The Impact of Purified Granules Sourced from Potato, Maize and Wheat on Disulfide Bond Formation in Urea-Solubilized Glutenin

The addition of potato and maize powders to wheat-based dough systems has been identified as a common practice for enhancing the dietary fiber content of cereal products. However, their product quality remains problematic due to inadequate comprehension of the manner in which starch granules regulate disulfide bond formation within wheat gluten proteins. In order to address this evident gap in the existing literature, this study investigated the effects of different starch granules—including potato, maize, and wheat—on disulfide bond formation of urea-solubilized glutenin (USG). The experimental results indicate that the optimal conditions for enhancing disulfide bonding in potato, maize, and wheat granules (from 0.2162 to 0.5319, 0.3502 and 0.9488 μmol/g, respectively) were as follows: a USG: granule ratio of 3:1 (w/w), a temperature of 45 °C for 30 min, a USG: granule ratio of 3:1 (w/w), a temperature of 35 °C for 120 min, a USG: granule ratio of 1:2 (w/w), a temperature of 25 °C, and a duration of 60 min, respectively. Under low-granule conditions, the possible mechanism was that all granules might leach out predominantly amylopectin (no blue color is observed when attached to an iodine solution) to facilitate disulfide bond formation of USG. Conversely, under high-granule conditions, the interaction between granule proteins may be excessive, potentially leading to the precipitation of amylose (dark blue color is observed when attached to an iodine solution). This process may result in a reduction in disulfide bond contents due to the competitive interaction of water molecules. Spectroscopic and structural analyses further indicated that the attenuation of the nuclear magnetic resonance (NMR) signal of C1 hydroxyl groups of amylopectin/amylose and peptide amide bonds of USG arose from physical entanglement based on the hydrogen bonds between them. Upon interaction between USG and potato/maize starch granules, the X-ray diffraction pattern of USG vanished, and the intramolecular β-sheet conformation was markedly diminished. Collectively, these findings provide a mechanistic foundation for the rational design and optimization of high-fiber, high-quality cereal-based food products.