THERMAL CHARACTERIZATION OF NATIVE AND MODIFIED WHITE SORGHUM (SORGHUM BICOLOR) STARCH

Gelatinization and retrogradation characteristics of native and modified white sorghum (Sorghum bicolor) starches were studied using differential scanning calorimetry. The biopolymer was modified through acetylation, oxidation, and acid thinning reactions to prepare single-and dual-modified white sorghum starches. The results revealed that peak gelatinization temperature (T-p) of AWSS (acetylated white sorghum starch) and AOWSS (acetylated-oxidized white sorghum starch) was less than that of NWSS (native white sorghum starch), while oxidation and acid thinning significantly increased the peak gelatinization temperature. Gelatinization enthalpy (DH) of ATWSS (acid-thinned white sorghum starch) was the least among both native and modified starches, which indicates weakening of starch granules after acid modification. Rate of retrogradation was lower in AWSS, OWSS, and AOWSS than NWSS, whereas acid thinning increased the rate of retrogradation. After 12 days of refrigerated storage at 4 degrees C, percent retrogradation was in the order ATWSS>NWSS>AWSS similar to AOWSS>OWSS. However, percent increment in retrogradation enthalpy was the least in AWSS.