The other day I was at the library and I stumbled across an excerpt from the diary of Mary Clayton*, a Mormon pioneer settler. Here, she explains her method for starting a sourdough culture:
“Boil one good-sized potato until mealy. Mash about ¼ of the potato real fine and add to approximately two teacups of the water in which potato was cooked. Add one teaspoon sugar to lukewarm potato water. Add enough flour [about two cups] to make a sponge and put it in a warm place and let it work. Let it stand for 5 days. For pancakes pour off what you would like for breakfast and leave a starter of the sponge. Store starter in a cool place.”
In this method, Clayton relies on airborn yeasts and bacteria to settle on a nutrient-rich environment to begin working. The potato water attracts yeast in the same way as a ripe grape or apple. On the grape we see wild yeast as a dusty film attracted to the sugars of the grape. In Clayton's petri dish, the yeasts settle on the potato water and begin eating the starches. Once the culture has begun to work, it creates a colony we can use for leavening bread, biscuits and cakes. Give it a try at home, and see what happens!
*Mary Clayton's diary excerpt was found in Kitchen Treasures, 1830-1980: 150 Years of Mormon Culture. Produced by the Roy 13th Ward, found in the Special Collections of Weber State University. If anyone knows the whereabouts of the original diary, I'd love to take a peek at it.