Engineering Resistant Rice Starch via Hot-Melt Extrusion for Glycemic and Lipid Control: Structural Changes and In Vitro Functional Assessment

Consumption of white rice, characterized by a high glycemic index (GI) and rapid digestibility, contributes to postprandial glucose spikes and an increased risk of metabolic disorders such as diabetes and obesity. While resistant starch (RS) offers a dietary solution, conventional modification techniques often lack the efficiency to produce high-yield RS. This study utilized hot-melt extrusion (HME) technology to develop functional resistant rice formulations with enhanced physiological properties. Physicochemical characterization using SEM, XRD, FTIR, and TGA revealed that HME processing induced a transition from crystalline to amorphous states, evidenced by the collapse of A-type crystallinity, weakening of hydrogen-bond networks, and partial starch retrogradation. In in vitro functional assays, all HME-processed formulations exhibited superior α-amylase inhibitory activity compared to the control. Notably, formulations F4 and F5 exhibited strong α-amylase inhibition, reaching 62.5% and 68.8%, respectively, even at the lowest tested concentration (1.25 mg/mL). In addition, F5 showed the highest pancreatic lipase inhibition, reaching approximately 80–90%, indicating dual functionality in regulating carbohydrate digestion and lipid hydrolysis. These findings validate HME as an effective, continuous processing strategy for engineering RS-enriched rice matrices. The developed formulations show significant potential as functional food ingredients for obesity management and postprandial glycemic control.