, I embarked on my first loaf of naturally leavened bread.

Step one is to turn a small amount of the starter into a "sponge" or "leaven"-basically, use it to inoculate a much bigger ma.s.s of sourdough culture, which in turn would inoculate and leaven the entire dough I would mix the next morning. Placing a gla.s.s bowl on my new (digital) kitchen scale, I zeroed it out and added two hundred grams of flour (the same fifty-fifty mix I used to feed my starter), then an equal amount of warm water. To this I introduced a heaping tablespoon of my starter, mixed it all together, covered the bowl with a dish towel, and went off to bed.

I faced a test in the morning, one that many of the partic.i.p.ants in the chat rooms and discussion groups on line had struggled to pa.s.s. To wit: Would this so-called sponge take on enough air overnight so that, when dropped into a bowl of water, it would float? If instead it sank, that would indicate there wasn't enough microbial activity to leaven a loaf of bread.

The question would be decided while I slept: There was nothing to do now but wait, while my culture either did or failed to do its fermentative thing. Already this felt like a radically different way of "cooking" than I had done up to now, but not because it was any more exacting or precise. To the contrary: I'd delegated my accustomed kitchen powers and responsibilities to this invisible cohort of unidentified microbes.

Up to now, most of the things I'd cooked and ingredients I'd cooked with had been dead, after all, and therefore more or less tractable. The raw materials responded in predictable ways to physical and chemical processes that I controlled; whatever did or didn't happen to them could be explained in terms of either chemistry or physics. Obviously those laws play an important part in baking, too, but the most important processes unfolding in a naturally leavened bread are biological. Though the baker might be able to influence and even manage those processes, "control" would be far too strong a word for what he does. It's a little like the difference between gardening and building. As with the plants or the soil in a garden, the gardener is working with living creatures that have their own interests and agency. He succeeds not by dictating to them, as a carpenter might to lumber, but by aligning his interests with theirs. To use a metaphor a little closer to Chad Robertson's frame of reference, what the baker does is a little like the surfer's relations.h.i.+p to the wave.

This lack of control has never sat well with our species, which probably explains why the modern history of bread baking can be told as a series of steps aimed at taking the unruliness, uncertainty, and comparative slowness of biology out of the process. Milling white flour was the first such step. Whole-grain flours, as I would soon learn, are much more complex and biologically active than white flour. That's because white flour consists chiefly of dead starch, whereas the germ and the bran removed in milling it contain living cells. Whole grains teem with enzymes and volatile oils that make their flours more perishable and fermentation more difficult to manage.

Around the same time that the advent of roller mills made white flour widely available in the 1880s, the introduction of commercial yeast gave bakers an even more decisive gain in control. Now, instead of having to rely on an unruly community of unidentified fungi and bacteria to leaven bread, as had been the case for thousands of years, they could enlist a single species of yeast to do the job on command. Called Saccharomyces cerevisiae, this species had been (as its name suggests) found in beer, selected over countless generations, and optimized for the role of putting gas in dough. Commercial bread yeast is a purified monoculture of S. cerevisiae, raised on a diet of mola.s.ses, then washed, dried, and powdered. Like any monoculture, it does one thing predictably and well: Feed it enough sugars and it will promptly cough up large quant.i.ties of carbon dioxide.

Though commercial yeast is alive, its behavior is linear, mechanical, and predictable, a simple matter of inputs and outputs-which is no doubt why it so quickly caught on. S. cerevisiae can be counted on to perform the same way everywhere and give the same results, making it supremely well suited to industrial production. Yeast could now be treated simply as another ingredient rather than as a locally variable community of organisms in need of special care and feeding. In fact, as microbes go, S. cerevisiae is notable for not playing well with others, especially bacteria. Compared with wild yeasts, commercial yeast cannot survive very long in the acidic environment created by lactobacilli.

While scientists have known about yeast since Louis Pasteur first identified it in 1857, the intricate microbial world within a wild sourdough culture like mine was a complete mystery until fairly recently-and remains at least a partial mystery even today. In 1970, a team of USDA scientists based in Albany, California, collected samples of sourdough starter from five San Francis...o...b..keries and conducted a kind of microbial census. Why San Francisco? Because the city was famous for its sourdough bread. The scientists were hoping to identify the local microbes responsible for the bread's distinctive qualities. Their landmark 1971 paper, "Microorganisms of the San Francisco Sour Dough French Bread Process," helped to spur a revival in naturally leavened breads and almost single-handedly established the (albeit still minor) field of sourdough microbiology.*

The USDA team discovered that unlike what happens in the straightforward fermentation performed by S. cerevisiae, no single yeast species was responsible for what takes place in a sourdough culture. Rather, the process depended on a complex, semisymbiotic a.s.sociation between a yeast (Candida milleri) and a previously unknown bacterium. a.s.suming-wrongly, as it turned out-that the bacterium they had identified was unique to San Francisco's famed sourdoughs, they named it Lactobacillus sanfranciscensis. It has since been found in bakeries all over the world. Oh well.

Though not exactly dependent on each other, the yeast and the bacteria are ideally suited to living together. Each microbe consumes a different type of sugar, so they don't compete for food. And when the yeasts die, their proteins break down into amino acids that the lactobacilli need to grow.

At the same time, the lactobacilli produce organic acids that shape the environment in ways agreeable to C. milleri (which is acid-tolerant), but disagreeable to other yeasts and bacteria. L. sanfranciscensus also produces an antibiotic compound that prevents competing microbes from gaining a toehold in the culture, but which doesn't trouble C. milleri in the least. Thus the sourdough culture defends itself from colonization by outsiders. This biochemical defense is a boon to us as well, since it extends the shelf life of the bread.

Perhaps the USDA team's most important contribution was to demonstrate that a sourdough culture functions as a kind of ecosystem, with the various species performing distinct roles that lend stability to the culture over time. Once established, the system exhibits more cooperation than compet.i.tion, so that no one organism ever dominates. Subsequent research in other parts of the world has greatly expanded the list of species found in sourdough cultures-at least twenty types of yeast and fifty different bacteria-but most of them seem to fall into similar niches, organize themselves into similar relations.h.i.+ps, and perform similar functions. Same play, different actors. Presumably these yeasts and bacteria coevolved with one another, which might explain why many of them have been found nowhere except in sourdough cultures, their "natural habitat." Which in turn suggests these microbes probably coevolved with us: Their culture depends upon our culture of bread making, and (until recently) vice versa.

In the microuniverse of a sourdough culture, the baker performs in the role of G.o.d, or at least of natural selection. It may well be that the requisite microbes are everywhere, but by shaping their environment-the food and feeding schedule, the ambient temperature, the amount of water-the baker, wittingly or unwittingly, selects which microbes will thrive and which will fail. Frequent feedings and warm temperatures tend to favor the yeasts, for example, creating an airier, milder loaf, whereas skipping meals and refrigerating the culture favors the bacteria, leading to a more acidic environment, and a more strongly flavored bread.

"Baking well really comes down to managing fermentation," according to Robertson. The flavor and quality of a naturally leavened bread depends to a great extent on how skillfully the baker governs this invisible microbial world. And if the baker fails to care for his culture? It may take awhile, but once the sun of his attention goes dark, the culture eventually dies.

The morning after starting my sponge, I woke up eager to head down to the kitchen to see what, if anything, had happened overnight. When I'd mixed the stuff the night before, the heavy paste of flour and water filled a two-cup measuring bowl halfway to the top. Incredibly, it had doubled in volume overnight, and I could feel it had lightened considerably, achieving a consistency reminiscent of marshmallow. Through the gla.s.s I could see that the paste had become a ga.s.sy foam, shot through with millions of air bubbles. I felt certain it would float.

So into a larger bowl I measured out the quant.i.ty of warm water called for in the recipe (750 grams), and then, using a spatula, scooped out the sponge. It slid into the warm bath and then bobbed up to the surface of the water like a raft, buoyant. I was in business! Next I added 900 grams of white flour and 100 grams of whole-wheat flour. I mixed everything together by hand, squeezing the flour and water through my fingers to make sure there were no unhydrated lumps of flour-what bakers call "chestnuts." The result was a dough wetter than anything I had ever worked with before. This promised to be a challenge.*

Before any salt is added, the dough gets to rest for twenty minutes or so. Called the "autolyse," this period gives the flour a chance to fully hydrate, the gluten to begin to swell and get itself organized, the enzymes to begin cleaving complex starches into simpler sugars, and the fermentation of those sugars to commence. Salt acts as a check on all these processes, which in its absence would proceed too rapidly. The goal is a long, slow fermentation in order to build maximum flavor. As one nineteenth-century cookbook put it, salt serves as the bridle on the wild horse of fermentation.

After I mixed in the twenty grams of salt, the dough felt dull and sticky to the touch-a wet, heavy, lifeless clay. I covered the bowl with a towel and went back to work, setting my phone to alert me in forty-five minutes. "Bulk fermentation" was now under way-a period of between three and four hours during which the princ.i.p.al development and fermentation of the dough takes place.

A complex drama unfolds during the bulk fermentation, one that the baker cannot see but can infer by the evolving texture, smell, and taste of his dough. Within the dough, a spongiform structure is taking shape, a three-dimensional lacework of air. The structure is the result of two separate developments-one chemical in nature, the other biological-that in a dough made from wheat flour happen, fortunately for the panivore, to coincide and intersect just so.

The chemical development is the formation of gluten (the word means "glue" in Latin), an interesting if somewhat problematic substance that is found primarily in wheat, and to a much lesser extent in rye, another species of gra.s.s. To be precise, gluten as such is not found in wheat itself, but, rather, its two precursors are, the proteins gliadin and glutenin, which when moistened in water combine to form the mesh of proteins known as gluten. Unprepossessing on its own, each of these proteins contributes a different but equally important quality to a bread: extensibility on the part of gliadin, and elasticity on the part of glutenin. As in the fibers of a muscle, these qualities exist in a productive tension, the former allowing the dough to be stretched and shaped, while the latter impels it to bounce back to something close to its original form. In fact, the Chinese call gluten "the muscle of flour," and all bakers speak in terms of a dough's "strength" or "weakness," qualities that correspond to the amount of gluten in it.

The pliable yet rubbery properties of gluten make it the ideal medium for trapping air, which happens to be the crucial by-product of the second, biological development under way in a wet ma.s.s of fermenting dough. While the gluten network is forming and gaining strength, the community of yeasts and bacteria introduced by the starter are dining on starches "damaged" during milling, when some of them are broken into sugars. Various enzymes (some of which are present in the flour, others produced by the bacteria and yeasts) go to work on the undamaged starches and proteins, breaking them down into simple sugars and amino acids to feed the microbes. Thus fed, the bacteria proliferate, producing lactic and acetic acids, which help to strengthen the gluten while contributing new flavors. And, most important of all, the yeasts are busy transforming each molecule of glucose they consume into two molecules of alcohol and two of carbon dioxide. The carbon dioxide gas, which is a by-product of alcohol production, would simply escape into the atmosphere if not for the rubbery matrix of gluten, which stretches like a balloon to contain it. Without the extensible and elastic gluten to trap the carbon dioxide, bread would never rise.

The properties of gluten have commended wheat to humanity since the Egyptians first recognized what it could do. Before that, wheat was just one edible gra.s.s among many, part of a crowded field that included millet, barley, oats, and rye and, later, corn and rice. Barley barely registers in our eating lives today, but before the invention of bread it was just as important a staple food in the West. It grows more quickly than wheat, and in more places, from the tropics to the Arctic Circle. Highly nutritious, it was the food of choice of the Roman gladiators, who were in fact called hordearii, the barley eaters. But though barley made nouris.h.i.+ng porridges and flat breads (and beer, as I would discover), no amount of leavening could raise it off an oven floor.

Wheat's own ancestors couldn't rise, either. Einkorn, the earliest known form of wheat, has been cultivated in southeastern Turkey for nearly ten thousand years, but eaten mostly as a porridge or brewed as beer. It has too much gliadin and not enough glutenin to trap fermentation gases. The ancestry of bread wheat is tangled and still a subject of botanical debate, but it took thousands of years of accidental crosses and mutations before a civilization-altering curiosity showed up in a farmer's field somewhere in the Fertile Crescent: a stalk of wheat with big fat seeds that just happened to contain the proteins gliadin and glutenin in just the right proportions. Gluten, and with it the possibility of leavened bread, had come into the world.*

What had been one edible gra.s.s among many became the imperial gra.s.s, spreading from the Fertile Crescent of the Middle East to Europe by 3000 B.C., to Asia two thousand years later, and then, soon after 1492, to both continents of the New World. Bread wheat spread because people liked to eat bread, but also because of its central place in the Christian liturgy; priests needed bread to give communion, and in the New World would plant it expressly for that purpose. The only continent where wheat had not made significant inroads until well into the twentieth century was Africa. But after World War II the United States began giving food aid to Africa in the form of wheat, and then promoted its consumption in cultures where it had never before been eaten. It caught on, completing the plant's global triumph.

Today, wheat is planted more widely than any other single crop, waving its golden seed heads over more than 550 million acres worldwide; there is no month of the year when wheat is not being harvested somewhere in the world. It is true that, by weight, the world's farmers produce more corn than wheat, but most of that crop ends up in the stomachs of animals or the gas tanks of automobiles (in the form of ethanol). As a food for humans, no crop is more important than wheat. (Rice comes second.) Worldwide, wheat flour accounts for a fifth of the calories in the human diet. And that's low by historical standards: For most of European history, bread represented more than half the calories in the diet of the peasantry and the urban poor, according to French historian Fernand Braudel.

When you consider that other cereal crops produce more calories per acre (corn, rice) and others are easier to grow (corn, barley, rye) and still others are more nutritious (quinoa), tritic.u.m's triumph appears even more unlikely and impressive. The secret of wheat's success? Gluten. Which is another way of saying, the human love of leavened bread. Yet to put it that way is not to have found a case-closing answer so much as another question. Because what in the world is so wonderful about aerated porridge?

An hour into the bulk fermentation, the dough already felt slightly different to the touch-still flabby but slightly less yielding, and maybe a little lighter. Robertson recommends "turning" the dough in a container rather than kneading it on a flat surface-nearly impossible anyway with a dough this wet. A turn involves reaching your fingers down along the inside wall of the bowl, lifting the ma.s.s of dough up from the bottom, and then folding it over the top; repeat the move three or four times as you rotate the bowl with your other hand, so each quadrant gets at least one fold. That's one complete turn. (Wetting your fingers helps keep the dough from sticking to them.) Robertson advises a complete turn every half hour to start, and then with diminis.h.i.+ng frequency, and a gentler touch, as the dough begins to billow with air. The folds help to exercise and so strengthen the gluten, while trapping a certain amount of ambient air in the dough-each fold creating minuscule pockets that will later balloon with carbon dioxide and ethanol.

By the third or fourth turn, the character of the dough has changed substantially. No longer clinging to the sides of the bowl, it has cohered into a distinct ma.s.s and developed what feels like muscle tone. When you pull it upward for a fold, it stretches without tearing and then pulls back down. The dough now feels less like clay than living flesh, something in possession of will, seemingly, and an ident.i.ty. It's also begun to smell yeasty, and what was tasteless before is now sweet on the tongue.

Nowadays, I usually get some writing done during bulk fermentation. The intervals between turns are just right for getting up from my desk to take a break, and the process is sufficiently forgiving in the event I get so absorbed in my work that I miss a turn. The dough is largely developing itself-or, rather, my sourdough culture is developing the dough while I develop something else, like this chapter. As I've heard some bakers say, baking takes a lot of time, but for the most part it's not your time.

As a means of processing a raw foodstuff, a sourdough fermentation is a wonder of nature and culture, an example of an ancient vernacular "technology" the ingenuity of which science is just now coming to appreciate. "You could not survive on wheat flour," Bruce German, the food chemist at UC Davis, told me, "but you can survive on bread." The reason you can is largely due to the work of these microbes going about their unseen lives. And though modern food science can simulate many of their effects in commercial bread production, by using commercial yeasts and other leavening agents, sweeteners, preservatives, and dough conditioners, it still can't do everything a sourdough culture can do to render gra.s.s seeds nouris.h.i.+ng to humans.

The waste products of the various microbes are the key to this transformation. Carbon dioxide gases produced by both the yeasts and bacteria are what leaven the bread, while the ethanol excreted by the yeasts contributes aromas. The organic acids produced by the lactobacilli have a whole range of crucial effects: They contribute flavor, strengthen the dough, and, perhaps most important, help to activate various enzymes already present in the seed.

Think of a seed as a well-stocked pantry for the future plant: Energy, amino acids, and minerals are stored there in the form of stable, hard-to-access molecules called polymers. The various enzymes are molecular keys that unlock the pantry by breaking down the various polymers so that the developing embryo will have something to eat in the period before it puts down roots. But the seed can also be tricked into unlocking all that sequestered food for the microbes in the starter and, in turn, for us.

The acids produced by sourdough bacteria rouse the sleeping enzymes and put them to work. Amylase attacks the complex carbohydrates, breaking the tightly wound (and tasteless) b.a.l.l.s of yarn that starches resemble into shorter, more accessible snippets of sugar. The proteases break the long protein chains into their amino acid building blocks. These sugars and amino acids contribute to the flavor and beauty of the bread, by feeding the chemical reactions (both Maillard and caramelization) that, in the oven, will brown the crust. They also feed the yeasts, thereby helping to make the bread airier. But airiness in bread does more than make it attractive. The air pockets provide a place for steam to form, and since steam gets considerably hotter than water (which never exceeds the boiling point), it helps to more completely cook (or "gelatinize") the starches, rendering them both tastier and more digestible.

Sourdough fermentation also partially breaks down gluten, making it easier to digest and, according to some recent research from Italy (a nation of wheat eaters with high rates of celiac disease and gluten intolerance), destroying at least some of the peptides thought to be responsible for gluten intolerance. Some researchers attribute the increase in gluten intolerance and celiac disease to the fact that modern breads no longer receive a lengthy fermentation. The organic acids produced by the sourdough culture also seem to slow our bodies' absorption of the sugars in white flour, reducing the dangerous spikes of insulin that refined carbohydrates can cause. (Put another way, a sourdough bread will have a lower "glycemic index" than a bread leavened with yeast.) Lastly, the acids activate an enzyme called phytase, which unlocks many of the minerals that, in a seed, have been carefully locked up (or "chelated") for the eventual use of the germinating plant.

To learn about the many beneficial transformations taking place in my lump of dough during its bulk fermentation is to gain a deeper appreciation for the genius of human culture-for having "figured out" how to process gra.s.s this way-but equally for the ingenuity of the microbial culture that actually does the most important work of bread making. The dance of mutual exploitation that these two cultures have performed for six thousand years now has served both of us well, and required no conscious awareness on our part beyond the recognition and remembering of what seemed to work. Much like a soil, which it in some ways resembles, a sourdough culture can be nurtured and cultivated without having to be understood. But now that science has given us a belated understanding of all that a sourdough fermentation can do to render gra.s.s seed so nouris.h.i.+ng and tasty, we can only marvel that we would have so blithely abandoned it, for no good reason other than our impatience-and, perhaps, our desire to control rather than to dance or surf.

I decided the bulk fermentation was complete after about six hours, when my dough was soft and billowy and showed more interest in clinging to itself than to me or its container. What had felt reluctant in my hands now felt willing and lively. Fat marbles of gas had formed directly beneath its snowy skin, and the dough gave off a nice, yeasty aroma tinged with alcohol and vinegar. I sampled a pinch of dough; it tasted sweet and slightly acidic. To let it go any longer was to risk too sour a bread, so I decided the time had come to move on to the next step: shaping the dough into loaves.

Here is where my difficulties began. The book said to scoop the ma.s.s of dough onto a floured work surface, divide it into two pieces with a bench knife (basically a big plastic knife), and shape each piece of the still sticky but now perky ma.s.s into a globe, or boule, the French word for a round country loaf. (Also the root of the French word for baker, boulanger.) The dough was so wet that this proved difficult and messy, but after dusting my hands and the cutting board and every other surface in the kitchen with white flour, I was able to coax the dough into a pair of vaguely globular shapes. The instructions said to take a round of dough in both hands and rotate it while maintaining contact with the work surface; the bottom of the dough should cling, slightly, to the countertop, thereby creating some tension in the surface of the sphere as it takes shape. At first my globe resembled an attractive white b.u.t.tock with some muscle tone, but it soon relaxed into something considerably more flaccid and pancakelike.

The two rounds of dough now got another twenty or so minutes of rest, covered with a dish towel to keep the air from crusting them. I peeked under a few times and could see that the dough was continuing to percolate and expand even as it relaxed and subsided.

Now it was time to execute the set of shaping maneuvers I'd been dreading since I first studied the instructions and accompanying sequence of how-to photographs in the book. Unless you're the kind of person who can learn a dance step from a diagram or figure out how to diaper a baby from a book, printed instructions for properly shaping a loaf of Tartine bread are nearly impossible to follow.

Why bother shaping at all? you might legitimately wonder at this point. Because a dough as wet and flabby as this one will not achieve a good oven spring unless the baker endows it with some internal tension and structure. This is achieved as follows: With your fingers, take hold of each quadrant of the dough in turn, stretch it outward, and then fold it back over the center, until it forms a neat rectangular package, a bit like a papoose. Do this again with each of the four corners. Then roll the package of dough away from you until the seams come around to the bottom and the surface has grown smooth and tight. Each fold builds structural tension in the gluten at a different point within the loaf, while the rolling creates surface tension in the crust. At least that's the idea.

It took me several aborted attempts and another kitchenwide blizzard of flour, but eventually I was able to form the dough into taut rounds of powdery-white flesh. The impulse to cup the soft globes in my hands was irresistible. I have to say, not one of the bakers I had read or talked to had adequately prepared me for the erotics of leavened, shaped dough.

I carefully slipped the shaped loaves, seam side up, into bowls lined with kitchen towels that I had rubbed with flour to keep them from sticking. I wrapped the corners of the towel over the top to keep the loaves from exposure to drafts, which might dry out their skins and so impede their rise. Now came the second fermentation. Called "proofing," this final step takes between two and four hours, depending on the temperature and the degree of sourness the baker desires. The dough is ready for the oven when its volume has expanded by a third or so but looks like it still has some life left in it. An overproofed loaf is liable to be sour and sticky, and, its yeasts having exhausted their supply of sugars, incapable of much oven spring.

Toward the end of the proofing process, I preheated the oven to 500F with a cast-iron Dutch oven in it. Baking in a covered pot represents something of a breakthrough in home bread making. A steamy oven is the key to achieving a good oven spring as well as a chewy crust. The steam delays the moment when the bread forms a crust, allowing the dough to expand as long as possible before solidifying. Professional bakers inject steam into their ovens for precisely this reason, but home ovens have been designed to vent steam. By baking bread in the sealed environment of a Dutch oven or covered ca.s.serole, the home baker can closely approximate the steamy interior of a bakery oven without having to add any water: The moisture from the dough creates all the steam needed for a good spring.

When the oven temperature reached 500F, I removed the Dutch oven with oven mitts and rested it on top of the stove. Now came Moment of Truth Number One: I flipped the bowl over the open pot, dropping the ball of dough onto its blazingly hot bottom. My aim was a few degrees off, however, because the dough caught the edge of the pot and landed lopsidedly, wrecking its perfect symmetry and no doubt disturbing its hard-won internal structure. My poor loaf suffered a second insult when it came time to score it with a razor blade-Moment of Truth Number Two. The idea here is that slas.h.i.+ng the loaf's skin will release some of its surface tension and by doing so facilitate a greater spring. The slash also serves as a kind of baker's signature, especially when, in Robertson's words, it "opens elegantly."

One mark of a good loaf is a p.r.o.nounced "ear"-a crisp edge of crust thrust up, like a tectonic plate, by the bread's sudden expansion in the oven. Two problems here: Since my Dutch oven is much deeper than the ball of dough is tall, it was tricky to reach in there for the scoring without burning the meat of my hand on its 500-degree edge. Second, I failed to be as "decisive" in my scoring as Robertson had advised. I'm sorry, but after all the time spent coddling this gorgeous round of dough, slas.h.i.+ng it with a razor blade was just hard to do. It seemed reckless, violent even. I hesitated-fatally, as it turned out: Some dough snagged on the corner of the blade, and tore as I tried to draw my line. The result was a sloppy signature.