Wild Yeast 101: Sourdough

Bread has been a core food source in many cultures for millennia, and the process of making it has deep traditional roots–leavening, or fermenting of the dough with yeast, likely began in ancient Egypt.  Some scientists believe non-leavened bread was consumed as early as 30,000 years ago, though the archaeological evidence is uncertain.

Many will agree that leavening these sumptuous loaves with wild yeast is much more an art than a science, but since the introduction of commercially produced and isolated strains of Active Dry Yeast around the turn of the century, homemade bread baking is becoming a few hours’ process rather than one of several days.  This week, I decided to embark on a wild yeast bread leavening journey to recapture this art for myself.

All I knew when I started was that yeast occurs naturally on grains and in the air (San Francisco’s air has famously delicious yeast, for example), and when left sitting out for days, the yeast ferments the dough, creating a wonderful sour flavor–no commercial yeast needed, just flour and water.  My guide for this process was King Arthur Flour’s helpful sourdough starter recipe, though I did not follow it exactly (I rarely do that, actually…).  It emphasizes exact measurements by weight while I am more of an eyeballer with my cooking, and I used tips from many different recipes.  After talking to fellow bakers and doing some googling, I’ve learned that everyone has their own method of making sourdough bread, and some families/bakeries have had the same starter for generations!  This guide details one way to make a sourdough starter that, if maintained, can last hundreds of years! Wow.


– A big bag of unbleached white flour–I used Bob’s Red Mill because it’s made here in Oregon and has a jolly bearded man on the front
– Water–preferably filtered, and definitely non-chlorinated, you don’t want to kill the yeast!
– A mixing bowl
– About five days

Start with 2 cups whole grain flour and 2 cups water.  (One source said whole grain flour is good to use for the first feeding cycle only because it helps give the yeast an initial push? It might not matter but I’ll take it.)  Mix together and cover with a dry towel–the yeast need to breathe.  Let the bowl sit in a room temperature place, at least 68 degrees F but preferably 70, for 24 hours.  My house is quite cold so I wrapped my little yeast babies in a scarf to keep them warm:


Not much may have happened after the first day, depending on the season and the vigor of your yeast, but you may see some bubbles and expansion after the first day.  I saw quite a bit; I guess my yeasts are fighters.

Now here’s the trick: after mixing out most of the bubbles, remove 1 cup of the mixture and discard it.  Then add in 1 cup of new white (unbleached) flour and about 1/2 cup of lukewarm water, and mix it into the remaining starter.  This is called feeding the starter.  Discarding is necessary because, in the words of King Arthur Flour, “unless you discard, eventually you’ll end up with The Sourdough That Ate Milwaukee – too much starter.” Also, the pH stays balanced when the volume remains the same.  And, controlling the volume “offers the yeast more food to eat each time you feed it; it’s not fighting with quite so many other little yeast cells to get enough to eat.” Cooking is so interesting.

For the next two days, feed the sourdough starter once every 24 hours, keeping tabs on its progress. You should see more bubbles each time.  After the third day, begin feeding the starter every 12 hours, or as close to 12 as your schedule allows.  Remember: art, not science.  Once the starter doubles in size and bubbles immensely in 12 hours or less, your little yeasts are all grown up and your starter is ready.  For me, that was the end of day four. After feeding it once more, it’s time to bake!

Freshly fed:


After about 10 hours:


Yay! I made my own sourdough starter with wild yeast!  I can now keep a 1/2 cup of the mixture in the fridge pretty much forever, feeding it regularly. Learn how to maintain a starter here. (Note that ‘equal parts’ is referring to weight, not volume, which would be 2:1 flour:water.)

Check back soon to see how my bread turns out! While you’re waiting, you can watch this neat History channel documentary about the history of bread, as well as browse Slow Food UO’s bountiful recipe box!

History of Bread, Food timeline, Red Star Yeast


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