Shear-induced molecular fragmentation decreases the bioaccessibility of fully gelatinized starch and its gelling capacity

This work provides information on the feasibility of molecular shear scissions that promote interactions resulting in slowly digestible foods. Extrusion using nine different Specific Mechanical Energy (SME) was performed to obtain amylose and amylopectin with different hydrodynamic radius (R-h) and molecular weight (M-w) from banana starch. The work also aims to find a potential size threshold that decreases starch bio-accessibility through the formation of structural assemblies. Shear-induced fragmentation enabled molecules to get in closer proximity promoting interactions that caused a 36% reduction in their digestion rate. Results suggested that the nature of the structurally-driven slowly digestible starch is mostly due to molecular interactions involving amylopectin, which do not necessarily worsen the food mechanical properties. The R-h and M-w threshold to significantly decrease starch bio-accessibility was estimated to be in the range of 54.3-58.9 nm and 9.9 x 10(6)-17.1x10(6) g/mol, respectively, which was attained in the SME range of 177-274 kJ/kg.