Effects of different amounts of steamed Polygonatum sibiricum on in-vitro digestion of extruded rice

In this study, steamed Polygonatum sibiricum (SPS) was utilized as a novel source of polysaccharides and saponins to improve the glycemic response of extruded rice by combining rice flour with various amounts of SPS (0 %, 3 %,   and 5 % w /w), to reform extruded rice-SPS complexes using twin-screw extrusion. The effects of SPS on cooking and textural properties, in vitro starch digestion, thermal properties, crystalline structure, and morphology were thoroughly investigated. The results indicated that SPS enhanced cooking performance, leading to longer cooking times, improved water absorption, and increased cooking loss. In vitro digestion experiments revealed a significant increase in slowly digestible starch (SDS) and resistant starch (RS) levels with adding SPS, indicating a deceleration in starch hydrolysis. Structural analyses using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) showed that SPS interacted with rice starch during extrusion, resulting in decreased crystallinity due to complex formation. The expected glycemic index (eGI) of the extruded rice decreased significantly from 90.39 to 83.72 with adding SPS. These findings suggest that SPS is a valuable supplement for enhancing the glycemic response of extruded rice by lowering its eGI and improving water absorption.