Sourdough Cultures

By: Matthew Morse Booker

Introduction: An Embodied Multispecies Environmental Humanities Experience

As one of the first Alumni Fellows at the Rachel Carson Center (RCC), I wanted to return something to the remarkable community of RCC staff, students, and fellows. In North Carolina I am part of the Sourdough Project, a global public science experiment using sourdough bread culture to explore the biological diversity in our homes.[1] With some effort, sourdough allowed us to share an embodied, multispecies environmental humanities experience together.

Family Sourdough

This culture entered my family tree around 1900, the year that 22-year old Charles E. Bunnell and his wife Mary Ann Kline migrated to Kodiak, Alaska to work as teachers.[2] According to their daughter Jean, the Bunnells got the culture as a gift from a “sourdough,” a prospector in the 1898 Klondike Gold Rush, who in turn made it locally or brought it from unknown origins outside Alaska.[3]

“Dr. Charles Bunnell and his moose calf. Calf died of eating too many pancakes.” Courtesy of the Alaska Digital Archives.

After working as a frontier lawyer and federal judge, Charles Bunnell became the first president of the University of Alaska from 1921 to 1949. He and Mary Ann raised a daughter, and the family ate bread, waffles, and pancakes made from this sourdough culture. So did their family pet, unfortunately. A surviving photograph of Charles Bunnell and his pet moose calf is captioned, “Calf died from eating too many pancakes.”[4]

“At the Alaska College. Sunday May 5, 1929. Mrs. Bunnell, Harry Goffrey, Myself [Charles E. Bunnell], Jean Bunnell, Harlan Youel at the Alaska College.” Courtesy of the Alaska Digital Archives.

Young Jean Bunnell spent her teen years on the new campus of the University of Alaska, which had only a handful of students in the early years, and fewer women. One of the first female students praised the sense of community in the fledgling college of fifty-two students and ten faculty members. “What an eager, energetic, excited group we were! Dr. Bunnell, with his tremendous vision and optimism, made us all feel we were partners in a great adventure; he and the young teachers made us all feel so important. We were in on all the plans; we were making a university.”[5] The university archives show Jean sitting with the campus Glee club; hands on hips, posing with her mother and father in an Aleut parka; “out for a ride” with her father in his automobile. Jean left Alaska to attend Stanford University, graduating in French literature in 1931.[6]

Jean Bunnell in California, ca. 1930s. Photo: Matthew Morse Booker.

Jean brought her sourdough with her to California, where she became close friends with Catherine Morse, another northerner from Bellingham, Washington. Catherine married fellow Stanford student Philip Kennedy and they had two daughters. Then Catherine sickened with cancer. She made her closest friend promise to raise her daughters as her own. In 1958, Catherine Morse died. Jean Bunnell left her post at San Francisco State University and married Phil Kennedy. Together they raised Sheila and Robin Morse Kennedy in San Rafael, just north of the Golden Gate Bridge. A family tradition was making bread, waffles, and pancakes from their mother’s sourdough.[7]

Phil and Jean Kennedy, ca. 1990s. Photo: Matthew Morse Booker.

Always a family of many talents and great generosity, Phil and Jean and their daughters loved and cared for many lonely hearts. In 1958, Catherine Morse’s 21-year old cousin, Patricia, moved alone, without connections, to San Francisco to start life as an artist. Jean and Phil befriended Patricia. Patricia’s four children visited Jean and Phil many times and ate sourdough waffles in their kitchen with its zinc countertops in the breeze blowing off San Francisco Bay.[8]

About 1990, Jean and Phil moved to Eugene, Oregon to be near their daughter Robin, who taught at the Waldorf School there for many years.[9] Robin and her husband Jim raised three children in Eugene, feeding them bread and pancakes and their specialty, waffles, made from this sourdough. Sheila, who had moved to Bellingham, did the same with her husband and three sons. When Patricia’s Morse’s son Matthew Morse Booker graduated from college and moved to Bellingham, and then Eugene, Sheila and Robin and Jean and Phil sustained him with sourdough cinnamon rolls and bread. In the years before Jean died in 1998, she and Phil gave Matthew a sacred gift: a stoneware crock containing the sourdough culture. He managed to kill it, so Robin gave him more. That sourdough is now dispersed through the Morse, Morris, and Booker extended families, fed by and feeding dozens of family members across North America.

This sourdough culture left California and traveled across the United States with me to North Carolina in 2004. It remains an anchor to family nearly 5,000 kilometers away. It has been fed and been eaten hundreds of times. I brought the culture to Munich, where it flourished. Maybe it is the regular feeding, or the city tap water, or the local bacteria and yeast in the air, but the starter is exceptionally energetic and rises high and foamy.

Microbiologists describe sourdough as an assemblage of bacteria and yeast living on the sugars in wheat flour. The flour and water provides a home where the microorganisms ferment sugars into alcohol and lactic and acetic acid, releasing bubbles of carbon dioxide to produce the sour, bubbly mix that enlivens breads. As scientists, they are fascinated by sourdough’s remarkable diversity, its evolutionary history, its adaptability (each sourdough culture changes when it is moved, adding local bacteria and yeasts from the air, flour and water of its new home), and they note its ancient relationship to human beings who have both shaped and been shaped by sourdough.[10]

Science of Sourdough. Photo: Lauren Nichols.

Grain, water, fermentation: these are the origin and basis of much of the human diet since the agricultural revolutions some 10,000 years ago. In a study of Belgium bakers, Dunn and Madden found that human bakers impart a distinct, individual microbial signature on their sourdoughs, and vice versa. (Not human DNA, but the DNA of microbes living on human hands.) Traces of Charles E. and Mary Ann, of Jean and Phil, Sheila and Robin, may be present in the sourdough culture I eat and that I may even carry on my body.[11]

Sourdough Experience

Microbial ecologist Jessica Lee describes sourdough cultures as a garden, “home to micro-organisms of diverse species and functions. It is an intimate working relationship between microbes and humans; it is also a potent reminder of the culinary benefits of biodiversity.”[12] But if sourdough is a community, what determines who joins the community? Sourdough cultures are alive and changeable. They contain a collection of bacteria and yeasts that have proven resilient and compatible, but they also respond to their environment. When that environment changes—such as when the sourdough moves with its human companions—sourdoughs also accommodate microbes from their new homes. A study of Belgian bakers suggests that sourdoughs also absorb some of the microbial community carried on the hands of bakers. But exactly why and how new microbes are able to join remains an understudied mystery.

Bowls of sourdough starter. Photo: Matthew Morse Booker.

At the Rachel Carson Center, we decided to test the influences of different kitchens and hands on bread flavor. We adapted a citizen science experiment designed by microbiologist Erin McKenney to control as many variables as possible. Participants committed to a rigorous protocol. We began with the same sourdough culture, commercial baking flour, and a protocol for feeding the culture and for baking. Participants agreed to feed the starters daily for seven days, passively harvesting bacteria and wild yeasts from the air in their homes. Then we would use a standard, precise recipe to bake one loaf of bread.

All participants began with a jar of the same sourdough “culture,” or mix of bacteria and yeasts. Each morning, participants threw away half their sourdough and added a measured quantity of flour and tap water. This process, called “backslopping,” encouraged colonization of the sourdough culture by bacteria and yeasts in participants’ homes. Repeating this process for a week, each participant created a new sourdough community. Some of the original sourdough bacteria and yeast remained, but the community now included microbial residents from each participant’s home.

Now the task was to ascertain how those communities differed. Rather than using a DNA analysis to sort the various species in the sourdough, we decided to use the powerful human senses of smell and taste to ascertain difference. On the last night of the experiment, we added flour and set the dough to rise. On the morning of 27 June—the hottest day of 2019—we baked the loaves for tasting.

At that afternoon’s Lunchtime Colloquium, we tasted the breads for the differences in flavor added by each baker’s own bacteria and yeasts added by their hands as well as the changes added to the sourdough culture by the bacteria in different homes. Using a sensory analysis rubric designed by food scientists at Tufts University, the fifty tasters found quite a diversity of flavors in the breads, ranging from green apple, nutty, earthy, a range of sours (vinegary, cheesy, winy) to wet dog and burned hair.


Sourdough bread tasting at the Lunchtime Colloquium. Photo: Sevgi Mutlu.


As part of the experiment, all participants were asked to record daily observations of their sourdough culture. These included the smell, amount of rise or bubbles, changes in color, the presence or absence of liquid in the culture. But since our participants are humanities scholars, participants were also invited to reflect on the experiment and describe their own feelings and reactions. This journaling component transformed the experiment into an “experience,” in which the care and feeding of a bacterial and yeast culture became a mirror for emotions. Most of the 25 participants agreed to share their journals for use in this blog post. The entries indicate the difficulty of sticking to an artificially strict protocol, the surprising diversity of cultural behaviors in the sourdough, and the emotional volatility of caring for a living organism. Many participants experienced a shared emotional trajectory during the seven days: anticipation, commitment, disappointment, and resolution. An unprecedented heat wave struck Munich during the week of our experiment, complicating the experiment. The city’s mostly non-air conditioned apartments baked in the heat, and so did the sourdough. RCC Office Manager Lena Engel captured the general mood in a note written on the margin of her journal: “Temperature in apartment too high.”

engel journal
Lena Engel’s sourdough journal. Photo: Lena Engel.

Doctoral student Sarah Yoho described a typical experimental arc ranging from anticipation through heat-related frustration to commitment and resolution. On the first morning, her sourdough “Smells of grape musk, some tiny bubbles, yellowed white in color, quite liquid, plastic-like sheen on top, bubbles double after mixing in flour and water.” The next day, she wrote, “The 3yr old of the house says the starter smells gross. I think it smells like yeast. Some hooch on top. Hot day. No mood for cooking. Letting the dough rise.” And, finally, “27 June 2019. Bread day! My dough didn’t rise. I am disappointed but I will bake it anyway. Baking smells sour. The crust became a lovely golden color. I’ve decided to feed my starter 2x a day in order to get it bubbling. Next up: pancakes!” Like many others, Yoho experienced a gap between her expectations and the reality. But she found satisfaction in the lovely golden crust and determined to forge ahead.

Managing Director Arielle Helmick’s response showed her sense of humor and fearless honesty. Initially, she wrote, “I had visions of myself becoming a great sourdough baker, with this simple and easy starter method.” But after an epic effort to produce a viable bread dough amidst blistering heat and family responsibilities, Helmick threw away the flat mix, concluding that her sourdough “had died at some point along the way.”

Carson Fellow Seth Peabody shared his personal interaction with the sourdough, which he contrasted with his long experience baking with commercial yeast. Peabody felt responsible for the living sourdough community, where baking with commercial yeast was “just mixing ingredients in a bowl.”

Fellow Rob Gioielli found that working with sourdough expanded his sense of community. Gioielli concluded that “What was most interesting to me about this experience was having the conscious knowledge that through feeding the starter and baking, I was bringing all of the microbes, smells, bacteria, etc. from my body, home, and neighborhood into my cooking.”

Like Gioielli, Carson fellow Erin Ryan found meaning in the community of organisms required to make her food. “It very much felt like a partnership process between us and the yeast. We had to feed and care for it, and it had to survive our randomness and error-prone caretaking. Together, we produced something that both lives on, and that we can feed on over time.”

Doctoral candidate Sasha Gora has published on the revival of the sourdough movement and contributed recipes to a bread cookbook. Yet her previous attempts baking with sourdough fell disappointingly flat. This time she found it cathartic: “Feeding a starter is not too different from trying to finish a draft of a doctoral dissertation. One has to feed it every day. The weather—and so much more— influences its mood, and for it to grow and get to where one can actually share it, it is important to discard a good number of words before proceeding to add fresh ones.”

These responses, shared with typical Rachel Carson Center generosity, show how intimate a scientific experiment could be.

Conclusion: Sourdough is a Multi-generational, Multi-species Community

Sourdough in our kitchens is a rich and biologically diverse reflection of its evolutionary past. And our sourdoughs are also filled with meaning. I make sourdough for my family because I love them, and the love of my ancestors and for my children passes through the sourdough and my hands into the food I serve them.

This deeper meaning of sourdough came home to me with special force this summer. The day we started the experiment, my mother called to say that Robin Morse Bunnell Kennedy Morris was ending her long struggle with cancer. She slipped in and out of consciousness as I mixed flour and water together, added her culture, and stirred. Just after midnight on 20 June, Robin passed away.[13]

Robin Bunnel Kennedy Morris. Photo: Matthew Morse Booker.

Robin had one of the greatest laughs I’ve ever heard, a rising, bubbling song of a laugh that provoked almost everyone around her to smile. Robin’s irresistible laugh and her lively sourdough seem very similar to me. I keep both in my memory, in my heart, and on my hands.

I have come to see sourdough as a multi-generational human and nonhuman community. Seeking to expand that community, I brought my family sourdough to Munich and offered it to Rachel Carson Center students, staff, and fellows. In doing so, we fed and sustained another kind of community. Community is what goes on after we depart. It is what makes life worth living.

Feature image: Soup Spoon Blog via flickr, CC BY-NC-ND 2.0 

[1] “The Sourdough Project,” The Public Science Lab, accessed 30 July 2019,

[2] “Charles Bunnell,” University of Alaska Fairbanks Centennial, accessed 21 June 2019,

[3] “1921–1949 Charles Bunnell: Fitting Tribute to a Great Alaskan, An Editorial,” University of Alaska, accessed 21 June 2019,; “The History of Sourdough in Alaska,” Area 907: The Last Word on the Last Frontier, last modified 30 July 2014,; “according to his daughter”—Aaron Booker, personal communication, 19 June 2019.

[4] “Dr. Charles Bunnell and his moose calf.” (n/d, circa 1940?). UAF-1972-142-17. Elmer E. Rasmuson Library, University of Alaska Fairbanks, accessed 23 July 2019

[5] Margaret E. Murie, Two in the Far North (New York: Alfred A. Knopf, 1957; reprint and foreword by Terry Tempest Williams, Alaska Northwest Books, 1997), chapter 10.

[6] “Fitting Tribute.” Photographs: Alaska’s Digital Archives. University of Alaska Fairbanks, accessed 19 June 2019, “Registrar Issues Graduation Lists for Coming June,” Stanford Daily 79:40 (23 April 1931), page 4, accessed 20 June 2019,

[7] David C. Morse Jr., Kate Morse, Patricia Morse, personal communications, 19 June 2019.

[8] Patricia Morse, pers. comm., 19 June 2019.

[9] “Robin Morris Obituary,” Eugene Register-Guard, 21 June 2019

[10] “The Sourdough Project,” accessed 21 June 2019,

[11] Lindsay Patterson, “Sourdough Hands: How Bakers and Bread are a Microbial Match,” The Salt: National Public Radio, accessed 21 June 2019

[12] Jessica A. Lee, “Yeasts are People Too: Sourdough Fermentation from the Microbe’s Point of View,” in Cured, Fermented and Smoked Foods: Proceedings of the Oxford Symposium on Food and Cookery 2010, ed. Helen Saberi (Devon, UK: Prospect Books, 2011), 175–88.

[13] “Robin Morris Obituary,” Eugene Register-Guard, 21 June 2019

One Comment on “Sourdough Cultures

  1. I’m a confectioner and since we had lockdown I started my first sour bread it’s the best thing I have done in all my year’s of bakeing


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