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Demystifying Sourdough Starter

Sourdough fermentation
24 hours

The Basics: What is a Sourdough Starter?

In its most rudimentary form, a sourdough starter is a mixture of flour and water that captures wild yeasts and bacteria from the environment, a process sometimes referred to as spontaneous inoculation. This microbial assembly begins to ferment the sugars present in the flour. Yeasts produce carbon dioxide and alcohol as byproducts, giving the dough its rise and characteristic holes. Simultaneously, the bacteria, predominantly lactobacilli, engage in a symbiotic relationship with the yeast. They metabolize the alcohol produced, breaking it down into simpler components like acids, primarily lactic and acetic acid. These acids contribute to the tangy flavor of sourdough and also create an environment less hospitable to undesirable microbes. Thus, the yeast provides the rise, and the bacteria offer the signature tang while also making the ecosystem of the starter more stable and self-preserving. Together, these microorganisms work in concert to impart sourdough with its unique rise and tangy flavor.

In this symbiosis of microbiology, both the yeasts and bacteria are essential performers. Each brings unique qualities to the process, resulting in the rich, complex character that defines sourdough bread. It is this very collaborative effort between yeast and bacteria that elevates sourdough starter from a simple mixture of flour and water into a living, breathing entity with culinary and even, some might say, spiritual significance.

The Ancestry of Sourdough

Food anthropology suggests that sourdough likely has ancient origins, possibly dating back to 6,000 years ago in ancient Egypt. Each starter carries the unique fingerprint of its locale, capturing yeasts and bacteria endemic to its environment. This fascinating aspect of sourdough adds an extraordinary layer of complexity to this seemingly simple mixture. It also means that a sourdough from San Francisco will inherently differ in texture and taste from a starter originating in Naples, Florida, or any other part of the world. Intriguingly, if you were to take a San Francisco sourdough starter to Naples, over time, the local yeasts and bacteria would recolonize the mixture. The starter would undergo a sort of 'microbial makeover,' gradually adopting the characteristics of its new environment. This process of microbial recolonization means that sourdough starter isn't just a static mix of flour and water; it's a living, evolving entity, constantly shaped by its surroundings.

In essence, the 'terroir' of sourdough isn't just about where it begins but also where it travels and how it adapts. This dynamic aspect adds yet another layer to the rich tapestry of sourdough's cultural and scientific narrative.

The Science Behind the Culture

The intersection of food and biochemistry. When you're tending to your sourdough starter, you're engaged in a form of biological chemistry. On one hand, you have yeasts, which are facultative anaerobes. This means they can either respire in the presence of oxygen or switch to fermentation when oxygen is scarce. During fermentation, yeasts produce ethanol and carbon dioxide, leading to the dough's rise and characteristic air pockets.

But let's not forget the unsung heroes in this microbial factory—the bacteria, predominantly lactobacilli. These bacteria metabolize the alcohol generated by the yeast into simpler compounds like lactic and acetic acids. These acids are responsible for sourdough's unique tanginess and also create a less welcoming environment for unwanted microbes. Essentially, the bacteria serve a dual role: they're both the flavor specialists and the security team of this microscopic operation.

So, when you stir that flour and water together, you're not just making a dough; you're kickstarting a complex biochemical reaction. Yeasts set the production lines humming, filling the dough with bubbles of carbon dioxide, while the bacteria ensure quality control, fine-tuning the flavor profile and keeping potential spoilage at bay. Together, these microscopic agents transform the simple blend into the complex, nuanced, and delicious entity that is sourdough bread.

The Art of Maintenance

The care of a sourdough starter often seems shrouded in a veil of complexity. To illustrate, one of my culinary school instructors was planning a trip to Seattle. He had a cat and a few houseplants, all of which he entrusted to a housesitter for four days. Their care instructions took up just the front of a single sheet of paper. In contrast, his sourdough starter commanded a four-page, front-and-back manual. While this might sound like caring for a starter is akin to running the Manhattan Project, the reality is far less intimidating.

Maintaining a sourdough starter does indeed hinge on understanding a wealth of underlying science, but the day-to-day care is surprisingly straightforward. At its most basic, a well-tended starter only requires regular 'feedings' of flour and water. The frequency and quantity of these feedings can be influenced by a range of factors, including ambient temperature, humidity, and how often you intend to bake.

In this role, you have choices. You can approach the task with the casual demeanor of a pet owner, offering your starter its daily sustenance and enjoying the delicious benefits in a relaxed manner. Alternatively, you could embrace the meticulousness of a scientist, controlling every variable with the precision of a jet propulsion physicist. So, whether you're a casual pet owner or a rigorous scientist in the kitchen, rest assured that maintaining a sourdough starter is both an art and a science—and the results are, without question, delicious.

The Proof

So, at its essence, a sourdough starter is both incredibly simple and profoundly complex, a dichotomy that only adds to its allure. This humble mixture of flour and water, when left to interact with the natural yeasts and bacteria in its environment, becomes a fascinating microcosm of life that reflects a tapestry from strands of biochemistry, geography, and the love of cooking.

For the curious, it offers endless opportunities for scientific exploration and gastronomic experiments. Whether you care for it as you would a beloved pet or with the meticulous precision of a scientific project, the choice is yours. It accommodates the casual baker and the culinary scholar, providing an accessible entry point for anyone interested in the alchemy of bread-making.

In every jar of bubbling sourdough starter lies a history lesson, a science project, and an art. It's a living entity that adapts, evolves, and transcends its basic ingredients, a testament to the possibilities of nature. It's a culinary tradition that has stood the test of time, dating back to ancient civilizations, yet it thrives in modern kitchens around the globe. It is, in essence, a gift that keeps on giving—as long as you feed it, of course.

Your sourdough starter is your metaphor for life itself: It can be as simple or as complex as you make it, but either way, the rewards are delicious. Whether you are a casual baker or a dedicated culinary anthropologist, a sourdough starter is your passport to a world of flavor, culture, and the ceaseless wonder that is the art and science of food.

Fig-Aged Sourdough Starter


Dried figs, aged for 3-5 years (Alternatively, 5-6 raisins if you are not a nut job like me and don’t age your own figs)

All-purpose flour



A clean glass jar with a lid

A wooden or plastic spoon for stirring

Measuring cups

Day One:

Initial Mixture: In a clean jar, combine 1 cup of flour with 1 cup of water.

Five year old aged figs
Five year aged figs

Add Fig: Drop one aged fig into the mixture. If aged figs are not available, a few raisins can be used as a substitute.

Mix and Rest: Stir the mixture well until all ingredients are well incorporated. Allow to rest at room temperature for 12-18 hours.

Day Two & Beyond:

First Feeding: After the initial rest period, add 1/2 cup of flour to the mixture.

Regular Stirring: Stir the mixture every 8 hours to keep it active.

Day Three:

Second Feeding: 28 to 30 hours after your initial mixture was made, add another 1/2 cup of flour. Stir well.

Extended Aging: Continue to stir every 8 hours for another 48-72 hours.


Feeding Post-Dormancy: At this point, your starter is dormant as you've exhausted the nutrients for the yeast and bacteria. Add 2 cups of flour and 1 cup of water to revive it.

Stir and Observe: Stir the new mixture well. Your starter will come back to life quickly.

Standard Starter Care: From this point on, proceed with your usual sourdough starter maintenance routine.


The use of figs adds not just flavor but a microbiological twist to the starter, enhancing both its character and its performance.

This fig-aged sourdough starter is a rich, flavorful base for many kinds of sourdough breads. It also provides an intriguing opportunity to observe and appreciate the transformational power of time and nature in culinary arts.


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