Physicochemical Evolution of Glutinous Rice Flour and Its Influence on Tangyuan Processing Performance

The quality of glutinous rice flour (GRF) plays a critical role in determining the processing suitability of Tangyuan, a traditional Chinese glutinous rice-based food. This study systematically characterized the physicochemical, pasting, textural and digestive properties of twelve representative GRFs, as well as the cooking behaviors of the resulting product of Tangyuan. The results revealed that different GRFs displayed varied protein, total starch and amylopectin contents. The microstructure of Tangyuan exhibited three main types: robust and dense (e.g., H1 and H3), porous and soft (e.g., S1 and S4), and fragmented and disrupted (e.g., S2 and S3) networks. Rheological and pasting profiling revealed that doughs with extreme rigidity (G' > 10⁴ Pa) and high setback values exhibited rapid retrogradation, leading to severe frost cracking during cold-chain storage. Tangyuan with moderate G', loss tangent (tan δ) below 0.35, and balanced peak viscosities provided optimal viscoelasticity for both mechanical machinability and freeze-thaw stability. Furthermore, S5 with naturally high resistant starch contents significantly attenuated the hydrolysis index, successfully shifting Tangyuan from a high-glycemic to a medium-glycemic profile. The results provide valuable insights into the screening of raw glutinous rice flour from different origins, offering theoretical guidance for the standardized production of freeze-thaw-stable and low-glycemic functional Tangyuan.