The Scientific Reason San Francisco Sourdough Tastes Different

San Francisco sourdough loaves tend to have more of a notable tanginess and a pronounced flavor that brings life to the simplest of soups, sandwiches, and salads. Have a slice of San Francisco sourdough topped with butter and a sprinkle of flaky sea salt — your taste buds will thank you. All the better if you've got an espresso drink like a latte or flat white to accompany it. With so much tasty depth of flavor, it makes you wonder how San Francisco sourdough manages to have such a unique taste.

Nathan Myhrvold, sourdough connoisseur, founder of Modernist Cuisine, and co-author of "Modernist Bread at Home," offers insight into what gives these sourdough loaves such character. "Sourdough breads from San Francisco are famously tart and have crispy golden crusts," he says. "San Francisco–style sourdough bread, as well as many other sourdoughs from around the world, derives its characteristic tangy flavor from a lactic acid bacteria called L. sanfranciscensis."

The proof is in the sourdough starter (which should be fed pretty frequently, by the way). As Myhrvold explains, "Truly authentic San Francisco sourdough would be made in that city, with starter born and raised there, fed by the specific wild yeast and bacteria in its air. If a baker in San Francisco gives you some of their starter, you can make that acidic sourdough for a few days once you return home, but the starter will change as local yeasts and bacteria take over."

A sourdough starter can hugely shape the final flavor profile of sourdough bread, but that does raise the question: how exactly did San Francisco's unique sourdough tradition begin? Originally, San Francisco sourdough was not good. Scrounged together by miners during the Gold Rush of 1849, it only existed because it was easy to make from readily-available ingredients.

These miners (now dubbed 49ers) arrived with meager, basic ingredients like flour, yeast, and baking powder. When the baking powder ran out they turned to sourdough-making methods. With little prior knowledge about sourdough starter, the 49ers began to experiment, knowing they could make this type of bread with just flour, water, and air. It wasn't ideal, as Americans in the 1800s generally preferred fluffy, sweet, and soft bread. Between the naturally crispy sourdough and the miners' poor baking skills, sourdough left a bad taste in most mouths and was seen as little more than a tool for survival. These explorers tested ways to make the sourdough taste better but achieved little success. Eventually, the 49ers began to grow ill from the bread, although their nutritionally poor low-fiber, low-protein diet likely also contributed.

It wasn't until French and Italian bakers arrived in San Francisco did public opinion on sourdough begin to evolve. Armed with years of sourdough experience from European baking traditions, these immigrants changed the future of sourdough in the United States. Some even founded Boudin Bakery, a cultural institution that still carries a strong presence in San Francisco baking today.

Of course, like most things in life, fads come and go, and even the best things fall out of style. Sourdough lost its prominence for 50 years or so, until sourdough clubs formed in the early 20th century. These were meant for senior miners who wanted to contemplate (and occasionally glamorize) the gold old days. Local tourism boards promoted this nostalgic bread, more bakeries garnered attention with their loaves, and sourdough regained popularity across the country.

Interestingly, two of the sourdough starters attributed to this region are actively used today and have even become some of the oldest sourdough starters in the world. These are the San Francisco Sour (which is over 100 years old and known for its extremely tangy taste) and the San Francisco Heirloom, which is a whopping 200+ years old. If you visit San Francisco, try purchasing a starter from a local baker, but remember Myhrvold's advice and consider how factors like the flour, water, and air used to maintain the starter will alter the contents. Ultimately, your starter won't make the same-tasting bread for long, although it is a unique souvenir to take home. 

Conveniently, you can even buy 100+ Year Old San Francisco Sourdough Starter online. Alternatively, opt to start from scratch with a Cultures For Health Sourdough Starter Jar Kit. So whether you're upgrading your everyday peanut butter and jelly sandwich with sourdough slices or you're a foodie visiting San Francisco eager to try it all, remember the history as you savor that celebrated tang.