Regulation of composite gel properties of buckwheat starch by insoluble dietary fiber from large-leaf yellow tea and its application in 3D printing.

This study constructed BS-TIDF composite systems with different levels of addition using large-leaf yellow tea insoluble dietary fiber (TIDF) and buckwheat starch (BS), and investigated their physicochemical properties, in vitro digestibility, and 3D printing characteristics. Dietary fiber is generally resistant to digestion and absorption in the upper gastrointestinal tract and therefore passes through the digestive system largely intact, contributing to satiety, accelerating intestinal transit, and increasing fecal bulk. The results showed that with increasing TIDF content, the L⁎ value of the samples significantly decreased, the a⁎ value first increased and then decreased, and the b⁎ value markedly increased. The final viscosity increased from 4721.00 cP to 5374.00 cP, while the breakdown and setback values decreased. Textural properties, including hardness, cohesiveness, gumminess, chewiness, and resilience, were overall reduced, whereas adhesiveness increased. The microstructure became more compact, with cracks appearing at higher TIDF levels. Particle size first decreased and then stabilized; the short-range ordered structure of starch was weakened, and the relative crystallinity dropped from 11.54 to 6.60. The mobility of weakly bound water and free water was enhanced, promoting partial transformation of free water into bound water. Meanwhile, resistant starch (RS) content rose from 21.44% to 32.80%, and the predicted glycemic index (pGI) decreased from 74.70 to 61.76. In terms of 3D printing performance, formulations with 0-3% TIDF maintained good shape fidelity, whereas printing accuracy decreased when the addition level exceeded 6%. These findings provided a theoretical basis for dietary fiber-modified starch systems and the development of glycemic index (low-GI) and 3D-printed functional foods.