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 makes sourdough unique? ›
Sourdough gets its signature sourness from its ingredients – specifically, the lactic acid. The yeast within the sourdough produces carbon dioxide gas, which leavens the dough and the lactic acid bacteria produces lactic acid, which is what gives sourdough its sour flavour.
Why did sourdough become so popular? ›
The Sourdough Trend: 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. As people returned to their routines, TikTok kept sourdough in the spotlight.
What makes sourdough bread sour? ›
There are two main acids produced in a sourdough culture: lactic acid and acetic acid. Acetic acid, or vinegar, is the acid that gives sourdough much of its tang. Giving acetic acid-producing organisms optimal conditions to thrive and multiply will produce a more tangy finished product.
What element makes sourdough bread special? ›
The main difference is the leavening ingredient. Like I mentioned before, in sourdough bread the leavening ingredient is sourdough starter, whereas in conventional bread, instant yeast is used. The other thing that sets it apart is the fermentation process the dough undergoes prior to baking.
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.
Why is sourdough so delicious? ›
Sourdough improves the texture and palatability of whole-grain and fiber-rich products. Each starter imparts its own unique flavor to the bread, based on the wild yeast and bacteria that inhabit the starter.
What is the big deal about sourdough? ›
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 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.
What are the three advantages of using sourdough? ›
Studies show that sourdough has less of an impact on blood sugar levels compared to refined breads made with baker's yeast and may be easier to digest as it contains lower levels of gluten, FODMAPs, and anti-nutrient compounds.
The yeasts cause the dough to rise by creating carbon dioxide bubbles, while the lactic acid bacteria provide the sour flavor (in the form of acetic acid and lactic acid) and preserve the bread by lowering its pH, which prevents the growth of food borne pathogens.
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.
Why does sourdough bread have a unique taste and chewy texture? ›
The long, slow fermentation process that sourdough requires allows the yeast and bacteria to break down the proteins in the flour, making it easier to digest and giving the bread a chewy texture. In addition to contributing to the flavor and texture of sourdough bread, the yeast in sourdough has other benefits as well.
What makes sourdough bread unique? ›
Sourdough is naturally leavened bread, which means it doesn't use commercial yeast to rise. Instead, it uses a 'starter' – a fermented flour and water mixture that contains wild yeast and good bacteria – to rise. This also produces the tangy flavour and slightly chewy texture you'll find in sourdough.
What is one of the key qualities of a sourdough? ›
Sourdough fermentation improves nutritional qualities by altering the structure and function of proteins and starch, enhancing dietary fiber, volatile compound profiles, and antioxidant activity, and reducing FODMAPs.
What makes the best sourdough? ›
There are a few key components that are needed to bake the perfect sourdough bread. These are fresh flour, water, salt, and a natural starter (leaven or levain). Real sourdough bread is made without the use of commercial yeast or any other commercially available leavening agent.
What are the special features of sourdough bread? ›
The use of sourdough in bread making improves loaf volume and flavor, delays staling, and inhibits the growth of spoilage fungi and bacteria. Sourdough fermentation has been associated with the health-promoting properties of bread, such as a reduction of the postprandial glycemic response in human blood.
What is the Speciality of sourdough bread? ›
Sourdough bread is completely natural, as there are no additives from yeast, and it's a rich source of vitamins and minerals. The lactic acid bacteria found naturally in a sourdough starter is the same good bacteria that's found in other fermented foods, like kimchi, kefir and sauerkraut, which are good for gut health.
How is sourdough different from regular bread? ›
Sourdough relies on a mix of wild yeast and lactic acid bacteria, rather than baker's yeast, to leaven the dough. It's richer in nutrients, less likely to spike your blood sugar, contains lower amounts of gluten, and is generally easier to digest than bread made with baker's yeast.
