The combined effects of extrusion and heat-moisture treatment on the physicochemical properties and digestibility of corn starch

The combined effects of extrusion (ET) and heat-moisture treatments (EHMT) on the physicochemical properties and in vitro digestibility of corn starch were investigated. Extrusion played a dominant role in reducing relative crystallinity and resistant starch (RS) content, but the swelling power, solubility, rapidly digestible starch (RDS) and slowly digestible starch (SDS) content were increased compared to native starch. EHMT resulted in a decreased swelling power, solubility and a transition in the X-ray diffraction from V- to V+A-type pattern, indicating a structural transformation toward an increased thermodynamic stability. The gelatinization temperatures shifted to higher values while the enthalpy was increased from 1.556 J/g in ET to 3.542 J/g in EHMT. The SDS and RS contents of starch granules were significantly increased, with the latter being increased from 63.03% in ET starch to 71.48% in EHMT starch.