Hydrophobic interactions between gallic acid and buckwheat: Impacts on structural, rheological, and digestive properties of extruded noodles

This study investigated the impact of gallic acid on the structural, rheological, antioxidant, and digestive properties of extruded buckwheat noodles. XRD, FTIR, TGA, rheological tests and intermolecular force showed that Gallic acid mainly binds with buckwheat through hydrophobic interactions disrupted the starch gel network, reducing viscosity, gel strength, and rheological stability. However, it enhanced thermal stability, decreasing rehydration time and cooking loss by 12% and 25%. The low-field NMR data showed that the addition of gallic acid affected the water distribution in the extruded buckwheat noodles, resulting in the conversion of more water into bound water. XRD data showed that the addition of gallic acid changed the starch structure of extruded buckwheat noodles from the original A-type to A+V-type, and reduced its starch crystallinity. The intermolecular forces and Fourier data further demonstrated that the intermolecular forces between gallic acid and buckwheat were mainly hydrophobic, supplemented by hydrogen bonding. In vitro digestion revealed reduced starch hydrolysis, glycemic index; and rapidly digestible starch decreased from 29.49% to 19.84% and resistant starch increased from 49.53% to 57.96%. Antioxidant assays confirmed gallic acid’s stability post-extrusion, reinforcing its functional potential. These results highlight its dual role in improving processing performance and nutritional quality, supporting its application in functional food development. • Gallic acid through hydrophobic force disrupted the starch gel, reducing viscosity. • Rehydration time and cooking loss decreased by 12% and 25%, improving noodle quality. • Starch hydrolysis and Estimated glycemic index decreased and resistant starch content increased. • Antioxidant activity was retained after extrusion, supporting functional food applications.