Cooked: A Natural History of Transformation

by Michael Pollan

  What had been one edible grass among many became the imperial grass, 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), triticum’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 mass 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 diminishing 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 mass 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 identity. 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 grass seeds nourishing 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) balls 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 grass 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 som
e 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 grass seed so nourishing 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 mass 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 mass 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 buttock 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 500°F 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 casserole, 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 500˚F, 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 slashing 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 pronounced “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, slashing 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.

  Having thus mangled my gorgeous dough, I had little hope for the finished bread. But when the third and biggest Moment of Truth arrived, twenty minutes after the loaf went into the oven, I was pleasantly surprised. I lifted the lid to find that the loaf had mostly self-corrected for its lopsidedness, and had sprung up—not spectacularly but respectably. Here was a round, puffy, fawn-colored pillow easily twice as large as the flop of dough I’d dropped in the pot only twenty minutes before.

  I closed the oven door gently to make sure I didn’t deflate the risen loaf while it finished baking. I needn’t have worried: By now, the starches in the dough had “gelatinized”—stiffened enough to formalize the matrix of gluten, which had itself stiffened. During the early moments of baking, the cells in that matrix had ballooned under the pressure of gases expanding in the heat. At least for the first six to eight minutes of oven time, new alveoli continue to form, since the yeasts keep working until the temperature reaches a lethal 130°F. During this period, provided there remain enough sugars to feed them, the rapid flush of heat inspires one last, climactic burst of fermentation.

  When I took the bread out of the oven twenty-five minutes later, it smelled better than it looked, but it didn’t look too bad. It had thrown no ear to speak of: My too-tentative slash had merely opened a pale scar in the crust. The crust was smooth
er and more tentatively colored than a Tartine loaf, but it was handsome even so, marred only slightly by these two curious blackened humps. A roasty aroma filled the kitchen. Still wearing oven mitts, I tapped on the bottom of the loaf and listened for the hollow, woody timbre indicating the bread was cooked through. It was. I held the loaf up to my cheek to feel its radiating warmth. The bread gave off a pleasing low static as it cooled.

  The sense of accomplishment surprised me. I hadn’t done much, after all, except mix together some flour, water, and a little sourdough starter, and then babied it for several hours. And yet—here was this substantial thing that hadn’t existed before, this fragrant risen form. I might as well have pulled a rabbit out of a hat, and indeed my family, whose expectations for this latest project of mine were modest, reacted as if I had. Something from nothing: You can see why the prescientific mind (and the skeptics in Jesus’s audience) might have been impressed. Bread science would eventually offer a material explanation for this apparent miracle, but even now that we have it, the fresh-baked loaf still feels like a creation ex nihilo, its from-mud-wrested form a refutation of cosmic entropy, its sheer plusness a tasty proof of the non-zero sum or, to put it in more homely terms, the free lunch.