Time and Temperature Effects of Ultrasound Treatments on the Resistant Starch Content of Canna edulis Ker

Abstract

Ultrasonication was applied to Ganyong (Canna edulis Ker) starch for three treatment of times (15, 30, and 45 minutes) at controlled temperature (30⁰, 45⁰, and 60⁰C). Ganyong as a local indigenous plant was chosen as the material in this study because it has big potential to produce resistant starch from its high content of amylose compared to other tuber’s starch, such as cassava, sweet potato, yam and arrowroot. Ultrasonication at 60⁰C and 45 minute was chosen as best treatment combination in this study due to the highest yield of resistant starch produced. Native canna starch was observed to have 1.45±0.24 % of resistant starch, however the number significantly increased to 48.19 ± 0.84% of resistant starch after modification (p<0.05). Further physicochemical changes of native and modified starch were observed. The results showed that there were no significant changes in the proximate analysis profiles before and after treatment. However, the ultrasonication significantly influence the pasting profiles (p<0.05) which was also expected due to the increase of starch granule size range from 30-160 μm to 45-179 μm after modification. The morphological changes were clearly observed by SEM and PLM, which showed swollen granule with rougher surface and fissures after modification. Thermal analysis using DSC did not significantly influenced the gelatinization temperature of the granule starch, however the increase of enthalpy (ΔH) occured from 2.99 to 10.86 J/kg. This result indicated the increase of resistant starch within canna starch granule.