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 gained modern traction during the Covid pandemic when many people had extra time on their hands. The multi-day process of making sourdough at home turned into a popular hobby.
Why is SF sourdough so sour? ›
So let me try to repeat that: San Francisco sourdough tastes sour because of a unique local bacteria called lactobacillus San Francisco. That, and a yeast called candida milleri are the real secret to San Francisco sourdough bread. In other words, the secret ingredient is no secret at all: It's blowing in the wind.
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.
Why is sourdough unique? ›
What makes sourdough unique. Mass-produced wheat and white breads rely on baker's yeast, the fungus Saccharomyces cerevisiae, to rise. Sourdough, in comparison, uses a combination of wild yeast and microbes to help the bread rise through fermentation.
Why is everyone eating sourdough? ›
Made from wheat, sourdough bread fuels the production of good bacteria in your gut – much like the inulin and oligosaccharides found in onions, leeks, bananas, garlic, asparagus, and so on. 10. It's nutritious. Sourdough contains a variety of vitamins and nutrients, making it super beneficial to your day-to-day health.
What makes those pandemic era sourdoughs so deliciously uniquely sour? ›
The key taste compounds include salt, which is directly added to the dough, as well as acetic and lactic acid, produced during fermentation.
What state makes the best sourdough bread? ›
"San Francisco sourdough bread is the epitome of 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.
Trader Joe's has discontinued their beloved San Francisco Sourdough bread, a staple in many households.
Why not to eat sourdough bread? ›
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 city is famous for sourdough? ›
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 store bought sourdough so sour? ›
The Science Behind the Sour Flavor in Sourdough Bread
This is done by using a ripe and active starter to mix into bread dough. The dough goes through a fermentation cycle until it is ready to rise and bake. A sourdough starter is made up of wild yeast and bacteria working together.
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 sourdough so hyped? ›
(in my opinion) a well made sourdough that isn't ultra sour has an extra dimension of flavor that a standard store yeast bread can't have and I really like how it tastes. The texture is really nice too. long fermentation breaks down the gliand (so), which is the protein people generally have difficulty digesting .
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.
What's the big deal with sourdough? ›
Although the beneficial microbes in the starter tend to be lost during the baking process, the fibre and plant compounds, called polyphenols, become more bio-available. These act as an important fuel source for our gut microbes, which explains why sourdough is a gut-friendly choice.
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.
