High temperature 1H DOSY NMR reveals sourdough fermentation of wheat flour alters the molecular structure of water-extractable arabinoxylans

Abstract: Arabinoxylans are constituents of wheat flour that contribute to the dietary fiber properties of wheat. They exist in water-extractable and water-unextractable forms and contribute to human health. In bakery technology, especially the water-extractable arabinoxylans (WE-AX) are important due to their impact on viscosity and dough rheology. This study provides insights into the impact of wheat flour fermentation on WE-AX during sourdough production, offering potential applications for improving sourdough bread quality and its health benefits. The production of sourdoughs is known to increase the WE-AX fraction, yet the underlying (bio)chemical mechanisms remain unclear. This study investigated the alteration of WE-AX during the fermentation of wheat flour for sourdough production using 1H Diffusion Ordered SpectroscopY (DOSY) Nuclear Magnetic Resonance (NMR) at elevated temperature to analyze the structural changes of WE-AX during wheat flour fermentation for sourdough production with different lactic acid bacteria (LAB) strains. The results confirmed that DOSY NMR at elevated temperatures greatly improved the applicability of the method for analyzing larger biomolecules. Overall, a size reduction of the WE-AX compounds with increasing fermentation time was found. This was indicated both by the occurrence of higher self-diffusion coefficients, and increased transverse relaxation times. Further research is necessary to explain deviations from the general trend.