Optimisation of the preparation of sweet potato resistant starch by dry heating with pectin

Abstract

The technological conditions for preparing sweet potato resistant starch (RS) by utilising the synergy of dry heating with pectin were optimised. By applying a response surface method, the influences of concentration of pectin, dry-heating treatment time, and dry-heating treatment temperature on starch anti-digestibility of sweet potato starches were analysed. The results showed that the optimal technological conditions were as follows: the content of pectin, dry-heating time, and dry-heating temperature were 2.18 %, 2.09 h, and 121.73 °C, respectively. The RS content in sweet potato starches prepared under these conditions was within 18.48 % ± 0.73 %. The result obtained through differential scanning calorimetry (DSC) revealed that the heat enthalpy (ΔH) of sweet potato starch increased from 2.475 to 3.698 J/g after being subjected to dry heating with pectin. Moreover, the result of in vitro digestibility tests suggested that the glycemic index of sweet potato RS prepared through dry heating with pectin was 69.09.