|
|
My mother wanted her sons to be strong and self-reliant. That was why she started us early doing household chores like vacuuming, dusting, cleaning bathrooms, doing laundry, and washing dishes—or in our time, loading the dishwasher. She also taught us the rudiments of cooking: how to measure and pour, boil an egg, and fry bacon without splattering ourselves or setting the kitchen on fire, all so that we could at least survive without the contemporary equivalent of McDonald’s or Taco Bell.
Because her own mother had been an excellent baker, and she was a fair hand at it herself, she taught me how to make bread and scones. Sure, you can buy these things in the store readymade, but she believed in knowing how to rustle up a meal from the basics you have on hand. And with kneading dough and watching it rise, I discovered the miracle of yeast.
Yeast—Saccharomyces cerevisiae, for the most common species, used in baking and brewing—is one of the most complex of all single-celled microorganisms. Yeast is actually part of the fungus kingdom. Unlike bacteria, yeast cells hold their genetic complement inside a nucleus, as do most plants and animals, rather than letting it float freely inside the cell body where it can transcribe and translate willy-nilly. Thus yeasts are eukaryotes, just as we are, because secluding the genome inside a nucleus is the first step toward developing a multicellular organism, capable of differentiated and specialized tissue types. In fact, yeasts are believed to have evolved from multicellular organisms. But now yeasts reproduce asexually, by budding new cells off existing parent cells.
The yeast genome (see the Saccharomyces Genome Database) has 6,275 genes—of which about 5,800 are thought to be functional—in more than 12 million base pairs. These genes are packed on 16 chromosomes, which doesn’t compare badly with the human’s three billion base pairs on 23 chromosomes. In fact, about a third of yeast genes are shared with the human genome. For comparison, most bacteria have just one or two chromosomes, looped in a circular shape called a plasmid for easy transcription, and containing about 1,500 genes.
Because of the antiquity of bread and beer making, anthropologists believe yeast was humankind’s first domesticated species, predating wheat or rice, cows or sheep, and perhaps even the dog. It certainly came into our lives after the hunter-gatherer stage, when we settled down in one place long enough to brew up a pot of beer. It also must have come sometime after the discovery and taming of fire, because you can’t bake bread on a flat, sun-heated rock.
Yeast is not hard to get. In the second novel of my time-travel series, The House at the Crossroads, a young woman from the far future learns the basic skills of a medieval housewife:
Dame Agnes also taught her how to isolate and nurture the yeast cultures she would need—both for fermenting and to make her dough rise—by putting fruit skins and vegetable peels in a jar with water and leaving them in a warm, dark place overnight.
The basic function of yeast—that is, for human purposes—is to eat up sugars and starches, known as carbohydrates, and excrete ethyl alcohol and carbon dioxide. For making beer and wine, we capture the alcohol and let the carbon dioxide waft away. For making bread rise, we let the carbon dioxide pump up the dough—which is why bread has tiny holes throughout the loaf, while a cracker does not—and let the alcohol evaporate in the baking.
Anyone who has seen a lump of dough, kept for an hour under a tea towel on the back of the stove, rise into a glorious dome twice the size of the original lump will know what I mean by a miracle.1 It’s a form of magic to see this grainy, yellowish powder—store-bought yeast—which becomes a gray muck when mixed with warm water, turn out anything as sweet and pleasant smelling as good bread. And yeah, that smell is the alcohol. The same miracle occurs when a bushel of crushed up grapes, or spouted and dried barley, or even mashed up potatoes plus water turns into wine, beer, or vodka.
Christ’s miracle of turning water into wine at the wedding in Cana just speeded up the process. He might as easily, although less dramatically, have made the balls of dough for the feast’s bread pop up before being put into the oven. These are miracles of time, not necessarily of substance, nor of reversing the normal course of events—such as the raising of Lazarus.
Cooking has other small miracles, too. There is the moment when you are mixing the dough in the first place, and the flour, water, and other ingredients go from a soggy mass to a plastic lump. Or when you’re making gravy, and the isolated streams of beef drippings, water or wine, and those little clumps of flour come together into a smooth paste and then a glistening liquid. Or the moment when an egg beaten with milk and seasonings and poured into a hot pan simmering with olive oil or melted butter turns from a runny yellow liquid into light and fluffy solids—or into a foamy custard, if you have more patience and you’re trying to make an omelet.
A young man who thinks food comes from the kitchen, or prefers to spend his money at McDonald’s or Taco Bell, never gets to see these things. And that’s a pity.
1. For certain applications, such as biscuits and scones, you can also use baking powder. This is a mixture of the alkaline sodium bicarbonate and a weak acid like potassium bitartrate, or cream of tartar. It releases carbon dioxide through an acid-base reaction once you get it wet. You can also use sodium bicarbonate to make soda bread. These chemicals are easier to handle than yeast, which can be killed with too much heat during the rising process or an unsatisfactory ingredient in the bread making—such as the time I tried to make Jim Beam bread, don’t ask. Dead yeast leaves you with a flat loaf like a paving stone.