Insight into the insoluble dietary fiber from quinoa bran on the physicochemical and in vitro digestibility properties of quinoa starch: from perspective of bound phenolics removal

Bound phenolics (BP) are crucial for maintaining insoluble dietary fiber (IDF) integrity and functionality, but their role in fiber-starch interactions remains under-explored. This study investigated the role of BP in modulating interactions between quinoa IDF (QIDF) and quinoa starch (QS). QIDF with BP removed (QIDF-BP) was prepared through de-phenolization treatment. Results showed that BP removal reduced QIDF's water-holding capacity, increased crystallinity, and loosened its structure. Furthermore, physicochemical properties, in vitro digestibility, and multi-scale structures of QS samples incorporated with QIDF or QIDF-BP were investigated. Results indicated that incorporating QIDF or QIDF-BP into QS enhanced pasting properties, thermal stability, and rheological behavior, including increased breakdown viscosity, pasting temperature, transition temperatures, and flow index ( P < 0.05). In vitro digestion revealed that both QIDF and QIDF-BP promoted the conversion of rapidly digestible starch and resistant starch to slowly digestible starch. Notably, QIDF inhibited QS digestion more effectively than QIDF-BP ( P < 0.05). Structural analyses confirmed that QIDF and QIDF-BP enhanced QS's ordered and double-helical structure. These findings clarify how BP modulate the starch-fiber interactions, providing a theoretical foundation for future research, and offering new insights into how modifying BP levels in dietary fibers can optimize food properties for health-promoting applications. • Bound phenolics regulated the interaction between IDF and starch. • BP removal reduced QIDF's water-holding capacity and increased its crystallinity. • QIDF and QIDF-BP exerted distinct impacts on the physicochemical properties of QS. • BP in QIDF strengthen its inhibition on QS digestion compared to QIDF-BP.