Xylanase/β-Glucanase Synergy: Enhancing Dough Structure and Bread Quality in Highland Barley–Wheat Blend

Highland barley (HB), a nutrient-rich grain, is limited in bread applications due to its weak gluten network and high content of non-starch polysaccharides (NSPs) such as β-glucan and arabinoxylan. This study aimed to improve the dough properties and bread quality of a composite flour containing 40% whole-grain highland barley through synergistic use of xylanase and β-glucanase. Rheological analysis revealed that dual-enzyme treatment significantly reduced dough rigidity (G' decreased by ~40%) and increased extensibility (tan δ raised by ~25%), shifting the network from a brittle NSP-dominated gel toward an elastic gluten-based structure. Low-field NMR showed that enzymes promoted redistribution of water from tightly bound states with NSPs to protein phases, enhancing gluten hydration. Microstructural observations confirmed a more continuous and uniform gluten network with finely embedded starch granules. Consequently, enzyme-treated bread exhibited a 35% higher specific volume, reduced hardness (~50% lower), improved springiness and cohesiveness, and superior sensory scores in texture, taste, and overall acceptability compared to the untreated composite. Single-enzyme treatments yielded partial improvements, highlighting the necessity of synergistic action. These results demonstrate that combined xylanase and β-glucanase treatment effectively mitigates the negative impact of NSPs, enabling the production of high-quality, sensorially appealing HB-enriched bread with optimized structural and textural properties.