Sucrose-induced structural modification of in situ exopolysaccharides: Effects on rheological and baking properties of gluten-free sourdough

초록

Pseudocereals have gained attention as nutritious gluten-free alternatives due to their high content of bioactive compounds. However, they inherently lack gluten, making it difficult to form a viscoelastic dough network, often resulting in poor bread quality. Microbial exopolysaccharide (EPS) production during sourdough fermentation has been proposed as a promising strategy to improve the quality of gluten-free bread. This study investigated the effects of sucrose concentration on the structural and functional properties of EPS produced during gluten-free sourdough fermentation and their impact on dough rheology and bread quality. Gluten-free sourdoughs were fermented with mixed microbial starters at sucrose concentrations of 0%, 10%, and 20%, and incorporated into dough to achieve final EPS concentrations of 0.2% and 0.3%. EPS yield decreased with increasing sucrose concentration, suggesting biosynthesis inhibition under excess carbon and low pH. Structural analysis revealed that the EPS was a glucose-based homopolysaccharide. Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR) confirmed that increasing sucrose concentrations promoted the formation of branch linkages while reducing the molecular weight. These structural changes enhanced starch granule interaction and dough matrix stability. At 0.3% EPS, doughs exhibited higher complex modulus (|G*|) and tan delta, indicating improved strength and viscosity. Breads made with high-sucrose sourdoughs containing 0.3% EPS showed improved porosity, with fewer large and more medium-sized alveoli, and greater textural stability. These findings emphasize the critical role of sucrose concentration in modulating EPS structure during gluten-free sourdough fermentation and its impact on bread quality, offering insights into the functional use of alternative grains.

키워드