Will climate change impact San Francisco’s famous sourdough?

‘The microclimate we have in S.F. is unique and has helped shape the flavor of the bread’

It is said that San Francisco’s famous sourdough was born from the air itself; that our briny fog imbued the dough with microbial magic, imparting its sharp flavor and characteristic chew.

The mythology of The City’s distinctive bread looms large: Museums have been built, bread-making traditions passed down. “Mother doughs” are carefully guarded and preserved, regularly fluffed up with flour and water to keep the fermentation of yeast and beneficial bacteria alive.

Here, bread bowls are not just a medium for clam chowder, but the entire point.

But as climate change brings intensifying drought and deluge to wheat fields and warms the Bay Area’s chilly microclimates, what will the future hold for San Francisco’s celebrated bread?

The good news in the short term is that scientists say the yeasts and bacteria that boost our bread will be largely unaffected by climate change. Longer-term, the answer becomes less clear.

“We know that yeasts, like other fungi, tend to thrive in moist environments and that different types of yeasts and bacteria adapt to different climates,” said Erin McKenney, a professor of applied ecology at North Carolina State University and co-author of a study that looked at sourdough starter microbiomes.

“Of particular interest to San Francisco sourdough bakers, we found that Fructilactobacillus sanfranciscensis (formerly Lactobacillus sanfranciscensis) was strongly associated with starters from locations with lower maximum temperatures,” she said, referencing the lactic acid bacteria that gives sourdough its signature flavor.

That’s bad news for a warming Bay Area, where temperatures have been gradually increasing for decades. Higher average temperatures may favor different heat-loving yeast strains, said McKenney, thereby changing fermentation rates and the flavor of the bread. More extreme weather events, on the other hand, could provoke a shift to different species entirely.

One such species that thrives in more extreme conditions is Candida — commonly found inside the human body — which could change bread’s aromatics and rise time.

Considered one of the oldest leavened breads, sourdough has played an important role in human nutrition and culture for thousands of years, tracing its origins back as far as ancient Egypt. Pliny the Elder described the method in his Roman compendium Natural History.

San Francisco’s sourdough gurgled into existence during the Gold Rush era, when Isidore Boudin, the son of master bakers from France, is said to have received a wild yeast starter from 49ers for whom bread and pancakes were a staple. Boudin’s starter, called the “mother dough,” is still used in the loaves produced by his namesake bakery today.

Louise Boudin, the wife of Boudin Bakery founder Isidore Boudin, who started the bakery in 1849 and died in 1887, alongside their daughter, Lucie and others outside a new Boudin French Bakery location at 815 Broadway, which the bakery moved to in 1890 as its popularity continued to grow. (Courtesy Boudin)

Louise Boudin, the wife of Boudin Bakery founder Isidore Boudin, who started the bakery in 1849 and died in 1887, alongside their daughter, Lucie and others outside a new Boudin French Bakery location at 815 Broadway, which the bakery moved to in 1890 as its popularity continued to grow. (Courtesy Boudin)

“The microclimate that we have in San Francisco is unique and has helped shape the flavor of the sourdough bread,” said Dan Giraudo, CEO of Boudin Bakery, whose grandfather “Papa Steve,” bought the bakery in 1941 and helmed the brand for 60 years as its master baker. “It’s hard to replicate in other climates because even if you tried — the air that is going throughout the bakery still impacts the product.”

Scientists have since found strains of Fructilactobacillus sanfranciscensis in other geographies and climates, suggesting that it’s not the specific bacteria that gives San Francisco’s bread its unique quality, though many bakers insist that the Bay Area’s climate informs the cultures and quality of their bread.

Boudin Master Baker Fernando Padilla pulls a large tray of sourdough loaves out of the oven. (Courtesy Boudin)

Boudin Master Baker Fernando Padilla pulls a large tray of sourdough loaves out of the oven. (Courtesy Boudin)

A sourdough starter is a universe unto itself. Made by combining flour, water and a lot of patience, a starter is both mesmerizingly simple and exasperatingly complex. It takes time to let the wild yeasts and bacterial communities bubble to life, a pre-fermentation that gives the bread its characteristic sour flavor.

But sourdoughs can be finicky loaves. Bakers say that starters prefer cooler, more acidic environments and swings in temperature fluctuations during the baking process can spell disaster. “Bread — especially sourdough bread — it is extremely sensitive to temperature,” said Josey Baker, owner of Josey Baker Bread in NoPa. “The difference of 10 degrees to a loaf of bread is major. It majorly changes the rate of fermentation.”

So far, Baker said he’s been able to manage temperatures within his bakery, even on sweltering summer days. But while he can manipulate his organic doughs and ferments, he’s unable to control what happens in the wheat fields his business depends on.

“That is a very, very real thing that keeps me up at night,” he said. “What are the next few years — five years, 10 years — what are they going to look like from the perspective of the quality of ingredients that we’re able to get, but also the prices?”

David Torres bags a soughdough bread loaf at The Mill cafe on Friday, Jan. 21, 2022. (Craig Lee/The Examiner)

David Torres bags a soughdough bread loaf at The Mill cafe on Friday, Jan. 21, 2022. (Craig Lee/The Examiner)

This year, the West’s historic drought has challenged a significant portion of wheat-growing areas, according to the USDA, driving the total yields down 10 percent below 2020 levels. Lower yields, combined with pandemic-fueled supply chain issues have caused massive headaches for local bakers who have seen prices skyrocket.

“Flour right now is at close to an all-time high,” said Giraudo. “In the last six months, the price [of wheat] has risen close to 80 percent.”

The situation is complex. While droughts are expected to become more extreme under warming conditions, climate change may actually benefit wheat, expanding its growing range, according to new research by NASA.

Ultimately though, San Francisco’s sourdough is a survivor. It was pulled from the wreckage of the 1906 earthquake and fermented its way through the Summer of Love and, now, the pandemic — sustaining The City’s miners, hippies, beatniks and “tech bros” along the way. Climate change or not, said Giraudo, it will be here for many more years to come.

“We make bread in the same way we did in 1849 (as we do in) 2022,” said Giraudo. “My grandfather always said, take care of the bread and the bread will take care of you.”

jwolfrom@sfexaminer.com

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