That wasn’t good enough for Antoni van Leeuwenhoek, one of those wonderfully eccentric figures who thankfully pop up throughout history to enliven dull science texts. A Dutch draper from Delft (which sounds like the opening of a limerick), Leeuwenhoek was born in the same city and year as the artist Jan Vermeer. In fact, their baptisms are recorded on the same page in the Delft baptismal register, surely making it one of the most valuable register pages in the world. Leeuwenhoek became enamored—one might say obsessed—with microscopes and the invisible world after coming across a hot new best seller that was sweeping Europe in 1665, Robert Hooke’s Micrographia. Filled with spectacular copper engravings made from Hooke’s own drawings of the miniature world as seen through his microscope, the book enthralled Europe with its details of a fly’s eye, a plant cell, and, most famously, a foldout of a louse that was four times the size of the book itself. (Contemporary Playmates can only blush with envy.)
Inspired by Hooke’s best seller, Leeuwenhoek set about making his own microscopes, even grinding his own lenses, while his drapery business seemingly ran itself. But unlike Hooke’s compound microscope, with its familiar lens tube holding an eyepiece and a second lens close to the object, Leeuwenhoek’s microscope was remarkably simple: a single lens only about a half inch in diameter, held in place by two metal plates. In appearance it resembled the magnifying glass he used to examine his draper’s cloth far more than it did a microscope. The whole thing could be concealed in the palm of his hand, yet he saw objects that were hidden to every other microscope in the world. Leeuwenhoek had an extraordinary talent for grinding lenses. In fact, his pocket microscopes—he made dozens, only a handful of which survive—with a magnification of up to 266 times, are superior to most microscopes used in university classrooms today. What other instrument from the seventeenth century can you say that about?
Leeuwenhoek (he added the “van” as an affectation at the age of fifty-two) had no scientific training whatsoever, but he was blessed with boundless curiosity and started looking at everything from rainwater to mouth scrapings under his microscopes. One of his first investigations has become a ritual experienced by millions of elementary school children: bringing pond water to the classroom and examining it under a microscope. Leeuwenhoek coined the delightful term animalcules (meaning “little animals”) for the single-celled creatures—protozoa and the like—that he discovered in the water, swimming “upwards, downwards, and round about.”
He sent colorful letters in layman’s language describing his observations of these sightless, wriggling microbes, “the most wretched creatures that I have ever seen,” to the Royal Society of London for the Improvement of Natural Knowledge (more commonly called simply the Royal Society), which is like my sending doodles of my garden to Scientific American. One can imagine the initial reception his letters must have received: a Dutch cloth merchant telling the London intelligentsia that he had discovered microorganisms and bacteria under a microscope he made in his kitchen. Leeuwenhoek might have vanished into obscurity had not Hooke, after initially failing to substantiate the draper’s wild claims of microscopic life, gone back and built a better microscope, thus becoming the second man in history to view microorganisms.
Eventually, Leeuwenhoek got around to looking at a little brewer’s yeast under his microscope.* He described seeing clusters of “globules,” as he called them, and went so far as to make a wax model to play with. He squished it with his hands, tugged it, and twisted it, trying to understand the meaning and purpose behind the structure. His letter to the Royal Academy describing his findings included these sketches:
Most likely, Leeuwenhoek’s globules were yeast cells in the process of “budding.” Yeast reproduces asexually by growing a small bud that forms into a new yeast organism before breaking off, the process of cell division called mitosis.
I figured I should be able to easily observe yeast cells in the act, and I wondered if I would see anything close to what Leeuwenhoek drew three hundred years before. With the microscope set up in the kitchen, I smeared a drop of this week’s poolish onto a glass slide and called Katie into our impromptu kitchen laboratory. Silly me. All we could see were huge particles of flour obscuring the microscopic yeast. So we stirred about a teaspoon of instant yeast into warm water to which we’d added a pinch of sugar as a nutrient. Fifteen minutes later, the mixture had turned almost creamy, frothing as small bubbles rose to the surface, and we prepared a new slide. Under the microscope, the drop of water seemed to contain a host of yeast cells, many clustered together, but at this magnification it was hard to see any detail. Yet when I moved to the highest power of the microscope, the field was too dark to see anything. I moaned to Katie.
“Let me see,” she said, nudging me out of the chair to take over the microscope just as her mother had done twenty years earlier. Katie reached under the microscope stage and turned a diaphragm I hadn’t seen, letting in more light and revealing the yeast. At high power now, several of the clusters looked similar to Leeuwenhoek’s sketches, but I couldn’t see anything that I could conclusively say was budding yeast. This was confusing. We should be seeing reproducing yeast in various forms of development. I kept searching across the field of view, moving the slide up, down, left, and right, and then I saw what I was looking for: budding yeast.
There was, however, surprisingly little of this budding going on. We prepared a few more slides but still couldn’t find much evidence. This bothered me. Had I overestimated the amount of reproduction taking place? But if the yeast wasn’t reproducing all that much, then where did all the gas that makes the dough swell come from? Just that tiny bit of yeast originally added? And I had another question: Carbon dioxide is odorless, but there were some strong, pungent smells coming out of that bubbling yeast. I wondered exactly what was going on in there.
As did Leeuwenhoek. Aside from the budding, something else puzzled him: “I saw a great number of gaseous bubbles rising from a blackish particle which was a thousand times smaller than a grain of sand,” he wrote, “but in spite of all my pains I was unable to arrive at their cause.”
In fact, it would be nearly two centuries before anyone would “arrive at their cause,” and it would happen almost by accident. In 1854 a young chemist named Louis Pasteur took a position at the new Faculty of Sciences in Lille, in northern France. This industrial city, home to a number of sugar beet distilleries, had recently underwritten the school in hopes of training its young men in practical industrial applications of science. Pasteur, though, seemed ill suited for that role, needing to be reminded by his dean to make sure his “applications adapt themselves to the real needs of the country.”
Pasteur griped about this privately but descended from his ivory tower long enough to help the father of one of his students, a distiller who was having a problem. A number of M. Bigo’s sugar beet vats were sick; rather than fermenting into alcohol, they were going sour. When Pasteur examined the contents of the healthy vats under his microscope, he saw, as expected, many yeast cells. But in the sick vats, the yeast was being crowded out by something else—microorganisms far smaller than yeast cells and shaped like long rods.
Bacteria.
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Choreography
Chance favors the prepared mind.
—Louis Pasteur
Louis Pasteur claimed credit for being the first person to observe bacteria, but this life form had in fact been observed and described in some detail by that draper from Delft two hundred years earlier. Pasteur, equipped with knowledge and tools that Leeuwenhoek could only dream of, set about understanding the chemistry and biology of what was happening in both the sick and the healthy yeasty vats. One of his contemporaries, the famous German scientist Justus von Liebig, had for years loudly insisted that it was chemical decomposition of the yeast cells, not a living process, that was responsible for the bubbles in beer and dough and for the change that yeast brought to beer and wine. How could it be otherwise? Everyone knew that l
ife required oxygen and could not possibly exist in the bottom of a beer vat.
Pasteur, however, didn’t “know.” Instead, he performed experiments in the laboratory, proving beyond a doubt that the bubbles in the vats and the dough—the bubbles Leeuwenhoek had seen—were due to a living process: Yeast, in the absence of oxygen, converts sugar into alcohol and carbon dioxide. As for the bacteria, it was also feeding on the sugar but producing lactic acid, not alcohol, causing the vats to sour.
We have no record of what became of M. Bigo’s distillery business, but today, Lesaffre, the largest yeast producer in the world, has a state-of-the-art plant in Lille, where sugar beets still go to be fermented. As for Pasteur, he was off and running on a career in practical science. He would continue to study bacteria and, after proving conclusively that microorganisms were not created through spontaneous generation (a fact Leeuwenhoek had pretty much established), go on to save the French silkworm industry, return to studying yeast in a patriotic mission to make French beer the equal of German (most would say he failed), and develop vaccinations for smallpox and rabies. Not to mention that, finally, Pasteur had discovered the secret of what makes bread rise, this action called fermentation, which he defined simply as “la vie sans air”—life without air—living yeast cells feeding on sugar and producing, as waste products, carbon dioxide and alcohol. Chemically speaking,
How simple and elegant. Notice how all the numbers add up on both sides of the equation, those six carbon, twelve hydrogen, and six oxygen atoms of a molecule of sugar rearranging almost in a divine plan to form two new, quite different substances.
This formula explained more than what makes dough rise. That pungent smell I’d detected in my fermenting poolish? Alcohol. But the left side of the equation still bothered me. Sugar is obviously present in a vat of sugar beets, but where was the sugar in the dough coming from? My bread contained only flour, yeast, water, and salt.
I found the answer in “my Pyler,” as I’d started calling my two-volume reference book. Some of the starch granules in flour are inevitably damaged in the milling process. And it so happens that flour contains enzymes that, in the presence of water, convert these “broken” starch granules into the sugars glucose, fructose, and maltose. Not much of the flour is damaged (maybe 5 percent on average), but it’s enough to feed the yeast and to fuel fermentation, aided by a tiny amount of malt flour that is added at the mill to each bag.
What wonderful choreography of nature and man. Subtract any one dancer—the miller, for example, whose mill inadvertently damages the starch—and the ballet falls apart. Aesthetics aside, I felt I now had the full picture of what was happening with my bread. It wasn’t just rising; it was literally fermenting on the countertop, like wine and beer. Quite literally, in fact. A fully fermented poolish has an alcohol content of 3 percent—nearly the equivalent of a bottle of light beer.
Could understanding this process be key to baking exceptional bread? Surely fermentation must be as important to bread as it is to its alcoholic cousins, beer and wine. At dinner, eating another unsatisfactory loaf of peasant bread (made with a poolish that I’d fermented overnight, hoping to extract more flavor), I mentioned that I needed to know more about yeast.
“But why?” Katie asked. “How is this going to help you make the perfect loaf ?”
“You never know where basic science is going to lead. Look at Pasteur.” I pushed the gallon jug of milk across the table. “Read the label.”
“Pasteurized.”
After dinner, surprised at how little of the bread we’d eaten, I put the remainder of the loaf in the refrigerator, since it looked as if it was going to be around for a while.
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Note to Self
Dear Heloise,*
Recently I put the remains of a loaf of peasant bread (against my wife’s better judgment) in the refrigerator. Afterward, it seemed more stale than if I’d just left it out. What gives?
— Intrepid Baker
Dear Intrepid,
Your wife, as usual, is right. Refrigerating bread actually hastens staling. To see why this is, let’s back up to examine what happens when bread bakes. As the dough warms, starch granules absorb moisture from the gluten, swelling and giving bread its structure. This is what keeps the loaf from deflating after it comes out of the oven. After the bread cools, the action begins to reverse: water gradually moves from the starchy walls back into the gluten, leaving the crumb dry and crumbly. This process is highly temperature-dependent, occurring much faster at 34 degrees Fahrenheit than at 70 degrees, so keep bread out of the fridge! And out of plastic.
The best way to store fresh bread is on a breadboard, cut side down. A whole loaf can be stored in a paper or cloth bag, or frozen in a plastic bag and thawed in the oven or on the breadboard. And remember that stale peasant bread makes great french toast.
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14
Metric Madness
The metric system is the tool of the devil! My car gets forty rods to the hogshead, and that’s the way I like it!
— Grandpa Simpson, The Simpsons
Water: 1 lb. 9.6 oz.
Salt: 0.3 oz.
I looked from the recipe to my digital kitchen scale and back again. The scale had two modes: imperial, which displayed pounds and ounces in increments of one-eighth of an ounce; and metric, which was calibrated to the nearest gram. But 0.3 ounces salt? How many eighths was that? I started scribbling on paper . . . ¼ was 0.25 . . . too little . . . and ⅜ was . . . let’s see . . . 3 divided by 8 . . . 30 divided by 8 is 3, leaving 60 divided by 8 . . .
This was insane. What would possess jeffrey Hamelman, King Arthur Flour’s head baker and one of the most respected baking instructors in the country, who undoubtedly uses metric measurements in his bakery and his teaching, to give measurements in tenths of an ounce, in essence mixing the metric and imperial systems? In fact, what would possess him to give measurements in ounces at all? Probably his editor, who properly pointed out that he was publishing Bread: A Baker’s Book of Techniques and Recipes in the United States, not the United Kingdom.
Memo to the United States of America: CAN WE PLEASE, EVERYONE, JUST GO TO THE METRIC SYSTEM AND BE DONE WITH IT?
Weren’t we supposed to do this, like, forty years ago? I remember being prepared for this earth-shattering change when I was in high school, where the metric system was and still is used in science labs. Since virtually all Americans have attended at least some high school, we’ve all been exposed to kilograms by now, and we all know what a two-liter bottle of soda looks like, so what are we waiting for? The Metric Conversion Act of 1975 stated, “It is therefore declared that the policy of the United States shall be to coordinate and plan the increasing use of the metric system in the United States and to establish a United States Metric Board to coordinate the voluntary conversion to the metric system.” The operative word there is voluntary. Americans didn’t want to hear weather forecasts in degrees Celsius or buy gas by the liter. So we simply volunteered not to. President Ronald Reagan, who was probably convinced this was yet another Communist plot to destroy the American way of life, abolished the Metric Board in 1982, leaving the United States standing alone with the super-powers Liberia and Burma as the only nations in the world that haven’t adopted the metric system. Even Canada converted, letting pounds, ounces, and miles go the way of the cubit. Anne was in the country as an exchange student at the time (Why go to, say, Paris or London when you can be an exchange student in Saskatchewan? must have been her thinking) and tells me they did it cold turkey. One day the meteorologists started giving the temperature in both Celsius and Fahrenheit, and then one day they simply stopped giving the Fahrenheit, at which point you stopped doing conversions in your head and just started to understand what 21 degrees Celsius felt like.
Meanwhile, here, south of the border, every time I need to tighten a nut, I have to fumble through two sets of nearly identical wrenches—the ones in fractions of an inch, and the
ones in millimeters—not knowing which system the hardware was made to. Every time I want to halve or double a recipe, I struggle with fractions and conversions between pounds and ounces. Well, damn it, this week I was adapting the metric system in my own kitchen! Not only that, I was going to start measuring by weight, not volume. After watching Lindsay weigh everything that went into Bobolink’s bread, from the yeast to the firewood, I’d finally seen the light and, heeding the advice of numerous authors and bakers, purchased an inexpensive digital kitchen scale.
The “scoop and sweep” method of measuring flour is at best an estimate, affected by how tightly the flour is packed in the measuring cup and even how much it has settled in the bag. It would turn out that weighing is also easier than measuring. Rather than dipping the measuring cup repeatedly into the canister, leveling off the top with the back of a knife, and switching between different measuring cups to achieve 4⅓ cups flour, it is far quicker simply to place the mixing bowl on the scale, press the Zero (or Tare) button, and pour out flour till it reaches, say, 500 grams. This is especially true with water. Instead of waiting for the liquid to settle, then bending over and peering at the side of the measuring cup, trying to locate the meniscus—the curvature of the water surface caused by attraction of water to the container—just pour out 215 grams.
I had purchased Hamelman’s book after reading on an online bread forum, “I finally got holes!! I used jeffrey Hamelman’s technique of folding!” As for those pesky fractions of an ounce, I converted Hamelman’s peasant bread recipe to grams and was soon ready to fold some dough and make some holes. Not everyone shares my passion for these gas holes, by the way. Some prefer a more even crumb, and I’ll be the first to admit the difficulty of making a tuna fish sandwich on a slice of bread with a gas hole the size of a Buick. Still, some holes would be nice, and not just for texture; I’d read that holes play an important role in drying out the bread by giving the moisture a path out of the loaf. This was good news, for it meant that my two problems—moisture and tight crumb—were intertwined. Solving one would also fix the other.
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