WEEK
15
We Make Biomass

While the dough is rising, life goes on.
— Peter Reinhart, Brother Juniper’s Bread Book, 1991

“We make biomass,” Gary Edwards, president of the American Yeast Division of Lallemand, declared, as if no other explanation were required.

Within the hour I would learn that this was a little like Noah saying, “I’m building a rowboat,” but for the moment, as I sipped coffee in a comfortable conference room a few blocks from downtown Montreal, I was oblivious to the hundreds of tons of biomass feeding, growing, and doubling in quantity every four hours under my seat. If I’d known, I might have been a bit nervous.

Lallemand, though not a household name like Red Star or Fleischmann’s, is one of the major yeast producers in North America, supplying the yeast for Wonder bread and other large commercial bakeries as well as countless corner bakeries and wineries and even the home baking enthusiast (a real enthusiast—their smallest package of dried yeast is a one-pound bag). My microscopic exploration of yeast had left me wanting to know more about this mysterious substance, so I’d come to Lallemand to see firsthand how yeast is made. Or rather, since we technically don’t make living things, farmed.

Hairnet and hard hat in place, I was distinctly underwhelmed by my first sight of a yeast production factory. Two young lab technicians in white coats were bent over a lab bench, scraping a trace of yeast from a “slant”—a small tube in which the pure strain of yeast is stored in agar—onto a wire loop to be transferred to a garden-variety test tube. A few previously inoculated test tubes sat nearby in a rack. On another table sat six five-gallon jugs with hoses coming out the top, filled with a wicked-looking brew that resembled Guinness stout. The place seemed eerily familiar. I’d been here before, but when? Slowly it dawned on me. This was a small (very small) version of my high school chemistry lab. “This is your research laboratory?” I asked Gary.

“Oh, no!” he said, nearly taking offense. “This is the beginning of a production batch.”

This little room? He pointed to the row of test tubes. “This is the first stage. Each batch begins in a test tube with a sterile growth medium we inoculate from the slants. That’s what we’re doing right now.” None of the techs took their eyes off their work as we talked about them. “Now, over there”—Gary gestured toward a table of conical flasks directly behind me—“is the next stage.” As I swung around, my arm nearly struck a flask that was sitting out in the open. “After about twenty-four hours in the test tube, the yeast is transferred to Erlenmeyer flasks.”

I took a step back so as to not destroy an entire production cycle of yeast with my clumsiness. And just how much yeast would that have been?

“In six days each of these test tubes will become six hundred thousand pounds of wet yeast, if everything goes according to plan.” Disbelieving, I made him repeat the figure. “Six hundred thousand pounds, if all goes well,” he repeated. “You can also end up with six hundred thousand pounds of crap.”

And what can go wrong? Aside from an errant visitor knocking over a flask, there’s M. Bigo’s problem (namely, bacterial infection), improper growth of the yeast, or infection by the wild yeast that is always present in the air. But barring problems, less than a week from now, the scrapings of a few yeast cells from a slant into those six test tubes would multiply into, altogether, a mind-boggling 3.6 million pounds of yeast!

We make biomass.

Looking into the Erlenmeyer flask, that familiar conical flask with the narrow cylindrical throat,* commercial yeast seemed an impossibly long way off. But the distance would be covered quickly. After spending a day in the flask, the yeast is transferred into a five-gallon sterile glass bottle called a carboy. The glass car-boys resembled nothing so much as a science fair exhibit, with hoses coming out the top, air bubbling through the thick brown molasses, and—get this—aluminum foil topping the whole assembly. The only thing missing was the poster listing your hypothesis and homeroom.

“This is the first time that oxygen is introduced,” Gary said, explaining the hoses. I was surprised to hear the reference to oxygen. Everything I’d read about yeast referred to it as anaerobic, living only in the absence of oxygen. “Yeast is an interesting critter,” he explained. “It can live with or without air. And it’s brilliant in its simplicity. When air and sugar are present, the yeast says, ‘Times are good. I’ve got air to breath, sugar to eat; I’m going to make some more yeast cells!’ This tendency of yeast to grow and reproduce when large amounts of oxygen is present is called the Pasteur effect.

“But when it has sugar but no air,” Gary continued, “the yeast says, ‘I’ve got to convert this sugar into something that will help preserve me. If I don’t, the bacteria are going to come in and crowd me out.’” So it switches over to anaerobic fermentation, producing carbon dioxide and alcohol. This is the fermentation we are interested in, the process that bakers and brewers utilize to make the bread rise and the beer brew. Anaerobic fermentation has another advantage for the yeast: if times get hard and all the sugar is used up, the yeast can dine on the very alcohol it produced. Most bacteria cannot, so this serves as yet another defense mechanism against bacteria, in addition to being a third way that this simple, one-celled organism can feed. Yeast, by the way, can only tolerate alcohol up to a point—about 14 or 15 percent. This is why wine always has an alcohol content of roughly 11 to 13 percent. You can’t make yeast produce more alcohol than that, or the yeast itself will die.

The fact that yeast has these distinct aerobic and anaerobic lifestyles explained why I hadn’t seen much budding going on in my microscopic experiment. If I was going to see budding, I’d have to force in air with the sugar, as Lallemand was doing, to get the yeast to metabolize aerobically and reproduce. But even then I wouldn’t have seen all that much in a few minutes under the microscope. Gary told me that yeast reproduces only about every four hours. Leeuwenhoek and I were lucky to have seen any budding at all.* As for the bubbles Leeuwenhoek had seen, and the doubling of the volume of dough in a few hours that all bakers witness? Both are due primarily to the anaerobic respiration of the original yeast, not an increase in the colony size. In other words, bubbles, not budding. We moved onto the production floor to see the fermenters. This was the part I’d been looking forward to. I expected we’d step onto a long stretch of white tile floor so clean you could eat off it, with gleaming stainless steel vats lined up on either side, accompanied by the warm hum of bubbling yeast and perhaps a slight bakery smell. The reality was more like stepping onto the deck of an aircraft carrier while jets were landing and taking off. The noise was deafening, the reek of molasses overpowering. And eating off the floor? Not recommended. True, I was in a food factory, but the entire milieu suggested more “factory” than “food.”

“This is the next stage,” Gary yelled over the din as we stood in front of the first fermenter, a stainless steel tank not much larger than a bathtub, into which a technician had emptied the contents of two carboys a few hours earlier. I could barely make out his words as he yelled over the roar of the huge blowers that force air into the fermenters. Because yeast needs oxygen, and lots of it, in order to be induced to undergo reproduction, huge quantities of air were being drawn in from the skies over Montreal. After being passed through a HEPA filter to remove, among other things, any wild yeast that might be present in it, the air is bubbled up through the yeast and molasses broth in very fine bubbles. This takes a lot of pressure—and electricity—as the volume of air in the tanks is replaced every minute.

I had envisioned yeast production as a low-energy, environmentally friendly process, but I’d had it completely wrong. It takes a tremendous amount of electricity to make lots of yeast in this short a time: power to blow in the air, heat exchangers to draw off the excess heat generated by the yeast. I mentioned to Gary that it was as energy-intensive as any other factory farm.

“We are farmers,” he said. “With a much shorter growing season.”

Gary took me through the next several steps of making yeast, the first- through fifth-stage fermenters, full of bubbling molasses, until we finally reached a huge rotating drum. Something that was now recognizable as yeast was coming off it as it turned. I caught some in my hand. It had a consistency remarkably similar to Play-Doh. This was fresh crumbled yeast, about 30 percent solid, ready to be packaged into fifty-pound poly-lined bags and sent out on refrigerated trucks to commercial bakeries. Or pressed into five-pound blocks of compressed yeast. Or dried further into instant dry yeast, the kind of yeast that home bakers use. This is what I wanted to see.

Next we came to an extruder, essentially a giant cookie press fitted with an extrusion die, which is a steel plate with hundreds of tiny holes. I held my hand under it as little squiggles of yeast—drier than what had come off the drum but still pliable—collected in my palm. The yeast had a surprisingly satisfying feel in my hand, not wet, but not dry, either, and when I brushed it off my hands, it left behind a pleasant dryness and yeasty aroma, a persisting reminder that I would savor for hours afterward, like the faint, lingering memory of a woman’s perfume.

The final drying takes place in a large cylindrical tank in which the yeast flies around in a vortex of warm air for about twenty minutes, until the solid content is up to 96 percent, putting the yeast into a dormant stage, ready to be siphoned off into vacuum-sealed bags for shipping.

The yeast Lallemand was making was instant dry yeast, different from the active dry yeast that was developed during World War II (so that, according to Fleischmann’s, our boys could have fresh bread abroad). Active dry yeast quickly replaced fresh yeast in American home kitchens, where it reigned for some fifty years before instant yeast (variously labeled instant, fast-acting, breadmachine, or RapidRise) joined it on the shelves. Active and instant dried yeast look similar, but active dry has to be rehydrated before use to bring the yeast out of dormancy and make the cell walls permeable again. This is why many cookbooks call for “proofing” the yeast (not to be confused with proofing the dough, another name for the second rise), mixing it with a little warm water and a pinch of sugar before adding it to the dry ingredients.*

The instant dried yeast I was holding was developed in the 1980s from a different strain than active dry (but the same species—all commercial yeast sold for fermentation belongs to the species Saccharomyces cerevisiae) and, dried at a lower temperature in the vortex, doesn’t have to be rehydrated or proofed (in fact, Gary told me it’s better not to rehydrate), doesn’t have to be refrigerated, and has a room-temperature shelf life in its vacuum-packed bag of two years. Once opened, it is susceptible to oxidation and needs to be stored in an airtight container if not used within a few weeks.

I was leaving the factory floor with my one-pound bag of instant yeast, which would last me an entire year (and then some), when I noticed a wall with sacks of yeast stacked to the ceiling.

“That’s for corn,” Gary explained.

“Corn bread?” I didn’t understand.

“Ethanol. It’s becoming a big market.”

Of course—how do you turn corn into alcohol? You ferment it. I would find myself thinking of that wall of yeast six months later, as corn and wheat prices soared, sowing hunger and threatening civil unrest in Africa and the Middle East, but for now, it was just a curiosity. I was getting ready to leave for the long drive back home when I remembered why I was here: my lousy bread.

I described the problem I was having with my dense crumb and lack of holes, hoping for the little nugget, the missing link, that would give me the perfect loaf. Gary was impressed that, as a home baker, I was “running sponge and dough,” as he called my poolish. He confirmed my instinct that the long fermentation in the sponge produces some complex and sophisticated flavors that you don’t find in a straight dough loaf. And as a bonus, thanks to the compounds formed during a preferment, the resulting bread stales less quickly. “The other thing that does for you is it’s actually giving you a different crumb structure, a different texture and feel in your mouth.”

So the yeast, in addition to supplying the gas for rising and the compounds for flavor, has an effect on the crumb! This was something I’d not heard before; I’d thought the crumb was determined solely by the other factors I’d been playing with: the gluten and protein levels of the flour, the kneading, resting, and rising processes. There seemed to be no end to yeast’s influence on bread, and more and more, it was becoming apparent that making the dough rise was the least of its roles.

I left with a new respect for yeast and felt I was on the right track with sponge and dough methods, but how to get rid of that dense crumb? How to make some air holes?

“You need to ask a baker,” Gary suggested. “An authority.”