Cooked: A Natural History of Transformation (56 page)

Alcohol is a powerful and versatile drug,
and for most of human history was the most important drug in the pharmacopeia—a panacea,
literally. It reduces stress. It also muffles pain, and for most of history served as
humankind’s principal analgesic and anesthetic. (Opium probably wasn’t
cultivated until 3400 B.C.) Also, many of the plant drugs, like opium, require alcohol
as a solvent to unlock their powerful chemistries and make them available to us. In
fact, it was once common practice to add various psychoactive plants (including opium
and wormwood) to beer and wine; the addition of hops flowers to beer is all that remains
of that venerable tradition.
^*

We humans owe a large debt to
S.
cerevisiae
. Were it a creature that people could see, they might well decide
this yeast has a stronger
claim to the title of man’s best
friend than the dog. Some evolutionary biologists contend that it was the world’s
very first domesticated species. Using DNA analysis, they’ve constructed an
evolutionary tree for
S. cerevisiae
demonstrating that, more than ten thousand
years ago, it diverged from a few, and possibly just one, wild ancestor into several
distinct strains under the pressure of human selection. When humans began making mead
and wine, brewing beer and sake, and baking bread, the yeast evolved and diversified to
take maximum advantage of the rich new opportunities, or niches, humans presented
it—whether a mash of grain, or diluted honey, or pressed grapes. Several thousand years
later, the various strains of
S. cerevisiae
exhibit substantially different
qualities, levels of alcohol production (and tolerance), and flavors. The process of
“artificial selection” that shaped these yeasts is much like the one that
transformed the wild wolf into a variety of different dogs, except that in the case of
S. cerevisiae
, the selection came earlier and was entirely unconscious.

In some cases,
S. cerevisiae
appears to have hybridized with other yeast species to acquire the genes it needed to
make the most of a human fermentation opportunity. Consider lager, the class of light,
effervescent beers made by fermenting a mash of grain under cold conditions. Most
strains of
S.
cerevisiae
go dormant at temperatures below 55°F. But when people in Bavaria
began trying to ferment beers in caves during the winter, a novel strain of yeast that
could thrive under those conditions soon appeared. (We now know it as
Saccharomyces
pastorianus.
) New tools of genetic analysis indicate that this hearty lager
strain contains genes from a distantly related species of
Saccharomyces
, called
Saccharomyces eubayanus
, that has been traced to Patagonia, where it is
found on the bark of certain trees.
^*
Researchers
hypothesize that, shortly after Columbus’s voyages, this cold-tolerant yeast
found its way to Europe, perhaps in a shipment of lumber, or in a barrel that was then
used to brew beer. So it appears that lager, like the tomato and the potato and the
chili pepper, is yet another gift from the New World to the Old, tendered as part of the
Columbian Exchange.

S. cerevisiae
has demonstrated
remarkable ingenuity in exploiting the human desire for alcohol, particularly in finding
ways to transport itself from one batch of the stuff to another. Some strains get
themselves passed on by colonizing the vessels in which alcohol is fermented, or the
wooden tools used to stir the pot. “Brewing sticks” are prized possessions
in parts of Africa, believed to inaugurate the miracle of fermentation when used to stir
a mash—and so they do, much like Sister Noëlla’s wooden paddle. Other yeasts, like
the ones that give us ale, evolved the trick of floating to the top of a fermented
liquid, where they are much more likely to hitch a ride to the next sugary feast.
That’s because brewers typically scoop yeasts from the top of one batch to start
the next. The most successful yeasts were the ones that learned to clump together and
then float to the surface by attaching themselves to the rising bubbles of carbon
dioxide—a conveyance that they of course created.

But surely the greatest evolutionary trick
of all came when
S. cerevisiae
first figured out—unconsciously, of course—that
the very same molecule it had originally devised to poison its enemies was also capable
of making it a coevolutionary partner as powerful, ingenious, and well traveled as
Homo sapiens
. The human desire for alcohol has been a tremendous boon to
Saccharomyces cerevisiae
. To supply it with endless rivers of liquid
substrate to ferment, we have reconfigured vast swaths of the earth’s surface,
planting tens of millions of acres of grain and fruit, in the process creating a
paradise of fermentable sugars to sustain this supremely enterprising family of
fungi.

In the 1980s, an anthropologist at the
University of Pennsylvania by the name of Solomon Katz put forth the arresting theory
that it was the human desire for a steady supply of alcohol, not food, that drove the
shift from hunting and gathering to agriculture and settlement. Beer, in other words,
came before bread, and as soon as people got a taste of it, Katz reasoned, they would
have wanted more than could be produced by gathering seeds or fruits or honey. The
hypothesis is difficult to prove, but plausible. It would certainly help explain why
early humans would ever have traded the comparatively easy lifestyle of the
hunter-gatherer, who typically devotes far less time and effort to obtaining food than
the farmer, for the toil and inferior diet of the early agriculturist. A reliable supply
of food is much easier to secure in the wild than fermentable sugars, which tend to be
rare and hard to find. There is only so much honey in the forest, and what there is, is
well defended by bees. The only way to guarantee an adequate year-round supply of
fermentable sugars would be to take up agriculture. Analysis of yeast DNA indicates that
the domesticated strains go back at least as far as the domestication of grain, and
perhaps further.

One suggestive new piece of evidence for the
beer-before-bread hypothesis comes from the analysis of the carbon isotopes in the
skeletons of ancient people in South America. Though corn had been domesticated by 6000
B.C., bones from the period immediately following give no evidence of corn proteins in
the diet. This suggests that people were consuming the corn they were growing not as
solid food but as an alcoholic beverage, since alcohol made from corn would contain
little protein, hence leave little trace of it in bone. So it appears likely that Native
Americans were drinking corn before they began eating it.

Yet it isn’t at all self-evident how
one would go about turning a pile of corn, or any other grain, into alcohol. To learn
how to make
beer is to marvel at the ingenuity of the people who first
figured it out. The process is much more complicated, and involves many more steps, than
making mead, or for that matter wine. Charlie Bamforth, the Anheuser-Busch Endowed
Professor of Brewing Science at the University of California, Davis, likes to begin his
lectures with a little joke. “Do you know why Jesus performed the miracle of
turning water into wine? Because it’s so much easier than making beer!”

Corn kernels, like the seeds of many other
grasses, contain plenty of sugars, but they are not in a form that
S.
cerevisiae
can make use of. The sugars are tightly bound together in long
carbohydrate chains that the tiny yeasts can’t break apart. This well serves the
seed, which has an interest in keeping its precious cargo of sugars intact and safe from
microbial attack until the germinating plant needs them. But certain enzymes can cleave
those carbohydrate chains into simple, fermentable sugars, and, as the earliest beer
makers discovered, one of those enzymes—ptyalin—is present in human saliva. The first
beers were made by chewing kernels of corn and other seeds, mixing them with saliva, and
then spitting the resulting slurry into a vessel, where it would readily begin to
ferment. (The desire for an alcoholic drink must have been keen indeed.) To this day,
there are indigenous groups in South America that rely on the chewing method to make an
alcoholic beverage called chicha—a corn-and-saliva beer.

Surely there had to be a better way, and
eventually it was discovered. Instead of chewing the grain to release its sugars, our
ancestors figured out that if they briefly germinated the seeds before mashing them in
water, the mash would become sweet enough to ferment. Malting, as this process is
called, is essentially a way to trick the seed into releasing its own diastatic enzymes,
to break down its carbohydrates into sugars to nourish the (supposed) new plant. In beer
making, seeds of grain, most often barley (which contain high levels of both fermentable
sugars and enzymes), are moistened and allowed to
germinate for a few
days before being dried in a kiln. The heat kills the embryonic barley plant, but not
before the enzymes have been released and begun breaking down the seed’s stash of
carbohydrates.

In time, maltsters, as they were called,
figured out that, by adjusting the cooking time and temperature in the kiln, they could
take advantage of the browning reactions—Maillard and caramelization—to manipulate the
flavor, aroma, and color of their beers. At the Oak Barrel, the long central aisle is
lined with wooden bins with glass windows displaying more than a dozen different
malts—cooked seeds of barley in colors ranging from pale gold to ebony, and giving off
aromas as various and wonderful as raisin, coffee, chocolate, fresh bread, dark toast,
biscuit, toffee, smoked peat, and caramel. It’s a remarkably rich palette of
flavors and aromas—sense metaphors, really—to tease out of a simple, and all but
tasteless, seed of grass simply by cooking it.

But as I was about to discover, the choice of
malt is only one of the daunting number of variables in brewing beer; there is also the
type of hops that, depending on the strain, can impart completely different flavors
(spicy, fruity, herbal, grassy, earthy, floral, citrus, or evergreen). Then there is the
yeast, which helps determine exactly how sweet, bitter, fruity, or spicy your beer will
be. Finally, there is the fermentation temperature and time, which can yield a crisp,
light, bubbly lager at 45°F (in forty-five days) or a softer, richer ale at room
temperature (in fourteen days). The first time I set foot in the Oak Barrel, I was so
daunted by the sheer number of decisions that went into brewing a beer—a beer!—that I
turned around and left without buying a thing.

The second time, I bought one of the Oak
Barrel’s beer-brewing
kits and, with the help of Isaac, brewed
my first batch of beer. We opted for an English Pale Ale. The kit makes all the hard
decisions, in effect, and contains everything you need: the malt (an English type called
Crystal in our case), the hops (Magnum, Sterling, and Cascade), some flavoring grains
(malted Carawheat), and a bag of priming sugars we would need when it came time to
bottle. But when you buy a kit, the malted grain comes in the form of a liquid extract
(made by grinding the malted barley, soaking it in hot water, and then evaporating the
resulting “wort” down to a sweet, black syrup), and the hops come in little
pale-green pellets. As Kel packed up our purchases, I wondered, were we somehow cheating
by using a kit?

Brewing beer, even from a kit, turned out to
be an enjoyable way for Isaac and me to spend a Saturday afternoon together. Being an
eighteen-year-old, Isaac had an acute interest in beer, and he approached the making of
it in a spirit of high seriousness. It probably didn’t hurt that fermenting
alcohol was a grown-up enterprise that I knew no more about than he did, and which
carried a faint whiff of outlawry. His mother wasn’t entirely sure about the
advisability of this particular father-son project, which also counted in its favor. The
work itself called for four hands and at least one strong back (for lifting and pouring
five-gallon kettles and heavy glass carboys), all of which combined to make for an
agreeable collaboration of equals. Working side by side is always a good recipe for easy
conversation with a teenager, and I learned more than I probably wanted to about various
other beer exploits, involving consumption rather than production.

Following the Oak Barrel recipe, we began by
boiling tap water in a five-gallon pot, poured in the malt extract, and then added the
Magnum hops, a type used to bitter the beer. With a rolling pin, Isaac cracked the
grains, which came in a muslin bag, and then suspended
the bag in the
rapidly boiling wort like a big tea bag. At the thirty-minute mark, we added the
Sterling hops. After an hour, we took the kettle off the heat and added yet a third type
of hops, Cascade, which is meant to contribute aroma. We cooled the liquid to room
temperature, poured it through a strainer into a five-gallon glass carboy, and then
“pitched” the yeast into it. The whole operation, which took slightly more
than two hours from start to finish, felt a little like working from a cake mix,
frankly. It might produce a decent cake, but would you be justified in calling the final
product, however tasty, “homemade”?