Study of sago starch (Metroxylon sagu) gelatinization by differential scanning calorimetry

Differential scanning calorimetry (DSC), at various heating rates (1-30C/ min) and water:starch ratios (0.1:1-4. 1), was used to study gelatinization phenomena of sage starch. The results showed that the gelatinization temperature and enthalpy (DeltaH) of starches in excess water were 60-77C and 15.5-15.8 J/g, respectively. DeltaH of gelatinization remained substantially the same at excess water contents, but decreased significantly beyond a water:starch ratio of 1.3:1. A single endothermic transition (G) that transformed into a double endotherm (G and M-1) and only M, occurred, respectively, at excess, intermediate and limited water contents. At 50% water content, evidence of the M, endotherm was observed, and 85C represented the effective conclusion temperature (T-m) at the end of melting for sage starch. The experimental data were treated thermodynamically by applying an equation describing phase transitions of semi-crystalline polymers. The calculated value for the melting point of the undiluted polymer (T-m(o)) was 432 K (R-2=0.96).