WEEK
12
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 life 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.