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.
What gives sourdough bread its sour taste? ›
Sourdough bread's signature taste comes from friendly bacteria and yeast, which produce flavorful lactic and acetic acids in rising bread dough.
What is so special about sourdough bread? ›
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 did sourdough become so popular? ›
The popularity of sourdough is understandable. We know that it tastes great and has a unique flavor that can't be replicated with other types of bread or baked products. We also know that it is relatively easy to make although it does take a lot of time.
Why is San Francisco sourdough so sour? ›
The key to sourdough bread tasting the way it does is the strain of bacteria, lactobacillus sanfranciscensis. And if that name looks like it has ties to San Francisco, it does. "This special strain of lactic acid bacteria thrives in our salty, cold environment," says Kosoy.
Is sourdough supposed to be very sour? ›
In general, many beginners at sourdough have the preconceived notion that sourdough bread should be very sour. Like the classic San Francisco Sourdough Bread, or like the 100% whole wheat bread mentioned above. However, most sourdough breads aren't that sour, and most breads shouldn't be that sour.
Why is store bought sourdough so sour? ›
Many store-bought “sourdough” breads use just a small amount of sourdough starter and throw that and other flavors in there to give the bread a sourdough taste — while the action of rising the bread is done with commercial yeast.
Is sourdough bread anti-inflammatory? ›
The best bread to reduce gut inflammation is bread made from whole grains. Refined grains, such as the grains found in white bread and white pasta, are known to increase inflammation across the whole body. Sourdough bread and rye bread are both good options for an anti-inflammatory diet.
Why is everyone making sourdough bread in 2024? ›
The continued popularity of homemade sourdough bread is rooted in a confluence of factors which has gained momentum as more people gravitate towards more nutrient-dense foods made from scratch and many families adopt a homesteading lifestyle.
Is it okay to eat sourdough bread every day? ›
Is it healthy to eat sourdough everyday? You could eat sourdough every day, but it isn't necessarily healthy to do so. A healthy diet is characterized by balance and moderation. Whether or not it is healthy for you to consume sourdough every day depends on the rest of your diet.
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.
What's the rage about sourdough bread? ›
Why is sourdough good for me? One of the big benefits of sourdough over commercially-baked bread is that, thanks to the fermentation process, it's easier to digest.
How old is the oldest sourdough? ›
The World's 'Oldest' Sourdough Starter Was Made With 4,500-Year-Old Yeast. There's no bread quite like sourdough. In addition to being tasty as a sandwich bread, delicious as sourdough croutons, and even great just toasted with butter, sourdough's production process is decidedly unlike other breads.
Why is sourdough only in California? ›
San Franciscans proudly trace their city's iconic bread back to the Gold Rush of 1849. The men who flocked to Northern California in search of gold made bread in their wilderness camps not with store-bought yeast, but with their own supply of sour, fermented dough.
Why is sourdough better in California? ›
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.
What makes sourdough taste different? ›
hom*ofermentative bacteria break down simple sugars to form lactic acid. That lactic acid lingers in the finished loaf of bread, significantly contributing to the sourness of sourdough bread. These particular bacteria do well in temperatures between 30–35°C or lower.
How to reduce the sour taste in sourdough bread? ›
It's an easy variable to manage using water temperature and a Proofer and/or a Sourdough Home. For less acidity: Use water around 80°F (27°C) and a fermentation temperature of 70-76°F (21-24°C) to favor the yeast and create milder flavors.
Why is it called sourdough if it's not sour? ›
Sourdough bread is called “sourdough” because it is made using a naturally occurring yeast and bacteria culture known as a sourdough starter. The starter is a mixture of flour and water that is left to ferment over time, which allows wild yeast and bacteria to colonize it.
What does over fermented sourdough taste like? ›
A very sour taste (not a pleasantly sour tang like properly fermented sourdough) A sour/fermented smell. You might notice a “corn” flavor to the baked crust (sometimes there is a faint odor like popcorn) Crust may have small tears in it, randomly over the surface.
How should a good sourdough bread taste? ›
Taste. This bread has an almost imperceptible hint of sour, and because of this, the wheat flavors from the flour come forward. It has an incredibly tender, soft crumb that almost dissolves in your mouth. It's one of those rare foods whereupon taking that first bite your mouth begins to water.
