Foraging for Wild Yeast

Enlarge Image Image Gallery The fixin's for our sourdough starter include flour, water, a handful of yeast-covered berries, and a glass container... The powdery-white leavening coats the fruit of the juniper shrub and... the Oregon grape... Gases from the fermenting ""sponge"" expand in the jar's plastic cover.

You can enjoy the zesty, robust flavor of natural sourdough breads by . . .

My first experience with wild yeast took place a few years back, while I was conducting a primitive living expedition in the rugged terrain of the Pacific Northwest. At the start of the trip—as is the usual procedure on such survival adventures—each member was given a ration of whole wheat flour sweetened with a lump or two of raw sugar . . . as "basic food" to supplement our gathered wild fare. Every evening we'd mix the flour with water, form the paste into a kind of tortilla, and then cook the dough in the hot coals of the fire.

The resulting "ash cakes" actually tasted good on the first day, and were even edible when the third evening came around. But by our eighth day in the woods, we all hungered for a taste of fresh-from-the-oven risen bread!

Little did we guess that the means of satisfying our craving was growing all around us! On one of the daily foraging hikes, a member of the group (who was a biochemist, budding botanist, and well-versed historian, to boot) picked a handful of autumn-ripe Oregon grape berries and explained that the white powder covering the fruit was actually an atmospheric fungus . . . more commonly known as yeast!

Wild yeast spores are, he went on to tell us, practically everywhere, and—if they happen to land where there's moisture, sugar, and warm temperatures—the delicate plants will begin to grow and multiply. (Given ideal conditions, yeast can increase its own volume by more than ten times, overnight!)

The airborne microflora are especially attracted to the sweet skin of berries and grapes. They first appear as a whitish powder, but when the membrane of the ripened fruit becomes injured (by pecking birds, perhaps), the yeasty critters slip in and begin to ferment the juice's sugars. (That's why a bowl of overripe fruit—when left in a warm room—will begin to give off a vinous odor.)

Obviously, the fermentation process is no secret . . . it was long ago perfected by our ancestors, and produces a number of soughtafter beverages today! But—somewhere along the line—an enterprising soul (or perhaps a tipsy Egyptian baker) realized that the same yeast that ferments drinks could, when mixed with dough, be used as a leavening agent.

And after delivering that short lecture, the foraging scientist—who was warming up to the subject—went on to tell us the story of sourdough bread.

Legends about the origin of sourdough bread have, it seems, been almost forgotten. According to the tales, the old-time Californian and Alaskan prospectors guarded their sourdough starter—or "sponge", as they called it—closer than they would a poke of gold. The perpetually fermenting yeast culture was the wellspring of every meal ... and often meant the difference between feasting on fresh bread and choking down a weevil-infested, hard-as-a-rock biscuit.