Mechanisms of processing-driven changes on digestibility of fermented Indica rice noodles

To elucidate how sequential processing steps modulate the digestibility of fermented indica rice noodles (FIRN), a combination of in vitro digestion, structural analysis (Fourier Transform Infrared Spectroscopy, FTIR; X-Ray Diffraction, XRD; Scanning Electron Microscopy, SEM) and correlation analysis was employed, revealing a distinct "destruction and reconstruction" mechanism. Thermal steps initially disrupted the native starch structure by gelatinization, significantly reducing relative crystallinity (RC) and short-range order, which increased rapidly digestible starch (RDS) and glycemic index (GI). Conversely, nonthermal steps facilitated starch recrystallization, notably enhancing the formation of enzyme-resistant structures. These structures characterized by increased RC and A/V-type crystals, significantly elevated slow-digestible (SDS) and resistant starch (RS) contents, impeding digestibility and leading to a low GI profile. Correlation analysis confirmed that GI was positively correlated with RDS but negatively with SDS, RS, amylose, and RC. This work establishes a processing-structure-digestibility relationship, providing a strategic foundation for designing low-GI starch-based staple foods for glycometabolism-disordered populations.