Enhancing Enzymatic Resistance in Corn Starch through RS3 Formation, Guar Gum Complexation, and Heat-Moisture Treatment

Diabetes is a major public-health problem, and the rapid digestion of starch-rich foods is relevant to postprandial glucose exposure. This study tested whether a sequence of type III resistant starch (RS3) formation, guar gum complexation, and heat-moisture treatment could make native corn starch more resistant to in vitro digestion. Native corn starch was gelatinized, debranched with pullulanase, and recrystallized to form RS3. Guar gum was added at 20% of the RS3 dry mass, followed by heat-moisture treatment. In vitro digestion was used to measure rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS). X-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) were used to examine structural and thermal changes. Mean RS content increased from 16.36% in native corn starch to 32.22% in RS3, 45.00% after guar gum addition, and 57.10% after heat-moisture treatment. RDS fell from 77.13% to 36.64%. The crystal pattern changed from A-type to mixed B+V-type, and relative crystallinity increased from 16.90% to 86.8%. SEM and DSC also showed changes in particle form and thermal behavior. These results link structural changes in the starch-guar gum system with stronger resistance to in vitro digestion. Glycemic index and postprandial blood glucose were not measured, so in vivo studies are still needed.