• Yield: Makes about 1 3/4 cups

Traditional fermented sodas need a starter -- beneficial bacteria and wild yeasts that help to convert sugars into acids and, more importantly, generate the carbon dioxide that gives these sodas their natural bubbles. Much like I keep a jar of sourdough starter, feeding it weekly and dipping into it as I need, I also keep a pint-sized jar of a yeasty ginger brew fermenting on my kitchen counter for our homemade sodas and herbal tonics. The combination of ginger and sugar provides a happy home to wild strains of yeasts and lactobacillus bacteria that begin to proliferate, bubble, and foam within a few days' time. I add the brew to sweetened herbal infusions, and, about 3 days later, the wild yeasts and native bacteria in the starter will have eaten most of the sugar in the herbal infusion, leaving it less sweet and somewhat tart, with a delightful fizz. 

  • Fresh ginger

  • Unrefined cane sugar

  • Water, preferably filtered

Break off a knob of ginger that's about 2 inches long and 1/2 inch thick. Peel away its skin and grate it until you have 2 heaping tablespoons. Place the grated ginger in a pint‑size jar and whisk in 2 tablespoons of unrefined cane sugar and 2 tablespoons of water. Cover the jar with a small square of butter muslin or cheesecloth and secure it tightly to the jar's rim with a length of kitchen twine or a large rubber band. Place the covered jar in a warm spot in your kitchen, a bit out of the way so it won't disturb your normal cooking routine, to ferment.

Every day for at least 5 days, mix an additional 2 tablespoons of grated ginger, 2 tablespoons of sugar, and 2 tablespoons of filtered water into your jar. The ginger will begin to foam and bubble at its top and will develop the yeasty aroma of beer.

After 5 days, it should be ready to use as a starter culture for homemade sodas and probiotic herbal tonics; however, if you see no signs of fermentation -- no bubbles, no foam, or no yeasty and faintly sour aroma -- continue feeding it until it develops these characteristics.

To store the wild yeast and ginger starter for long-term use, tightly cover the jar and transfer it to the refrigerator. Take care to feed the starter weekly by first removing it from the refrigerator, then mixing in 2 tablespoons of grated ginger, 2 tablespoons of unrefined sugar, and 2 tablespoons of water.

Let it sit on the counter for 1 to 2 hours after a feeding, then return it to the refrigerator. When using the wild yeast and ginger starter to prepare homemade sodas and probiotic tonics, remember to replace the amount of starter you remove with an equal amount of fresh ginger and sugar slurry; that is, if you remove 1/4 cup starter to prepare a homemade soda or tonic, whisk together enough grated ginger, sugar, and water to replace the amount you removed. 

Well kept and routinely fed, your ginger bug will last indefinitely.

[More: Jennifer McGruther's interview about ginger bug]

Reprinted with permission from The Nourished Kitchen written and photographed by Jennifer McGruther (Ten Speed Press, © 2014).