Optimization of enzyme-assisted preparation and characterization of Arenga pinnata resistant starch

Preparation of Arenga pinnata resistant starch (APRS) by pullulanase combined with ultrasonic was studied and the properties of APRS was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Differential Scanning Calorimeter (DSC). SEM revealed that the APRS lost native granular structure and had irregular shape; and the purified APRS displayed roughly spherical and square structures with many holes. XRD showed that there was a crystalline transformation from C-type (native Arenga pinnata starch) to B-type (APRS) and the relative crystallinity decreased significantly. FTIR results exhibited that the molecular order of APRS was reduced. The significant increase of DSC enthalpy indicated that resistant starch (RS) had higher thermal stability than Arenga pinnata starch (APS). In vitro digestion demonstrated that resistant starch had strong digestive resistance.