During the pandemic, homemade Bread baking became a global phenomenon, accompanied by the experimentation of traditional fermentation techniques using spontaneously activated microbial flora. This microbial flora consists of microorganisms, particularly yeast and lactic acid bacteria, which have the ability to develop unique flavors and characteristics in the resulting products. Since most of these microorganisms originate from the local bakery environment, there is a geographical and climatic specificity to the aromas associated with the local bakeries.

A well-known example in this regard is the San Francisco sourdough starter, which imparts a specific lactic Taste to local bakery products. There are even local legends about this starter, for instance, Boudin Bakery, considered San Francisco’s oldest continuously operating business since 1849, allegedly obtained the original wild yeast starter from a gold miner and managed to preserve it through successive generations for over 170 years. In the 1970s, researchers Frank Sugihara and Leo Kline set out to discover the exact type of lactic microorganism that gave San Francisco’s bread its characteristic taste. They eventually identified an uncataloged bacterium, which they named Lactobacillus sanfranciscensis, after the city, convinced that it was specific to the region. However, L. sanfranciscensis has since been discovered in about 90 countries, thriving in growth conditions that include a pH range from 3.9 to 6.7 and fermentation temperatures between 20°C and 27°C.

According to StudyFinds.com, a team of researchers from Germany, led by Professor Thomas Hofmann from the Technical University of Munich, identified and quantified 21 key chemical compounds contributing to the unique taste and aroma of bread. They compared the levels of these compounds in different types of bread using a series of techniques collectively known as „sensomics”, involving the separation of chemical entities responsible for flavor and taste in food, as well as their identification and quantification. The researchers isolated 10 key „taste” components and 11 key „odor” components, combining them into a „essence” of fermented dough, whose aroma was confirmed by a human sensory panel. The 10 essential chemical components for bread taste were: sodium, potassium, ammonium, chloride, magnesium, calcium, d-fructose, l-glutamic acid, acetic acid, and lactic acid. The 11 key aroma components were: acetic acid, butyric acid, vanillin, 3-methylbutyric acid, hexanal, 2,3-butanedione, phenylacetaldehyde, 3-methylbutanal, methional, (E,E)-decadienal, and (E))-2-nonenal.

The experiments were initiated by having a trained group taste the crumb of rye bread, mixed-type bread, and wheat flour bread. Regardless of the type of Sourdough Bread evaluated, salinity and acidity were the predominant taste impressions, with scores of 2.4, 2.5, and 2.6 (salty), as well as 2.5, 2.1, and 1.5 (sour) for rye, mixed-type, and wheat bread, respectively. The remaining taste attributes of sweetness, bitterness, astringency, umami, and kokumi were rated with lower intensities of 1 and were therefore assumed to have a minor impact on the overall taste of the bread crumb. Rye bread crumb exhibited a more pronounced taste compared to the other two based on the perceived intensities of all taste qualities, except for saltiness. Based on these findings, rye bread crumb served as a reference and was selected for initial taste recombination experiments.

The research team then applied a technique known as „unified aroma quantitation,” previously developed by the team of Prof. Hofmann, to the dough-based bread. This allowed them to simultaneously analyze the unique taste and aroma compounds. In new studies, they used this method to quantify the concentrations of these compounds in different types of bread. By collecting both yeast-based and sourdough bread from local bakeries and supermarkets, made with either rye or wheat flour, the team found that while key yeast compounds, including lactic and acetic acids, were present in yeast-based bread, they were present in much smaller quantities compared to sourdough bread. These results highlight the importance of the fermentation process for the unique aroma of bread.

References

Amann, L.S.; Frank, O.; Dawid, C.; Hofmann, T.F. The Sensory-Directed Elucidation of the Key Tastants and Odorants in Sourdough Bread Crumb. Foods 2022, 11, 2325.