Structural characteristics of slowly digestible starch and resistant starch isolated from heat-moisture treated waxy potato starch

The objective of this study was to investigate the structural characteristics of slowly digestible starch (SDS) and resistant starch (RS) fractions isolated from heat-moisture treated waxy potato starch. The waxy potato starch with 25.7% moisture content was heated at 120 °C for 5.3 h. Scanning electron micrographs of the cross sections of RS and SDS + RS fractions revealed a growth ring structure. The branch chain-length distribution of debranched amylopectin from the RS fraction had a higher proportion of long chains (DP ≥ 37) than the SDS + RS fraction. The X-ray diffraction intensities of RS and SDS + RS fractions were increased compared to the control. The SDS + RS fraction showed a lower gelatinization enthalpy than the control while the RS fraction had a higher value than the SDS + RS fraction. In this study we showed the RS fraction is composed mainly of crystalline structure and the SDS fraction consists of weak crystallites and amorphous regions.