| Abstract: | The objective of this work was to investigate and compare the structural and physicochemical properties of Dioscorea opposita Thunb. flour(DF), starch(DS) and purified starch(PDS). DS and PDS showed higher total starch and amylose content as compared to DF. Starch granules of DF were oval shape with rough surface while DS and PDS were relatively smooth by SEM. According to XRD measurements, FT-IR spectroscopy and 13 C CP/MAS NMR spectroscopy, all samples displayed C-type crystalline pattern, and PDS displayed the highest relative crystallinity and short-range order structure. However, DF contained the greatest content of the amorphous-phase. DF displayed the absorption peaks at 1730 and 1560 cm~(-1) related to the characteristic groups of lipid and protein using FT-IR spectroscopy. Furthermore, DF exhibited significantly higher pasting temperature while DS displayed the great peak and breakdown viscosity, as well as PDS had the highest setback and final viscosity, presumably due to the chemical composition and structural differences. DF exhibited the highest gelatinization temperature whereas PDS displayed the greatest gelatinization enthalpy. The pasting and gelatinization properties of flour and starch might be related to the relative crystallinity, short-range order structure or the interactions between starch and its associated compounds. The results allow the improvement in the manufacture of Dioscorea opposita Thunb. flour and starch with desirable pasting and gelatinization properties. |
