Wild Fermentation (Chelsea Green Publishing, 2003) by Sandor Ellix Katz explores the variety of dishes that can be made via fermentation. This excerpt comes from Chapter 8, “Bread (and Pancakes).”
You can purchase this book from the MOTHER EARTH NEWS store: Wild Fermentation.
Basic Sourdough Starter:
Starting a sourdough is as easy as mixing flour and water in a bowl and leaving it on the kitchen counter for a few days, stirring periodically. The yeast is there, along with lactic acid bacteria and many others, and they will all reveal themselves. The work is in building the vigor of the starter, then maintaining it and keeping it alive and fresh. A sourdough starter requires regular feeding and attention, not unlike a small pet.
Time frame: About 1 week
• 4 cups/640 grams flour (any kind)
1. Combine. In a small jar or bowl, mix 1/4 cup/40 grams of the flour and 1/4 cup/60 milliliters dechlorinated room temperature water. The reason to start with such a small amount is that with each subsequent feeding you will add three times as much fresh flour and water, so it will get big fast! I have generally used rye flour because it gets bubbly faster, and I love rye bread, but the flour of any grain will do.
2. Stir frequently. This speeds the process by distributing microbial activity and also by aerating, which stimulates rapid yeast growth. Stirring also protects the developing ferment by keeping the surface fresh. All you need to do is keep stirring a couple of times a day. If you are impatient, drop a few pieces of whole small fruits into it. Often on grapes and berries you can actually see the chalky film of yeast (“the bloom”) that is drawn to their sweetness. These and other fruits with edible skins (not bananas or citrus) are great for getting sourdoughs bubbling. If you do this, use local or organic fruit; who knows what antimicrobial compounds could lurk on the skins of the fruits of chemical agriculture?
3. Cover with a cloth that will keep out flies but allow for free circulation of air.
4. Ferment. A warm place (70–80 degrees F/21–27 degrees C) with good air circulation is ideal, but work with what you have. Stir vigorously at least a couple of times each day. After a few days you will notice tiny bubbles releasing at the surface of the batter. Note that the action of stirring the batter may create some bubbles. Do not confuse these with the bubbles the batter produces when you are not actively introducing air into the mixture. The number of days it will take for yeast to become active in your batter will depend upon temperature, your flour, your water, and environmental factors. If you do not find bubbles forming after 3 or 4 days, try to find a warmer spot.
5. Feed the starter. Once bubbling is evident, the starter is alive and needs to be fed. In a larger bowl, mix together 3/4 cup/120 grams flour and 3/4 cup/185 milliliters water. Add the bubbly starter (with any fruit removed) to that and stir vigorously. It is important to feed the developing starter a high proportion of fresh flour and water rather than feeding it a small amount of fresh flour, because this dilutes and decreases the acidity, which makes for a more hospitable environment for yeast activity to build vigor.
6. Stir a couple of times a day.
7. Observe that the starter will get bubbly, and then the vigor will recede.
8. Feed it again. When the bubbling slows, feed it a high proportion of fresh flour again. In a larger bowl mix together 3 cups/480 grams flour and 3 cups/750 milliliters water. Add the bubbly starter to that and stir vigorously. Once this gets bubbly, your starter is ready to use.
Always save starter. Use sourdough starter as directed in the recipes that follow, or in other ways. Each time you use it, be sure to save some of the starter. All you need to save is a little. I keep mine in a jar (1-pint/125-milliliter size) and replenish the starter with what remains on the edges of the jar. To replenish the starter, I add about 3/4 cup/120 grams flour and 3/4 cup/185 milliliters dechlorinated water, stir well, and leave it in a warm place to bubble.
Maintaining Your Starter
Generally, the more frequently a sourdough is used and fed, the more vigorous it will be. If you use the starter only sporadically, refrigerate it a day after feeding to slow microbial metabolism. A day or two before you plan to use it, move the starter from the fridge to a warm location and feed it a larger volume of flour and water, to get it active again. If you neglect your sourdough, it may get very acidic, then eventually become putrid. Even if they become putrid, starters can generally be revived. Pour off any liquid that has risen to the top and discard the entire top half of the sourdough starter. Take a teaspoonful from the bottom of the jar and place it in a fresh jar. Add 1 cup/160 grams flour and 1 cup/250 milliliters water to this and stir well. This high-proportion feeding will dilute the putrid flavor and reawaken the dormant yeasts and lactic acid bacteria. Pamper it: Stir daily, keep it warm, and feed it every day or two. Sourdoughs are very resilient and can come back from even extreme neglect.