Effect of guar gum on the physicochemical properties and in vitro digestive characteristics of extruded starches

The present study assessed the impact of guar gum (GG) on the physical and chemical attributes and the in vitro digestibility of maize starch (MS), pea starch (PS), and sweet potato starch (SPS) subjected to extrusion treatment. Starch with 25 % moisture content and combined with GG in a 9:1 ratio was selected for extrusion. Scanning electron microscopy and differential scanning calorimetry reveal that extrusion disrupts the ordered structure of starch and induces aggregation of starch granules, resulting in a more cohesive structure, and GG addition led to the further evolution of this structure into a more intricate and irregular form. Rheological assessments demonstrated a remarkable enhancement in the gelatinization characteristics of starch with GG addition, which led to elevated flow resistance and increased viscosity. On evaluating the in vitro digestive characteristics, we noted that adding GG to starch augmented the levels of slow-digestible starch and resistant starch. Consequently, this resulted in diminished digestibility and a lowered glycemic index. In summary, GG synergistically interacts with starch, forming intricately assimilable components. Moreover, the effects of extrusion vary across different starches, which proves advantageous for SPS and GG amalgamation, thereby enhancing their resistant components. Conversely, extrusion manifests contrasting outcomes for MS and PS.