Starch-phenolic Complexes Are Built on Physical CH-π Interactions and Can Persist After Hydrothermal Treatments Altering Hydrodynamic Radius and Digestibility of Model Starch-based Foods

Leveraging phenolic complexation to optimize starch functionality and digestibility is restrained by the obscurity of their physicochemical nature and molecular basis. To define starch-phenolic complexes under hydrothermal treatments, maize amylopectin and potato starch were complexed with caffeic acid, ferulic acid and gallic acid. Starch hydrothermal stability and digestibility were measured by differential scanning calorimeter and Englyst's method, respectively. While monosaccharide compositions and glycosidic linkages were analyzed by GC-MS, hydrodynamic radius and proton magnetic resonance of gelatinized complexes were measured by dynamic light scattering and NMR respectively. Compared with native starches, starch-phenolic complexes were not chemically modified and had modestly lower estimated glycemic indexes and significantly lower gelatinization temperatures (p < 0.05). Starch-phenolic complexes also had significantly lower levels of phenolic proton intensities and hydrodynamic radii relative to the control starch-phenolic mixtures (p < 0.05). These results suggested that phenolics may complex with starch through non-covalent CH-π bonds along α-(1 → 4) glycosidic chains.