SAN FRANCISCO, Aug. 16, 2023 — A few years ago, amid lockdown boredom, it seemed like everyone was perfecting their sourdoughs. A simple, fermented mixture of flour and water, the bread is powered by microbes that provide its one-of-a-kind tangy flavor. For over a hundred years, sourdough bread has been synonymous with San Francisco, where today, scientists will report that they’ve identified and quantified 21 key chemical compounds that make this bread taste and smell so unique. They’ve also compared the levels of the compounds in different breads.
The researchers will present their results at the fall meeting of the American Chemical Society (ACS). ACS Fall 2023 is a hybrid meeting being held virtually and in-person Aug. 13–17, and features about 12,000 presentations on a wide range of science topics.
Sourdough breads have existed for centuries, dating back to ancient Egypt — well before they hit their recent peak of popularity in 2020. Unlike other wheat or white breads, which often rely on baker’s yeast to rise, sourdough breads use a “starter” — a living colony of bacteria and wild yeast that causes the bread’s dough to rise through fermentation. Since the microbes come from the air of the local environment, certain places are reportedly home to the best loaves. For example, San Francisco’s unique foggy climate is said to help make its sourdoughs so famously delicious.
Even though these breads are common, little work has been done to understand what chemical compounds provide their characteristic taste and smell. This knowledge could be important to bakers who need to control the quality of their breads, preventing them from becoming too sour, and it could also help them create more consistent sourdoughs for consumers to enjoy. So, Thomas Hofmann’s team at the Technical University of Munich wanted to apply an updated version of a technique known as “sensomics” to sourdough bread crumb — the soft inside part of a loaf. Hofmann currently serves as editor-in-chief of ACS’ Journal of Agricultural and Food Chemistry.
“With sensomics, you can take just a few key compounds and completely recreate the characteristic taste of a food,” says Laura Eckrich, a graduate student in Hofmann’s lab, who is presenting the work at the meeting. The approach involves chromatography, mass spectrometry and similar methods. The team has applied the method previously to other foods to isolate all the flavor-active compounds and to determine their structures and concentrations, as well as how they contribute to taste. The team has used this knowledge to re-engineer the flavor profile of various foods from the bottom up.
Hofmann’s team isolated, identified and quantified the flavor compounds in sourdough bread crumb, and then determined which ones were the most important. The resulting 10 key “tastants” and 11 key “odorants” were then combined into a sourdough “essence,” the flavor of which was confirmed by a human sensory panel. The key taste compounds include salt, which is directly added to the dough, as well as acetic and lactic acid, produced during fermentation. After these experiments, they applied a technique called “unified flavor quantitation,” which was previously developed by Hofmann’s team, to the sourdough bread. For the first time, this technique allowed them to analyze these unique taste and aroma compounds simultaneously.
The team then used the method in brand-new studies to quantify the concentrations of these compounds in different types of bread. They collected both yeast-based and sourdough breads from local bakeries and supermarkets made with either rye or wheat flours. Though key sourdough compounds, including lactic and acetic acids, were found in the yeast-based breads, they were present in much smaller amounts. These results confirmed the importance of the fermentation process to the sourdough’s special flavor.
Next on the researchers’ plates was an analysis of the best way to reduce the salt content in breads. They addressed this issue by unevenly distributing saltier doughs throughout a dough mixture. Since breads, especially sourdoughs, can contribute significantly to one's daily salt intake, the method could help reduce the amount of sodium while maintaining the bread’s unique taste.
Ultimately, the team says their discoveries should be welcome news for the baking industry. “This was the first time the key taste and aroma compounds of bread crumb were elucidated using the sensomics approach, and we hope what we learned will help bakers create the best sourdough breads they can,” says Eckrich.
The researchers acknowledge support and funding from the German Research Foundation.
A recorded media briefing on this topic will be posted Wednesday, Aug. 16, by 10 a.m. Eastern time at www.acs.org/acsfall2023briefings. Reporters can request access to media briefings during the embargo period by contacting newsroom@acs.org.
For health and safety information for ACS Fall 2023, please visit the FAQ webpage.
FAQs
The key taste compounds include salt, which is directly added to the dough, as well as acetic and lactic acid, produced during fermentation.
Why has sourdough become so popular? ›
Sourdough has surged in popularity in recent years, thanks in part to the Covid pandemic and TikTok trends. From dining out to store-bought options, and even homemade attempts, sourdough bread has truly made a comeback.
What makes SF sourdough special? ›
Some say the foggy climate gives San Francisco's sourdough bread a special bounce, and others say it's a specific local strain of yeast that gives the characteristic flavor. That bounce and flavor are notes that pair perfectly with a California Chardonnay or Chenin Blanc.
Why is everyone making sourdough bread in 2024? ›
For many folks, the renewed interest in sourdough is health-related. Some are going even further than baking their own bread: They're milling their own flour from whole wheat berries, too.
What makes sourdough bread sour? ›
Sourdough bread's signature taste comes from friendly bacteria and yeast, which produce flavorful lactic and acetic acids in rising bread dough.
What makes those pandemic era sourdoughs so deliciously uniquely sour? ›
Though key sourdough compounds, including lactic and acetic acids, were found in the yeast-based breads, they were present in much smaller amounts. These results confirmed the importance of the fermentation process to the sourdough's special flavor.
Why is sourdough bread unique? ›
Why Is Sourdough Bread Different? Unlike other yeast bread recipes that use baker's yeast as the leavening agent, traditional sourdough recipes use a starter made of water and flour. The starter ferments over time, producing natural yeast and the slightly acidic flavor that sets sourdough apart.
What city has the best sourdough bread? ›
That said, the bacteria does particularly well in San Francisco's climate. As a result, this city is highly conducive to making excellent sourdough bread.
Is San Francisco sourdough real sourdough? ›
Founder Isidore Boudin, a French immigrant and bakers' son, obtained the bakery's original wild yeast starter from a gold miner, and they've been using the same mother dough (another name for sourdough starter) for more than 170 years.
What is the difference between sourdough and San Francisco sourdough? ›
However, San Francisco sourdough tends to be more sour, aerated and chewy than other types. All sourdough bread is leavened with a starter prepared by spontaneous fermentation of a mixture of flour and water. Large-scale commercial sourdough usually has extra yeast added to speed up production.
While sourdough bread is usually lower in gluten, it is not gluten-free. People with a gluten intolerance may find that sourdough is easier to digest, but people with celiac disease will likely still experience symptoms if they eat sourdough bread.
What is the fad with sourdough? ›
Sourdough is making a big comeback in American kitchens, and it's not just about the unique tangy taste. This resurgence taps into deeper cultural and health trends reshaping food relationships.
Is it cheaper to buy or make sourdough? ›
So if you look solely at the ingredients, it is cheaper to make your own sourdough. But if you bring other factors into it - it might not be as cheap.
Why is store bought sourdough so sour? ›
One consequence of the common belief that sourdough should be sour is that commercial sourdough is too sour. Sadly, most commercial sourdoughs aren't actually sourdough breads. They are yeasted breads that have had acetic acid, malic acid, and/or fumaric acid added to them.
Should I stir my sourdough starter between feedings? ›
It is important that you stir the sourdough starter every day in the morning and in the evening. Feed the starter. Add 60 g flour and 60 g lukewarm water, stir well to combine, and let sit out for 24 hours.
Why does my sourdough not taste like sourdough? ›
Still, there are three specific factors that can really affect your bread's flavor: The health of your starter. The level of the bread dough's organic acids. The complex relationships over time between levain, dough, fermentation, and proofing.
Why is everyone eating sourdough? ›
May be easier to digest
Traditional sourdough undergoes a slow fermentation, the result of which is an increase in the bioavailability of the bread's vitamins and minerals. This process also starts the breakdown of protein (including gluten), making sourdough easier to digest.
Why is everyone making sourdough bread today? ›
…is due to its unique flavor, texture, and health benefits. Sourdough bread tends to have a chewy crust and a soft, airy interior, making it a favorite among bread enthusiasts. Additionally, many people are drawn to sourdough because it is easier to digest than traditional bread.
When did sourdough bread become popular? ›
Sourdough breads gave way to bread with commercial years in the 19th Century, as it was quicker to make. However, in the 1980s the world began to see a resurgence in the ancient fermented bread and it's now enjoyed by millions every day across the world.
Why does everyone love sourdough? ›
Unlike bread made with commercial yeast, sourdough relies on wild yeasts and bacteria in its environment. This process, known as fermentation, gives sourdough its distinctive tangy flavor. It also breaks down gluten more extensively than regular bread-making techniques, potentially making it easier to digest.
