Sourdough Starter—What Is It?

Wild Yeast is found on the skins of fruits, vegetables, and whole grains. A quick way to isolate and capture the wild yeast is to put one of these ingredients in a container of water. For example, immerse a cup of red grapes in water for a few days. When the fruit is strained and discarded, you are left with water teeming with thousands of wild yeast cells.

Like most living organisms, the yeast cells need a temperate environment, water, oxygen, and a reliable food source to establish a colony. On a daily basis, you add fresh flour and water to the strained yeast water to nourish it.