Debranching by enzymatic extrusion of oat flour for enhanced amylose-lipid complex formation: Effects on in vitro digestibility and functional properties

Abstract

The amylose-lipid complex, also known as resistant starch type 5, is classified as dietary fibre with well-recognized health benefits. This study investigated its formation in pre-gelatinized whole oat flour using enzymatic extrusion-debranching and evaluated its effects on in vitro digestibility and functional properties. Whole oat grains were cooked in a steam oven, dried, ground, blended with pullulanase (60 U/g), and extruded enzymatically. Enzymatic extrusion increased oat flour's amylose content from 16.71 % to 26.93 % and resistant starch from 6.87 % to 31.99 %. Enzyme-extruded oat flour exhibited a V-type crystallinity pattern, confirmed amylose-lipid complex formation, and showed good thermal stability with two endothermic peaks at 90-110 °C and 110-130 °C. Additionally, enzymatic extrusion reduced the flour's viscosity and increased the water solubility index. These findings confirm that pullulanase extrusion effectively enhances resistant starch in lipid-rich cereal flour.