Researchers at Vrije Universiteit Brussel have found that sourdough fermentation activates enzymes in wheat to break down arabinoxylans, influencing bread texture, digestibility and flavor. The study highlights how acidity drives this process more than microbes. Specific bacteria contribute to distinctive tastes like buttery aromas.
Bread remains a staple, with sourdough gaining popularity for its natural appeal and flavor. Víctor González Alonso, in his doctoral research at Vrije Universiteit Brussel (VUB), examined how arabinoxylans—key wheat dietary fibers—behave during fermentation. These fibers come in water-extractable (WE-AX), which have beneficial or neutral effects on dough, and water-unextractable (WU-AX), which can harm bread quality. Wheat supplies much of Europe's calories and fiber, and arabinoxylans affect bread structure, as González Alonso notes: “Wheat provides a large share of the calories and fiber consumed in Europe, and arabinoxylans play an important part in this. They help determine the structure and quality of bread.” Using DNA analysis and metabolite profiling on various flours, including AX-enriched ones, the team observed stable microbial ecosystems of lactic acid bacteria and yeasts. Higher fiber content had little effect, but fermentation converted some WE-AX to WU-AX. Surprisingly, wheat enzymes, activated by the dough's increasing acidity, drove the breakdown into smaller fragments, impacting digestibility and texture. Bacteria like Lactococcus lactis produced buttery aromas, while Limosilactobacillus fermentum added mild sweetness via sugar alcohols. In a pilot baking trial with AX-enriched flour, loaves showed higher nutrition and varied flavors. González Alonso concludes: “Sourdough remains a fascinating interplay of biology and craftsmanship. And our research shows that sourdough fermentation influences wheat fibers to a greater extent than previously thought.”
